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Document and Entity Information - shares	9 Months Ended
Document and Entity Information - shares	Sep. 30, 2016	Nov. 02, 2016
Document And Entity Information [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Sep. 30, 2016
Document Fiscal Year Focus	2016
Document Fiscal Period Focus	Q3
Entity Registrant Name	U.S. Silica Holdings, Inc.
Entity Central Index Key	0001524741
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		70,636,892

Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Current Assets:
Cash and cash equivalents	$ 264,060	$ 277,077
Short-term investments	0	21,849
Accounts receivable, net	70,725	58,706
Inventories, net	77,429	65,004
Prepaid expenses and other current assets	14,092	9,921
Income tax deposits	8,017	6,583
Total current assets	434,323	439,140
Property, plant and mine development, net	790,565	561,196
Goodwill	233,196	68,647
Trade names	32,318	14,474
Other assets	16,031	18,709
Total assets	1,620,833	1,108,619
Current Liabilities:
Accounts payable	68,692	49,631
Dividends payable	4,546	3,453
Accrued liabilities	12,821	11,708
Accrued interest	57	58
Current portion of capital leases	1,136	0
Current portion of long-term debt	6,745	3,330
Deferred revenue	9,131	15,738
Total current liabilities	103,128	83,918
Long-term debt	499,886	488,375
Deferred revenue	66,030	59,676
Obligations under capital lease	1,281	0
Liability for pension and other post-retirement benefits	63,715	55,893
Deferred income taxes, net	57,330	19,513
Other long-term obligations	18,668	17,077
Total liabilities	810,038	724,452
Stockholders’ Equity:
Preferred stock	0	0
Common stock	708	539
Additional paid-in capital	660,448	194,670
Retained earnings	175,210	220,974
Treasury stock, at cost	(5,105)	(15,845)
Accumulated other comprehensive loss	(20,466)	(16,171)
Total stockholders’ equity	810,795	384,167
Total liabilities and stockholders’ equity	1,620,833	1,108,619
Trade Names
Current Assets:
Finite-lived intangible assets, net	57,700	0
Customer Relationships
Current Assets:
Finite-lived intangible assets, net	$ 56,700	$ 6,453

Condensed Consolidated Statements of Operations - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Income Statement [Abstract]
Sales	$ 137,748	$ 155,408	$ 377,252	$ 506,877
Cost of goods sold (excluding depreciation, depletion and amortization)	119,426	122,599	328,884	378,452
Operating expenses
Selling, general and administrative	18,472	13,559	48,560	47,095
Depreciation, depletion and amortization	17,175	15,158	46,940	42,096
Total operating expenses	35,647	28,717	95,500	89,191
Operating income (loss)	(17,325)	4,092	(47,132)	39,234
Other income (expense)
Interest expense	(6,684)	(6,684)	(19,974)	(20,448)
Other income, net, including interest income	493	309	2,891	818
Total other (expenses) income	(6,191)	(6,375)	(17,083)	(19,630)
Income (loss) before income taxes	(23,516)	(2,283)	(64,215)	19,604
Income tax benefit	12,177	4,695	30,102	7,584
Net income (loss)	$ (11,339)	$ 2,412	$ (34,113)	$ 27,188
Earnings (loss) per share:
Basic (in usd per share)	$ (0.17)	$ 0.05	$ (0.55)	$ 0.51
Diluted (in usd per share)	$ (0.17)	$ 0.04	$ (0.55)	$ 0.51
Weighted average shares outstanding:
Weighted average number of shares outstanding, basic	66,676	53,321	61,512	53,386
Weighted average number of shares outstanding, diluted	66,676	53,742	61,512	53,831
Common stock cash dividend declared, per share	$ 0.0625	$ 0.125	$ 0.1875	$ 0.38

Condensed Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Statement of Comprehensive Income [Abstract]
Net income (loss)	$ (11,339)	$ 2,412	$ (34,113)	$ 27,188
Other comprehensive income (loss):
Unrealized gain (loss) on derivatives (net of tax of ($2) and $10 for the three months ended September 30, 2016 and 2015, respectively, and $7 and $18 for the nine months ended September 30, 2016 and 2015, respectively)	(3)	17	12	29
Unrealized gain (loss) on investments (net of tax of $0 and $3 for the three months ended September 30, 2016 and 2015, respectively, and ($4) and $33 for the nine months ended September 30, 2016 and 2015, respectively)	0	4	(6)	53
Pension and other post-retirement benefits liability adjustment (net of tax of $176 and ($2,431) for the three months ended September 30, 2016 and 2015, respectively, and ($2,592) and $157 for the nine months ended September 30, 2016 and 2015, respectively)	293	(3,924)	(4,301)	254
Comprehensive income (loss)	$ (11,049)	$ (1,491)	$ (38,408)	$ 27,524

- Definition

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

+ References + Details

Condensed Consolidated Statements of Comprehensive Income (Parenthetical) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Statement of Comprehensive Income [Abstract]
Unrealized gain (loss) on derivatives, tax	$ (2)	$ 10	$ 7	$ 18
Unrealized gain (loss) on investments, tax	0	3	(4)	33
Pension and other post-retirement benefits liability adjustment, tax	$ 176	$ (2,431)	$ (2,592)	$ 157

Condensed Consolidated Statements of Stockholders' Equity - 9 months ended Sep. 30, 2016 - USD ($) $ in Thousands	Total	Common Stock	Treasury Stock	Additional Paid-In Capital	Retained Earnings (Deficit)	Accumulated Other Comprehensive Income (Loss)
Balance at December 31, 2015 at Dec. 31, 2015	$ 384,167	$ 539	$ (15,845)	$ 194,670	$ 220,974	$ (16,171)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	(34,113)				(34,113)
Issuance of common stock (secondary offering at $20 per share, net of issuance costs of $13,798)	186,202	100		186,102
Issuance of common stock for acquisitions (net of issuance costs of $170)	278,059	69		277,990
Unrealized gain on derivatives	12					12
Unrealized loss on short-term investments	(6)					(6)
Pension and post-retirement liability	(4,301)					(4,301)
Cash dividend declared ($0.1875 per share)	(11,799)				(11,799)
Common stock-based compensation plans activity:	9,075			9,075
Net tax effect	148				148
Unrealized loss on short-term investments	4,333		7,665	(3,332)
Issuance of restricted stock	0		1,388	(1,388)
Pension and post-retirement liability	(982)		1,687	(2,669)
Balance at September 30, 2016 at Sep. 30, 2016	$ 810,795	$ 708	$ (5,105)	$ 660,448	$ 175,210	$ (20,466)

Condensed Consolidated Statements of Stockholders' Equity (Parenthetical) $ in Thousands	3 Months Ended	9 Months Ended
	Sep. 30, 2016 $ / shares	Sep. 30, 2016 USD ($) $ / shares
Statement of Stockholders' Equity [Abstract]
Price per share (in USD per share) \| $ / shares	$ 20	$ 20
Stock issuance costs \| $		$ 13,798
Stock issuance costs related to acquisition \| $		$ 170
Common stock cash dividend declared, per share \| $ / shares	$ 0.0625	$ 0.1875

Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015
Operating activities:
Net income (loss)	$ (34,113)	$ 27,188
Adjustments to reconcile net income (loss) to net cash provided by operating activities:
Depreciation, depletion and amortization	46,940	42,096
Debt issuance amortization	1,045	1,054
Original issue discount amortization	283	288
Deferred income taxes	(29,858)	(8,463)
Deferred revenue	(5,644)	(12,712)
Loss on disposal of property, plant and equipment	240	1,007
Equity-based compensation	9,075	1,824
Excess tax benefit from equity-based compensation	0	(225)
Bad debt provision	(86)	(426)
Other	2,560	(7,462)
Changes in operating assets and liabilities, net of effects of acquisitions:
Accounts receivable	2,979	35,702
Inventories	(8,931)	(3,959)
Prepaid expenses and other current assets	(2,259)	(3,303)
Income taxes	5,223	(5,514)
Accounts payable and accrued liabilities	11,679	(31,655)
Accrued interest	(1)	(2)
Liability for pension and other post-retirement benefits	938	978
Net cash provided by operating activities	70	36,416
Investing activities:
Capital expenditures	(32,756)	(38,167)
Capitalized intellectual property costs	(259)	0
Maturities of short-term investments	21,872	29,388
Acquisition of business, net of cash acquired	(176,447)	0
Proceeds from sale of property, plant and equipment	84	77
Net cash used in investing activities	(187,506)	(8,702)
Financing activities:
Dividends paid	(10,706)	(20,117)
Repurchase of common stock	0	(15,255)
Issuance of common stock	200,000	0
Common stock issuance costs	(13,968)	0
Proceeds from options exercised	4,333	364
Excess tax benefit from equity-based compensation	0	225
Tax payments related to shares withheld for vested restricted stock	(982)	(747)
Repayment of long-term debt	(4,035)	(3,826)
Principal payments on capital lease obligations	(223)	0
Financing fees	0	(64)
Net cash provided by/(used in) financing activities	174,419	(39,420)
Net (decrease) in cash and cash equivalents	(13,017)	(11,706)
Cash and cash equivalents, beginning of period	277,077	263,066
Cash and cash equivalents, end of period	264,060	251,360
Cash paid (received) during the period for:
Interest	15,953	16,359
Taxes	(5,445)	6,176
Non-cash Items:
Capital lease obligations incurred to acquire assets	165	0
Common stock issued in connection with acquisitions	$ 278,229	$ 0

Summary of Significant Accounting Policies	9 Months Ended
Summary of Significant Accounting Policies	Sep. 30, 2016
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	NOTE A—SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES Basis of Presentation and Consolidation The accompanying Condensed Consolidated Financial Statements (the “Financial Statements”) of U.S. Silica Holdings, Inc. (“Holdings,” and together with its subsidiaries “we,” “us” or the “Company”) included in this Quarterly Report on Form 10-Q, have been prepared in accordance with generally accepted accounting principles in the United States (“GAAP”) for interim financial information and with the instructions to Form 10-Q and Article 10 of Regulation S-X issued by the U.S. Securities and Exchange Commission (“SEC”). They do not contain certain information included in our Annual Report on Form 10-K for the fiscal year ended December 31, 2015; therefore, the interim Condensed Consolidated Financial Statements should be read in conjunction with that Annual Report on Form 10-K. In the opinion of management, all adjustments necessary for a fair presentation of the Financial Statements have been included. Such adjustments are of a normal, recurring nature. We have reclassified certain immaterial amounts in the prior years’ operating activities section of the consolidated statement of cash flows to conform to the current year presentation. These reclassifications had no effect on previously reported net cash flows from operations. In order to make this report easier to read, we refer throughout to (i) our Condensed Consolidated Balance Sheets as our “Balance Sheets,” (ii) our Condensed Consolidated Statements of Operations as our “Income Statements,” and (iii) our Condensed Consolidated Statements of Cash Flows as our “Cash Flows.” Unaudited Interim Financial Statements The accompanying Balance Sheet as of September 30, 2016; the Income Statements and Condensed Consolidated Statements of Comprehensive Income for the three and nine months ended September 30, 2016 and 2015; the Condensed Consolidated Statements of Stockholders' Equity and Cash Flows for the nine months ended September 30, 2016; and other information disclosed in the related notes are unaudited. The Balance Sheet as of December 31, 2015 was derived from our audited consolidated financial statements as included in our 2015 Annual Report. Use of Estimates and Assumptions The preparation of the Financial Statements requires us to make estimates and assumptions that affect the reported amounts of assets and liabilities and the related disclosure of contingent assets and liabilities at the date of the Financial Statements and the reported amounts of revenues and expenses during the reporting period. The more significant areas requiring the use of management estimates and assumptions relate to purchase price allocation for businesses acquired; mineral reserves that are the basis for future cash flow estimates utilized in impairment calculations and units-of-production amortization calculations; environmental, reclamation and closure obligations; estimates of recoverable minerals; estimates of allowance for doubtful accounts; estimates of fair value for certain reporting units and asset impairments (including impairments of goodwill and other long-lived assets); write-downs of inventory to net realizable value; equity-based compensation expense; post-employment, post-retirement and other employee benefit liabilities; valuation allowances for deferred tax assets; 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. Recently Issued Accounting Pronouncements In February 2016, the Financial Accounting Standards Board (FASB) issued an Accounting Standards Update 2016-02, "Leases", which supersedes the existing lease guidance and requires all leases with a term greater than 12 months to be recognized on the balance sheet as assets and obligations. 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; early application is permitted. This standard mandates a modified retrospective transition method. We are currently evaluating the effect that the new guidance will have on our financial statements and related disclosures. On July 22, 2015, the FASB issued Accounting Standards Update 2015-11, "Simplifying the Measurement of Inventory". The new standard requires an entity to measure most inventory at the lower of cost and net realizable value, thereby simplifying the current guidance under which an entity must measure inventory at the lower of cost or market. The new standard will not apply to inventories that are measured using either the last-in, first-out (LIFO) method or the retail inventory method. This Update is effective for public entities for financial statements issued for fiscal years beginning after December 15, 2016, including interim periods within those fiscal years; early application is permitted. We have elected to adopt the standard early effective January 1, 2016 prospectively and have measured our inventory at the lower of cost and net realizable value on our Balance Sheet as of September 30, 2016. The impacts of the early adoption of this Update on our Financial Statements are not significant. In March 2016, the FASB issued Accounting Standards Update 2016-09, "Compensation-Stock Compensation." The update requires that excess tax benefits and deficiencies be recorded in the income statement when the awards vest or are settled. It also eliminates the requirement that excess tax benefits be realized (reduce cash taxes payable) before being recognized. Previously, an entity could not recognize excess tax benefits if the tax deduction increased a net operating loss ("NOL") or tax credit carryforward. The updated standard no longer requires cash flows related to excess tax benefits to be presented as a financing activity separate from other income tax cash flows. The update also allows the employer to repurchase more of an employee's shares for tax withholding purposes without triggering liability accounting, clarifies that all cash payments to taxing authorities made on an employee's behalf for withheld shares should be presented as a financing activity on the statement of cash flows, and provides for an accounting policy election to account for forfeitures as they occur. The update is effective for annual periods beginning after December 15, 2016, and interim periods within those annual periods, with early adoption permitted. We elected to early adopt this update during the three months ended September 30, 2016, which requires any adjustments to be reflected as of January 1, 2016. This resulted in the recognition of excess tax benefits on our Balance Sheet that were previously not recognized, as the benefits would have increased our NOL or tax credit carryforwards. The recognition decreased net deferred tax liability by $0.1 million and $1.7 million as of January 1, 2016 and September 30, 2016, respectively. Retained earnings on January 1, 2016 was increased accordingly by $0.1 million. In addition, we will recognize excess tax benefits in the provision for income taxes rather than paid-in capital for 2016 and future periods. Adoption of the update resulted in the recognition of excess tax benefits in the provision for income taxes of $1.8 million and $1.7 million for the three and nine months ended September 30, 2016, respectively. The effect of the adoption of this update on our previously reported income tax provision on our Income Statement was a decrease in tax benefit of $0.3 million for the three months ended March 31, 2016 and an increase in tax benefit of $0.2 million for the three months ended June 30, 2016, respectively. We elected to include excess tax benefits as operating activities in the Cash Flow on a prospective basis. Prior periods are not adjusted. We also made the accounting policy election to account for forfeitures as they occur.

Capital Structure and Accumulated Comprehensive Income

9 Months Ended

Sep. 30, 2016

Equity [Abstract]

Capital Structure and Accumulated Comprehensive Income

NOTE B—CAPITAL STRUCTURE AND ACCUMULATED COMPREHENSIVE INCOME

Common Stock

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

In March 2016, we completed a public offering of 10,000,000 shares of our common stock for total cash proceeds of approximately $186.2 million net of underwriting discounts and offering costs. In August 2016, we issued an additional 6,825,693 shares of our common stock to complete two acquisitions discussed in Note C - Business Combinations. There were 70,615,466 shares of common stock issued and outstanding at September 30, 2016. As of September 30, 2015, there were 53,386,174 shares issued and outstanding.

During the nine months ended September 30, 2016, our Board of Directors declared quarterly cash dividends as follows:



Dividends per Common Share		Declaration Date	Record Date	Payable Date
$	0.0625	February 22, 2016	March 15, 2016	April 5, 2016
$	0.0625	May 5, 2016	June 15, 2016	July 6, 2016
$	0.0625	July 21, 2016	September 15, 2016	October 4, 2016

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 conditions, our 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 either September 30, 2016 or December 31, 2015. At present, we have no plans to issue any preferred stock.

Employee Stock Awards

We grant stock options, restricted stock, restricted stock units and performance share units to our employees and directors under the Amended and Restated U.S. Silica Holdings, Inc. 2011 Incentive Compensation Plan. The weighted-average stock awards (in thousands) that are antidilutive and are therefore excluded from the calculation of our diluted earnings per common share are:



	Three Months Ended September 30,		Nine Months Ended September 30,
	2016	2015	2016	2015
Weighted-average outstanding stock options excluded	1,095	726	1,217	464
Weighted-average outstanding restricted stock awards excluded	1,493	729	1,062	598

Share Repurchase Program

We are authorized by our Board of Directors to repurchase shares of our outstanding common stock from time to time on the open market or in privately negotiated transactions. As of September 30, 2016, we are authorized to repurchase up to $50 million of our common stock through December 11, 2016. 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. Under our share repurchase program, as of September 30, 2016, we have repurchased 706,093 shares of our common stock at an average price of $23.83 and are authorized to repurchase up to an additional $33.2 million of our common stock.

Accumulated Other Comprehensive Income

Accumulated other comprehensive income (loss) consists of fair value adjustments associated with cash flow hedges and accumulated adjustments for net experience losses and prior service cost related to employee benefit plans. The following table presents the changes in accumulated other comprehensive income (in thousands) by component during the nine months ended September 30, 2016:



	For the Nine Months Ended September 30, 2016
	Unrealized gain/(loss) on cash flow hedges			Unrealized gain/(loss) on short-term investments			Pension and other post-retirement benefits liability			Total
Beginning Balance	$	(81	)	$	6		$	(16,096	)	$	(16,171	)
Other comprehensive (loss) before reclassifications	(69		)	(6		)	(4,387		)	(4,462		)
Amounts reclassed from accumulated other comprehensive income	81			—			86			167
Ending Balance	$	(69	)	$	—		$	(20,397	)	$	(20,466	)

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

- Definition

The entire disclosure for comprehensive income, which includes, but is not limited to, 1) the amount of income tax expense or benefit allocated to each component of other comprehensive income, including reclassification adjustments, 2) the reclassification adjustments for each classification of other comprehensive income and 3) the ending accumulated balances for each component of comprehensive income.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 15
-URI http://asc.fasb.org/extlink&oid=36458714&loc=d3e689-108580

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 1A
-URI http://asc.fasb.org/extlink&oid=36458714&loc=SL7669619-108580

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 12
-URI http://asc.fasb.org/extlink&oid=36458714&loc=d3e640-108580

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 17
-URI http://asc.fasb.org/extlink&oid=36458714&loc=d3e716-108580

Reference 5: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 16
-URI http://asc.fasb.org/extlink&oid=36458714&loc=d3e709-108580

Reference 6: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.3-04)
-URI http://asc.fasb.org/extlink&oid=27012166&loc=d3e187085-122770

Reference 7: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 11
-URI http://asc.fasb.org/extlink&oid=36458714&loc=d3e637-108580

Reference 8: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
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-URI http://asc.fasb.org/extlink&oid=36458714&loc=d3e681-108580

Reference 9: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Reclassification Adjustments
-URI http://asc.fasb.org/extlink&oid=6522872

+ Details

Business Combination

9 Months Ended

Sep. 30, 2016

Business Combinations [Abstract]

Business Combinations

NOTE C—BUSINESS COMBINATIONS

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 operating segment.

The preliminary consideration paid to the stockholders of NBI at the closing of the NBI Acquisition consisted of $106.6 million of cash (net of $9.0 million cash acquired), subject to customary post-closing adjustments and 2,630,513 shares of common stock. The calculation of the preliminary purchase price (in thousands, except shares) is as follows:




Cash consideration paid			$	115,555
Number of U.S. Silica common shares delivered	2,630,513
Multiplied by closing market price per share of U.S. Silica common stock on August 16, 2016	$	40.51
Total value of U.S. Silica common shares delivered			$	106,562
Less, cash acquired			$	(9,002	)
Total purchase price			$	213,115

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



Preliminary allocation of purchase price:
Accounts receivable	$	2,680
Inventories	3,494
Other current assets	439
Income tax deposits	6,657
Property, plant and mine development	209,378
Identifiable intangible assets	1,600
Goodwill	82,080
Total assets acquired	306,328
Accounts payable, accrued expenses and other current liabilities	1,484
Deferred revenue	500
Notes payable	17,633
Capital lease liabilities	2,475
Asset retirement obligations	710
Deferred tax liabilities	70,411
Total liabilities assumed	93,213
Net assets acquired	$	213,115

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	15

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 regional frac sand markets and synergies expected to be achieved from integrating the operations of U.S. Silica and NBI. The goodwill amount is included in our Oil & Gas Proppants segment. Both customer relationships and goodwill are not expected to be deductible for tax purposes.

We incurred $1.0 million and $1.4 million of acquisition-related charges which are included in selling, general and administrative expenses during the three and nine months ended September 30, 2016, respectively. Additionally, we incurred $0.5 million related to the inventory write-up values in cost of goods sold during the three months ended September 30, 2016. Revenue and earnings for NBI 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 Houston, Midland/Odessa, Texas, Morgantown, West Virginia, western North Dakota, northeast of Denver, Colorado, Oklahoma City, OK and Cambridge, Ohio, where its major customers are located. By acquiring Sandbox, we are able to expand our frac sand offering directly to customers' wellhead locations.

The preliminary consideration paid includes $69.9 million of cash (net of $1.3 million cash acquired), subject to customary post-closing adjustments and 4,195,180 shares of our common stock. The calculation of preliminary purchase price (in thousands, except shares) is as follows:




Cash consideration paid			$	71,200
Number of U.S. Silica common shares delivered	4,195,180
Multiplied by closing market price per share of U.S. Silica common stock on August 22, 2016	$	40.92
Total value of U.S. Silica common shares delivered			$	171,667
Less, cash acquired			$	(1,306	)
Total purchase price			$	241,561

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



Preliminary allocation of purchase price:
Accounts receivable	$	12,232
Prepaid expenses and other	1,482
Property, plant and mine development	32,336
Identifiable intangible assets	124,944
Goodwill	82,469
Total assets acquired	253,463
Accounts payable	4,112
Deferred revenue	4,891
Accrued expenses and other current liabilities	2,899
Total liabilities assumed	11,902
Net assets acquired	$	241,561

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	49,400		14
Total fair value of identifiable intangible assets	$	124,944

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

Our 2016 Income Statement included revenue of $7.5 million associated with Sandbox following the date of acquisition during the three months ended September 30, 2016. Sandbox's impact on our net loss was not significant for the three months ended September 30, 2016. We incurred $2.7 million and $2.8 million of acquisition-related charges which are included in selling, general and administrative expenses on the Income Statement for the three and nine months ended September 30, 2016, respectively.

The cost related to the issuance of the 6,825,693 shares of common stock to complete the two acquisitions totaled $0.2 million, which is included in additional paid-in capital on our Condensed Consolidated Statements of Stockholders' Equity for the nine months ended September 30, 2016.

With the two above mentioned acquisitions, as of September 30, 2016, the gross carrying amount of the customer relationships intangible asset was $60.5 million with accumulated amortization of $3.8 million. As of September 30, 2016, the weighted average remaining useful life of our customer relationships was 13.7 years. The estimated annual amortization in each of the next five years is $4.1 million.

Both acquisitions were accounted for using the acquisition method of accounting. The purchase price and purchase price allocations for both acquisitions are preliminary and subject to customary post-closing adjustments and changes in the fair value of assets and liabilities. As a result, our final purchase price allocations may be significantly different than those reflected in the tables above.

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



	Three months ended September 30,					Nine months ended September 30,
	2016			2015		2016			2015
Sales	$	153,358		$	189,425	$	433,179		$	589,203
Net income	$	(18,111	)	$	8,703	$	(38,207	)	$	45,429
Basic earnings per share	$	(0.27	)	$	0.16	$	(0.62	)	$	0.85
Diluted earnings per share	$	(0.27	)	$	0.16	$	(0.62	)	$	0.84

- Definition

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

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
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-Name Accounting Standards Codification
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Reference 2: http://www.xbrl.org/2003/role/presentationRef
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-Topic 805
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Reference 3: http://www.xbrl.org/2003/role/presentationRef
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Reference 4: http://www.xbrl.org/2003/role/presentationRef
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Reference 5: http://www.xbrl.org/2003/role/presentationRef
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Reference 9: http://www.xbrl.org/2003/role/presentationRef
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Reference 10: http://www.xbrl.org/2003/role/presentationRef
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Reference 14: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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Reference 15: http://www.xbrl.org/2003/role/presentationRef
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+ Details

Accounts Receivable

9 Months Ended

Sep. 30, 2016

Receivables [Abstract]

Accounts Receivable

NOTE D—ACCOUNTS RECEIVABLE

At September 30, 2016 and December 31, 2015, accounts receivable (in thousands) consisted of the following:



	September 30, 2016			December 31, 2015
Trade receivables	$	77,262		$	64,821
Less: Allowance for doubtful accounts	(7,358		)	(7,686		)
Net trade receivables	69,904			57,135
Other receivables	821			1,571
Total accounts receivable	$	70,725		$	58,706

Changes in our allowance for doubtful accounts (in thousands) during the nine months ended September 30, 2016 are as follows:



	September 30, 2016
Beginning balance	$	7,686
Bad debt provision	(86		)
Write-offs	(242		)
Ending balance	$	7,358

Inventories

9 Months Ended

Sep. 30, 2016

Inventory Disclosure [Abstract]

Inventories

NOTE E—INVENTORIES

At September 30, 2016 and December 31, 2015, inventories (in thousands) consisted of the following:



	September 30, 2016		December 31, 2015
Supplies	$	18,279	$	18,029
Raw materials and work in process	24,750		18,113
Finished goods	34,400		28,862
Total inventories	$	77,429	$	65,004

Property, Plant and Mine Development

9 Months Ended

Sep. 30, 2016

Property, Plant and Equipment [Abstract]

Property, Plant and Mine Development

NOTE F—PROPERTY, PLANT AND MINE DEVELOPMENT

At September 30, 2016 and December 31, 2015, property, plant and mine development (in thousands) consisted of the following:



	September 30, 2016			December 31, 2015
Mining property and mine development	$	417,065		$	222,439
Asset retirement cost	10,597			9,889
Land	35,842			30,322
Land improvements	39,959			37,791
Buildings	52,301			51,280
Machinery and equipment	444,017			360,817
Furniture and fixtures	2,554			1,917
Construction-in-progress	41,814			56,130
	1,044,149			770,585
Accumulated depletion, depreciation and amortization	(253,584		)	(209,389		)
Total property, plant and mine development, net	$	790,565		$	561,196

At September 30, 2016, the aggregate cost of the machinery and equipment acquired under capital leases was $4.3 million, reduced by accumulated depreciation of $1.7 million. The amount of interest costs capitalized in property, plant and mine development was $209 and $465 for the nine months ended September 30, 2016 and 2015, respectively.

Debt And Capital Leases

9 Months Ended

Sep. 30, 2016

Debt Disclosure [Abstract]

Debt And Capital Leases

NOTE G—DEBT AND CAPITAL LEASES

At September 30, 2016 and December 31, 2015, debt (in thousands) consisted of the following:



	September 30, 2016			December 31, 2015
Senior secured credit facility:
Revolver expiring July 23, 2018 (5% at September 30, 2016 and December 31, 2015)	$	—		$	—
Term loan facility—final maturity July 23, 2020 (4% - 4.5% at September 30, 2016 and December 31, 2015)	495,450			499,275
Less: Unamortized original issue discount	(1,413		)	(1,696		)
Less: Unamortized debt issuance cost	(4,829		)	(5,874		)
Note payable secured by royalty interest (includes $3,053 unamortized fair value premium)	15,571			—
Customer note payable	1,852			—
Total debt	506,631			491,705
Less: current portion	(6,745		)	(3,330		)
Total long-term portion of debt	$	499,886		$	488,375

Revolving Line-of-Credit

We have a $50 million revolving line-of-credit (the “Revolver”), with zero drawn and $4.0 million allocated for letters of credit as of September 30, 2016, leaving $46.0 million available under the Revolver.

Senior Secured Credit Facility

At September 30, 2016, contractual maturities of long-term debt (in thousands) are as follows:



2016	$	1,275
2017	5,100
2018	5,100
2019	5,100
2020	478,875
	$	495,450

Our senior secured credit facility is secured by substantially all of our assets and a pledge of the equity interests in certain of our subsidiaries. The facility contains covenants that, among other things, govern our ability to create, incur or assume indebtedness and liens, to make acquisitions or investments, to pay dividends and to sell assets. The facility also requires us to maintain a consolidated total net leverage ratio of no more than 3.75:1.00 as of the last day of any fiscal quarter whenever usage of the Revolver (other than certain undrawn letters of credit) exceeds 25% of the Revolver commitment. As of September 30, 2016, we are in compliance with all covenants in accordance with our senior secured credit facility.

Note Payable Secured by Royalty Interest

In conjunction with our NBI Acquisition, 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:



2016	$	247
2017	1,750
2018	1,750
2019	1,750
2020	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 $15.7 million on the acquisition date. The estimate was made using a probabilistic model which calculated the present value assuming alternative possible future cash payment scenarios. As a result, a premium of $3.1 million was added to the existing $12.6 million principal on that date. The premium is being amortized over the life of the agreement using the effective interest method and a weighted average discount rate of 2.10%.

Customer Note Payable

In connection with our NBI Acquisition, we assumed a customer note payable that was entered into by NBI. Effective January 1, 2016, NBI entered into an amendment to a supply agreement whereby the outstanding principal balance due under the initial supply agreement was reduced to $3.0 million. Terms of the amended agreement call for repayment of $2.5 million at 0% interest, in equal monthly payments beginning January 1, 2016 for 60 months. We discounted the required future cash payments using an interest rate of 3.5% and recorded the note balance at $1.9 million as of September 30, 2016. Contractual maturities of this note payable (in thousands) are as follows:



2016	$	108
2017	440
2018	456
2019	472
2020	376
Total	$	1,852

The remaining $0.5 million will be repaid in the form of product load credits. In the event the load credits do not result in full repayment of the $0.5 million by December 31, 2020, any remaining balance will be canceled. This $0.5 million is recorded on our Balance Sheet as deferred revenue as of September 30, 2016.

Capital Leases

In conjunction with our NBI Acquisition, we assumed multiple capital lease obligations that were entered into by NBI. NBI enters into these financing arrangements from time to time to purchase machinery and equipment utilized in operations. At September 30, 2016, scheduled future minimum lease payments under capital lease obligations (in thousands) are as follows:



2016	$	332
2017	1,433
2018	712
Total minimum lease payments	2,477
Less: amount representing interest	(60		)
Present value of minimum lease payments	2,417
Less: current portion of capital lease obligations	(1,136		)
Non-current portion of capital lease obligations	$	1,281

Asset Retirement Obligations

9 Months Ended

Sep. 30, 2016

Asset Retirement Obligation Disclosure [Abstract]

Asset Retirement Obligations

NOTE H—ASSET RETIREMENT OBLIGATION

Mine reclamation costs, 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 September 30, 2016, we had a liability of $13.7 million in other long-term obligations related to our asset retirement obligation. Changes in the asset retirement obligation (in thousands) during the nine months ended September 30, 2016 are as follows:



	September 30, 2016
Beginning balance	$	12,254
Payments	—
Accretion	720
Additions due to NBI Acquisition	710
Ending balance	$	13,684

Fair Value Accounting

9 Months Ended

Sep. 30, 2016

Fair Value Disclosures [Abstract]

Fair Value Accounting

NOTE I—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 September 30, 2016 and December 31, 2015 approximate their reported carrying values.

Short-Term Investments

In general, the fair value of our short-term investments is based on quoted prices for similar assets in active markets, or for identical assets or similar assets in markets in which there were fewer transactions (Level 2). Money market mutual funds are based on calculated net asset value and are reported in Level 1. Variable rate demand obligations underwritten and remarketed by a financial institution are priced at par value.

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

Although we have determined that the majority of the inputs used to value our derivatives fall within Level 2 of the fair value hierarchy, the credit valuation adjustments associated with our derivatives utilize Level 3 inputs, such as estimates of current credit spreads to evaluate the likelihood of default of ourselves and our counterparties. However, as of September 30, 2016, we have assessed that the impact of the credit valuation adjustments on the overall valuation of our derivative positions is not significant. As a result, we have determined that our derivative valuations in their entirety are classified in Level 2 of the fair value hierarchy.

In accordance with the fair value hierarchy, the following table presents the fair value as of September 30, 2016 of those assets that we measure at fair value on a recurring basis:



	Level 1		Level 2		Total
Interest rate derivatives	$	—	$	12	$	12
Net asset	$	—	$	12	$	12

- Definition

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

+ References + Details

Commitments and Contingencies

9 Months Ended

Sep. 30, 2016

Commitments and Contingencies Disclosure [Abstract]

Commitments and Contingencies

NOTE J—COMMITMENTS AND CONTINGENCIES

Future Minimum Annual Commitments at September 30, 2016:



	Operating Leases		Minimum Purchase Commitments
2016	$	12,451	$	7,413
2017	51,524		17,944
2018	59,791		14,693
2019	53,218		11,790
2020	48,612		6,369
Thereafter	157,414		17,136
Total future lease and purchase commitments	$	383,010	$	75,345

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 $12.6 million and $13.2 million for the three months ended September 30, 2016 and 2015, respectively, and $37.7 million and $34.9 million for the nine months ended September 30, 2016 and 2015, respectively.

Minimum Purchase Commitments

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

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 nine months ended September 30, 2016, one new claim was brought against U.S. Silica. As of September 30, 2016, 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 September 30, 2016, and December 31, 2015 other non-current assets included $0.3 million for insurance for third-party products liability claims and other long-term obligations included $1.3 million in third-party products claims liability.

Additionally, during the three months ended March 31, 2015, we received an unfavorable ruling in an arbitration proceeding as a result of exiting a toll manufacturing contract. The amount of the ruling was approximately $7.6 million. The matter was settled and the settlement amount of $6.5 million was paid on June 9, 2015, which was included in selling, general and administrative expense in our Income Statement for the nine months ended September 30, 2015.

Income Taxes	9 Months Ended
Income Taxes	Sep. 30, 2016
Income Tax Disclosure [Abstract]
Income Taxes	NOTE K—INCOME TAXES For interim period reporting, we record income taxes using an estimated annual effective tax rate based upon projected annual income, forecasted permanent tax differences, discrete items and statutory rates in states in which we operate. At the end of each interim period, we update the estimated annual effective tax rate, and if the estimated tax rate changes based on new information, we make a cumulative adjustment in the period. We record the tax effect of an unusual or infrequently occurring item in the interim period in which it occurs as a discrete item of tax. In the nine months ended September 30, 2016, we recorded a discrete tax benefit of $2.1 million, which primarily relates to the early adoption of ASU 2016-09, as discussed in Note A - Summary of Significant Accounting Policies. The effective tax rate was 47% and (39)% for the nine months ended September 30, 2016 and 2015, respectively. The tax rate for the nine months ended September 30, 2016 would have been 44% without the discrete tax benefit. Historically, our actual effective tax rates have differed from the statutory effective rate primarily due to the benefit received from statutory percentage depletion allowances. The deduction for statutory percentage depletion does not necessarily change proportionately to changes in income before income taxes.

Pension and Post-Retirement Benefits

9 Months Ended

Sep. 30, 2016

Compensation and Retirement Disclosure [Abstract]

Pension and Post-Retirement Benefits

NOTE L—PENSION AND POST-RETIREMENT BENEFITS

We maintain a single-employer noncontributory defined benefit pension plan covering certain employees. Net pension benefit cost (in thousands) recognized for the three and nine months ended September 30, 2016 and 2015 are as follows:



	Three Months Ended September 30,						Nine Months Ended September 30,
	2016			2015			2016			2015
Service cost	$	267		$	324		$	559		$	971
Interest cost	1,009			1,203			2,257			3,610
Expected return on plan assets	(1,361		)	(1,375		)	(2,768		)	(4,124		)
Net amortization and deferral	395			666			884			1,999
Net pension benefit costs	$	310		$	818		$	932		$	2,456

In addition, we provide defined benefit post-retirement health care and life insurance benefits to some employees. Net periodic post-retirement benefit cost recognized for the three and nine months ended September 30, 2016 and 2015 are as follows:



	Three Months Ended September 30,					Nine Months Ended September 30,
	2016			2015		2016		2015
Service cost	$	(28	)	$	36	$	60	$	124
Interest cost	(187		)	221		425		776
Expected return on plan assets	—			—		—		(2		)
Special termination benefit	—			47		21		47
Net amortization and deferral	—			58		270		250
Net post-retirement costs	$	(215	)	$	362	$	776	$	1,195

The weighted average discount rate used to determine the projected pension and post-retirement obligations was updated during the six months ended September 30, 2016, and was decreased from 4.5% at December 31, 2015 to 3.8% at September 30, 2016. We made no contributions to the qualified pension plan for the three and nine months ended September 30, 2016. We contributed $1.8 million and $2.0 million to the qualified pension plan for the three and nine months ended September 30, 2015, respectively. Total expected employer funding contributions during the fiscal year ending December 31, 2016 are $0 for the pension plan and $1.0 million for the post-retirement medical and life plan.

Obligations under Guarantees	9 Months Ended
Obligations under Guarantees	Sep. 30, 2016
Guarantees [Abstract]
Obligations Under Guarantees	NOTE M— OBLIGATIONS UNDER GUARANTEES We have indemnified Travelers Casualty and Surety Company of America (“Travelers”) against any loss Travelers may incur in the event that holders of surety bonds, issued on behalf of us by Travelers, execute the bonds. As of September 30, 2016, Travelers had $10.5 million in bonds outstanding for us. The majority of these bonds, $10.1 million, relate to reclamation requirements issued by various governmental authorities. Reclamation bonds remain outstanding until the mining area is reclaimed and the authority issues a formal release. The remaining bonds relate to such indefinite purposes as licenses, permits, and tax collection.

Segment Reporting

9 Months Ended

Sep. 30, 2016

Segment Reporting [Abstract]

Segment Reporting

NOTE N— 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 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 210 products and materials used in a variety of industries, including container glass, fiberglass, specialty glass, flat glass, building products, fillers and extenders, foundry products, chemicals, recreation products and filtration products.

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

The following table presents sales and segment contribution margin (in thousands) for the reporting segments and other operating results not allocated to the reported segments for the three and nine months ended September 30, 2016 and 2015:



	Three Months Ended September 30,						Nine Months Ended September 30,
	2016			2015			2016			2015
Sales:
Oil & Gas Proppants	$	86,782		$	101,987		$	225,573		$	341,593
Industrial & Specialty Products	50,966			53,421			151,679			165,284
Total Sales	137,748			155,408			377,252			506,877
Segment contribution margin:
Oil & Gas Proppants	(1,897		)	16,521			(7,041		)	81,972
Industrial & Specialty Products	21,587			19,967			59,967			54,953
Total segment contribution margin	19,690			36,488			52,926			136,925
Operating activities excluded from segment cost of goods sold	(1,368		)	(3,679		)	(4,558		)	(8,500		)
Selling, general and administrative	(18,472		)	(13,559		)	(48,560		)	(47,095		)
Depreciation, depletion and amortization	(17,175		)	(15,158		)	(46,940		)	(42,096		)
Interest expense	(6,684		)	(6,684		)	(19,974		)	(20,448		)
Other income, net, including interest income	493			309			2,891			818
Income tax benefit	12,177			4,695			30,102			7,584
Net income (loss)	$	(11,339	)	$	2,412		$	(34,113	)	$	27,188

Asset information, including capital expenditures and depreciation, depletion, and amortization, by segment is not included in reports used by management in its monitoring of performance and, therefore, is not reported by segment. Goodwill of $233.2 million has been allocated to these segments with $212.5 million assigned to Oil & Gas Proppants and $20.7 million to Industrial & Specialty Products as of September 30, 2016. Goodwill assigned to Oil & Gas Proppants segment increased by $164.5 million compared to $68.6 million as of December 31, 2015 due to the acquisitions discussed in Note C - Business Combinations.

- Definition

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

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
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-Name Accounting Standards Codification
-Topic 280
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Reference 2: http://www.xbrl.org/2003/role/presentationRef
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Reference 3: http://www.xbrl.org/2003/role/presentationRef
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Reference 4: http://www.xbrl.org/2003/role/presentationRef
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Reference 5: http://www.xbrl.org/2003/role/presentationRef
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Reference 6: http://www.xbrl.org/2003/role/presentationRef
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Reference 7: http://www.xbrl.org/2003/role/presentationRef
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Reference 8: http://www.xbrl.org/2003/role/presentationRef
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Reference 9: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
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-URI http://asc.fasb.org/extlink&oid=51669610&loc=d3e9031-108599

Reference 10: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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-Name Accounting Standards Codification
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Reference 12: http://www.xbrl.org/2003/role/presentationRef
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Reference 13: http://www.xbrl.org/2003/role/presentationRef
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Reference 14: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
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-URI http://asc.fasb.org/extlink&oid=51669610&loc=d3e8906-108599

+ Details

Subsequent Events	9 Months Ended
Subsequent Events	Sep. 30, 2016
Subsequent Events [Abstract]
Subsequent Events	NOTE O— SUBSEQUENT EVENTS On October 4, 2016, we paid a cash dividend of $0.0625 per share to common stockholders of record on September 15, 2016, which had been declared by our Board of Directors on July 21, 2016. On November 3, 2016, 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 December 15, 2016, payable on January 5, 2017. Also on November 3, 2016, our Board of Directors extended our $50 million stock repurchase program through December 11, 2017. This program had been scheduled to expire on December 11, 2016.

Summary of Significant Accounting Policies (Policies)	9 Months Ended
Summary of Significant Accounting Policies (Policies)	Sep. 30, 2016
Accounting Policies [Abstract]
Basis of Presentation and Consolidation	Basis of Presentation and Consolidation The accompanying Condensed Consolidated Financial Statements (the “Financial Statements”) of U.S. Silica Holdings, Inc. (“Holdings,” and together with its subsidiaries “we,” “us” or the “Company”) included in this Quarterly Report on Form 10-Q, have been prepared in accordance with generally accepted accounting principles in the United States (“GAAP”) for interim financial information and with the instructions to Form 10-Q and Article 10 of Regulation S-X issued by the U.S. Securities and Exchange Commission (“SEC”). They do not contain certain information included in our Annual Report on Form 10-K for the fiscal year ended December 31, 2015; therefore, the interim Condensed Consolidated Financial Statements should be read in conjunction with that Annual Report on Form 10-K. In the opinion of management, all adjustments necessary for a fair presentation of the Financial Statements have been included. Such adjustments are of a normal, recurring nature. We have reclassified certain immaterial amounts in the prior years’ operating activities section of the consolidated statement of cash flows to conform to the current year presentation. These reclassifications had no effect on previously reported net cash flows from operations. In order to make this report easier to read, we refer throughout to (i) our Condensed Consolidated Balance Sheets as our “Balance Sheets,” (ii) our Condensed Consolidated Statements of Operations as our “Income Statements,” and (iii) our Condensed Consolidated Statements of Cash Flows as our “Cash Flows.”
Unaudited Interim Financial Statements	Unaudited Interim Financial Statements The accompanying Balance Sheet as of September 30, 2016; the Income Statements and Condensed Consolidated Statements of Comprehensive Income for the three and nine months ended September 30, 2016 and 2015; the Condensed Consolidated Statements of Stockholders' Equity and Cash Flows for the nine months ended September 30, 2016; and other information disclosed in the related notes are unaudited. The Balance Sheet as of December 31, 2015 was derived from our audited consolidated financial statements as included in our 2015 Annual Report.
Use of Estimates and Assumptions	Use of Estimates and Assumptions The preparation of the Financial Statements requires us to make estimates and assumptions that affect the reported amounts of assets and liabilities and the related disclosure of contingent assets and liabilities at the date of the Financial Statements and the reported amounts of revenues and expenses during the reporting period. The more significant areas requiring the use of management estimates and assumptions relate to purchase price allocation for businesses acquired; mineral reserves that are the basis for future cash flow estimates utilized in impairment calculations and units-of-production amortization calculations; environmental, reclamation and closure obligations; estimates of recoverable minerals; estimates of allowance for doubtful accounts; estimates of fair value for certain reporting units and asset impairments (including impairments of goodwill and other long-lived assets); write-downs of inventory to net realizable value; equity-based compensation expense; post-employment, post-retirement and other employee benefit liabilities; valuation allowances for deferred tax assets; 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.
Recently Issued Accounting Pronouncements	Recently Issued Accounting Pronouncements In February 2016, the Financial Accounting Standards Board (FASB) issued an Accounting Standards Update 2016-02, "Leases", which supersedes the existing lease guidance and requires all leases with a term greater than 12 months to be recognized on the balance sheet as assets and obligations. 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; early application is permitted. This standard mandates a modified retrospective transition method. We are currently evaluating the effect that the new guidance will have on our financial statements and related disclosures. On July 22, 2015, the FASB issued Accounting Standards Update 2015-11, "Simplifying the Measurement of Inventory". The new standard requires an entity to measure most inventory at the lower of cost and net realizable value, thereby simplifying the current guidance under which an entity must measure inventory at the lower of cost or market. The new standard will not apply to inventories that are measured using either the last-in, first-out (LIFO) method or the retail inventory method. This Update is effective for public entities for financial statements issued for fiscal years beginning after December 15, 2016, including interim periods within those fiscal years; early application is permitted. We have elected to adopt the standard early effective January 1, 2016 prospectively and have measured our inventory at the lower of cost and net realizable value on our Balance Sheet as of September 30, 2016. The impacts of the early adoption of this Update on our Financial Statements are not significant. In March 2016, the FASB issued Accounting Standards Update 2016-09, "Compensation-Stock Compensation." The update requires that excess tax benefits and deficiencies be recorded in the income statement when the awards vest or are settled. It also eliminates the requirement that excess tax benefits be realized (reduce cash taxes payable) before being recognized. Previously, an entity could not recognize excess tax benefits if the tax deduction increased a net operating loss ("NOL") or tax credit carryforward. The updated standard no longer requires cash flows related to excess tax benefits to be presented as a financing activity separate from other income tax cash flows. The update also allows the employer to repurchase more of an employee's shares for tax withholding purposes without triggering liability accounting, clarifies that all cash payments to taxing authorities made on an employee's behalf for withheld shares should be presented as a financing activity on the statement of cash flows, and provides for an accounting policy election to account for forfeitures as they occur. The update is effective for annual periods beginning after December 15, 2016, and interim periods within those annual periods, with early adoption permitted. We elected to early adopt this update during the three months ended September 30, 2016, which requires any adjustments to be reflected as of January 1, 2016. This resulted in the recognition of excess tax benefits on our Balance Sheet that were previously not recognized, as the benefits would have increased our NOL or tax credit carryforwards. The recognition decreased net deferred tax liability by $0.1 million and $1.7 million as of January 1, 2016 and September 30, 2016, respectively. Retained earnings on January 1, 2016 was increased accordingly by $0.1 million. In addition, we will recognize excess tax benefits in the provision for income taxes rather than paid-in capital for 2016 and future periods. Adoption of the update resulted in the recognition of excess tax benefits in the provision for income taxes of $1.8 million and $1.7 million for the three and nine months ended September 30, 2016, respectively. The effect of the adoption of this update on our previously reported income tax provision on our Income Statement was a decrease in tax benefit of $0.3 million for the three months ended March 31, 2016 and an increase in tax benefit of $0.2 million for the three months ended June 30, 2016, respectively. We elected to include excess tax benefits as operating activities in the Cash Flow on a prospective basis. Prior periods are not adjusted. We also made the accounting policy election to account for forfeitures as they occur.

Capital Structure and Accumulated Comprehensive Income (Tables)

9 Months Ended

Sep. 30, 2016

Equity [Abstract]

Schedule of Quarterly Cash Dividends

During the nine months ended September 30, 2016, our Board of Directors declared quarterly cash dividends as follows:



Dividends per Common Share		Declaration Date	Record Date	Payable Date
$	0.0625	February 22, 2016	March 15, 2016	April 5, 2016
$	0.0625	May 5, 2016	June 15, 2016	July 6, 2016
$	0.0625	July 21, 2016	September 15, 2016	October 4, 2016

Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share [Table Text Block]

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



	Three Months Ended September 30,		Nine Months Ended September 30,
	2016	2015	2016	2015
Weighted-average outstanding stock options excluded	1,095	726	1,217	464
Weighted-average outstanding restricted stock awards excluded	1,493	729	1,062	598

Changes in Accumulated Other Comprehensive Income

The following table presents the changes in accumulated other comprehensive income (in thousands) by component during the nine months ended September 30, 2016:



	For the Nine Months Ended September 30, 2016
	Unrealized gain/(loss) on cash flow hedges			Unrealized gain/(loss) on short-term investments			Pension and other post-retirement benefits liability			Total
Beginning Balance	$	(81	)	$	6		$	(16,096	)	$	(16,171	)
Other comprehensive (loss) before reclassifications	(69		)	(6		)	(4,387		)	(4,462		)
Amounts reclassed from accumulated other comprehensive income	81			—			86			167
Ending Balance	$	(69	)	$	—		$	(20,397	)	$	(20,466	)

Business Combination (Tables)

9 Months Ended

Sep. 30, 2016

Business Combinations [Abstract]

Schedule of Purchase Price Calculation

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




Cash consideration paid			$	115,555
Number of U.S. Silica common shares delivered	2,630,513
Multiplied by closing market price per share of U.S. Silica common stock on August 16, 2016	$	40.51
Total value of U.S. Silica common shares delivered			$	106,562
Less, cash acquired			$	(9,002	)
Total purchase price			$	213,115

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




Cash consideration paid			$	71,200
Number of U.S. Silica common shares delivered	4,195,180
Multiplied by closing market price per share of U.S. Silica common stock on August 22, 2016	$	40.92
Total value of U.S. Silica common shares delivered			$	171,667
Less, cash acquired			$	(1,306	)
Total purchase price			$	241,561

The following table set

Schedule of Purchase Price Allocation

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



Preliminary allocation of purchase price:
Accounts receivable	$	12,232
Prepaid expenses and other	1,482
Property, plant and mine development	32,336
Identifiable intangible assets	124,944
Goodwill	82,469
Total assets acquired	253,463
Accounts payable	4,112
Deferred revenue	4,891
Accrued expenses and other current liabilities	2,899
Total liabilities assumed	11,902
Net assets acquired	$	241,561

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



Preliminary allocation of purchase price:
Accounts receivable	$	2,680
Inventories	3,494
Other current assets	439
Income tax deposits	6,657
Property, plant and mine development	209,378
Identifiable intangible assets	1,600
Goodwill	82,080
Total assets acquired	306,328
Accounts payable, accrued expenses and other current liabilities	1,484
Deferred revenue	500
Notes payable	17,633
Capital lease liabilities	2,475
Asset retirement obligations	710
Deferred tax liabilities	70,411
Total liabilities assumed	93,213
Net assets acquired	$	213,115

Schedule of Intangible Assets Acquired as Part of Business Combination

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	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	49,400		14
Total fair value of identifiable intangible assets	$	124,944

Schedule of Pro Forma Financial Information

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



	Three months ended September 30,					Nine months ended September 30,
	2016			2015		2016			2015
Sales	$	153,358		$	189,425	$	433,179		$	589,203
Net income	$	(18,111	)	$	8,703	$	(38,207	)	$	45,429
Basic earnings per share	$	(0.27	)	$	0.16	$	(0.62	)	$	0.85
Diluted earnings per share	$	(0.27	)	$	0.16	$	(0.62	)	$	0.84

Accounts Receivable (Tables)

9 Months Ended

Sep. 30, 2016

Receivables [Abstract]

Schedule of Accounts Receivable

At September 30, 2016 and December 31, 2015, accounts receivable (in thousands) consisted of the following:



	September 30, 2016			December 31, 2015
Trade receivables	$	77,262		$	64,821
Less: Allowance for doubtful accounts	(7,358		)	(7,686		)
Net trade receivables	69,904			57,135
Other receivables	821			1,571
Total accounts receivable	$	70,725		$	58,706

Changes in our allowance for doubtful accounts (in thousands) during the nine months ended September 30, 2016 are as follows:



	September 30, 2016
Beginning balance	$	7,686
Bad debt provision	(86		)
Write-offs	(242		)
Ending balance	$	7,358

Inventories (Tables)

9 Months Ended

Sep. 30, 2016

Inventory Disclosure [Abstract]

Schedule of Inventories

At September 30, 2016 and December 31, 2015, inventories (in thousands) consisted of the following:



	September 30, 2016		December 31, 2015
Supplies	$	18,279	$	18,029
Raw materials and work in process	24,750		18,113
Finished goods	34,400		28,862
Total inventories	$	77,429	$	65,004

Property, Plant and Mine Development (Tables)

9 Months Ended

Sep. 30, 2016

Property, Plant and Equipment [Abstract]

Schedule of Property, Plant and Mine Development

At September 30, 2016 and December 31, 2015, property, plant and mine development (in thousands) consisted of the following:



	September 30, 2016			December 31, 2015
Mining property and mine development	$	417,065		$	222,439
Asset retirement cost	10,597			9,889
Land	35,842			30,322
Land improvements	39,959			37,791
Buildings	52,301			51,280
Machinery and equipment	444,017			360,817
Furniture and fixtures	2,554			1,917
Construction-in-progress	41,814			56,130
	1,044,149			770,585
Accumulated depletion, depreciation and amortization	(253,584		)	(209,389		)
Total property, plant and mine development, net	$	790,565		$	561,196

Debt And Capital Leases (Tables)

9 Months Ended

Sep. 30, 2016

Debt Disclosure [Abstract]

Schedule of Debt

At September 30, 2016 and December 31, 2015, debt (in thousands) consisted of the following:



	September 30, 2016			December 31, 2015
Senior secured credit facility:
Revolver expiring July 23, 2018 (5% at September 30, 2016 and December 31, 2015)	$	—		$	—
Term loan facility—final maturity July 23, 2020 (4% - 4.5% at September 30, 2016 and December 31, 2015)	495,450			499,275
Less: Unamortized original issue discount	(1,413		)	(1,696		)
Less: Unamortized debt issuance cost	(4,829		)	(5,874		)
Note payable secured by royalty interest (includes $3,053 unamortized fair value premium)	15,571			—
Customer note payable	1,852			—
Total debt	506,631			491,705
Less: current portion	(6,745		)	(3,330		)
Total long-term portion of debt	$	499,886		$	488,375

Schedule of Contractual Maturities of Debt

At September 30, 2016, contractual maturities of long-term debt (in thousands) are as follows:



2016	$	1,275
2017	5,100
2018	5,100
2019	5,100
2020	478,875
	$	495,450

Contractual maturities of this note payable (in thousands) are as follows:



2016	$	108
2017	440
2018	456
2019	472
2020	376
Total	$	1,852

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



2016	$	247
2017	1,750
2018	1,750
2019	1,750
2020	1,750

Schedule of Future Minimum Lease Payments for Capital Leases

At September 30, 2016, scheduled future minimum lease payments under capital lease obligations (in thousands) are as follows:



2016	$	332
2017	1,433
2018	712
Total minimum lease payments	2,477
Less: amount representing interest	(60		)
Present value of minimum lease payments	2,417
Less: current portion of capital lease obligations	(1,136		)
Non-current portion of capital lease obligations	$	1,281

Asset Retirement Obligations (Tables)

9 Months Ended

Sep. 30, 2016

Asset Retirement Obligation Disclosure [Abstract]

Schedule of Changes in Asset Retirement Obligation

Changes in the asset retirement obligation (in thousands) during the nine months ended September 30, 2016 are as follows:



	September 30, 2016
Beginning balance	$	12,254
Payments	—
Accretion	720
Additions due to NBI Acquisition	710
Ending balance	$	13,684

Fair Value Accounting (Tables)

9 Months Ended

Sep. 30, 2016

Fair Value Disclosures [Abstract]

Schedule of Measure at Fair Value on Recurring Basis

In accordance with the fair value hierarchy, the following table presents the fair value as of September 30, 2016 of those assets that we measure at fair value on a recurring basis:



	Level 1		Level 2		Total
Interest rate derivatives	$	—	$	12	$	12
Net asset	$	—	$	12	$	12

Commitments and Contingencies (Tables)

9 Months Ended

Sep. 30, 2016

Commitments and Contingencies Disclosure [Abstract]

Schedule of Future Minimum Annual Commitments

Future Minimum Annual Commitments at September 30, 2016:



	Operating Leases		Minimum Purchase Commitments
2016	$	12,451	$	7,413
2017	51,524		17,944
2018	59,791		14,693
2019	53,218		11,790
2020	48,612		6,369
Thereafter	157,414		17,136
Total future lease and purchase commitments	$	383,010	$	75,345

Pension and Post-Retirement Benefits (Tables)

9 Months Ended

Sep. 30, 2016

Compensation and Retirement Disclosure [Abstract]

Summarizes Information about Pension and Post-Retirement Benefit Plans



	Three Months Ended September 30,						Nine Months Ended September 30,
	2016			2015			2016			2015
Service cost	$	267		$	324		$	559		$	971
Interest cost	1,009			1,203			2,257			3,610
Expected return on plan assets	(1,361		)	(1,375		)	(2,768		)	(4,124		)
Net amortization and deferral	395			666			884			1,999
Net pension benefit costs	$	310		$	818		$	932		$	2,456



	Three Months Ended September 30,					Nine Months Ended September 30,
	2016			2015		2016		2015
Service cost	$	(28	)	$	36	$	60	$	124
Interest cost	(187		)	221		425		776
Expected return on plan assets	—			—		—		(2		)
Special termination benefit	—			47		21		47
Net amortization and deferral	—			58		270		250
Net post-retirement costs	$	(215	)	$	362	$	776	$	1,195

Segment Reporting (Tables)

9 Months Ended

Sep. 30, 2016

Segment Reporting [Abstract]

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



	Three Months Ended September 30,						Nine Months Ended September 30,
	2016			2015			2016			2015
Sales:
Oil & Gas Proppants	$	86,782		$	101,987		$	225,573		$	341,593
Industrial & Specialty Products	50,966			53,421			151,679			165,284
Total Sales	137,748			155,408			377,252			506,877
Segment contribution margin:
Oil & Gas Proppants	(1,897		)	16,521			(7,041		)	81,972
Industrial & Specialty Products	21,587			19,967			59,967			54,953
Total segment contribution margin	19,690			36,488			52,926			136,925
Operating activities excluded from segment cost of goods sold	(1,368		)	(3,679		)	(4,558		)	(8,500		)
Selling, general and administrative	(18,472		)	(13,559		)	(48,560		)	(47,095		)
Depreciation, depletion and amortization	(17,175		)	(15,158		)	(46,940		)	(42,096		)
Interest expense	(6,684		)	(6,684		)	(19,974		)	(20,448		)
Other income, net, including interest income	493			309			2,891			818
Income tax benefit	12,177			4,695			30,102			7,584
Net income (loss)	$	(11,339	)	$	2,412		$	(34,113	)	$	27,188

Summary of Significant Accounting Policies (Detail) - USD ($) $ in Thousands	3 Months Ended				9 Months Ended
	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015	Jan. 01, 2016
New Accounting Pronouncement, Early Adoption [Line Items]
Discrete tax benefit related to early adoption	$ 1,800				$ 1,700
Increase (decrease) in Income tax benefit	$ 12,177			$ 4,695	$ 30,102	$ 7,584
New Accounting Pronouncement, Early Adoption, Effect \| Accounting Standards Update 2016-09
New Accounting Pronouncement, Early Adoption [Line Items]
Deferred income tax liabilities, net				$ 1,700		$ 1,700	$ 100
Retained Earnings \| New Accounting Pronouncement, Early Adoption, Effect \| Accounting Standards Update 2016-09
New Accounting Pronouncement, Early Adoption [Line Items]
Cumulative effect adjustment							$ 100
Restatement Adjustment \| New Accounting Pronouncement, Early Adoption, Effect \| Accounting Standards Update 2016-09
New Accounting Pronouncement, Early Adoption [Line Items]
Increase (decrease) in Income tax benefit		$ 200	$ (300)

Capital Structure and Accumulated Comprehensive Income (Detail) $ / shares in Units, $ in Thousands	1 Months Ended		9 Months Ended
	Aug. 31, 2016 acquisition shares	Mar. 31, 2016 USD ($)	Sep. 30, 2016 USD ($) acquisition $ / shares shares	Sep. 30, 2015 shares	Mar. 31, 2015 shares
Capital Structure And Accumulated Comprehensive Income (Loss)
Secondary offering shares (in shares)					10,000,000
Cash proceeds \| $		$ 186,200	$ 186,202
Number of acquisitions \| acquisition	2		2
Common stock issued (shares)			70,615,466	53,386,174
Common stock outstanding (shares)			70,615,466	53,386,174
Preferred stock issued (shares)			0	0
Preferred stock outstanding (shares)			0	0
Repurchase of common stock (shares)			706,093
Average price per common share of repurchase common stock (in USD per share) \| $ / shares			$ 23.83
Remaining authorized repurchase of common stock amount \| $			$ 33,200
Common Stock
Capital Structure And Accumulated Comprehensive Income (Loss)
Common stock authorized (shares)			500,000,000
Common stock, par value (in dollars per share) \| $ / shares			$ 0.01
Shares issued to complete acquisitions (in shares)	6,825,693
Preferred Stock
Capital Structure And Accumulated Comprehensive Income (Loss)
Preferred stock authorized (shares)			10,000,000
Preferred stock, par value (in dollars per share) \| $ / shares			$ 0.01

Capital Structure and Accumulated Comprehensive Income - Schedule of Quarterly Cash Dividends (Details) - $ / shares	Jul. 21, 2016	May 05, 2016	Feb. 22, 2016
Equity [Abstract]
Dividends per common share (per share)	$ 0.0625	$ 0.0625	$ 0.0625
Declaration date	Jul. 21, 2016	May 05, 2016	Feb. 22, 2016
Record date	Sep. 15, 2016	Jun. 15, 2016	Mar. 15, 2016
Payable date	Oct. 04, 2016	Jul. 06, 2016	Apr. 05, 2016

Capital Structure and Accumulated Comprehensive Income - Earnings Per Share (Details) - shares shares in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Employee Stock Option
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Weighted-average outstanding stock options excluded (in shares)	1,095	726	1,217	464
Restricted Stock and Restricted Stock Units
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Weighted-average outstanding stock options excluded (in shares)	1,493	729	1,062	598

Capital Structure and Accumulated Comprehensive Income - Changes in Accumulated Other Comprehensive Income (Detail) $ in Thousands	9 Months Ended
	Sep. 30, 2016 USD ($)
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Balance at December 31, 2015	$ 384,167
Other comprehensive income (loss) before reclassifications	(4,462)
Amounts reclassed from accumulated other comprehensive income	167
Balance at September 30, 2016	810,795
Unrealized Gains and Losses on Cash Flow Hedges
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Balance at December 31, 2015	(81)
Other comprehensive income (loss) before reclassifications	(69)
Amounts reclassed from accumulated other comprehensive income	81
Balance at September 30, 2016	(69)
Unrealized Gain/(Loss) on Short-Term Investments
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Balance at December 31, 2015	6
Other comprehensive income (loss) before reclassifications	(6)
Amounts reclassed from accumulated other comprehensive income	0
Balance at September 30, 2016	0
Pension and Other Postretirement Benefits Liability
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Balance at December 31, 2015	(16,096)
Other comprehensive income (loss) before reclassifications	(4,387)
Amounts reclassed from accumulated other comprehensive income	86
Balance at September 30, 2016	(20,397)
AOCI Attributable to Parent
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Balance at December 31, 2015	(16,171)
Balance at September 30, 2016	$ (20,466)

Business Combination (Details) $ in Thousands			1 Months Ended	3 Months Ended	9 Months Ended
Business Combination (Details) $ in Thousands	Aug. 22, 2016 USD ($) shares	Aug. 16, 2016 USD ($) shares	Aug. 31, 2016 acquisition shares	Sep. 30, 2016 USD ($)	Sep. 30, 2016 USD ($) acquisition	Sep. 30, 2015 USD ($)
Business Acquisition [Line Items]
Payments to acquire businesses, net of cash acquired					$ 176,447	$ 0
Number of acquisitions \| acquisition			2		2
Cash proceeds					$ 13,968	$ 0
Amortization expense, next twelve months				$ 4,100	4,100
Amortization expense, year two				4,100	4,100
Amortization expense, year three				4,100	4,100
Amortization expense, year four				4,100	4,100
Amortization expense, year five				4,100	4,100
New Birmingham, Inc
Business Acquisition [Line Items]
Payments to acquire businesses, net of cash acquired		$ 106,600
Cash acquired		$ 9,002
Number of U.S. Silica common shares delivered \| shares		2,630,513
Acquisition related costs				1,000	1,400
Inventory write-down				500
Sandbox Enterprises LLC
Business Acquisition [Line Items]
Payments to acquire businesses, net of cash acquired	$ 69,900
Cash acquired	$ 1,306
Number of U.S. Silica common shares delivered \| shares	4,195,180
Acquisition related costs				2,700	2,800
Revenue				7,500
Common Stock
Business Acquisition [Line Items]
Shares issued to complete acquisitions (in shares) \| shares			6,825,693
Cash proceeds					200
Customer Relationships
Business Acquisition [Line Items]
Finite-lived intangible assets, gross				60,500	60,500
Finite-lived intangible assets, accumulated amortization				$ 3,800	$ 3,800
Weighted average useful life					13 years 8 months 12 days

Business Combination - Schedule of Purchase Price Calculation (Details) - USD ($) $ / shares in Units, $ in Thousands	Aug. 22, 2016	Aug. 16, 2016
Business Acquisition [Line Items]
Multiplied by closing market price per share of U.S. Silica common stock	$ 40.92	$ 40.51
Sandbox Enterprises LLC
Business Acquisition [Line Items]
Cash consideration paid for common shares	$ 71,200
Number of U.S. Silica common shares delivered	4,195,180
Total value of U.S. Silica common shares delivered	$ 171,667
Cash acquired	(1,306)
Total purchase price	$ 241,561
New Birmingham, Inc
Business Acquisition [Line Items]
Cash consideration paid for common shares		$ 115,555
Number of U.S. Silica common shares delivered		2,630,513
Total value of U.S. Silica common shares delivered		$ 106,562
Cash acquired		(9,002)
Total purchase price		$ 213,115

Business Combination - Schedule of Purchase Price Allocation (Details) - USD ($) $ in Thousands	Sep. 30, 2016	Aug. 22, 2016	Aug. 16, 2016	Dec. 31, 2015
Business Acquisition [Line Items]
Goodwill	$ 233,196			$ 68,647
Sandbox Enterprises LLC
Business Acquisition [Line Items]
Accounts receivable		$ 12,232
Prepaid expenses and other		1,482
Property, plant and mine development		32,336
Identifiable intangible assets		124,944
Goodwill		82,469
Total assets acquired		253,463
Accounts payable		4,112
Deferred revenue		4,891
Accrued expenses and other current liabilities		2,899
Total liabilities assumed		11,902
Net assets acquired		$ 241,561
New Birmingham, Inc
Business Acquisition [Line Items]
Accounts receivable			$ 2,680
Inventories			3,494
Other current assets			439
Income tax deposits			6,657
Property, plant and mine development			209,378
Identifiable intangible assets			1,600
Goodwill			82,080
Total assets acquired			306,328
Accounts payable, accrued expenses and other current liabilities			1,484
Deferred revenue			500
Notes payable			17,633
Capital lease liabilities			2,475
Asset retirement obligations			710
Deferred tax liabilities			70,411
Total liabilities assumed			93,213
Net assets acquired			$ 213,115

Business Combination - Schedule of Intangible Assets Acquired as Part of Business Combination (Details) - USD ($) $ in Thousands	Aug. 22, 2016	Aug. 16, 2016
Sandbox Enterprises LLC
Business Acquisition [Line Items]
Finite-lived intangible assets	$ 124,944
Sandbox Enterprises LLC \| Technology and Intellectual Property
Business Acquisition [Line Items]
Finite-lived intangible assets	$ 57,700
Estimated Useful Lives	15 years
Sandbox Enterprises LLC \| Customer Relationships
Business Acquisition [Line Items]
Finite-lived intangible assets	$ 49,400
Estimated Useful Lives	14 years
New Birmingham, Inc
Business Acquisition [Line Items]
Estimated Useful Lives		15 years
New Birmingham, Inc \| Customer Relationships
Business Acquisition [Line Items]
Finite-lived intangible assets		$ 1,600
Trade Names \| Sandbox Enterprises LLC
Business Acquisition [Line Items]
Indefinite-lived intangible assets	$ 17,844

Business Combination - Schedule of Pro Forma Financial Information (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Business Combinations [Abstract]
Sales	$ 189,425	$ 153,358	$ 589,203	$ 433,179
Net income	$ 8,703	$ (18,111)	$ 45,429	$ (38,207)
Basic earnings per share (in dollars per share)	$ 0.16	$ (0.27)	$ 0.85	$ (0.62)
Diluted earnings per share (in dollars per share)	$ 0.16	$ (0.27)	$ 0.84	$ (0.62)

Accounts Receivable - Schedule of Accounts Receivable (Detail) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Receivables [Abstract]
Trade receivables	$ 77,262	$ 64,821
Less: Allowance for doubtful accounts	(7,358)	(7,686)
Net trade receivables	69,904	57,135
Other receivables	821	1,571
Total accounts receivable	$ 70,725	$ 58,706

Accounts Receivable - Allowance for Doubtful Accounts (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015
Allowance for Doubtful Accounts Receivable
Beginning balance	$ 7,686
Bad debt provision	(86)	$ (426)
Write-offs	(242)
Ending balance	$ 7,358

Inventories - Schedule of Inventories (Detail) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Inventory Disclosure [Abstract]
Supplies	$ 18,279	$ 18,029
Raw materials and work in process	24,750	18,113
Finished goods	34,400	28,862
Total inventories	$ 77,429	$ 65,004

Property, Plant and Mine Development - Schedule of Property, Plant and Mine Development (Detail) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Property, Plant and Equipment
Property, plant and mine development	$ 1,044,149	$ 770,585
Accumulated depletion, depreciation and amortization	(253,584)	(209,389)
Total property, plant and mine development, net	790,565	561,196
Mining Property and Mine Development
Property, Plant and Equipment
Property, plant and mine development	417,065	222,439
Asset Retirement Cost
Property, Plant and Equipment
Property, plant and mine development	10,597	9,889
Land
Property, Plant and Equipment
Property, plant and mine development	35,842	30,322
Land Improvements
Property, Plant and Equipment
Property, plant and mine development	39,959	37,791
Buildings
Property, Plant and Equipment
Property, plant and mine development	52,301	51,280
Machinery and Equipment
Property, Plant and Equipment
Property, plant and mine development	444,017	360,817
Furniture and Fixtures
Property, Plant and Equipment
Property, plant and mine development	2,554	1,917
Construction-in-Progress
Property, Plant and Equipment
Property, plant and mine development	$ 41,814	$ 56,130

Property, Plant and Mine Development (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Dec. 31, 2015
Property, Plant and Equipment
Machinery and equipment	$ 1,044,149		$ 770,585
Accumulated depletion, depreciation and amortization	253,584		$ 209,389
Interest costs capitalized	209	$ 465
Assets Held under Capital Leases
Property, Plant and Equipment
Machinery and equipment	4,300
Accumulated depletion, depreciation and amortization	$ 1,700

Debt And Capital Leases - Schedule of Debt (Detail) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2016	Dec. 31, 2015
Line of Credit Facility
Long-term debt	$ 506,631	$ 491,705
Less: Unamortized debt issuance cost	(4,829)	(5,874)
Less: current portion	(6,745)	(3,330)
Total long-term portion of debt	499,886	488,375
Revolving Line-of-Credit
Line of Credit Facility
Total debt	$ 0	$ 0
Credit facility, maturity date	Jul. 23, 2018
Credit facility, interest rate	5.00%	5.00%
Term Loan Facility
Line of Credit Facility
Long-term debt	$ 495,450	$ 499,275
Less: Unamortized original issue discount	$ (1,413)	$ (1,696)
Credit facility, maturity date	Jul. 23, 2020
Minimum \| Term Loan Facility
Line of Credit Facility
Credit facility, interest rate	4.00%	4.00%
Maximum \| Term Loan Facility
Line of Credit Facility
Credit facility, interest rate	4.50%	4.50%

Debt And Capital Leases (Detail)	9 Months Ended
Debt And Capital Leases (Detail)	Sep. 30, 2016 USD ($)	Aug. 16, 2016 USD ($)	Jan. 01, 2016 USD ($)	Dec. 31, 2015 USD ($)
Short-term Debt
Long-term debt	$ 506,631,000			$ 491,705,000
Credit facility consolidated total net leverage ratio	0.0375
Net leverage ratio, credit facility threshold (percentage)	25.00%
Revolving Line-of-Credit
Short-term Debt
Available borrowing base	$ 50,000,000
Amount drawn from borrowing base	0
Amount available for general corporate use under this revolving credit agreement	46,000,000
Letter of Credit
Short-term Debt
Amount allocated for letters of credit	4,000,000
Note Payable Secured by Royalty Interest \| Notes Payable, Other Payables
Short-term Debt
Long-term debt	15,571,000
Annual minimum payments	500,000
Debt instrument, fair value		$ 15,700,000
Debt instrument, unamortized premium	$ 3,053,000	3,100,000
Outstanding principal		$ 12,623,000
Debt, weighted average interest rate	2.10%
Interest rate, effective percentage	2.10%
Customer Note Payable \| Notes Payable, Other Payables
Short-term Debt
Long-term debt	$ 1,852,000
Outstanding principal	$ 2,500,000
Interest rate, stated percentage		0.00%
Debt Instrument, Term	60 months
Interest rate, effective percentage	3.50%
Load Credits
Short-term Debt
Remaining repayment of debt	$ 500,000
New Birmingham, Inc \| Customer Note Payable \| Notes Payable, Other Payables
Short-term Debt
Outstanding principal			$ 3,000,000

Debt And Capital Leases - Schedule of Contractual Maturities of Debt (Detail) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Debt Instrument [Line Items]
Total debt	$ 506,631	$ 491,705
Term Loan Facility
Debt Instrument [Line Items]
2016	1,275
2017	5,100
2018	5,100
2019	5,100
2020	478,875
Total debt	$ 495,450

Debt And Capital Leases - Schedule of Contractual Maturities of Note Payable Secured by Royalty Interest (Details) - Notes Payable, Other Payables - Note Payable Secured by Royalty Interest $ in Thousands	Sep. 30, 2016 USD ($)
Debt Instrument [Line Items]
2016	$ 247
2017	1,750
2018	1,750
2019	1,750
2020	$ 1,750

Debt And Capital Leases - Schedule of Contractual Maturities of Customer Note Payable (Details) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Debt Instrument [Line Items]
Total debt	$ 506,631	$ 491,705
Notes Payable, Other Payables \| Customer Note Payable
Debt Instrument [Line Items]
2017	108
2018	440
2019	456
2020	472
2021	376
Total debt	$ 1,852

Debt And Capital Leases - Schedule of Future Minimum Payments for Capital Leases (Detail) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Debt Disclosure [Abstract]
2016	$ 332
2017	1,433
2018	712
Total minimum lease payments	2,477
Less: amount representing interest	(60)
Present value of minimum lease payments	2,417
Less: current portion of capital lease obligations	(1,136)	$ 0
Non-current portion of capital lease obligations	$ 1,281	$ 0

Asset Retirement Obligations (Detail) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Asset Retirement Obligation Disclosure [Abstract]
Asset Retirement Obligation	$ 13,684	$ 12,254

Asset Retirement Obligations - Schedule of Changes in Asset Retirement Obligation (Detail) $ in Thousands	9 Months Ended
	Sep. 30, 2016 USD ($)
Asset Retirement Obligation Disclosure [Abstract]
Beginning balance	$ 12,254
Payments	0
Accretion	720
Additions due to NBI Acquisition	710
Ending balance	$ 13,684

Fair Value Accounting - Schedule of Measure at Fair Value on Recurring Basis (Detail) - Measured at Fair Value on Recurring Basis $ in Thousands	Sep. 30, 2016 USD ($)
Defined Benefit Plan Disclosure
Interest rate derivatives	$ 12
Net asset	12
Level 1
Defined Benefit Plan Disclosure
Interest rate derivatives	0
Net asset	0
Level 2
Defined Benefit Plan Disclosure
Interest rate derivatives	12
Net asset	$ 12

Commitments and Contingencies - Schedule of Future Minimum Annual Commitments (Details) $ in Thousands	Sep. 30, 2016 USD ($)
Operating Leases
2016	$ 12,451
2017	51,524
2018	59,791
2019	53,218
2020	48,612
Thereafter	157,414
Total future lease commitments	383,010
Minimum Purchase Commitments
2016	7,413
2017	17,944
2018	14,693
2019	11,790
2020	6,369
Thereafter	17,136
Total future purchase commitments	$ 75,345

Commitments and Contingencies (Detail) $ in Millions		3 Months Ended			9 Months Ended
Commitments and Contingencies (Detail) $ in Millions	Jun. 09, 2015 USD ($)	Sep. 30, 2016 USD ($) claim	Sep. 30, 2015 USD ($)	Mar. 31, 2015 USD ($)	Sep. 30, 2016 USD ($) claim	Sep. 30, 2015 USD ($)	Dec. 31, 2015 USD ($)
Insurance [Abstract]
Expenses related to operating leases and rental agreements		$ 12.6	$ 13.2		$ 37.7	$ 34.9
New claims filed \| claim					1
Third party products claims liability under insurance in other assets		0.3			$ 0.3		$ 0.3
Third party products claims liability under insurance in other long-term obligations		$ 1.3			$ 1.3		$ 1.3
Selling, General and Administrative Expense
Loss Contingencies
Litigation settlement expense				$ 7.6
Payments for legal settlements	$ 6.5
Pending Litigation
Loss Contingencies
Number of pending claims \| claim		74			74

Income Taxes (Details) $ in Millions	9 Months Ended
Income Taxes (Details) $ in Millions	Sep. 30, 2016 USD ($)	Sep. 30, 2015
Income Tax Disclosure [Abstract]
Discrete tax benefit	$ 2.1
Effective income tax rate (percentage)	47.00%	(39.00%)
Effective income tax rate without discrete tax benefit (percentage)	0.44

Pension and Post-Retirement Benefits - Summarizes Information about Pension and Post-Retirement Benefit Plans (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Pension Benefits
Defined Benefit Plan Disclosure
Service cost	$ 267	$ 324	$ 559	$ 971
Interest cost	1,009	1,203	2,257	3,610
Expected return on plan assets	(1,361)	(1,375)	(2,768)	(4,124)
Net amortization and deferral	395	666	884	1,999
Net pension benefit costs	310	818	932	2,456
Post-retirement Benefits
Defined Benefit Plan Disclosure
Service cost	(28)	36	60	124
Interest cost	(187)	221	425	776
Expected return on plan assets	0	0	0	(2)
Special termination benefit	0	47	21	47
Net amortization and deferral	0	58	270	250
Net pension benefit costs	$ (215)	$ 362	$ 776	$ 1,195

Pension and Post-Retirement Benefits (Detail) - USD ($)	3 Months Ended		9 Months Ended
Pension and Post-Retirement Benefits (Detail) - USD ($)	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015	Dec. 31, 2015
Pension Benefits
Defined Benefit Plan Disclosure
Weighted average discount rate used to calculate benefit obligation (percentage)	3.80%		3.80%		4.50%
Contributions to plan by employer	$ 0	$ 1,800,000	$ 0	$ 2,000,000
Expected contributions in current fiscal year			0
Post-retirement Benefits
Defined Benefit Plan Disclosure
Expected contributions in current fiscal year			$ 1,000,000

Obligations Under Guarantees (Detail) - Travelers Casualty and Surety Company $ in Millions	Sep. 30, 2016 USD ($)
Surety Bonds
Loss Contingencies
Surety bonds outstanding	$ 10.5
Reclamation Bonds
Loss Contingencies
Bonds related to reclamation requirements	$ 10.1

Segment Reporting (Detail) $ in Thousands	9 Months Ended
Segment Reporting (Detail) $ in Thousands	Sep. 30, 2016 USD ($) Segment Product	Dec. 31, 2015 USD ($)
Segment Reporting Information
Number of reportable segments \| Segment	2
Number of products in Industrial & Specialty segment (over 210) \| Product	210
Goodwill	$ 233,196	$ 68,647
Industrial & Specialty Products segment description	Over 210 products and materials used in a variety of industries including, container glass, fiberglass, specialty glass, flat glass, building products, fillers and extenders, foundry products, chemicals, recreation products and filtration products.
Oil & Gas Proppants
Segment Reporting Information
Goodwill	$ 212,500	$ 68,600
Goodwill, acquired during period	164,500
Industrial & Specialty Products
Segment Reporting Information
Goodwill	$ 20,700

Segment Reporting - Presentation of Sales and Segment Contribution Margin for Reporting Segments and Other Operating Results (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Segment Reporting Information
Total Sales	$ 137,748	$ 155,408	$ 377,252	$ 506,877
Total segment contribution margin	19,690	36,488	52,926	136,925
Operating activities excluded from segment cost of goods sold	(1,368)	(3,679)	(4,558)	(8,500)
Selling, general and administrative	(18,472)	(13,559)	(48,560)	(47,095)
Depreciation, depletion and amortization	(17,175)	(15,158)	(46,940)	(42,096)
Interest expense	(6,684)	(6,684)	(19,974)	(20,448)
Other income, net, including interest income	493	309	2,891	818
Income tax benefit	(12,177)	(4,695)	(30,102)	(7,584)
Net income (loss)	(11,339)	2,412	(34,113)	27,188
Oil & Gas Proppants
Segment Reporting Information
Total Sales	86,782	101,987	225,573	341,593
Total segment contribution margin	(1,897)	16,521	(7,041)	81,972
Industrial & Specialty Products
Segment Reporting Information
Total Sales	50,966	53,421	151,679	165,284
Total segment contribution margin	$ 21,587	$ 19,967	$ 59,967	$ 54,953

Subsequent Events (Details) - USD ($)	Nov. 03, 2016	Oct. 04, 2016	Jul. 21, 2016	May 05, 2016	Feb. 22, 2016
Subsequent Event
Payable date			Oct. 04, 2016	Jul. 06, 2016	Apr. 05, 2016
Dividends per common share (per share)			$ 0.0625	$ 0.0625	$ 0.0625
Record date			Sep. 15, 2016	Jun. 15, 2016	Mar. 15, 2016
Declaration date			Jul. 21, 2016	May 05, 2016	Feb. 22, 2016
Subsequent Event
Subsequent Event
Payable date	Jan. 05, 2017	Oct. 04, 2016
Dividends per common share paid (per share)		$ 0.0625
Dividends per common share (per share)	$ 0.0625
Record date	Dec. 15, 2016	Sep. 15, 2016
Declaration date		Jul. 21, 2016
Authorization to repurchase common stock	$ 50,000,000