Document and Entity Information - USD ($)	12 Months Ended
Document and Entity Information - USD ($)	Dec. 31, 2017	Feb. 16, 2018	Jun. 30, 2017
Document And Entity Information [Abstract]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2017
Document Fiscal Year Focus	2017
Document Fiscal Period Focus	FY
Entity Registrant Name	U.S. Silica Holdings, Inc.
Entity Central Index Key	0001524741
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	Yes
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		80,539,945
Entity Public Float			$ 2,870,547,820

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Current Assets:
Cash and cash equivalents	$ 384,567	$ 711,225
Accounts receivable, net	212,586	89,006
Inventories, net	92,376	78,709
Prepaid expenses and other current assets	13,715	12,323
Income tax deposits	0	1,682
Total current assets	703,244	892,945
Property, plant and mine development, net	1,169,155	783,313
Goodwill	272,079	240,975
Trade names	33,068	32,318
Finite-lived intangible assets	116,939	108,160
Other assets	12,798	15,509
Total assets	2,307,283	2,073,220
Current Liabilities:
Accounts payable	148,772	70,778
Dividends payable	5,229	5,221
Accrued liabilities	16,841	13,034
Accrued interest	199	169
Current portion of long-term debt	4,504	4,821
Current portion of capital leases	706	2,237
Current portion of deferred revenue	36,128	13,700
Income tax payable	1,566	0
Total current liabilities	213,945	109,960
Long-term debt, net	506,732	508,417
Liability for pension and other post-retirement benefits	52,867	56,746
Deferred revenue	82,286	58,090
Deferred income taxes, net	29,856	50,075
Obligations under capital lease	0	717
Other long-term obligations	25,091	15,925
Total liabilities	910,777	799,930
Commitments and Contingencies (Note O)
Preferred stock, $0.01 par value, 10,000,000 shares authorized; 0 issued and outstanding at December 31, 2017 and 2016	0	0
Common stock, $0.01 par value, 500,000,000 shares authorized; 81,267,205 issued and 80,524,255 outstanding at December 31, 2017; 81,184,042 issued and 81,028,898 outstanding at December 31 2016	812	811
Additional paid-in capital	1,147,084	1,129,051
Retained earnings	287,992	163,173
Treasury stock, at cost, 742,950 and 155,144 shares at December 31, 2017 and 2016, respectively	(25,456)	(3,869)
Accumulated other comprehensive loss	(13,926)	(15,876)
Total stockholders’ equity	1,396,506	1,273,290
Total liabilities and stockholders’ equity	2,307,283	2,073,220
Intellectual property, net
Current Assets:
Finite-lived intangible assets	64,786	57,270
Customer relationships, net
Current Assets:
Finite-lived intangible assets	$ 52,153	$ 50,890

Consolidated Balance Sheets (Parenthetical) - $ / shares	Dec. 31, 2017	Dec. 31, 2016
Statement of Financial Position [Abstract]
Preferred stock, par value (in dollars per share)	$ 0.01	$ 0.01
Preferred stock, shares authorized (in shares)	10,000,000	10,000,000
Preferred stock issued (in shares)	0	0
Preferred stock, shares outstanding (in shares)	0	0
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock authorized (in shares)	500,000,000	500,000,000
Common stock issued (in shares)	81,267,205	81,184,042
Common stock, shares outstanding (in shares)	80,524,255	81,028,898
Treasury stock (in shares)	742,950	155,144

Consolidated Statements of Operations - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Sales:
Product	$ 1,057,553	$ 523,900	$ 640,464
Service	183,298	35,725	2,525
Total sales	1,240,851	559,625	642,989
Cost of sales (excluding depreciation, depletion and amortization):
Product	720,312	455,189	494,814
Service	147,203	22,106	252
Total cost of sales (excluding depreciation, depletion and amortization)	867,515	477,295	495,066
Operating expenses:
Selling, general and administrative	107,592	67,727	62,777
Depreciation, depletion and amortization	97,233	68,134	58,474
Total operating expenses	204,825	135,861	121,251
Operating income (loss)	168,511	(53,531)	26,672
Other (expense) income:
Interest expense	(31,342)	(27,972)	(27,283)
Other income (expense), net, including interest income	(643)	3,758	728
Total other (expenses) income	(31,985)	(24,214)	(26,555)
Income (loss) before income taxes	136,526	(77,745)	117
Income tax benefit	8,680	36,689	11,751
Net income (loss)	$ 145,206	$ (41,056)	$ 11,868
Earnings (loss) per share:
Basic (in usd per share)	$ 1.79	$ (0.63)	$ 0.22
Diluted (in usd per share)	$ 1.77	$ (0.63)	$ 0.22
Weighted average shares outstanding:
Weighted Average Number of Shares Outstanding, Basic (in shares)	81,051	65,037	53,344
Weighted Average Number of Shares Outstanding, Diluted (in shares)	81,960	65,037	53,601
Dividend declared per share (in usd per share)	$ 0.25	$ 0.25	$ 0.438

Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Statement of Comprehensive Income [Abstract]
Net income (loss)	$ 71,952	$ 41,273	$ 29,459	$ 2,522	$ (6,942)	$ (11,339)	$ (11,772)	$ (11,003)	$ 145,206	$ (41,056)	$ 11,868
Other comprehensive income (loss):
Unrealized gain (loss) on derivatives (net of tax of $(27), $29 and $34 for 2017, 2016, and 2015, respectively)									(44)	49	53
Foreign currency translation adjustment (net of tax of $2, $0 and $0 for 2017, 2016 and 2015, respectively)									(6)	0	0
Unrealized gain (loss) on investments (net of tax of $0, $(4) and $29 for 2017, 2016, and 2015, respectively)									0	(6)	47
Pension and other post-retirement benefits liability adjustment (net of tax of $1,205, $152 and $2,469 for 2017, 2016, and 2015, respectively)									2,000	252	3,547
Comprehensive income (loss)									$ 147,156	$ (40,761)	$ 15,515

Consolidated Statements of Comprehensive Income (Parenthetical) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Statement of Comprehensive Income [Abstract]
Tax expense (benefit) on unrealized gain (loss) on derivatives	$ (27)	$ 29	$ 34
Tax expense (benefit) on foreign currency translation adjustment	2	0	0
Tax expense (benefit) on unrealized gain (loss) on investments	0	(4)	29
Tax expense (benefit) on pension and other post-retirement benefits liability adjustment	$ 1,205	$ 152	$ 2,469

Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Total	Common Stock	Treasury Stock	Additional Paid-In Capital	Retained Earnings	Accumulated Other Comprehensive (Loss)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Total stockholders’ equity	$ 403,816	$ 539	$ (542)	$ 191,086	$ 232,551	$ (19,818)
Beginning balance at Dec. 31, 2014	403,816	539	(542)	191,086	232,551	(19,818)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	11,868				11,868
Unrealized gain (loss) on derivatives	53					53
Unrealized gain (loss) on short-term investments	47					47
Foreign currency translation adjustment	0
Pension and post-retirement liability	3,547					3,547
Cash dividends declared ($0.25, $0.438 and $0.50 per share of common stock for 2016, 2015 and 2014 respectively))	(23,445)				(23,445)
Equity-based compensation	3,857			3,857
Proceeds from options exercised	473		744	(271)
Shares withheld for employee taxes related to vested restricted stock and stock units	(794)		(792)	(2)
Repurchase of common stock	(15,255)		(15,255)
Total stockholders’ equity	403,816	539	(542)	191,086	232,551	(19,818)
Total stockholders’ equity	384,167	539	(15,845)	194,670	220,974	(16,171)
Beginning balance at Dec. 31, 2015	384,167	539	(15,845)	194,670	220,974	(16,171)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	(41,056)				(41,056)
Issuance of common stock (stock offerings net of issuance costs of $25,732)	931,288	272		931,016
Unrealized gain (loss) on derivatives	49					49
Unrealized gain (loss) on short-term investments	(6)					(6)
Foreign currency translation adjustment	0
Pension and post-retirement liability	252					252
Cash dividends declared ($0.25, $0.438 and $0.50 per share of common stock for 2016, 2015 and 2014 respectively))	(16,893)				(16,893)
Equity-based compensation	12,107			12,107
Excess tax benefit from equity-based compensation	148				148
Proceeds from options exercised	4,825		8,465	(3,640)
Issuance of restricted stock	0		1,437	(1,437)
Shares withheld for employee taxes related to vested restricted stock and stock units	(1,591)		2,074	(3,665)
Total stockholders’ equity	384,167	539	(15,845)	194,670	220,974	(16,171)
Total stockholders’ equity	1,273,290	811	(3,869)	1,129,051	163,173	(15,876)
Beginning balance at Dec. 31, 2016	1,273,290	811	(3,869)	1,129,051	163,173	(15,876)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	145,206				145,206
Unrealized gain (loss) on derivatives	(44)					(44)
Unrealized gain (loss) on short-term investments	0
Foreign currency translation adjustment	(6)					(6)
Pension and post-retirement liability	2,000					2,000
Cash dividends declared ($0.25, $0.438 and $0.50 per share of common stock for 2016, 2015 and 2014 respectively))	(20,387)				(20,387)
Equity-based compensation	25,050			25,050
Proceeds from options exercised	798		1,190	(392)
Issuance of restricted stock	0		1,859	(1,859)
Shares withheld for employee taxes related to vested restricted stock and stock units	(4,379)	1	386	(4,766)
Repurchase of common stock	(25,022)		(25,022)
Total stockholders’ equity	1,273,290	811	(3,869)	1,129,051	163,173	(15,876)
Total stockholders’ equity	$ 1,396,506	$ 812	$ (25,456)	$ 1,147,084	$ 287,992	$ (13,926)

Consolidated Statements of Stockholders' Equity (Parenthetical) - USD ($)					3 Months Ended								12 Months Ended
	Nov. 03, 2016	Jul. 21, 2016	May 05, 2016	Feb. 22, 2016	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Statement of Stockholders' Equity [Abstract]
Dividend declared per share (in usd per share)	$ 0.0625	$ 0.0625	$ 0.0625	$ 0.0625	$ 0.06	$ 0.06	$ 0.06	$ 0.06	$ 0.06	$ 0.06	$ 0.06	$ 0.06	$ 0.25	$ 0.25	$ 0.438	$ 0.438
Common stock issuance costs														$ 25,732

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Operating activities:
Net income (loss)	$ 145,206	$ (41,056)	$ 11,868
Adjustments to reconcile net income (loss) to net cash provided by operating activities:
Depreciation, depletion and amortization	97,233	68,134	58,474
Debt issuance amortization	1,382	1,392	1,401
Original issue discount amortization	372	378	382
Deferred income taxes	(20,601)	(36,903)	(10,473)
Loss on disposal of property, plant and equipment	415	563	383
Deferred revenue	28,438	(9,026)	(16,079)
Equity-based compensation	25,050	12,107	3,857
Bad debt provision	1,529	(1,232)	(290)
Other	5,529	3,643	(5,257)
Changes in assets and liabilities, net of effects of acquisitions:
Accounts receivable	(110,920)	(12,996)	62,465
Inventories	(4,825)	(10,211)	1,708
Prepaid expenses and other current assets	8,787	(509)	(708)
Income taxes	1,469	11,558	(5,837)
Accounts payable and accrued liabilities	59,769	13,121	(42,353)
Accrued interest	28	111	(2)
Liability for pension and other post-retirement benefits	(705)	1,307	1,953
Net cash provided by operating activities	238,156	381	61,492
Investing activities:
Capital expenditures	(384,622)	(46,450)	(53,646)
Capitalized intellectual property costs	(3,586)	(959)	0
Maturities of short-term investments	0	21,872	53,568
Acquisition of businesses, net of cash acquired	(119,801)	(176,617)	0
Proceeds from sale of property, plant and equipment	337	497	127
Net cash provided by (used in) investing activities	(507,672)	(201,657)	49
Financing activities:
Issuance of common stock	0	678,791
Common stock issuance costs	0	(25,732)
Dividends paid	(20,377)	(15,125)	(26,797)
Repurchase of common stock	(25,022)	0	(15,255)
Proceeds from options exercised	798	4,825	473
Tax payments related to shares withheld for vested restricted stock and stock units	(4,379)	(1,591)	(794)
Repayment of long-term debt	(7,211)	(5,202)	(5,093)
Principal payments on capital lease obligations	(951)	(542)	0
Financing fees	0	0	(64)
Net cash provided by (used in) financing activities	(57,142)	635,424	(47,530)
Net increase (decrease) in cash and cash equivalents	(326,658)	434,148	14,011
Cash and cash equivalents, beginning of period	711,225	277,077	263,066
Cash and cash equivalents, end of period	384,567	711,225	277,077
Cash paid (received) during the period for:
Interest	24,490	21,994	21,729
Taxes, net of refunds	8,958	(11,322)	4,568
Related party purchases	4,942	446	0
Non-cash items:
Common stock issued in connection with acquisitions	0	278,229	0
Capital lease obligations incurred to acquire assets	0	165	0
Equipment received	18,185	0	0
Accrued capital expenditures	$ 16,534	$ 391	$ 1,154

Organization	12 Months Ended
Organization	Dec. 31, 2017
Accounting Policies [Abstract]
Organization	NOTE A—ORGANIZATION U.S. Silica Holdings, Inc. (“Holdings,” and together with its subsidiaries “we,” “us” or the “Company”) is a domestic producer of commercial silica, a specialized mineral that is a critical input into a variety of end markets. During our 118-year history, we have developed core competencies in mining, processing, logistics and materials science that enable us to produce and cost-effectively deliver products to customers across these markets. We manufacture frac sand used to stimulate and maintain the flow of hydrocarbons in oil and natural gas wells. Our silica is also used as a raw material in a wide range of industrial applications, including glassmaking and chemical manufacturing. We operate in two business segments based on end markets served: (1) Oil & Gas Proppants and (2) Industrial & Specialty Products (see Note T - Segment Reporting for additional details). On August 16, 2016, we completed the acquisition of New Birmingham, Inc. (“NBI”), the ultimate parent company of NBR Sand, LLC (“NBR”), a regional sand producer located near Tyler, Texas. On August 22, 2016, we completed the acquisition of Sandbox Enterprises, LLC (“Sandbox” or the "Sandbox acquisition"), as a “last mile” logistics solution for frac sand in the oil and gas industry. On April 1, 2017, we completed the acquisition of White Armor, a product line of cool roof granules used in industrial roofing applications. On August 16, 2017, we completed the acquisition of Mississippi Sand, LLC ("MS Sand"). MS Sand is a frac sand mining and logistics company based in St. Louis, Missouri. See Note D - Business Combinations for additional details relating to these acquisitions.

Summary of Significant Accounting Policies

12 Months Ended

Dec. 31, 2017

Accounting Policies [Abstract]

Summary of Significant Accounting Policies

NOTE B—SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES

Basis of Presentation and Consolidation

The accompanying Consolidated Financial Statements (the “Financial Statements”) have been prepared in accordance with generally accepted accounting principles in the United States (“GAAP”). In the opinion of management, all adjustments necessary for a fair presentation of the Financial Statements have been included. Such adjustments are of a normal, recurring nature. Certain reclassifications of prior years’ amounts have been made to conform to the current year presentation.

In order to make this report easier to read, we refer throughout to (i) our Consolidated Balance Sheets as our “Balance Sheets,” (ii) our Consolidated Statements of Operations as our “Income Statements,” and (iii) our Consolidated Statements of Cash Flows as our “Cash Flows.”

Consolidation

The Financial Statements include the accounts of Holdings and its direct and indirect wholly-owned subsidiaries. All significant intercompany balances and transactions have been eliminated in consolidation.

We follow FASB Accounting Standards Codification (“ASC”) guidance for identification and reporting of entities over which control is achieved through means other than voting rights. The guidance defines such entities as Variable Interest Entities (“VIEs”). For the periods presented herein, we have identified no VIE entities over which we maintain any level of control that would require consolidation under ASC guidance.

Use of Estimates and Assumptions

The preparation of the Financial Statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and the related disclosure of contingent assets and liabilities at the date of the Financial Statements and the reported amounts of revenues and expenses during the reporting period. The more significant areas requiring the use of management estimates and assumptions relate to purchase price allocation for businesses acquired; mineral reserves that are the basis for future cash flow estimates utilized in impairment calculations and units-of-production amortization calculations; environmental, reclamation and closure obligations; estimates of recoverable minerals; estimates of allowance for doubtful accounts; estimates of fair value for certain reporting units and asset impairments (including impairments of goodwill and other long-lived assets); write-downs of inventory to net realizable value; equity-based compensation expense; post-employment, post-retirement and other employee benefit liabilities; valuation allowances for deferred tax assets; contingent considerations; reserves for contingencies and litigation; and the fair value and accounting treatment of financial instruments including derivative instruments. We base our estimates on historical experience and on various other assumptions that are believed to be reasonable under the circumstances. Accordingly, actual results may differ significantly from these estimates under different assumptions or conditions.

Revenue Recognition

We derive most of our sales by mining and processing minerals that our customers purchase for various uses. Our product sales are primarily a function of the price per ton and the number of tons sold. The amount invoiced reflects product, transportation and/or additional services as applicable, such as storage, transloading the product from railcars to trucks and last mile logistics to the customer site.

Revenue is recognized from a sale when persuasive evidence of an arrangement exists, the price is fixed and determinable, the product has been delivered, legal title has been transferred to the customer or services are completed and collection of the sale is reasonably assured. Amounts received from customers in advance of revenue recognition are deferred as liabilities.

We primarily sell our products under short-term price agreements or at prevailing market rates. For a limited number of customers, we sell under long-term, minimum purchase supply agreements. As of December 31, 2017, we had 23 minimum purchase supply agreements in the Oil & Gas Proppants segment with initial terms expiring between 2018 and 2022. These agreements define, among other commitments, the volume of product that our customers must purchase, the volume of product that we must provide and the price that we will charge and that our customers will pay for each product. Prices under these agreements are generally fixed and subject to certain contractual adjustments. Sometimes these agreements may undergo negotiations regarding pricing and volume requirements, which may often occur in volatile market conditions. While these negotiations continue, we may deliver sand at prices or at volumes below the requirements in our existing supply agreements.

We invoice the majority of our product customers on a per shipment basis, although for some larger customers, we consolidate invoices weekly or monthly. Standard terms are net 30 days, although extended terms are offered in competitive situations. Sales and other transaction taxes imposed by government entities are reported on a net basis.

We invoice services periodically after the services are completed. Depending on the types of services, the total amount billed may include labor, equipment costs, freight, handling and other costs.

Cash and Cash Equivalents

Cash and cash equivalents consist of all highly liquid investments with a maturity of three months or less when purchased. Because of the short maturity of these investments, the carrying amounts approximate their fair value. Cash and cash equivalents are invested primarily in money market securities held by financial institutions with high credit ratings. Accounts at each institution are insured by the Federal Deposit Insurance Corporation. Cash balances at times may exceed federally-insured limits. We have not experienced any losses in such accounts and believe we are not exposed to any significant credit risk on cash.

Accounts Receivable

The majority of our accounts receivable are due from companies in the oil and natural gas drilling, glass, building products, filler and extenders, foundries and other major industries. Credit is extended based on evaluation of a customer’s financial condition and, generally, collateral is not required. Accounts receivable are stated at amounts due from customers net of an allowance for doubtful accounts. Accounts outstanding longer than the payment terms are considered past due. We determine our allowance by considering a number of factors, including the length of time trade accounts receivable are past due, our previous loss history, the customer’s current ability to pay its obligation to us, and the condition of the general economy and the industry as a whole. Ongoing credit evaluations are performed. We write-off accounts receivable when they are deemed uncollectible, and payments subsequently received on such receivables are credited to the allowance for doubtful accounts.

Inventories

Inventories include raw stockpiles and silica and other industrial sand available for shipment, as well as spare parts and supplies for routine facility maintenance. We value inventory at the lower of cost and net realizable value. Cost is determined using the first-in, first-out and average cost methods. Costs of our raw stockpiles and silica and other industrial sand inventories include production costs and transportation and additional service costs as applicable.

Property, Plant and Mine Development

Plant and equipment

Plant and equipment is recorded at cost and depreciated over their estimated useful lives. Interest incurred during construction of facilities is capitalized and depreciated over the life of the asset. Costs for normal repairs and maintenance that do not extend economic life or improve service potential are expensed as incurred. Costs of improvements that extend economic life or improve service potential are capitalized and depreciated over the estimated remaining useful life.

Depreciation is recorded using the straight-line method over the assets’ estimated useful lifes as follows: buildings (15 years); land improvements (10 years); machinery and equipment, including computer equipment and software (3-10 years); furniture and fixtures (8 years). Leasehold improvements are depreciated over the shorter of the asset life or lease term. Construction-in-progress is primarily comprised of machinery and equipment which have not yet been placed in service.

Mining property and development

Mining property and development includes mineral deposits and mine exploration and development. Mineral deposits are initially recognized at cost, which approximates the estimated fair value on the date of purchase. Mine exploration and development costs include engineering and mineral studies, drilling and other related costs to delineate an ore body, and the removal of overburden to initially expose an ore body for production. Costs incurred before mineralization are classified as proven and probable reserves are expensed and classified as exploration or advanced projects, research and development expense. Capitalization of mine development project costs, that meet the definition of an asset, begins once mineralization is classified as proven and probable reserves.

The cost of removing overburden and waste materials to access the ore body at an open pit mine prior to the production phase are referred to as “pre-stripping costs.” Pre-stripping costs are capitalized during the development of an open pit mine. The production phase of an open pit mine commences when saleable minerals, beyond a de minimis amount, are produced. Stripping costs incurred during the production phase of a mine are variable production costs that are included as a component of inventory to be recognized in costs applicable to sales in the same period as the revenue from the sale of inventory.

Depletion and amortization of mineral deposits and mine development costs are recorded as the minerals are extracted, based on units of production and engineering estimates of mineable reserves. The impact of revisions to reserve estimates is recognized on a prospective basis.

Mine reclamation costs and asset retirement obligations

We recognize the fair value of any liability for conditional asset retirement obligations, including environmental remediation liabilities when incurred, which is generally upon acquisition, construction or development and/or through the normal operation of the asset, if sufficient information exists to reasonably estimate the fair value of the liability. These obligations generally include the estimated net future costs of dismantling, restoring and reclaiming operating mines and related mine sites, in accordance with federal, state, local regulatory and land lease agreement requirements. The liability is accreted over time through periodic charges to earnings. In addition, the asset retirement cost is capitalized as part of the asset’s carrying value and amortized over the life of the related asset. Reclamation costs are periodically adjusted to reflect changes in the estimated present value resulting from the passage of time and revisions to the estimates of either the timing or amount of the reclamation and abandonment costs. The reclamation obligation is based on when spending for an existing environmental disturbance will occur. If the asset retirement obligation is settled for other than the carrying amount of the liability, a gain or loss is recognized on settlement. We review, on an annual basis, unless otherwise deemed necessary, the reclamation obligation at each mine site in accordance with ASC guidance for accounting reclamation obligations.

Future remediation costs for inactive mines are accrued based on management’s best estimate at the end of each period of the costs expected to be incurred at a site. Such cost estimates include, where applicable, ongoing care, maintenance and monitoring costs. Changes in estimates at inactive mines are reflected in earnings in the period an estimate is revised.

In connection with our annual review of our reclamation obligations, we have determined that some of our estimates required revision due primarily to the additions of new plant and transload facilities and other changes in cost estimates and settlement dates at various sites. These additions and changes in estimates resulted in an additional $7.0 million and $(2.1) million of asset retirement obligations in 2017 and 2016, respectively.

Our asset retirement obligations are reported in other long-term obligations. The changes in these obligations (in thousands) during the years ending December 31, 2017 and 2016 are as follows:



	2017		2016
Beginning balance	$	11,159	$	12,254
Accretion	879		979
Additions and revisions of prior estimates	6,994		(2,074		)
Ending balance	$	19,032	$	11,159

Impairment or Disposal of Property, Plant and Mine Development

Gains on the sale of property, plant and mine development are included in income when the assets are disposed of provided there is more than reasonable certainty of the collectability of the sales price and any future activities required to be performed by us relating to the disposal of the assets are complete or insignificant. Upon retirement or disposal of assets, all costs and related accumulated depreciation or amortization are written-off.

We periodically evaluate whether current events or circumstances indicate that the carrying value of our property, plant and equipment assets may not be recoverable. If circumstances indicate that the carrying value may not be recoverable, we estimate future undiscounted net cash flows using estimates of proven and probable sand reserves, estimated future sales prices (considering historical and current prices, price trends and related factors) and operating costs and anticipated capital expenditures. If the undiscounted cash flows are less than the carrying value of the assets, we recognize an impairment loss equal to the amount by which the carrying value exceeds the fair value of the assets.

Goodwill and Other Intangible Assets and Related Impairment

Our intangible assets consist of goodwill, which is not being amortized, indefinite lived intangibles, which consist of certain trade names that are not subject to amortization, intellectual property and customer relationships.

Intellectual property mainly consists of patents and technology, and it is amortized on a straight-line basis over an average useful life of 15 years. Customer relationships are amortized on a straight-line basis over their useful life of 20, 15 or 13 years.

Goodwill represents the excess of purchase price over the fair value of net assets from business acquisitions. Goodwill and trade names are reviewed for impairment annually as of October 31 or more frequently whenever events or circumstances change that would more likely than not reduce the fair value of those assets. Prior to conducting a formal impairment test, we have an option to assess qualitative factors to determine whether the existence of events or circumstances leads to a determination that is more likely than not (more than 50%) that the fair value of a reporting unit is less than its carrying amount. Such qualitative factors may include the following: macroeconomic conditions; industry and market considerations; cost factors; overall financial performance; and other relevant entity-specific events. If the qualitative assessment determines that an impairment is more likely than not, or if we choose to bypass the qualitative assessment, we perform a quantitative comparison of the fair value with the carrying amount, including goodwill. If this comparison reflects impairment, then the loss would be measured as the excess of recorded goodwill, or other intangible assets with indefinite lives, over its implied fair value. Implied fair value is the excess of our fair value over the fair value of all recognized and unrecognized assets and liabilities. As of October 31, 2017, our qualitative assessment did not indicate that it was more likely than not that an impairment had occurred. Further, no triggering events have subsequently transpired that would indicate a potential impairment as of December 31, 2017.

Debt Issuance Costs

The Company defers costs directly associated with acquiring third-party financing, primarily loan origination costs and related professional expenses. Debt issuance costs are deferred and amortized using the effective interest rate method over the term of our senior secured term loan facility (the “Term Loan”) and the straight-line method for our revolving line-of-credit (the "Revolver"). Debt issuance costs related to long-term debt are reflected as a direct deduction from the carrying amount of the debt. Amortization included in interest expense was $1.4 million for each of the years ended December 31, 2017, 2016 and 2015, respectively.

Environmental Costs

Environmental costs, other than qualifying capital expenditures, are accrued at the time the exposure becomes known and costs can be reasonably estimated. Costs are accrued based upon management’s estimates of all direct costs, after taking into account expected reimbursement by third parties (primarily the sellers of acquired businesses), and are reviewed by outside consultants. Environmental costs are charged to expense unless a settlement with an indemnifying party has been reached.

Self-Insurance

We are self-insured for various levels of employee health insurance coverage, workers’ compensation and third party product liability claims alleging occupational disease. We purchase insurance coverage for claim amounts which exceed our self-insured retentions. Depending on the type of insurance, these self-insured retentions range from $0.1 million to $0.5 million per occurrence. Our insurance reserves are accrued based on estimates of the ultimate cost of claims expected to occur during the covered period. The current portion of our self-insurance reserves is included in accrued liabilities and the non-current portion is included in other long-term obligations in our Balance Sheets. At December 31, 2017 and 2016, our self-insurance reserves totaled $5.5 million and $5.3 million, respectively, of which $1.7 million and $1.3 million, respectively, was classified as current.

Research and Development Costs

We may incur immaterial internal research and development (“R&D”) expenditures, and research and development conducted for others, all of which are expensed as incurred, and included in selling, general and administrative expense. R&D costs may include, but are not limited to, research and administrative salaries, contractor fees, building costs, utilities, administrative expenses, and allocations of corporate costs.

Advertising Costs

We recognize advertising expense when incurred as selling, general and administrative expense.

Equity-based Compensation

We grant stock options, restricted stock, restricted stock units and performance share units to certain of our employees and directors under the Amended and Restated U.S. Silica Holdings, Inc. 2011 Incentive Compensation Plan. We recognize the cost of employee services rendered in exchange for awards of equity instruments.

Vesting of restricted stock and restricted stock units is based on the individual continuing to render service over a three-year vesting schedule. Cash dividend equivalents are accrued and paid to the holders of time based restricted stock units and restricted stock. The fair value of the restricted stock awards is equal to the market price of our stock at date of grant. The restricted award-related compensation expense is recognized, on a straight-line basis, over the vesting period.

We grant performance share units to certain employees in which the number of shares of common stock ultimately received is determined based on achievement of certain performance thresholds over a specified performance period (generally three years) in accordance with the stock award agreement. Cash dividend equivalents are not accrued or paid on performance share units. We recognize expense based on the estimated vesting of our performance share units granted and the grant date market price. The estimated vesting of the performance share units is principally based on the probability of achieving certain financial performance levels during the vesting periods. In the period it becomes probable that the minimum performance criteria specified in the award agreement will be achieved, we recognize expense for the proportionate share of the total fair value of the award related to the vesting period that has already lapsed. The remaining fair value of the award is expensed on a straight-line basis over the remaining vesting period.

During the years ended December 31, 2017 and 2016, we granted certain employees performance share units, the vesting of which is based on the Company’s total shareholder return (“TSR”) ranking among a peer group over the three-year period from January 1, 2017 through December 31, 2019 for the 2017 awards and from January 1, 2016 through December 31, 2018 for the 2016 awards. The number of units that will vest will depend on the percentage ranking of the Company's TSR compared to the TSRs for each of the companies in the peer group over the performance period. For these awards subject to market conditions, a binomial-lattice model (i.e., Monte Carlo simulation model) is used to fair value these awards at grant date. The related compensation expense is recognized, on a straight-line basis, over the vesting period.

We grant stock options to certain employees and directors. Stock options vest on a vesting schedule and the related compensation expense is recognized over the vesting period, usually over 3 or 4 years. In calculating the compensation expense for stock options granted, we estimate the fair value of each grant using the Black-Scholes option-pricing model.

The fair value of stock options granted is based on the exercise price of the option and certain assumptions, which are evaluated and revised, as necessary, to reflect market conditions and experience. Our expected forfeiture rate is the estimated percentage of options granted that are expected to be forfeited or canceled on an annual basis before becoming fully vested. Our expected term is the period of time over which the options are expected to remain outstanding. An increase in the expected term will increase compensation expense. The computation of the expected term is based on the simplified method, under which the expected term is presumed to be the mid-point between the average vesting date and the end of the contractual term. The assumptions for expected volatility are based on historical experience for the same periods as our expected lives. Risk-free interest rates are set using grant-date U.S. Treasury yield curves for the same periods as our expected lives. The expected dividend yield is based on our future dividend expectations for the same periods as our expected lives.

Income Taxes

Deferred taxes are provided on the liability method whereby deferred tax assets are recognized for deductible temporary differences and operating loss and tax credit carry forwards and deferred tax liabilities are recognized for taxable temporary differences. This approach requires recognition of deferred tax liabilities and assets for the expected future tax consequences of events that have been included in the financial statements or tax returns. Under this method, deferred tax liabilities and assets are determined based upon the difference between the financial statement and tax basis of assets and liabilities using enacted tax rates in effect for the year in which the expenses are expected to reverse. Valuation allowances are provided if, based on the weight of available evidence, it is more likely than not that some or all of the deferred tax assets will not be realized.

We recognize a tax benefit associated with an uncertain tax position when, in management’s judgment, it is more likely than not that the position will be sustained upon examination by a taxing authority. For a tax position that meets the more-likely-than-not recognition threshold, we initially and subsequently measure the tax benefit as the largest amount that we judge to have a greater than 50% likelihood of being realized upon ultimate settlement with a taxing authority. The liability associated with unrecognized tax benefits is adjusted periodically due to changing circumstances, such as the progress of tax audits, case law developments and new or emerging legislation. Such adjustments are recognized entirely in the period in which they are identified. The effective tax rate includes the net impact of changes in the liability for unrecognized tax benefits and subsequent adjustments as considered appropriate by management.

The largest permanent item in computing both our effective tax rate and taxable income is the deduction allowed for statutory depletion. The deduction for statutory depletion does not necessarily change proportionately to changes in income before income taxes.

Earnings per Share

Basic and diluted earnings per share is presented for net income (loss). Basic earnings per common share is computed by dividing income available to common stockholders by the weighted average number of common shares outstanding for the period. Diluted earnings per common share is computed similarly to basic earnings per common share except that the weighted average number of common shares outstanding is increased to include the number of additional common shares that would have been outstanding if the potentially dilutive common shares had been issued. In accordance with the applicable accounting guidance for calculating earnings per share, we did not include in our calculation of diluted earnings per share for the applicable periods stock options where the exercise prices were greater than the average market prices. The weighted-average stock awards (in thousands) that are antidilutive and are, therefore, excluded from the calculation of diluted earnings per common share are as follows:



	For the Year Ended December 31,
	2017	2016	2015
Weighted-average outstanding stock options excluded	195	573	528
Weighted-average outstanding restricted stock and performance share units awards excluded	305	166	66

Comprehensive Income (loss)

In addition to net income (loss), comprehensive income (loss) includes all changes in equity during a period, such as adjustments to minimum pension liabilities and the effective portion of changes in fair value of derivative instruments that qualify as cash flow hedges.

Financial Instruments

We currently use interest rate hedge agreements to manage interest costs and the risk associated with changing interest rates. Amounts to be paid or received under these hedge agreements are accrued as interest rates change and are recognized over the life of the hedge agreements as an adjustment to interest expense. Our policy is to not hold or issue derivative financial instruments for trading or speculative purposes. When entered into, these financial instruments are designated as hedges of underlying exposures, associated with our long-term debt, and are monitored to determine if they remain effective hedges. Gains and losses on derivatives designated as cash flow hedges are recorded in other comprehensive income (loss), net of tax, and reclassified to earnings in a manner that matches the timing of the earnings impact of the hedged transactions. The ineffective portion of all hedges, if any, is recognized currently in income. Additional disclosures for derivative instruments are presented in Note M - Derivative Instruments to these financial statements.

Business Combinations

The Company accounts for business combinations using the acquisition method of accounting. Under this method, acquired assets, including separately identifiable intangible assets and any assumed liabilities, are recorded at their acquisition date estimated fair value. The excess of purchase price over the fair value amounts assigned to the assets acquired and liabilities assumed represents the goodwill amount resulting from the acquisition. Determining the fair value of assets acquired and liabilities assumed involves the use of significant estimates and assumptions. Additional disclosures for business combinations are presented in Note D - Business Combinations to these financial statements.

Recently Issued Accounting Pronouncements

In May 2014, the Financial Accounting Standards Board ("FASB") issued Accounting Standards Update (“ASU”) 2014-09, Revenue from Contracts with Customers (Topic 606) which supersedes previous revenue recognition guidance. The new guidance introduces a new principles-based framework for revenue recognition and disclosure. Since its issuance, the FASB has issued additional ASUs, amending the guidance and the effective dates of amendments, and the SEC has rescinded certain related SEC guidance. The pronouncements are effective for annual reporting periods beginning after December 15, 2017, including interim reporting periods within that reporting period. Based on our reviews, there is no material impact to the Company’s results of operations, financial position and cash flows as a result of this guidance. Companies can use either a full retrospective or modified retrospective method to adopt the standard. The Company has elected to apply the modified retrospective approach. Under the modified retrospective method, prior periods are not updated to be presented on an accounting basis that is consistent with 2018; rather, a cumulative adjustment for the effects of applying the new standard to periods prior to 2018 is recorded to retained earnings as of January 1, 2018. Because only 2018 revenues will reflect application of the new standard, incremental disclosures are required to present 2018 revenues under the prior standard.

The new standard requires companies to identify contractual performance obligations and determine whether revenue should be recognized at a point in time or over time based on when control of goods and services transfer to a customer. As a result of our implementation review, we do not expect significant changes in the presentation of our financial statements, including either: (1) timing of revenue recognition, or (2) changes in classification between revenue and costs. The new standard will have no cash flow impact and, as such, does not affect the underlying economics of our customer contracts. The effect of applying the new guidance to our existing book of contracts will be minimal.

Application of this method will not result in a material cumulative effect adjustment as of the date of adoption. We do not expect application of the new guidance to result in increases or decreases in revenue within our segments, or any material impact on our balance sheets.

In February 2016, the FASB issued ASU 2016-02, Leases (Topic 842). The new standard establishes a right-of-use (ROU) model that requires a lessee to record an ROU asset and a lease liability on the balance sheet for all leases with terms greater than 12 months. Leases will be classified as either finance or operating, with classification affecting the pattern of expense recognition. Similarly, lessors will be required to classify leases as sales-type, finance or operating, with classification affecting the pattern of income recognition. Classification for both lessees and lessors will be based on an assessment of whether risks and rewards as well as substantive control have been transferred through a lease contract. This update is effective for public entities for financial statements issued for fiscal years beginning after December 15, 2018, including interim periods within those fiscal years, and early adoption is permitted. This standard mandates a modified retrospective transition method. While we continue to evaluate the effect of the standard, we anticipate that the adoption will result in a material increase in assets and liabilities on our consolidated balance sheet and will not have a material impact on our consolidated income statement or statement of cash flows.

In August 2016, the FASB issued ASU 2016-15, “Classification of Certain Cash Receipts and Cash Payments,” which amends guidance on the classification of certain cash receipts and payments in the statement of cash flows. This ASU adds or clarifies guidance on eight specific cash flow issues. Additionally, guidance on the presentation of restricted cash is addressed in ASU 2016-18, Statement of Cash Flows (Topic 230): Restricted Cash, which was issued in November 2016. Both standards are effective for annual reporting periods beginning after December 15, 2017, and interim reporting periods within those annual reporting periods. Early adoption is permitted. Adoption of these standards will not have a material impact on our consolidated Statements of Cash Flows.

In January 2017, the FASB issued ASU 2017-01, Business Combinations (Topic 805): Clarifying the Definition of a Business. The new guidance clarifies the definition of a business with the objective of adding guidance to assist companies and other reporting organizations with evaluating whether transactions should be accounted for as acquisitions (or disposals) of assets or businesses. The changes to the definition of a business will likely result in more acquisitions being accounted for as asset acquisitions. ASU 2017-01 is effective for annual periods beginning after December 15, 2017, including interim periods within those periods. Early application of the amendments in ASU 2017-01 is allowed for a transaction(s) for which the acquisition date occurs before the issuance date or effective date of the amendments, a subsidiary is deconsolidated or a group of assets is derecognized only when the transaction(s) has (have) not been reported in financial statements that have been issued or made available for issuance. We do not expect the adoption of this standard to have a material impact on our consolidated financial statements.

In January 2017, the FASB issued ASU 2017-04, Intangibles - Goodwill and Other (Topic 350): Simplifying the Test for Goodwill Impairment, which removes Step 2 from the goodwill impairment test. It is effective for annual and interim periods beginning after December 15, 2019. Early adoption is permitted for interim or annual goodwill impairment tests performed with a measurement date after January 1, 2017. We do not expect the adoption of this standard to have a material impact on our consolidated financial statements.

In March 2017, the FASB issued ASU 2017-07, Compensation-Retirement Benefits (Topic 715), Improving the Presentation of Net Periodic Pension Cost and Net Periodic Postretirement Benefit. ASU 2017-07 amends presentation requirements related to reporting the service cost component of net benefit costs to require that the service cost component be reported in the same line item or items as other compensation costs arising from services rendered by the pertinent employees during the period, disaggregating the component from other net benefit costs. ASU 2017-07 also limits the components of net benefit cost eligible to be capitalized to service cost. ASU 2017-07 is effective for fiscal years beginning after December 15, 2017, including interim periods within those annual periods for public business entities. Early adoption is permitted as of the beginning of an annual period for which financial statements (interim or annual) have not been issued or made available for issuance. Early adoption should be within the first interim period if an employer issues interim financial statements. Disclosures of the nature of and reason for the change in accounting principle are required in the first interim and annual periods of adoption. We do not expect the adoption of this standard to have a material impact on our consolidated financial statements.

In May 2017, the FASB issued ASU 2017-09, Compensation-Stock Compensation (Topic 718), Scope of Modification Accounting. This update amends the scope of modification accounting for share-based payment arrangements. ASU 2017-09 provides guidance on the types of the changes to the terms or conditions of share-based payments awards to which an entity would be required to apply modification accounting. Specifically, an entity would not apply modification accounting if the fair value, vesting conditions, and classification of the awards are the same immediately before and after the modification. ASU 2017-09 is effective for fiscal years beginning after December 15, 2017, including interim periods within those annual periods for all entities. Early adoption is permitted, including adoption in any interim period, for public business entities for reporting periods for which financial statements have not yet been issued. We do not expect the adoption of this standard to have a material impact on our consolidated financial statements.

Capital Structure and Accumulated Comprehensive Income

12 Months Ended

Dec. 31, 2017

Equity [Abstract]

Capital Structure and Accumulated Comprehensive Income

NOTE C—CAPITAL STRUCTURE AND ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS)

Common Stock

Our Amended and Restated Certificate of Incorporation, authorizes up to 500,000,000 shares of common stock, par value of $0.01. Subject to the rights of holders of any series of preferred stock, all of the voting power of the stockholders of Holdings shall be vested in the holders of the common stock.

In March 2016, we completed a public offering of 10,000,000 shares of our common stock for total cash proceeds of approximately $186.2 million net of underwriting discounts and offering costs. In August 2016, we issued an additional 6,825,693 shares of our common stock to complete two acquisitions discussed in Note D - Business Combinations. In November 2016, we executed another offering of 10,350,000 shares of common stock raising net cash proceeds of $467.0 million.

There were 81,267,205 shares issued and 80,524,255 shares outstanding at December 31, 2017. There were 81,184,042 shares issued and 81,028,898 shares outstanding at December 31, 2016.

In 2017, our Board of Directors declared quarterly cash dividends as follows:



Dividends per Common Share		Declaration Date	Record Date	Payable Date
$	0.0625	February 16, 2017	March 15, 2017	April 5, 2017
$	0.0625	May 4, 2017	June 15, 2017	July 6, 2017
$	0.0625	July 21, 2017	September 15, 2017	October 3, 2017
$	0.0625	November 2, 2017	December 15, 2017	January 5, 2018

All dividends were paid as scheduled.

Any determination to pay dividends and other distributions in cash, stock, or property by Holdings in the future will be at the discretion of our Board of Directors and will be dependent on then-existing conditions, including our business and financial condition, results of operations, liquidity, capital requirements, contractual restrictions, including restrictive covenants contained in our debt agreements, and other factors. Additionally, because we are a holding company, our ability to pay dividends on our common stock may be limited by restrictions on the ability of our subsidiaries to pay dividends or make distributions to us, including restrictions under the terms of the agreements governing our indebtedness.

Preferred Stock

Our Amended and Restated Certificate of Incorporation authorizes our Board of Directors to issue up to 10,000,000 shares, in the aggregate, of preferred stock, par value of $0.01 in one or more series, to fix the powers, preferences and other rights of such series, and any qualifications, limitations or restrictions thereof, including the dividend rate, conversion rights, voting rights, redemption rights and liquidation preference, and to fix the number of shares to be included in any such series, without any further vote or action by our stockholders.

There were no shares of preferred stock issued or outstanding at December 31, 2017 and 2016. At present, we have no plans to issue any preferred stock.

Share Repurchase Program

We are authorized by our Board of Directors to repurchase shares of our outstanding common stock from time to time on the open market or in privately negotiated transactions. As of December 31, 2017, we are authorized to repurchase up to $100.0 million of our common stock through December 11, 2018. Stock repurchases, if any, will be funded using our available liquidity. The timing and amount of stock repurchases will depend on a variety of factors, including the market conditions as well as corporate and regulatory considerations. As of December 31, 2017, we have repurchased 727,081 shares of our common stock at an average price of $34.41 under this program and are authorized to repurchase up to an additional $75.0 million of our common stock.

Our Board of Directors previously had authorized the repurchase of up to $50.0 million of our common stock. This program expired on December 11, 2017. We repurchased a total of 706,093 shares of our common stock at an average price of $23.83 under this program.

Accumulated Other Comprehensive Income (Loss)

Accumulated other comprehensive income (loss) consists of fair value adjustments associated with cash flow hedges, accumulated adjustments for net experience losses and prior service cost related to employee benefit plans and foreign currency translation adjustments primarily related to accounts payable denominated in Euros. The following table presents the changes in accumulated other comprehensive income (loss) by component (in thousands) during the year ended December 31, 2017:



	For the Year Ended December 31, 2017
	Unrealized gain/(loss) on cash flow hedges			Foreign currency translation adjustment			Pension and other post- retirement benefits liability			Total
Beginning Balance	$	(32	)	$	—		$	(15,844	)	$	(15,876	)
Other comprehensive gain (loss) before reclassifications	(45		)	(6		)	871			820
Amounts reclassed from accumulated other comprehensive income	1			—			1,129			1,130
Ending Balance	$	(76	)	$	(6	)	$	(13,844	)	$	(13,926	)

Amounts reclassified from accumulated other comprehensive income (loss) related to cash flow hedges are included in interest expense in our Income Statements and amounts reclassified related to pension and other post-retirement benefits are included in the computation of net periodic pension costs, at their pre-tax amounts.

- Definition

The entire disclosure for shareholders' equity comprised of portions attributable to the parent entity and noncontrolling interest, including other comprehensive income. Includes, but is not limited to, balances of common stock, preferred stock, additional paid-in capital, other capital and retained earnings, accumulated balance for each classification of other comprehensive income and amount of comprehensive income.

+ References

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+ Details

Business Combinations

12 Months Ended

Dec. 31, 2017

Business Combinations [Abstract]

Business Combinations

NOTE D—BUSINESS COMBINATIONS

Goodwill

Goodwill represents the excess of the purchase price over the fair value of the underlying net assets acquired.

Trade Names

A trade name is a legally protected trade or similar mark. Acquired trade names are valued using an income method approach, generally the relief-from-royalty valuation method. The method uses a royalty rate based on comparable marketplace royalty agreements for similar types of trade names, and applies it to the after-tax discounted free cash flow attributed to the trade name. The discount rate used is based on an estimated weighted average cost of capital and the anticipated risk for intangible assets.

The valued trade name has an indefinite life based on our plans and expectations for the trade name going forward, and is reviewed for impairment under ASC 360-10.

Intellectual Property and Technology

Intellectual property and technology (“IP”) is a design, work or invention that is the result of creativity to which one has ownership rights that may be protected through a patent, copyright, trademark or service mark. IP is valued using the relief from royalty valuation method. The method uses a royalty rate based on comparable market-place royalty agreements for similar types of IP, and applies it to the after-tax discounted free cash flow attributed to the IP. The discount rate used is based on an estimated weighted average cost of capital and the anticipated risk for intangible assets.

The IP is amortized following the pattern in which the expected benefits will be consumed or otherwise used up over each component’s useful life, based on our plans and expectations for the IP going forward, which is generally the underlying IP’s legal expiration dates. IP is reviewed for impairment under ASC 360-10.

Customer Relationships

Customer relationships are intangible assets that consist of historical and factual information about customers and contacts collected from repeat transactions with customers, with or without any underlying contracts. The information is generally organized as customer lists or customer databases. We have the expectation of repeat patronage from these customers based on the customers’ historical purchase activity, which creates the intrinsic value over a finite period of time and translates into the expectation of future revenue, income, and cash flow.

Customer relationships are valued using projected operating income, adjusted for estimated future existing customer growth less estimated future customer attrition, net of charges for net tangible assets, IP charge, trade name charge and work force. The concluded value is the after-tax discounted free cash flow. Customer relationships are reviewed for impairment under ASC 360-10.

The tax rate applied for each class of intangible assets is pursuant to current tax legislation (15-year period for intangible assets).

2017 Acquisitions

White Armor Acquisition:

On April 1, 2017, we completed the acquisition of White Armor, a product line of cool roof granules used in industrial roofing applications, for cash consideration of $18.6 million. The preliminary purchase price was allocated to goodwill of approximately $3.9 million, identifiable intangible assets of $12.8 million and other net assets of approximately $1.9 million.

Goodwill in this transaction is attributable to planned growth in our specialty industrial sand segment. The goodwill amount is included in our Industrial & Specialty Products segment. Identifiable definite lived intangibles, including customer relationships, and goodwill are expected to be deductible for tax purposes.

We incurred $0.2 million of acquisition-related charges which are included in selling, general and administrative expenses during the year ended December 31, 2017. Revenue and earnings for White Armor after the acquisition date are not presented as the business was integrated into our operations subsequent to the acquisition and therefore impracticable to quantify.

MS Sand Acquisition:

On August 16, 2017, we completed the acquisition of Mississippi Sand, LLC ("MS Sand"), a Missouri limited liability company, for cash consideration of approximately $95.4 million, net of cash acquired of $2.2 million. As is normal and customary, subsequent adjustments were made including $(0.5) million to the net working capital adjustment plus an additional $6.1 million consideration paid related to a pre-existing contracted asset sale, which was entered into prior to our acquisition, for total cash consideration of $101.0 million. MS Sand is a frac sand mining and logistics company based in St. Louis, Missouri. The acquisition of MS Sand increased our regional frac sand product offering in our Oil & Gas Proppants segment.

We have accounted for the acquisition of MS Sand under the acquisition method of accounting in accordance with ASC 805, Business Combinations, and have accounted for measurement period adjustments in accordance with ASU 2015-16, Simplifying the Accounting for Measurement-Period Adjustments. Estimates of fair value included in the consolidated financial statements represent our best estimates and valuations. In accordance with the acquisition method of accounting, the allocation of consideration value is subject to adjustment until we complete our analysis, in a period of time, but not to exceed one year after the date of acquisition, or August 16, 2018, in order to provide us with the time to complete the valuation of its assets and liabilities.

The following table sets forth the current allocation of the purchase price to MS Sands' identifiable tangible and intangible assets acquired and liabilities assumed, including measurement period adjustments (in thousands):



	Initial Estimate		Measurement Period Adjustments			Purchase Price Allocation
Accounts receivable	$	11,201	$	—		$	11,201
Inventories	6,087		1,980			8,067
Other current assets	362		—			362
Assets held for sale	9,523		(70		)	9,453
Property, plant and mine development	26,440		1,018			27,458
Mineral rights	—		26,300			26,300
Other non-current assets	1,136		—			1,136
Goodwill	52,187		(29,665		)	22,522
Customer relationships	—		1,840			1,840
Total assets acquired	106,936		1,403			108,339
Accounts payable and accrued expenses	3,815		(54		)	3,761
Unfavorable leasehold positions	—		2,237			2,237
Notes Payable	866		—			866
Other long term liabilities	1,254		(1,254		)	—
Asset retirement obligations	—		474			474
Total liabilities assumed	5,935		1,403			7,338
Net assets acquired	$	101,001	$	—		$	101,001

The acquired intangible assets and the related estimated useful lives consist of the following:



	Approximate Fair Value		Estimated Useful Life
	(in thousands)		(in years)
Customer relationships	$	1,840	15

Goodwill in this transaction is attributable to planned growth in our regional frac sand product offering in our Oil & Gas Proppants segment. The goodwill amount is included in our Oil & Gas Proppants segment. Identifiable definite lived intangibles, including customer relationships, and goodwill are expected to be deductible for tax purposes.

We incurred $0.7 million of acquisition-related charges which are included in selling, general and administrative expenses during the year ended December 31, 2017. Revenue and earnings for MS Sand after the acquisition date are not presented as the business was integrated into our operations subsequent to the acquisition and therefore impracticable to quantify.

Both acquisitions were accounted for using the acquisition method of accounting. The purchase price and purchase price allocation for both White Armor and MS Sand acquisitions are preliminary and subject to customary post-closing adjustments and changes in the fair value of assets and liabilities. The above estimated fair values of net assets acquired are based on the information that was available as of the reporting date. We believe that the information provides a reasonable basis for estimating the fair values of the acquired assets and assumed liabilities, but the potential for measurement period adjustments exists based on our continuing review of matters related to the acquisitions. As a result, our final purchase price allocations may be significantly different than those reflected above. We expect to complete the purchase price allocations as soon as practicable, but no later than one year from the acquisition dates.

Unaudited Pro Forma Results

The results of MS Sand’s operations have been included in the consolidated financial statements subsequent to the acquisition dates. The following unaudited pro forma consolidated financial information reflects the results of operations as if the MS Sand Acquisition had occurred on January 1, 2016, after giving effect to certain purchase accounting adjustments. These adjustments mainly include incremental depreciation expense related to the fair value adjustment of property, plant, equipment and mine development, amortization expense related to identifiable intangible assets and tax expense related to the combined tax provisions. This information does not purport to be indicative of the actual results that would have occurred if the acquisition had actually been completed on the date indicated, nor is it necessarily indicative of the future operating results or the financial position of the combined company (in thousands, except per share amounts):



	For the year ended December 31,
	2017		2016
Sales	$	1,287,202	$	642,951
Net income (loss)	$	143,604	$	(55,835	)
Basic earnings (loss) per share	$	1.77	$	(0.86	)
Diluted earnings (loss) per share	$	1.75	$	(0.86	)

2016 Acquisitions

NBI Acquisition:

On August 16, 2016, we completed the acquisition of New Birmingham, Inc. (“NBI”), the ultimate parent company of NBR Sand, LLC (“NBR”), by acquiring all of the outstanding capital stock of NBI through the merger of New Birmingham Merger Corp., a Nevada corporation and wholly owned subsidiary of the Company, with and into NBI, followed immediately by the merger of NBI with and into NBI Merger Subsidiary II, Inc., a Delaware corporation and wholly owned subsidiary of the Company, which subsequently changed its name to Tyler Silica Company (the “NBI Acquisition”). NBR is a regional sand producer located near Tyler, Texas. The acquisition of NBI increased our regional frac sand product offering in our Oil & Gas Proppants segment.

The consideration paid to the stockholders of NBI at the closing of the NBI Acquisition consisted of $107.2 million in cash (net of $9.0 million cash acquired) and 2,630,513 shares of common stock valued at $106.6 million.

The calculation of the purchase price (in thousands, except shares) is as follows:




Cash consideration paid			$	116,165
Number of Holdings common shares delivered	2,630,513
Multiplied by closing market price per share of U.S. Silica common stock on August 16, 2016	$	40.51
Total value of Holdings common shares delivered			$	106,562
Less, cash acquired			$	(9,002	)
Total purchase price			$	213,725

We have accounted for the acquisition of NBI under the acquisition method of accounting in accordance with ASC 805, Business Combinations, and have accounted for measurement period adjustments in accordance with ASU 2015-16, Simplifying the Accounting for Measurement-Period Adjustments. Estimates of fair value included in the consolidated financial statements represent our best estimates and valuations. In accordance with the acquisition method of accounting, the allocation of consideration value was subject to adjustment until we completed our analysis, in a period of time, but not to exceed one year after the date of acquisition, or August 16, 2016, in order to provide us with the time to complete the valuation of its assets and liabilities. We have completed our analysis and allocation of consideration value to assets acquired and liabilities assumed.

The following table sets forth the final allocation of the purchase price to NBI’s identifiable tangible and intangible assets acquired and liabilities assumed, including measurement period adjustments (in thousands):



	Initial Estimate		Measurement Period Adjustments			Purchase Price Allocation
Accounts receivable	$	2,680	$	—		$	2,680
Inventories	3,494		—			3,494
Other current assets	428		—			428
Income tax deposits	6,657		(217		)	6,440
Property, plant and mine development	210,913		(4,281		)	206,632
Identifiable intangible assets	1,600		—			1,600
Goodwill	86,228		4,670			90,898
Total assets acquired	312,000		172			312,172
Accounts payable, accrued expenses and other current liabilities	1,938		726			2,664
Deferred revenue	500		—			500
Notes payable	24,361		243			24,604
Capital lease liabilities	3,331		—			3,331
Asset retirement obligations	710		—			710
Deferred tax liabilities	67,435		(797		)	66,638
Total liabilities assumed	98,275		172			98,447
Net assets acquired	$	213,725	$	—		$	213,725

In addition to the changes in the balances reflected above, we recorded an adjustment to depreciation expense of $(0.6) million during the year ended December 31, 2017.

The acquired intangible assets and the related estimated useful lives consist of the following:



	Approximate Fair Value		Estimated Useful Life
	(in thousands)		(in years)
Customer relationships	$	1,600	13

Goodwill in this transaction is attributable to planned growth in regional frac sand markets and synergies expected to be achieved from integrating the operations of our operating subsidiary, U.S. Silica Company (“U.S. Silica”), and NBI. The goodwill amount is included in our Oil & Gas Proppants segment. Both customer relationships and goodwill are not expected to be deductible for tax purposes.

We incurred $1.4 million of acquisition-related charges which are included in selling, general and administrative expenses during the year ended December 31, 2016. Additionally, we incurred $1.7 million related to the inventory write-up values in cost of goods sold during the year ended December 31, 2016.

Revenue and earnings for NBR after the acquisition date are not presented as the business was integrated into our operations subsequent to the acquisition and therefore impracticable to quantify.

Sandbox Acquisition:

On August 22, 2016, we completed the purchase of all of the outstanding units of membership interest of Sandbox Enterprises, LLC, a Texas limited liability company ("Sandbox" or the “Sandbox Acquisition”). Sandbox earns revenues from providing “last mile” transportation services to companies in the oil and gas industry. Sandbox has operations in Texas (Midland/Odessa, Kenedy, Dallas/Fort Worth, Tyler); Morgantown, West Virginia; western North Dakota; northeast of Denver, Colorado; Oklahoma City, Oklahoma; Cambridge, Ohio and Mansfield, Pennsylvania, where its major customers are located.

The consideration paid to the unit-holders consisted of $69.5 million in cash (net of $1.3 million cash acquired) and 4,195,180 shares of our common stock valued at $171.7 million. The calculation of the purchase price (in thousands, except shares) is as follows:




Cash consideration paid			$	70,760
Number of Holdings common shares delivered	4,195,180
Multiplied by closing market price per share of U.S. Silica common stock on August 22, 2016	$	40.92
Total value of Holdings common shares delivered			$	171,667
Less, cash acquired			$	(1,306	)
Total purchase price			$	241,121

The following table sets forth the allocation of the purchase price to Sandbox’s identifiable tangible and intangible assets acquired and liabilities assumed (in thousands):



Allocation of Purchase price:	(in thousands)
Accounts receivable	$	13,392
Prepaid expenses and other	1,465
Property, plant and mine development	32,336
Identifiable intangible assets	120,144
Goodwill	86,100
Total assets acquired	253,437
Accounts payable	4,122
Deferred revenue	4,902
Accrued expenses and other current liabilities	3,292
Total liabilities assumed	12,316
Net assets acquired	$	241,121

The acquired intangible assets and the related estimated useful lives consist of the following:



	Approximate Fair Value		Estimated Useful Life
	(in thousands)		(in years)
Indefinite lived intangible assets - Trade names	$	17,844	Indefinite
Definite lived intangible assets - Technology and intellectual property	57,700		15
Definite lived intangible asset - Customer relationships	44,600		13
Total fair value of identifiable intangible assets	$	120,144

Goodwill in this transaction is attributable to expected growth in frac sand demand at the wellhead and synergies expected to be achieved from integrating the operations of U.S. Silica and Sandbox. The goodwill amount is included in our Oil & Gas Proppants segment. Goodwill and all intangible assets identified above are expected to be deductible for tax purposes.

Our 2016 Income Statement included revenue of $31.0 million associated with Sandbox following the date of acquisition. Sandbox's impact on our net loss was not significant for the year ended December 31, 2016. We incurred $3.0 million of acquisition-related charges which are included in selling, general and administrative expenses on the Income Statement for the year ended December 31, 2016.

The cost related to the issuance of the 6,825,693 shares of common stock to complete the two acquisitions totaled $0.3 million, which is included in additional paid-in capital on our Consolidated Statements of Stockholders' Equity for the year ended December 31, 2016.

Combined Unaudited Pro Forma Results

The results of NBI's and Sandbox’s operations have been included in the consolidated financial statements subsequent to the acquisition dates. The following unaudited pro forma consolidated financial information reflects the results of operations as if the NBI Acquisition and Sandbox Acquisition had occurred on January 1, 2015, after giving effect to certain purchase accounting adjustments. These adjustments mainly include incremental depreciation expense related to the fair value adjustment of property, plant, equipment and mine development, amortization expense related to identifiable intangible assets and tax expense related to the combined tax provisions. This information does not purport to be indicative of the actual results that would have occurred if the acquisition had actually been completed on the date indicated, nor is it necessarily indicative of the future operating results or the financial position of the combined company (in thousands, except per share amounts):



	For the year ended December 31,
	2016			2015
Sales	$	615,552		$	753,287
Net income (loss)	$	(45,161	)	$	43,163
Basic earnings per share	$	(0.69	)	$	0.81
Diluted earnings per share	$	(0.69	)	$	0.81

- Definition

The entire disclosure for a business combination (or series of individually immaterial business combinations) completed during the period, including background, timing, and recognized assets and liabilities. The disclosure may include leverage buyout transactions (as applicable).

+ References

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Reference 3: http://www.xbrl.org/2003/role/presentationRef
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+ Details

Accounts Receivable

12 Months Ended

Dec. 31, 2017

Receivables [Abstract]

Accounts Receivable

NOTE E—ACCOUNTS RECEIVABLE

At December 31, 2017 and 2016, accounts receivable (in thousands) consisted of the following:



	At December 31,
	2017			2016
Trade receivables	$	217,649		$	93,982
Less: Allowance for doubtful accounts	(7,100		)	(7,042		)
Net trade receivables	210,549			86,940
Other receivables	2,037			2,066
Total accounts receivable	$	212,586		$	89,006

Changes in our allowance for doubtful accounts (in thousands) during the years ended December 31, 2017 and 2016 are as follows:



	Allowance for Doubtful Accounts
	2017			2016
Balance at January 1,	$	7,042		$	7,686
Bad debt provision	1,529			(1,232		)
Write-offs and recoveries, net	(1,471		)	588
Balance at December 31,	$	7,100		$	7,042

Our ten largest customers accounted for approximately 58%, 52%, and 56% of sales during the years ended December 31, 2017, 2016 and 2015, respectively. Sales to two of our customers accounted for 15% and 12% of our total sales during the year ended December 31, 2017. Sales to one of our customers accounted for 13% of our total sales during the year ended December 31, 2016. Sales to two of our customers accounted for 13% and 12% of our total sales during the year ended December 31, 2015. No other customers accounted for 10% or more of our total sales. At December 31, 2017, two of our customers' accounts receivable represented 19% and 11% of our total accounts receivable, net of allowance. At December 31, 2016, two of our customers' accounts receivable represented 14% and 10% of our total accounts receivable, net of allowance. No other customers accounted for 10% or more of our total accounts receivable.

- Definition

The entire disclosure for claims held for amounts due a entity, excluding financing receivables. Examples include, but are not limited to, trade accounts receivables, notes receivables, loans receivables. Includes disclosure for allowance for credit losses.

+ References + Details

Property, Plant and Mine Development

12 Months Ended

Dec. 31, 2017

Property, Plant and Equipment [Abstract]

Property, Plant and Mine Development

NOTE G—PROPERTY, PLANT AND MINE DEVELOPMENT

At December 31, 2017 and 2016, property, plant and mine development (in thousands) consisted of the following:



	At December 31,
	2017			2016
Mining property and mine development	$	586,242		$	414,434
Asset retirement cost	14,184			8,062
Land	36,552			35,052
Land improvements	45,878			42,738
Buildings	56,330			52,178
Machinery and equipment	590,566			450,881
Furniture and fixtures	2,953			2,566
Construction-in-progress	189,970			43,790
	1,522,675			1,049,701
Accumulated depletion, depreciation and amortization	(353,520		)	(266,388		)
Total property, plant and mine development, net	$	1,169,155		$	783,313

At December 31, 2017 and 2016, the aggregate cost of the machinery and equipment originally acquired under capital leases was $0.9 million and $4.7 million, respectively, reduced by accumulated depreciation of $0.2 million and $0.3 million, respectively. The decrease in machinery and equipment acquired under capital leases is due to lease terminations.

The amount of interest costs capitalized in property, plant and mine development was $1.6 million, $0.2 million and $0.5 million for the years ended December 31, 2017, 2016 and 2015, respectively.

Goodwill and Intangible Assets

12 Months Ended

Dec. 31, 2017

Goodwill and Intangible Assets Disclosure [Abstract]

Goodwill and Intangible Assets

NOTE H—GOODWILL AND INTANGIBLE ASSETS

Goodwill

The changes in the carrying amount of goodwill (in thousands) consisted of the following:



	Goodwill
Balance at December 31, 2015	$	68,647
NBI acquisition	86,228
Sandbox acquisition	86,100
Balance at December 31, 2016	240,975
White Armor acquisition	3,912
NBI acquisition measurement period adjustment	4,670
MS Sand acquisition	52,187
MS Sand acquisition measurement period adjustment	(29,665		)
Balance at December 31, 2017	$	272,079

Goodwill represents the excess of purchase price over the fair value of net assets acquired from business acquisitions. Goodwill and trade names are reviewed for impairment annually as of October 31 or more frequently whenever events or circumstances change that would more likely than not reduce the fair value of those assets. We completed our annual impairment test by performing a qualitative assessment of goodwill. In performing this qualitative assessment, we evaluated events and circumstances since the date of the last quantitative impairment test, including the results of that test, macroeconomic conditions, industry and market conditions, and our overall financial performance. After assessing the totality of the events and circumstances, we determined that it was not more likely than not that the fair value of our reporting units was less than their carrying amount and, therefore, the first and second steps of the quantitative goodwill impairment test were deemed unnecessary. Further, no triggering events have subsequently transpired that would indicate a potential impairment as of December 31, 2017. Goodwill of $247.5 million has been allocated to the Oil & Gas Proppants business segment and $24.6 million to the Industrial & Specialty Products business segment at December 31, 2017. Goodwill of $220.3 million has been allocated to the Oil & Gas Proppants business segment and $20.7 million to the Industrial & Specialty Products business segment at December 31, 2016.

Intangible Assets

The changes in the carrying amount of intangible assets (in thousands) consisted of the following:



		December 31, 2017							December 31, 2016
	Estimated Useful Life	Gross Carrying Amount		Accumulated Amortization			Net		Gross Carrying Amount		Accumulated Amortization			Net
	(in years)
Technology and intellectual property	15	$	70,703	$	(5,917	)	$	64,786	$	58,658	$	(1,388	)	$	57,270
Customer relationships	13 - 15	61,229		(9,076		)	52,153		55,689		(4,799		)	50,890
Total definite-lived intangible assets:		$	131,932	$	(14,993	)	$	116,939	$	114,347	$	(6,187	)	$	108,160
Trade name		33,068		—			33,068		32,318		—			32,318
Total intangible assets:		$	165,000	$	(14,993	)	$	150,007	$	146,665	$	(6,187	)	$	140,478

Amortization expense was $8.8 million, $3.2 million and $0.5 million for the years ended December 31, 2017, 2016 and 2015.

The estimated amortization expense related to definite-lived intangible assets (in thousands) for the five succeeding years is as follows:



2018	$	9,239
2019	9,239
2020	9,239
2021	9,239
2022	9,224

- Definition

The entire disclosure for the aggregate amount of goodwill and a description of intangible assets, which may include (a) for amortizable intangible assets (also referred to as finite-lived intangible assets), the carrying amount, the amount of any significant residual value, and the weighted-average amortization period, (b) for intangible assets not subject to amortization (also referred to as indefinite-lived intangible assets), the carrying amount, and (c) the amount of research and development assets acquired and written off in the period, including the line item in the income statement in which the amounts written off are aggregated, if not readily apparent from the income statement. Also discloses (a) for amortizable intangibles assets in total and by major class, the gross carrying amount and accumulated amortization, the total amortization expense for the period, and the estimated aggregate amortization expense for each of the five succeeding fiscal years, (b) for intangible assets not subject to amortization the carrying amount in total and by major class, and (c) for goodwill, in total and for each reportable segment, the changes in the carrying amount of goodwill during the period (including the aggregate amount of goodwill acquired, the aggregate amount of impairment losses recognized, and the amount of goodwill included in the gain (loss) on disposal of a reporting unit). If any part of goodwill has not been allocated to a reportable segment, discloses the unallocated amount and the reasons for not allocating. For each impairment loss recognized related to an intangible asset (excluding goodwill), discloses: (a) a description of the impaired intangible asset and the facts and circumstances leading to the impairment, (b) the amount of the impairment loss and the method for determining fair value, (c) the caption in the income statement or the statement of activities in which the impairment loss is aggregated, and (d) the segment in which the impaired intangible asset is reported. For each goodwill impairment loss recognized, discloses: (a) a description of the facts and circumstances leading to the impairment, (b) the amount of the impairment loss and the method of determining the fair value of the associated reporting unit, and (c) if a recognized impairment loss is an estimate not finalized and the reasons why the estimate is not final. May also disclose the nature and amount of any significant adjustments made to a previous estimate of an impairment loss.

+ References + Details

Debt and Capital Leases

12 Months Ended

Dec. 31, 2017

Debt Disclosure [Abstract]

Debt and Capital Leases

NOTE J—DEBT AND CAPITAL LEASES

At December 31, 2017 and 2016, debt (in thousands) consisted of the following:



	December 31, 2017			December 31, 2016
Senior secured credit facility:
Revolver expiring July 23, 2018 (5.75% at December 31, 2017 and 5.25% at December 31, 2016)	$	—		$	—
Term loan facility—final maturity July 23, 2020 (4.75%-5.25% at December 31, 2017 and 4.00% - 4.50% at December 31, 2016)	489,075			494,175
Less: Unamortized original issue discount	(944		)	(1,318		)
Less: Unamortized debt issuance cost	(3,099		)	(4,482		)
Note payable secured by royalty interest	24,740			23,076
Customer note payable	745			1,787
Equipment notes payable	719			—
Total debt	511,236			513,238
Less: current portion	(4,504		)	(4,821		)
Total long-term portion of debt	$	506,732		$	508,417

Revolving Line-of-Credit

We have a $50 million revolving line-of-credit (the "Revolver"), with zero drawn and $4.5 million allocated for letters of credit as of December 31, 2017, leaving $45.5 million available under the Revolver.

Senior Secured Credit Facility

At December 31, 2017, contractual maturities of our senior secured credit facility (in thousands) are as follows:



2018	$	5,100
2019	5,100
2020	478,875
Total	$	489,075

On July 23, 2013, we refinanced our then existing senior secured debt by amending our Term Loan and replacing our then existing revolving line-of-credit. The Term Loan amendment refinanced our then existing senior debt by entering into a new $425 million senior secured credit facility, consisting of a $375 million Term Loan and the $50 million Revolver that may also be used for swingline loans (up to $5 million) or letters of credit (up to $20 million). The Term Loan amendment also, among other things, removed and amended certain financial and other covenants to provide additional operating flexibility, and lowered interest rates on borrowed amounts. The Term Loan will expire on July 23, 2020 and the Revolver will expire on July 23, 2018. On December 5, 2014, we further increased our Term Loan by an additional $135 million to a total of approximately $502 million in accordance with the incremental borrowing feature in our senior secured credit facility.

Our senior secured credit facility is secured by a pledge of substantially all of our assets, including accounts receivable, inventory, property, plant and mine development, and a pledge of the equity interests in certain of our subsidiaries. The facility contains covenants that, among other things, govern our ability to create, incur or assume indebtedness and liens, to make acquisitions or investments, to sell assets and to pay dividends. This includes a restriction on the ability of our operating subsidiaries to make distributions to us to the extent that the incurrence ratio (as defined in the senior secured credit facility) after giving effect to the distribution is 3:1 or greater. The facility also requires us to maintain a consolidated total net leverage ratio of no more than 3.75:1.00 as of the last day of any fiscal quarter whenever usage of the Revolver (other than certain undrawn letters of credit) exceeds 25% of the Revolver commitment. As of December 31, 2017 and December 31, 2016, we are in compliance with all covenants in accordance with our senior secured credit facility.

Note Payable Secured by Royalty Interest

In connection with the acquisition of NBI in August 2016, we assumed a note payable secured by a royalty interest. The monthly royalty payment is calculated based on future tonnages and sales related to the sand shipped from our Tyler, Texas facility. The note payable is due by June 30, 2032. The note does not provide a stated interest rate. The minimum payments (in thousands) for the next five years required by the note are as follows:



2018	$	1,750
2019	1,750
2020	1,750
2021	1,750
2022	1,750
Thereafter	15,990
Total	$	24,740

Under this agreement, once a certain number of tons have been shipped from the Tyler facility, the minimum payments will decrease to $0.5 million per year, subject to proration in the period this threshold is met.

The note payable fair value was estimated to be $22.5 million on the acquisition date. The estimate was made using a discounted cash flow model, which calculated the present value of projected future cash payments required under the agreement using a discount rate of 14%. As of December 31, 2017, the note payable had a balance of $24.7 million. The increase in this note payable amount is due to interest paid-in-kind. The effective interest rate based on the updated projected future cash payments is 24% at December 31, 2017.

Customer Note Payable

In connection with the acquisition of NBI in August 2016, we assumed a customer note payable that was entered into by NBI. NBI entered into an amendment effective January 1, 2016. Terms of the amended agreement call for repayment of $2.5 million at 0% interest, in equal monthly payments beginning January 1, 2016 for 60 months, or $0.5 million per year. Additionally, the principal of this customer note payable can be reduced via future product load credit. We discounted the required future cash payments and projected product load credit using an effective interest rate of 3.5% and recorded the customer note payable at $1.9 million on the acquisition date. At December 31, 2017, the customer note payable had a balance of $0.7 million.

Equipment Notes Payable

In connection with the acquisition of MS Sand in August 2017, we assumed notes payable, which are secured by equipment and bear interest rates between 0% to 5.2%. Maturities (in thousands) for the next five years required by the notes are as follows:



2018	$	316
2019	286
2020	117
Total	$	719

Capital Leases

We enter into financing arrangements from time to time to purchase machinery and equipment utilized in operations. At December 31, 2017, scheduled future minimum lease payments under capital lease obligations (in thousands) are as follows:



2018	721
Total minimum lease payments	721
Less: amount representing interest	(15		)
Present value of minimum lease payments	706
Less: current portion of capital lease obligations	(706		)
Non-current portion of capital lease obligations	$	—

Deferred Revenue	12 Months Ended
Deferred Revenue	Dec. 31, 2017
Deferred Revenue Disclosure [Abstract]
Deferred Revenue	NOTE K—DEFERRED REVENUE We enter into certain customer supply agreements which give the customers the right to purchase certain products for a discounted price at certain volumes over an average initial contract term of one to five years. The advance payments represent future purchases and are recorded as deferred revenue, recognized as revenue over the contract term of each supply agreement. During the year ended December 31, 2017 we received advances of $50.5 million. At December 31, 2017 and 2016, the total deferred revenue balance was $118.4 million and $71.8 million, respectively, of which $36.1 million and $13.7 million was classified as current in our Balance Sheets.

- Definition

The entire disclosure for deferred revenues at the end of the reporting period, and description and amounts of significant changes that occurred during the reporting period. Deferred revenue is a liability as of the balance sheet date related to a revenue producing activity for which revenue has not yet been recognized. Generally, an entity records deferred revenue when it receives consideration from a customer before achieving certain criteria that must be met for revenue to be recognized in conformity with GAAP.

+ References + Details

Fair Value Accounting

12 Months Ended

Dec. 31, 2017

Fair Value Disclosures [Abstract]

Fair Value Accounting

NOTE L—FAIR VALUE ACCOUNTING

Fair value is defined as the exchange price that would be received for an asset or paid to transfer a liability (an exit price) in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants on the measurement date. Fair value is estimated by applying the following hierarchy, which prioritizes the inputs used to measure fair value into three levels and bases the categorization within the hierarchy upon the lowest level of input that is available and significant to the fair value measurement:

Level 1—Quoted prices in active markets for identical assets or liabilities

Level 2—Observable inputs other than quoted prices in active markets for identical assets and liabilities, quoted prices for identical or similar assets or liabilities in inactive markets, or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the assets or liabilities.

Level 3—Inputs that are generally unobservable and typically reflect management’s estimate of assumptions that market participants would use in pricing the asset or liability.

Cash Equivalents

Due to the short-term maturity, we believe our cash equivalent instruments at December 31, 2017 and 2016 approximate their reported carrying values.

Long-Term Debt, Including Current Maturities

We believe that the fair values of our long-term debt, including current maturities, approximates their carrying values based on their effective interest rates compared to current market rates.

Derivative Instruments

The estimated fair value of our derivative instruments (interest rate caps) are recorded at each reporting period and are based upon widely accepted valuation techniques, including discounted cash flow analysis on the expected cash flows of each derivative contract. This analysis reflects the contractual terms of the derivatives, including the period to maturity, and uses observable market-based inputs, including interest rate curves and implied volatilities. We also incorporate credit valuation adjustments to appropriately reflect both our nonperformance risk as well as that of the respective counterparty in the fair value measurements. Additional disclosures for derivative instruments are presented in Note M - Derivative Instruments to these financial statements.

Although we have determined that the majority of the inputs used to value our derivatives fall with Level 2 of the fair value hierarchy, the credit valuation adjustments associated with our derivatives utilize Level 3 inputs, such as estimates of current credit spreads to evaluate the likelihood of default of ourselves and our counterparties. However, as of December 31, 2017, we have assessed that the impact of the credit valuation adjustments on the overall valuation of our derivative positions is not significant. As a result, we have determined that our derivative valuations in their entirety are classified in Level 2 of the fair value hierarchy.

In accordance with the fair value hierarchy, the following table presents the fair value as of December 31, 2017 and 2016, respectively, of those instruments (in thousands) that we measure at fair value on a recurring basis:



	December 31, 2017						December 31, 2016
	Level 1		Level 2		Total		Level 1		Level 2		Total
Interest rate derivatives	—		—		—		—		72		72
Net asset	$	—	$	—	$	—	$	—	$	72	$	72

- Definition

The entire disclosure for the fair value of financial instruments (as defined), including financial assets and financial liabilities (collectively, as defined), and the measurements of those instruments as well as disclosures related to the fair value of non-financial assets and liabilities. Such disclosures about the financial instruments, assets, and liabilities would include: (1) the fair value of the required items together with their carrying amounts (as appropriate); (2) for items for which it is not practicable to estimate fair value, disclosure would include: (a) information pertinent to estimating fair value (including, carrying amount, effective interest rate, and maturity, and (b) the reasons why it is not practicable to estimate fair value; (3) significant concentrations of credit risk including: (a) information about the activity, region, or economic characteristics identifying a concentration, (b) the maximum amount of loss the entity is exposed to based on the gross fair value of the related item, (c) policy for requiring collateral or other security and information as to accessing such collateral or security, and (d) the nature and brief description of such collateral or security; (4) quantitative information about market risks and how such risks are managed; (5) for items measured on both a recurring and nonrecurring basis information regarding the inputs used to develop the fair value measurement; and (6) for items presented in the financial statement for which fair value measurement is elected: (a) information necessary to understand the reasons for the election, (b) discussion of the effect of fair value changes on earnings, (c) a description of [similar groups] items for which the election is made and the relation thereof to the balance sheet, the aggregate carrying value of items included in the balance sheet that are not eligible for the election; (7) all other required (as defined) and desired information.

+ References + Details

Derivative Instruments

12 Months Ended

Dec. 31, 2017

Derivative Instruments and Hedging Activities Disclosure [Abstract]

Derivative Instruments

NOTE M—DERIVATIVE INSTRUMENTS

Cash Flow Hedges of Interest Rate Risk

We enter into interest rate cap agreements in connection with the Term Loan to add stability to interest expense and to manage our exposure to interest rate movements. Interest rate caps designated as cash flow hedges involve the receipt of variable-rate amounts from a counterparty if interest rates rise above the strike rate on the contract in exchange for an upfront premium.

The following table summarizes the fair value of our derivative instruments (in thousands, except contract/notional amount). See Note L - Fair Value Accounting for additional disclosures regarding the estimated fair values of our derivative instruments at December 31, 2017, and 2016.



		December 31, 2017								December 31, 2016
	Maturity Date	Contract/Notional Amount			Carrying Amount		Fair Value		Maturity Date	Contract/Notional Amount			Carrying Amount		Fair Value
Interest rate cap agreement⁽¹⁾	2019	$	249	million	$	—	$	—	2019	$	249	million	$	72	$	72

⁽¹⁾Agreements limit the LIBOR floating interest rate base to 4%.

We have designated these contracts as qualified cash flow hedges. Accordingly, the effective portion of the gain or loss on the derivative instrument is reported as a component of other comprehensive income and recognized in earnings in the same period or periods during which the hedged transaction affects earnings. During the years ended December 31, 2017 and 2016, we had no ineffectiveness for such contracts.

The following table summarizes the effect of derivatives instruments (in thousands) on our income statements and our consolidated statements of comprehensive income for the years ended December 31, 2017, 2016 and 2015.



	2017			2016			2015
Deferred losses from derivatives in OCI, beginning of period	$	(32	)	$	(81	)	$	(134	)
Loss recognized in OCI from derivative instruments	(45		)	(32		)	—
Gain reclassified from Accumulated OCI	1			81			53
Deferred losses from derivatives in OCI, end of period	$	(76	)	$	(32	)	$	(81	)

- Definition

The entire disclosure for derivative instruments and hedging activities including, but not limited to, risk management strategies, non-hedging derivative instruments, assets, liabilities, revenue and expenses, and methodologies and assumptions used in determining the amounts.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
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-Name Accounting Standards Codification
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+ Details

Equity-Based Compensation

12 Months Ended

Dec. 31, 2017

Disclosure of Compensation Related Costs, Share-based Payments [Abstract]

Equity-Based Compensation

NOTE N—EQUITY-BASED COMPENSATION

In July 2011, we adopted the U.S. Silica Holdings, Inc. 2011 Incentive Compensation Plan (the “2011 Plan”), which was amended and restated in May 2015. The 2011 Plan provides for grants of stock options, restricted stock, performance share units and other incentive-based awards. We believe our 2011 Plan aligns the interests of our employees and directors with those of our common stockholders. At December 31, 2017, we have 4,452,870 shares of common stock that may be issued under the 2011 Plan. We use a combination of treasury stock and new shares if necessary to satisfy option exercises or vesting of restricted awards and performance share units.

Stock Options

The following table summarizes the status of, and changes in, our stock option awards during the year ended December 31, 2017:



	Number of Shares		Weighted Average Exercise Price	Aggregate Intrinsic Value (in thousands)		Weighted Average Remaining Contractual Term in Years
Outstanding at December 31, 2016	952,693		27.99
Granted	—		—
Exercised	(43,774	)	18.22
Forfeited	—		—
Outstanding at December 31, 2017	908,919		28.46	$	7,008	6.1 years
Exercisable at December 31, 2017	736,480		26.79	$	6,707	5.8 years

There were no grants of stock options during the years ended December 31, 2017 and 2016.

The total intrinsic value of stock options exercised was $1.2 million, $7.6 million, and $0.4 million for the years ended December 31, 2017, 2016 and 2015 respectively. Cash received from options exercised in 2017 was $0.8 million. The tax benefit realized from option exercises totaled $0.4 million, $2.9 million, and zero for the years ended December 31, 2017, 2016 and 2015, respectively.

We recognized $2.5 million, $3.0 million, and $3.4 million of equity-based compensation expense related to these options during the years ended December 31, 2017, 2016 and 2015, respectively. As of December 31, 2017, there was $1.2 million of total unrecognized compensation expense related to these options, which is expected to be recognized over a weighted-average period of approximately 0.7 years. We account for forfeitures as they occur.

Restricted Stock and Restricted Stock Unit Awards

The following table summarizes the status of, and changes in, our unvested restricted stock awards during the year ended December 31, 2017:



	Number of Shares		Grant Date Weighted Average Fair Value
Unvested, December 31, 2016	557,716		$	24.33
Granted	156,164		44.45
Vested	(248,031	)	24.92
Forfeited	(4,503	)	30.94
Unvested, December 31, 2017	461,346		$	30.76

We granted 156,164 restricted stock and restricted stock unit awards during the year ended December 31, 2017. The fair value of the awards was based on the market price of our stock at date of grant.

We recognized $7.1 million, $5.7 million, and $3.9 million of equity-based compensation expense related to these restricted stock awards during the years ended December 31, 2017, 2016 and 2015 respectively. As of December 31, 2017, there was $9.2 million of total unrecognized compensation expense related to these restricted stock awards, which is expected to be recognized over a weighted-average period of 1.7 years.

Performance Share Unit Awards

The following table summarizes the status of, and changes in, our performance share unit awards during the year ended December 31, 2017:



	Number of Shares		Grant Date Weighted Average Fair Value
Unvested, December 31, 2016	963,613		$	37.43
Granted	90,501		67.69
Vested	—		—
Cancelled	(172,698	)	29.12
Unvested, December 31, 2017	881,416		$	42.16

We granted 90,501 performance share unit awards during the year ended December 31, 2017. The grant date fair value for these awards was estimated to be $67.69 and the number of units that will vest will depend on the percentage ranking of the Company's total shareholder return ("TSR") compared to the TSRs for each of the companies in the peer group over the three year period from January 1, 2017 through December 31, 2019. The related compensation expense is recognized on a straight-line basis over the vesting period.

The grant date fair value for these awards was estimated using a Monte Carlo simulation model. The Monte Carlo simulation model requires the use of highly subjective assumptions. Our key assumptions in the model included the price and the expected volatility of our and our self-determined peer group companies’ stock, risk-free rate of interest, dividend yields and cross-correlations between our and our self-determined peer group companies' stock.

We recognized $15.5 million, $3.3 million, and $3.4 million of compensation expense related to these performance share unit awards during the years ended December 31, 2017, 2016 and 2015 respectively. As of December 31, 2017, there was $18.3 million of estimated total unrecognized compensation expense related to these performance share unit awards, which is expected to be recognized over a weighted-average period of 1.2 years.

- Definition

The entire disclosure for compensation-related costs for equity-based compensation, which may include disclosure of policies, compensation plan details, allocation of equity compensation, incentive distributions, equity-based arrangements to obtain goods and services, deferred compensation arrangements, employee stock ownership plan details and employee stock purchase plan details.

+ References + Details

Commitments and Contingencies

12 Months Ended

Dec. 31, 2017

Commitments and Contingencies Disclosure [Abstract]

Commitments and Contingencies

NOTE O—COMMITMENTS AND CONTINGENCIES

Future Minimum Annual Commitments at December 31, 2017



Amounts in thousands Year ending December 31,	Operating Lease Minimum Rental Payments		Minimum Purchase Commitments
2018	$	69,892	$	28,099
2019	62,294		18,938
2020	51,162		10,168
2021	35,915		5,736
2022	30,303		3,886
Thereafter	55,626		11,200
Total future lease and purchase commitments	$	305,192	$	78,027

Operating Leases

We are obligated under certain operating leases for railroad cars, office space, mining property, mining/processing equipment and transportation and other equipment. Certain operating lease agreements include options to purchase the equipment for fair market value at the end of the original lease term. In general, the above leases include renewal options and provide that we pay for all utilities, insurance, taxes and maintenance. Expense related to operating leases and rental agreements for the years ended December 31, 2017, 2016 and 2015 totaled approximately $68.3 million, $54.1 million and $48.2 million, respectively.

Minimum Purchase Commitments

We enter into service agreements with our transload service providers and transportation service providers. Some of these agreements require us to purchase a minimum amount of services over a specific period of time. Any inability to meet these minimum contract requirements requires us to pay a shortfall fee, which is based on the difference between the minimum amount contracted for and the actual amount purchased.

Contingent Liability on Royalty Agreement

On May 17, 2017, we purchased reserves in Crane County, Texas, for $94.4 million cash consideration plus contingent consideration. The contingent consideration is a royalty that is based on the tonnage shipped to third-parties. Because the contingent consideration is dependent on future tonnage sold, the amounts of which are uncertain, it is not currently possible to estimate the fair value of these future payments. The contingent consideration will be capitalized at the time a payment is probable and reasonably estimable, and the related depletion expense will be adjusted prospectively.

Other Commitments and Contingencies

Our operating subsidiary, U.S. Silica Company ("U.S. Silica"), has been named as a defendant in various product liability claims alleging silica exposure causing silicosis. During the year ended December 31, 2017, no new claims were brought against U.S. Silica. U.S. Silica was named as a defendant in two claims filed during the year ended December 31, 2016 and no claims filed in 2015. As of December 31, 2017, there were 59 active silica-related products liability claims pending in which U.S. Silica is a defendant. Although the outcomes of these claims cannot be predicted with certainty, in the opinion of management, it is not reasonably possible that the ultimate resolution of these matters will have a material adverse effect on our financial position or results of operations that exceeds the accrual amounts.

For periods prior to 1986, U.S. Silica had numerous insurance policies and an indemnity from a former owner that covered silicosis claims. In the fourth quarter of 2012, U.S. Silica settled all rights under the indemnity and its underlying insurance. The settlement was received during the first quarter of 2013. As a result of the settlement, the indemnity and related policies are no longer available to U.S. Silica and U.S. Silica will not seek reimbursement for any defense costs or claim payments. Other insurance policies, however, continue to remain available to U.S. Silica.

We have recorded estimated liabilities for these claims in other long-term obligations as well as estimated recoveries under the indemnity agreement and an estimate of future recoveries under insurance in other assets on our consolidated balance sheets. As of December 31, 2017 and 2016, other non-current assets included zero and $0.3 million, respectively, for insurance for third-party products liability claims. As of December 31, 2017 and 2016, other long-term obligations included $1.0 million and $1.3 million, respectively, in third-party products claims liability.

Additionally, during 2015, we received an unfavorable ruling in an arbitration proceeding as a result of exiting a toll manufacturing contract. The matter was settled and the settlement amount of $6.5 million was paid on June 9, 2015, which was included in selling, general and administrative expense in our Income Statement for the year ended December 31, 2015

Pension and Post-Retirement Benefits

12 Months Ended

Dec. 31, 2017

Compensation and Retirement Disclosure [Abstract]

Pension and Post-Retirement Benefits

NOTE P—PENSION AND POST-RETIREMENT BENEFITS

We maintain a single-employer noncontributory defined benefit pension plan covering certain employees. There have been no new entrants to the plan since May 2009 when the plan was frozen to all new employees. The plan provides benefits based on each covered employee’s years of qualifying service. Our funding policy is to contribute amounts within the range of the minimum required and maximum deductible contributions for the plan consistent with a goal of appropriate minimization of the unfunded projected benefit obligation. The pension plan uses a benefit level per year of service for covered hourly employees and a final average pay method for covered salaried employees. The plan uses the projected unit credit cost method to determine the actuarial valuation.

We employ a total rate of return investment approach whereby a mix of equities and fixed income investments are used to maximize the long-term return of plan assets for a prudent level of risk. Risk tolerance is established through careful consideration of plan liabilities, plan funded status, and corporate financial condition. The investment portfolio contains a diversified blend of equity and fixed-income investments. Furthermore, equity investments are diversified across U.S. and non-U.S. stocks, as well as growth, value and small and large capitalizations. Investment risk is measured and monitored on an ongoing basis through quarterly investment portfolio reviews, annual liability measurements, and periodic asset/liability studies.

We employ a building block approach in determining the long-term rate of return for plan assets. Historical markets are studied and long-term historical relationships between equities and fixed-income are preserved consistent with the widely accepted capital market principle that assets with higher volatility generate a greater return over the long run. Current market factors such as inflation and interest rates are evaluated before long-term capital market assumptions are determined. The long-term portfolio return is established via a building block approach with proper consideration of diversification and rebalancing. Peer data and historical returns are reviewed to check for reasonability and appropriateness.

In addition, we provide defined benefit post-retirement healthcare and life insurance benefits to some employees. Covered employees become eligible for these benefits at retirement after meeting minimum age and service requirements. The projected future cost of providing post-retirement benefits, such as healthcare and life insurance, is recognized as an expense as employees render services.

We previously maintained a Voluntary Employees’ Beneficiary Association trust that was used to partially fund health care benefits for future retirees. Benefits were funded to the extent contributions were tax deductible, which under current legislation is limited. In 2017, the trust terminated upon depletion of its assets, which were used in accordance with trust terms. In general, retiree health benefits are paid as covered expenses are incurred

Net pension benefit cost (in thousands) consisted of the following for the years ended December 31, 2017, 2016 and 2015:



	Years Ended December 31,
	2017			2016			2015
Service cost	$	1,037		$	1,078		$	1,295
Interest cost	3,971			4,067			4,813
Expected return on plan assets	(5,265		)	(5,495		)	(5,498		)
Net amortization and deferral	1,773			1,592			2,665
Net pension benefit costs	$	1,516		$	1,242		$	3,275

Net post-retirement cost (in thousands) consisted of the following for the years ended December 31, 2017, 2016 and 2015:



	Years Ended December 31,
	2017			2016			2015
Service cost	$	107		$	132		$	176
Interest cost	753			876			1,074
Expected return on plan assets	(1		)	(1		)	(1		)
Net amortization and deferral	—			—			281
Special termination benefit	—			21			48
Net post-retirement costs	$	859		$	1,028		$	1,578

The changes in benefit obligations and plan assets (in thousands), as well as the funded status (in thousands) of our pension and post-retirement plans at December 31, 2017 and 2016 are as follows:



	Pension Benefits						Post-retirement Benefits
	2017			2016			2017			2016
Benefit obligation at January 1,	$	116,145		$	115,420		$	24,393		$	25,091
Service cost	1,037			1,078			107			132
Interest cost	3,971			4,067			753			876
Actuarial (gain) loss	6,824			1,640			(1,576		)	(802		)
Benefits paid	(6,685		)	(6,517		)	(1,280		)	(1,332		)
Amendments	760			457			—			—
Special termination benefits	—			—			—			21
Other	—			—			374			407
Benefit obligation at December 31,	$	122,052		$	116,145		$	22,771		$	24,393
Fair value of plan assets at January 1,	$	83,850		$	84,716		$	14		$	17
Actual return on plan assets	12,757			5,651			(1		)	(3		)
Employer contributions	2,145			—			893			925
Benefits paid	(6,685		)	(6,517		)	(1,280		)	(1,332		)
Other	—			—			374			407
Fair value of plan assets at December 31,	$	92,067		$	83,850		$	—		$	14
Plan assets less than benefit obligations at December 31 recognized as liability for pension and other post-retirement benefits	$	(29,985	)	$	(32,295	)	$	(22,771	)	$	(24,379	)

The accumulated benefit obligation for the defined benefit pension plans, which excludes the assumption of future salary increases, totaled $122.0 million and $116.0 million at December 31, 2017 and 2016, respectively.

The amendments in 2017 and 2016 reflect plan changes including increases in the benefit multiplier for certain participants.

We also sponsor unfunded, nonqualified pension plans. The projected benefit obligation, accumulated benefit obligation and fair value of plan assets for these plans were $1.6 million, $1.6 million and zero at December 31, 2017 and $1.6 million, $1.6 million and zero at December 31, 2016. Future estimated annual benefit payments (in thousands) for pension and post-retirement benefit obligations at December 31, 2017 are as follows:



	Benefits
			Post-retirement
	Pension		Before Medicare Subsidy		After Medicare Subsidy
2018	$	7,195	$	1,536	$	1,400
2019	7,334		1,480		1,345
2020	7,409		1,490		1,358
2021	7,446		1,571		1,438
2022	7,573		1,600		1,465
2023-2027	38,030		7,892		7,178

Our best estimate of expected contributions to the pension and post-retirement medical benefit plans for the 2018 fiscal year are $2.5 million and $1.4 million, respectively.

The amounts in accumulated other comprehensive income expected to be recognized as components of net periodic benefit cost (in thousands) during the following fiscal year are as follows:



	Benefits
	Pension		Post-retirement		Total
Net actuarial loss	$	1,877	$	—	$	1,877
Prior service cost	534		—		534
	$	2,411	$	—	$	2,411

The total amounts in accumulated other comprehensive income (loss) related to net actuarial loss, net of tax, for both qualified plans was $13.5 million and $13.8 million as of December 31, 2017 and 2016, respectively. The total amounts in accumulated other comprehensive income (loss) related to prior service cost, net of tax, for both plans, was $0.5 million as of December 31, 2017 and 2016.

The following weighted-average assumptions were used to determine our obligations under the plans:



	Pension Benefits				Post-retirement Benefits
	2017		2016		2017		2016
Discount rate	3.7	%	4.2	%	3.7	%	4.2	%
Long-term rate of compensation increase	3.5	%	3.5	%	N/A		N/A
Long-term rate of return on plan assets	6.8	%	7.0	%	7.0	%	7.0	%
Health care cost trend rate:
Pre-65 initial rate/ultimate rate	N/A		N/A		7.3%/4.5%		7.3%/5.0%
Pre-65 ultimate year	N/A		N/A		—		—
Post-65 initial rate/ultimate rate	N/A		N/A		8.0%/4.5%		8.5%/5.0%
Post-65 ultimate year	N/A		N/A		2025/2026		2024/2025

The weighted average discount rate used to determine the projected pension and post-retirement obligations was updated in 2017, and was decreased from 4.2% at December 31, 2016 to 3.7% at December 31, 2017. The discount rate reflects the expected long-term rates of return with maturities comparable to payments for the plan obligations utilizing Aon Hewitt's AA Only Above Medium Curve.

In 2016, we changed the method utilized to estimate the service cost and interest cost components of net periodic benefit costs for our defined benefit pension and other post-retirement benefit plans. Historically, we estimated the service cost and interest cost components using a single weighted average discount rate derived from the yield curve used to measure the benefit obligation at the beginning of the period. We have elected to use a spot rate approach in the estimation of these components of benefit cost by applying the specific rates along the yield curve to the relevant projected cash flows, as we believe this provides a better estimate of service and interest costs. We consider this a change in estimate and, accordingly, have accounted for it prospectively starting in 2016. This change does not affect the measurement of our total benefit obligation.

Mortality tables used for pension benefits and post-retirement benefits plans are the following:



	Pension Benefits and Post-retirement Benefits
	2017	2016
Healthy Lives	RP-2014 mortality table, adjusted back to 2006 base rates, with generational mortality improvements using Scale MP-2017	RP-2014 mortality table, adjusted back to 2006 base rates, with generational mortality improvements using Scale MP-2016
Disabled Lives	RP-2014 disabled retiree mortality table, adjusted back to 2006 base rates, with generational mortality improvements using Scale MP-2017	RP-2014 disabled retiree mortality table, adjusted back to 2006 base rates, with generational mortality improvements using Scale MP-2016

Assumed health care cost trend rates have a significant effect on the amounts reported for the health care plans. A one-percentage-point change in assumed health care cost trend rates would have the following effects (in thousands):



	One-Percentage-Point
	Increase		Decrease
Effect on total of service and interest cost	$	113	$	(95	)
Effect on post-retirement benefit obligation	2,598		(2,209		)

The major investment categories and their relative percentage of the fair value of total plan assets as invested at December 31, 2017, and 2016 are as follows:



	Pension Benefits				Post-retirement Benefits
	2017		2016		2017		2016
Equity securities	51.8	%	59.4	%	—	%	64.0	%
Debt securities	46.3	%	38.3	%	—	%	39.1	%
Cash	1.9	%	2.3	%	—	%	(3.1	)%

The fair values of the pension plan assets (in thousands) at December 31, 2017, by asset category, are as follows:



	Level 1		Level 2		Level 3		Total
Cash and cash equivalents	$	—	$	1,727	$	—	$	1,727
Mutual funds:
Diversified emerging markets	8,300		—		—		8,300
Foreign large blend	11,856		—		—		11,856
Large-cap blend	15,643		—		—		15,643
Mid-cap blend	8,334		—		—		8,334
Real estate	3,591		—		—		3,591
Fixed income securities:
Corporate notes and bonds	28,108		—		—		28,108
Government agencies	—		—		—		—
U.S. Treasuries	10,846		—		—		10,846
Mortgage-backed securities	—		2,615		—		2,615
Asset-backed securities	—		1,047		—		1,047
Net asset	$	86,678	$	5,389	$	—	$	92,067

The fair values of the pension plan assets (in thousands) at December 31, 2016, by asset category, are as follows:



	Level 1		Level 2		Level 3		Total
Cash and cash equivalents	$	—	$	1,893	$	—	$	1,893
Mutual funds:
Diversified emerging markets	7,700		—		—		7,700
Foreign large blend	12,621		—		—		12,621
Large-cap blend	16,687		—		—		16,687
Mid-cap blend	8,674		—		—		8,674
Real estate	4,070		—		—		4,070
Fixed income securities:
Corporate notes and bonds	21,357		—		—		21,357
Government agencies	301		—		—		301
U.S. Treasuries	7,495		—		—		7,495
Mortgage-backed securities	—		2,022		—		2,022
Asset-backed securities	—		983		—		983
Insurance policies	—		—		47		47
Net asset	$	78,905	$	4,898	$	47	$	83,850

We contribute to three multiemployer defined benefit pension plans under the terms of collective-bargaining agreements for union-represented employees. A multiemployer plan is subject to collective bargaining for employees of two or more unrelated companies. These plans allow multiple employers to pool their pension resources and realize efficiencies associated with the daily administration of the plan. Multiemployer plans are generally governed by a board of trustees composed of management and labor representatives and are funded through employer contributions. However, in most cases, management is not directly represented.

The risks of participating in multiemployer plans differ from single employer plans as follows: 1) assets contributed to a multiemployer plan by one employer may be used to provide benefits to employees of other participating employers, 2) if a participating employer stops contributing to the plan, the unfunded obligations of the plan may be borne by the remaining participating employers, and 3) if we cease to have an obligation to contribute to one or more of the multiemployer plans to which we contribute, we may be required to pay those plans an amount based on the underfunded status of the plan, referred to as a withdrawal liability.

A summary of each multiemployer pension plan for which we participate is presented below:

Pension

Fund

EIN/ Pension

Plan No.

Pension Protection Act

Zone Status⁽¹⁾

FIP/RP Status

Pending/

Implemented

Company

Contributions

(in thousands)

Surcharge

Imposed

Expiration

Date of

CBA

2017

2016

2017

2016

2015

LIUNA

52-6074345/001

Red

Yes

223

167

182

Yes

5/31/2020

IUOE

36-6052390/001

Green

7/29/2018

CSSS⁽²⁾

36-6044243/001

Red

Yes


(1)	The Pension Protection Act of 2006 defines the zone status as follows: green—healthy, yellow—endangered, orange—seriously endangered and red—critical.


(2)	In 2011, we withdrew from the Central States, Southeast and Southwest Areas Pension Plan. The withdrawal liability of $1.0 million will be paid in monthly installments of $4,000 until 2031.

Our contributions to individual multiemployer pension funds did not exceed 5% of the fund’s total contributions in any of the three years ended December 31, 2017. Additionally, our contributions to multiemployer post-retirement benefit plans were immaterial for all periods presented in the accompanying consolidated financial statements.

We also sponsor a defined contribution plan covering certain employees. We contribute to the plan in two ways. For certain employees not covered by the defined benefit plan, we make a contribution equal to 4% of their salary. We also contribute an employee match of 25 cents, for each dollar contributed by an employee, up to 8% of their earnings. For certain employees, we make a profit sharing match up to 25 cents, based on financial performance, for each dollar contributed up to 8% of their earnings. Finally, for some employees, we make a catch-up match of 25 cents for each dollar of catch-up contributions. Contributions were $3.0 million, $2.4 million and $2.8 million for the years ended December 31, 2017, 2016 and 2015, respectively.

Income Taxes

12 Months Ended

Dec. 31, 2017

Income Tax Disclosure [Abstract]

Income Taxes

NOTE Q—INCOME TAXES

We evaluate our deferred tax assets periodically to determine if valuation allowances are required. Ultimately, the realization of deferred tax assets is dependent upon generation of future taxable income during those periods in which temporary differences become deductible and/or credits can be utilized. To this end, management considers the level of historical taxable income, the scheduled reversal of deferred tax liabilities, tax-planning strategies and projected future taxable income. Based on these considerations, and the carry-forward availability of a portion of the deferred tax assets, management believes it is more likely than not that we will realize the benefit of the deferred tax assets.

On December 22, 2017, the U.S. government enacted comprehensive tax legislation commonly referred to as the Tax Cuts and Jobs Act (the “Tax Act”). The Tax Act makes broad and complex changes to the U.S. tax code including, but not limited to, (1) bonus depreciation that will allow for full expensing of qualified property; (2) reduction of the U.S. federal corporate tax rate; (3) elimination of the corporate alternative minimum tax; (4) a new limitation on deductible interest expense; (5) the repeal of the domestic production activity deduction; (6) limitations on the deductibility of certain executive compensation; and (7) limitations on net operating losses generated after December 31, 2017, to 80 percent of taxable income. We are not currently subject to the various international changes of the Tax Act.

The SEC staff issued SAB 118, which provides guidance on accounting for the tax effects of the Tax Act. SAB 118 provides a measurement period that should not extend beyond one year from the Tax Act enactment date for companies to complete the accounting under ASC 740. In accordance with SAB 118, a company must reflect the income tax effects of those aspects of the Act for which the accounting under ASC 740 is complete. To the extent that a company’s accounting for certain income tax effects of the Tax Act is incomplete but it is able to determine a reasonable estimate, it must record a provisional estimate in the financial statements. If a company cannot determine a provisional estimate to be included in the financial statements, it should continue to apply ASC 740 on the basis of the provisions of the tax laws that were in effect immediately before the enactment of the Tax Act. As we are not subject to either the international changes of the Tax Act or other applicable provisions, we believe that the income tax effects of the Tax Act applicable to our accounting under ASC 740 is substantially complete for the year ended December 31, 2017. Additional information that may affect the accounting under ASC 740 would include further clarification and guidance on how the Internal Revenue Service and state taxing authorities will implement the Tax Act. We do not believe potential adjustments in future periods would materially impact the Company’s financial condition or results of operations.

The Tax Act reduces the corporate tax rate to 21 percent, effective January 1, 2018. Because ASC 740-10-25-47 requires the effect of a change in tax laws or rates to be recognized as of the date of enactment, we are required to adjust deferred tax assets and liabilities as of December 22, 2017. Accordingly, we have recorded a decrease related to deferred tax assets and liabilities of $45.0 million and $80.8 million, respectively, with a corresponding net adjustment to deferred income tax benefit of $35.8 million for the year ended December 31, 2017.

The expense or benefit for income taxes (in thousands) consisted of the following for the years ended December 31, 2017, 2016 and 2015:



	Years Ended December 31,
	2017			2016			2015
Current:
Federal	$	(10,754	)	$	60		$	(170	)
State	(1,167		)	(274		)	1,448
	$	(11,921	)	$	(214	)	$	1,278
Deferred:
Federal	22,641			32,944			7,439
State	(2,040		)	3,959			3,034
	$	20,601		$	36,903		$	10,473
Income tax (expense) benefit	$	8,680		$	36,689		$	11,751

Deferred tax assets and liabilities are recognized for the estimated future tax effects, based on enacted tax laws, of temporary differences between the values of assets and liabilities recorded for financial reporting and for tax purposes and of net operating loss and other carry forwards.

The tax effects of the types of temporary differences and carry forwards that gave rise to deferred tax assets and liabilities (in thousands) at December 31, 2017 and 2016 consisted of the following:



	At December 31,
	2017			2016
Gross deferred tax assets:
Net operating loss carry forward and state tax credits	$	22,783		$	65,022
Pension and post-retirement benefit costs	13,710			22,920
Alternative minimum tax credit carry forward	30,401			19,431
Property, plant and equipment	5,750			6,112
Accrued expenses	10,755			6,752
Inventories	4,354			4,362
Third-party products liability	249			511
Stock-based compensation expense	8,785			5,576
Note payable	3,133			4,009
Other	5,095			5,458
Total deferred tax assets	$	105,015		$	140,153
Gross deferred tax liabilities:
Land and mineral property basis difference	$	(78,520	)	$	(126,315	)
Fixed assets and depreciation	(51,556		)	(61,531		)
Intangibles	(4,795		)	(2,260		)
Other	—			(122		)
Total deferred tax liabilities	$	(134,871	)	$	(190,228	)
Net deferred tax liabilities	$	(29,856	)	$	(50,075	)

We have federal net operating loss carry forwards of approximately $93.4 million at December 31, 2017. The losses will expire in years 2027 through 2036. Approximately $69.0 million of the losses are subject to an annual limitation under Internal Revenue Code Section 382, but are expected to be fully realized. Under the Tax Act, net operating loss (NOL) deductions arising in tax years beginning after December 31, 2017 can only offset up to 80 percent of future taxable income. The Act also prohibits NOL carrybacks, but allows indefinite carryforwards for NOLs arising in tax years beginning after December 31, 2017. Net operating losses arising before January 1, 2018 are accounted for under the previous tax rules that imposed no limit on the amount of the taxable income that can be set off using NOLs (except for a 90 percent limit for AMT carryforwards) and that can be carried back 2 years, and carried forward 20 years.

At December 31, 2017 and 2016, we have an alternative minimum tax credit carry forward of approximately $30.4 million and $19.4 million, respectively. The Tax Act repeals the corporate alternative minimum tax (AMT), effective for tax years beginning after December 31, 2017, but allows an entity to claim portions of any unused AMT credits over the next four years to offset its regular tax liability. An entity with unused AMT credits as of December 31, 2017 can first use these credits to offset its regular tax for 2017, and can then claim up to 50 percent of the remaining AMT credits in 2018, 2019, and 2020, with all remaining AMT credits refundable in 2021.

At the end of each reporting period as presented, there were no material amounts of interest and penalties recognized in the statement of operations or balance sheets. We have no material unrecognized tax benefits or any known material tax contingencies at December 31, 2017 or December 31, 2016 and do not expect this to change significantly within the next twelve months. Tax returns filed with the IRS for the years 2014 through 2016 along with tax returns filed with numerous state entities remain subject to examination.

The income tax expense or benefit (in thousands) differed from the amount that would be provided by applying the U.S. federal statutory rate for the years ended December 31, 2017, 2016 and 2015 due to the following:



	Years Ended December 31,
	2017			2016			2015
Income tax (expense) benefit computed at U.S. federal statutory rate	$	(47,784	)	$	27,211		$	(41	)
Decrease (increase) resulting from:
Statutory depletion	20,259			4,734			8,918
Prior year tax return reconciliation	219			435			393
State income taxes, net of federal benefit	(2,267		)	2,369			1,370
Adjustment to deferred taxes from the Tax Act rate reduction	35,772			—			—
Equity compensation	2,602			2,003			—
Other, net	(121		)	(63		)	1,111
Income tax (expense) benefit	$	8,680		$	36,689		$	11,751

Obligations Under Guarantees	12 Months Ended
Obligations Under Guarantees	Dec. 31, 2017
Guarantees [Abstract]
Obligations Under Guarantees	NOTE R—OBLIGATIONS UNDER GUARANTEES We have indemnified The Travelers Companies, Inc. and subsidiaries (“Travelers”) against any loss Travelers may incur in the event that holders of surety bonds, issued on behalf of us by Travelers, execute the bonds. As of December 31, 2017, Travelers had $12.1 million in bonds outstanding for us. The majority of these bonds, $10.3 million, relate to reclamation requirements issued by various governmental authorities. Reclamation bonds remain outstanding until the mining area is reclaimed and the authority issues a formal release. The remaining bonds relate to such indefinite purposes as licenses, permits, and tax collection.

Segment Reporting

12 Months Ended

Dec. 31, 2017

Segment Reporting [Abstract]

Segment Reporting

NOTE T—SEGMENT REPORTING

Our business is organized into two reportable segments, Oil & Gas Proppants and Industrial & Specialty Products, based on end markets. The reportable segments are consistent with how management views the markets that we serve and the financial information reviewed by the chief operating decision maker. We manage our Oil & Gas Proppants and Industrial & Specialty Products businesses as components of an enterprise for which separate information is available and is evaluated regularly by the chief operating decision maker in deciding how to allocate resources and assess performance.

In the Oil & Gas Proppants segment, we serve the oil and gas recovery market primarily by providing and delivering fracturing sand, or “frac sand,” which is pumped down oil and natural gas wells to prop open rock fissures and increase the flow rate of oil and natural gas from the wells.

The Industrial & Specialty Products segment consists of over 221 products and materials used in a variety of industries, including container glass, fiberglass, specialty glass, flat glass, building products, fillers and extenders, foundry products, chemicals, recreation products and filtration products.

An operating segment’s performance is primarily evaluated based on segment contribution margin, which excludes certain corporate costs not associated with the operations of the segment. These corporate costs are separately stated below and include costs that are related to functional areas such as operations management, corporate purchasing, accounting, treasury, information technology, legal and human resources. We believe that segment contribution margin, as defined above, is an appropriate measure for evaluating the operating performance of our segments. However, this measure should be considered in addition to, not a substitute for, or superior to, net income (loss) or other measures of financial performance prepared in accordance with generally accepted accounting principles. The other accounting policies of each of the two reporting segments are the same as those in Note B - Summary of Significant Accounting Policies to these financial statements.

The following table presents sales and segment contribution margin (in thousands) for the reporting segments and other operating results not allocated to the reported segments for the years ended December 31, 2017, 2016 and 2015:



	Years Ended December 31,
	2017			2016			2015
Sales:
Oil & Gas Proppants	$	1,020,365		$	362,550		$	430,435
Industrial & Specialty Products	220,486			197,075			212,554
Total sales	$	1,240,851		$	559,625		$	642,989
Segment contribution margin:
Oil & Gas Proppants	$	301,972		$	11,445		$	88,928
Industrial & Specialty Products	88,781			78,988			70,137
Total segment contribution margin	$	390,753		$	90,433		$	159,065
Operating activities excluded from segment cost of sales	(17,417		)	(8,103		)	(11,142		)
Selling, general and administrative	(107,592		)	(67,727		)	(62,777		)
Depreciation, depletion and amortization	(97,233		)	(68,134		)	(58,474		)
Interest expense	(31,342		)	(27,972		)	(27,283		)
Other income (expense), net, including interest income	(643		)	3,758			728
Income tax (expense) benefit	8,680			36,689			11,751
Net income (loss)	$	145,206		$	(41,056	)	$	11,868

Asset information, including capital expenditures and depreciation, depletion, and amortization, by segment is not included in reports used by management in its monitoring of performance and, therefore, is not reported by segment. Goodwill of $272.1 million has been allocated to these segments with $247.5 million assigned to Oil & Gas Proppants and $24.6 million to Industrial & Specialty Products at December 31, 2017. Goodwill of $241.0 million has been allocated to these segments with $220.3 million assigned to Oil & Gas Proppants and $20.7 million to Industrial & Specialty Products at December 31, 2016.

- Definition

The entire disclosure for reporting segments including data and tables. Reportable segments include those that meet any of the following quantitative thresholds a) it's reported revenue, including sales to external customers and intersegment sales or transfers is 10 percent or more of the combined revenue, internal and external, of all operating segments b) the absolute amount of its reported profit or loss is 10 percent or more of the greater, in absolute amount of 1) the combined reported profit of all operating segments that did not report a loss or 2) the combined reported loss of all operating segments that did report a loss c) its assets are 10 percent or more of the combined assets of all operating segments.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 34
-URI http://asc.fasb.org/extlink&oid=68060357&loc=d3e8981-108599

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 41
-URI http://asc.fasb.org/extlink&oid=68060357&loc=d3e9038-108599

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 33
-URI http://asc.fasb.org/extlink&oid=68060357&loc=d3e8971-108599

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 12
-URI http://asc.fasb.org/extlink&oid=68060357&loc=d3e8595-108599

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-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
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-Name Accounting Standards Codification
-Topic 280
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-Section 50
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-Section 50
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-Name Accounting Standards Codification
-Topic 280
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-Name Accounting Standards Codification
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-Section 50
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-Name Accounting Standards Codification
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-Name Accounting Standards Codification
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-Section 50
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-Name Accounting Standards Codification
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-Paragraph 31
-URI http://asc.fasb.org/extlink&oid=68060357&loc=d3e8924-108599

Reference 14: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 30
-URI http://asc.fasb.org/extlink&oid=68060357&loc=d3e8906-108599

+ Details

Unaudited Supplementary Data

12 Months Ended

Dec. 31, 2017

Quarterly Financial Information Disclosure [Abstract]

Unaudited Supplementary Data

NOTE U—UNAUDITED SUPPLEMENTARY DATA

The following table sets forth our unaudited quarterly consolidated statements of operations (in thousands, except per share data) for each of the four quarters in the years ended December 31, 2017 and 2016. This unaudited quarterly information has been prepared on the same basis as our annual audited financial statements and includes all adjustments, consisting only of normal recurring adjustments that are necessary to present fairly the financial information for the fiscal quarters presented. The income tax benefit amounts for 2016 first quarter and second quarter include the impacts from the early adoption of ASU 2016-09 discussed in Note B - Summary of Significant Accounting Policies to these financial statements.



	First Quarter			Second Quarter			Third Quarter			Fourth Quarter
2017	(Unaudited)
Sales:
Product	$	209,321		$	246,022		$	295,768		$	306,442
Service	35,476			44,443			49,255			54,124
Cost of sales (excluding depreciation, depletion and amortization):
Product	162,637			164,025			189,105			204,545
Service	24,838			33,386			38,818			50,161
Operating expenses:
Selling, general and administrative	22,341			26,012			29,602			29,637
Depreciation, depletion and amortization	21,599			23,626			24,673			27,335
Total operating expenses	$	43,940		$	49,638		$	54,275		$	56,972
Operating income	13,382			43,416			62,825			48,888
Other income (expense):
Interest expense	(7,646		)	(8,105		)	(8,347		)	(7,244		)
Other income (expense), net, including interest income	(4,928		)	1,258			1,502			1,525
Total other expense	$	(12,574	)	$	(6,847	)	$	(6,845	)	$	(5,719	)
Income before income taxes	808			36,569			55,980			43,169
Income tax (expense) benefit	1,714			(7,110		)	(14,707		)	28,783
Net income	$	2,522		$	29,459		$	41,273		$	71,952
Earnings per share, basic	$	0.03		$	0.36		$	0.51		$	0.89
Earnings per share, diluted	$	0.03		$	0.36		$	0.50		$	0.88
Weighted average shares outstanding, basic	80,983			81,087			81,121			81,014
Weighted average shares outstanding, diluted	82,244			81,945			81,783			81,921
Dividends declared per share	$	0.06		$	0.06		$	0.06		$	0.06

	First Quarter			Second Quarter			Third Quarter			Fourth Quarter
2016	(Unaudited)
Sales:
Product	$	121,627		$	116,039		$	125,805		$	160,429
Service	883			955			11,943			21,944
Cost of sales (excluding depreciation, depletion and amortization):
Product	106,629			102,587			112,215			133,758
Service	122			120			7,211			14,653
Operating expenses:
Selling, general and administrative	15,503			14,585			18,472			19,167
Depreciation, depletion and amortization	14,556			15,209			17,175			21,194



Total operating expenses	$	30,059		$	29,794		$	35,647		$	40,361
Operating loss	(14,300		)	(15,507		)	(17,325		)	(6,399		)
Other income (expense):
Interest expense	(6,643		)	(6,647		)	(6,684		)	(7,998		)
Other income, net, including interest income	1,790			608			493			867
Total other expense	$	(4,853	)	$	(6,039	)	$	(6,191	)	$	(7,131	)
Loss before income taxes	(19,153		)	(21,546		)	(23,516		)	(13,530		)
Income tax benefit (expense)	8,150			9,774			12,177			6,588
Net income (loss)	$	(11,003	)	$	(11,772	)	$	(11,339	)	$	(6,942	)
Loss per share, basic	$	(0.20	)	$	(0.19	)	$	(0.17	)	$	(0.09	)
Loss per share, diluted	$	(0.20	)	$	(0.19	)	$	(0.17	)	$	(0.09	)
Weighted average shares, basic	54,470			63,417			66,676			75,539
Weighted average shares, diluted	54,470			63,417			66,676			75,539
Dividends declared per share	$	0.06		$	0.06		$	0.06		$	0.06

Parent Company Financials

12 Months Ended

Dec. 31, 2017

Organization, Consolidation and Presentation of Financial Statements [Abstract]

Parent Company Financials

NOTE V—PARENT COMPANY FINANCIALS

U.S. SILICA HOLDINGS, INC.

(PARENT COMPANY ONLY)

CONDENSED BALANCE SHEETS



	December 31,
	2017			2016
	(in thousands)
ASSETS
Current Assets:
Cash and cash equivalents	$	230,647		$	534,378
Due from affiliates	146,683			—
Total current assets	377,330			534,378
Investment in subsidiaries	1,024,511			854,860
Total assets	$	1,401,841		$	1,389,238
LIABILITIES AND STOCKHOLDERS’ EQUITY
Current Liabilities:
Accrued expenses and other current liabilities	$	106		$	461
Dividends payable	5,229			5,222
Due to affiliates	—			110,265
Total current liabilities	5,335			115,948
Deferred income taxes, net	—			—
Total liabilities	5,335			115,948
Stockholders’ Equity:
Preferred stock	—			—
Common stock	812			811
Additional paid-in capital	1,147,084			1,129,051
Retained earnings	287,992			163,173
Treasury stock, at cost	(25,456		)	(3,869		)
Accumulated other comprehensive loss	(13,926		)	(15,876		)
Total stockholders’ equity	1,396,506			1,273,290
Total liabilities and stockholders’ equity	$	1,401,841		$	1,389,238

U.S. SILICA HOLDINGS, INC.

(PARENT COMPANY ONLY)

CONDENSED STATEMENT OF OPERATIONS AND COMPREHENSIVE INCOME (LOSS)



	Year Ended December 31,
	2017			2016			2015
	(in thousands, except per share amounts)
Sales	$	—		$	—		$	—
Cost of sales	—			—			—
Operating expenses
Selling, general and administrative	252			184			185
Other	—			10			19
Total operating expenses	252			194			204
Operating loss	(252		)	(194		)	(204		)
Other income (expense)
Interest income	3,854			1,046			262
Other income, net, including interest income	—			—			1
Total other income (expense)	3,854			1,046			263
Income before income taxes and equity in net earnings of subsidiaries	3,602			852			59
Income tax benefit (expense)	(1,453		)	(344		)	(24		)
Income before equity in net earnings of subsidiaries	2,149			508			35
Equity in earnings of subsidiaries, net of tax	143,057			(41,564		)	11,833
Net income (loss)	145,206			(41,056		)	11,868
Other comprehensive income (loss), net of deferred income taxes:
Unrealized gain (loss) on investments (net of tax of $0, $(4), and $29 for 2017, 2016, and 2015, respectively)	—			(6		)	47
Unrealized gain (loss) on derivatives, (net of tax of $(27), $29 and $34 for 2017, 2016 and 2015, respectively)	(44		)	49			53
Foreign currency translation adjustment (net of tax of $2, $0 and $0 for 2017, 2016 and 2015, respectively)	(6		)	—			—
Pension and post-retirement liability (net of tax of $1,205, $152, and $2,469 for 2017, 2016 and 2015, respectively)	2,000			252			3,547
Other comprehensive income (loss), net of deferred income taxes	1,950			295			3,647
Comprehensive income (loss) attributable to U.S. Silica Holdings, Inc.	$	147,156		$	(40,761	)	$	15,515

U.S. SILICA HOLDINGS, INC.

(PARENT COMPANY ONLY)

CONDENSED STATEMENT OF STOCKHOLDERS' EQUITY



												Accumulated
						Additional			Retained			Other			Total
	Par		Treasury			Paid-In			Earnings-			Comprehensive			Stockholders'
	Value		Stock			Capital			Present			Income (Loss)			Equity
Balance at January 1, 2015	$	539	$	(542	)	$	191,086		$	232,551		$	(19,818	)	$	403,816
Net income	—		—			—			11,868			—			11,868
Unrealized gain on derivatives	—		—			—			—			53			53
Unrealized gain on short-term investments	—		—			—			—			47			47
Pension and post-retirement liability	—		—			—			—			3,547			3,547
Cash dividend declared ($0.438 per share)	—		—			—			(23,445		)	—			(23,445		)
Common stock-based compensation plans activity:
Equity-based compensation	—		—			3,857			—			—			3,857
Proceeds from options exercised	—		744			(271		)	—			—			473
Shares withheld for employee taxes related to
vested restricted stock and stock units	—		(792		)	(2		)	—			—			(794		)
Repurchase of common stock	—		(15,255		)	—			—			—			(15,255		)
Balance at December 31, 2015	$	539	$	(15,845	)	$	194,670		$	220,974		$	(16,171	)	$	384,167
Net loss	—		—			—			(41,056		)	—			(41,056		)
Issuance of common stock (stock offerings net of issuance costs of $25,732)	272		—			931,016			—			—			931,288
Unrealized gain on derivatives	—		—			—			—			49			49
Unrealized loss on short-term investments	—		—			—			—			(6		)	(6		)
Pension and post-retirement liability	—		—			—			—			252			252
Cash dividend declared ($0.25 per share)	—		—			—			(16,893		)	—			(16,893		)
Common stock-based compensation plans activity:
Equity-based compensation	—		—			12,107			—			—			12,107
Excess tax benefit from equity-based compensation	—		—			—			148			—			148
Proceeds from options exercised	—		8,465			(3,640		)	—			—			4,825
Issuance of restricted stock	—		1,437			(1,437		)	—			—			—
Shares withheld for employee taxes related to
vested restricted stock and stock units	—		2,074			(3,665		)	—			—			(1,591		)
Balance at December 31, 2016	$	811	$	(3,869	)	$	1,129,051		$	163,173		$	(15,876	)	$	1,273,290
Net Income	—		—			—			145,206			—			145,206
Unrealized loss on derivatives	—		—			—			—			(44		)	(44		)
Foreign currency translation adjustment												(6		)	(6		)
Pension and post-retirement liability	—		—			—			—			2,000			2,000
Cash dividend declared ($0.25 per share)	—		—			—			(20,387		)	—			(20,387		)
Common stock-based compensation plans activity:
Equity-based compensation	—		—			25,050			—			—			25,050
Proceeds from options exercised	—		1,190			(392		)	—			—			798
Issuance of restricted stock	—		1,859			(1,859		)	—			—			—
Shares withheld for employee taxes related to
vested restricted stock and stock units	1		386			(4,766		)	—			—			(4,379		)
Repurchase of common stock	—		(25,022		)										(25,022		)
Balance at December 31, 2017	$	812	$	(25,456	)	$	1,147,084		$	287,992		$	(13,926	)	$	1,396,506

U.S. SILICA HOLDINGS, INC.

(PARENT COMPANY ONLY)

CONDENSED STATEMENT OF CASH FLOWS



	Year Ended December 31,
	2017			2016			2015
	(in thousands)
Operating activities:
Net income (loss)	$	145,206		$	(41,056	)	$	11,868
Adjustments to reconcile net income (loss) to net cash provided by operating activities:
Undistributed (Income) loss from equity method investment, net	(143,057		)	41,564			(11,833		)
Other	—			(30		)	(195		)
Changes in assets and liabilities, net of effects of acquisitions:
Accounts payable and accrued liabilities	48			353			29
Net cash provided by (used in) operating activities	2,197			831			(131		)
Investing activities:
Proceeds from sales and maturities of short-term investments	—			21,872			53,568
Investment in subsidiary	(143,654		)	(188,177		)	—
Net cash provided by (used in) investing activities	(143,654		)	(166,305		)	53,568
Financing activities:
Dividends paid	(20,377		)	(15,125		)	(26,797		)
Repurchase of common stock	(25,022		)	—			(15,255		)
Proceeds from options exercised	798			4,603			473
Tax payments related to shares withheld for vested restricted stock and stock units	(4,379		)	(1,590		)	(794		)
Issuance of common stock (secondary offering)	—			678,791			—
Issuance of treasury stock	—			221			—
Costs of common stock issuance	—			(25,733		)	—
Net financing activities with subsidiaries	(113,294		)	106			223
Net cash provided by (used in) financing activities	(162,274		)	641,273			(42,150		)
Net increase in cash and cash equivalents	(303,731		)	475,799			11,287
Cash and cash equivalents, beginning of period	534,378			58,579			47,292
Cash and cash equivalents, end of period	$	230,647		$	534,378		$	58,579
Non-cash financing activities:
Supplemental cash flow information:
Cash paid (received) during the period for:
Interest	$	(3,853	)	$	(1,046	)	$	(263	)
Non-cash transactions
Common stock issued for business acquisitions	$	—		$	278,229		$	—

Notes to Condensed Financial Statements of Registrant (Parent Company Only)

These condensed parent company only financial statements have been prepared in accordance with Rule 12-04, Schedule I of Regulation S-X, because the restricted net assets of the subsidiaries of U.S. Silica Holdings, Inc. (as defined in Rule 4-08(e)(3) of Regulation S-X) exceed 25% of the consolidated net assets of the Company. The ability of the Company's operating subsidiaries to pay dividends may be restricted due to the terms of the Company's senior credit facility, as discussed in Note I - Accrued Liabilities to these financial statements.

These condensed parent company financial statements have been prepared using the same accounting principles and policies described in the notes to the consolidated financial statements; the only exceptions are that (a) the parent company accounts for its subsidiaries using the equity method of accounting, (b) taxes are allocated to the parent from the subsidiary using the separate return method, and (c) intercompany loans are not eliminated. In the parent company financial statements, the Company's investment in subsidiaries is stated at cost plus equity in undistributed earnings of subsidiaries since the date of acquisition. These condensed parent company financial statements should be read in conjunction with the Company's consolidated financial statements and related notes thereto included elsewhere in this report.

No cash dividends were paid to the parent by its consolidated entities for the years presented in the condensed financial statements.

- Definition

The entire disclosure for condensed financial information, including the financial position, cash flows, and the results of operations of the registrant (parent company) as of the same dates or for the same periods for which audited consolidated financial statements are being presented. Alternatively, the details of this disclosure can be reported by the specific parent company taxonomy elements, indicating the appropriate date and period contexts in an instance document.

+ References + Details

Related Party Transactions	12 Months Ended
Related Party Transactions	Dec. 31, 2017
Related Party Transactions [Abstract]
Related Party Transactions	NOTE S—RELATED PARTY TRANSACTIONS A current officer of one of our operating subsidiaries holds an ownership interest in a transportation brokerage and logistics services vendor, from which we made purchases of approximately $4.7 million and $0.8 million for the years ended December 31, 2017 and 2016, respectively.

Summary of Significant Accounting Policies (Policies)	12 Months Ended
Summary of Significant Accounting Policies (Policies)	Dec. 31, 2017
Accounting Policies [Abstract]
Basis of Presentation and Consolidation	Basis of Presentation and Consolidation The accompanying Consolidated Financial Statements (the “Financial Statements”) have been prepared in accordance with generally accepted accounting principles in the United States (“GAAP”). In the opinion of management, all adjustments necessary for a fair presentation of the Financial Statements have been included. Such adjustments are of a normal, recurring nature. Certain reclassifications of prior years’ amounts have been made to conform to the current year presentation. In order to make this report easier to read, we refer throughout to (i) our Consolidated Balance Sheets as our “Balance Sheets,” (ii) our Consolidated Statements of Operations as our “Income Statements,” and (iii) our Consolidated Statements of Cash Flows as our “Cash Flows.”
Consolidation	Consolidation The Financial Statements include the accounts of Holdings and its direct and indirect wholly-owned subsidiaries. All significant intercompany balances and transactions have been eliminated in consolidation. We follow FASB Accounting Standards Codification (“ASC”) guidance for identification and reporting of entities over which control is achieved through means other than voting rights. The guidance defines such entities as Variable Interest Entities (“VIEs”). For the periods presented herein, we have identified no VIE entities over which we maintain any level of control that would require consolidation under ASC guidance.
Use of Estimates and Assumptions	Use of Estimates and Assumptions The preparation of the Financial Statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and the related disclosure of contingent assets and liabilities at the date of the Financial Statements and the reported amounts of revenues and expenses during the reporting period. The more significant areas requiring the use of management estimates and assumptions relate to purchase price allocation for businesses acquired; mineral reserves that are the basis for future cash flow estimates utilized in impairment calculations and units-of-production amortization calculations; environmental, reclamation and closure obligations; estimates of recoverable minerals; estimates of allowance for doubtful accounts; estimates of fair value for certain reporting units and asset impairments (including impairments of goodwill and other long-lived assets); write-downs of inventory to net realizable value; equity-based compensation expense; post-employment, post-retirement and other employee benefit liabilities; valuation allowances for deferred tax assets; contingent considerations; reserves for contingencies and litigation; and the fair value and accounting treatment of financial instruments including derivative instruments. We base our estimates on historical experience and on various other assumptions that are believed to be reasonable under the circumstances. Accordingly, actual results may differ significantly from these estimates under different assumptions or conditions.
Revenue Recognition	The preparation of the Financial Statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and the related disclosure of contingent assets and liabilities at the date of the Financial Statements and the reported amounts of revenues and expenses during the reporting period. The more significant areas requiring the use of management estimates and assumptions relate to purchase price allocation for businesses acquired; mineral reserves that are the basis for future cash flow estimates utilized in impairment calculations and units-of-production amortization calculations; environmental, reclamation and closure obligations; estimates of recoverable minerals; estimates of allowance for doubtful accounts; estimates of fair value for certain reporting units and asset impairments (including impairments of goodwill and other long-lived assets); write-downs of inventory to net realizable value; equity-based compensation expense; post-employment, post-retirement and other employee benefit liabilities; valuation allowances for deferred tax assets; contingent considerations; reserves for contingencies and litigation; and the fair value and accounting treatment of financial instruments including derivative instruments. We base our estimates on historical experience and on various other assumptions that are believed to be reasonable under the circumstances. Accordingly, actual results may differ significantly from these estimates under different assumptions or conditions. Revenue Recognition We derive most of our sales by mining and processing minerals that our customers purchase for various uses. Our product sales are primarily a function of the price per ton and the number of tons sold. The amount invoiced reflects product, transportation and/or additional services as applicable, such as storage, transloading the product from railcars to trucks and last mile logistics to the customer site. Revenue is recognized from a sale when persuasive evidence of an arrangement exists
Cash and Cash Equivalents	Cash and Cash Equivalents Cash and cash equivalents consist of all highly liquid investments with a maturity of three months or less when purchased. Because of the short maturity of these investments, the carrying amounts approximate their fair value. Cash and cash equivalents are invested primarily in money market securities held by financial institutions with high credit ratings. Accounts at each institution are insured by the Federal Deposit Insurance Corporation. Cash balances at times may exceed federally-insured limits. We have not experienced any losses in such accounts and believe we are not exposed to any significant credit risk on cash.
Accounts Receivable	Accounts Receivable The majority of our accounts receivable are due from companies in the oil and natural gas drilling, glass, building products, filler and extenders, foundries and other major industries. Credit is extended based on evaluation of a customer’s financial condition and, generally, collateral is not required. Accounts receivable are stated at amounts due from customers net of an allowance for doubtful accounts. Accounts outstanding longer than the payment terms are considered past due. We determine our allowance by considering a number of factors, including the length of time trade accounts receivable are past due, our previous loss history, the customer’s current ability to pay its obligation to us, and the condition of the general economy and the industry as a whole. Ongoing credit evaluations are performed. We write-off accounts receivable when they are deemed uncollectible, and payments subsequently received on such receivables are credited to the allowance for doubtful accounts.
Inventories	Inventories Inventories include raw stockpiles and silica and other industrial sand available for shipment, as well as spare parts and supplies for routine facility maintenance. We value inventory at the lower of cost and net realizable value. Cost is determined using the first-in, first-out and average cost methods. Costs of our raw stockpiles and silica and other industrial sand inventories include production costs and transportation and additional service costs as applicable.
Property, Plant and Mine Development	Property, Plant and Mine Development Plant and equipment Plant and equipment is recorded at cost and depreciated over their estimated useful lives. Interest incurred during construction of facilities is capitalized and depreciated over the life of the asset. Costs for normal repairs and maintenance that do not extend economic life or improve service potential are expensed as incurred. Costs of improvements that extend economic life or improve service potential are capitalized and depreciated over the estimated remaining useful life. Depreciation is recorded using the straight-line method over the assets’ estimated useful lifes as follows: buildings (15 years); land improvements (10 years); machinery and equipment, including computer equipment and software (3-10 years); furniture and fixtures (8 years). Leasehold improvements are depreciated over the shorter of the asset life or lease term. Construction-in-progress is primarily comprised of machinery and equipment which have not yet been placed in service. Mining property and development Mining property and development includes mineral deposits and mine exploration and development. Mineral deposits are initially recognized at cost, which approximates the estimated fair value on the date of purchase. Mine exploration and development costs include engineering and mineral studies, drilling and other related costs to delineate an ore body, and the removal of overburden to initially expose an ore body for production. Costs incurred before mineralization are classified as proven and probable reserves are expensed and classified as exploration or advanced projects, research and development expense. Capitalization of mine development project costs, that meet the definition of an asset, begins once mineralization is classified as proven and probable reserves. The cost of removing overburden and waste materials to access the ore body at an open pit mine prior to the production phase are referred to as “pre-stripping costs.” Pre-stripping costs are capitalized during the development of an open pit mine. The production phase of an open pit mine commences when saleable minerals, beyond a de minimis amount, are produced. Stripping costs incurred during the production phase of a mine are variable production costs that are included as a component of inventory to be recognized in costs applicable to sales in the same period as the revenue from the sale of inventory. Depletion and amortization of mineral deposits and mine development costs are recorded as the minerals are extracted, based on units of production and engineering estimates of mineable reserves. The impact of revisions to reserve estimates is recognized on a prospective basis. Mine reclamation costs and asset retirement obligations We recognize the fair value of any liability for conditional asset retirement obligations, including environmental remediation liabilities when incurred, which is generally upon acquisition, construction or development and/or through the normal operation of the asset, if sufficient information exists to reasonably estimate the fair value of the liability. These obligations generally include the estimated net future costs of dismantling, restoring and reclaiming operating mines and related mine sites, in accordance with federal, state, local regulatory and land lease agreement requirements. The liability is accreted over time through periodic charges to earnings. In addition, the asset retirement cost is capitalized as part of the asset’s carrying value and amortized over the life of the related asset. Reclamation costs are periodically adjusted to reflect changes in the estimated present value resulting from the passage of time and revisions to the estimates of either the timing or amount of the reclamation and abandonment costs. The reclamation obligation is based on when spending for an existing environmental disturbance will occur. If the asset retirement obligation is settled for other than the carrying amount of the liability, a gain or loss is recognized on settlement. We review, on an annual basis, unless otherwise deemed necessary, the reclamation obligation at each mine site in accordance with ASC guidance for accounting reclamation obligations. Future remediation costs for inactive mines are accrued based on management’s best estimate at the end of each period of the costs expected to be incurred at a site. Such cost estimates include, where applicable, ongoing care, maintenance and monitoring costs. Changes in estimates at inactive mines are reflected in earnings in the period an estimate is revised. In connection with our annual review of our reclamation obligations, we have determined that some of our estimates required revision due primarily to the additions of new plant and transload facilities and other changes in cost estimates and settlement dates at various sites. These additions and changes in estimates resulted in an additional $7.0 million and $(2.1) million of asset retirement obligations in 2017 and 2016, respectively.
Impairment or Disposal of Property, Plant and Mine Development	Impairment or Disposal of Property, Plant and Mine Development Gains on the sale of property, plant and mine development are included in income when the assets are disposed of provided there is more than reasonable certainty of the collectability of the sales price and any future activities required to be performed by us relating to the disposal of the assets are complete or insignificant. Upon retirement or disposal of assets, all costs and related accumulated depreciation or amortization are written-off. We periodically evaluate whether current events or circumstances indicate that the carrying value of our property, plant and equipment assets may not be recoverable. If circumstances indicate that the carrying value may not be recoverable, we estimate future undiscounted net cash flows using estimates of proven and probable sand reserves, estimated future sales prices (considering historical and current prices, price trends and related factors) and operating costs and anticipated capital expenditures. If the undiscounted cash flows are less than the carrying value of the assets, we recognize an impairment loss equal to the amount by which the carrying value exceeds the fair value of the assets.
Goodwill and Other Intangible Assets and Related Impairment	Goodwill and Other Intangible Assets and Related Impairment Our intangible assets consist of goodwill, which is not being amortized, indefinite lived intangibles, which consist of certain trade names that are not subject to amortization, intellectual property and customer relationships. Intellectual property mainly consists of patents and technology, and it is amortized on a straight-line basis over an average useful life of 15 years. Customer relationships are amortized on a straight-line basis over their useful life of 20, 15 or 13 years. Goodwill represents the excess of purchase price over the fair value of net assets from business acquisitions. Goodwill and trade names are reviewed for impairment annually as of October 31 or more frequently whenever events or circumstances change that would more likely than not reduce the fair value of those assets. Prior to conducting a formal impairment test, we have an option to assess qualitative factors to determine whether the existence of events or circumstances leads to a determination that is more likely than not (more than 50%) that the fair value of a reporting unit is less than its carrying amount. Such qualitative factors may include the following: macroeconomic conditions; industry and market considerations; cost factors; overall financial performance; and other relevant entity-specific events. If the qualitative assessment determines that an impairment is more likely than not, or if we choose to bypass the qualitative assessment, we perform a quantitative comparison of the fair value with the carrying amount, including goodwill. If this comparison reflects impairment, then the loss would be measured as the excess of recorded goodwill, or other intangible assets with indefinite lives, over its implied fair value. Implied fair value is the excess of our fair value over the fair value of all recognized and unrecognized assets and liabilities. As of October 31, 2017, our qualitative assessment did not indicate that it was more likely than not that an impairment had occurred. Further, no triggering events have subsequently transpired that would indicate a potential impairment as of December 31, 2017.
Debt Issuance Costs	Debt Issuance Costs The Company defers costs directly associated with acquiring third-party financing, primarily loan origination costs and related professional expenses. Debt issuance costs are deferred and amortized using the effective interest rate method over the term of our senior secured term loan facility (the “Term Loan”) and the straight-line method for our revolving line-of-credit (the "Revolver"). Debt issuance costs related to long-term debt are reflected as a direct deduction from the carrying amount of the debt. Amortization included in interest expense was $1.4 million for each of the years ended December 31, 2017, 2016 and 2015, respectively.
Environmental Costs	Environmental Costs Environmental costs, other than qualifying capital expenditures, are accrued at the time the exposure becomes known and costs can be reasonably estimated. Costs are accrued based upon management’s estimates of all direct costs, after taking into account expected reimbursement by third parties (primarily the sellers of acquired businesses), and are reviewed by outside consultants. Environmental costs are charged to expense unless a settlement with an indemnifying party has been reached.
Self-Insurance	Self-Insurance We are self-insured for various levels of employee health insurance coverage, workers’ compensation and third party product liability claims alleging occupational disease. We purchase insurance coverage for claim amounts which exceed our self-insured retentions. Depending on the type of insurance, these self-insured retentions range from $0.1 million to $0.5 million per occurrence. Our insurance reserves are accrued based on estimates of the ultimate cost of claims expected to occur during the covered period. The current portion of our self-insurance reserves is included in accrued liabilities and the non-current portion is included in other long-term obligations in our Balance Sheets. At December 31, 2017 and 2016, our self-insurance reserves totaled $5.5 million and $5.3 million, respectively, of which $1.7 million and $1.3 million, respectively, was classified as current
Equity-based Compensation	Equity-based Compensation We grant stock options, restricted stock, restricted stock units and performance share units to certain of our employees and directors under the Amended and Restated U.S. Silica Holdings, Inc. 2011 Incentive Compensation Plan. We recognize the cost of employee services rendered in exchange for awards of equity instruments. Vesting of restricted stock and restricted stock units is based on the individual continuing to render service over a three-year vesting schedule. Cash dividend equivalents are accrued and paid to the holders of time based restricted stock units and restricted stock. The fair value of the restricted stock awards is equal to the market price of our stock at date of grant. The restricted award-related compensation expense is recognized, on a straight-line basis, over the vesting period. We grant performance share units to certain employees in which the number of shares of common stock ultimately received is determined based on achievement of certain performance thresholds over a specified performance period (generally three years) in accordance with the stock award agreement. Cash dividend equivalents are not accrued or paid on performance share units. We recognize expense based on the estimated vesting of our performance share units granted and the grant date market price. The estimated vesting of the performance share units is principally based on the probability of achieving certain financial performance levels during the vesting periods. In the period it becomes probable that the minimum performance criteria specified in the award agreement will be achieved, we recognize expense for the proportionate share of the total fair value of the award related to the vesting period that has already lapsed. The remaining fair value of the award is expensed on a straight-line basis over the remaining vesting period. During the years ended December 31, 2017 and 2016, we granted certain employees performance share units, the vesting of which is based on the Company’s total shareholder return (“TSR”) ranking among a peer group over the three-year period from January 1, 2017 through December 31, 2019 for the 2017 awards and from January 1, 2016 through December 31, 2018 for the 2016 awards. The number of units that will vest will depend on the percentage ranking of the Company's TSR compared to the TSRs for each of the companies in the peer group over the performance period. For these awards subject to market conditions, a binomial-lattice model (i.e., Monte Carlo simulation model) is used to fair value these awards at grant date. The related compensation expense is recognized, on a straight-line basis, over the vesting period. We grant stock options to certain employees and directors. Stock options vest on a vesting schedule and the related compensation expense is recognized over the vesting period, usually over 3 or 4 years. In calculating the compensation expense for stock options granted, we estimate the fair value of each grant using the Black-Scholes option-pricing model. The fair value of stock options granted is based on the exercise price of the option and certain assumptions, which are evaluated and revised, as necessary, to reflect market conditions and experience. Our expected forfeiture rate is the estimated percentage of options granted that are expected to be forfeited or canceled on an annual basis before becoming fully vested. Our expected term is the period of time over which the options are expected to remain outstanding. An increase in the expected term will increase compensation expense. The computation of the expected term is based on the simplified method, under which the expected term is presumed to be the mid-point between the average vesting date and the end of the contractual term. The assumptions for expected volatility are based on historical experience for the same periods as our expected lives. Risk-free interest rates are set using grant-date U.S. Treasury yield curves for the same periods as our expected lives. The expected dividend yield is based on our future dividend expectations for the same periods as our expected lives.
Income Taxes	Income Taxes Deferred taxes are provided on the liability method whereby deferred tax assets are recognized for deductible temporary differences and operating loss and tax credit carry forwards and deferred tax liabilities are recognized for taxable temporary differences. This approach requires recognition of deferred tax liabilities and assets for the expected future tax consequences of events that have been included in the financial statements or tax returns. Under this method, deferred tax liabilities and assets are determined based upon the difference between the financial statement and tax basis of assets and liabilities using enacted tax rates in effect for the year in which the expenses are expected to reverse. Valuation allowances are provided if, based on the weight of available evidence, it is more likely than not that some or all of the deferred tax assets will not be realized. We recognize a tax benefit associated with an uncertain tax position when, in management’s judgment, it is more likely than not that the position will be sustained upon examination by a taxing authority. For a tax position that meets the more-likely-than-not recognition threshold, we initially and subsequently measure the tax benefit as the largest amount that we judge to have a greater than 50% likelihood of being realized upon ultimate settlement with a taxing authority. The liability associated with unrecognized tax benefits is adjusted periodically due to changing circumstances, such as the progress of tax audits, case law developments and new or emerging legislation. Such adjustments are recognized entirely in the period in which they are identified. The effective tax rate includes the net impact of changes in the liability for unrecognized tax benefits and subsequent adjustments as considered appropriate by management. The largest permanent item in computing both our effective tax rate and taxable income is the deduction allowed for statutory depletion. The deduction for statutory depletion does not necessarily change proportionately to changes in income before income taxes.
Earnings per Share	Earnings per Share Basic and diluted earnings per share is presented for net income (loss). Basic earnings per common share is computed by dividing income available to common stockholders by the weighted average number of common shares outstanding for the period. Diluted earnings per common share is computed similarly to basic earnings per common share except that the weighted average number of common shares outstanding is increased to include the number of additional common shares that would have been outstanding if the potentially dilutive common shares had been issued. In accordance with the applicable accounting guidance for calculating earnings per share, we did not include in our calculation of diluted earnings per share for the applicable periods stock options where the exercise prices were greater than the average market prices.
Comprehensive Income (loss)	Comprehensive Income (loss) In addition to net income (loss), comprehensive income (loss) includes all changes in equity during a period, such as adjustments to minimum pension liabilities and the effective portion of changes in fair value of derivative instruments that qualify as cash flow hedges.
Financial Instruments	Financial Instruments We currently use interest rate hedge agreements to manage interest costs and the risk associated with changing interest rates. Amounts to be paid or received under these hedge agreements are accrued as interest rates change and are recognized over the life of the hedge agreements as an adjustment to interest expense. Our policy is to not hold or issue derivative financial instruments for trading or speculative purposes. When entered into, these financial instruments are designated as hedges of underlying exposures, associated with our long-term debt, and are monitored to determine if they remain effective hedges. Gains and losses on derivatives designated as cash flow hedges are recorded in other comprehensive income (loss), net of tax, and reclassified to earnings in a manner that matches the timing of the earnings impact of the hedged transactions. The ineffective portion of all hedges, if any, is recognized currently in income. Additional disclosures for derivative instruments are presented in Note M - Derivative Instruments to these financial statements.
Business Combinations	Business Combinations The Company accounts for business combinations using the acquisition method of accounting. Under this method, acquired assets, including separately identifiable intangible assets and any assumed liabilities, are recorded at their acquisition date estimated fair value. The excess of purchase price over the fair value amounts assigned to the assets acquired and liabilities assumed represents the goodwill amount resulting from the acquisition. Determining the fair value of assets acquired and liabilities assumed involves the use of significant estimates and assumptions.
Recently Adopted and Issued Accounting Pronouncements	Recently Issued Accounting Pronouncements In May 2014, the Financial Accounting Standards Board ("FASB") issued Accounting Standards Update (“ASU”) 2014-09, Revenue from Contracts with Customers (Topic 606) which supersedes previous revenue recognition guidance. The new guidance introduces a new principles-based framework for revenue recognition and disclosure. Since its issuance, the FASB has issued additional ASUs, amending the guidance and the effective dates of amendments, and the SEC has rescinded certain related SEC guidance. The pronouncements are effective for annual reporting periods beginning after December 15, 2017, including interim reporting periods within that reporting period. Based on our reviews, there is no material impact to the Company’s results of operations, financial position and cash flows as a result of this guidance. Companies can use either a full retrospective or modified retrospective method to adopt the standard. The Company has elected to apply the modified retrospective approach. Under the modified retrospective method, prior periods are not updated to be presented on an accounting basis that is consistent with 2018; rather, a cumulative adjustment for the effects of applying the new standard to periods prior to 2018 is recorded to retained earnings as of January 1, 2018. Because only 2018 revenues will reflect application of the new standard, incremental disclosures are required to present 2018 revenues under the prior standard. The new standard requires companies to identify contractual performance obligations and determine whether revenue should be recognized at a point in time or over time based on when control of goods and services transfer to a customer. As a result of our implementation review, we do not expect significant changes in the presentation of our financial statements, including either: (1) timing of revenue recognition, or (2) changes in classification between revenue and costs. The new standard will have no cash flow impact and, as such, does not affect the underlying economics of our customer contracts. The effect of applying the new guidance to our existing book of contracts will be minimal. Application of this method will not result in a material cumulative effect adjustment as of the date of adoption. We do not expect application of the new guidance to result in increases or decreases in revenue within our segments, or any material impact on our balance sheets. In February 2016, the FASB issued ASU 2016-02, Leases (Topic 842). The new standard establishes a right-of-use (ROU) model that requires a lessee to record an ROU asset and a lease liability on the balance sheet for all leases with terms greater than 12 months. Leases will be classified as either finance or operating, with classification affecting the pattern of expense recognition. Similarly, lessors will be required to classify leases as sales-type, finance or operating, with classification affecting the pattern of income recognition. Classification for both lessees and lessors will be based on an assessment of whether risks and rewards as well as substantive control have been transferred through a lease contract. This update is effective for public entities for financial statements issued for fiscal years beginning after December 15, 2018, including interim periods within those fiscal years, and early adoption is permitted. This standard mandates a modified retrospective transition method. While we continue to evaluate the effect of the standard, we anticipate that the adoption will result in a material increase in assets and liabilities on our consolidated balance sheet and will not have a material impact on our consolidated income statement or statement of cash flows. In August 2016, the FASB issued ASU 2016-15, “Classification of Certain Cash Receipts and Cash Payments,” which amends guidance on the classification of certain cash receipts and payments in the statement of cash flows. This ASU adds or clarifies guidance on eight specific cash flow issues. Additionally, guidance on the presentation of restricted cash is addressed in ASU 2016-18, Statement of Cash Flows (Topic 230): Restricted Cash, which was issued in November 2016. Both standards are effective for annual reporting periods beginning after December 15, 2017, and interim reporting periods within those annual reporting periods. Early adoption is permitted. Adoption of these standards will not have a material impact on our consolidated Statements of Cash Flows. In January 2017, the FASB issued ASU 2017-01, Business Combinations (Topic 805): Clarifying the Definition of a Business. The new guidance clarifies the definition of a business with the objective of adding guidance to assist companies and other reporting organizations with evaluating whether transactions should be accounted for as acquisitions (or disposals) of assets or businesses. The changes to the definition of a business will likely result in more acquisitions being accounted for as asset acquisitions. ASU 2017-01 is effective for annual periods beginning after December 15, 2017, including interim periods within those periods. Early application of the amendments in ASU 2017-01 is allowed for a transaction(s) for which the acquisition date occurs before the issuance date or effective date of the amendments, a subsidiary is deconsolidated or a group of assets is derecognized only when the transaction(s) has (have) not been reported in financial statements that have been issued or made available for issuance. We do not expect the adoption of this standard to have a material impact on our consolidated financial statements. In January 2017, the FASB issued ASU 2017-04, Intangibles - Goodwill and Other (Topic 350): Simplifying the Test for Goodwill Impairment, which removes Step 2 from the goodwill impairment test. It is effective for annual and interim periods beginning after December 15, 2019. Early adoption is permitted for interim or annual goodwill impairment tests performed with a measurement date after January 1, 2017. We do not expect the adoption of this standard to have a material impact on our consolidated financial statements. In March 2017, the FASB issued ASU 2017-07, Compensation-Retirement Benefits (Topic 715), Improving the Presentation of Net Periodic Pension Cost and Net Periodic Postretirement Benefit. ASU 2017-07 amends presentation requirements related to reporting the service cost component of net benefit costs to require that the service cost component be reported in the same line item or items as other compensation costs arising from services rendered by the pertinent employees during the period, disaggregating the component from other net benefit costs. ASU 2017-07 also limits the components of net benefit cost eligible to be capitalized to service cost. ASU 2017-07 is effective for fiscal years beginning after December 15, 2017, including interim periods within those annual periods for public business entities. Early adoption is permitted as of the beginning of an annual period for which financial statements (interim or annual) have not been issued or made available for issuance. Early adoption should be within the first interim period if an employer issues interim financial statements. Disclosures of the nature of and reason for the change in accounting principle are required in the first interim and annual periods of adoption. We do not expect the adoption of this standard to have a material impact on our consolidated financial statements. In May 2017, the FASB issued ASU 2017-09, Compensation-Stock Compensation (Topic 718), Scope of Modification Accounting. This update amends the scope of modification accounting for share-based payment arrangements. ASU 2017-09 provides guidance on the types of the changes to the terms or conditions of share-based payments awards to which an entity would be required to apply modification accounting. Specifically, an entity would not apply modification accounting if the fair value, vesting conditions, and classification of the awards are the same immediately before and after the modification. ASU 2017-09 is effective for fiscal years beginning after December 15, 2017, including interim periods within those annual periods for all entities. Early adoption is permitted, including adoption in any interim period, for public business entities for reporting periods for which financial statements have not yet been issued. We do not expect the adoption of this standard to have a material impact on our consolidated financial statements.

Summary of Significant Accounting Policies (Tables)

12 Months Ended

Dec. 31, 2017

Accounting Policies [Abstract]

Changes in Asset Retirement Obligation

The changes in these obligations (in thousands) during the years ending December 31, 2017 and 2016 are as follows:



	2017		2016
Beginning balance	$	11,159	$	12,254
Accretion	879		979
Additions and revisions of prior estimates	6,994		(2,074		)
Ending balance	$	19,032	$	11,159

Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share

The weighted-average stock awards (in thousands) that are antidilutive and are, therefore, excluded from the calculation of diluted earnings per common share are as follows:



	For the Year Ended December 31,
	2017	2016	2015
Weighted-average outstanding stock options excluded	195	573	528
Weighted-average outstanding restricted stock and performance share units awards excluded	305	166	66

Capital Structure and Accumulated Comprehensive Income (Tables)

12 Months Ended

Dec. 31, 2017

Equity [Abstract]

Schedule of Declared Quarterly Dividends

In 2017, our Board of Directors declared quarterly cash dividends as follows:



Dividends per Common Share		Declaration Date	Record Date	Payable Date
$	0.0625	February 16, 2017	March 15, 2017	April 5, 2017
$	0.0625	May 4, 2017	June 15, 2017	July 6, 2017
$	0.0625	July 21, 2017	September 15, 2017	October 3, 2017
$	0.0625	November 2, 2017	December 15, 2017	January 5, 2018

Changes in Accumulated Other Comprehensive Income

The following table presents the changes in accumulated other comprehensive income (loss) by component (in thousands) during the year ended December 31, 2017:



	For the Year Ended December 31, 2017
	Unrealized gain/(loss) on cash flow hedges			Foreign currency translation adjustment			Pension and other post- retirement benefits liability			Total
Beginning Balance	$	(32	)	$	—		$	(15,844	)	$	(15,876	)
Other comprehensive gain (loss) before reclassifications	(45		)	(6		)	871			820
Amounts reclassed from accumulated other comprehensive income	1			—			1,129			1,130
Ending Balance	$	(76	)	$	(6	)	$	(13,844	)	$	(13,926	)

Business Combinations (Tables)

12 Months Ended

Dec. 31, 2017

Business Combinations [Abstract]

Schedule of Business Acquisitions, by Acquisition

The calculation of the purchase price (in thousands, except shares) is as follows:




Cash consideration paid			$	116,165
Number of Holdings common shares delivered	2,630,513
Multiplied by closing market price per share of U.S. Silica common stock on August 16, 2016	$	40.51
Total value of Holdings common shares delivered			$	106,562
Less, cash acquired			$	(9,002	)
Total purchase price			$	213,725

The calculation of the purchase price (in thousands, except shares) is as follows:




Cash consideration paid			$	70,760
Number of Holdings common shares delivered	4,195,180
Multiplied by closing market price per share of U.S. Silica common stock on August 22, 2016	$	40.92
Total value of Holdings common shares delivered			$	171,667
Less, cash acquired			$	(1,306	)
Total purchase price			$	241,121

Schedule of Identifiable Assets Acquired and Liabilities Assumed

The following table sets forth the allocation of the purchase price to Sandbox’s identifiable tangible and intangible assets acquired and liabilities assumed (in thousands):



Allocation of Purchase price:	(in thousands)
Accounts receivable	$	13,392
Prepaid expenses and other	1,465
Property, plant and mine development	32,336
Identifiable intangible assets	120,144
Goodwill	86,100
Total assets acquired	253,437
Accounts payable	4,122
Deferred revenue	4,902
Accrued expenses and other current liabilities	3,292
Total liabilities assumed	12,316
Net assets acquired	$	241,121



	Initial Estimate		Measurement Period Adjustments			Purchase Price Allocation
Accounts receivable	$	11,201	$	—		$	11,201
Inventories	6,087		1,980			8,067
Other current assets	362		—			362
Assets held for sale	9,523		(70		)	9,453
Property, plant and mine development	26,440		1,018			27,458
Mineral rights	—		26,300			26,300
Other non-current assets	1,136		—			1,136
Goodwill	52,187		(29,665		)	22,522
Customer relationships	—		1,840			1,840
Total assets acquired	106,936		1,403			108,339
Accounts payable and accrued expenses	3,815		(54		)	3,761
Unfavorable leasehold positions	—		2,237			2,237
Notes Payable	866		—			866
Other long term liabilities	1,254		(1,254		)	—
Asset retirement obligations	—		474			474
Total liabilities assumed	5,935		1,403			7,338
Net assets acquired	$	101,001	$	—		$	101,001



	Initial Estimate		Measurement Period Adjustments			Purchase Price Allocation
Accounts receivable	$	2,680	$	—		$	2,680
Inventories	3,494		—			3,494
Other current assets	428		—			428
Income tax deposits	6,657		(217		)	6,440
Property, plant and mine development	210,913		(4,281		)	206,632
Identifiable intangible assets	1,600		—			1,600
Goodwill	86,228		4,670			90,898
Total assets acquired	312,000		172			312,172
Accounts payable, accrued expenses and other current liabilities	1,938		726			2,664
Deferred revenue	500		—			500
Notes payable	24,361		243			24,604
Capital lease liabilities	3,331		—			3,331
Asset retirement obligations	710		—			710
Deferred tax liabilities	67,435		(797		)	66,638
Total liabilities assumed	98,275		172			98,447
Net assets acquired	$	213,725	$	—		$	213,725

Summary of Identifiable Intangible Assets

The acquired intangible assets and the related estimated useful lives consist of the following:



	Approximate Fair Value		Estimated Useful Life
	(in thousands)		(in years)
Customer relationships	$	1,840	15

The acquired intangible assets and the related estimated useful lives consist of the following:



	Approximate Fair Value		Estimated Useful Life
	(in thousands)		(in years)
Indefinite lived intangible assets - Trade names	$	17,844	Indefinite
Definite lived intangible assets - Technology and intellectual property	57,700		15
Definite lived intangible asset - Customer relationships	44,600		13
Total fair value of identifiable intangible assets	$	120,144

The acquired intangible assets and the related estimated useful lives consist of the following:



	Approximate Fair Value		Estimated Useful Life
	(in thousands)		(in years)
Customer relationships	$	1,600	13

Pro Forma Summary

This information does not purport to be indicative of the actual results that would have occurred if the acquisition had actually been completed on the date indicated, nor is it necessarily indicative of the future operating results or the financial position of the combined company (in thousands, except per share amounts):



	For the year ended December 31,
	2016			2015
Sales	$	615,552		$	753,287
Net income (loss)	$	(45,161	)	$	43,163
Basic earnings per share	$	(0.69	)	$	0.81
Diluted earnings per share	$	(0.69	)	$	0.81



	For the year ended December 31,
	2017		2016
Sales	$	1,287,202	$	642,951
Net income (loss)	$	143,604	$	(55,835	)
Basic earnings (loss) per share	$	1.77	$	(0.86	)
Diluted earnings (loss) per share	$	1.75	$	(0.86	)

Accounts Receivable (Tables)

12 Months Ended

Dec. 31, 2017

Receivables [Abstract]

Schedule of Accounts Receivable

At December 31, 2017 and 2016, accounts receivable (in thousands) consisted of the following:



	At December 31,
	2017			2016
Trade receivables	$	217,649		$	93,982
Less: Allowance for doubtful accounts	(7,100		)	(7,042		)
Net trade receivables	210,549			86,940
Other receivables	2,037			2,066
Total accounts receivable	$	212,586		$	89,006

Changes in our allowance for doubtful accounts (in thousands) during the years ended December 31, 2017 and 2016 are as follows:



	Allowance for Doubtful Accounts
	2017			2016
Balance at January 1,	$	7,042		$	7,686
Bad debt provision	1,529			(1,232		)
Write-offs and recoveries, net	(1,471		)	588
Balance at December 31,	$	7,100		$	7,042

Inventories (Tables)

12 Months Ended

Dec. 31, 2017

Inventory Disclosure [Abstract]

Schedule of Inventories

At December 31, 2017 and 2016, inventories (in thousands) consisted of the following:



	At December 31,
	2017		2016
Supplies	$	21,277	$	18,824
Raw materials and work in process	28,034		25,161
Finished goods	43,065		34,724
Total inventories	$	92,376	$	78,709

Property, Plant and Mine Development (Tables)

12 Months Ended

Dec. 31, 2017

Property, Plant and Equipment [Abstract]

Schedule of Property, Plant and Mine Development

At December 31, 2017 and 2016, property, plant and mine development (in thousands) consisted of the following:



	At December 31,
	2017			2016
Mining property and mine development	$	586,242		$	414,434
Asset retirement cost	14,184			8,062
Land	36,552			35,052
Land improvements	45,878			42,738
Buildings	56,330			52,178
Machinery and equipment	590,566			450,881
Furniture and fixtures	2,953			2,566
Construction-in-progress	189,970			43,790
	1,522,675			1,049,701
Accumulated depletion, depreciation and amortization	(353,520		)	(266,388		)
Total property, plant and mine development, net	$	1,169,155		$	783,313

Goodwill and Intangible Assets (Tables)

12 Months Ended

Dec. 31, 2017

Goodwill and Intangible Assets Disclosure [Abstract]

Schedule of Changes in the Carrying Amount of Goodwill

The changes in the carrying amount of goodwill (in thousands) consisted of the following:



	Goodwill
Balance at December 31, 2015	$	68,647
NBI acquisition	86,228
Sandbox acquisition	86,100
Balance at December 31, 2016	240,975
White Armor acquisition	3,912
NBI acquisition measurement period adjustment	4,670
MS Sand acquisition	52,187
MS Sand acquisition measurement period adjustment	(29,665		)
Balance at December 31, 2017	$	272,079

Schedule of Changes in the Carrying Amount of Definite-Lived Intangible Assets

The changes in the carrying amount of intangible assets (in thousands) consisted of the following:



		December 31, 2017							December 31, 2016
	Estimated Useful Life	Gross Carrying Amount		Accumulated Amortization			Net		Gross Carrying Amount		Accumulated Amortization			Net
	(in years)
Technology and intellectual property	15	$	70,703	$	(5,917	)	$	64,786	$	58,658	$	(1,388	)	$	57,270
Customer relationships	13 - 15	61,229		(9,076		)	52,153		55,689		(4,799		)	50,890
Total definite-lived intangible assets:		$	131,932	$	(14,993	)	$	116,939	$	114,347	$	(6,187	)	$	108,160
Trade name		33,068		—			33,068		32,318		—			32,318
Total intangible assets:		$	165,000	$	(14,993	)	$	150,007	$	146,665	$	(6,187	)	$	140,478

Schedule of Changes in the Carrying Amount of Indefinite-Lived Intangible Assets

The changes in the carrying amount of intangible assets (in thousands) consisted of the following:



		December 31, 2017							December 31, 2016
	Estimated Useful Life	Gross Carrying Amount		Accumulated Amortization			Net		Gross Carrying Amount		Accumulated Amortization			Net
	(in years)
Technology and intellectual property	15	$	70,703	$	(5,917	)	$	64,786	$	58,658	$	(1,388	)	$	57,270
Customer relationships	13 - 15	61,229		(9,076		)	52,153		55,689		(4,799		)	50,890
Total definite-lived intangible assets:		$	131,932	$	(14,993	)	$	116,939	$	114,347	$	(6,187	)	$	108,160
Trade name		33,068		—			33,068		32,318		—			32,318
Total intangible assets:		$	165,000	$	(14,993	)	$	150,007	$	146,665	$	(6,187	)	$	140,478

Schedule of Estimated Amortization Expense Related to Definite-Lived Intangible Assets

The estimated amortization expense related to definite-lived intangible assets (in thousands) for the five succeeding years is as follows:



2018	$	9,239
2019	9,239
2020	9,239
2021	9,239
2022	9,224

Debt and Capital Leases (Tables)

12 Months Ended

Dec. 31, 2017

Debt Disclosure [Abstract]

Schedule of Debt

At December 31, 2017 and 2016, debt (in thousands) consisted of the following:



	December 31, 2017			December 31, 2016
Senior secured credit facility:
Revolver expiring July 23, 2018 (5.75% at December 31, 2017 and 5.25% at December 31, 2016)	$	—		$	—
Term loan facility—final maturity July 23, 2020 (4.75%-5.25% at December 31, 2017 and 4.00% - 4.50% at December 31, 2016)	489,075			494,175
Less: Unamortized original issue discount	(944		)	(1,318		)
Less: Unamortized debt issuance cost	(3,099		)	(4,482		)
Note payable secured by royalty interest	24,740			23,076
Customer note payable	745			1,787
Equipment notes payable	719			—
Total debt	511,236			513,238
Less: current portion	(4,504		)	(4,821		)
Total long-term portion of debt	$	506,732		$	508,417

Schedule of Contractual Maturities of Debt

At December 31, 2017, contractual maturities of our senior secured credit facility (in thousands) are as follows:



2018	$	5,100
2019	5,100
2020	478,875
Total	$	489,075

The minimum payments (in thousands) for the next five years required by the note are as follows:



2018	$	1,750
2019	1,750
2020	1,750
2021	1,750
2022	1,750
Thereafter	15,990
Total	$	24,740

Debt and Capital Leases Disclosures

At December 31, 2017, scheduled future minimum lease payments under capital lease obligations (in thousands) are as follows:



2018	721
Total minimum lease payments	721
Less: amount representing interest	(15		)
Present value of minimum lease payments	706
Less: current portion of capital lease obligations	(706		)
Non-current portion of capital lease obligations	$	—

Fair Value Accounting (Tables)

12 Months Ended

Dec. 31, 2017

Fair Value Disclosures [Abstract]

Schedule of Measure at Fair Value on Recurring Basis



	December 31, 2017						December 31, 2016
	Level 1		Level 2		Total		Level 1		Level 2		Total
Interest rate derivatives	—		—		—		—		72		72
Net asset	$	—	$	—	$	—	$	—	$	72	$	72

Derivative Instruments (Tables)

12 Months Ended

Dec. 31, 2017

Derivative Instruments and Hedging Activities Disclosure [Abstract]

Estimated Fair Values of Derivative Instruments



		December 31, 2017								December 31, 2016
	Maturity Date	Contract/Notional Amount			Carrying Amount		Fair Value		Maturity Date	Contract/Notional Amount			Carrying Amount		Fair Value
Interest rate cap agreement⁽¹⁾	2019	$	249	million	$	—	$	—	2019	$	249	million	$	72	$	72

⁽¹⁾Agreements limit the LIBOR floating interest rate base to 4%.

Effect of Derivatives Instruments on Combined Statements of Operations and Comprehensive Income



	2017			2016			2015
Deferred losses from derivatives in OCI, beginning of period	$	(32	)	$	(81	)	$	(134	)
Loss recognized in OCI from derivative instruments	(45		)	(32		)	—
Gain reclassified from Accumulated OCI	1			81			53
Deferred losses from derivatives in OCI, end of period	$	(76	)	$	(32	)	$	(81	)

Equity-Based Compensation (Tables)

12 Months Ended

Dec. 31, 2017

Disclosure of Compensation Related Costs, Share-based Payments [Abstract]

Summary of Activity with Respect to Stock Options

The following table summarizes the status of, and changes in, our stock option awards during the year ended December 31, 2017:



	Number of Shares		Weighted Average Exercise Price	Aggregate Intrinsic Value (in thousands)		Weighted Average Remaining Contractual Term in Years
Outstanding at December 31, 2016	952,693		27.99
Granted	—		—
Exercised	(43,774	)	18.22
Forfeited	—		—
Outstanding at December 31, 2017	908,919		28.46	$	7,008	6.1 years
Exercisable at December 31, 2017	736,480		26.79	$	6,707	5.8 years

Summary of Restricted Stock Award Activity

The following table summarizes the status of, and changes in, our performance share unit awards during the year ended December 31, 2017:



	Number of Shares		Grant Date Weighted Average Fair Value
Unvested, December 31, 2016	963,613		$	37.43
Granted	90,501		67.69
Vested	—		—
Cancelled	(172,698	)	29.12
Unvested, December 31, 2017	881,416		$	42.16

The following table summarizes the status of, and changes in, our unvested restricted stock awards during the year ended December 31, 2017:



	Number of Shares		Grant Date Weighted Average Fair Value
Unvested, December 31, 2016	557,716		$	24.33
Granted	156,164		44.45
Vested	(248,031	)	24.92
Forfeited	(4,503	)	30.94
Unvested, December 31, 2017	461,346		$	30.76

Pension and Post-Retirement Benefits (Tables)

12 Months Ended

Dec. 31, 2017

Compensation and Retirement Disclosure [Abstract]

Summarizes Information about Pension and Post-Retirement Benefit Plans

Net pension benefit cost (in thousands) consisted of the following for the years ended December 31, 2017, 2016 and 2015:



	Years Ended December 31,
	2017			2016			2015
Service cost	$	1,037		$	1,078		$	1,295
Interest cost	3,971			4,067			4,813
Expected return on plan assets	(5,265		)	(5,495		)	(5,498		)
Net amortization and deferral	1,773			1,592			2,665
Net pension benefit costs	$	1,516		$	1,242		$	3,275

Net post-retirement cost (in thousands) consisted of the following for the years ended December 31, 2017, 2016 and 2015:



	Years Ended December 31,
	2017			2016			2015
Service cost	$	107		$	132		$	176
Interest cost	753			876			1,074
Expected return on plan assets	(1		)	(1		)	(1		)
Net amortization and deferral	—			—			281
Special termination benefit	—			21			48
Net post-retirement costs	$	859		$	1,028		$	1,578

Changes in Benefit Obligations and Plan Assets

The changes in benefit obligations and plan assets (in thousands), as well as the funded status (in thousands) of our pension and post-retirement plans at December 31, 2017 and 2016 are as follows:



	Pension Benefits						Post-retirement Benefits
	2017			2016			2017			2016
Benefit obligation at January 1,	$	116,145		$	115,420		$	24,393		$	25,091
Service cost	1,037			1,078			107			132
Interest cost	3,971			4,067			753			876
Actuarial (gain) loss	6,824			1,640			(1,576		)	(802		)
Benefits paid	(6,685		)	(6,517		)	(1,280		)	(1,332		)
Amendments	760			457			—			—
Special termination benefits	—			—			—			21
Other	—			—			374			407
Benefit obligation at December 31,	$	122,052		$	116,145		$	22,771		$	24,393
Fair value of plan assets at January 1,	$	83,850		$	84,716		$	14		$	17
Actual return on plan assets	12,757			5,651			(1		)	(3		)
Employer contributions	2,145			—			893			925
Benefits paid	(6,685		)	(6,517		)	(1,280		)	(1,332		)
Other	—			—			374			407
Fair value of plan assets at December 31,	$	92,067		$	83,850		$	—		$	14
Plan assets less than benefit obligations at December 31 recognized as liability for pension and other post-retirement benefits	$	(29,985	)	$	(32,295	)	$	(22,771	)	$	(24,379	)

Estimated Future Pension and Post-Retirement Benefit Payments

Future estimated annual benefit payments (in thousands) for pension and post-retirement benefit obligations at December 31, 2017 are as follows:



	Benefits
			Post-retirement
	Pension		Before Medicare Subsidy		After Medicare Subsidy
2018	$	7,195	$	1,536	$	1,400
2019	7,334		1,480		1,345
2020	7,409		1,490		1,358
2021	7,446		1,571		1,438
2022	7,573		1,600		1,465
2023-2027	38,030		7,892		7,178

Amounts in Accumulated Other Comprehensive Income Expected to be Recognized as Components of Net Periodic Benefit Cost

The amounts in accumulated other comprehensive income expected to be recognized as components of net periodic benefit cost (in thousands) during the following fiscal year are as follows:



	Benefits
	Pension		Post-retirement		Total
Net actuarial loss	$	1,877	$	—	$	1,877
Prior service cost	534		—		534
	$	2,411	$	—	$	2,411

Company's Obligations Determined under Weighted-Average Assumptions

The following weighted-average assumptions were used to determine our obligations under the plans:



	Pension Benefits				Post-retirement Benefits
	2017		2016		2017		2016
Discount rate	3.7	%	4.2	%	3.7	%	4.2	%
Long-term rate of compensation increase	3.5	%	3.5	%	N/A		N/A
Long-term rate of return on plan assets	6.8	%	7.0	%	7.0	%	7.0	%
Health care cost trend rate:
Pre-65 initial rate/ultimate rate	N/A		N/A		7.3%/4.5%		7.3%/5.0%
Pre-65 ultimate year	N/A		N/A		—		—
Post-65 initial rate/ultimate rate	N/A		N/A		8.0%/4.5%		8.5%/5.0%
Post-65 ultimate year	N/A		N/A		2025/2026		2024/2025

Schedule of Mortality Tables Used

Mortality tables used for pension benefits and post-retirement benefits plans are the following:



	Pension Benefits and Post-retirement Benefits
	2017	2016
Healthy Lives	RP-2014 mortality table, adjusted back to 2006 base rates, with generational mortality improvements using Scale MP-2017	RP-2014 mortality table, adjusted back to 2006 base rates, with generational mortality improvements using Scale MP-2016
Disabled Lives	RP-2014 disabled retiree mortality table, adjusted back to 2006 base rates, with generational mortality improvements using Scale MP-2017	RP-2014 disabled retiree mortality table, adjusted back to 2006 base rates, with generational mortality improvements using Scale MP-2016

Effect of One-Percentage-Point Change in Assumed Health Care Cost Trend Rates



	One-Percentage-Point
	Increase		Decrease
Effect on total of service and interest cost	$	113	$	(95	)
Effect on post-retirement benefit obligation	2,598		(2,209		)

Fair Value of Pension Plan Assets

The major investment categories and their relative percentage of the fair value of total plan assets as invested at December 31, 2017, and 2016 are as follows:



	Pension Benefits				Post-retirement Benefits
	2017		2016		2017		2016
Equity securities	51.8	%	59.4	%	—	%	64.0	%
Debt securities	46.3	%	38.3	%	—	%	39.1	%
Cash	1.9	%	2.3	%	—	%	(3.1	)%

Fair Value of Pension Plan Assets, by Asset Category

The fair values of the pension plan assets (in thousands) at December 31, 2017, by asset category, are as follows:



	Level 1		Level 2		Level 3		Total
Cash and cash equivalents	$	—	$	1,727	$	—	$	1,727
Mutual funds:
Diversified emerging markets	8,300		—		—		8,300
Foreign large blend	11,856		—		—		11,856
Large-cap blend	15,643		—		—		15,643
Mid-cap blend	8,334		—		—		8,334
Real estate	3,591		—		—		3,591
Fixed income securities:
Corporate notes and bonds	28,108		—		—		28,108
Government agencies	—		—		—		—
U.S. Treasuries	10,846		—		—		10,846
Mortgage-backed securities	—		2,615		—		2,615
Asset-backed securities	—		1,047		—		1,047
Net asset	$	86,678	$	5,389	$	—	$	92,067

The fair values of the pension plan assets (in thousands) at December 31, 2016, by asset category, are as follows:



	Level 1		Level 2		Level 3		Total
Cash and cash equivalents	$	—	$	1,893	$	—	$	1,893
Mutual funds:
Diversified emerging markets	7,700		—		—		7,700
Foreign large blend	12,621		—		—		12,621
Large-cap blend	16,687		—		—		16,687
Mid-cap blend	8,674		—		—		8,674
Real estate	4,070		—		—		4,070
Fixed income securities:
Corporate notes and bonds	21,357		—		—		21,357
Government agencies	301		—		—		301
U.S. Treasuries	7,495		—		—		7,495
Mortgage-backed securities	—		2,022		—		2,022
Asset-backed securities	—		983		—		983
Insurance policies	—		—		47		47
Net asset	$	78,905	$	4,898	$	47	$	83,850

Summary of Multiemployer Pension Plan

A summary of each multiemployer pension plan for which we participate is presented below:

Pension

Fund

EIN/ Pension

Plan No.

Pension Protection Act

Zone Status⁽¹⁾

FIP/RP Status

Pending/

Implemented

Company

Contributions

(in thousands)

Surcharge

Imposed

Expiration

Date of

CBA

2017

2016

2017

2016

2015

LIUNA

52-6074345/001

Red

Yes

223

167

182

Yes

5/31/2020

IUOE

36-6052390/001

Green

7/29/2018

CSSS⁽²⁾

36-6044243/001

Red

Yes


(1)	The Pension Protection Act of 2006 defines the zone status as follows: green—healthy, yellow—endangered, orange—seriously endangered and red—critical.


(2)	In 2011, we withdrew from the Central States, Southeast and Southwest Areas Pension Plan. The withdrawal liability of $1.0 million will be paid in monthly installments of $4,000 until 2031.

Income Taxes (Tables)

12 Months Ended

Dec. 31, 2017

Income Tax Disclosure [Abstract]

Summary of Income Tax (Expense) Benefit

The expense or benefit for income taxes (in thousands) consisted of the following for the years ended December 31, 2017, 2016 and 2015:



	Years Ended December 31,
	2017			2016			2015
Current:
Federal	$	(10,754	)	$	60		$	(170	)
State	(1,167		)	(274		)	1,448
	$	(11,921	)	$	(214	)	$	1,278
Deferred:
Federal	22,641			32,944			7,439
State	(2,040		)	3,959			3,034
	$	20,601		$	36,903		$	10,473
Income tax (expense) benefit	$	8,680		$	36,689		$	11,751

Summary of Tax Effects on Deferred Tax Assets and Liabilities

The tax effects of the types of temporary differences and carry forwards that gave rise to deferred tax assets and liabilities (in thousands) at December 31, 2017 and 2016 consisted of the following:



	At December 31,
	2017			2016
Gross deferred tax assets:
Net operating loss carry forward and state tax credits	$	22,783		$	65,022
Pension and post-retirement benefit costs	13,710			22,920
Alternative minimum tax credit carry forward	30,401			19,431
Property, plant and equipment	5,750			6,112
Accrued expenses	10,755			6,752
Inventories	4,354			4,362
Third-party products liability	249			511
Stock-based compensation expense	8,785			5,576
Note payable	3,133			4,009
Other	5,095			5,458
Total deferred tax assets	$	105,015		$	140,153
Gross deferred tax liabilities:
Land and mineral property basis difference	$	(78,520	)	$	(126,315	)
Fixed assets and depreciation	(51,556		)	(61,531		)
Intangibles	(4,795		)	(2,260		)
Other	—			(122		)
Total deferred tax liabilities	$	(134,871	)	$	(190,228	)
Net deferred tax liabilities	$	(29,856	)	$	(50,075	)

Summary of Effective Income Tax Rate on Pretax Earnings



	Years Ended December 31,
	2017			2016			2015
Income tax (expense) benefit computed at U.S. federal statutory rate	$	(47,784	)	$	27,211		$	(41	)
Decrease (increase) resulting from:
Statutory depletion	20,259			4,734			8,918
Prior year tax return reconciliation	219			435			393
State income taxes, net of federal benefit	(2,267		)	2,369			1,370
Adjustment to deferred taxes from the Tax Act rate reduction	35,772			—			—
Equity compensation	2,602			2,003			—
Other, net	(121		)	(63		)	1,111
Income tax (expense) benefit	$	8,680		$	36,689		$	11,751

Segment Reporting (Tables)

12 Months Ended

Dec. 31, 2017

Segment Reporting [Abstract]

Presentation of Sales and Segment Contribution Margin for Reporting Segments and Other Operating Results



	Years Ended December 31,
	2017			2016			2015
Sales:
Oil & Gas Proppants	$	1,020,365		$	362,550		$	430,435
Industrial & Specialty Products	220,486			197,075			212,554
Total sales	$	1,240,851		$	559,625		$	642,989
Segment contribution margin:
Oil & Gas Proppants	$	301,972		$	11,445		$	88,928
Industrial & Specialty Products	88,781			78,988			70,137
Total segment contribution margin	$	390,753		$	90,433		$	159,065
Operating activities excluded from segment cost of sales	(17,417		)	(8,103		)	(11,142		)
Selling, general and administrative	(107,592		)	(67,727		)	(62,777		)
Depreciation, depletion and amortization	(97,233		)	(68,134		)	(58,474		)
Interest expense	(31,342		)	(27,972		)	(27,283		)
Other income (expense), net, including interest income	(643		)	3,758			728
Income tax (expense) benefit	8,680			36,689			11,751
Net income (loss)	$	145,206		$	(41,056	)	$	11,868

Unaudited Supplementary Data (Tables)

12 Months Ended

Dec. 31, 2017

Quarterly Financial Information Disclosure [Abstract]

Unaudited Quarterly Information



	First Quarter			Second Quarter			Third Quarter			Fourth Quarter
2017	(Unaudited)
Sales:
Product	$	209,321		$	246,022		$	295,768		$	306,442
Service	35,476			44,443			49,255			54,124
Cost of sales (excluding depreciation, depletion and amortization):
Product	162,637			164,025			189,105			204,545
Service	24,838			33,386			38,818			50,161
Operating expenses:
Selling, general and administrative	22,341			26,012			29,602			29,637
Depreciation, depletion and amortization	21,599			23,626			24,673			27,335
Total operating expenses	$	43,940		$	49,638		$	54,275		$	56,972
Operating income	13,382			43,416			62,825			48,888
Other income (expense):
Interest expense	(7,646		)	(8,105		)	(8,347		)	(7,244		)
Other income (expense), net, including interest income	(4,928		)	1,258			1,502			1,525
Total other expense	$	(12,574	)	$	(6,847	)	$	(6,845	)	$	(5,719	)
Income before income taxes	808			36,569			55,980			43,169
Income tax (expense) benefit	1,714			(7,110		)	(14,707		)	28,783
Net income	$	2,522		$	29,459		$	41,273		$	71,952
Earnings per share, basic	$	0.03		$	0.36		$	0.51		$	0.89
Earnings per share, diluted	$	0.03		$	0.36		$	0.50		$	0.88
Weighted average shares outstanding, basic	80,983			81,087			81,121			81,014
Weighted average shares outstanding, diluted	82,244			81,945			81,783			81,921
Dividends declared per share	$	0.06		$	0.06		$	0.06		$	0.06

	First Quarter			Second Quarter			Third Quarter			Fourth Quarter
2016	(Unaudited)
Sales:
Product	$	121,627		$	116,039		$	125,805		$	160,429
Service	883			955			11,943			21,944
Cost of sales (excluding depreciation, depletion and amortization):
Product	106,629			102,587			112,215			133,758
Service	122			120			7,211			14,653
Operating expenses:
Selling, general and administrative	15,503			14,585			18,472			19,167
Depreciation, depletion and amortization	14,556			15,209			17,175			21,194



Total operating expenses	$	30,059		$	29,794		$	35,647		$	40,361
Operating loss	(14,300		)	(15,507		)	(17,325		)	(6,399		)
Other income (expense):
Interest expense	(6,643		)	(6,647		)	(6,684		)	(7,998		)
Other income, net, including interest income	1,790			608			493			867
Total other expense	$	(4,853	)	$	(6,039	)	$	(6,191	)	$	(7,131	)
Loss before income taxes	(19,153		)	(21,546		)	(23,516		)	(13,530		)
Income tax benefit (expense)	8,150			9,774			12,177			6,588
Net income (loss)	$	(11,003	)	$	(11,772	)	$	(11,339	)	$	(6,942	)
Loss per share, basic	$	(0.20	)	$	(0.19	)	$	(0.17	)	$	(0.09	)
Loss per share, diluted	$	(0.20	)	$	(0.19	)	$	(0.17	)	$	(0.09	)
Weighted average shares, basic	54,470			63,417			66,676			75,539
Weighted average shares, diluted	54,470			63,417			66,676			75,539
Dividends declared per share	$	0.06		$	0.06		$	0.06		$	0.06

Parent Company Financials (Tables)

12 Months Ended

Dec. 31, 2017

Organization, Consolidation and Presentation of Financial Statements [Abstract]

Condensed Balance Sheet



	December 31,
	2017			2016
	(in thousands)
ASSETS
Current Assets:
Cash and cash equivalents	$	230,647		$	534,378
Due from affiliates	146,683			—
Total current assets	377,330			534,378
Investment in subsidiaries	1,024,511			854,860
Total assets	$	1,401,841		$	1,389,238
LIABILITIES AND STOCKHOLDERS’ EQUITY
Current Liabilities:
Accrued expenses and other current liabilities	$	106		$	461
Dividends payable	5,229			5,222
Due to affiliates	—			110,265
Total current liabilities	5,335			115,948
Deferred income taxes, net	—			—
Total liabilities	5,335			115,948
Stockholders’ Equity:
Preferred stock	—			—
Common stock	812			811
Additional paid-in capital	1,147,084			1,129,051
Retained earnings	287,992			163,173
Treasury stock, at cost	(25,456		)	(3,869		)
Accumulated other comprehensive loss	(13,926		)	(15,876		)
Total stockholders’ equity	1,396,506			1,273,290
Total liabilities and stockholders’ equity	$	1,401,841		$	1,389,238

Condensed Income Statement



	Year Ended December 31,
	2017			2016			2015
	(in thousands, except per share amounts)
Sales	$	—		$	—		$	—
Cost of sales	—			—			—
Operating expenses
Selling, general and administrative	252			184			185
Other	—			10			19
Total operating expenses	252			194			204
Operating loss	(252		)	(194		)	(204		)
Other income (expense)
Interest income	3,854			1,046			262
Other income, net, including interest income	—			—			1
Total other income (expense)	3,854			1,046			263
Income before income taxes and equity in net earnings of subsidiaries	3,602			852			59
Income tax benefit (expense)	(1,453		)	(344		)	(24		)
Income before equity in net earnings of subsidiaries	2,149			508			35
Equity in earnings of subsidiaries, net of tax	143,057			(41,564		)	11,833
Net income (loss)	145,206			(41,056		)	11,868
Other comprehensive income (loss), net of deferred income taxes:
Unrealized gain (loss) on investments (net of tax of $0, $(4), and $29 for 2017, 2016, and 2015, respectively)	—			(6		)	47
Unrealized gain (loss) on derivatives, (net of tax of $(27), $29 and $34 for 2017, 2016 and 2015, respectively)	(44		)	49			53
Foreign currency translation adjustment (net of tax of $2, $0 and $0 for 2017, 2016 and 2015, respectively)	(6		)	—			—
Pension and post-retirement liability (net of tax of $1,205, $152, and $2,469 for 2017, 2016 and 2015, respectively)	2,000			252			3,547
Other comprehensive income (loss), net of deferred income taxes	1,950			295			3,647
Comprehensive income (loss) attributable to U.S. Silica Holdings, Inc.	$	147,156		$	(40,761	)	$	15,515

Condensed Equity Statement



												Accumulated
						Additional			Retained			Other			Total
	Par		Treasury			Paid-In			Earnings-			Comprehensive			Stockholders'
	Value		Stock			Capital			Present			Income (Loss)			Equity
Balance at January 1, 2015	$	539	$	(542	)	$	191,086		$	232,551		$	(19,818	)	$	403,816
Net income	—		—			—			11,868			—			11,868
Unrealized gain on derivatives	—		—			—			—			53			53
Unrealized gain on short-term investments	—		—			—			—			47			47
Pension and post-retirement liability	—		—			—			—			3,547			3,547
Cash dividend declared ($0.438 per share)	—		—			—			(23,445		)	—			(23,445		)
Common stock-based compensation plans activity:
Equity-based compensation	—		—			3,857			—			—			3,857
Proceeds from options exercised	—		744			(271		)	—			—			473
Shares withheld for employee taxes related to
vested restricted stock and stock units	—		(792		)	(2		)	—			—			(794		)
Repurchase of common stock	—		(15,255		)	—			—			—			(15,255		)
Balance at December 31, 2015	$	539	$	(15,845	)	$	194,670		$	220,974		$	(16,171	)	$	384,167
Net loss	—		—			—			(41,056		)	—			(41,056		)
Issuance of common stock (stock offerings net of issuance costs of $25,732)	272		—			931,016			—			—			931,288
Unrealized gain on derivatives	—		—			—			—			49			49
Unrealized loss on short-term investments	—		—			—			—			(6		)	(6		)
Pension and post-retirement liability	—		—			—			—			252			252
Cash dividend declared ($0.25 per share)	—		—			—			(16,893		)	—			(16,893		)
Common stock-based compensation plans activity:
Equity-based compensation	—		—			12,107			—			—			12,107
Excess tax benefit from equity-based compensation	—		—			—			148			—			148
Proceeds from options exercised	—		8,465			(3,640		)	—			—			4,825
Issuance of restricted stock	—		1,437			(1,437		)	—			—			—
Shares withheld for employee taxes related to
vested restricted stock and stock units	—		2,074			(3,665		)	—			—			(1,591		)
Balance at December 31, 2016	$	811	$	(3,869	)	$	1,129,051		$	163,173		$	(15,876	)	$	1,273,290
Net Income	—		—			—			145,206			—			145,206
Unrealized loss on derivatives	—		—			—			—			(44		)	(44		)
Foreign currency translation adjustment												(6		)	(6		)
Pension and post-retirement liability	—		—			—			—			2,000			2,000
Cash dividend declared ($0.25 per share)	—		—			—			(20,387		)	—			(20,387		)
Common stock-based compensation plans activity:
Equity-based compensation	—		—			25,050			—			—			25,050
Proceeds from options exercised	—		1,190			(392		)	—			—			798
Issuance of restricted stock	—		1,859			(1,859		)	—			—			—
Shares withheld for employee taxes related to
vested restricted stock and stock units	1		386			(4,766		)	—			—			(4,379		)
Repurchase of common stock	—		(25,022		)										(25,022		)
Balance at December 31, 2017	$	812	$	(25,456	)	$	1,147,084		$	287,992		$	(13,926	)	$	1,396,506

Condensed Cash Flow Statement



	Year Ended December 31,
	2017			2016			2015
	(in thousands)
Operating activities:
Net income (loss)	$	145,206		$	(41,056	)	$	11,868
Adjustments to reconcile net income (loss) to net cash provided by operating activities:
Undistributed (Income) loss from equity method investment, net	(143,057		)	41,564			(11,833		)
Other	—			(30		)	(195		)
Changes in assets and liabilities, net of effects of acquisitions:
Accounts payable and accrued liabilities	48			353			29
Net cash provided by (used in) operating activities	2,197			831			(131		)
Investing activities:
Proceeds from sales and maturities of short-term investments	—			21,872			53,568
Investment in subsidiary	(143,654		)	(188,177		)	—
Net cash provided by (used in) investing activities	(143,654		)	(166,305		)	53,568
Financing activities:
Dividends paid	(20,377		)	(15,125		)	(26,797		)
Repurchase of common stock	(25,022		)	—			(15,255		)
Proceeds from options exercised	798			4,603			473
Tax payments related to shares withheld for vested restricted stock and stock units	(4,379		)	(1,590		)	(794		)
Issuance of common stock (secondary offering)	—			678,791			—
Issuance of treasury stock	—			221			—
Costs of common stock issuance	—			(25,733		)	—
Net financing activities with subsidiaries	(113,294		)	106			223
Net cash provided by (used in) financing activities	(162,274		)	641,273			(42,150		)
Net increase in cash and cash equivalents	(303,731		)	475,799			11,287
Cash and cash equivalents, beginning of period	534,378			58,579			47,292
Cash and cash equivalents, end of period	$	230,647		$	534,378		$	58,579
Non-cash financing activities:
Supplemental cash flow information:
Cash paid (received) during the period for:
Interest	$	(3,853	)	$	(1,046	)	$	(263	)
Non-cash transactions
Common stock issued for business acquisitions	$	—		$	278,229		$	—

Summary of Significant Accounting Policies - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2017 USD ($) Agreement	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)
Organization And Significant Accounting Policies
Number of customers in the oil & gas proppants segment \| Agreement	23
Additions and revisions of prior estimates	$ 6,994,000	$ (2,074,000)
Gross Carrying Amount	131,932,000	114,347,000
Amortization of Intangible Assets	8,800,000	3,200,000	$ 500,000
Accumulated amortization	14,993,000	6,187,000
Estimated annual amortization, 2017	9,239,000
Estimated annual amortization, 2018	9,239,000
Estimated annual amortization, 2019	9,239,000
Estimated annual amortization, 2020	9,239,000
Estimated annual amortization, 2021	$ 9,224,000
Percentage of fair value of reporting unit less than carrying amount	50.00%
Amortization in interest expense	$ 1,382,000	1,392,000	$ 1,401,000
Self insurance reserve	5,500,000	5,300,000
Self-insurance reserve current	$ 1,700,000	1,300,000
Buildings
Organization And Significant Accounting Policies
Depreciation over the assets estimated useful life	15 years
Land improvements
Organization And Significant Accounting Policies
Depreciation over the assets estimated useful life	10 years
Furniture and fixtures
Organization And Significant Accounting Policies
Depreciation over the assets estimated useful life	8 years
Customer relationships
Organization And Significant Accounting Policies
Estimated Useful Life	20 years
Gross Carrying Amount	$ 61,229,000	55,689,000
Accumulated amortization	9,076,000	4,799,000
Estimated annual amortization, 2018	4,000,000
Estimated annual amortization, 2019	4,000,000
Estimated annual amortization, 2020	4,000,000
Estimated annual amortization, 2021	$ 4,000,000
Technology and intellectual property
Organization And Significant Accounting Policies
Estimated Useful Life	15 years
Gross Carrying Amount	$ 70,703,000	58,658,000
Accumulated amortization	5,917,000	$ 1,388,000
Estimated annual amortization, 2018	3,800,000
Estimated annual amortization, 2019	3,800,000
Estimated annual amortization, 2020	3,800,000
Estimated annual amortization, 2021	3,800,000
Minimum
Organization And Significant Accounting Policies
Self-insured retentions	$ 100,000
Minimum \| Machinery and equipment
Organization And Significant Accounting Policies
Depreciation over the assets estimated useful life	3 years
Minimum \| Customer relationships
Organization And Significant Accounting Policies
Estimated Useful Life	13 years
Maximum
Organization And Significant Accounting Policies
Self-insured retentions	$ 500,000
Maximum \| Machinery and equipment
Organization And Significant Accounting Policies
Depreciation over the assets estimated useful life	10 years
Maximum \| Customer relationships
Organization And Significant Accounting Policies
Estimated Useful Life	15 years
Ten Largest Customers \| Product concentration risk \| Sales Revenue, Net
Organization And Significant Accounting Policies
Percentage of sales in which customers accounted	58.00%	52.00%	56.00%

Summary of Significant Accounting Policies - Change in Asset Retirement Obligation (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Asset Retirement Obligation
Beginning balance	$ 11,159	$ 12,254
Accretion	879	979
Additions and revisions of prior estimates	6,994	(2,074)
Ending balance	$ 19,032	$ 11,159

Summary of Significant Accounting Policies - Equity-Based Compensation (Details) - shares	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted (in shares)	0	0
Restricted stock and restricted stock units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock vesting period	3 years
Minimum \| Stock option
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock vesting period	3 years
Maximum \| Stock option
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock vesting period	4 years

Summary of Significant Accounting Policies - Weighted-average Outstanding Stock Options Excluded Schedule (Details) - shares shares in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Employee Stock Option
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Weighted-average outstanding stock options excluded (in shares)	195	573	528
Restricted Stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Weighted-average outstanding stock options excluded (in shares)	305	166	66

Summary of Significant Accounting Policies - Recently Adopted Accounting Pronouncements (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
New Accounting Pronouncement, Early Adoption [Line Items]
Deferred income taxes, net	$ 29,856				$ 50,075				$ 29,856	$ 50,075
Income tax benefit (expense)	$ (28,783)	$ 14,707	$ 7,110	$ (1,714)	$ (6,588)	$ (12,177)	$ (9,774)	$ (8,150)	$ (8,680)	$ (36,689)	$ (11,751)

Capital Structure and Accumulated Comprehensive Income - Additional Information (Detail)					1 Months Ended				3 Months Ended								11 Months Ended	12 Months Ended
	Nov. 03, 2016 $ / shares	Jul. 21, 2016 $ / shares	May 05, 2016 $ / shares	Feb. 22, 2016 $ / shares	Dec. 31, 2017 USD ($) $ / shares shares	Nov. 30, 2016 USD ($) shares	Aug. 31, 2016 acquisition shares	Mar. 31, 2016 USD ($) shares	Dec. 31, 2017 USD ($) $ / shares shares	Sep. 30, 2017 $ / shares	Jun. 30, 2017 $ / shares	Mar. 31, 2017 $ / shares	Dec. 31, 2016 $ / shares shares	Sep. 30, 2016 $ / shares	Jun. 30, 2016 $ / shares	Mar. 31, 2016 $ / shares shares	Dec. 11, 2017 USD ($) $ / shares shares	Dec. 31, 2017 USD ($) $ / shares shares	Dec. 31, 2016 USD ($) acquisition $ / shares shares	Dec. 31, 2015 $ / shares	Dec. 31, 2014 $ / shares
Class of Stock [Line Items]
Common stock authorized (in shares)					500,000,000				500,000,000				500,000,000					500,000,000	500,000,000
Common stock, par value (in dollars per share) \| $ / shares					$ 0.01				$ 0.01				$ 0.01					$ 0.01	$ 0.01
Secondary offering (in shares)								10,000,000								10,000,000
Public offering, proceeds from issuance of common stock \| $						$ 467,000,000		$ 186,200,000											$ 931,288,000
Number of acquisitions \| acquisition							2												2
Common stock issued (in shares)					81,267,205				81,267,205				81,184,042					81,267,205	81,184,042
Common stock, shares outstanding (in shares)					80,524,255				80,524,255				81,028,898					80,524,255	81,028,898
Dividend declared per share (in usd per share) \| $ / shares	$ 0.0625	$ 0.0625	$ 0.0625	$ 0.0625					$ 0.06	$ 0.06	$ 0.06	$ 0.06	$ 0.06	$ 0.06	$ 0.06	$ 0.06		$ 0.25	$ 0.25	$ 0.438	$ 0.438
Declaration Date	Nov. 02, 2017	Jul. 21, 2017	May 04, 2017	Feb. 16, 2017
Record Date	Dec. 15, 2017	Sep. 15, 2017	Jun. 15, 2017	Mar. 15, 2017
Payable Date	Jan. 05, 2018	Oct. 03, 2017	Jul. 06, 2017	Apr. 05, 2017
Preferred stock, shares authorized (in shares)					10,000,000				10,000,000				10,000,000					10,000,000	10,000,000
Preferred stock, par value (in dollars per share) \| $ / shares					$ 0.01				$ 0.01				$ 0.01					$ 0.01	$ 0.01
Preferred stock issued (in shares)					0				0				0					0	0
Preferred stock, shares outstanding (in shares)					0				0				0					0	0
Authorization to repurchase common stock \| $					$ 100,000,000.0				$ 100,000,000.0								$ 50,000,000	$ 100,000,000.0
Repurchase of common stock (shares)					727,081												706,093
Average price per common share of repurchase common stock (in dollars per share) \| $ / shares					$ 34.41												$ 23.83
Remaining authorized repurchase of common stock amount \| $					$ 75,000,000				$ 75,000,000									$ 75,000,000
Common Stock
Class of Stock [Line Items]
Additional offering, shares issued (in shares)							6,825,693												6,825,693
Common Stock
Class of Stock [Line Items]
Public offering, proceeds from issuance of common stock \| $																			$ 272,000
Additional offering, shares issued (in shares)						10,350,000

Capital Structure and Accumulated Comprehensive Income - Changes in Accumulated Other Comprehensive Income (Detail) $ in Thousands	12 Months Ended
	Dec. 31, 2017 USD ($)
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	$ 1,273,290
Ending balance	1,396,506
Unrealized gain/(loss) on cash flow hedges
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	(32)
Other comprehensive gain (loss) before reclassifications	(45)
Amounts reclassed from accumulated other comprehensive income	1
Ending balance	(76)
Foreign currency translation adjustment
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	0
Other comprehensive gain (loss) before reclassifications	(6)
Amounts reclassed from accumulated other comprehensive income	0
Ending balance	(6)
Pension and other post- retirement benefits liability
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	(15,844)
Other comprehensive gain (loss) before reclassifications	871
Amounts reclassed from accumulated other comprehensive income	1,129
Ending balance	(13,844)
Accumulated Other Comprehensive (Loss)
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	(15,876)
Other comprehensive gain (loss) before reclassifications	820
Amounts reclassed from accumulated other comprehensive income	(1,130)
Ending balance	$ (13,926)

Business Combinations - Additional Information (Detail) $ in Thousands					1 Months Ended	3 Months Ended	8 Months Ended	12 Months Ended
	Aug. 16, 2017 USD ($)	Apr. 01, 2017 USD ($)	Aug. 22, 2016 USD ($) shares	Aug. 16, 2016 USD ($) shares	Aug. 31, 2016 acquisition shares	Mar. 31, 2013 USD ($)	Aug. 16, 2017 USD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($) acquisition shares	Dec. 31, 2015 USD ($)
Business Acquisition [Line Items]
Cash consideration								$ 119,801	$ 176,617	$ 0
Goodwill								272,079	240,975	68,647
Total cash consideration for pre-existing contracted asset sale								384,622	$ 46,450	$ 53,646
Number of acquisitions \| acquisition					2				2
Payments of Stock Issuance Costs						$ 0		0	$ 25,732
White Armor acquisition
Business Acquisition [Line Items]
Goodwill		$ 3,900
Identifiable intangible assets		12,800
Other net assets		1,900
Acquisition-related costs								200
Cash payments to acquire business		$ 18,600
MS Sand
Business Acquisition [Line Items]
Cash consideration	$ 95,400
Goodwill	22,522						$ 22,522
Cash acquired	2,200
Net working capital adjustment	(500)
Additional consideration paid	$ 6,100
Acquisition-related costs								700
NBI acquisition
Business Acquisition [Line Items]
Cash consideration				$ 107,200
Goodwill				90,898
Identifiable intangible assets				1,600
Cash acquired				$ 9,002
Number of U.S. Silica common shares delivered \| shares				2,630,513
Acquisition-related costs									1,400
Adjustment to depreciation expense								$ (1,000)
Inventory write-down									1,700
Cash payments to acquire business				$ 116,165
Total value of Holdings common shares delivered				$ 106,562
Sandbox acquisition
Business Acquisition [Line Items]
Cash consideration			$ 69,500
Goodwill			86,100
Identifiable intangible assets			120,144
Cash acquired			$ 1,306
Number of U.S. Silica common shares delivered \| shares			4,195,180
Acquisition-related costs									3,000
Revenue									$ 31,000
Cash payments to acquire business			$ 70,760
Total value of Holdings common shares delivered			$ 171,667
Common Stock
Business Acquisition [Line Items]
Shares issued to complete acquisitions (in shares) \| shares					6,825,693				6,825,693
Payments of Stock Issuance Costs									$ 300
MS Sand
Business Acquisition [Line Items]
Total cash consideration for pre-existing contracted asset sale							$ 101,000

Business Combination - Schedule of Purchase Price Calculation (Details) - USD ($) $ / shares in Units, $ in Thousands	Aug. 22, 2016	Aug. 16, 2016
Business Acquisition [Line Items]
Multiplied by closing market price per share of U.S. Silica common stock on August 16, 2016	$ 40.92	$ 40.51
Sandbox acquisition
Business Acquisition [Line Items]
Cash consideration paid	$ 70,760
Number of Holdings common shares delivered	4,195,180
Total value of Holdings common shares delivered	$ 171,667
Less, cash acquired	(1,306)
Total purchase price	$ 241,121
NBI acquisition
Business Acquisition [Line Items]
Cash consideration paid		$ 116,165
Number of Holdings common shares delivered		2,630,513
Total value of Holdings common shares delivered		$ 106,562
Less, cash acquired		(9,002)
Total purchase price		$ 213,725

Business Combination - Schedule of Purchase Price Allocation (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Aug. 16, 2017	Dec. 31, 2016	Aug. 22, 2016	Aug. 16, 2016	Dec. 31, 2015
Business Acquisition [Line Items]
Goodwill	$ 272,079		$ 240,975			$ 68,647
MS Sand
Business Acquisition [Line Items]
Accounts receivable		$ 11,201
Inventories		8,067
Other current assets		362
Assets held for sale		9,453
Property, plant and mine development		27,458
Mineral rights		26,300
Other non-current assets		1,136
Goodwill		22,522
Total assets acquired		108,339
Accounts payable, accrued expenses and other current liabilities		3,761
Unfavorable leasehold positions		0
Notes payable		866
Other long term liabilities		2,237
Asset retirement obligations		474
Total liabilities assumed		7,338
Net assets acquired		101,001
Sandbox acquisition
Business Acquisition [Line Items]
Accounts receivable				$ 13,392
Prepaid expenses and other				1,465
Property, plant and mine development				32,336
Goodwill				86,100
Identifiable intangible assets				120,144
Total assets acquired				253,437
Accounts payable				4,122
Deferred revenue				4,902
Accrued expenses and other current liabilities				3,292
Total liabilities assumed				12,316
Net assets acquired				$ 241,121
NBI acquisition
Business Acquisition [Line Items]
Accounts receivable					$ 2,680
Inventories					3,494
Other current assets					428
Property, plant and mine development					206,632
Income tax deposits					6,440
Goodwill					90,898
Identifiable intangible assets					1,600
Total assets acquired					312,172
Accounts payable, accrued expenses and other current liabilities					2,664
Deferred revenue					500
Notes payable					24,604
Capital lease liabilities					3,331
Asset retirement obligations					710
Deferred tax liabilities					66,638
Total liabilities assumed					98,447
Net assets acquired					213,725
Customer relationships \| MS Sand
Business Acquisition [Line Items]
Identifiable intangible assets		1,840
Initial Estimate \| MS Sand
Business Acquisition [Line Items]
Accounts receivable		11,201
Inventories		6,087
Other current assets		362
Assets held for sale		9,523
Property, plant and mine development		26,440
Mineral rights		0
Other non-current assets		1,136
Goodwill		52,187
Total assets acquired		106,936
Accounts payable, accrued expenses and other current liabilities		3,815
Unfavorable leasehold positions		1,254
Notes payable		866
Other long term liabilities		0
Asset retirement obligations		0
Total liabilities assumed		5,935
Net assets acquired		101,001
Initial Estimate \| NBI acquisition
Business Acquisition [Line Items]
Accounts receivable					2,680
Inventories					3,494
Other current assets					428
Property, plant and mine development					210,913
Income tax deposits					6,657
Goodwill					86,228
Identifiable intangible assets					1,600
Total assets acquired					312,000
Accounts payable, accrued expenses and other current liabilities					1,938
Deferred revenue					500
Notes payable					24,361
Capital lease liabilities					3,331
Asset retirement obligations					710
Deferred tax liabilities					67,435
Total liabilities assumed					98,275
Net assets acquired					213,725
Initial Estimate \| Customer relationships \| MS Sand
Business Acquisition [Line Items]
Identifiable intangible assets		0
Measurement Period Adjustments \| MS Sand
Business Acquisition [Line Items]
Accounts receivable		0
Inventories		1,980
Other current assets		0
Assets held for sale		(70)
Property, plant and mine development		1,018
Mineral rights		26,300
Other non-current assets		0
Goodwill		(29,665)
Total assets acquired		1,403
Accounts payable, accrued expenses and other current liabilities		(54)
Unfavorable leasehold positions		(1,254)
Notes payable		0
Other long term liabilities		2,237
Asset retirement obligations		474
Total liabilities assumed		1,403
Net assets acquired		0
Measurement Period Adjustments \| NBI acquisition
Business Acquisition [Line Items]
Accounts receivable					0
Inventories					0
Other current assets					0
Property, plant and mine development					(4,281)
Income tax deposits					(217)
Goodwill					4,670
Identifiable intangible assets					0
Total assets acquired					172
Accounts payable, accrued expenses and other current liabilities					726
Deferred revenue					0
Notes payable					243
Capital lease liabilities					0
Asset retirement obligations					0
Deferred tax liabilities					(797)
Total liabilities assumed					172
Net assets acquired					$ 0
Measurement Period Adjustments \| Customer relationships \| MS Sand
Business Acquisition [Line Items]
Identifiable intangible assets		$ 1,840

Business Combination - Schedule of Intangible Assets Acquired as Part of Business Combination (Details) - USD ($) $ in Thousands				12 Months Ended
	Aug. 16, 2017	Aug. 22, 2016	Aug. 16, 2016	Dec. 31, 2017
Sandbox acquisition
Business Acquisition [Line Items]
Definite lived intangible assets - approximate fair value		$ 120,144
NBI acquisition
Business Acquisition [Line Items]
Finite-lived intangible asset, useful life			13 years
Customer relationships
Business Acquisition [Line Items]
Finite-lived intangible asset, useful life				20 years
Customer relationships \| MS Sand
Business Acquisition [Line Items]
Definite lived intangible assets - approximate fair value	$ 1,840
Finite-lived intangible asset, useful life	15 years
Customer relationships \| Sandbox acquisition
Business Acquisition [Line Items]
Definite lived intangible assets - approximate fair value		$ 44,600
Finite-lived intangible asset, useful life		13 years
Customer relationships \| NBI acquisition
Business Acquisition [Line Items]
Definite lived intangible assets - approximate fair value			$ 1,600
Developed Technology Rights \| Sandbox acquisition
Business Acquisition [Line Items]
Definite lived intangible assets - approximate fair value		$ 57,700
Finite-lived intangible asset, useful life		15 years
Trade name \| Sandbox acquisition
Business Acquisition [Line Items]
Indefinite lived intangible assets - Trade names		$ 17,844

Business Combinations - Pro Forma Information (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Business Acquisition [Line Items]
Sales		$ 615,552	$ 753,287
Net income		$ (45,161)	$ 43,163
Basic earnings per share (in dollars per share)		$ (0.69)	$ 0.81
Diluted earnings per share (in dollars per share)		$ (0.69)	$ 0.81
MS Sand
Business Acquisition [Line Items]
Sales	$ 1,287,202	$ 642,951
Net income	$ 143,604	$ (55,835)
Basic earnings per share (in dollars per share)	$ 1.77	$ (0.86)
Diluted earnings per share (in dollars per share)	$ 1.75	$ (0.86)

Accounts Receivable - Schedule of Accounts Receivable (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Receivables [Abstract]
Trade receivables	$ 217,649	$ 93,982
Less: Allowance for doubtful accounts	(7,100)	(7,042)
Net trade receivables	210,549	86,940
Other receivables	2,037	2,066
Total accounts receivable	$ 212,586	$ 89,006

Inventories - Schedule of Inventories (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Inventory Disclosure [Abstract]
Supplies	$ 21,277	$ 18,824
Raw materials and work in process	28,034	25,161
Finished goods	43,065	34,724
Total inventories	$ 92,376	$ 78,709

Accounts Receivable - Allowance for Doubtful Accounts (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Allowance for Doubtful Accounts Receivable [Roll Forward]
Balance at January 1,	$ 7,042	$ 7,686
Bad debt provision	1,529	(1,232)	$ (290)
Write-offs and recoveries, net	(1,471)	588
Balance at December 31,	$ 7,100	$ 7,042	$ 7,686

Accounts Receivable - Additional Information (Details) - Product concentration risk	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Sales \| Ten Largest Customers
Concentration Risk [Line Items]
Concentration risk (as a percent)	58.00%	52.00%	56.00%
Sales \| Customer one
Concentration Risk [Line Items]
Concentration risk (as a percent)	15.00%	13.00%	13.00%
Sales \| Customer two
Concentration Risk [Line Items]
Concentration risk (as a percent)	12.00%		12.00%
Accounts receivable \| Customer one
Concentration Risk [Line Items]
Concentration risk (as a percent)	19.00%	14.00%
Accounts receivable \| Customer two
Concentration Risk [Line Items]
Concentration risk (as a percent)	11.00%	10.00%

Property, Plant and Mine Development - Schedule of Property, Plant and Mine Development (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Property, Plant and Equipment
Property, plant and mine development	$ 1,522,675	$ 1,049,701
Accumulated depletion, depreciation and amortization	(353,520)	(266,388)
Total property, plant and mine development, net	1,169,155	783,313
Mining property and mine development
Property, Plant and Equipment
Property, plant and mine development	586,242	414,434
Asset retirement cost
Property, Plant and Equipment
Property, plant and mine development	14,184	8,062
Land
Property, Plant and Equipment
Property, plant and mine development	36,552	35,052
Land improvements
Property, Plant and Equipment
Property, plant and mine development	45,878	42,738
Buildings
Property, Plant and Equipment
Property, plant and mine development	56,330	52,178
Machinery and equipment
Property, Plant and Equipment
Property, plant and mine development	590,566	450,881
Furniture and fixtures
Property, Plant and Equipment
Property, plant and mine development	2,953	2,566
Construction-in-progress
Property, Plant and Equipment
Property, plant and mine development	$ 189,970	$ 43,790

Property, Plant and Mine Development - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Property, Plant and Equipment
Machinery and equipment acquired under capital lease	$ 1,522,675	$ 1,049,701
Accumulated depletion, depreciation and amortization	353,520	266,388
Property plant equipment interest capitalization	1,600	200	$ 500
Assets Held under Capital Leases
Property, Plant and Equipment
Machinery and equipment acquired under capital lease	900	4,700
Accumulated depletion, depreciation and amortization	$ 200	$ 300

Goodwill and Intangible Assets - Schedule of Changes in the Carrying Amount of Goodwill (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Goodwill [Roll Forward]
Beginning balance	$ 240,975	$ 68,647
Ending balance	272,079	240,975
NBI acquisition
Goodwill [Roll Forward]
Acquisition		86,228
Acquisition measurement period adjustment	4,670
Sandbox acquisition
Goodwill [Roll Forward]
Acquisition		$ 86,100
White Armor acquisition
Goodwill [Roll Forward]
Acquisition	3,912
MS Sand acquisition
Goodwill [Roll Forward]
Acquisition	52,187
Acquisition measurement period adjustment	$ (29,665)

Goodwill and Intangible Assets - Narrative (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Goodwill [Line Items]
Goodwill	$ 272,079	$ 240,975	$ 68,647
Amortization expense	8,800	3,200	$ 500
Operating Segments \| Oil & Gas Proppants
Goodwill [Line Items]
Goodwill	247,500	220,300
Operating Segments \| Industrial & Specialty Products
Goodwill [Line Items]
Goodwill	$ 24,600	$ 20,700

Goodwill and Intangible Assets - Schedule of Changes in the Carrying Amount of Intangible Assets (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 131,932	$ 114,347
Accumulated Amortization	(14,993)	(6,187)
Net	116,939	108,160
Indefinite-lived Intangible Assets [Line Items]
Gross Carrying Amount	165,000	146,665
Accumulated Amortization	(14,993)	(6,187)
Net	150,007	140,478
Trade name
Indefinite-lived Intangible Assets [Line Items]
Gross Carrying Amount/Net	$ 33,068	32,318
Technology and intellectual property
Finite-Lived Intangible Assets [Line Items]
Estimated Useful Life	15 years
Gross Carrying Amount	$ 70,703	58,658
Accumulated Amortization	(5,917)	(1,388)
Net	64,786	57,270
Indefinite-lived Intangible Assets [Line Items]
Accumulated Amortization	$ (5,917)	(1,388)
Customer relationships
Finite-Lived Intangible Assets [Line Items]
Estimated Useful Life	20 years
Gross Carrying Amount	$ 61,229	55,689
Accumulated Amortization	(9,076)	(4,799)
Net	52,153	50,890
Indefinite-lived Intangible Assets [Line Items]
Accumulated Amortization	$ (9,076)	$ (4,799)
Customer relationships \| Minimum
Finite-Lived Intangible Assets [Line Items]
Estimated Useful Life	13 years
Customer relationships \| Maximum
Finite-Lived Intangible Assets [Line Items]
Estimated Useful Life	15 years

Goodwill and Intangible Assets - Schedule of Estimated Amortization Expense Related to Definite-Lived Intangible Assets (Details) $ in Thousands	Dec. 31, 2017 USD ($)
Goodwill and Intangible Assets Disclosure [Abstract]
2018	$ 9,239
2019	9,239
2020	9,239
2021	9,239
2022	$ 9,224

Accrued Liabilities - Schedule of Accrued Liabilities (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Payables and Accruals [Abstract]
Accrued salaries and wages	$ 6,126	$ 3,794
Accrued vacation liability	2,906	2,471
Current portion of liability for pension and post-retirement benefits	1,524	1,553
Accrued healthcare liability	1,837	1,307
Accrued property taxes and sales taxes	2,720	1,815
Other accrued liabilities	1,728	2,094
Total accrued liabilities	$ 16,841	$ 13,034

Debt and Capital Leases - Additional Information (Detail)	1 Months Ended	12 Months Ended
	Aug. 31, 2016 USD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Dec. 05, 2014 USD ($)	Jul. 23, 2013 USD ($)
Short-term Debt
Available borrowing base					$ 425,000,000
Incurrence ratio		3
Facility consolidated total net leverage ratio		3.75
Increase of commitment		25.00%
Long-term debt		$ 511,236,000	$ 513,238,000
Revolving Credit Facility
Short-term Debt
Available borrowing base		50,000,000			50,000,000
Long-term line of credit		0
Remaining borrowing capacity under Revolver		45,500,000
Long-term debt		0	0
Swingline loans
Short-term Debt
Available borrowing base					5,000,000
Letter of Credit
Short-term Debt
Available borrowing base					20,000,000
Letters of credit outstanding, amount		4,500,000
Term loan facility
Short-term Debt
Available borrowing base				$ 502,000,000	$ 375,000,000.0
Increase in borrowing capacity				$ 135,000,000
Notes Payable, Other Payables \| Note Payable Secured by Royalty Interest
Short-term Debt
Annual minimum payments		500,000
Debt instrument, fair value		$ 22,500,000
Fair value inputs, discount rate		14.00%
Interest rate, effective percentage		24.00%
Long-term debt		$ 24,740,000	23,076,000
Notes Payable, Other Payables \| Customer Note Payable
Short-term Debt
Annual minimum payments	$ 500,000
Outstanding principal	$ 2,500,000.0
Debt instrument, stated interest rate percentage	0.00%
Consumer notes payable, term	60 months
Interest rate, effective percentage	3.50%
Long-term debt	$ 1,900,000	$ 745,000	$ 1,787,000
Minimum \| Notes Payable, Other Payables
Short-term Debt
Debt instrument, stated interest rate percentage	0.00%
Maximum \| Notes Payable, Other Payables
Short-term Debt
Debt instrument, stated interest rate percentage	5.20%

Debt and Capital Leases - Schedule of Debt (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Aug. 31, 2016
Line of Credit Facility
Total debt	$ 511,236	$ 513,238
Less: Unamortized original issue discount	(944)	(1,318)
Less: Unamortized debt issuance cost	(3,099)	(4,482)
Less: current portion	(4,504)	(4,821)
Total long-term portion of debt	506,732	508,417
Revolving Credit Facility
Line of Credit Facility
Total debt	0	0
Senior Secured Credit Facility \| Term loan facility
Line of Credit Facility
Total debt	489,075	494,175
Equipment Notes Payable
Line of Credit Facility
Total debt	719
Notes Payable, Other Payables \| Note Payable Secured by Royalty Interest
Line of Credit Facility
Total debt	24,740	23,076
Notes Payable, Other Payables \| Equipment Notes Payable
Line of Credit Facility
Total debt	719	0
Notes Payable, Other Payables \| Customer Note Payable
Line of Credit Facility
Total debt	$ 745	$ 1,787	$ 1,900

Debt and Capital Leases - Schedule of Debt (Phantom) (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Senior Secured Credit Facility \| Revolver
Line of Credit Facility
Credit facility, interest rate	5.25%	5.00%
Senior Secured Credit Facility \| Minimum \| Term loan facility
Line of Credit Facility
Credit facility, interest rate	4.00%	4.00%
Senior Secured Credit Facility \| Maximum \| Term loan facility
Line of Credit Facility
Credit facility, interest rate	4.50%	4.50%
Notes Payable, Other Payables \| Note Payable Secured by Royalty Interest
Line of Credit Facility
Unamortized premium	$ 3,053

Debt and Capital Leases - Schedule of Contractual Maturities of Debt (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Debt Instrument [Line Items]
Total debt	$ 511,236	$ 513,238
Equipment Notes Payable
Debt Instrument [Line Items]
2018	316
2019	286
2020	117
Total debt	719
Term loan facility \| Senior Secured Credit Facility
Debt Instrument [Line Items]
2018	5,100
2019	5,100
2020	478,875
Total debt	$ 489,075	$ 494,175

Debt and Capital Leases - Schedule of Debt Backed by Secured Royalty Interest (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Debt Instrument [Line Items]
Total debt	$ 511,236	$ 513,238
Notes Payable, Other Payables \| Note Payable Secured by Royalty Interest
Debt Instrument [Line Items]
2018	1,750
2019	1,750
2020	1,750
2021	1,750
2022	1,750
Thereafter	15,990
Total debt	$ 24,740	$ 23,076

Debt and Capital Leases - Schedule of Capital Leases (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Debt Disclosure [Abstract]
2019	$ 721
Total minimum lease payments	721
Less: amount representing interest	15
Present value of minimum lease payments	706
Current portion of capital leases	706	$ 2,237
Obligations under capital lease	$ 0	$ 717

Deferred Revenue (Detail) - USD ($) $ in Thousands	12 Months Ended
Deferred Revenue (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Deferred Revenue Arrangement [Line Items]
Advances received	$ 50,500
Total deferred revenue balance	118,400	$ 71,800
Current portion of deferred revenue	$ 36,128	$ 13,700
Minimum \| Supply Agreement
Deferred Revenue Arrangement [Line Items]
Average initial contract term	1 year
Maximum \| Supply Agreement
Deferred Revenue Arrangement [Line Items]
Average initial contract term	5 years

- Definition

The carrying amount of consideration received or receivable as of the balance sheet date on potential earnings that were not recognized as revenue in conformity with GAAP, and which are expected to be recognized as such within one year or the normal operating cycle, if longer, including sales, license fees, and royalties, but excluding interest income.

+ References + Details

Fair Value Accounting - Schedule of Measure at Fair Value on Recurring Basis (Detail) - Measured at Fair Value on Recurring Basis - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Pension Plans, Postretirement and Other Employee Benefits
Interest rate derivatives	$ 0	$ 72
Net asset	0	72
Level 1
Pension Plans, Postretirement and Other Employee Benefits
Interest rate derivatives	0	0
Net asset	0	0
Level 2
Pension Plans, Postretirement and Other Employee Benefits
Interest rate derivatives	0	72
Net asset	$ 0	$ 72

Derivative Instruments - Estimated Fair Values of Derivative Instruments (Detail) - USD ($)	Dec. 31, 2017	Dec. 31, 2016
Interest Rate Cap Agreement
Derivative Instruments, Gain (Loss)
Contract/Notional Amount	$ 249,000,000	$ 249,000,000
Carrying Amount	$ 0	72,000
Maximum
Derivative Instruments, Gain (Loss)
Derivative, basis spread on variable rate	4.00%
Fair Value, Measurements, Recurring
Derivative Instruments, Gain (Loss)
Fair Value	$ 0	72,000
Fair Value, Inputs, Level 2 \| Fair Value, Measurements, Recurring
Derivative Instruments, Gain (Loss)
Fair Value	0	72,000
Fair Value, Inputs, Level 2 \| Fair Value, Measurements, Recurring \| Interest Rate Cap Agreement
Derivative Instruments, Gain (Loss)
Fair Value	$ 0	$ 72,000

Derivative Instruments - Effect of Derivatives Instruments on Combined Statements of Operations and Comprehensive Income (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Deferred Losses from Derivatives in OCI [Roll Forward]
Deferred losses from derivatives in OCI, beginning of period	$ (32)	$ (81)	$ (134)
Loss recognized in OCI from derivative instruments	(45)	(32)	0
Gain reclassified from Accumulated OCI	1	81	53
Deferred losses from derivatives in OCI, end of period	$ (76)	$ (32)	$ (81)

Equity-Based Compensation - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Option Indexed to Issuer's Equity
Stock options granted (in shares)	0	0
Intrinsic value of stock options exercised	$ 1.2	$ 7.6	$ 0.4
Cash received from options exercised	0.8
Actual tax benefit realized for the tax deductions from option exercises	0.4	2.9	0.0
Stock option
Option Indexed to Issuer's Equity
Recognized compensation expense (benefit)	2.5	3.0	3.4
Unrecognized compensation expense related to stock options	$ 1.2
Recognized weighted-average period	8 months
Restricted Stock and Restricted Stock Units
Option Indexed to Issuer's Equity
Performance share units granted (in shares)	156,164
Estimated grant date fair value (in dollars per share)	$ 44.45
Recognized compensation expense (benefit)	$ 7.1	5.7	3.9
Total unrecognized compensation expense	$ 9.2
Recognized weighted-average period	1 year 8 months 2 days
Performance Shares
Option Indexed to Issuer's Equity
Performance share units granted (in shares)	90,501
Estimated grant date fair value (in dollars per share)	$ 67.69
Recognized compensation expense (benefit)	$ 15.5	$ (3.3)	$ 3.4
Total unrecognized compensation expense	$ 18.3
Recognized weighted-average period	1 year 2 months
2011 Incentive Compensation Plan
Option Indexed to Issuer's Equity
Common stock that may be issued (in shares)	4,452,870

Equity-Based Compensation - Summary of Activity with Respect to Stock Options (Detail) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Number of Shares
Outstanding at beginning of period (in shares)	952,693
Granted (in shares)	0	0
Exercised (in shares)	(43,774)
Forfeited (in shares)	0
Outstanding at period end (in shares)	908,919	952,693
Exercisable at period end (in shares)	736,480,000
Weighted Average Exercise Price
Outstanding at beginning of period, weighted average exercise price (in dollars per share)	$ 27.99
Granted, weighted average exercise price (in dollars per share)	0.00
Exercised, weighted average exercise price (in dollars per share)	18.22
Forfeited, weighted average exercise price (in dollars per share)	0.00
Outstanding at period end, weighted average exercise price (in dollars per share)	28.46	$ 27.99
Exercisable at period end, weighted average exercise price (in dollars per share)	$ 26.79
Weighted Average Remaining Contractual Term in Years
Outstanding at period end, weighted average remaining contractual term in years	6 years 1 month
Exercisable at period end, weighted average remaining contractual term in years	5 years 10 months
Aggregate Intrinsic Value (in thousands)
Intrinsic value options outstanding	$ 7,008
Intrinsic value options exercisable	$ 6,707

Equity-Based Compensation - Restricted Stock Activity (Details) - Restricted Stock	12 Months Ended
	Dec. 31, 2017 $ / shares shares
Number of Shares
Unvested at beginning of period (in shares) \| shares	557,716
Granted (in shares) \| shares	156,164
Vested (in shares) \| shares	(248,031)
Forfeited (in shares) \| shares	(4,503)
Unvested at period end (in shares) \| shares	461,346
Grant Date Weighted Average Fair Value
Unvested at beginning of period (in dollars per share) \| $ / shares	$ 24.33
Granted (in dollars per share) \| $ / shares	44.45
Vested (in dollars per share) \| $ / shares	24.92
Forfeited (in dollars per share) \| $ / shares	30.94
Unvested at period end (in dollars per share) \| $ / shares	$ 30.76

Equity-Based Compensation - Performance Stock Activity (Details) - Performance Shares	12 Months Ended
	Dec. 31, 2017 $ / shares shares
Number of Shares
Unvested at beginning of period (in shares) \| shares	963,613
Granted (in shares) \| shares	90,501
Vested (in shares) \| shares	0
Forfeited (in shares) \| shares	(172,698)
Unvested at period end (in shares) \| shares	881,416
Weighted Average
Unvested at beginning of period (in dollars per share) \| $ / shares	$ 37.43
Granted (in dollars per share) \| $ / shares	67.69
Vested (in dollars per share) \| $ / shares	0.00
Forfeited (in dollars per share) \| $ / shares	29.12
Unvested at period end (in dollars per share) \| $ / shares	$ 42.16

Commitments and Contingencies - Contractual Obligations (Details) $ in Thousands	Dec. 31, 2017 USD ($)
Operating Lease Minimum Rental Payments
2017	$ 69,892
2018	62,294
2019	51,162
2020	35,915
2021	30,303
Thereafter	55,626
Total future lease and purchase commitments	305,192
Minimum Purchase Commitments
2017	28,099
2018	18,938
2019	10,168
2020	5,736
2021	3,886
Thereafter	11,200
Total future lease and purchase commitments	$ 78,027

Commitments and Contingencies - Additional Information (Detail) $ in Thousands			12 Months Ended
	May 17, 2017 USD ($)	Jun. 09, 2015 USD ($)	Dec. 31, 2017 USD ($) claim	Dec. 31, 2016 USD ($) claim	Dec. 31, 2015 USD ($) claim
Expense related to operating leases and rental agreements			$ 68,300	$ 54,100	$ 48,200
Payments to Acquire Oil and Gas Property	$ 94,400
Current portion of capital leases			$ 706	$ 2,237
New claims filed \| claim				2	0
Products liability claims outstanding \| claim			59
Third-party products claims liability under insurance in other assets				$ 300
Selling, General and Administrative Expenses
Payments for legal settlements		$ 6,500
Other Non-current Assets
Third-party products claims liability under insurance in other long-term obligations			$ 0	300
Other Non-current Liabilities
Third-party products claims liability under insurance in other long-term obligations			$ 1,000	$ 1,300

Pension and Post-Retirement Benefits - Summarizes Information about Pension and Post-Retirement Benefit Plans (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Pension Benefits
Pension Plans, Postretirement and Other Employee Benefits
Service cost	$ 1,037	$ 1,078	$ 1,295
Interest cost	3,971	4,067	4,813
Expected return on plan assets	(5,265)	(5,495)	(5,498)
Net amortization and deferral	1,773	1,592	2,665
Net pension benefit or post-retirement costs	1,516	1,242	3,275
Post-retirement Benefits
Pension Plans, Postretirement and Other Employee Benefits
Service cost	107	132	176
Interest cost	753	876	1,074
Expected return on plan assets	(1)	(1)	(1)
Net amortization and deferral	0	0	281
Special termination benefit	0	21	48
Net pension benefit or post-retirement costs	$ 859	$ 1,028	$ 1,578

Pension and Post-Retirement Benefits - Changes in Benefit Obligations and Plan Assets (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Pension Benefits
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit obligation, beginning balance	$ 116,145	$ 115,420
Service cost	1,037	1,078	$ 1,295
Interest cost	3,971	4,067	4,813
Actuarial (gain) loss	6,824	1,640
Benefits paid	(6,685)	(6,517)
Amendments	760	457
Other	0	0
Benefit obligation, ending balance	122,052	116,145	115,420
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets, beginning balance	83,850	84,716
Actual return on plan assets	12,757	5,651
Employer contributions	2,145	0
Benefits paid	(6,685)	(6,517)
Other	0	0
Fair value of plan assets, ending balance	92,067	83,850	84,716
Plan assets less than benefit obligations at December 31 recognized as liability for pension and other post-retirement benefits	(29,985)	(32,295)
Post-retirement Benefits
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit obligation, beginning balance	24,393	25,091
Service cost	107	132	176
Interest cost	753	876	1,074
Actuarial (gain) loss	(1,576)	(802)
Benefits paid	(1,280)	(1,332)
Amendments	0	0
Other	374	407
Benefit obligation, ending balance	22,771	24,393	25,091
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets, beginning balance	14	17
Actual return on plan assets	(1)	(3)
Employer contributions	893	925
Benefits paid	(1,280)	(1,332)
Other	374	407
Fair value of plan assets, ending balance	0	14	$ 17
Plan assets less than benefit obligations at December 31 recognized as liability for pension and other post-retirement benefits	$ (22,771)	$ (24,379)

Pension and Post-Retirement Benefits - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Pension Plans, Postretirement and Other Employee Benefits
Projected benefit obligation, nonqualified pension plan	$ 1.6	$ 1.6
Defined benefit plan, pension plans with accumulated benefit obligations in excess of plan assets, aggregate accumulated benefit obligation	1.6	1.6
Fair value of plan assets, nonqualified pension plan	0.0	0.0
Defined benefit plan, accumulated other comprehensive income net gains (losses), after tax	(13.5)	$ (13.8)
Defined benefit plan, accumulated other comprehensive income net prior service cost (credit), after tax	$ 0.5
Percentage of contributions to individual multiemployer pension funds	5.00%	5.00%	5.00%
Company contribution over defined benefit plan	4.00%
Company contributing percentage on defined benefit plan	25.00%
Employee contribution over defined benefit plan	8.00%
Company contributions to defined contribution plan	$ 3.0	$ 2.4	$ 2.8
Pension Benefits
Pension Plans, Postretirement and Other Employee Benefits
Accumulated benefit obligation	122.0	$ 116.0
Expected contributions to the plans for fiscal year	2.5
Post-retirement Benefits
Pension Plans, Postretirement and Other Employee Benefits
Expected contributions to the plans for fiscal year	$ 1.4
Certain Employees
Pension Plans, Postretirement and Other Employee Benefits
Employee contribution over defined benefit plan	8.00%
Company contribution on profit sharing match	25.00%
Other Employees
Pension Plans, Postretirement and Other Employee Benefits
Company contribution on profit sharing match	25.00%

Pension and Post-Retirement Benefits - Estimated Future Pension and Post-Retirement Benefit Payments (Detail) $ in Thousands	Dec. 31, 2017 USD ($)
Pension Benefits
Defined Benefit Plan, Expected Future Benefit Payments, Fiscal Year Maturity [Abstract]
2017	$ 7,195
2018	7,334
2019	7,409
2020	7,446
2021	7,573
2023-2027	38,030
Post-retirement Benefits \| Before Medicare Subsidy
Defined Benefit Plan, Expected Future Benefit Payments, Fiscal Year Maturity [Abstract]
2017	1,536
2018	1,480
2019	1,490
2020	1,571
2021	1,600
2023-2027	7,892
Post-retirement Benefits \| After Medicare Subsidy
Defined Benefit Plan, Expected Future Benefit Payments, Fiscal Year Maturity [Abstract]
2017	1,400
2018	1,345
2019	1,358
2020	1,438
2021	1,465
2023-2027	$ 7,178

Pension and Post-Retirement Benefits - Amounts in Accumulated Other Comprehensive Income Expected to be Recognized as Components of Net Periodic Benefit Cost (Detail) $ in Thousands	12 Months Ended
	Dec. 31, 2017 USD ($)
Pension Plans, Postretirement and Other Employee Benefits
Net actuarial loss	$ 1,877
Prior service cost	534
Total	2,411
Pension Benefits
Pension Plans, Postretirement and Other Employee Benefits
Net actuarial loss	1,877
Prior service cost	534
Total	2,411
Post-retirement Benefits
Pension Plans, Postretirement and Other Employee Benefits
Net actuarial loss	0
Prior service cost	0
Total	$ 0

Pension and Post-Retirement Benefits - Company's Obligations Determined under Weighted-Average Assumptions (Detail)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Pension Benefits
Pension Plans, Postretirement and Other Employee Benefits
Discount rate	3.70%	4.20%
Long-term rate of compensation increase	3.50%	3.50%
Long-term rate of return on plan assets	6.80%	7.00%
Post-retirement Benefits
Pension Plans, Postretirement and Other Employee Benefits
Discount rate	3.70%	4.20%
Long-term rate of return on plan assets	7.00%	7.00%
Post-retirement Benefits \| Pre-65
Pension Plans, Postretirement and Other Employee Benefits
Ultimate rate	0.00%	5.00%
Post-retirement Benefits \| Pre-65 \| Maximum
Pension Plans, Postretirement and Other Employee Benefits
Initial rate	0.00%	7.30%
Post-retirement Benefits \| Post-65
Pension Plans, Postretirement and Other Employee Benefits
Ultimate rate	0.00%	5.00%
Post-retirement Benefits \| Post-65 \| Minimum
Pension Plans, Postretirement and Other Employee Benefits
Initial rate	0.00%	8.50%

Pension and Post-Retirement Benefits - Effect of One-Percentage-Point Change in Assumed Health Care Cost Trend Rates (Detail) $ in Thousands	12 Months Ended
	Dec. 31, 2017 USD ($)
Compensation and Retirement Disclosure [Abstract]
Effect on total of service and interest cost, increase	$ 113
Effect on post-retirement benefit obligation, increase	2,598
Effect on total of service and interest cost, decrease	(95)
Effect on post-retirement benefit obligation, decrease	$ (2,209)

Pension and Post-Retirement Benefits - Fair Value of Pension Plan Assets (Detail)	Dec. 31, 2017	Dec. 31, 2016
Pension Benefits \| Equity securities
Pension Plans, Postretirement and Other Employee Benefits
Percentage of the fair value of the total plan assets	51.80%	59.40%
Pension Benefits \| Debt securities
Pension Plans, Postretirement and Other Employee Benefits
Percentage of the fair value of the total plan assets	46.30%	38.30%
Pension Benefits \| Cash
Pension Plans, Postretirement and Other Employee Benefits
Percentage of the fair value of the total plan assets	1.90%	2.30%
Post-retirement Benefits \| Equity securities
Pension Plans, Postretirement and Other Employee Benefits
Percentage of the fair value of the total plan assets	0.00%	64.00%
Post-retirement Benefits \| Debt securities
Pension Plans, Postretirement and Other Employee Benefits
Percentage of the fair value of the total plan assets	0.00%	39.10%
Post-retirement Benefits \| Cash
Pension Plans, Postretirement and Other Employee Benefits
Percentage of the fair value of the total plan assets	0.00%	(3.10%)

Pension and Post-Retirement Benefits - Summary of Multiemployer Pension Plan (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
LIUNA
Pension Plans, Postretirement and Other Employee Benefits
EIN/ Pension Plan No.	52-6074345/001
Pension Protection Act Zone Status	Red	Red
Company Contributions (in thousands)	$ 223,000	$ 167,000	$ 182,000
Surcharge Imposed	Yes
Expiration Date of CBA	May 31, 2020
IUOE
Pension Plans, Postretirement and Other Employee Benefits
EIN/ Pension Plan No.	36-6052390/001
Pension Protection Act Zone Status	Green	Green
Company Contributions (in thousands)	$ 40,000	$ 28,000	29,000
Surcharge Imposed	No
Expiration Date of CBA	Jul. 29, 2018
CSSS
Pension Plans, Postretirement and Other Employee Benefits
EIN/ Pension Plan No.	36-6044243/001
Pension Protection Act Zone Status	Red	Red
Company Contributions (in thousands)	$ 51,000	$ 51,000	$ 51,000
Surcharge Imposed	NA
Central States, Southeast and Southwest Areas Pension Plan
Pension Plans, Postretirement and Other Employee Benefits
Withdrawal liability from pension plan	$ 1,000,000
Withdrawal liability paid on monthly installments	$ 4,000

Income Taxes - Summary of Income Tax (Expense) Benefit (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Current:
Federal									$ (10,754)	$ 60	$ (170)
State									(1,167)	(274)	1,448
Current income tax total									(11,921)	(214)	1,278
Deferred:
Federal									22,641	32,944	7,439
State									(2,040)	3,959	3,034
Deferred income tax total									20,601	36,903	10,473
Income tax (expense) benefit	$ 28,783	$ (14,707)	$ (7,110)	$ 1,714	$ 6,588	$ 12,177	$ 9,774	$ 8,150	$ 8,680	$ 36,689	$ 11,751

Income Taxes - Summary of Tax Effects on Deferred Tax Assets and Liabilities (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Gross deferred tax assets:
Net operating loss carry forward and state tax credits	$ 22,783	$ 65,022
Pension and post-retirement benefit costs	13,710	22,920
Alternative minimum tax credit carry forward	30,401	19,431
Property, plant and equipment	5,750	6,112
Accrued expenses	10,755	6,752
Inventories	4,354	4,362
Third-party products liability	249	511
Stock-based compensation expense	8,785	5,576
Note payable	3,133	4,009
Other	5,095	5,458
Deferred Tax Assets, Gross	105,015	140,153
Gross deferred tax liabilities:
Land and mineral property basis difference	(78,520)	(126,315)
Fixed assets and depreciation	(51,556)	(61,531)
Intangibles	(4,795)	(2,260)
Other	0	(122)
Total deferred tax liabilities	(134,871)	(190,228)
Net deferred tax liabilities	$ (29,856)	$ (50,075)

Income Taxes - Operating Loss Carryforwards (Details) - IRS $ in Millions	Dec. 31, 2017 USD ($)
Operating Loss Carryforwards [Line Items]
Federal net operating loss carryforwards	$ 93.4
Cadre Services, Inc.
Operating Loss Carryforwards [Line Items]
Federal net operating loss carryforwards	$ 69.0

Income Taxes - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Income Tax Disclosure [Abstract]
Decrease related to deferred tax assets	$ 45,000,000
Decrease related to deferred tax liabilities	80,800,000
Corresponding net adjustment to deferred income tax benefit	35,800,000
Alternative minimum tax credit carry forward	30,400,000	$ 19,400,000
Unrecognized tax benefits	$ 0	$ 0

Income Taxes - Summary of Effective Income Tax Rate on Pretax Earnings (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Income tax (expense) benefit computed at U.S. federal statutory rate									$ (47,784)	$ 27,211	$ (41)
Decrease (increase) resulting from:
Statutory depletion									20,259	4,734	8,918
Prior year tax return reconciliation									219	435	393
State income taxes, net of federal benefit									(2,267)	2,369	1,370
Adjustment to deferred taxes from the Tax Act rate reduction									35,772	0	0
Equity compensation									2,602	2,003	0
Other, net									(121)	(63)	1,111
Income tax (expense) benefit	$ 28,783	$ (14,707)	$ (7,110)	$ 1,714	$ 6,588	$ 12,177	$ 9,774	$ 8,150	$ 8,680	$ 36,689	$ 11,751

Obligations Under Guarantees (Detail) - Travelers Casualty and Surety Company $ in Millions	Dec. 31, 2017 USD ($)
Surety Bonds
Loss Contingencies
Surety bonds outstanding	$ 12.1
Reclamation Bonds
Loss Contingencies
Bonds related to reclamation requirements	$ 10.3

Segment Reporting - Additional Information (Detail) $ in Thousands	12 Months Ended
	Dec. 31, 2017 USD ($) Segment Product	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)
Segment Reporting Information
Number of reportable segments \| Segment	2
Number of products \| Product	221
Goodwill	$ 272,079	$ 240,975	$ 68,647
Operating Segments \| Oil & Gas Proppants
Segment Reporting Information
Goodwill	247,500	220,300
Operating Segments \| Industrial & Specialty Products
Segment Reporting Information
Goodwill	$ 24,600	$ 20,700

Segment Reporting - Presentation of Sales and Segment Contribution Margin for Reporting Segments and Other Operating Results (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Segment Reporting Information
Sales:									$ 1,240,851	$ 559,625	$ 642,989
Selling, general and administrative	$ (29,637)	$ (29,602)	$ (26,012)	$ (22,341)	$ (19,167)	$ (18,472)	$ (14,585)	$ (15,503)	(107,592)	(67,727)	(62,777)
Depreciation, depletion and amortization	(27,335)	(24,673)	(23,626)	(21,599)	(21,194)	(17,175)	(15,209)	(14,556)	(97,233)	(68,134)	(58,474)
Interest expense	(7,244)	(8,347)	(8,105)	(7,646)	(7,998)	(6,684)	(6,647)	(6,643)
Income tax (expense) benefit	28,783	(14,707)	(7,110)	1,714	6,588	12,177	9,774	8,150	8,680	36,689	11,751
Net income (loss)	$ 71,952	$ 41,273	$ 29,459	$ 2,522	$ (6,942)	$ (11,339)	$ (11,772)	$ (11,003)	145,206	(41,056)	11,868
Operating Segments
Segment Reporting Information
Sales:									1,240,851	559,625	642,989
Total segment contribution margin									390,753	90,433	159,065
Operating Segments \| Oil & Gas Proppants
Segment Reporting Information
Sales:									1,020,365	362,550	430,435
Total segment contribution margin									301,972	11,445	88,928
Operating Segments \| Industrial & Specialty Products
Segment Reporting Information
Sales:									220,486	197,075	212,554
Total segment contribution margin									88,781	78,988	70,137
Segment Reconciling Items
Segment Reporting Information
Operating activities excluded from segment cost of sales									(17,417)	(8,103)	(11,142)
Selling, general and administrative									(107,592)	(67,727)	(62,777)
Depreciation, depletion and amortization									(97,233)	(68,134)	(58,474)
Interest expense									(31,342)	(27,972)	(27,283)
Other income (expense), net, including interest income									$ (643)	$ 3,758	$ 728

Unaudited Supplementary Data (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands					3 Months Ended								12 Months Ended
	Nov. 03, 2016	Jul. 21, 2016	May 05, 2016	Feb. 22, 2016	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Sales:
Product					$ 306,442	$ 295,768	$ 246,022	$ 209,321	$ 160,429	$ 125,805	$ 116,039	$ 121,627	$ 1,057,553	$ 523,900	$ 640,464
Service					54,124	49,255	44,443	35,476	21,944	11,943	955	883	183,298	35,725	2,525
Cost of sales (excluding depreciation, depletion and amortization):
Product					204,545	189,105	164,025	162,637	133,758	112,215	102,587	106,629	720,312	455,189	494,814
Service					50,161	38,818	33,386	24,838	14,653	7,211	120	122	147,203	22,106	252
Operating expenses
Selling, general and administrative					29,637	29,602	26,012	22,341	19,167	18,472	14,585	15,503	107,592	67,727	62,777
Depreciation, depletion and amortization					27,335	24,673	23,626	21,599	21,194	17,175	15,209	14,556	97,233	68,134	58,474
Total operating expenses					56,972	54,275	49,638	43,940	40,361	35,647	29,794	30,059	204,825	135,861	121,251
Operating income (loss)					48,888	62,825	43,416	13,382	(6,399)	(17,325)	(15,507)	(14,300)	168,511	(53,531)	26,672
Other (expense) income:
Interest expense					(7,244)	(8,347)	(8,105)	(7,646)	(7,998)	(6,684)	(6,647)	(6,643)
Other income (expense), net, including interest income					1,525	1,502	1,258	(4,928)	867	493	608	1,790	(643)	3,758	728
Total other (expenses) income					(5,719)	(6,845)	(6,847)	(12,574)	(7,131)	(6,191)	(6,039)	(4,853)	(31,985)	(24,214)	(26,555)
Income (loss) before income taxes					43,169	55,980	36,569	808	(13,530)	(23,516)	(21,546)	(19,153)	136,526	(77,745)	117
Income tax benefit					28,783	(14,707)	(7,110)	1,714	6,588	12,177	9,774	8,150	8,680	36,689	11,751
Net income (loss)					$ 71,952	$ 41,273	$ 29,459	$ 2,522	$ (6,942)	$ (11,339)	$ (11,772)	$ (11,003)	$ 145,206	$ (41,056)	$ 11,868
Earnings (loss) per share, basic (in usd per share)					$ 0.89	$ 0.51	$ 0.36	$ 0.03	$ (0.09)	$ (0.17)	$ (0.19)	$ (0.20)	$ 1.79	$ (0.63)	$ 0.22
Earnings (loss) per share, diluted (in usd per share)					$ 0.88	$ 0.50	$ 0.36	$ 0.03	$ (0.09)	$ (0.17)	$ (0.19)	$ (0.20)	$ 1.77	$ (0.63)	$ 0.22
Weighted average common shares outstanding, basic (in shares)					81,014	81,121	81,087	80,983	75,539	66,676	63,417	54,470	81,051	65,037	53,344
Weighted average common shares outstanding, diluted (in shares)					81,921	81,783	81,945	82,244	75,539	66,676	63,417	54,470
Dividend declared per share (in usd per share)	$ 0.0625	$ 0.0625	$ 0.0625	$ 0.0625	$ 0.06	$ 0.06	$ 0.06	$ 0.06	$ 0.06	$ 0.06	$ 0.06	$ 0.06	$ 0.25	$ 0.25	$ 0.438	$ 0.438

Parent Company Financials - Balance Sheet - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Current Assets:
Cash and cash equivalents	$ 384,567	$ 711,225	$ 277,077	$ 263,066
Due from affiliates	146,683	0
Total current assets	703,244	892,945
Total assets	2,307,283	2,073,220
Current Liabilities:
Dividends payable	5,229	5,221
Total current liabilities	213,945	109,960
Deferred income taxes, net	29,856	50,075
Total liabilities	910,777	799,930
Stockholders’ Equity:
Preferred stock, $0.01 par value, 10,000,000 shares authorized; 0 issued and outstanding at December 31, 2017 and 2016	0	0
Common stock, $0.01 par value, 500,000,000 shares authorized; 81,267,205 issued and 80,524,255 outstanding at December 31, 2017; 81,184,042 issued and 81,028,898 outstanding at December 31 2016	812	811
Additional paid-in capital	1,147,084	1,129,051
Retained earnings	287,992	163,173
Treasury stock, at cost, 742,950 and 155,144 shares at December 31, 2017 and 2016, respectively	(25,456)	(3,869)
Accumulated other comprehensive loss	(13,926)	(15,876)
Total stockholders’ equity	1,396,506	1,273,290	384,167	403,816
Total liabilities and stockholders’ equity	2,307,283	2,073,220
Parent Company
Current Assets:
Cash and cash equivalents	230,647	534,378	58,579	47,292
Total current assets	377,330	534,378
Investment in subsidiaries	1,024,511	854,860
Total assets	1,401,841	1,389,238
Current Liabilities:
Accrued expenses and other current liabilities	106	461
Dividends payable	5,229	5,222
Due to affiliates	0	110,265
Total current liabilities	5,335	115,948
Deferred income taxes, net	0	0
Total liabilities	5,335	115,948
Stockholders’ Equity:
Preferred stock, $0.01 par value, 10,000,000 shares authorized; 0 issued and outstanding at December 31, 2017 and 2016	0	0
Common stock, $0.01 par value, 500,000,000 shares authorized; 81,267,205 issued and 80,524,255 outstanding at December 31, 2017; 81,184,042 issued and 81,028,898 outstanding at December 31 2016	812	811
Additional paid-in capital	1,147,084	1,129,051
Retained earnings	287,992	163,173
Treasury stock, at cost, 742,950 and 155,144 shares at December 31, 2017 and 2016, respectively	(25,456)	(3,869)
Accumulated other comprehensive loss	(13,926)	(15,876)
Total stockholders’ equity	1,396,506	1,273,290	$ 384,167	$ 403,816
Total liabilities and stockholders’ equity	$ 1,401,841	$ 1,389,238

Parent Company Financials- Income Statement (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Operating Income (Loss) [Abstract]
Sales									$ 1,240,851	$ 559,625	$ 642,989
Cost of sales	$ 204,545	$ 189,105	$ 164,025	$ 162,637	$ 133,758	$ 112,215	$ 102,587	$ 106,629	720,312	455,189	494,814
Operating expenses:
Selling, general and administrative	29,637	29,602	26,012	22,341	19,167	18,472	14,585	15,503	107,592	67,727	62,777
Total operating expenses	56,972	54,275	49,638	43,940	40,361	35,647	29,794	30,059	204,825	135,861	121,251
Operating income (loss)	48,888	62,825	43,416	13,382	(6,399)	(17,325)	(15,507)	(14,300)	168,511	(53,531)	26,672
Other income (expense)
Interest income									(31,342)	(27,972)	(27,283)
Other income (expense), net, including interest income	1,525	1,502	1,258	(4,928)	867	493	608	1,790	(643)	3,758	728
Total other (expenses) income	(5,719)	(6,845)	(6,847)	(12,574)	(7,131)	(6,191)	(6,039)	(4,853)	(31,985)	(24,214)	(26,555)
Income tax benefit	28,783	(14,707)	(7,110)	1,714	6,588	12,177	9,774	8,150	8,680	36,689	11,751
Net income (loss)	$ 71,952	$ 41,273	$ 29,459	$ 2,522	$ (6,942)	$ (11,339)	$ (11,772)	$ (11,003)	145,206	(41,056)	11,868
Other comprehensive income (loss), net of deferred income taxes:
Unrealized gain (loss) on investments (net of tax of $0, $(4) and $29 for 2017, 2016, and 2015, respectively)									0	(6)	47
Unrealized gain (loss) on derivatives (net of tax of $(27), $29 and $34 for 2017, 2016, and 2015, respectively)									(44)	49	53
Foreign currency translation adjustment (net of tax of $2, $0 and $0 for 2017, 2016 and 2015, respectively)									(6)	0	0
Pension and other post-retirement benefits liability adjustment (net of tax of $1,205, $152 and $2,469 for 2017, 2016, and 2015, respectively)									2,000	252	3,547
Comprehensive income (loss)									147,156	(40,761)	15,515
Pension and post-retirement liability									2,000	252	3,547
Tax expense (benefit) on unrealized gain (loss) on investments									0	(4)	29
Tax expense (benefit) on unrealized gain (loss) on derivatives									(27)	29	34
Tax expense (benefit) on pension and other post-retirement benefits liability adjustment									1,205	152	2,469
Parent Company
Operating Income (Loss) [Abstract]
Sales									0	0	0
Cost of sales									0	0	0
Operating expenses:
Selling, general and administrative									252	184	185
Other									0	10	19
Total operating expenses									252	194	204
Operating income (loss)									(252)	(194)	(204)
Other income (expense)
Interest income									3,854	1,046	262
Other income (expense), net, including interest income									0	0	1
Total other (expenses) income									3,854	1,046	263
Income before income taxes and equity in net earnings of subsidiaries									3,602	852	59
Income tax benefit									(1,453)	(344)	(24)
Income before equity in net earnings of subsidiaries									2,149	508	35
Equity in earnings of subsidiaries, net of tax									143,057	(41,564)	11,833
Net income (loss)									145,206	(41,056)	11,868
Other comprehensive income (loss), net of deferred income taxes:
Unrealized gain (loss) on investments (net of tax of $0, $(4) and $29 for 2017, 2016, and 2015, respectively)									0	(6)	47
Unrealized gain (loss) on derivatives (net of tax of $(27), $29 and $34 for 2017, 2016, and 2015, respectively)									(44)	49	53
Foreign currency translation adjustment (net of tax of $2, $0 and $0 for 2017, 2016 and 2015, respectively)									(6)	0	0
Pension and other post-retirement benefits liability adjustment (net of tax of $1,205, $152 and $2,469 for 2017, 2016, and 2015, respectively)									2,000	252	3,547
Other comprehensive income (loss), net of deferred income taxes									1,950	295	3,647
Comprehensive income (loss)									147,156	(40,761)	15,515
Pension and post-retirement liability									2,000	252	3,547
Tax expense (benefit) on unrealized gain (loss) on investments									(4)	29	(8)
Tax expense (benefit) on unrealized gain (loss) on derivatives									29	34	(32)
Tax expense (benefit) on pension and other post-retirement benefits liability adjustment									$ 152	$ 2,469	$ (9,678)

Parent Company Financials - Statement of Equity (Details) - USD ($)					1 Months Ended		3 Months Ended								12 Months Ended
	Nov. 03, 2016	Jul. 21, 2016	May 05, 2016	Feb. 22, 2016	Nov. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Beginning balance										$ 1,273,290,000				$ 384,167,000	$ 1,273,290,000	$ 384,167,000	$ 403,816,000
Net income (loss)							$ 71,952,000	$ 41,273,000	$ 29,459,000	$ 2,522,000	$ (6,942,000)	$ (11,339,000)	$ (11,772,000)	$ (11,003,000)	145,206,000	(41,056,000)	11,868,000
Issuance of common stock (stock offerings net of issuance costs of $25,732)					$ 467,000,000	$ 186,200,000										931,288,000
Unrealized gain (loss) on derivatives															(44,000)	49,000	53,000
Foreign currency translation adjustment															(6,000)	0	0
Unrealized gain (loss) on short-term investments															0	(6,000)	47,000
Pension and post-retirement liability															2,000,000	252,000	3,547,000
Cash dividends declared ($0.25, $0.438 and $0.500 per share of common stock for 2016, 2015 and 2014 respectively))															(20,387,000)	(16,893,000)	(23,445,000)
Equity-based compensation															25,050,000	12,107,000	3,857,000
Excess tax benefit from equity-based compensation																148,000
Proceeds from options exercised															798,000	4,825,000	473,000
Issuance of restricted stock															0	0
Shares withheld for employee taxes related to vested restricted stock and stock units															(4,379,000)	(1,591,000)	(794,000)
Repurchase of common stock															(25,022,000)		(15,255,000)
Ending balance							$ 1,396,506,000				$ 1,273,290,000				$ 1,396,506,000	$ 1,273,290,000	$ 384,167,000	$ 403,816,000
Dividend declared per share (in usd per share)	$ 0.0625	$ 0.0625	$ 0.0625	$ 0.0625			$ 0.06	$ 0.06	$ 0.06	$ 0.06	$ 0.06	$ 0.06	$ 0.06	$ 0.06	$ 0.25	$ 0.25	$ 0.438	$ 0.438
Common stock issuance costs																$ 25,732
Common Stock
Beginning balance										$ 811,000				$ 539,000	$ 811,000	539,000	$ 539,000
Issuance of common stock (stock offerings net of issuance costs of $25,732)																272,000
Shares withheld for employee taxes related to vested restricted stock and stock units															1,000
Ending balance							$ 812,000				$ 811,000				812,000	811,000	539,000	$ 539,000
Treasury Stock
Beginning balance										(3,869,000)				(15,845,000)	(3,869,000)	(15,845,000)	(542,000)
Proceeds from options exercised															1,190,000	8,465,000	744,000
Issuance of restricted stock															1,859,000	1,437,000
Shares withheld for employee taxes related to vested restricted stock and stock units															386,000	2,074,000	(792,000)
Repurchase of common stock															(25,022,000)		(15,255,000)
Ending balance							(25,456,000)				(3,869,000)				(25,456,000)	(3,869,000)	(15,845,000)	(542,000)
Additional Paid-In Capital
Beginning balance										1,129,051,000				194,670,000	1,129,051,000	194,670,000	191,086,000
Issuance of common stock (stock offerings net of issuance costs of $25,732)																931,016,000
Equity-based compensation															25,050,000	12,107,000	3,857,000
Proceeds from options exercised															(392,000)	(3,640,000)	(271,000)
Issuance of restricted stock															(1,859,000)	(1,437,000)
Shares withheld for employee taxes related to vested restricted stock and stock units															(4,766,000)	(3,665,000)	(2,000)
Ending balance							1,147,084,000				1,129,051,000				1,147,084,000	1,129,051,000	194,670,000	191,086,000
Retained Earnings
Beginning balance										163,173,000				220,974,000	163,173,000	220,974,000	232,551,000
Net income (loss)															145,206,000	(41,056,000)	11,868,000
Cash dividends declared ($0.25, $0.438 and $0.500 per share of common stock for 2016, 2015 and 2014 respectively))															(20,387,000)	(16,893,000)	(23,445,000)
Excess tax benefit from equity-based compensation																148,000
Ending balance							287,992,000				163,173,000				287,992,000	163,173,000	220,974,000	232,551,000
Accumulated Other Comprehensive (Loss)
Beginning balance										(15,876,000)				(16,171,000)	(15,876,000)	(16,171,000)	(19,818,000)
Unrealized gain (loss) on derivatives															(44,000)	49,000	53,000
Foreign currency translation adjustment															(6,000)
Unrealized gain (loss) on short-term investments																(6,000)	47,000
Pension and post-retirement liability															2,000,000	252,000	3,547,000
Ending balance							(13,926,000)				(15,876,000)				(13,926,000)	(15,876,000)	(16,171,000)	(19,818,000)
Parent Company
Beginning balance										1,273,290,000				384,167,000	1,273,290,000	384,167,000	403,816,000
Net income (loss)															145,206,000	(41,056,000)	11,868,000
Issuance of common stock (stock offerings net of issuance costs of $25,732)																931,288,000
Unrealized gain (loss) on derivatives															(44,000)	49,000	53,000
Foreign currency translation adjustment															(6,000)	0	0
Unrealized gain (loss) on short-term investments															0	(6,000)	47,000
Pension and post-retirement liability															2,000,000	252,000	3,547,000
Cash dividends declared ($0.25, $0.438 and $0.500 per share of common stock for 2016, 2015 and 2014 respectively))															(20,387,000)	(16,893,000)	(23,445,000)
Equity-based compensation															25,050,000	12,107,000	3,857,000
Excess tax benefit from equity-based compensation																148,000
Proceeds from options exercised															798,000	4,825,000	473,000
Issuance of restricted stock															0	0
Shares withheld for employee taxes related to vested restricted stock and stock units															(4,379,000)	(1,591,000)	(794,000)
Repurchase of common stock															25,022,000		(15,255,000)
Ending balance							1,396,506,000				1,273,290,000				$ 1,396,506,000	$ 1,273,290,000	$ 384,167,000	403,816,000
Dividend declared per share (in usd per share)															$ 0.25	$ 0.438	$ 0.500
Common stock issuance costs															$ 25,732
Parent Company \| Common Stock
Beginning balance										811,000				539,000	811,000	$ 539,000	$ 539,000
Issuance of common stock (stock offerings net of issuance costs of $25,732)																272,000
Shares withheld for employee taxes related to vested restricted stock and stock units															1,000
Ending balance							812,000				811,000				812,000	811,000	539,000	539,000
Parent Company \| Treasury Stock
Beginning balance										(3,869,000)				(15,845,000)	(3,869,000)	(15,845,000)	(542,000)
Proceeds from options exercised															1,190,000	8,465,000	744,000
Issuance of restricted stock															1,859,000	1,437,000
Shares withheld for employee taxes related to vested restricted stock and stock units															386,000	2,074,000	(792,000)
Repurchase of common stock															25,022,000		(15,255,000)
Ending balance							(25,456,000)				(3,869,000)				(25,456,000)	(3,869,000)	(15,845,000)	(542,000)
Parent Company \| Additional Paid-In Capital
Beginning balance										1,129,051,000				194,670,000	1,129,051,000	194,670,000	191,086,000
Issuance of common stock (stock offerings net of issuance costs of $25,732)																931,016,000
Equity-based compensation															25,050,000	12,107,000	3,857,000
Proceeds from options exercised															(392,000)	(3,640,000)	(271,000)
Issuance of restricted stock															(1,859,000)	(1,437,000)
Shares withheld for employee taxes related to vested restricted stock and stock units															(4,766,000)	(3,665,000)	(2,000)
Ending balance							1,147,084,000				1,129,051,000				1,147,084,000	1,129,051,000	194,670,000	191,086,000
Parent Company \| Retained Earnings
Beginning balance										163,173,000				220,974,000	163,173,000	220,974,000	232,551,000
Net income (loss)															145,206,000	(41,056,000)	11,868,000
Cash dividends declared ($0.25, $0.438 and $0.500 per share of common stock for 2016, 2015 and 2014 respectively))															(20,387,000)	(16,893,000)	(23,445,000)
Excess tax benefit from equity-based compensation																148,000
Ending balance							287,992,000				163,173,000				287,992,000	163,173,000	220,974,000	232,551,000
Parent Company \| Accumulated Other Comprehensive (Loss)
Beginning balance										$ (15,876,000)				$ (16,171,000)	(15,876,000)	(16,171,000)	(19,818,000)
Unrealized gain (loss) on derivatives															(44,000)	49,000	53,000
Foreign currency translation adjustment															(6,000)
Unrealized gain (loss) on short-term investments																(6,000)	47,000
Pension and post-retirement liability															2,000,000	252,000	3,547,000
Ending balance							$ (13,926,000)				$ (15,876,000)				$ (13,926,000)	$ (15,876,000)	$ (16,171,000)	$ (19,818,000)

Parent Company Financials - Statement of Cash Flow (Details) - USD ($) $ in Thousands	3 Months Ended									12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Mar. 31, 2013	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Operating activities:
Net income (loss)	$ 71,952	$ 41,273	$ 29,459	$ 2,522	$ (6,942)	$ (11,339)	$ (11,772)	$ (11,003)		$ 145,206	$ (41,056)	$ 11,868
Adjustments to reconcile net income (loss) to net cash provided by operating activities:
Other										5,529	3,643	(5,257)
Accounts payable and accrued liabilities										59,769	13,121	(42,353)
Net cash provided by operating activities										238,156	381	61,492
Investing activities:
Maturities of short-term investments										0	21,872	53,568
Net cash provided by (used in) investing activities										(507,672)	(201,657)	49
Financing activities:
Dividends paid										(20,377)	(15,125)	(26,797)
Repurchase of common stock										(25,022)	0	(15,255)
Proceeds from options exercised										798	4,825	473
Tax payments related to shares withheld for vested restricted stock and stock units										(4,379)	(1,591)	(794)
Issuance of common stock									$ 0	0	678,791
Common stock issuance costs									$ 0	0	(25,732)
Net cash provided by (used in) financing activities										(57,142)	635,424	(47,530)
Net increase (decrease) in cash and cash equivalents										(326,658)	434,148	14,011
Cash and cash equivalents, beginning of period				711,225				277,077		711,225	277,077	263,066
Cash and cash equivalents, end of period	384,567				711,225					384,567	711,225	277,077
Cash paid (received) during the period for:
Interest										24,490	21,994	21,729
Common stock issued for business acquisitions										0	165	0
Parent Company
Operating activities:
Net income (loss)										145,206	(41,056)	11,868
Adjustments to reconcile net income (loss) to net cash provided by operating activities:
Undistributed (Income) loss from equity method investment, net										(143,057)	41,564	(11,833)
Other										0	(30)	(195)
Accounts payable and accrued liabilities										48	353	29
Net cash provided by operating activities										2,197	831	(131)
Investing activities:
Maturities of short-term investments										0	21,872	53,568
Investment in subsidiary										(143,654)	(188,177)	0
Net cash provided by (used in) investing activities										(143,654)	(166,305)	53,568
Financing activities:
Dividends paid										(20,377)	(15,125)	(26,797)
Repurchase of common stock										(25,022)	0	(15,255)
Proceeds from options exercised										798	4,603	473
Tax payments related to shares withheld for vested restricted stock and stock units										(4,379)	(1,590)	(794)
Issuance of common stock										0	678,791	0
Issuance of treasury stock										0	221	0
Common stock issuance costs										0	(25,733)	0
Net financing activities with subsidiaries										(113,294)	106	223
Net cash provided by (used in) financing activities										(162,274)	641,273	(42,150)
Net increase (decrease) in cash and cash equivalents										(303,731)	475,799	11,287
Cash and cash equivalents, beginning of period				$ 534,378				$ 58,579		534,378	58,579	47,292
Cash and cash equivalents, end of period	$ 230,647				$ 534,378					230,647	534,378	58,579
Cash paid (received) during the period for:
Interest										(3,853)	(1,046)	(263)
Common stock issued for business acquisitions										$ 0	$ 278,229	$ 0

Subsequent Events (Detail) - $ / shares						3 Months Ended								12 Months Ended
Subsequent Events (Detail) - $ / shares	Feb. 16, 2018	Nov. 03, 2016	Jul. 21, 2016	May 05, 2016	Feb. 22, 2016	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Subsequent Event
Common stock cash dividend declared, per share		$ 0.0625	$ 0.0625	$ 0.0625	$ 0.0625	$ 0.06	$ 0.06	$ 0.06	$ 0.06	$ 0.06	$ 0.06	$ 0.06	$ 0.06	$ 0.25	$ 0.25	$ 0.438	$ 0.438
Subsequent Event
Subsequent Event
Common stock cash dividend declared, per share	$ 0.0625

Subsequent Events	12 Months Ended
Subsequent Events	Dec. 31, 2017
Subsequent Events [Abstract]
Subsequent Events	NOTE W—SUBSEQUENT EVENTS On February 16, 2018, our Board of Directors declared a quarterly cash dividend of $0.0625 per share to common stockholders of record at the close of business on March 15, 2018, payable on April 5, 2018.

Organization - (Detail)	12 Months Ended
Organization - (Detail)	Dec. 31, 2017 Segment
Organization And Nature Of Business
Number of business segments	2