Document and Entity Information - shares	6 Months Ended
Document and Entity Information - shares	Jun. 30, 2018	Jul. 27, 2018
Document And Entity Information [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Jun. 30, 2018
Document Fiscal Year Focus	2018
Document Fiscal Period Focus	Q2
Entity Registrant Name	U.S. Silica Holdings, Inc.
Entity Central Index Key	0001524741
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		77,477,209

Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Current Assets:
Cash and cash equivalents	$ 322,357	$ 384,567
Accounts receivable, net	280,019	212,586
Inventories, net	167,415	92,376
Prepaid expenses and other current assets	14,439	13,715
Income tax deposits	3,191	0
Total current assets	787,421	703,244
Property, plant and mine development, net	1,825,653	1,169,155
Goodwill	414,257	272,079
Intangible assets, net	194,795	150,007
Other assets	27,219	12,798
Total assets	3,249,345	2,307,283
Current Liabilities:
Accounts payable and accrued expenses	206,994	171,041
Current portion of long-term debt	13,969	6,867
Current portion of deferred revenue	52,021	36,128
Income tax payable	0	1,566
Total current liabilities	272,984	215,602
Long-term debt, net	1,253,384	505,075
Deferred revenue	59,424	82,286
Liability for pension and other post-retirement benefits	47,022	52,867
Deferred income taxes, net	172,610	29,856
Other long-term obligations	85,417	25,091
Total liabilities	1,890,841	910,777
Commitments and Contingencies (Note O)
Stockholders’ Equity:
Preferred stock, $0.01 par value, 10,000,000 shares authorized; zero issued and outstanding at June 30, 2018 and December 31, 2017	0	0
Common stock, $0.01 par value, 500,000,000 shares authorized; 81,734,599 issued and 77,681,643 outstanding at June 30, 2018; 81,267,205 issued and 80,524,255 outstanding at December 31, 2017	815	812
Additional paid-in capital	1,160,235	1,147,084
Retained earnings	327,173	287,992
Treasury stock, at cost, 4,052,956 and 742,950 shares at June 30, 2018 and December 31, 2017, respectively	(120,056)	(25,456)
Accumulated other comprehensive loss	(9,663)	(13,926)
Total stockholders’ equity	1,358,504	1,396,506
Total liabilities and stockholders’ equity	$ 3,249,345	$ 2,307,283

Condensed Consolidated Balance Sheets (Parenthetical) - $ / shares	Jun. 30, 2018	Dec. 31, 2017
Statement of Financial Position [Abstract]
Preferred stock, par value (in dollars per share)	$ 0.01	$ 0.01
Preferred stock authorized (shares)	10,000,000	10,000,000
Preferred stock issued (shares)	0	0
Preferred stock outstanding (shares)	0	0
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock authorized (shares)	500,000,000	500,000,000
Common stock issued (shares)	81,734,599	81,267,205
Common stock outstanding (shares)	77,681,643	80,524,255
Treasury stock, at cost (shares)	4,052,956	742,950

Condensed Consolidated Statements of Operations - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Sales:
Total sales	$ 427,433	$ 290,465	$ 796,746	$ 535,262
Cost of sales (excluding depreciation, depletion and amortization):
Product	236,236	162,238	443,475	324,134
Service	56,609	34,726	110,280	60,018
Total cost of sales (excluding depreciation, depletion and amortization)	292,845	196,964	553,755	384,152
Operating expenses:
Selling, general and administrative	42,232	25,839	76,823	47,978
Depreciation, depletion and amortization	36,563	23,626	65,155	45,225
Asset impairment	16,184	0	16,184	0
Total operating expenses	94,979	49,465	158,162	93,203
Operating income	39,609	44,036	84,829	57,907
Other (expense) income:
Interest expense	(20,214)	(8,105)	(27,284)	(15,751)
Other income (expense), net, including interest income	1,081	638	1,746	(4,779)
Total other expense	(19,133)	(7,467)	(25,538)	(20,530)
Income before income taxes	20,476	36,569	59,291	37,377
Income tax expense	(2,832)	(7,110)	(10,353)	(5,396)
Net income	$ 17,644	$ 29,459	$ 48,938	$ 31,981
Earnings per share:
Basic (in dollars per share)	$ 0.23	$ 0.36	$ 0.62	$ 0.39
Diluted (in dollars per share)	$ 0.22	$ 0.36	$ 0.62	$ 0.39
Weighted average shares outstanding:
Basic (shares)	77,784	81,087	78,636	81,032
Diluted (shares)	78,480	81,945	79,328	82,103
Dividends declared per share (in dollars per share)	$ 0.0625	$ 0.0625	$ 0.13	$ 0.13
Product
Sales:
Total sales	$ 345,957	$ 235,891	$ 640,745	$ 439,143
Service
Sales:
Total sales	$ 81,476	$ 54,574	$ 156,001	$ 96,119

Condensed Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Statement of Comprehensive Income [Abstract]
Net income	$ 17,644	$ 29,459	$ 48,938	$ 31,981
Other comprehensive income (loss):
Unrealized gain (loss) on derivatives (net of tax of $1 and $(2) for the three months ended June 30, 2018 and 2017, respectively, and $2 and $(23) for the six months ended June 30, 2018 and 2017, respectively)	4	(3)	6	(39)
Foreign currency translation adjustment (net of tax of $(7) and zero for the three months ended June 30, 2018 and 2017, respectively, and $(9) and zero for the six months ended June 30, 2018 and 2017, respectively)	(544)	0	(541)	0
Pension and other post-retirement benefits liability adjustment (net of tax of $799 and $(1,185) for the three months ended June 30, 2018 and 2017, respectively, and $1,529 and $(845) for the six months ended June 30, 2018 and 2017, respectively)	2,505	(1,967)	4,798	(1,402)
Comprehensive income	$ 19,609	$ 27,489	$ 53,201	$ 30,540

- Definition

The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

+ References + Details

Condensed Consolidated Statements of Comprehensive Income (Parenthetical) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Statement of Comprehensive Income [Abstract]
Tax expense (benefit) on unrealized gain (loss) on derivatives	$ 1	$ (2)	$ 2	$ (23)
Tax expense (benefit) on foreign currency translation adjustment	(7)	0	(9)	0
Tax expense (benefit) on pension and other post-retirement benefits liability adjustment	$ 799	$ (1,185)	$ 1,529	$ (845)

Condensed Consolidated Statements of Stockholders' Equity - 6 months ended Jun. 30, 2018 - USD ($) $ in Thousands	Total	Common Stock	Treasury Stock	Additional Paid-In Capital	Retained Earnings	Accumulated Other Comprehensive Loss
Beginning Balance at Dec. 31, 2017	$ 1,396,506	$ 812	$ (25,456)	$ 1,147,084	$ 287,992	$ (13,926)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	48,938				48,938
Unrealized gain on derivatives	6					6
Foreign currency translation adjustment	(541)					(541)
Pension and post-retirement liability	4,798					4,798
Cash dividend declared ($0.0625 per share)	(9,757)				(9,757)
Equity-based compensation	13,185			13,185
Proceeds from options exercised	62		93	(31)
Shares withheld for employee taxes related to vested restricted stock and stock units	(4,194)	3	(4,194)	(3)
Repurchase of common stock	(90,499)		(90,499)
Ending Balance at Jun. 30, 2018	$ 1,358,504	$ 815	$ (120,056)	$ 1,160,235	$ 327,173	$ (9,663)

Condensed Consolidated Statements of Cash Flows - USD ($)	6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017
Operating activities:
Net income	$ 48,938,000	$ 31,981,000
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation, depletion and amortization	65,155,000	45,225,000
Asset impairment	16,184,000	0
Debt issuance amortization	4,421,000	692,000
Original issue discount amortization	561,000	188,000
Deferred income taxes	11,023,000	2,149,000
Deferred revenue	(6,970,000)	15,235,000
(Gain) loss on disposal of property, plant and equipment	(5,619,000)	394,000
Equity-based compensation	13,185,000	11,952,000
Bad debt provision, net of recoveries	387,000	848,000
Other	(4,516,000)	767,000
Changes in operating assets and liabilities, net of effects of acquisitions:
Accounts receivable	(24,472,000)	(69,400,000)
Inventories	6,040,000	5,207,000
Prepaid expenses and other current assets	1,333,000	2,069,000
Income taxes	(4,757,000)	4,257,000
Accounts payable and accrued expenses	(2,883,000)	25,443,000
Short-term and long-term obligations-vendor incentives	54,632,000	0
Liability for pension and other post-retirement benefits	301,000	454,000
Net cash provided by operating activities	172,943,000	77,461,000
Investing activities:
Capital expenditures	(159,196,000)	(152,087,000)
Capitalized intellectual property costs	(3,863,000)	(1,973,000)
Acquisition of business, net of cash acquired	(742,841,000)	(18,636,000)
Proceeds from sale of property, plant and equipment	26,179,000	12,000
Net cash used in investing activities	(879,721,000)	(172,684,000)
Financing activities:
Dividends paid	(10,132,000)	(10,187,000)
Repurchase of common stock	(90,499,000)	0
Proceeds from options exercised	62,000	547,000
Tax payments related to shares withheld for vested restricted stock and stock units	(4,194,000)	(3,926,000)
Proceeds from long-term debt	1,280,000,000	0
Payments on long-term debt	(493,231,000)	(3,270,000)
Financing fees paid	(37,273,000)	0
Principal payments on capital lease obligations	(165,000)	(631,000)
Net cash provided by (used in) financing activities	644,568,000	(17,467,000)
Net decrease in cash and cash equivalents	(62,210,000)	(112,690,000)
Cash and cash equivalents, beginning of period	384,567,000	711,225,000
Cash and cash equivalents, end of period	322,357,000	598,535,000
Cash paid (received) during the period for:
Interest	22,689,000	12,766,000
Taxes, net of refunds	3,778,000	(1,010,000)
Related party purchases	1,604,000	1,870,000
Non-cash Items:
Equipment received	0	18,185,000
Accrued capital expenditures	21,966,000	7,171,000
Capital lease assumed by third-party	119,000	0
Asset retirement obligation assumed by third-party	$ 2,116,000	$ 0

Summary of Significant Accounting Policies

6 Months Ended

Jun. 30, 2018

Accounting Policies [Abstract]

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES

NOTE A—SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES

Basis of Presentation and Consolidation

The accompanying Condensed Consolidated Financial Statements (the “Financial Statements”) of U.S. Silica Holdings, Inc. (“Holdings,” and together with its subsidiaries “we,” “us” or the “Company”) included in this Quarterly Report on Form 10-Q, have been prepared in accordance with generally accepted accounting principles in the United States (“GAAP”) for interim financial information and with the instructions to Form 10-Q and Article 10 of Regulation S-X issued by the U.S. Securities and Exchange Commission (“SEC”). They do not contain certain information included in our Annual Report on Form 10-K for the fiscal year ended December 31, 2017; therefore, the interim Condensed Consolidated Financial Statements should be read in conjunction with that Annual Report on Form 10-K. 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 year's amounts have been made to conform to the current year presentation. In conforming to the current year's presentation, the Company identified and corrected an immaterial amount in its statement of cash flows for the six months ended June 30, 2017. The correction reduced Capital Expenditures within Net Cash Used in Investing Activities with a corresponding decrease to Accounts Payable and Accrued Expenses within Net Cash Used in Operating Activities. The amount is presented as Non-cash Accrued Capital Expenditures and had no impact in the Company's Balance Sheet, Income Statement or Net Change in Cash and Cash Equivalents in the Statement of Cash Flows.

Throughout this report we refer to (i) our Condensed Consolidated Balance Sheets as our “Balance Sheets,” (ii) our Condensed Consolidated Statements of Operations as our “Income Statements,” and (iii) our Condensed Consolidated Statements of Cash Flows as our “Cash Flows.”

Unaudited Interim Financial Statements

The accompanying Balance Sheet as of June 30, 2018; the Income Statements and Condensed Consolidated Statements of Comprehensive Income for the three and six months ended June 30, 2018 and 2017; the Condensed Consolidated Statements of Stockholders' Equity and Cash Flows for the six months ended June 30, 2018; and other information disclosed in the related notes are unaudited. The Balance Sheet as of December 31, 2017, was derived from our audited consolidated financial statements included in our 2017 Annual Report on Form 10-K.

Use of Estimates and Assumptions

The preparation of the Financial Statements requires us 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 the 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

Products

We derive our product 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. We primarily sell our products through individual purchase orders executed under short-term price agreements or at prevailing market rates. The amount invoiced reflects product, transportation and / or additional handling services as applicable, such as storage, transloading the product from railcars to trucks and last mile logistics to the customer site. We invoice most of our product customers on a per shipment basis, although for some larger customers, we consolidate invoices weekly or monthly. Standard collection terms are net 30 days, although extended terms are offered in competitive situations.

We recognize revenue for products and materials at a point in time following the transfer of control of such items to the customer, which typically occurs upon shipment or delivery depending on the terms of the underlying contracts. We account for shipping and handling activities related to product and material sales contracts with customers as costs to fulfill our promise to transfer the associated products pursuant to the accounting policy election allowed under ASC 606-10-18. Accordingly, we record amounts billed for shipping and handling costs as a component of net sales and accrue and classify related costs as a component of cost of sales at the time revenue is recognized.

For a limited number of customers, we sell under long-term, minimum purchase supply agreements. 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 do not consider these agreements solely representative of contracts with customers. An executed order specifying the type and quantity of product to be delivered, in combination with the noted agreements, comprise our contracts in these arrangements.

Service

We derive our service revenues primarily through the provision of transportation, equipment rental, and contract labor services to companies in the oil and gas industry. Transportation services typically consist of transporting customer proppant from storage facilities to proximal well-sites and are contracted through work orders executed under established pricing agreements. The amount invoiced reflects the transportation services rendered. Equipment rental services provide customers with use of either dedicated or nonspecific wellhead proppant delivery equipment solutions for contractual periods defined either through formal lease agreements or executed work orders under established pricing agreements. The amounts invoiced reflect the length of time the equipment set was utilized in the billing period. Contract labor services provide customers with proppant delivery equipment operators through work orders executed under established pricing agreements. The amounts invoiced reflect the amount of time our labor services were utilized in the billing period.

We typically invoice our customers on a weekly or monthly basis; however, some customers receive invoices upon well-site operation completion. Standard collection terms are net 30 days, although extended terms are offered in competitive situations. We typically recognize revenue for specific, dedicated equipment set rental arrangements under ASC 840, Leases. For the remaining components of service revenue, we have applied the practical expedient allowed under ASC 606-10-55-18 to recognize transportation revenues in proportion to the amount we have the right to invoice.

Contracts with Multiple Performance Obligations

For contracts that contain multiple performance obligations, such as work orders containing a combination of product, transportation, equipment rentals, and contract labor services, we allocate the transaction price to each performance obligation identified in the contract based on relative standalone selling prices, or estimates of such prices, and recognize the related revenue as control of each individual product or service is transferred to the customer, in satisfaction of the corresponding performance obligations. We typically invoice our customers on a weekly or monthly basis; however, some customers receive invoices upon well-site operation completion. Standard collection terms are net 30 days, although extended terms are offered in competitive situations.

Taxes Collected from Customers and Remitted to Governmental Authorities.

We exclude from our measurement of transaction prices all taxes assessed by governmental authorities that are both (i) imposed on and concurrent with a specific revenue-producing transaction and (ii) collected from customers. Accordingly, such tax amounts are not included as a component of net sales or cost of sales.

Deferred Revenues

For a limited number of customers, we enter into supply agreements which give customers the right to make advanced payments toward the purchase of certain products at specified volumes over an average initial period of one to five years. These payments represent consideration that is unconditional for which we have yet to transfer the related product. These payments are recorded as contract liabilities referred to as “deferred revenues” upon receipt and recognized as revenue upon delivery of the related product.

Unbilled Receivables

Revenues recognized in advance of invoice issuance create assets referred to as “unbilled receivables.” Any portion of our unbilled receivables for which our right to consideration is conditional on a factor other than the passage of time is considered a contract asset. These assets are presented on a combined basis with accounts receivable and are converted to accounts receivable once billed.

Foreign Currency Translation

For our operations in countries where the functional currency is other than the U.S. dollar, balance sheet amounts are translated using the exchange rate in effect at the balance sheet date. Income statement amounts are translated monthly using the average exchange rate for the respective month. The gains and losses resulting from the changes in exchange rates from year-to-year are recorded as a component of accumulated other comprehensive income or loss as currency translation adjustments, net of tax. Any gains or losses on transactions in currencies other than the functional currency are included in other income (expense), net, including interest income. For the six months ended June 30, 2018, other income (expense), net, including interest income, includes a net realized foreign currency transaction gain of $0.3 million.

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.

On January 1, 2018, we adopted the new accounting standard and all of the related amendments (“new revenue standard”) to all contracts using the modified retrospective method. Adoption of the new revenue standard did not result in a material cumulative effect adjustment to the opening balance of retained earnings. The comparative information has not been restated and continues to be reported under the accounting standards in effect for those periods. We do not expect the adoption of the new revenue standard to have a material impact to our net income on an ongoing basis. See Note S -Revenue to these Financial Statements for additional disclosures.

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. We have established a project team in order to analyze the standard and have begun to review our current accounting policies and procedures to identify potential differences and changes which would result from applying the requirements of the new standard to our lease contracts. We have identified our population of lease agreements and are currently assessing the impact of other arrangements for embedded leases. 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 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. The update requires companies to include the service cost component of net periodic benefit costs in the same line item or items as compensation costs arising from services rendered by the associated employees during the period. The update also disallows capitalization of the other components of net periodic benefit costs and requires those costs to be presented in the income statement separately from the service cost component and outside of a subtotal of income from operations. The update is effective for fiscal years beginning after December 15, 2017, including interim periods within those annual periods for public business entities. Companies are required to retrospectively apply the requirement for a separate presentation in the income statement of service costs and other components of net benefit cost and prospectively adopt the requirement to limit the capitalization of benefit costs to the service component. Application of a practical expedient is allowed permitting an employer to use the amounts disclosed in its pension and other postretirement benefit plan note for the prior comparative periods as the estimation basis for applying the retrospective presentation requirements.

We implemented the update on January 1, 2018 and utilized the practical expedient to estimate the impact on the prior comparative period information presented in the interim and annual financial statements. We previously capitalized all net periodic benefit costs incurred for plant personnel in inventory and recorded the majority of net periodic benefit costs incurred by corporate personnel and retirees into selling, general, and administrative expenses.

The following is a reconciliation of the effect of the reclassification (in thousands) of the net benefit cost in the Company’s condensed consolidated statements of income for the three and six months ended June 30, 2017. In addition, the table reflects the effect of the reclassification between product sales and services sales to conform to the current year's presentation for the three and six months ended June 30, 2017:



	Three Months Ended June 30, 2017
	As Previously Reported		Services Reclassifications			ASU 2017-07 Adjustments			As Revised
Product Sales	$	246,022	$	(10,131	)	$	—		$	235,891
Service Sales	44,443		10,131			—			54,574
Total sales	290,465		—			—			290,465
Product cost of sales	164,025		(1,340		)	(447		)	162,238
Service cost of sales	33,386		1,340			—			34,726
Total cost of sales (excluding depreciation, depletion and amortization)	197,411		—			(447		)	196,964
Selling, general and administrative expenses	26,012		—			(173		)	25,839
Operating income	43,416		—			620			44,036
Other income (expense)	1,258		—			(620		)	638



	Six Months Ended June 30, 2017
	As Previously Reported			Services Reclassifications			ASU 2017-07 Adjustments			As Revised
Product Sales	$	455,343		$	(16,200	)	$	—		$	439,143
Service Sales	79,919			16,200			—			96,119
Total sales	535,262			—			—			535,262
Product cost of sales	326,662			(1,794		)	(734		)	324,134
Service cost of sales	58,224			1,794			—			60,018
Total cost of sales (excluding depreciation, depletion and amortization)	384,886			—			(734		)	384,152
Selling, general and administrative expenses	48,353			—			(375		)	47,978
Operating income	56,798			—			1,109			57,907
Other income (expense)	(3,670		)	—			(1,109		)	(4,779		)

In February 2018, the FASB issued Accounting Standards Update ASU 2018-02, Income Statement-Reporting Comprehensive Income (Topic 220): Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income. The ASU provides that the stranded tax effects from the Tax Act in accumulated other comprehensive loss may be reclassified to retained earnings. The ASU is effective February 1, 2019, with early adoption permitted. We are currently evaluating the effect that the transition guidance will have on our financial statements and related disclosures.

Earnings Per Share

6 Months Ended

Jun. 30, 2018

Earnings Per Share [Abstract]

EARNINGS PER SHARE

NOTE B—EARNINGS PER SHARE

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.

The following table shows the computation of basic and diluted earnings per share for the three and six months ended June 30, 2018 and 2017:



In thousands, except per share amounts	Three Months Ended June 30,				Six Months Ended June 30,
	2018		2017		2018		2017
Numerator:
Net income	$	17,644	$	29,459	$	48,938	$	31,981

Denominator:
Weighted average shares outstanding	77,784		81,087		78,636		81,032
Diluted effect of stock awards	696		858		692		1,071
Weighted average shares outstanding assuming dilution	78,480		81,945		79,328		82,103

Basic earnings per share	$	0.23	$	0.36	$	0.62	$	0.39
Diluted earnings per share	$	0.22	$	0.36	$	0.62	$	0.39

Certain stock options, restricted stock awards and performance share units were excluded from the computation of diluted earnings per share because their effect would have been anti-dilutive. Weighted-average stock awards (in thousands) excluded from the calculation of diluted earnings per common share were as follows:



	Three Months Ended June 30,		Six Months Ended June 30,
	2018	2017	2018	2017
Weighted-average outstanding stock options excluded	426	195	427	195
Weighted-average outstanding restricted stock and performance share units awards excluded	264	426	319	48

Capital Structure and Accumulated Other Comprehensive Income (Loss)

6 Months Ended

Jun. 30, 2018

Equity [Abstract]

CAPITAL STRUCTURE AND ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS)

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. There were 81,734,599 shares issued and 77,681,643 shares outstanding at June 30, 2018. There were 81,267,205 shares issued and 80,524,255 shares outstanding at December 31, 2017.

During the six months ended June 30, 2018, our Board of Directors declared quarterly cash dividends as follows:



Dividends per Common Share		Declaration Date	Record Date	Payable Date
$	0.0625	February 16, 2018	March 15, 2018	April 5, 2018
$	0.0625	May 14, 2018	June 15, 2018	July 6, 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 June 30, 2018 or December 31, 2017. 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. 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.

In May 2018, our Board of Directors authorized the repurchase of up to $200 million of our common stock. During the three months ended June 30, 2018, we repurchased 536,139 shares of our common stock at an average price of $28.91 and had $184.5 million of remaining availability under this program.

In October 2017, our Board of Directors authorized us to repurchase up to $100 million of our common stock by December 11, 2018. During the three months ended March 31, 2018, we repurchased 2,828,023 shares of our common stock at an average price of $26.52 under this program. As of March 31, 2018, we had repurchased a total of 3,555,104 shares of our common stock at an average price of $28.13, and fully utilized our shares authorized to be repurchased at such time.

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 Loss

Accumulated other comprehensive 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, net of tax. The following table presents the changes in accumulated other comprehensive loss by component (in thousands) during the six months ended June 30, 2018:



	For the Six Months Ended June 30, 2018
	Unrealized gain/(loss) on cash flow hedges			Foreign currency translation adjustments			Pension and other post-retirement benefits liability			Total
Beginning Balance	$	(76	)	$	(6	)	$	(13,844	)	$	(13,926	)
Other comprehensive gain (loss) before reclassifications	—			(541		)	4,314			3,773
Amounts reclassed from accumulated other comprehensive loss	6			—			484			490
Ending Balance	$	(70	)	$	(547	)	$	(9,046	)	$	(9,663	)

Amounts reclassified from accumulated other comprehensive 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 benefit costs at their pre-tax amounts.

Business Combinations

6 Months Ended

Jun. 30, 2018

Business Combinations [Abstract]

BUSINESS COMBINATIONS

NOTE D—BUSINESS COMBINATIONS

2018 Acquisition:

On May 1, 2018, we completed the acquisition of all of the outstanding capital stock of EP Acquisition Parent, Inc., a Delaware corporation (“EPAP”), and the ultimate parent of EP Minerals, LLC ("EPM"). Contemporaneous with the merger, EPAP was renamed EP Minerals Holdings, Inc. ("EPMH"). The consideration paid consisted of $742.8 million of cash, net of cash acquired of $19.1 million, subject to customary post-closing adjustments. A portion of the cash consideration has been deposited into escrow to support the post-closing purchase price adjustment. EPM is a global producer of engineered materials derived from industrial minerals, including diatomaceous earth, clay (calcium bentonite) and perlite. EPM's industrial minerals are used as filter aids, absorbents and functional additives for a variety of industries including food and beverage, biofuels, recreational water, oil and gas, farm and home, landscape, sports turf, paint, plastics, and insecticides. The acquisition of EPM increased our industrial materials product offering in our Industrial & Specialty Products segment.

We have accounted for the acquisition of EPMH under the acquisition method of accounting in accordance with ASC 805, Business Combinations. 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, within a period of time not to exceed one year after the date of acquisition, or May 1, 2019, in order to provide us with the time to complete the valuation of its assets and liabilities.

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



Preliminary allocation of purchase price:	(In thousands)
Accounts receivable, net	$	43,354
Inventories	84,395
Property, plant and mine development	123,086
Mineral rights	462,050
Identifiable intangible assets - finite lived	21,050
Identifiable intangible assets - indefinite lived	25,050
Prepaids and deposits	2,054
Other assets	4,089
Goodwill	139,378
Total assets acquired	904,506
Accounts payable	13,435
Accrued expenses and other current liabilities	8,255
Deferred tax liabilities	130,209
Long term obligations	9,766
Total liabilities assumed	$	161,665
Net assets acquired	$	742,841

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



	Approximate Fair Value		Estimated Useful Life
	(in thousands)		(in years)
Technology and intellectual property	2,000		15
Customer relationships	$	19,050	15
Total identifiable intangible assets - finite lived	$	21,050

Goodwill represents the excess of the purchase price over the fair value of the underlying net assets acquired. Goodwill in this transaction is attributable to planned growth in our industrial materials product offering in our Industrial & Specialty Products segment. Intangibles and goodwill are not expected to be deductible for tax purposes.

Our Income Statement included revenue of $41.7 million and a net loss of $0.7 million for both the three and six months ended June 30, 2018, associated with EPMH following the date of acquisition. We incurred $8.8 million and $10.9 million of acquisition-related charges, excluding debt issuance costs, for the three and six months ended June 30, 2018, respectively, which are included in selling, general and administrative expenses on our Income Statement.

The acquisition of EPMH was accounted for using the acquisition method of accounting. The purchase price and purchase price allocation is 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 acquisition. As a result, our final purchase price allocation may be significantly different than reflected above. We expect to complete the purchase price allocation as soon as practicable, but no later than one year from the acquisition date.

Unaudited Pro Forma Results

The results of EPMH's operations have been included in the consolidated financial statements subsequent to the acquisition date. EPMH's fiscal year end was November 30 and the Company's fiscal year end was December 31. Under SEC regulations, if a target's fiscal year end varies by more than 93 days from the acquirer's fiscal year end, it is required to adjust interim periods until it is within 93 days. Since EPMH’s fiscal year end was within 93 days of the Company's fiscal year end, no adjustment is necessary and EPMH’s fiscal year end and interim period ends are used as if they coincided with the Company's fiscal year end and interim period end. The following unaudited pro forma consolidated financial information reflects the results of operations as if the EPMH acquisition had occurred on January 1, 2017, after giving effect to certain purchase accounting adjustments. Material non-recurring transaction costs attributable to the business combination were $15.2 million. Pro forma net income includes incremental interest expense due to the related debt financing, incremental depreciation and depletion expense related to the fair value adjustment of property, plant 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):



	Three Months Ended June 30,				Six Months Ended June 30,
	2018		2017		2018		2017
Sales	$	451,566	$	341,113	$	879,493	$	629,196
Net income	$	19,693	$	13,196	$	70,539	$	8,097
Basic earnings per share	$	0.25	$	0.16	$	0.90	$	0.10
Diluted earnings per share	$	0.25	$	0.16	$	0.89	$	0.10

Basic shares	77,784		81,087		78,636		81,032
Diluted shares	78,480		81,945		79,328		82,103

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 final 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):



	Estimate as of December 31, 2017		Measurement Period Adjustments			Purchase Price Allocation
Accounts receivable	$	11,201	$	—		$	11,201
Inventories	8,067		—			8,067
Other current assets	362		—			362
Assets held for sale	9,453		—			9,453
Property, plant and mine development	27,458		—			27,458
Mineral rights	26,300		(2,800		)	23,500
Other non-current assets	1,136		—			1,136
Goodwill	22,522		2,800			25,322
Customer relationships	1,840		—			1,840
Total assets acquired	108,339		—			108,339
Accounts payable and accrued expenses	3,761		—			3,761
Unfavorable leasehold positions	2,237		—			2,237
Notes Payable	866		—			866
Other long term liabilities	—		—			—
Asset retirement obligations	474		—			474
Total liabilities assumed	7,338		—			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 have incurred $1.0 million to date of acquisition-related charges which are included in selling, general and administrative expenses. 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 the MS Sand acquisition is 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 acquisition. As a result, our final purchase price allocation may be significantly different than reflected above. We expect to complete the purchase price allocation as soon as practicable, but no later than one year from the acquisition date.

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	)

Accounts Receivable

6 Months Ended

Jun. 30, 2018

Receivables [Abstract]

ACCOUNTS RECEIVABLE

NOTE E—ACCOUNTS RECEIVABLE

At June 30, 2018 and December 31, 2017, accounts receivable (in thousands) consisted of the following:



	June 30, 2018			December 31, 2017
Trade receivables	$	281,951		$	217,649
Less: Allowance for doubtful accounts	(7,773		)	(7,100		)
Net trade receivables	274,178			210,549
Other receivables	5,841			2,037
Total accounts receivable	$	280,019		$	212,586

Changes in our allowance for doubtful accounts (in thousands) during the six months ended June 30, 2018 are as follows:



	June 30, 2018
Beginning balance	$	7,780
Bad debt provision	387
Write-offs	(394		)
Ending balance	$	7,773

Our ten largest customers accounted for approximately 50% and 58% of total sales during the six months ended June 30, 2018 and 2017, respectively. Sales to one of our customers accounted for 14% of our total sales during the six months ended June 30, 2018. Sales to two of our customers accounted for 14% and 12% of our total sales during the six months ended June 30, 2017. No other customers accounted for 10% or more of our total sales. At June 30, 2018, one of our customers' accounts receivable represented 15% of our total accounts receivable, net of allowance. At December 31, 2017, two of our customers' accounts receivable represented 19% and 11% 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

Inventories

6 Months Ended

Jun. 30, 2018

Inventory Disclosure [Abstract]

INVENTORIES

NOTE F—INVENTORIES

At June 30, 2018 and December 31, 2017, inventories (in thousands) consisted of the following:



	June 30, 2018		December 31, 2017
Supplies	$	36,639	$	21,277
Raw materials and work in process	72,238		28,034
Finished goods	58,538		43,065
Total inventories	$	167,415	$	92,376

Property, Plant and Mine Development

6 Months Ended

Jun. 30, 2018

Property, Plant and Equipment [Abstract]

PROPERTY, PLANT AND MINE DEVELOPMENT

NOTE G—PROPERTY, PLANT AND MINE DEVELOPMENT

At June 30, 2018 and December 31, 2017, property, plant and mine development (in thousands) consisted of the following:



	June 30, 2018			December 31, 2017
Mining property and mine development	$	1,051,824		$	586,242
Asset retirement cost	14,308			14,184
Land	42,189			36,552
Land improvements	66,336			45,878
Buildings	73,150			56,330
Machinery and equipment	790,655			590,566
Furniture and fixtures	4,053			2,953
Construction-in-progress	183,222			189,970
	2,225,737			1,522,675
Accumulated depletion, depreciation and amortization	(400,084		)	(353,520		)
Total property, plant and mine development, net	$	1,825,653		$	1,169,155

At June 30, 2018 and December 31, 2017, the aggregate cost of machinery and equipment acquired under capital leases was $1.1 million and $0.9 million, respectively, reduced by accumulated depreciation of $0.2 million and $0.2 million, respectively. The amount of interest costs capitalized in property, plant and mine development was $3.3 million for the six months ended June 30, 2018. There were no interest costs capitalized for the six months ended June 30, 2017.

On March 21, 2018, we completed the sale of three transload facilities located in the Permian, Eagle Ford, and Marcellus Basins to CIG Logistics (“CIG”) for total consideration of $86.1 million, including the assumption by CIG of $2.2 million of Company obligations. Total cash consideration was $83.9 million. The consideration includes receipt of a vendor incentive from CIG to enter into master transloading service arrangements. Of the total consideration, $25.8 million was allocated to the fair value of the transload facilities, which had a net book value of $20.0 million and resulted in a gain on sale of $5.8 million. The consideration included a related asset retirement obligation of $2.1 million and an equipment note of $0.1 million assumed by CIG. In addition, $60.3 million of the consideration received in excess of the facilities' fair value was allocated to vendor incentives to be recognized as a reduction of costs using a service-level methodology over the contract lives of the transloading service arrangements. At June 30, 2018, vendor incentives of $10.6 million and $46.3 million were classified in accounts payable and accrued expenses and in other long-term obligations, respectively, on our balance sheet.

Separately, on March 21, 2018, we accrued $7.9 million in contract termination costs for facilities contracts operated by third-parties, which will not transfer to CIG. During the three months ended June 30, 2018, as a result of the final settlement of these contracts, we recorded a $2.7 million credit in selling, general and administrative expenses on our Income Statement.

During the three months ended June 30, 2018, we recorded a $16.2 million asset impairment related to the closure of our resin coating facility and associated product portfolio.

Goodwill and Intangible Assets

6 Months Ended

Jun. 30, 2018

Goodwill and Intangible Assets Disclosure [Abstract]

GOODWILL AND INTANGIBLE ASSETS

NOTE H—GOODWILL AND INTANGIBLE ASSETS

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



	Goodwill
Balance at December 31, 2017	$	272,079
EPMH acquisition	139,378
MS Sand acquisition measurement period adjustment	2,800
Balance at June 30, 2018	$	414,257

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



		June 30, 2018							December 31, 2017
	Estimated Useful Life	Gross Carrying Amount		Accumulated Amortization			Net		Gross Carrying Amount		Accumulated Amortization			Net
	(in years)
Technology and intellectual property	15	$	76,588	$	(8,413	)	$	68,175	$	70,703	$	(5,917	)	$	64,786
Customer relationships	13 - 15	80,279		(11,777		)	68,502		61,229		(9,076		)	52,153
Total definite-lived intangible assets:		$	156,867	$	(20,190	)	$	136,677	$	131,932	$	(14,993	)	$	116,939
Trade name		58,118		—			58,118		33,068		—			33,068
Total intangible assets:		$	214,985	$	(20,190	)	$	194,795	$	165,000	$	(14,993	)	$	150,007

Amortization expense was $2.9 million and $5.2 million for the three and six months ended June 30, 2018, respectively. Amortization expense was $2.2 million and $4.2 million for the three and six months ended June 30, 2017, respectively.

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



2018	$	5,586
2019	10,894
2020	10,894
2021	10,894
2022	10,894

Debt

6 Months Ended

Jun. 30, 2018

Debt Disclosure [Abstract]

DEBT

NOTE I—DEBT

At June 30, 2018 and December 31, 2017, debt (in thousands) consisted of the following:



	June 30, 2018			December 31, 2017
Senior secured credit facility:
Revolver expiring May 1, 2023 (8.0% at June 30, 2018 and 5.75% at December 31, 2017)	$	—		$	—
Term loan facility—final maturity May 1, 2025 (6.13% at June 30, 2018 and 4.75%-5.25% December 31, 2017)	1,276,800			489,075
Less: Unamortized original issue discount	(6,670		)	(944		)
Less: Unamortized debt issuance cost	(29,665		)	(3,099		)
Note payable secured by royalty interest	25,410			24,740
Customer note payable	286			745
Equipment notes payable	448			719
Capital leases	744			706
Total debt	1,267,353			511,942
Less: current portion	(13,969		)	(6,867		)
Total long-term portion of debt	$	1,253,384		$	505,075

Revolving Line-of-Credit

We have a $100.0 million revolving line-of-credit (the “Revolver”), with zero drawn and $4.0 million allocated for letters of credit as of June 30, 2018, leaving $96.0 million available under the Revolver.

Senior Secured Credit Facility

At June 30, 2018, contractual maturities of our senior secured credit facility (in thousands) are as follows:



2018	$	6,400
2019	12,800
2020	12,800
2021	12,800
Thereafter	1,232,000
Total	$	1,276,800

On May 1, 2018, we entered into the Third Amended and Restated Credit Agreement (the "Credit Agreement"). The Credit Agreement increases our existing senior debt by entering into a new $1.380 billion senior secured credit facility, consisting of a $1.280 billion term loan and a $100 million revolving credit facility that may also be used for swingline loans or letters of credit, and we may elect to increase the term loan in accordance with the terms of the Credit Agreement. Borrowings under the Credit Agreement will bear interest at variable rates as determined at our election, at LIBOR or a base rate, in each case, plus an applicable margin. In addition, under the Credit Agreement, we are required to pay a per annum facility fee and fees for letters of credit. The Credit Agreement is secured by substantially all of our assets and of our domestic subsidiaries' assets and a pledge of the equity interests in such entities. The term loan matures on May 1, 2025, and the revolving credit facility expires May 1, 2023. We incurred $37.3 million in debt issuance costs and original issue discount, of which $35.0 million was capitalized, as result of the new Credit Agreement, and wrote-off $1.1 million of capitalized debt issuance costs relating to the previously existing senior debt.

The facility contains covenants that, among other things, govern our ability, and certain of our subsidiaries' abilities, to create, incur or assume indebtedness and liens, to make acquisitions or investments, to sell assets and to pay dividends. The Credit Agreement also requires us to maintain a consolidated 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 30% of the Revolver commitment. These covenants are subject to a number of important exceptions and qualifications. The Credit Agreement includes events of default and other affirmative and negative covenants that are usual for facilities and transactions of this type. As of June 30, 2018, and December 31, 2017, we are in compliance with all covenants in accordance with our senior secured credit facility.

Note Payable Secured by Royalty Interest

In conjunction 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	$	875
2019	1,750
2020	1,750
2021	1,750
2022	1,750

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 royalty 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 discounted rate of 14%. As of June 30, 2018, the note payable had a balance of $25.4 million. The increase in the note payable amount is due to interest paid-in-kind. The effective interest rate based on the updated projected future cash payments was 22% at June 30, 2018.

Deferred Revenue

6 Months Ended

Jun. 30, 2018

Deferred Revenue Disclosure [Abstract]

DEFERRED REVENUE

NOTE J—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 six months ended June 30, 2018 we received advances of $13.4 million. At June 30, 2018 and December 31, 2017, the total deferred revenue balance was $111.4 million and $118.4 million, respectively, of which $52.0 million and $36.1 million was classified as current on our Balance Sheets.

NOTE S— REVENUE

We consider sales disaggregated at the product and service level by segment to depict how the nature, amount, timing and uncertainty of revenues and cash flow are impacted by changes in economic factors. The following table disaggregates our sales by major source for the three and six months ended June 30, 2018 (in thousands):



	Three Months Ended June 30, 2018						Six Months Ended June 30, 2018
Category	Oil & Gas Proppants		Industrial & Specialty Products		Total Sales		Oil & Gas Proppants		Industrial & Specialty Products		Total Sales
Product	$	242,587	$	103,370	$	345,957	$	481,009	$	159,736	$	640,745
Service	81,476		—		81,476		155,984		17		156,001
Total Sales	$	324,063	$	103,370	$	427,433	$	636,993	$	159,753	$	796,746

The following tables reflect the changes in our contract assets, which we classify as unbilled receivables and our contract liabilities, which we classify as deferred revenues, for the six months ended June 30, 2018 (in thousands):



	Unbilled Receivables
December 31, 2017	$	5,245
Reclassifications to billed receivables	(8,161		)
Revenues recognized in excess of period billings	5,428
June 30, 2018	$	2,512



	Deferred Revenue
December 31, 2017	$	118,414
Revenues recognized from balances held at the beginning of the period	(20,344		)
Revenues deferred from period collections on unfulfilled performance obligations	13,375
June 30, 2018	$	111,445

We have elected to use the practical expedients allowed under ASC 606-10-50-14, pursuant to which we have excluded disclosures of transaction prices allocated to remaining performance obligations and when we expect to recognize such revenue. The majority of our remaining performance obligations are primarily comprised of unfulfilled product, transportation service, and labor service orders, all of which hold a remaining duration of less than one year. The long term portion of deferred revenue primarily represents a combination of refundable and nonrefundable customer prepayments for which related current performance obligations do not yet exist, but are expected to arise, before the expiration of the contract. Our residual unfulfilled performance obligations are comprised primarily of long-term equipment rental arrangements in which we recognize revenues equal to what we have a right to invoice. Generally, no variable consideration exists related to our remaining performance obligations and no consideration is excluded from the associated transaction prices.

Asset Retirement Obligation

6 Months Ended

Jun. 30, 2018

Asset Retirement Obligation Disclosure [Abstract]

ASSET RETIREMENT OBLIGATION

NOTE K—ASSET RETIREMENT OBLIGATION

Mine reclamation or 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.

As of June 30, 2018, we had a liability of $19.8 million in other long-term obligations related to our asset retirement obligation. Changes in the asset retirement obligation (in thousands) during the six months ended June 30, 2018 are as follows:



	June 30, 2018
Beginning balance	$	19,032
Accretion	611
Additions and revisions of prior estimates	(487		)
Addition related to EPMH acquisition	2,733
Disposal related to sale of transloads	(2,116		)
Ending balance	$	19,773

Fair Value Accounting	6 Months Ended
Fair Value Accounting	Jun. 30, 2018
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 June 30, 2018 and December 31, 2017 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, approximate 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. Although we have determined that the majority of the inputs used to value our derivatives fall within 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 June 30, 2018, 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. As of June 30, 2018, and December 31, 2017, the fair value of our derivative instruments was zero. Additional disclosures for derivative instruments are presented in Note M - Derivative Instruments to these Financial Statements.

- 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

6 Months Ended

Jun. 30, 2018

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 our term loan facility (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 June 30, 2018 and December 31, 2017.



		June 30, 2018								December 31, 2017
	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	$	—	$	—

⁽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 six months ended June 30, 2018, we had no material ineffectiveness for such contract. During the six months ended June 30, 2017, we had no ineffectiveness for such contract.

The following table summarizes the effect of derivatives instruments (in thousands) on our income statements and our consolidated statements of comprehensive income for the three months ended June 30, 2018 and 2017.



	June 30, 2018			June 30, 2017
Deferred losses from derivatives in OCI, beginning of period	$	(76	)	$	(32	)
Loss recognized in OCI from derivative instruments	—			(39		)
Gain reclassified from Accumulated OCI	6			—
Deferred losses from derivatives in OCI, end of period	$	(70	)	$	(71	)

Equity-Based Compensation

6 Months Ended

Jun. 30, 2018

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 June 30, 2018, we have 3,650,262 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 six months ended June 30, 2018:



	Number of Shares		Weighted Average Exercise Price		Aggregate Intrinsic Value (in thousands)		Weighted Average Remaining Contractual Term in Years
Outstanding at December 31, 2017	908,919		$	28.46	$	7,008	6.1 years
Granted	—		—		—
Exercised	(4,167	)	14.65		—
Forfeited	(918	)	31.30		—
Expired	(1,838	)	$	31.30	$	—
Outstanding at June 30, 2018	901,996		$	28.52	$	3,692	5.3 years
Exercisable at June 30, 2018	855,446		$	27.38	$	3,692	5.2 years

There were no grants of stock options during the three and six months ended June 30, 2018 and 2017.

There were 4,167 stock options exercised during both the three and six months ended June 30, 2018. There were 2,083 and 26,935 stock options exercised during the three and six months ended June 30, 2017, respectively. The total intrinsic value of stock options exercised was $0.1 million for the three and six months ended June 30, 2018. The total intrinsic value of stock options exercised was $0.1 million and $0.9 million for the three and six months ended June 30, 2017, respectively. Cash received from options exercised during the three and six months ended June 30, 2018 was $62 thousand. Cash received from options exercised during the three and six months ended June 30, 2017 was thirty thousand and $0.5 million, respectively. The tax benefit realized from option exercises was fourteen thousand for the three and six months ended June 30, 2018. The tax benefit realized from option exercises was twenty thousand and $0.3 million for the three and six months ended June 30, 2017, respectively.

We recognized $0.4 million and $0.9 million of equity-based compensation expense related to options during the three and six months ended June 30, 2018, respectively. We recognized $0.6 million and $1.3 million of equity-based compensation expense related to options during the three and six months ended June 30, 2017, respectively. As of June 30, 2018, there was $0.3 million of total unrecognized compensation expense related to these options, which is expected to be recognized over a weighted-average period of approximately 0.3 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 six months ended June 30, 2018:



	Number of Shares		Grant Date Weighted Average Fair Value
Unvested, December 31, 2017	461,346		$	30.76
Granted	237,931		26.34
Vested	(216,228	)	30.04
Forfeited	(22,827	)	31.76
Unvested, June 30, 2018	460,222		$	28.77

We granted 234,079 and 237,931 restricted stock and restricted stock unit awards during the three and six months ended June 30, 2018, respectively. We granted 139,451 and 140,951 restricted stock and restricted stock unit awards during the three and six months ended June 30, 2017, respectively. The fair value of the awards was based on the market price of our stock at date of grant.

We recognized $2.0 million and $3.8 million of equity-based compensation expense related to restricted stock awards during the three and six months ended June 30, 2018, respectively. We recognized $1.8 million and $3.3 million of equity-based compensation expense related to restricted stock awards during the three and six months ended June 30, 2017, respectively. As of June 30, 2018, there was $11.0 million of total unrecognized compensation expense related to these restricted stock awards, which is expected to be recognized over a weighted-average period of 1.9 years.

Performance Share Unit Awards

The following table summarizes the status of, and changes in, our performance share unit awards during the six months ended June 30, 2018:



	Number of Shares		Grant Date Weighted Average Fair Value
Unvested, December 31, 2017	881,416		$	42.16
Granted	201,417		31.24
Vested	(225,000	)	41.99
Forfeited	(8,072	)	52.92
Unvested, June 30, 2018	849,761		$	39.31

We granted 201,417 and 90,501 of performance share unit awards during the three and six months ended June 30, 2018 and 2017, respectively. The grant date fair value of these awards was estimated to be $31.24 and $67.69 for both the three and six months ended June 30, 2018 and 2017, respectively, 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, 2018 through December 31, 2020 for the current period grant, and from January 1, 2017 through December 31, 2019 for the prior year grant. 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 common stock and our self-determined peer group companies’ stock, risk-free rate of interest, dividend yields and cross-correlations between our common stock and our self-determined peer group companies' stock.

We recognized $4.5 million and $8.6 million of compensation expense related to performance share unit awards during the three and six months ended June 30, 2018, respectively. We recognized $4.0 million and $7.4 million of compensation expense related to performance share unit awards during the three and six months ended June 30, 2017, respectively. As of June 30, 2018, there was $15.5 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 1.4 year.

Commitments and Contingencies

6 Months Ended

Jun. 30, 2018

Commitments and Contingencies Disclosure [Abstract]

COMMITMENTS AND CONTINGENCIES

NOTE O—COMMITMENTS AND CONTINGENCIES

Future Minimum Annual Commitments at June 30, 2018 (in thousands):



Year ending December 31,	Operating Lease Minimum Rental Payments		Minimum Purchase Commitments
2018	$	39,115	$	12,413
2019	73,080		21,037
2020	57,683		15,663
2021	38,639		8,008
2022	31,652		5,640
Thereafter	61,790		4,141
Total future lease and purchase commitments	$	301,959	$	66,902

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 totaled approximately $24.9 million and $47.7 million for the three and six months ended June 30, 2018. Expense related to operating leases and rental agreements totaled approximately $15.8 million and $31.2 million for the three and six months ended June 30, 2017, 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 six months ended June 30, 2018, one new claim was brought against U.S. Silica. As of June 30, 2018, there were 56 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.

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 condensed consolidated balance sheets. As of both June 30, 2018, and December 31, 2017 other non-current assets included zero for insurance for third-party products liability claims and other long-term obligations included $1.0 million for third-party products liability claims.

Pension and Post-Retirement Benefits

6 Months Ended

Jun. 30, 2018

Retirement Benefits [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.

Net pension benefit cost (in thousands) consisted of the following for the three and six months ended June 30, 2018 and 2017:



	Three Months Ended June 30,						Six Months Ended June 30,
	2018			2017			2018			2017
Service cost	$	322		$	149		$	601		$	444
Interest cost	1,158			571			2,136			1,454
Expected return on plan assets	(1,491		)	(757		)	(2,734		)	(2,088		)
Net amortization and deferral	631			255			1,264			948
Net pension benefit costs	$	620		$	218		$	1,267		$	758

In addition, we provide defined benefit post-retirement health care 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 post-retirement benefit cost (in thousands) consisted of the following for the three and six months ended June 30, 2018 and 2017:



	Three Months Ended June 30,					Six Months Ended June 30,
	2018		2017			2018			2017
Service cost	$	27	$	33		$	54		$	65
Interest cost	188		191			376			383
Expected return on plan assets	—		(1		)	(1		)	(1		)
Net amortization and deferral	—		53			—			107
Net post-retirement benefit costs	$	215	$	276		$	429		$	554

We contributed $0.5 million and $0.8 million to the qualified pension plan for the three and six months ended June 30, 2018, respectively. We contributed $0.3 million to the qualified pension plan for the three and six months ended June 30, 2017. Total expected employer funding contributions during the fiscal year ending December 31, 2018 are $2.5 million for the pension plan and $1.4 million for the post-retirement medical and life plan.

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. Our contributions to individual multiemployer pension funds did not exceed 5% of the fund’s total contributions. Additionally, our contributions to the multiemployer post-retirement benefit plans were immaterial for the three and six months ended June 30, 2018 and 2017.

Obligations Under Guarantees	6 Months Ended
Obligations Under Guarantees	Jun. 30, 2018
Guarantees [Abstract]
OBLIGATIONS UNDER GUARANTEES	NOTE Q— OBLIGATIONS UNDER GUARANTEES We have indemnified our insurers against any loss they may incur in the event that holders of surety bonds, issued on our behalf, execute the bonds. As of June 30, 2018, there was $28.6 million in bonds outstanding. The majority of these bonds, $25.6 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.

Income Taxes	6 Months Ended
Income Taxes	Jun. 30, 2018
Income Tax Disclosure [Abstract]
INCOME TAXES	NOTE R— INCOME TAXES 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. 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 as of June 30, 2018. 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 did not make any Tax Act adjustments to the accounting under ASC 740 for the three and six months ended June 30, 2018, and 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 were required to adjust deferred tax assets and liabilities as of December 22, 2017. Accordingly, for the year ended December 31, 2017, we 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. 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 and that can be carried back 2 years, and carried forward 20 years. 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. For interim period reporting, we record income taxes using an estimated annual effective tax rate based upon projected annual income, forecasted permanent tax differences, discrete items and statutory rates in states in which we operate. At the end of each interim period, we update the estimated annual effective tax rate, and if the estimated tax rate changes based on new information, we make a cumulative adjustment in the period. We record the tax effect of an unusual or infrequently occurring item in the interim period in which it occurs as a discrete item of tax. For the three and six months ended June 30, 2018, we recorded a tax expense of $0.2 million and $0.7 million, respectively, related to equity compensation pursuant to ASU 2016-09. For the three and six months ended June 30, 2017, we recorded a tax benefit of $0.2 million and $1.7 million, respectively, related to equity compensation pursuant to ASU 2016-09. The effective tax rate was 14% and 17% for the three and six months ended June 30, 2018, respectively. The effective tax rate was 19% and 14% for the three and six months ended and June 30, 2017, respectively. The effective tax rate for the three and six months ended June 30, 2018 would have been 13% and 16%, respectively, without the equity compensation tax benefit or expense recorded discretely. The effective tax rate for the three and six months ended June 30, 2017 would have been 20% and 19%, respectively, without the equity compensation tax benefit or expense recorded discretely. Historically, our actual effective tax rates have differed from the statutory effective rate primarily due to the benefit received from statutory percentage depletion allowances. The deduction for statutory percentage depletion does not necessarily change proportionately to changes in income before income taxes.

Revenue

6 Months Ended

Jun. 30, 2018

Revenue from Contract with Customer [Abstract]

REVENUE

NOTE J—DEFERRED REVENUE

NOTE S— REVENUE



	Three Months Ended June 30, 2018						Six Months Ended June 30, 2018
Category	Oil & Gas Proppants		Industrial & Specialty Products		Total Sales		Oil & Gas Proppants		Industrial & Specialty Products		Total Sales
Product	$	242,587	$	103,370	$	345,957	$	481,009	$	159,736	$	640,745
Service	81,476		—		81,476		155,984		17		156,001
Total Sales	$	324,063	$	103,370	$	427,433	$	636,993	$	159,753	$	796,746



	Unbilled Receivables
December 31, 2017	$	5,245
Reclassifications to billed receivables	(8,161		)
Revenues recognized in excess of period billings	5,428
June 30, 2018	$	2,512



	Deferred Revenue
December 31, 2017	$	118,414
Revenues recognized from balances held at the beginning of the period	(20,344		)
Revenues deferred from period collections on unfulfilled performance obligations	13,375
June 30, 2018	$	111,445

Related Party Transactions	6 Months Ended
Related Party Transactions	Jun. 30, 2018
Related Party Transactions [Abstract]
RELATED PARTY TRANSACTIONS	NOTE T— 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 $0.9 million and $1.8 million for the three and six months ended June 30, 2018, respectively, and $1.2 million and $1.9 million for the three and six months ended June 30, 2017, respectively.

Segment Reporting

6 Months Ended

Jun. 30, 2018

Segment Reporting [Abstract]

SEGMENT REPORTING

NOTE U— 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 400 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 A - 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 three and six months ended June 30, 2018 and 2017:



	Three Months Ended June 30,						Six Months Ended June 30,
	2018			2017			2018			2017
Sales:
Oil & Gas Proppants	$	324,063		$	235,018		$	636,993		$	427,976
Industrial & Specialty Products	103,370			55,447			159,753			107,286
Total sales	427,433			290,465			796,746			535,262
Segment contribution margin:
Oil & Gas Proppants	114,607			71,222			214,041			110,062
Industrial & Specialty Products	41,301			23,267			61,831			43,484
Total segment contribution margin	155,908			94,489			275,872			153,546
Operating activities excluded from segment cost of sales	(21,320		)	(988		)	(32,881		)	(2,436		)
Selling, general and administrative	(42,232		)	(25,839		)	(76,823		)	(47,978		)
Depreciation, depletion and amortization	(36,563		)	(23,626		)	(65,155		)	(45,225		)
Asset impairment	(16,184		)	—			(16,184		)	—
Interest expense	(20,214		)	(8,105		)	(27,284		)	(15,751		)
Other income (expense), net, including interest income	1,081			638			1,746			(4,779		)
Income tax expense	(2,832		)	(7,110		)	(10,353		)	(5,396		)
Net income	$	17,644		$	29,459		$	48,938		$	31,981

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. At June 30, 2018, goodwill of $414.3 million has been allocated to these segments with $250.3 million assigned to Oil & Gas Proppants and $164.0 million to Industrial & Specialty Products. At December 31, 2017, goodwill of $272.1 million had been allocated to these segments with $247.5 million assigned to Oil & Gas Proppants and $24.6 million to Industrial & Specialty Products.

Subsequent Events	6 Months Ended
Subsequent Events	Jun. 30, 2018
Subsequent Events [Abstract]
SUBSEQUENT EVENTS	NOTE V— SUBSEQUENT EVENTS On July 6, 2018, we paid a cash dividend of $0.0625 per share to common stockholders of record on June 15, 2018, which had been declared by our Board of Directors on May 14, 2018. On July 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 September 14, 2018, payable on October 3, 2018.

Summary of Significant Accounting Policies (Policies)	6 Months Ended
Summary of Significant Accounting Policies (Policies)	Jun. 30, 2018
Accounting Policies [Abstract]
Basis of Presentation and Consolidation	Basis of Presentation and Consolidation The accompanying Condensed Consolidated Financial Statements (the “Financial Statements”) of U.S. Silica Holdings, Inc. (“Holdings,” and together with its subsidiaries “we,” “us” or the “Company”) included in this Quarterly Report on Form 10-Q, have been prepared in accordance with generally accepted accounting principles in the United States (“GAAP”) for interim financial information and with the instructions to Form 10-Q and Article 10 of Regulation S-X issued by the U.S. Securities and Exchange Commission (“SEC”). They do not contain certain information included in our Annual Report on Form 10-K for the fiscal year ended December 31, 2017; therefore, the interim Condensed Consolidated Financial Statements should be read in conjunction with that Annual Report on Form 10-K. 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 year's amounts have been made to conform to the current year presentation. In conforming to the current year's presentation, the Company identified and corrected an immaterial amount in its statement of cash flows for the six months ended June 30, 2017. The correction reduced Capital Expenditures within Net Cash Used in Investing Activities with a corresponding decrease to Accounts Payable and Accrued Expenses within Net Cash Used in Operating Activities. The amount is presented as Non-cash Accrued Capital Expenditures and had no impact in the Company's Balance Sheet, Income Statement or Net Change in Cash and Cash Equivalents in the Statement of Cash Flows. Throughout this report we refer to (i) our Condensed Consolidated Balance Sheets as our “Balance Sheets,” (ii) our Condensed Consolidated Statements of Operations as our “Income Statements,” and (iii) our Condensed Consolidated Statements of Cash Flows as our “Cash Flows.”
Reclassifications	Certain reclassifications of prior year's amounts have been made to conform to the current year presentation.
Unaudited Interim Financial Statements	Unaudited Interim Financial Statements The accompanying Balance Sheet as of June 30, 2018; the Income Statements and Condensed Consolidated Statements of Comprehensive Income for the three and six months ended June 30, 2018 and 2017; the Condensed Consolidated Statements of Stockholders' Equity and Cash Flows for the six months ended June 30, 2018; and other information disclosed in the related notes are unaudited. The Balance Sheet as of December 31, 2017, was derived from our audited consolidated financial statements included in our 2017 Annual Report on Form 10-K.
Use of Estimates and Assumptions	Use of Estimates and Assumptions The preparation of the Financial Statements requires us 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 the 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 and Deferred Revenue	Revenue Recognition Products We derive our product 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. We primarily sell our products through individual purchase orders executed under short-term price agreements or at prevailing market rates. The amount invoiced reflects product, transportation and / or additional handling services as applicable, such as storage, transloading the product from railcars to trucks and last mile logistics to the customer site. We invoice most of our product customers on a per shipment basis, although for some larger customers, we consolidate invoices weekly or monthly. Standard collection terms are net 30 days, although extended terms are offered in competitive situations. We recognize revenue for products and materials at a point in time following the transfer of control of such items to the customer, which typically occurs upon shipment or delivery depending on the terms of the underlying contracts. We account for shipping and handling activities related to product and material sales contracts with customers as costs to fulfill our promise to transfer the associated products pursuant to the accounting policy election allowed under ASC 606-10-18. Accordingly, we record amounts billed for shipping and handling costs as a component of net sales and accrue and classify related costs as a component of cost of sales at the time revenue is recognized. For a limited number of customers, we sell under long-term, minimum purchase supply agreements. 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 do not consider these agreements solely representative of contracts with customers. An executed order specifying the type and quantity of product to be delivered, in combination with the noted agreements, comprise our contracts in these arrangements. Service We derive our service revenues primarily through the provision of transportation, equipment rental, and contract labor services to companies in the oil and gas industry. Transportation services typically consist of transporting customer proppant from storage facilities to proximal well-sites and are contracted through work orders executed under established pricing agreements. The amount invoiced reflects the transportation services rendered. Equipment rental services provide customers with use of either dedicated or nonspecific wellhead proppant delivery equipment solutions for contractual periods defined either through formal lease agreements or executed work orders under established pricing agreements. The amounts invoiced reflect the length of time the equipment set was utilized in the billing period. Contract labor services provide customers with proppant delivery equipment operators through work orders executed under established pricing agreements. The amounts invoiced reflect the amount of time our labor services were utilized in the billing period. We typically invoice our customers on a weekly or monthly basis; however, some customers receive invoices upon well-site operation completion. Standard collection terms are net 30 days, although extended terms are offered in competitive situations. We typically recognize revenue for specific, dedicated equipment set rental arrangements under ASC 840, Leases. For the remaining components of service revenue, we have applied the practical expedient allowed under ASC 606-10-55-18 to recognize transportation revenues in proportion to the amount we have the right to invoice. Contracts with Multiple Performance Obligations For contracts that contain multiple performance obligations, such as work orders containing a combination of product, transportation, equipment rentals, and contract labor services, we allocate the transaction price to each performance obligation identified in the contract based on relative standalone selling prices, or estimates of such prices, and recognize the related revenue as control of each individual product or service is transferred to the customer, in satisfaction of the corresponding performance obligations. We typically invoice our customers on a weekly or monthly basis; however, some customers receive invoices upon well-site operation completion. Standard collection terms are net 30 days, although extended terms are offered in competitive situations. Taxes Collected from Customers and Remitted to Governmental Authorities. We exclude from our measurement of transaction prices all taxes assessed by governmental authorities that are both (i) imposed on and concurrent with a specific revenue-producing transaction and (ii) collected from customers. Accordingly, such tax amounts are not included as a component of net sales or cost of sales. Deferred Revenues For a limited number of customers, we enter into supply agreements which give customers the right to make advanced payments toward the purchase of certain products at specified volumes over an average initial period of one to five years. These payments represent consideration that is unconditional for which we have yet to transfer the related product. These payments are recorded as contract liabilities referred to as “deferred revenues” upon receipt and recognized as revenue upon delivery of the related product.
Unbilled Receivables	Unbilled Receivables Revenues recognized in advance of invoice issuance create assets referred to as “unbilled receivables.” Any portion of our unbilled receivables for which our right to consideration is conditional on a factor other than the passage of time is considered a contract asset. These assets are presented on a combined basis with accounts receivable and are converted to accounts receivable once billed.
Foreign Currency Translation	Foreign Currency Translation For our operations in countries where the functional currency is other than the U.S. dollar, balance sheet amounts are translated using the exchange rate in effect at the balance sheet date. Income statement amounts are translated monthly using the average exchange rate for the respective month. The gains and losses resulting from the changes in exchange rates from year-to-year are recorded as a component of accumulated other comprehensive income or loss as currency translation adjustments, net of tax. Any gains or losses on transactions in currencies other than the functional currency are included in other income (expense), net, including interest income.
Recently 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. On January 1, 2018, we adopted the new accounting standard and all of the related amendments (“new revenue standard”) to all contracts using the modified retrospective method. Adoption of the new revenue standard did not result in a material cumulative effect adjustment to the opening balance of retained earnings. The comparative information has not been restated and continues to be reported under the accounting standards in effect for those periods. We do not expect the adoption of the new revenue standard to have a material impact to our net income on an ongoing basis. See Note S -Revenue to these Financial Statements for additional disclosures. 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. We have established a project team in order to analyze the standard and have begun to review our current accounting policies and procedures to identify potential differences and changes which would result from applying the requirements of the new standard to our lease contracts. We have identified our population of lease agreements and are currently assessing the impact of other arrangements for embedded leases. 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 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. The update requires companies to include the service cost component of net periodic benefit costs in the same line item or items as compensation costs arising from services rendered by the associated employees during the period. The update also disallows capitalization of the other components of net periodic benefit costs and requires those costs to be presented in the income statement separately from the service cost component and outside of a subtotal of income from operations. The update is effective for fiscal years beginning after December 15, 2017, including interim periods within those annual periods for public business entities. Companies are required to retrospectively apply the requirement for a separate presentation in the income statement of service costs and other components of net benefit cost and prospectively adopt the requirement to limit the capitalization of benefit costs to the service component. Application of a practical expedient is allowed permitting an employer to use the amounts disclosed in its pension and other postretirement benefit plan note for the prior comparative periods as the estimation basis for applying the retrospective presentation requirements. We implemented the update on January 1, 2018 and utilized the practical expedient to estimate the impact on the prior comparative period information presented in the interim and annual financial statements. We previously capitalized all net periodic benefit costs incurred for plant personnel in inventory and recorded the majority of net periodic benefit costs incurred by corporate personnel and retirees into selling, general, and administrative expenses. In February 2018, the FASB issued Accounting Standards Update ASU 2018-02, Income Statement-Reporting Comprehensive Income (Topic 220): Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income. The ASU provides that the stranded tax effects from the Tax Act in accumulated other comprehensive loss may be reclassified to retained earnings. The ASU is effective February 1, 2019, with early adoption permitted. We are currently evaluating the effect that the transition guidance will have on our financial statements and related disclosures.
Fair Value Measurement	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 June 30, 2018 and December 31, 2017 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, approximate 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. Although we have determined that the majority of the inputs used to value our derivatives fall within 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 June 30, 2018, 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.

Summary of Significant Accounting Policies (Tables)

6 Months Ended

Jun. 30, 2018

Accounting Policies [Abstract]

Schedule of Reconciliation of Effects of Reclassification on Statements of Income



	Three Months Ended June 30, 2017
	As Previously Reported		Services Reclassifications			ASU 2017-07 Adjustments			As Revised
Product Sales	$	246,022	$	(10,131	)	$	—		$	235,891
Service Sales	44,443		10,131			—			54,574
Total sales	290,465		—			—			290,465
Product cost of sales	164,025		(1,340		)	(447		)	162,238
Service cost of sales	33,386		1,340			—			34,726
Total cost of sales (excluding depreciation, depletion and amortization)	197,411		—			(447		)	196,964
Selling, general and administrative expenses	26,012		—			(173		)	25,839
Operating income	43,416		—			620			44,036
Other income (expense)	1,258		—			(620		)	638



	Six Months Ended June 30, 2017
	As Previously Reported			Services Reclassifications			ASU 2017-07 Adjustments			As Revised
Product Sales	$	455,343		$	(16,200	)	$	—		$	439,143
Service Sales	79,919			16,200			—			96,119
Total sales	535,262			—			—			535,262
Product cost of sales	326,662			(1,794		)	(734		)	324,134
Service cost of sales	58,224			1,794			—			60,018
Total cost of sales (excluding depreciation, depletion and amortization)	384,886			—			(734		)	384,152
Selling, general and administrative expenses	48,353			—			(375		)	47,978
Operating income	56,798			—			1,109			57,907
Other income (expense)	(3,670		)	—			(1,109		)	(4,779		)

Earnings Per Share (Tables)

6 Months Ended

Jun. 30, 2018

Earnings Per Share [Abstract]

Schedule of Computation of Basic and Diluted Earnings Per Share

The following table shows the computation of basic and diluted earnings per share for the three and six months ended June 30, 2018 and 2017:



In thousands, except per share amounts	Three Months Ended June 30,				Six Months Ended June 30,
	2018		2017		2018		2017
Numerator:
Net income	$	17,644	$	29,459	$	48,938	$	31,981

Denominator:
Weighted average shares outstanding	77,784		81,087		78,636		81,032
Diluted effect of stock awards	696		858		692		1,071
Weighted average shares outstanding assuming dilution	78,480		81,945		79,328		82,103

Basic earnings per share	$	0.23	$	0.36	$	0.62	$	0.39
Diluted earnings per share	$	0.22	$	0.36	$	0.62	$	0.39

Schedule of Antidilutive Securities Excluded from Computation of Diluted Earnings Per Share



	Three Months Ended June 30,		Six Months Ended June 30,
	2018	2017	2018	2017
Weighted-average outstanding stock options excluded	426	195	427	195
Weighted-average outstanding restricted stock and performance share units awards excluded	264	426	319	48

Capital Structure and Accumulated Other Comprehensive Income (Loss) (Tables)

6 Months Ended

Jun. 30, 2018

Equity [Abstract]

Schedule of Declared Quarterly Cash Dividends

During the six months ended June 30, 2018, our Board of Directors declared quarterly cash dividends as follows:



Dividends per Common Share		Declaration Date	Record Date	Payable Date
$	0.0625	February 16, 2018	March 15, 2018	April 5, 2018
$	0.0625	May 14, 2018	June 15, 2018	July 6, 2018

Schedule of Changes in Accumulated Other Comprehensive Income (Loss)

The following table presents the changes in accumulated other comprehensive loss by component (in thousands) during the six months ended June 30, 2018:



	For the Six Months Ended June 30, 2018
	Unrealized gain/(loss) on cash flow hedges			Foreign currency translation adjustments			Pension and other post-retirement benefits liability			Total
Beginning Balance	$	(76	)	$	(6	)	$	(13,844	)	$	(13,926	)
Other comprehensive gain (loss) before reclassifications	—			(541		)	4,314			3,773
Amounts reclassed from accumulated other comprehensive loss	6			—			484			490
Ending Balance	$	(70	)	$	(547	)	$	(9,046	)	$	(9,663	)

Business Combinations (Tables)

6 Months Ended

Jun. 30, 2018

Business Combinations [Abstract]

Schedule of Identifiable Assets Acquired and Liabilities Assumed

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



Preliminary allocation of purchase price:	(In thousands)
Accounts receivable, net	$	43,354
Inventories	84,395
Property, plant and mine development	123,086
Mineral rights	462,050
Identifiable intangible assets - finite lived	21,050
Identifiable intangible assets - indefinite lived	25,050
Prepaids and deposits	2,054
Other assets	4,089
Goodwill	139,378
Total assets acquired	904,506
Accounts payable	13,435
Accrued expenses and other current liabilities	8,255
Deferred tax liabilities	130,209
Long term obligations	9,766
Total liabilities assumed	$	161,665
Net assets acquired	$	742,841



	Estimate as of December 31, 2017		Measurement Period Adjustments			Purchase Price Allocation
Accounts receivable	$	11,201	$	—		$	11,201
Inventories	8,067		—			8,067
Other current assets	362		—			362
Assets held for sale	9,453		—			9,453
Property, plant and mine development	27,458		—			27,458
Mineral rights	26,300		(2,800		)	23,500
Other non-current assets	1,136		—			1,136
Goodwill	22,522		2,800			25,322
Customer relationships	1,840		—			1,840
Total assets acquired	108,339		—			108,339
Accounts payable and accrued expenses	3,761		—			3,761
Unfavorable leasehold positions	2,237		—			2,237
Notes Payable	866		—			866
Other long term liabilities	—		—			—
Asset retirement obligations	474		—			474
Total liabilities assumed	7,338		—			7,338
Net assets acquired	$	101,001	$	—		$	101,001

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)
Technology and intellectual property	2,000		15
Customer relationships	$	19,050	15
Total identifiable intangible assets - finite lived	$	21,050

Schedule of Pro Forma Information

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	)

The following unaudited pro forma consolidated financial information reflects the results of operations as if the EPMH acquisition had occurred on January 1, 2017, after giving effect to certain purchase accounting adjustments. Material non-recurring transaction costs attributable to the business combination were $15.2 million. Pro forma net income includes incremental interest expense due to the related debt financing, incremental depreciation and depletion expense related to the fair value adjustment of property, plant 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):



	Three Months Ended June 30,				Six Months Ended June 30,
	2018		2017		2018		2017
Sales	$	451,566	$	341,113	$	879,493	$	629,196
Net income	$	19,693	$	13,196	$	70,539	$	8,097
Basic earnings per share	$	0.25	$	0.16	$	0.90	$	0.10
Diluted earnings per share	$	0.25	$	0.16	$	0.89	$	0.10

Basic shares	77,784		81,087		78,636		81,032
Diluted shares	78,480		81,945		79,328		82,103

Accounts Receivable (Tables)

6 Months Ended

Jun. 30, 2018

Receivables [Abstract]

Schedule of Accounts Receivable and Allowance for Doubtful Accounts

At June 30, 2018 and December 31, 2017, accounts receivable (in thousands) consisted of the following:



	June 30, 2018			December 31, 2017
Trade receivables	$	281,951		$	217,649
Less: Allowance for doubtful accounts	(7,773		)	(7,100		)
Net trade receivables	274,178			210,549
Other receivables	5,841			2,037
Total accounts receivable	$	280,019		$	212,586

Changes in our allowance for doubtful accounts (in thousands) during the six months ended June 30, 2018 are as follows:



	June 30, 2018
Beginning balance	$	7,780
Bad debt provision	387
Write-offs	(394		)
Ending balance	$	7,773

Inventories (Tables)

6 Months Ended

Jun. 30, 2018

Inventory Disclosure [Abstract]

Schedule of Inventories

At June 30, 2018 and December 31, 2017, inventories (in thousands) consisted of the following:



	June 30, 2018		December 31, 2017
Supplies	$	36,639	$	21,277
Raw materials and work in process	72,238		28,034
Finished goods	58,538		43,065
Total inventories	$	167,415	$	92,376

Property, Plant and Mine Development (Tables)

6 Months Ended

Jun. 30, 2018

Property, Plant and Equipment [Abstract]

Schedule of Property, Plant and Mine Development

At June 30, 2018 and December 31, 2017, property, plant and mine development (in thousands) consisted of the following:



	June 30, 2018			December 31, 2017
Mining property and mine development	$	1,051,824		$	586,242
Asset retirement cost	14,308			14,184
Land	42,189			36,552
Land improvements	66,336			45,878
Buildings	73,150			56,330
Machinery and equipment	790,655			590,566
Furniture and fixtures	4,053			2,953
Construction-in-progress	183,222			189,970
	2,225,737			1,522,675
Accumulated depletion, depreciation and amortization	(400,084		)	(353,520		)
Total property, plant and mine development, net	$	1,825,653		$	1,169,155

Goodwill and Intangible Assets (Tables)

6 Months Ended

Jun. 30, 2018

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, 2017	$	272,079
EPMH acquisition	139,378
MS Sand acquisition measurement period adjustment	2,800
Balance at June 30, 2018	$	414,257

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:



		June 30, 2018							December 31, 2017
	Estimated Useful Life	Gross Carrying Amount		Accumulated Amortization			Net		Gross Carrying Amount		Accumulated Amortization			Net
	(in years)
Technology and intellectual property	15	$	76,588	$	(8,413	)	$	68,175	$	70,703	$	(5,917	)	$	64,786
Customer relationships	13 - 15	80,279		(11,777		)	68,502		61,229		(9,076		)	52,153
Total definite-lived intangible assets:		$	156,867	$	(20,190	)	$	136,677	$	131,932	$	(14,993	)	$	116,939
Trade name		58,118		—			58,118		33,068		—			33,068
Total intangible assets:		$	214,985	$	(20,190	)	$	194,795	$	165,000	$	(14,993	)	$	150,007

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:



		June 30, 2018							December 31, 2017
	Estimated Useful Life	Gross Carrying Amount		Accumulated Amortization			Net		Gross Carrying Amount		Accumulated Amortization			Net
	(in years)
Technology and intellectual property	15	$	76,588	$	(8,413	)	$	68,175	$	70,703	$	(5,917	)	$	64,786
Customer relationships	13 - 15	80,279		(11,777		)	68,502		61,229		(9,076		)	52,153
Total definite-lived intangible assets:		$	156,867	$	(20,190	)	$	136,677	$	131,932	$	(14,993	)	$	116,939
Trade name		58,118		—			58,118		33,068		—			33,068
Total intangible assets:		$	214,985	$	(20,190	)	$	194,795	$	165,000	$	(14,993	)	$	150,007

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	$	5,586
2019	10,894
2020	10,894
2021	10,894
2022	10,894

Debt (Tables)

6 Months Ended

Jun. 30, 2018

Debt Disclosure [Abstract]

Schedule of Debt

At June 30, 2018 and December 31, 2017, debt (in thousands) consisted of the following:



	June 30, 2018			December 31, 2017
Senior secured credit facility:
Revolver expiring May 1, 2023 (8.0% at June 30, 2018 and 5.75% at December 31, 2017)	$	—		$	—
Term loan facility—final maturity May 1, 2025 (6.13% at June 30, 2018 and 4.75%-5.25% December 31, 2017)	1,276,800			489,075
Less: Unamortized original issue discount	(6,670		)	(944		)
Less: Unamortized debt issuance cost	(29,665		)	(3,099		)
Note payable secured by royalty interest	25,410			24,740
Customer note payable	286			745
Equipment notes payable	448			719
Capital leases	744			706
Total debt	1,267,353			511,942
Less: current portion	(13,969		)	(6,867		)
Total long-term portion of debt	$	1,253,384		$	505,075

Schedule of Contractual Maturities of Debt

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



2018	$	875
2019	1,750
2020	1,750
2021	1,750
2022	1,750

At June 30, 2018, contractual maturities of our senior secured credit facility (in thousands) are as follows:



2018	$	6,400
2019	12,800
2020	12,800
2021	12,800
Thereafter	1,232,000
Total	$	1,276,800

Asset Retirement Obligations (Tables)

6 Months Ended

Jun. 30, 2018

Asset Retirement Obligation Disclosure [Abstract]

Schedule of Changes in Asset Retirement Obligation

Changes in the asset retirement obligation (in thousands) during the six months ended June 30, 2018 are as follows:



	June 30, 2018
Beginning balance	$	19,032
Accretion	611
Additions and revisions of prior estimates	(487		)
Addition related to EPMH acquisition	2,733
Disposal related to sale of transloads	(2,116		)
Ending balance	$	19,773

Derivative Instruments (Tables)

6 Months Ended

Jun. 30, 2018

Derivative Instruments and Hedging Activities Disclosure [Abstract]

Schedule of Estimated Fair Values of Derivative Instruments



		June 30, 2018								December 31, 2017
	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	$	—	$	—

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

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



	June 30, 2018			June 30, 2017
Deferred losses from derivatives in OCI, beginning of period	$	(76	)	$	(32	)
Loss recognized in OCI from derivative instruments	—			(39		)
Gain reclassified from Accumulated OCI	6			—
Deferred losses from derivatives in OCI, end of period	$	(70	)	$	(71	)

Equity-Based Compensation (Tables)

6 Months Ended

Jun. 30, 2018

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

Schedule of Stock Options Activity

The following table summarizes the status of, and changes in, our stock option awards during the six months ended June 30, 2018:



	Number of Shares		Weighted Average Exercise Price		Aggregate Intrinsic Value (in thousands)		Weighted Average Remaining Contractual Term in Years
Outstanding at December 31, 2017	908,919		$	28.46	$	7,008	6.1 years
Granted	—		—		—
Exercised	(4,167	)	14.65		—
Forfeited	(918	)	31.30		—
Expired	(1,838	)	$	31.30	$	—
Outstanding at June 30, 2018	901,996		$	28.52	$	3,692	5.3 years
Exercisable at June 30, 2018	855,446		$	27.38	$	3,692	5.2 years

Schedule of Restricted Stock, Restricted Stock Unit and Performance Share Unit Awards Activity

The following table summarizes the status of, and changes in, our performance share unit awards during the six months ended June 30, 2018:



	Number of Shares		Grant Date Weighted Average Fair Value
Unvested, December 31, 2017	881,416		$	42.16
Granted	201,417		31.24
Vested	(225,000	)	41.99
Forfeited	(8,072	)	52.92
Unvested, June 30, 2018	849,761		$	39.31

Restricted Stock and Restricted Stock Unit Awards

The following table summarizes the status of, and changes in, our unvested restricted stock awards during the six months ended June 30, 2018:



	Number of Shares		Grant Date Weighted Average Fair Value
Unvested, December 31, 2017	461,346		$	30.76
Granted	237,931		26.34
Vested	(216,228	)	30.04
Forfeited	(22,827	)	31.76
Unvested, June 30, 2018	460,222		$	28.77

Commitments and Contingencies (Tables)

6 Months Ended

Jun. 30, 2018

Commitments and Contingencies Disclosure [Abstract]

Schedule of Future Minimum Annual Commitments

Future Minimum Annual Commitments at June 30, 2018 (in thousands):



Year ending December 31,	Operating Lease Minimum Rental Payments		Minimum Purchase Commitments
2018	$	39,115	$	12,413
2019	73,080		21,037
2020	57,683		15,663
2021	38,639		8,008
2022	31,652		5,640
Thereafter	61,790		4,141
Total future lease and purchase commitments	$	301,959	$	66,902

Pension and Post-Retirement Benefits (Tables)

6 Months Ended

Jun. 30, 2018

Retirement Benefits [Abstract]

Schedule of Net Pension and Post-retirement Benefit Costs

Net pension benefit cost (in thousands) consisted of the following for the three and six months ended June 30, 2018 and 2017:



	Three Months Ended June 30,						Six Months Ended June 30,
	2018			2017			2018			2017
Service cost	$	322		$	149		$	601		$	444
Interest cost	1,158			571			2,136			1,454
Expected return on plan assets	(1,491		)	(757		)	(2,734		)	(2,088		)
Net amortization and deferral	631			255			1,264			948
Net pension benefit costs	$	620		$	218		$	1,267		$	758

Net post-retirement benefit cost (in thousands) consisted of the following for the three and six months ended June 30, 2018 and 2017:



	Three Months Ended June 30,					Six Months Ended June 30,
	2018		2017			2018			2017
Service cost	$	27	$	33		$	54		$	65
Interest cost	188		191			376			383
Expected return on plan assets	—		(1		)	(1		)	(1		)
Net amortization and deferral	—		53			—			107
Net post-retirement benefit costs	$	215	$	276		$	429		$	554

Revenue (Tables)

6 Months Ended

Jun. 30, 2018

Revenue from Contract with Customer [Abstract]

Schedule of Sales by Major Source

The following table disaggregates our sales by major source for the three and six months ended June 30, 2018 (in thousands):



	Three Months Ended June 30, 2018						Six Months Ended June 30, 2018
Category	Oil & Gas Proppants		Industrial & Specialty Products		Total Sales		Oil & Gas Proppants		Industrial & Specialty Products		Total Sales
Product	$	242,587	$	103,370	$	345,957	$	481,009	$	159,736	$	640,745
Service	81,476		—		81,476		155,984		17		156,001
Total Sales	$	324,063	$	103,370	$	427,433	$	636,993	$	159,753	$	796,746

Schedule of Changes in Contract Assets and Liabilities



	Unbilled Receivables
December 31, 2017	$	5,245
Reclassifications to billed receivables	(8,161		)
Revenues recognized in excess of period billings	5,428
June 30, 2018	$	2,512



	Deferred Revenue
December 31, 2017	$	118,414
Revenues recognized from balances held at the beginning of the period	(20,344		)
Revenues deferred from period collections on unfulfilled performance obligations	13,375
June 30, 2018	$	111,445

Segment Reporting (Tables)

6 Months Ended

Jun. 30, 2018

Segment Reporting [Abstract]

Schedule of Sales and Segment Contribution Margin for Reporting Segments and Operating Results



	Three Months Ended June 30,						Six Months Ended June 30,
	2018			2017			2018			2017
Sales:
Oil & Gas Proppants	$	324,063		$	235,018		$	636,993		$	427,976
Industrial & Specialty Products	103,370			55,447			159,753			107,286
Total sales	427,433			290,465			796,746			535,262
Segment contribution margin:
Oil & Gas Proppants	114,607			71,222			214,041			110,062
Industrial & Specialty Products	41,301			23,267			61,831			43,484
Total segment contribution margin	155,908			94,489			275,872			153,546
Operating activities excluded from segment cost of sales	(21,320		)	(988		)	(32,881		)	(2,436		)
Selling, general and administrative	(42,232		)	(25,839		)	(76,823		)	(47,978		)
Depreciation, depletion and amortization	(36,563		)	(23,626		)	(65,155		)	(45,225		)
Asset impairment	(16,184		)	—			(16,184		)	—
Interest expense	(20,214		)	(8,105		)	(27,284		)	(15,751		)
Other income (expense), net, including interest income	1,081			638			1,746			(4,779		)
Income tax expense	(2,832		)	(7,110		)	(10,353		)	(5,396		)
Net income	$	17,644		$	29,459		$	48,938		$	31,981

Summary of Significant Accounting Policies - Additional Information (Details) $ in Millions	6 Months Ended
	Jun. 30, 2018 USD ($)
Other income (expense) net, including interest income
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Realized foreign currency translation gain	$ 0.3
Supply Agreement \| Minimum
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Deferred revenue, average initial contract term	1 year
Supply Agreement \| Maximum
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Deferred revenue, average initial contract term	5 years

Summary of Significant Accounting Policies - Reconciliation of Effects of Reclassification on Statements of Income (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
New Accounting Pronouncement, Early Adoption [Line Items]
Total Sales	$ 427,433	$ 290,465	$ 796,746	$ 535,262
Product cost of sales	236,236	162,238	443,475	324,134
Service cost of sales	56,609	34,726	110,280	60,018
Total cost of sales (excluding depreciation, depletion and amortization)	292,845	196,964	553,755	384,152
Selling, general and administrative expenses	42,232	25,839	76,823	47,978
Operating income	39,609	44,036	84,829	57,907
Other income (expense)	1,081	638	1,746	(4,779)
Product
New Accounting Pronouncement, Early Adoption [Line Items]
Total Sales	345,957	235,891	640,745	439,143
Service
New Accounting Pronouncement, Early Adoption [Line Items]
Total Sales	$ 81,476	54,574	$ 156,001	96,119
As Previously Reported
New Accounting Pronouncement, Early Adoption [Line Items]
Total Sales		290,465		535,262
Product cost of sales		164,025		326,662
Service cost of sales		33,386		58,224
Total cost of sales (excluding depreciation, depletion and amortization)		197,411		384,886
Selling, general and administrative expenses		26,012		48,353
Operating income		43,416		56,798
Other income (expense)		1,258		(3,670)
As Previously Reported \| Product
New Accounting Pronouncement, Early Adoption [Line Items]
Total Sales		246,022		455,343
As Previously Reported \| Service
New Accounting Pronouncement, Early Adoption [Line Items]
Total Sales		44,443		79,919
ASU 2017-07 Adjustments
New Accounting Pronouncement, Early Adoption [Line Items]
Total Sales		0		0
Product cost of sales		(1,340)		(1,794)
Service cost of sales		1,340		1,794
Total cost of sales (excluding depreciation, depletion and amortization)		0		0
Selling, general and administrative expenses		0		0
Operating income		0		0
Other income (expense)		0		0
ASU 2017-07 Adjustments \| Product
New Accounting Pronouncement, Early Adoption [Line Items]
Total Sales		(10,131)		(16,200)
ASU 2017-07 Adjustments \| Service
New Accounting Pronouncement, Early Adoption [Line Items]
Total Sales		10,131		16,200
ASU 2017-07 Adjustments \| Accounting Standards Update 2017-07
New Accounting Pronouncement, Early Adoption [Line Items]
Total Sales		0		0
Product cost of sales		(447)		(734)
Service cost of sales		0		0
Total cost of sales (excluding depreciation, depletion and amortization)		(447)		(734)
Selling, general and administrative expenses		(173)		(375)
Operating income		620		1,109
Other income (expense)		(620)		(1,109)
ASU 2017-07 Adjustments \| Accounting Standards Update 2017-07 \| Product
New Accounting Pronouncement, Early Adoption [Line Items]
Total Sales		0		0
ASU 2017-07 Adjustments \| Accounting Standards Update 2017-07 \| Service
New Accounting Pronouncement, Early Adoption [Line Items]
Total Sales		$ 0		$ 0

Earnings Per Share - Computation of Basic and Diluted Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Numerator:
Net income	$ 17,644	$ 29,459	$ 48,938	$ 31,981
Denominator:
Weighted average shares outstanding (shares)	77,784	81,087	78,636	81,032
Diluted effect of stock awards (shares)	696	858	692	1,071
Weighted average shares outstanding assuming dilution (shares)	78,480	81,945	79,328	82,103
Basic earnings per share (in dollars per share)	$ 0.23	$ 0.36	$ 0.62	$ 0.39
Diluted earnings per share (in dollars per share)	$ 0.22	$ 0.36	$ 0.62	$ 0.39

- Definition

The amount of net income (loss) for the period per each share of common stock or unit outstanding during the reporting period.

+ References

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+ Details

- Definition

The amount of net income (loss) for the period available to each share of common stock or common unit outstanding during the reporting period and to each share or unit that would have been outstanding assuming the issuance of common shares or units for all dilutive potential common shares or units outstanding during the reporting period.

+ References

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+ Details

- Definition

The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

+ References + Details

Earnings Per Share - Antidilutive Securities Excluded From Calculation of Diluted Earnings Per Share (Details) - shares shares in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Stock Options
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Weighted-average outstanding stock options and restricted stock awards excluded (shares)	426	195	427	195
Restricted Stock and Performance Share Units
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Weighted-average outstanding stock options and restricted stock awards excluded (shares)	264	426	319	48

Capital Structure and Accumulated Other Comprehensive Income (Loss) - Additional Information (Details) - USD ($)		3 Months Ended		5 Months Ended
	Dec. 11, 2017	Jun. 30, 2018	Mar. 31, 2018	Mar. 31, 2018	May 31, 2018	Dec. 31, 2017	Oct. 31, 2017
Capital Structure And Accumulated Comprehensive Income (Loss)
Common stock authorized (shares)		500,000,000				500,000,000
Common stock, par value (in dollars per share)		$ 0.01				$ 0.01
Common stock issued (shares)		81,734,599				81,267,205
Common stock outstanding (shares)		77,681,643				80,524,255
Preferred stock authorized (shares)		10,000,000				10,000,000
Preferred stock, par value (in dollars per share)		$ 0.01				$ 0.01
Preferred stock issued (shares)		0				0
Preferred stock outstanding (shares)		0				0
May 2018 Share Repurchase Program
Capital Structure And Accumulated Comprehensive Income (Loss)
Share repurchase program authorized amount					$ 200,000,000
Repurchase of common stock (shares)		536,139
Average price per common share of repurchase common stock (in dollars per share)		$ 28.91
Remaining authorized repurchase amount		$ 184,500,000
Share Repurchase Program Expiring March 2018
Capital Structure And Accumulated Comprehensive Income (Loss)
Share repurchase program authorized amount							$ 100,000,000
Repurchase of common stock (shares)			2,828,023	3,555,104
Average price per common share of repurchase common stock (in dollars per share)			$ 26.52	$ 28.13
Share Repurchase Program Expiring December 2017
Capital Structure And Accumulated Comprehensive Income (Loss)
Share repurchase program authorized amount	$ 50,000,000.0
Repurchase of common stock (shares)	706,093
Average price per common share of repurchase common stock (in dollars per share)	$ 23.83

Capital Structure and Accumulated Other Comprehensive Income (Loss) - Changes in Accumulated Other Comprehensive Loss (Details) $ in Thousands	6 Months Ended
	Jun. 30, 2018 USD ($)
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning Balance	$ 1,396,506
Other comprehensive gain (loss) before reclassifications	3,773
Amounts reclassed from accumulated other comprehensive loss	490
Ending Balance	1,358,504
Unrealized gain/(loss) on cash flow hedges
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning Balance	(76)
Other comprehensive gain (loss) before reclassifications	0
Amounts reclassed from accumulated other comprehensive loss	6
Ending Balance	(70)
Foreign currency translation adjustments
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning Balance	(6)
Other comprehensive gain (loss) before reclassifications	(541)
Amounts reclassed from accumulated other comprehensive loss	0
Ending Balance	(547)
Pension and other post-retirement benefits liability
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning Balance	(13,844)
Other comprehensive gain (loss) before reclassifications	4,314
Amounts reclassed from accumulated other comprehensive loss	484
Ending Balance	(9,046)
Total
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning Balance	(13,926)
Ending Balance	$ (9,663)

Business Combinations - Additional Information (Details) - USD ($) $ in Thousands				3 Months Ended		6 Months Ended		7 Months Ended	8 Months Ended	12 Months Ended
	May 01, 2018	Aug. 16, 2017	Apr. 01, 2017	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Mar. 31, 2018	Aug. 16, 2017	Dec. 31, 2017	Dec. 31, 2016
Business Acquisition [Line Items]
Consideration paid, net of cash acquired						$ 742,841	$ 18,636
Goodwill				$ 414,257		414,257				$ 272,079
Total cash consideration for pre-existing contracted asset sale						159,196	152,087
EPMH
Business Acquisition [Line Items]
Consideration paid, net of cash acquired	$ 742,800
Cash acquired	19,100
Revenues from acquiree included in Income Statement				41,700		41,700
Net loss from acquiree included in Income Statement				700		700
Non-recurring transaction costs attributable to business combination excluded from pro-forma information				(19,693)	$ (13,196)	(70,539)	$ (8,097)
Goodwill	$ 139,378
EPMH \| Acquisition-related Costs
Business Acquisition [Line Items]
Non-recurring transaction costs attributable to business combination excluded from pro-forma information						15,200
EPMH \| Selling, General and Administrative Expenses
Business Acquisition [Line Items]
Acquisition-related costs				$ 8,800		$ 10,900
White Armor acquisition
Business Acquisition [Line Items]
Cash consideration paid			$ 18,600
Goodwill			3,900
Identifiable intangible assets			12,800
Other net assets			$ 1,900
White Armor acquisition \| Selling, General and Administrative Expenses
Business Acquisition [Line Items]
Acquisition-related costs										200
MS Sand
Business Acquisition [Line Items]
Consideration paid, net of cash acquired		$ 95,400
Cash acquired		2,200
Non-recurring transaction costs attributable to business combination excluded from pro-forma information										(143,604)	$ 55,835
Goodwill										$ 25,322
Net working capital adjustment		(500)
Additional consideration paid		$ 6,100
Total cash consideration for pre-existing contracted asset sale									$ 101,000
MS Sand \| Selling, General and Administrative Expenses
Business Acquisition [Line Items]
Acquisition-related costs								$ 1,000

Business Combinations - Purchase Price Allocation (Details) - USD ($) $ in Thousands	Jun. 30, 2018	May 01, 2018	Dec. 31, 2017
Business Acquisition [Line Items]
Goodwill	$ 414,257		$ 272,079
EPMH
Business Acquisition [Line Items]
Accounts receivable, net		$ 43,354
Inventories		84,395
Property, plant and mine development		123,086
Mineral rights		462,050
Identifiable intangible assets - finite lived		21,050
Identifiable intangible assets - indefinite lived		25,050
Prepaids and deposits		2,054
Other non-current assets		4,089
Goodwill		139,378
Total assets acquired		904,506
Accounts payable and accrued expenses		13,435
Accrued expenses and other current liabilities		8,255
Deferred tax liabilities		130,209
Other long term liabilities		9,766
Total liabilities assumed		161,665
Net assets acquired		$ 742,841
MS Sand
Business Acquisition [Line Items]
Accounts receivable, net			11,201
Inventories			8,067
Property, plant and mine development			27,458
Mineral rights			23,500
Identifiable intangible assets - finite lived			1,840
Other current assets			362
Assets held for sale			9,453
Other non-current assets			1,136
Goodwill			25,322
Total assets acquired			108,339
Accounts payable and accrued expenses			3,761
Unfavorable leasehold positions			2,237
Notes Payable			866
Other long term liabilities			0
Asset retirement obligations			474
Total liabilities assumed			7,338
Net assets acquired			101,001
MS Sand \| Estimate as of December 31, 2017
Business Acquisition [Line Items]
Accounts receivable, net			11,201
Inventories			8,067
Property, plant and mine development			27,458
Mineral rights			26,300
Identifiable intangible assets - finite lived			1,840
Other current assets			362
Assets held for sale			9,453
Other non-current assets			1,136
Goodwill			22,522
Total assets acquired			108,339
Accounts payable and accrued expenses			3,761
Unfavorable leasehold positions			2,237
Notes Payable			866
Other long term liabilities			0
Asset retirement obligations			474
Total liabilities assumed			7,338
Net assets acquired			101,001
MS Sand \| Measurement Period Adjustments
Business Acquisition [Line Items]
Accounts receivable, net			0
Inventories			0
Property, plant and mine development			0
Mineral rights			(2,800)
Identifiable intangible assets - finite lived			0
Other current assets			0
Assets held for sale			0
Other non-current assets			0
Goodwill			2,800
Total assets acquired			0
Accounts payable and accrued expenses			0
Unfavorable leasehold positions			0
Notes Payable			0
Other long term liabilities			0
Asset retirement obligations			0
Total liabilities assumed			0
Net assets acquired			$ 0

Business Combinations - Intangible Assets Acquired (Details) - USD ($) $ in Thousands	May 01, 2018	Aug. 16, 2017	Dec. 31, 2017
EPMH
Business Acquisition [Line Items]
Approximate fair value	$ 21,050
EPMH \| Technology and intellectual property
Business Acquisition [Line Items]
Approximate fair value	$ 2,000
Estimated useful life (in years)	15 years
EPMH \| Customer relationships
Business Acquisition [Line Items]
Approximate fair value	$ 19,050
Estimated useful life (in years)	15 years
MS Sand
Business Acquisition [Line Items]
Approximate fair value			$ 1,840
MS Sand \| Customer relationships
Business Acquisition [Line Items]
Approximate fair value		$ 1,840
Estimated useful life (in years)		15 years

Business Combinations - Pro Forma Information (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017	Dec. 31, 2016
EPMH
Business Acquisition [Line Items]
Sales	$ 451,566	$ 341,113	$ 879,493	$ 629,196
Net income (loss)	$ 19,693	$ 13,196	$ 70,539	$ 8,097
Basic earnings per share (in dollars per share)	$ 0.25	$ 0.16	$ 0.90	$ 0.10
Diluted earnings per share (in dollars per share)	$ 0.25	$ 0.16	$ 0.89	$ 0.10
Basic shares (in shares)	77,784	81,087	78,636	81,032
Diluted shares (in shares)	78,480	81,945	79,328	82,103
MS Sand
Business Acquisition [Line Items]
Sales					$ 1,287,202	$ 642,951
Net income (loss)					$ 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 (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Receivables [Abstract]
Trade receivables	$ 281,951	$ 217,649
Less: Allowance for doubtful accounts	(7,773)	(7,100)
Net trade receivables	274,178	210,549
Other receivables	5,841	2,037
Total accounts receivable	$ 280,019	$ 212,586

Accounts Receivable - Allowance for Doubtful Accounts (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017
Allowance for Doubtful Accounts Receivable
Beginning balance	$ 7,780
Bad debt provision	387	$ 848
Write-offs	(394)
Ending balance	$ 7,773

Accounts Receivable - Additional Information (Details) - Product Concentration Risk	6 Months Ended		12 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017
Sales \| Ten Largest Customers
Concentration Risk [Line Items]
Concentration risk percentage	50.00%	58.00%
Sales \| Customer One
Concentration Risk [Line Items]
Concentration risk percentage	14.00%	14.00%
Sales \| Customer Two
Concentration Risk [Line Items]
Concentration risk percentage		12.00%
Accounts Receivable, Net \| Customer One
Concentration Risk [Line Items]
Concentration risk percentage	15.00%		19.00%
Accounts Receivable, Net \| Customer Two
Concentration Risk [Line Items]
Concentration risk percentage			11.00%

Inventories (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Inventory Disclosure [Abstract]
Supplies	$ 36,639	$ 21,277
Raw materials and work in process	72,238	28,034
Finished goods	58,538	43,065
Total inventories	$ 167,415	$ 92,376

Property, Plant and Mine Development (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Property, Plant and Equipment
Property, plant and mine development, gross	$ 2,225,737	$ 1,522,675
Accumulated depletion, depreciation and amortization	(400,084)	(353,520)
Total property, plant and mine development, net	1,825,653	1,169,155
Mining property and mine development
Property, Plant and Equipment
Property, plant and mine development, gross	1,051,824	586,242
Asset retirement cost
Property, Plant and Equipment
Property, plant and mine development, gross	14,308	14,184
Land
Property, Plant and Equipment
Property, plant and mine development, gross	42,189	36,552
Land improvements
Property, Plant and Equipment
Property, plant and mine development, gross	66,336	45,878
Buildings
Property, Plant and Equipment
Property, plant and mine development, gross	73,150	56,330
Machinery and equipment
Property, Plant and Equipment
Property, plant and mine development, gross	790,655	590,566
Furniture and fixtures
Property, Plant and Equipment
Property, plant and mine development, gross	4,053	2,953
Construction-in-progress
Property, Plant and Equipment
Property, plant and mine development, gross	$ 183,222	$ 189,970

Property, Plant and Mine Development - Additional Information (Details)		3 Months Ended		6 Months Ended
	Mar. 21, 2018 USD ($) transload	Jun. 30, 2018 USD ($)	Jun. 30, 2017 USD ($)	Jun. 30, 2018 USD ($)	Jun. 30, 2017 USD ($)	Dec. 31, 2017 USD ($)
Property, Plant and Equipment
Aggregate cost of machinery and equipment under capital lease		$ 2,225,737,000		$ 2,225,737,000		$ 1,522,675,000
Accumulated depreciation of machinery and equipment under capital lease		400,084,000		400,084,000		353,520,000
Gain on sale of transload facilities				5,619,000	$ (394,000)
Consideration received allocated to asset retirement obligations liabilities of transload facilities				2,116,000
Asset impairment charges		16,184,000	$ 0	16,184,000	0
Permian, Eagle Ford, and Appalachian Basins \| Disposal Group, Disposed of by Sale, Not Discontinued Operations \| CIG Logistics
Property, Plant and Equipment
Number of transload facilities sold \| transload	3
Total consideration received on sale of transload facilities	$ 86,100,000
Liabilities assumed by buyer on sale of transload facilities	2,200,000
Cash consideration received on sale of transload facilities	83,900,000
Gain on sale of transload facilities	5,800,000
Consideration received allocated to asset retirement obligations liabilities of transload facilities	2,100,000
Equipment note assumed the buyer on sale of transload facilities	100,000
Consideration allocated to vendor incentives in sale of transload facilities	60,300,000
Accrued contract termination costs for facilities operated by third parties on sale of transload facilities	7,900,000
Settlement credit for contract termination costs on facilities operated by third parties on sale of transload facilities		2,700,000		2,700,000
Permian, Eagle Ford, and Appalachian Basins \| Disposal Group, Disposed of by Sale, Not Discontinued Operations \| CIG Logistics \| Accounts payables and accrued liabilities
Property, Plant and Equipment
Consideration allocated to vendor incentives in sale of transload facilities		10,600,000		10,600,000
Permian, Eagle Ford, and Appalachian Basins \| Disposal Group, Disposed of by Sale, Not Discontinued Operations \| CIG Logistics \| Other long-term obligations
Property, Plant and Equipment
Consideration allocated to vendor incentives in sale of transload facilities		46,300,000		46,300,000
Assets Held under Capital Leases
Property, Plant and Equipment
Aggregate cost of machinery and equipment under capital lease		1,100,000		1,100,000		900,000
Accumulated depreciation of machinery and equipment under capital lease		200,000		200,000		200,000
Mining property and mine development
Property, Plant and Equipment
Aggregate cost of machinery and equipment under capital lease		1,051,824,000		1,051,824,000		$ 586,242,000
Interest cost capitalized in property, plant and mine development				$ 3,300,000	$ 0
Transload Facilities \| Permian, Eagle Ford, and Appalachian Basins \| Disposal Group, Disposed of by Sale, Not Discontinued Operations \| CIG Logistics
Property, Plant and Equipment
Consideration received allocated to fair value of transload facilities	25,800,000
Net book value of transload facilities	$ 20,000,000
Resin Coating Facility
Property, Plant and Equipment
Asset impairment charges		$ 16,200,000

Goodwill and Intangible Assets - Changes in Carrying Amount of Goodwill (Details) $ in Thousands	6 Months Ended
	Jun. 30, 2018 USD ($)
Goodwill [Roll Forward]
Balance at December 31, 2017	$ 272,079
Balance at June 30, 2018	414,257
EPMH acquisition
Goodwill [Roll Forward]
Acquisitions and measurement period adjustments	139,378
MS Sand acquisition
Goodwill [Roll Forward]
Balance at December 31, 2017	25,322
Acquisitions and measurement period adjustments	$ 2,800

Goodwill and Intangible Assets - Changes in the Carrying Amount of Intangible Assets (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2018	Dec. 31, 2017
Finite-Lived Intangible Assets
Gross Carrying Amount	$ 156,867	$ 131,932
Accumulated Amortization	(20,190)	(14,993)
Net	136,677	116,939
Total Intangible Assets
Gross Carrying Amount	214,985	165,000
Accumulated Amortization	(20,190)	(14,993)
Intangible assets, net	194,795	150,007
Trade name
Indefinite-lived Intangible Assets
Gross Carrying Amount	$ 58,118	33,068
Technology and intellectual property
Finite-Lived Intangible Assets
Estimated Useful Life	15 years
Gross Carrying Amount	$ 76,588	70,703
Accumulated Amortization	(8,413)	(5,917)
Net	68,175	64,786
Total Intangible Assets
Accumulated Amortization	(8,413)	(5,917)
Customer relationships
Finite-Lived Intangible Assets
Gross Carrying Amount	80,279	61,229
Accumulated Amortization	(11,777)	(9,076)
Net	68,502	52,153
Total Intangible Assets
Accumulated Amortization	$ (11,777)	$ (9,076)
Customer relationships \| Minimum
Finite-Lived Intangible Assets
Estimated Useful Life	13 years
Customer relationships \| Maximum
Finite-Lived Intangible Assets
Estimated Useful Life	15 years

Goodwill and Intangible Assets - Additional Information (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Goodwill and Intangible Assets Disclosure [Abstract]
Amortization expense	$ 2.9	$ 2.2	$ 5.2	$ 4.2

Goodwill and Intangible Assets - Estimated Amortization Expense Related to Definite-Lived Intangible Assets (Details) $ in Thousands	Jun. 30, 2018 USD ($)
Goodwill and Intangible Assets Disclosure [Abstract]
2018	$ 5,586
2019	10,894
2020	10,894
2021	10,894
2022	$ 10,894

Debt (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Line of Credit Facility
Less: Unamortized original issue discount	$ (6,670)	$ (944)
Less: Unamortized debt issuance cost	(29,665)	(3,099)
Capital leases	744	706
Total debt	1,267,353	511,942
Less: current portion	(13,969)	(6,867)
Total long-term portion of debt	1,253,384	505,075
Notes Payable, Other Payables \| Note payable secured by royalty interest
Line of Credit Facility
Total	25,410	24,740
Notes Payable, Other Payables \| Customer note payable
Line of Credit Facility
Total	286	745
Notes Payable, Other Payables \| Equipment notes payable
Line of Credit Facility
Total	448	719
Revolving Line-of-Credit \| Revolver
Line of Credit Facility
Total	$ 0	$ 0
Credit facility, interest rate	8.00%	5.75%
Senior Secured Credit Facility \| Term loan facility
Line of Credit Facility
Total	$ 1,276,800	$ 489,075
Credit facility, interest rate	6.13%
Senior Secured Credit Facility \| Term loan facility \| Minimum
Line of Credit Facility
Credit facility, interest rate		4.75%
Senior Secured Credit Facility \| Term loan facility \| Maximum
Line of Credit Facility
Credit facility, interest rate		5.25%

Debt - Additional Information (Details)		6 Months Ended
Debt - Additional Information (Details)	May 01, 2018 USD ($)	Jun. 30, 2018 USD ($)	Jun. 30, 2017 USD ($)	Aug. 16, 2016 USD ($)
Debt Instrument [Line Items]
Write-off of capitalized debt issuance costs		$ 4,421,000	$ 692,000
Revolving Line-of-Credit \| Revolver
Debt Instrument [Line Items]
Available borrowing base		100,000,000
Amount drawn from borrowing base		0
Amount available for general corporate use under this revolving credit agreement		96,000,000
Letter of Credit \| Revolver
Debt Instrument [Line Items]
Amount allocated for letters of credit		4,000,000
Senior Secured Credit Facility \| Revolver
Debt Instrument [Line Items]
Net leverage ratio, credit facility threshold percentage	30.00%
Senior Secured Credit Facility \| Term loan facility
Debt Instrument [Line Items]
Credit facility consolidated total net leverage ratio	0.0375
Senior Secured Credit Facility
Debt Instrument [Line Items]
Debt issued	$ 1,380,000,000.000
Senior Secured Credit Facility \| Term loan facility
Debt Instrument [Line Items]
Debt issued	1,280,000,000.000
Senior Secured Credit Facility \| Revolving Line-of-Credit \| Revolver
Debt Instrument [Line Items]
Available borrowing base	100,000,000
Debt issuance costs	37,300,000
Debt Issuance costs capitalized	35,000,000
Write-off of capitalized debt issuance costs	$ 1,100,000
Notes Payable, Other Payables \| Note payable secured by royalty interest
Debt Instrument [Line Items]
Annual minimum payments		500,000
Debt instrument, fair value		$ 25,400,000		$ 22,500,000
Interest rate, effective percentage		22.00%
Notes Payable, Other Payables \| Note payable secured by royalty interest \| Measurement Input, Discount Rate
Debt Instrument [Line Items]
Fair value discount rate				0.14

Debt - Contractual Maturities of Senior Secured Credit Facility (Details) - Senior Secured Credit Facility - Term loan facility - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Debt Instrument [Line Items]
2018	$ 6,400
2019	12,800
2020	12,800
2021	12,800
Thereafter	1,232,000
Total	$ 1,276,800	$ 489,075

Debt - Contractual Maturities of Note Payable Secured by Royalty Interest (Details) - Notes Payable, Other Payables - Note payable secured by royalty interest $ in Thousands	Jun. 30, 2018 USD ($)
Debt Instrument [Line Items]
2018	$ 875
2019	1,750
2020	1,750
2021	1,750
2022	$ 1,750

Deferred Revenue (Details) - USD ($) $ in Thousands	6 Months Ended
Deferred Revenue (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Deferred Revenue Arrangement [Line Items]
Deferred revenue, advances received	$ 13,375
Deferred revenue	111,445	$ 118,414
Deferred revenue, current	$ 52,000	$ 36,100
Supply Agreement \| Minimum
Deferred Revenue Arrangement [Line Items]
Deferred revenue, average initial contract term	1 year
Supply Agreement \| Maximum
Deferred Revenue Arrangement [Line Items]
Deferred revenue, average initial contract term	5 years

Asset Retirement Obligations (Details) $ in Thousands	6 Months Ended
Asset Retirement Obligations (Details) $ in Thousands	Jun. 30, 2018 USD ($)
Asset Retirement Obligation Disclosure [Abstract]
Other long-term liabilities related to asset retirement obligation	$ 19,800
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Beginning balance	19,032
Accretion	611
Additions and revisions of prior estimates	(487)
Addition related to EPMH acquisition	2,733
Disposal related to sale of transloads	(2,116)
Ending balance	$ 19,773

Fair Value Accounting (Details) - USD ($)	Jun. 30, 2018	Dec. 31, 2017
Fair Value, Measurements, Recurring \| Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of derivative instruments (interest rate caps)	$ 0	$ 0

Derivative Instruments - Estimated Fair Values of Derivative Instruments (Details) - USD ($)	Jun. 30, 2018	Dec. 31, 2017
Interest rate cap agreement
Derivative Instruments, Gain (Loss)
Contract/Notional Amount	$ 249,000,000	$ 249,000,000
Carrying Amount	$ 0	$ 0
LIBOR \| Maximum
Derivative Instruments, Gain (Loss)
Derivative, basis spread on variable rate (maximum)	4.00%	4.00%
Fair Value, Measurements, Recurring \| Level 2
Derivative Instruments, Gain (Loss)
Fair Value	$ 0	$ 0
Fair Value, Measurements, Recurring \| Level 2 \| Interest rate cap agreement
Derivative Instruments, Gain (Loss)
Fair Value	$ 0	$ 0

Derivative Instruments - Additional Information (Details) - USD ($)	6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Ineffective portion of derivative contracts	$ 0	$ 0

Derivative Instruments - Effect of Derivatives Instruments on Combined Statements of Operations and Comprehensive Income (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017
Deferred Losses from Derivatives in OCI [Roll Forward]
Deferred losses from derivatives in OCI, beginning of period	$ (76)	$ (32)
Loss recognized in OCI from derivative instruments	0	(39)
Gain reclassified from Accumulated OCI	6	0
Deferred losses from derivatives in OCI, end of period	$ (70)	$ (71)

Equity-Based Compensation - Additional Information (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock options granted (in shares)	0	0	0	0
Stock options exercised (in shares)	4,167	2,083	4,167	26,935
Intrinsic value of stock options exercised	$ 100,000	$ 100,000	$ 100,000	$ 900,000
Proceeds from options exercised	62,000	30,000	62,000	547,000
Actual tax benefit realized for the tax deductions from option exercises	14,000	20,000	14,000	300,000
Stock Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Recognized equity-based compensation	400,000	600,000	900,000	1,300,000
Unrecognized compensation expense related to stock options	300,000		$ 300,000
Recognized weighted-average period			4 months
Restricted Stock and Restricted Stock Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Recognized equity-based compensation	$ 2,000,000	$ 1,800,000	$ 3,800,000	$ 3,300,000
Recognized weighted-average period			1 year 11 months
Awards share units granted (in shares)	234,079	139,451	237,931	140,951
Unrecognized compensation expense related to awards	$ 11,000,000		$ 11,000,000
Grant date fair value of awards granted (in dollars per share)			$ 26.34
Performance Share Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Recognized equity-based compensation	$ 4,500,000	$ 4,000,000	$ 8,600,000	$ 7,400,000
Recognized weighted-average period			1 year 5 months
Awards share units granted (in shares)	201,417	201,417	90,501	90,501
Unrecognized compensation expense related to awards	$ 15,500,000		$ 15,500,000
Grant date fair value of awards granted (in dollars per share)	$ 31.24	$ 30.37	$ 67.69	$ 67.69
2011 Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock that may be issued (in shares)	3,650,262		3,650,262

Equity-Based Compensation - Stock Options Activity (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017
Number of Shares
Outstanding at December 31, 2017 (in shares)			908,919
Granted (in shares)	0	0	0	0
Exercised (in shares)	(4,167)	(2,083)	(4,167)	(26,935)
Forfeited (in shares)			(918)
Expired (in shares)			(1,838)
Outstanding at June 30, 2018 (in shares)	901,996		901,996		908,919
Exercisable at June 30, 2018 (in shares)	855,446		855,446
Weighted Average Exercise Price
Outstanding at December 31, 2017, (in dollars per share)			$ 28.46
Granted (in dollars per share)			0.00
Exercised (in dollars per share)			14.65
Forfeited (in dollars per share)			31.30
Expired (in dollars per share)			31.30
Outstanding at June 30, 2018, (in dollars per share)	$ 28.52		28.52		$ 28.46
Exercisable at June 30, 2018 (in dollars per share)	$ 27.38		$ 27.38
Aggregate Intrinsic Value (in thousands)
Outstanding at June 30, 2018, aggregate intrinsic value	$ 3,692		$ 3,692		$ 7,008
Exercisable at June 30, 2018, aggregate intrinsic value	$ 3,692		$ 3,692
Weighted Average Remaining Contractual Term in Years
Outstanding at June 30, 2018, weighted average remaining contractual term in years			5 years 3 months		6 years 1 month
Exercisable at June 30, 2018, weighted average remaining contractual term in years			5 years 2 months

Equity-Based Compensation - Restricted Stock and Restricted Stock Units Activity (Details) - Restricted Stock and Restricted Stock Units - $ / shares	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Number of Shares
Unvested, December 31, 2017 (in shares)			461,346
Granted (in shares)	234,079	139,451	237,931	140,951
Vested (in shares)			(216,228)
Forfeited (in shares)			(22,827)
Unvested, June 30, 2018 (in shares)	460,222		460,222
Grant Date Weighted Average Fair Value
Unvested, December 31, 2017 (in dollars per share)			$ 30.76
Granted (in dollars per share)			26.34
Vested (in dollars per share)			30.04
Forfeited (in dollars per share)			31.76
Unvested, June 30, 2018 (in dollars per share)	$ 28.77		$ 28.77

Equity-Based Compensation - Performance Share Unit Activity (Details) - Performance Share Units - $ / shares	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Number of Shares
Unvested, December 31, 2017 (in shares)			881,416
Granted (in shares)	201,417	201,417	90,501	90,501
Vested (in shares)			(225,000)
Forfeited (in shares)			(8,072)
Unvested, June 30, 2018 (in shares)	849,761		849,761
Weighted Average
Unvested, December 31, 2017 (in dollars per share)			$ 42.16
Granted (in dollars per share)	$ 31.24	$ 30.37	67.69	$ 67.69
Vested (in dollars per share)			41.99
Forfeited (in dollars per share)			52.92
Unvested, June 30, 2018 (in dollars per share)	$ 39.31		$ 39.31

Commitments and Contingencies - Future Minimum Annual Commitments (Details) $ in Thousands	Jun. 30, 2018 USD ($)
Operating Lease Minimum Rental Payments
2018	$ 39,115
2019	73,080
2020	57,683
2021	38,639
2022	31,652
Thereafter	61,790
Total future lease commitments	301,959
Minimum Purchase Commitments
2018	12,413
2019	21,037
2020	15,663
2021	8,008
2022	5,640
Thereafter	4,141
Total future purchase commitments	$ 66,902

Commitments and Contingencies (Details)		3 Months Ended		6 Months Ended
Commitments and Contingencies (Details)	May 17, 2017 USD ($)	Jun. 30, 2018 USD ($) claim	Jun. 30, 2017 USD ($)	Jun. 30, 2018 USD ($) claim	Jun. 30, 2017 USD ($)	Dec. 31, 2017 USD ($)
Loss Contingencies
Expenses related to operating leases and rental agreements		$ 24,900,000	$ 15,800,000	$ 47,700,000	$ 31,200,000
Purchased reserves	$ 94,400,000
Other non-current assets
Loss Contingencies
Third party products claims liability under insurance in other long-term obligations		0		0		$ 0
Other long-term obligations
Loss Contingencies
Third party products claims liability under insurance in other long-term obligations		$ 1,000,000		$ 1,000,000		$ 1,000,000
Pending Litigation
Loss Contingencies
New claims filed \| claim				1
Number of pending claims \| claim		56		56

Pension and Post-Retirement Benefits - Net Pension and Post-Retirement Benefit Costs (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Pension Benefits
Defined Benefit Plan Disclosure
Service cost	$ 322	$ 149	$ 601	$ 444
Interest cost	1,158	571	2,136	1,454
Expected return on plan assets	(1,491)	(757)	(2,734)	(2,088)
Net amortization and deferral	631	255	1,264	948
Net pension benefit costs	620	218	1,267	758
Post-retirement Benefits
Defined Benefit Plan Disclosure
Service cost	27	33	54	65
Interest cost	188	191	376	383
Expected return on plan assets	0	(1)	(1)	(1)
Net amortization and deferral	0	53	0	107
Net pension benefit costs	$ 215	$ 276	$ 429	$ 554

Pension and Post-Retirement Benefits - Additional Information (Details) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018 USD ($) plan	Jun. 30, 2017 USD ($)	Jun. 30, 2018 USD ($) plan	Jun. 30, 2017 USD ($)
Defined Benefit Plan Disclosure
Number of multiemployer plans \| plan	3		3
Multiemployer plan, percentage of fund's total contributions			5.00%
Pension Benefits
Defined Benefit Plan Disclosure
Contributions to plan by employer	$ 0.5	$ 0.3	$ 0.8	$ 0.3
Expected contributions in current fiscal year	2.5		2.5
Post-retirement Benefits
Defined Benefit Plan Disclosure
Expected contributions in current fiscal year	$ 1.4		$ 1.4

Obligations Under Guarantees (Details) $ in Millions	Jun. 30, 2018 USD ($)
Surety Bonds
Loss Contingencies
Surety bonds outstanding	$ 28.6
Reclamation Bonds
Loss Contingencies
Bonds related to reclamation requirements	$ 25.6

Income Taxes (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended		12 Months Ended
Income Taxes (Details) - USD ($) $ in Millions	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017
Operating Loss Carryforwards [Line Items]
Income tax expense, decrease in deferred tax assets due to change in tax rate					$ 45.0
Income tax benefit, decrease in deferred tax liability due to change in tax rate					80.8
Income tax expense (benefit), net decrease in tax assets and liabilities due to change in tax rate					$ (35.8)
Effective income tax rate	14.00%	19.00%	17.00%	14.00%
Effective income tax rate without discrete tax benefit	13.00%	20.00%	16.00%	19.00%
Accounting Standards Update 2016-09
Operating Loss Carryforwards [Line Items]
Recorded tax expense (benefit) related to excess tax benefits on equity compensation	$ 0.2	$ (0.2)	$ 0.7	$ (1.7)

Revenue - Sales by Major Source (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Disaggregation of Revenue [Line Items]
Total Sales	$ 427,433	$ 290,465	$ 796,746	$ 535,262
Oil & Gas Proppants
Disaggregation of Revenue [Line Items]
Total Sales	324,063		636,993
Industrial & Specialty Products
Disaggregation of Revenue [Line Items]
Total Sales	103,370		159,753
Product
Disaggregation of Revenue [Line Items]
Total Sales	345,957	235,891	640,745	439,143
Product \| Oil & Gas Proppants
Disaggregation of Revenue [Line Items]
Total Sales	242,587		481,009
Product \| Industrial & Specialty Products
Disaggregation of Revenue [Line Items]
Total Sales	103,370		159,736
Service
Disaggregation of Revenue [Line Items]
Total Sales	81,476	$ 54,574	156,001	$ 96,119
Service \| Oil & Gas Proppants
Disaggregation of Revenue [Line Items]
Total Sales	81,476		155,984
Service \| Industrial & Specialty Products
Disaggregation of Revenue [Line Items]
Total Sales	$ 0		$ 17

Revenue - Changes in Contract Assets and Liabilities (Details) $ in Thousands	6 Months Ended
	Jun. 30, 2018 USD ($)
Unbilled Receivables
December 31, 2017	$ 5,245
Reclassifications to billed receivables	(8,161)
Revenues recognized in excess of period billings	5,428
June 30, 2018	2,512
Deferred Revenue
December 31, 2017	118,414
Revenues recognized from balances held at the beginning of the period	(20,344)
Revenues deferred from period collections on unfulfilled performance obligations	13,375
June 30, 2018	$ 111,445

Revenue - Additional Information (Details)	Jun. 30, 2018
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2018-07-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Remaining duration period of expected satisfaction of performance obligations	1 year

Related Party Transactions (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Related Party Transaction [Line Items]
Related party purchases			$ 1,604	$ 1,870
Officer \| Transportation Brokerage And Logistics Services Vendor
Related Party Transaction [Line Items]
Related party purchases	$ 900	$ 1,200	$ 1,800	$ 1,900

Segment Reporting - Additional Information (Details) $ in Thousands	6 Months Ended
	Jun. 30, 2018 USD ($) Product Segment	Dec. 31, 2017 USD ($)
Segment Reporting Information
Number of reportable segments \| Segment	2
Number of products in Industrial & Specialty segment (over 400) \| Product	400
Goodwill	$ 414,257	$ 272,079
Operating Segments \| Oil & Gas Proppants
Segment Reporting Information
Goodwill	250,300	247,500
Operating Segments \| Industrial & Specialty Products
Segment Reporting Information
Goodwill	$ 164,000	$ 24,600

Segment Reporting - Sales and Segment Contribution Margin for Reporting Segments and Other Operating Results (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Segment Reporting Information
Total sales	$ 427,433	$ 290,465	$ 796,746	$ 535,262
Selling, general and administrative	(42,232)	(25,839)	(76,823)	(47,978)
Depreciation, depletion and amortization	(36,563)	(23,626)	(65,155)	(45,225)
Asset impairment	(16,184)	0	(16,184)	0
Interest expense	(20,214)	(8,105)	(27,284)	(15,751)
Other income (expense), net, including interest income	1,081	638	1,746	(4,779)
Income tax expense	(2,832)	(7,110)	(10,353)	(5,396)
Net income	17,644	29,459	48,938	31,981
Operating Segments
Segment Reporting Information
Total sales	427,433	290,465	796,746	535,262
Total segment contribution margin	155,908	94,489	275,872	153,546
Segment Reconciling Items
Segment Reporting Information
Operating activities excluded from segment cost of sales	(21,320)	(988)	(32,881)	(2,436)
Selling, general and administrative	(42,232)	(25,839)	(76,823)	(47,978)
Depreciation, depletion and amortization	(36,563)	(23,626)	(65,155)	(45,225)
Asset impairment	(16,184)	0	(16,184)	0
Interest expense	(20,214)	(8,105)	(27,284)	(15,751)
Other income (expense), net, including interest income	1,081	638	1,746	(4,779)
Oil & Gas Proppants
Segment Reporting Information
Total sales	324,063		636,993
Oil & Gas Proppants \| Operating Segments
Segment Reporting Information
Total sales	324,063	235,018	636,993	427,976
Total segment contribution margin	114,607	71,222	214,041	110,062
Industrial & Specialty Products
Segment Reporting Information
Total sales	103,370		159,753
Industrial & Specialty Products \| Operating Segments
Segment Reporting Information
Total sales	103,370	55,447	159,753	107,286
Total segment contribution margin	$ 41,301	$ 23,267	$ 61,831	$ 43,484

Subsequent Events (Details) - $ / shares			3 Months Ended		6 Months Ended
Subsequent Events (Details) - $ / shares	Jul. 16, 2018	Jul. 06, 2018	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Subsequent Event
Cash dividend declared (in dollars per share)			$ 0.0625	$ 0.0625	$ 0.13	$ 0.13
Subsequent Event
Subsequent Event
Cash dividends paid (in dollars per share)		$ 0.0625
Cash dividend declared (in dollars per share)	$ 0.0625

Condensed Consolidated Statements of Stockholders' Equity (Parenthetical)	6 Months Ended
	Jun. 30, 2018 $ / shares
Cash dividend declared (in dollars per share)	$ 0.13
Retained Earnings
Cash dividend declared (in dollars per share)	$ 0.0625

Capital Structure and Accumulated Other Comprehensive Income (Loss) - Declared Quarterly Cash Dividends (Details) - $ / shares	May 14, 2018	Feb. 16, 2018
Equity [Abstract]
Dividends per Common Share (in dollars per share)	$ 0.0625	$ 0.0625