Document and Entity Information (USD $)	12 Months Ended
Document and Entity Information (USD $)	Dec. 31, 2014	Feb. 24, 2015	Jun. 30, 2014
Document And Entity Information [Abstract]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2014
Document Fiscal Year Focus	2014
Document Fiscal Period Focus	FY
Entity Registrant Name	U.S. Silica Holdings, Inc.
Entity Central Index Key	0001524741
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	Yes
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		53,324,845
Entity Public Float			$ 2,978,580,861

Consolidated Balance Sheets (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Current Assets:
Cash and cash equivalents	$ 267,281	$ 78,256
Short-term investments	75,143	74,980
Accounts receivable, net	120,881	75,207
Inventories, net	66,712	64,212
Prepaid expenses and other current assets	9,267	7,140
Deferred income taxes, net	22,295	17,737
Income tax deposits	746	0
Total current assets	562,325	317,532
Property, plant and mine development, net	565,755	442,116
Debt issuance costs, net	7,211	5,255
Goodwill	68,647	68,403
Trade names	14,914	10,436
Customer relationships, net	6,984	6,120
Other assets	12,317	13,599
Total assets	1,238,153	863,461
Current Liabilities:
Book overdraft	4,215	4,659
Accounts payable	85,781	37,376
Dividends payable	6,805	6,709
Accrued liabilities	17,911	10,823
Accrued interest	60	41
Current portion of long-term debt	4,718	3,488
Income tax payable	0	1,037
Current portion of deferred revenue	26,771	0
Total current liabilities	146,261	64,133
Long-term debt	497,579	367,963
Liability for pension and other post-retirement benefits	59,932	36,802
Deferred revenue	64,722	0
Deferred revenue	49,749	71,318
Other long-term obligations	16,094	13,951
Total liabilities	834,337	554,167
Stockholders’ Equity:
Preferred stock	0	0
Common stock	539	534
Additional paid-in capital	191,086	174,799
Additional paid-in capital	232,551	137,978
Retained earnings	(542)	0
Treasury stock, at cost	(19,818)	(4,017)
Accumulated other comprehensive loss	403,816	309,294
Total stockholders’ equity	$ 1,238,153	$ 863,461

Consolidated Statements of Operations (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Income Statement [Abstract]
Sales	$ 249,589	$ 241,256	$ 205,801	$ 180,095	$ 149,474	$ 144,372	$ 129,828	$ 122,311	$ 876,741	$ 545,985	$ 441,921
Cost of goods sold (excluding depreciation, depletion and amortization)	157,700	149,697	132,417	126,770	102,875	90,983	80,297	74,412	566,584	348,567	256,535
Operating expenses
Selling, general and administrative	35,659	18,600	19,267	15,445	14,456	12,800	10,099	12,404	88,971	49,759	41,299
Depreciation, depletion and amortization	12,664	12,425	10,341	9,589	10,098	9,152	8,890	8,278	45,019	36,418	25,099
Total operating expenses	48,323	31,025	29,608	25,034	24,554	21,952	18,989	20,682	133,990	86,177	66,398
Operating income	43,566	60,534	43,776	28,291	22,045	31,437	30,542	27,217	176,167	111,241	118,988
Other (expense) income
Interest expense	(5,431)	(4,950)	(4,013)	(3,808)	(4,086)	(4,144)	(3,535)	(3,576)	(18,202)	(15,341)	(13,795)
Early extinguishment of debt					0	480	0	0	0	480	0
Other income, net, including interest income	379	120	221	38	152	260	63	122	758	597	4,612
Total other (expenses) income	(5,052)	(4,830)	(3,792)	(3,770)	(3,934)	(4,364)	(3,472)	(3,454)	(17,444)	(15,224)	(9,183)
Income before income taxes	38,514	55,704	39,984	24,521	18,111	27,073	27,070	23,763	158,723	96,017	109,805
Income tax expense	(5,276)	(14,427)	(11,330)	(6,150)	(1,658)	(5,739)	(6,878)	(6,486)	(37,183)	(20,761)	(30,651)
Net income	$ 33,238	$ 41,277	$ 28,654	$ 18,371	$ 16,453	$ 21,334	$ 20,192	$ 17,277	$ 121,540	$ 75,256	$ 79,154
Earnings per share:
Basic (in usd per share)	$ 0.62	$ 0.77	$ 0.53	$ 0.34	$ 0.31	$ 0.40	$ 0.38	$ 0.33	$ 2.26	$ 1.42	$ 1.50
Diluted (in usd per share)	$ 0.61	$ 0.76	$ 0.53	$ 0.34	$ 0.31	$ 0.40	$ 0.38	$ 0.32	$ 2.23	$ 1.41	$ 1.50

Consolidated Statements of Comprehensive Income (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Statement of Comprehensive Income [Abstract]
Net income	$ 121,540	$ 75,256	$ 79,154
Other comprehensive income:
Unrealized gain (loss) on derivatives (net of tax of $(32), $66 and $144 for 2014, 2013, and 2012, respectively)	(55)	103	227
Unrealized loss on investments (net of tax of $(8), $(17) and $0 for the years ended December 31 2014, 2013, and 2012, respectively)	(14)	(27)	0
Pension and other post-retirement benefits liability adjustment (net of tax of $(9,678), $6,419 and $(1,299) for the years ended December 31 2014, 2013, and 2012, respectively)	(15,732)	10,082	(2,041)
Comprehensive income	$ 105,739	$ 85,414	$ 77,340

- Definition

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

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- Definition

Amount after tax of increase (decrease) in accumulated gain (loss) from derivative instruments designated and qualifying as the effective portion of cash flow hedges and an entity's share of an equity investee's increase (decrease) in deferred hedging gain (loss).

+ References+ Details

Consolidated Statements of Comprehensive Income (Parenthetical) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Statement of Comprehensive Income [Abstract]
Tax expense (benefit) on unrealized gain (loss) on derivatives	$ (32)	$ 66	$ 144
Tax expense (benefit) on unrealized gain (loss) on investments	(8)	(17)	0
Tax expense (benefit) on pension and other post-retirement benefits liability adjustment	$ (9,678)	$ 6,419	$ (1,299)

Consolidated Statements of Stockholders' Equity (USD $)	Total	Common Stock	Treasury Stock	Additional Paid-In Capital	Retained Earnings	Accumulated Other Comprehensive Loss
Beginning balance at Dec. 31, 2011	$ 121,934,000	$ 500,000	$ 0	$ 103,757,000	$ 30,038,000	$ (12,361,000)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	79,154,000				79,154,000
Unrealized gain (loss) on derivatives	227,000					227,000
Unrealized loss on short-term investments	0
Pension and postretirement liability	(2,041,000)					(2,041,000)
Cash dividends declared ($0.50, $0.375 and $0.50 per share of common stock for 2014, 2013 and 2012 respectively))	(26,461,000)				(26,461,000)
Equity-based compensation	2,330,000			2,330,000
Excess tax benefit from equity compensation	0
Issuance of common stock (January 2012 IPO at $17.00 per share, net of issuance costs of $9,171)	40,829,000	29,000		40,800,000
Issuance of treasury stock	102,000		102,000
Repurchase of common stock	(1,072,000)		(1,072,000)
Capital contributed by parent	16,692,000			16,692,000
Ending balance at Dec. 31, 2012	231,694,000	529,000	(970,000)	163,579,000	82,731,000	(14,175,000)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	75,256,000				75,256,000
Unrealized gain (loss) on derivatives	103,000					103,000
Unrealized loss on short-term investments	(27,000)					(27,000)
Pension and postretirement liability	10,082,000					10,082,000
Cash dividends declared ($0.50, $0.375 and $0.50 per share of common stock for 2014, 2013 and 2012 respectively))	(20,009,000)				(20,009,000)
Equity-based compensation	3,039,000			3,039,000
Excess tax benefit from equity compensation	1,380,000			1,380,000
Proceeds from options exercised	7,942,000	5,000	1,136,000	6,801,000
Shares withheld for employee taxes related to vested restricted stock and stock units	(166,000)		(166,000)
Ending balance at Dec. 31, 2013	309,294,000	534,000	0	174,799,000	137,978,000	(4,017,000)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	121,540,000				121,540,000
Unrealized gain (loss) on derivatives	(55,000)					(55,000)
Unrealized loss on short-term investments	(14,000)					(14,000)
Pension and postretirement liability	(15,732,000)					(15,732,000)
Cash dividends declared ($0.50, $0.375 and $0.50 per share of common stock for 2014, 2013 and 2012 respectively))	(26,967,000)				(26,967,000)
Equity-based compensation	7,487,000			7,487,000
Excess tax benefit from equity compensation	3,813,000			3,813,000
Proceeds from options exercised	5,563,000	4,000	572,000	4,987,000
Shares withheld for employee taxes related to vested restricted stock and stock units	(614,000)	1,000	(615,000)
Repurchase of common stock	(499,000)		(499,000)
Ending balance at Dec. 31, 2014	$ 403,816,000	$ 539,000	$ (542,000)	$ 191,086,000	$ 232,551,000	$ (19,818,000)

Consolidated Statements of Stockholders' Equity (Parenthetical) (USD $) In Thousands, except Per Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2012
Common stock cash dividend declared, per share	$ 0.50
Common stock issuance costs	$ 9,171
IPO
Common stock issuance costs	$ 9,171
Issuance of common stock, per share	$ 17.00

Consolidated Statements of Cash Flows (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Operating activities:
Net income	$ 121,540	$ 75,256	$ 79,154
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation, depletion and amortization	45,019	36,418	25,099
Debt issuance amortization	912	680	515
Original issue discount amortization	272	209	168
Early extinguishment of debt	0	480	0
Deferred income taxes	(2,442)	(1,889)	2,249
Gain on disposal of property, plant and equipment	222	(162)	(472)
Deferred revenue	(8,508)	(4,855)	(7,666)
Equity-based compensation	7,487	3,039	2,330
Excess tax benefit from equity-based compensation	(3,813)	(1,380)	0
Other	8,420	(863)	(1,297)
Changes in assets and liabilities:
Accounts receivable	(46,829)	(16,965)	(13,239)
Inventories	34	(24,377)	(10,528)
Prepaid expenses and other current assets	(2,158)	(2,959)	4,114
Income taxes	2,063	(18,179)	24,491
Accounts payable and accrued liabilities	51,357	1,385	8,458
Accrued interest	15	39	(1,657)
Liability for pension and other post-retirement benefits	(2,180)	574	(2,769)
Advisory services termination fee to Golden Gate Capital	0	0	(8,000)
Net cash provided by operating activities	171,411	46,451	100,950
Investing activities:
Capital expenditures	(92,609)	(60,470)	(105,719)
Purchase of short-term investments	0	(75,000)	0
Acquisition of business, net of cash acquired	(98,317)	0	0
Proceeds from sale of property, plant and equipment	20	357	1,258
Net cash provided by operating activities	(190,906)	(135,113)	(104,461)
Financing activities:
Proceeds from issuance of common stock in initial public offering	0	0	50,000
Dividends paid	(26,871)	(13,300)	(26,461)
Repurchase of common stock	(499)	0	(1,072)
Issuance of treasury stock	0	0	102
Proceeds from options exercised	5,563	7,942	0
Excess tax benefit from equity-based compensation	3,813	1,380	0
Tax payments related to shares withheld for vested restricted stock and stock units	(614)	(166)	0
Advances from customers	100,000	0	0
Issuance of long-term debt	134,325	373,792	0
Repayment of long-term debt	(3,750)	(257,976)	(2,600)
Repayment of short-term debt	0	0	(3,932)
Change in book overdraft	(444)	(731)	(198)
Prepayment penalties	0	(250)	0
Principal payments on capital lease obligations	(132)	(744)	0
Financing fees	(2,871)	(4,051)	(1,334)
Common stock issuance costs	0	0	(9,171)
Net cash provided by financing activities	208,520	105,896	5,334
Net increase in cash and cash equivalents	189,025	17,234	1,823
Cash and cash equivalents, beginning of period	78,256	61,022	59,199
Cash and cash equivalents, end of period	267,281	78,256	61,022
Non-cash financing activities:
Contribution of note from parent and related accrued interest	0	0	16,692
Capital lease obligations incurred to acquire assets	0	744	0
Cash paid during the period for:
Interest	15,920	14,716	12,436
Taxes	$ 37,637	$ 40,760	$ 3,883

Organization	12 Months Ended
Organization	Dec. 31, 2014
Accounting Policies [Abstract]
Organization	ORGANIZATION U.S. Silica Holdings, Inc. (“Holdings,” and together with its subsidiaries “we,” “us” or the “Company”) is a domestic producer of commercial silica, a specialized mineral that is a critical input into a variety of end markets. During our 114 year history, we have developed core competencies in mining, processing, logistics and materials science that enable us to produce and cost-effectively deliver products to customers across these markets. We manufacture frac sand used to stimulate and maintain the flow of hydrocarbons in oil and natural gas wells. Our silica is also used as a raw material in a wide range of industrial applications, including glassmaking and chemical manufacturing. We operate in two business segments: (1) Oil & Gas Proppants and (2) Industrial & Specialty Products (see Note U - Segment Reporting for additional details). We completed our initial public offering of common stock (the “IPO”) through a Registration Statement on Form S-1 (File No. 333-175636) on January 31, 2012. As a result of the offering, we received net proceeds of approximately $40.8 million after deducting $3.5 million of underwriting discounts and commissions and offering expenses of $5.7 million. On July 31, 2014, we completed our acquisition of Cadre Services, Inc. ("Cadre"), a regional sand mining company based in Voca, Texas, for approximately $98.3 million in cash. (See Note E - Business Combinations)

- Definition

The entire disclosure for organization, consolidation and basis of presentation of financial statements disclosure.

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Summary of Significant Accounting Policies

12 Months Ended

Dec. 31, 2014

Accounting Policies [Abstract]

Summary of Significant Accounting Policies

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES

Basis of Presentation and Consolidation

The accompanying Consolidated Financial Statements (the “Financial Statements”) have been prepared in accordance with generally accepted accounting principles in the United States (“GAAP”). In the opinion of management, all adjustments necessary for a fair presentation of the Financial Statements have been included. Such adjustments are of a normal, recurring nature. We have reclassified certain immaterial amounts in the prior years’ assets section of the consolidated balance sheets and 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 total assets and net cash flows from operations.

In order to make this report easier to read, we refer throughout to (i) our Consolidated Balance Sheets as our “Balance Sheets,” (ii) our Consolidated Statements of Operations as our “Income Statements,” and (iii) our Consolidated Statements of Cash Flows as our “Cash Flows.”

Consolidation

The Financial Statements include the accounts of Holdings and its direct and indirect wholly-owned subsidiaries. All significant intercompany balances and transactions have been eliminated in consolidation.

We follow FASB Accounting Standards Codification (“ASC”) guidance for identification and reporting of entities over which control is achieved through means other than voting rights. The guidance defines such entities as Variable Interest Entities (“VIEs”). For the periods presented herein, we have identified no entities over which we maintain any level of control that would qualify for consolidation under ASC guidance.

Use of Estimates and Assumptions

The preparation of the consolidated financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the amounts reported in the Financial Statements. Actual results could differ from these estimates.

Revenue Recognition

We derive our sales by mining and processing minerals that our customers purchase for various uses. Our sales are primarily a function of the price per ton and the number of tons sold. The price invoiced reflects product, transportation and additional services as applicable, such as storage and transloading the product from railcars to trucks for delivery to the customer site.

Revenue is recognized from a sale when persuasive evidence of an arrangement exists, the price is determinable, the product has been delivered or legal title has been transferred to the customer and collection of the sales is reasonably assured. Amounts received from customers in advance of revenue recognition are deferred as liabilities.

We primarily sell our products under short-term price agreements or at prevailing market rates. For a limited number of customers, we sell under long-term, competitively-bid take-or-pay supply agreements. During the course of the year ended December 31, 2014, we were party to take-or-pay supply agreements with ten of our customers in the Oil & Gas Proppants segment with initial terms expiring between 2014 and 2019. These agreements define, among other commitments, the volume of product that our customers must purchase, the volume of product that we must provide and the price that we will charge that our customers will pay for each product. Prices under these agreements are generally fixed and subject to upward adjustment in response to certain cost increases.

We invoice the majority of our clients on a per shipment basis, although for some larger customers, we consolidate invoices weekly or monthly. Standard terms are net 30 days, although extended terms are offered in competitive situations.

Cash and Cash Equivalents

Cash and cash equivalents consist of all highly liquid investments with a maturity of three months or less when purchased. Because of the short maturity of these investments, the carrying amounts approximate their fair value. Cash and cash equivalents are invested primarily in money market securities with high quality institutions. Accounts at each institution are insured by Federal Deposit Insurance Corporation. Cash balances at times may exceed federally-insured limits. We have not experienced any losses in such accounts and believe we are not exposed to any significant credit risk on cash.

Accounts Receivable

The majority of our accounts receivable are due from companies in the glass, oil and natural gas drilling, building products, filler and extenders, foundries and other major industries. Credit is extended based on evaluation of a customer’s financial condition and, generally, collateral is not required. Accounts receivable are generally due within 30 days and are stated at amounts due from customers net of an allowance for doubtful accounts. Accounts outstanding longer than the payment terms are considered past due. We determine our allowance by considering a number of factors, including the length of time trade accounts receivable are past due, our previous loss history, the customer’s current ability to pay its obligation to us, and the condition of the general economy and the industry as a whole. Ongoing credit evaluations are performed. We write-off accounts receivable when they are deemed uncollectible, and payments subsequently received on such receivables are credited to the allowance for doubtful accounts.

Our ten largest customers accounted for approximately 57%, 52%, and 37% of sales in the years ended December 31, 2014, 2013 and 2012, respectively.

Inventories

Inventories include raw stockpiles and silica and other industrial sand available for shipment, as well as spare parts and supplies for routine facilities maintenance. We value inventory at the lower of cost or market. Cost is determined using the first-in, first-out and average cost methods. Costs of our raw stockpiles and silica and other industrial sand inventories include production costs and transportation and additional service costs as applicable.

Property, Plant and Mine Development

Property and equipment

Property and equipment is recorded at cost and depreciated over their estimated useful lives. Interest incurred during construction of facilities is capitalized and depreciated over the life of the asset. Depreciable properties, mining properties, and mineral deposits acquired in connection with business acquisitions are recorded at fair market value as of the date of acquisition.

Costs for normal repairs and maintenance that do not extend economic life or improve service potential are expensed as incurred. Costs of improvements that extend economic life or improve service potential are capitalized and depreciated over the estimated remaining useful life.

Depreciation is recorded using the straight-line method over the assets’ estimated useful life as follows: buildings (15 years); land improvements (10 years); machinery & equipment, including computer equipment and software (3-10 years); furniture & fixtures (8 years). Leasehold improvements are depreciated over the shorter of the asset life or lease term. Construction-in-progress is primarily comprised of machinery and equipment, which has not yet been placed in service.

Gains on the sale of assets are included in income when the assets are disposed of provided there is more than reasonable certainty of the collectability of the sales price and any future activities required to be performed by us relating to the disposal of the assets are complete or insignificant. Upon retirement or disposal of assets, all costs and related accumulated depreciation or amortization are written-off.

Depletion and amortization of mineral deposits are recorded as the minerals are extracted, based on units of production and engineering estimates of mineable reserves. The impact of revisions to reserve estimates is recognized on a prospective basis.

We periodically evaluate whether current events or circumstances indicate that the carrying value of our property, plant and equipment assets may not be recoverable. If circumstances indicate that the carrying value may not be recoverable, we estimate future undiscounted net cash flows using estimates of proven and probable sand reserves, estimated future sales prices (considering historical and current prices, price trends and related factors) and operating costs and anticipated capital expenditures. If the undiscounted cash flows are less than the carrying value of the assets, we recognize an impairment loss equal to the amount by which the carrying value exceeds the fair value of the assets.

Mine exploration and development

Mine exploration and development costs include engineering and mineral studies, drilling and other related costs to delineate an ore body, and the removal of overburden to initially expose an ore body for production. Costs incurred before mineralization are classified as proven and probable reserves are expensed and classified as exploration or advanced projects, research and development expense. Capitalization of mine development project costs, that meet the definition of an asset, begins once mineralization is classified as proven and probable reserves.

Drilling and related costs are capitalized for an ore body where proven and probable reserves exist and the activities are directed at obtaining additional information on the ore body or converting non-reserve mineralization to proven and probable reserves and the benefit is expected to be realized over a period beyond one year. All other drilling and related costs are expensed as incurred. Drilling costs incurred during the production phase for operational ore control are allocated to inventory costs and then included as a component of costs applicable to sales.

The cost of removing overburden and waste materials to access the ore body at an open pit mine prior to the production phase are referred to as “pre-stripping costs.” Pre-stripping costs are capitalized during the development of an open pit mine. Where multiple open pits exist at a mining complex utilizing common processing facilities, pre-stripping costs are capitalized at each pit. The removal, production, and sale of de minimis saleable materials may occur during development and are recorded as other income, net of incremental mining and processing costs.

The production phase of an open pit mine commences when saleable minerals, beyond a de minimis amount, are produced. Stripping costs incurred during the production phase of a mine are variable production costs that are included as a component of inventory to be recognized in costs applicable to sales in the same period as the revenue from the sale of inventory.

Mine development costs are amortized using the units-of-production method based on estimated recoverable tons in proven and probable reserves. To the extent that these costs benefit an entire ore body, they are amortized over the estimated life of the ore body. Costs incurred to access specific ore blocks or areas that only provide benefit over the life of that area are amortized over the estimated life of that specific ore block or area.

Mine reclamation costs and asset retirement obligations

We recognize the fair value of any liability for conditional asset retirement obligations, including environmental remediation liabilities when incurred, which is generally upon acquisition, construction or development and/or through the normal operation of the asset, if sufficient information exists to reasonably estimate the fair value of the liability. These obligations generally include the estimated net future costs of dismantling, restoring and reclaiming operating mines and related mine sites, in accordance with federal, state, local regulatory and land lease agreement requirements. The liability is accreted over time through periodic charges to earnings. In addition, the asset retirement cost is capitalized as part of the asset’s carrying value and amortized over the life of the related asset. Reclamation costs are periodically adjusted to reflect changes in the estimated present value resulting from the passage of time and revisions to the estimates of either the timing or amount of the reclamation and abandonment costs. The reclamation obligation is based on when spending for an existing environmental disturbance will occur. If the asset retirement obligation is settled for other than the carrying amount of the liability, a gain or loss is recognized on settlement. We review, on an annual basis, unless otherwise deemed necessary, the reclamation obligation at each mine site in accordance with ASC guidance for accounting reclamation obligations.

Future remediation costs for inactive mines are accrued based on management’s best estimate at the end of each period of the costs expected to be incurred at a site. Such cost estimates include, where applicable, ongoing care, maintenance and monitoring costs. Changes in estimates at inactive mines are reflected in earnings in the period an estimate is revised.

In connection with our annual review of our reclamation obligations, we have determined that some of our estimates required revision due primarily to the additions of new plant and transload facilities and other changes in cost estimates and settlement dates at numerous sites. These additions and changes in estimates resulted in an additional $2.0 million and $2.3 million of asset retirement obligations in 2014 and 2013, respectively.

Our asset retirement obligations are reported in other long-term obligations. The changes in these obligations during the year ending December 31, 2014 and 2013 are as follows:



	2014			2013
Beginning balance	$	9,378		$	6,659
Payments	(782		)	—
Accretion	676			456
Additions and revisions of prior estimates	2,011			2,263
Ending balance	$	11,283		$	9,378

Goodwill and Other Intangible Assets and Related Impairment

Our intangible assets consist of goodwill, which is not being amortized; indefinite lived intangibles, which consist of certain trade names that are not subject to amortization; and customer relationships, which are being amortized on a straight-line basis over their useful life of 20 years. Goodwill represents the excess of purchase price over the fair value of net assets from business acquisitions including the Cadre acquisition in 2014.

Goodwill and other intangible assets with indefinite lives are reviewed for impairment annually as of October 31 or more frequently whenever events or circumstances change that would more likely than not reduce the fair value of those assets. Prior to conducting a formal impairment test, we assess qualitative factors to determine whether the existence of events or circumstances leads to a determination that is more likely than not (more than 50%) that the fair value of a reporting unit is less than its carrying amount. Such qualitative factors may include the following: macroeconomic conditions; industry and market considerations; cost factors; overall financial performance; and other relevant entity-specific events.

If the qualitative assessment determines that an impairment is more likely than not, then the impairment test for goodwill, or other intangible assets with indefinite lives, requires a comparison of the fair value with the carrying amount, including goodwill. If this comparison reflects impairment, then the loss would be measured as the excess of recorded goodwill, or other intangible assets with indefinite lives, over its implied fair value. Implied fair value is the excess of our fair value over the fair value of all recognized and unrecognized assets and liabilities.

The evaluation of goodwill, or other intangible assets with indefinite lives, for possible impairment includes estimating our fair value using discounted cash flows and multiples of cash earnings valuation techniques, plus valuation comparisons to similar businesses. These valuations require us to make estimates and assumptions regarding future operating results, cash flows, changes in working capital and capital expenditures, selling prices, profitability, and the cost of capital. Although we believe that the estimates and assumptions used were reasonable, actual results could differ from those estimates and assumptions. As of December 31, 2014 our qualitative assessment did not indicate that it was more likely than not that an impairment had occurred.

As of December 31, 2014, the gross carrying amount of the customer relationships intangible asset was $9.5 million with accumulated amortization of $2.5 million. We review all finite-lived intangible assets for impairment when circumstances indicate that their carrying amounts may not be recoverable. We evaluate the carrying value of all finite-lived intangible assets for impairment by comparing the expected undiscounted future cash flows of the asset to the net book value of the asset. If the expected undiscounted future cash flows are less than the net book value of the assets, the excess of the net book value over the estimated fair value is recorded in our consolidated statements of operations as impairment loss. Fair value is generally estimated using valuation techniques that consider the discounted cash flows of the asset at rates deemed reasonable for the type of asset and prevailing market conditions, replacement cost, appraisals, including recent similar transactions in the market and if appropriate, current estimated net sales proceeds from pending offers. As of December 31, 2014, the weighted average remaining useful life of our customer relationships was 13.9 years. The estimated annual amortization in each of the next five years is $496.

Debt Issuance Costs

Debt issuance costs consist of loan origination costs, which are being amortized using the effective interest method over the term of the related debt principal. Amortization included in interest expense was $912, $680 and $515 for the years ended December 31, 2014, 2013 and 2012, respectively.

Environmental Costs

Environmental costs, other than qualifying capital expenditures, are accrued at the time the exposure becomes known and costs can be reasonably estimated. Costs are accrued based upon management’s estimates of all direct costs, after taking into account expected reimbursement by third parties (primarily the sellers of acquired businesses), and are reviewed by outside consultants. Environmental costs are charged to expense unless a settlement with an indemnifying party has been reached.

Self-Insurance

We are self-insured for various levels of employee health insurance coverage, workers’ compensation and third party product liability claims alleging occupational disease. We purchase insurance coverage for claim amounts which exceed our self-insured retentions. Depending on the type of insurance, these self-insured retentions range from $100,000 to $500,000 per occurrence.

Our insurance reserves are accrued based on estimates of the ultimate cost of claims expected to occur during the covered period. These estimates are prepared with the assistance of outside actuaries and consultants. Our actuaries periodically review the volume and amount of claims activity, and based upon their findings, we adjust our insurance reserves accordingly. The ultimate cost of claims for a covered period may differ from our original estimates.

The current portion of our self-insurance reserves is included in accrued liabilities and the non-current portion is included in other long-term obligations in our consolidated balance sheets. Our self-insurance reserves totaled $5.7 million and $5.4 million at December 31, 2014 and 2013, respectively. Of these amounts, $1.8 million and $1.7 million, respectively, were classified as current.

Equity-based Compensation

We recognize the cost of employee services rendered in exchange for awards of equity instruments, such as stock options and restricted stock, based on the fair value of those awards at the date of the grant.

Vesting of restricted stock and restricted stock units is based on the individual continuing to render service over a three year vesting schedule. Additionally, we grant performance share units to certain employees in which the number of shares of common stock ultimately received is determined based on achievement of certain performance thresholds or a specified performance period in accordance with the stock award agreement. Cash dividend equivalents are accrued and paid to the holders of time based restricted stock units and restricted stock only after the performance period has lapsed. Cash dividend equivalents are not accrued or paid on performance share units.

The restricted award related compensation expense is recognized, on a straight-line basis, over the vesting period of each separately vesting portion. The fair value of the restricted stock awards is equal to the market price of our stock at date of grant.

The options vest on a vesting schedule and the related compensation expense is recognized over the vesting period of each separately vesting portion, usually over four years. In calculating the compensation expense for options granted, we estimate the fair value of each grant using the Black-Scholes option-pricing model. The weighted-average fair value per share of options granted during the years ended December 31, 2014, 2013 and 2012 was $19.37, $10.03 and $5.68 respectively. The fair value of stock options granted have been calculated based on the exercise price of the option and the following assumptions, which are evaluated and revised, as necessary, to reflect market conditions and experience.



	Weighted-average
	Year ended December 31,
	2014		2013		2012
Risk-free interest rate	1.81%		1.03 – 1.31%		0.83 - 1.05%
Expected volatility	45	%	45	%	45	%
Expected term	6.25 years		6.25 years		6.25 years
Expected dividend yield	1	%	0	%	0	%
Expected forfeiture yield	0	%	0	%	0	%

Since January 31, 2012, the date of our initial public offering, we declared a special dividend of $0.50 per share on December 10, 2012, three quarterly dividends of $0.125 per share during 2013, and four quarterly dividends of $0.125 during 2014. Options issued in 2013 all occurred early in the year before dividends were consistently declared. As a result, the dividend yield assumptions for those and all prior options issued was 0%. For grants during 2014, we believe a dividend yield of 1% is appropriate.

Our expected forfeiture rate is the estimated percentage of options granted that are expected to be forfeited or canceled on an annual basis before becoming fully vested. We have assumed that there will be no forfeitures due to the fact that we do not have adequate historical forfeiture data on which to base the assumption.

Our expected term is the period of time over which the options are expected to remain outstanding. An increase in the expected term will increase compensation expense. The computation of the expected term is based on the simplified method as our stock options are standard options and we have little recent history of exercise data. Under the simplified method, the expected term is presumed to be the mid-point between the average vesting date and the end of the contractual term.

The assumptions for expected volatility are based on historical experience for the same periods as our expected lives. Risk-free interest rates are set using grant-date U.S. Treasury yield curves for the same periods as our expected lives.

Income Taxes

Deferred taxes are provided on the liability method whereby deferred tax assets are recognized for deductible temporary differences and operating loss and tax credit carry forwards and deferred tax liabilities are recognized for taxable temporary differences. This approach requires recognition of deferred tax liabilities and assets for the expected future tax consequences of events that have been included in the financial statements or tax returns. Under this method, deferred tax liabilities and assets are determined based upon the difference between the financial statement and tax basis of assets and liabilities using enacted tax rates in effect for the year in which the expenses are expected to reverse. Valuation allowances are provided if, based on the weight of available evidence, it is more likely than not that some or all of the deferred tax assets will not be realized.

We recognize a tax benefit associated with an uncertain tax position when, in management’s judgment, it is more likely than not that the position will be sustained upon examination by a taxing authority. For a tax position that meets the more-likely-than-not recognition threshold, we initially and subsequently measure the tax benefit as the largest amount that it judges to have a greater than 50% likelihood of being realized upon ultimate settlement with a taxing authority. The liability associated with unrecognized tax benefits is adjusted periodically due to changing circumstances, such as the progress of tax audits, case law developments and new or emerging legislation. Such adjustments are recognized entirely in the period in which they are identified. The effective tax rate includes the net impact of changes in the liability for unrecognized tax benefits and subsequent adjustments as considered appropriate by management.

The largest permanent item in computing both our effective tax rate and taxable income is the deduction allowed for statutory depletion. The impact of statutory depletion on the effective tax rate is presented in Note Q - Income Taxes. The deduction for statutory depletion does not necessarily change proportionately to changes in income before income taxes.

Earnings per Share

Basic and diluted earnings per share is presented for net income. Basic earnings per share is computed by dividing income available to common stockholders by the weighted-average number of outstanding common shares for the period. Diluted earnings per share reflects the potential dilution that could occur if securities or other contracts that may require the issuance of common shares in the future were converted. Diluted earnings per share is computed by increasing the weighted-average number of outstanding common shares to include the additional common shares that would be outstanding after conversion and adjusting net income for changes that would result from the conversion. Only those securities or other contracts that result in a reduction in earnings per share are included in the calculation.

Comprehensive Income

In addition to net income, comprehensive income (loss) includes all changes in equity during a period, such as adjustments to minimum pension liabilities, unrealized gain or loss on our short term investments and the effective portion of changes in fair value of derivative instruments that qualify as cash flow hedges.

Short-Term Investments

Our short-term investments consist of fixed income securities that have been classified and accounted for as available-for-sale. We determine the appropriate classification of our investments at the time of purchase and reevaluate the designations at each balance sheet date. We classify these securities as either short-term or long-term based on each instrument’s underlying contractual maturity date. Fixed income securities with maturities of 12 months or less are classified as short-term and fixed income securities with maturities greater than 12 months are classified as long-term. These investments are carried at fair value, with the unrealized gains and losses, net of taxes, reported as a separate component of accumulated other comprehensive income. The cost of securities sold is based upon the specific identification method.

We typically invest in highly-rated securities, and our investment policy generally limits the amount of credit exposure to any one issuer. The policy requires investments generally to be investment grade, with the primary objective of minimizing the potential risk of principal loss. Fair values were determined for each individual security in the investment portfolio. When evaluating an investment for other-than-temporary impairment, we review factors such as the length of time and extent to which fair value has been below its cost basis, the financial condition of the issuer and any changes thereto, changes in market interest rates, and our intent to sell, or whether it is more likely than not we will be required to sell, the investment before recovery of the investment’s cost basis. As of December 31, 2014, and 2013, we considered any losses in our short-term investment portfolio to be temporary in nature and did not consider any of our investments other-than-temporarily impaired.

Financial Instruments

We currently use interest rate hedge agreements and have historically utilized natural gas hedge agreements to manage interest and energy costs and the risk associated with changing interest rates and natural gas prices. Amounts to be paid or received under these hedge agreements are accrued as interest rates or natural gas prices change and are recognized over the life of the hedge agreements as an adjustment to interest expense or, in the case of natural gas, cost of goods sold. Our policy is to not hold or issue derivative financial instruments for trading or speculative purposes. When entered into, these financial instruments are designated as hedges of underlying exposures, associated with our long-term debt and energy costs, and are monitored to determine if they remain effective hedges. Gains and losses on derivatives designated as cash flow hedges are recorded in other comprehensive income net of tax and reclassified to earnings in a manner that matches the timing of the earnings impact of the hedged transactions. The ineffective portion of all hedges, if any, is recognized currently in income. Additional disclosures for derivative instruments are presented in Note N to these financial statements.

Recently Adopted Accounting Pronouncements

In May 2014, the Financial Accounting Standards Board ("FASB") issued an ASU 2014-08, Revenue from Contracts with Customers, which supersedes previous revenue recognition guidance. The new standard requires that a company recognize revenue when it transfers promised goods or services to customers in an amount that reflects the consideration the company expects to receive in exchange for those goods or services. Companies will need to use more judgment and estimates than under the guidance currently in effect, including estimating the amount of variable revenue to recognize over each identified performance obligation. Additional disclosures will be required to help users of financial statements understand the nature, amount and timing of revenue and cash flows arising from contracts. The new standard will become effective beginning with the first quarter 2017 and can be adopted either retrospectively to each prior reporting period presented or as a cumulative effect adjustment as of the date of adoption. We are currently evaluating the impact of adopting this new guidance on the consolidated financial statements.

- Definition

The entire disclosure for all significant accounting policies of the reporting entity.

+ References+ Details

Earnings Per Share

12 Months Ended

Dec. 31, 2014

Earnings Per Share [Abstract]

Earnings Per Share

EARNINGS PER SHARE

Basic earnings per common share is computed by dividing income available to common stockholders by the weighted average number of common shares outstanding for the period. Diluted earnings per common share is computed similarly to basic earnings per common share except that the weighted average number of common shares outstanding is increased to include the number of additional common shares that would have been outstanding if the potentially dilutive common shares had been issued. In accordance with the applicable accounting guidance for calculating earnings per share, we did not include in our calculation of diluted earnings per share for the applicable periods stock options where the exercise prices were greater than the average market prices.



	For the Year Ended December 31,
	2014			2013			2012
Net income	$	121,540		$	75,256		$	79,154
Less: net income allocated to outstanding restricted stockholders	(230		)	(175		)	(105		)
Net income allocated to common stockholders	$	121,310		$	75,081		$	79,049
Weighted-average common stock
Outstanding	53,719			53,035			52,592
Outstanding assuming dilution	54,296			53,409			52,641

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



	For the Year Ended December 31,
	2014	2013	2012
Weighted-average outstanding stock options excluded	33	175	1,070

- Definition

The entire disclosure for earnings per share.

+ References+ Details

Capital Structure and Accumulated Comprehensive Income

12 Months Ended

Dec. 31, 2014

Equity [Abstract]

Capital Structure and Accumulated Comprehensive Income

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. There were 53,902,475 shares of common stock issued and outstanding at December 31, 2014. As of December 31, 2013, there were 53,492,278 shares issued and outstanding.

In 2014, our Board of Directors declared quarterly cash dividends as follows:



Dividends per Common Share		Declaration Date	Record Date	Payable Date
$	0.125	February 6, 2014	March 14, 2014	April 1, 2014
$	0.125	April 25, 2014	June 13, 2014	July 3, 2014
$	0.125	July 25, 2014	September 15, 2014	October 3, 2014
$	0.125	October 24, 2014	December 15, 2014	January 5, 2015

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 and to fix the preferences, powers and relative, participating, optional or other special rights and 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 are no shares of preferred stock issued or outstanding at December 31, 2014 and 2013. At present, we have no plans to issue any preferred stock.

Share Repurchase Program

We are authorized by our Board of Directors to repurchase shares of our outstanding common stock on the open market or in privately negotiated transactions. As of December 31, 2014, we are authorized to repurchase up to $50 million of our common stock through December 11, 2015. Stock repurchases 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 December 31, 2014, we have repurchased 118,961 shares of our common stock at an average price of $13.21 and are authorized to repurchase up to an additional $48.4 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 by component during the year ended December 31, 2014:



	For the Year Ended December 31, 2014
	Unrealized gain/(loss) on cash flow hedges			Unrealized gain/(loss) on short-term investments			Pension and other post- retirement benefits liability			Total
Beginning Balance	$	(79	)	$	(27	)	$	(3,911	)	$	(4,017	)
Other comprehensive income (loss) before reclassifications	(65		)	(14		)	(16,388		)	(16,467		)
Amounts reclassed from accumulated other comprehensive income	10			—			656			666
Ending Balance	$	(134	)	$	(41	)	$	(19,643	)	$	(19,818	)

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

- Definition

The entire disclosure for shareholders' equity comprised of portions attributable to the parent entity and noncontrolling interest, including other comprehensive income. Includes, but is not limited to, balances of common stock, preferred stock, additional paid-in capital, other capital and retained earnings, accumulated balance for each classification of other comprehensive income and amount of comprehensive income.

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+ Details

Business Combinations

12 Months Ended

Dec. 31, 2014

Business Combinations [Abstract]

Business Combinations

BUSINESS COMBINATIONS

On July 31, 2014, we completed our acquisition of Cadre, a regional sand mining company based in Voca, Texas, for approximately $98.3 million in cash.

The acquisition of Cadre resulted in goodwill of approximately $0.2 million, none of which is deductible for tax purposes. This amount represents the residual amount of the total purchase price after allocation to the assets acquired and liabilities assumed.

The table below represents the tangible and identifiable intangible assets and liabilities based on management’s assessment of the acquisition date fair value of the assets acquired and liabilities assumed:



Accounts receivable	$	6,898
Inventory	2,534
Other current assets	174
Fixed assets (net)	73,138
Deferred tax assets (net)	13,966
Accounts payable, accrued expenses and other liabilities	(4,389		)
Net tangible assets acquired	92,321
Customer relationships	1,274
Trade name	4,478
Goodwill	244
Preliminary purchase price, net of cash acquired	$	98,317

The following table summarizes the allocation of identifiable intangible assets resulting from the acquisition:



	Useful Lives	Value
Customer relationships	15 years	$	1,274
Trade name	Indefinite	4,478
Total intangible assets		$	5,752

Pro Forma Adjusted Summary

The results of Cadre’s operations have been included in the consolidated financial statements subsequent to the acquisition date.

The following unaudited pro forma consolidated financial information reflects the combined results of operations as if the Cadre acquisition had occurred on January 1, 2012, 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):



	For the Year Ended December 31,
	2014		2013		2012
Sales	$	901,916	$	578,453	$	481,100
Net income	$	126,960	$	76,942	$	82,782
Basic earnings per share	$	2.36	$	1.45	$	1.57
Diluted earnings per share	$	2.33	$	1.44	$	1.57

- 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).

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+ Details

Accounts Receivable

12 Months Ended

Dec. 31, 2014

Receivables [Abstract]

Accounts Receivable

ACCOUNTS RECEIVABLE

At December 31, 2014 and 2013, accounts receivable consisted of the following:



	At December 31,
	2014			2013
Trade receivables	$	128,498		$	76,223
Less: Allowance for doubtful accounts	(10,429		)	(2,376		)
Net trade receivables	118,069			73,847
Other receivables	2,812			1,360
Total accounts receivable	$	120,881		$	75,207

The increase of $44.2 million in trade receivables is mainly driven by the sales increase for the year ended December 31, 2014.

Changes in our allowance for doubtful accounts during the years ended December 31, 2014 and 2013 are as follows:



	Allowance for Doubtful Accounts
	2014			2013
Balance at January 1,	$	2,376		$	1,053
Bad debt provision	10,200			1,330
Write-offs	(2,147		)	(7		)
Balance at December 31,	$	10,429		$	2,376

- Definition

The entire disclosure for claims held for amounts due a entity, excluding financing receivables. Examples include, but are not limited to, trade accounts receivables, notes receivables, loans receivables. Includes disclosure for allowance for credit losses.

+ References+ Details

Inventories

12 Months Ended

Dec. 31, 2014

Inventory Disclosure [Abstract]

Inventories

INVENTORIES

At December 31, 2014 and 2013, inventories consisted of the following:



	At December 31,
	2014		2013
Supplies	$	17,528	$	15,576
Raw materials and work in process	12,562		11,728
Finished goods	36,622		36,908
Total inventories	$	66,712	$	64,212

- Definition

The entire disclosure for inventory. This may include, but is not limited to, the basis of stating inventory, the method of determining inventory cost, the major classes of inventory, and the nature of the cost elements included in inventory. If inventory is stated above cost, accrued net losses on firm purchase commitments for inventory and losses resulting from valuing inventory at the lower-of-cost-or-market may also be included. For LIFO inventory, may disclose the amount and basis for determining the excess of replacement or current cost over stated LIFO value and the effects of a LIFO quantities liquidation that impacts net income.

+ References+ Details

Property, Plant and Mine Development

12 Months Ended

Dec. 31, 2014

Property, Plant and Equipment [Abstract]

Property, Plant and Mine Development

PROPERTY, PLANT AND MINE DEVELOPMENT

At December 31, 2014 and 2013, property, plant and mine development consisted of the following:



	At December 31,
	2014			2013
Mining property and mine development	$	197,824		$	164,609
Asset retirement cost	9,559			7,275
Land	28,443			25,738
Land improvements	35,322			31,093
Buildings	47,149			36,311
Machinery and equipment	323,618			263,304
Furniture and fixtures	1,599			1,131
Construction-in-progress	78,997			25,974
	722,511			555,435
Accumulated depletion, depreciation and amortization	(156,756		)	(113,319		)
Total property, plant and mine development, net	$	565,755		$	442,116

The property, plant and mine development balances for December 31, 2014 include additions from the Cadre acquisition described in Note E - Business Combinations.

The amount of interest costs capitalized in property, plant and equipment was $1,376, $533 and $934 for the year ended December 31, 2014, 2013 and 2012, respectively. As of December 31, 2014, we hold no assets under a capital lease obligation.

- Definition

The entire disclosure for long-lived, physical assets used in the normal conduct of business and not intended for resale. Includes, but is not limited to, accounting policies and methodology, roll forwards, depreciation, depletion and amortization expense, including composite depreciation, accumulated depreciation, depletion and amortization expense, useful lives and method used, income statement disclosures, assets held for sale and public utility disclosures.

+ References+ Details

Accrued Liabilities

12 Months Ended

Dec. 31, 2014

Payables and Accruals [Abstract]

Accrued Liabilities

ACCRUED LIABILITIES

At December 31, 2014 and 2013, accrued liabilities consisted of the following:



	At December 31,
	2014		2013
Accrued salaries and wages	$	3,144	$	2,411
Accrued vacation liability	2,616		2,396
Current portion of liability for pension and post-retirement benefits	1,530		1,428
Accrued healthcare liability	1,745		1,662
Accrued property taxes and sales taxes	2,737		1,421
Other accrued liabilities	6,139		1,505
Total accrued liabilities	$	17,911	$	10,823

Other accrued liabilities consist of accrued transportation and related costs, customer rebates, royalties payable, and other items.

Debt

12 Months Ended

Dec. 31, 2014

Debt Disclosure [Abstract]

Debt

DEBT

At December 31, 2014 and 2013, debt consisted of the following:



	December 31, 2014			December 31, 2013
Senior secured credit facility:
Revolver expiring July 23, 2018 (4.75% at December 31, 2014 and December 31, 2013)	$	—		$	—
Term loan facility—final maturity July 23, 2020 (4% - 5.25% at December 31, 2014 and 4% at December 31, 2013), net of unamortized original issue discount of $2,078 and $1,674, respectively	502,297			371,451
Total debt	502,297			371,451
Less: current portion	(4,718		)	(3,488		)
Total long-term portion of debt	$	497,579		$	367,963

Revolving Line-of-Credit

We have a $50 million revolving line-of-credit (the "Revolver"), with zero drawn and $3.2 million allocated for letters of credit as of December 31, 2014, leaving $46.8 million available for general corporate use under the Revolver.

Debt Maturities

At December 31, 2014, contractual maturities of long-term debt are as follows:



2015	$	4,718
2016	4,722
2017	4,725
2018	4,729
2019	4,733
Thereafter	478,670
	$	502,297

On January 31, 2012, we amended our senior secured term loan facility (the “Term Loan”). The primary revisions to the Term Loan were to eliminate a requirement to provide monthly financial reports, to remove financial covenant restrictions related to capital expenditures, to provide flexibility to make investments and acquisitions and to incur indebtedness, and to provide a new subsidiary guarantee from Coated Sand Solutions, LLC.

On December 31, 2012, we amended our then existing revolving line-of-credit. The primary revisions were to include an increase of the commitment under the revolving line-of-credit from $35 million to $50 million, and the letter of credit sublimit from $15 million to $20 million; provided, however, that the aggregate principal amount of the loans and letters of credit obligations outstanding at any one time shall not exceed the borrowing base as calculated pursuant to the agreement. The amendment also extended the termination date of the revolving line-of-credit from October 31, 2015 to October 31, 2016, reduced prices and fees on borrowings, letters of credit and unused commitments and added an additional subsidiary, Coated Sand Solutions, LLC, as a co-borrower.

On July 23, 2013, we refinanced our existing senior secured debt by amending our Term Loan and replacing our existing revolving line-of-credit. The Term Loan amendment refinanced our existing senior debt by entering into a new $425 million senior secured credit facility, consisting of a $375 million Term Loan and the $50 million Revolver that may also be used for swingline loans (up to $5 million) or letters of credit (up to $20 million). The Term Loan amendment also, among other things, removed and amended certain financial and other covenants to provide additional operating flexibility, and lowered interest rates on borrowed amounts. The existing revolving line-of-credit was terminated. The Term Loan will expire on July 23, 2020 and the Revolver will expire on July 23, 2018. As a result of refinancing our Term Loan and replacing our revolving line-of-credit, we expensed $1.8 million of costs, consisting of $1.3 million related to third party fees in selling, general, and administrative expenses and $0.5 million related to early extinguishment of debt.

On December 5, 2014, we further increased our Term Loan by an additional $135 million to a total of approximately $502 million in accordance with the incremental borrowing feature in our senior secured credit facility.

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 December 31, 2014 and December 31, 2013, we are in compliance with all covenants in accordance with our senior secured credit facility.

- Definition

The entire disclosure for information about short-term and long-term debt arrangements, which includes amounts of borrowings under each line of credit, note payable, commercial paper issue, bonds indenture, debenture issue, own-share lending arrangements and any other contractual agreement to repay funds, and about the underlying arrangements, rationale for a classification as long-term, including repayment terms, interest rates, collateral provided, restrictions on use of assets and activities, whether or not in compliance with debt covenants, and other matters important to users of the financial statements, such as the effects of refinancing and noncompliance with debt covenants.

+ References+ Details

Deferred Revenue	12 Months Ended
Deferred Revenue	Dec. 31, 2014
Deferred Revenue Disclosure [Abstract]
Deferred Revenue	DEFERRED REVENUE On July 3, 2014, we received an advance of $100 million from a customer under a supply agreement which gives the customer the right to purchase certain products for a fixed price at certain volumes. The customer has an unsecured promissory note related to this deposit, which has been recorded as deferred revenue in the Balance Sheets. The unused portion of the deposit has a stated interest rate of 4.9% compounded quarterly. The deposit obligation and related interest are reduced as shipments occur with a portion of the sales price being received in cash and a smaller noncash portion reducing first any accrued interest and then, to the extent available, any outstanding deposit. We can, through December 31, 2019, repay the unused deposit obligation at any time without penalty.

Fair Value Accounting

12 Months Ended

Dec. 31, 2014

Fair Value Disclosures [Abstract]

Fair Value Accounting

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, quote prices for identical or similar assets or liabilities in inactive markets, or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the assets or liabilities.

Level 3—Inputs that are generally unobservable and typically reflect management’s estimate of assumptions that market participants would use in pricing the asset or liability.

Cash equivalents

Due to the short-term maturity, we believe our cash equivalent instruments at December 31, 2014 and 2013 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, approximates their carrying values and 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 with Level 2 of the fair value hierarchy, the credit valuation adjustments associated with our derivatives utilize Level 3 inputs, such as estimates of current credit spreads to evaluate the likelihood of default of ourselves and our counterparties. However, as of December 31, 2014, 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 December 31, 2014 and 2013, respectively, of those assets that we measure at fair value on a recurring basis:



	December 31, 2014						December 31, 2013
	Level 1		Level 2		Total		Level 1		Level 2		Total
Short-term investments	$	666	$	74,477	$	75,143	$	622	$	74,358	$	74,980
Interest rate derivatives	—		5		5		—		109		109
Net asset	$	666	$	74,482	$	75,148	$	622	$	74,467	$	75,089

- 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

Short-Term Investments

12 Months Ended

Dec. 31, 2014

Investments, Debt and Equity Securities [Abstract]

Short-Term Investments

SHORT-TERM INVESTMENTS

We have segregated funds into designated accounts with investment brokers who manage our short-term investment portfolio. Those funds are held on an available-for-sale basis and are therefore reported at fair value on the balance sheet.

The following table summarizes our available-for-sale short-term investments:



	Aggregate Cost		Gross Unrealized Gains		Gross Unrealized Losses			Fair Value
December 31, 2013
Money market mutual funds	$	622	$	—	$	—		$	622
Fixed income securities:
Certificates of deposit	25,218		—		(34		)	25,184
Commercial paper	15,168		4		(1		)	15,171
Corporate notes and bonds	9,495		—		(9		)	9,486
Government agencies	13,979		6		—			13,985
U.S. Treasuries	4,828		—		(10		)	4,818
Variable Rate Demand Obligations	5,714		—		—			5,714
Total available-for-sale investments	$	75,024	$	10	$	(54	)	$	74,980

December 31, 2014
Money market mutual funds	$	666	$	—	$	—		$	666
Fixed income securities:
Certificates of deposit	29,233		—		(23		)	29,210
Commercial paper	10,187		7		(2		)	10,192
Corporate notes and bonds	12,076		—		(29		)	12,047
Government agencies	16,681		4		(17		)	16,668
U.S. Treasuries	2,151		—		(4		)	2,147
Variable Rate Demand Obligations	4,213		—		—			4,213
Total available-for-sale investments	$	75,207	$	11	$	(75	)	$	75,143

- Definition

The entire disclosure for investments in certain debt and equity securities.

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Derivative Instruments

12 Months Ended

Dec. 31, 2014

Derivative Instruments and Hedging Activities Disclosure [Abstract]

Derivative Instruments

DERIVATIVE INSTRUMENTS

Cash Flow Hedges of Interest Rate Risk

We enter into interest rate cap agreements in connection with the Term Loan to add stability to interest expense and to manage our exposure to interest rate movements. Interest rate caps designated as cash flow hedges involve the receipt of variable-rate amounts from a counterparty if interest rates rise above the strike rate on the contract in exchange for an upfront premium.

The following table summarizes the fair value of our derivative instruments. See Note L - Fair Value Accounting for additional disclosures regarding the estimated fair values of our derivative instruments at December 31, 2014, and 2013.



		December 31, 2014							December 31, 2013
	Maturity Date	Contract/Notional Amount			Carrying Amount		Fair Value		Contract/Notional Amount			Carrying Amount		Fair Value
Interest rate cap agreement(1)	2016	$	188	million	$	5	$	5	$	188	million	$	109	$	109


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

We have designated these contracts as qualified cash flow hedges. Accordingly, the effective portion of the gain or loss on the derivative instrument is reported as a component of other comprehensive income and recognized in earnings in the same period or periods during which the hedged transaction affects earnings. During the year ended December 31, 2014 and 2013, we had no ineffectiveness for such contracts.

The following table summarizes the effect of derivatives instruments on our income statements and our consolidated statements of comprehensive income for the years ended December 31, 2014, 2013 and 2012.



	2014			2013			2012
Deferred losses from derivatives in OCI, beginning of period	$	(79	)	$	(182	)	$	(409	)
Loss recognized in OCI from derivative instruments	(65		)	(82		)	—
Loss reclassified from Accumulated OCI	10			185			227
Deferred losses from derivatives in OCI, end of period	$	(134	)	$	(79	)	$	(182	)

- Definition

The entire disclosure for derivative instruments and hedging activities including, but not limited to, risk management strategies, non-hedging derivative instruments, assets, liabilities, revenue and expenses, and methodologies and assumptions used in determining the amounts.

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-Subparagraph (SX 210.4-08.(n))

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+ Details

Equity-Based Compensation

12 Months Ended

Dec. 31, 2014

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

Equity-Based Compensation

EQUITY-BASED COMPENSATION

During 2009, the board of directors of our then parent company, GGC USS Holdings, LLC, approved, and the parent company implemented, a management equity program (the “Equity Program”). The Equity Program granted Class C and Class D member units in the then parent company, GGC USS Holdings, LLC, to three members of executive management. As of December 31, 2014, all Class C and Class D equity units were fully vested.

The Class C units vested ratably over five years. These units have no exercise price and as such the fair value of the incentive units is equal to the fair value of the underlying equity units. The Class D units were fully vested upon grant in 2009. During 2013, the vesting of 210,333 Class C equity units was accelerated, resulting in a total vesting for the year of 420,667. Even though the equity was granted at the former parent company level, we recognized compensation expense related to Class C equity incentive units of $91 and $109 in the years ended December 31, 2014 and 2013 respectively. All Class C units were vested by December 31, 2013. There was no activity related to the Class C units and no expenses incurred during the year ended December 31, 2014.

In July 2011, we adopted the U.S. Silica Holdings, Inc. 2011 Incentive Compensation Plan (the “2011 Plan”), which provides for grants of stock options, stock appreciation rights, restricted stock and other incentive-based awards. We believe our 2011 Plan aligns the interests of our employees and directors with those of our common stockholders. At December 31, 2014, we have 5,740,961 shares of common stock which may be issued under the 2011 Plan.

Stock Options

The following table summarizes the status of and changes in our stock option grants during the year ended December 31, 2014:



	Number of Shares		Weighted Average Exercise Price		Weighted Average Remaining Contractual Term in Years
Outstanding at December 31, 2013	1,231,540		$	15.01
Granted	206,400		49.39
Exercised	(389,264	)	14.29
Forfeited	(65,622	)	16.46
Outstanding at December 31, 2014	983,054		22.42		7.78
Exercisable at December 31, 2014	273,752		$	15.25	7.09

The total intrinsic value of stock options exercised was $10.9 million, $5.9 million and $0.1 million for the years ended December 31, 2014, 2013 and 2012 respectively. Cash received from options exercised in 2014 was $5.6 million. The actual tax benefit realized for the tax deductions from option exercises totaled $4.2 million, $2.3 million, and $0.02 million for the years ended December 31, 2014, 2013 and 2012, respectively.

We recognized $1.9 million, $2.0 million , and $2.2 million of equity-based compensation expense related to these options during the years ended December 31, 2014, 2013 and 2012, respectively. As of December 31, 2014, there was $5.9 million of total unrecognized compensation expense related to these options, which is expected to be recognized over a weighted-average period of approximately 3.1 years.

Restricted Awards

The following table summarizes the status of and changes in our unvested restricted stock awards during the year ended December 31, 2014:



	Number of Shares		Grant Date Weighted Average Fair Value
Unvested, December 31, 2013	228,403		$	20.95
Granted	204,786		31.31
Vested	(51,866	)	20.62
Forfeited	(573	)	35.26
Unvested, December 31, 2014	380,750		$	26.55

We recognized $5.5 million, $1.0 million and $0.1 million of equity-based compensation expense related to these restricted stock awards during the years ended December 31, 2014, 2013 and 2012 respectively. As of December 31, 2014, there was $7.0 million of total unrecognized compensation expense related to these restricted stock awards, which is expected to be recognized over a period of 1.7 years.

- Definition

The entire disclosure for compensation-related costs for equity-based compensation, which may include disclosure of policies, compensation plan details, allocation of equity compensation, incentive distributions, equity-based arrangements to obtain goods and services, deferred compensation arrangements, employee stock ownership plan details and employee stock purchase plan details.

+ References+ Details

Commitments and Contingencies

12 Months Ended

Dec. 31, 2014

Commitments and Contingencies Disclosure [Abstract]

Commitments and Contingencies

COMMITMENTS AND CONTINGENCIES

Future Minimum Annual Commitments at December 31, 2014:



Year ending December 31,	Operating Leases		Minimum Purchase Commitments
2015	$	32,178	$	30,635
2016	29,895		22,373
2017	27,496		17,012
2018	26,001		12,895
2019	19,312		6,601
Thereafter	38,522		16,000
Total future lease commitments	$	173,404	$	105,516

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 for the years ended December 31, 2014, 2013 and 2012 totaled approximately $32.6 million, $16.3 million and $11.9 million, respectively. As of December 31, 2014, we have no obligations under a capital lease.

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. U.S. Silica was named as a defendant in one claim filed during the year ended December 31, 2014, three filed in 2013 and two filed in 2012. U.S. Silica has been named as a defendant in similar suits since 1975. As of December 31, 2014, there were 86 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.

For periods prior to 1986, U.S. Silica had numerous insurance policies and an indemnity from a former owner that covered silicosis claims. In the fourth quarter of 2012, U.S. Silica settled all rights under the indemnity and its underlying insurance policies receiving $5.1 million from the parties involved. As a result of the settlement, the indemnity and related policies are no longer available to U.S. Silica and U.S. Silica will not seek reimbursement for any defense costs or claim payments. Other insurance policies, however, continue to remain available to U.S. Silica.

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 December 31, 2014 and 2013, other non-current assets included $311 and $313, respectively, for insurance for third-party products liability claims and other long-term obligations included $1.6 million and $1.6 million, respectively, in third-party products claims liability. Based on decreases in the actual claims filed during the periods along with decreases in the estimated future product liability claims and their related costs, as well as the aforementioned settlement, we recorded pre-tax adjustments to selling, general and administrative expenses related to silica claims (including a $0.2 million loss in 2014, $0.5 million loss in 2013, and a $3.4 million gain in 2012).

- Definition

The entire disclosure for commitments and contingencies.

+ References+ Details

Income Taxes

12 Months Ended

Dec. 31, 2014

Income Tax Disclosure [Abstract]

Income Taxes

INCOME TAXES

We evaluate our deferred tax assets periodically to determine if valuation allowances are required. Ultimately, the realization of deferred tax assets is dependent upon generation of future taxable income during those periods in which temporary differences become deductible and/or credits can be utilized. To this end, management considers the level of historical taxable income, the scheduled reversal of deferred tax liabilities, tax-planning strategies and projected future taxable income. Based on these considerations, and the carry-forward availability of a portion of the deferred tax assets, management believes it is more likely than not that we will realize the benefit of the deferred tax assets.

The (expense) benefit for income taxes consisted of the following for the years ended December 31, 2014, 2013 and 2012:



	Years Ended December 31,
	2014			2013			2012
Current:
Federal	$	(34,790	)	$	(20,819	)	$	(22,165	)
State	(4,835		)	(1,831		)	(6,237		)
	(39,625		)	(22,650		)	(28,402		)
Deferred:
Federal	(308		)	1,453			(3,645		)
State	2,750			436			1,396
	2,442			1,889			(2,249		)
Income tax expense	$	(37,183	)	$	(20,761	)	$	(30,651	)

Deferred tax assets and liabilities are recognized for the estimated future tax effects, based on enacted tax laws, of temporary differences between the values of assets and liabilities recorded for financial reporting and for tax purposes and of net operating loss and other carry forwards.

The tax effects of the types of temporary differences and carry forwards that gave rise to deferred tax assets and liabilities at December 31, 2014 and 2013 consisted of the following:



	At December 31,
	2014			2013
Gross deferred tax assets:
State tax credits and net operating loss carry forward	$	25,042		$	1,007
Pension and post-retirement benefit costs	24,788			15,579
Alternative minimum tax credit carry forward	18,819			22,528
Property, plant and equipment	6,580			6,109
Accrued expenses	8,237			3,818
Inventories	5,366			5,863
Third-party products liability	636			674
Stock-based compensation expense	3,019			1,306
Other	8,457			5,502
Total deferred tax assets	$	100,944		$	62,386
Gross deferred tax liabilities:
Land and mineral property basis difference	$	(65,217	)	$	(61,366	)
Fixed assets and depreciation	(53,383		)	(47,016		)
Intangible assets	(8,587		)	(6,788		)
Other	(1,211		)	(797		)
Total deferred tax liabilities	(128,398		)	(115,967		)
Net deferred tax liabilities	(27,454		)	(53,581		)
Less: Net current deferred tax assets	22,295			17,737
Net long-term deferred tax liabilities	$	(49,749	)	$	(71,318	)

As a result of the Cadre acquisition, we have federal net operating loss carry forwards of approximately $69.0 million at December 31, 2014. The losses will expire in years 2027 through 2033. The losses are subject to an annual limitation under Internal Revenue Code Section 382, but are expected to be fully realized.

December 31, 2014 and 2013, we have an alternative minimum tax credit carry forward of approximately $18.8 million and $22.5 million, respectively. The credit carry forward may be carried forward indefinitely to offset any excess of regular tax liability over alternative minimum tax liability subject to certain limitations.

Ultimately, the realization of deferred tax assets is dependent upon generation of future taxable income during those periods in which temporary differences become deductible and/or credits can be utilized. To this end, management considers the level of historical taxable income, the scheduled reversal of deferred tax liabilities, tax-planning strategies and projected future taxable income. Based on these considerations, and the carry-forward availability of a portion of the deferred tax assets, management believes it is more likely than not that we will realize the benefit of the deferred tax assets.

At the end of each reporting period as presented, there were no material amounts of interest and penalties recognized in the statement of operations or balance sheets. We have no material unrecognized tax benefits or any known material tax contingencies at December 31, 2014 or December 31, 2013 and does not expect this to change significantly within the next twelve months. Tax returns filed with the IRS for the years 2011 through 2013 along with tax returns filed with numerous state entities remain subject to examination.

Excess tax benefits from equity-based compensation are credited to stockholders’ equity. The excess tax benefits credited to stockholders’ equity were $3.8 million and $1.4 million for the years ended December 31, 2014 and December 31, 2013, respectively. There were no excess tax benefits for the year ended December 31, 2012.

The effective income tax rate on pretax earnings differed from the U.S. federal statutory rate for the years ended December 31, 2014, 2013 and 2012 for the following reasons:



	Years Ended December 31,
	2014		2013		2012
(Expense) benefit computed at U.S. federal statutory rate	(35.0	)%	(35.0	)%	(35.0	)%
Decrease (increase) resulting from:
Statutory depletion	9.8		11.0		9.9
Prior year tax return reconciliation	0.6		1.9		(0.5	)
State income taxes, net of federal benefit	(2.1	)	(2.4	)	(2.7	)
Domestic production deduction	2.5		2.4		0.7
Equity-based compensation	—		—		(0.1	)
Other, net	0.8		0.5		(0.2	)
Income tax (expense) benefit	(23.4	)%	(21.6	)%	(27.9	)%

The largest permanent item in computing both our effective tax rate and taxable income is the deduction allowed for statutory depletion. The deduction for statutory depletion does not necessarily change proportionately to changes in income before income taxes.

- Definition

The entire disclosure for income taxes. Disclosures may include net deferred tax liability or asset recognized in an enterprise's statement of financial position, net change during the year in the total valuation allowance, approximate tax effect of each type of temporary difference and carryforward that gives rise to a significant portion of deferred tax liabilities and deferred tax assets, utilization of a tax carryback, and tax uncertainties information.

+ References+ Details

Pension and Post-Retirement Benefits

12 Months Ended

Dec. 31, 2014

Compensation and Retirement Disclosure [Abstract]

Pension and Post-Retirement Benefits

PENSION AND POST-RETIREMENT BENEFITS

We maintain a single-employer noncontributory defined benefit pension plan covering certain employees. There have been no new entrants to the plan since May 2009 when the plan was frozen to all new employees. The plan provides benefits based on each covered employee’s years of qualifying service. Our funding policy is to contribute amounts within the range of the minimum required and maximum deductible contributions for the plan consistent with a goal of appropriate minimization of the unfunded projected benefit obligation. The pension plan uses a benefit level per year of service for covered hourly employees and a final average pay method for covered salaried employees. The plan uses the projected unit credit cost method to determine the actuarial valuation.

We employ a total rate of return investment approach whereby a mix of equities and fixed income investments are used to maximize the long-term return of plan assets for a prudent level of risk. Risk tolerance is established through careful consideration of plan liabilities, plan funded status, and corporate financial condition. The investment portfolio contains a diversified blend of equity and fixed-income investments. Furthermore, equity investments are diversified across U.S. and non-U.S. stocks, as well as growth, value and small and large capitalizations. Investment risk is measured and monitored on an ongoing basis through quarterly investment portfolio reviews, annual liability measurements, and periodic asset/liability studies.

We employ a building block approach in determining the long-term rate of return for plan assets. Historical markets are studied and long-term historical relationships between equities and fixed-income are preserved consistent with the widely accepted capital market principle that assets with higher volatility generate a greater return over the long run. Current market factors such as inflation and interest rates are evaluated before long-term capital market assumptions are determined. The long-term portfolio return is established via a building block approach with proper consideration of diversification and rebalancing. Peer data and historical returns are reviewed to check for reasonability and appropriateness.

In addition, we provide defined benefit post-retirement healthcare and life insurance benefits to some employees. Covered employees become eligible for these benefits at retirement after meeting minimum age and service requirements. The projected future cost of providing post-retirement benefits, such as healthcare and life insurance, is recognized as an expense as employees render services.

We contribute to a Voluntary Employees’ Beneficiary Association trust that will be used to partially fund health care benefits for future retirees. Benefits are funded to the extent contributions are tax deductible, which under current legislation is limited. In general, retiree health benefits are paid as covered expenses are incurred.

Net pension benefit cost consisted of the following for the years ended December 31, 2014, 2013 and 2012:



	Years Ended December 31,
	2014			2013			2012
Service cost—benefits earned during the period	$	1,080		$	1,280		$	1,118
Interest cost	4,811			4,198			4,734
Expected return on plan assets	(5,146		)	(5,061		)	(5,381		)
Net amortization and deferral	1,037			1,904			1,105
Net pension benefit costs	$	1,782		$	2,321		$	1,576

Net post-retirement cost consisted of the following for the years ended December 31, 2014, 2013 and 2012:



	Years Ended December 31,
	2014			2013			2012
Service cost—benefits earned during the period	$	151		$	193		$	197
Interest cost	1,030			947			1,163
Expected return on plan assets	(4		)	(4		)	(4		)
Net amortization and deferral	—			87			177
Net post-retirement costs	$	1,177		$	1,223		$	1,533

The changes in benefit obligations and plan assets, as well as the funded status of our pension and post-retirement plans at December 31, 2014 and 2013 are as follows:



	Pension Benefits						Post-retirement Benefits
	2014			2013			2014			2013
Benefit obligation at January 1,	$	99,828		$	107,619		$	22,261		$	25,717
Service cost	1,080			1,280			151			193
Interest cost	4,811			4,198			1,030			947
Actuarial gain (loss)	22,163			(8,071		)	5,340			(3,933		)
Benefits paid	(6,017		)	(5,749		)	(996		)	(1,102		)
Amendments	471			551			—			—
Other	—			—			503			439
Benefit obligation at December 31,	$	122,336		$	99,828		$	28,289		$	22,261
Fair value of plan assets at January 1,	$	85,367		$	80,850		$	51		$	54
Actual return on plan assets	6,937			7,986			3			8
Employer contributions	4,610			2,280			492			652
Benefits paid	(6,017		)	(5,749		)	(996		)	(1,102		)
Other	—			—			469			439
Fair value of plan assets at December 31,	$	90,897		$	85,367		$	19		$	51
Plan assets less than benefit obligations at December 31 recognized as liability for pension and other post-retirement benefits	$	(31,439	)	$	(14,461	)	$	(28,270	)	$	(22,210	)

The accumulated benefit obligation for the defined benefit pension plans, which excludes the assumption of future salary increases, totaled $122.0 million and $99.4 million at December 31, 2014 and 2013, respectively.

The amendments in 2014 reflect plan changes including increases in the benefit multiplier for certain participants.

We also sponsor unfunded, nonqualified pension plans. The projected benefit obligation, accumulated benefit obligation and fair value of plan assets for these plans were $1.7 million, $1.7 million and $0 million at December 31, 2014 and $1.6 million, $1.6 million and $0 million at December 31, 2013.

Future estimated annual benefit payments for pension and post-retirement benefit obligations at December 31, 2014 are as follows:



	Benefits
			Post-retirement
	Pension		Before Medicare Subsidy		After Medicare Subsidy
2015	$	6,569	$	1,587	$	1,426
2016	6,756		1,640		1,472
2017	7,048		1,716		1,540
2018	7,187		1,710		1,527
2019	7,370		1,747		1,557
2020-2024	38,348		9,545		8,522

Our best estimate of expected contributions to the pension and post-retirement medical benefit plans for the 2015 fiscal year are $2.8 million and $1.4 million , respectively.

The amounts in accumulated other comprehensive income expected to be recognized as components of net periodic benefit cost during the year ended December 31, 2015 are as follows:



	Benefits
	Pension		Post-retirement		Total
Net actuarial loss	$	2,310	$	392	$	2,702
Prior service cost	274		—		274
	$	2,584	$	392	$	2,976

The total amounts in accumulated other comprehensive income related to net actuarial loss, net of tax, for both plans was $17.7 million and $2.3 million as of December 31, 2014 and 2013, respectively. The total amounts in accumulated other comprehensive income related to prior service cost, net of tax, for both plans, net of tax, was $1.6 million and $1.4 million as of December 31, 2014 and 2013, respectively.

The following weighted-average assumptions were used to determine our obligations under the plans:



	Pension Benefits				Post-retirement Benefits
	2014		2013		2014		2013
Discount rate	4.1	%	4.8	%	4.1	%	4.8	%
Long-term rate of compensation increase	3.5	%	3.5	%	N/A		N/A
Long-term rate of return on plan assets	7.0	%	7.5	%	7.0	%	7.5	%
Health care cost trend rate:
Pre-65 initial rate/ultimate rate	N/A		N/A		7.5%/5.0%		8.0%/5.0%
Pre-65 ultimate year	N/A		N/A		—		—
Post-65 initial rate/ultimate rate	N/A		N/A		7.0%/5.0%		7.3%/5.0%
Post-65 ultimate year	N/A		N/A		2022		2021

The discount rate reflects the expected long-term rates of return with maturities comparable to payments for the plan obligations utilizing Aon Hewitt’s AA Only Above Medium Curve, rounded down to the next 0.05%.

Mortality table used for pension benefits and post-retirement benefits plans are the following:



	Pension Benefits and Post-retirement Benefits
	2014	2013
Healthy lives	RP-2014 Employee and Healthy Annuitant Mortality Table with generational mortality improvements using Scale MP-2014	2014 IRS Static Mortality Table for Annuitants and Non-Annuitants per §1.430(h)(3)-1(e)
Disabled lives	RP-2014 Disabled Retiree Mortality Table with generational mortality improvements using Scale MP-2014	RP-2000 Disabled Retiree Mortality Table

Assumed health care cost trend rates have a significant effect on the amounts reported for the health care plans. A one-percentage-point change in assumed health care cost trend rates would have the following effects:



	One-Percentage-Point
	Increase		Decrease
Effect on total of service and interest cost	$	136	$	(115	)
Effect on post-retirement benefit obligation	3,879		(3,217		)

The major investment categories and their relative percentage of the fair value of total plan assets as invested at December 31, 2014, and 2013 are as follows:



	Pension Benefits				Post-retirement Benefits
	2014		2013		2014		2013
Equity securities	57.4	%	57.4	%	45.3	%	59.0	%
Debt securities	40.5	%	36.6	%	30.1	%	29.5	%
Cash	2.1	%	6.0	%	24.6	%	11.5	%

The fair values of the pension plan assets at December 31, 2014, by asset category, are as follows:



	Level 1		Level 2		Level 3		Total
Cash and cash equivalents	$	1,897	$	—	$	—	$	1,897
Mutual funds:
Diversified emerging markets	8,136		—		—		8,136
Foreign large blend	13,216		—		—		13,216
Large-cap blend	19,662		—		—		19,662
Long-term bonds	36,782		—		—		36,782
Mid-cap blend	6,293		—		—		6,293
Real estate	4,844		—		—		4,844
Insurance policies	—		—		65		65
Net asset	$	90,832	$	—	$	65	$	90,897

The fair values of the pension plan assets at December 31, 2013, by asset category, are as follows:



	Level 1		Level 2		Level 3		Total
Cash and cash equivalents	$	5,067	$	—	$	—	$	5,067
Mutual funds:
Diversified emerging markets	7,753		—		—		7,753
Foreign large blend	13,851		—		—		13,851
Large-cap blend	17,804		—		—		17,804
Long-term bonds	31,230		—		—		31,230
Mid-cap blend	5,807		—		—		5,807
Real estate	3,776		—		—		3,776
Insurance policies	—		—		79		79
Net asset	$	85,288	$	—	$	79	$	85,367

We contribute to three multiemployer defined benefit pension plans under the terms of collective-bargaining agreements for union-represented employees. A multiemployer plan is subject to collective bargaining for employees of two or more unrelated companies. These plans allow multiple employers to pool their pension resources and realize efficiencies associated with the daily administration of the plan. Multiemployer plans are generally governed by a board of trustees composed of management and labor representatives and are funded through employer contributions. However, in most cases, management is not directly represented.

The risks of participating in multiemployer plans differ from single employer plans as follows: 1) assets contributed to a multiemployer plan by one employer may be used to provide benefits to employees of other participating employers, 2) if a participating employer stops contributing to the plan, the unfunded obligations of the plan may be borne by the remaining participating employers, and 3) if we cease to have an obligation to contribute to one or more of the multiemployer plans to which we contribute, we may be required to pay those plans an amount based on the underfunded status of the plan, referred to as a withdrawal liability.

A summary of each multiemployer pension plan for which we participate is presented below:

Pension

Fund

EIN/ Pension

Plan No.

Pension Protection Act

Zone Status⁽¹⁾

FIP/RP Status

Pending/

Implemented

Company

Contributions

Surcharge

Imposed

Expiration

Date of

CBA

2014

2013

2014

2013

2012

LIUNA

52-6074345/001

Red

Yes

149

124

123

Yes

5/31/2017

IUOE

36-6052390/001

Green

7/31/2015

CSSS⁽²⁾

36-6044243/001

Red

Yes


(1)	The Pension Protection Act of 2006 defines the zone status as follows: green—healthy, yellow—endangered, orange—seriously endangered and red—critical.


(2)	In 2011, we withdrew from the Central States, Southeast and Southwest Areas Pension Plan. The withdrawal liability of $1.0 million will be paid in monthly installments of $4 until 2031.

Our contributions to individual multiemployer pension funds did not exceed 5% of the fund’s total contributions in any of the three years ended December 31, 2014. Additionally, our contributions to multiemployer postretirement benefit plans were immaterial for all periods presented in the accompanying consolidated financial statements.

We also sponsor a defined contribution plan covering certain employees. We contribute to the plan in two ways. For certain employees not covered by the defined benefit plan, we make a contribution equal to 4% of their salary. We also contribute an employee match of 25 cents, based on financial performance, for each dollar contributed by an employee, up to 8% of their earnings. For certain employees, we make a profit sharing match up to 75 cents, based on financial performance, for each dollar contributed up to 8% of their earnings. Finally, for some employees, we make a catch-up match of 25 cents for each dollar of catch-up contributions. Contributions were $2.1 million, $1.7 million and $1.4 million for the years ended December 31, 2014, 2013 and 2012, respectively.

Obligations Under Guarantees	12 Months Ended
Obligations Under Guarantees	Dec. 31, 2014
Guarantees [Abstract]
Obligations Under Guarantees	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 December 31, 2014, Travelers had $8.5 million in bonds outstanding for us. The majority of these bonds ($8.2 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. U.S. Silica is the contingent guarantor of Kanawha Rail Corporation’s (“KRC”) obligations as lessee of 199 covered hopper railroad cars, which are used by U.S. Silica to ship sand to its customers. KRC’s obligation as lessee includes paying monthly rent of $66 until June 30, 2015, maintaining the cars, paying for any cars damaged or destroyed, and indemnifying all other parties to the lease transaction against liabilities including any loss of certain tax benefits. By separate agreement between U.S. Silica and KRC, KRC may, upon the occurrence of certain events, assign the lease obligations to U.S. Silica, but none of these events have occurred.

Related Party Transactions	12 Months Ended
Related Party Transactions	Dec. 31, 2014
Related Party Transactions [Abstract]
Related Party Transactions	RELATED PARTY TRANSACTIONS Advisory Agreement In connection with our acquisition by Golden Gate Capital in 2008, we entered into an Advisory Agreement with Golden Gate Capital whereby Golden Gate Capital agreed to provide business and organizational strategy and financial and advisory services. Such services included support and assistance to management with respect to negotiating and analyzing acquisitions and divestitures, negotiating and analyzing financing alternatives, preparing financial projections, monitoring compliance with financing agreements, marketing functions and searching for and hiring management personnel. As compensation for these services, we agreed to pay Golden Gate Capital (1) an annual advisory fee in the aggregate amount equal to $1.25 million, payable quarterly in arrears, and (2) a transaction fee of 1.25% of the aggregate value of each transaction resulting in a change in control of GGC Holdings or its subsidiaries, along with each acquisition, divestiture, recapitalization and financing. In addition to the fees described above, we also reimbursed Golden Gate Capital for all out-of-pocket costs incurred by Golden Gate Capital in connection with its activities under the Advisory Agreement, and indemnified Golden Gate Capital from and against all losses, claims, damages and liabilities related to the performance of its duties under the Advisory Agreement. On February 6, 2012, we paid $8.0 million to Golden Gate Capital to terminate the Advisory Agreement. The $8.0 million termination fee was accrued for at December 31, 2011 and no additional expense has been recognized during the year ended December 31, 2012. Advisory fees paid to Golden Gate Capital under the Advisory Agreement in 2011 were $1.3 million. These expenses are included in other operating expenses and presented as advisory fees to parent within our income statements. Promissory Note On December 22, 2010, we entered into a $15.0 million promissory note with our former parent, GGC USS Holdings, LLC. The note provided working capital for a new subsidiary and was scheduled to mature on December 22, 2015. The note bore interest at 10%. Outstanding principal and interest under the note were payable upon demand, but no later than the maturity date. Upon sole election by GGC Holdings, any unpaid interest could be paid in cash on each December 22 of each year until the maturity date. As of and for the year ended December 31, 2011, interest on the note is recorded in interest expense in the Income Statements and any unpaid interest is included in accrued interest on the Balance Sheet. On January 31, 2012, simultaneously with the IPO, GGC Holdings contributed to us all of the stock of GGC RCS Holdings, Inc. and converted the $15.0 million promissory note, including $1.7 million of accrued interest, to equity. GGC USS Holdings, LLC held no interest in U.S. Silica after divesting its ownership interest in U.S. Silica during 2013.

- Definition

The entire disclosure for related party transactions. Examples of related party transactions include transactions between (a) a parent company and its subsidiary; (b) subsidiaries of a common parent; (c) and entity and its principal owners; and (d) affiliates.

+ References+ Details

Segment Reporting

12 Months Ended

Dec. 31, 2014

Segment Reporting [Abstract]

Segment Reporting

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.

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 its segments. However, this measure should be considered in addition to, not a substitute for, or superior to, income from operations 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 the summary of significant accounting policies included in Note B.

In the Oil & Gas Proppants segment, we serve the oil and gas recovery market 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 natural gas and oil from the wells.

The Industrial & Specialty Products segment consists of over 250 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.

The following table presents sales and segment contribution margin for the reporting segments and other operating results not allocated to the reported segments for the years ended December 31, 2014, 2013 and 2012:



	Years Ended December 31,
	2014			2013			2012
Sales:
Oil & Gas Proppants	$	662,770		$	347,439		$	243,765
Industrial & Specialty Products	213,971			198,546			198,156
Total sales	876,741			545,985			441,921
Segment contribution margin:
Oil & Gas Proppants	256,137			145,916			140,070
Industrial & Specialty Products	61,102			56,983			53,601
Total segment contribution margin	317,239			202,899			193,671
Operating activities excluded from segment cost of goods sold	(7,082		)	(5,481		)	(8,285		)
Selling, general and administrative	(88,971		)	(49,759		)	(41,299		)
Depreciation, depletion and amortization	(45,019		)	(36,418		)	(25,099		)
Interest expense	(18,202		)	(15,341		)	(13,795		)
Early extinguishment of debt	—			(480		)	—
Other income, net, including interest income	758			597			4,612
Income before income taxes	$	158,723		$	96,017		$	109,805

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 $68.4 million has been allocated to these segments with $47.7 million assigned to Oil & Gas Proppants and $20.7 million to Industrial & Specialty Products.

- 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

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+ Details

Unaudited Supplementary Data

12 Months Ended

Dec. 31, 2014

Quarterly Financial Information Disclosure [Abstract]

Unaudited Supplementary Data

UNAUDITED SUPPLEMENTARY DATA

The following table sets forth our unaudited quarterly consolidated statements of operations for each of the last four quarters in the years ended December 31, 2014 and 2013. This unaudited quarterly information has been prepared on the same basis as our annual audited financial statements and includes all adjustments, consisting only of normal recurring adjustments that are necessary to present fairly the financial information for the fiscal quarters presented.



	First Quarter			Second Quarter			Third Quarter			Fourth Quarter
2014	(Unaudited)
Sales	$	180,095		$	205,801		$	241,256		$	249,589
Costs of goods sold	126,770			132,417			149,697			157,700
Operating expenses										—
Selling, general and administrative	15,445			19,267			18,600			35,659
Depreciation, depletion and amortization	9,589			10,341			12,425			12,664
	25,034			29,608			31,025			48,323
Operating income	28,291			43,776			60,534			43,566
Other (expense) income
Interest expense	(3,808		)	(4,013		)	(4,950		)	(5,431		)
Other income, net, including interest income	38			221			120			379
	(3,770		)	(3,792		)	(4,830		)	(5,052		)
Income before income taxes	24,521			39,984			55,704			38,514
Income tax expense	(6,150		)	(11,330		)	(14,427		)	(5,276		)
Net income	$	18,371		$	28,654		$	41,277		$	33,238
Earnings per share, basic	$	0.34		$	0.53		$	0.77		$	0.62
Earnings per share, diluted	$	0.34		$	0.53		$	0.76		$	0.61
Weighted average common shares outstanding (in thousands), basic	53,505			53,733			53,801			53,838
Weighted average common shares outstanding (in thousands), diluted	54,054			54,262			54,393			54,340

	First Quarter			Second Quarter			Third Quarter			Fourth Quarter
2013	(Unaudited)
Sales	$	122,311		$	129,828		$	144,372		$	149,474
Costs of goods sold	74,412			80,297			90,983			102,875
Operating expenses
Selling, general and administrative	12,404			10,099			12,800			14,456
Depreciation, depletion and amortization	8,278			8,890			9,152			10,098
	20,682			18,989			21,952			24,554
Operating income	27,217			30,542			31,437			22,045
Other (expense) income
Interest expense	(3,576		)	(3,535		)	(4,144		)	(4,086		)
Early extinguishment of debt	—			—			(480		)	—
Other income, net, including interest income	122			63			260			152
	(3,454		)	(3,472		)	(4,364		)	(3,934		)
Income before income taxes	23,763			27,070			27,073			18,111
Income tax (expense) benefit	(6,486		)	(6,878		)	(5,739		)	(1,658		)
Net income	$	17,277		$	20,192		$	21,334		$	16,453
Earnings per share, basic	$	0.33		$	0.38		$	0.40		$	0.31
Earnings per share, diluted	$	0.32		$	0.38		$	0.40		$	0.31
Weighted average common shares outstanding (in thousands), basic	52,946			52,948			53,103			53,035
Weighted average common shares outstanding (in thousands), diluted	52,211			53,227			53,429			53,409

Summary of Significant Accounting Policies (Policies)

12 Months Ended

Dec. 31, 2014

Accounting Policies [Abstract]

Basis of Presentation and Consolidation

Consolidation

Use of Estimates and Assumptions

Revenue Recognition

Cash and Cash Equivalents

Accounts Receivable

Our ten largest customers accounted for approximately 57%, 52%, and 37% of sales in the years ended December 31, 2014, 2013 and 2012, respectively.

Inventories

Property, Plant and Mine Development

Property and equipment

Mine exploration and development

Mine reclamation costs and asset retirement obligations

Our asset retirement obligations are reported in other long-term obligations. The changes in these obligations during the year ending December 31, 2014 and 2013 are as follows:



	2014			2013
Beginning balance	$	9,378		$	6,659
Payments	(782		)	—
Accretion	676			456
Additions and revisions of prior estimates	2,011			2,263
Ending balance	$	11,283		$	9,378

Goodwill and Other Intangible Assets and Related Impairment

Debt Issuance Costs

Environmental Costs

Self-Insurance

Equity-based Compensation

Income Taxes

Earnings per Share

Comprehensive Income

Short-Term Investments

Financial Instruments

Recently Adopted Accounting Pronouncements

Summary of Significant Accounting Policies (Tables)

12 Months Ended

Dec. 31, 2014

Accounting Policies [Abstract]

Changes in Asset Retirement Obligation

The changes in these obligations during the year ending December 31, 2014 and 2013 are as follows:



	2014			2013
Beginning balance	$	9,378		$	6,659
Payments	(782		)	—
Accretion	676			456
Additions and revisions of prior estimates	2,011			2,263
Ending balance	$	11,283		$	9,378

Summary of Valuation Assumptions



	Weighted-average
	Year ended December 31,
	2014		2013		2012
Risk-free interest rate	1.81%		1.03 – 1.31%		0.83 - 1.05%
Expected volatility	45	%	45	%	45	%
Expected term	6.25 years		6.25 years		6.25 years
Expected dividend yield	1	%	0	%	0	%
Expected forfeiture yield	0	%	0	%	0	%

Earnings Per Share (Tables)

12 Months Ended

Dec. 31, 2014

Earnings Per Share [Abstract]

Schedule of Basic and Diluted Earnings Per Share



	For the Year Ended December 31,
	2014			2013			2012
Net income	$	121,540		$	75,256		$	79,154
Less: net income allocated to outstanding restricted stockholders	(230		)	(175		)	(105		)
Net income allocated to common stockholders	$	121,310		$	75,081		$	79,049
Weighted-average common stock
Outstanding	53,719			53,035			52,592
Outstanding assuming dilution	54,296			53,409			52,641

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



	For the Year Ended December 31,
	2014	2013	2012
Weighted-average outstanding stock options excluded	33	175	1,070

Capital Structure and Accumulated Comprehensive Income (Tables)

12 Months Ended

Dec. 31, 2014

Equity [Abstract]

Schedule of Declared Quarterly Dividends

In 2014, our Board of Directors declared quarterly cash dividends as follows:



Dividends per Common Share		Declaration Date	Record Date	Payable Date
$	0.125	February 6, 2014	March 14, 2014	April 1, 2014
$	0.125	April 25, 2014	June 13, 2014	July 3, 2014
$	0.125	July 25, 2014	September 15, 2014	October 3, 2014
$	0.125	October 24, 2014	December 15, 2014	January 5, 2015

Changes in Accumulated Other Comprehensive Income

The following table presents the changes in accumulated other comprehensive income by component during the year ended December 31, 2014:



	For the Year Ended December 31, 2014
	Unrealized gain/(loss) on cash flow hedges			Unrealized gain/(loss) on short-term investments			Pension and other post- retirement benefits liability			Total
Beginning Balance	$	(79	)	$	(27	)	$	(3,911	)	$	(4,017	)
Other comprehensive income (loss) before reclassifications	(65		)	(14		)	(16,388		)	(16,467		)
Amounts reclassed from accumulated other comprehensive income	10			—			656			666
Ending Balance	$	(134	)	$	(41	)	$	(19,643	)	$	(19,818	)

Business Combinations (Tables)

12 Months Ended

Dec. 31, 2014

Business Combinations [Abstract]

Schedule of Identifiable Assets Acquired and Liabilities Assumed



Accounts receivable	$	6,898
Inventory	2,534
Other current assets	174
Fixed assets (net)	73,138
Deferred tax assets (net)	13,966
Accounts payable, accrued expenses and other liabilities	(4,389		)
Net tangible assets acquired	92,321
Customer relationships	1,274
Trade name	4,478
Goodwill	244
Preliminary purchase price, net of cash acquired	$	98,317

Summary of Identifiable Intangible Assets

The following table summarizes the allocation of identifiable intangible assets resulting from the acquisition:



	Useful Lives	Value
Customer relationships	15 years	$	1,274
Trade name	Indefinite	4,478
Total intangible assets		$	5,752

Pro Forma Summary

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



	For the Year Ended December 31,
	2014		2013		2012
Sales	$	901,916	$	578,453	$	481,100
Net income	$	126,960	$	76,942	$	82,782
Basic earnings per share	$	2.36	$	1.45	$	1.57
Diluted earnings per share	$	2.33	$	1.44	$	1.57

Accounts Receivable (Tables)

12 Months Ended

Dec. 31, 2014

Receivables [Abstract]

Schedule of Accounts Receivable

Changes in our allowance for doubtful accounts during the years ended December 31, 2014 and 2013 are as follows:



	Allowance for Doubtful Accounts
	2014			2013
Balance at January 1,	$	2,376		$	1,053
Bad debt provision	10,200			1,330
Write-offs	(2,147		)	(7		)
Balance at December 31,	$	10,429		$	2,376

At December 31, 2014 and 2013, accounts receivable consisted of the following:



	At December 31,
	2014			2013
Trade receivables	$	128,498		$	76,223
Less: Allowance for doubtful accounts	(10,429		)	(2,376		)
Net trade receivables	118,069			73,847
Other receivables	2,812			1,360
Total accounts receivable	$	120,881		$	75,207

Property, Plant and Mine Development (Tables)

12 Months Ended

Dec. 31, 2014

Property, Plant and Equipment [Abstract]

Schedule of Property, Plant and Mine Development

At December 31, 2014 and 2013, property, plant and mine development consisted of the following:



	At December 31,
	2014			2013
Mining property and mine development	$	197,824		$	164,609
Asset retirement cost	9,559			7,275
Land	28,443			25,738
Land improvements	35,322			31,093
Buildings	47,149			36,311
Machinery and equipment	323,618			263,304
Furniture and fixtures	1,599			1,131
Construction-in-progress	78,997			25,974
	722,511			555,435
Accumulated depletion, depreciation and amortization	(156,756		)	(113,319		)
Total property, plant and mine development, net	$	565,755		$	442,116

Debt (Tables)

12 Months Ended

Dec. 31, 2014

Debt Disclosure [Abstract]

Schedule of Debt

At December 31, 2014 and 2013, debt consisted of the following:



	December 31, 2014			December 31, 2013
Senior secured credit facility:
Revolver expiring July 23, 2018 (4.75% at December 31, 2014 and December 31, 2013)	$	—		$	—
Term loan facility—final maturity July 23, 2020 (4% - 5.25% at December 31, 2014 and 4% at December 31, 2013), net of unamortized original issue discount of $2,078 and $1,674, respectively	502,297			371,451
Total debt	502,297			371,451
Less: current portion	(4,718		)	(3,488		)
Total long-term portion of debt	$	497,579		$	367,963

Schedule of Contractual Maturities of Debt

At December 31, 2014, contractual maturities of long-term debt are as follows:



2015	$	4,718
2016	4,722
2017	4,725
2018	4,729
2019	4,733
Thereafter	478,670
	$	502,297

Fair Value Accounting (Tables)

12 Months Ended

Dec. 31, 2014

Fair Value Disclosures [Abstract]

Schedule of Measure at Fair Value on Recurring Basis



	December 31, 2014						December 31, 2013
	Level 1		Level 2		Total		Level 1		Level 2		Total
Short-term investments	$	666	$	74,477	$	75,143	$	622	$	74,358	$	74,980
Interest rate derivatives	—		5		5		—		109		109
Net asset	$	666	$	74,482	$	75,148	$	622	$	74,467	$	75,089

Short-Term Investments (Tables)

12 Months Ended

Dec. 31, 2014

Investments, Debt and Equity Securities [Abstract]

Summary of Available-for-sale Short-Term Investments

The following table summarizes our available-for-sale short-term investments:



	Aggregate Cost		Gross Unrealized Gains		Gross Unrealized Losses			Fair Value
December 31, 2013
Money market mutual funds	$	622	$	—	$	—		$	622
Fixed income securities:
Certificates of deposit	25,218		—		(34		)	25,184
Commercial paper	15,168		4		(1		)	15,171
Corporate notes and bonds	9,495		—		(9		)	9,486
Government agencies	13,979		6		—			13,985
U.S. Treasuries	4,828		—		(10		)	4,818
Variable Rate Demand Obligations	5,714		—		—			5,714
Total available-for-sale investments	$	75,024	$	10	$	(54	)	$	74,980

December 31, 2014
Money market mutual funds	$	666	$	—	$	—		$	666
Fixed income securities:
Certificates of deposit	29,233		—		(23		)	29,210
Commercial paper	10,187		7		(2		)	10,192
Corporate notes and bonds	12,076		—		(29		)	12,047
Government agencies	16,681		4		(17		)	16,668
U.S. Treasuries	2,151		—		(4		)	2,147
Variable Rate Demand Obligations	4,213		—		—			4,213
Total available-for-sale investments	$	75,207	$	11	$	(75	)	$	75,143

- Definition

Tabular disclosure of available-for-sale securities which includes, but is not limited to, changes in the cost basis and fair value, fair value and gross unrealized gain (loss), fair values by type of security, contractual maturity and classification, amortized cost basis, contracts to acquire securities to be accounted for as available-for-sale, debt maturities, transfers to trading, change in net unrealized holding gain (loss) net of tax, continuous unrealized loss position fair value, aggregate losses qualitative disclosures, other than temporary impairment (OTTI) losses or other disclosures related to available for sale securities.

+ References+ Details

Derivative Instruments (Tables)

12 Months Ended

Dec. 31, 2014

Derivative Instruments and Hedging Activities Disclosure [Abstract]

Estimated Fair Values of Derivative Instruments



		December 31, 2014							December 31, 2013
	Maturity Date	Contract/Notional Amount			Carrying Amount		Fair Value		Contract/Notional Amount			Carrying Amount		Fair Value
Interest rate cap agreement(1)	2016	$	188	million	$	5	$	5	$	188	million	$	109	$	109


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

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



	2014			2013			2012
Deferred losses from derivatives in OCI, beginning of period	$	(79	)	$	(182	)	$	(409	)
Loss recognized in OCI from derivative instruments	(65		)	(82		)	—
Loss reclassified from Accumulated OCI	10			185			227
Deferred losses from derivatives in OCI, end of period	$	(134	)	$	(79	)	$	(182	)

Equity-Based Compensation (Tables)

12 Months Ended

Dec. 31, 2014

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

Summary of Activity with Respect to Stock Options

The following table summarizes the status of and changes in our stock option grants during the year ended December 31, 2014:



	Number of Shares		Weighted Average Exercise Price		Weighted Average Remaining Contractual Term in Years
Outstanding at December 31, 2013	1,231,540		$	15.01
Granted	206,400		49.39
Exercised	(389,264	)	14.29
Forfeited	(65,622	)	16.46
Outstanding at December 31, 2014	983,054		22.42		7.78
Exercisable at December 31, 2014	273,752		$	15.25	7.09

Summary of Restricted Stock Award Activity

The following table summarizes the status of and changes in our unvested restricted stock awards during the year ended December 31, 2014:



	Number of Shares		Grant Date Weighted Average Fair Value
Unvested, December 31, 2013	228,403		$	20.95
Granted	204,786		31.31
Vested	(51,866	)	20.62
Forfeited	(573	)	35.26
Unvested, December 31, 2014	380,750		$	26.55

Income Taxes (Tables)

12 Months Ended

Dec. 31, 2014

Income Tax Disclosure [Abstract]

Summary of Income Tax (Expense) Benefit



	Years Ended December 31,
	2014			2013			2012
Current:
Federal	$	(34,790	)	$	(20,819	)	$	(22,165	)
State	(4,835		)	(1,831		)	(6,237		)
	(39,625		)	(22,650		)	(28,402		)
Deferred:
Federal	(308		)	1,453			(3,645		)
State	2,750			436			1,396
	2,442			1,889			(2,249		)
Income tax expense	$	(37,183	)	$	(20,761	)	$	(30,651	)

Summary of Tax Effects on Deferred Tax Assets and Liabilities



	At December 31,
	2014			2013
Gross deferred tax assets:
State tax credits and net operating loss carry forward	$	25,042		$	1,007
Pension and post-retirement benefit costs	24,788			15,579
Alternative minimum tax credit carry forward	18,819			22,528
Property, plant and equipment	6,580			6,109
Accrued expenses	8,237			3,818
Inventories	5,366			5,863
Third-party products liability	636			674
Stock-based compensation expense	3,019			1,306
Other	8,457			5,502
Total deferred tax assets	$	100,944		$	62,386
Gross deferred tax liabilities:
Land and mineral property basis difference	$	(65,217	)	$	(61,366	)
Fixed assets and depreciation	(53,383		)	(47,016		)
Intangible assets	(8,587		)	(6,788		)
Other	(1,211		)	(797		)
Total deferred tax liabilities	(128,398		)	(115,967		)
Net deferred tax liabilities	(27,454		)	(53,581		)
Less: Net current deferred tax assets	22,295			17,737
Net long-term deferred tax liabilities	$	(49,749	)	$	(71,318	)

Summary of Effective Income Tax Rate on Pretax Earnings



	Years Ended December 31,
	2014		2013		2012
(Expense) benefit computed at U.S. federal statutory rate	(35.0	)%	(35.0	)%	(35.0	)%
Decrease (increase) resulting from:
Statutory depletion	9.8		11.0		9.9
Prior year tax return reconciliation	0.6		1.9		(0.5	)
State income taxes, net of federal benefit	(2.1	)	(2.4	)	(2.7	)
Domestic production deduction	2.5		2.4		0.7
Equity-based compensation	—		—		(0.1	)
Other, net	0.8		0.5		(0.2	)
Income tax (expense) benefit	(23.4	)%	(21.6	)%	(27.9	)%

Pension and Post-Retirement Benefits (Tables)

12 Months Ended

Dec. 31, 2014

Compensation and Retirement Disclosure [Abstract]

Summarizes Information about Pension and Post-Retirement Benefit Plans

Net pension benefit cost consisted of the following for the years ended December 31, 2014, 2013 and 2012:



	Years Ended December 31,
	2014			2013			2012
Service cost—benefits earned during the period	$	1,080		$	1,280		$	1,118
Interest cost	4,811			4,198			4,734
Expected return on plan assets	(5,146		)	(5,061		)	(5,381		)
Net amortization and deferral	1,037			1,904			1,105
Net pension benefit costs	$	1,782		$	2,321		$	1,576

Net post-retirement cost consisted of the following for the years ended December 31, 2014, 2013 and 2012:



	Years Ended December 31,
	2014			2013			2012
Service cost—benefits earned during the period	$	151		$	193		$	197
Interest cost	1,030			947			1,163
Expected return on plan assets	(4		)	(4		)	(4		)
Net amortization and deferral	—			87			177
Net post-retirement costs	$	1,177		$	1,223		$	1,533

Changes in Benefit Obligations and Plan Assets

The changes in benefit obligations and plan assets, as well as the funded status of our pension and post-retirement plans at December 31, 2014 and 2013 are as follows:



	Pension Benefits						Post-retirement Benefits
	2014			2013			2014			2013
Benefit obligation at January 1,	$	99,828		$	107,619		$	22,261		$	25,717
Service cost	1,080			1,280			151			193
Interest cost	4,811			4,198			1,030			947
Actuarial gain (loss)	22,163			(8,071		)	5,340			(3,933		)
Benefits paid	(6,017		)	(5,749		)	(996		)	(1,102		)
Amendments	471			551			—			—
Other	—			—			503			439
Benefit obligation at December 31,	$	122,336		$	99,828		$	28,289		$	22,261
Fair value of plan assets at January 1,	$	85,367		$	80,850		$	51		$	54
Actual return on plan assets	6,937			7,986			3			8
Employer contributions	4,610			2,280			492			652
Benefits paid	(6,017		)	(5,749		)	(996		)	(1,102		)
Other	—			—			469			439
Fair value of plan assets at December 31,	$	90,897		$	85,367		$	19		$	51
Plan assets less than benefit obligations at December 31 recognized as liability for pension and other post-retirement benefits	$	(31,439	)	$	(14,461	)	$	(28,270	)	$	(22,210	)

Estimated Future Pension and Post-Retirement Benefit Payments

Future estimated annual benefit payments for pension and post-retirement benefit obligations at December 31, 2014 are as follows:



	Benefits
			Post-retirement
	Pension		Before Medicare Subsidy		After Medicare Subsidy
2015	$	6,569	$	1,587	$	1,426
2016	6,756		1,640		1,472
2017	7,048		1,716		1,540
2018	7,187		1,710		1,527
2019	7,370		1,747		1,557
2020-2024	38,348		9,545		8,522

Amounts in Accumulated Other Comprehensive Income Expected to be Recognized as Components of Net Periodic Benefit Cost

The amounts in accumulated other comprehensive income expected to be recognized as components of net periodic benefit cost during the year ended December 31, 2015 are as follows:



	Benefits
	Pension		Post-retirement		Total
Net actuarial loss	$	2,310	$	392	$	2,702
Prior service cost	274		—		274
	$	2,584	$	392	$	2,976

Company's Obligations Determined under Weighted-Average Assumptions

The following weighted-average assumptions were used to determine our obligations under the plans:



	Pension Benefits				Post-retirement Benefits
	2014		2013		2014		2013
Discount rate	4.1	%	4.8	%	4.1	%	4.8	%
Long-term rate of compensation increase	3.5	%	3.5	%	N/A		N/A
Long-term rate of return on plan assets	7.0	%	7.5	%	7.0	%	7.5	%
Health care cost trend rate:
Pre-65 initial rate/ultimate rate	N/A		N/A		7.5%/5.0%		8.0%/5.0%
Pre-65 ultimate year	N/A		N/A		—		—
Post-65 initial rate/ultimate rate	N/A		N/A		7.0%/5.0%		7.3%/5.0%
Post-65 ultimate year	N/A		N/A		2022		2021

Schedule of Mortality Tables Used

Mortality table used for pension benefits and post-retirement benefits plans are the following:



	Pension Benefits and Post-retirement Benefits
	2014	2013
Healthy lives	RP-2014 Employee and Healthy Annuitant Mortality Table with generational mortality improvements using Scale MP-2014	2014 IRS Static Mortality Table for Annuitants and Non-Annuitants per §1.430(h)(3)-1(e)
Disabled lives	RP-2014 Disabled Retiree Mortality Table with generational mortality improvements using Scale MP-2014	RP-2000 Disabled Retiree Mortality Table

Effect of One-Percentage-Point Change in Assumed Health Care Cost Trend Rates



	One-Percentage-Point
	Increase		Decrease
Effect on total of service and interest cost	$	136	$	(115	)
Effect on post-retirement benefit obligation	3,879		(3,217		)

Fair Value of Pension Plan Assets

The major investment categories and their relative percentage of the fair value of total plan assets as invested at December 31, 2014, and 2013 are as follows:



	Pension Benefits				Post-retirement Benefits
	2014		2013		2014		2013
Equity securities	57.4	%	57.4	%	45.3	%	59.0	%
Debt securities	40.5	%	36.6	%	30.1	%	29.5	%
Cash	2.1	%	6.0	%	24.6	%	11.5	%

Fair Value of Pension Plan Assets, by Asset Category

The fair values of the pension plan assets at December 31, 2014, by asset category, are as follows:



	Level 1		Level 2		Level 3		Total
Cash and cash equivalents	$	1,897	$	—	$	—	$	1,897
Mutual funds:
Diversified emerging markets	8,136		—		—		8,136
Foreign large blend	13,216		—		—		13,216
Large-cap blend	19,662		—		—		19,662
Long-term bonds	36,782		—		—		36,782
Mid-cap blend	6,293		—		—		6,293
Real estate	4,844		—		—		4,844
Insurance policies	—		—		65		65
Net asset	$	90,832	$	—	$	65	$	90,897

The fair values of the pension plan assets at December 31, 2013, by asset category, are as follows:



	Level 1		Level 2		Level 3		Total
Cash and cash equivalents	$	5,067	$	—	$	—	$	5,067
Mutual funds:
Diversified emerging markets	7,753		—		—		7,753
Foreign large blend	13,851		—		—		13,851
Large-cap blend	17,804		—		—		17,804
Long-term bonds	31,230		—		—		31,230
Mid-cap blend	5,807		—		—		5,807
Real estate	3,776		—		—		3,776
Insurance policies	—		—		79		79
Net asset	$	85,288	$	—	$	79	$	85,367

Summary of Multiemployer Pension Plan

A summary of each multiemployer pension plan for which we participate is presented below:

Pension

Fund

EIN/ Pension

Plan No.

Pension Protection Act

Zone Status⁽¹⁾

FIP/RP Status

Pending/

Implemented

Company

Contributions

Surcharge

Imposed

Expiration

Date of

CBA

2014

2013

2014

2013

2012

LIUNA

52-6074345/001

Red

Yes

149

124

123

Yes

5/31/2017

IUOE

36-6052390/001

Green

7/31/2015

CSSS⁽²⁾

36-6044243/001

Red

Yes


(1)	The Pension Protection Act of 2006 defines the zone status as follows: green—healthy, yellow—endangered, orange—seriously endangered and red—critical.


(2)	In 2011, we withdrew from the Central States, Southeast and Southwest Areas Pension Plan. The withdrawal liability of $1.0 million will be paid in monthly installments of $4 until 2031.

Segment Reporting (Tables)

12 Months Ended

Dec. 31, 2014

Segment Reporting [Abstract]

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



	Years Ended December 31,
	2014			2013			2012
Sales:
Oil & Gas Proppants	$	662,770		$	347,439		$	243,765
Industrial & Specialty Products	213,971			198,546			198,156
Total sales	876,741			545,985			441,921
Segment contribution margin:
Oil & Gas Proppants	256,137			145,916			140,070
Industrial & Specialty Products	61,102			56,983			53,601
Total segment contribution margin	317,239			202,899			193,671
Operating activities excluded from segment cost of goods sold	(7,082		)	(5,481		)	(8,285		)
Selling, general and administrative	(88,971		)	(49,759		)	(41,299		)
Depreciation, depletion and amortization	(45,019		)	(36,418		)	(25,099		)
Interest expense	(18,202		)	(15,341		)	(13,795		)
Early extinguishment of debt	—			(480		)	—
Other income, net, including interest income	758			597			4,612
Income before income taxes	$	158,723		$	96,017		$	109,805

Unaudited Supplementary Data (Tables)

12 Months Ended

Dec. 31, 2014

Quarterly Financial Information Disclosure [Abstract]

Unaudited Quarterly Information



	First Quarter			Second Quarter			Third Quarter			Fourth Quarter
2014	(Unaudited)
Sales	$	180,095		$	205,801		$	241,256		$	249,589
Costs of goods sold	126,770			132,417			149,697			157,700
Operating expenses										—
Selling, general and administrative	15,445			19,267			18,600			35,659
Depreciation, depletion and amortization	9,589			10,341			12,425			12,664
	25,034			29,608			31,025			48,323
Operating income	28,291			43,776			60,534			43,566
Other (expense) income
Interest expense	(3,808		)	(4,013		)	(4,950		)	(5,431		)
Other income, net, including interest income	38			221			120			379
	(3,770		)	(3,792		)	(4,830		)	(5,052		)
Income before income taxes	24,521			39,984			55,704			38,514
Income tax expense	(6,150		)	(11,330		)	(14,427		)	(5,276		)
Net income	$	18,371		$	28,654		$	41,277		$	33,238
Earnings per share, basic	$	0.34		$	0.53		$	0.77		$	0.62
Earnings per share, diluted	$	0.34		$	0.53		$	0.76		$	0.61
Weighted average common shares outstanding (in thousands), basic	53,505			53,733			53,801			53,838
Weighted average common shares outstanding (in thousands), diluted	54,054			54,262			54,393			54,340

	First Quarter			Second Quarter			Third Quarter			Fourth Quarter
2013	(Unaudited)
Sales	$	122,311		$	129,828		$	144,372		$	149,474
Costs of goods sold	74,412			80,297			90,983			102,875
Operating expenses
Selling, general and administrative	12,404			10,099			12,800			14,456
Depreciation, depletion and amortization	8,278			8,890			9,152			10,098
	20,682			18,989			21,952			24,554
Operating income	27,217			30,542			31,437			22,045
Other (expense) income
Interest expense	(3,576		)	(3,535		)	(4,144		)	(4,086		)
Early extinguishment of debt	—			—			(480		)	—
Other income, net, including interest income	122			63			260			152
	(3,454		)	(3,472		)	(4,364		)	(3,934		)
Income before income taxes	23,763			27,070			27,073			18,111
Income tax (expense) benefit	(6,486		)	(6,878		)	(5,739		)	(1,658		)
Net income	$	17,277		$	20,192		$	21,334		$	16,453
Earnings per share, basic	$	0.33		$	0.38		$	0.40		$	0.31
Earnings per share, diluted	$	0.32		$	0.38		$	0.40		$	0.31
Weighted average common shares outstanding (in thousands), basic	52,946			52,948			53,103			53,035
Weighted average common shares outstanding (in thousands), diluted	52,211			53,227			53,429			53,409

Organization - (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended	0 Months Ended
	Dec. 31, 2014 Segment	Jan. 31, 2012 IPO	Jul. 31, 2014 Cadre Services, Inc.
Organization And Nature Of Business
Number of business segments	2
Net proceeds		$ 40.8
Underwriting discounts and commissions		3.5
Offering expenses		5.7
Cash payments to acquire business			$ 98.3

Summary of Significant Accounting Policies - Additional Information (Detail) (USD $)	12 Months Ended
	Dec. 31, 2014 Customer	Dec. 31, 2013	Dec. 31, 2012
Organization And Significant Accounting Policies
Number of customers in the oil & gas proppants segment	10
Agreements expiring period	2014
Agreements expiring period	2019
Standard term invoice	30 days
Accounts receivable due	30 days
Number of customers accounted for sales percentage	10
Additions and revisions of prior estimates	$ 2,011,000	$ 2,263,000
Percentage of fair value of reporting unit less than carrying amount	50.00%
Accumulated amortization	2,500,000
Estimated annual amortization, 2015	496,000
Estimated annual amortization, 2016	496,000
Estimated annual amortization, 2017	496,000
Estimated annual amortization, 2018	496,000
Estimated annual amortization, 2019	496,000
Amortization in interest expense	912,000	680,000	515,000
Self-insurance reserve total	5,700,000	5,400,000
Self-insurance reserve current	1,800,000	1,700,000
Percentage of refund from taxing authority	50.00%
Short-term and fixed income securities with maturities	12 months or less
Long-term and fixed income securities with maturities	Greater than 12 months
Buildings
Organization And Significant Accounting Policies
Depreciation over the assets estimated useful life	15 years
Land improvements
Organization And Significant Accounting Policies
Depreciation over the assets estimated useful life	10 years
Furniture and fixtures
Organization And Significant Accounting Policies
Depreciation over the assets estimated useful life	8 years
Customer Relationships
Organization And Significant Accounting Policies
Weighted average amortization useful life	20 years
Gross carrying amount of intangible asset	9,500,000
Remaining useful life	13 years 10 months 24 days
Minimum
Organization And Significant Accounting Policies
Self-insured retentions	100,000
Minimum \| Machinery and equipment
Organization And Significant Accounting Policies
Depreciation over the assets estimated useful life	3 years
Maximum
Organization And Significant Accounting Policies
Self-insured retentions	$ 500,000
Maximum \| Machinery and equipment
Organization And Significant Accounting Policies
Depreciation over the assets estimated useful life	10 years
Product concentration risk \| Sales Revenue, Net
Organization And Significant Accounting Policies
Percentage of sales in which customers accounted	57.00%	52.00%	37.00%

Summary of Significant Accounting Policies - Equity-Based Compensation (Details) (USD $)	0 Months Ended					12 Months Ended
	Oct. 24, 2014	Jul. 25, 2014	Apr. 25, 2014	Feb. 06, 2014	Jan. 31, 2012	Dec. 31, 2014 payment	Dec. 31, 2013 payment	Dec. 31, 2012
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock vesting period						5 years
Weighted average fair value, grants during period (in dollars per share)						$ 19.37	$ 10.03	$ 5.68
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions and Methodology [Abstract]
Risk-free interest rate						1.81%
Risk-free interest rate - minimum							1.03%	1.31%
Risk-free interest rate, maximum							0.83%	1.05%
Expected volatility (percentage)						45.00%	45.00%	45.00%
Expected term						6 years 3 months	6 years 3 months	6 years 3 months
Expected divided yield						1.00%	0.00%	0.00%
Expected forfeiture yield						0.00%	0.00%	0.00%
Common stock cash dividend declared, per share	$ 0.125	$ 0.125	$ 0.125	$ 0.125	$ 0.50	$ 0.50	$ 0.375	$ 0.50
Number of dividend payments (quarterly)						4	3
Common stock, quarterly cash dividend declared, per share						$ 0.125	$ 0.125
Restricted stock and restricted stock units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock vesting period						3 years
Stock option
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock vesting period						4 years

Summary of Significant Accounting Policies - Change in Asset Retirement Obligation (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013
Asset Retirement Obligation
Beginning balance	$ 9,378	$ 6,659
Payments	(782)	0
Accretion	676	456
Additions and revisions of prior estimates	2,011	2,263
Ending balance	$ 11,283	$ 9,378

Earnings Per Share - Schedule of Basic and Diluted Earnings Per Share (Detail) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Earnings Per Share [Abstract]
Net income	$ 33,238	$ 41,277	$ 28,654	$ 18,371	$ 16,453	$ 21,334	$ 20,192	$ 17,277	$ 121,540	$ 75,256	$ 79,154
Less: net income allocated to outstanding restricted stockholders									(230)	(175)	(105)
Net income allocated to common stockholders									$ 121,310	$ 75,081	$ 79,049
Outstanding	53,838,000	53,801,000	53,733,000	53,505,000	53,035,000	53,103,000	52,948,000	52,946,000	53,719	53,035	52,592
Outstanding assuming dilution									54,296	53,409	52,641

- Definition

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

+ References

+ Details

Earnings Per Share Earnings Per Share - Antidilutive Securities Excluded from EPS Calculation (Details) (Stock option) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Stock option
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Weighted-average outstanding stock options excluded	33	175	1,070

- Definition

Securities (including those issuable pursuant to contingent stock agreements) that could potentially dilute basic earnings per share (EPS) or earnings per unit (EPU) in the future that were not included in the computation of diluted EPS or EPU because to do so would increase EPS or EPU amounts or decrease loss per share or unit amounts for the period presented.

+ References+ Details

Capital Structure and Accumulated Comprehensive Income - Additional Information (Detail) (USD $)	0 Months Ended					12 Months Ended
	Oct. 24, 2014	Jul. 25, 2014	Apr. 25, 2014	Feb. 06, 2014	Jan. 31, 2012	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Equity [Abstract]
Common stock authorized, shares						500,000,000
Common stock, par value						$ 0.01
Common stock issued						53,902,475	53,492,278
Common stock, shares outstanding						53,902,475	52,920,704
Quarterly cash dividend declared	$ 0.125	$ 0.125	$ 0.125	$ 0.125	$ 0.50	$ 0.50	$ 0.375	$ 0.50
Declaration Date	Oct. 24, 2014	Jul. 25, 2014	Apr. 25, 2014	Feb. 06, 2014		Dec. 15, 2014
Record Date	Dec. 15, 2014	Sep. 15, 2014	Jun. 13, 2014	Mar. 14, 2014		Oct. 23, 2014
Payable Date	Jan. 05, 2015	Oct. 03, 2014	Jul. 03, 2014	Apr. 01, 2014
Preferred stock, shares authorized						10,000,000
Preferred stock, par value						$ 0.01
Preferred stock issued						0	0
Preferred stock, shares outstanding						0	0
Authorization to repurchase common stock						$ 50,000,000
Repurchase of common stock (shares)						118,961
Average price per common share of repurchase common stock (in USD per share)						$ 13.21
Remaining authorized repurchase of common stock amount						$ 48,400,000

Capital Structure and Accumulated Comprehensive Income - Changes in Accumulated Other Comprehensive Income (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning Balance	$ (4,017)
Other comprehensive income (loss) before reclassifications	(16,467)
Amounts reclassed from accumulated other comprehensive income	666
Ending Balance	(19,818)
Unrealized gain/(loss) on cash flow hedges
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning Balance	(79)
Other comprehensive income (loss) before reclassifications	(65)
Amounts reclassed from accumulated other comprehensive income	10
Ending Balance	(134)
Unrealized gain/(loss) on short-term investments
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning Balance	(27)
Other comprehensive income (loss) before reclassifications	(14)
Amounts reclassed from accumulated other comprehensive income	0
Ending Balance	(41)
Pension and other post- retirement benefits liability
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning Balance	(3,911)
Other comprehensive income (loss) before reclassifications	(16,388)
Amounts reclassed from accumulated other comprehensive income	656
Ending Balance	$ (19,643)

- Definition

Accumulated change in equity from transactions and other events and circumstances from non-owner sources, net of tax effect, at period end. Excludes Net Income (Loss), and accumulated changes in equity from transactions resulting from investments by owners and distributions to owners. Includes foreign currency translation items, certain pension adjustments, unrealized gains and losses on certain investments in debt and equity securities, other than temporary impairment (OTTI) losses related to factors other than credit losses on available-for-sale and held-to-maturity debt securities that an entity does not intend to sell and it is not more likely than not that the entity will be required to sell before recovery of the amortized cost basis, as well as changes in the fair value of derivatives related to the effective portion of a designated cash flow hedge.

+ References+ Details

Business Combinations - Additional Information (Detail) (USD $)			0 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Jul. 31, 2014 Cadre Services, Inc.	Jul. 31, 2014 Cadre Services, Inc.
Business Acquisition [Line Items]
Cash payments to acquire business			$ 98,300,000
Goodwill	68,647,000	68,403,000		244,000
Goodwill expected to be deductible for tax purposes				$ 0

Business Combinations - Summary of Assets Acquired and Liabilities Assumes (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Jul. 31, 2014 Cadre Services, Inc.
Business Acquisition [Line Items]
Accounts receivable			$ 6,898
Inventory			2,534
Other current assets			174
Fixed assets (net)			73,138
Deferred tax assets (net)			13,966
Accounts payable, accrued expenses and other liabilities			(4,389)
Net tangible assets acquired			92,321
Customer relationships			1,274
Trade name			4,478
Goodwill	68,647	68,403	244
Preliminary purchase price, net of cash acquired			$ 98,317

Business Combinations - Acquired Intangibles (Details) (Cadre Services, Inc., USD $) In Thousands, unless otherwise specified	0 Months Ended
	Jul. 31, 2014
Business Acquisition [Line Items]
Customer relationships	$ 1,274
Trade name	4,478
Total intangible assets	$ 5,752
Customer Relationships
Business Acquisition [Line Items]
Useful life of acquired intangible asset	15 years

Business Combinations - Pro Forma Information (Details) (Cadre Services, Inc., USD $) In Thousands, except Per Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Cadre Services, Inc.
Business Acquisition [Line Items]
Sales	$ 901,916	$ 578,453	$ 481,100
Net income	$ 126,960	$ 76,942	$ 82,782
Basic earnings per share (in USD per share)	$ 2.36	$ 1.45	$ 1.57
Diluted earnings per share (in USD per share)	$ 2.33	$ 1.44	$ 1.57

Accounts Receivable - Schedule of Accounts Receivable (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Receivables [Abstract]
Trade receivables	$ 128,498	$ 76,223
Less: Allowance for doubtful accounts	(10,429)	(2,376)
Net trade receivables	118,069	73,847
Other receivables	2,812	1,360
Total accounts receivable	$ 120,881	$ 75,207

Accounts Receivable - Allowance for Doubtful Accounts (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013
Allowance for Doubtful Accounts Receivable [Roll Forward]
Balance at January 1,	$ 2,376	$ 1,053
Bad debt provision	10,200	1,330
Write-offs	(2,147)	(7)
Balance at December 31,	$ 10,429	$ 2,376

Inventories - Schedule of Inventories (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Inventory Disclosure [Abstract]
Supplies	$ 17,528	$ 15,576
Raw materials and work in process	12,562	11,728
Finished goods	36,622	36,908
Total inventories	$ 66,712	$ 64,212

Property, Plant and Mine Development - Additional Information (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Property, Plant and Equipment [Abstract]
Property, plant and equipment interest capitalization	$ 1,376	$ 533	$ 934
Capital lease obligation	$ 0

Property, Plant and Mine Development - Schedule of Property, Plant and Mine Development (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Property, Plant and Equipment
Property, plant and mine development	$ 722,511	$ 555,435
Accumulated depletion, depreciation and amortization	(156,756)	(113,319)
Total property, plant and mine development, net	565,755	442,116
Mining property and mine development
Property, Plant and Equipment
Property, plant and mine development	197,824	164,609
Asset retirement cost
Property, Plant and Equipment
Property, plant and mine development	9,559	7,275
Land
Property, Plant and Equipment
Property, plant and mine development	28,443	25,738
Land improvements
Property, Plant and Equipment
Property, plant and mine development	35,322	31,093
Buildings
Property, Plant and Equipment
Property, plant and mine development	47,149	36,311
Machinery and equipment
Property, Plant and Equipment
Property, plant and mine development	323,618	263,304
Furniture and fixtures
Property, Plant and Equipment
Property, plant and mine development	1,599	1,131
Construction-in-progress
Property, Plant and Equipment
Property, plant and mine development	$ 78,997	$ 25,974

Accrued Liabilities - Schedule of Accrued Liabilities (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Payables and Accruals [Abstract]
Accrued salaries and wages	$ 3,144	$ 2,411
Accrued vacation liability	2,616	2,396
Current portion of liability for pension and post-retirement benefits	1,530	1,428
Accrued healthcare liability	1,745	1,662
Accrued property taxes and sales taxes	2,737	1,421
Other accrued liabilities	6,139	1,505
Total accrued liabilities	$ 17,911	$ 10,823

- Definition

Carrying value as of the balance sheet date of obligations incurred through that date and payable to insurance entities to mitigate potential loss from various risks or to satisfy a promise to provide certain coverage's to employees. Used to reflect the current portion of the liabilities (due within one year or within the normal operating cycle if longer).

+ References+ Details

- Definition

Carrying value as of the balance sheet date of the obligations incurred through that date and payable for employees' services provided. Used to reflect the current portion of the liabilities (due within one year or within the normal operating cycle if longer).

+ References+ Details

- Definition

Carrying value as of the balance sheet date of obligations incurred through that date and payable arising from transactions not otherwise specified in the taxonomy. Used to reflect the current portion of the liabilities (due within one year or within the normal operating cycle if longer).

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- Definition

The current liability recognized in the balance sheet that is associated with defined benefit pension plans and other postretirement and postemployment benefit plans.

+ References+ Details

Debt - Additional Information (Detail) (USD $)	0 Months Ended	12 Months Ended		0 Months Ended	12 Months Ended			12 Months Ended					0 Months Ended
Debt - Additional Information (Detail) (USD $)	Jul. 23, 2013	Dec. 31, 2014	Jul. 23, 2013	Jul. 23, 2013 Revolving Line-of-Credit	Dec. 31, 2012 Revolving Line-of-Credit	Dec. 31, 2014 Revolving Line-of-Credit	Jul. 23, 2013 Revolving Line-of-Credit	Dec. 31, 2012 Revolving Line-of-Credit Minimum	Dec. 31, 2012 Revolving Line-of-Credit Maximum	Jul. 23, 2013 Swingline loans	Dec. 31, 2014 Letter of Credit	Jul. 23, 2013 Letter of Credit	Jul. 23, 2013 Term loan facility	Dec. 05, 2014 Term loan facility	Jul. 23, 2013 Term loan facility
Short-term Debt
Available borrowing base			$ 425,000,000			$ 50,000,000	$ 50,000,000			$ 5,000,000		$ 20,000,000		$ 502,000,000	$ 375,000,000
Amount drawn from borrowing base						0
Amount allocated for letters of credit											3,200,000
Amount available for general corporate use under this revolving credit agreement		46,800,000
Increase of commitment								35,000,000	50,000,000
Letter of credit sublimit								15,000,000	20,000,000
New Revolver expiration Date				Jul. 23, 2018	Oct. 31, 2016								Jul. 23, 2020
Expense associated with refinancing our Term Loan and replacing Revolver	1,800,000
Third party fees in selling general, and administrative expenses	1,300,000
Expense associated with related to early extinguishment of debt	500,000
Increase in borrowing capacity														$ 135,000,000
Facility consolidated total net leverage ratio		0.03751
Increase of commitment		25.00%

Debt - Schedule of Debt (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Line of Credit Facility
Long-term Debt	$ 502,297	$ 371,451
Less: current portion	(4,718)	(3,488)
Total long-term portion of debt	497,579	367,963
Senior Secured Credit Facility \| Revolver
Line of Credit Facility
Long-term Debt	0	0
Senior Secured Credit Facility \| Term loan facility
Line of Credit Facility
Long-term Debt	$ 502,297	$ 371,451

- Definition

Carrying amount of long-term debt, net of unamortized discount or premium, including current and noncurrent amounts. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

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Debt - Schedule of Contractual Maturities of Debt (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Debt Disclosure [Abstract]
2015	$ 4,718
2016	4,722
2017	4,725
2018	4,729
2019	4,733
Thereafter	478,670
Long-term Debt	$ 502,297	$ 371,451

- Definition

+ References+ Details

Debt - Schedule of Debt (Phantom) (Detail) (USD $) In Thousands, unless otherwise specified	0 Months Ended	12 Months Ended	0 Months Ended	12 Months Ended				12 Months Ended
	Jul. 23, 2013 Revolver	Dec. 31, 2012 Revolver	Jul. 23, 2013 Term loan facility	Dec. 31, 2014 Senior Secured Credit Facility Revolver	Dec. 31, 2013 Senior Secured Credit Facility Revolver	Dec. 31, 2014 Senior Secured Credit Facility Term loan facility	Dec. 31, 2013 Senior Secured Credit Facility Term loan facility	Dec. 31, 2014 Senior Secured Credit Facility Minimum Term loan facility	Dec. 31, 2014 Senior Secured Credit Facility Maximum Term loan facility
Line of Credit Facility
Credit facility, maturity date	Jul. 23, 2018	Oct. 31, 2016	Jul. 23, 2020	Jul. 23, 2018	Oct. 31, 2016			Jul. 23, 2020
Credit facility, interest rate				4.75%	4.75%		4.00%	4.00%	5.25%
Term loan facility unamortized original issue discount						$ 2,078	$ 1,674

Fair Value Accounting - Schedule of Measure at Fair Value on Recurring Basis (Detail) (Measured at Fair Value on Recurring Basis, USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Defined Benefit Plan Disclosure
Short-term investments	$ 75,143	$ 74,980
Interest rate derivatives	5	109
Net asset	75,148	75,089
Level 1
Defined Benefit Plan Disclosure
Short-term investments	666	622
Interest rate derivatives	0	0
Net asset	666	622
Level 2
Defined Benefit Plan Disclosure
Short-term investments	74,477	74,358
Interest rate derivatives	5	109
Net asset	$ 74,482	$ 74,467

- Definition

Fair value of financial asset or other contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset, elected not to be offset against an obligation to return collateral under a master netting arrangement.

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Short-Term Investments - Schedule of Available-for-Sale Short-Term Investments (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Schedule of Available-for-sale Securities
Aggregate Cost	$ 75,207	$ 75,024
Gross Unrealized Gains	11	10
Gross Unrealized Losses	(75)	(54)
Fair Value	75,143	74,980
Money market mutual funds
Schedule of Available-for-sale Securities
Aggregate Cost	666	622
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Fair Value	666	622
Certificates of deposit
Schedule of Available-for-sale Securities
Aggregate Cost	29,233	25,218
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(23)	(34)
Fair Value	29,210	25,184
Commercial paper
Schedule of Available-for-sale Securities
Aggregate Cost	10,187	15,168
Gross Unrealized Gains	7	4
Gross Unrealized Losses	(2)	(1)
Fair Value	10,192	15,171
Corporate notes and bonds
Schedule of Available-for-sale Securities
Aggregate Cost	12,076	9,495
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(29)	(9)
Fair Value	12,047	9,486
Government agencies
Schedule of Available-for-sale Securities
Aggregate Cost	16,681	13,979
Gross Unrealized Gains	4	6
Gross Unrealized Losses	(17)	0
Fair Value	16,668	13,985
U.S. Treasuries
Schedule of Available-for-sale Securities
Aggregate Cost	2,151	4,828
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(4)	(10)
Fair Value	2,147	4,818
Variable Rate Demand Obligation
Schedule of Available-for-sale Securities
Aggregate Cost	4,213	5,714
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Fair Value	$ 4,213	$ 5,714

Derivative Instruments - Additional Information (Detail) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Upper limit of LIBOR for one-month	4.00%
Ineffective portion of derivative contracts	$ 0	$ 0

Derivative Instruments - Estimated Fair Values of Derivative Instruments (Detail) (Interest Rate Cap Agreement, USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013
Interest Rate Cap Agreement
Derivative Instruments, Gain (Loss)
Maturity Date	2016
Contract/Notional Amount	$ 188,000,000	$ 188,000,000
Carrying Amount	5,000	109,000
Fair Value	$ 5,000	$ 109,000

Derivative Instruments - Effect of Derivatives Instruments on Combined Statements of Operations and Comprehensive Income (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Deferred losses from derivatives in OCI, beginning of period	$ (79)	$ (182)	$ (409)
Loss recognized in OCI from derivative instruments	(65)	(82)	0
Loss reclassified from Accumulated OCI	10	185	227
Deferred losses from derivatives in OCI, end of period	$ (134)	$ (79)	$ (182)

Equity-Based Compensation - Additional Information (Detail) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Option Indexed to Issuer's Equity
Stock vesting period	5 years
Intrinsic value of stock options exercised	$ 10,900,000	$ 5,900,000	$ 100,000
Cash received from options exercised	5,563,000	7,942,000	0
Actual tax benefit realized for the tax deductions from option exercises	4,200,000	2,300,000	20,000
Unrecognized compensation expense related to stock options	5,900,000
Stock option
Option Indexed to Issuer's Equity
Stock vesting period	4 years
Recognized compensation expense	1,900,000	2,000,000	2,200,000
Recognized weighted-average period	3 years 1 month 6 days
Restricted Stock
Option Indexed to Issuer's Equity
Number of share vested during period	51,866
Recognized compensation expense	5,500,000	1,000,000	100,000
Recognized weighted-average period	1 year 8 months 12 days
Total unrecognized compensation expense	7,000,000
Class C Units
Option Indexed to Issuer's Equity
Number of shares vested, accelerated	210,333
Number of share vested during period	420,667
Recognized compensation expense	$ 91,000	$ 109,000
2011 Incentive Compensation Plan
Option Indexed to Issuer's Equity
Common Stock, Capital Shares Reserved for Future Issuance	5,740,961

Equity-Based Compensation - Summary of Activity with Respect to Stock Options (Detail) (USD $)	12 Months Ended
	Dec. 31, 2014
Number of Shares
Outstanding at December 31, 2013 (shares)	1,231,540
Granted (shares)	206,400
Exercised (shares)	(389,264)
Forfeited (shares)	(65,622)
Outstanding at December 31, 2014 (shares)	983,054
Exercisable at December 31, 2014 (shares)	273,752
Weighted Average Exercise Price
Outstanding at December 31, 2013 (in dollars per share)	$ 15.01
Granted (in dollars per share)	$ 49.39
Exercised (in dollars per share)	$ 14.29
Forfeited (in dollars per share)	$ 16.46
Outstanding at December 31, 2014 (in dollars per share)	$ 22.42
Exercisable at December 31, 2014 (in dollars per share)	$ 15.25
Weighted Average Remaining Contractual Term in Years
Outstanding at December 31, 2014 (years)	7 years 9 months 11 days
Exercisable at December 31, 2014 (years)	7 years 1 month 2 days

Equity-Based Compensation - Restricted Stock Activity (Details) (Restricted Stock, USD $)	12 Months Ended
	Dec. 31, 2014
Restricted Stock
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Unvested, December 31, 2013 (shares)	228,403
Granted (shares)	204,786
Vested (shares)	(51,866)
Forfeited (shares)	(573)
Unvested, December 31, 2014 (shares)	380,750
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract]
Unvested, December 31, 2013 (in dollars per share)	$ 20.95
Granted (in dollars per share)	$ 31.31
Vested (in dollars per share)	$ 20.62
Forfeited (in dollars per share)	$ 35.26
Unvested, December 31, 2014 (in dollars per share)	$ 26.55

Commitments and Contingencies - Additional Information (Detail) (USD $)	3 Months Ended	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2014 claim	Dec. 31, 2013 claim	Dec. 31, 2012 claim
Insurance [Abstract]
Expense related to operating leases and rental agreements		$ 32,600,000	$ 16,300,000	$ 11,900,000
New claims filed		1	3	2
Products liability claims outstanding		86
Underlying insurance policies receivable	5,100,000
Third-party products claims liability under insurance in other assets	313,000	311,000	313,000
Third-party products claims liability under insurance in other long-term obligations	1,600,000	1,600,000	1,600,000
Gain (loss) from pre-tax adjustments		$ (200,000)	$ (500,000)	$ 3,400,000

Commitments and Contingencies - Contractual Obligations (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014
Operating Lease:
2015	$ 32,178
2016	29,895
2017	27,496
2018	26,001
2019	19,312
Thereafter	38,522
Total future lease commitments	173,404
Minimum Purchase Commitments:
2015	30,635
2016	22,373
2017	17,012
2018	12,895
2019	6,601
Thereafter	16,000
Total minimum purchase commitments	$ 105,516

Income Taxes - Additional Information (Detail) (USD $)	12 Months Ended
Income Taxes - Additional Information (Detail) (USD $)	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Income Tax Disclosure [Abstract]
Alternative minimum tax credit carry forward	$ 18,800,000	$ 22,500,000
Unrecognized tax benefits	0	0
Excess tax benefit	$ 3,813,000	$ 1,380,000	$ 0

Income Taxes - Summary of Income Tax (Expense) Benefit (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Current:
Federal									$ (34,790)	$ (20,819)	$ (22,165)
State									(4,835)	(1,831)	(6,237)
Current income tax total									(39,625)	(22,650)	(28,402)
Deferred:
Federal									(308)	1,453	(3,645)
State									2,750	436	1,396
Deferred income tax total									2,442	1,889	(2,249)
Income tax expense	$ (5,276)	$ (14,427)	$ (11,330)	$ (6,150)	$ (1,658)	$ (5,739)	$ (6,878)	$ (6,486)	$ (37,183)	$ (20,761)	$ (30,651)

- Definition

Amount of current income tax expense (benefit) pertaining to taxable income (loss) from continuing operations.

+ References+ Details

- Definition

Amount of current state and local tax expense (benefit) pertaining to income (loss) from continuing operations.

+ References+ Details

- Definition

Amount of deferred federal income tax expense (benefit) pertaining to income (loss) from continuing operations.

+ References+ Details

- Definition

Amount of deferred state and local tax expense (benefit) pertaining to income (loss) from continuing operations.

+ References+ Details

Income Taxes - Summary of Tax Effects on Deferred Tax Assets and Liabilities (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Gross deferred tax assets:
State tax credits and net operating loss carry forward	$ 25,042	$ 1,007
Pension and post-retirement benefit costs	24,788	15,579
Alternative minimum tax credit carry forward	18,819	22,528
Property, plant and equipment	6,580	6,109
Accrued expenses	8,237	3,818
Inventories	5,366	5,863
Third-party products liability	636	674
Stock-based compensation expense	3,019	1,306
Other	8,457	5,502
Total deferred tax assets	100,944	62,386
Gross deferred tax liabilities:
Land and mineral property basis difference	(65,217)	(61,366)
Fixed assets and depreciation	(53,383)	(47,016)
Intangible assets	(8,587)	(6,788)
Other	(1,211)	(797)
Total deferred tax liabilities	(128,398)	(115,967)
Net deferred tax liabilities	(27,454)	(53,581)
Deferred income taxes, net	22,295	17,737
Net long-term deferred tax liabilities	$ (49,749)	$ (71,318)

Income Taxes - Summary of Effective Income Tax Rate on Pretax Earnings (Detail)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Income Tax Disclosure [Abstract]
(Expense) benefit computed at U.S. federal statutory rate	(35.00%)	(35.00%)	(35.00%)
Decrease (increase) resulting from:
Statutory depletion	9.80%	11.00%	9.90%
Prior year tax return reconciliation	0.60%	1.90%	(0.50%)
State income taxes, net of federal benefit	(2.10%)	(2.40%)	(2.70%)
Domestic production deduction	2.50%	2.40%	0.70%
Equity-based compensation	0.00%	0.00%	(0.10%)
Other, net	0.80%	0.50%	(0.20%)
Income tax (expense) benefit	(23.40%)	(21.60%)	(27.90%)

Pension and Post-Retirement Benefits - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Defined Benefit Plan Disclosure
Projected benefit obligation, nonqualified pension plan	$ 1.7	$ 1.6
Accumulated benefit obligation of plan assets, nonqualified pension plan	1.7	1.6
Fair value of plan assets, nonqualified pension plan	0	0
Total amounts in accumulated other comprehensive income related to net actuarial gain (loss), net of tax	17.7	2.3
Total amounts in accumulated other comprehensive income related to prior service cost, net of tax	1.6	1.4
Discount rate reflects the expected long-term rates of return	0.05%
Percentage of contributions to individual multiemployer pension funds	5.00%
Company contribution over defined benefit plan	4.00%
Company contributing percentage on defined benefit plan	25.00%
Employee contribution over defined benefit plan	8.00%
Company contributions to defined contribution plan	2.1	1.7	1.4
Pension Benefits
Defined Benefit Plan Disclosure
Accumulated benefit obligation	122.0	99.4
Expected contributions to the plans for the 2015 fiscal year	2.8
Post-retirement Benefits
Defined Benefit Plan Disclosure
Expected contributions to the plans for the 2015 fiscal year	$ 1.4
Certain Employees
Defined Benefit Plan Disclosure
Employee contribution over defined benefit plan	8.00%
Company contribution on profit sharing match	75.00%
Other Employees
Defined Benefit Plan Disclosure
Company contribution on profit sharing match	25.00%

Pension and Post-Retirement Benefits - Summarizes Information about Pension and Post-Retirement Benefit Plans (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Pension Benefits
Pension Plans, Postretirement and Other Employee Benefits
Service cost—benefits earned during the period	$ 1,080	$ 1,280	$ 1,118
Interest cost	4,811	4,198	4,734
Expected return on plan assets	(5,146)	(5,061)	(5,381)
Net amortization and deferral	1,037	1,904	1,105
Net pension benefit or post-retirement costs	1,782	2,321	1,576
Post-retirement Benefits
Pension Plans, Postretirement and Other Employee Benefits
Service cost—benefits earned during the period	151	193	197
Interest cost	1,030	947	1,163
Expected return on plan assets	(4)	(4)	(4)
Net amortization and deferral	0	87	177
Net pension benefit or post-retirement costs	$ 1,177	$ 1,223	$ 1,533

Pension and Post-Retirement Benefits - Changes in Benefit Obligations and Plan Assets (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Pension Benefits
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit obligation, beginning balance	$ 99,828	$ 107,619
Service cost	1,080	1,280	1,118
Interest cost	4,811	4,198	4,734
Actuarial gain (loss)	22,163	(8,071)
Benefits paid	(6,017)	(5,749)
Amendments	471	551
Other	0	0
Benefit obligation, ending balance	122,336	99,828	107,619
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets, beginning balance	85,367	80,850
Actual return on plan assets	6,937	7,986
Employer contributions	4,610	2,280
Benefits paid	(6,017)	(5,749)
Other	0	0
Fair value of plan assets, ending balance	90,897	85,367	80,850
Plan assets less than benefit obligations at December 31 recognized as liability for pension and other post-retirement benefits	(31,439)	(14,461)
Post-retirement Benefits
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit obligation, beginning balance	22,261	25,717
Service cost	151	193	197
Interest cost	1,030	947	1,163
Actuarial gain (loss)	5,340	(3,933)
Benefits paid	(996)	(1,102)
Amendments	0	0
Other	503	439
Benefit obligation, ending balance	28,289	22,261	25,717
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets, beginning balance	51	54
Actual return on plan assets	3	8
Employer contributions	492	652
Benefits paid	(996)	(1,102)
Other	469	439
Fair value of plan assets, ending balance	19	51	54
Plan assets less than benefit obligations at December 31 recognized as liability for pension and other post-retirement benefits	$ (28,270)	$ (22,210)

Pension and Post-Retirement Benefits - Estimated Future Pension and Post-Retirement Benefit Payments (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014
Pension Benefits
Pension Plans, Postretirement and Other Employee Benefits
2015	$ 6,569
2016	6,756
2017	7,048
2018	7,187
2019	7,370
2020-2024	38,348
Post-retirement Benefits \| Before Medicare Subsidy
Pension Plans, Postretirement and Other Employee Benefits
2015	1,587
2016	1,640
2017	1,716
2018	1,710
2019	1,747
2020-2024	9,545
Post-retirement Benefits \| After Medicare Subsidy
Pension Plans, Postretirement and Other Employee Benefits
2015	1,426
2016	1,472
2017	1,540
2018	1,527
2019	1,557
2020-2024	$ 8,522

Pension and Post-Retirement Benefits - Amounts in Accumulated Other Comprehensive Income Expected to be Recognized as Components of Net Periodic Benefit Cost (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014
Pension Plans, Postretirement and Other Employee Benefits
Net actuarial loss	$ 2,702
Prior service cost	274
Total	2,976
Pension Benefits
Pension Plans, Postretirement and Other Employee Benefits
Net actuarial loss	2,310
Prior service cost	274
Total	2,584
Post-retirement Benefits
Pension Plans, Postretirement and Other Employee Benefits
Net actuarial loss	392
Prior service cost	0
Total	$ 392

Pension and Post-Retirement Benefits - Company's Obligations Determined under Weighted-Average Assumptions (Detail)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013
Pension Benefits
Pension Plans, Postretirement and Other Employee Benefits
Discount rate	4.10%	4.80%
Long-term rate of compensation increase	3.50%	3.50%
Long-term rate of return on plan assets	7.00%	7.50%
Post-retirement Benefits
Pension Plans, Postretirement and Other Employee Benefits
Discount rate	4.10%	4.80%
Long-term rate of return on plan assets	7.00%	7.50%
Post-retirement Benefits \| Pre-65
Pension Plans, Postretirement and Other Employee Benefits
Ultimate rate	5.00%	5.00%
Ultimate year
Post-retirement Benefits \| Pre-65 \| Maximum
Pension Plans, Postretirement and Other Employee Benefits
Initial rate	7.50%	8.00%
Post-retirement Benefits \| Post-65
Pension Plans, Postretirement and Other Employee Benefits
Ultimate rate	5.00%	5.00%
Ultimate year	2022	2021
Post-retirement Benefits \| Post-65 \| Minimum
Pension Plans, Postretirement and Other Employee Benefits
Initial rate	7.00%	7.30%

Pension and Post-Retirement Benefits - Effect of One-Percentage-Point Change in Assumed Health Care Cost Trend Rates (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014
Compensation and Retirement Disclosure [Abstract]
Effect on total of service and interest cost, increase	$ 136
Effect on post-retirement benefit obligation, increase	3,879
Effect on total of service and interest cost, decrease	(115)
Effect on post-retirement benefit obligation, decrease	$ (3,217)

Pension and Post-Retirement Benefits - Fair Value of Pension Plan Assets (Detail)	Dec. 31, 2014	Dec. 31, 2013
Pension Benefits \| Equity Securities
Pension Plans, Postretirement and Other Employee Benefits
Percentage of the fair value of the total plan assets	57.40%	57.40%
Pension Benefits \| Debt Securities
Pension Plans, Postretirement and Other Employee Benefits
Percentage of the fair value of the total plan assets	40.50%	36.60%
Pension Benefits \| Cash
Pension Plans, Postretirement and Other Employee Benefits
Percentage of the fair value of the total plan assets	2.10%	6.00%
Post-retirement Benefits \| Equity Securities
Pension Plans, Postretirement and Other Employee Benefits
Percentage of the fair value of the total plan assets	45.30%	59.00%
Post-retirement Benefits \| Debt Securities
Pension Plans, Postretirement and Other Employee Benefits
Percentage of the fair value of the total plan assets	30.10%	29.50%
Post-retirement Benefits \| Cash
Pension Plans, Postretirement and Other Employee Benefits
Percentage of the fair value of the total plan assets	24.60%	11.50%

Pension and Post-Retirement Benefits - Summary of Multiemployer Pension Plan (Detail) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
LIUNA
Pension Plans, Postretirement and Other Employee Benefits
EIN/Pension Plan No.	52-6074345/001
Pension Protection Act Zone Status	Red	Red
Company Contributions	$ 149,000	$ 124,000	$ 123,000
Surcharge Imposed	Yes
Expiration Date of CBA	May 31, 2017
IUOE
Pension Plans, Postretirement and Other Employee Benefits
EIN/Pension Plan No.	36-6052390/001
Pension Protection Act Zone Status	Green	Green
Company Contributions	28,000	22,000	19,000
Surcharge Imposed	No
Expiration Date of CBA	Jul. 31, 2015
CSSS
Pension Plans, Postretirement and Other Employee Benefits
EIN/Pension Plan No.	36-6044243/001
Pension Protection Act Zone Status	Red	Red
Company Contributions	51,000	51,000	51,000
Surcharge Imposed	NA
Central States, Southeast and Southwest Areas Pension Plan
Pension Plans, Postretirement and Other Employee Benefits
Withdrawal liability from Pension Plan			1,000,000
Withdrawal liability paid on monthly installments			$ 4,000
Description of withdrawal liability payment schedule			The withdrawal liability of $1.0 million will be paid in monthly installments of $4 until 2031.

Obligations Under Guarantees (Detail) (USD $)	12 Months Ended
Obligations Under Guarantees (Detail) (USD $)	Dec. 31, 2014 railroad_car
Surety Bonds \| Travelers Casualty and Surety Company
Loss Contingencies
Surety bonds outstanding	$ 8,500,000
Reclamation Bonds \| Travelers Casualty and Surety Company
Loss Contingencies
Bonds related to reclamation requirements	8,200,000
Leased Railroad Hopper Cars \| Kanawha Rail Corporation
Loss Contingencies
Number of railroad cars	199
Payment of monthly rent	$ 66,000

Related Party Transactions (Detail) (USD $) In Millions, unless otherwise specified	0 Months Ended	12 Months Ended			1 Months Ended	12 Months Ended
	Feb. 06, 2012 Golden Gate Capital Acquisition Advisory Agreement	Dec. 31, 2014 Golden Gate Capital Acquisition Advisory Agreement	Dec. 31, 2012 Golden Gate Capital Acquisition Advisory Agreement	Dec. 31, 2011 Golden Gate Capital Acquisition Advisory Agreement	Jan. 31, 2012 Promissory Note	Dec. 31, 2014 Promissory Note	Dec. 31, 2013 Promissory Note	Dec. 22, 2010 Promissory Note
Related Party Transaction
Advisory fee to parent		$ 1.25		$ 1.30
Transaction fee percent		1.25%
Termination of advisory agreement	8.0
Termination fee			8.0
Additional expense			0
Promissory note with GGC USS Holdings, LLC.								15.0
Promissory note, maturity date						Dec. 22, 2015
Interest rate of promissory note								10.00%
Promissory note, payment terms						Outstanding principal and interest under the note was payable upon demand, but no later than the maturity date. Upon sole election by the parent, any unpaid interest could be paid in cash on December 22 of each year until the maturity date.
Conversion of promissory note to equity					15.0
Accrued interest					$ 1.7
Percentage of Interest held							0.00%

Segment Reporting - Additional Information (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014 Product Segment	Dec. 31, 2013
Segment Reporting Information
Number of reportable segments	2
Number of products in Industrial & Specialty segment (over 250)	250
Industrial & Specialty Products segment, description	The Industrial & Specialty Products segment consists of over 250 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.
Goodwill	$ 68,647	$ 68,403
Operating Segments
Segment Reporting Information
Goodwill	68,400
Operating Segments \| Oil and Gas Proppants
Segment Reporting Information
Goodwill	47,700
Operating Segments \| Industrial and 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, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Segment Reporting Information
Total sales	$ 249,589	$ 241,256	$ 205,801	$ 180,095	$ 149,474	$ 144,372	$ 129,828	$ 122,311	$ 876,741	$ 545,985	$ 441,921
Selling, general and administrative	(35,659)	(18,600)	(19,267)	(15,445)	(14,456)	(12,800)	(10,099)	(12,404)	(88,971)	(49,759)	(41,299)
Depreciation, depletion and amortization	(12,664)	(12,425)	(10,341)	(9,589)	(10,098)	(9,152)	(8,890)	(8,278)	(45,019)	(36,418)	(25,099)
Interest expense	(5,431)	(4,950)	(4,013)	(3,808)	(4,086)	(4,144)	(3,535)	(3,576)	(18,202)	(15,341)	(13,795)
Early extinguishment of debt					0	(480)	0	0	0	(480)	0
Other income, net, including interest income	379	120	221	38	152	260	63	122	758	597	4,612
Income before income taxes	38,514	55,704	39,984	24,521	18,111	27,073	27,070	23,763	158,723	96,017	109,805
Operating Segments
Segment Reporting Information
Total sales									876,741	545,985	441,921
Total segment contribution margin									317,239	202,899	193,671
Operating Segments \| Oil and Gas Proppants
Segment Reporting Information
Total sales									662,770	347,439	243,765
Total segment contribution margin									256,137	145,916	140,070
Operating Segments \| Industrial and Specialty Products
Segment Reporting Information
Total sales									213,971	198,546	198,156
Total segment contribution margin									61,102	56,983	53,601
Segment Reconciling Items
Segment Reporting Information
Operating activities excluded from segment cost of goods sold									7,082	5,481	8,285
Selling, general and administrative									88,971	49,759	41,299
Depreciation, depletion and amortization									45,019	36,418	25,099
Interest expense									18,202	15,341	13,795
Early extinguishment of debt									0	(480)	0
Other income, net, including interest income									$ 758	$ 597	$ 4,612

Unaudited Supplementary Data (Detail) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Quarterly Financial Information Disclosure [Abstract]
Sales	$ 249,589	$ 241,256	$ 205,801	$ 180,095	$ 149,474	$ 144,372	$ 129,828	$ 122,311	$ 876,741	$ 545,985	$ 441,921
Costs of goods sold	157,700	149,697	132,417	126,770	102,875	90,983	80,297	74,412	566,584	348,567	256,535
Operating expenses
Selling, general and administrative	35,659	18,600	19,267	15,445	14,456	12,800	10,099	12,404	88,971	49,759	41,299
Depreciation, depletion and amortization	12,664	12,425	10,341	9,589	10,098	9,152	8,890	8,278	45,019	36,418	25,099
Total operating expenses	48,323	31,025	29,608	25,034	24,554	21,952	18,989	20,682	133,990	86,177	66,398
Operating income	43,566	60,534	43,776	28,291	22,045	31,437	30,542	27,217	176,167	111,241	118,988
Other (expense) income
Interest expense	(5,431)	(4,950)	(4,013)	(3,808)	(4,086)	(4,144)	(3,535)	(3,576)	(18,202)	(15,341)	(13,795)
Early extinguishment of debt					0	(480)	0	0	0	(480)	0
Other income, net, including interest income	379	120	221	38	152	260	63	122	758	597	4,612
Total other (expenses) income	(5,052)	(4,830)	(3,792)	(3,770)	(3,934)	(4,364)	(3,472)	(3,454)	(17,444)	(15,224)	(9,183)
Income before income taxes	38,514	55,704	39,984	24,521	18,111	27,073	27,070	23,763	158,723	96,017	109,805
Income tax expense	(5,276)	(14,427)	(11,330)	(6,150)	(1,658)	(5,739)	(6,878)	(6,486)	(37,183)	(20,761)	(30,651)
Net income	$ 33,238	$ 41,277	$ 28,654	$ 18,371	$ 16,453	$ 21,334	$ 20,192	$ 17,277	$ 121,540	$ 75,256	$ 79,154
Earnings per share, basic	$ 0.62	$ 0.77	$ 0.53	$ 0.34	$ 0.31	$ 0.40	$ 0.38	$ 0.33	$ 2.26	$ 1.42	$ 1.50
Earnings per share, diluted	$ 0.61	$ 0.76	$ 0.53	$ 0.34	$ 0.31	$ 0.40	$ 0.38	$ 0.32	$ 2.23	$ 1.41	$ 1.50
Weighted average common shares outstanding (in thousands), basic	53,838,000	53,801,000	53,733,000	53,505,000	53,035,000	53,103,000	52,948,000	52,946,000	53,719	53,035	52,592
Weighted average common shares outstanding (in thousands), diluted	54,340,000	54,393,000	54,262,000	54,054,000	53,409,000	53,429,000	53,227,000	52,211,000

Subsequent Events (Detail) (USD $) In Thousands, except Share data, unless otherwise specified	0 Months Ended					12 Months Ended			0 Months Ended		2 Months Ended
	Oct. 24, 2014	Jul. 25, 2014	Apr. 25, 2014	Feb. 06, 2014	Jan. 31, 2012	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Feb. 12, 2015 Subsequent Event	Jan. 05, 2015 Subsequent Event	Feb. 25, 2015 Subsequent Event
Subsequent Event
Cash dividend paid										$ 0.125
Dividend declared date	Oct. 24, 2014	Jul. 25, 2014	Apr. 25, 2014	Feb. 06, 2014		Dec. 15, 2014
Dividend declared, record date	Dec. 15, 2014	Sep. 15, 2014	Jun. 13, 2014	Mar. 14, 2014		Oct. 23, 2014
Common stock cash dividend declared, per share	$ 0.125	$ 0.125	$ 0.125	$ 0.125	$ 0.50	$ 0.50	$ 0.375	$ 0.50	$ 0.125
Number of repurchased shares, common stock											587,132
Payments made for repurchase of common stock						$ 499	$ 0	$ 1,072			$ 15,000

Subsequent Events	12 Months Ended
Subsequent Events	Dec. 31, 2014
Subsequent Events [Abstract]
Subsequent Events	SUBSEQUENT EVENTS On January 5, 2015, we paid a cash dividend of $0.125 per share to common stockholders of record on December 15, 2014, as had been declared by our Board of Directors on October 23, 2014. On February 12, 2015, our Board of Directors declared a quarterly cash dividend of $0.125 per share to common stockholders of record at the close of business on March 16, 2015, payable on April 3, 2015.

Deferred Revenue (Detail) (Supply Agreement, USD $) In Millions, unless otherwise specified	0 Months Ended
	Jul. 03, 2014	Jul. 03, 2014
Supply Agreement
Deferred Revenue Arrangement [Line Items]
Advances received from a customer	$ 100
Deferred revenue, interest rate on unused customer deposits		0.049

Accounts Receivable - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014
Receivables [Abstract]
Net trade receivables increase	$ 44.2

Income Taxes - Operating Loss Carryforwards (Details) (Cadre Services, Inc., IRS, USD $) In Millions, unless otherwise specified	Dec. 31, 2014
Cadre Services, Inc. \| IRS
Operating Loss Carryforwards [Line Items]
Federal net operating loss carryforwards	$ 69.0