U.S. Silica (SLCA) 10-Q 1 May 19 2019 Q1 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	3 Months Ended
	Mar. 31, 2019	Apr. 26, 2019
Document And Entity Information [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Mar. 31, 2019
Document Fiscal Year Focus	2019
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 Emerging Growth Company	false
Entity Small Business	false
Entity Common Stock, Shares Outstanding		73,553,442

CONDENSED CONSOLIDATED BALANCE

CONDENSED CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Current Assets:
Cash and cash equivalents	$ 161,615	$ 202,498
Accounts receivable, net	258,348	215,486
Inventories, net	143,149	162,087
Prepaid expenses and other current assets	14,572	17,966
Income tax deposits	1,388	2,200
Total current assets	579,072	600,237
Property, plant and mine development, net	1,820,102	1,826,303
Operating lease right-of-use assets	209,699	0
Goodwill	273,524	261,340
Intangible assets, net	190,584	194,626
Other assets	16,459	18,334
Total assets	3,089,440	2,900,840
Current Liabilities:
Accounts payable and accrued expenses	223,611	216,400
Current portion of operating lease liabilities	61,583	0
Current portion of long-term debt	13,112	13,327
Current portion of deferred revenue	28,838	31,612
Total current liabilities	327,144	261,339
Long-term debt, net	1,245,242	1,246,428
Deferred revenue	86,930	81,707
Liability for pension and other post-retirement benefits	56,879	57,194
Deferred income taxes, net	131,053	137,239
Operating lease liabilities	149,040	0
Other long-term obligations	59,054	64,629
Total liabilities	2,055,342	1,848,536
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, 2019 and December 31, 2018	0	0
Common stock, $0.01 par value, 500,000,000 shares authorized; 82,455,734 issued and 73,524,817 outstanding at March 31, 2019; 81,811,977 issued and 73,148,853 outstanding at December 31, 2018	820	818
Additional paid-in capital	1,173,259	1,169,383
Retained earnings	43,920	67,854
Treasury stock, at cost, 8,930,917 and 8,663,124 shares at March 31, 2019 and December 31, 2018, respectively	(180,125)	(178,215)
Accumulated other comprehensive loss	(15,985)	(15,020)
Total U.S. Silica Holdings, Inc. stockholders’ equity	1,021,889	1,044,820
Non-controlling interest	12,209	7,484
Total stockholders' equity	1,034,098	1,052,304
Total liabilities and stockholders’ equity	$ 3,089,440	$ 2,900,840

CONDENSED CONSOLIDATED BALANC_2

CONDENSED CONSOLIDATED BALANCE SHEETS (Parenthetical) - $ / shares	Mar. 31, 2019	Dec. 31, 2018
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)	82,455,734	81,811,977
Common stock outstanding (shares)	73,524,817	73,148,853
Treasury stock, at cost (shares)	8,930,917	8,663,124

CONDENSED CONSOLIDATED STATEMEN

CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Sales:
Total sales	$ 378,750	$ 369,313
Cost of sales (excluding depreciation, depletion and amortization):
Product	234,916	207,239
Service	62,622	53,671
Total cost of sales (excluding depreciation, depletion and amortization)	297,538	260,910
Operating expenses:
Selling, general and administrative	34,656	34,591
Depreciation, depletion and amortization	44,600	28,592
Total operating expenses	79,256	63,183
Operating income	1,956	45,220
Other (expense) income:
Interest expense	(23,978)	(7,070)
Other income, net, including interest income	722	665
Total other expense	(23,256)	(6,405)
(Loss) income before income taxes	(21,300)	38,815
Income tax benefit (expense)	1,972	(7,521)
Net (loss) income	(19,328)	31,294
Less: Net income (loss) attributable to non-controlling interest	(4)	0
Net (loss) income attributable to U.S. Silica Holdings, Inc.	$ (19,324)	$ 31,294
Earnings (loss) per share attributable to U.S. Silica Holdings, Inc.:
Basic (in dollars per share)	$ (0.26)	$ 0.39
Diluted (in dollars per share)	$ (0.26)	$ 0.39
Weighted average shares outstanding:
Basic (shares)	73,040	79,496
Diluted (shares)	73,040	80,309
Dividends declared per share (in dollars per share)	$ 0.0625	$ 0.0625
Product
Sales:
Total sales	$ 296,860	$ 294,788
Service
Sales:
Total sales	$ 81,890	$ 74,525

CONDENSED CONSOLIDATED STATMENT

CONDENSED CONSOLIDATED STATMENTS OF COMPREHENSIVE INCOME (LOSS) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Statement of Comprehensive Income [Abstract]
Net (loss) income	$ (19,328)	$ 31,294
Other comprehensive (loss) income:
Unrealized loss on derivatives (net of tax of $(299) and $1 for the three months ended March 31, 2019 and 2018, respectively)	(940)	(2)
Foreign currency translation adjustment (net of tax of $(60) and $1 for the three months ended March 31, 2019 and 2018, respectively)	(199)	3
Pension and other post-retirement benefits liability adjustment (net of tax of $55 and $730 for the three months ended March 31, 2019 and 2018, respectively)	174	2,293
Comprehensive (loss) income	(20,293)	33,588
Less: Comprehensive (loss) income attributable to non-controlling interest	(4)	0
Comprehensive (loss) income attributable to U.S. Silica Holdings, Inc.	$ (20,289)	$ 33,588

CONDENSED CONSOLIDATED STATME_2

CONDENSED CONSOLIDATED STATMENTS OF COMPREHENSIVE INCOME (LOSS) (Parenthetical) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Statement of Comprehensive Income [Abstract]
Tax expense (benefit) on unrealized gain (loss) on derivatives	$ (299)	$ 1
Tax expense (benefit) on foreign currency translation adjustment	(60)	1
Tax (expense) benefit on pension and other post-retirement benefits liability adjustment	$ 55	$ 730

CONDENSED CONSOLIDATED STATEM_2

CONDENSED CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY - USD ($) $ in Thousands	Total	Total U.S. Silica Holdings Inc., Stockholders’ Equity	Common Stock	Treasury Stock	Additional Paid-In Capital	Retained Earnings	Accumulated Other Comprehensive Loss	Non-controlling Interest
Beginning Balance at Dec. 31, 2017	$ 1,396,506	$ 1,396,506	$ 812	$ (25,456)	$ 1,147,084	$ 287,992	$ (13,926)	$ 0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net (loss) income	31,294	31,294				31,294		0
Unrealized loss on derivatives	(2)	(2)					(2)
Foreign currency translation adjustment	3	3					3
Pension and post-retirement liability	2,293	2,293					2,293
Cash dividend declared ($0.0625 per share)	(4,881)	(4,881)				(4,881)
Common stock-based compensation plans activity:
Equity-based compensation	6,254	6,254			6,254
Tax payments related to shares withheld for vested restricted stock and stock units	(3,484)	(3,484)	2	(3,484)	(2)
Repurchase of common stock	(75,000)	(75,000)		(75,000)
Ending Balance at Mar. 31, 2018	1,352,983	1,352,983	814	(103,940)	1,153,336	314,405	(11,632)	0
Beginning Balance at Dec. 31, 2018	1,052,304	1,044,820	818	(178,215)	1,169,383	67,854	(15,020)	7,484
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net (loss) income	(19,328)	(19,324)				(19,324)		(4)
Unrealized loss on derivatives	(940)	(940)					(940)
Foreign currency translation adjustment	(199)	(199)					(199)
Pension and post-retirement liability	174	174					174
Cash dividend declared ($0.0625 per share)	(4,610)	(4,610)				(4,610)
Contributions from non-controlling interest	4,729							4,729
Common stock-based compensation plans activity:
Equity-based compensation	4,045	4,045			4,045
Proceeds from options exercised	128	128		295	(167)
Tax payments related to shares withheld for vested restricted stock and stock units	(2,205)	(2,205)	2	(2,205)	(2)
Ending Balance at Mar. 31, 2019	$ 1,034,098	$ 1,021,889	$ 820	$ (180,125)	$ 1,173,259	$ 43,920	$ (15,985)	$ 12,209

CONDENSED CONSOLIDATED STATEM_3

CONDENSED CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY (Parenthetical) - $ / shares	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Statement of Stockholders' Equity [Abstract]
Cash dividend declared (in dollars per share)	$ 0.0625	$ 0.0625

CONDENSED CONSOLIDATED STATEM_4

CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Operating activities:
Net (loss) income	$ (19,328)	$ 31,294
Adjustments to reconcile net (loss) income to net cash provided by operating activities:
Depreciation, depletion and amortization	44,600	28,592
Debt issuance amortization	1,322	345
Original issue discount amortization	265	93
Deferred income taxes	(2,553)	7,786
Deferred revenue	(7,576)	3,562
(Gain) loss on disposal of property, plant and equipment	113	(5,799)
Equity-based compensation	4,045	6,254
Bad debt provision, net of recoveries	721	237
Other	(3,872)	(871)
Changes in operating assets and liabilities, net of effects of acquisitions:
Accounts receivable	(43,583)	(39,077)
Inventories	18,938	15,797
Prepaid expenses and other current assets	3,151	694
Income taxes	812	(961)
Accounts payable and accrued expenses	12,970	(27,930)
Short-term and long-term obligations-vendor incentives	0	57,986
Liability for pension and other post-retirement benefits	924	212
Other noncurrent assets and liabilities	(48)	(605)
Net cash provided by operating activities	10,901	77,609
Investing activities:
Capital expenditures	(44,376)	(72,327)
Capitalized intellectual property costs	(1,307)	(1,011)
Proceeds from sale of property, plant and equipment	0	25,960
Net cash used in investing activities	(45,683)	(47,378)
Financing activities:
Dividends paid	(4,690)	(5,069)
Repurchase of common stock	0	(75,000)
Proceeds from options exercised	128	0
Tax payments related to shares withheld for vested restricted stock and stock units	(2,205)	(3,485)
Payments on long-term debt	(4,043)	(1,657)
Contributions from non-controlling interest	4,729	0
Principal payments on finance lease obligations	(20)	(75)
Net cash used in financing activities	(6,101)	(85,286)
Net decrease in cash and cash equivalents	(40,883)	(55,055)
Cash and cash equivalents, beginning of period	202,498	384,567
Cash and cash equivalents, end of period	161,615	329,512
Cash paid (received) during the period for:
Interest	21,557	6,592
Taxes, net of refunds	(472)	770
Related party purchases	0	672
Non-cash Items:
Accrued capital expenditures	39,239	20,170
Capital lease assumed by third-party	0	119
Asset retirement obligation assumed by third-party	$ 0	$ 2,116

Organization and Basis of Prese

Organization and Basis of Presentation	3 Months Ended
	Mar. 31, 2019
Organization, Consolidation and Presentation of Financial Statements [Abstract]
ORGANIZATION AND BASIS OF PRESENTATION	NOTE A—ORGANIZATION AND BASIS OF PRESENTATION Organization U.S. Silica Holdings, Inc. (“Holdings,” and together with its subsidiaries “we,” “us” or the “Company”) is a performance materials company and one of the largest domestic producers of commercial silica used in the oil and gas industry and in a wide range of industrial applications. In addition, through our acquisition of EP Minerals, LLC ("EPM") and its affiliated companies, we are an industry leader in the production of industrial minerals, including diatomaceous earth, clay (calcium bentonite and calcium montmorillonite) and perlite. During our 119 -year history, we have developed core competencies in mining, processing, logistics and materials science that enable us to produce and cost-effectively deliver products to customers across our end markets. Our operations are organized into two reportable segments based on end markets served: (1) Oil & Gas Proppants and (2) Industrial & Specialty Products. See Note U - Segment Reporting for more information on our reportable segments. Basis of Presentation and Consolidation The accompanying unaudited Condensed Consolidated Financial Statements for the quarter ended March 31, 2019 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, 2018 ; therefore, the unaudited 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 have been included. Such adjustments are of a normal, recurring nature. The Condensed Consolidated Financial Statements include the accounts of Holdings and its direct and indirect wholly-owned subsidiaries. All significant intercompany balances and transactions have been eliminated in consolidation. We follow Financial Accounting Standards Board ("FASB") Accounting Standards Codification (“ASC”) guidance for identification and reporting of entities over which control is achieved through means other than voting rights. The guidance defines such entities as Variable Interest Entities (“VIEs”). We consolidate VIEs when we have variable interests and are the primary beneficiary. We continually evaluate our involvement with VIEs to determine when these criteria are met. During the third quarter of 2018 we finalized a shareholders' agreement with unrelated parties to form a limited liability company with the purpose of constructing and operating a water pipeline to transport and sell water. In connection with the shareholders’ agreement, we acquired a 50% equity ownership for $3.2 million , with a maximum capital contribution of $7.0 million , and a water rights intangible asset for $0.7 million . Based on our evaluation, we determined that we are the primary beneficiary of this VIE and therefore we are required to consolidate it, including the current construction work in progress of $19.0 million . During the fourth quarter of 2018 we contributed an additional $3.8 million for a total of $7.0 million in capital contributions for the year ended December 31, 2018. We did no t make any capital contributions during the three months ended March 31, 2019 .

Summary of Significant Accounti

Summary of Significant Accounting Policies	3 Months Ended
	Mar. 31, 2019
Accounting Policies [Abstract]
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES	NOTE B—SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES Use of Estimates and Assumptions The preparation of Consolidated Financial Statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and the related disclosure of contingent assets and liabilities at the date of the Consolidated Financial Statements and the reported amounts of revenues and expenses during the reporting period. The more significant areas requiring the use of management estimates and assumptions relate to the purchase price allocation for businesses acquired; mineral reserves that are the basis for future cash flow estimates utilized in impairment calculations and units-of-production amortization calculations; environmental, reclamation and closure obligations; estimates of recoverable minerals; estimates of allowance for doubtful accounts; estimates of fair value for certain reporting units and asset impairments (including impairments of goodwill, intangible assets 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. Leases We lease railroad cars, office space, mining property, mining/processing equipment and transportation and other equipment. Operating leases are included in operating lease right-of-use (“ROU”) assets, current portion of operating lease liabilities, and operating lease liabilities in our consolidated balance sheets. Finance leases are included in property, plant and mine development, current portion of long-term debt, and long-term debt in our consolidated balance sheets. Leases with an initial term of 12 months or less are not recorded on the balance sheet. ROU assets represent our right to use an underlying asset for the lease term and lease liabilities represent our obligation to make lease payments arising from the lease. ROU assets and liabilities are recognized at the commencement date of the lease based on the present value of lease payments over the lease term. As most of our leases do not provide an implicit rate, we use our incremental borrowing rate based on the information available at the commencement date in determining the present value of lease payments. The ROU assets also include any lease payments made at or before the commencement date of the lease and excludes lease incentives. Our lease terms may include options to extend or terminate the lease when it is reasonably certain that we will exercise that option. Lease expense for lease payments is recognized on a straight-line basis over the lease term. We have lease agreements with lease and non-lease components, the latter of which are generally accounted for separately. See Note Q - Leases Foreign Operations Foreign sales were approximately $15.3 million of our consolidated sales; pre-tax income was $0.9 million and net income was $0.8 million for the three months ended March 31, 2019 . Foreign operations constituted approximately $10.1 million of consolidated assets as of March 31, 2019 . We had no significant foreign operations during the three months ended March 31, 2018 . New Accounting Pronouncements Recently Adopted In February 2016, the FASB issued ASU 2016-02, Leases (Topic 842) and issued ASU 2018-11 Leases (Topic 842): Targeted Improvements. The new standard(s) established a right-of-use ("ROU") model that requires a lessee to record an ROU asset and a corresponding 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 the lease risks and rewards, as well as substantive control, have been transferred through a lease contract. On January 1, 2019, we adopted the new accounting standard using the modified retrospective approach. We elected the package of practical expedients permitted under the transition guidance, which allowed us to account for our existing operating leases without reassessing (a) whether the contracts contain a lease under the new standard, (b) whether classification of the operating leases would be different in accordance with the new standard, or (c) whether the unamortized initial direct costs before transition adjustments would have met the definition of initial direct costs in the new standard at lease commencement. Adoption of the new standard resulted in the recognition of operating lease right-of-use assets of $223.0 million and lease liabilities of $222.7 million . The standard did not have a material impact on our consolidated statements of operations or cash flows. The comparative information has not been restated and continues to be reported under the accounting standards in effect for those periods. See Note Q - Leases . 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 January 1, 2019, with early adoption permitted. We adopted the new accounting standard on January 1, 2019, and we do not intend to exercise the option to reclassify stranded tax effects within accumulated other comprehensive income. New Accounting Pronouncements Not Yet Adopted In August 2018, the FASB issued ASU 2018-15, Intangibles-Goodwill and Other-Internal-Use Software (Subtopic 350-40): Customer’s Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement That Is a Service Contract. The new guidance requires a customer in a cloud computing arrangement (i.e., hosting arrangement) that is a service contract to follow the internal-use software guidance in ASC 350-40 to determine which implementation costs to capitalize as assets or expense as incurred. Capitalized implementation costs related to a hosting arrangement that is a service contract will be amortized over the term of the hosting arrangement, beginning when the module or component of the hosting arrangement is ready for its intended use. The update is effective for calendar-year public business entities in 2020. For all other calendar-year entities, it is effective for annual periods beginning in 2021 and interim periods in 2022. Early adoption is permitted. We are currently evaluating the effect that the guidance will have on our financial statements and related disclosures. In October 2018, FASB issued ASU 2018-17, Consolidation (Topic 810): Targeted Improvements to Related Party Guidance for Variable Interest Entities. This ASU is intended to reduce the cost and complexity of financial reporting associated with consolidation of VIEs. This ASU affects organizations that are required to determine whether they should consolidate a legal entity under the guidance within Subtopic 810-10, Consolidation. The update is effective for fiscal years beginning after December 15, 2019, and interim periods within those fiscal years. Early adoption is permitted. We are currently evaluating the adoption of this standard and the impact to our consolidated financial statements. In November 2018, the FASB issued 2018-18, Collaborative Arrangements (Topic 808), Clarifying the Interaction between Topic 808 and Topic 606. The amendments in this ASU provide clarification and guidance on whether certain transactions between collaborative arrangement participants should be accounting for with revenue under Topic 606 (Revenue from Contracts with Customers). The amendments provide narrow scope improvements for lessors. The amendments in this ASU are effective for fiscal years beginning after December 15, 2019 and interim periods within those fiscal years. We are currently evaluating the adoption of this standard and the impact to our consolidated financial statements.

Earnings Per Share

Earnings Per Share	3 Months Ended
	Mar. 31, 2019
Earnings Per Share [Abstract]
EARNINGS PER SHARE	NOTE C—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. Diluted net earnings per share assumes the conversion of contingently convertible securities and stock options under the treasury stock method, if dilutive. Contingently convertible securities and stock options are excluded from the calculation of fully diluted earnings per share if they are anti-dilutive, including when we incur a loss from continuing operations. The following table shows the computation of basic and diluted earnings per share for the three months ended March 31, 2019 , and 2018 : In thousands, except per share amounts Three Months Ended 2019 2018 Numerator: Net (loss) income attributable to U.S. Silica Holdings, Inc. $ (19,324 ) $ 31,294 Denominator: Weighted average shares outstanding 73,040 79,496 Diluted effect of stock awards — 813 Weighted average shares outstanding assuming dilution 73,040 80,309 Earnings (loss) per share attributable to U.S. Silica Holdings, Inc.: Basic (loss) earnings per share $ (0.26 ) $ 0.39 Diluted (loss) earnings per share $ (0.26 ) $ 0.39 We excluded potentially dilutive shares of 171 for the three months ended March 31, 2019 from the calculation of diluted weighted average shares outstanding and diluted earnings per share because we were in a net loss position. 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. Stock awards (in thousands) excluded from the calculation of diluted earnings per common share were as follows: Three Months Ended 2019 2018 Stock options excluded 736 428 Restricted stock and performance share units awards excluded 353 337

Capital Structure and Accumulat

Capital Structure and Accumulated Other Comprehensive Income (Loss)	3 Months Ended
	Mar. 31, 2019
Equity [Abstract]
CAPITAL STRUCTURE AND ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS)	NOTE D—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 82,455,734 shares issued and 73,524,817 shares outstanding at March 31, 2019 . There were 81,811,977 shares issued and 73,148,853 shares outstanding at December 31, 2018 . During the three months ended March 31, 2019 , our Board of Directors declared quarterly cash dividends as follows: Dividends per Common Share Declaration Date Record Date Payable Date $ 0.0625 February 15, 2019 March 14, 2019 April 4, 2019 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, 2019 or December 31, 2018 . At present, we have no plans to issue any preferred stock. Share Repurchase Program We are authorized by our Board of Directors to repurchase shares of our outstanding common stock from time to time on the open market or in privately negotiated transactions. Stock repurchases, if any, will be funded using our available liquidity. The timing and amount of stock repurchases will depend on a variety of factors, including the market conditions as well as corporate and regulatory considerations. In May 2018, our Board of Directors authorized the repurchase of up to $200 million of our common stock. As of March 31, 2019 , we have repurchased a total of 5,036,139 shares of our common stock at an average price of $14.59 and have $126.5 million of remaining availability under this program. Accumulated Other Comprehensive Loss Accumulated other comprehensive loss consists of fair value adjustments associated with cash flow hedges, accumulated adjustments for net experience losses and prior service cost related to employee benefit plans and foreign currency translation adjustments, net of tax. The following table presents the changes in accumulated other comprehensive loss by component (in thousands) during the three months ended March 31, 2019 : For the Three Months Ended March 31, 2019 Unrealized loss on cash flow hedges Foreign currency translation adjustments Pension and other post-retirement benefits liability Total Beginning Balance $ (1,621 ) $ (620 ) $ (12,779 ) $ (15,020 ) Other comprehensive gain (loss) before reclassifications (940 ) (199 ) (76 ) (1,215 ) Amounts reclassified from accumulated other comprehensive loss — — 250 250 Ending Balance $ (2,561 ) $ (819 ) $ (12,605 ) $ (15,985 )

Business Combinations

Business Combinations	3 Months Ended
	Mar. 31, 2019
Business Combinations [Abstract]
BUSINESS COMBINATIONS	NOTE E—BUSINESS COMBINATIONS 2018 Acquisition: On May 1, 2018, we completed the acquisition of all of the outstanding capital stock of EP Acquisition Parent, Inc., a Delaware corporation (“EPAP”), and the ultimate parent of EP Minerals, LLC ("EPM"). Contemporaneous with the merger, EPAP was renamed EP Minerals Holdings, Inc. ("EPMH"). The consideration paid consisted of $743.2 million of cash, net of cash acquired of $19.1 million , including $0.5 million of post-closing adjustments. EPM is a global producer of engineered materials derived from industrial minerals, including diatomaceous earth, clay (calcium bentonite and calcium montmorillonite) and perlite. EPM's industrial minerals are used as filter aids, absorbents and functional additives for a variety of industries including food and beverage, biofuels, recreational water, oil and gas, farm and home, landscape, sports turf, paint, plastics, and insecticides. The acquisition of EPM increased our industrial materials product offering in our Industrial & Specialty Products business segment. We have accounted for the acquisition of EPMH under the acquisition method of accounting in accordance with ASC 805, Business Combinations. Estimates of fair value included in the Consolidated Financial Statements represent our best estimates and valuations. In accordance with the acquisition method of accounting, the allocation of consideration value is subject to adjustment until we complete our analysis, within a period of time not to exceed one year after the date of acquisition, or May 1, 2019, in order to provide us with the time to complete the valuation of its assets and liabilities. We are still completing our analysis of the fair value of property, plant and mine development, mineral rights and intangible assets. The following table sets forth the preliminary allocation of the purchase price to EPMH's identifiable tangible and intangible assets acquired and liabilities assumed, including measurement period adjustments (in thousands): Preliminary allocation of purchase price: Estimate as of December 31, 2018 Measurement Period Adjustments Purchase Price Allocation Accounts receivable, net $ 43,305 $ — $ 43,305 Inventories 86,112 — 86,112 Property, plant and mine development 148,495 (1,937 ) 146,558 Mineral rights 419,469 (10,580 ) 408,889 Identifiable intangible assets - finite lived 10,270 (1,500 ) 8,770 Identifiable intangible assets - indefinite lived 38,050 (1,250 ) 36,800 Prepaids and deposits 2,072 (245 ) 1,827 Other assets 7,474 — 7,474 Goodwill 150,628 12,184 162,812 Total assets acquired 905,875 (3,328 ) 902,547 Accounts payable 13,435 — 13,435 Accrued expenses and other current liabilities 10,304 — 10,304 Deferred tax liabilities 122,811 (3,328 ) 119,483 Long term liabilities 16,076 — 16,076 Total liabilities assumed $ 162,626 $ (3,328 ) $ 159,298 Net assets acquired $ 743,249 $ — $ 743,249 The acquired intangible assets and the related estimated useful lives consist of the following: Approximate Fair Value Estimated Useful Life (in thousands) (in years) Technology and intellectual property $ 1,400 15 Customer relationships 7,370 15 Total identifiable intangible assets - finite lived $ 8,770 Trade names $ 36,800 Total identifiable intangible assets - indefinite lived $ 36,800 Goodwill represents the excess of the purchase price over the fair value of the underlying net assets acquired. Goodwill in this transaction is attributable to planned growth in our industrial materials product offering in our Industrial & Specialty Products business segment. Intangibles and goodwill are not expected to be deductible for tax purposes. Unaudited Pro Forma Results The results of EPMH's operations have been included in the Consolidated Financial Statements subsequent to the acquisition date. EPMH's fiscal year end was November 30 and the Company's fiscal year end was December 31. Under SEC regulations, if a target's fiscal year end varies by more than 93 days from the acquirer's fiscal year end, it is required to adjust interim periods until it is within 93 days. Since EPMH’s fiscal year end was within 93 days of the Company's fiscal year end, no adjustment is necessary and EPMH’s fiscal year end and interim period ends are used as if they coincided with the Company's fiscal year end and interim period end. The following unaudited pro forma consolidated financial information reflects the results of operations as if the EPMH acquisition had occurred on January 1, 2017, after giving effect to certain purchase accounting adjustments. Material non-recurring transaction costs attributable to the business combination were $15.2 million . Pro forma net income includes incremental interest expense due to the related debt financing, incremental depreciation and depletion expense related to the fair value adjustment of property, plant and mine development, amortization expense related to identifiable intangible assets, and tax expense related to the combined tax provisions. This information does not purport to be indicative of the actual results that would have occurred if the acquisition had actually been completed on the date indicated, nor is it necessarily indicative of the future operating results or the financial position of the combined company (in thousands, except per share amounts): For the Year Ended December 31, 2018 Sales $ 1,659,775 Net loss $ (179,220 ) Basic loss per share $ (2.34 ) Diluted loss per share $ (2.34 )

Accounts Receivable

Accounts Receivable	3 Months Ended
	Mar. 31, 2019
Receivables [Abstract]
ACCOUNTS RECEIVABLE	NOTE F—ACCOUNTS RECEIVABLE At March 31, 2019 and December 31, 2018 , accounts receivable (in thousands) consisted of the following: March 31, December 31, Trade receivables $ 241,100 $ 198,435 Less: Allowance for doubtful accounts (7,437 ) (6,751 ) Net trade receivables 233,663 191,684 Other receivables (1) 24,685 23,802 Total accounts receivable $ 258,348 $ 215,486 (1 ) At March 31, 2019 and December 31, 2018, other receivables included $16.0 million of refundable alternative minimum tax credits. Changes in our allowance for doubtful accounts (in thousands) during the three months ended March 31, 2019 and 2018 are as follows: March 31, March 31, 2018 Beginning balance $ 6,751 $ 7,100 Bad debt provision 721 237 Write-offs (35 ) (87 ) Ending balance $ 7,437 $ 7,250 Our ten largest customers accounted for approximately 42% and 52% of total sales during the three months ended March 31, 2019 and 2018 , respectively. Sales to one of our customers accounted for 12% and 15% of our total sales during the three months ended March 31, 2019 and 2018 , respectively. No other customers accounted for 10% or more of our total sales. At March 31, 2019 , one of our customers' accounts receivable represented 16% of our total trade accounts receivable, net of allowance. At December 31, 2018 , one of our customers' accounts receivable represented 18%

Inventories

Inventories	3 Months Ended
	Mar. 31, 2019
Inventory Disclosure [Abstract]
INVENTORIES	NOTE G—INVENTORIES At March 31, 2019 and December 31, 2018 , inventories (in thousands) consisted of the following: March 31, 2019 December 31, 2018 Supplies $ 44,479 $ 41,453 Raw materials and work in process 60,910 68,474 Finished goods 37,760 52,160 Total inventories $ 143,149 $ 162,087

Property, Plant and Mine Develo

Property, Plant and Mine Development	3 Months Ended
	Mar. 31, 2019
Property, Plant and Equipment [Abstract]
PROPERTY, PLANT AND MINE DEVELOPMENT	NOTE H—PROPERTY, PLANT AND MINE DEVELOPMENT At March 31, 2019 and December 31, 2018 , property, plant and mine development (in thousands) consisted of the following: March 31, December 31, Mining property and mine development $ 983,517 $ 995,759 Asset retirement cost 12,727 12,732 Land 55,502 55,502 Land improvements 68,992 67,729 Buildings 65,047 64,515 Machinery and equipment 1,027,782 958,357 Furniture and fixtures 3,611 3,599 Construction-in-progress 137,982 167,933 2,355,160 2,326,126 Accumulated depletion, depreciation and amortization (535,058 ) (499,823 ) Total property, plant and mine development, net $ 1,820,102 $ 1,826,303 At March 31, 2019 and December 31, 2018 , the aggregate cost of machinery and equipment acquired under finance leases was $0.3 million and $0.9 million , respectively, reduced by accumulated depreciation of $0.1 million and $0.2 million , respectively. The amount of interest costs capitalized in property, plant and mine development was $1.0 million and $1.8 million for the three months ended March 31, 2019 and 2018 , respectively. 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, 2019 , vendor incentives of $12.1 million and $28.0 million were classified in accounts payable and accrued expenses and in other long-term liabilities, respectively, on our balance sheet. Separately, on March 21, 2018, we accrued $7.9 million in contract termination costs for facilities contracts operated by third-parties, which will not transfer to CIG. During the second quarter of 2018, as a result of the final settlement of these contracts, we recorded a $2.7 million

Goodwill and Intangible Assets

Goodwill and Intangible Assets	3 Months Ended
	Mar. 31, 2019
Goodwill and Intangible Assets Disclosure [Abstract]
GOODWILL AND INTANGIBLE ASSETS	NOTE I—GOODWILL AND INTANGIBLE ASSETS The changes in the carrying amount of goodwill (in thousands) by business segment consisted of the following: Oil & Gas Proppants Segment Industrial & Specialty Products Segment Totals Goodwill Impairments Goodwill Impairments Balance at December, 2018 $ 250,267 $ (164,167 ) $ 86,100 $ 175,240 $ — $ 175,240 $ 261,340 EPM acquisition measurement period adjustment — — — 12,184 — 12,184 12,184 Balance at March 31, 2019 $ 250,267 $ (164,167 ) $ 86,100 $ 187,424 — $ 187,424 $ 273,524 Goodwill and trade names are evaluated for impairment annually as of October 31, or more frequently when indicators of impairment exist. We evaluated events and circumstances since the date of our last qualitative assessment, including macroeconomic conditions, industry and market conditions, and our overall financial performance. After assessing the totality of the events and circumstances, we determined that it was not more likely than not that the fair value of our reporting units was less than their carrying amount and no impairment existed. The changes in the carrying amount of intangible assets (in thousands) consisted of the following: March 31, 2019 December 31, 2018 Estimated Useful Life Gross Carrying Amount Accumulated Amortization Net Gross Carrying Amount Accumulated Amortization Net (in years) Technology and intellectual property 15 $ 83,497 $ (12,610 ) $ 70,887 $ 83,616 $ (11,168 ) $ 72,448 Customer relationships 13 - 15 68,659 (15,052 ) 53,607 68,664 (13,826 ) 54,838 Total definite-lived intangible assets: $ 152,156 $ (27,662 ) $ 124,494 $ 152,280 $ (24,994 ) $ 127,286 Trade names 65,390 — 65,390 66,640 — 66,640 Other 700 — 700 700 — 700 Total intangible assets: $ 218,246 $ (27,662 ) $ 190,584 $ 219,620 $ (24,994 ) $ 194,626 Measurement period adjustments related to the Company's EPMH acquisition impacted the March 31, 2019 gross carrying amounts of the technology and intellectual property intangibles by $(1.5) million and the trade names by $(1.3) million . See Note E - Business Combinations . Amortization expense was $2.7 million and $2.3 million for the three months ended March 31, 2019 and 2018 , respectively. The estimated amortization expense related to definite-lived intangible assets (in thousands) for the five succeeding years is as follows: 2019 $ 8,022 2020 10,696 2021 10,694 2022 10,679 2023 10,674

Debt

Debt	3 Months Ended
	Mar. 31, 2019
Debt Disclosure [Abstract]
DEBT	NOTE J—DEBT At March 31, 2019 and December 31, 2018 , debt (in thousands) consisted of the following: March 31, December 31, Senior secured credit facility: Revolver expiring May 1, 2023 (8.50% at March 31, 2019 and December 31, 2018) $ — $ — Term Loan facility—final maturity May 1, 2025 (6.50% at March 31, 2019 and 6.56% December 31, 2018) 1,267,200 1,270,400 Less: Unamortized original issue discount (6,246 ) (6,511 ) Less: Unamortized debt issuance cost (29,988 ) (31,310 ) Note payable secured by royalty interest 26,991 26,511 Equipment notes payable 267 321 Finance leases 130 344 Total debt 1,258,354 1,259,755 Less: current portion (13,112 ) (13,327 ) Total long-term portion of debt $ 1,245,242 $ 1,246,428 Revolving Line-of-Credit We have a $100.0 million Revolver with zero drawn and $4.8 million allocated for letters of credit as of March 31, 2019 , leaving $95.2 million available under the Revolver. Senior Secured Credit Facility At March 31, 2019 , contractual maturities of our senior secured Credit Facility (in thousands) are as follows: 2019 $ 9,600 2020 12,800 2021 12,800 2022 12,800 2023 12,800 Thereafter 1,206,400 Total $ 1,267,200 On May 1, 2018, we entered into the Credit Agreement, which increased our existing senior debt by entering into a new $1.380 billion senior secured Credit Facility, consisting of a $1.280 billion Term Loan and a $100 million Revolver that may also be used for swingline loans or letters of credit, and we may elect to increase the term loan in accordance with the terms of the Credit Agreement. Borrowings under the Credit Agreement will bear interest at variable rates as determined at our election, at LIBOR or a base rate, in each case, plus an applicable margin. In addition, under the Credit Agreement, we are required to pay a per annum facility fee and fees for letters of credit. The Credit Agreement is secured by substantially all of our assets and of our domestic subsidiaries' assets and a pledge of the equity interests in such entities. The Term Loan matures on May 1, 2025, and the Revolver expires May 1, 2023. We capitalized $38.7 million in debt issuance costs and original issue discount as a result of the new Credit Agreement. The Credit Facility contains covenants that, among other things, limit our ability, and certain of our subsidiaries' abilities, to create, incur or assume indebtedness and liens, to make acquisitions or investments, to sell assets and to pay dividends. The Credit Agreement also requires us to maintain a consolidated leverage ratio of no more than 3.75 :1.00 as of the last day of any fiscal quarter whenever usage of the Revolver (other than certain undrawn letters of credit) exceeds 30% of the Revolver commitment. These covenants are subject to a number of important exceptions and qualifications. The Credit Agreement includes events of default and other affirmative and negative covenants that are usual for facilities and transactions of this type. As of March 31, 2019 , and December 31, 2018 , 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 New Birmingham, Inc. 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: 2019 $ 1,750 2020 1,750 2021 1,750 2022 1,750 2023 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, 2019 , the note payable had a balance of $27.0 million . The increase in the note payable amount is due to interest paid-in-kind. The effective interest rate based on the updated projected future cash payments was 19% at March 31, 2019

Asset Retirement Obligations

Asset Retirement Obligations	3 Months Ended
	Mar. 31, 2019
Asset Retirement Obligation Disclosure [Abstract]
ASSET RETIREMENT OBLIGATIONS	NOTE K—ASSET RETIREMENT OBLIGATIONS 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, 2019 and 2018 , we had a liability of $18.8 million and $16.8 million , respectively, in other long-term liabilities related to our asset retirement obligations. Changes in the asset retirement obligations (in thousands) during the three months ended March 31, 2019 and 2018 are as follows: Three Months Ended 2019 2018 Beginning balance $ 18,413 $ 19,032 Accretion 373 326 Additions and revisions of prior estimates — (486 ) Disposal related to sale of transloads — (2,116 ) Ending balance $ 18,786 $ 16,756

Fair Value Accounting

Fair Value Accounting	3 Months Ended
	Mar. 31, 2019
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, 2019 and December 31, 2018 , 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 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, 2019 , 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. See Note M - Derivative Instruments

Derivative Instruments

Derivative Instruments	3 Months Ended
	Mar. 31, 2019
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 swap agreements in connection with our Term Loan facility to add stability to interest expense and to manage our exposure to interest rate movements. The derivative instruments are recorded on the balance sheet within other long-term assets or liabilities at their fair values. As of March 31, 2019 , the fair value of our interest rate swaps was a liability of $2.3 million and a liability of $1.0 million and classified within other long-term liabilities on our balance sheet, and the fair value of our interest rate cap was zero . At December 31, 2018 , the fair value of our interest rate swaps was a liability of $1.5 million and a liability of $0.7 million and classified within other long-term liabilities on our balance sheet, and the fair value of our interest rate cap was zero . We have designated the interest rate swap agreements 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. The following table summarizes the fair value of our derivative instruments (in thousands, except contract/notional amount). See Note L - Fair Value Accounting for more information regarding the estimated fair values of our derivative instruments at March 31, 2019 and December 31, 2018 . March 31, 2019 December 31, 2018 Maturity Contract/Notional Carrying Fair Maturity Date Contract/Notional Carrying Fair LIBOR (1) interest rate swap agreement 2020 $440 million $ (2,332 ) $ (2,332 ) 2020 $440 million $ (1,475 ) $ (1,475 ) LIBOR (1) interest rate swap agreement 2020 $200 million $ (1,046 ) $ (1,046 ) 2020 $200 million $ (663 ) $ (663 ) LIBOR interest rate cap agreement 2019 $249 million $ — $ — 2019 $249 million $ — $ — (1) Agreements fix the LIBOR interest rate base to 2.74% During the three months ended March 31, 2019 we had no ineffectiveness for the interest rate swap derivatives. The following table summarizes the effect of derivative instruments (in thousands) on our income statements and our consolidated statements of comprehensive income for the three months ended March 31, 2019 and 2018 . Three Months Ended 2019 2018 Deferred losses from derivatives in OCI, beginning of period $ (1,621 ) $ (76 ) Loss recognized in OCI from derivative instruments (940 ) — Loss reclassified from Accumulated OCI — 2 Deferred losses from derivatives in OCI, end of period $ (2,561 ) $ (74 )

Equity-Based Compensation

Equity-Based Compensation	3 Months Ended
	Mar. 31, 2019
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, 2019 , we have 4,119,834 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, 2019 : Number of Weighted Aggregate Intrinsic Value Weighted Outstanding at December 31, 2018 901,996 $ 28.52 $ 18,566 4.8 years Granted — — — Exercised (10,000 ) 12.87 — Forfeited — — — Expired (58,463 ) $ 24.42 $ — Outstanding at March 31, 2019 833,533 $ 28.99 $ 1,061,512 4.9 years Exercisable at March 31, 2019 833,533 $ 28.99 $ 1,061,512 4.9 years There were no grants of stock options during the three months ended March 31, 2019 and 2018 . There were 10,000 and zero stock options exercised during the three months ended March 31, 2019 and 2018 , respectively. The total intrinsic value of stock options exercised was $12 thousand for the three months ended March 31, 2019 . Cash received from stock options exercised during the three months ended March 31, 2019 was $128 thousand . The tax benefit realized from stock option exercises was $3 thousand for the three months ended March 31, 2019 . We recognized zero and $0.5 million of equity-based compensation expense related to options during the three months ended March 31, 2019 and 2018 , respectively. As of March 31, 2019 , there was no unrecognized compensation expense related to these options. 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, 2019 : Number of Shares Grant Date Weighted Average Fair Value Unvested, December 31, 2018 587,577 $ 25.18 Granted 732,860 12.89 Vested (101,601 ) 23.32 Forfeited (9,957 ) 29.87 Unvested, March 31, 2019 1,208,879 $ 17.85 We granted 732,860 and 3,852 restricted stock and restricted stock unit awards during the three months ended March 31, 2019 and 2018 , respectively. The increase is due to changing the timing of our annual equity grants to the first quarter from the second quarter. The fair value of the awards was based on the market price of our stock at date of grant. We recognized $2.3 million and $1.8 million of equity-based compensation expense related to restricted stock awards during the three months ended March 31, 2019 and 2018 , respectively. As of March 31, 2019 , there was $16.4 million of unrecognized compensation expense related to these restricted stock awards, which is expected to be recognized over a weighted-average period of 2.0 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, 2019 : Number of Shares Grant Date Weighted Unvested, December 31, 2018 838,188 $ 39.44 Granted 607,130 15.58 Vested (522,098 ) 37.76 Forfeited (11,258 ) 41.45 Unvested, March 31, 2019 911,962 $ 24.69 We granted 607,130 and zero performance share units during the three months ended March 31, 2019 and 2018 , respectively. The increase is due to changing the timing of our annual equity grants to the first quarter from the second quarter. The grant date fair value for these awards are estimated using a Monte Carlo simulation model. The Monte Carlo simulation model requires the use of highly subjective assumptions. Our key assumptions in the model included the price and the expected volatility of our common stock and our self-determined peer group companies’ stock, risk-free rate of interest, dividend yields and cross-correlations between our common stock and our self-determined peer group companies' stock. We recognized $1.7 million and $4.3 million of compensation expense related to performance share unit awards during the three months ended March 31, 2019 and 2018 , respectively. As of March 31, 2019 , there was $13.5 million of unrecognized compensation expense related to these performance share unit awards, which is expected to be recognized over a weighted-average period of 1.5

Commitments and Contingencies

Commitments and Contingencies	3 Months Ended
	Mar. 31, 2019
Commitments and Contingencies Disclosure [Abstract]
COMMITMENTS AND CONTINGENCIES	NOTE O—COMMITMENTS AND CONTINGENCIES Future Minimum Annual Commitments at March 31, 2019 (in thousands): Year ending December 31, Minimum Purchase Commitments 2019 $ 17,803 2020 14,464 2021 8,308 2022 5,640 2023 4,915 Thereafter 6,084 Total future purchase commitments $ 57,214 Minimum Purchase Commitments We enter into service agreements with our transload 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, 2019 , one new claim was brought against U.S. Silica. As of March 31, 2019 , there were 58 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 liabilities as well as estimated recoveries under the indemnity agreement and an estimate of future recoveries under insurance in other assets on our consolidated balance sheets. As of both March 31, 2019 and December 31, 2018 , other non-current assets included zero for insurance for third-party products liability claims. As of March 31, 2019 and December 31, 2018 other long-term liabilities included $0.9 million and $1.0 million , respectively, for third-party products liability claims. One of our subsidiaries has also been named as a defendant in lawsuits regarding certain labor practices. If we are unsuccessful in defending the litigation, these cases could result in material liability for us. Obligations under Guarantees We have indemnified our insurers against any loss they may incur in the event that holders of surety bonds, issued on our behalf, execute the bonds. As of March 31, 2019 , there was $41.9 million in bonds outstanding. The majority of these bonds, $30.4 million

Pension and Post-Retirement Ben

Pension and Post-Retirement Benefits	3 Months Ended
	Mar. 31, 2019
Retirement Benefits [Abstract]
PENSION AND POST-RETIREMENT BENEFITS	NOTE P—PENSION AND POST-RETIREMENT BENEFITS We maintain single-employer noncontributory defined benefit pension plans covering certain employees. There have been no new entrants to the US Silica Company plan since May 2009 and to the EP Management Corporation plan since January 2007 for salaried participants and January 2010 for hourly participants when the plans were frozen to all new employees. The plans provide 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 plans consistent with a goal of appropriate minimization of the unfunded projected benefit obligations. The pension plans use a benefit level per year of service for covered hourly employees and a final average pay method for covered salaried employees. The plans use the projected unit credit cost method to determine the actuarial valuation. 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 pension benefit cost (in thousands) consisted of the following for the three months ended March 31, 2019 and 2018 : Three Months Ended 2019 2018 Service cost $ 586 $ 279 Interest cost 2,584 978 Expected return on plan assets (3,184 ) (1,243 ) Net amortization and deferral 624 631 Net pension benefit costs $ 610 $ 645 Net post-retirement benefit cost (in thousands) consisted of the following for the three months ended March 31, 2019 and 2018 : Three Months Ended 2019 2018 Service cost $ 24 $ 27 Interest cost 196 188 Net post-retirement benefit costs $ 220 $ 215 We contributed $0.7 million and $0.3 million to the qualified pension plans for the three months ended March 31, 2019 and 2018 , respectively. Our best estimate of expected contributions to the pension and post-retirement medical benefit plans for the 2019 fiscal year are $4.7 million and $1.4 million , respectively. 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 for the three months ended March 31, 2019 and 2018 . Additionally, our contributions to multiemployer post-retirement benefit plans were immaterial for all periods presented in the accompanying consolidated financial statements. We also sponsor a defined contribution plan covering certain employees. We contribute to the plan in two ways. For certain employees not covered by the defined benefit plan, we make a contribution equal to 4% of their salary. We may also contribute an employee discretionary match of 50 cents for each dollar contributed by an employee, up to 4% of their earnings. Finally, for some employees, we make a catch-up match of one dollar for each dollar contributed by an employee, up to 6% of catch-up contributions. Contributions were $1.3 million and $0.8 million for the three months ended March 31, 2019 and 2018

Leases

Leases	3 Months Ended
	Mar. 31, 2019
Leases [Abstract]
Leases	NOTE Q— LEASES We lease railroad cars, office space, mining property, mining/processing equipment and transportation and other equipment. The majority of our leases have remaining lease terms of one year to 20 years. Our lease terms may include options to extend or terminate the lease when it is reasonably certain that we will exercise that option. As most of our leases do not provide an implicit rate, we use our incremental borrowing rate based on the information available at the commencement date in determining the present value of lease payments. We have lease agreements with lease and non-lease components, the latter of which are generally accounted for separately. Supplemental balance sheet information related to leases was as follows: Leases Classification March 31, Assets Operating Operating lease right-of-use assets $ 209,699 Total leased assets $ 209,699 Liabilities Current Operating Current portion of operating lease liabilities $ 61,583 Non-current Operating Operating lease liabilities 149,040 Total lease liabilities $ 210,623 Lease Term and Discount Rate Weighted average remaining lease term (years): Operating leases 4.7 years Weighted average discount rate: Operating leases 5.6% The components of lease expense were as follows: Lease Costs Classification Three Months Ended Operating lease costs (1) Cost of sales $ 25,115 Operating lease costs (2) Selling, general and administrative 1,169 $ 26,284 (1) Includes short-term operating lease costs of $6.6 million for the three months ended March 31, 2019. (2) Includes short-term operating lease costs of $0.2 million for the three months ended March 31, 2019. Supplemental cash flow information related to leases was as follows: Three Months Ended Cash paid for amounts included in the measurement of lease liabilities: Operating cash flows from operating leases $ 2,584 Right-of-use assets obtained in exchange for new lease liabilities: Operating leases $ 223,027 Maturities of lease liabilities as of March 31, 2019 : Maturities of lease liabilities Operating leases 2019 $ 55,828 2020 60,066 2021 41,065 2022 31,407 2023 22,042 Thereafter 36,024 Total lease payments $ 246,432 Less: Interest 35,809 Total $ 210,623
Leases	NOTE Q— LEASES We lease railroad cars, office space, mining property, mining/processing equipment and transportation and other equipment. The majority of our leases have remaining lease terms of one year to 20 years. Our lease terms may include options to extend or terminate the lease when it is reasonably certain that we will exercise that option. As most of our leases do not provide an implicit rate, we use our incremental borrowing rate based on the information available at the commencement date in determining the present value of lease payments. We have lease agreements with lease and non-lease components, the latter of which are generally accounted for separately. Supplemental balance sheet information related to leases was as follows: Leases Classification March 31, Assets Operating Operating lease right-of-use assets $ 209,699 Total leased assets $ 209,699 Liabilities Current Operating Current portion of operating lease liabilities $ 61,583 Non-current Operating Operating lease liabilities 149,040 Total lease liabilities $ 210,623 Lease Term and Discount Rate Weighted average remaining lease term (years): Operating leases 4.7 years Weighted average discount rate: Operating leases 5.6% The components of lease expense were as follows: Lease Costs Classification Three Months Ended Operating lease costs (1) Cost of sales $ 25,115 Operating lease costs (2) Selling, general and administrative 1,169 $ 26,284 (1) Includes short-term operating lease costs of $6.6 million for the three months ended March 31, 2019. (2) Includes short-term operating lease costs of $0.2 million for the three months ended March 31, 2019. Supplemental cash flow information related to leases was as follows: Three Months Ended Cash paid for amounts included in the measurement of lease liabilities: Operating cash flows from operating leases $ 2,584 Right-of-use assets obtained in exchange for new lease liabilities: Operating leases $ 223,027 Maturities of lease liabilities as of March 31, 2019 : Maturities of lease liabilities Operating leases 2019 $ 55,828 2020 60,066 2021 41,065 2022 31,407 2023 22,042 Thereafter 36,024 Total lease payments $ 246,432 Less: Interest 35,809 Total $ 210,623

Income Taxes

Income Taxes	3 Months Ended
	Mar. 31, 2019
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. December 22, 2018 marked the end of the measurement period for purposes of SAB 118. As such, we have completed the accounting for the tax effects of the Tax Act. The Tax Act reduced the corporate tax rate to 21 percent, effective January 1, 2018. Because ASC 740-10-25-47 requires the effect of a change in tax laws or rates to be recognized as of the date of enactment, we were required to adjust deferred tax assets and liabilities as of December 22, 2017. Accordingly, for the year ended December 31, 2017, we recorded a decrease related to deferred tax assets and liabilities of $45.0 million and $80.8 million , respectively, with a corresponding net adjustment to deferred income tax benefit of $35.8 million . Under the Tax Act, net operating loss (NOL) deductions arising in tax years beginning after December 31, 2017 can only offset up to 80 percent of future taxable income. The Act also prohibits NOL carrybacks, but allows indefinite carryforwards for NOLs arising in tax years beginning after December 31, 2017. Net operating losses arising before January 1, 2018 are accounted for under the previous tax rules that imposed no limit on the amount of the taxable income that can be set off using NOLs and that can be carried back 2 years and carried forward 20 years. The Tax Act repeals the corporate alternative minimum tax (AMT), effective for tax years beginning after December 31, 2017, but allows an entity to claim portions of any unused AMT credits over the next four years to offset its regular tax liability. An entity with unused AMT credits as of December 31, 2017 can first use these credits to offset its regular tax for 2017 and can then claim up to 50 percent of the remaining AMT credits in 2018, 2019, and 2020, with all remaining AMT credits refundable in 2021. For interim period reporting, we record income taxes using an estimated annual effective tax rate based upon projected annual income, forecasted permanent tax differences, discrete items and statutory rates in states in which we operate. At the end of each interim period, we update the estimated annual effective tax rate, and if the estimated tax rate changes based on new information, we make a cumulative adjustment in the period. We record the tax effect of an unusual or infrequently occurring item in the interim period in which it occurs as a discrete item of tax. For the three months ended March 31, 2019 , we had a tax benefit of $2.0 million . For the three months ended March 31, 2018 , we had a tax expense of $7.5 million . The effective tax rate was 9% and 19% for the three months ended March 31, 2019 and 2018 , respectively. The effective tax rate for the three months ended March 31, 2019 and 2018 would have been 29% and 18% , respectively, without the below items recorded discretely. During the three months ended March 31, 2019 and 2018 , we recorded a tax expense of $3.9 million and $0.5 million , respectively, related to equity compensation pursuant to ASU 2016-09.

Revenue

Revenue	3 Months Ended
	Mar. 31, 2019
Revenue from Contract with Customer [Abstract]
REVENUE	NOTE S— REVENUE We consider sales disaggregated at the product and service level by business 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, 2019 (in thousands): Three Months Ended Category Oil & Gas Proppants Industrial & Specialty Products Total Sales Product $ 178,587 $ 118,273 $ 296,860 Service 81,890 — 81,890 Total Sales $ 260,477 $ 118,273 $ 378,750 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, 2019 (in thousands): Unbilled Receivables December 31, 2018 $ 90 Reclassifications to billed receivables (90 ) Revenues recognized in excess of period billings 1,641 March 31, 2019 $ 1,641 Deferred Revenue December 31, 2018 $ 113,319 Revenues recognized from balances held at the beginning of the period (6,704 ) Revenues deferred from period collections on unfulfilled performance obligations 10,025 Revenues recognized from period collections (872 ) March 31, 2019 $ 115,768 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

Related Party Transactions

Related Party Transactions	3 Months Ended
	Mar. 31, 2019
Related Party Transactions [Abstract]
RELATED PARTY TRANSACTIONS	NOTE T— RELATED PARTY TRANSACTIONS A former employee, who was an officer of one of our operating subsidiaries prior to the third quarter of 2018, held an ownership interest in a transportation brokerage and logistics services vendor, from which we made purchases of approximately $0.9 million for the three months ended March 31, 2018

Segment Reporting

Segment Reporting	3 Months Ended
	Mar. 31, 2019
Segment Reporting [Abstract]
SEGMENT REPORTING	NOTE U— SEGMENT REPORTING Our business is organized into two reportable segments, Oil & Gas Proppants and Industrial & Specialty Products, based on end markets. The reportable segments are consistent with how management views the markets that we serve and the financial information reviewed by the chief operating decision maker. We manage our Oil & Gas Proppants and Industrial & Specialty Products businesses as components of an enterprise for which separate information is available and is evaluated regularly by the chief operating decision maker in deciding how to allocate resources and assess performance. In the Oil & Gas Proppants segment, we serve the oil and gas recovery market primarily by providing and delivering fracturing sand, or “frac sand,” which is pumped down oil and natural gas wells to prop open rock fissures and increase the flow rate of oil and natural gas from the wells. The Industrial & Specialty Products segment consists of over 400 product types 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 directly related to 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, segment contribution margin is a non-GAAP measure and 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 GAAP. The other accounting policies of each of the two reportable segments are the same as those in Note B - Summary of Significant Accounting Policies to the Consolidated Financial Statements in Item 8 of our 2018 Annual Report on Form 10-K. The following table presents sales and segment contribution margin (in thousands) for the reportable segments and other operating results not allocated to the reported segments for the three months ended March 31, 2019 and 2018 : Three Months Ended 2019 2018 Sales: Oil & Gas Proppants $ 260,477 $ 312,930 Industrial & Specialty Products 118,273 56,383 Total sales 378,750 369,313 Segment contribution margin: Oil & Gas Proppants 58,588 99,433 Industrial & Specialty Products 44,561 20,530 Total segment contribution margin 103,149 119,963 Operating activities excluded from segment cost of sales (21,937 ) (11,560 ) Selling, general and administrative (34,656 ) (34,591 ) Depreciation, depletion and amortization (44,600 ) (28,592 ) Interest expense (23,978 ) (7,070 ) Other income, net, including interest income 722 665 Income tax benefit (expense) 1,972 (7,521 ) Net (loss) income $ (19,328 ) $ 31,294 Less: Net (loss) income attributable to non-controlling interest (4 ) — Net (loss) income attributable to U.S. Silica Holdings, Inc. $ (19,324 ) $ 31,294 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, 2019 , goodwill of $273.5 million has been allocated to these segments with $86.1 million assigned to Oil & Gas Proppants and $187.4 million to Industrial & Specialty Products. At December 31, 2018 , goodwill of $261.3 million had been allocated to these segments with $86.1 million assigned to Oil & Gas Proppants and $175.2 million

Subsequent Events

Subsequent Events	3 Months Ended
	Mar. 31, 2019
Subsequent Events [Abstract]
SUBSEQUENT EVENTS	NOTE V— SUBSEQUENT EVENTS On April 4, 2019, we paid a cash dividend of $4.6 million or $0.0625

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	3 Months Ended
	Mar. 31, 2019
Accounting Policies [Abstract]
Basis of Presentation	The accompanying unaudited Condensed Consolidated Financial Statements for the quarter ended March 31, 2019 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, 2018
Consolidation	The Condensed Consolidated Financial Statements include the accounts of Holdings and its direct and indirect wholly-owned subsidiaries. All significant intercompany balances and transactions have been eliminated in consolidation.We follow Financial Accounting Standards Board ("FASB") Accounting Standards Codification (“ASC”) guidance for identification and reporting of entities over which control is achieved through means other than voting rights. The guidance defines such entities as Variable Interest Entities (“VIEs”). We consolidate VIEs when we have variable interests and are the primary beneficiary. We continually evaluate our involvement with VIEs to determine when these criteria are met.
Use of Estimates and Assumptions	Use of Estimates and Assumptions The preparation of Consolidated Financial Statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and the related disclosure of contingent assets and liabilities at the date of the Consolidated Financial Statements and the reported amounts of revenues and expenses during the reporting period. The more significant areas requiring the use of management estimates and assumptions relate to the purchase price allocation for businesses acquired; mineral reserves that are the basis for future cash flow estimates utilized in impairment calculations and units-of-production amortization calculations; environmental, reclamation and closure obligations; estimates of recoverable minerals; estimates of allowance for doubtful accounts; estimates of fair value for certain reporting units and
Leases	Leases We lease railroad cars, office space, mining property, mining/processing equipment and transportation and other equipment.
New Accounting Pronouncements Recently Adopted and New Accounting Pronouncements Not Yet Adopted	New Accounting Pronouncements Recently Adopted In February 2016, the FASB issued ASU 2016-02, Leases (Topic 842) and issued ASU 2018-11 Leases (Topic 842): Targeted Improvements. The new standard(s) established a right-of-use ("ROU") model that requires a lessee to record an ROU asset and a corresponding 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 the lease risks and rewards, as well as substantive control, have been transferred through a lease contract. On January 1, 2019, we adopted the new accounting standard using the modified retrospective approach. We elected the package of practical expedients permitted under the transition guidance, which allowed us to account for our existing operating leases without reassessing (a) whether the contracts contain a lease under the new standard, (b) whether classification of the operating leases would be different in accordance with the new standard, or (c) whether the unamortized initial direct costs before transition adjustments would have met the definition of initial direct costs in the new standard at lease commencement. Adoption of the new standard resulted in the recognition of operating lease right-of-use assets of $223.0 million and lease liabilities of $222.7 million . The standard did not have a material impact on our consolidated statements of operations or cash flows. The comparative information has not been restated and continues to be reported under the accounting standards in effect for those periods. See Note Q - Leases . 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 January 1, 2019, with early adoption permitted. We adopted the new accounting standard on January 1, 2019, and we do not intend to exercise the option to reclassify stranded tax effects within accumulated other comprehensive income. New Accounting Pronouncements Not Yet Adopted In August 2018, the FASB issued ASU 2018-15, Intangibles-Goodwill and Other-Internal-Use Software (Subtopic 350-40): Customer’s Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement That Is a Service Contract. The new guidance requires a customer in a cloud computing arrangement (i.e., hosting arrangement) that is a service contract to follow the internal-use software guidance in ASC 350-40 to determine which implementation costs to capitalize as assets or expense as incurred. Capitalized implementation costs related to a hosting arrangement that is a service contract will be amortized over the term of the hosting arrangement, beginning when the module or component of the hosting arrangement is ready for its intended use. The update is effective for calendar-year public business entities in 2020. For all other calendar-year entities, it is effective for annual periods beginning in 2021 and interim periods in 2022. Early adoption is permitted. We are currently evaluating the effect that the guidance will have on our financial statements and related disclosures. In October 2018, FASB issued ASU 2018-17, Consolidation (Topic 810): Targeted Improvements to Related Party Guidance for Variable Interest Entities. This ASU is intended to reduce the cost and complexity of financial reporting associated with consolidation of VIEs. This ASU affects organizations that are required to determine whether they should consolidate a legal entity under the guidance within Subtopic 810-10, Consolidation. The update is effective for fiscal years beginning after December 15, 2019, and interim periods within those fiscal years. Early adoption is permitted. We are currently evaluating the adoption of this standard and the impact to our consolidated financial statements. In November 2018, the FASB issued 2018-18, Collaborative Arrangements (Topic 808), Clarifying the Interaction between Topic 808 and Topic 606. The amendments in this ASU provide clarification and guidance on whether certain transactions between collaborative arrangement participants should be accounting for with revenue under Topic 606 (Revenue from Contracts with Customers). The amendments provide narrow scope improvements for lessors. The amendments in this ASU are effective for fiscal years beginning after December 15, 2019 and interim periods within those fiscal years. We are currently evaluating the adoption of this standard and the impact to our consolidated financial statements.
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, 2019 and December 31, 2018 , 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 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, 2019

Earnings Per Share (Tables)

Earnings Per Share (Tables)	3 Months Ended
	Mar. 31, 2019
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, 2019 , and 2018 : In thousands, except per share amounts Three Months Ended 2019 2018 Numerator: Net (loss) income attributable to U.S. Silica Holdings, Inc. $ (19,324 ) $ 31,294 Denominator: Weighted average shares outstanding 73,040 79,496 Diluted effect of stock awards — 813 Weighted average shares outstanding assuming dilution 73,040 80,309 Earnings (loss) per share attributable to U.S. Silica Holdings, Inc.: Basic (loss) earnings per share $ (0.26 ) $ 0.39 Diluted (loss) earnings per share $ (0.26 ) $ 0.39
Schedule of Antidilutive Securities Excluded from Computation of Diluted Earnings Per Share	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. Stock awards (in thousands) excluded from the calculation of diluted earnings per common share were as follows: Three Months Ended 2019 2018 Stock options excluded 736 428 Restricted stock and performance share units awards excluded 353 337

Capital Structure and Accumul_2

Capital Structure and Accumulated Other Comprehensive Income (Loss) (Tables)	3 Months Ended
	Mar. 31, 2019
Equity [Abstract]
Schedule of Declared Quarterly Cash Dividends	During the three months ended March 31, 2019 , our Board of Directors declared quarterly cash dividends as follows: Dividends per Common Share Declaration Date Record Date Payable Date $ 0.0625 February 15, 2019 March 14, 2019 April 4, 2019
Schedule of Changes in Accumulated Other Comprehensive Income (Loss)	The following table presents the changes in accumulated other comprehensive loss by component (in thousands) during the three months ended March 31, 2019 : For the Three Months Ended March 31, 2019 Unrealized loss on cash flow hedges Foreign currency translation adjustments Pension and other post-retirement benefits liability Total Beginning Balance $ (1,621 ) $ (620 ) $ (12,779 ) $ (15,020 ) Other comprehensive gain (loss) before reclassifications (940 ) (199 ) (76 ) (1,215 ) Amounts reclassified from accumulated other comprehensive loss — — 250 250 Ending Balance $ (2,561 ) $ (819 ) $ (12,605 ) $ (15,985 )

Business Combinations (Tables)

Business Combinations (Tables)	3 Months Ended
	Mar. 31, 2019
Business Combinations [Abstract]
Schedule of Identifiable Assets Acquired and Liabilities Assumed	The following table sets forth the preliminary allocation of the purchase price to EPMH's identifiable tangible and intangible assets acquired and liabilities assumed, including measurement period adjustments (in thousands): Preliminary allocation of purchase price: Estimate as of December 31, 2018 Measurement Period Adjustments Purchase Price Allocation Accounts receivable, net $ 43,305 $ — $ 43,305 Inventories 86,112 — 86,112 Property, plant and mine development 148,495 (1,937 ) 146,558 Mineral rights 419,469 (10,580 ) 408,889 Identifiable intangible assets - finite lived 10,270 (1,500 ) 8,770 Identifiable intangible assets - indefinite lived 38,050 (1,250 ) 36,800 Prepaids and deposits 2,072 (245 ) 1,827 Other assets 7,474 — 7,474 Goodwill 150,628 12,184 162,812 Total assets acquired 905,875 (3,328 ) 902,547 Accounts payable 13,435 — 13,435 Accrued expenses and other current liabilities 10,304 — 10,304 Deferred tax liabilities 122,811 (3,328 ) 119,483 Long term liabilities 16,076 — 16,076 Total liabilities assumed $ 162,626 $ (3,328 ) $ 159,298 Net assets acquired $ 743,249 $ — $ 743,249
Schedule of Identifiable Intangible Assets Acquired	The acquired intangible assets and the related estimated useful lives consist of the following: Approximate Fair Value Estimated Useful Life (in thousands) (in years) Technology and intellectual property $ 1,400 15 Customer relationships 7,370 15 Total identifiable intangible assets - finite lived $ 8,770 Trade names $ 36,800 Total identifiable intangible assets - indefinite lived $ 36,800
Schedule of Pro Forma Information	The following unaudited pro forma consolidated financial information reflects the results of operations as if the EPMH acquisition had occurred on January 1, 2017, after giving effect to certain purchase accounting adjustments. Material non-recurring transaction costs attributable to the business combination were $15.2 million . Pro forma net income includes incremental interest expense due to the related debt financing, incremental depreciation and depletion expense related to the fair value adjustment of property, plant and mine development, amortization expense related to identifiable intangible assets, and tax expense related to the combined tax provisions. This information does not purport to be indicative of the actual results that would have occurred if the acquisition had actually been completed on the date indicated, nor is it necessarily indicative of the future operating results or the financial position of the combined company (in thousands, except per share amounts): For the Year Ended December 31, 2018 Sales $ 1,659,775 Net loss $ (179,220 ) Basic loss per share $ (2.34 ) Diluted loss per share $ (2.34 )

Accounts Receivable (Tables)

Accounts Receivable (Tables)	3 Months Ended
	Mar. 31, 2019
Receivables [Abstract]
Schedule of Accounts Receivable and Allowance for Doubtful Accounts	At March 31, 2019 and December 31, 2018 , accounts receivable (in thousands) consisted of the following: March 31, December 31, Trade receivables $ 241,100 $ 198,435 Less: Allowance for doubtful accounts (7,437 ) (6,751 ) Net trade receivables 233,663 191,684 Other receivables (1) 24,685 23,802 Total accounts receivable $ 258,348 $ 215,486 (1 ) At March 31, 2019 and December 31, 2018, other receivables included $16.0 million of refundable alternative minimum tax credits. Changes in our allowance for doubtful accounts (in thousands) during the three months ended March 31, 2019 and 2018 are as follows: March 31, March 31, 2018 Beginning balance $ 6,751 $ 7,100 Bad debt provision 721 237 Write-offs (35 ) (87 ) Ending balance $ 7,437 $ 7,250

Inventories (Tables)

Inventories (Tables)	3 Months Ended
	Mar. 31, 2019
Inventory Disclosure [Abstract]
Schedule of Inventories	At March 31, 2019 and December 31, 2018 , inventories (in thousands) consisted of the following: March 31, 2019 December 31, 2018 Supplies $ 44,479 $ 41,453 Raw materials and work in process 60,910 68,474 Finished goods 37,760 52,160 Total inventories $ 143,149 $ 162,087

Property, Plant and Mine Deve_2

Property, Plant and Mine Development (Tables)	3 Months Ended
	Mar. 31, 2019
Property, Plant and Equipment [Abstract]
Schedule of Property, Plant and Mine Development	At March 31, 2019 and December 31, 2018 , property, plant and mine development (in thousands) consisted of the following: March 31, December 31, Mining property and mine development $ 983,517 $ 995,759 Asset retirement cost 12,727 12,732 Land 55,502 55,502 Land improvements 68,992 67,729 Buildings 65,047 64,515 Machinery and equipment 1,027,782 958,357 Furniture and fixtures 3,611 3,599 Construction-in-progress 137,982 167,933 2,355,160 2,326,126 Accumulated depletion, depreciation and amortization (535,058 ) (499,823 ) Total property, plant and mine development, net $ 1,820,102 $ 1,826,303

Goodwill and Intangible Assets

Goodwill and Intangible Assets (Tables)	3 Months Ended
	Mar. 31, 2019
Goodwill and Intangible Assets Disclosure [Abstract]
Schedule of Carrying Amount of Goodwill by Business Segment	The changes in the carrying amount of goodwill (in thousands) by business segment consisted of the following: Oil & Gas Proppants Segment Industrial & Specialty Products Segment Totals Goodwill Impairments Goodwill Impairments Balance at December, 2018 $ 250,267 $ (164,167 ) $ 86,100 $ 175,240 $ — $ 175,240 $ 261,340 EPM acquisition measurement period adjustment — — — 12,184 — 12,184 12,184 Balance at March 31, 2019 $ 250,267 $ (164,167 ) $ 86,100 $ 187,424 — $ 187,424 $ 273,524
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, 2019 December 31, 2018 Estimated Useful Life Gross Carrying Amount Accumulated Amortization Net Gross Carrying Amount Accumulated Amortization Net (in years) Technology and intellectual property 15 $ 83,497 $ (12,610 ) $ 70,887 $ 83,616 $ (11,168 ) $ 72,448 Customer relationships 13 - 15 68,659 (15,052 ) 53,607 68,664 (13,826 ) 54,838 Total definite-lived intangible assets: $ 152,156 $ (27,662 ) $ 124,494 $ 152,280 $ (24,994 ) $ 127,286 Trade names 65,390 — 65,390 66,640 — 66,640 Other 700 — 700 700 — 700 Total intangible assets: $ 218,246 $ (27,662 ) $ 190,584 $ 219,620 $ (24,994 ) $ 194,626
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, 2019 December 31, 2018 Estimated Useful Life Gross Carrying Amount Accumulated Amortization Net Gross Carrying Amount Accumulated Amortization Net (in years) Technology and intellectual property 15 $ 83,497 $ (12,610 ) $ 70,887 $ 83,616 $ (11,168 ) $ 72,448 Customer relationships 13 - 15 68,659 (15,052 ) 53,607 68,664 (13,826 ) 54,838 Total definite-lived intangible assets: $ 152,156 $ (27,662 ) $ 124,494 $ 152,280 $ (24,994 ) $ 127,286 Trade names 65,390 — 65,390 66,640 — 66,640 Other 700 — 700 700 — 700 Total intangible assets: $ 218,246 $ (27,662 ) $ 190,584 $ 219,620 $ (24,994 ) $ 194,626
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: 2019 $ 8,022 2020 10,696 2021 10,694 2022 10,679 2023 10,674

Debt (Tables)

Debt (Tables)	3 Months Ended
	Mar. 31, 2019
Debt Disclosure [Abstract]
Schedule of Debt	At March 31, 2019 and December 31, 2018 , debt (in thousands) consisted of the following: March 31, December 31, Senior secured credit facility: Revolver expiring May 1, 2023 (8.50% at March 31, 2019 and December 31, 2018) $ — $ — Term Loan facility—final maturity May 1, 2025 (6.50% at March 31, 2019 and 6.56% December 31, 2018) 1,267,200 1,270,400 Less: Unamortized original issue discount (6,246 ) (6,511 ) Less: Unamortized debt issuance cost (29,988 ) (31,310 ) Note payable secured by royalty interest 26,991 26,511 Equipment notes payable 267 321 Finance leases 130 344 Total debt 1,258,354 1,259,755 Less: current portion (13,112 ) (13,327 ) Total long-term portion of debt $ 1,245,242 $ 1,246,428
Schedule of Contractual Maturities of Debt	The minimum payments (in thousands) for the next five years required by the note are as follows: 2019 $ 1,750 2020 1,750 2021 1,750 2022 1,750 2023 1,750 March 31, 2019 , contractual maturities of our senior secured Credit Facility (in thousands) are as follows: 2019 $ 9,600 2020 12,800 2021 12,800 2022 12,800 2023 12,800 Thereafter 1,206,400 Total $ 1,267,200

Asset Retirement Obligations (T

Asset Retirement Obligations (Tables)	3 Months Ended
	Mar. 31, 2019
Asset Retirement Obligation Disclosure [Abstract]
Schedule of Changes in Asset Retirement Obligations	Changes in the asset retirement obligations (in thousands) during the three months ended March 31, 2019 and 2018 are as follows: Three Months Ended 2019 2018 Beginning balance $ 18,413 $ 19,032 Accretion 373 326 Additions and revisions of prior estimates — (486 ) Disposal related to sale of transloads — (2,116 ) Ending balance $ 18,786 $ 16,756

Derivative Instruments (Tables)

Derivative Instruments (Tables)	3 Months Ended
	Mar. 31, 2019
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Schedule of Estimated Fair Values of Derivative Instruments	The following table summarizes the fair value of our derivative instruments (in thousands, except contract/notional amount). See Note L - Fair Value Accounting for more information regarding the estimated fair values of our derivative instruments at March 31, 2019 and December 31, 2018 . March 31, 2019 December 31, 2018 Maturity Contract/Notional Carrying Fair Maturity Date Contract/Notional Carrying Fair LIBOR (1) interest rate swap agreement 2020 $440 million $ (2,332 ) $ (2,332 ) 2020 $440 million $ (1,475 ) $ (1,475 ) LIBOR (1) interest rate swap agreement 2020 $200 million $ (1,046 ) $ (1,046 ) 2020 $200 million $ (663 ) $ (663 ) LIBOR interest rate cap agreement 2019 $249 million $ — $ — 2019 $249 million $ — $ — (1) Agreements fix the LIBOR interest rate base to 2.74%
Schedule of Effect of Derivatives Instruments on Combined Statements of Operations and Comprehensive Income	The following table summarizes the effect of derivative instruments (in thousands) on our income statements and our consolidated statements of comprehensive income for the three months ended March 31, 2019 and 2018 . Three Months Ended 2019 2018 Deferred losses from derivatives in OCI, beginning of period $ (1,621 ) $ (76 ) Loss recognized in OCI from derivative instruments (940 ) — Loss reclassified from Accumulated OCI — 2 Deferred losses from derivatives in OCI, end of period $ (2,561 ) $ (74 )

Equity-Based Compensation (Tabl

Equity-Based Compensation (Tables)	3 Months Ended
	Mar. 31, 2019
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, 2019 : Number of Weighted Aggregate Intrinsic Value Weighted Outstanding at December 31, 2018 901,996 $ 28.52 $ 18,566 4.8 years Granted — — — Exercised (10,000 ) 12.87 — Forfeited — — — Expired (58,463 ) $ 24.42 $ — Outstanding at March 31, 2019 833,533 $ 28.99 $ 1,061,512 4.9 years Exercisable at March 31, 2019 833,533 $ 28.99 $ 1,061,512 4.9 years
Schedule of Restricted Stock, Restricted Stock Unit and Performance Share Unit Awards Activity	The following table summarizes the status of, and changes in, our performance share unit awards during the three months ended March 31, 2019 : Number of Shares Grant Date Weighted Unvested, December 31, 2018 838,188 $ 39.44 Granted 607,130 15.58 Vested (522,098 ) 37.76 Forfeited (11,258 ) 41.45 Unvested, March 31, 2019 911,962 $ 24.69 three months ended March 31, 2019 : Number of Shares Grant Date Weighted Average Fair Value Unvested, December 31, 2018 587,577 $ 25.18 Granted 732,860 12.89 Vested (101,601 ) 23.32 Forfeited (9,957 ) 29.87 Unvested, March 31, 2019 1,208,879 $ 17.85

Commitments and Contingencies (

Commitments and Contingencies (Tables)	3 Months Ended
	Mar. 31, 2019
Commitments and Contingencies Disclosure [Abstract]
Schedule of Future Minimum Annual Commitments	Future Minimum Annual Commitments at March 31, 2019 (in thousands): Year ending December 31, Minimum Purchase Commitments 2019 $ 17,803 2020 14,464 2021 8,308 2022 5,640 2023 4,915 Thereafter 6,084 Total future purchase commitments $ 57,214

Pension and Post-Retirement B_2

Pension and Post-Retirement Benefits (Tables)	3 Months Ended
	Mar. 31, 2019
Retirement Benefits [Abstract]
Schedule of Net Pension and Post-Retirement Benefit Plans	Net pension benefit cost (in thousands) consisted of the following for the three months ended March 31, 2019 and 2018 : Three Months Ended 2019 2018 Service cost $ 586 $ 279 Interest cost 2,584 978 Expected return on plan assets (3,184 ) (1,243 ) Net amortization and deferral 624 631 Net pension benefit costs $ 610 $ 645 Net post-retirement benefit cost (in thousands) consisted of the following for the three months ended March 31, 2019 and 2018 : Three Months Ended 2019 2018 Service cost $ 24 $ 27 Interest cost 196 188 Net post-retirement benefit costs $ 220 $ 215

Leases (Tables)

Leases (Tables)	3 Months Ended
	Mar. 31, 2019
Leases [Abstract]
Schedule of Supplemental Balance Sheet Information	Leases Classification March 31, Assets Operating Operating lease right-of-use assets $ 209,699 Total leased assets $ 209,699 Liabilities Current Operating Current portion of operating lease liabilities $ 61,583 Non-current Operating Operating lease liabilities 149,040 Total lease liabilities $ 210,623 Lease Term and Discount Rate Weighted average remaining lease term (years): Operating leases 4.7 years Weighted average discount rate: Operating leases 5.6%
Schedule of Components of Lease Expense and Supplemental Cash Flow Information	The components of lease expense were as follows: Lease Costs Classification Three Months Ended Operating lease costs (1) Cost of sales $ 25,115 Operating lease costs (2) Selling, general and administrative 1,169 $ 26,284 (1) Includes short-term operating lease costs of $6.6 million for the three months ended March 31, 2019. (2) Includes short-term operating lease costs of $0.2 million for the three months ended March 31, 2019. Supplemental cash flow information related to leases was as follows: Three Months Ended Cash paid for amounts included in the measurement of lease liabilities: Operating cash flows from operating leases $ 2,584 Right-of-use assets obtained in exchange for new lease liabilities: Operating leases $ 223,027
Schedule of Maturity of Lease Liabilities	Maturities of lease liabilities as of March 31, 2019 : Maturities of lease liabilities Operating leases 2019 $ 55,828 2020 60,066 2021 41,065 2022 31,407 2023 22,042 Thereafter 36,024 Total lease payments $ 246,432 Less: Interest 35,809 Total $ 210,623

Revenue (Tables)

Revenue (Tables)	3 Months Ended
	Mar. 31, 2019
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, 2019 (in thousands): Three Months Ended Category Oil & Gas Proppants Industrial & Specialty Products Total Sales Product $ 178,587 $ 118,273 $ 296,860 Service 81,890 — 81,890 Total Sales $ 260,477 $ 118,273 $ 378,750
Schedule of Changes in Contract Assets and Liabilities	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, 2019 (in thousands): Unbilled Receivables December 31, 2018 $ 90 Reclassifications to billed receivables (90 ) Revenues recognized in excess of period billings 1,641 March 31, 2019 $ 1,641 Deferred Revenue December 31, 2018 $ 113,319 Revenues recognized from balances held at the beginning of the period (6,704 ) Revenues deferred from period collections on unfulfilled performance obligations 10,025 Revenues recognized from period collections (872 ) March 31, 2019 $ 115,768

Segment Reporting (Tables)

Segment Reporting (Tables)	3 Months Ended
	Mar. 31, 2019
Segment Reporting [Abstract]
Schedule of Sales and Segment Contribution Margin for Reporting Segments and Operating Results	The following table presents sales and segment contribution margin (in thousands) for the reportable segments and other operating results not allocated to the reported segments for the three months ended March 31, 2019 and 2018 : Three Months Ended 2019 2018 Sales: Oil & Gas Proppants $ 260,477 $ 312,930 Industrial & Specialty Products 118,273 56,383 Total sales 378,750 369,313 Segment contribution margin: Oil & Gas Proppants 58,588 99,433 Industrial & Specialty Products 44,561 20,530 Total segment contribution margin 103,149 119,963 Operating activities excluded from segment cost of sales (21,937 ) (11,560 ) Selling, general and administrative (34,656 ) (34,591 ) Depreciation, depletion and amortization (44,600 ) (28,592 ) Interest expense (23,978 ) (7,070 ) Other income, net, including interest income 722 665 Income tax benefit (expense) 1,972 (7,521 ) Net (loss) income $ (19,328 ) $ 31,294 Less: Net (loss) income attributable to non-controlling interest (4 ) — Net (loss) income attributable to U.S. Silica Holdings, Inc. $ (19,324 ) $ 31,294

Organization and Basis of Pre_2

Organization and Basis of Presentation (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2019USD ($)Segment	Dec. 31, 2018USD ($)	Sep. 30, 2018USD ($)	Mar. 31, 2018USD ($)
Organization And Nature Of Business
Number of business segments | Segment	2
Water rights intangibles acquired in VIE	$ 1,307			$ 1,011
Property, plant and mine development, gross	2,355,160	$ 2,326,126
Construction-in-progress
Organization And Nature Of Business
Property, plant and mine development, gross	137,982	167,933
Variable Interest Entity, Primary Beneficiary
Organization And Nature Of Business
Equity ownership percentage acquired in VIE			50.00%
Payments to acquire interest in VIE			$ 3,200
Maximum capital contribution in VIE		7,000	7,000
Additional capital contribution paid to acquire interest in VIE	$ 0	$ 3,800
Variable Interest Entity, Primary Beneficiary | Water rights
Organization And Nature Of Business
Water rights intangibles acquired in VIE			700
Variable Interest Entity, Primary Beneficiary | Construction-in-progress
Organization And Nature Of Business
Property, plant and mine development, gross			$ 19,000

Summary of Significant Accoun_3

Summary of Significant Accounting Policies (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Jan. 01, 2019	Dec. 31, 2018
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Consolidated sales	$ 378,750	$ 369,313
Pre-tax income	(21,300)	38,815
Net income	(19,324)	$ 31,294
Consolidated assets	3,089,440			$ 2,900,840
Operating lease right-of-use assets	209,699			$ 0
Lease liabilities	210,623
ASU 2016-02
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating lease right-of-use assets			$ 223,000
Lease liabilities			$ 222,700
Foreign Operations
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Consolidated sales	15,300
Pre-tax income	900
Net income	800
Consolidated assets	$ 10,100

Earnings Per Share - Computatio

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, 2019	Mar. 31, 2018
Numerator:
Net (loss) income attributable to U.S. Silica Holdings, Inc.	$ (19,324)	$ 31,294
Denominator:
Weighted average shares outstanding, basic (in shares)	73,040	79,496
Diluted effect of stock awards (shares)	0	813
Weighted average shares outstanding assuming dilution (shares)	73,040	80,309
Earnings (loss) per share attributable to U.S. Silica Holdings, Inc.:
Basic earnings (loss) per share (in dollars per share)	$ (0.26)	$ 0.39
Diluted earnings (loss) per share (in dollars per share)	$ (0.26)	$ 0.39

Earnings Per Share - Antidiluti

Earnings Per Share - Antidilutive Securities Excluded From Calculation of Diluted Earnings Per Share (Details) - shares shares in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Weighted-average outstanding stock options and restricted stock awards excluded (shares)	171
Stock options excluded
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Weighted-average outstanding stock options and restricted stock awards excluded (shares)	736	428
Restricted stock and performance share units awards excluded
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Weighted-average outstanding stock options and restricted stock awards excluded (shares)	353	337

Capital Structure and Accumul_3

Capital Structure and Accumulated Other Comprehensive Income (Loss) - Additional Information (Details) - USD ($)	10 Months Ended
	Mar. 31, 2019	Dec. 31, 2018	May 31, 2018
Capital Structure And Accumulated Comprehensive Income (Loss)
Common stock authorized (shares)	500,000,000	500,000,000
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock issued (shares)	82,455,734	81,811,977
Common stock outstanding (shares)	73,524,817	73,148,853
Preferred stock authorized (shares)	10,000,000	10,000,000
Preferred stock, par value (in dollars per share)	$ 0.01	$ 0.01
Preferred stock issued (shares)	0	0
Preferred stock outstanding (shares)	0	0
May 2018 Share Repurchase Program
Capital Structure And Accumulated Comprehensive Income (Loss)
Share repurchase program authorized amount			$ 200,000,000
Repurchase of common stock (shares)	5,036,139
Average price per common share of repurchase common stock (in dollars per share)	$ 14.59
Remaining authorized repurchase amount	$ 126,500,000

Capital Structure and Accumul_4

Capital Structure and Accumulated Other Comprehensive Income (Loss) - Declared Quarterly Cash Dividends (Details)	Feb. 15, 2019$ / shares
Equity [Abstract]
Dividends per Common Share (in dollars per share)	$ 0.0625

Capital Structure and Accumul_5

Capital Structure and Accumulated Other Comprehensive Income (Loss) - Changes in Accumulated Other Comprehensive Loss (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2019USD ($)
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning Balance	$ 1,044,820
Other comprehensive gain (loss) before reclassifications	(1,215)
Amounts reclassified from accumulated other comprehensive loss	250
Ending Balance	1,021,889
Unrealized loss on cash flow hedges
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning Balance	(1,621)
Other comprehensive gain (loss) before reclassifications	(940)
Amounts reclassified from accumulated other comprehensive loss	0
Ending Balance	(2,561)
Foreign currency translation adjustments
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning Balance	(620)
Other comprehensive gain (loss) before reclassifications	(199)
Amounts reclassified from accumulated other comprehensive loss	0
Ending Balance	(819)
Pension and other post-retirement benefits liability
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning Balance	(12,779)
Other comprehensive gain (loss) before reclassifications	(76)
Amounts reclassified from accumulated other comprehensive loss	250
Ending Balance	(12,605)
Total
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning Balance	(15,020)
Ending Balance	$ (15,985)

Business Combinations - Additio

Business Combinations - Additional Information (Details) - EPMH - USD ($) $ in Thousands	May 01, 2018	Mar. 31, 2019	Dec. 31, 2018
Business Acquisition [Line Items]
Consideration paid, net of cash acquired	$ 743,200
Cash acquired	19,100
Net working capital post-closing adjustments	$ 500
Material non-recurring transaction costs attributable to business combination			$ 179,220
Acquisition-related Costs
Business Acquisition [Line Items]
Material non-recurring transaction costs attributable to business combination		$ 15,200

Business Combinations - Purchas

Business Combinations - Purchase Price Allocation (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Dec. 31, 2018
Purchase Price
Goodwill	$ 273,524	$ 261,340
EPMH
Purchase Price
Accounts receivable, net	43,305	43,305
Inventories	86,112	86,112
Property, plant and mine development	146,558	148,495
Mineral rights	408,889	419,469
Identifiable intangible assets - finite lived	8,770	10,270
Identifiable intangible assets - indefinite lived	36,800	38,050
Prepaids and deposits	1,827	2,072
Other assets	7,474	7,474
Goodwill	162,812	150,628
Total assets acquired	902,547	905,875
Accounts payable	13,435	13,435
Accrued expenses and other current liabilities	10,304	10,304
Deferred tax liabilities	119,483	122,811
Other long term liabilities	16,076	16,076
Total liabilities assumed	159,298	162,626
Net assets acquired	743,249	$ 743,249
Measurement Period Adjustments
Accounts receivable, net	0
Inventories	0
Property, plant and mine development	(1,937)
Mineral rights	(10,580)
Identifiable intangible assets - finite lived	(1,500)
Identifiable intangible assets - indefinite lived	(1,250)
Prepaids and deposits	(245)
Other assets	0
Goodwill	12,184
Total assets acquired	(3,328)
Accounts payable	0
Accrued expenses and other current liabilities	0
Deferred tax liabilities	(3,328)
Long term liabilities	0
Total liabilities assumed	(3,328)
Net assets acquired	$ 0

Business Combinations - Intangi

Business Combinations - Intangible Assets Acquired (Details) - EPMH - USD ($) $ in Thousands	May 01, 2018	Mar. 31, 2019	Dec. 31, 2018
Business Acquisition [Line Items]
Identifiable intangible assets - finite lived, Approximate Fair Value		$ 8,770	$ 10,270
Identifiable intangible assets - indefinite lived, Approximate Fair Value		36,800	$ 38,050
Trade names
Business Acquisition [Line Items]
Identifiable intangible assets - indefinite lived, Approximate Fair Value		36,800
Technology and intellectual property
Business Acquisition [Line Items]
Identifiable intangible assets - finite lived, Approximate Fair Value		1,400
Identifiable intangible assets - finite lived, Estimated Useful Life (in years)	15 years
Customer relationships
Business Acquisition [Line Items]
Identifiable intangible assets - finite lived, Approximate Fair Value		$ 7,370
Identifiable intangible assets - finite lived, Estimated Useful Life (in years)	15 years

Business Combinations - Pro For

Business Combinations - Pro Forma Information (Details) - EPMH $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2018USD ($)$ / shares
Business Acquisition [Line Items]
Sales | $	$ 1,659,775
Net income (loss) | $	$ (179,220)
Basic earnings per share (in dollars per share) | $ / shares	$ (2.34)
Diluted earnings per share (in dollars per share) | $ / shares	$ (2.34)

Accounts Receivable (Details)

Accounts Receivable (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Receivables [Abstract]
Trade receivables	$ 241,100	$ 198,435
Less: Allowance for doubtful accounts	(7,437)	(6,751)
Net trade receivables	233,663	191,684
Other receivables	24,685	23,802
Total accounts receivable	258,348	215,486
Refundable alternative minimum tax credits	$ 16,000	$ 16,000

Accounts Receivable - Allowance

Accounts Receivable - Allowance for Doubtful Accounts (Details) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018
Allowance for Doubtful Accounts Receivable Roll Forward
Beginning balance	$ 6,751	$ 7,100	$ 7,100
Bad debt provision	721	237	237
Write-offs	(35)		(87)
Ending balance	$ 7,437	$ 7,250	$ 6,751

Accounts Receivable - Additiona

Accounts Receivable - Additional Information (Details) - Customer Concentration Risk	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Sales | Ten Largest Customers
Concentration Risk [Line Items]
Concentration risk percentage	42.00%	52.00%
Sales | Customer One
Concentration Risk [Line Items]
Concentration risk percentage	12.00%	15.00%
Trade Accounts Receivables | Customer One
Concentration Risk [Line Items]
Concentration risk percentage	16.00%	18.00%

Inventories (Details)

Inventories (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Inventory Disclosure [Abstract]
Supplies	$ 44,479	$ 41,453
Raw materials and work in process	60,910	68,474
Finished goods	37,760	52,160
Total inventories	$ 143,149	$ 162,087

Property, Plant and Mine Deve_3

Property, Plant and Mine Development (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Property, Plant and Equipment
Property, plant and mine development, gross	$ 2,355,160	$ 2,326,126
Accumulated depletion, depreciation and amortization	(535,058)	(499,823)
Total property, plant and mine development, net	1,820,102	1,826,303
Mining property and mine development
Property, Plant and Equipment
Property, plant and mine development, gross	983,517	995,759
Asset retirement cost
Property, Plant and Equipment
Property, plant and mine development, gross	12,727	12,732
Land
Property, Plant and Equipment
Property, plant and mine development, gross	55,502	55,502
Land improvements
Property, Plant and Equipment
Property, plant and mine development, gross	68,992	67,729
Buildings
Property, Plant and Equipment
Property, plant and mine development, gross	65,047	64,515
Machinery and equipment
Property, Plant and Equipment
Property, plant and mine development, gross	1,027,782	958,357
Furniture and fixtures
Property, Plant and Equipment
Property, plant and mine development, gross	3,611	3,599
Construction-in-progress
Property, Plant and Equipment
Property, plant and mine development, gross	$ 137,982	$ 167,933

Property, Plant and Mine Deve_4

Property, Plant and Mine Development - Additional Information (Details) $ in Thousands	Mar. 21, 2018USD ($)transload	Mar. 31, 2019USD ($)	Mar. 31, 2018USD ($)	Dec. 31, 2018USD ($)	Jun. 30, 2018USD ($)
Property, Plant and Equipment
Aggregate cost of machinery and equipment under capital lease		$ 2,355,160		$ 2,326,126
Accumulated depreciation of machinery and equipment under capital lease		535,058		499,823
Gain on sale of transload facilities		(113)	$ 5,799
Consideration received allocated to asset retirement obligations liabilities of transload facilities		0	2,116
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
Liabilities assumed by buyer on sale of transload facilities	2,200
Cash consideration received on sale of transload facilities	83,900
Gain on sale of transload facilities	5,800
Consideration received allocated to asset retirement obligations liabilities of transload facilities	2,100
Equipment note assumed the buyer on sale of transload facilities	100
Consideration allocated to vendor incentives in sale of transload facilities	60,300
Accrued contract termination costs for facilities operated by third parties on sale of transload facilities	7,900
Settlement credit for contract termination costs on facilities operated by third parties on sale of transload facilities					$ 2,700
Permian, Eagle Ford, and Appalachian Basins | Disposal Group, Disposed of by Sale, Not Discontinued Operations | CIG Logistics | Accounts payables and accrued liabilities
Property, Plant and Equipment
Consideration allocated to vendor incentives in sale of transload facilities		12,100
Permian, Eagle Ford, and Appalachian Basins | Disposal Group, Disposed of by Sale, Not Discontinued Operations | CIG Logistics | Other long-term obligations
Property, Plant and Equipment
Consideration allocated to vendor incentives in sale of transload facilities		28,000
Assets under Finance Lease
Property, Plant and Equipment
Aggregate cost of machinery and equipment under capital lease		300		900
Accumulated depreciation of machinery and equipment under capital lease		100		200
Mining property and mine development
Property, Plant and Equipment
Aggregate cost of machinery and equipment under capital lease		983,517		$ 995,759
Interest cost capitalized in property, plant and mine development		$ 1,000	$ 1,800
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
Net book value of transload facilities	$ 20,000

Goodwill and Intangible Asset_2

Goodwill and Intangible Assets - Carrying Amount of Goodwill by Business Segment (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2019USD ($)
Goodwill [Roll Forward]
Balance at December 31, 2018, Goodwill	$ 261,340
Balance at March 31, 2019, Goodwill	273,524
EPMH
Goodwill [Roll Forward]
Balance at December 31, 2018, Goodwill	150,628
EPM acquisition measurement period adjustment	12,184
Balance at March 31, 2019, Goodwill	162,812
Oil & Gas Proppants
Goodwill [Roll Forward]
Balance at December 31, 2018, Goodwill, Gross	250,267
Balance at December 31, 2018, Impairments	(164,167)
Balance at December 31, 2018, Goodwill	86,100
Balance at March 31, 2019, Goodwill, Gross	250,267
Balance at March 31, 2019, Impairments	(164,167)
Balance at March 31, 2019, Goodwill	86,100
Oil & Gas Proppants | EPMH
Goodwill [Roll Forward]
EPM acquisition measurement period adjustment	0
Industrial & Specialty Products
Goodwill [Roll Forward]
Balance at December 31, 2018, Goodwill, Gross	175,240
Balance at December 31, 2018, Impairments	0
Balance at December 31, 2018, Goodwill	175,240
Balance at March 31, 2019, Goodwill, Gross	187,424
Balance at March 31, 2019, Impairments	0
Balance at March 31, 2019, Goodwill	187,424
Industrial & Specialty Products | EPMH
Goodwill [Roll Forward]
EPM acquisition measurement period adjustment	$ 12,184

Goodwill and Intangible Asset_3

Goodwill and Intangible Assets - Changes in the Carrying Amount of Intangible Assets (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Dec. 31, 2018
Finite-Lived Intangible Assets
Gross Carrying Amount	$ 152,156	$ 152,280
Accumulated Amortization	(27,662)	(24,994)
Net	124,494	127,286
Total Intangible Assets
Gross Carrying Amount	218,246	219,620
Accumulated Amortization	(27,662)	(24,994)
Intangible assets, net	190,584	194,626
Trade names
Indefinite-lived Intangible Assets
Gross Carrying Amount	65,390	66,640
Other
Indefinite-lived Intangible Assets
Gross Carrying Amount	$ 700	700
Technology and intellectual property
Finite-Lived Intangible Assets
Estimated Useful Life	15 years
Gross Carrying Amount	$ 83,497	83,616
Accumulated Amortization	(12,610)	(11,168)
Net	70,887	72,448
Total Intangible Assets
Accumulated Amortization	(12,610)	(11,168)
Customer relationships
Finite-Lived Intangible Assets
Gross Carrying Amount	68,659	68,664
Accumulated Amortization	(15,052)	(13,826)
Net	53,607	54,838
Total Intangible Assets
Accumulated Amortization	$ (15,052)	$ (13,826)
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 Asset_4

Goodwill and Intangible Assets - Additional Information (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Acquired Finite-Lived Intangible Assets [Line Items]
Amortization expense	$ 2,700	$ 2,300
EPMH
Acquired Finite-Lived Intangible Assets [Line Items]
Acquired finite-lived intangibles, measurement period adjustment	(1,500)
Identifiable intangible assets - indefinite lived	(1,250)
EPMH | Trade names
Acquired Finite-Lived Intangible Assets [Line Items]
Identifiable intangible assets - indefinite lived	(1,300)
EPMH | Technology and intellectual property
Acquired Finite-Lived Intangible Assets [Line Items]
Acquired finite-lived intangibles, measurement period adjustment	$ (1,500)

Goodwill and Intangible Asset_5

Goodwill and Intangible Assets - Estimated Amortization Expense Related to Definite-Lived Intangible Assets (Details) $ in Thousands	Mar. 31, 2019USD ($)
Goodwill and Intangible Assets Disclosure [Abstract]
2019	$ 8,022
2020	10,696
2021	10,694
2022	10,679
2023	$ 10,674

Debt (Details)

Debt (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Line of Credit Facility
Less: Unamortized original issue discount	$ (6,246)	$ (6,511)
Less: Unamortized debt issuance cost	(29,988)	(31,310)
Finance leases	130	344
Total debt	1,258,354	1,259,755
Less: current portion	(13,112)	(13,327)
Total long-term portion of debt	1,245,242	1,246,428
Note payable secured by royalty interest | Notes Payable, Other Payables
Line of Credit Facility
Total	26,991	26,511
Equipment notes payable | Notes Payable, Other Payables
Line of Credit Facility
Total	267	321
Revolving Line-of-Credit | Revolver
Line of Credit Facility
Total	$ 0	$ 0
Credit facility, interest rate	8.50%	8.50%
Senior Secured Credit Facility | Term loan facility
Line of Credit Facility
Total	$ 1,267,200	$ 1,270,400
Credit facility, interest rate	6.50%
Senior Secured Credit Facility | Term loan facility | Minimum
Line of Credit Facility
Credit facility, interest rate		6.50%

Debt - Additional Information (

Debt - Additional Information (Details)	May 01, 2018USD ($)	Mar. 31, 2019USD ($)	Mar. 31, 2018USD ($)	Aug. 16, 2016USD ($)
Debt Instrument [Line Items]
Write-off of capitalized debt issuance costs		$ 1,322,000	$ 345,000
Revolving Line-of-Credit | Revolver
Debt Instrument [Line Items]
Available borrowing base		100,000,000
Amount drawn from borrowing base		0
Amount available for general corporate use under this revolving credit agreement		95,200,000
Letter of Credit | Revolver
Debt Instrument [Line Items]
Amount allocated for letters of credit		4,800,000
Senior Secured Credit Facility | Revolver
Debt Instrument [Line Items]
Net leverage ratio, credit facility threshold percentage	30.00%
Senior Secured Credit Facility | Term loan facility
Debt Instrument [Line Items]
Credit facility consolidated total net leverage ratio	0.0375
Senior Secured Credit Facility
Debt Instrument [Line Items]
Debt issued	$ 1,380,000,000
Senior Secured Credit Facility | Term loan facility
Debt Instrument [Line Items]
Debt issued	1,280,000,000
Senior Secured Credit Facility | Revolving Line-of-Credit | Revolver
Debt Instrument [Line Items]
Available borrowing base	100,000,000
Capitalized debt issuance costs	$ 38,700,000
Notes Payable, Other Payables | Note payable secured by royalty interest
Debt Instrument [Line Items]
Annual minimum payments		500,000
Debt instrument, fair value		$ 27,000,000		$ 22,500,000
Interest rate, effective percentage		19.00%
Notes Payable, Other Payables | Note payable secured by royalty interest | Measurement Input, Discount Rate
Debt Instrument [Line Items]
Fair value discount rate				0.14

Debt - Contractual Maturities o

Debt - Contractual Maturities of Senior Secured Credit Facility (Details) - Senior Secured Credit Facility - Term loan facility - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Debt Instrument [Line Items]
2019	$ 9,600
2020	12,800
2021	12,800
2022	12,800
2023	12,800
Thereafter	1,206,400
Total	$ 1,267,200	$ 1,270,400

Debt - Contractual Maturities_2

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, 2019USD ($)
Debt Instrument [Line Items]
2019	$ 1,750
2020	1,750
2021	1,750
2022	1,750
2023	$ 1,750

Asset Retirement Obligations (D

Asset Retirement Obligations (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018
Asset Retirement Obligation Disclosure [Abstract]
Other long-term liabilities related to asset retirement obligation	$ 18,800		$ 16,800
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Beginning balance	18,413	$ 19,032
Accretion	373	326
Additions and revisions of prior estimates	0	(486)
Disposal related to sale of transloads	0	(2,116)
Ending balance	$ 18,786	$ 16,756

Derivative Instruments - Estima

Derivative Instruments - Estimated Fair Values of Derivative Instruments (Details) - USD ($)	Mar. 31, 2019	Dec. 31, 2018
Interest rate swap agreement $440 million
Derivative Instruments, Gain (Loss)
Contract/Notional Amount	$ 440,000,000	$ 440,000,000
Carrying Amount	(2,332,000)	(1,475,000)
Fair Value	$ (2,332,000)	$ (1,475,000)
Interest rate swap agreement $440 million | LIBOR
Derivative Instruments, Gain (Loss)
Derivative, basis spread on variable rate (maximum)	2.74%	2.74%
Interest rate swap agreement $200 million
Derivative Instruments, Gain (Loss)
Contract/Notional Amount	$ 200,000,000	$ 200,000,000
Carrying Amount	(1,046,000)	(663,000)
Fair Value	$ (1,046,000)	$ (663,000)
Interest rate swap agreement $200 million | LIBOR
Derivative Instruments, Gain (Loss)
Derivative, basis spread on variable rate (maximum)	2.74%	2.74%
Interest rate cap agreement
Derivative Instruments, Gain (Loss)
Contract/Notional Amount	$ 249,000,000	$ 249,000,000
Carrying Amount	0	0
Fair Value	$ 0	0
Fair Value, Measurements, Recurring | Interest rate cap agreement
Derivative Instruments, Gain (Loss)
Fair Value		$ 0

Derivative Instruments - Additi

Derivative Instruments - Additional Information (Details) - USD ($)	3 Months Ended
	Mar. 31, 2019	Dec. 31, 2018
Interest rate swap agreement $440 million
Derivative [Line Items]
Fair value of derivatives, assets (liabilities)	$ 2,332,000	$ 1,475,000
Ineffective portion of derivative contracts	0
Interest rate swap agreement $440 million | Other long-term obligations | Cash Flow Hedges
Derivative [Line Items]
Fair value of derivatives, assets (liabilities)	2,300,000	1,500,000
Interest rate swap agreement $200 million
Derivative [Line Items]
Fair value of derivatives, assets (liabilities)	1,046,000	663,000
Interest rate swap agreement $200 million | Other long-term obligations | Cash Flow Hedges
Derivative [Line Items]
Fair value of derivatives, assets (liabilities)	1,000,000	700,000
Interest rate cap agreement
Derivative [Line Items]
Fair value of derivatives, assets (liabilities)	$ 0	$ 0

Derivative Instruments - Effect

Derivative Instruments - Effect of Derivatives Instruments on Combined Statements of Operations and Comprehensive Income (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Deferred Losses from Derivatives in OCI [Roll Forward]
Deferred losses from derivatives in OCI, beginning of period	$ (1,621)	$ (76)
Loss recognized in OCI from derivative instruments	(940)	0
Loss reclassified from Accumulated OCI	0	2
Deferred losses from derivatives in OCI, end of period	$ (2,561)	$ (74)

Equity-Based Compensation - Add

Equity-Based Compensation - Additional Information (Details) - USD ($)	3 Months Ended		12 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock options exercised (in shares)	10,000	0
Intrinsic value of stock options exercised	$ 12,000
Proceeds from options exercised	128,000	$ 0
Tax benefit realized for deductions from stock options exercises	3,000
Stock Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Recognized equity-based compensation	0	500,000
Unrecognized compensation expense related to stock options	0
Restricted Stock and Restricted Stock Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Recognized equity-based compensation	$ 2,300,000	$ 1,800,000
Awards share units granted (in shares)	732,860	3,852
Recognized weighted-average period	2 years
Unrecognized compensation expense related to awards	$ 16,400,000
Performance Share Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Recognized equity-based compensation	$ 1,700,000	$ 4,300,000
Awards share units granted (in shares)	607,130		0
Recognized weighted-average period	1 year 6 months
Unrecognized compensation expense related to awards	$ 13,500,000
2011 Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock that may be issued (in shares)	4,119,834

Equity-Based Compensation - Sto

Equity-Based Compensation - Stock Options Activity (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018
Number of Shares
Outstanding at December 31, 2018 (in shares)	901,996
Granted (in shares)	0	0
Exercised (in shares)	(10,000)	0
Forfeited (in shares)	0
Expired (in shares)	(58,463)
Outstanding at March 31, 2019 (in shares)	833,533		901,996
Exercisable at March 31, 2019 (in shares)	833,533
Weighted Average Exercise Price
Outstanding at December 31, 2018 (in dollars per share)	$ 28.52
Granted (in dollars per share)	0
Exercised (in dollars per share)	12.87
Forfeited (in dollars per share)	0
Expired (in dollars per share)	24.42
Outstanding at March 31, 2019 (in dollars per share)	28.99		$ 28.52
Exercisable at March 31, 2019 (in dollars per share)	$ 28.99
Aggregate Intrinsic Value (in thousands)
Outstanding, aggregate intrinsic value	$ 1,061,512		$ 18,566
Exercisable, aggregate intrinsic value	$ 1,061,512
Weighted Average Remaining Contractual Term in Years
Outstanding, weighted average remaining contractual term in years	4 years 10 months 24 days		4 years 9 months 18 days
Exercisable, weighted average remaining contractual term in years	4 years 10 months 24 days

Equity-Based Compensation - Res

Equity-Based Compensation - Restricted Stock and Restricted Stock Units Activity (Details) - Restricted Stock and Restricted Stock Units - $ / shares	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Number of Shares
Unvested, December 31, 2018 (in shares)	587,577
Granted (in shares)	732,860	3,852
Vested (in shares)	(101,601)
Forfeited (in shares)	(9,957)
Unvested, March 31, 2019 (in shares)	1,208,879
Grant Date Weighted Average Fair Value
Unvested, December 31, 2018 (in dollars per share)	$ 25.18
Granted (in dollars per share)	12.89
Vested (in dollars per share)	23.32
Forfeited (in dollars per share)	29.87
Unvested, March 31, 2019 (in dollars per share)	$ 17.85

Equity-Based Compensation - Per

Equity-Based Compensation - Performance Share Unit Activity (Details) - Performance Share Units - $ / shares	3 Months Ended	12 Months Ended
	Mar. 31, 2019	Dec. 31, 2018
Number of Shares
Unvested, December 31, 2018 (in shares)	838,188
Granted (in shares)	607,130	0
Vested (in shares)	(522,098)
Forfeited (in shares)	(11,258)
Unvested, March 31, 2019 (in shares)	911,962	838,188
Weighted Average
Unvested, December 31, 2018 (in dollars per share)	$ 39.44
Granted (in dollars per share)	15.58
Vested (in dollars per share)	37.76
Forfeited (in dollars per share)	41.45
Unvested, March 31, 2019 (in dollars per share)	$ 24.69	$ 39.44

Commitments and Contingencies -

Commitments and Contingencies - Future Minimum Annual Commitments (Details) $ in Thousands	Mar. 31, 2019USD ($)
Minimum Purchase Commitments
2019	$ 17,803
2020	14,464
2021	8,308
2022	5,640
2023	4,915
Thereafter	6,084
Total future purchase commitments	$ 57,214

Commitments and Contingencies_2

Commitments and Contingencies - Additional Information (Details)	May 17, 2017USD ($)	Mar. 31, 2019USD ($)claimshares	Dec. 31, 2018USD ($)shares
Loss Contingencies
Purchased reserves	$ 94,400,000
Surety Bonds
Loss Contingencies
Surety bonds outstanding		$ 41,900,000
Reclamation Bonds
Loss Contingencies
Surety bonds outstanding		30,400,000
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		$ 900,000	$ 1,000,000
Pending Litigation
Loss Contingencies
Number of pending claims | claim		58
Performance Share Units
Loss Contingencies
Awards share units granted (in shares) | shares		607,130	0

Pension and Post-Retirement B_3

Pension and Post-Retirement Benefits - Net Pension and Post-Retirement Benefit Plans (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Pension Benefits
Pension Plans, Postretirement and Other Employee Benefits
Service cost	$ 586	$ 279
Interest cost	2,584	978
Expected return on plan assets	(3,184)	(1,243)
Net amortization and deferral	624	631
Net benefit costs	610	645
Post-retirement Benefits
Pension Plans, Postretirement and Other Employee Benefits
Service cost	24	27
Interest cost	196	188
Net benefit costs	$ 220	$ 215

Pension and Post-Retirement B_4

Pension and Post-Retirement Benefits - Additional Information (Details) $ in Millions	3 Months Ended
	Mar. 31, 2019USD ($)plan	Mar. 31, 2018USD ($)
Pension Plans, Postretirement and Other Employee Benefits
Number of multiemployer defined benefit plans | plan	3
Percentage of contributions to individual multiemployer pension funds	5.00%
Company contributing percentage on defined benefit plan	50.00%
Employee contribution over defined benefit plan	4.00%
Company contributions to qualified pension plans	$ 1.3	$ 0.8
Certain Employees
Pension Plans, Postretirement and Other Employee Benefits
Percentage of contribution over defined benefit plan	4.00%
Some Employees
Pension Plans, Postretirement and Other Employee Benefits
Employee contribution over defined benefit plan	6.00%
Company contribution on profit sharing match	100.00%
Pension Plans
Pension Plans, Postretirement and Other Employee Benefits
Company's contributions to qualified plans	$ 0.7	$ 0.3
Expected contributions to the plans for next fiscal year	4.7
Post-retirement Medical Plan
Pension Plans, Postretirement and Other Employee Benefits
Expected contributions to the plans for next fiscal year	$ 1.4

Leases - Additional Information

Leases - Additional Information (Details)	3 Months Ended
	Mar. 31, 2019
Minimum
Lessee, Lease, Description [Line Items]
Remaining term of lease contracts	1 year
Maximum
Lessee, Lease, Description [Line Items]
Remaining term of lease contracts	20 years

Leases - Supplemental Balance S

Leases - Supplemental Balance Sheet Information (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Leases [Abstract]
Operating lease right-of-use assets	$ 209,699	$ 0
Current portion of operating lease liabilities	61,583	0
Non-current operating lease liabilities	149,040	$ 0
Total lease liabilities	$ 210,623
Operating leases, weighted average remaining lease term (years)	4 years 8 months 12 days
Operating leases, weighted average discount rate	5.60%

Leases - Components of Lease Ex

Leases - Components of Lease Expense (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2019USD ($)
Cost of sales
Lessee, Lease, Description [Line Items]
Operating lease costs	$ 25,115
Short-term operating lease costs	6,600
Selling, general and administrative
Lessee, Lease, Description [Line Items]
Operating lease costs	1,169
Total lease costs	26,284
Short-term operating lease costs	$ 200

Leases - Supplemental Cash Flow

Leases - Supplemental Cash Flow Information (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2019USD ($)
Leases [Abstract]
Cash paid for amounts included in the measurement of lease liabilities, operating leases	$ 2,584
Right-of-use assets obtained in exchange for new lease liabilities, operating leases	$ 223,027

Leases - Maturities of Lease Li

Leases - Maturities of Lease Liabilities (Details) $ in Thousands	Mar. 31, 2019USD ($)
Leases [Abstract]
2019	$ 55,828
2020	60,066
2021	41,065
2022	31,407
2023	22,042
Thereafter	36,024
Total lease payments	246,432
Less: Interest	35,809
Total	$ 210,623

Income Taxes (Details)

Income Taxes (Details) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2017
Operating Loss Carryforwards [Line Items]
Income tax expense, decrease in deferred tax assets due to change in tax rate			$ 45,000
Income tax benefit, decrease in deferred tax liability due to change in tax rate			80,800
Deferred income tax benefit, decrease in tax assets and liabilities due to change in tax rate			$ 35,800
Income tax benefit (expense)	$ 1,972	$ (7,521)
Effective tax rate	9.00%	19.00%
Effective tax rate without the effects of discrete tax items	29.00%	18.00%
ASU 2016-09
Operating Loss Carryforwards [Line Items]
Tax expense related equity compensation	$ 3,900	$ 500

Revenue - Sales by Major Source

Revenue - Sales by Major Source (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Disaggregation of Revenue [Line Items]
Total Sales	$ 378,750	$ 369,313
Oil & Gas Proppants
Disaggregation of Revenue [Line Items]
Total Sales	260,477
Industrial & Specialty Products
Disaggregation of Revenue [Line Items]
Total Sales	118,273
Product
Disaggregation of Revenue [Line Items]
Total Sales	296,860	294,788
Product | Oil & Gas Proppants
Disaggregation of Revenue [Line Items]
Total Sales	178,587
Product | Industrial & Specialty Products
Disaggregation of Revenue [Line Items]
Total Sales	118,273
Service
Disaggregation of Revenue [Line Items]
Total Sales	81,890	$ 74,525
Service | Oil & Gas Proppants
Disaggregation of Revenue [Line Items]
Total Sales	81,890
Service | Industrial & Specialty Products
Disaggregation of Revenue [Line Items]
Total Sales	$ 0

Revenue - Changes in Contract A

Revenue - Changes in Contract Assets and Liabilities (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2019USD ($)
Unbilled Receivables
December 31, 2018	$ 90
Reclassifications to billed receivables	(90)
Revenues recognized in excess of period billings	1,641
March 31, 2019	1,641
Deferred Revenue
December 31, 2018	113,319
Revenues recognized from balances held at the beginning of the period	(6,704)
Revenues deferred from period collections on unfulfilled performance obligations	10,025
Revenues recognized from period collections	(872)
March 31, 2019	$ 115,768

Revenue - Additional Informatio

Revenue - Additional Information (Details)	Mar. 31, 2019
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2019-04-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Remaining duration period of expected satisfaction of performance obligations	1 year

Related Party Transactions (Det

Related Party Transactions (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Related Party Transaction [Line Items]
Related party purchases	$ 0	$ 672
Officer | Transportation Brokerage And Logistics Services Vendor
Related Party Transaction [Line Items]
Related party purchases		$ 900

Segment Reporting - Additional

Segment Reporting - Additional Information (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2019USD ($)SegmentProduct	Dec. 31, 2018USD ($)
Segment Reporting Information
Number of reportable segments | Segment	2
Number of product types | Product	400
Goodwill	$ 273,524	$ 261,340
Oil & Gas Proppants
Segment Reporting Information
Goodwill	86,100	86,100
Industrial & Specialty Products
Segment Reporting Information
Goodwill	187,424	175,240
Operating Segments | Oil & Gas Proppants
Segment Reporting Information
Goodwill	86,100	86,100
Operating Segments | Industrial & Specialty Products
Segment Reporting Information
Goodwill	$ 187,400	$ 175,200

Segment Reporting - Sales and S

Segment Reporting - Sales and Segment Contribution Margin for Reporting Segments and Other Operating Results (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Segment Reporting Information
Total sales	$ 378,750	$ 369,313
Selling, general and administrative	(34,656)	(34,591)
Depreciation, depletion and amortization	(44,600)	(28,592)
Interest expense	(23,978)	(7,070)
Other income, net, including interest income	722	665
Income tax benefit (expense)	1,972	(7,521)
Net (loss) income	(19,328)	31,294
Less: Net income (loss) attributable to non-controlling interest	(4)	0
Net (loss) income attributable to U.S. Silica Holdings, Inc.	(19,324)	31,294
Operating Segments
Segment Reporting Information
Total sales	378,750	369,313
Total segment contribution margin	103,149	119,963
Segment Reconciling Items
Segment Reporting Information
Operating activities excluded from segment cost of sales	(21,937)	(11,560)
Selling, general and administrative	(34,656)	(34,591)
Depreciation, depletion and amortization	(44,600)	(28,592)
Interest expense	(23,978)	(7,070)
Other income, net, including interest income	722	665
Oil & Gas Proppants
Segment Reporting Information
Total sales	260,477
Oil & Gas Proppants | Operating Segments
Segment Reporting Information
Total sales	260,477	312,930
Total segment contribution margin	58,588	99,433
Industrial & Specialty Products
Segment Reporting Information
Total sales	118,273
Industrial & Specialty Products | Operating Segments
Segment Reporting Information
Total sales	118,273	56,383
Total segment contribution margin	$ 44,561	$ 20,530

Subsequent Events (Details)

Subsequent Events (Details) - USD ($) $ / shares in Units, $ in Thousands	Apr. 04, 2019	Mar. 31, 2019	Mar. 31, 2018
Subsequent Event
Cash dividend paid amount		$ 4,610	$ 4,881
Subsequent Event
Subsequent Event
Cash dividend paid amount	$ 4,600
Cash dividend paid per share (in dollars per share)	$ 0.0625