U.S. Silica (SLCA) 10-K 20 Feb 19 2018 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($)	12 Months Ended
	Dec. 31, 2018	Feb. 14, 2019	Jun. 30, 2018
Document And Entity Information [Abstract]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2018
Document Fiscal Year Focus	2,018
Document Fiscal Period Focus	FY
Entity Registrant Name	U.S. Silica Holdings, Inc.
Entity Central Index Key	1,524,741
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	Yes
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Entity Filer Category	Large Accelerated Filer
Entity Emerging Growth Company	false
Entity Small Business	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		73,152,701
Entity Public Float			$ 1,933,539,379

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Current Assets:
Cash and cash equivalents	$ 202,498	$ 384,567
Accounts receivable, net	215,486	212,586
Inventories, net	162,087	92,376
Prepaid expenses and other current assets	17,966	13,715
Income tax deposits	2,200	0
Total current assets	600,237	703,244
Property, plant and mine development, net	1,826,303	1,169,155
Goodwill	261,340	272,079
Intangible assets, net	194,626	150,007
Other assets	18,334	12,798
Total assets	2,900,840	2,307,283
Current Liabilities:
Accounts payable and accrued expenses	216,400	171,041
Current portion of long-term debt	13,327	6,867
Current portion of deferred revenue	31,612	36,128
Income tax payable	0	1,566
Total current liabilities	261,339	215,602
Long-term debt, net	1,246,428	505,075
Deferred revenue	81,707	82,286
Liability for pension and other post-retirement benefits	57,194	52,867
Deferred income taxes, net	137,239	29,856
Other long-term obligations	64,629	25,091
Total liabilities	1,848,536	910,777
Commitments and Contingencies (Note Q)
Stockholders’ Equity:
Preferred stock, $0.01 par value, 10,000,000 shares authorized; zero issued and outstanding at December 31, 2018 and 2017	0	0
Common stock, $0.01 par value, 500,000,000 shares authorized; 81,811,977 issued and 73,148,853 outstanding at December 31, 2018; 81,267,205 issued and 80,524,255 outstanding at December 31, 2017	818	812
Additional paid-in capital	1,169,383	1,147,084
Retained earnings	67,854	287,992
Treasury stock, at cost, 8,663,124 and 742,950 shares at December 31, 2018 and 2017, respectively	(178,215)	(25,456)
Accumulated other comprehensive loss	(15,020)	(13,926)
Total U.S. Silica Holdings, Inc. stockholders’ equity	1,044,820	1,396,506
Non-controlling interest	7,484	0
Total stockholders' equity	1,052,304	1,396,506
Total liabilities and stockholders’ equity	$ 2,900,840	$ 2,307,283

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - $ / shares	Dec. 31, 2018	Dec. 31, 2017
Statement of Financial Position [Abstract]
Preferred stock, par value (in dollars per share)	$ 0.01	$ 0.01
Preferred stock authorized (shares)	10,000,000	10,000,000
Preferred stock issued (shares)	0	0
Preferred stock outstanding (shares)	0	0
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock authorized (shares)	500,000,000	500,000,000
Common stock issued (shares)	81,811,977	81,267,205
Common stock outstanding (shares)	73,148,853	80,524,255
Treasury stock, at cost (shares)	8,663,124	742,950

Consolidated Statements of Oper

Consolidated Statements of Operations - USD ($) shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Sales:
Total sales									$ 1,577,298	$ 1,240,851	$ 559,625
Cost of sales (excluding depreciation, depletion and amortization):
Product	$ 241,624	$ 270,370	$ 236,236	$ 207,239	$ 202,466	$ 187,634	$ 162,238	$ 162,183	955,469	714,521	456,783
Service	45,414	51,966	56,609	53,671	52,126	40,155	34,726	25,292	207,660	152,299	20,027
Total cost of sales (excluding depreciation, depletion and amortization)									1,163,129	866,820	476,810
Operating expenses:
Selling, general and administrative	32,168	37,980	42,232	34,591	29,334	29,542	25,839	22,341	146,971	107,056	67,172
Depreciation, depletion and amortization	46,527	37,150	36,563	28,592	27,335	24,673	23,626	21,599	148,832	97,233	68,134
Goodwill and other asset impairments	265,715	0	16,184	0					281,899	0	0
Total operating expenses	344,410	75,130	94,979	63,183	56,669	54,215	49,465	43,940	577,702	204,289	135,306
Operating income (loss)	(274,068)	25,706	39,609	45,220	49,305	63,019	44,036	13,382	(163,533)	169,742	(52,491)
Other (expense) income:
Interest expense	(21,281)	(21,999)	(20,214)	(7,070)	(7,244)	(8,347)	(8,105)	(7,646)	(70,564)	(31,342)	(27,972)
Other income (expense), net, including interest income	1,336	1,062	1,081	665	1,108	1,308	638	(4,928)	4,144	(1,874)	2,718
Total other expense	(19,945)	(20,937)	(19,133)	(6,405)	(6,136)	(7,039)	(7,467)	(12,574)	(66,420)	(33,216)	(25,254)
Income (loss) before income taxes	(294,013)	4,769	20,476	38,815	43,169	55,980	36,569	808	(229,953)	136,526	(77,745)
Income tax benefit	37,938	1,547	(2,832)	(7,521)	28,783	(14,707)	(7,110)	1,714	29,132	8,680	36,689
Net income (loss)	(256,075)	6,316	17,644	31,294	71,952	41,273	29,459	2,522	(200,821)	145,206	(41,056)
Less: Net income (loss) attributable to non-controlling interest	(13)	0	0	0	0	0	0	0	(13)	0	0
Net income (loss) attributable to U.S. Silica Holdings, Inc.	$ (256,062)	$ 6,316	$ 17,644	$ 31,294	$ 71,952	$ 41,273	$ 29,459	$ 2,522	$ (200,808)	$ 145,206	$ (41,056)
Earnings (loss) per share attributable to U.S. Silica Holdings, Inc.:
Basic (in dollars per share)	$ (3.44)	$ 0.08	$ 0.23	$ 0.39	$ 0.95	$ 0.51	$ 0.36	$ 0.03	$ (2.63)	$ 1.79	$ (0.63)
Diluted (in dollars per share)	$ (3.44)	$ 0.08	$ 0.22	$ 0.39	$ 0.95	$ 0.50	$ 0.36	$ 0.03	$ (2.63)	$ 1.77	$ (0.63)
Weighted average shares outstanding:
Basic (shares)	74,485	77,365	77,784	79,496	75,539	81,121	81,087	80,983	76,453	81,051	65,037
Diluted (shares)									76,453	81,960	65,037
Dividends declared per share (in dollars per share)	$ 0.06	$ 0.06	$ 0.06	$ 0.06	$ 0.06	$ 0.06	$ 0.06	$ 0.06	$ 0.25	$ 0.25	$ 0.25
Product
Sales:
Total sales	$ 293,419	$ 348,635	$ 345,957	$ 294,788	$ 290,114	$ 281,138	$ 235,891	$ 203,251	$ 1,282,799	$ 1,010,394	$ 524,137
Service
Sales:
Total sales	$ 63,961	$ 74,537	$ 81,476	$ 74,525	$ 70,452	$ 63,885	$ 54,574	$ 41,546	$ 294,499	$ 230,457	$ 35,488

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Income (Loss) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Statement of Comprehensive Income [Abstract]
Net income (loss)	$ (200,821)	$ 145,206	$ (41,056)
Other comprehensive income (loss):
Unrealized gain (loss) on derivatives (net of tax of $(470) $(27) and $29 for 2018, 2017, and 2016, respectively)	(1,545)	(44)	49
Foreign currency translation adjustment (net of tax of $(196) $2 and zero for 2018, 2017 and 2016, respectively)	(614)	(6)	0
Unrealized gain (loss) on investments (net of tax of zero, zero, and $(4) for 2018, 2017 and 2016, respectively)	0	0	(6)
Pension and other post-retirement benefits liability adjustment (net of tax of $339, $1,205 and $152 for 2018, 2017 and 2016, respectively)	1,065	2,000	252
Comprehensive income (loss)	(201,915)	147,156	(40,761)
Less: Comprehensive income (loss) attributable to non-controlling interest	(13)	0	0
Comprehensive income (loss) attributable to U.S. Silica Holdings, Inc.	$ (201,902)	$ 147,156	$ (40,761)

Consolidated Statements of Co_2

Consolidated Statements of Comprehensive Income (Loss) (Parenthetical) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Statement of Comprehensive Income [Abstract]
Tax expense (benefit) on unrealized gain (loss) on derivatives	$ (470)	$ (27)	$ 29
Tax expense (benefit) on foreign currency translation adjustment	(196)	2	0
Tax expense (benefit) on unrealized gain (loss) on investments	0	0	(4)
Tax (expense) benefit on pension and other post-retirement benefits liability adjustment	$ 339	$ 1,205	$ 152

Consolidated Statements of Stoc

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, 2015	$ 384,167	$ 384,167	$ 539	$ (15,845)	$ 194,670	$ 220,974	$ (16,171)	$ 0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	(41,056)	(41,056)				(41,056)
Issuance of common stock (stock offerings net of issuance costs of $25,732)	931,288	931,288	272		931,016
Unrealized gain (loss) on derivatives (net of tax)	49	49					49
Foreign currency translation adjustment (net of tax)	0
Unrealized loss on short-term investments (net of tax)	(6)	(6)					(6)
Pension and post-retirement liability	252	252					252
Cash dividend declared ($0.25 per share for 2018, 2017 and 2016, respectively)	(16,893)	(16,893)				(16,893)
Equity-based compensation	12,107	12,107			12,107
Excess tax benefit from equity-based compensation	148	148				148
Proceeds from options exercised	4,825	4,825		8,465	(3,640)
Issuance of restricted stock	0			1,437	(1,437)
Shares withheld for tax payments related to vested restricted stock and stock units	(1,591)	(1,591)		2,074	(3,665)
Ending Balance at Dec. 31, 2016	1,273,290	1,273,290	811	(3,869)	1,129,051	163,173	(15,876)	0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	145,206	145,206				145,206
Unrealized gain (loss) on derivatives (net of tax)	(44)	(44)					(44)
Foreign currency translation adjustment (net of tax)	(6)	(6)					(6)
Unrealized loss on short-term investments (net of tax)	0
Pension and post-retirement liability	2,000	2,000					2,000
Cash dividend declared ($0.25 per share for 2018, 2017 and 2016, respectively)	(20,387)	(20,387)				(20,387)
Equity-based compensation	25,050	25,050			25,050
Proceeds from options exercised	798	798		1,190	(392)
Issuance of restricted stock	0			1,859	(1,859)
Shares withheld for tax payments related to vested restricted stock and stock units	(4,379)	(4,379)	1	386	(4,766)
Repurchase of common stock	(25,022)	(25,022)		(25,022)
Ending 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 income (loss)	(200,821)	(200,808)				(200,808)		(13)
Unrealized gain (loss) on derivatives (net of tax)	(1,545)	(1,545)					(1,545)
Foreign currency translation adjustment (net of tax)	(614)	(614)					(614)
Unrealized loss on short-term investments (net of tax)	0
Pension and post-retirement liability	1,065	1,065					1,065
Cash dividend declared ($0.25 per share for 2018, 2017 and 2016, respectively)	(19,330)	(19,330)				(19,330)
Contributions from non-controlling interest	7,497							7,497
Equity-based compensation	22,337	22,337			22,337
Proceeds from options exercised	61	61		93	(32)
Shares withheld for tax payments related to vested restricted stock and stock units	(4,383)	(4,383)	6	(4,383)	(6)
Repurchase of common stock	(148,469)	(148,469)		(148,469)
Ending Balance at Dec. 31, 2018	$ 1,052,304	$ 1,044,820	$ 818	$ (178,215)	$ 1,169,383	$ 67,854	$ (15,020)	$ 7,484

Consolidated Statements of St_2

Consolidated Statements of Stockholders' Equity (Parenthetical) - USD ($)	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Statement of Stockholders' Equity [Abstract]
Common stocks issuance costs											$ 25,732
Cash dividend declared (in dollars per share)	$ 0.06	$ 0.06	$ 0.06	$ 0.06	$ 0.06	$ 0.06	$ 0.06	$ 0.06	$ 0.25	$ 0.25	$ 0.25

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Operating activities:
Net income (loss)	$ (200,821)	$ 145,206	$ (41,056)
Adjustments to reconcile net income (loss) to net cash provided by operating activities:
Depreciation, depletion and amortization	148,832	97,233	68,134
Goodwill and other asset impairments	281,899	0	0
Debt issuance amortization	4,044	1,382	1,392
Original issue discount amortization	832	372	378
Deferred income taxes	(31,070)	(20,601)	(36,903)
Deferred revenue	(36,720)	28,438	(9,026)
(Gain) loss on disposal of property, plant and equipment	(5,170)	415	563
Equity-based compensation	22,337	25,050	12,107
Bad debt provision, net of recoveries	315	1,529	(1,232)
Other	(13,536)	13,929	5,300
Changes in operating assets and liabilities, net of effects of acquisitions:
Accounts receivable	56,815	(110,920)	(12,996)
Inventories	13,085	(4,825)	(10,211)
Prepaid expenses and other current assets	(2,678)	8,787	(509)
Income taxes	(3,764)	1,469	11,558
Accounts payable and accrued expenses	26,907	43,654	13,232
Short-term and long-term obligations-vendor incentives	52,806	0	0
Liability for pension and other post-retirement benefits	4,608	(705)	1,307
Other noncurrent assets and liabilities	(8,015)	(8,400)	(1,657)
Net cash provided by operating activities	310,706	222,013	381
Investing activities:
Capital expenditures	(339,815)	(368,479)	(46,450)
Capitalized intellectual property costs	(10,046)	(3,586)	(959)
Maturities of short-term investments	0	0	21,872
Acquisition of businesses, net of cash acquired	(743,249)	(119,801)	(176,617)
Proceeds from sale of property, plant and equipment	26,231	337	497
Net cash used in investing activities	(1,066,879)	(491,529)	(201,657)
Financing activities:
Issuance of common stock	0	0	678,791
Common stock issuance costs	0	0	(25,732)
Dividends paid	(19,912)	(20,377)	(15,125)
Repurchase of common stock	(148,469)	(25,022)	0
Proceeds from options exercised	61	798	4,825
Tax payments related to shares withheld for vested restricted stock and stock units	(4,383)	(4,379)	(1,591)
Proceeds from long-term debt	1,280,000	0	0
Payments on long-term debt	(501,425)	(7,211)	(5,202)
Financing fees paid	(38,701)	0	0
Contributions from non-controlling interest	7,497	0	0
Principal payments on capital lease obligations	(564)	(951)	(542)
Net cash provided by (used in) financing activities	574,104	(57,142)	635,424
Net (decrease) increase in cash and cash equivalents	(182,069)	(326,658)	434,148
Cash and cash equivalents, beginning of period	384,567	711,225	277,077
Cash and cash equivalents, end of period	202,498	384,567	711,225
Cash paid (received) during the period for:
Interest	66,769	24,490	21,994
Taxes, net of refunds	5,373	8,958	(11,322)
Related party purchases	2,958	4,942	446
Non-cash Items:
Common stock issued in connection with acquisitions	0	0	278,229
Capital lease obligations incurred to acquire assets	0	0	165
Equipment received	0	18,185	0
Accrued capital expenditures	36,008	16,534	391
Capital lease assumed by third-party	119	0	0
Asset retirement obligation assumed by third-party	$ 2,116	$ 0	$ 0

Organization

Organization	12 Months Ended
	Dec. 31, 2018
Organization, Consolidation and Presentation of Financial Statements [Abstract]
ORGANIZATION	NOTE A—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. We manufacture frac sand used to stimulate and maintain the flow of hydrocarbons in oil and natural gas wells. Our products are also used as a raw material in a wide range of industrial applications. 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 W - Segment Reporting for more information on our reportable segments. 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 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 perlite. EPM's industrial minerals are used as filter aids, absorbents and functional additives for a variety of industries including food and beverage, biofuels, recreational water, oil and gas, farm and home, landscape, sports turf, paint, plastics, and insecticides. The acquisition of EPM increased our industrial materials product offering in our Industrial & Specialty Products segment. On August 16, 2017, we completed the acquisition of Mississippi Sand, LLC ("MS Sand"). MS Sand is a frac sand mining and logistics company based in St. Louis, Missouri. On April 1, 2017, we completed the acquisition of White Armor, a product line of cool roof granules used in industrial roofing applications. On August 22, 2016, we completed the acquisition of Sandbox Enterprises, LLC ("Sandbox") as a “last mile” logistics solution for frac sand in the oil and gas industry. On August 16, 2016, we completed the acquisition of New Birmingham, Inc. (“NBI”), the ultimate parent company of NBR Sand, LLC (“NBR”), a regional sand producer located near Tyler, Texas. The acquisition of NBI increased our regional frac sand product offering in our Oil & Gas Proppants segment. See Note E - Business Combinations for more information.

Summary of Significant Accounti

Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2018
Accounting Policies [Abstract]
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES	NOTE B—SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES Basis of Presentation and Consolidation The accompanying Consolidated Financial Statements have been prepared in accordance with generally accepted accounting principles in the United States (“GAAP”). In the opinion of management, all adjustments necessary for a fair presentation of the Consolidated Financial Statements have been included. Such adjustments are of a normal, recurring nature. Certain reclassifications of prior year's amounts have been made to conform to the current year presentation. In conforming to the current year's presentation, the Company identified and corrected an amount in its statement of cash flows for the year ended December 31, 2017 . The correction reduced Capital Expenditures within Net Cash Used in Investing Activities with a corresponding decrease to Accounts Payable and Accrued Expenses within Net Cash Used in Operating Activities. The amount is presented as Non-cash Accrued Capital Expenditures and had no impact in the Company's Balance Sheet, Income Statement or Net Change in Cash and Cash Equivalents in the Statement of Cash Flows. Throughout this report we refer to (i) our Consolidated Balance Sheets as our “Balance Sheets,” (ii) our Consolidated Statements of Operations as our “Income Statements,” and (iii) our Consolidated Statements of Cash Flows as our “Cash Flows.” Consolidation The 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 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 $12.0 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 . 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. Cash and Cash Equivalents Cash and cash equivalents consist of all highly liquid investments with a maturity of three months or less when purchased. Because of the short maturity of these investments, the carrying amounts approximate their fair value. Cash and cash equivalents are invested primarily in money market securities held by financial institutions with high credit ratings. Accounts at each institution are insured by the Federal Deposit Insurance Corporation. Cash balances at times may exceed federally-insured limits. We have not experienced any losses in such accounts and believe we are not exposed to any significant credit risk on cash. Accounts Receivable The majority of our accounts receivable are due from companies in the oil and natural gas drilling, glass, building products, filler and extenders, foundries and other major industries. Credit is extended based on evaluation of a customer’s financial condition and, generally, collateral is not required. Accounts receivable are stated at amounts due from customers net of an allowance for doubtful accounts. Accounts outstanding longer than the payment terms are considered past due. We determine our allowance by considering a number of factors, including the length of time trade accounts receivable are past due, our previous loss history, the customer’s current ability to pay its obligation to us, and the condition of the general economy and the industry as a whole. Ongoing credit evaluations are performed. We write-off accounts receivable when they are deemed uncollectible, and payments subsequently received on such receivables are credited to the allowance for doubtful accounts. See Note F - Accounts Receivable and Note U - Revenue . Inventories Inventories include raw stockpiles, in-process product and finished product available for shipment, as well as spare parts and supplies for routine facility maintenance. We value inventory at the lower of cost and net realizable value. Cost is determined using the first-in, first-out and average cost methods. Our inventoriable costs include production costs and transportation and additional service costs as applicable. See Note G - Inventories . Property, Plant and Mine Development Plant and equipment Plant and equipment is recorded at cost and depreciated over their estimated useful lives. Interest incurred during construction of facilities is capitalized and depreciated over the life of the asset. Costs for normal repairs and maintenance that do not extend economic life or improve service potential are expensed as incurred. Costs of improvements that extend economic life or improve service potential are capitalized and depreciated over the estimated remaining useful life. Depreciation is recorded using the straight-line method over the assets’ estimated useful lives as follows: buildings ( 15 years); land improvements ( 10 years); machinery and equipment, including computer equipment and software ( 3 - 10 years); furniture and fixtures ( 8 years). Leasehold improvements are depreciated over the shorter of the asset life or lease term. Construction-in-progress is primarily comprised of machinery and equipment which have not yet been placed in service. Mining property and development Mining property and development includes mineral deposits and mine exploration and development. Mineral deposits are initially recognized at cost, which approximates the estimated fair value on the date of purchase. Mine exploration and development costs include engineering and mineral studies, drilling and other related costs to delineate an ore body, and the removal of overburden to initially expose an ore body for production. Costs incurred before mineralization are classified as proven and probable reserves are expensed and classified as exploration or advanced projects, research and development expense. Capitalization of mine development project costs, that meet the definition of an asset, begins once mineralization is classified as proven and probable reserves. The cost of removing overburden and waste materials to access the ore body at an open pit mine prior to the production phase are referred to as “pre-stripping costs.” Pre-stripping costs are capitalized during the development of an open pit mine. The production phase of an open pit mine commences when saleable minerals, beyond a de minimis amount, are produced. Stripping costs incurred during the production phase of a mine are variable production costs that are included as a component of inventory to be recognized in costs applicable to sales in the same period as the revenue from the sale of inventory. Depletion and amortization of mineral deposits and mine development costs are recorded as the minerals are extracted, based on units of production and engineering estimates of mineable reserves. The impact of revisions to reserve estimates is recognized on a prospective basis. See Note H - Property, Plant and Mine Development . Mine reclamation costs and asset retirement obligations We recognize the fair value of any liability for conditional asset retirement obligations, including environmental remediation liabilities when incurred, which is generally upon acquisition, construction or development and/or through the normal operation of the asset, if sufficient information exists to reasonably estimate the fair value of the liability. These obligations generally include the estimated net future costs of dismantling, restoring and reclaiming operating mines and related mine sites, in accordance with federal, state, local regulatory and land lease agreement requirements. The liability is accreted over time through periodic charges to earnings. In addition, the asset retirement cost is capitalized as part of the asset’s carrying value and amortized over the life of the related asset. Reclamation costs are periodically adjusted to reflect changes in the estimated present value resulting from the passage of time and revisions to the estimates of either the timing or amount of the reclamation and abandonment costs. The reclamation obligation is based on when spending for an existing environmental disturbance will occur. If the asset retirement obligation is settled for other than the carrying amount of the liability, a gain or loss is recognized on settlement. We review, on an annual basis, unless otherwise deemed necessary, the reclamation obligation at each mine site in accordance with ASC guidance for accounting for reclamation obligations. Future remediation costs for inactive mines are accrued based on management’s best estimate at the end of each period of the costs expected to be incurred at a site. Such cost estimates include, where applicable, ongoing care, maintenance and monitoring costs. Changes in estimates at inactive mines are reflected in earnings in the period an estimate is revised. See Note M - Asset Retirement Obligations . Impairment or Disposal of Property, Plant and Mine Development We periodically evaluate whether current events or circumstances indicate that the carrying value of our property, plant and equipment assets may not be recoverable. If circumstances indicate that the carrying value may not be recoverable, we estimate future undiscounted net cash flows using estimates of proven and probable sand reserves, estimated future sales prices (considering historical and current prices, price trends and related factors) and operating costs and anticipated capital expenditures. If the undiscounted cash flows are less than the carrying value of the assets, we recognize an impairment loss equal to the amount by which the carrying value exceeds the fair value of the assets. The recoverability of the carrying value of our mineral properties is dependent upon the successful development, start-up and commercial production of our mineral deposit and the related processing facilities. Our evaluation of mineral properties for potential impairment primarily includes assessing the existence or availability of required permits and evaluating changes in our mineral reserves, or the underlying estimates and assumptions, including estimated production costs. Assessing the economic feasibility requires certain estimates, including the prices of products to be produced and processing recovery rates, as well as operating and capital costs. Gains on the sale of property, plant and mine development are included in income when the assets are disposed of provided there is more than reasonable certainty of the collectability of the sales price and any future activities required to be performed by us relating to the disposal of the assets are complete or insignificant. Upon retirement or disposal of assets, all costs and related accumulated depreciation or amortization are written-off. Goodwill and Other Intangible Assets and Related Impairment Our intangible assets consist of goodwill, which is not being amortized, indefinite-lived intangibles, which consist of certain trade names that are not subject to amortization, intellectual property and customer relationships. Intellectual property mainly consists of patents and technology, and it is amortized on a straight-line basis over an average useful life of 15 years. Customer relationships are amortized on a straight-line basis over their useful life of 20 , 15 or 13 years. Goodwill represents the excess of the purchase price of business combinations over the fair value of net assets acquired. Goodwill and trade names are reviewed for impairment annually as of October 31, or more frequently when indicators of impairment exist. An impairment exists if the fair value of a reporting unit to which goodwill has been allocated, or the fair value of indefinite-lived intangible assets, is less than their respective carrying values. Prior to conducting a formal impairment test, we have an option to assess qualitative factors to determine whether the existence of events or circumstances leads to a determination that is more likely than not (more than 50% ) that the fair value of a reporting unit is less than its carrying amount. Such qualitative factors may include the following: macroeconomic conditions; industry and market considerations; cost factors; overall financial performance; and other relevant entity-specific events. If the qualitative assessment determines that an impairment is more likely than not, or if we choose to bypass the qualitative assessment, we perform a quantitative assessment by comparing the fair value of a reporting unit with its carrying amount and recognize an impairment charge for the amount by which the carrying amount exceeds the reporting unit’s fair value; however, the loss recognized should not exceed the total amount of goodwill allocated to that reporting unit. See Note I - Goodwill and Intangible Assets . Revenue Recognition Products We derive our product sales by mining and processing minerals that our customers purchase for various uses. Our product sales are primarily a function of the price per ton and the number of tons sold. We primarily sell our products through individual purchase orders executed under short-term price agreements or at prevailing market rates. The amount invoiced reflects product, transportation and / or additional handling services as applicable, such as storage, transloading the product from railcars to trucks and last mile logistics to the customer site. We invoice most of our product customers on a per shipment basis, although for some larger customers, we consolidate invoices weekly or monthly. Standard collection terms are net 30 days, although extended terms are offered in competitive situations. We recognize revenue for products and materials at a point in time following the transfer of control of such items to the customer, which typically occurs upon shipment or delivery depending on the terms of the underlying contracts. We account for shipping and handling activities related to product and material sales contracts with customers as costs to fulfill our promise to transfer the associated products pursuant to the accounting policy election allowed under ASC 606-10-25-18b. Accordingly, we record amounts billed for shipping and handling costs as a component of net sales and accrue and classify related costs as a component of cost of sales at the time revenue is recognized. For a limited number of customers, we sell under long-term, minimum purchase supply agreements. These agreements define, among other commitments, the volume of product that our customers must purchase, the volume of product that we must provide and the price that we will charge and that our customers will pay for each product. Prices under these agreements are generally fixed and subject to certain contractual adjustments. Sometimes these agreements may undergo negotiations regarding pricing and volume requirements, which may often occur in volatile market conditions. While these negotiations continue, we may deliver sand at prices or at volumes below the requirements in our existing supply agreements. We do not consider these agreements solely representative of contracts with customers. An executed order specifying the type and quantity of product to be delivered, in combination with the noted agreements, comprise our contracts in these arrangements. Service We derive our service revenues primarily through the provision of transportation, equipment rental, and contract labor services to companies in the oil and gas industry. Transportation services typically consist of transporting customer proppant from storage facilities to proximal well-sites and are contracted through work orders executed under established pricing agreements. The amount invoiced reflects the transportation services rendered. Equipment rental services provide customers with use of either dedicated or nonspecific wellhead proppant delivery equipment solutions for contractual periods defined either through formal lease agreements or executed work orders under established pricing agreements. The amounts invoiced reflect the length of time the equipment set was utilized in the billing period. Contract labor services provide customers with proppant delivery equipment operators through work orders executed under established pricing agreements. The amounts invoiced reflect the amount of time our labor services were utilized in the billing period. We typically invoice our customers on a weekly or monthly basis; however, some customers receive invoices upon well-site operation completion. Standard collection terms are net 30 days, although extended terms are offered in competitive situations. We typically recognize revenue for specific, dedicated equipment set rental arrangements under ASC 840, Leases. For the remaining components of service revenue, we have applied the practical expedient allowed under ASC 606-10-55-18 to recognize transportation revenues in proportion to the amount we have the right to invoice. Contracts with Multiple Performance Obligations For contracts that contain multiple performance obligations, such as work orders containing a combination of product, transportation, equipment rentals, and contract labor services, we allocate the transaction price to each performance obligation identified in the contract based on relative standalone selling prices, or estimates of such prices, and recognize the related revenue as control of each individual product or service is transferred to the customer, in satisfaction of the corresponding performance obligations. We typically invoice our customers on a weekly or monthly basis; however, some customers receive invoices upon well-site operation completion. Standard collection terms are net 30 days, although extended terms are offered in competitive situations. Taxes Collected from Customers and Remitted to Governmental Authorities. We exclude from our measurement of transaction prices all taxes assessed by governmental authorities that are both (i) imposed on and concurrent with a specific revenue-producing transaction and (ii) collected from customers. Accordingly, such tax amounts are not included as a component of net sales or cost of sales. Foreign Operations Foreign operations constituted approximately $44.0 million of our consolidated sales; $7.3 million of consolidated assets; $2.6 million of pre-tax income and $2.4 million of net income as of and for the year ended December 31, 2018. We had no significant foreign operations during the years ended December 31, 2017 and 2016. See Note U - Revenue . Deferred Revenues For a limited number of customers, we enter into supply agreements which give customers the right to make advanced payments toward the purchase of certain products at specified volumes over an average initial period of one to fifteen years. These payments represent consideration that is unconditional for which we have yet to transfer the related product. These payments are recorded as contract liabilities referred to as “deferred revenues” upon receipt and recognized as revenue upon delivery of the related product. Unbilled Receivables Revenues recognized in advance of invoice issuance create assets referred to as “unbilled receivables.” Any portion of our unbilled receivables for which our right to consideration is conditional on a factor other than the passage of time is considered a contract asset. These assets are presented on a combined basis with accounts receivable and are converted to accounts receivable once billed. Debt Issuance Costs The Company defers costs directly associated with acquiring third-party financing, primarily loan origination costs and related professional expenses. Debt issuance costs are deferred and amortized using the effective interest rate method over the term of our senior secured Term Loan facility and the straight-line method for our Revolver facility. Debt issuance costs related to long-term debt are reflected as a direct deduction from the carrying amount of the debt. Amortization included in interest expense was $4.0 million for the year ended December 31, 2018 , and $1.4 million for each of the years ended December 31, 2017 and 2016 . See Note K - Debt . Employee Benefit Plans We provide a range of benefits to our employees and retired employees, including pensions and post-retirement healthcare and life insurance benefits. We record annual amounts relating to these plans based on calculations specified by generally accepted accounting principles, which include various actuarial assumptions, including discount rates, assumed rates of returns, compensation increases, turnover rates, mortality table, and healthcare cost trend rates. We review the actuarial assumptions on an annual basis and make modifications to the assumptions based on current rates and trends when it is deemed appropriate to do so. As required by U.S. generally accepted accounting principles, the effect of the modifications is generally recorded or amortized over future periods. We believe that the assumptions utilized in recording our obligations under the plans are reasonable based on advice from our actuaries and information as to assumptions used by other employers. See Note R - Pension and Post-Retirement Benefits . Environmental Costs Environmental costs, other than qualifying capital expenditures, are accrued at the time the exposure becomes known and costs can be reasonably estimated. Costs are accrued based upon management’s estimates of all direct costs, after taking into account expected reimbursement by third parties (primarily the sellers of acquired businesses) and are reviewed by outside consultants. Environmental costs are charged to expense unless a settlement with an indemnifying party has been reached. Self-Insurance We are self-insured for various levels of employee health insurance coverage, workers’ compensation and third-party product liability claims alleging occupational disease. We purchase insurance coverage for claim amounts which exceed our self-insured retentions. Depending on the type of insurance, these self-insured retentions range from $0.1 million to $0.5 million per occurrence. Our insurance reserves are accrued based on estimates of the ultimate cost of claims expected to occur during the covered period. Our insurance reserves are accrued based on estimates of the ultimate cost of claims expected to occur during the covered period. These estimates are prepared with the assistance of outside actuaries and consultants. Our actuaries periodically review the volume and amount of claims activity, and based upon their findings, we adjust our insurance reserves accordingly. The ultimate cost of claims for a covered period may differ from our original estimates. The current portion of our self-insurance reserves is included in accrued liabilities and the non-current portion is included in other long-term obligations in our Balance Sheets. As of December 31, 2018 and 2017 , our self-insurance reserves totaled $5.4 million and $5.5 million , respectively, of which $2.6 million and $1.7 million , respectively, was classified as current. Research and Development Costs We may incur immaterial internal research and development (“R&D”) expenditures, and research and development conducted for others, all of which are expensed as incurred, and included in selling, general and administrative expense. R&D costs may include, but are not limited to, research and administrative salaries, contractor fees, building costs, utilities, administrative expenses, and allocations of corporate costs. Advertising Costs We recognize advertising expense when incurred as selling, general and administrative expense. Equity-based Compensation We grant stock options, restricted stock, restricted stock units and performance share units to certain of our employees and directors under the Amended and Restated U.S. Silica Holdings, Inc. 2011 Incentive Compensation Plan. We recognize the cost of employee services rendered in exchange for awards of equity instruments. Vesting of restricted stock and restricted stock units is based on the individual continuing to render service over a pre-defined vesting schedule, generally three years. Cash dividend equivalents are accrued and paid to the holders of time-based restricted stock units and restricted stock. The fair value of the restricted stock awards is equal to the market price of our stock at date of grant. The restricted award-related compensation expense is recognized, on a straight-line basis, over the vesting period. We grant performance share units to certain employees in which the number of shares of common stock ultimately received is determined based on achievement of certain performance thresholds over a specified performance period (generally three years) in accordance with the stock award agreement. Cash dividend equivalents are not accrued or paid on performance share units. We recognize expense based on the estimated vesting of our performance share units granted and the grant date market price. The estimated vesting of the performance share units is principally based on the probability of achieving certain financial performance levels during the vesting periods. In the period it becomes probable that the minimum performance criteria specified in the award agreement will be achieved, we recognize expense for the proportionate share of the total fair value of the award related to the vesting period that has already lapsed. The remaining fair value of the award is expensed on a straight-line basis over the remaining vesting period. We grant certain employees performance share units, the vesting of which is based on the Company’s total shareholder return (“TSR”) ranking among a peer group over a three -year period. The number of units that will vest will depend on the percentage ranking of the Company's TSR compared to the TSRs for each of the companies in the peer group over the performance period. For these awards subject to market conditions, a binomial-lattice model (i.e., Monte Carlo simulation model) is used to fair value these awards at grant date. The related compensation expense is recognized, on a straight-line basis, over the vesting period. We grant stock options to certain employees and directors. Stock options vest on a vesting schedule and the related compensation expense is recognized over the vesting period, usually over 3 or 4 years. In calculating the compensation expense for stock options granted, we estimate the fair value of each grant using the Black-Scholes option-pricing model. The fair value of stock options granted is based on the exercise price of the option and certain assumptions, which are evaluated and revised, as necessary, to reflect market conditions and experience. Our expected forfeiture rate is the estimated percentage of options granted that are expected to be forfeited or canceled on an annual basis before becoming fully vested. Our expected term is the period of time over which the options are expected to remain outstanding. An increase in the expected term will increase compensation expense. The computation of the expected term is based on the simplified method, under which the expected term is presumed to be the mid-point between the average vesting date and the end of the contractual term. The assumptions for expected volatility are based on historical experience for the same periods as our expected lives. Risk-free interest rates are set using grant-date U.S. Treasury yield curves for the same periods as our expected lives. The expected dividend yield is based on our future dividend expectations for the same periods as our expected lives. See Note P - Equity-based Compensation . 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. In August 2018, the Internal Revenue Service released Tax Act guidance on limitations on executive compensation which clarified transition rules for certain compensation agreements in existence on November 2, 2017. Based on the issued guidance, we recorded a discrete tax expense of $0.7 million to remove deferred tax assets on certain executive compensation agreements that were not eligible for transition relief. The Tax Act reduces the corporate tax rate to 21 percent, effective January 1, 2018. Because ASC 740-10-25-47 requires the effect of a change in tax laws or rates to be recognized as of the date of enactment, we were required to adjust deferred tax assets and liabilities as of December 22, 2017. Accordingly, for the year ended December 31, 2017, we recorded a decrease related to deferred tax assets and liabilities of $45.0 million and $80.8 million , respectively, with a corresponding net adjustment to deferred income tax benefit of $35.8 million . Under the Tax Act, net operating loss (NOL) deductions arising in tax years beginning after December 31, 2017 can only offset up to 80 percent of future taxable income. The Act also prohibits NOL carrybacks, but allows indef

Earnings Per Share

Earnings Per Share	12 Months Ended
	Dec. 31, 2018
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. The following table shows the computation of basic and diluted earnings per share for the years ended December 31, 2018 , 2017 and 2016 : In thousands, except per share amounts Year ended December 31, 2018 2017 2016 Numerator: Net income (loss) attributable to U.S. Silica Holdings, Inc. $ (200,808 ) $ 145,206 $ (41,056 ) Denominator: Weighted average shares outstanding 76,453 81,051 65,037 Diluted effect of stock awards — 909 — Weighted average shares outstanding assuming dilution 76,453 81,960 65,037 Earnings (loss) per share attributable to U.S. Silica Holdings, Inc.: Basic earnings (loss) per share $ (2.63 ) $ 1.79 $ (0.63 ) Diluted earnings (loss) per share $ (2.63 ) $ 1.77 $ (0.63 ) Potentially dilutive shares of 443 and 732 for the year ended December 31, 2018 and 2016, respectively, were excluded from the calculation of diluted weighted average shares outstanding and diluted earnings per share because we were in a 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: Year ended December 31, 2018 2017 2016 Stock options excluded 574 195 573 Restricted stock and performance share units awards excluded 155 305 166

Capital Structure and Accumulat

Capital Structure and Accumulated Other Comprehensive Income (Loss)	12 Months Ended
	Dec. 31, 2018
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 81,811,977 shares issued and 73,148,853 shares outstanding at December 31, 2018 . There were 81,267,205 shares issued and 80,524,255 shares outstanding at December 31, 2017 . During the year ended December 31, 2018 , our Board of Directors declared quarterly cash dividends as follows: Dividends per Common Share Declaration Date Record Date Payable Date $ 0.0625 February 16, 2018 March 15, 2018 April 5, 2018 $ 0.0625 May 14, 2018 June 15, 2018 July 6, 2018 $ 0.0625 July 16, 2018 September 14, 2018 October 3, 2018 $ 0.0625 November 13, 2018 December 14, 2018 January 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 December 31, 2018 or December 31, 2017 . At present, we have no plans to issue any preferred stock. Share Repurchase Program We are authorized by our Board of Directors to repurchase shares of our outstanding common stock from time to time on the open market or in privately negotiated transactions. 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 December 31, 2018 , 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. In October 2017, our Board of Directors authorized us to repurchase up to $100 million of our common stock by December 11, 2018. As of March 31, 2018, we had repurchased a total of 3,555,104 shares of our common stock at an average price of $28.13 , and fully utilized our shares authorized to be repurchased at such time. Our Board of Directors previously had authorized the repurchase of up to $50.0 million of our common stock. This program expired on December 11, 2017. We repurchased a total of 706,093 shares of our common stock at an average price of $23.83 under this program. Accumulated Other Comprehensive Loss Accumulated other comprehensive loss consists of fair value adjustments associated with cash flow hedges, accumulated adjustments for net experience losses and prior service cost related to employee benefit plans and foreign currency translation adjustments, net of tax. The following table presents the changes in accumulated other comprehensive loss by component (in thousands) during the year ended December 31, 2018 : For the Year Ended December 31, 2018 Unrealized gain/(loss) on cash flow hedges Foreign currency translation adjustments Pension and other post-retirement benefits liability Total Beginning Balance $ (76 ) $ (6 ) $ (13,844 ) $ (13,926 ) Other comprehensive gain (loss) before reclassifications (1,622 ) (614 ) (879 ) (3,115 ) Amounts reclassed from accumulated other comprehensive loss 77 — 1,944 2,021 Ending Balance $ (1,621 ) $ (620 ) $ (12,779 ) $ (15,020 ) Amounts reclassified from accumulated other comprehensive loss related to cash flow hedges are included in interest expense in our Income Statements and amounts reclassified related to pension and other post-retirement benefits are included in the computation of net periodic benefit costs at their pre-tax amounts.

Business Combinations

Business Combinations	12 Months Ended
	Dec. 31, 2018
Business Combinations [Abstract]
BUSINESS COMBINATIONS	NOTE E—BUSINESS COMBINATIONS Goodwill Goodwill represents the excess of the purchase price over the fair value of the underlying net assets acquired. Trade Names A trade name is a legally protected trade or similar mark. Acquired trade names are valued using an income method approach, generally the relief-from-royalty valuation method. The method uses a royalty rate based on comparable marketplace royalty agreements for similar types of trade names and applies it to the after-tax discounted free cash flow attributed to the trade name. The discount rate used is based on an estimated weighted average cost of capital and the anticipated risk for intangible assets. The valued trade names have an indefinite life based on our plans and expectations for the trade names going forward and is reviewed for impairment under ASC 360-10. Intellectual Property and Technology Intellectual property and technology (“IP”) is a design, work or invention that is the result of creativity to which one has ownership rights that may be protected through a patent, copyright, trademark or service mark. IP is valued using the relief from royalty valuation method. The method uses a royalty rate based on comparable market-place royalty agreements for similar types of IP and applies it to the after-tax discounted free cash flow attributed to the IP. The discount rate used is based on an estimated weighted average cost of capital and the anticipated risk for intangible assets. The IP is amortized following the pattern in which the expected benefits will be consumed or otherwise used up over each component’s useful life, based on our plans and expectations for the IP going forward, which is generally the underlying IP’s legal expiration dates. IP is reviewed for impairment under ASC 360-10. Customer Relationships Customer relationships are intangible assets that consist of historical and factual information about customers and contacts collected from repeat transactions with customers, with or without any underlying contracts. The information is generally organized as customer lists or customer databases. We have the expectation of repeat patronage from these customers based on the customers’ historical purchase activity, which creates the intrinsic value over a finite period of time and translates into the expectation of future revenue, income, and cash flow. Customer relationships are valued using projected operating income, adjusted for estimated future existing customer growth less estimated future customer attrition, net of charges for net tangible assets, IP charge, trade name charge and work force. The concluded value is the after-tax discounted free cash flow. Customer relationships are reviewed for impairment under ASC 360-10. 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 May 1, 2018 Measurement Period Adjustments Purchase Price Allocation Accounts receivable, net $ 43,354 $ (49 ) $ 43,305 Inventories 84,395 1,717 86,112 Property, plant and mine development 123,086 25,409 148,495 Mineral rights 462,050 (42,581 ) 419,469 Identifiable intangible assets - finite lived 21,050 (10,780 ) 10,270 Identifiable intangible assets - indefinite lived 25,050 13,000 38,050 Prepaids and deposits 2,054 18 2,072 Other assets 4,088 3,386 7,474 Goodwill 139,787 10,841 150,628 Total assets acquired 904,914 961 905,875 Accounts payable 13,435 — 13,435 Accrued expenses and other current liabilities 8,255 2,049 10,304 Deferred tax liabilities 130,209 (7,398 ) 122,811 Long term obligations 9,766 6,310 16,076 Total liabilities assumed $ 161,665 $ 961 $ 162,626 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 $ 2,900 15 Customer relationships 7,370 15 Total identifiable intangible assets - finite lived $ 10,270 Trade names $ 38,050 Total identifiable intangible assets - indefinite lived $ 38,050 Goodwill represents the excess of the purchase price over the fair value of the underlying net assets acquired. Goodwill in this transaction is attributable to planned growth in our industrial materials product offering in our Industrial & Specialty Products business segment. Intangibles and goodwill are not expected to be deductible for tax purposes. Our Income Statement included revenue of $158.8 million and a net loss of $0.6 million for the year ended December 31, 2018 , associated with EPMH following the date of acquisition. We incurred $13.6 million of acquisition-related charges, excluding debt issuance costs, for the year ended December 31, 2018 , which are included in selling, general and administrative expenses on our Income Statement. The acquisition of EPMH was accounted for using the acquisition method of accounting. The purchase price and purchase price allocation are subject to customary post-closing adjustments and changes in the fair value of assets and liabilities. The above estimated fair values of net assets acquired are based on the information that was available as of the reporting date. We believe that the information provides a reasonable basis for estimating the fair values of the acquired assets and assumed liabilities, but the potential for measurement period adjustments exists based on our continuing review of matters related to the acquisition. As a result, our final purchase price allocation may be significantly different than reflected above. We expect to complete the purchase price allocation as soon as practicable, but no later than one year from the acquisition date. Unaudited Pro Forma Results The results of EPMH's operations have been included in the Consolidated Financial Statements subsequent to the acquisition date. EPMH's fiscal year end was November 30 and the Company's fiscal year end was December 31. Under SEC regulations, if a target's fiscal year end varies by more than 93 days from the acquirer's fiscal year end, it is required to adjust interim periods until it is within 93 days. Since EPMH’s fiscal year end was within 93 days of the Company's fiscal year end, no adjustment is necessary and EPMH’s fiscal year end and interim period ends are used as if they coincided with the Company's fiscal year end and interim period end. The following unaudited pro forma consolidated financial information reflects the results of operations as if the EPMH acquisition had occurred on January 1, 2017, after giving effect to certain purchase accounting adjustments. Material non-recurring transaction costs attributable to the business combination were $15.2 million . Pro forma net income includes incremental interest expense due to the related debt financing, incremental depreciation and depletion expense related to the fair value adjustment of property, plant and mine development, amortization expense related to identifiable intangible assets, and tax expense related to the combined tax provisions. This information does not purport to be indicative of the actual results that would have occurred if the acquisition had actually been completed on the date indicated, nor is it necessarily indicative of the future operating results or the financial position of the combined company (in thousands, except per share amounts): For the year ended December 31, 2018 2017 Sales $ 1,659,775 $ 1,454,070 Net income (loss) $ (179,220 ) $ 116,899 Basic earnings (loss) per share $ (2.34 ) $ 1.44 Diluted earnings (loss) per share $ (2.34 ) $ 1.43 2017 Acquisitions: White Armor Acquisition: On April 1, 2017, we completed the acquisition of White Armor, a product line of cool roof granules used in industrial roofing applications, for cash consideration of $18.6 million . The final purchase price was allocated to goodwill of approximately $3.9 million , identifiable intangible assets of $12.8 million and other net assets of approximately $1.9 million . Goodwill in this transaction is attributable to planned growth in our specialty industrial sand business segment. The goodwill amount is included in our Industrial & Specialty Products business segment. Identifiable definite lived intangibles, including customer relationships, and goodwill are expected to be deductible for tax purposes. We incurred $0.2 million of acquisition-related charges which are included in selling, general and administrative expenses during the year ended December 31, 2017. Revenue and earnings for White Armor after the acquisition date are not presented as the business was integrated into our operations subsequent to the acquisition and therefore impracticable to quantify. MS Sand Acquisition: On August 16, 2017, we completed the acquisition of Mississippi Sand, LLC ("MS Sand"), a Missouri limited liability company, for cash consideration of approximately $95.4 million , net of cash acquired of $2.2 million . As is normal and customary, subsequent adjustments were made including $(0.5) million of net working capital adjustments plus an additional $6.1 million consideration paid related to a pre-existing contracted asset sale, which was entered into prior to our acquisition, for total cash consideration of $101.0 million . MS Sand is a frac sand mining and logistics company based in St. Louis, Missouri. The acquisition of MS Sand increased our regional frac sand product offering in our Oil & Gas Proppants business segment. We have accounted for the acquisition of MS Sand under the acquisition method of accounting in accordance with ASC 805, Business Combinations, and have accounted for measurement period adjustments in accordance with ASU 2015-16, Simplifying the Accounting for Measurement-Period Adjustments. In accordance with the acquisition method of accounting, the allocation of consideration value was subject to adjustment until we completed our analysis in the third quarter of 2018. The following table sets forth the final allocation of the purchase price to MS Sands' identifiable tangible and intangible assets acquired and liabilities assumed, including measurement period adjustments (in thousands): Estimate as of December 31, 2017 Measurement Period Adjustments Purchase Price Allocation Accounts receivable $ 11,201 $ — $ 11,201 Inventories 8,067 — 8,067 Other current assets 362 — 362 Assets held for sale 9,453 — 9,453 Property, plant and mine development 27,458 — 27,458 Mineral rights 26,300 (2,800 ) 23,500 Other non-current assets 1,136 — 1,136 Goodwill 22,522 2,800 25,322 Customer relationships 1,840 — 1,840 Total assets acquired 108,339 — 108,339 Accounts payable and accrued expenses 3,761 — 3,761 Unfavorable leasehold positions 2,237 — 2,237 Notes Payable 866 — 866 Other long term liabilities — — — Asset retirement obligations 474 — 474 Total liabilities assumed 7,338 — 7,338 Net assets acquired $ 101,001 $ — $ 101,001 The acquired intangible assets and the related estimated useful lives consist of the following: Approximate Fair Value Estimated Useful Life (in thousands) (in years) Customer relationships $ 1,840 15 Goodwill in this transaction is attributable to planned growth in our regional frac sand product offering in our Oil & Gas Proppants business segment. The goodwill amount is included in our Oil & Gas Proppants business segment. Identifiable definite lived intangibles, including customer relationships, and goodwill are expected to be deductible for tax purposes. We incurred $1.0 million of acquisition-related charges which are included in selling, general and administrative expenses. Revenue and earnings for MS Sand after the acquisition date are not presented as the business was integrated into our operations subsequent to the acquisition and therefore impracticable to quantify. Unaudited Pro Forma Results The results of MS Sand’s operations have been included in the Consolidated Financial Statements subsequent to the acquisition dates. The following unaudited pro forma consolidated financial information reflects the results of operations as if the MS Sand Acquisition had occurred on January 1, 2016, after giving effect to certain purchase accounting adjustments. These adjustments mainly include incremental depreciation expense related to the fair value adjustment of property, plant, equipment and mine development, amortization expense related to identifiable intangible assets and tax expense related to the combined tax provisions. This information does not purport to be indicative of the actual results that would have occurred if the acquisition had actually been completed on the date indicated, nor is it necessarily indicative of the future operating results or the financial position of the combined company (in thousands, except per share amounts): For the year ended December 31, 2017 2016 Sales $ 1,287,202 $ 642,951 Net income (loss) $ 143,604 $ (55,835 ) Basic earnings (loss) per share $ 1.77 $ (0.86 ) Diluted earnings (loss) per share $ 1.75 $ (0.86 ) 2016 Acquisitions: NBI Acquisition: On August 16, 2016, we completed the acquisition of New Birmingham, Inc. (“NBI”), the ultimate parent company of NBR Sand, LLC (“NBR”), by acquiring all of the outstanding capital stock of NBI through the merger of New Birmingham Merger Corp., a Nevada corporation and wholly owned subsidiary of the Company, with and into NBI, followed immediately by the merger of NBI with and into NBI Merger Subsidiary II, Inc., a Delaware corporation and wholly owned subsidiary of the Company, which subsequently changed its name to Tyler Silica Company (the “NBI Acquisition”). NBR is a regional sand producer located near Tyler, Texas. The acquisition of NBI increased our regional frac sand product offering in our Oil & Gas Proppants business segment. The consideration paid to the stockholders of NBI at the closing of the NBI Acquisition was approximately $213.7 million , consisting of $107.2 million in cash (net of $9.0 million cash acquired) and 2,630,513 shares of common stock valued at $106.6 million . We have accounted for the acquisition of NBI under the acquisition method of accounting in accordance with ASC 805, Business Combinations, and have accounted for measurement period adjustments in accordance with ASU 2015-16, Simplifying the Accounting for Measurement-Period Adjustments. In accordance with the acquisition method of accounting, the allocation of consideration value was subject to adjustment until we completed our analysis in the third quarter of 2017 The following table sets forth the final allocation of the purchase price to NBI’s identifiable tangible and intangible assets acquired and liabilities assumed, including measurement period adjustments (in thousands): Initial Estimate Measurement Period Adjustments Purchase Price Allocation Accounts receivable $ 2,680 $ — $ 2,680 Inventories 3,494 — 3,494 Other current assets 428 — 428 Income tax deposits 6,657 (217 ) 6,440 Property, plant and mine development 210,913 (4,281 ) 206,632 Identifiable intangible assets 1,600 — 1,600 Goodwill 86,228 4,670 90,898 Total assets acquired 312,000 172 312,172 Accounts payable, accrued expenses and other current liabilities 1,938 726 2,664 Deferred revenue 500 — 500 Notes payable 24,361 243 24,604 Capital lease liabilities 3,331 — 3,331 Asset retirement obligations 710 — 710 Deferred tax liabilities 67,435 (797 ) 66,638 Total liabilities assumed 98,275 172 98,447 Net assets acquired $ 213,725 $ — $ 213,725 In addition to the changes in the balances reflected above, we recorded an adjustment to depreciation expense of $(0.6) million during the year ended December 31, 2017. The acquired intangible assets and the related estimated useful lives consist of the following: Approximate Fair Value Estimated Useful Life (in thousands) (in years) Customer relationships $ 1,600 13 Goodwill in this transaction is attributable to planned growth in regional frac sand markets and synergies expected to be achieved from integrating the operations of our operating subsidiary, U.S. Silica Company (“U.S. Silica”), and NBI. The goodwill amount is included in our Oil & Gas Proppants business segment. Both customer relationships and goodwill are not expected to be deductible for tax purposes. We incurred $1.4 million of acquisition-related charges which are included in selling, general and administrative expenses during the year ended December 31, 2016. Additionally, we incurred $1.7 million related to the inventory write-up values in cost of goods sold during the year ended December 31, 2016. Revenue and earnings for NBR after the acquisition date are not presented as the business was integrated into our operations subsequent to the acquisition and therefore impracticable to quantify. Sandbox Acquisition: On August 22, 2016, we completed the purchase of all of the outstanding units of membership interest of Sandbox Enterprises, LLC, a Texas limited liability company ("Sandbox" or the “Sandbox Acquisition”). Sandbox earns revenues from providing “last mile” transportation services to companies in the oil and gas industry. Sandbox has operations in Texas (Midland/Odessa, Kenedy, Dallas/Fort Worth, Tyler); Morgantown, West Virginia; western North Dakota; northeast of Denver, Colorado; Oklahoma City, Oklahoma; Cambridge, Ohio and Mansfield, Pennsylvania, where its major customers are located. The consideration paid to the unit-holders was approximately $241.1 million , consisting of $69.5 million in cash (net of $1.3 million cash acquired) and 4,195,180 shares of our common stock valued at $171.7 million . The following table sets forth the allocation of the purchase price to Sandbox’s identifiable tangible and intangible assets acquired and liabilities assumed (in thousands): Allocation of Purchase price: (in thousands) Accounts receivable $ 13,392 Prepaid expenses and other 1,465 Property, plant and mine development 32,336 Identifiable intangible assets 120,144 Goodwill 86,100 Total assets acquired 253,437 Accounts payable 4,122 Deferred revenue 4,902 Accrued expenses and other current liabilities 3,292 Total liabilities assumed 12,316 Net assets acquired $ 241,121 The acquired intangible assets and the related estimated useful lives consist of the following: Approximate Fair Value Estimated Useful Life (in thousands) (in years) Indefinite lived intangible assets - Trade names $ 17,844 Indefinite Definite lived intangible assets - Technology and intellectual property 57,700 15 Definite lived intangible asset - Customer relationships 44,600 13 Total fair value of identifiable intangible assets $ 120,144 Goodwill in this transaction is attributable to expected growth in frac sand demand at the wellhead and synergies expected to be achieved from integrating the operations of U.S. Silica and Sandbox. The goodwill amount is included in our Oil & Gas Proppants business segment. Goodwill and all intangible assets identified above are expected to be deductible for tax purposes. Our 2016 Income Statement included revenue of $31.0 million associated with Sandbox following the date of acquisition. Sandbox's impact on our net loss was not significant for the year ended December 31, 2016. We incurred $3.0 million of acquisition-related charges which are included in selling, general and administrative expenses on the Income Statement for the year ended December 31, 2016. The cost related to the issuance of the 6,825,693 shares of common stock to complete the two acquisitions totaled $0.3 million , which is included in additional paid-in capital on our Consolidated Statements of Stockholders' Equity for the year ended December 31, 2016. Combined Unaudited Pro Forma Results The results of NBI's and Sandbox’s operations have been included in the consolidated financial statements subsequent to the acquisition dates. The following unaudited pro forma consolidated financial information reflects the results of operations as if the NBI Acquisition and Sandbox Acquisition had occurred on January 1, 2015, after giving effect to certain purchase accounting adjustments. These adjustments mainly include incremental depreciation expense related to the fair value adjustment of property, plant, equipment and mine development, amortization expense related to identifiable intangible assets and tax expense related to the combined tax provisions. This information does not purport to be indicative of the actual results that would have occurred if the acquisition had actually been completed on the date indicated, nor is it necessarily indicative of the future operating results or the financial position of the combined company (in thousands, except per share amounts): For the year ended December 31, 2016 Sales $ 615,552 Net income (loss) $ (45,161 ) Basic earnings (loss) per share $ (0.69 ) Diluted earnings (loss) per share $ (0.69 )

Accounts Receivable

Accounts Receivable	12 Months Ended
	Dec. 31, 2018
Receivables [Abstract]
ACCOUNTS RECEIVABLE	NOTE F—ACCOUNTS RECEIVABLE At December 31, 2018 and December 31, 2017 , accounts receivable (in thousands) consisted of the following: December 31, December 31, Trade receivables $ 198,435 $ 217,649 Less: Allowance for doubtful accounts (6,751 ) (7,100 ) Net trade receivables 191,684 210,549 Other receivables (1) 23,802 2,037 Total accounts receivable $ 215,486 $ 212,586 (1 ) At December 31, 2018, other receivables include $16.0 million of refundable alternative minimum tax credits. Changes in our allowance for doubtful accounts (in thousands) during the years ended December 31, 2018 and 2017 are as follows: December 31, December 31, Beginning balance $ 7,100 $ 7,042 Bad debt provision 315 1,529 Write-offs (664 ) (1,471 ) Ending balance $ 6,751 $ 7,100 Our ten largest customers accounted for approximately 48% , 58% and 52% of total sales during the year ended December 31, 2018 , 2017 and 2016 , respectively. Sales to one of our customers accounted for 15% of our total sales during the year ended December 31, 2018 . Sales to two of our customers accounted for 15% and 12% of our total sales during the year ended December 31, 2017 . Sales to one of our customers accounted for 13% of our total sales during the year ended December 31, 2016 . No other customers accounted for 10% or more of our total sales. At December 31, 2018 , one of our customers' accounts receivable represented 18% of our total trade accounts receivable, net of allowance. At December 31, 2017 , two of our customers' accounts receivable represented 19% and 11% of our total trade accounts receivable, net of allowance. No other customers accounted for 10% or more of our total trade accounts receivable.

Inventories

Inventories	12 Months Ended
	Dec. 31, 2018
Inventory Disclosure [Abstract]
INVENTORIES	NOTE G—INVENTORIES At December 31, 2018 and December 31, 2017 , inventories (in thousands) consisted of the following: December 31, 2018 December 31, 2017 Supplies $ 41,453 $ 21,277 Raw materials and work in process 68,474 28,034 Finished goods 52,160 43,065 Total inventories $ 162,087 $ 92,376

Property, Plant and Mine Develo

Property, Plant and Mine Development	12 Months Ended
	Dec. 31, 2018
Property, Plant and Equipment [Abstract]
PROPERTY, PLANT AND MINE DEVELOPMENT	NOTE H—PROPERTY, PLANT AND MINE DEVELOPMENT At December 31, 2018 and December 31, 2017 , property, plant and mine development (in thousands) consisted of the following: December 31, December 31, Mining property and mine development $ 995,759 $ 586,242 Asset retirement cost 12,732 14,184 Land 55,502 36,552 Land improvements 67,729 45,878 Buildings 64,515 56,330 Machinery and equipment 958,357 590,566 Furniture and fixtures 3,599 2,953 Construction-in-progress 167,933 189,970 2,326,126 1,522,675 Accumulated depletion, depreciation and amortization (499,823 ) (353,520 ) Total property, plant and mine development, net $ 1,826,303 $ 1,169,155 At December 31, 2018 and December 31, 2017 , the aggregate cost of machinery and equipment acquired under capital leases was $0.5 million and $0.9 million , respectively, reduced by accumulated depreciation of $0.2 million and $0.2 million , respectively. The amount of interest costs capitalized in property, plant and mine development was $6.7 million and $1.6 million for the year ended December 31, 2018 and 2017 , 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 December 31, 2018 , vendor incentives of $12.5 million and $33.8 million were classified in accounts payable and accrued expenses and in other long-term obligations, respectively, on our balance sheet. Separately, on March 21, 2018, we accrued $7.9 million in contract termination costs for facilities contracts operated by third-parties, which will not transfer to CIG. During the second quarter of 2018, as a result of the final settlement of these contracts, we recorded a $2.7 million credit in selling, general and administrative expenses on our Income Statement. During the second quarter of 2018, we recorded a $16.2 million asset impairment related to the closure of our resin coating facility and associated product portfolio. During the fourth quarter of 2018, we experienced a declining shift in demand for Northern White sand caused by some of our customers shifting to local in-basin frac sands with lower logistics costs. Our largest customer at our Voca, Texas plant did not renew their contract, instead opting to sign a new contract with us for local in-basin frac sand. Additionally, Northern White Sand operations and reserves in Fairchild, Wisconsin and Peru, Illinois experienced a similar significant fourth quarter decline in demand due to customers' shift to local in-basin sand closer to their operations. Due to the resulting decline in demand for our Northern White sand, we recognized $97.0 million and $4.5 million in long-lived asset and intangible impairments in our Oil & Gas Proppants business segment.

Goodwill and Intangible Assets

Goodwill and Intangible Assets	12 Months Ended
	Dec. 31, 2018
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 Total Goodwill $ 47,947 $ 20,700 $ 68,647 Impairment losses — — — Balance at January 1, 2016 $ 47,947 $ 20,700 $ 68,647 NBI acquisition 86,228 — 86,228 Sandbox acquisition 86,100 — 86,100 Goodwill 220,275 20,700 240,975 Impairment losses — — — Balance at December 31, 2016 220,275 20,700 240,975 White Armor acquisition — 3,912 3,912 NBI acquisition measurement period adjustment 4,670 — 4,670 MS Sand acquisition 52,187 — 52,187 MS Sand acquisition measurement period adjustment (29,665 ) — (29,665 ) Goodwill 247,467 24,612 272,079 Impairment losses — — — Balance at December 31, 2017 247,467 24,612 272,079 MS Sand acquisition measurement period adjustment 2,800 — 2,800 EPMH acquisition — 139,787 139,787 EPMH acquisition measurement period adjustment — 10,841 10,841 Oil & Gas Sand impairment (164,167 ) — (164,167 ) Goodwill 250,267 175,240 425,507 Impairment losses (164,167 ) — (164,167 ) Balance at December 31, 2018 $ 86,100 $ 175,240 $ 261,340 Goodwill and trade names are evaluated for impairment annually as of October 31, or more frequently when indicators of impairment exist. We performed our annual impairment test by performing a qualitative assessment of goodwill. In performing this qualitative assessment, we evaluated events and circumstances since the date of 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. Subsequent to our annual impairment test, we experienced a declining shift in demand for Northern White sand caused by some of our customers shifting to local in-basin frac sands with lower logistics costs. Our largest customer at our Voca, Texas plant did not renew their contract, instead opting to sign a new contract with us for local in-basin frac sand. Additionally, Northern White Sand operations and reserves in Fairchild, Wisconsin and Peru, Illinois experienced a similar significant fourth quarter decline in demand due to customers' shift to local in-basin sand closer to their operations. As a result of these triggering events, we performed a quantitative analysis and determined that the goodwill of our Oil & Gas Sand reporting unit was impaired. We recognized goodwill impairment charges of $164.2 million and intangible impairment charges of $4.5 million during the fourth quarter of 2018. The fair value of our reporting units was determined using a combination of the discounted cash flow method and the market multiples approach. The changes in the carrying amount of intangible assets (in thousands) consisted of the following: December 31, 2018 December 31, 2017 Estimated Useful Life Gross Carrying Amount Accumulated Amortization Net Gross Carrying Amount Accumulated Amortization Net (in years) Technology and intellectual property 15 $ 83,616 $ (11,168 ) $ 72,448 $ 70,703 $ (5,917 ) $ 64,786 Customer relationships 13 - 15 68,379 (13,541 ) 54,838 61,229 (9,076 ) 52,153 Total definite-lived intangible assets: $ 151,995 $ (24,709 ) $ 127,286 $ 131,932 $ (14,993 ) $ 116,939 Trade names 66,640 — 66,640 33,068 — 33,068 Other 700 — 700 — — — Total intangible assets: $ 219,335 $ (24,709 ) $ 194,626 $ 165,000 $ (14,993 ) $ 150,007 Measurement period adjustments related to the Company's EPMH acquisition impacted the gross carrying amounts of the technology and intellectual property and customer relationship intangibles by $0.9 million and $(11.7) million , respectively, and the trade names by $13.0 million . See Note E - Business Combinations . Amortization expense was $9.7 million , $8.8 million and $3.2 million for the year ended December 31, 2018 , 2017 , and 2016 , respectively. The estimated amortization expense related to definite-lived intangible assets (in thousands) for the five succeeding years is as follows: 2019 $ 12,396 2020 12,397 2021 12,396 2022 12,381 2023 12,376

Accounts Payable and Accrued Li

Accounts Payable and Accrued Liabilities	12 Months Ended
	Dec. 31, 2018
Payables and Accruals [Abstract]
ACCOUNTS PAYABLE AND ACCRUED LIABILITIES	NOTE J—ACCOUNTS PAYABLE AND ACCRUED LIABILITIES At December 31, 2018 and 2017 , accounts payable and accrued liabilities (in thousands) consisted of the following: December 31, 2018 2017 Trade payables $ 178,804 $ 148,772 Accrued salaries and wages 12,291 6,126 Accrued vacation liability 3,503 2,906 Current portion of liability for pension and post-retirement benefits 2,708 1,524 Accrued healthcare liability 2,702 1,837 Accrued property taxes and sales taxes 4,490 2,720 Other accrued liabilities 11,902 7,156 Accounts payable and accrued liabilities $ 216,400 $ 171,041 Other accrued liabilities consist of customer rebates, royalties payable, employer related expenses, dividends payable and other items.

Debt

Debt	12 Months Ended
	Dec. 31, 2018
Debt Disclosure [Abstract]
DEBT	NOTE K—DEBT At December 31, 2018 and 2017 , debt (in thousands) consisted of the following: December 31, December 31, Senior secured credit facility: Revolver expiring May 1, 2023 (8.50% at December 31, 2018 and 5.75% at December 31, 2017) $ — $ — Term Loan facility—final maturity May 1, 2025 (6.56% at December 31, 2018 and 4.75%-5.25% December 31, 2017) 1,270,400 489,075 Less: Unamortized original issue discount (6,511 ) (944 ) Less: Unamortized debt issuance cost (31,310 ) (3,099 ) Note payable secured by royalty interest 26,511 24,740 Customer note payable — 745 Equipment notes payable 321 719 Capital leases 344 706 Total debt 1,259,755 511,942 Less: current portion (13,327 ) (6,867 ) Total long-term portion of debt $ 1,246,428 $ 505,075 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 December 31, 2018 , leaving $95.2 million available under the Revolver. Senior Secured Credit Facility At December 31, 2018 , contractual maturities of our senior secured Credit Facility (in thousands) are as follows: 2019 $ 12,800 2020 12,800 2021 12,800 2022 12,800 2023 12,800 Thereafter 1,206,400 Total $ 1,270,400 On May 1, 2018, we entered into the Credit Agreement, which increases our existing senior debt by entering into a new $1.380 billion senior secured Credit Facility, consisting of a $1.280 billion Term Loan and a $100 million 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, govern our ability, and certain of our subsidiaries' abilities, to create, incur or assume indebtedness and liens, to make acquisitions or investments, to sell assets and to pay dividends. The Credit Agreement also requires us to maintain a consolidated leverage ratio of no more than 3.75 :1.00 as of the last day of any fiscal quarter whenever usage of the Revolver (other than certain undrawn letters of credit) exceeds 30% of the Revolver commitment. These covenants are subject to a number of important exceptions and qualifications. The Credit Agreement includes events of default and other affirmative and negative covenants that are usual for facilities and transactions of this type. As of December 31, 2018 , and 2017 , we are in compliance with all covenants in accordance with our senior secured Credit Facility. Note Payable Secured by Royalty Interest In conjunction with the acquisition of NBI in August 2016, we assumed a note payable secured by a royalty interest. The monthly royalty payment is calculated based on future tonnages and sales related to the sand shipped from our Tyler, Texas facility. The note payable is due by June 30, 2032 . The note does not provide a stated interest rate. The minimum payments (in thousands) for the next five years required by the note are as follows: 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 December 31, 2018 , the note payable had a balance of $26.5 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 20% at December 31, 2018 .

Deferred Revenue

Deferred Revenue	12 Months Ended
	Dec. 31, 2018
Deferred Revenue Disclosure [Abstract]
DEFERRED REVENUE	NOTE L—DEFERRED REVENUE We enter into certain customer supply agreements which give the customers the right to purchase certain products for a discounted price at certain volumes over an average initial contract term of one to fifteen years. The advance payments represent future purchases and are recorded as deferred revenue, recognized as revenue over the contract term of each supply agreement. During the year ended December 31, 2018 we received advances of $31.6 million , including a customer's purchase of an interest in our sand reserves in Lamesa, Texas, which secured them a long-term supply of sand. At December 31, 2018 and 2017 , the total deferred revenue balance was $113.3 million and $118.4 million , respectively, of which $31.6 million and $36.1 million was classified as current on our Balance Sheets. NOTE U— 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 year ended December 31, 2018 (in thousands): Year Ended Category Oil & Gas Proppants Industrial & Specialty Products Total Sales Product $ 888,509 $ 394,290 $ 1,282,799 Service 294,482 17 294,499 Total Sales $ 1,182,991 $ 394,307 $ 1,577,298 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 year ended December 31, 2018 (in thousands): Unbilled Receivables December 31, 2017 $ 5,245 Reclassifications to billed receivables (11,157 ) Revenues recognized in excess of period billings 6,002 December 31, 2018 $ 90 Deferred Revenue December 31, 2017 $ 118,414 Revenues recognized from balances held at the beginning of the period (33,381 ) Revenues deferred from period collections on unfulfilled performance obligations 31,625 Revenues recognized from period collections (3,339 ) December 31, 2018 $ 113,319 We have elected to use the practical expedients allowed under ASC 606-10-50-14, pursuant to which we have excluded disclosures of transaction prices allocated to remaining performance obligations and when we expect to recognize such revenue. The majority of our remaining performance obligations are primarily comprised of unfulfilled product, transportation service, and labor service orders, all of which hold a remaining duration of less than one year. The long term portion of deferred revenue primarily represents a combination of refundable and nonrefundable customer prepayments for which related current performance obligations do not yet exist, but are expected to arise, before the expiration of the contract. Our residual unfulfilled performance obligations are comprised primarily of long-term equipment rental arrangements in which we recognize revenues equal to what we have a right to invoice. Generally, no variable consideration exists related to our remaining performance obligations and no consideration is excluded from the associated transaction prices.

Asset Retirement Obligations

Asset Retirement Obligations	12 Months Ended
	Dec. 31, 2018
Asset Retirement Obligation Disclosure [Abstract]
ASSET RETIREMENT OBLIGATIONS	NOTE M—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 December 31, 2018 and 2017 , we had a liability of $18.4 million and $19.0 million , respectively, in other long-term obligations related to our asset retirement obligations. Changes in the asset retirement obligations (in thousands) during the years ended December 31, 2018 and 2017 are as follows: December 31, December 31, 2017 Beginning balance $ 19,032 $ 11,159 Accretion 1,214 879 Additions and revisions of prior estimates (319 ) 6,994 Addition related to EPMH acquisition 2,733 — EPMH measurement period adjustment (2,131 ) — Disposal related to sale of transloads (2,116 ) — Ending balance $ 18,413 $ 19,032 During the year ended December 31, 2017, in connection with the annual review of our reclamation obligations, we determined that some of our estimates required revision due primarily to the additions of new plant and transload facilities and other changes in cost estimates and settlement dates at various sites. These additions and changes in estimates resulted in an additional $7.0 million of asset retirement obligations.

Fair Value Accounting

Fair Value Accounting	12 Months Ended
	Dec. 31, 2018
Fair Value Disclosures [Abstract]
FAIR VALUE ACCOUNTING	NOTE N—FAIR VALUE ACCOUNTING Fair value is defined as the exchange price that would be received for an asset or paid to transfer a liability (an exit price) in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants on the measurement date. Fair value is estimated by applying the following hierarchy, which prioritizes the inputs used to measure fair value into three levels and bases the categorization within the hierarchy upon the lowest level of input that is available and significant to the fair value measurement: Level 1—Quoted prices in active markets for identical assets or liabilities. Level 2—Observable inputs other than quoted prices in active markets for identical assets and liabilities, quoted prices for identical or similar assets or liabilities in inactive markets, or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the assets or liabilities. Level 3—Inputs that are generally unobservable and typically reflect management’s estimate of assumptions that market participants would use in pricing the asset or liability. Cash Equivalents Due to the short-term maturity, we believe our cash equivalent instruments at December 31, 2018 and 2017 , approximate their reported carrying values. Long-Term Debt, Including Current Maturities We believe that the fair values of our long-term debt, including current maturities, approximate their carrying values based on their effective interest rates compared to current market rates. Derivative Instruments The estimated fair value of our derivative instruments 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 December 31, 2018 , we have assessed that the impact of the credit valuation adjustments on the overall valuation of our derivative positions is not significant. As a result, we have determined that our derivative valuations in their entirety are classified in Level 2 of the fair value hierarchy. See Note O - Derivative Instruments for more information.

Derivative Instruments

Derivative Instruments	12 Months Ended
	Dec. 31, 2018
Derivative Instruments and Hedging Activities Disclosure [Abstract]
DERIVATIVE INSTRUMENTS	NOTE O—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 December 31, 2018 , the fair value of our interest rate swaps was $1.5 million and $0.7 million and classified within other long-term obligations on our balance sheet, and the fair value of our interest rate cap was zero . At December 31, 2017 , 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 N - Fair Value Accounting for more information regarding the estimated fair values of our derivative instruments at December 31, 2018 and 2017 . December 31, 2018 December 31, 2017 Maturity Contract/Notional Carrying Fair Maturity Date Contract/Notional Carrying Fair LIBOR (1) interest rate swap agreement 2020 $440 million $ (1,475 ) $ (1,475 ) — $ — $ — $ — LIBOR (1) interest rate swap agreement 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% On May 1, 2018, as a result of entering into the new Credit Agreement, we determined the existing interest rate cap derivative no longer qualified for hedge accounting. During the year ended December 31, 2018 we recognized $76 thousand of deferred losses in accumulated other comprehensive loss into earnings. During the year ended December 31, 2018 , 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 years ended December 31, 2018 , 2017 and 2016 . 2018 2017 2016 Deferred losses from derivatives in OCI, beginning of period $ (76 ) $ (32 ) $ (81 ) Gain (loss) recognized in OCI from derivative instruments (1,622 ) (45 ) (32 ) Loss reclassified from Accumulated OCI 77 1 81 Deferred losses from derivatives in OCI, end of period $ (1,621 ) $ (76 ) $ (32 )

Equity-Based Compensation

Equity-Based Compensation	12 Months Ended
	Dec. 31, 2018
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
EQUITY-BASED COMPENSATION	NOTE P—EQUITY-BASED COMPENSATION In July 2011, we adopted the U.S. Silica Holdings, Inc. 2011 Incentive Compensation Plan (the “2011 Plan”), which was amended and restated in May 2015. The 2011 Plan provides for grants of stock options, restricted stock, performance share units and other incentive-based awards. We believe our 2011 Plan aligns the interests of our employees and directors with those of our common stockholders. At December 31, 2018 , we have 3,447,363 shares of common stock that may be issued under the 2011 Plan. We use a combination of treasury stock and new shares if necessary to satisfy option exercises or vesting of restricted awards and performance share units. Stock Options The following table summarizes the status of, and changes in, our stock option awards during the year ended December 31, 2018 : Number of Weighted Aggregate Intrinsic Value Weighted Outstanding at December 31, 2017 908,919 $ 28.46 $ 7,008 6.1 years Granted — — — Exercised (4,167 ) 14.65 — Forfeited (918 ) 31.30 — Expired (1,838 ) $ 31.30 $ — Outstanding at December 31, 2018 901,996 $ 28.52 $ 18,566 4.8 years Exercisable at December 31, 2018 901,996 $ 28.52 $ 18,566 4.8 years There were no grants of stock options during the years ended December 31, 2018 , 2017 and 2016 . There were 4,167 , 43,774 and 326,884 stock options exercised during the year ended December 31, 2018 , 2017 and 2016 , respectively. The total intrinsic value of stock options exercised was $0.1 million , $1.2 million and $7.6 million for the year ended December 31, 2018 , 2017 and 2016 , respectively. Cash received from stock options exercised during the year ended December 31, 2018 , 2017 and 2016 was $0.1 million , $0.8 million and $4.8 million , respectively. The tax benefit realized from stock option exercises was $14 thousand , $0.4 million and $2.9 million for the year ended December 31, 2018 , 2017 and 2016 , respectively. We recognized $1.4 million , $2.5 million and $3.0 million of equity-based compensation expense related to options during the year ended December 31, 2018 , 2017 and 2016 , respectively. As of December 31, 2018 , there was $34 thousand of 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 year ended December 31, 2018 : Number of Shares Grant Date Weighted Average Fair Value Unvested, December 31, 2017 461,346 $ 30.76 Granted 415,110 21.57 Vested (256,012 ) 28.66 Forfeited (32,867 ) 30.82 Unvested, December 31, 2018 587,577 $ 25.18 We granted 415,110 , 156,164 and 364,710 restricted stock and restricted stock unit awards during the year ended December 31, 2018 , 2017 and 2016 , respectively. The fair value of the awards was based on the market price of our stock at date of grant. We recognized $7.6 million , $7.1 million and $5.7 million of equity-based compensation expense related to restricted stock awards during the year ended December 31, 2018 , 2017 and 2016 , respectively. As of December 31, 2018 , there was $9.5 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 year ended December 31, 2018 : Number of Shares Grant Date Weighted Unvested, December 31, 2017 881,416 $ 42.16 Granted 261,500 31.24 Vested (225,000 ) 41.99 Forfeited (79,728 ) 40.45 Unvested, December 31, 2018 838,188 $ 39.44 We granted 261,500 , 90,501 and 850,143 of performance share unit awards during the year ended December 31, 2018 , 2017 and 2016 , respectively. The grant date weighted average fair value of these awards was estimated to be $31.24 , $67.69 and $39.36 for the year ended December 31, 2018 , 2017 and 2016 , respectively, and the number of units that will vest will depend on the percentage ranking of the Company's total shareholder return ("TSR") compared to the TSRs for each of the companies in the peer group over the three year period from January 1, 2018 through December 31, 2020 for the 2018 grant, from January 1, 2017 through December 31, 2019 for the 2017 grant, and from January 1, 2016 through December 31, 2018 for the 2016 grant. The related compensation expense is recognized on a straight-line basis over the vesting period. The grant date fair value for these awards was estimated using a Monte Carlo simulation model. The Monte Carlo simulation model requires the use of highly subjective assumptions. Our key assumptions in the model included the price and the expected volatility of our common stock and our self-determined peer group companies’ stock, risk-free rate of interest, dividend yields and cross-correlations between our common stock and our self-determined peer group companies' stock. We recognized $13.3 million , $15.5 million and $3.3 million of compensation expense related to performance share unit awards during the year ended December 31, 2018 , 2017 and 2016 , respectively. As of December 31, 2018 , there was $7.5 million of unrecognized compensation expense related to these performance share unit awards, which is expected to be recognized over a weighted-average period of 1.7 year.

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2018
Commitments and Contingencies Disclosure [Abstract]
COMMITMENTS AND CONTINGENCIES	NOTE Q—COMMITMENTS AND CONTINGENCIES Future Minimum Annual Commitments at December 31, 2018 (in thousands): Year ending December 31, Operating Lease Minimum Rental Payments Minimum Purchase Commitments 2019 $ 74,884 $ 23,243 2020 59,490 15,406 2021 40,302 8,307 2022 31,853 5,640 2023 22,596 4,915 Thereafter 40,148 6,084 Total future lease and purchase commitments $ 269,273 $ 63,595 Operating Leases We are obligated under certain operating leases for railroad cars, office space, mining property, mining/processing equipment and transportation and other equipment. Certain operating lease agreements include options to purchase the equipment for fair market value at the end of the original lease term. In general, the above leases include renewal options and provide that we pay for all utilities, insurance, taxes and maintenance. Expense related to operating leases and rental agreements totaled approximately $100.2 million , $68.3 million and $54.1 million for the years ended December 31, 2018 , 2017 and 2016 , respectively. 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 year ended December 31, 2018 , 2017 and 2016 , twenty , zero and two claims, respectively, were brought against U.S. Silica. As of December 31, 2018 , there were 74 active silica-related products liability claims pending in which U.S. Silica is a defendant. Although the outcomes of these claims cannot be predicted with certainty, in the opinion of management, it is not reasonably possible that the ultimate resolution of these matters will have a material adverse effect on our financial position or results of operations that exceeds the accrual amounts. We have recorded estimated liabilities for these claims in other long-term obligations as well as estimated recoveries under the indemnity agreement and an estimate of future recoveries under insurance in other assets on our consolidated balance sheets. As of both December 31, 2018 and 2017 , other non-current assets included zero for insurance for third-party products liability claims and other long-term obligations included $0.9 million and $1.0 million , respectively, for third-party products liability claims.

Pension and Post-Retirement Ben

Pension and Post-Retirement Benefits	12 Months Ended
	Dec. 31, 2018
Retirement Benefits [Abstract]
PENSION AND POST-RETIREMENT BENEFITS	NOTE R— 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. We employ a total rate of return investment approach whereby a mix of equities and fixed income investments are used to maximize the long-term return of plan assets for a prudent level of risk. Risk tolerance is established through careful consideration of plan liabilities, plan funded status, and corporate financial condition. The investment portfolio contains a diversified blend of equity and fixed-income investments. Furthermore, equity investments are diversified across U.S. and non-U.S. stocks, as well as growth, value and small and large capitalizations. Investment risk is measured and monitored on an ongoing basis through quarterly investment portfolio reviews, annual liability measurements, and periodic asset/liability studies. We employ a building block approach in determining the long-term rate of return for plan assets. Historical markets are studied and long-term historical relationships between equities and fixed-income are preserved consistent with the widely accepted capital market principle that assets with higher volatility generate a greater return over the long run. Current market factors such as inflation and interest rates are evaluated before long-term capital market assumptions are determined. The long-term portfolio return is established via a building block approach with proper consideration of diversification and rebalancing. Peer data and historical returns are reviewed to check for reasonability and appropriateness. In addition, we provide defined benefit post-retirement 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 years ended December 31, 2018 , 2017 and 2016 : Year Ended 2018 2017 2016 Service cost $ 1,307 $ 1,037 $ 1,078 Interest cost 4,632 3,971 4,067 Expected return on plan assets (5,969 ) (5,265 ) (5,495 ) Net amortization and deferral 2,526 1,773 1,592 Net pension benefit costs $ 2,496 $ 1,516 $ 1,242 Net post-retirement benefit cost (in thousands) consisted of the following for the years ended December 31, 2018 , 2017 and 2016 : Year Ended December 31, 2018 2017 2016 Service cost $ 102 $ 107 $ 132 Interest cost 740 753 876 Expected return on plan assets — (1 ) (1 ) Special termination benefit — — 21 Net post-retirement benefit costs $ 842 $ 859 $ 1,028 The changes in benefit obligations and plan assets (in thousands), as well as the funded status (in thousands) of our pension and post-retirement plans at December 31, 2018 and 2017 are as follows: Pension Benefits Post-retirement Benefits 2018 2017 2018 2017 Benefit obligation at January 1, $ 122,052 $ 116,145 $ 22,771 $ 24,393 Service cost 1,307 1,037 102 107 Interest cost 4,632 3,971 740 753 Actuarial (gain) loss (10,263 ) 6,824 (965 ) (1,576 ) Benefits paid (8,202 ) (6,685 ) (1,499 ) (1,280 ) Amendments — 760 — — Other (1) 29,374 — 421 374 Benefit obligation at December 31, $ 138,900 $ 122,052 $ 21,570 $ 22,771 Fair value of plan assets at January 1, $ 92,067 $ 83,850 $ — $ 14 Actual return on plan assets (6,204 ) 12,757 — (1 ) Employer contributions 3,350 2,145 1,078 893 Benefits paid (8,202 ) (6,685 ) (1,499 ) (1,280 ) Other (1) 21,385 — 421 374 Fair value of plan assets at December 31, $ 102,396 $ 92,067 $ — $ — Plan assets less than benefit obligations at December 31 recognized as liability for pension and other post-retirement benefits $ (36,504 ) $ (29,985 ) $ (21,570 ) $ (22,771 ) (1 ) Includes opening pension benefit obligation and plan assets balances related to the May 1, 2018, EPMH acquisition. The accumulated benefit obligation for the defined benefit pension plans, which excludes the assumption of future salary increases, totaled $138.9 million and $122.1 million at December 31, 2018 and 2017 , respectively. The amendments in 2018 and 2017 reflect plan changes, including increases in the benefit multiplier for certain participants. We also sponsor unfunded, nonqualified pension plans. The projected benefit obligation, accumulated benefit obligation and fair value of plan assets for these plans were $1.5 million , $1.5 million and zero , respectively, at December 31, 2018 and $1.6 million , $1.6 million and zero . respectively, at December 31, 2017 . Future estimated annual benefit payments (in thousands) for pension and post-retirement benefit obligations at December 31, 2018 are as follows: Benefits Post-retirement Pension Before After 2019 $ 10,022 $ 1,553 $ 1,394 2020 9,166 1,592 1,433 2021 9,236 1,653 1,496 2022 9,394 1,691 1,535 2023 9,380 1,686 1,528 2024-2028 47,737 8,262 7,442 Our best estimate of expected contributions to the pension and post-retirement medical benefit plans for the 2019 fiscal year are $4.5 million and $1.4 million , respectively. The amounts in accumulated other comprehensive income (loss) expected to be recognized as components of net periodic benefit cost (in thousands) during the following fiscal year are as follows: Benefits Pension Post-retirement Total Net actuarial loss $ 1,034 $ — $ 1,034 Prior service cost 534 — 534 $ 1,568 $ — $ 1,568 The total amounts in accumulated other comprehensive income (loss) related to net actuarial loss, net of tax, for the pension and post-retirement plans was $17.6 million and $13.5 million as of December 31, 2018 and 2017 , respectively. The total amounts in accumulated other comprehensive income (loss) related to prior service cost, net of tax, for the pension and post-retirement plans, was $2.8 million and $0.5 million as of December 31, 2018 and 2017 , respectively. The following weighted-average assumptions were used to determine our obligations under the plans: Pension Benefits Post-retirement Benefits 2018 2017 2018 2017 Discount rate 4.4 % 3.7 % 4.3 % 3.7 % Long-term rate of compensation increase 3.0%-3.5% 3.5 % N/A N/A Long-term rate of return on plan assets 6.25%-7.15% 6.8 % N/A 7.0 % Health care cost trend rate: Pre-65 initial rate/ultimate rate N/A N/A 7.3%/4.5% 7.3%/4.5% Pre-65 ultimate year N/A N/A — — Post-65 initial rate/ultimate rate N/A N/A 8.0%/4.5% 8.0%/4.5% Post-65 ultimate year N/A N/A 2026/2027 2025/2026 The weighted average discount rate used to determine the projected pension and post-retirement obligations was updated to 4.4% at December 31, 2018 from 3.7% at December 31, 2017. The discount rate reflects the expected long-term rates of return with maturities comparable to payments for the plan obligations utilizing Aon Hewitt's AA Above Medium Curve. In 2016, we changed the method utilized to estimate the service cost and interest cost components of net periodic benefit costs for our defined benefit pension and other post-retirement benefit plans. Historically, we estimated the service cost and interest cost components using a single weighted average discount rate derived from the yield curve used to measure the benefit obligation at the beginning of the period. We have elected to use a spot rate approach in the estimation of these components of benefit cost by applying the specific rates along the yield curve to the relevant projected cash flows, as we believe this provides a better estimate of service and interest costs. We consider this a change in estimate and, accordingly, have accounted for it prospectively starting in 2016. This change does not affect the measurement of our total benefit obligation. Mortality tables used for pension benefits and post-retirement benefits plans are the following: Pension and Post-retirement Benefits 2018 2017 Healthy Lives RP-2014 mortality table, adjusted back to 2006 base rates, with generational mortality improvements using Scale MP-2018 RP-2014 mortality table, adjusted back to 2006 base rates, with generational mortality improvements using Scale MP-2017 Disabled Lives RP-2014 disabled retiree mortality table, adjusted back to 2006 base rates, with generational mortality improvements using Scale MP-2018 RP-2014 disabled retiree mortality table, adjusted back to 2006 base rates, with generational mortality improvements using Scale MP-2017 Assumed health care cost trend rates have a significant effect on the amounts reported for the health care plans. A one-percentage-point change in assumed health care cost trend rates would have the following effects (in thousands): One-Percentage-Point Increase Decrease Effect on total of service and interest cost $ 109 $ (92 ) Effect on post-retirement benefit obligation 2,291 (1,967 ) The major investment categories and their relative percentage of the fair value of total plan assets as invested at December 31, 2018 , and 2017 are as follows: Pension Benefits Post-retirement Benefits (1) 2018 2017 2018 2017 Equity securities 42.1 % 51.8 % — % — % Debt securities 55.5 % 46.3 % — % — % Cash 2.4 % 1.9 % — % — % (1 ) Retiree health benefits are paid by the Company as covered expenses are incurred. The fair values of the pension plan assets (in thousands) at December 31, 2018 , by asset category, are as follows: Level 1 Level 2 Level 3 Total Cash and cash equivalents $ — $ 2,449 $ — $ 2,449 Mutual funds: Diversified emerging markets 6,638 — — 6,638 Foreign large blend 11,689 — — 11,689 Large-cap blend 14,226 — — 14,226 Mid-cap blend 6,819 — — 6,819 Small-cap blend 522 — — 522 Real estate 3,192 — — 3,192 Fixed income securities: Corporate notes and bonds 43,745 — — 43,745 U.S. Treasuries 8,486 — — 8,486 Mortgage-backed securities — 3,578 — 3,578 Asset-backed securities — 1,052 — 1,052 Net asset $ 95,317 $ 7,079 $ — $ 102,396 The fair values of the pension plan assets (in thousands) at December 31, 2017 , by asset category, are as follows: Level 1 Level 2 Level 3 Total Cash and cash equivalents $ — $ 1,727 $ — $ 1,727 Mutual funds: Diversified emerging markets 8,300 — — 8,300 Foreign large blend 11,856 — — 11,856 Large-cap blend 15,643 — — 15,643 Mid-cap blend 8,334 — — 8,334 Real estate 3,591 — — 3,591 Fixed income securities: Corporate notes and bonds 28,108 — — 28,108 U.S. Treasuries 10,846 — — 10,846 Mortgage-backed securities — 2,615 — 2,615 Asset-backed securities — 1,047 — 1,047 Net asset $ 86,678 $ 5,389 $ — $ 92,067 We contribute to three multiemployer defined benefit pension plans under the terms of collective-bargaining agreements for union-represented employees. A multiemployer plan is subject to collective bargaining for employees of two or more unrelated companies. These plans allow multiple employers to pool their pension resources and realize efficiencies associated with the daily administration of the plan. Multiemployer plans are generally governed by a board of trustees composed of management and labor representatives and are funded through employer contributions. However, in most cases, management is not directly represented. The risks of participating in multiemployer plans differ from single employer plans as follows: 1) assets contributed to a multiemployer plan by one employer may be used to provide benefits to employees of other participating employers, 2) if a participating employer stops contributing to the plan, the unfunded obligations of the plan may be borne by the remaining participating employers, and 3) if we cease to have an obligation to contribute to one or more of the multiemployer plans to which we contribute, we may be required to pay those plans an amount based on the underfunded status of the plan, referred to as a withdrawal liability. A summary of each multiemployer pension plan for which we participate is presented below: Pension Fund EIN/ Pension Plan No. Pension Protection Act Zone Status (1) FIP/RP Status Pending/ Implemented Company Contributions (in thousands) Surcharge Imposed Expiration Date of CBA 2018 2017 2018 2017 2016 LIUNA 52-6074345/001 Red Red Yes $ 573 $ 223 $ 167 Yes 5/31/2020 IUOE 36-6052390/001 Green Green No 1,385 40 28 No 7/31/2022 CSSS (2) 36-6044243/001 Red Red Yes 51 51 51 NA NA (1) The Pension Protection Act of 2006 defines the zone status as follows: green—healthy, yellow—endangered, orange—seriously endangered and red—critical. (2) In 2011, we withdrew from the Central States, Southeast and Southwest Areas Pension Plan. The withdrawal liability of $1.0 million will be paid in monthly installments of $4,000 until 2031. Our contributions to individual multiemployer pension funds did not exceed 5% of the fund’s total contributions for the years ended December 31, 2018 , 2017 and 2016 . 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 $2.6 million , $3.0 million and $2.4 million for the years ended December 31, 2018 , 2017 and 2016, respectively.

Obligations Under Guarantees

Obligations Under Guarantees	12 Months Ended
	Dec. 31, 2018
Guarantees [Abstract]
OBLIGATIONS UNDER GUARANTEES	NOTE S— 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 December 31, 2018 , there was $34.4 million in bonds outstanding. The majority of these bonds, $29.8 million , relate to reclamation requirements issued by various governmental authorities. Reclamation bonds remain outstanding until the mining area is reclaimed and the authority issues a formal release. The remaining bonds relate to such indefinite purposes as licenses, permits, and tax collection.

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2018
Income Tax Disclosure [Abstract]
INCOME TAXES	NOTE T— 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. In August 2018, the Internal Revenue Service released Tax Act guidance on limitations on executive compensation which clarified transition rules for certain compensation agreements in existence on November 2, 2017. Based on the issued guidance, we recorded a discrete tax expense of $0.7 million to remove deferred tax assets on certain executive compensation agreements that were not eligible for transition relief. 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. We evaluate our deferred tax assets periodically to determine if valuation allowances are required. Ultimately, the realization of deferred tax assets is dependent upon generation of future taxable income during those periods in which temporary differences become deductible and/or credits can be utilized. To this end, management considers the level of historical taxable income, the scheduled reversal of deferred tax liabilities, tax-planning strategies and projected future taxable income. Based on these considerations, and the carry-forward availability of a portion of the deferred tax assets, management believes it is more likely than not that we will realize the benefit of the deferred tax assets. Income (loss) before income taxes (in thousands) consisted of the following: Year ended December 31, 2018 2017 2016 United States $ (232,597 ) $ 136,526 $ (77,745 ) Foreign 2,644 — — Total $ (229,953 ) $ 136,526 $ (77,745 ) Income tax (expense) benefit (in thousands) consisted of the following for the years ended December 31, 2018 , 2017 and 2016 : Year ended December 31, 2018 2017 2016 Current: Federal $ 1,076 $ (10,754 ) $ 60 State (2,496 ) (1,167 ) (274 ) Foreign (518 ) — — (1,938 ) (11,921 ) (214 ) Deferred: Federal 25,578 22,641 32,944 State 5,492 (2,040 ) 3,959 Foreign — — — 31,070 20,601 36,903 Income tax benefit $ 29,132 $ 8,680 $ 36,689 Income tax (expense) benefit (in thousands) differed from the amount that would be provided by applying the U.S. federal statutory rate for the years ended December 31, 2018 , 2017 and 2016 due to the following: Year ended December 31, 2018 2017 2016 Income tax (expense) benefit computed at U.S. federal statutory rate $ 48,290 $ (47,784 ) $ 27,211 Decrease (increase) resulting from: Statutory depletion 12,090 20,259 4,734 Goodwill impairment (29,157 ) — — Prior year tax return reconciliation 530 219 435 State income taxes, net of federal benefit 2,592 (2,267 ) 2,369 Adjustment to deferred taxes from the Tax Act rate reduction — 35,772 — Equity compensation (653 ) 2,602 2,003 Other, net (4,560 ) (121 ) (63 ) Income tax benefit $ 29,132 $ 8,680 $ 36,689 The largest permanent item in computing both our effective tax rate and taxable income is the deduction allowed for statutory percentage depletion. The deduction for statutory percentage depletion does not necessarily change proportionately to changes in income before income taxes. For the year ended December 31, 2018, the tax effect of the goodwill impairment described in Note I - Goodwill and Intangible Assets is a significant permanent item in the effective tax rate calculation. Deferred tax assets and liabilities are recognized for the estimated future tax effects, based on enacted tax laws, of temporary differences between the values of assets and liabilities recorded for financial reporting and for tax purposes and of net operating loss and other carry forwards. The tax effects of the types of temporary differences and carry forwards that gave rise to deferred tax assets and liabilities (in thousands) at December 31, 2018 and 2017 consisted of the following: December 31, 2018 2017 Gross deferred tax assets: Net operating loss carry forward and state tax credits $ 11,089 $ 22,783 Pension and post-retirement benefit costs 13,303 13,710 Alternative minimum tax credit carry forward 15,971 30,401 Property, plant and equipment 5,474 5,750 Accrued expenses 27,025 10,755 Inventories 774 4,354 Third-party products liability 231 249 Stock-based compensation expense 8,199 8,785 Note payable 3,724 3,133 Other 8,116 5,095 Total deferred tax assets 93,906 105,015 Gross deferred tax liabilities: Land and mineral property basis difference (165,002 ) (78,520 ) Fixed assets and depreciation (55,596 ) (51,556 ) Intangibles (10,346 ) (4,795 ) Other (201 ) — Total deferred tax liabilities (231,145 ) (134,871 ) Net deferred tax liabilities $ (137,239 ) $ (29,856 ) We have federal net operating loss carry forwards of approximately $41.9 million at December 31, 2018 . The losses will expire in years 2027 through 2036 . The losses are subject to an annual limitation under Internal Revenue Code Section 382, but are expected to be fully realized. Under the Tax Act, net operating loss (NOL) deductions arising in tax years beginning after December 31, 2017 can only offset up to 80 percent of future taxable income. The Act also prohibits NOL carrybacks, but allows indefinite carryforwards for NOLs arising in tax years beginning after December 31, 2017. Net operating losses arising before January 1, 2018 are accounted for under the previous tax rules that imposed no limit on the amount of the taxable income that can be set off using NOLs (except for a 90 percent limit for AMT carryforwards) and that can be carried back 2 years and carried forward 20 years. At December 31, 2018 and 2017 , we have an alternative minimum tax credit carry forward of approximately $16.0 million and $30.4 million , respectively. The Tax Act repeals the corporate alternative minimum tax (AMT), effective for tax years beginning after December 31, 2017, but allows an entity to claim portions of any unused AMT credits over the next four years to offset its regular tax liability. An entity with unused AMT credits as of December 31, 2017 can first use these credits to offset its regular tax for 2017 and can then claim up to 50 percent of the remaining AMT credits in 2018, 2019, and 2020, with all remaining AMT credits refundable in 2021. Based on the Tax Act repeal of AMT, $16.0 million was reclassified from deferred tax assets to other receivables. See Note F - Accounts Receivable . At the end of each reporting period as presented, there were no material amounts of interest and penalties recognized in the statement of operations or balance sheets. We have no material unrecognized tax benefits or any known material tax contingencies at December 31, 2018 or December 31, 2017 and do not expect this to change significantly within the next twelve months. Tax returns filed with the IRS for the years 2015 through 2017 along with tax returns filed with numerous state entities remain subject to examination.

Revenue

Revenue	12 Months Ended
	Dec. 31, 2018
Revenue from Contract with Customer [Abstract]
REVENUE	NOTE L—DEFERRED REVENUE We enter into certain customer supply agreements which give the customers the right to purchase certain products for a discounted price at certain volumes over an average initial contract term of one to fifteen years. The advance payments represent future purchases and are recorded as deferred revenue, recognized as revenue over the contract term of each supply agreement. During the year ended December 31, 2018 we received advances of $31.6 million , including a customer's purchase of an interest in our sand reserves in Lamesa, Texas, which secured them a long-term supply of sand. At December 31, 2018 and 2017 , the total deferred revenue balance was $113.3 million and $118.4 million , respectively, of which $31.6 million and $36.1 million was classified as current on our Balance Sheets. NOTE U— 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 year ended December 31, 2018 (in thousands): Year Ended Category Oil & Gas Proppants Industrial & Specialty Products Total Sales Product $ 888,509 $ 394,290 $ 1,282,799 Service 294,482 17 294,499 Total Sales $ 1,182,991 $ 394,307 $ 1,577,298 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 year ended December 31, 2018 (in thousands): Unbilled Receivables December 31, 2017 $ 5,245 Reclassifications to billed receivables (11,157 ) Revenues recognized in excess of period billings 6,002 December 31, 2018 $ 90 Deferred Revenue December 31, 2017 $ 118,414 Revenues recognized from balances held at the beginning of the period (33,381 ) Revenues deferred from period collections on unfulfilled performance obligations 31,625 Revenues recognized from period collections (3,339 ) December 31, 2018 $ 113,319 We have elected to use the practical expedients allowed under ASC 606-10-50-14, pursuant to which we have excluded disclosures of transaction prices allocated to remaining performance obligations and when we expect to recognize such revenue. The majority of our remaining performance obligations are primarily comprised of unfulfilled product, transportation service, and labor service orders, all of which hold a remaining duration of less than one year. The long term portion of deferred revenue primarily represents a combination of refundable and nonrefundable customer prepayments for which related current performance obligations do not yet exist, but are expected to arise, before the expiration of the contract. Our residual unfulfilled performance obligations are comprised primarily of long-term equipment rental arrangements in which we recognize revenues equal to what we have a right to invoice. Generally, no variable consideration exists related to our remaining performance obligations and no consideration is excluded from the associated transaction prices.

Related Party Transactions

Related Party Transactions	12 Months Ended
	Dec. 31, 2018
Related Party Transactions [Abstract]
RELATED PARTY TRANSACTIONS	NOTE V— RELATED PARTY TRANSACTIONS An employee, who was an officer of one of our operating subsidiaries prior to the third quarter of 2018, holds an ownership interest in a transportation brokerage and logistics services vendor, from which we made purchases of approximately $2.9 million , $4.7 million , and $0.8 million for the year ended December 31, 2018 , 2017 , and 2016 , respectively

Segment Reporting

Segment Reporting	12 Months Ended
	Dec. 31, 2018
Segment Reporting [Abstract]
SEGMENT REPORTING	NOTE W— 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 these Consolidated Financial Statements. 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 years ended December 31, 2018 , 2017 and 2016 : Year Ended 2018 2017 2016 Sales: Oil & Gas Proppants $ 1,182,991 $ 1,020,365 $ 362,550 Industrial & Specialty Products 394,307 220,486 197,075 Total sales 1,577,298 1,240,851 559,625 Segment contribution margin: Oil & Gas Proppants 357,846 301,972 11,445 Industrial & Specialty Products 155,084 88,781 78,988 Total segment contribution margin 512,930 390,753 90,433 Operating activities excluded from segment cost of sales (1) (98,761 ) (16,722 ) (7,618 ) Selling, general and administrative (146,971 ) (107,056 ) (67,172 ) Depreciation, depletion and amortization (148,832 ) (97,233 ) (68,134 ) Goodwill and other asset impairments (281,899 ) — — Interest expense (70,564 ) (31,342 ) (27,972 ) Other income (expense), net, including interest income 4,144 (1,874 ) 2,718 Income tax benefit (expense) 29,132 8,680 36,689 Net income (loss) $ (200,821 ) $ 145,206 $ (41,056 ) Less: Net income (loss) attributable to non-controlling interest (13 ) — — Net income (loss) attributable to U.S. Silica Holdings, Inc. $ (200,808 ) $ 145,206 $ (41,056 ) (1) 2018 increase driven by plant capacity expansion expenses and amortization of purchase accounting inventory fair value step-up. 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 December 31, 2018 , goodwill of $261.3 million has been allocated to these segments with $86.1 million assigned to Oil & Gas Proppants and $175.2 million to Industrial & Specialty Products. At December 31, 2017, goodwill of $272.1 million had been allocated to these segments with $247.5 million assigned to Oil & Gas Proppants and $24.6 million to Industrial & Specialty Products.

Unaudited Supplementary Data

Unaudited Supplementary Data	12 Months Ended
	Dec. 31, 2018
Quarterly Financial Information Disclosure [Abstract]
UNAUDITED SUPPLEMENTARY DATA	NOTE X— UNAUDITED SUPPLEMENTARY DATA The following table sets forth our unaudited quarterly consolidated statements of operations (in thousands, except per share data) for each of the four quarters in the years ended December 31, 2018 and 2017 . This unaudited quarterly information has been prepared on the same basis as our annual audited financial statements and includes all adjustments, consisting only of normal recurring adjustments that are necessary to present fairly the financial information for the fiscal quarters presented. First Second Third Fourth 2018 (Unaudited) Sales: Product $ 294,788 $ 345,957 $ 348,635 $ 293,419 Service 74,525 81,476 74,537 63,961 Cost of sales (excluding depreciation, depletion and amortization): Product 207,239 236,236 270,370 241,624 Service 53,671 56,609 51,966 45,414 Operating expenses: Selling, general and administrative 34,591 42,232 37,980 32,168 Depreciation, depletion and amortization 28,592 36,563 37,150 46,527 Goodwill and other asset impairments — 16,184 — 265,715 Total operating expenses 63,183 94,979 75,130 344,410 Operating income (loss) 45,220 39,609 25,706 (274,068 ) Other (expense) income: Interest expense (7,070 ) (20,214 ) (21,999 ) (21,281 ) Other income (expense), net, including interest income 665 1,081 1,062 1,336 Total other expense (6,405 ) (19,133 ) (20,937 ) (19,945 ) Income (loss) before income taxes 38,815 20,476 4,769 (294,013 ) Income tax benefit (7,521 ) (2,832 ) 1,547 37,938 Net income (loss) 31,294 17,644 6,316 (256,075 ) Less: Net income (loss) attributable to non-controlling interest — — — (13 ) Net income (loss) attributable to U.S. Silica Holdings, Inc. $ 31,294 $ 17,644 $ 6,316 $ (256,062 ) Earnings (loss) per share, basic $ 0.39 $ 0.23 $ 0.08 $ (3.44 ) Earnings (loss) per share, diluted $ 0.39 $ 0.22 $ 0.08 $ (3.44 ) Weighted average shares outstanding, basic 79,496 77,784 77,365 74,485 Weighted average shares outstanding, diluted 80,309 78,480 77,859 74,485 Dividends declared per share $ 0.06 $ 0.06 $ 0.06 $ 0.06 First Second Third Fourth 2017 (Unaudited) Sales: Product $ 203,251 $ 235,891 $ 281,138 $ 290,114 Service 41,546 54,574 63,885 70,452 Cost of sales (excluding depreciation, depletion and amortization): Product 162,183 162,238 187,634 202,466 Service 25,292 34,726 40,155 52,126 Operating expenses: Selling, general and administrative 22,341 25,839 29,542 29,334 Depreciation, depletion and amortization 21,599 23,626 24,673 27,335 Total operating expenses 43,940 49,465 54,215 56,669 Operating income (loss) 13,382 44,036 63,019 49,305 Other (expense) income: Interest expense (7,646 ) (8,105 ) (8,347 ) (7,244 ) Other income (expense), net, including interest income (4,928 ) 638 1,308 1,108 Total other expense (12,574 ) (7,467 ) (7,039 ) (6,136 ) Income (loss) before income taxes 808 36,569 55,980 43,169 Income tax benefit 1,714 (7,110 ) (14,707 ) 28,783 Net income (loss) 2,522 29,459 41,273 71,952 Less: Net income (loss) attributable to non-controlling interest — — — — Net income (loss) attributable to U.S. Silica Holdings, Inc. $ 2,522 $ 29,459 $ 41,273 $ 71,952 Earnings (loss) per share, basic $ 0.03 $ 0.36 $ 0.51 $ 0.95 Earnings (loss) per share, diluted $ 0.03 $ 0.36 $ 0.50 $ 0.95 Weighted average shares, basic 80,983 81,087 81,121 75,539 Weighted average shares, diluted 82,244 81,945 81,783 75,539 Dividends declared per share $ 0.06 $ 0.06 $ 0.06 $ 0.06

Parent Company Financials

Parent Company Financials	12 Months Ended
	Dec. 31, 2018
Condensed Financial Information Disclosure [Abstract]
PARENT COMPANY FINANCIALS	NOTE Y— PARENT COMPANY FINANCIALS U.S. SILICA HOLDINGS, INC. (PARENT COMPANY ONLY) CONDENSED BALANCE SHEETS December 31, 2018 2017 (in thousands) ASSETS Current Assets: Cash and cash equivalents $ 107,151 $ 230,647 Due from affiliates 100,094 146,683 Total current assets 207,245 377,330 Investment in subsidiaries 850,099 1,024,511 Total assets $ 1,057,344 $ 1,401,841 LIABILITIES AND STOCKHOLDERS’ EQUITY Current Liabilities: Accrued expenses and other current liabilities $ 217 $ 106 Dividends payable 4,823 5,229 Total current liabilities 5,040 5,335 Deferred income taxes, net — — Total liabilities 5,040 5,335 Stockholders’ Equity: Preferred stock — — Common stock 818 812 Additional paid-in capital 1,169,383 1,147,084 Retained earnings 67,854 287,992 Treasury stock, at cost (178,215 ) (25,456 ) Accumulated other comprehensive loss (15,020 ) (13,926 ) Total U.S. Silica Holdings, Inc. stockholders’ equity 1,044,820 1,396,506 Non-controlling interest 7,484 — Total stockholders' equity 1,052,304 1,396,506 Total liabilities and stockholders’ equity $ 1,057,344 $ 1,401,841 U.S. SILICA HOLDINGS, INC. (PARENT COMPANY ONLY) CONDENSED STATEMENTS OF OPERATIONS AND COMPREHENSIVE INCOME (LOSS) Year ended December 31, 2018 2017 2016 (in thousands, except per share amounts) Sales $ — $ — $ — Cost of sales — — — Operating expenses Selling, general and administrative 254 252 184 Other — — 10 Total operating expenses 254 252 194 Operating loss (254 ) (252 ) (194 ) Other income (expense) Interest income 2,784 3,854 1,046 Other income, net, including interest income — — — Total other income (expense) 2,784 3,854 1,046 Income before income taxes and equity in net earnings of subsidiaries 2,530 3,602 852 Income tax benefit (expense) (696 ) (1,453 ) (344 ) Income before equity in net earnings of subsidiaries 1,834 2,149 508 Equity in earnings of subsidiaries, net of tax (202,655 ) 143,057 (41,564 ) Net income (loss) (200,821 ) 145,206 (41,056 ) Less: Net income (loss) attributable to non-controlling interest (13 ) — — Net income (loss) attributable to U.S. Silica Holdings, Inc. (200,808 ) 145,206 (41,056 ) Net income (loss) (200,821 ) 145,206 (41,056 ) Other comprehensive income (loss) Unrealized gain (loss) on investments (net of tax of z er o, zero, and $(4) for 2018, 2017 and 2016, respectively) — — (6 ) Unrealized gain (loss) on derivatives (net of tax of $(470) $(27) and $29 for 2018, 2017, and 2016, respectively) (1,545 ) (44 ) 49 Foreign currency translation adjustment (net of tax of $ (19 6) $2 and zero for 2018, 2017 and 2016, respectively) (614 ) (6 ) — Pension and other post-retirement benefits liability a djus tment (net of tax of $339, $1,205 and $152 for 2018, 2017 and 2016, respectively) 1,065 2,000 252 Comprehensive income (loss) (201,915 ) 147,156 (40,761 ) Less: Comprehensive income (loss) attributable to non-controlling interest $ (13 ) $ — $ — Comprehensive income (loss) attributable to U.S. Silica Holdings, Inc. $ (201,902 ) $ 147,156 $ (40,761 ) U.S. SILICA HOLDINGS, INC. (PARENT COMPANY ONLY) CONDENSED STATEMENTS OF STOCKHOLDERS' EQUITY Par Value Treasury Stock Additional Paid-In Capital Retained Earnings - Present Accumulated Other Comprehensive Income (Loss) Total U.S. Silica, Inc., Stockholders' Equity Non-controlling Interest Total Balance at January 1, 2016 $ 539 $ (15,845 ) $ 194,670 $ 220,974 $ (16,171 ) $ 384,167 $ — $ 384,167 Net loss — — — (41,056 ) — (41,056 ) — (41,056 ) Issuance of common stock (stock offerings net of issuance costs of $25,732) 272 — 931,016 — — 931,288 — 931,288 Unrealized gain on derivatives — — — — 49 49 — 49 Unrealized loss on short-term investments — — — — (6 ) (6 ) — (6 ) Pension and post-retirement liability — — — — 252 252 — 252 Cash dividend declared ($0.25 per share) — — — (16,893 ) — (16,893 ) — (16,893 ) Common stock-based compensation plans activity: Equity-based compensation — — 12,107 — — 12,107 — 12,107 Excess tax benefit from equity-based compensation — — — 148 — 148 — 148 Proceeds from options exercised — 8,465 (3,640 ) — — 4,825 — 4,825 Issuance of restricted stock — 1,437 (1,437 ) — — — — — Shares withheld for employee taxes related to vested restricted stock and stock units — 2,074 (3,665 ) — — (1,591 ) — (1,591 ) Balance at December 31, 2016 $ 811 $ (3,869 ) $ 1,129,051 $ 163,173 $ (15,876 ) $ 1,273,290 $ — $ 1,273,290 Net Income — — — 145,206 — 145,206 — 145,206 Unrealized loss on derivatives — — — — (44 ) (44 ) — (44 ) Foreign currency translation adjustment — — — — (6 ) (6 ) — (6 ) Pension and post-retirement liability — — — — 2,000 2,000 — 2,000 Cash dividend declared ($0.25 per share) — — — (20,387 ) — (20,387 ) — (20,387 ) Common stock-based compensation plans activity: Equity-based compensation — — 25,050 — — 25,050 — 25,050 Proceeds from options exercised — 1,190 (392 ) — — 798 — 798 Issuance of restricted stock — 1,859 (1,859 ) — — — — — Shares withheld for employee taxes related to vested restricted stock and stock units 1 386 (4,766 ) — — (4,379 ) — (4,379 ) Repurchase of common stock — (25,022 ) — — — (25,022 ) — (25,022 ) Balance at December 31, 2017 $ 812 $ (25,456 ) $ 1,147,084 $ 287,992 $ (13,926 ) $ 1,396,506 $ — $ 1,396,506 Net loss — — — (200,808 ) — (200,808 ) (13 ) (200,821 ) Unrealized loss on derivatives — — — — (1,545 ) (1,545 ) — (1,545 ) Foreign currency translation adjustment — — — — (614 ) (614 ) — (614 ) Pension and post-retirement liability — — — — 1,065 1,065 — 1,065 Cash dividend declared ($0.25 per share) — — — (19,330 ) — (19,330 ) — (19,330 ) Contributions from non-controlling interest — — — — — — 7,497 7,497 Common stock-based compensation plans activity: Equity-based compensation — — 22,337 — — 22,337 — 22,337 Proceeds from options exercised — 93 (32 ) — — 61 — 61 Shares withheld for employee taxes related to vested restricted stock and stock units 6 (4,383 ) (6 ) — — (4,383 ) — (4,383 ) Repurchase of common stock — (148,469 ) — — — (148,469 ) — (148,469 ) Balance at December 31, 2018 $ 818 $ (178,215 ) $ 1,169,383 $ 67,854 $ (15,020 ) $ 1,044,820 $ 7,484 $ 1,052,304 U.S. SILICA HOLDINGS, INC. (PARENT COMPANY ONLY) CONDENSED STATEMENTS OF CASH FLOWS Year ended December 31, 2018 2017 2016 (in thousands, except per share amounts) Operating activities: Net income (loss) $ (200,821 ) $ 145,206 $ (41,056 ) Adjustments to reconcile net income (loss) to net cash provided by operating activities: Undistributed (Income) loss from equity method investment, net 202,655 (143,057 ) 41,564 Other — — (30 ) Changes in assets and liabilities, net of effects of acquisitions: Accounts payable and accrued liabilities (295 ) 48 353 Net cash provided by operating activities 1,539 2,197 831 Investing activities: Proceeds from sales and maturities of short-term investments — — 21,872 Investment in subsidiary — (143,654 ) (188,177 ) Net cash provided by (used in) investing activities — (143,654 ) (166,305 ) Financing activities: Dividends paid (19,912 ) (20,377 ) (15,125 ) Repurchase of common stock (148,469 ) (25,022 ) — Proceeds from options exercised 61 798 4,603 Tax payments related to shares withheld for vested restricted stock and stock units (4,383 ) (4,379 ) (1,590 ) Issuance of common stock (secondary offering) — — 678,791 Issuance of treasury stock — — 221 Costs of common stock issuance — — (25,733 ) Contributions from non-controlling interest 7,497 — — Net financing activities with subsidiaries 40,171 (113,294 ) 106 Net cash provided by (used in) financing activities (125,035 ) (162,274 ) 641,273 Net increase (decrease) in cash and cash equivalents (123,496 ) (303,731 ) 475,799 Cash and cash equivalents, beginning of period 230,647 534,378 58,579 Cash and cash equivalents, end of period $ 107,151 $ 230,647 $ 534,378 Non-cash financing activities: Supplemental cash flow information: Cash paid (received) during the period for: Interest $ (2,784 ) $ (3,853 ) $ (1,046 ) Non-cash transactions Common stock issued for business acquisitions $ — $ — $ 278,229 Notes to Condensed Financial Statements of Registrant (Parent Company Only) These condensed parent company only financial statements have been prepared in accordance with Rule 12-04, Schedule I of Regulation S-X, because the restricted net assets of the subsidiaries of U.S. Silica Holdings, Inc. (as defined in Rule 4-08(e)(3) of Regulation S-X) exceed 25% of the consolidated net assets of the Company. The ability of the Company's operating subsidiaries to pay dividends may be restricted due to the terms of the Company's senior Credit Facility, as discussed in Note K - Debt to these financial statements. These condensed parent company financial statements have been prepared using the same accounting principles and policies described in the notes to the consolidated financial statements; the only exceptions are that (a) the parent company accounts for its subsidiaries using the equity method of accounting, (b) taxes are allocated to the parent from the subsidiary using the separate return method, and (c) intercompany loans are not eliminated. In the parent company financial statements, the Company's investment in subsidiaries is stated at cost plus equity in undistributed earnings of subsidiaries since the date of acquisition. These condensed parent company financial statements should be read in conjunction with the Company's consolidated financial statements and related notes thereto included elsewhere in this report. No cash dividends were paid to the parent by its consolidated entities for the years presented in the condensed financial statements.

Subsequent Events

Subsequent Events	12 Months Ended
	Dec. 31, 2018
Subsequent Events [Abstract]
SUBSEQUENT EVENTS	NOTE Z— SUBSEQUENT EVENTS On January 4, 2019, we paid a cash dividend of $0.0625 per share to common stockholders of record on December 14, 2018, which had been declared by our Board of Directors on November 13, 2018. On February 15, 2019, Our Board of Directors declared a quarterly cash dividend of $0.0625 per share to common stockholders of record at the close of business on March 14, 2019, payable on April 4, 2019.

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2018
Accounting Policies [Abstract]
Basis of Presentation and Consolidation	Basis of Presentation and Consolidation The accompanying Consolidated Financial Statements have been prepared in accordance with generally accepted accounting principles in the United States (“GAAP”). In the opinion of management, all adjustments necessary for a fair presentation of the Consolidated Financial Statements have been included. Such adjustments are of a normal, recurring nature. In conforming to the current year's presentation, the Company identified and corrected an amount in its statement of cash flows for the year ended December 31, 2017 . The correction reduced Capital Expenditures within Net Cash Used in Investing Activities with a corresponding decrease to Accounts Payable and Accrued Expenses within Net Cash Used in Operating Activities. The amount is presented as Non-cash Accrued Capital Expenditures and had no impact in the Company's Balance Sheet, Income Statement or Net Change in Cash and Cash Equivalents in the Statement of Cash Flows. Throughout this report we refer to (i) our Consolidated Balance Sheets as our “Balance Sheets,” (ii) our Consolidated Statements of Operations as our “Income Statements,” and (iii) our Consolidated Statements of Cash Flows as our “Cash Flows.”
Reclassifications	Certain reclassifications of prior year's amounts have been made to conform to the current year presentation.
Consolidation	Consolidation The 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 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 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.
Cash and Cash Equivalents	Cash and Cash Equivalents Cash and cash equivalents consist of all highly liquid investments with a maturity of three months or less when purchased. Because of the short maturity of these investments, the carrying amounts approximate their fair value. Cash and cash equivalents are invested primarily in money market securities held by financial institutions with high credit ratings. Accounts at each institution are insured by the Federal Deposit Insurance Corporation. Cash balances at times may exceed federally-insured limits. We have not experienced any losses in such accounts and believe we are not exposed to any significant credit risk on cash.
Accounts Receivables	Accounts Receivable The majority of our accounts receivable are due from companies in the oil and natural gas drilling, glass, building products, filler and extenders, foundries and other major industries. Credit is extended based on evaluation of a customer’s financial condition and, generally, collateral is not required. Accounts receivable are stated at amounts due from customers net of an allowance for doubtful accounts. Accounts outstanding longer than the payment terms are considered past due. We determine our allowance by considering a number of factors, including the length of time trade accounts receivable are past due, our previous loss history, the customer’s current ability to pay its obligation to us, and the condition of the general economy and the industry as a whole. Ongoing credit evaluations are performed. We write-off accounts receivable when they are deemed uncollectible, and payments subsequently received on such receivables are credited to the allowance for doubtful accounts.
Inventories	Inventories Inventories include raw stockpiles, in-process product and finished product available for shipment, as well as spare parts and supplies for routine facility maintenance. We value inventory at the lower of cost and net realizable value. Cost is determined using the first-in, first-out and average cost methods. Our inventoriable costs include production costs and transportation and additional service costs as applicable.
Property, Plant and Mine Development	Property, Plant and Mine Development Plant and equipment Plant and equipment is recorded at cost and depreciated over their estimated useful lives. Interest incurred during construction of facilities is capitalized and depreciated over the life of the asset. Costs for normal repairs and maintenance that do not extend economic life or improve service potential are expensed as incurred. Costs of improvements that extend economic life or improve service potential are capitalized and depreciated over the estimated remaining useful life. Depreciation is recorded using the straight-line method over the assets’ estimated useful lives as follows: buildings ( 15 years); land improvements ( 10 years); machinery and equipment, including computer equipment and software ( 3 - 10 years); furniture and fixtures ( 8 years). Leasehold improvements are depreciated over the shorter of the asset life or lease term. Construction-in-progress is primarily comprised of machinery and equipment which have not yet been placed in service. Mining property and development Mining property and development includes mineral deposits and mine exploration and development. Mineral deposits are initially recognized at cost, which approximates the estimated fair value on the date of purchase. Mine exploration and development costs include engineering and mineral studies, drilling and other related costs to delineate an ore body, and the removal of overburden to initially expose an ore body for production. Costs incurred before mineralization are classified as proven and probable reserves are expensed and classified as exploration or advanced projects, research and development expense. Capitalization of mine development project costs, that meet the definition of an asset, begins once mineralization is classified as proven and probable reserves. The cost of removing overburden and waste materials to access the ore body at an open pit mine prior to the production phase are referred to as “pre-stripping costs.” Pre-stripping costs are capitalized during the development of an open pit mine. The production phase of an open pit mine commences when saleable minerals, beyond a de minimis amount, are produced. Stripping costs incurred during the production phase of a mine are variable production costs that are included as a component of inventory to be recognized in costs applicable to sales in the same period as the revenue from the sale of inventory. Depletion and amortization of mineral deposits and mine development costs are recorded as the minerals are extracted, based on units of production and engineering estimates of mineable reserves. The impact of revisions to reserve estimates is recognized on a prospective basis. See Note H - Property, Plant and Mine Development . Mine reclamation costs and asset retirement obligations We recognize the fair value of any liability for conditional asset retirement obligations, including environmental remediation liabilities when incurred, which is generally upon acquisition, construction or development and/or through the normal operation of the asset, if sufficient information exists to reasonably estimate the fair value of the liability. These obligations generally include the estimated net future costs of dismantling, restoring and reclaiming operating mines and related mine sites, in accordance with federal, state, local regulatory and land lease agreement requirements. The liability is accreted over time through periodic charges to earnings. In addition, the asset retirement cost is capitalized as part of the asset’s carrying value and amortized over the life of the related asset. Reclamation costs are periodically adjusted to reflect changes in the estimated present value resulting from the passage of time and revisions to the estimates of either the timing or amount of the reclamation and abandonment costs. The reclamation obligation is based on when spending for an existing environmental disturbance will occur. If the asset retirement obligation is settled for other than the carrying amount of the liability, a gain or loss is recognized on settlement. We review, on an annual basis, unless otherwise deemed necessary, the reclamation obligation at each mine site in accordance with ASC guidance for accounting for reclamation obligations. Future remediation costs for inactive mines are accrued based on management’s best estimate at the end of each period of the costs expected to be incurred at a site. Such cost estimates include, where applicable, ongoing care, maintenance and monitoring costs. Changes in estimates at inactive mines are reflected in earnings in the period an estimate is revised.
Impairment or Disposal of Property, Plant and Mine Development	Impairment or Disposal of Property, Plant and Mine Development We periodically evaluate whether current events or circumstances indicate that the carrying value of our property, plant and equipment assets may not be recoverable. If circumstances indicate that the carrying value may not be recoverable, we estimate future undiscounted net cash flows using estimates of proven and probable sand reserves, estimated future sales prices (considering historical and current prices, price trends and related factors) and operating costs and anticipated capital expenditures. If the undiscounted cash flows are less than the carrying value of the assets, we recognize an impairment loss equal to the amount by which the carrying value exceeds the fair value of the assets. The recoverability of the carrying value of our mineral properties is dependent upon the successful development, start-up and commercial production of our mineral deposit and the related processing facilities. Our evaluation of mineral properties for potential impairment primarily includes assessing the existence or availability of required permits and evaluating changes in our mineral reserves, or the underlying estimates and assumptions, including estimated production costs. Assessing the economic feasibility requires certain estimates, including the prices of products to be produced and processing recovery rates, as well as operating and capital costs. Gains on the sale of property, plant and mine development are included in income when the assets are disposed of provided there is more than reasonable certainty of the collectability of the sales price and any future activities required to be performed by us relating to the disposal of the assets are complete or insignificant. Upon retirement or disposal of assets, all costs and related accumulated depreciation or amortization are written-off.
Goodwill and Other Intangible Assets and Related Impairment	Goodwill and Other Intangible Assets and Related Impairment Our intangible assets consist of goodwill, which is not being amortized, indefinite-lived intangibles, which consist of certain trade names that are not subject to amortization, intellectual property and customer relationships. Intellectual property mainly consists of patents and technology, and it is amortized on a straight-line basis over an average useful life of 15 years. Customer relationships are amortized on a straight-line basis over their useful life of 20 , 15 or 13 years. Goodwill represents the excess of the purchase price of business combinations over the fair value of net assets acquired. Goodwill and trade names are reviewed for impairment annually as of October 31, or more frequently when indicators of impairment exist. An impairment exists if the fair value of a reporting unit to which goodwill has been allocated, or the fair value of indefinite-lived intangible assets, is less than their respective carrying values. Prior to conducting a formal impairment test, we have an option to assess qualitative factors to determine whether the existence of events or circumstances leads to a determination that is more likely than not (more than 50% ) that the fair value of a reporting unit is less than its carrying amount. Such qualitative factors may include the following: macroeconomic conditions; industry and market considerations; cost factors; overall financial performance; and other relevant entity-specific events. If the qualitative assessment determines that an impairment is more likely than not, or if we choose to bypass the qualitative assessment, we perform a quantitative assessment by comparing the fair value of a reporting unit with its carrying amount and recognize an impairment charge for the amount by which the carrying amount exceeds the reporting unit’s fair value; however, the loss recognized should not exceed the total amount of goodwill allocated to that reporting unit.
Revenue Recognition and Deferred Revenues	Revenue Recognition Products We derive our product sales by mining and processing minerals that our customers purchase for various uses. Our product sales are primarily a function of the price per ton and the number of tons sold. We primarily sell our products through individual purchase orders executed under short-term price agreements or at prevailing market rates. The amount invoiced reflects product, transportation and / or additional handling services as applicable, such as storage, transloading the product from railcars to trucks and last mile logistics to the customer site. We invoice most of our product customers on a per shipment basis, although for some larger customers, we consolidate invoices weekly or monthly. Standard collection terms are net 30 days, although extended terms are offered in competitive situations. We recognize revenue for products and materials at a point in time following the transfer of control of such items to the customer, which typically occurs upon shipment or delivery depending on the terms of the underlying contracts. We account for shipping and handling activities related to product and material sales contracts with customers as costs to fulfill our promise to transfer the associated products pursuant to the accounting policy election allowed under ASC 606-10-25-18b. Accordingly, we record amounts billed for shipping and handling costs as a component of net sales and accrue and classify related costs as a component of cost of sales at the time revenue is recognized. For a limited number of customers, we sell under long-term, minimum purchase supply agreements. These agreements define, among other commitments, the volume of product that our customers must purchase, the volume of product that we must provide and the price that we will charge and that our customers will pay for each product. Prices under these agreements are generally fixed and subject to certain contractual adjustments. Sometimes these agreements may undergo negotiations regarding pricing and volume requirements, which may often occur in volatile market conditions. While these negotiations continue, we may deliver sand at prices or at volumes below the requirements in our existing supply agreements. We do not consider these agreements solely representative of contracts with customers. An executed order specifying the type and quantity of product to be delivered, in combination with the noted agreements, comprise our contracts in these arrangements. Service We derive our service revenues primarily through the provision of transportation, equipment rental, and contract labor services to companies in the oil and gas industry. Transportation services typically consist of transporting customer proppant from storage facilities to proximal well-sites and are contracted through work orders executed under established pricing agreements. The amount invoiced reflects the transportation services rendered. Equipment rental services provide customers with use of either dedicated or nonspecific wellhead proppant delivery equipment solutions for contractual periods defined either through formal lease agreements or executed work orders under established pricing agreements. The amounts invoiced reflect the length of time the equipment set was utilized in the billing period. Contract labor services provide customers with proppant delivery equipment operators through work orders executed under established pricing agreements. The amounts invoiced reflect the amount of time our labor services were utilized in the billing period. We typically invoice our customers on a weekly or monthly basis; however, some customers receive invoices upon well-site operation completion. Standard collection terms are net 30 days, although extended terms are offered in competitive situations. We typically recognize revenue for specific, dedicated equipment set rental arrangements under ASC 840, Leases. For the remaining components of service revenue, we have applied the practical expedient allowed under ASC 606-10-55-18 to recognize transportation revenues in proportion to the amount we have the right to invoice. Contracts with Multiple Performance Obligations For contracts that contain multiple performance obligations, such as work orders containing a combination of product, transportation, equipment rentals, and contract labor services, we allocate the transaction price to each performance obligation identified in the contract based on relative standalone selling prices, or estimates of such prices, and recognize the related revenue as control of each individual product or service is transferred to the customer, in satisfaction of the corresponding performance obligations. We typically invoice our customers on a weekly or monthly basis; however, some customers receive invoices upon well-site operation completion. Standard collection terms are net 30 days, although extended terms are offered in competitive situations. Taxes Collected from Customers and Remitted to Governmental Authorities. We exclude from our measurement of transaction prices all taxes assessed by governmental authorities that are both (i) imposed on and concurrent with a specific revenue-producing transaction and (ii) collected from customers. Accordingly, such tax amounts are not included as a component of net sales or cost of sales. Foreign Operations Foreign operations constituted approximately $44.0 million of our consolidated sales; $7.3 million of consolidated assets; $2.6 million of pre-tax income and $2.4 million of net income as of and for the year ended December 31, 2018. We had no significant foreign operations during the years ended December 31, 2017 and 2016. See Note U - Revenue . Deferred Revenues For a limited number of customers, we enter into supply agreements which give customers the right to make advanced payments toward the purchase of certain products at specified volumes over an average initial period of one to fifteen years. These payments represent consideration that is unconditional for which we have yet to transfer the related product. These payments are recorded as contract liabilities referred to as “deferred revenues” upon receipt and recognized as revenue upon delivery of the related product.
Unbilled Receivables	Unbilled Receivables Revenues recognized in advance of invoice issuance create assets referred to as “unbilled receivables.” Any portion of our unbilled receivables for which our right to consideration is conditional on a factor other than the passage of time is considered a contract asset. These assets are presented on a combined basis with accounts receivable and are converted to accounts receivable once billed.
Debt Issuance Costs	Debt Issuance Costs The Company defers costs directly associated with acquiring third-party financing, primarily loan origination costs and related professional expenses. Debt issuance costs are deferred and amortized using the effective interest rate method over the term of our senior secured Term Loan facility and the straight-line method for our Revolver facility. Debt issuance costs related to long-term debt are reflected as a direct deduction from the carrying amount of the debt.
Employee Benefit Plans	Employee Benefit Plans We provide a range of benefits to our employees and retired employees, including pensions and post-retirement healthcare and life insurance benefits. We record annual amounts relating to these plans based on calculations specified by generally accepted accounting principles, which include various actuarial assumptions, including discount rates, assumed rates of returns, compensation increases, turnover rates, mortality table, and healthcare cost trend rates. We review the actuarial assumptions on an annual basis and make modifications to the assumptions based on current rates and trends when it is deemed appropriate to do so. As required by U.S. generally accepted accounting principles, the effect of the modifications is generally recorded or amortized over future periods. We believe that the assumptions utilized in recording our obligations under the plans are reasonable based on advice from our actuaries and information as to assumptions used by other employers.
Environmental Costs	Environmental Costs Environmental costs, other than qualifying capital expenditures, are accrued at the time the exposure becomes known and costs can be reasonably estimated. Costs are accrued based upon management’s estimates of all direct costs, after taking into account expected reimbursement by third parties (primarily the sellers of acquired businesses) and are reviewed by outside consultants. Environmental costs are charged to expense unless a settlement with an indemnifying party has been reached.
Self-Insurance	Self-Insurance We are self-insured for various levels of employee health insurance coverage, workers’ compensation and third-party product liability claims alleging occupational disease. We purchase insurance coverage for claim amounts which exceed our self-insured retentions. Depending on the type of insurance, these self-insured retentions range from $0.1 million to $0.5 million per occurrence. Our insurance reserves are accrued based on estimates of the ultimate cost of claims expected to occur during the covered period. Our insurance reserves are accrued based on estimates of the ultimate cost of claims expected to occur during the covered period. These estimates are prepared with the assistance of outside actuaries and consultants. Our actuaries periodically review the volume and amount of claims activity, and based upon their findings, we adjust our insurance reserves accordingly. The ultimate cost of claims for a covered period may differ from our original estimates. The current portion of our self-insurance reserves is included in accrued liabilities and the non-current portion is included in other long-term obligations in our Balance Sheets.
Research and Development Costs	Research and Development Costs We may incur immaterial internal research and development (“R&D”) expenditures, and research and development conducted for others, all of which are expensed as incurred, and included in selling, general and administrative expense. R&D costs may include, but are not limited to, research and administrative salaries, contractor fees, building costs, utilities, administrative expenses, and allocations of corporate costs.
Advertising Costs	Advertising Costs We recognize advertising expense when incurred as selling, general and administrative expense.
Equity-based Compensation	Equity-based Compensation We grant stock options, restricted stock, restricted stock units and performance share units to certain of our employees and directors under the Amended and Restated U.S. Silica Holdings, Inc. 2011 Incentive Compensation Plan. We recognize the cost of employee services rendered in exchange for awards of equity instruments. Vesting of restricted stock and restricted stock units is based on the individual continuing to render service over a pre-defined vesting schedule, generally three years. Cash dividend equivalents are accrued and paid to the holders of time-based restricted stock units and restricted stock. The fair value of the restricted stock awards is equal to the market price of our stock at date of grant. The restricted award-related compensation expense is recognized, on a straight-line basis, over the vesting period. We grant performance share units to certain employees in which the number of shares of common stock ultimately received is determined based on achievement of certain performance thresholds over a specified performance period (generally three years) in accordance with the stock award agreement. Cash dividend equivalents are not accrued or paid on performance share units. We recognize expense based on the estimated vesting of our performance share units granted and the grant date market price. The estimated vesting of the performance share units is principally based on the probability of achieving certain financial performance levels during the vesting periods. In the period it becomes probable that the minimum performance criteria specified in the award agreement will be achieved, we recognize expense for the proportionate share of the total fair value of the award related to the vesting period that has already lapsed. The remaining fair value of the award is expensed on a straight-line basis over the remaining vesting period. We grant certain employees performance share units, the vesting of which is based on the Company’s total shareholder return (“TSR”) ranking among a peer group over a three -year period. The number of units that will vest will depend on the percentage ranking of the Company's TSR compared to the TSRs for each of the companies in the peer group over the performance period. For these awards subject to market conditions, a binomial-lattice model (i.e., Monte Carlo simulation model) is used to fair value these awards at grant date. The related compensation expense is recognized, on a straight-line basis, over the vesting period. We grant stock options to certain employees and directors. Stock options vest on a vesting schedule and the related compensation expense is recognized over the vesting period, usually over 3 or 4 years. In calculating the compensation expense for stock options granted, we estimate the fair value of each grant using the Black-Scholes option-pricing model. The fair value of stock options granted is based on the exercise price of the option and certain assumptions, which are evaluated and revised, as necessary, to reflect market conditions and experience. Our expected forfeiture rate is the estimated percentage of options granted that are expected to be forfeited or canceled on an annual basis before becoming fully vested. Our expected term is the period of time over which the options are expected to remain outstanding. An increase in the expected term will increase compensation expense. The computation of the expected term is based on the simplified method, under which the expected term is presumed to be the mid-point between the average vesting date and the end of the contractual term. The assumptions for expected volatility are based on historical experience for the same periods as our expected lives. Risk-free interest rates are set using grant-date U.S. Treasury yield curves for the same periods as our expected lives. The expected dividend yield is based on our future dividend expectations for the same periods as our expected lives.
Income Taxes	Income Taxes 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. In August 2018, the Internal Revenue Service released Tax Act guidance on limitations on executive compensation which clarified transition rules for certain compensation agreements in existence on November 2, 2017. Based on the issued guidance, we recorded a discrete tax expense of $0.7 million to remove deferred tax assets on certain executive compensation agreements that were not eligible for transition relief. The Tax Act reduces the corporate tax rate to 21 percent, effective January 1, 2018. Because ASC 740-10-25-47 requires the effect of a change in tax laws or rates to be recognized as of the date of enactment, we were required to adjust deferred tax assets and liabilities as of December 22, 2017. Accordingly, for the year ended December 31, 2017, we recorded a decrease related to deferred tax assets and liabilities of $45.0 million and $80.8 million , respectively, with a corresponding net adjustment to deferred income tax benefit of $35.8 million . Under the Tax Act, net operating loss (NOL) deductions arising in tax years beginning after December 31, 2017 can only offset up to 80 percent of future taxable income. The Act also prohibits NOL carrybacks, but allows indefinite carryforwards for NOLs arising in tax years beginning after December 31, 2017. Net operating losses arising before January 1, 2018 are accounted for under the previous tax rules that imposed no limit on the amount of the taxable income that can be set off using NOLs and that can be carried back 2 years and carried forward 20 years. The Tax Act repeals the corporate alternative minimum tax (AMT), effective for tax years beginning after December 31, 2017, but allows an entity to claim portions of any unused AMT credits over the next four years to offset its regular tax liability. An entity with unused AMT credits as of December 31, 2017 can first use these credits to offset its regular tax for 2017 and can then claim up to 50 percent of the remaining AMT credits in 2018, 2019, and 2020, with all remaining AMT credits refundable in 2021. Deferred taxes are provided on the liability method whereby deferred tax assets are recognized for deductible temporary differences and operating loss and tax credit carry forwards and deferred tax liabilities are recognized for taxable temporary differences. This approach requires recognition of deferred tax liabilities and assets for the expected future tax consequences of events that have been included in the financial statements or tax returns. Under this method, deferred tax liabilities and assets are determined based upon the difference between the financial statement and tax basis of assets and liabilities using enacted tax rates in effect for the year in which the expenses are expected to reverse. Valuation allowances are provided if, based on the weight of available evidence, it is more likely than not that some or all of the deferred tax assets will not be realized. We recognize a tax benefit associated with an uncertain tax position when, in management’s judgment, it is more likely than not that the position will be sustained upon examination by a taxing authority. For a tax position that meets the more-likely-than-not recognition threshold, we initially and subsequently measure the tax benefit as the largest amount that we judge to have a greater than 50% likelihood of being realized upon ultimate settlement with a taxing authority. The liability associated with unrecognized tax benefits is adjusted periodically due to changing circumstances, such as the progress of tax audits, case law developments and new or emerging legislation. Such adjustments are recognized entirely in the period in which they are identified. The effective tax rate includes the net impact of changes in the liability for unrecognized tax benefits and subsequent adjustments as considered appropriate by management. The largest permanent item in computing both our effective tax rate and taxable income is the deduction allowed for statutory depletion. The deduction for statutory depletion does not necessarily change proportionately to changes in income before income taxes.
Financial Instruments	Financial Instruments We currently use interest rate hedge agreements to manage interest costs and the risk associated with changing interest rates. Amounts to be paid or received under these hedge agreements are accrued as interest rates change and are recognized over the life of the hedge agreements as an adjustment to interest expense. Our policy is to not hold or issue derivative financial instruments for trading or speculative purposes. When entered into, these financial instruments are designated as hedges of underlying exposures, associated with our long-term debt, and are monitored to determine if they remain effective hedges. Gains and losses on derivatives designated as cash flow hedges are recorded in other comprehensive income (loss), net of tax, and reclassified to earnings in a manner that matches the timing of the earnings impact of the hedged transactions. The ineffective portion of all hedges, if any, is recognized currently in income.
Foreign Currency Translation	Foreign Currency Translation For our operations in countries where the functional currency is other than the U.S. dollar, balance sheet amounts are translated using the exchange rate in effect at the balance sheet date. Income statement amounts are translated monthly using the average exchange rate for the respective month. The gains and losses resulting from the changes in exchange rates from year-to-year are recorded as a component of accumulated other comprehensive income or loss as currency translation adjustments, net of tax. Any gains or losses on transactions in currencies other than the functional currency are included in other income (expense), net, including interest income.
Comprehensive Income (Loss)	Comprehensive Income (loss) In addition to net income (loss), comprehensive income (loss) includes all changes in equity during a period, such as adjustments to minimum pension liabilities and the effective portion of changes in fair value of derivative instruments that qualify as cash flow hedges.
Business Combinations	Business Combinations The Company accounts for business combinations using the acquisition method of accounting. Under this method, acquired assets, including separately identifiable intangible assets and any assumed liabilities, are recorded at their acquisition date estimated fair value. The excess of purchase price over the fair value amounts assigned to the assets acquired and liabilities assumed represents the goodwill amount resulting from the acquisition. Determining the fair value of assets acquired and liabilities assumed involves the use of significant estimates and assumptions.
New Accounting Pronouncements Recently Adopted and New Accounting Pronouncements Not Yet Adopted	In October 2018, the FASB issued ASU 2018-16, Derivatives and Hedging (Topic 815): Inclusion of the Secured Overnight Financing Rate (SOFR) Overnight Index Swap (OIS) Rate as a Benchmark Interest Rate for Hedge Accounting Purposes. The amendments in this ASU permit the use of the Overnight Index Swap ("OIS") rate based on the Secured Overnight Financing Rate ("SOFR") as a U.S. benchmark interest rate for hedge accounting purposes under Topic 815 in addition to the U.S. government ("UST"), the London Interbank Offered Rate ("LIBOR") swap rate, the OIS rate based on the Fed Funds Effective Rate and the Securities Industry and Financial Markets Association ("SIFMA") Municipal Swap Rate. For public entities, the amendments in this Update are effective for fiscal years beginning after December 15, 2018, and interim periods within those fiscal years. Early application is permitted in any interim period after issuance of this ASU. We early adopted this standard with no impact to our consolidated financial statements. New Accounting Pronouncements Not Yet 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. This update is effective for public entities for financial statements issued for fiscal years beginning after December 15, 2018, including interim periods within those fiscal years, and early adoption is permitted. The new transition method allows companies to use the effective date of the new lease standard as the date of initial application on transition. We established a project team in order to analyze the standard and have reviewed our current accounting policies and procedures to identify potential differences and changes which would result from applying the requirements of the new standard to our lease contracts. We selected a lease software to help us account for the new lease standard. We identified our population of lease agreements and assessed the impact of other arrangements for embedded leases. Using the modified retrospective approach, we evaluated the effect of the standard and expect to recognize right-of-use assets of $223.0 million and lease liabilities of $222.7 million as of January 1, 2019, and determined that the standard will not have a material impact on our consolidated statements of operations or cash flows. 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 are currently evaluating the effect that the transition guidance will have on our financial statements and related disclosures. 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. In November 2018, FASB issued ASU 2018-19, Codification Improvements to Topic 326, Financial Instruments-Credit Losses. The amendments in this ASU clarified issues related to Topic 326. In Issue 1, the amendment in this ASU mitigate transition complexity by requiring that for nonpublic business entities the amendments in ASU 2016-13 are effective for fiscal years after December 15, 2021, including interim periods within those fiscal years. In Issue 2, the amendment clarifies that receivable arising from operating leases are not within the scope of Subtopic 326-20. Impairment of receivables arising from operating leases should be accounting for in accordance with Topic 842, Leases. The ASU is effective for all entities for fiscal years beginning after December 15, 2019, including interim periods therein. Early adoption is permitted for any eliminated or modified disclosures upon issuance of this ASU. We are currently evaluating the adoption of this standard and the impact to our consolidated financial statements. New Accounting Pronouncements Recently Adopted In May 2014, the Financial Accounting Standards Board ("FASB") issued Accounting Standards Update (“ASU”) 2014-09, Revenue from Contracts with Customers (Topic 606), which supersedes previous revenue recognition guidance. The new guidance introduces a new principles-based framework for revenue recognition and disclosure. Since its issuance, the FASB has issued additional ASUs, amending the guidance and the effective dates of amendments, and the SEC has rescinded certain related SEC guidance. On January 1, 2018, we adopted the new accounting standard and all of the related amendments (“new revenue standard”) to all contracts using the modified retrospective method. Adoption of the new revenue standard did not result in a material cumulative effect adjustment to the opening balance of retained earnings. The comparative information has not been restated and continues to be reported under the accounting standards in effect for those periods. Adoption of the new revenue standard will not have material impact to our net income on an ongoing basis. See Note U - Revenue . In January 2017, the FASB issued ASU 2017-04, Intangibles - Goodwill and Other (Topic 350): Simplifying the Test for Goodwill Impairment, which removes Step 2 from the goodwill impairment test. It is effective for annual and interim periods beginning after December 15, 2019. Early adoption is permitted for interim or annual goodwill impairment tests performed with a measurement date after January 1, 2017. We early adopted this standard on a prospective basis in the fourth quarter of 2018 for our annual impairment test. We performed a quantitative assessment by comparing the fair value of our reporting units with their carrying amount and determined that the goodwill of our Oil & Gas Sand reporting unit was impaired. We recognized a goodwill impairment charge of $164.2 million during the fourth quarter of 2018. See Note I - Goodwill and Intangible Assets . In March 2017, the FASB issued ASU 2017-07, Compensation-Retirement Benefits (Topic 715), Improving the Presentation of Net Periodic Pension Cost and Net Periodic Postretirement Benefit. The update required companies to include the service cost component of net periodic benefit costs in the same line item or items as compensation costs arising from services rendered by the associated employees during the period. The update disallowed capitalization of the other components of net periodic benefit costs and required those costs to be presented in the income statement separately from the service cost component and outside of a subtotal of income from operations. The update was effective for fiscal years beginning after December 15, 2017, including interim periods within those annual periods for public business entities. Companies were required to retrospectively apply the requirement for a separate presentation in the income statement of service costs and other components of net benefit cost and prospectively adopt the requirement to limit the capitalization of benefit costs to the service component. Application of a practical expedient was allowed permitting an employer to use the amounts disclosed in its pension and other postretirement benefit plan note for the prior comparative periods as the estimation basis for applying the retrospective presentation requirements. We implemented the update on January 1, 2018 and utilized the practical expedient to estimate the impact on the prior comparative period information presented in the interim and annual financial statements. We previously capitalized all net periodic benefit costs incurred for plant personnel in inventory and recorded the majority of net periodic benefit costs incurred by corporate personnel and retirees into selling, general, and administrative expenses.
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 December 31, 2018 and 2017 , approximate their reported carrying values. Long-Term Debt, Including Current Maturities We believe that the fair values of our long-term debt, including current maturities, approximate their carrying values based on their effective interest rates compared to current market rates. Derivative Instruments The estimated fair value of our derivative instruments 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 December 31, 2018 , we have assessed that the impact of the credit valuation adjustments on the overall valuation of our derivative positions is not significant. As a result, we have determined that our derivative valuations in their entirety are classified in Level 2 of the fair value hierarchy.

Summary of Significant Accoun_3

Summary of Significant Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2018
Accounting Policies [Abstract]
Schedule of Reconciliation of Effects of Reclassification on Statements of Income	The following is a reconciliation of the effect of the reclassification (in thousands) of the net benefit cost in the Company’s Income Statements for the years ended December 31, 2017 and 2016 . In addition, the table reflects the effect of the reclassification between product sales and services sales to conform to the current year's presentation for the years ended December 31, 2017 and 2016 : Year ended December 31, 2017 As Previously Reported Services Reclassifications ASU 2017-07 Adjustments As Revised Product Sales $ 1,057,553 $ (47,159 ) $ — $ 1,010,394 Service Sales 183,298 47,159 — 230,457 Total sales 1,240,851 — — 1,240,851 Product cost of sales 720,312 (5,096 ) (695 ) 714,521 Service cost of sales 147,203 5,096 — 152,299 Total cost of sales (excluding depreciation, depletion and amortization) 867,515 — (695 ) 866,820 Selling, general and administrative expenses 107,592 — (536 ) 107,056 Operating income 168,511 — 1,231 169,742 Other income (expense) (643 ) — (1,231 ) (1,874 ) Year ended December 31, 2016 As Previously Reported Services Reclassifications ASU 2017-07 Adjustments As Revised Product Sales $ 523,900 $ 237 $ — $ 524,137 Service Sales 35,725 (237 ) — 35,488 Total sales 559,625 — — 559,625 Product cost of sales 455,189 2,079 (485 ) 456,783 Service cost of sales 22,106 (2,079 ) — 20,027 Total cost of sales (excluding depreciation, depletion and amortization) 477,295 — (485 ) 476,810 Selling, general and administrative expenses 67,727 — (555 ) 67,172 Operating income (53,531 ) — 1,040 (52,491 ) Other income (expense) 3,758 — (1,040 ) 2,718

Earnings Per Share (Tables)

Earnings Per Share (Tables)	12 Months Ended
	Dec. 31, 2018
Earnings Per Share [Abstract]
Schedule of Computation of Basic and Diluted Earnings Per Share	The following table shows the computation of basic and diluted earnings per share for the years ended December 31, 2018 , 2017 and 2016 : In thousands, except per share amounts Year ended December 31, 2018 2017 2016 Numerator: Net income (loss) attributable to U.S. Silica Holdings, Inc. $ (200,808 ) $ 145,206 $ (41,056 ) Denominator: Weighted average shares outstanding 76,453 81,051 65,037 Diluted effect of stock awards — 909 — Weighted average shares outstanding assuming dilution 76,453 81,960 65,037 Earnings (loss) per share attributable to U.S. Silica Holdings, Inc.: Basic earnings (loss) per share $ (2.63 ) $ 1.79 $ (0.63 ) Diluted earnings (loss) per share $ (2.63 ) $ 1.77 $ (0.63 )
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: Year ended December 31, 2018 2017 2016 Stock options excluded 574 195 573 Restricted stock and performance share units awards excluded 155 305 166

Capital Structure and Accumul_2

Capital Structure and Accumulated Other Comprehensive Income (Loss) (Tables)	12 Months Ended
	Dec. 31, 2018
Equity [Abstract]
Schedule of Declared Quarterly Cash Dividends	During the year ended December 31, 2018 , our Board of Directors declared quarterly cash dividends as follows: Dividends per Common Share Declaration Date Record Date Payable Date $ 0.0625 February 16, 2018 March 15, 2018 April 5, 2018 $ 0.0625 May 14, 2018 June 15, 2018 July 6, 2018 $ 0.0625 July 16, 2018 September 14, 2018 October 3, 2018 $ 0.0625 November 13, 2018 December 14, 2018 January 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 year ended December 31, 2018 : For the Year Ended December 31, 2018 Unrealized gain/(loss) on cash flow hedges Foreign currency translation adjustments Pension and other post-retirement benefits liability Total Beginning Balance $ (76 ) $ (6 ) $ (13,844 ) $ (13,926 ) Other comprehensive gain (loss) before reclassifications (1,622 ) (614 ) (879 ) (3,115 ) Amounts reclassed from accumulated other comprehensive loss 77 — 1,944 2,021 Ending Balance $ (1,621 ) $ (620 ) $ (12,779 ) $ (15,020 )

Business Combinations (Tables)

Business Combinations (Tables)	12 Months Ended
	Dec. 31, 2018
Business Combinations [Abstract]
Schedule of Identifiable Assets Acquired and Liabilities Assumed	The following table sets forth the preliminary allocation of the purchase price to EPMH's identifiable tangible and intangible assets acquired and liabilities assumed, including measurement period adjustments (in thousands): Preliminary allocation of purchase price: Estimate as of May 1, 2018 Measurement Period Adjustments Purchase Price Allocation Accounts receivable, net $ 43,354 $ (49 ) $ 43,305 Inventories 84,395 1,717 86,112 Property, plant and mine development 123,086 25,409 148,495 Mineral rights 462,050 (42,581 ) 419,469 Identifiable intangible assets - finite lived 21,050 (10,780 ) 10,270 Identifiable intangible assets - indefinite lived 25,050 13,000 38,050 Prepaids and deposits 2,054 18 2,072 Other assets 4,088 3,386 7,474 Goodwill 139,787 10,841 150,628 Total assets acquired 904,914 961 905,875 Accounts payable 13,435 — 13,435 Accrued expenses and other current liabilities 8,255 2,049 10,304 Deferred tax liabilities 130,209 (7,398 ) 122,811 Long term obligations 9,766 6,310 16,076 Total liabilities assumed $ 161,665 $ 961 $ 162,626 Net assets acquired $ 743,249 $ — $ 743,249 The following table sets forth the final allocation of the purchase price to MS Sands' identifiable tangible and intangible assets acquired and liabilities assumed, including measurement period adjustments (in thousands): Estimate as of December 31, 2017 Measurement Period Adjustments Purchase Price Allocation Accounts receivable $ 11,201 $ — $ 11,201 Inventories 8,067 — 8,067 Other current assets 362 — 362 Assets held for sale 9,453 — 9,453 Property, plant and mine development 27,458 — 27,458 Mineral rights 26,300 (2,800 ) 23,500 Other non-current assets 1,136 — 1,136 Goodwill 22,522 2,800 25,322 Customer relationships 1,840 — 1,840 Total assets acquired 108,339 — 108,339 Accounts payable and accrued expenses 3,761 — 3,761 Unfavorable leasehold positions 2,237 — 2,237 Notes Payable 866 — 866 Other long term liabilities — — — Asset retirement obligations 474 — 474 Total liabilities assumed 7,338 — 7,338 Net assets acquired $ 101,001 $ — $ 101,001 The following table sets forth the final allocation of the purchase price to NBI’s identifiable tangible and intangible assets acquired and liabilities assumed, including measurement period adjustments (in thousands): Initial Estimate Measurement Period Adjustments Purchase Price Allocation Accounts receivable $ 2,680 $ — $ 2,680 Inventories 3,494 — 3,494 Other current assets 428 — 428 Income tax deposits 6,657 (217 ) 6,440 Property, plant and mine development 210,913 (4,281 ) 206,632 Identifiable intangible assets 1,600 — 1,600 Goodwill 86,228 4,670 90,898 Total assets acquired 312,000 172 312,172 Accounts payable, accrued expenses and other current liabilities 1,938 726 2,664 Deferred revenue 500 — 500 Notes payable 24,361 243 24,604 Capital lease liabilities 3,331 — 3,331 Asset retirement obligations 710 — 710 Deferred tax liabilities 67,435 (797 ) 66,638 Total liabilities assumed 98,275 172 98,447 Net assets acquired $ 213,725 $ — $ 213,725 The following table sets forth the allocation of the purchase price to Sandbox’s identifiable tangible and intangible assets acquired and liabilities assumed (in thousands): Allocation of Purchase price: (in thousands) Accounts receivable $ 13,392 Prepaid expenses and other 1,465 Property, plant and mine development 32,336 Identifiable intangible assets 120,144 Goodwill 86,100 Total assets acquired 253,437 Accounts payable 4,122 Deferred revenue 4,902 Accrued expenses and other current liabilities 3,292 Total liabilities assumed 12,316 Net assets acquired $ 241,121
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) Customer relationships $ 1,600 13 The acquired intangible assets and the related estimated useful lives consist of the following: Approximate Fair Value Estimated Useful Life (in thousands) (in years) Technology and intellectual property $ 2,900 15 Customer relationships 7,370 15 Total identifiable intangible assets - finite lived $ 10,270 Trade names $ 38,050 Total identifiable intangible assets - indefinite lived $ 38,050 The acquired intangible assets and the related estimated useful lives consist of the following: Approximate Fair Value Estimated Useful Life (in thousands) (in years) Customer relationships $ 1,840 15 The acquired intangible assets and the related estimated useful lives consist of the following: Approximate Fair Value Estimated Useful Life (in thousands) (in years) Indefinite lived intangible assets - Trade names $ 17,844 Indefinite Definite lived intangible assets - Technology and intellectual property 57,700 15 Definite lived intangible asset - Customer relationships 44,600 13 Total fair value of identifiable intangible assets $ 120,144
Schedule of Pro Forma Information	The following unaudited pro forma consolidated financial information reflects the results of operations as if the MS Sand Acquisition had occurred on January 1, 2016, after giving effect to certain purchase accounting adjustments. These adjustments mainly include incremental depreciation expense related to the fair value adjustment of property, plant, equipment and mine development, amortization expense related to identifiable intangible assets and tax expense related to the combined tax provisions. This information does not purport to be indicative of the actual results that would have occurred if the acquisition had actually been completed on the date indicated, nor is it necessarily indicative of the future operating results or the financial position of the combined company (in thousands, except per share amounts): For the year ended December 31, 2017 2016 Sales $ 1,287,202 $ 642,951 Net income (loss) $ 143,604 $ (55,835 ) Basic earnings (loss) per share $ 1.77 $ (0.86 ) Diluted earnings (loss) per share $ 1.75 $ (0.86 ) The following unaudited pro forma consolidated financial information reflects the results of operations as if the EPMH acquisition had occurred on January 1, 2017, after giving effect to certain purchase accounting adjustments. Material non-recurring transaction costs attributable to the business combination were $15.2 million . Pro forma net income includes incremental interest expense due to the related debt financing, incremental depreciation and depletion expense related to the fair value adjustment of property, plant and mine development, amortization expense related to identifiable intangible assets, and tax expense related to the combined tax provisions. This information does not purport to be indicative of the actual results that would have occurred if the acquisition had actually been completed on the date indicated, nor is it necessarily indicative of the future operating results or the financial position of the combined company (in thousands, except per share amounts): For the year ended December 31, 2018 2017 Sales $ 1,659,775 $ 1,454,070 Net income (loss) $ (179,220 ) $ 116,899 Basic earnings (loss) per share $ (2.34 ) $ 1.44 Diluted earnings (loss) per share $ (2.34 ) $ 1.43 The following unaudited pro forma consolidated financial information reflects the results of operations as if the NBI Acquisition and Sandbox Acquisition had occurred on January 1, 2015, after giving effect to certain purchase accounting adjustments. These adjustments mainly include incremental depreciation expense related to the fair value adjustment of property, plant, equipment and mine development, amortization expense related to identifiable intangible assets and tax expense related to the combined tax provisions. This information does not purport to be indicative of the actual results that would have occurred if the acquisition had actually been completed on the date indicated, nor is it necessarily indicative of the future operating results or the financial position of the combined company (in thousands, except per share amounts): For the year ended December 31, 2016 Sales $ 615,552 Net income (loss) $ (45,161 ) Basic earnings (loss) per share $ (0.69 ) Diluted earnings (loss) per share $ (0.69 )

Accounts Receivable (Tables)

Accounts Receivable (Tables)	12 Months Ended
	Dec. 31, 2018
Receivables [Abstract]
Schedule of Accounts Receivable and Allowance for Doubtful Accounts	At December 31, 2018 and December 31, 2017 , accounts receivable (in thousands) consisted of the following: December 31, December 31, Trade receivables $ 198,435 $ 217,649 Less: Allowance for doubtful accounts (6,751 ) (7,100 ) Net trade receivables 191,684 210,549 Other receivables (1) 23,802 2,037 Total accounts receivable $ 215,486 $ 212,586 (1 ) At December 31, 2018, other receivables include $16.0 million of refundable alternative minimum tax credits. Changes in our allowance for doubtful accounts (in thousands) during the years ended December 31, 2018 and 2017 are as follows: December 31, December 31, Beginning balance $ 7,100 $ 7,042 Bad debt provision 315 1,529 Write-offs (664 ) (1,471 ) Ending balance $ 6,751 $ 7,100

Inventories (Tables)

Inventories (Tables)	12 Months Ended
	Dec. 31, 2018
Inventory Disclosure [Abstract]
Schedule of Inventories	At December 31, 2018 and December 31, 2017 , inventories (in thousands) consisted of the following: December 31, 2018 December 31, 2017 Supplies $ 41,453 $ 21,277 Raw materials and work in process 68,474 28,034 Finished goods 52,160 43,065 Total inventories $ 162,087 $ 92,376

Property, Plant and Mine Deve_2

Property, Plant and Mine Development (Tables)	12 Months Ended
	Dec. 31, 2018
Property, Plant and Equipment [Abstract]
Schedule of Property, Plant and Mine Development	At December 31, 2018 and December 31, 2017 , property, plant and mine development (in thousands) consisted of the following: December 31, December 31, Mining property and mine development $ 995,759 $ 586,242 Asset retirement cost 12,732 14,184 Land 55,502 36,552 Land improvements 67,729 45,878 Buildings 64,515 56,330 Machinery and equipment 958,357 590,566 Furniture and fixtures 3,599 2,953 Construction-in-progress 167,933 189,970 2,326,126 1,522,675 Accumulated depletion, depreciation and amortization (499,823 ) (353,520 ) Total property, plant and mine development, net $ 1,826,303 $ 1,169,155

Goodwill and Intangible Assets

Goodwill and Intangible Assets (Tables)	12 Months Ended
	Dec. 31, 2018
Goodwill and Intangible Assets Disclosure [Abstract]
Schedule of Changes in the Carrying Amount of Goodwill	The changes in the carrying amount of goodwill (in thousands) by business segment consisted of the following: Oil & Gas Proppants Segment Industrial & Specialty Products Segment Total Goodwill $ 47,947 $ 20,700 $ 68,647 Impairment losses — — — Balance at January 1, 2016 $ 47,947 $ 20,700 $ 68,647 NBI acquisition 86,228 — 86,228 Sandbox acquisition 86,100 — 86,100 Goodwill 220,275 20,700 240,975 Impairment losses — — — Balance at December 31, 2016 220,275 20,700 240,975 White Armor acquisition — 3,912 3,912 NBI acquisition measurement period adjustment 4,670 — 4,670 MS Sand acquisition 52,187 — 52,187 MS Sand acquisition measurement period adjustment (29,665 ) — (29,665 ) Goodwill 247,467 24,612 272,079 Impairment losses — — — Balance at December 31, 2017 247,467 24,612 272,079 MS Sand acquisition measurement period adjustment 2,800 — 2,800 EPMH acquisition — 139,787 139,787 EPMH acquisition measurement period adjustment — 10,841 10,841 Oil & Gas Sand impairment (164,167 ) — (164,167 ) Goodwill 250,267 175,240 425,507 Impairment losses (164,167 ) — (164,167 ) Balance at December 31, 2018 $ 86,100 $ 175,240 $ 261,340
Schedule of Changes in the Carrying Amount of Definite-Lived Intangible Assets	The changes in the carrying amount of intangible assets (in thousands) consisted of the following: December 31, 2018 December 31, 2017 Estimated Useful Life Gross Carrying Amount Accumulated Amortization Net Gross Carrying Amount Accumulated Amortization Net (in years) Technology and intellectual property 15 $ 83,616 $ (11,168 ) $ 72,448 $ 70,703 $ (5,917 ) $ 64,786 Customer relationships 13 - 15 68,379 (13,541 ) 54,838 61,229 (9,076 ) 52,153 Total definite-lived intangible assets: $ 151,995 $ (24,709 ) $ 127,286 $ 131,932 $ (14,993 ) $ 116,939 Trade names 66,640 — 66,640 33,068 — 33,068 Other 700 — 700 — — — Total intangible assets: $ 219,335 $ (24,709 ) $ 194,626 $ 165,000 $ (14,993 ) $ 150,007
Schedule of Changes in the Carrying Amount of Indefinite-Lived Intangible Assets	The changes in the carrying amount of intangible assets (in thousands) consisted of the following: December 31, 2018 December 31, 2017 Estimated Useful Life Gross Carrying Amount Accumulated Amortization Net Gross Carrying Amount Accumulated Amortization Net (in years) Technology and intellectual property 15 $ 83,616 $ (11,168 ) $ 72,448 $ 70,703 $ (5,917 ) $ 64,786 Customer relationships 13 - 15 68,379 (13,541 ) 54,838 61,229 (9,076 ) 52,153 Total definite-lived intangible assets: $ 151,995 $ (24,709 ) $ 127,286 $ 131,932 $ (14,993 ) $ 116,939 Trade names 66,640 — 66,640 33,068 — 33,068 Other 700 — 700 — — — Total intangible assets: $ 219,335 $ (24,709 ) $ 194,626 $ 165,000 $ (14,993 ) $ 150,007
Schedule of Estimated Amortization Expense Related to Definite-Lived Intangible Assets	The estimated amortization expense related to definite-lived intangible assets (in thousands) for the five succeeding years is as follows: 2019 $ 12,396 2020 12,397 2021 12,396 2022 12,381 2023 12,376

Accounts Payable and Accrued _2

Accounts Payable and Accrued Liabilities (Tables)	12 Months Ended
	Dec. 31, 2018
Payables and Accruals [Abstract]
Schedule of Accounts Payables and Accrued Liabilities	At December 31, 2018 and 2017 , accounts payable and accrued liabilities (in thousands) consisted of the following: December 31, 2018 2017 Trade payables $ 178,804 $ 148,772 Accrued salaries and wages 12,291 6,126 Accrued vacation liability 3,503 2,906 Current portion of liability for pension and post-retirement benefits 2,708 1,524 Accrued healthcare liability 2,702 1,837 Accrued property taxes and sales taxes 4,490 2,720 Other accrued liabilities 11,902 7,156 Accounts payable and accrued liabilities $ 216,400 $ 171,041

Debt (Tables)

Debt (Tables)	12 Months Ended
	Dec. 31, 2018
Debt Disclosure [Abstract]
Schedule of Debt	At December 31, 2018 and 2017 , debt (in thousands) consisted of the following: December 31, December 31, Senior secured credit facility: Revolver expiring May 1, 2023 (8.50% at December 31, 2018 and 5.75% at December 31, 2017) $ — $ — Term Loan facility—final maturity May 1, 2025 (6.56% at December 31, 2018 and 4.75%-5.25% December 31, 2017) 1,270,400 489,075 Less: Unamortized original issue discount (6,511 ) (944 ) Less: Unamortized debt issuance cost (31,310 ) (3,099 ) Note payable secured by royalty interest 26,511 24,740 Customer note payable — 745 Equipment notes payable 321 719 Capital leases 344 706 Total debt 1,259,755 511,942 Less: current portion (13,327 ) (6,867 ) Total long-term portion of debt $ 1,246,428 $ 505,075
Schedule of Contractual Maturities of Debt	The minimum payments (in thousands) for the next five years required by the note are as follows: 2019 $ 1,750 2020 1,750 2021 1,750 2022 1,750 2023 1,750 At December 31, 2018 , contractual maturities of our senior secured Credit Facility (in thousands) are as follows: 2019 $ 12,800 2020 12,800 2021 12,800 2022 12,800 2023 12,800 Thereafter 1,206,400 Total $ 1,270,400

Asset Retirement Obligations (T

Asset Retirement Obligations (Tables)	12 Months Ended
	Dec. 31, 2018
Asset Retirement Obligation Disclosure [Abstract]
Schedule of Changes in Asset Retirement Obligations	Changes in the asset retirement obligations (in thousands) during the years ended December 31, 2018 and 2017 are as follows: December 31, December 31, 2017 Beginning balance $ 19,032 $ 11,159 Accretion 1,214 879 Additions and revisions of prior estimates (319 ) 6,994 Addition related to EPMH acquisition 2,733 — EPMH measurement period adjustment (2,131 ) — Disposal related to sale of transloads (2,116 ) — Ending balance $ 18,413 $ 19,032

Derivative Instruments (Tables)

Derivative Instruments (Tables)	12 Months Ended
	Dec. 31, 2018
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 N - Fair Value Accounting for more information regarding the estimated fair values of our derivative instruments at December 31, 2018 and 2017 . December 31, 2018 December 31, 2017 Maturity Contract/Notional Carrying Fair Maturity Date Contract/Notional Carrying Fair LIBOR (1) interest rate swap agreement 2020 $440 million $ (1,475 ) $ (1,475 ) — $ — $ — $ — LIBOR (1) interest rate swap agreement 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 years ended December 31, 2018 , 2017 and 2016 . 2018 2017 2016 Deferred losses from derivatives in OCI, beginning of period $ (76 ) $ (32 ) $ (81 ) Gain (loss) recognized in OCI from derivative instruments (1,622 ) (45 ) (32 ) Loss reclassified from Accumulated OCI 77 1 81 Deferred losses from derivatives in OCI, end of period $ (1,621 ) $ (76 ) $ (32 )

Equity-Based Compensation (Tabl

Equity-Based Compensation (Tables)	12 Months Ended
	Dec. 31, 2018
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Schedule of Stock Options Activity	The following table summarizes the status of, and changes in, our stock option awards during the year ended December 31, 2018 : Number of Weighted Aggregate Intrinsic Value Weighted Outstanding at December 31, 2017 908,919 $ 28.46 $ 7,008 6.1 years Granted — — — Exercised (4,167 ) 14.65 — Forfeited (918 ) 31.30 — Expired (1,838 ) $ 31.30 $ — Outstanding at December 31, 2018 901,996 $ 28.52 $ 18,566 4.8 years Exercisable at December 31, 2018 901,996 $ 28.52 $ 18,566 4.8 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 year ended December 31, 2018 : Number of Shares Grant Date Weighted Unvested, December 31, 2017 881,416 $ 42.16 Granted 261,500 31.24 Vested (225,000 ) 41.99 Forfeited (79,728 ) 40.45 Unvested, December 31, 2018 838,188 $ 39.44 The following table summarizes the status of, and changes in, our unvested restricted stock awards during the year ended December 31, 2018 : Number of Shares Grant Date Weighted Average Fair Value Unvested, December 31, 2017 461,346 $ 30.76 Granted 415,110 21.57 Vested (256,012 ) 28.66 Forfeited (32,867 ) 30.82 Unvested, December 31, 2018 587,577 $ 25.18

Commitments and Contingencies (

Commitments and Contingencies (Tables)	12 Months Ended
	Dec. 31, 2018
Commitments and Contingencies Disclosure [Abstract]
Schedule of Future Minimum Annual Commitments	Future Minimum Annual Commitments at December 31, 2018 (in thousands): Year ending December 31, Operating Lease Minimum Rental Payments Minimum Purchase Commitments 2019 $ 74,884 $ 23,243 2020 59,490 15,406 2021 40,302 8,307 2022 31,853 5,640 2023 22,596 4,915 Thereafter 40,148 6,084 Total future lease and purchase commitments $ 269,273 $ 63,595

Pension and Post-Retirement B_2

Pension and Post-Retirement Benefits (Tables)	12 Months Ended
	Dec. 31, 2018
Retirement Benefits [Abstract]
Schedule of Net Pension and Post-Retirement Benefit Plans	Net pension benefit cost (in thousands) consisted of the following for the years ended December 31, 2018 , 2017 and 2016 : Year Ended 2018 2017 2016 Service cost $ 1,307 $ 1,037 $ 1,078 Interest cost 4,632 3,971 4,067 Expected return on plan assets (5,969 ) (5,265 ) (5,495 ) Net amortization and deferral 2,526 1,773 1,592 Net pension benefit costs $ 2,496 $ 1,516 $ 1,242 Net post-retirement benefit cost (in thousands) consisted of the following for the years ended December 31, 2018 , 2017 and 2016 : Year Ended December 31, 2018 2017 2016 Service cost $ 102 $ 107 $ 132 Interest cost 740 753 876 Expected return on plan assets — (1 ) (1 ) Special termination benefit — — 21 Net post-retirement benefit costs $ 842 $ 859 $ 1,028
Schedule of Changes in Benefit Obligations and Plan Assets	The changes in benefit obligations and plan assets (in thousands), as well as the funded status (in thousands) of our pension and post-retirement plans at December 31, 2018 and 2017 are as follows: Pension Benefits Post-retirement Benefits 2018 2017 2018 2017 Benefit obligation at January 1, $ 122,052 $ 116,145 $ 22,771 $ 24,393 Service cost 1,307 1,037 102 107 Interest cost 4,632 3,971 740 753 Actuarial (gain) loss (10,263 ) 6,824 (965 ) (1,576 ) Benefits paid (8,202 ) (6,685 ) (1,499 ) (1,280 ) Amendments — 760 — — Other (1) 29,374 — 421 374 Benefit obligation at December 31, $ 138,900 $ 122,052 $ 21,570 $ 22,771 Fair value of plan assets at January 1, $ 92,067 $ 83,850 $ — $ 14 Actual return on plan assets (6,204 ) 12,757 — (1 ) Employer contributions 3,350 2,145 1,078 893 Benefits paid (8,202 ) (6,685 ) (1,499 ) (1,280 ) Other (1) 21,385 — 421 374 Fair value of plan assets at December 31, $ 102,396 $ 92,067 $ — $ — Plan assets less than benefit obligations at December 31 recognized as liability for pension and other post-retirement benefits $ (36,504 ) $ (29,985 ) $ (21,570 ) $ (22,771 ) (1 ) Includes opening pension benefit obligation and plan assets balances related to the May 1, 2018, EPMH acquisition.
Schedule of Estimated Future Pension and Post-Retirement Benefit Payments	Future estimated annual benefit payments (in thousands) for pension and post-retirement benefit obligations at December 31, 2018 are as follows: Benefits Post-retirement Pension Before After 2019 $ 10,022 $ 1,553 $ 1,394 2020 9,166 1,592 1,433 2021 9,236 1,653 1,496 2022 9,394 1,691 1,535 2023 9,380 1,686 1,528 2024-2028 47,737 8,262 7,442
Schedule of Amounts in Accumulated Other Comprehensive Income Expected to be Recognized as Components of Net Periodic Benefit Cost	The amounts in accumulated other comprehensive income (loss) expected to be recognized as components of net periodic benefit cost (in thousands) during the following fiscal year are as follows: Benefits Pension Post-retirement Total Net actuarial loss $ 1,034 $ — $ 1,034 Prior service cost 534 — 534 $ 1,568 $ — $ 1,568
Schedule of Weighted-Average Assumptions Used to Determine Benefit Obligations	The following weighted-average assumptions were used to determine our obligations under the plans: Pension Benefits Post-retirement Benefits 2018 2017 2018 2017 Discount rate 4.4 % 3.7 % 4.3 % 3.7 % Long-term rate of compensation increase 3.0%-3.5% 3.5 % N/A N/A Long-term rate of return on plan assets 6.25%-7.15% 6.8 % N/A 7.0 % Health care cost trend rate: Pre-65 initial rate/ultimate rate N/A N/A 7.3%/4.5% 7.3%/4.5% Pre-65 ultimate year N/A N/A — — Post-65 initial rate/ultimate rate N/A N/A 8.0%/4.5% 8.0%/4.5% Post-65 ultimate year N/A N/A 2026/2027 2025/2026
Schedule of Mortality Tables Used	Mortality tables used for pension benefits and post-retirement benefits plans are the following: Pension and Post-retirement Benefits 2018 2017 Healthy Lives RP-2014 mortality table, adjusted back to 2006 base rates, with generational mortality improvements using Scale MP-2018 RP-2014 mortality table, adjusted back to 2006 base rates, with generational mortality improvements using Scale MP-2017 Disabled Lives RP-2014 disabled retiree mortality table, adjusted back to 2006 base rates, with generational mortality improvements using Scale MP-2018 RP-2014 disabled retiree mortality table, adjusted back to 2006 base rates, with generational mortality improvements using Scale MP-2017
Schedule of Effect of One-Percentage-Point Change in Assumed Health Care Cost Trend Rates	Assumed health care cost trend rates have a significant effect on the amounts reported for the health care plans. A one-percentage-point change in assumed health care cost trend rates would have the following effects (in thousands): One-Percentage-Point Increase Decrease Effect on total of service and interest cost $ 109 $ (92 ) Effect on post-retirement benefit obligation 2,291 (1,967 )
Schedule of Major Investments Categories and Their Relative Percentage of the Fair Value to Total Plan Assets	The major investment categories and their relative percentage of the fair value of total plan assets as invested at December 31, 2018 , and 2017 are as follows: Pension Benefits Post-retirement Benefits (1) 2018 2017 2018 2017 Equity securities 42.1 % 51.8 % — % — % Debt securities 55.5 % 46.3 % — % — % Cash 2.4 % 1.9 % — % — % (1 ) Retiree health benefits are paid by the Company as covered expenses are incurred.
Schedule of Fair Value of Pension Plan Assets by Asset Category	The fair values of the pension plan assets (in thousands) at December 31, 2018 , by asset category, are as follows: Level 1 Level 2 Level 3 Total Cash and cash equivalents $ — $ 2,449 $ — $ 2,449 Mutual funds: Diversified emerging markets 6,638 — — 6,638 Foreign large blend 11,689 — — 11,689 Large-cap blend 14,226 — — 14,226 Mid-cap blend 6,819 — — 6,819 Small-cap blend 522 — — 522 Real estate 3,192 — — 3,192 Fixed income securities: Corporate notes and bonds 43,745 — — 43,745 U.S. Treasuries 8,486 — — 8,486 Mortgage-backed securities — 3,578 — 3,578 Asset-backed securities — 1,052 — 1,052 Net asset $ 95,317 $ 7,079 $ — $ 102,396 The fair values of the pension plan assets (in thousands) at December 31, 2017 , by asset category, are as follows: Level 1 Level 2 Level 3 Total Cash and cash equivalents $ — $ 1,727 $ — $ 1,727 Mutual funds: Diversified emerging markets 8,300 — — 8,300 Foreign large blend 11,856 — — 11,856 Large-cap blend 15,643 — — 15,643 Mid-cap blend 8,334 — — 8,334 Real estate 3,591 — — 3,591 Fixed income securities: Corporate notes and bonds 28,108 — — 28,108 U.S. Treasuries 10,846 — — 10,846 Mortgage-backed securities — 2,615 — 2,615 Asset-backed securities — 1,047 — 1,047 Net asset $ 86,678 $ 5,389 $ — $ 92,067
Schedule of Summary of Multiemployer Pension Plan	A summary of each multiemployer pension plan for which we participate is presented below: Pension Fund EIN/ Pension Plan No. Pension Protection Act Zone Status (1) FIP/RP Status Pending/ Implemented Company Contributions (in thousands) Surcharge Imposed Expiration Date of CBA 2018 2017 2018 2017 2016 LIUNA 52-6074345/001 Red Red Yes $ 573 $ 223 $ 167 Yes 5/31/2020 IUOE 36-6052390/001 Green Green No 1,385 40 28 No 7/31/2022 CSSS (2) 36-6044243/001 Red Red Yes 51 51 51 NA NA (1) The Pension Protection Act of 2006 defines the zone status as follows: green—healthy, yellow—endangered, orange—seriously endangered and red—critical. (2) In 2011, we withdrew from the Central States, Southeast and Southwest Areas Pension Plan. The withdrawal liability of $1.0 million will be paid in monthly installments of $4,000 until 2031.

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2018
Income Tax Disclosure [Abstract]
Schedule of Income (Loss) Before Income Taxes	Income (loss) before income taxes (in thousands) consisted of the following: Year ended December 31, 2018 2017 2016 United States $ (232,597 ) $ 136,526 $ (77,745 ) Foreign 2,644 — — Total $ (229,953 ) $ 136,526 $ (77,745 )
Schedule of Income Tax Benefit (Expense)	Income tax (expense) benefit (in thousands) consisted of the following for the years ended December 31, 2018 , 2017 and 2016 : Year ended December 31, 2018 2017 2016 Current: Federal $ 1,076 $ (10,754 ) $ 60 State (2,496 ) (1,167 ) (274 ) Foreign (518 ) — — (1,938 ) (11,921 ) (214 ) Deferred: Federal 25,578 22,641 32,944 State 5,492 (2,040 ) 3,959 Foreign — — — 31,070 20,601 36,903 Income tax benefit $ 29,132 $ 8,680 $ 36,689
Schedule of Effective Income Tax Rate on Pretax Earnings	Income tax (expense) benefit (in thousands) differed from the amount that would be provided by applying the U.S. federal statutory rate for the years ended December 31, 2018 , 2017 and 2016 due to the following: Year ended December 31, 2018 2017 2016 Income tax (expense) benefit computed at U.S. federal statutory rate $ 48,290 $ (47,784 ) $ 27,211 Decrease (increase) resulting from: Statutory depletion 12,090 20,259 4,734 Goodwill impairment (29,157 ) — — Prior year tax return reconciliation 530 219 435 State income taxes, net of federal benefit 2,592 (2,267 ) 2,369 Adjustment to deferred taxes from the Tax Act rate reduction — 35,772 — Equity compensation (653 ) 2,602 2,003 Other, net (4,560 ) (121 ) (63 ) Income tax benefit $ 29,132 $ 8,680 $ 36,689
Schedule of Tax Effects on Deferred Tax Assets and Liabilities	The tax effects of the types of temporary differences and carry forwards that gave rise to deferred tax assets and liabilities (in thousands) at December 31, 2018 and 2017 consisted of the following: December 31, 2018 2017 Gross deferred tax assets: Net operating loss carry forward and state tax credits $ 11,089 $ 22,783 Pension and post-retirement benefit costs 13,303 13,710 Alternative minimum tax credit carry forward 15,971 30,401 Property, plant and equipment 5,474 5,750 Accrued expenses 27,025 10,755 Inventories 774 4,354 Third-party products liability 231 249 Stock-based compensation expense 8,199 8,785 Note payable 3,724 3,133 Other 8,116 5,095 Total deferred tax assets 93,906 105,015 Gross deferred tax liabilities: Land and mineral property basis difference (165,002 ) (78,520 ) Fixed assets and depreciation (55,596 ) (51,556 ) Intangibles (10,346 ) (4,795 ) Other (201 ) — Total deferred tax liabilities (231,145 ) (134,871 ) Net deferred tax liabilities $ (137,239 ) $ (29,856 )

Revenue (Tables)

Revenue (Tables)	12 Months Ended
	Dec. 31, 2018
Revenue from Contract with Customer [Abstract]
Schedule of Sales by Major Source	The following table disaggregates our sales by major source for the year ended December 31, 2018 (in thousands): Year Ended Category Oil & Gas Proppants Industrial & Specialty Products Total Sales Product $ 888,509 $ 394,290 $ 1,282,799 Service 294,482 17 294,499 Total Sales $ 1,182,991 $ 394,307 $ 1,577,298
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 year ended December 31, 2018 (in thousands): Unbilled Receivables December 31, 2017 $ 5,245 Reclassifications to billed receivables (11,157 ) Revenues recognized in excess of period billings 6,002 December 31, 2018 $ 90 Deferred Revenue December 31, 2017 $ 118,414 Revenues recognized from balances held at the beginning of the period (33,381 ) Revenues deferred from period collections on unfulfilled performance obligations 31,625 Revenues recognized from period collections (3,339 ) December 31, 2018 $ 113,319

Segment Reporting (Tables)

Segment Reporting (Tables)	12 Months Ended
	Dec. 31, 2018
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 years ended December 31, 2018 , 2017 and 2016 : Year Ended 2018 2017 2016 Sales: Oil & Gas Proppants $ 1,182,991 $ 1,020,365 $ 362,550 Industrial & Specialty Products 394,307 220,486 197,075 Total sales 1,577,298 1,240,851 559,625 Segment contribution margin: Oil & Gas Proppants 357,846 301,972 11,445 Industrial & Specialty Products 155,084 88,781 78,988 Total segment contribution margin 512,930 390,753 90,433 Operating activities excluded from segment cost of sales (1) (98,761 ) (16,722 ) (7,618 ) Selling, general and administrative (146,971 ) (107,056 ) (67,172 ) Depreciation, depletion and amortization (148,832 ) (97,233 ) (68,134 ) Goodwill and other asset impairments (281,899 ) — — Interest expense (70,564 ) (31,342 ) (27,972 ) Other income (expense), net, including interest income 4,144 (1,874 ) 2,718 Income tax benefit (expense) 29,132 8,680 36,689 Net income (loss) $ (200,821 ) $ 145,206 $ (41,056 ) Less: Net income (loss) attributable to non-controlling interest (13 ) — — Net income (loss) attributable to U.S. Silica Holdings, Inc. $ (200,808 ) $ 145,206 $ (41,056 ) (1) 2018 increase driven by plant capacity expansion expenses and amortization of purchase accounting inventory fair value step-up.

Unaudited Supplementary Data (T

Unaudited Supplementary Data (Tables)	12 Months Ended
	Dec. 31, 2018
Quarterly Financial Information Disclosure [Abstract]
Schedule of Unaudited Quarterly Information	The following table sets forth our unaudited quarterly consolidated statements of operations (in thousands, except per share data) for each of the four quarters in the years ended December 31, 2018 and 2017 . This unaudited quarterly information has been prepared on the same basis as our annual audited financial statements and includes all adjustments, consisting only of normal recurring adjustments that are necessary to present fairly the financial information for the fiscal quarters presented. First Second Third Fourth 2018 (Unaudited) Sales: Product $ 294,788 $ 345,957 $ 348,635 $ 293,419 Service 74,525 81,476 74,537 63,961 Cost of sales (excluding depreciation, depletion and amortization): Product 207,239 236,236 270,370 241,624 Service 53,671 56,609 51,966 45,414 Operating expenses: Selling, general and administrative 34,591 42,232 37,980 32,168 Depreciation, depletion and amortization 28,592 36,563 37,150 46,527 Goodwill and other asset impairments — 16,184 — 265,715 Total operating expenses 63,183 94,979 75,130 344,410 Operating income (loss) 45,220 39,609 25,706 (274,068 ) Other (expense) income: Interest expense (7,070 ) (20,214 ) (21,999 ) (21,281 ) Other income (expense), net, including interest income 665 1,081 1,062 1,336 Total other expense (6,405 ) (19,133 ) (20,937 ) (19,945 ) Income (loss) before income taxes 38,815 20,476 4,769 (294,013 ) Income tax benefit (7,521 ) (2,832 ) 1,547 37,938 Net income (loss) 31,294 17,644 6,316 (256,075 ) Less: Net income (loss) attributable to non-controlling interest — — — (13 ) Net income (loss) attributable to U.S. Silica Holdings, Inc. $ 31,294 $ 17,644 $ 6,316 $ (256,062 ) Earnings (loss) per share, basic $ 0.39 $ 0.23 $ 0.08 $ (3.44 ) Earnings (loss) per share, diluted $ 0.39 $ 0.22 $ 0.08 $ (3.44 ) Weighted average shares outstanding, basic 79,496 77,784 77,365 74,485 Weighted average shares outstanding, diluted 80,309 78,480 77,859 74,485 Dividends declared per share $ 0.06 $ 0.06 $ 0.06 $ 0.06 First Second Third Fourth 2017 (Unaudited) Sales: Product $ 203,251 $ 235,891 $ 281,138 $ 290,114 Service 41,546 54,574 63,885 70,452 Cost of sales (excluding depreciation, depletion and amortization): Product 162,183 162,238 187,634 202,466 Service 25,292 34,726 40,155 52,126 Operating expenses: Selling, general and administrative 22,341 25,839 29,542 29,334 Depreciation, depletion and amortization 21,599 23,626 24,673 27,335 Total operating expenses 43,940 49,465 54,215 56,669 Operating income (loss) 13,382 44,036 63,019 49,305 Other (expense) income: Interest expense (7,646 ) (8,105 ) (8,347 ) (7,244 ) Other income (expense), net, including interest income (4,928 ) 638 1,308 1,108 Total other expense (12,574 ) (7,467 ) (7,039 ) (6,136 ) Income (loss) before income taxes 808 36,569 55,980 43,169 Income tax benefit 1,714 (7,110 ) (14,707 ) 28,783 Net income (loss) 2,522 29,459 41,273 71,952 Less: Net income (loss) attributable to non-controlling interest — — — — Net income (loss) attributable to U.S. Silica Holdings, Inc. $ 2,522 $ 29,459 $ 41,273 $ 71,952 Earnings (loss) per share, basic $ 0.03 $ 0.36 $ 0.51 $ 0.95 Earnings (loss) per share, diluted $ 0.03 $ 0.36 $ 0.50 $ 0.95 Weighted average shares, basic 80,983 81,087 81,121 75,539 Weighted average shares, diluted 82,244 81,945 81,783 75,539 Dividends declared per share $ 0.06 $ 0.06 $ 0.06 $ 0.06

Parent Company Financials (Tabl

Parent Company Financials (Tables)	12 Months Ended
	Dec. 31, 2018
Condensed Financial Information Disclosure [Abstract]
Condensed Balance Sheets	U.S. SILICA HOLDINGS, INC. (PARENT COMPANY ONLY) CONDENSED BALANCE SHEETS December 31, 2018 2017 (in thousands) ASSETS Current Assets: Cash and cash equivalents $ 107,151 $ 230,647 Due from affiliates 100,094 146,683 Total current assets 207,245 377,330 Investment in subsidiaries 850,099 1,024,511 Total assets $ 1,057,344 $ 1,401,841 LIABILITIES AND STOCKHOLDERS’ EQUITY Current Liabilities: Accrued expenses and other current liabilities $ 217 $ 106 Dividends payable 4,823 5,229 Total current liabilities 5,040 5,335 Deferred income taxes, net — — Total liabilities 5,040 5,335 Stockholders’ Equity: Preferred stock — — Common stock 818 812 Additional paid-in capital 1,169,383 1,147,084 Retained earnings 67,854 287,992 Treasury stock, at cost (178,215 ) (25,456 ) Accumulated other comprehensive loss (15,020 ) (13,926 ) Total U.S. Silica Holdings, Inc. stockholders’ equity 1,044,820 1,396,506 Non-controlling interest 7,484 — Total stockholders' equity 1,052,304 1,396,506 Total liabilities and stockholders’ equity $ 1,057,344 $ 1,401,841
Condensed Statements of Operations and Comprehensive Income (Loss)	U.S. SILICA HOLDINGS, INC. (PARENT COMPANY ONLY) CONDENSED STATEMENTS OF OPERATIONS AND COMPREHENSIVE INCOME (LOSS) Year ended December 31, 2018 2017 2016 (in thousands, except per share amounts) Sales $ — $ — $ — Cost of sales — — — Operating expenses Selling, general and administrative 254 252 184 Other — — 10 Total operating expenses 254 252 194 Operating loss (254 ) (252 ) (194 ) Other income (expense) Interest income 2,784 3,854 1,046 Other income, net, including interest income — — — Total other income (expense) 2,784 3,854 1,046 Income before income taxes and equity in net earnings of subsidiaries 2,530 3,602 852 Income tax benefit (expense) (696 ) (1,453 ) (344 ) Income before equity in net earnings of subsidiaries 1,834 2,149 508 Equity in earnings of subsidiaries, net of tax (202,655 ) 143,057 (41,564 ) Net income (loss) (200,821 ) 145,206 (41,056 ) Less: Net income (loss) attributable to non-controlling interest (13 ) — — Net income (loss) attributable to U.S. Silica Holdings, Inc. (200,808 ) 145,206 (41,056 ) Net income (loss) (200,821 ) 145,206 (41,056 ) Other comprehensive income (loss) Unrealized gain (loss) on investments (net of tax of z er o, zero, and $(4) for 2018, 2017 and 2016, respectively) — — (6 ) Unrealized gain (loss) on derivatives (net of tax of $(470) $(27) and $29 for 2018, 2017, and 2016, respectively) (1,545 ) (44 ) 49 Foreign currency translation adjustment (net of tax of $ (19 6) $2 and zero for 2018, 2017 and 2016, respectively) (614 ) (6 ) — Pension and other post-retirement benefits liability a djus tment (net of tax of $339, $1,205 and $152 for 2018, 2017 and 2016, respectively) 1,065 2,000 252 Comprehensive income (loss) (201,915 ) 147,156 (40,761 ) Less: Comprehensive income (loss) attributable to non-controlling interest $ (13 ) $ — $ — Comprehensive income (loss) attributable to U.S. Silica Holdings, Inc. $ (201,902 ) $ 147,156 $ (40,761 )
Condensed Statements of Stockholders' Equity	U.S. SILICA HOLDINGS, INC. (PARENT COMPANY ONLY) CONDENSED STATEMENTS OF STOCKHOLDERS' EQUITY Par Value Treasury Stock Additional Paid-In Capital Retained Earnings - Present Accumulated Other Comprehensive Income (Loss) Total U.S. Silica, Inc., Stockholders' Equity Non-controlling Interest Total Balance at January 1, 2016 $ 539 $ (15,845 ) $ 194,670 $ 220,974 $ (16,171 ) $ 384,167 $ — $ 384,167 Net loss — — — (41,056 ) — (41,056 ) — (41,056 ) Issuance of common stock (stock offerings net of issuance costs of $25,732) 272 — 931,016 — — 931,288 — 931,288 Unrealized gain on derivatives — — — — 49 49 — 49 Unrealized loss on short-term investments — — — — (6 ) (6 ) — (6 ) Pension and post-retirement liability — — — — 252 252 — 252 Cash dividend declared ($0.25 per share) — — — (16,893 ) — (16,893 ) — (16,893 ) Common stock-based compensation plans activity: Equity-based compensation — — 12,107 — — 12,107 — 12,107 Excess tax benefit from equity-based compensation — — — 148 — 148 — 148 Proceeds from options exercised — 8,465 (3,640 ) — — 4,825 — 4,825 Issuance of restricted stock — 1,437 (1,437 ) — — — — — Shares withheld for employee taxes related to vested restricted stock and stock units — 2,074 (3,665 ) — — (1,591 ) — (1,591 ) Balance at December 31, 2016 $ 811 $ (3,869 ) $ 1,129,051 $ 163,173 $ (15,876 ) $ 1,273,290 $ — $ 1,273,290 Net Income — — — 145,206 — 145,206 — 145,206 Unrealized loss on derivatives — — — — (44 ) (44 ) — (44 ) Foreign currency translation adjustment — — — — (6 ) (6 ) — (6 ) Pension and post-retirement liability — — — — 2,000 2,000 — 2,000 Cash dividend declared ($0.25 per share) — — — (20,387 ) — (20,387 ) — (20,387 ) Common stock-based compensation plans activity: Equity-based compensation — — 25,050 — — 25,050 — 25,050 Proceeds from options exercised — 1,190 (392 ) — — 798 — 798 Issuance of restricted stock — 1,859 (1,859 ) — — — — — Shares withheld for employee taxes related to vested restricted stock and stock units 1 386 (4,766 ) — — (4,379 ) — (4,379 ) Repurchase of common stock — (25,022 ) — — — (25,022 ) — (25,022 ) Balance at December 31, 2017 $ 812 $ (25,456 ) $ 1,147,084 $ 287,992 $ (13,926 ) $ 1,396,506 $ — $ 1,396,506 Net loss — — — (200,808 ) — (200,808 ) (13 ) (200,821 ) Unrealized loss on derivatives — — — — (1,545 ) (1,545 ) — (1,545 ) Foreign currency translation adjustment — — — — (614 ) (614 ) — (614 ) Pension and post-retirement liability — — — — 1,065 1,065 — 1,065 Cash dividend declared ($0.25 per share) — — — (19,330 ) — (19,330 ) — (19,330 ) Contributions from non-controlling interest — — — — — — 7,497 7,497 Common stock-based compensation plans activity: Equity-based compensation — — 22,337 — — 22,337 — 22,337 Proceeds from options exercised — 93 (32 ) — — 61 — 61 Shares withheld for employee taxes related to vested restricted stock and stock units 6 (4,383 ) (6 ) — — (4,383 ) — (4,383 ) Repurchase of common stock — (148,469 ) — — — (148,469 ) — (148,469 ) Balance at December 31, 2018 $ 818 $ (178,215 ) $ 1,169,383 $ 67,854 $ (15,020 ) $ 1,044,820 $ 7,484 $ 1,052,304
Condensed Statements of Cash Flows	U.S. SILICA HOLDINGS, INC. (PARENT COMPANY ONLY) CONDENSED STATEMENTS OF CASH FLOWS Year ended December 31, 2018 2017 2016 (in thousands, except per share amounts) Operating activities: Net income (loss) $ (200,821 ) $ 145,206 $ (41,056 ) Adjustments to reconcile net income (loss) to net cash provided by operating activities: Undistributed (Income) loss from equity method investment, net 202,655 (143,057 ) 41,564 Other — — (30 ) Changes in assets and liabilities, net of effects of acquisitions: Accounts payable and accrued liabilities (295 ) 48 353 Net cash provided by operating activities 1,539 2,197 831 Investing activities: Proceeds from sales and maturities of short-term investments — — 21,872 Investment in subsidiary — (143,654 ) (188,177 ) Net cash provided by (used in) investing activities — (143,654 ) (166,305 ) Financing activities: Dividends paid (19,912 ) (20,377 ) (15,125 ) Repurchase of common stock (148,469 ) (25,022 ) — Proceeds from options exercised 61 798 4,603 Tax payments related to shares withheld for vested restricted stock and stock units (4,383 ) (4,379 ) (1,590 ) Issuance of common stock (secondary offering) — — 678,791 Issuance of treasury stock — — 221 Costs of common stock issuance — — (25,733 ) Contributions from non-controlling interest 7,497 — — Net financing activities with subsidiaries 40,171 (113,294 ) 106 Net cash provided by (used in) financing activities (125,035 ) (162,274 ) 641,273 Net increase (decrease) in cash and cash equivalents (123,496 ) (303,731 ) 475,799 Cash and cash equivalents, beginning of period 230,647 534,378 58,579 Cash and cash equivalents, end of period $ 107,151 $ 230,647 $ 534,378 Non-cash financing activities: Supplemental cash flow information: Cash paid (received) during the period for: Interest $ (2,784 ) $ (3,853 ) $ (1,046 ) Non-cash transactions Common stock issued for business acquisitions $ — $ — $ 278,229

Organization (Details)

Organization (Details) $ in Thousands	May 01, 2018USD ($)	Dec. 31, 2018USD ($)Segment	Dec. 31, 2017USD ($)	Dec. 31, 2016USD ($)
Organization And Nature Of Business
Number of business segments | Segment		2
Consideration paid, net of cash acquired		$ 743,249	$ 119,801	$ 176,617
EPMH
Organization And Nature Of Business
Consideration paid, net of cash acquired	$ 743,200
Cash acquired	19,100
Net working capital post-closing adjustments	$ 500

Summary of Significant Accoun_4

Summary of Significant Accounting Policies - Additional Information (Details) - USD ($)	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Jan. 01, 2019
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Water rights intangibles acquired in VIE									$ 10,046,000	$ 3,586,000	$ 959,000
Property, plant and mine development, gross	$ 2,326,126,000				$ 1,522,675,000				$ 2,326,126,000	1,522,675,000
Percent or reporting unit fair value less than carrying value									50.00%
Consolidated sales									$ 1,577,298,000	1,240,851,000	559,625,000
Consolidated assets	2,900,840,000				2,307,283,000				2,900,840,000	2,307,283,000
Pre-tax income	(294,013,000)	$ 4,769,000	$ 20,476,000	$ 38,815,000	43,169,000	$ 55,980,000	$ 36,569,000	$ 808,000	(229,953,000)	136,526,000	(77,745,000)
Net income	(256,062,000)	$ 6,316,000	$ 17,644,000	$ 31,294,000	71,952,000	$ 41,273,000	$ 29,459,000	$ 2,522,000	(200,808,000)	145,206,000	(41,056,000)
Debt issuance amortization									4,044,000	1,382,000	1,392,000
Self-insurance reserves	5,400,000				5,500,000				5,400,000	5,500,000
Self-insurance reserves classified as current	2,600,000				1,700,000				2,600,000	1,700,000
Discrete tax expense related to certain executive compensation agreements not eligible for transition relief									653,000	(2,602,000)	$ (2,003,000)
Income tax expense, decrease in deferred tax assets due to change in tax rate										45,000,000
Income tax benefit, decrease in deferred tax liability due to change in tax rate										80,800,000
Deferred income tax benefit, decrease in tax assets and liabilities due to change in tax rate										$ 35,800,000
Goodwill impairment									164,167,000
ASC 740
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Discrete tax expense related to certain executive compensation agreements not eligible for transition relief									700,000
ASU 2016-02 | Subsequent Event | Scenario, Forecast
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Right-of-use assets												$ 223,000,000
Lease liabilities												$ 222,700,000
Other income (expense) net, including interest income
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Net realized foreign currency translation loss									$ 600,000
Restricted Stock and Restricted Stock Units
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Vesting period for awards of equity instruments									3 years
Performance Share Units
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Vesting period for awards of equity instruments									3 years
Performance Share Units | Certain Employees
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Vesting period for awards of equity instruments										3 years
Foreign Operations
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Consolidated sales									$ 44,000,000
Consolidated assets	7,300,000								7,300,000
Pre-tax income									2,600,000
Net income									$ 2,400,000
Intellectual property
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Estimated useful live of finite-lived intangible assets									15 years
Customer relationships
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Estimated useful live of finite-lived intangible assets									20 years
Oil & Gas Sand
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Goodwill impairment	164,200,000
Construction-in-progress
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Property, plant and mine development, gross	167,933,000				189,970,000				$ 167,933,000	$ 189,970,000
Buildings
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Property, plant and mine development, gross	64,515,000				56,330,000				$ 64,515,000	56,330,000
Estimated useful lives of property, plant and mine equipment									15 years
Land improvements
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Property, plant and mine development, gross	67,729,000				45,878,000				$ 67,729,000	45,878,000
Estimated useful lives of property, plant and mine equipment									10 years
Machinery and equipment
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Property, plant and mine development, gross	958,357,000				590,566,000				$ 958,357,000	590,566,000
Furniture and fixtures
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Property, plant and mine development, gross	3,599,000				$ 2,953,000				$ 3,599,000	$ 2,953,000
Estimated useful lives of property, plant and mine equipment									8 years
Minimum
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Self-insurance retention amount									$ 100,000
Minimum | Stock options excluded
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Vesting period for awards of equity instruments									3 years
Minimum | Supply Agreement
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Deferred revenue, average initial contract term									one
Minimum | Customer relationships
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Estimated useful live of finite-lived intangible assets									13 years
Minimum | Machinery and equipment
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Estimated useful lives of property, plant and mine equipment									3 years
Maximum
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Self-insurance retention amount									$ 500,000
Maximum | Stock options excluded
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Vesting period for awards of equity instruments									4 years
Maximum | Supply Agreement
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Deferred revenue, average initial contract term									fifteen
Maximum | Customer relationships
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Estimated useful live of finite-lived intangible assets									15 years
Maximum | Machinery and equipment
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Estimated useful lives of property, plant and mine equipment									10 years
Variable Interest Entity, Primary Beneficiary
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Equity ownership percentage acquired in VIE		50.00%
Payments to acquire interest in VIE		$ 3,200,000
Maximum capital contribution in VIE	7,000,000	7,000,000							$ 7,000,000
Additional contribution paid to acquire interest in VIE	$ 3,800,000
Variable Interest Entity, Primary Beneficiary | Construction-in-progress
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Property, plant and mine development, gross		12,000,000
Variable Interest Entity, Primary Beneficiary | Water rights
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Water rights intangibles acquired in VIE		$ 700,000

Summary of Significant Accoun_5

Summary of Significant Accounting Policies - Reconciliation of Effects of Reclassification on Statements of Income (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
New Accounting Pronouncement, Early Adoption [Line Items]
Total Sales									$ 1,577,298	$ 1,240,851	$ 559,625
Product cost of sales	$ 241,624	$ 270,370	$ 236,236	$ 207,239	$ 202,466	$ 187,634	$ 162,238	$ 162,183	955,469	714,521	456,783
Service cost of sales	45,414	51,966	56,609	53,671	52,126	40,155	34,726	25,292	207,660	152,299	20,027
Total cost of sales (excluding depreciation, depletion and amortization)									1,163,129	866,820	476,810
Selling, general and administrative expenses	32,168	37,980	42,232	34,591	29,334	29,542	25,839	22,341	146,971	107,056	67,172
Operating income	(274,068)	25,706	39,609	45,220	49,305	63,019	44,036	13,382	(163,533)	169,742	(52,491)
Other income (expense)	1,336	1,062	1,081	665	1,108	1,308	638	(4,928)	4,144	(1,874)	2,718
Product
New Accounting Pronouncement, Early Adoption [Line Items]
Total Sales	293,419	348,635	345,957	294,788	290,114	281,138	235,891	203,251	1,282,799	1,010,394	524,137
Service
New Accounting Pronouncement, Early Adoption [Line Items]
Total Sales	$ 63,961	$ 74,537	$ 81,476	$ 74,525	$ 70,452	$ 63,885	$ 54,574	$ 41,546	$ 294,499	230,457	35,488
As Previously Reported
New Accounting Pronouncement, Early Adoption [Line Items]
Total Sales										1,240,851	559,625
Product cost of sales										720,312	455,189
Service cost of sales										147,203	22,106
Total cost of sales (excluding depreciation, depletion and amortization)										867,515	477,295
Selling, general and administrative expenses										107,592	67,727
Operating income										168,511	(53,531)
Other income (expense)										(643)	3,758
As Previously Reported | Product
New Accounting Pronouncement, Early Adoption [Line Items]
Total Sales										1,057,553	523,900
As Previously Reported | Service
New Accounting Pronouncement, Early Adoption [Line Items]
Total Sales										183,298	35,725
Reclassifications | ASU 2017-07
New Accounting Pronouncement, Early Adoption [Line Items]
Total Sales										0	0
Product cost of sales										(5,096)	2,079
Service cost of sales										5,096	(2,079)
Total cost of sales (excluding depreciation, depletion and amortization)										0	0
Selling, general and administrative expenses										0	0
Operating income										0	0
Other income (expense)										0	0
Reclassifications | ASU 2017-07 | Product
New Accounting Pronouncement, Early Adoption [Line Items]
Total Sales										(47,159)	237
Reclassifications | ASU 2017-07 | Service
New Accounting Pronouncement, Early Adoption [Line Items]
Total Sales										47,159	(237)
Adjustments | ASU 2017-07
New Accounting Pronouncement, Early Adoption [Line Items]
Total Sales										0	0
Product cost of sales										(695)	(485)
Service cost of sales										0	0
Total cost of sales (excluding depreciation, depletion and amortization)										(695)	(485)
Selling, general and administrative expenses										(536)	(555)
Operating income										1,231	1,040
Other income (expense)										(1,231)	(1,040)
Adjustments | ASU 2017-07 | Product
New Accounting Pronouncement, Early Adoption [Line Items]
Total Sales										0	0
Adjustments | ASU 2017-07 | Service
New Accounting Pronouncement, Early Adoption [Line Items]
Total Sales										$ 0	$ 0

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								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Numerator:
Net income (loss) attributable to U.S. Silica Holdings, Inc.	$ (256,062)	$ 6,316	$ 17,644	$ 31,294	$ 71,952	$ 41,273	$ 29,459	$ 2,522	$ (200,808)	$ 145,206	$ (41,056)
Denominator:
Weighted average shares outstanding, basic (in shares)	74,485	77,365	77,784	79,496	75,539	81,121	81,087	80,983	76,453	81,051	65,037
Diluted effect of stock awards (shares)									0	909	0
Weighted average shares outstanding assuming dilution (shares)									76,453	81,960	65,037
Earnings (loss) per share attributable to U.S. Silica Holdings, Inc.:
Basic earnings (loss) per share (in dollars per share)	$ (3.44)	$ 0.08	$ 0.23	$ 0.39	$ 0.95	$ 0.51	$ 0.36	$ 0.03	$ (2.63)	$ 1.79	$ (0.63)
Diluted earnings (loss) per share (in dollars per share)	$ (3.44)	$ 0.08	$ 0.22	$ 0.39	$ 0.95	$ 0.50	$ 0.36	$ 0.03	$ (2.63)	$ 1.77	$ (0.63)

Earnings Per Share - Antidiluti

Earnings Per Share - Antidilutive Securities Excluded From Calculation of Diluted Earnings Per Share (Details) - shares shares in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Weighted-average outstanding stock options and restricted stock awards excluded (shares)	443		732
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)	574	195	573
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)	155	305	166

Capital Structure and Accumul_3

Capital Structure and Accumulated Other Comprehensive Income (Loss) - Additional Information (Details) - USD ($)	Dec. 11, 2017	Mar. 31, 2018	Dec. 31, 2018	May 31, 2018	Dec. 31, 2017	Oct. 31, 2017
Capital Structure And Accumulated Comprehensive Income (Loss)
Common stock authorized (shares)			500,000,000		500,000,000
Common stock, par value (in dollars per share)			$ 0.01		$ 0.01
Common stock issued (shares)			81,811,977		81,267,205
Common stock outstanding (shares)			73,148,853		80,524,255
Preferred stock authorized (shares)			10,000,000		10,000,000
Preferred stock, par value (in dollars per share)			$ 0.01		$ 0.01
Preferred stock issued (shares)			0		0
Preferred stock outstanding (shares)			0		0
May 2018 Share Repurchase Program
Capital Structure And Accumulated Comprehensive Income (Loss)
Share repurchase program authorized amount				$ 200,000,000
Repurchase of common stock (shares)			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
Share Repurchase Program Expiring December 11, 2018
Capital Structure And Accumulated Comprehensive Income (Loss)
Share repurchase program authorized amount						$ 100,000,000
Repurchase of common stock (shares)		3,555,104
Average price per common share of repurchase common stock (in dollars per share)		$ 28.13
Share Repurchase Program Expiring December 11, 2017
Capital Structure And Accumulated Comprehensive Income (Loss)
Share repurchase program authorized amount	$ 50,000,000
Repurchase of common stock (shares)	706,093
Average price per common share of repurchase common stock (in dollars per share)	$ 23.83

Capital Structure and Accumul_4

Capital Structure and Accumulated Other Comprehensive Income (Loss) - Declared Quarterly Cash Dividends (Details) - $ / shares	Nov. 13, 2018	Jul. 16, 2018	May 14, 2018	Feb. 16, 2018
Equity [Abstract]
Dividends per Common Share (in dollars per share)	$ 0.0625	$ 0.0625	$ 0.0625	$ 0.0625

Capital Structure and Accumul_5

Capital Structure and Accumulated Other Comprehensive Income (Loss) - Changes in Accumulated Other Comprehensive Loss (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2018USD ($)
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning Balance	$ 1,396,506
Other comprehensive gain (loss) before reclassifications	(3,115)
Amounts reclassed from accumulated other comprehensive loss	2,021
Ending Balance	1,044,820
Unrealized gain/(loss) on cash flow hedges
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning Balance	(76)
Other comprehensive gain (loss) before reclassifications	(1,622)
Amounts reclassed from accumulated other comprehensive loss	77
Ending Balance	(1,621)
Foreign currency translation adjustments
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning Balance	(6)
Other comprehensive gain (loss) before reclassifications	(614)
Amounts reclassed from accumulated other comprehensive loss	0
Ending Balance	(620)
Pension and other post-retirement benefits liability
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning Balance	(13,844)
Other comprehensive gain (loss) before reclassifications	(879)
Amounts reclassed from accumulated other comprehensive loss	1,944
Ending Balance	(12,779)
Total
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning Balance	(13,926)
Ending Balance	$ (15,020)

Business Combinations - Additio

Business Combinations - Additional Information (Details) $ in Thousands	May 01, 2018USD ($)	Aug. 16, 2017USD ($)	Apr. 01, 2017USD ($)	Aug. 22, 2016USD ($)shares	Aug. 16, 2016USD ($)shares	Mar. 31, 2018USD ($)	Aug. 16, 2017USD ($)	Dec. 31, 2018USD ($)	Dec. 31, 2017USD ($)	Dec. 31, 2016USD ($)acquisitionshares	Aug. 16, 2018USD ($)	Dec. 31, 2015USD ($)
Business Acquisition [Line Items]
Consideration paid, net of cash acquired								$ 743,249	$ 119,801	$ 176,617
Goodwill								261,340	272,079	240,975		$ 68,647
Total cash consideration for pre-existing contracted asset sale								339,815	368,479	$ 46,450
Number of acquisitions | acquisition										2
Common Stock
Business Acquisition [Line Items]
Shares of common stock issued in acquisition (in shares) | shares										6,825,693
Value of shares of common stock issued in acquisition										$ 300
EPMH
Business Acquisition [Line Items]
Consideration paid, net of cash acquired	$ 743,200
Cash acquired	19,100
Net working capital post-closing adjustments	500
Revenues from acquiree included in Income Statement								158,800
Net loss from acquiree included in Income Statement								600
Non-recurring transaction costs attributable to business combination excluded from pro-forma information								179,220	(116,899)
Goodwill	$ 139,787							150,628
EPMH | Acquisition-related Costs
Business Acquisition [Line Items]
Non-recurring transaction costs attributable to business combination excluded from pro-forma information								15,200
EPMH | Selling, General and Administrative Expenses
Business Acquisition [Line Items]
Acquisition-related costs								$ 13,600
White Armor
Business Acquisition [Line Items]
Cash consideration paid			$ 18,600
Goodwill			3,900
Identifiable intangible assets			12,800
Other net assets			$ 1,900
White Armor | Selling, General and Administrative Expenses
Business Acquisition [Line Items]
Acquisition-related costs									200
MS Sand
Business Acquisition [Line Items]
Consideration paid, net of cash acquired		$ 95,400
Cash acquired		2,200
Net working capital post-closing adjustments		(500)
Non-recurring transaction costs attributable to business combination excluded from pro-forma information									(143,604)	55,835
Goodwill		22,522					$ 22,522				$ 25,322
Additional consideration paid		6,100
Total cash consideration for pre-existing contracted asset sale							101,000
MS Sand | Selling, General and Administrative Expenses
Business Acquisition [Line Items]
Acquisition-related costs						$ 1,000
NBI
Business Acquisition [Line Items]
Consideration paid, net of cash acquired					$ 107,200
Cash acquired					9,000
Goodwill		$ 90,898			86,228		$ 90,898
Consideration paid					$ 213,700
Adjustment to depreciation expense									$ (600)
Inventory write-down										1,700
NBI | Common Stock
Business Acquisition [Line Items]
Shares of common stock issued in acquisition (in shares) | shares					2,630,513
Value of shares of common stock issued in acquisition					$ 106,600
NBI | Selling, General and Administrative Expenses
Business Acquisition [Line Items]
Acquisition-related costs										1,400
Sandbox
Business Acquisition [Line Items]
Consideration paid, net of cash acquired				$ 69,500
Cash acquired				1,300
Revenues from acquiree included in Income Statement										31,000
Non-recurring transaction costs attributable to business combination excluded from pro-forma information										45,161
Goodwill				86,100
Identifiable intangible assets				120,144
Consideration paid				$ 241,100
Sandbox | Common Stock
Business Acquisition [Line Items]
Shares of common stock issued in acquisition (in shares) | shares				4,195,180
Value of shares of common stock issued in acquisition				$ 171,700
Sandbox | Selling, General and Administrative Expenses
Business Acquisition [Line Items]
Acquisition-related costs										$ 3,000

Business Combinations - Purchas

Business Combinations - Purchase Price Allocation (Details) - USD ($) $ in Thousands	8 Months Ended	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2018	Aug. 15, 2018	Dec. 31, 2017	Aug. 15, 2017	Aug. 16, 2018	May 01, 2018	Aug. 16, 2017	Dec. 31, 2016	Aug. 22, 2016	Aug. 16, 2016	Dec. 31, 2015
Purchase Price
Goodwill	$ 261,340	$ 261,340		$ 272,079					$ 240,975			$ 68,647
EPMH
Purchase Price
Accounts receivable, net	43,305	43,305					$ 43,354
Inventories	86,112	86,112					84,395
Property, plant and mine development	148,495	148,495					123,086
Mineral rights	419,469	419,469					462,050
Identifiable intangible assets - finite lived	10,270	10,270					21,050
Identifiable intangible assets - indefinite lived	38,050	38,050					25,050
Prepaids and deposits	2,072	2,072					2,054
Other non-current assets	7,474	7,474					4,088
Goodwill	150,628	150,628					139,787
Total assets acquired	905,875	905,875					904,914
Accounts payable	13,435	13,435					13,435
Accrued expenses and other current liabilities	10,304	10,304					8,255
Deferred tax liabilities	122,811	122,811					130,209
Other long term liabilities	16,076	16,076					9,766
Total liabilities assumed	162,626	162,626					161,665
Net assets acquired	743,249	743,249					$ 743,249
Measurement Period Adjustments
Accounts receivable, net	(49)
Inventories	1,717
Property, plant and mine development	25,409
Mineral rights	(42,581)
Identifiable intangible assets - finite lived	(10,780)
Identifiable intangible assets - indefinite lived	13,000
Prepaids and deposits	18
Other assets	3,386
Goodwill	10,841	10,841
Total assets acquired	961
Accounts payable	0
Accrued expenses and other current liabilities	2,049
Deferred tax liabilities	(7,398)
Long term obligations	6,310
Total liabilities assumed	961
Net assets acquired	$ 0
MS Sand
Purchase Price
Accounts receivable, net						$ 11,201		$ 11,201
Inventories						8,067		8,067
Other current assets						362		362
Assets held for sale						9,453		9,453
Property, plant and mine development						27,458		27,458
Mineral rights						23,500		26,300
Identifiable intangible assets - finite lived						1,840		1,840
Other non-current assets						1,136		1,136
Goodwill						25,322		22,522
Total assets acquired						108,339		108,339
Accounts payable and accrued expenses						3,761		3,761
Unfavorable leasehold positions						2,237		2,237
Notes Payable						866		866
Asset retirement obligations						474		474
Other long term liabilities						0		0
Total liabilities assumed						7,338		7,338
Net assets acquired						$ 101,001		101,001
Measurement Period Adjustments
Accounts receivable, net			$ 0
Inventories			0
Other current assets			0
Assets held for sale			0
Property, plant and mine development			0
Mineral rights			(2,800)
Identifiable intangible assets - finite lived			0
Other assets			0
Goodwill		$ 2,800	2,800	(29,665)
Total assets acquired			0
Accounts payable and accrued expenses			0
Unfavorable leasehold positions			0
Notes Payable			0
Other long term liabilities			0
Asset retirement obligations			0
Total liabilities assumed			0
Net assets acquired			$ 0
NBI
Purchase Price
Accounts receivable, net								2,680			$ 2,680
Inventories								3,494			3,494
Other current assets								428			428
Income tax deposits								6,440			6,657
Property, plant and mine development								206,632			210,913
Identifiable intangible assets - finite lived								1,600			1,600
Goodwill								90,898			86,228
Total assets acquired								312,172			312,000
Accounts payable, accrued expenses and other current liabilities								2,664			1,938
Deferred revenue								500			500
Notes Payable								24,604			24,361
Capital lease liabilities								3,331			3,331
Deferred tax liabilities								66,638			67,435
Asset retirement obligations								710			710
Total liabilities assumed								98,447			98,275
Net assets acquired								$ 213,725			$ 213,725
Measurement Period Adjustments
Accounts receivable, net					$ 0
Inventories					0
Other current assets					0
Income tax deposits					(217)
Property, plant and mine development					(4,281)
Identifiable intangible assets - finite lived					0
Goodwill				$ 4,670	4,670
Total assets acquired					172
Accounts payable, accrued expenses and other current liabilities					726
Deferred revenue					0
Deferred tax liabilities					(797)
Notes Payable					243
Capital lease liabilities					0
Asset retirement obligations					0
Total liabilities assumed					172
Net assets acquired					$ 0
Sandbox
Purchase Price
Accounts receivable, net										$ 13,392
Prepaid expenses and other										1,465
Property, plant and mine development										32,336
Identifiable intangible assets										120,144
Identifiable intangible assets - finite lived										120,144
Goodwill										86,100
Total assets acquired										253,437
Accounts payable										4,122
Accrued expenses and other current liabilities										3,292
Deferred revenue										4,902
Total liabilities assumed										12,316
Net assets acquired										$ 241,121

Business Combinations - Intangi

Business Combinations - Intangible Assets Acquired (Details) - USD ($) $ in Thousands	May 01, 2018	Aug. 16, 2017	Aug. 22, 2016	Dec. 31, 2018	Aug. 16, 2018	Aug. 16, 2016
EPMH
Business Acquisition [Line Items]
Identifiable intangible assets - finite lived, Approximate Fair Value	$ 21,050			$ 10,270
Identifiable intangible assets - indefinite lived, Approximate Fair Value	$ 25,050			38,050
EPMH | Trade names
Business Acquisition [Line Items]
Identifiable intangible assets - indefinite lived, Approximate Fair Value				38,050
EPMH | Intellectual property
Business Acquisition [Line Items]
Identifiable intangible assets - finite lived, Approximate Fair Value				2,900
Identifiable intangible assets - finite lived, Estimated Useful Life (in years)	15 years
EPMH | 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
MS Sand
Business Acquisition [Line Items]
Identifiable intangible assets - finite lived, Approximate Fair Value		$ 1,840			$ 1,840
MS Sand | Customer relationships
Business Acquisition [Line Items]
Identifiable intangible assets - finite lived, Approximate Fair Value		$ 1,840
Identifiable intangible assets - finite lived, Estimated Useful Life (in years)		15 years
NBI
Business Acquisition [Line Items]
Identifiable intangible assets - finite lived, Approximate Fair Value		$ 1,600				$ 1,600
NBI | Customer relationships
Business Acquisition [Line Items]
Identifiable intangible assets - finite lived, Approximate Fair Value		$ 1,600
Identifiable intangible assets - finite lived, Estimated Useful Life (in years)		13 years
Sandbox
Business Acquisition [Line Items]
Identifiable intangible assets - finite lived, Approximate Fair Value			$ 120,144
Sandbox | Trade names
Business Acquisition [Line Items]
Identifiable intangible assets - indefinite lived, Approximate Fair Value			17,844
Sandbox | Intellectual property
Business Acquisition [Line Items]
Identifiable intangible assets - finite lived, Approximate Fair Value			$ 57,700
Identifiable intangible assets - finite lived, Estimated Useful Life (in years)			15 years
Sandbox | Customer relationships
Business Acquisition [Line Items]
Identifiable intangible assets - finite lived, Approximate Fair Value			$ 44,600
Identifiable intangible assets - finite lived, Estimated Useful Life (in years)			13 years

Business Combinations - Pro For

Business Combinations - Pro Forma Information (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
EPMH
Business Acquisition [Line Items]
Sales	$ 1,659,775	$ 1,454,070
Net income (loss)	$ (179,220)	$ 116,899
Basic earnings per share (in dollars per share)	$ (2.34)	$ 1.44
Diluted earnings per share (in dollars per share)	$ (2.34)	$ 1.43
MS Sand
Business Acquisition [Line Items]
Sales		$ 1,287,202	$ 642,951
Net income (loss)		$ 143,604	$ (55,835)
Basic earnings per share (in dollars per share)		$ 1.77	$ (0.86)
Diluted earnings per share (in dollars per share)		$ 1.75	$ (0.86)
Sandbox
Business Acquisition [Line Items]
Sales			$ 615,552
Net income (loss)			$ (45,161)
Basic earnings per share (in dollars per share)			$ (0.69)
Diluted earnings per share (in dollars per share)			$ (0.69)

Accounts Receivable (Details)

Accounts Receivable (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Receivables [Abstract]
Trade receivables	$ 198,435	$ 217,649
Less: Allowance for doubtful accounts	(6,751)	(7,100)
Net trade receivables	191,684	210,549
Other receivables	23,802	2,037
Total accounts receivable	215,486	$ 212,586
Refundable alternative minimum tax credits	$ 16,000

Accounts Receivable - Allowance

Accounts Receivable - Allowance for Doubtful Accounts (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Allowance for Doubtful Accounts Receivable Roll Forward
Beginning balance	$ 7,100	$ 7,042
Bad debt provision	315	1,529	$ (1,232)
Write-offs	(664)	(1,471)
Ending balance	$ 6,751	$ 7,100	$ 7,042

Accounts Receivable - Additiona

Accounts Receivable - Additional Information (Details) - Product Concentration Risk	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Sales | Ten Largest Customers
Concentration Risk [Line Items]
Concentration risk percentage	48.00%	58.00%	52.00%
Sales | Customer One
Concentration Risk [Line Items]
Concentration risk percentage	15.00%	15.00%
Sales | Customer Two
Concentration Risk [Line Items]
Concentration risk percentage		12.00%	13.00%
Trade Accounts Receivables | Customer One
Concentration Risk [Line Items]
Concentration risk percentage	18.00%	19.00%
Trade Accounts Receivables | Customer Two
Concentration Risk [Line Items]
Concentration risk percentage		11.00%

Inventories (Details)

Inventories (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Inventory Disclosure [Abstract]
Supplies	$ 41,453	$ 21,277
Raw materials and work in process	68,474	28,034
Finished goods	52,160	43,065
Total inventories	$ 162,087	$ 92,376

Property, Plant and Mine Deve_3

Property, Plant and Mine Development (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Property, Plant and Equipment
Property, plant and mine development, gross	$ 2,326,126	$ 1,522,675
Accumulated depletion, depreciation and amortization	(499,823)	(353,520)
Total property, plant and mine development, net	1,826,303	1,169,155
Mining property and mine development
Property, Plant and Equipment
Property, plant and mine development, gross	995,759	586,242
Asset retirement cost
Property, Plant and Equipment
Property, plant and mine development, gross	12,732	14,184
Land
Property, Plant and Equipment
Property, plant and mine development, gross	55,502	36,552
Land improvements
Property, Plant and Equipment
Property, plant and mine development, gross	67,729	45,878
Buildings
Property, Plant and Equipment
Property, plant and mine development, gross	64,515	56,330
Machinery and equipment
Property, Plant and Equipment
Property, plant and mine development, gross	958,357	590,566
Furniture and fixtures
Property, Plant and Equipment
Property, plant and mine development, gross	3,599	2,953
Construction-in-progress
Property, Plant and Equipment
Property, plant and mine development, gross	$ 167,933	$ 189,970

Property, Plant and Mine Deve_4

Property, Plant and Mine Development - Additional Information (Details) $ in Thousands	Mar. 21, 2018USD ($)transload	Dec. 31, 2018USD ($)	Sep. 30, 2018USD ($)	Jun. 30, 2018USD ($)	Mar. 31, 2018USD ($)	Dec. 31, 2018USD ($)	Dec. 31, 2017USD ($)	Dec. 31, 2016USD ($)
Property, Plant and Equipment
Aggregate cost of machinery and equipment under capital lease		$ 2,326,126				$ 2,326,126	$ 1,522,675
Accumulated depreciation of machinery and equipment under capital lease		499,823				499,823	353,520
Gain on sale of transload facilities						5,170	(415)	$ (563)
Consideration received allocated to asset retirement obligations liabilities of transload facilities						2,116	0
Asset impairment charges		265,715	$ 0	$ 16,184	$ 0	281,899	0	$ 0
Oil & Gas Proppants
Property, Plant and Equipment
Long-lived assets impairment		97,000
Intangible assets impairment		4,500
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		12,500				12,500
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		33,800				33,800
Assets Held under Capital Leases
Property, Plant and Equipment
Aggregate cost of machinery and equipment under capital lease		500				500	900
Accumulated depreciation of machinery and equipment under capital lease		200				200	200
Mining property and mine development
Property, Plant and Equipment
Aggregate cost of machinery and equipment under capital lease		$ 995,759				995,759	586,242
Interest cost capitalized in property, plant and mine development						$ 6,700	$ 1,600
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
Resin Coating Facility
Property, Plant and Equipment
Asset impairment charges				$ 16,200

Goodwill and Intangible Asset_2

Goodwill and Intangible Assets - Changes in Carrying Amount of Goodwill (Details) - USD ($) $ in Thousands	8 Months Ended	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2018	Aug. 15, 2018	Dec. 31, 2017	Aug. 15, 2017	Dec. 31, 2016	Dec. 31, 2015
Goodwill [Line Items]
Goodwill	$ 425,507	$ 425,507		$ 272,079		$ 240,975	$ 68,647
Impairment losses	(164,167)	(164,167)		0		0	0
Goodwill [Roll Forward]
Beginning balance		272,079		240,975		68,647
Impairments		(164,167)
Ending balance	261,340	261,340		272,079		240,975
NBI
Goodwill [Roll Forward]
Beginning balance			$ 90,898		$ 86,228
Acquisitions						86,228
Measurement period adjustments				4,670	$ 4,670
Sandbox
Goodwill [Roll Forward]
Acquisitions						86,100
White Armor
Goodwill [Roll Forward]
Acquisitions				3,912
MS Sand
Goodwill [Roll Forward]
Beginning balance			22,522
Acquisitions				52,187
Measurement period adjustments		2,800	$ 2,800	(29,665)
EPMH
Goodwill [Roll Forward]
Acquisitions		139,787
Measurement period adjustments	10,841	10,841
Ending balance	150,628	150,628
Oil & Gas Proppants
Goodwill [Line Items]
Goodwill	250,267	250,267		247,467		220,275	47,947
Impairment losses	(164,167)	(164,167)		0		0	0
Goodwill [Roll Forward]
Beginning balance		247,467		220,275		47,947
Impairments		(164,167)
Ending balance	86,100	86,100		247,467		220,275
Oil & Gas Proppants | NBI
Goodwill [Roll Forward]
Acquisitions						86,228
Measurement period adjustments				4,670
Oil & Gas Proppants | Sandbox
Goodwill [Roll Forward]
Acquisitions						86,100
Oil & Gas Proppants | White Armor
Goodwill [Roll Forward]
Acquisitions				0
Oil & Gas Proppants | MS Sand
Goodwill [Roll Forward]
Acquisitions				52,187
Measurement period adjustments		2,800		(29,665)
Oil & Gas Proppants | EPMH
Goodwill [Roll Forward]
Acquisitions		0
Measurement period adjustments		0
Industrial & Specialty Products
Goodwill [Line Items]
Goodwill	175,240	175,240		24,612		20,700	20,700
Impairment losses	0	0		0		0	$ 0
Goodwill [Roll Forward]
Beginning balance		24,612		20,700		20,700
Impairments		0
Ending balance	$ 175,240	175,240		24,612		20,700
Industrial & Specialty Products | NBI
Goodwill [Roll Forward]
Acquisitions						0
Measurement period adjustments				0
Industrial & Specialty Products | Sandbox
Goodwill [Roll Forward]
Acquisitions						$ 0
Industrial & Specialty Products | White Armor
Goodwill [Roll Forward]
Acquisitions				3,912
Industrial & Specialty Products | MS Sand
Goodwill [Roll Forward]
Acquisitions				0
Measurement period adjustments		0		$ 0
Industrial & Specialty Products | EPMH
Goodwill [Roll Forward]
Acquisitions		139,787
Measurement period adjustments		$ 10,841

Goodwill and Intangible Asset_3

Goodwill and Intangible Assets - Changes in the Carrying Amount of Intangible Assets (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Finite-Lived Intangible Assets
Gross Carrying Amount	$ 151,995	$ 131,932
Accumulated Amortization	(24,709)	(14,993)
Net	127,286	116,939
Total Intangible Assets
Gross Carrying Amount	219,335	165,000
Accumulated Amortization	(24,709)	(14,993)
Intangible assets, net	194,626	150,007
Trade names
Indefinite-lived Intangible Assets
Gross Carrying Amount	66,640	33,068
Other
Indefinite-lived Intangible Assets
Gross Carrying Amount	$ 700	0
Technology and intellectual property
Finite-Lived Intangible Assets
Estimated Useful Life	15 years
Gross Carrying Amount	$ 83,616	70,703
Accumulated Amortization	(11,168)	(5,917)
Net	72,448	64,786
Total Intangible Assets
Accumulated Amortization	$ (11,168)	(5,917)
Customer relationships
Finite-Lived Intangible Assets
Estimated Useful Life	20 years
Gross Carrying Amount	$ 68,379	61,229
Accumulated Amortization	(13,541)	(9,076)
Net	54,838	52,153
Total Intangible Assets
Accumulated Amortization	$ (13,541)	$ (9,076)
Customer relationships | Minimum
Finite-Lived Intangible Assets
Estimated Useful Life	13 years
Customer relationships | Maximum
Finite-Lived Intangible Assets
Estimated Useful Life	15 years

Goodwill and Intangible Asset_4

Goodwill and Intangible Assets - Additional Information (Details) - USD ($) $ in Thousands	3 Months Ended	8 Months Ended	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2018	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Acquired Finite-Lived Intangible Assets [Line Items]
Goodwill impairment			$ 164,167
Amortization expense			$ 9,700	$ 8,800	$ 3,200
EPMH
Acquired Finite-Lived Intangible Assets [Line Items]
Acquired finite-lived intangibles, measurement period adjustment		$ (10,780)
Identifiable intangible assets - indefinite lived		13,000
EPMH | Trade names
Acquired Finite-Lived Intangible Assets [Line Items]
Identifiable intangible assets - indefinite lived		13,000
EPMH | Technology and intellectual property
Acquired Finite-Lived Intangible Assets [Line Items]
Acquired finite-lived intangibles, measurement period adjustment		900
EPMH | Customer relationships
Acquired Finite-Lived Intangible Assets [Line Items]
Acquired finite-lived intangibles, measurement period adjustment		$ (11,700)
Oil & Gas Sand
Acquired Finite-Lived Intangible Assets [Line Items]
Goodwill impairment	$ 164,200
Intangible impairment charges	$ 4,500

Goodwill and Intangible Asset_5

Goodwill and Intangible Assets - Estimated Amortization Expense Related to Definite-Lived Intangible Assets (Details) $ in Thousands	Dec. 31, 2018USD ($)
Goodwill and Intangible Assets Disclosure [Abstract]
2,019	$ 12,396
2,020	12,397
2,021	12,396
2,022	12,381
2,023	$ 12,376

Accounts Payable and Accrued _3

Accounts Payable and Accrued Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Payables and Accruals [Abstract]
Trade payables	$ 178,804	$ 148,772
Accrued salaries and wages	12,291	6,126
Accrued vacation liability	3,503	2,906
Current portion of liability for pension and post-retirement benefits	2,708	1,524
Accrued healthcare liability	2,702	1,837
Accrued property taxes and sales taxes	4,490	2,720
Other accrued liabilities	11,902	7,156
Accounts payable and accrued liabilities	$ 216,400	$ 171,041

Debt (Details)

Debt (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Line of Credit Facility
Capital leases	$ 344	$ 706
Less: Unamortized original issue discount	(6,511)	(944)
Less: Unamortized debt issuance cost	(31,310)	(3,099)
Total debt	1,259,755	511,942
Less: current portion	(13,327)	(6,867)
Total long-term portion of debt	1,246,428	505,075
Notes Payable, Other Payables | Note payable secured by royalty interest
Line of Credit Facility
Total	26,511	24,740
Notes Payable, Other Payables | Customer note payable
Line of Credit Facility
Total	0	745
Notes Payable, Other Payables | Equipment notes payable
Line of Credit Facility
Total	321	719
Revolving Line-of-Credit | Revolver
Line of Credit Facility
Total	$ 0	$ 0
Credit facility, interest rate	8.50%	5.75%
Senior Secured Credit Facility | Term loan facility
Line of Credit Facility
Total	$ 1,270,400	$ 489,075
Credit facility, interest rate	6.56%
Senior Secured Credit Facility | Term loan facility | Minimum
Line of Credit Facility
Credit facility, interest rate		4.75%
Senior Secured Credit Facility | Term loan facility | Maximum
Line of Credit Facility
Credit facility, interest rate		5.25%

Debt - Additional Information (

Debt - Additional Information (Details)	May 01, 2018USD ($)	Dec. 31, 2018USD ($)	Dec. 31, 2017USD ($)	Dec. 31, 2016USD ($)	Aug. 16, 2016USD ($)
Debt Instrument [Line Items]
Write-off of capitalized debt issuance costs		$ 4,044,000	$ 1,382,000	$ 1,392,000
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		$ 26,500,000			$ 22,500,000
Interest rate, effective percentage		20.00%
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	Dec. 31, 2018	Dec. 31, 2017
Debt Instrument [Line Items]
2,019	$ 12,800
2,020	12,800
2,021	12,800
2,022	12,800
2,023	12,800
Thereafter	1,206,400
Total	$ 1,270,400	$ 489,075

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	Dec. 31, 2018USD ($)
Debt Instrument [Line Items]
2,019	$ 1,750
2,020	1,750
2,021	1,750
2,022	1,750
2,023	$ 1,750

Deferred Revenue (Details)

Deferred Revenue (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Deferred Revenue Arrangement [Line Items]
Deferred revenue, advances received	$ 31,625
Deferred revenue	113,319	$ 118,414
Deferred revenue, current	$ 31,612	$ 36,128
Supply Agreement | Minimum
Deferred Revenue Arrangement [Line Items]
Deferred revenue, average initial contract term	one
Supply Agreement | Maximum
Deferred Revenue Arrangement [Line Items]
Deferred revenue, average initial contract term	fifteen

Asset Retirement Obligations (D

Asset Retirement Obligations (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Asset Retirement Obligation Disclosure [Abstract]
Other long-term liabilities related to asset retirement obligation	$ 18,400	$ 19,000
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Beginning balance	19,032	11,159
Accretion	1,214	879
Additions and revisions of prior estimates	(319)	6,994
Addition related to EPMH acquisition	2,733	0
EPMH measurement period adjustment	(2,131)	0
Disposal related to sale of transloads	(2,116)	0
Ending balance	$ 18,413	19,032
Additional charges to asset retirement obligation		$ 7,000

Derivative Instruments - Estima

Derivative Instruments - Estimated Fair Values of Derivative Instruments (Details) - USD ($)	Dec. 31, 2018	Dec. 31, 2017
Interest rate swap agreement $440 million
Derivative Instruments, Gain (Loss)
Contract/Notional Amount	$ 440,000,000	$ 0
Carrying Amount	(1,475,000)	0
Fair Value	$ (1,475,000)	0
Interest rate swap agreement $440 million | LIBOR
Derivative Instruments, Gain (Loss)
Derivative, basis spread on variable rate (maximum)	2.74%
Interest rate swap agreement $200 million
Derivative Instruments, Gain (Loss)
Contract/Notional Amount	$ 200,000,000	0
Carrying Amount	(663,000)	0
Fair Value	$ (663,000)	0
Interest rate swap agreement $200 million | LIBOR
Derivative Instruments, Gain (Loss)
Derivative, basis spread on variable rate (maximum)	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 ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Derivative [Line Items]
Recognized deferred losses on derivatives in accumulated other comprehensive income into earnings	$ 77,000	$ 1,000	$ 81,000
Interest rate swap agreement $440 million
Derivative [Line Items]
Fair value of derivatives	1,475,000	0
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	1,500,000
Interest rate swap agreement $200 million
Derivative [Line Items]
Fair value of derivatives	663,000	0
Interest rate swap agreement $200 million | Other long-term obligations | Cash Flow Hedges
Derivative [Line Items]
Fair value of derivatives	700,000
Interest rate cap agreement
Derivative [Line Items]
Fair value of derivatives	0	$ 0
Recognized deferred losses on derivatives in accumulated other comprehensive income into earnings	$ 76,000

Derivative Instruments - Effect

Derivative Instruments - Effect of Derivatives Instruments on Combined Statements of Operations and Comprehensive Income (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Deferred Losses from Derivatives in OCI [Roll Forward]
Deferred losses from derivatives in OCI, beginning of period	$ (76)	$ (32)	$ (81)
Gain (loss) recognized in OCI from derivative instruments	(1,622)	(45)	(32)
Loss reclassified from Accumulated OCI	77	1	81
Deferred losses from derivatives in OCI, end of period	$ (1,621)	$ (76)	$ (32)

Equity-Based Compensation - Add

Equity-Based Compensation - Additional Information (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock options granted (in shares)	0	0	0
Stock options exercised (in shares)	4,167	43,774	326,884
Intrinsic value of stock options exercised	$ 100	$ 1,200	$ 7,600
Proceeds from options exercised	61	798	4,825
Tax benefit realized for deductions from stock options exercises	14	400	2,900
Stock options excluded
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Recognized equity-based compensation	1,400	2,500	3,000
Unrecognized compensation expense related to stock options	34
Restricted Stock and Restricted Stock Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Recognized equity-based compensation	$ 7,600	$ 7,100	$ 5,700
Awards share units granted (in shares)	415,110	156,164	364,710
Recognized weighted-average period	1 year 12 months
Unrecognized compensation expense related to awards	$ 9,500
Grant date fair value of awards granted (in dollars per share)	$ 21.57
Vesting period for awards of equity instruments	3 years
Performance Share Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Recognized equity-based compensation	$ 13,300	$ 15,500	$ 3,300
Awards share units granted (in shares)	261,500	90,501	850,143
Recognized weighted-average period	1 year 8 months 12 days
Unrecognized compensation expense related to awards	$ 7,500
Grant date fair value of awards granted (in dollars per share)	$ 31.24	$ 67.69	$ 39.36
Vesting period for awards of equity instruments	3 years
2011 Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock that may be issued (in shares)	3,447,363

Equity-Based Compensation - Sto

Equity-Based Compensation - Stock Options Activity (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Number of Shares
Outstanding at December 31, 2017 (in shares)	908,919
Granted (in shares)	0	0	0
Exercised (in shares)	(4,167)	(43,774)	(326,884)
Forfeited (in shares)	(918)
Expired (in shares)	(1,838)
Outstanding at December 31, 2018 (in shares)	901,996	908,919
Exercisable at December 31, 2018 (in shares)	901,996
Weighted Average Exercise Price
Outstanding at December 31, 2017, (in dollars per share)	$ 28.46
Granted (in dollars per share)	0
Exercised (in dollars per share)	14.65
Forfeited (in dollars per share)	31.30
Expired (in dollars per share)	31.30
Outstanding at December 31, 2018, (in dollars per share)	28.52	$ 28.46
Exercisable at December 31, 2018 (in dollars per share)	$ 28.52
Aggregate Intrinsic Value (in thousands)
Outstanding, aggregate intrinsic value	$ 18,566	$ 7,008
Exercisable, aggregate intrinsic value	$ 18,566
Weighted Average Remaining Contractual Term in Years
Outstanding, weighted average remaining contractual term in years	4 years 9 months 18 days	6 years 1 month
Exercisable, weighted average remaining contractual term in years	4 years 9 months 18 days

Equity-Based Compensation - Res

Equity-Based Compensation - Restricted Stock and Restricted Stock Units Activity (Details) - Restricted Stock and Restricted Stock Units - $ / shares	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Number of Shares
Unvested, December 31, 2017 (in shares)	461,346
Granted (in shares)	415,110	156,164	364,710
Vested (in shares)	(256,012)
Forfeited (in shares)	(32,867)
Unvested, December 31, 2018 (in shares)	587,577	461,346
Grant Date Weighted Average Fair Value
Unvested, December 31, 2017 (in dollars per share)	$ 30.76
Granted (in dollars per share)	21.57
Vested (in dollars per share)	28.66
Forfeited (in dollars per share)	30.82
Unvested, December 31, 2018 (in dollars per share)	$ 25.18	$ 30.76

Equity-Based Compensation - Per

Equity-Based Compensation - Performance Share Unit Activity (Details) - Performance Share Units - $ / shares	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Number of Shares
Unvested, December 31, 2017 (in shares)	881,416
Granted (in shares)	261,500	90,501	850,143
Vested (in shares)	(225,000)
Forfeited (in shares)	(79,728)
Unvested, December 31, 2018 (in shares)	838,188	881,416
Weighted Average
Unvested, December 31, 2017 (in dollars per share)	$ 42.16
Granted (in dollars per share)	31.24	$ 67.69	$ 39.36
Vested (in dollars per share)	41.99
Forfeited (in dollars per share)	40.45
Unvested, December 31, 2018 (in dollars per share)	$ 39.44	$ 42.16

Commitments and Contingencies -

Commitments and Contingencies - Future Minimum Annual Commitments (Details) $ in Thousands	Dec. 31, 2018USD ($)
Operating Lease Minimum Rental Payments
2,019	$ 74,884
2,020	59,490
2,021	40,302
2,022	31,853
2,023	22,596
Thereafter	40,148
Total future lease commitments	269,273
Minimum Purchase Commitments
2,019	23,243
2,020	15,406
2,021	8,307
2,022	5,640
2,023	4,915
Thereafter	6,084
Total future purchase commitments	$ 63,595

Commitments and Contingencies_2

Commitments and Contingencies - Additional Information (Details)	May 17, 2017USD ($)	Dec. 31, 2018USD ($)claim	Dec. 31, 2017USD ($)claim	Dec. 31, 2016USD ($)claim
Loss Contingencies
Expenses related to operating leases and rental agreements		$ 100,200,000	$ 68,300,000	$ 54,100,000
Purchased reserves	$ 94,400,000
Other non-current assets
Loss Contingencies
Third party products claims liability under insurance in other long-term obligations		0	0
Other long-term obligations
Loss Contingencies
Third party products claims liability under insurance in other long-term obligations		$ 900,000	$ 1,000,000
Pending Litigation
Loss Contingencies
Number of new claims filed | claim		20	0	2
Number of pending claims | claim		74

Pension and Post-Retirement B_3

Pension and Post-Retirement Benefits - Net Pension and Post-Retirement Benefit Plans (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Pension Benefits
Pension Plans, Postretirement and Other Employee Benefits
Service cost	$ 1,307	$ 1,037	$ 1,078
Interest cost	4,632	3,971	4,067
Expected return on plan assets	(5,969)	(5,265)	(5,495)
Net amortization and deferral	2,526	1,773	1,592
Net pension benefit or post-retirement costs	2,496	1,516	1,242
Post-retirement Benefits
Pension Plans, Postretirement and Other Employee Benefits
Service cost	102	107	132
Interest cost	740	753	876
Expected return on plan assets	0	(1)	(1)
Special termination benefit	0	0	21
Net pension benefit or post-retirement costs	$ 842	$ 859	$ 1,028

Pension and Post-Retirement B_4

Pension and Post-Retirement Benefits - Changes in Benefit Obligations and Plan Assets (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets, beginning balance	$ 92,067
Fair value of plan assets, ending balance	102,396	$ 92,067
Pension Benefits
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit obligation, beginning balance	122,052	116,145
Service cost	1,307	1,037	$ 1,078
Interest cost	4,632	3,971	4,067
Actuarial (gain) loss	(10,263)	6,824
Benefits paid	(8,202)	(6,685)
Amendments	0	760
Other	29,374	0
Benefit obligation, ending balance	138,900	122,052	116,145
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets, beginning balance	92,067	83,850
Actual return on plan assets	(6,204)	12,757
Employer contributions	3,350	2,145
Benefits paid	(8,202)	(6,685)
Other	21,385	0
Fair value of plan assets, ending balance	102,396	92,067	83,850
Plan assets less than benefit obligations at December 31 recognized as liability for pension and other post-retirement benefits	(36,504)	(29,985)
Post-retirement Benefits
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit obligation, beginning balance	22,771	24,393
Service cost	102	107	132
Interest cost	740	753	876
Actuarial (gain) loss	(965)	(1,576)
Benefits paid	(1,499)	(1,280)
Amendments	0	0
Other	421	374
Benefit obligation, ending balance	21,570	22,771	24,393
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets, beginning balance	0	14
Actual return on plan assets	0	(1)
Employer contributions	1,078	893
Benefits paid	(1,499)	(1,280)
Other	421	374
Fair value of plan assets, ending balance	0	0	$ 14
Plan assets less than benefit obligations at December 31 recognized as liability for pension and other post-retirement benefits	$ (21,570)	$ (22,771)

Pension and Post-Retirement B_5

Pension and Post-Retirement Benefits - Additional Information (Details) $ in Millions	12 Months Ended
	Dec. 31, 2018USD ($)plan	Dec. 31, 2017USD ($)	Dec. 31, 2016USD ($)
Pension Plans, Postretirement and Other Employee Benefits
Projected benefit obligation, nonqualified pension plan	$ 1.5	$ 1.6
Defined benefit plan, pension plans with accumulated benefit obligations in excess of plan assets, aggregate accumulated benefit obligation	1.5	1.6
Fair value of plan assets, nonqualified pension plan	0	0
Defined benefit plan, accumulated other comprehensive income net gains (losses), after tax	17.6	13.5
Defined benefit plan, accumulated other comprehensive income net prior service cost (credit), after tax	$ 2.8	$ 0.5
Weighted average discount rate used to determine projected pension and post-retirement obligations	4.40%	3.70%
Number of multiemployer defined benefit plans | plan	3
Percentage of contributions to individual multiemployer pension funds	5.00%	5.00%	5.00%
Company contributing percentage on defined benefit plan	50.00%
Employee contribution over defined benefit plan	4.00%
Company contributions to defined contribution plan	$ 2.6	$ 3	$ 2.4
Certain Employees
Pension Plans, Postretirement and Other Employee Benefits
Company 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 Benefits
Pension Plans, Postretirement and Other Employee Benefits
Accumulated benefit obligation	$ 138.9	$ 122.1
Expected contributions to the plans for next fiscal year	$ 4.5
Weighted average discount rate used to determine projected pension and post-retirement obligations	4.40%	3.70%
Post-retirement Benefits
Pension Plans, Postretirement and Other Employee Benefits
Expected contributions to the plans for next fiscal year	$ 1.4
Weighted average discount rate used to determine projected pension and post-retirement obligations	4.30%	3.70%

Pension and Post-Retirement B_6

Pension and Post-Retirement Benefits - Estimated Future Pension and Post-Retirement Benefit Payments (Details) $ in Thousands	Dec. 31, 2018USD ($)
Pension Benefits
Defined Benefit Plan, Expected Future Benefit Payment [Abstract]
2,019	$ 10,022
2,020	9,166
2,021	9,236
2,022	9,394
2,023	9,380
2024-2028	47,737
Post-retirement Benefits | Before Medicare Subsidy
Defined Benefit Plan, Expected Future Benefit Payment [Abstract]
2,019	1,553
2,020	1,592
2,021	1,653
2,022	1,691
2,023	1,686
2024-2028	8,262
Post-retirement Benefits | After Medicare Subsidy
Defined Benefit Plan, Expected Future Benefit Payment [Abstract]
2,019	1,394
2,020	1,433
2,021	1,496
2,022	1,535
2,023	1,528
2024-2028	$ 7,442

Pension and Post-Retirement B_7

Pension and Post-Retirement Benefits - Amounts in Accumulated Other Comprehensive Income Expected to be Recognized as Components of Net Periodic Benefit Cost (Details) $ in Thousands	Dec. 31, 2018USD ($)
Pension Plans, Postretirement and Other Employee Benefits
Net actuarial loss	$ 1,034
Prior service cost	534
Total	1,568
Pension Benefits
Pension Plans, Postretirement and Other Employee Benefits
Net actuarial loss	1,034
Prior service cost	534
Total	1,568
Post-retirement Benefits
Pension Plans, Postretirement and Other Employee Benefits
Net actuarial loss	0
Prior service cost	0
Total	$ 0

- Weighted-Average Assumptions

- Weighted-Average Assumptions Used (Details)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Pension Plans, Postretirement and Other Employee Benefits
Discount rate	4.40%	3.70%
Pension Benefits
Pension Plans, Postretirement and Other Employee Benefits
Discount rate	4.40%	3.70%
Long-term rate of compensation increase		3.50%
Long-term rate of return on plan assets		6.80%
Pension Benefits | Minimum
Pension Plans, Postretirement and Other Employee Benefits
Long-term rate of compensation increase	3.00%
Long-term rate of return on plan assets	6.25%
Pension Benefits | Maximum
Pension Plans, Postretirement and Other Employee Benefits
Long-term rate of compensation increase	3.50%
Long-term rate of return on plan assets	7.15%
Post-retirement Health Care
Pension Plans, Postretirement and Other Employee Benefits
Discount rate	4.30%	3.70%
Long-term rate of return on plan assets		7.00%
Post-retirement Health Care | Pre-65 | Minimum
Pension Plans, Postretirement and Other Employee Benefits
Initial rate	7.30%	7.30%
Post-retirement Health Care | Pre-65 | Maximum
Pension Plans, Postretirement and Other Employee Benefits
Ultimate rate	4.50%	4.50%
Post-retirement Health Care | Post-65 | Minimum
Pension Plans, Postretirement and Other Employee Benefits
Initial rate	8.00%	8.00%
Post-retirement Health Care | Post-65 | Maximum
Pension Plans, Postretirement and Other Employee Benefits
Ultimate rate	4.50%	4.50%

Pension and Post-Retirement B_8

Pension and Post-Retirement Benefits - Effect of One-Percentage-Point Change in Assumed Health Care Cost Trend Rates (Details) - Post-retirement Benefits $ in Thousands	12 Months Ended
	Dec. 31, 2018USD ($)
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Effect on total of service and interest cost, increase	$ 109
Effect on post-retirement benefit obligation, increase	2,291
Effect on total of service and interest cost, decrease	(92)
Effect on post-retirement benefit obligation, decrease	$ (1,967)

Pension and Post-Retirement B_9

Pension and Post-Retirement Benefits - Investment Categories and Their Relative Percentage of Fair Value to Total Plan Assets (Details)	Dec. 31, 2018	Dec. 31, 2017
Pension Benefits | Equity securities
Pension Plans, Postretirement and Other Employee Benefits
Percentage of the fair value of the total plan assets	42.10%	51.80%
Pension Benefits | Debt securities
Pension Plans, Postretirement and Other Employee Benefits
Percentage of the fair value of the total plan assets	55.50%	46.30%
Pension Benefits | Cash
Pension Plans, Postretirement and Other Employee Benefits
Percentage of the fair value of the total plan assets	2.40%	1.90%
Post-retirement Benefits | Equity securities
Pension Plans, Postretirement and Other Employee Benefits
Percentage of the fair value of the total plan assets	0.00%	0.00%
Post-retirement Benefits | Debt securities
Pension Plans, Postretirement and Other Employee Benefits
Percentage of the fair value of the total plan assets	0.00%	0.00%
Post-retirement Benefits | Cash
Pension Plans, Postretirement and Other Employee Benefits
Percentage of the fair value of the total plan assets	0.00%	0.00%

Pension and Post-Retirement _10

Pension and Post-Retirement Benefits - Fair Value of Pension Plan Assets, by Asset Category (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Pension Plans, Postretirement and Other Employee Benefits
Fair value of pension plan assets	$ 102,396	$ 92,067
Cash and cash equivalents
Pension Plans, Postretirement and Other Employee Benefits
Fair value of pension plan assets	2,449	1,727
Diversified emerging markets
Pension Plans, Postretirement and Other Employee Benefits
Fair value of pension plan assets	6,638	8,300
Foreign large blend
Pension Plans, Postretirement and Other Employee Benefits
Fair value of pension plan assets	11,689	11,856
Large-cap blend
Pension Plans, Postretirement and Other Employee Benefits
Fair value of pension plan assets	14,226	15,643
Mid-cap blend
Pension Plans, Postretirement and Other Employee Benefits
Fair value of pension plan assets	6,819	8,334
Small-cap blend
Pension Plans, Postretirement and Other Employee Benefits
Fair value of pension plan assets	522
Real estate
Pension Plans, Postretirement and Other Employee Benefits
Fair value of pension plan assets	3,192	3,591
Corporate notes and bonds
Pension Plans, Postretirement and Other Employee Benefits
Fair value of pension plan assets	43,745	28,108
U.S. Treasuries
Pension Plans, Postretirement and Other Employee Benefits
Fair value of pension plan assets	8,486	10,846
Mortgage-backed securities
Pension Plans, Postretirement and Other Employee Benefits
Fair value of pension plan assets	3,578	2,615
Asset-backed securities
Pension Plans, Postretirement and Other Employee Benefits
Fair value of pension plan assets	1,052	1,047
Level 1
Pension Plans, Postretirement and Other Employee Benefits
Fair value of pension plan assets	95,317	86,678
Level 1 | Cash and cash equivalents
Pension Plans, Postretirement and Other Employee Benefits
Fair value of pension plan assets	0	0
Level 1 | Diversified emerging markets
Pension Plans, Postretirement and Other Employee Benefits
Fair value of pension plan assets	6,638	8,300
Level 1 | Foreign large blend
Pension Plans, Postretirement and Other Employee Benefits
Fair value of pension plan assets	11,689	11,856
Level 1 | Large-cap blend
Pension Plans, Postretirement and Other Employee Benefits
Fair value of pension plan assets	14,226	15,643
Level 1 | Mid-cap blend
Pension Plans, Postretirement and Other Employee Benefits
Fair value of pension plan assets	6,819	8,334
Level 1 | Small-cap blend
Pension Plans, Postretirement and Other Employee Benefits
Fair value of pension plan assets	522
Level 1 | Real estate
Pension Plans, Postretirement and Other Employee Benefits
Fair value of pension plan assets	3,192	3,591
Level 1 | Corporate notes and bonds
Pension Plans, Postretirement and Other Employee Benefits
Fair value of pension plan assets	43,745	28,108
Level 1 | U.S. Treasuries
Pension Plans, Postretirement and Other Employee Benefits
Fair value of pension plan assets	8,486	10,846
Level 1 | Mortgage-backed securities
Pension Plans, Postretirement and Other Employee Benefits
Fair value of pension plan assets	0	0
Level 1 | Asset-backed securities
Pension Plans, Postretirement and Other Employee Benefits
Fair value of pension plan assets	0	0
Level 2
Pension Plans, Postretirement and Other Employee Benefits
Fair value of pension plan assets	7,079	5,389
Level 2 | Cash and cash equivalents
Pension Plans, Postretirement and Other Employee Benefits
Fair value of pension plan assets	2,449	1,727
Level 2 | Diversified emerging markets
Pension Plans, Postretirement and Other Employee Benefits
Fair value of pension plan assets	0	0
Level 2 | Foreign large blend
Pension Plans, Postretirement and Other Employee Benefits
Fair value of pension plan assets	0	0
Level 2 | Large-cap blend
Pension Plans, Postretirement and Other Employee Benefits
Fair value of pension plan assets	0	0
Level 2 | Mid-cap blend
Pension Plans, Postretirement and Other Employee Benefits
Fair value of pension plan assets	0	0
Level 2 | Small-cap blend
Pension Plans, Postretirement and Other Employee Benefits
Fair value of pension plan assets	0
Level 2 | Real estate
Pension Plans, Postretirement and Other Employee Benefits
Fair value of pension plan assets	0	0
Level 2 | Corporate notes and bonds
Pension Plans, Postretirement and Other Employee Benefits
Fair value of pension plan assets	0	0
Level 2 | U.S. Treasuries
Pension Plans, Postretirement and Other Employee Benefits
Fair value of pension plan assets	0	0
Level 2 | Mortgage-backed securities
Pension Plans, Postretirement and Other Employee Benefits
Fair value of pension plan assets	3,578	2,615
Level 2 | Asset-backed securities
Pension Plans, Postretirement and Other Employee Benefits
Fair value of pension plan assets	1,052	1,047
Level 3
Pension Plans, Postretirement and Other Employee Benefits
Fair value of pension plan assets	0	0
Level 3 | Cash and cash equivalents
Pension Plans, Postretirement and Other Employee Benefits
Fair value of pension plan assets	0	0
Level 3 | Diversified emerging markets
Pension Plans, Postretirement and Other Employee Benefits
Fair value of pension plan assets	0	0
Level 3 | Foreign large blend
Pension Plans, Postretirement and Other Employee Benefits
Fair value of pension plan assets	0	0
Level 3 | Large-cap blend
Pension Plans, Postretirement and Other Employee Benefits
Fair value of pension plan assets	0	0
Level 3 | Mid-cap blend
Pension Plans, Postretirement and Other Employee Benefits
Fair value of pension plan assets	0	0
Level 3 | Small-cap blend
Pension Plans, Postretirement and Other Employee Benefits
Fair value of pension plan assets	0
Level 3 | Real estate
Pension Plans, Postretirement and Other Employee Benefits
Fair value of pension plan assets	0	0
Level 3 | Corporate notes and bonds
Pension Plans, Postretirement and Other Employee Benefits
Fair value of pension plan assets	0	0
Level 3 | U.S. Treasuries
Pension Plans, Postretirement and Other Employee Benefits
Fair value of pension plan assets	0	0
Level 3 | Mortgage-backed securities
Pension Plans, Postretirement and Other Employee Benefits
Fair value of pension plan assets	0	0
Level 3 | Asset-backed securities
Pension Plans, Postretirement and Other Employee Benefits
Fair value of pension plan assets	$ 0	$ 0

Pension and Post-Retirement _11

Pension and Post-Retirement Benefits - Summary of Multiemployer Pension Plan (Details) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
LIUNA
Pension Plans, Postretirement and Other Employee Benefits
EIN/ Pension Plan No.	52-6074345/001
Pension Protection Act Zone Status	Red
Company Contributions (in thousands)	$ 573,000	$ 223,000	$ 167,000
Surcharge Imposed	Yes
Expiration Date of CBA	May 31, 2020
IUOE
Pension Plans, Postretirement and Other Employee Benefits
EIN/ Pension Plan No.	36-6052390/001
Pension Protection Act Zone Status	Green
Company Contributions (in thousands)	$ 1,385,000	40,000	28,000
Surcharge Imposed	No
Expiration Date of CBA	Jul. 31, 2022
CSSS
Pension Plans, Postretirement and Other Employee Benefits
EIN/ Pension Plan No.	36-6044243/001
Pension Protection Act Zone Status	Red
Company Contributions (in thousands)	$ 51,000	$ 51,000	$ 51,000
Central States, Southeast and Southwest Areas Pension Plan
Pension Plans, Postretirement and Other Employee Benefits
Withdrawal liability from pension plan	1,000,000
Withdrawal liability paid on monthly installments	$ 4,000

Obligations Under Guarantees (D

Obligations Under Guarantees (Details) $ in Millions	Dec. 31, 2018USD ($)
Surety Bonds
Loss Contingencies
Surety bonds outstanding	$ 34.4
Reclamation Bonds
Loss Contingencies
Bonds related to reclamation requirements	$ 29.8

Income Taxes - Additional Infor

Income Taxes - Additional Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Operating Loss Carryforwards [Line Items]
Discrete tax expense related to certain executive compensation agreements not eligible for transition relief	$ 653	$ (2,602)	$ (2,003)
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
Alternative minimum tax credit carry forward	16,000	$ 30,400
Alternative minimum tax reclassified from deferred tax assets to other receivables	16,000
IRS
Operating Loss Carryforwards [Line Items]
Net operating loss carryforwards	41,900
ASC 740
Operating Loss Carryforwards [Line Items]
Discrete tax expense related to certain executive compensation agreements not eligible for transition relief	$ 700

Income Taxes - Income (Loss) Be

Income Taxes - Income (Loss) Before Income Taxes (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Tax Disclosure [Abstract]
United States									$ (232,597)	$ 136,526	$ (77,745)
Foreign									2,644	0	0
Income (loss) before income taxes	$ (294,013)	$ 4,769	$ 20,476	$ 38,815	$ 43,169	$ 55,980	$ 36,569	$ 808	$ (229,953)	$ 136,526	$ (77,745)

Income Taxes - Income Tax Benef

Income Taxes - Income Tax Benefit (Expense) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Current:
Federal									$ 1,076	$ (10,754)	$ 60
State									(2,496)	(1,167)	(274)
Foreign									(518)	0	0
Current income tax (expense) benefit									(1,938)	(11,921)	(214)
Deferred:
Federal									25,578	22,641	32,944
State									5,492	(2,040)	3,959
Foreign									0	0	0
Deferred income tax (expense) benefit									31,070	20,601	36,903
Income tax benefit	$ 37,938	$ 1,547	$ (2,832)	$ (7,521)	$ 28,783	$ (14,707)	$ (7,110)	$ 1,714	$ 29,132	$ 8,680	$ 36,689

Income Taxes - Effective Income

Income Taxes - Effective Income Tax Rate on Pretax Earnings (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Tax Disclosure [Abstract]
Income tax benefit (expense) computed at U.S. federal statutory rate									$ 48,290	$ (47,784)	$ 27,211
Decrease (increase) resulting from:
Statutory depletion									12,090	20,259	4,734
Goodwill impairment									(29,157)	0	0
Prior year tax return reconciliation									530	219	435
State income taxes, net of federal benefit									2,592	(2,267)	2,369
Adjustment to deferred taxes from the Tax Act rate reduction									0	35,772	0
Equity compensation									(653)	2,602	2,003
Other, net									(4,560)	(121)	(63)
Income tax benefit	$ 37,938	$ 1,547	$ (2,832)	$ (7,521)	$ 28,783	$ (14,707)	$ (7,110)	$ 1,714	$ 29,132	$ 8,680	$ 36,689

Income Taxes - Tax Effects on D

Income Taxes - Tax Effects on Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Gross deferred tax assets:
Net operating loss carry forward and state tax credits	$ 11,089	$ 22,783
Pension and post-retirement benefit costs	13,303	13,710
Alternative minimum tax credit carry forward	15,971	30,401
Property, plant and equipment	5,474	5,750
Accrued expenses	27,025	10,755
Inventories	774	4,354
Third-party products liability	231	249
Stock-based compensation expense	8,199	8,785
Note payable	3,724	3,133
Other	8,116	5,095
Total deferred tax assets	93,906	105,015
Gross deferred tax liabilities:
Land and mineral property basis difference	(165,002)	(78,520)
Fixed assets and depreciation	(55,596)	(51,556)
Intangibles	(10,346)	(4,795)
Other	(201)	0
Total deferred tax liabilities	(231,145)	(134,871)
Net deferred tax liabilities	$ (137,239)	$ (29,856)

Revenue - Sales by Major Source

Revenue - Sales by Major Source (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Disaggregation of Revenue [Line Items]
Total Sales									$ 1,577,298	$ 1,240,851	$ 559,625
Oil & Gas Proppants
Disaggregation of Revenue [Line Items]
Total Sales									1,182,991
Industrial & Specialty Products
Disaggregation of Revenue [Line Items]
Total Sales									394,307
Product
Disaggregation of Revenue [Line Items]
Total Sales	$ 293,419	$ 348,635	$ 345,957	$ 294,788	$ 290,114	$ 281,138	$ 235,891	$ 203,251	1,282,799	1,010,394	524,137
Product | Oil & Gas Proppants
Disaggregation of Revenue [Line Items]
Total Sales									888,509
Product | Industrial & Specialty Products
Disaggregation of Revenue [Line Items]
Total Sales									394,290
Service
Disaggregation of Revenue [Line Items]
Total Sales	$ 63,961	$ 74,537	$ 81,476	$ 74,525	$ 70,452	$ 63,885	$ 54,574	$ 41,546	294,499	$ 230,457	$ 35,488
Service | Oil & Gas Proppants
Disaggregation of Revenue [Line Items]
Total Sales									294,482
Service | Industrial & Specialty Products
Disaggregation of Revenue [Line Items]
Total Sales									$ 17

Revenue - Changes in Contract A

Revenue - Changes in Contract Assets and Liabilities (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2018USD ($)
Unbilled Receivables
December 31, 2017	$ 5,245
Reclassifications to billed receivables	(11,157)
Revenues recognized in excess of period billings	6,002
December 31, 2018	90
Deferred Revenue
December 31, 2017	118,414
Revenues recognized from balances held at the beginning of the period	(33,381)
Revenues deferred from period collections on unfulfilled performance obligations	31,625
Revenues recognized from period collections	(3,339)
December 31, 2018	$ 113,319

Revenue - Additional Informatio

Revenue - Additional Information (Details)	Dec. 31, 2018
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2019-01-01
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	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Related Party Transaction [Line Items]
Related party purchases	$ 2,958	$ 4,942	$ 446
Officer | Transportation Brokerage And Logistics Services Vendor
Related Party Transaction [Line Items]
Related party purchases	$ 2,900	$ 4,700	$ 800

Segment Reporting - Additional

Segment Reporting - Additional Information (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2018USD ($)SegmentProduct	Dec. 31, 2017USD ($)	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)
Segment Reporting Information
Number of reportable segments | Segment	2
Number of product types | Product	400
Goodwill	$ 261,340	$ 272,079	$ 240,975	$ 68,647
Oil & Gas Proppants
Segment Reporting Information
Goodwill	86,100	247,467	220,275	47,947
Industrial & Specialty Products
Segment Reporting Information
Goodwill	175,240	24,612	$ 20,700	$ 20,700
Operating Segments | Oil & Gas Proppants
Segment Reporting Information
Goodwill	86,100	247,500
Operating Segments | Industrial & Specialty Products
Segment Reporting Information
Goodwill	$ 175,200	$ 24,600

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								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Segment Reporting Information
Total sales									$ 1,577,298	$ 1,240,851	$ 559,625
Selling, general and administrative	$ (32,168)	$ (37,980)	$ (42,232)	$ (34,591)	$ (29,334)	$ (29,542)	$ (25,839)	$ (22,341)	(146,971)	(107,056)	(67,172)
Depreciation, depletion and amortization	(46,527)	(37,150)	(36,563)	(28,592)	(27,335)	(24,673)	(23,626)	(21,599)	(148,832)	(97,233)	(68,134)
Goodwill and other asset impairments	(265,715)	0	(16,184)	0					(281,899)	0	0
Interest expense	(21,281)	(21,999)	(20,214)	(7,070)	(7,244)	(8,347)	(8,105)	(7,646)	(70,564)	(31,342)	(27,972)
Other income (expense), net, including interest income	1,336	1,062	1,081	665	1,108	1,308	638	(4,928)	4,144	(1,874)	2,718
Income tax benefit	37,938	1,547	(2,832)	(7,521)	28,783	(14,707)	(7,110)	1,714	29,132	8,680	36,689
Net income (loss)	(256,075)	6,316	17,644	31,294	71,952	41,273	29,459	2,522	(200,821)	145,206	(41,056)
Less: Net income (loss) attributable to non-controlling interest	(13)	0	0	0	0	0	0	0	(13)	0	0
Net income (loss) attributable to U.S. Silica Holdings, Inc.	$ (256,062)	$ 6,316	$ 17,644	$ 31,294	$ 71,952	$ 41,273	$ 29,459	$ 2,522	(200,808)	145,206	(41,056)
Operating Segments
Segment Reporting Information
Total sales									1,577,298	1,240,851	559,625
Total segment contribution margin									512,930	390,753	90,433
Segment Reconciling Items
Segment Reporting Information
Operating activities excluded from segment cost of sales(1)									(98,761)	(16,722)	(7,618)
Selling, general and administrative									(146,971)	(107,056)	(67,172)
Depreciation, depletion and amortization									(148,832)	(97,233)	(68,134)
Goodwill and other asset impairments									(281,899)	0	0
Interest expense									(70,564)	(31,342)	(27,972)
Other income (expense), net, including interest income									4,144	(1,874)	2,718
Oil & Gas Proppants
Segment Reporting Information
Total sales									1,182,991
Oil & Gas Proppants | Operating Segments
Segment Reporting Information
Total sales									1,182,991	1,020,365	362,550
Total segment contribution margin									357,846	301,972	11,445
Industrial & Specialty Products
Segment Reporting Information
Total sales									394,307
Industrial & Specialty Products | Operating Segments
Segment Reporting Information
Total sales									394,307	220,486	197,075
Total segment contribution margin									$ 155,084	$ 88,781	$ 78,988

Unaudited Supplementary Data (D

Unaudited Supplementary Data (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Sales:
Total sales									$ 1,577,298	$ 1,240,851	$ 559,625
Cost of sales (excluding depreciation, depletion and amortization):
Product	$ 241,624	$ 270,370	$ 236,236	$ 207,239	$ 202,466	$ 187,634	$ 162,238	$ 162,183	955,469	714,521	456,783
Service	45,414	51,966	56,609	53,671	52,126	40,155	34,726	25,292	207,660	152,299	20,027
Operating expenses:
Selling, general and administrative	32,168	37,980	42,232	34,591	29,334	29,542	25,839	22,341	146,971	107,056	67,172
Depreciation, depletion and amortization	46,527	37,150	36,563	28,592	27,335	24,673	23,626	21,599	148,832	97,233	68,134
Goodwill and other asset impairments	265,715	0	16,184	0					281,899	0	0
Total operating expenses	344,410	75,130	94,979	63,183	56,669	54,215	49,465	43,940	577,702	204,289	135,306
Operating income (loss)	(274,068)	25,706	39,609	45,220	49,305	63,019	44,036	13,382	(163,533)	169,742	(52,491)
Other (expense) income:
Interest expense	(21,281)	(21,999)	(20,214)	(7,070)	(7,244)	(8,347)	(8,105)	(7,646)	(70,564)	(31,342)	(27,972)
Other income (expense), net, including interest income	1,336	1,062	1,081	665	1,108	1,308	638	(4,928)	4,144	(1,874)	2,718
Total other expense	(19,945)	(20,937)	(19,133)	(6,405)	(6,136)	(7,039)	(7,467)	(12,574)	(66,420)	(33,216)	(25,254)
Income (loss) before income taxes	(294,013)	4,769	20,476	38,815	43,169	55,980	36,569	808	(229,953)	136,526	(77,745)
Income tax benefit	37,938	1,547	(2,832)	(7,521)	28,783	(14,707)	(7,110)	1,714	29,132	8,680	36,689
Net income (loss)	(256,075)	6,316	17,644	31,294	71,952	41,273	29,459	2,522	(200,821)	145,206	(41,056)
Less: Net income (loss) attributable to non-controlling interest	(13)	0	0	0	0	0	0	0	(13)	0	0
Net income (loss) attributable to U.S. Silica Holdings, Inc.	$ (256,062)	$ 6,316	$ 17,644	$ 31,294	$ 71,952	$ 41,273	$ 29,459	$ 2,522	$ (200,808)	$ 145,206	$ (41,056)
Basic earnings (loss) per share (in dollars per share)	$ (3.44)	$ 0.08	$ 0.23	$ 0.39	$ 0.95	$ 0.51	$ 0.36	$ 0.03	$ (2.63)	$ 1.79	$ (0.63)
Diluted earnings (loss) per share (in dollars per share)	$ (3.44)	$ 0.08	$ 0.22	$ 0.39	$ 0.95	$ 0.50	$ 0.36	$ 0.03	$ (2.63)	$ 1.77	$ (0.63)
Weighted average shares outstanding, basic (in shares)	74,485	77,365	77,784	79,496	75,539	81,121	81,087	80,983	76,453	81,051	65,037
Weighted average common shares outstanding, diluted (in shares)	74,485	77,859	78,480	80,309	75,539	81,783	81,945	82,244
Dividends declared per share (in dollars per share)	$ 0.06	$ 0.06	$ 0.06	$ 0.06	$ 0.06	$ 0.06	$ 0.06	$ 0.06	$ 0.25	$ 0.25	$ 0.25
Service
Sales:
Total sales	$ 63,961	$ 74,537	$ 81,476	$ 74,525	$ 70,452	$ 63,885	$ 54,574	$ 41,546	$ 294,499	$ 230,457	$ 35,488
Product
Sales:
Total sales	$ 293,419	$ 348,635	$ 345,957	$ 294,788	$ 290,114	$ 281,138	$ 235,891	$ 203,251	$ 1,282,799	$ 1,010,394	$ 524,137

Parent Company Financials - Con

Parent Company Financials - Condensed Balance Sheets (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Current Assets:
Cash and cash equivalents	$ 202,498	$ 384,567	$ 711,225	$ 277,077
Total current assets	600,237	703,244
Total assets	2,900,840	2,307,283
Current Liabilities:
Accounts payable and accrued expenses	216,400	171,041
Total current liabilities	261,339	215,602
Deferred income taxes, net	137,239	29,856
Total liabilities	1,848,536	910,777
Stockholders’ Equity:
Common stock	818	812
Additional paid-in capital	1,169,383	1,147,084
Retained earnings	67,854	287,992
Treasury stock, at cost	(178,215)	(25,456)
Accumulated other comprehensive loss	(15,020)	(13,926)
Total U.S. Silica Holdings, Inc. stockholders’ equity	1,044,820	1,396,506
Non-controlling interest	7,484	0
Total stockholders' equity	1,052,304	1,396,506	1,273,290	384,167
Total liabilities and stockholders’ equity	2,900,840	2,307,283
Parent Company
Current Assets:
Cash and cash equivalents	107,151	230,647	534,378	58,579
Due from affiliates	100,094	146,683
Total current assets	207,245	377,330
Investment in subsidiaries	850,099	1,024,511
Total assets	1,057,344	1,401,841
Current Liabilities:
Accounts payable and accrued expenses	217	106
Dividends payable	4,823	5,229
Total current liabilities	5,040	5,335
Deferred income taxes, net	0	0
Total liabilities	5,040	5,335
Stockholders’ Equity:
Preferred stock	0	0
Common stock	818	812
Additional paid-in capital	1,169,383	1,147,084
Retained earnings	67,854	287,992
Treasury stock, at cost	(178,215)	(25,456)
Accumulated other comprehensive loss	(15,020)	(13,926)
Total U.S. Silica Holdings, Inc. stockholders’ equity	1,044,820	1,396,506
Non-controlling interest	7,484	0
Total stockholders' equity	1,052,304	1,396,506	$ 1,273,290	$ 384,167
Total liabilities and stockholders’ equity	$ 1,057,344	$ 1,401,841

Parent Company Financials - C_2

Parent Company Financials - Condensed Statements of Operations and Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Condensed Income Statements, Captions [Line Items]
Total sales									$ 1,577,298	$ 1,240,851	$ 559,625
Cost of sales									1,163,129	866,820	476,810
Operating expenses:
Selling, general and administrative	$ 32,168	$ 37,980	$ 42,232	$ 34,591	$ 29,334	$ 29,542	$ 25,839	$ 22,341	146,971	107,056	67,172
Total operating expenses	344,410	75,130	94,979	63,183	56,669	54,215	49,465	43,940	577,702	204,289	135,306
Operating income (loss)	(274,068)	25,706	39,609	45,220	49,305	63,019	44,036	13,382	(163,533)	169,742	(52,491)
Other income (expense)
Other income (expense), net, including interest income	1,336	1,062	1,081	665	1,108	1,308	638	(4,928)	4,144	(1,874)	2,718
Total other expense	(19,945)	(20,937)	(19,133)	(6,405)	(6,136)	(7,039)	(7,467)	(12,574)	(66,420)	(33,216)	(25,254)
Income tax benefit	37,938	1,547	(2,832)	(7,521)	28,783	(14,707)	(7,110)	1,714	29,132	8,680	36,689
Net income (loss)	(256,075)	6,316	17,644	31,294	71,952	41,273	29,459	2,522	(200,821)	145,206	(41,056)
Less: Net income (loss) attributable to non-controlling interest	(13)	0	0	0	0	0	0	0	(13)	0	0
Net income (loss) attributable to U.S. Silica Holdings, Inc.	(256,062)	6,316	17,644	31,294	71,952	41,273	29,459	2,522	(200,808)	145,206	(41,056)
Net income (loss)	$ (256,075)	$ 6,316	$ 17,644	$ 31,294	$ 71,952	$ 41,273	$ 29,459	$ 2,522	(200,821)	145,206	(41,056)
Other comprehensive income (loss)
Unrealized loss on short-term investments (net of tax)									0	0	(6)
Unrealized gain (loss) on derivatives (net of tax)									(1,545)	(44)	49
Comprehensive income (loss)									(201,915)	147,156	(40,761)
Less: Comprehensive income (loss) attributable to non-controlling interest									(13)	0	0
Comprehensive income (loss) attributable to U.S. Silica Holdings, Inc.									(201,902)	147,156	(40,761)
Tax expense (benefit) on unrealized gain (loss) on investments									0	0	(4)
Tax expense (benefit) on unrealized gain (loss) on derivatives									(470)	(27)	29
Parent Company
Condensed Income Statements, Captions [Line Items]
Total sales									0	0	0
Cost of sales									0	0	0
Operating expenses:
Selling, general and administrative									254	252	184
Other									0	0	10
Total operating expenses									254	252	194
Operating income (loss)									(254)	(252)	(194)
Other income (expense)
Interest income									2,784	3,854	1,046
Other income (expense), net, including interest income									0	0	0
Total other expense									2,784	3,854	1,046
Income before income taxes and equity in net earnings of subsidiaries									2,530	3,602	852
Income tax benefit									(696)	(1,453)	(344)
Income before equity in net earnings of subsidiaries									1,834	2,149	508
Equity in earnings of subsidiaries, net of tax									(202,655)	143,057	(41,564)
Net income (loss)									(200,821)	145,206	(41,056)
Less: Net income (loss) attributable to non-controlling interest									(13)	0	0
Net income (loss) attributable to U.S. Silica Holdings, Inc.									(200,808)	145,206	(41,056)
Net income (loss)									(200,821)	145,206	(41,056)
Other comprehensive income (loss)
Unrealized loss on short-term investments (net of tax)									0	0	(6)
Unrealized gain (loss) on derivatives (net of tax)									(1,545)	(44)	49
Foreign currency translation adjustment (net of tax)									(614)	(6)	0
Pension and post-retirement liability (net of tax)									1,065	2,000	252
Comprehensive income (loss)									(201,915)	147,156	(40,761)
Less: Comprehensive income (loss) attributable to non-controlling interest									(13)	0	0
Comprehensive income (loss) attributable to U.S. Silica Holdings, Inc.									(201,902)	147,156	(40,761)
Tax expense (benefit) on unrealized gain (loss) on investments									0	0	(4)
Tax expense (benefit) on unrealized gain (loss) on derivatives									(470)	(27)	29
Tax expense (benefit) on foreign currency translation adjustment									(196)	2	0
Tax (expense) benefit on pension and post-retirement liability									$ 339	$ 1,205	$ 152

Parent Company Financials - C_3

Parent Company Financials - Condensed Statements of Stockholders' Equity (Details) - USD ($)	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Condensed Stockholders' Equity Statement [Line Items]
Beginning Balance				$ 1,396,506,000				$ 1,273,290,000	$ 1,396,506,000	$ 1,273,290,000	$ 384,167,000
Net income (loss)	$ (256,075,000)	$ 6,316,000	$ 17,644,000	$ 31,294,000	$ 71,952,000	$ 41,273,000	$ 29,459,000	$ 2,522,000	(200,821,000)	145,206,000	(41,056,000)
Issuance of common stock (stock offerings net of issuance costs of $25,732)											931,288,000
Unrealized gain (loss) on derivatives (net of tax)									(1,545,000)	(44,000)	49,000
Unrealized loss on short-term investments (net of tax)									0	0	(6,000)
Foreign currency translation adjustment (net of tax)									(614,000)	(6,000)	0
Pension and post-retirement liability									1,065,000	2,000,000	252,000
Cash dividends declared ($0.25 per share of common stock for 2018, 2017 and 2016, respectively)									(19,330,000)	(20,387,000)	(16,893,000)
Contributions from non-controlling interest									7,497,000
Equity-based compensation									22,337,000	25,050,000	12,107,000
Excess tax benefit from equity-based compensation											148,000
Proceeds from options exercised									61,000	798,000	4,825,000
Issuance of restricted stock										0	0
Shares withheld for tax payments related to vested restricted stock and stock units									(4,383,000)	(4,379,000)	(1,591,000)
Repurchase of common stock									(148,469,000)	(25,022,000)
Ending Balance	$ 1,052,304,000				$ 1,396,506,000				$ 1,052,304,000	$ 1,396,506,000	1,273,290,000
Common stocks issuance costs											$ 25,732
Dividends declared per share (in dollars per share)	$ 0.06	$ 0.06	$ 0.06	$ 0.06	$ 0.06	$ 0.06	$ 0.06	$ 0.06	$ 0.25	$ 0.25	$ 0.25
Total U.S. Silica Holdings Inc., Stockholders’ Equity
Condensed Stockholders' Equity Statement [Line Items]
Beginning Balance				$ 1,396,506,000				$ 1,273,290,000	$ 1,396,506,000	$ 1,273,290,000	$ 384,167,000
Net income (loss)									(200,808,000)	145,206,000	(41,056,000)
Issuance of common stock (stock offerings net of issuance costs of $25,732)											931,288,000
Unrealized gain (loss) on derivatives (net of tax)									(1,545,000)	(44,000)	49,000
Unrealized loss on short-term investments (net of tax)											(6,000)
Foreign currency translation adjustment (net of tax)									(614,000)	(6,000)
Pension and post-retirement liability									1,065,000	2,000,000	252,000
Cash dividends declared ($0.25 per share of common stock for 2018, 2017 and 2016, respectively)									(19,330,000)	(20,387,000)	(16,893,000)
Equity-based compensation									22,337,000	25,050,000	12,107,000
Excess tax benefit from equity-based compensation											148,000
Proceeds from options exercised									61,000	798,000	4,825,000
Shares withheld for tax payments related to vested restricted stock and stock units									(4,383,000)	(4,379,000)	(1,591,000)
Repurchase of common stock									(148,469,000)	(25,022,000)
Ending Balance	$ 1,044,820,000				$ 1,396,506,000				1,044,820,000	1,396,506,000	1,273,290,000
Common Stock
Condensed Stockholders' Equity Statement [Line Items]
Beginning Balance				812,000				811,000	812,000	811,000	539,000
Issuance of common stock (stock offerings net of issuance costs of $25,732)											272,000
Shares withheld for tax payments related to vested restricted stock and stock units									6,000	1,000
Ending Balance	818,000				812,000				818,000	812,000	811,000
Treasury Stock
Condensed Stockholders' Equity Statement [Line Items]
Beginning Balance				(25,456,000)				(3,869,000)	(25,456,000)	(3,869,000)	(15,845,000)
Proceeds from options exercised									93,000	1,190,000	8,465,000
Issuance of restricted stock										1,859,000	1,437,000
Shares withheld for tax payments related to vested restricted stock and stock units									(4,383,000)	386,000	2,074,000
Repurchase of common stock									(148,469,000)	(25,022,000)
Ending Balance	(178,215,000)				(25,456,000)				(178,215,000)	(25,456,000)	(3,869,000)
Additional Paid-In Capital
Condensed Stockholders' Equity Statement [Line Items]
Beginning Balance				1,147,084,000				1,129,051,000	1,147,084,000	1,129,051,000	194,670,000
Issuance of common stock (stock offerings net of issuance costs of $25,732)											931,016,000
Equity-based compensation									22,337,000	25,050,000	12,107,000
Proceeds from options exercised									(32,000)	(392,000)	(3,640,000)
Issuance of restricted stock										(1,859,000)	(1,437,000)
Shares withheld for tax payments related to vested restricted stock and stock units									(6,000)	(4,766,000)	(3,665,000)
Ending Balance	1,169,383,000				1,147,084,000				1,169,383,000	1,147,084,000	1,129,051,000
Retained Earnings
Condensed Stockholders' Equity Statement [Line Items]
Beginning Balance				287,992,000				163,173,000	287,992,000	163,173,000	220,974,000
Net income (loss)									(200,808,000)	145,206,000	(41,056,000)
Cash dividends declared ($0.25 per share of common stock for 2018, 2017 and 2016, respectively)									(19,330,000)	(20,387,000)	(16,893,000)
Excess tax benefit from equity-based compensation											148,000
Ending Balance	67,854,000				287,992,000				67,854,000	287,992,000	163,173,000
Accumulated Other Comprehensive Loss
Condensed Stockholders' Equity Statement [Line Items]
Beginning Balance				(13,926,000)				(15,876,000)	(13,926,000)	(15,876,000)	(16,171,000)
Unrealized gain (loss) on derivatives (net of tax)									(1,545,000)	(44,000)	49,000
Unrealized loss on short-term investments (net of tax)											(6,000)
Foreign currency translation adjustment (net of tax)									(614,000)	(6,000)
Pension and post-retirement liability									1,065,000	2,000,000	252,000
Ending Balance	(15,020,000)				(13,926,000)				(15,020,000)	(13,926,000)	(15,876,000)
Non-controlling Interest
Condensed Stockholders' Equity Statement [Line Items]
Beginning Balance				0				0	0	0	0
Net income (loss)									(13,000)
Contributions from non-controlling interest									7,497,000
Ending Balance	7,484,000				0				7,484,000	0	0
Parent Company
Condensed Stockholders' Equity Statement [Line Items]
Beginning Balance				1,396,506,000				1,273,290,000	1,396,506,000	1,273,290,000	384,167,000
Net income (loss)									(200,821,000)	145,206,000	(41,056,000)
Issuance of common stock (stock offerings net of issuance costs of $25,732)											931,288,000
Unrealized gain (loss) on derivatives (net of tax)									(1,545,000)	(44,000)	49,000
Unrealized loss on short-term investments (net of tax)									0	0	(6,000)
Foreign currency translation adjustment (net of tax)									(614,000)	(6,000)
Pension and post-retirement liability									1,065,000	2,000,000	252,000
Cash dividends declared ($0.25 per share of common stock for 2018, 2017 and 2016, respectively)									(19,330,000)	(20,387,000)	(16,893,000)
Contributions from non-controlling interest									7,497,000
Equity-based compensation									22,337,000	25,050,000	12,107,000
Excess tax benefit from equity-based compensation											148,000
Proceeds from options exercised									61,000	798,000	4,825,000
Issuance of restricted stock										0	0
Shares withheld for tax payments related to vested restricted stock and stock units									(4,383,000)	(4,379,000)	(1,591,000)
Repurchase of common stock									(148,469,000)	(25,022,000)
Ending Balance	1,052,304,000				1,396,506,000				$ 1,052,304,000	$ 1,396,506,000	1,273,290,000
Common stocks issuance costs											$ 25,732
Dividends declared per share (in dollars per share)									$ 0.25	$ 0.25	$ 0.25
Parent Company | Total U.S. Silica Holdings Inc., Stockholders’ Equity
Condensed Stockholders' Equity Statement [Line Items]
Beginning Balance				1,396,506,000				1,273,290,000	$ 1,396,506,000	$ 1,273,290,000	$ 384,167,000
Net income (loss)									(200,808,000)	145,206,000	(41,056,000)
Issuance of common stock (stock offerings net of issuance costs of $25,732)											931,288,000
Unrealized gain (loss) on derivatives (net of tax)									(1,545,000)	(44,000)	49,000
Unrealized loss on short-term investments (net of tax)											(6,000)
Foreign currency translation adjustment (net of tax)									(614,000)	(6,000)
Pension and post-retirement liability									1,065,000	2,000,000	252,000
Cash dividends declared ($0.25 per share of common stock for 2018, 2017 and 2016, respectively)									(19,330,000)	(20,387,000)	(16,893,000)
Equity-based compensation									22,337,000	25,050,000	12,107,000
Excess tax benefit from equity-based compensation											148,000
Proceeds from options exercised									61,000	798,000	4,825,000
Issuance of restricted stock										0	0
Shares withheld for tax payments related to vested restricted stock and stock units									(4,383,000)	(4,379,000)	(1,591,000)
Repurchase of common stock									(148,469,000)	(25,022,000)
Ending Balance	1,044,820,000				1,396,506,000				1,044,820,000	1,396,506,000	1,273,290,000
Parent Company | Common Stock
Condensed Stockholders' Equity Statement [Line Items]
Beginning Balance				812,000				811,000	812,000	811,000	539,000
Issuance of common stock (stock offerings net of issuance costs of $25,732)											272,000
Shares withheld for tax payments related to vested restricted stock and stock units									6,000	1,000
Ending Balance	818,000				812,000				818,000	812,000	811,000
Parent Company | Treasury Stock
Condensed Stockholders' Equity Statement [Line Items]
Beginning Balance				(25,456,000)				(3,869,000)	(25,456,000)	(3,869,000)	(15,845,000)
Proceeds from options exercised									93,000	1,190,000	8,465,000
Issuance of restricted stock										1,859,000	1,437,000
Shares withheld for tax payments related to vested restricted stock and stock units									(4,383,000)	386,000	2,074,000
Repurchase of common stock									(148,469,000)	(25,022,000)
Ending Balance	(178,215,000)				(25,456,000)				(178,215,000)	(25,456,000)	(3,869,000)
Parent Company | Additional Paid-In Capital
Condensed Stockholders' Equity Statement [Line Items]
Beginning Balance				1,147,084,000				1,129,051,000	1,147,084,000	1,129,051,000	194,670,000
Issuance of common stock (stock offerings net of issuance costs of $25,732)											931,016,000
Equity-based compensation									22,337,000	25,050,000	12,107,000
Proceeds from options exercised									(32,000)	(392,000)	(3,640,000)
Issuance of restricted stock										(1,859,000)	(1,437,000)
Shares withheld for tax payments related to vested restricted stock and stock units									(6,000)	(4,766,000)	(3,665,000)
Ending Balance	1,169,383,000				1,147,084,000				1,169,383,000	1,147,084,000	1,129,051,000
Parent Company | Retained Earnings
Condensed Stockholders' Equity Statement [Line Items]
Beginning Balance				287,992,000				163,173,000	287,992,000	163,173,000	220,974,000
Net income (loss)									(200,808,000)	145,206,000	(41,056,000)
Cash dividends declared ($0.25 per share of common stock for 2018, 2017 and 2016, respectively)									(19,330,000)	(20,387,000)	(16,893,000)
Excess tax benefit from equity-based compensation											148,000
Ending Balance	67,854,000				287,992,000				67,854,000	287,992,000	163,173,000
Parent Company | Accumulated Other Comprehensive Loss
Condensed Stockholders' Equity Statement [Line Items]
Beginning Balance				(13,926,000)				(15,876,000)	(13,926,000)	(15,876,000)	(16,171,000)
Unrealized gain (loss) on derivatives (net of tax)									(1,545,000)	(44,000)	49,000
Unrealized loss on short-term investments (net of tax)											(6,000)
Foreign currency translation adjustment (net of tax)									(614,000)	(6,000)
Pension and post-retirement liability									1,065,000	2,000,000	252,000
Ending Balance	(15,020,000)				(13,926,000)				(15,020,000)	(13,926,000)	(15,876,000)
Parent Company | Non-controlling Interest
Condensed Stockholders' Equity Statement [Line Items]
Beginning Balance				$ 0				$ 0	0	0	0
Net income (loss)									(13,000)
Contributions from non-controlling interest									7,497,000
Ending Balance	$ 7,484,000				$ 0				$ 7,484,000	$ 0	$ 0

Parent Company Financials - C_4

Parent Company Financials - Condensed Statements of Cash Flows (Details) - USD ($)	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Condensed Cash Flow Statements, Captions [Line Items]
Net income (loss)	$ (256,075,000)	$ 6,316,000	$ 17,644,000	$ 31,294,000	$ 71,952,000	$ 41,273,000	$ 29,459,000	$ 2,522,000	$ (200,821,000)	$ 145,206,000	$ (41,056,000)
Adjustments to reconcile net income (loss) to net cash provided by operating activities:
Other									(13,536,000)	13,929,000	5,300,000
Accounts payable and accrued expenses									26,907,000	43,654,000	13,232,000
Net cash provided by operating activities									310,706,000	222,013,000	381,000
Investing activities:
Maturities of short-term investments									0	0	21,872,000
Net cash used in investing activities									(1,066,879,000)	(491,529,000)	(201,657,000)
Financing activities:
Repurchase of common stock									(148,469,000)	(25,022,000)	0
Proceeds from options exercised									61,000	798,000	4,825,000
Tax payments related to shares withheld for vested restricted stock and stock units									(4,383,000)	(4,379,000)	(1,591,000)
Issuance of common stock (secondary offering)									0	0	678,791,000
Costs of common stock issuance									0	0	(25,732,000)
Contributions from non-controlling interest									7,497,000	0	0
Net cash provided by (used in) financing activities									574,104,000	(57,142,000)	635,424,000
Net (decrease) increase in cash and cash equivalents									(182,069,000)	(326,658,000)	434,148,000
Cash and cash equivalents, beginning of period				384,567,000				711,225,000	384,567,000	711,225,000	277,077,000
Cash and cash equivalents, end of period	202,498,000				384,567,000				202,498,000	384,567,000	711,225,000
Supplemental cash flow information:
Interest									(66,769,000)	(24,490,000)	(21,994,000)
Common stock issued in connection with acquisitions									0	0	278,229,000
Cash dividends paid to parent by its consolidated entities									0	0	0
Parent Company
Condensed Cash Flow Statements, Captions [Line Items]
Net income (loss)									(200,821,000)	145,206,000	(41,056,000)
Adjustments to reconcile net income (loss) to net cash provided by operating activities:
Undistributed (Income) loss from equity method investment, net									202,655,000	(143,057,000)	41,564,000
Other									0	0	(30,000)
Accounts payable and accrued expenses									(295,000)	48,000	353,000
Net cash provided by operating activities									1,539,000	2,197,000	831,000
Investing activities:
Maturities of short-term investments									0	0	21,872,000
Investment in subsidiary									0	(143,654,000)	(188,177,000)
Net cash used in investing activities									0	(143,654,000)	(166,305,000)
Financing activities:
Dividends paid									(19,912,000)	(20,377,000)	(15,125,000)
Repurchase of common stock									(148,469,000)	(25,022,000)	0
Proceeds from options exercised									61,000	798,000	4,603,000
Tax payments related to shares withheld for vested restricted stock and stock units									(4,383,000)	(4,379,000)	(1,590,000)
Issuance of common stock (secondary offering)									0	0	678,791,000
Issuance of treasury stock									0	0	221,000
Costs of common stock issuance									0	0	(25,733,000)
Contributions from non-controlling interest									7,497,000	0	0
Net financing activities with subsidiaries									40,171,000	(113,294,000)	106,000
Net cash provided by (used in) financing activities									(125,035,000)	(162,274,000)	641,273,000
Net (decrease) increase in cash and cash equivalents									(123,496,000)	(303,731,000)	475,799,000
Cash and cash equivalents, beginning of period				$ 230,647,000				$ 534,378,000	230,647,000	534,378,000	58,579,000
Cash and cash equivalents, end of period	$ 107,151,000				$ 230,647,000				107,151,000	230,647,000	534,378,000
Supplemental cash flow information:
Interest									(2,784,000)	(3,853,000)	(1,046,000)
Common stock issued in connection with acquisitions									$ 0	$ 0	$ 278,229,000

Subsequent Events (Details)

Subsequent Events (Details) - $ / shares

Feb. 12, 2019

Jan. 04, 2019

Dec. 31, 2018

Sep. 30, 2018

Jun. 30, 2018

Mar. 31, 2018

Dec. 31, 2017

Sep. 30, 2017

Jun. 30, 2017

Mar. 31, 2017

Dec. 31, 2018

Dec. 31, 2017

Dec. 31, 2016

Subsequent Event

Cash dividend declared (in dollars per share)

$ 0.06

$ 0.06

$ 0.06

$ 0.06

$ 0.06

$ 0.06

$ 0.06

$ 0.06

$ 0.25

$ 0.25

$ 0.25

Subsequent Event

Subsequent Event

Cash dividend paid (in dollars per share)

$ 0.0625

Cash dividend declared (in dollars per share)

$ 0.0625