Document and Entity Information - shares	3 Months Ended
Document and Entity Information - shares	Mar. 31, 2018	Apr. 20, 2018
Document And Entity Information [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Mar. 31, 2018
Document Fiscal Year Focus	2018
Document Fiscal Period Focus	Q1
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		77,937,011

Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Current Assets:
Cash and cash equivalents	$ 329,512	$ 384,567
Accounts receivable, net	251,275	212,586
Inventories, net	76,579	92,376
Prepaid expenses and other current assets	13,023	13,715
Total current assets	670,389	703,244
Property, plant and mine development, net	1,195,722	1,169,155
Goodwill	274,879	272,079
Intangible assets, net	148,702	150,007
Other assets	17,346	12,798
Total assets	2,307,038	2,307,283
Current Liabilities:
Accounts payable and accrued expenses	154,148	171,041
Current portion of long-term debt	4,305	4,504
Current portion of capital leases	631	706
Current portion of deferred revenue	52,305	36,128
Income tax payable	605	1,566
Total current liabilities	211,994	213,945
Long-term debt, net	506,607	506,732
Deferred revenue	69,670	82,286
Liability for pension and other post-retirement benefits	50,167	52,867
Deferred income taxes, net	38,371	29,856
Other long-term obligations	77,246	25,091
Total liabilities	954,055	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 March 31, 2018 and December 31, 2017	0	0
Common stock, $0.01 par value, 500,000,000 shares authorized; 81,518,347 issued and 77,867,261 outstanding at March 31, 2018; 81,267,205 issued and 80,524,255 outstanding at December 31, 2017	814	812
Additional paid-in capital	1,153,336	1,147,084
Retained earnings	314,405	287,992
Treasury stock, at cost, 3,651,086 and 742,950 shares at March 31, 2018 and December 31, 2017, respectively	(103,940)	(25,456)
Accumulated other comprehensive loss	(11,632)	(13,926)
Total stockholders’ equity	1,352,983	1,396,506
Total liabilities and stockholders’ equity	$ 2,307,038	$ 2,307,283

Condensed Consolidated Balance Sheets (Parenthetical) - $ / shares	Mar. 31, 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)	81,518,347	81,267,205
Common stock outstanding (shares)	77,867,261	80,524,255
Treasury stock, at cost (shares)	3,651,086	742,950

Condensed Consolidated Statements of Operations - USD ($) shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Sales:
Product	$ 294,788	$ 203,251
Service	74,525	41,546
Total sales	369,313	244,797
Cost of sales (excluding depreciation, depletion and amortization):
Product	207,239	162,183
Service	53,671	25,292
Total cost of sales (excluding depreciation, depletion and amortization)	260,910	187,475
Operating expenses:
Selling, general and administrative	34,591	22,341
Depreciation, depletion and amortization	28,592	21,599
Total operating expenses	63,183	43,940
Operating income	45,220	13,382
Other (expense) income:
Interest expense	(7,070)	(7,646)
Other income (expense), net, including interest income	665	(4,928)
Total other expense	(6,405)	(12,574)
Income before income taxes	38,815	808
Income tax (expense) benefit	(7,521)	1,714
Net income	$ 31,294	$ 2,522
Earnings per share:
Basic (in dollars per share)	$ 0.39	$ 0.03
Diluted (in dollars per share)	$ 0.39	$ 0.03
Weighted average shares outstanding:
Basic (shares)	79,496	80,983
Diluted (shares)	80,309	82,244
Dividends declared per share (in dollars per share)	$ 0.06	$ 0.06

Condensed Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Statement of Comprehensive Income [Abstract]
Net income	$ 31,294	$ 2,522
Other comprehensive income (loss):
Unrealized gain (loss) on derivatives (net of tax of $1 and $(22) for the three months ended March 31, 2018 and 2017, respectively)	(2)	(36)
Foreign currency translation adjustment (net of tax of $1 and zero for the three months ended March 31, 2018 and 2017, respectively.)	3	0
Pension and other post-retirement benefits liability adjustment (net of tax of $730 and $340 for the three months ended March 31, 2018 and 2017, respectively)	2,293	565
Comprehensive income	$ 33,588	$ 3,051

Condensed Consolidated Statements of Comprehensive Income (Parenthetical) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Statement of Comprehensive Income [Abstract]
Unrealized gain (loss) on derivatives, tax	$ 1	$ (22)
Unrealized gain (loss) on investments, tax	1	0
Pension and other post-retirement benefits liability adjustment, tax	$ 730	$ 340

Condensed Consolidated Statements of Stockholders' Equity - 3 months ended Mar. 31, 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	31,294				31,294
Unrealized loss on derivatives	(2)					(2)
Foreign currency translation adjustment	3					3
Pension and post-retirement liability	2,293					2,293
Cash dividend declared ($0.0625 per share)	(4,881)				(4,881)
Equity-based compensation	6,254			6,254
Shares withheld for employee taxes related to vested restricted stock and stock units	(3,484)	2	(3,484)	(2)
Repurchase of common stock	(75,000)		(75,000)
Ending Balance at Mar. 31, 2018	$ 1,352,983	$ 814	$ (103,940)	$ 1,153,336	$ 314,405	$ (11,632)

Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Operating activities:
Net income	$ 31,294	$ 2,522
Adjustments to reconcile net income to net cash provided by (used in) operating activities:
Depreciation, depletion and amortization	28,592	21,599
Debt issuance amortization	345	347
Original issue discount amortization	93	94
Deferred income taxes	7,786	(1,726)
Deferred revenue	3,562	(4,689)
(Gain) loss on disposal of property, plant and equipment	(5,799)	59
Equity-based compensation	6,254	5,510
Bad debt provision, net of recoveries	237	783
Other	(1,476)	1,012
Changes in operating assets and liabilities, net of effects of acquisitions:
Accounts receivable	(39,077)	(51,747)
Inventories	15,797	9,251
Prepaid expenses and other current assets	694	(78)
Income taxes	(961)	68
Accounts payable and accrued expenses	(27,930)	(3,020)
Short-term and long-term obligations-vendor incentives	57,986	0
Liability for pension and other post-retirement benefits	212	497
Net cash provided by (used in) operating activities	77,609	(19,518)
Investing activities:
Capital expenditures	(72,327)	(19,896)
Capitalized intellectual property costs	(1,011)	(1,245)
Proceeds from sale of property, plant and equipment	25,960	12
Net cash used in investing activities	(47,378)	(21,129)
Financing activities:
Dividends paid	(5,069)	(5,092)
Repurchase of common stock	(75,000)	0
Proceeds from options exercised	0	517
Tax payments related to shares withheld for vested restricted stock and stock units	(3,485)	(3,377)
Repayment of long-term debt	(1,657)	(1,405)
Principal payments on capital lease obligations	(75)	(318)
Net cash used in financing activities	(85,286)	(9,675)
Net decrease in cash and cash equivalents	(55,055)	(50,322)
Cash and cash equivalents, beginning of period	384,567	711,225
Cash and cash equivalents, end of period	329,512	660,903
Cash paid (received) during the period for:
Interest	6,592	6,157
Taxes, net of refunds	770	(57)
Related party purchases	672	858
Non-cash Items:
Equipment received	0	18,185
Accrued capital expenditures	20,170	4,142
Capital lease assumed by third-party	119	0
Asset retirement obligation assumed by third-party	$ 2,116	$ 0

Summary of Significant Accounting Policies

3 Months Ended

Mar. 31, 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 three months ended March 31, 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.

In order to make this report easier to read, we refer throughout 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 March 31, 2018; the Income Statements and Condensed Consolidated Statements of Comprehensive Income for the three months ended March 31, 2018 and 2017; the Condensed Consolidated Statements of Stockholders' Equity and Cash Flows for the three months ended March 31, 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.

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 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.

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.

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. 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 months ended March 31, 2017:



	As Previously Reported			Adjustments			As Revised
Product cost of sales	$	162,637		$	(287	)	$	162,350
Total cost of sales	187,475			(287		)	187,188
Selling, general and administrative expenses	22,341			(202		)	22,139
Operating income	13,382			489			13,871
Other income (expense)	(4,928		)	(489		)	(5,417		)

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

3 Months Ended

Mar. 31, 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 months ended March 31, 2018 and 2017:



In thousands, except per share amounts	Three Months Ended March 31,
	2018			2017
Numerator:
Net income	$	31,294		$	2,522

Denominator:
Weighted average shares outstanding	79,496		—	80,983
Diluted effect of stock awards	813			1,261
Weighted average shares outstanding assuming dilution	80,309			82,244

Basic earnings per share	$	0.39		$	0.03
Diluted earnings per share	$	0.39		$	0.03

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 March 31,
	2018	2017
Weighted-average outstanding stock options excluded	428	195
Weighted-average outstanding restricted stock and performance share units awards excluded	337	—

Capital Structure and Accumulated Other Comprehensive Income (Loss)

3 Months Ended

Mar. 31, 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 81,518,347 shares issued and 77,867,261 shares outstanding at March 31, 2018. There were 81,267,205 shares issued and 80,524,255 shares outstanding at December 31, 2017.

During the three months ended March 31, 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

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 March 31, 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. As of March 31, 2018, we were authorized to repurchase up to $100 million of our common stock through December 11, 2018. Stock repurchases, if any, will be funded using our available liquidity. The timing and amount of stock repurchases will depend on a variety of factors, including the market conditions as well as corporate and regulatory considerations. 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. As of March 31, 2018, we have repurchased a total of 3,555,104 shares of our common stock at an average price of $28.13, completing the $100 million authorized under this program.

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

Accumulated Other Comprehensive Income (Loss)

Accumulated other comprehensive income (loss) consists of fair value adjustments associated with cash flow hedges, accumulated adjustments for net experience losses and prior service cost related to employee benefit plans and foreign currency translation adjustments primarily related to accounts payable denominated in Euros. The following table presents the changes in accumulated other comprehensive income (loss) by component (in thousands) during the three months ended March 31, 2018:



	For the Three Months Ended March 31, 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	—			(3		)	1,806			1,803
Amounts reclassed from accumulated other comprehensive income	2			—			489			491
Ending Balance	$	(74	)	$	(9	)	$	(11,549	)	$	(11,632	)

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

Business Combinations

3 Months Ended

Mar. 31, 2018

Business Combinations [Abstract]

BUSINESS COMBINATIONS

NOTE D—BUSINESS COMBINATIONS

2018 Acquisitions:

On March 22, 2018, U.S. Silica entered into a definitive agreement to acquire all of the outstanding capital stock of EP Minerals, a global producer of engineered materials derived from industrial minerals, including diatomaceous earth (DE), clay (calcium bentonite) and perlite. The consideration payable consists of $750.0 million of cash, subject to customary adjustments for net working capital, indebtedness, cash and transaction expenses as of the closing. U.S. Silica expects to fund the consideration with additional borrowings pursuant to a contemplated amendment to its existing credit facilities and with cash on hand. The consummation of the acquisition is subject to the satisfaction or waiver of closing conditions applicable to both U.S. Silica and EP Minerals and it is expected to close in the second quarter of 2018.

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 $0.9 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

3 Months Ended

Mar. 31, 2018

Receivables [Abstract]

ACCOUNTS RECEIVABLE

NOTE E—ACCOUNTS RECEIVABLE

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



	March 31, 2018			December 31, 2017
Trade receivables	$	247,178		$	217,649
Less: Allowance for doubtful accounts	(7,250		)	(7,100		)
Net trade receivables	239,928			210,549
Other receivables	11,347			2,037
Total accounts receivable	$	251,275		$	212,586

Changes in our allowance for doubtful accounts (in thousands) during the three months ended March 31, 2018 are as follows:



	March 31, 2018
Beginning balance	$	7,100
Bad debt provision	237
Write-offs	(87		)
Ending balance	$	7,250

Our ten largest customers accounted for approximately 52% and 55% of total sales during the three months ended March 31, 2018 and 2017, respectively. Sales to one of our customers accounted for 15% of our total sales during the three months ended March 31, 2018. Sales to two of our customers accounted for 14% and 11% of our total sales during the three months ended March 31, 2017. No other customers accounted for 10% or more of our total sales. At March 31, 2018, one of our customers' accounts receivable represented 17% 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

3 Months Ended

Mar. 31, 2018

Inventory Disclosure [Abstract]

INVENTORIES

NOTE F—INVENTORIES

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



	March 31, 2018		December 31, 2017
Supplies	$	22,338	$	21,277
Raw materials and work in process	24,175		28,034
Finished goods	30,066		43,065
Total inventories	$	76,579	$	92,376

Property, Plant and Mine Development

3 Months Ended

Mar. 31, 2018

Property, Plant and Equipment [Abstract]

PROPERTY, PLANT AND MINE DEVELOPMENT

NOTE G—PROPERTY, PLANT AND MINE DEVELOPMENT

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



	March 31, 2018			December 31, 2017
Mining property and mine development	$	584,778		$	586,242
Asset retirement cost	12,166			14,184
Land	36,552			36,552
Land improvements	50,793			45,878
Buildings	55,280			56,330
Machinery and equipment	634,807			590,566
Furniture and fixtures	2,862			2,953
Construction-in-progress	187,639			189,970
	1,564,877			1,522,675
Accumulated depletion, depreciation and amortization	(369,155		)	(353,520		)
Total property, plant and mine development, net	$	1,195,722		$	1,169,155

At March 31, 2018 and December 31, 2017, the aggregate cost of machinery and equipment acquired under capital leases was $0.9 million, reduced by accumulated depreciation of $0.2 million. The amount of interest costs capitalized in property, plant and mine development was $1.8 million for the three months ended March 31, 2018. There were no interest costs capitalized for the three months ended March 31, 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 March 31, 2018, vendor incentives are classified in accounts payable and accrued expenses and in other long-term obligations on our balance sheet.

Separately, the Company has accrued $7.9 million in contract termination costs for facilities contracts operated by third-parties, which will not transfer to CIG. These costs of $5.9 million in accounts payable and accrued expenses and $2.0 million of other long-term obligations are on our balance sheet.

Goodwill and Intangible Assets

3 Months Ended

Mar. 31, 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
MS Sand acquisition measurement period adjustment	2,800
Balance at March 31, 2018	$	274,879

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



		March 31, 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	$	71,713	$	(7,127	)	$	64,586	$	70,703	$	(5,917	)	$	64,786
Customer relationships	13 - 15	61,229		(10,181		)	51,048		61,229		(9,076		)	52,153
Total definite-lived intangible assets:		$	132,942	$	(17,308	)	$	115,634	$	131,932	$	(14,993	)	$	116,939
Trade name		33,068		—			33,068		33,068		—			33,068
Total intangible assets:		$	166,010	$	(17,308	)	$	148,702	$	165,000	$	(14,993	)	$	150,007

Amortization expense was $2.3 million and $2.0 million for the three months ended March 31, 2018 and 2017.

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



2018	$	6,980
2019	9,306
2020	9,306
2021	9,306
2022	9,291

- Definition

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

+ References + Details

Debt

3 Months Ended

Mar. 31, 2018

Debt Disclosure [Abstract]

DEBT

NOTE I—DEBT

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



	March 31, 2018			December 31, 2017
Senior secured credit facility:
Revolver expiring July 23, 2018 (6.25% at March 31, 2018 and 5.75% at December 31, 2017)	$	—		$	—
Term loan facility—final maturity July 23, 2020 (4.94%-5.44% at March 31, 2018 and 4.75%-5.25% December 31, 2017)	487,800			489,075
Less: Unamortized original issue discount	(850		)	(944		)
Less: Unamortized debt issuance cost	(2,755		)	(3,099		)
Note payable secured by royalty interest	25,635			24,740
Customer note payable	566			745
Equipment notes payable	516			719
Total debt	510,912			511,236
Less: current portion	(4,305		)	(4,504		)
Total long-term portion of debt	$	506,607		$	506,732

Revolving Line-of-Credit

We have a $50.0 million revolving line-of-credit (the “Revolver”), with zero drawn and $4.5 million allocated for letters of credit as of March 31, 2018, leaving $45.5 million available under the Revolver.

Senior Secured Credit Facility

At March 31, 2018, contractual maturities of our senior secured credit facility (in thousands) are as follows:



2018	$	3,825
2019	5,100
2020	478,875
Total	$	487,800

Our senior secured credit facility is secured by a pledge of substantially all of our assets, including accounts receivable, inventory, property, plant and mine development, and a pledge of the equity interests in certain of our subsidiaries. The facility contains covenants that, among other things, govern our ability to create, incur or assume indebtedness and liens, to make acquisitions or investments, to sell assets and to pay dividends. This includes a restriction on the ability of our operating subsidiaries to make distributions to us to the extent that the incurrence ratio (as defined in the senior secured credit facility) after giving effect to the distribution is 3:1 or greater. The facility also requires us to maintain a consolidated total net leverage ratio of no more than 3.75:1.00 as of the last day of any fiscal quarter whenever usage of the Revolver (other than certain undrawn letters of credit) exceeds 25% of the Revolver commitment. As of March 31, 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	$	1,313
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 March 31, 2018, the note payable has a balance of $25.6 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 is 22% at March 31, 2018.

Deferred Revenue	3 Months Ended
Deferred Revenue	Mar. 31, 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 three months ended March 31, 2018 we received advances of $10.5 million. At March 31, 2018 and December 31, 2017, the total deferred revenue balance was $122.0 million and $118.4 million, respectively, of which $52.3 million and $36.1 million was classified as current on our Balance Sheets.

Asset Retirement Obligation

3 Months Ended

Mar. 31, 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 March 31, 2018, we had a liability of $16.8 million in other long-term obligations related to our asset retirement obligation. Changes in the asset retirement obligation (in thousands) during the three months ended March 31, 2018 are as follows:



	March 31, 2018
Beginning balance	$	19,032
Accretion	326
Additions and revisions of prior estimates	(486		)
Disposal related to sale of transloads	(2,116		)
Ending balance	$	16,756

Fair Value Accounting	3 Months Ended
Fair Value Accounting	Mar. 31, 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 March 31, 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 March 31, 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 March 31, 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

3 Months Ended

Mar. 31, 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 March 31, 2018 and December 31, 2017.



		March 31, 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 three months ended March 31, 2018 and 2017, we had no ineffectiveness for such contracts.

The following table summarizes the effect of derivatives instruments (in thousands) on our income statements and our consolidated statements of comprehensive income for the three months ended March 31, 2018 and 2017.



	March 31, 2018			March 31, 2017
Deferred losses from derivatives in OCI, beginning of period	$	(76	)	$	(32	)
Loss recognized in OCI from derivative instruments	—			(36		)
Gain reclassified from Accumulated OCI	2			—
Deferred losses from derivatives in OCI, end of period	$	(74	)	$	(68	)

Equity-Based Compensation

3 Months Ended

Mar. 31, 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 March 31, 2018, we have 4,481,559 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 three months ended March 31, 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	—		—		—
Forfeited	(918	)	31.30		—
Outstanding at March 31, 2018	908,001		$	28.46	$	3,679	5.5 years
Exercisable at March 31, 2018	791,868		$	27.02	$	3,679	5.3 years

There were no grants of stock options during the three months ended March 31, 2018 and 2017.

There were zero and 24,852 stock options exercised during the three months ended March 31, 2018 and 2017, respectively. The total intrinsic value of stock options exercised was $0.9 million for the three months ended March 31, 2017. Cash received from options exercised during the three months ended March 31, 2017 was $0.5 million. The tax benefit realized from option exercises totaled $0.3 million for the three months ended March 31, 2017.

We recognized $0.5 million and $0.6 million of equity-based compensation expense related to options during the three months ended March 31, 2018 and 2017, respectively. As of March 31, 2018, there was $0.7 million of total unrecognized compensation expense related to these options, which is expected to be recognized over a weighted-average period of approximately 0.5 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 three months ended March 31, 2018:



	Number of Shares		Grant Date Weighted Average Fair Value
Unvested, December 31, 2017	461,346		$	30.76
Granted	3,852		30.11
Vested	(132,081	)	24.56
Forfeited	(10,309	)	35.65
Unvested, March 31, 2018	322,808		$	33.14

We granted 3,852 and 1,500 restricted stock and restricted stock unit awards during the three months ended March 31, 2018 and 2017, respectively. The fair value of the awards was based on the market price of our stock at date of grant.

We recognized $1.8 million and $1.5 million of equity-based compensation expense related to restricted stock awards during the three months ended March 31, 2018 and 2017, respectively. As of March 31, 2018, there was $7.2 million of total unrecognized compensation expense related to these restricted stock awards, which is expected to be recognized over a weighted-average period of 1.6 years.

Performance Share Unit Awards

The following table summarizes the status of, and changes in, our performance share unit awards during the three months ended March 31, 2018:



	Number of Shares		Grant Date Weighted Average Fair Value
Unvested, December 31, 2017	881,416		$	42.16
Granted	—		—
Vested	(225,000	)	41.99
Forfeited	(5,972	)	58.71
Unvested, March 31, 2018	650,444		$	42.07

There were no grants of performance share unit awards during the three months ended March 31, 2018 and 2017, respectively.

We recognized $4.3 million and $3.4 million of compensation expense related to performance share unit awards during the three months ended March 31, 2018 and 2017, respectively. As of March 31, 2018, there was $13.9 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 year.

Commitments and Contingencies

3 Months Ended

Mar. 31, 2018

Commitments and Contingencies Disclosure [Abstract]

COMMITMENTS AND CONTINGENCIES

NOTE O—COMMITMENTS AND CONTINGENCIES

Future Minimum Annual Commitments at March 31, 2018 (in thousands):



Year ending December 31,	Operating Lease Minimum Rental Payments		Minimum Purchase Commitments
2018	$	53,739	$	18,292
2019	64,746		22,829
2020	52,868		17,951
2021	36,031		9,459
2022	30,301		6,851
Thereafter	55,739		4,565
Total future lease and purchase commitments	$	293,424	$	79,947

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 $22.8 million and $15.4 million for the three months ended March 31, 2018 and 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 three months ended March 31, 2018, one new claim was brought against U.S. Silica. As of March 31, 2018, there were 60 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 March 31, 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

3 Months Ended

Mar. 31, 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 months ended March 31, 2018 and 2017:



	Three Months Ended March 31,
	2018			2017
Service cost	$	279		$	295
Interest cost	978			883
Expected return on plan assets	(1,243		)	(1,331		)
Net amortization and deferral	631			693
Net pension benefit costs	$	645		$	540

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 months ended March 31, 2018 and 2017:



	Three Months Ended March 31,
	2018		2017
Service cost	$	27	$	32
Interest cost	188		192
Net amortization and deferral	—		54
Net post-retirement benefit costs	$	215	$	278

We made $0.3 million and zero contributions to the qualified pension plan for the three months ended March 31, 2018 and 2017, respectively. 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 months ended March 31, 2018 and 2017

Obligations Under Guarantees	3 Months Ended
Obligations Under Guarantees	Mar. 31, 2018
Guarantees [Abstract]
OBLIGATIONS UNDER GUARANTEES	NOTE Q— OBLIGATIONS UNDER GUARANTEES We have indemnified the Travelers Companies, Inc. and subsidiaries (“Travelers”) against any loss Travelers may incur in the event that holders of surety bonds, issued on behalf of us by Travelers, execute the bonds. As of March 31, 2018, Travelers had $12.2 million in bonds outstanding for us. The majority of these bonds, $10.3 million, relate to reclamation requirements issued by various governmental authorities. Reclamation bonds remain outstanding until the mining area is reclaimed and the authority issues a formal release. The remaining bonds relate to such indefinite purposes as licenses, permits, and tax collection.

Income Taxes	3 Months Ended
Income Taxes	Mar. 31, 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. 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 months ending March 31, 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. In the three months ended March 31, 2018, we recorded a tax expense of $0.5 million related to equity compensation pursuant to ASU 2016-09. In the three months ended March 31, 2017, we recorded a tax benefit of $1.5 million related to equity compensation pursuant to ASU 2016-09. The effective tax rate was 19% and (212)% for the three months ended March 31, 2018 and 2017, respectively. The tax rate for the three months ended March 31, 2018 and 2017 would have been 18% and (26)%, respectively, without the equity compensation tax expense or benefit 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

3 Months Ended

Mar. 31, 2018

Revenue from Contract with Customer [Abstract]

REVENUE

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 months ended March 31, 2018 (in thousands):



Category	Oil & Gas Proppants		Industrial & Specialty Products		Total Sales
Product	$	238,422	$	56,366	$	294,788
Service	74,508		17		74,525
Total Sales	312,930		56,383		369,313

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 three months ended March 31, 2018 (in thousands):



	Unbilled Receivables
December 31, 2017	$	5,245
Reclassifications to billed receivables	(5,245		)
Revenues recognized in excess of period billings	2,939
March 31, 2018	$	2,939



	Deferred Revenue
December 31, 2017	$	118,414
Revenues recognized from balances held at the beginning of the period	(6,969		)
Revenues deferred from period collections on unfulfilled performance obligations	10,530
March 31, 2018	$	121,975

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.

Related Party Transactions	3 Months Ended
Related Party Transactions	Mar. 31, 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 $0.6 million for the three months ended March 31, 2018 and 2017, respectively.

Segment Reporting

3 Months Ended

Mar. 31, 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 200 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 months ended March 31, 2018 and 2017:



	Three Months Ended March 31,
	2018			2017
Sales:
Oil & Gas Proppants	$	312,930		$	192,959
Industrial & Specialty Products	56,383			51,838
Total sales	369,313			244,797
Segment contribution margin:
Oil & Gas Proppants	99,433			38,842
Industrial & Specialty Products	20,530			20,215
Total segment contribution margin	119,963			59,057
Operating activities excluded from segment cost of sales	(11,560		)	(1,735		)
Selling, general and administrative	(34,591		)	(22,341		)
Depreciation, depletion and amortization	(28,592		)	(21,599		)
Interest expense	(7,070		)	(7,646		)
Other income (expense), net, including interest income	665			(4,928		)
Income tax (expense) benefit	(7,521		)	1,714
Net income	$	31,294		$	2,522

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 March 31, 2018, goodwill of $274.9 million has been allocated to these segments with $250.3 million assigned to Oil & Gas Proppants and $24.6 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	3 Months Ended
Subsequent Events	Mar. 31, 2018
Subsequent Events [Abstract]
SUBSEQUENT EVENTS	NOTE V— SUBSEQUENT EVENTS On April 5, 2018, we paid a cash dividend of $0.0625 per share to common stockholders of record on March 15, 2018, which had been declared by our Board of Directors on February 16, 2018.

Summary of Significant Accounting Policies (Policies)

3 Months Ended

Mar. 31, 2018

Accounting Policies [Abstract]

Basis of Presentation and Consolidation

Reclassifications

Certain reclassifications of prior year's amounts have been made to conform to the current year presentation.

Unaudited Interim Financial Statements

Use of Estimates and Assumptions

Revenue Recognition

Products

Service

Contracts with Multiple Performance Obligations

Taxes Collected from Customers and Remitted to Governmental Authorities.

Deferred Revenues

Unbilled Receivables

Recently Issued Accounting Pronouncements



	As Previously Reported			Adjustments			As Revised
Product cost of sales	$	162,637		$	(287	)	$	162,350
Total cost of sales	187,475			(287		)	187,188
Selling, general and administrative expenses	22,341			(202		)	22,139
Operating income	13,382			489			13,871
Other income (expense)	(4,928		)	(489		)	(5,417		)

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 March 31, 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 March 31, 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)

3 Months Ended

Mar. 31, 2018

Accounting Policies [Abstract]

Schedule of Reconciliation of Effects of Reclassification

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 months ended March 31, 2017:



	As Previously Reported			Adjustments			As Revised
Product cost of sales	$	162,637		$	(287	)	$	162,350
Total cost of sales	187,475			(287		)	187,188
Selling, general and administrative expenses	22,341			(202		)	22,139
Operating income	13,382			489			13,871
Other income (expense)	(4,928		)	(489		)	(5,417		)

Earnings Per Share (Tables)

3 Months Ended

Mar. 31, 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 months ended March 31, 2018 and 2017:



In thousands, except per share amounts	Three Months Ended March 31,
	2018			2017
Numerator:
Net income	$	31,294		$	2,522

Denominator:
Weighted average shares outstanding	79,496		—	80,983
Diluted effect of stock awards	813			1,261
Weighted average shares outstanding assuming dilution	80,309			82,244

Basic earnings per share	$	0.39		$	0.03
Diluted earnings per share	$	0.39		$	0.03

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



	Three Months Ended March 31,
	2018	2017
Weighted-average outstanding stock options excluded	428	195
Weighted-average outstanding restricted stock and performance share units awards excluded	337	—

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

3 Months Ended

Mar. 31, 2018

Equity [Abstract]

Schedule of Declared Quarterly Cash Dividends

During the three months ended March 31, 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

Changes in Accumulated Other Comprehensive Income

The following table presents the changes in accumulated other comprehensive income (loss) by component (in thousands) during the three months ended March 31, 2018:



	For the Three Months Ended March 31, 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	—			(3		)	1,806			1,803
Amounts reclassed from accumulated other comprehensive income	2			—			489			491
Ending Balance	$	(74	)	$	(9	)	$	(11,549	)	$	(11,632	)

Business Combinations (Tables)

3 Months Ended

Mar. 31, 2018

Business Combinations [Abstract]

Schedule of Identifiable Assets Acquired and Liabilities Assumed



	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

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	)

Accounts Receivable (Tables)

3 Months Ended

Mar. 31, 2018

Receivables [Abstract]

Schedule of Accounts Receivable and Allowance for Doubtful Accounts

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



	March 31, 2018			December 31, 2017
Trade receivables	$	247,178		$	217,649
Less: Allowance for doubtful accounts	(7,250		)	(7,100		)
Net trade receivables	239,928			210,549
Other receivables	11,347			2,037
Total accounts receivable	$	251,275		$	212,586

Changes in our allowance for doubtful accounts (in thousands) during the three months ended March 31, 2018 are as follows:



	March 31, 2018
Beginning balance	$	7,100
Bad debt provision	237
Write-offs	(87		)
Ending balance	$	7,250

Inventories (Tables)

3 Months Ended

Mar. 31, 2018

Inventory Disclosure [Abstract]

Schedule of Inventories

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



	March 31, 2018		December 31, 2017
Supplies	$	22,338	$	21,277
Raw materials and work in process	24,175		28,034
Finished goods	30,066		43,065
Total inventories	$	76,579	$	92,376

Property, Plant and Mine Development (Tables)

3 Months Ended

Mar. 31, 2018

Property, Plant and Equipment [Abstract]

Schedule of Property, Plant and Mine Development

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



	March 31, 2018			December 31, 2017
Mining property and mine development	$	584,778		$	586,242
Asset retirement cost	12,166			14,184
Land	36,552			36,552
Land improvements	50,793			45,878
Buildings	55,280			56,330
Machinery and equipment	634,807			590,566
Furniture and fixtures	2,862			2,953
Construction-in-progress	187,639			189,970
	1,564,877			1,522,675
Accumulated depletion, depreciation and amortization	(369,155		)	(353,520		)
Total property, plant and mine development, net	$	1,195,722		$	1,169,155

Goodwill and Intangible Assets (Tables)

3 Months Ended

Mar. 31, 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
MS Sand acquisition measurement period adjustment	2,800
Balance at March 31, 2018	$	274,879

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:



		March 31, 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	$	71,713	$	(7,127	)	$	64,586	$	70,703	$	(5,917	)	$	64,786
Customer relationships	13 - 15	61,229		(10,181		)	51,048		61,229		(9,076		)	52,153
Total definite-lived intangible assets:		$	132,942	$	(17,308	)	$	115,634	$	131,932	$	(14,993	)	$	116,939
Trade name		33,068		—			33,068		33,068		—			33,068
Total intangible assets:		$	166,010	$	(17,308	)	$	148,702	$	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:



		March 31, 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	$	71,713	$	(7,127	)	$	64,586	$	70,703	$	(5,917	)	$	64,786
Customer relationships	13 - 15	61,229		(10,181		)	51,048		61,229		(9,076		)	52,153
Total definite-lived intangible assets:		$	132,942	$	(17,308	)	$	115,634	$	131,932	$	(14,993	)	$	116,939
Trade name		33,068		—			33,068		33,068		—			33,068
Total intangible assets:		$	166,010	$	(17,308	)	$	148,702	$	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	$	6,980
2019	9,306
2020	9,306
2021	9,306
2022	9,291

Debt (Tables)

3 Months Ended

Mar. 31, 2018

Debt Disclosure [Abstract]

Schedule of Debt

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



	March 31, 2018			December 31, 2017
Senior secured credit facility:
Revolver expiring July 23, 2018 (6.25% at March 31, 2018 and 5.75% at December 31, 2017)	$	—		$	—
Term loan facility—final maturity July 23, 2020 (4.94%-5.44% at March 31, 2018 and 4.75%-5.25% December 31, 2017)	487,800			489,075
Less: Unamortized original issue discount	(850		)	(944		)
Less: Unamortized debt issuance cost	(2,755		)	(3,099		)
Note payable secured by royalty interest	25,635			24,740
Customer note payable	566			745
Equipment notes payable	516			719
Total debt	510,912			511,236
Less: current portion	(4,305		)	(4,504		)
Total long-term portion of debt	$	506,607		$	506,732

Schedule of Contractual Maturities of Debt

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



2018	$	1,313
2019	1,750
2020	1,750
2021	1,750
2022	1,750

At March 31, 2018, contractual maturities of our senior secured credit facility (in thousands) are as follows:



2018	$	3,825
2019	5,100
2020	478,875
Total	$	487,800

Asset Retirement Obligations (Tables)

3 Months Ended

Mar. 31, 2018

Asset Retirement Obligation Disclosure [Abstract]

Schedule of Changes in Asset Retirement Obligation

Changes in the asset retirement obligation (in thousands) during the three months ended March 31, 2018 are as follows:



	March 31, 2018
Beginning balance	$	19,032
Accretion	326
Additions and revisions of prior estimates	(486		)
Disposal related to sale of transloads	(2,116		)
Ending balance	$	16,756

Derivative Instruments (Tables)

3 Months Ended

Mar. 31, 2018

Derivative Instruments and Hedging Activities Disclosure [Abstract]

Schedule of Estimated Fair Values of Derivative Instruments



		March 31, 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



	March 31, 2018			March 31, 2017
Deferred losses from derivatives in OCI, beginning of period	$	(76	)	$	(32	)
Loss recognized in OCI from derivative instruments	—			(36		)
Gain reclassified from Accumulated OCI	2			—
Deferred losses from derivatives in OCI, end of period	$	(74	)	$	(68	)

Equity-Based Compensation (Tables)

3 Months Ended

Mar. 31, 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 three months ended March 31, 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	—		—		—
Forfeited	(918	)	31.30		—
Outstanding at March 31, 2018	908,001		$	28.46	$	3,679	5.5 years
Exercisable at March 31, 2018	791,868		$	27.02	$	3,679	5.3 years

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

Restricted Stock and Restricted Stock Unit Awards

The following table summarizes the status of, and changes in, our unvested restricted stock awards during the three months ended March 31, 2018:



	Number of Shares		Grant Date Weighted Average Fair Value
Unvested, December 31, 2017	461,346		$	30.76
Granted	3,852		30.11
Vested	(132,081	)	24.56
Forfeited	(10,309	)	35.65
Unvested, March 31, 2018	322,808		$	33.14

The following table summarizes the status of, and changes in, our performance share unit awards during the three months ended March 31, 2018:



	Number of Shares		Grant Date Weighted Average Fair Value
Unvested, December 31, 2017	881,416		$	42.16
Granted	—		—
Vested	(225,000	)	41.99
Forfeited	(5,972	)	58.71
Unvested, March 31, 2018	650,444		$	42.07

Commitments and Contingencies (Tables)

3 Months Ended

Mar. 31, 2018

Commitments and Contingencies Disclosure [Abstract]

Schedule of Future Minimum Annual Commitments

Future Minimum Annual Commitments at March 31, 2018 (in thousands):



Year ending December 31,	Operating Lease Minimum Rental Payments		Minimum Purchase Commitments
2018	$	53,739	$	18,292
2019	64,746		22,829
2020	52,868		17,951
2021	36,031		9,459
2022	30,301		6,851
Thereafter	55,739		4,565
Total future lease and purchase commitments	$	293,424	$	79,947

Pension and Post-Retirement Benefits (Tables)

3 Months Ended

Mar. 31, 2018

Retirement Benefits [Abstract]

Schedule of Net Pension and Post-retirement Benefit Costs

Net post-retirement benefit cost (in thousands) consisted of the following for the three months ended March 31, 2018 and 2017:



	Three Months Ended March 31,
	2018		2017
Service cost	$	27	$	32
Interest cost	188		192
Net amortization and deferral	—		54
Net post-retirement benefit costs	$	215	$	278

Net pension benefit cost (in thousands) consisted of the following for the three months ended March 31, 2018 and 2017:



	Three Months Ended March 31,
	2018			2017
Service cost	$	279		$	295
Interest cost	978			883
Expected return on plan assets	(1,243		)	(1,331		)
Net amortization and deferral	631			693
Net pension benefit costs	$	645		$	540

Revenue (Tables)

3 Months Ended

Mar. 31, 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 months ended March 31, 2018 (in thousands):



Category	Oil & Gas Proppants		Industrial & Specialty Products		Total Sales
Product	$	238,422	$	56,366	$	294,788
Service	74,508		17		74,525
Total Sales	312,930		56,383		369,313

Schedule of Changes in Contract Assets and Liabilities



	Unbilled Receivables
December 31, 2017	$	5,245
Reclassifications to billed receivables	(5,245		)
Revenues recognized in excess of period billings	2,939
March 31, 2018	$	2,939



	Deferred Revenue
December 31, 2017	$	118,414
Revenues recognized from balances held at the beginning of the period	(6,969		)
Revenues deferred from period collections on unfulfilled performance obligations	10,530
March 31, 2018	$	121,975

Segment Reporting (Tables)

3 Months Ended

Mar. 31, 2018

Segment Reporting [Abstract]

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



	Three Months Ended March 31,
	2018			2017
Sales:
Oil & Gas Proppants	$	312,930		$	192,959
Industrial & Specialty Products	56,383			51,838
Total sales	369,313			244,797
Segment contribution margin:
Oil & Gas Proppants	99,433			38,842
Industrial & Specialty Products	20,530			20,215
Total segment contribution margin	119,963			59,057
Operating activities excluded from segment cost of sales	(11,560		)	(1,735		)
Selling, general and administrative	(34,591		)	(22,341		)
Depreciation, depletion and amortization	(28,592		)	(21,599		)
Interest expense	(7,070		)	(7,646		)
Other income (expense), net, including interest income	665			(4,928		)
Income tax (expense) benefit	(7,521		)	1,714
Net income	$	31,294		$	2,522

Summary of Significant Accounting Policies (Details) - USD ($) $ in Thousands			3 Months Ended
	Jan. 01, 2018	Dec. 31, 2017	Mar. 31, 2018	Mar. 31, 2017
Reconciliation of Effects of Reclassification
Product cost of sales	$ 162,350		$ 207,239	$ 162,183
Total cost of sales	187,188		260,910	187,475
Selling, general and administrative expenses	22,139		34,591	22,341
Operating income	13,871		45,220	13,382
Other income (expense)	(5,417)		$ 665	$ (4,928)
As Previously Reported
Reconciliation of Effects of Reclassification
Product cost of sales		$ 162,637
Total cost of sales		187,475
Selling, general and administrative expenses		22,341
Operating income		13,382
Other income (expense)		$ (4,928)
Adjustments \| Accounting Standards Update 2017-07
Reconciliation of Effects of Reclassification
Product cost of sales	(287)
Total cost of sales	(287)
Selling, general and administrative expenses	(202)
Operating income	489
Other income (expense)	$ (489)
Supply Agreement \| Minimum
New Accounting Pronouncement, Early Adoption [Line Items]
Deferred revenue, average initial contract term			1 year
Supply Agreement \| Maximum
New Accounting Pronouncement, Early Adoption [Line Items]
Deferred revenue, average initial contract term			5 years

Earnings Per Share - Computation of Basic and Diluted Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Numerator:
Net income	$ 31,294	$ 2,522
Denominator:
Weighted average shares outstanding (shares)	79,496	80,983
Diluted effect of stock awards (shares)	813	1,261
Weighted average shares outstanding assuming dilution (shares)	80,309	82,244
Basic earnings per share (in dollars per share)	$ 0.39	$ 0.03
Diluted earnings per share (in dollars per share)	$ 0.39	$ 0.03

Earnings Per Share - Antidilutive Securities Excluded From Calculation of Diluted Earnings Per Share (Details) - shares shares in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Stock Options
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Weighted-average outstanding stock options excluded (shares)	428	195
Restricted Stock and Restricted Stock Units
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Weighted-average outstanding stock options excluded (shares)	337	0

Capital Structure and Accumulated Other Comprehensive Income (Loss) - Additional Information (Details) - USD ($)	3 Months Ended	4 Months Ended
	Mar. 31, 2018	Mar. 31, 2018	Dec. 31, 2017	Dec. 11, 2017
Capital Structure And Accumulated Comprehensive Income (Loss)
Common stock authorized (shares)	500,000,000	500,000,000	500,000,000
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01	$ 0.01
Common stock issued (shares)	81,518,347	81,518,347	81,267,205
Common stock outstanding (shares)	77,867,261	77,867,261	80,524,255
Preferred stock authorized (shares)	10,000,000	10,000,000	10,000,000
Preferred stock, par value (in dollars per share)	$ 0.01	$ 0.01	$ 0.01
Preferred stock issued (shares)	0	0	0
Preferred stock outstanding (shares)	0	0	0
Repurchase of common stock (shares)		3,555,104
Average price per common share of repurchase common stock (in dollars per share)		$ 28.13
December 2018 Share Repurchase Program
Capital Structure And Accumulated Comprehensive Income (Loss)
Share repurchase program authorized amount	$ 100,000,000	$ 100,000,000
Repurchase of common stock (shares)	2,828,023
Average price per common share of repurchase common stock (in dollars per share)	$ 26.52
December 2017 Share Repurchase Program
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) - Declared Quarterly Cash Dividends (Details) - $ / shares	Apr. 05, 2018	Mar. 15, 2018	Feb. 16, 2018
Dividends Payable [Line Items]
Dividends per Common Share (in dollars per share)			$ 0.0625
Declaration Date			Feb. 16, 2018
Record Date		Mar. 15, 2018
Subsequent Event
Dividends Payable [Line Items]
Payable Date	Apr. 05, 2018

Capital Structure and Accumulated Other Comprehensive Income (Loss) - Changes in Accumulated Other Comprehensive Income (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2018 USD ($)
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning Balance	$ 1,396,506
Other comprehensive gain (loss) before reclassifications	1,803
Amounts reclassed from accumulated other comprehensive income	491
Ending Balance	1,352,983
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 income	2
Ending Balance	(74)
Foreign currency translation adjustments
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning Balance	(6)
Other comprehensive gain (loss) before reclassifications	(3)
Amounts reclassed from accumulated other comprehensive income	0
Ending Balance	(9)
Pension and other post-retirement benefits liability
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning Balance	(13,844)
Other comprehensive gain (loss) before reclassifications	1,806
Amounts reclassed from accumulated other comprehensive income	489
Ending Balance	(11,549)
Total
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning Balance	(13,926)
Ending Balance	$ (11,632)

Business Combinations - Additional Information (Details) - USD ($) $ in Thousands			3 Months Ended			7 Months Ended	8 Months Ended	12 Months Ended
	Aug. 16, 2017	Apr. 01, 2017	Jun. 30, 2018	Mar. 31, 2018	Mar. 31, 2017	Mar. 31, 2018	Aug. 16, 2017	Dec. 31, 2017
Business Acquisition [Line Items]
Goodwill				$ 274,879		$ 274,879		$ 272,079
Total cash consideration for pre-existing contracted asset sale				$ 72,327	$ 19,896
MS Sand
Business Acquisition [Line Items]
Total cash consideration for pre-existing contracted asset sale							$ 101,000
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
Acquisition-related costs								200
MS Sand
Business Acquisition [Line Items]
Goodwill								25,322
Identifiable intangible assets								$ 1,840
Consideration paid, net of cash acquired	$ 95,400
Cash acquired	2,200
Net working capital adjustment	(500)
Additional consideration paid	$ 6,100
MS Sand \| Selling, General and Administrative Expenses
Business Acquisition [Line Items]
Acquisition-related costs						$ 900
Scenario, Forecast \| EP Minerals
Business Acquisition [Line Items]
Consideration payable			$ 750,000

Business Combinations - Purchase Price Allocation (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Business Acquisition [Line Items]
Goodwill	$ 274,879	$ 272,079
MS Sand
Business Acquisition [Line Items]
Accounts receivable		11,201
Inventories		8,067
Other current assets		362
Assets held for sale		9,453
Property, plant and mine development		27,458
Mineral rights		23,500
Other non-current assets		1,136
Goodwill		25,322
Customer relationships		1,840
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		11,201
Inventories		8,067
Other current assets		362
Assets held for sale		9,453
Property, plant and mine development		27,458
Mineral rights		26,300
Other non-current assets		1,136
Goodwill		22,522
Customer relationships		1,840
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		0
Inventories		0
Other current assets		0
Assets held for sale		0
Property, plant and mine development		0
Mineral rights		(2,800)
Other non-current assets		0
Goodwill		2,800
Customer relationships		0
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) - MS Sand - Customer relationships $ in Thousands	Aug. 16, 2017 USD ($)
Business Acquisition [Line Items]
Definite lived intangible assets - approximate fair value	$ 1,840
Finite-lived intangible asset, useful life (in years)	15 years

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

Accounts Receivable (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Receivables [Abstract]
Trade receivables	$ 247,178	$ 217,649
Less: Allowance for doubtful accounts	(7,250)	(7,100)
Net trade receivables	239,928	210,549
Other receivables	11,347	2,037
Total accounts receivable	$ 251,275	$ 212,586

Accounts Receivable - Allowance for Doubtful Accounts (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Allowance for Doubtful Accounts Receivable
Beginning balance	$ 7,100
Bad debt provision	237	$ 783
Write-offs	(87)
Ending balance	$ 7,250

Accounts Receivable - Additional Information (Details) - Product Concentration Risk	3 Months Ended		12 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Sales \| Ten Largest Customers
Concentration Risk [Line Items]
Concentration risk percentage	52.00%	55.00%
Sales \| Customer One
Concentration Risk [Line Items]
Concentration risk percentage	15.00%	14.00%
Sales \| Customer Two
Concentration Risk [Line Items]
Concentration risk percentage		11.00%
Accounts Receivable, Net \| Customer One
Concentration Risk [Line Items]
Concentration risk percentage	17.00%		19.00%
Accounts Receivable, Net \| Customer Two
Concentration Risk [Line Items]
Concentration risk percentage			11.00%

Inventories (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Inventory Disclosure [Abstract]
Supplies	$ 22,338	$ 21,277
Raw materials and work in process	24,175	28,034
Finished goods	30,066	43,065
Total inventories	$ 76,579	$ 92,376

Property, Plant and Mine Development (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Property, Plant and Equipment
Property, plant and mine development, gross	$ 1,564,877	$ 1,522,675
Accumulated depletion, depreciation and amortization	(369,155)	(353,520)
Total property, plant and mine development, net	1,195,722	1,169,155
Mining property and mine development
Property, Plant and Equipment
Property, plant and mine development, gross	584,778	586,242
Asset retirement cost
Property, Plant and Equipment
Property, plant and mine development, gross	12,166	14,184
Land
Property, Plant and Equipment
Property, plant and mine development, gross	36,552	36,552
Land improvements
Property, Plant and Equipment
Property, plant and mine development, gross	50,793	45,878
Buildings
Property, Plant and Equipment
Property, plant and mine development, gross	55,280	56,330
Machinery and equipment
Property, Plant and Equipment
Property, plant and mine development, gross	634,807	590,566
Furniture and fixtures
Property, Plant and Equipment
Property, plant and mine development, gross	2,862	2,953
Construction-in-progress
Property, Plant and Equipment
Property, plant and mine development, gross	$ 187,639	$ 189,970

Property, Plant and Mine Development - Additional Information (Details)		3 Months Ended
	Mar. 21, 2018 USD ($) transload	Mar. 31, 2018 USD ($)	Mar. 31, 2017 USD ($)	Dec. 31, 2017 USD ($)
Property, Plant and Equipment
Aggregate cost of machinery and equipment under capital lease		$ 1,564,877,000		$ 1,522,675,000
Accumulated depreciation of machinery and equipment under capital lease		369,155,000		$ 353,520,000
Interest cost capitalized in property, plant and mine development		1,800,000	$ 1,000
Gain on sale of transload facilities		5,799,000	$ (59,000)
Consideration received allocated to asset retirement obligations liabilities of transload facilities		2,116,000
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
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
Accrued contract termination costs for facilities operated by third parties on sale of transload facilities	5,900,000
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
Accrued contract termination costs for facilities operated by third parties on sale of transload facilities	2,000,000
Assets Held under Capital Leases
Property, Plant and Equipment
Aggregate cost of machinery and equipment under capital lease		900,000
Accumulated depreciation of machinery and equipment under capital lease		$ 200,000
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

Goodwill and Intangible Assets - Changes in Carrying Amount of Goodwill (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2018 USD ($)
Goodwill [Roll Forward]
Balance at December 31, 2017	$ 272,079
Balance at March 31, 2018	274,879
MS Sand acquisition
Goodwill [Roll Forward]
Balance at December 31, 2017	25,322
MS Sand acquisition measurement period adjustment	$ 2,800

Goodwill and Intangible Assets - Changes in the Carrying Amount of Intangible Assets (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Dec. 31, 2017
Finite-Lived Intangible Assets
Gross Carrying Amount	$ 132,942	$ 131,932
Accumulated Amortization	(17,308)	(14,993)
Net	115,634	116,939
Total Intangible Assets
Gross Carrying Amount	166,010	165,000
Accumulated Amortization	(17,308)	(14,993)
Intangible assets, net	148,702	150,007
Trade name
Indefinite-lived Intangible Assets
Gross Carrying Amount	$ 33,068	33,068
Technology and intellectual property
Finite-Lived Intangible Assets
Estimated Useful Life	15 years
Gross Carrying Amount	$ 71,713	70,703
Accumulated Amortization	(7,127)	(5,917)
Net	64,586	64,786
Total Intangible Assets
Accumulated Amortization	(7,127)	(5,917)
Customer relationships
Finite-Lived Intangible Assets
Gross Carrying Amount	61,229	61,229
Accumulated Amortization	(10,181)	(9,076)
Net	51,048	52,153
Total Intangible Assets
Accumulated Amortization	$ (10,181)	$ (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
	Mar. 31, 2018	Mar. 31, 2017
Goodwill and Intangible Assets Disclosure [Abstract]
Amortization expense	$ 2.3	$ 2.0

Goodwill and Intangible Assets - Estimated Amortization Expense Related to Definite-Lived Intangible Assets (Details) $ in Thousands	Mar. 31, 2018 USD ($)
Goodwill and Intangible Assets Disclosure [Abstract]
2018	$ 6,980
2019	9,306
2020	9,306
2021	9,306
2022	$ 9,291

Debt (Details) - USD ($) $ in Thousands	3 Months Ended
Debt (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Line of Credit Facility
Long-term debt	$ 510,912	$ 511,236
Less: Unamortized original issue discount	(850)	(944)
Less: Unamortized debt issuance cost	(2,755)	(3,099)
Less: current portion	(4,305)	(4,504)
Total long-term portion of debt	506,607	506,732
Notes Payable, Other Payables \| Note payable secured by royalty interest
Line of Credit Facility
Long-term debt	25,635	24,740
Notes Payable, Other Payables \| Customer note payable
Line of Credit Facility
Long-term debt	566	745
Notes Payable, Other Payables \| Equipment notes payable
Line of Credit Facility
Long-term debt	516	719
Revolving Line-of-Credit \| Revolver
Line of Credit Facility
Long-term debt	$ 0	$ 0
Credit facility, maturity date	Jul. 23, 2018
Credit facility, interest rate	6.25%	5.75%
Secured Debt \| Term Loan Facility
Line of Credit Facility
Long-term debt	$ 487,800	$ 489,075
Credit facility, maturity date	Jul. 23, 2020
Secured Debt \| Term Loan Facility \| Minimum
Line of Credit Facility
Credit facility, interest rate	4.94%	4.75%
Secured Debt \| Term Loan Facility \| Maximum
Line of Credit Facility
Credit facility, interest rate	5.44%	5.25%

Debt - Additional Information (Details)		3 Months Ended
Debt - Additional Information (Details)	Aug. 16, 2016 USD ($)	Mar. 31, 2018 USD ($)
Notes Payable, Other Payables \| Note payable secured by royalty interest
Debt Instrument [Line Items]
Annual minimum payments		$ 500,000
Debt instrument, fair value	$ 22,500,000	$ 25,600,000
Fair value discount rate	14.00%
Interest rate, effective percentage		22.00%
Revolving Line-of-Credit \| Revolver
Debt Instrument [Line Items]
Available borrowing base		$ 50,000,000
Amount drawn from borrowing base		0
Amount available for general corporate use under this revolving credit agreement		$ 45,500,000
Secured Debt \| Term Loan Facility
Debt Instrument [Line Items]
Line of credit facility, covenant terms, minimum incurrence ratio		3
Credit facility consolidated total net leverage ratio		0.0375
Net leverage ratio, credit facility threshold percentage		25.00%
Letter of Credit \| Revolver
Debt Instrument [Line Items]
Amount allocated for letters of credit		$ 4,500,000

Debt - Contractual Maturities of Senior Secured Credit Facility (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Debt Instrument [Line Items]
Total	$ 510,912	$ 511,236
Secured Debt \| Term Loan Facility
Debt Instrument [Line Items]
2018	3,825
2019	5,100
2020	478,875
Total	$ 487,800	$ 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	Mar. 31, 2018 USD ($)
Debt Instrument [Line Items]
2018	$ 1,313
2019	1,750
2020	1,750
2021	1,750
2022	$ 1,750

Deferred Revenue (Details) - USD ($) $ in Thousands	3 Months Ended
Deferred Revenue (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Deferred Revenue Arrangement [Line Items]
Deferred revenue, advances received	$ 10,500
Deferred revenue	122,000	$ 118,400
Current portion of deferred revenue	$ 52,305	$ 36,128
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

- Definition

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

+ References + Details

Asset Retirement Obligations (Details) $ in Thousands	3 Months Ended
Asset Retirement Obligations (Details) $ in Thousands	Mar. 31, 2018 USD ($)
Asset Retirement Obligation Disclosure [Abstract]
Other long-term liabilities related to asset retirement obligation	$ 16,756
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Beginning balance	19,032
Accretion	326
Additions and revisions of prior estimates	(486)
Disposal related to sale of transloads	$ (2,116)

Fair Value Accounting (Details) $ in Thousands	Dec. 31, 2017 USD ($)
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

Derivative Instruments - Estimated Fair Values of Derivative Instruments (Details) - USD ($)	Mar. 31, 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
Fair Value, Measurements, Recurring \| Level 2 \| Interest rate cap agreement
Derivative Instruments, Gain (Loss)
Fair Value	$ 0	$ 0

Derivative Instruments - Additional Information (Details) - USD ($)	3 Months Ended
	Mar. 31, 2018	Mar. 31, 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	3 Months Ended
	Mar. 31, 2018	Mar. 31, 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	(36)
Gain reclassified from Accumulated OCI	2	0
Deferred losses from derivatives in OCI, end of period	$ (74)	$ (68)

Equity-Based Compensation - Additional Information (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock options granted (in shares)	0	0
Stock options exercised (in shares)	0	24,852
Intrinsic value of stock options exercised		$ 900
Proceeds from options exercised	$ 0	517
Actual tax benefit realized for the tax deductions from option exercises		300
Stock Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Recognized equity-based compensation	500	600
Unrecognized compensation expense related to stock options	$ 700
Recognized weighted-average period	6 months
Restricted Stock and Restricted Stock Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Recognized equity-based compensation	$ 1,800	$ 1,500
Recognized weighted-average period	1 year 7 months
Awards share units granted (in shares)	3,852	1,500
Total unrecognized compensation expense	$ 7,200
Performance Share Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Recognized equity-based compensation	$ 4,300	$ 3,400
Recognized weighted-average period	1 year
Awards share units granted (in shares)	0	0
Total unrecognized compensation expense	$ 13,900
2011 Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock that may be issued (in shares)	4,481,559

Equity-Based Compensation - Stock Options Activity (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Number of Shares
Outstanding at beginning of period (in shares)	908,919
Granted (in shares)	0	0
Exercised (in shares)	0	(24,852)
Forfeited (in shares)	(918)
Outstanding at period end (in shares)	908,001		908,919
Exercisable at period end (in shares)	791,868
Weighted Average Exercise Price
Outstanding at beginning of period, weighted average exercise price (in dollars per share)	$ 28.46
Granted, weighted average exercise price (in dollars per share)	0.00
Exercised, weighted average exercise price (in dollars per share)	0.00
Forfeited, weighted average exercise price (in dollars per share)	31.30
Outstanding at period end, weighted average exercise price (in dollars per share)	28.46		$ 28.46
Exercisable at period end, weighted average exercise price (in dollars per share)	$ 27.02
Aggregate Intrinsic Value (in thousands)
Intrinsic value options outstanding	$ 3,679		$ 7,008
Intrinsic value options exercisable	$ 3,679
Weighted Average Remaining Contractual Term in Years
Outstanding at period end, weighted average remaining contractual term in years	5 years 6 months		6 years 1 month
Exercisable at period end, weighted average remaining contractual term in years	5 years 3 months

Equity-Based Compensation - Restricted Stock and Restricted Stock Units Activity (Details) - Restricted Stock and Restricted Stock Units - $ / shares	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Number of Shares
Unvested at beginning of period (in shares)	461,346
Granted (in shares)	3,852	1,500
Vested (in shares)	(132,081)
Forfeited (in shares)	(10,309)
Unvested at period end (in shares)	322,808
Grant Date Weighted Average Fair Value
Unvested at beginning of period (in dollars per share)	$ 30.76
Granted (in dollars per share)	30.11
Vested (in dollars per share)	24.56
Forfeited (in dollars per share)	35.65
Unvested at period end (in dollars per share)	$ 33.14

Equity-Based Compensation - Performance Share Unit Activity (Details) - Performance Share Units - $ / shares	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Number of Shares
Unvested at beginning of period (in shares)	881,416
Granted (in shares)	0	0
Vested (in shares)	(225,000)
Forfeited (in shares)	(5,972)
Unvested at period end (in shares)	650,444
Weighted Average
Unvested at beginning of period (in dollars per share)	$ 42.16
Granted (in dollars per share)	0.00
Vested (in dollars per share)	41.99
Forfeited (in dollars per share)	58.71
Unvested at period end (in dollars per share)	$ 42.07

Commitments and Contingencies - Future Minimum Annual Commitments (Details) $ in Thousands	Mar. 31, 2018 USD ($)
Operating Lease Minimum Rental Payments
2018	$ 53,739
2019	64,746
2020	52,868
2021	36,031
2022	30,301
Thereafter	55,739
Total future lease commitments	293,424
Minimum Purchase Commitments
2018	18,292
2019	22,829
2020	17,951
2021	9,459
2022	6,851
Thereafter	4,565
Total future purchase commitments	$ 79,947

Commitments and Contingencies (Details)		3 Months Ended
Commitments and Contingencies (Details)	May 17, 2017 USD ($)	Mar. 31, 2018 USD ($) claim	Mar. 31, 2017 USD ($)	Dec. 31, 2017 USD ($)
Loss Contingencies
Expenses related to operating leases and rental agreements		$ 22,800,000	$ 15,400,000
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
Other long-term obligations
Loss Contingencies
Third party products claims liability under insurance in other long-term obligations		$ 1,000,000		$ 1,000,000
Pending Litigation
Loss Contingencies
New claims filed \| claim		1
Number of pending claims \| claim		60

Pension and Post-Retirement Benefits - Net Pension and Post-Retirement Benefit Costs (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Pension Benefits
Defined Benefit Plan Disclosure
Service cost	$ 279	$ 295
Interest cost	978	883
Expected return on plan assets	(1,243)	(1,331)
Net amortization and deferral	631	693
Net pension benefit costs	645	540
Post-retirement Benefits
Defined Benefit Plan Disclosure
Service cost	27	32
Interest cost	188	192
Net amortization and deferral	0	54
Net pension benefit costs	$ 215	$ 278

Pension and Post-Retirement Benefits - Additional Information (Details)	3 Months Ended
	Mar. 31, 2018 USD ($) plan	Mar. 31, 2017 USD ($)
Defined Benefit Plan Disclosure
Number of multiemployer plans \| plan	3
Multiemployer plan, percentage of fund's total contributions	5.00%
Pension Benefits
Defined Benefit Plan Disclosure
Contributions to plan by employer	$ 300,000	$ 0
Expected contributions in current fiscal year	2,500,000
Post-retirement Benefits
Defined Benefit Plan Disclosure
Expected contributions in current fiscal year	$ 1,400,000

Obligations Under Guarantees (Details) - Travelers Casualty and Surety Company $ in Millions	Mar. 31, 2018 USD ($)
Surety Bonds
Loss Contingencies
Surety bonds outstanding	$ 12.2
Reclamation Bonds
Loss Contingencies
Bonds related to reclamation requirements	$ 10.3

Income Taxes (Details) - USD ($) $ in Millions	3 Months Ended		12 Months Ended
Income Taxes (Details) - USD ($) $ in Millions	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Operating Loss Carryforwards [Line Items]
Provisional income tax expense, decrease in deferred tax assets due to change in tax rate			$ 45.0
Provisional income tax benefit, decrease in deferred tax liability due to change in tax rate			80.8
Provisional income tax benefit, net, decrease in tax assets and liabilities due to change in tax rate			$ 35.8
Effective income tax rate	19.00%	(212.00%)
Effective income tax rate without discrete tax benefit	18.00%	(26.00%)
Accounting Standards Update 2016-09
Operating Loss Carryforwards [Line Items]
Recorded tax expense (benefit) related to excess tax benefits on equity compensation	$ 0.5	$ (1.5)

Revenue - Sales by Major Source (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Disaggregation of Revenue [Line Items]
Product	$ 294,788	$ 203,251
Service	74,525	41,546
Total sales	369,313	$ 244,797
Oil & Gas Proppants
Disaggregation of Revenue [Line Items]
Product	238,422
Service	74,508
Total sales	312,930
Industrial & Specialty Products
Disaggregation of Revenue [Line Items]
Product	56,366
Service	17
Total sales	$ 56,383

Revenue - Changes in Contract Assets and Liabilities (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2018 USD ($)
Unbilled Receivables
December 31, 2017	$ 5,245
Reclassifications to billed receivables	(5,245)
Revenues recognized in excess of period billings	2,939
March 31, 2018	2,939
Deferred Revenue
December 31, 2017	118,414
Revenues recognized from balances held at the beginning of the period	(6,969)
Revenues deferred from period collections on unfulfilled performance obligations	10,530
March 31, 2018	$ 121,975

Revenue - Additional Information (Details)	3 Months Ended
Revenue - Additional Information (Details)	Mar. 31, 2018
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2018-04-01
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
	Mar. 31, 2018	Mar. 31, 2017
Related Party Transaction [Line Items]
Related party purchases	$ 672	$ 858
Officer \| Transportation Brokerage And Logistics Services Vendor
Related Party Transaction [Line Items]
Related party purchases	$ 900	$ 600

Segment Reporting (Details) $ in Thousands	3 Months Ended
Segment Reporting (Details) $ in Thousands	Mar. 31, 2018 USD ($) Segment Product	Dec. 31, 2017 USD ($)
Segment Reporting Information
Number of reportable segments \| Segment	2
Number of products in Industrial & Specialty segment \| Product	200
Goodwill	$ 274,879	$ 272,079
Operating Segments \| Oil & Gas Proppants
Segment Reporting Information
Goodwill	250,300	247,500
Operating Segments \| Industrial & Specialty Products
Segment Reporting Information
Goodwill	$ 24,600	$ 24,600

Segment Reporting - Sales and Segment Contribution Margin for Reporting Segments and Other Operating Results (Detail) - USD ($) $ in Thousands		3 Months Ended
	Jan. 01, 2018	Mar. 31, 2018	Mar. 31, 2017
Segment Reporting Information
Total sales		$ 369,313	$ 244,797
Selling, general and administrative	$ (22,139)	(34,591)	(22,341)
Depreciation, depletion and amortization		(28,592)	(21,599)
Interest expense		(7,070)	(7,646)
Other income (expense), net, including interest income	$ (5,417)	665	(4,928)
Income tax (expense) benefit		(7,521)	1,714
Net income		31,294	2,522
Operating Segments
Segment Reporting Information
Total sales		369,313	244,797
Total segment contribution margin		119,963	59,057
Segment Reconciling Items
Segment Reporting Information
Operating activities excluded from segment cost of sales		(11,560)	(1,735)
Selling, general and administrative		(34,591)	(22,341)
Depreciation, depletion and amortization		(28,592)	(21,599)
Interest expense		(7,070)	(7,646)
Other income (expense), net, including interest income		665	(4,928)
Oil & Gas Proppants
Segment Reporting Information
Total sales		312,930
Oil & Gas Proppants \| Operating Segments
Segment Reporting Information
Total sales		312,930	192,959
Total segment contribution margin		99,433	38,842
Industrial & Specialty Products
Segment Reporting Information
Total sales		56,383
Industrial & Specialty Products \| Operating Segments
Segment Reporting Information
Total sales		56,383	51,838
Total segment contribution margin		$ 20,530	$ 20,215

Subsequent Events (Details)	Apr. 05, 2018 $ / shares
Subsequent Event
Subsequent Event
Cash dividends paid (in dollars per share)	$ 0.0625

Condensed Consolidated Statements of Stockholders' Equity (Parenthetical)	3 Months Ended
	Mar. 31, 2018 $ / shares
Cash dividend declared (in dollars per share)	$ 0.06
Retained Earnings
Cash dividend declared (in dollars per share)	$ 0.0625