Continental Building Products (CBPX) 10-Q 9 Nov 18 2018 Q3 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	9 Months Ended
	Sep. 30, 2018	Nov. 05, 2018
Document and Entity Information [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Sep. 30, 2018
Document Fiscal Year Focus	2,018
Document Fiscal Period Focus	Q3
Trading Symbol	CBPX
Entity Registrant Name	CONTINENTAL BUILDING PRODUCTS, INC.
Entity Central Index Key	1,592,480
Current Fiscal Year End Date	--12-31
Entity Current Reporting Status	Yes
Entity Filer Category	Large Accelerated Filer
Entity Emerging Growth Company	false
Entity Small Business	false
Entity Common Stock, Shares Outstanding		36,841,935

Consolidated Statements of Oper

Consolidated Statements of Operations - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Income Statement [Abstract]
Net sales	$ 131,234	$ 116,526	$ 387,304	$ 357,771
Costs, expenses and other income:
Cost of goods sold	94,306	87,952	279,185	267,393
Selling and administrative	9,957	8,867	29,826	27,364
Total costs and operating expenses	104,263	96,819	309,011	294,757
Operating income	26,971	19,707	78,293	63,014
Other (expense)/income, net	(29)	146	(256)	(633)
Interest expense, net	(2,549)	(2,988)	(7,963)	(8,966)
Income before losses from equity method investment and provision for income taxes	24,393	16,865	70,074	53,415
Losses from equity method investment	(393)	(204)	(1,148)	(29)
Income before provision for income taxes	24,000	16,661	68,926	53,386
Provision for income taxes	(5,436)	(5,674)	(14,821)	(17,774)
Net income	$ 18,564	$ 10,987	$ 54,105	$ 35,612
Net income per share:
Basic (usd per share)	$ 0.51	$ 0.29	$ 1.46	$ 0.91
Diluted (usd per share)	$ 0.50	$ 0.29	$ 1.46	$ 0.91
Weighted average shares outstanding:
Basic (shares)	36,732,746	38,212,869	37,012,536	38,966,575
Diluted (shares)	36,918,904	38,345,556	37,181,387	39,080,973

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Statement of Comprehensive Income [Abstract]
Net income	$ 18,564	$ 10,987	$ 54,105	$ 35,612
Foreign currency translation adjustment	298	695	(496)	1,259
Net (losses)/gains on derivatives, net of taxes	(8)	127	1,489	(451)
Other comprehensive income	290	822	993	808
Comprehensive income	$ 18,854	$ 11,809	$ 55,098	$ 36,420

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Assets:
Cash and cash equivalents	$ 105,452	$ 72,521
Trade receivables, net	39,597	38,769
Inventories, net	32,439	24,882
Prepaid and other current assets	11,605	11,267
Total current assets	189,093	147,439
Property, plant and equipment, net	290,670	294,003
Customer relationships and other intangibles, net	64,661	70,807
Goodwill	119,945	119,945
Equity method investment	8,194	9,263
Debt issuance costs	341	477
Total Assets	672,904	641,934
Liabilities:
Accounts payable	32,253	30,809
Accrued and other liabilities	13,239	11,940
Notes payable, current portion	1,670	1,702
Total current liabilities	47,162	44,451
Deferred taxes and other long-term liabilities	15,392	15,847
Notes payable, non-current portion	262,400	263,610
Total Liabilities	324,954	323,908
Shareholders' Equity:
Undesignated preferred stock, par value $0.001 per share; 10,000,000 shares authorized, no shares issued and outstanding	0	0
Common stock, $0.001 par value per share; 190,000,000 shares authorized; 44,422,804 and 44,321,776 shares issued and 36,681,879 and 37,532,959 shares outstanding as of September 30, 2018 and December 31, 2017, respectively	44	44
Additional paid-in capital	327,643	325,391
Less: Treasury stock	(170,782)	(143,357)
Accumulated other comprehensive loss	(1,656)	(2,649)
Accumulated earnings	192,701	138,597
Total Shareholders' Equity	347,950	318,026
Total Liabilities and Shareholders' Equity	$ 672,904	$ 641,934

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - $ / shares	Sep. 30, 2018	Dec. 31, 2017
Statement of Financial Position [Abstract]
Undesignated preferred stock, par value (usd per share)	$ 0.001	$ 0.001
Undesignated preferred stock, shares authorized (in shares)	10,000,000	10,000,000
Undesignated preferred stock, shares issued (in shares)	0	0
Undesignated preferred stock, shares outstanding (in shares)	0	0
Common stock, par value (usd per share)	$ 0.001	$ 0.001
Common stock, shares authorized (in shares)	190,000,000	190,000,000
Common stock, shares issued (in shares)	44,422,804	44,321,776
Common stock, shares outstanding (in shares)	36,681,879	37,532,959

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Cash flows from operating activities:
Net income	$ 54,105	$ 35,612
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	32,966	35,817
Amortization of debt issuance costs and debt discount	931	885
Losses from equity method investment	1,148	29
Amortization of deferred gain on terminated swaps	(632)	0
Loss on debt extinguishment	0	686
Share-based compensation	2,459	2,101
Deferred taxes	(457)	92
Change in assets and liabilities:
Trade receivables	(914)	1,420
Inventories	(7,627)	(872)
Prepaid expenses and other current assets	1,264	(350)
Accounts payable	(52)	(87)
Accrued and other current liabilities	1,089	4
Other long-term liabilities	(226)	(245)
Net cash provided by operating activities	84,054	75,092
Cash flows from investing activities:
Capital expenditures	(19,761)	(14,077)
Software purchased or developed	(1,359)	(183)
Proceeds from the sale of property, plant and equipment	125	0
Capital contributions to equity method investment	(548)	(1,929)
Distributions from equity method investment	468	641
Net cash used in investing activities	(21,075)	(15,548)
Cash flows from financing activities:
Proceeds from exercise of stock options	145	230
Tax withholdings on share-based compensation	(547)	(240)
Proceeds from debt refinancing	0	273,625
Disbursements for debt refinancing	0	(273,625)
Payments of financing costs	0	(649)
Principal payments for debt	(2,037)	(2,052)
Payments to repurchase common stock	(27,425)	(49,128)
Net cash used in financing activities	(29,864)	(51,839)
Effect of foreign exchange rates on cash and cash equivalents	(184)	707
Net change in cash and cash equivalents	32,931	8,412
Cash, beginning of period	72,521	51,536
Cash, end of period	$ 105,452	$ 59,948

Background and Nature of Operat

Background and Nature of Operations	9 Months Ended
	Sep. 30, 2018
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Background and Nature of Operations	BACKGROUND AND NATURE OF OPERATIONS Description of Business Continental Building Products, Inc. (the "Company") is a Delaware corporation. Prior to the acquisition of the gypsum division of Lafarge North America Inc. ("Lafarge N.A.") described below, the Company had no operating activity. The Company manufactures gypsum wallboard related products for commercial and residential buildings and houses. The Company operates a network of three highly efficient wallboard facilities, all located in the eastern United States, and produces joint compound at one plant in the United States and at another plant in Canada. The Acquisition On June 24, 2013 , the Company's former controlling stockholder entered into a definitive agreement with Lafarge N.A. to purchase the assets of its North American gypsum division for an aggregate purchase price of approximately $703 million (the "Acquisition") in cash. The closing of the Acquisition occurred on August 30, 2013 .

Significant Accounting Policies

Significant Accounting Policies	9 Months Ended
	Sep. 30, 2018
Accounting Policies [Abstract]
Significant Accounting Policies	SIGNIFICANT ACCOUNTING POLICIES (a) Basis of Presentation The accompanying consolidated financial statements for the Company have been prepared in accordance with accounting principles generally accepted in the United States ("U.S. GAAP"). The consolidated financial statements include the accounts of the Company and its wholly-owned subsidiaries. All intercompany transactions have been eliminated. (b) Basis of Presentation for Interim Periods Certain information and footnote disclosures normally included for the annual financial statements prepared in accordance with U.S. GAAP have been condensed or omitted for the interim periods presented. Management believes that the unaudited interim financial statements include all adjustments (which are normal and recurring in nature) necessary to present fairly the financial position of the Company and the results of operations and cash flows for the periods presented. The results of operations for the periods presented are not necessarily indicative of the results that may be expected for the year ending December 31, 2018. Seasonal changes and other conditions can affect the sales volumes of the Company's products. Therefore, the financial results for any interim period do not necessarily indicate the expected results for the year. The financial statements should be read in conjunction with Company's audited consolidated financial statements and the notes thereto for the year ended December 31, 2017 included in the Company's Annual Report on Form 10-K for the fiscal year then ended. The Company has continued to follow the accounting policies set forth in those financial statements. (c) Revenue Disclosure Revenue from the sale of gypsum products is recognized when control of the promised products is transferred to the Company's customers, in an amount that reflects the consideration the Company expects to be entitled to in exchange for those products (the transaction price). A performance obligation is a promise in a contract to transfer a distinct product to a customer and is the unit of account under Financial Accounting Standards Board ("FASB") Accounting Standards Codification ("ASC") Topic 606. Control transfers to the customer at a point in time. To indicate the transfer of control, the Company must have a present right to payment, legal title must have passed to the customer and the customer must have the significant risks and rewards of ownership. Generally, the Company satisfies its performance obligations within a number of days from the time the contract is executed. The Company records estimated reductions to revenue for customer programs and incentive offerings, including promotions and other volume-based incentives, in the period in which the sale occurs. Amounts billed to a customer at the transaction price are included in net sales, and costs incurred for shipping and handling are treated as fulfillment costs and are classified as cost of goods sold in the Consolidated Statements of Operations. See Note 17, Segment reporting, for disaggregation of revenue by segment. As of September 30, 2018 , accounts receivables were $39.6 million . The Company had no material contract assets, contract liabilities or deferred contract costs recorded on the Consolidated Balance Sheets as of September 30, 2018 . The Company does not have any material payment terms as payment is received shortly after the point of sale. (d) Supplemental Cash Flow Disclosure Table 2.1: Certain Cash Transactions and Other Activity For the Nine Months Ended September 30, 2018 September 30, 2017 (in thousands) Cash paid during the period for: Interest paid on term loan, net $ 8,049 $ 7,582 Income taxes paid, net 15,903 16,338 Other activity: Amounts in accounts payable for capital expenditures 1,538 1,123 (e) Recent Accounting Pronouncements Accounting Standards Recently Adopted In May 2014, the FASB issued ASU No. 2014-9, "Revenue from Contracts with Customers (Topic 606)," which provides accounting guidance for all revenue arising from contracts with customers and affects all entities that enter into contracts to provide goods or services to their customers. In August 2015, the FASB issued ASU No. 2015-14, "Revenue from Contracts with Customers (Topic 606): Deferral of the Effective Date," which deferred the effective date of ASU No. 2014-9 for all entities by one year to annual reporting periods beginning after December 15, 2017. The ASU requires retroactive application on either a full or modified basis. The Company adopted the standard on January 1, 2018 using the modified retrospective approach. Based on its evaluation, the Company has concluded it has one revenue stream and the adoption of this new guidance did not have a material impact on its Consolidated Financial Statements. In August 2016, the FASB issued ASU 2016-15, "Classification of Certain Cash Receipts and Cash Payments." This ASU reduces existing diversity in the classification of certain cash receipts and cash payments on the statements of cash flows. ASU 2016-15 is effective for fiscal years beginning after December 15, 2017, and for interim periods within those fiscal years. The adoption of this standard did not have a material impact on the Company's Consolidated Financial Statements. In October 2016, the FASB issued ASU 2016-16, "Intra-Entity Transfers of Assets Other Than Inventory." The new standard requires companies to recognize the income tax effects of intercompany sales or transfers of assets, other than inventory, in the income statement as income tax expense (or benefit) in the period the sales or transfer occurs. The standard requires companies to apply a modified retrospective approach with a cumulative catch-up adjustment to opening retained earnings in the period of adoption. The provisions of this standard are effective for fiscal years beginning after December 15, 2017, and early adoption is permitted. The adoption of this standard did not have a material impact on the Company's Consolidated Financial Statements. Accounting Standards Not Yet Adopted In February 2016, the FASB issued ASU 2016-02, "Leases." ASU 2016-02 requires lessees to recognize a lease liability and a right-of-use asset on the balance sheet. ASU 2016-02 is effective for fiscal years beginning after December 15, 2018, including interim periods within those fiscal years. The Company will adopt the standard on January 1, 2019. The Company will take advantage of the transition package of practical expedients permitted within the new standard, which among other things, allows companies to carryforward the historical lease classification. In addition, the Company is electing the comparative period practical expedient, which allows the Company to implement the guidance as of the effective date without having to adjust the comparative financial statements. Instead, under this expedient, companies will recognize the cumulative effect adjustment in equity. The Company will also make an accounting policy election that leases with an initial term of 12 months or less will not be recorded on the balance sheet and will result in the recognition of those lease payments in the Consolidated Statements of Operations on a straight-line basis over the lease term. While the Company is continuing to evaluate the impact of adoption, it is not expected to have a material impact on its Consolidated Financial Statements. In June 2016, the FASB issued ASU 2016-13, "Financial Instruments – Credit Losses: Measurement of Credit Losses on Financial Instruments." This ASU is intended to introduce a revised approach to the recognition and measurement of credit losses, emphasizing an updated model based on expected losses rather than incurred losses. The provisions of this standard are effective for reporting periods beginning after December 15, 2019 and early adoption is permitted. The Company is currently evaluating the impact that this guidance may have on its Consolidated Financial Statements. In August 2017, the FASB issued ASU 2017-12, "Derivatives and Hedging (Topic 815), Targeted Improvements to Accounting for Hedging Activities." This ASU expands an entity's ability to hedge non-financial and financial risk components and reduce complexity in fair value hedges of interest rate risk. The guidance eliminates the requirement to separately measure and report hedge ineffectiveness and generally requires the entire change in the fair value of a hedging instrument to be presented in the same income statement line as the hedged item. The provisions of this standard are effective in 2019 for calendar-year public business entities and in 2020 for all other calendar-year companies. Early adoption of the standard is permitted. The Company is currently evaluating the impact that this guidance may have on its Consolidated Financial Statements. In February 2018, the FASB issued ASU 2018-02, "Income Statement - Reporting Comprehensive Income (Topic 220), Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income." This ASU allows a reclassification from accumulated other comprehensive income to retained earnings for stranded tax effects resulting from the Tax Cuts and Jobs Act. The provisions of this standard are effective for reporting periods beginning after December 15, 2018 and early adoption is permitted. The Company is currently evaluating the impact that this guidance may have on its Consolidated Financial Statements. In August 2018, the FASB issued ASU 2018-13, "Fair Value Measurements (Topic 820), Changes to the Disclosure Requirements for Fair Value Measurement." This ASU eliminates certain disclosure requirements for fair value measurements for all entities, requires public entities to disclose certain new information and modifies some disclosure requirements. The provisions of this standard are effective for reporting periods beginning after December 15, 2019 and early adoption is permitted. The Company is currently evaluating the impact that this guidance may have on its Consolidated Financial Statements. In August 2018, the FASB issued ASU 2018-15, "Intangibles - Goodwill and Other - Internal-Use Software (Subtopic 350-40), Customer's Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement That Is a Service Contract." This ASU requires a customer in a cloud computing arrangement that is a service contract to follow the internal-use software guidance in Accounting Standards Codification 350-40 to determine which implementation costs to defer and recognize as an asset. The provisions of this standard are effective for reporting periods beginning after December 15, 2019 and early adoption is permitted. The Company is currently evaluating the impact that this guidance may have on its Consolidated Financial Statements. (f) Reclassifications Certain reclassifications of prior year information were made to conform to the 2018 presentation. These reclassifications had no material impact on the Company's Consolidated Financial Statements.

Trade Receivables, Net

Trade Receivables, Net	9 Months Ended
	Sep. 30, 2018
Receivables [Abstract]
Trade Receivables, Net	TRADE RECEIVABLES, NET Table 3: Details of Trade Receivables, Net September 30, 2018 December 31, 2017 (in thousands) Trade receivables, gross $ 40,447 $ 39,577 Allowance for cash discounts and doubtful accounts (850 ) (808 ) Trade receivables, net $ 39,597 $ 38,769 Trade receivables are recorded net of credit memos issued during the normal course of business.

Inventories, Net

Inventories, Net	9 Months Ended
	Sep. 30, 2018
Inventory Disclosure [Abstract]
Inventories, Net	INVENTORIES, NET Table 4: Details of Inventories, Net September 30, 2018 December 31, 2017 (in thousands) Finished products $ 8,195 $ 5,893 Raw materials 16,821 11,663 Supplies and other 7,423 7,326 Inventories, net $ 32,439 $ 24,882

Property, Plant and Equipment,

Property, Plant and Equipment, Net	9 Months Ended
	Sep. 30, 2018
Property, Plant and Equipment [Abstract]
Property, Plant and Equipment, Net	PROPERTY, PLANT AND EQUIPMENT, NET Table 5: Details of Property, Plant and Equipment, Net September 30, 2018 December 31, 2017 (in thousands) Land $ 13,187 $ 13,187 Buildings 115,422 114,051 Plant machinery 284,151 281,786 Mobile equipment 12,828 10,366 Construction in progress 32,186 20,291 Property, plant and equipment, at cost 457,774 439,681 Accumulated depreciation (167,104 ) (145,678 ) Property, plant and equipment, net $ 290,670 $ 294,003 Depreciation expense was $9.1 million and $25.4 million for the three and nine months ended September 30, 2018 , respectively, compared to $9.0 million and $26.5 million for the three and nine months ended September 30, 2017 , respectively.

Customer Relationships and Othe

Customer Relationships and Other Intangibles, Net	9 Months Ended
	Sep. 30, 2018
Goodwill and Intangible Assets Disclosure [Abstract]
Customer Relationships and Other Intangibles, Net	CUSTOMER RELATIONSHIPS AND OTHER INTANGIBLES, NET Table 6.1: Details of Customer Relationships and Other Intangibles, Net September 30, 2018 December 31, 2017 Gross Accumulated Amortization Net Gross Accumulated Amortization Net (in thousands) Customer relationships $ 116,529 $ (64,041 ) $ 52,488 $ 116,711 $ (57,811 ) $ 58,900 Purchased and internally developed software 7,718 (5,340 ) 2,378 6,226 (4,871 ) 1,355 Trademarks 14,816 (5,021 ) 9,795 14,839 (4,287 ) 10,552 Total $ 139,063 $ (74,402 ) $ 64,661 $ 137,776 $ (66,969 ) $ 70,807 Amortization expense was $2.5 million and $7.5 million for the three and nine months ended September 30, 2018 , respectively, compared to $3.0 million and $9.3 million for the three and nine months ended September 30, 2017 , respectively. Table 6.2: Details of Future Amortization Expense of Customer Relationships and Other Intangibles As of September 30, 2018 (in thousands) October 1, 2018 through December 31, 2018 $ 2,766 2019 8,907 2020 8,150 2021 7,410 2022 6,746 Thereafter 30,682 Total $ 64,661

Investment in Seven Hills

Investment in Seven Hills	9 Months Ended
	Sep. 30, 2018
Equity Method Investments and Joint Ventures [Abstract]
Investment in Seven Hills	INVESTMENT IN SEVEN HILLS The Company is a party with an unaffiliated third party to a paperboard liner venture named Seven Hills Paperboard, LLC ("Seven Hills") that, pursuant to a paper supply agreement, provides the Company with a continuous supply of high-quality recycled paperboard liner to meet its ongoing production requirements. The Company has evaluated the characteristics of its investment and determined that Seven Hills is a variable interest entity, but that it does not have the power to direct the principal activities most impacting the economic performance of Seven Hills, and is thus not the primary beneficiary. As such, the Company accounts for this investment in Seven Hills under the equity method of accounting. Paperboard liner purchased from Seven Hills was $12.3 million and $37.4 million for the three and nine months ended September 30, 2018 , respectively, compared to $15.5 million and $42.3 million for the three and nine months ended September 30, 2017 , respectively. As of September 30, 2018 , the Company had certain purchase commitments for paper totaling $29.2 million through 2021 .

Accrued and Other Liabilities

Accrued and Other Liabilities	9 Months Ended
	Sep. 30, 2018
Payables and Accruals [Abstract]
Accrued and Other Liabilities	ACCRUED AND OTHER LIABILITIES Table 8: Details of Accrued and Other Liabilities September 30, 2018 December 31, 2017 (in thousands) Employee-related costs $ 8,471 $ 9,258 Property taxes 2,321 472 Other taxes 562 466 Other 1,885 1,744 Accrued and other liabilities $ 13,239 $ 11,940

Debt

Debt	9 Months Ended
	Sep. 30, 2018
Debt Disclosure [Abstract]
Debt	DEBT Table 9.1: Details of Debt September 30, 2018 December 31, 2017 (in thousands) Amended and Restated Credit Agreement ( 1 ) $ 269,536 $ 271,573 Less: Original issue discount (net of amortization) (1,442 ) (1,681 ) Less: Debt issuance costs (4,024 ) (4,580 ) Total debt 264,070 265,312 Less: Current portion of long-term debt (1,670 ) (1,702 ) Long-term debt $ 262,400 $ 263,610 (1) As of September 30, 2018 and December 31, 2017, the Amended and Restated Credit Agreement, as amended, had a maturity date of August 18, 2023 and an interest rate of LIBOR (with a 0.75% floor) plus 2.25% . On August 18, 2016, the Company, Continental Building Products Operating Company, LLC and Continental Building Products Canada Inc. and the lenders party thereto and Credit Suisse, as Administrative Agent, entered into an Amended and Restated Credit Agreement amending and restating the Company's First Lien Credit Agreement (the "Amended and Restated Credit Agreement"). The Amended and Restated Credit Agreement provides for a $275 million senior secured first lien term loan facility and a $75 million senior secured revolving credit facility (the "Revolver"), which mature on August 18, 2023 and August 18, 2021, respectively. The interest rate under the Amended and Restated Credit Agreement was a spread over LIBOR of 2.75% and floor of 0.75% . On February 21, 2017 , the Company repriced its term loan under the Amended and Restated Credit Agreement lowering its interest rate by 25 basis points to LIBOR plus 2.50% . Subsequently, on December 6, 2017 , the Company further repriced its term loan under the Amended and Restated Credit Agreement lowering its interest rate by an additional 25 basis points to LIBOR plus 2.25% . The Company may further reduce its interest rate to LIBOR plus 2.00% based on the attainment of a total leverage ratio of 1.1 or better. All other terms and conditions under the Amended and Restated Credit Agreement remained the same. During both the nine months ended September 30, 2018 and 2017 , the Company made $2.0 million of scheduled mandatory principal payments. As of September 30, 2018 , the annual effective interest rate, including original issue discount and amortization of debt issuance costs, was 5.0% . There were no amounts outstanding under the Revolver as of September 30, 2018 or 2017 . During the nine months ended September 30, 2018 and 2017 , the Company did not have any draws under the Revolver. Interest under the Revolver is floating, based on LIBOR plus 2.25% . In addition, the Company pays a facility fee of 50 basis points per annum on the total capacity under the Revolver. Availability under the Revolver as of September 30, 2018 , based on draws and outstanding letters of credit and absence of violations of covenants, was $73.6 million . Table 9.2: Details of Future Minimum Principal Payments Due Under the Amended and Restated Credit Agreement Amount Due (in thousands) October 1, 2018 through December 31, 2018 $ 679 2019 2,716 2020 2,716 2021 2,716 2022 2,716 Thereafter 257,993 Total Payments $ 269,536 Under the terms of the Amended and Restated Credit Agreement, the Company is required to comply with certain covenants, including among others, the limitation of indebtedness, limitation on liens, and limitations on certain cash distributions. One single financial covenant governs all of the Company's debt and only applies if the outstanding borrowings of the Revolver plus outstanding letters of credit are greater than $22.5 million as of the end of the quarter. The financial covenant is a total leverage ratio calculation, in which total debt less outstanding cash is divided by adjusted earnings before interest, taxes, depreciation and amortization. As the sum of outstanding borrowings under the Revolver and outstanding letters of credit were less than $22.5 million at September 30, 2018 , the total leverage ratio of no greater than 5.0 under the financial covenant was not applicable at September 30, 2018 . The Company was in compliance with all applicable covenants under the Amended and Restated Credit Agreement as of September 30, 2018 .

Derivative Instruments

Derivative Instruments	9 Months Ended
	Sep. 30, 2018
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Derivative Instruments	DERIVATIVE INSTRUMENTS Commodity Derivative Instruments As of September 30, 2018 , the Company had 2.1 million mmBTUs (millions of British Thermal Units) in aggregate notional amount outstanding natural gas swap contracts to manage commodity price exposures. All of these contracts mature by July 31, 2019 . The Company elected to designate these derivative instruments as cash flow hedges in accordance with ASC 815-20, "Derivatives – Hedging" . No ineffectiveness was recorded on these contracts during the three and nine months ended September 30, 2018 and 2017 . Interest Rate Derivative Instrument In September 2016, the Company entered into interest rate swap agreements for a combined notional amount of $100.0 million with a term of four years , which hedged the floating LIBOR on a portion of the term loan under the Amended and Restated Credit Agreement to an average fixed rate of 1.323% and LIBOR floor of 0.75% . The Company elected to designate these interest rate swaps as cash flow hedges for accounting purposes. On March 29, 2018, the Company terminated its interest rate swap agreements that were previously designated as a cash flow hedge and received $3.2 million in cash, the fair value of the swap on the termination date. The unrealized gain at termination remains in accumulated other comprehensive income and will be amortized into interest expense over the life of the original hedged instrument. On the same date, the Company entered into new interest rate swap agreements for a combined notional amount of $100.0 million , which expire on September 30, 2020 and hedge the floating LIBOR on a portion of the term loan under the Amended and Restated Credit Agreement to an average fixed rate of 2.46% and LIBOR floor of 0.75% . The Company elected to designate these interest rate swaps as cash flow hedges for accounting purposes. No ineffectiveness was recorded on these contracts during the three and nine months ended September 30, 2018 and 2017 . Table 10.1: Details of Derivatives Fair Value September 30, 2018 December 31, 2017 (in thousands) Assets Interest rate swap $ 697 $ 2,148 Commodity hedges 77 11 Total assets $ 774 $ 2,159 Liabilities Interest rate swap $ — $ — Commodity hedges 5 613 Total liabilities $ 5 $ 613 Table 10.2: Gains/(Losses) on Derivatives For the Three Months Ended September 30, For the Nine Months Ended September 30, 2018 2017 2018 2017 2018 2017 2018 2017 Gain/(loss) recognized in Other comprehensive income on derivatives (effective portion), net of tax Gain/(loss) reclassified from Accumulated other comprehensive loss into income (effective portion), net of tax Gain/(loss) recognized in Other comprehensive income on derivatives (effective portion), net of tax Gain/(loss) reclassified from Accumulated other comprehensive loss into income (effective portion), net of tax (in thousands) Interest rate swap $ 145 $ 37 $ 169 $ (7 ) $ 1,413 $ (318 ) $ 379 $ (133 ) Commodity hedges 7 (44 ) (9 ) (127 ) 251 (304 ) (204 ) (38 ) Total $ 152 $ (7 ) $ 160 $ (134 ) $ 1,664 $ (622 ) $ 175 $ (171 ) Counterparty Risk The Company is exposed to credit losses in the event of nonperformance by the counterparties to the Company's derivative instruments. As of September 30, 2018 , the Company's derivatives were in a $0.8 million net asset position and recorded in Other current assets. All of the Company's counterparties have investment grade credit ratings; accordingly, the Company anticipates that the counterparties will be able to fully satisfy their obligations under the contracts. The Company's agreements outline the conditions upon which it or the counterparties are required to post collateral. As of September 30, 2018 , the Company had no collateral posted with its counterparties related to the derivatives.

Treasury Stock

Treasury Stock	9 Months Ended
	Sep. 30, 2018
Equity [Abstract]
Treasury Stock	TREASURY STOCK On November 4, 2015 , the Company announced that the Board of Directors approved a new stock repurchase program authorizing the Company to repurchase up to $50 million of its common stock, at such times and prices as determined by management as market conditions warrant, through December 31, 2016 . Pursuant to this authorization, the Company has repurchased shares of its common stock in the open market and in private transactions. During 2017 and 2018 , the Company announced two expansions and extensions of its stock repurchase program. The most recent authorization on February 21, 2018 expanded the program to a total of $300 million and also extended the expiration date to December 31, 2019 . All repurchased shares are held in treasury, reducing the number of shares of common stock outstanding and used in the Company's earnings per share calculation. Table 11: Details of Treasury Stock Activity September 30, 2018 September 30, 2017 Shares Amount (1) Average Share Price (1) Shares Amount (1) Average Share Price (1) (in thousands, except share data) For the Three Months Ended: Beginning Balance 7,664,325 $ 167,919 $ 21.91 5,648,778 $ 116,592 $ 20.64 Repurchases on open market 76,600 2,863 37.38 941,039 21,292 22.63 Ending Balance 7,740,925 $ 170,782 $ 22.06 6,589,817 $ 137,884 $ 20.92 For the Nine Months Ended: Beginning Balance 6,788,817 $ 143,357 $ 21.12 4,499,655 $ 88,756 $ 19.73 Repurchases on open market 952,108 27,425 28.80 2,090,162 49,128 23.50 Ending Balance 7,740,925 $ 170,782 $ 22.06 6,589,817 $ 137,884 $ 20.92 ( 1 ) Includes commissions paid for repurchases on open market.

Share-Based Compensation

Share-Based Compensation	9 Months Ended
	Sep. 30, 2018
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Share-Based Compensation	SHARE-BASED COMPENSATION For the three and nine months ended September 30, 2018 , the Company recognized share-based compensation expenses of $0.8 million and $2.5 million in expense, respectively, compared to $0.6 million and $2.1 million for the three and nine months ended September 30, 2017 , respectively. The expenses related to share-based compensation awards were recorded in selling and administrative expenses. As of September 30, 2018 , there was $5.5 million of total unrecognized compensation cost related to non-vested stock options, restricted stock awards, restricted stock units and performance-based restricted stock units. This cost is expected to be recognized over a weighted average period of 2.3 years .

Accumulated Other Comprehensive

Accumulated Other Comprehensive Loss	9 Months Ended
	Sep. 30, 2018
Equity [Abstract]
Accumulated Other Comprehensive Loss	ACCUMULATED OTHER COMPREHENSIVE LOSS Table 13: Details of Changes in Accumulated Other Comprehensive Loss by Category Foreign currency translation adjustment Net unrealized gain on derivatives, net of tax Total (in thousands) Balance as of December 31, 2017 $ (3,636 ) $ 987 $ (2,649 ) Other comprehensive (loss)/income before reclassifications (496 ) 1,664 1,168 Amounts reclassified from accumulated other comprehensive loss — (175 ) (175 ) Net current period other comprehensive (loss)/income (496 ) 1,489 993 Balance as of September 30, 2018 $ (4,132 ) $ 2,476 $ (1,656 )

Income Taxes

Income Taxes	9 Months Ended
	Sep. 30, 2018
Income Tax Disclosure [Abstract]
Income Taxes	INCOME TAXES The Company’s estimated annual effective tax rate is 22.3% before discrete items. For the nine months ended September 30, 2018 , discrete items resulted in a tax benefit of $0.6 million , consisting of a stock compensation windfall of $0.1 million and a non-recurring benefit of $0.5 million related to re-measurement of deferred taxes resulting from state tax law change. Due to the timing of the enactment and the complexity involved in applying the provisions of the Tax Cuts and Jobs Act of 2017 (the "Act"), the Company calculated its best estimate of the impact of the Act in its 2017 year end income tax provision in accordance with its understanding of the Act and guidance available as of the date of its Annual Report on Form 10-K for fiscal year 2017 and as a result had recorded a provisional $9.2 million reduction in income tax expense in the fourth quarter of 2017. No adjustment was made to the provisional amount as a result of additional information obtained for the nine months ended September 30, 2018 . The Company is subject to audit examinations at federal, state and local levels by tax authorities in those jurisdictions. In addition, the Canadian operations are subject to audit examinations at federal and provincial levels by tax authorities in those jurisdictions. The tax matters challenged by the tax authorities are typically complex; therefore, the ultimate outcome of any challenges would be subject to uncertainty. The Company has not identified any issues that did not meet the recognition threshold or would be impacted by the measurement provisions of the uncertain tax position guidance.

Earnings Per Share

Earnings Per Share	9 Months Ended
	Sep. 30, 2018
Earnings Per Share [Abstract]
Earnings Per Share	EARNINGS PER SHARE The following table shows the weighted average number of shares used in computing earnings per share and the effect on the weighted average number of shares of potentially dilutive securities. Potentially dilutive common stock has no effect on income available to common stockholders. There were no anti-dilutive awards during the three months ended September 30, 2018 and 2017 . For the nine months ended September 30, 2018 and 2017 , awards that had an anti-dilutive impact on the Company's dilutive earnings per share computation excluded from the weighted average shares outstanding were 21,000 and 29,000 , respectively. Table 15: Details of Basic and Dilutive Earnings Per Share For the Three Months Ended For the Nine Months Ended September 30, 2018 September 30, 2017 September 30, 2018 September 30, 2017 (dollars in thousands, except for per share amounts) Net income $ 18,564 $ 10,987 $ 54,105 $ 35,612 Weighted average number of shares outstanding - basic 36,732,746 38,212,869 37,012,536 38,966,575 Effect of dilutive securities: Restricted stock awards — 6,852 1,170 7,598 Restricted stock units 89,750 48,175 72,650 54,171 Performance restricted stock units 68,384 58,199 67,231 30,853 Stock options 28,024 19,461 27,800 21,776 Total effect of dilutive securities 186,158 132,687 168,851 114,398 Weighted average number of shares outstanding - diluted 36,918,904 38,345,556 37,181,387 39,080,973 Basic earnings per share $ 0.51 $ 0.29 $ 1.46 $ 0.91 Diluted earnings per share $ 0.50 $ 0.29 $ 1.46 $ 0.91

Commitments and Contingencies

Commitments and Contingencies	9 Months Ended
	Sep. 30, 2018
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	COMMITMENTS AND CONTINGENCIES Commitments The Company leases certain buildings and equipment. The Company's facility and equipment leases may provide for escalations of rent or rent abatements and payment of pro rata portions of building operating expenses. Minimum lease payments are recognized on a straight-line basis over the minimum lease term. The total expenses under operating leases for the three and nine months ended September 30, 2018 were $0.6 million and $2.2 million , respectively, compared to $0.8 million and $2.5 million for the same periods in 2017 , respectively. The Company also has non-capital purchase commitments that primarily relate to gas, gypsum, paper and other raw materials. The total amounts purchased under such commitments were $22.7 million and $69.5 million for the three and nine months ended September 30, 2018 , respectively, compared to $22.0 million and $64.8 million for the three and nine months ended September 30, 2017 , respectively. Table 16: Details of Future Minimum Lease Payments Due Under Noncancellable Operating Leases and Purchase Commitments Future Minimum Lease Payments Purchase Commitments (in thousands) October 1, 2018 - December 31, 2018 $ 180 $ 17,958 2019 1,658 47,287 2020 48 46,141 2021 — 28,097 2022 — 25,069 2023 — 12,284 Thereafter — 53,621 Total $ 1,886 $ 230,457 Contingent obligations Under certain circumstances, the Company provides letters of credit related to its natural gas and other supply purchases. As of September 30, 2018 and December 31, 2017 , the Company had outstanding letters of credit of approximately $1.4 million . Legal Matters In the ordinary course of business, the Company executes contracts involving indemnifications standard in the industry. These indemnifications might include claims relating to any of the following: environmental and tax matters; intellectual property rights; governmental regulations and employment-related matters; customer, supplier, and other commercial contractual relationships; and financial matters. While the maximum amount to which the Company may be exposed under such agreements cannot be estimated, it is the opinion of management that these guarantees and indemnifications are not expected to have a material adverse effect on the Company's financial condition, results of operations or liquidity. In the ordinary course of business, the Company is involved in certain legal actions and claims, including proceedings under laws and regulations relating to environmental and other matters. Because such matters are subject to many uncertainties and the outcomes are not predictable with assurance, the total liability for these legal actions and claims cannot be determined with certainty. When the Company determines that it is probable that a liability for environmental matters, legal actions or other contingencies has been incurred and the amount of the loss is reasonably estimable, an estimate of the costs to be incurred is recorded as a liability in the financial statements. As of September 30, 2018 and December 31, 2017 , such liabilities were not expected to have a material adverse effect on the Company's financial condition, results of operations or liquidity. While management believes its accruals for such liabilities are adequate, the Company may incur costs in excess of the amounts provided. Although the ultimate amount of liability that may result from these matters or actions is not ascertainable, any amounts exceeding the recorded accruals are not expected to have a material adverse effect on the Company's financial condition, results of operations or liquidity.

Segment Reporting

Segment Reporting	9 Months Ended
	Sep. 30, 2018
Segment Reporting [Abstract]
Segment Reporting	SEGMENT REPORTING Segment information is presented in accordance with ASC 280, Segment Reporting, which establishes standards for reporting information about operating segments. It also establishes standards for related disclosures about products and geographic areas. The Company's primary reportable segment is wallboard, which represented approximately 97.6% and 97.3% of the Company's revenues for the three and nine months ended September 30, 2018 , respectively, compared to 96.8% of the Company's revenues for both the three and nine months ended September 30, 2017 , respectively. This segment produces wallboard for the commercial and residential construction sectors. The Company also manufactures finishing products, which complement the Company's full range of wallboard products. Revenues from the major products sold to external customers include gypsum wallboard and finishing products. The Company's two geographic areas consist of the United States and Canada for which it reports net sales, fixed assets and total assets. The Company evaluates operating performance based on profit or loss from operations before certain adjustments as shown below. Revenues are attributed to geographic areas based on the location of the customer generating the revenue. The Company did not provide asset information by segment as its Chief Operating Decision Maker does not use such information for purposes of allocating resources and assessing segment performance. Table 17.1: Segment Reporting For the Three Months Ended For the Nine Months Ended September 30, 2018 September 30, 2017 September 30, 2018 September 30, 2017 (in thousands) Net Sales: Wallboard $ 128,101 $ 112,796 $ 376,739 $ 346,466 Other 3,133 3,730 10,565 11,305 Total net sales $ 131,234 $ 116,526 $ 387,304 $ 357,771 Operating Income: Wallboard $ 27,551 $ 19,992 $ 79,702 $ 63,402 Other (580 ) (285 ) (1,409 ) (388 ) Total operating income $ 26,971 $ 19,707 $ 78,293 $ 63,014 Adjustments: Interest expense $ (2,549 ) $ (2,988 ) $ (7,963 ) $ (8,966 ) Losses from equity investment (393 ) (204 ) (1,148 ) (29 ) Other (expense)/income, net (29 ) 146 (256 ) (633 ) Income before provision for income taxes $ 24,000 $ 16,661 $ 68,926 $ 53,386 Depreciation and Amortization: Wallboard $ 11,299 $ 11,793 $ 32,016 $ 34,992 Other 281 264 950 825 Total depreciation and amortization $ 11,580 $ 12,057 $ 32,966 $ 35,817 Table 17.2: Details of Net Sales By Geographic Region For the Three Months Ended For the Nine Months Ended September 30, 2018 September 30, 2017 September 30, 2018 September 30, 2017 (in thousands) United States $ 125,430 $ 110,430 $ 367,917 $ 334,481 Canada 5,804 6,096 19,387 23,290 Net sales $ 131,234 $ 116,526 $ 387,304 $ 357,771 Table 17.3: Details of Assets By Geographic Region Fixed Assets Total Assets September 30, 2018 December 31, 2017 September 30, 2018 December 31, 2017 (in thousands) United States $ 287,255 $ 290,324 $ 654,965 $ 622,836 Canada 3,415 3,679 17,939 19,098 Total $ 290,670 $ 294,003 $ 672,904 $ 641,934

Fair Value Disclosures

Fair Value Disclosures	9 Months Ended
	Sep. 30, 2018
Fair Value Disclosures [Abstract]
Fair Value Disclosures	FAIR VALUE DISCLOSURES The Company estimates the fair value of its debt by discounting the future cash flows of each instrument using estimated market rates of debt instruments with similar maturities and credit profiles. These inputs are classified as Level 3 within the fair value hierarchy. As of September 30, 2018 and December 31, 2017 , the carrying value reported in the consolidated balance sheet for the Company's notes payable approximated its fair value. The only assets or liabilities the Company had at September 30, 2018 that are recorded at fair value on a recurring basis are the natural gas hedges and interest rate swaps. Generally, the Company obtains its Level 2 pricing inputs from its counterparties. Substantially all of these assumptions are observable in the marketplace throughout the full term of the instrument, can be derived from observable data or are supported by observable levels at which transactions are executed in the marketplace. Assets and liabilities that are measured at fair value on a non-recurring basis include intangible assets and goodwill. These items are recognized at fair value when they are considered to be impaired. There were no fair value adjustments for assets and liabilities measured on a non-recurring basis. The Company discloses fair value information about financial instruments for which it is practicable to estimate that value. Table 18.1: Fair Value Hierarchy - 2018 As of September 30, 2018 Level 1 Level 2 Level 3 Balance (in thousands) Asset Interest rate swap $ — $ 697 $ — $ 697 Commodity derivatives — 77 — 77 Total assets $ — $ 774 $ — $ 774 Liabilities Interest rate swap $ — $ — $ — $ — Commodity derivatives — 5 — 5 Total liabilities $ — $ 5 $ — $ 5 Table 18.2: Fair Value Hierarchy - 2017 As of December 31, 2017 Level 1 Level 2 Level 3 Balance (in thousands) Asset Interest rate swap $ — $ 2,148 $ — $ 2,148 Commodity derivatives — 11 — 11 Total assets $ — $ 2,159 $ — $ 2,159 Liabilities Interest rate swap $ — $ — $ — $ — Commodity derivatives — 613 — 613 Total liabilities $ — $ 613 $ — $ 613

Significant Accounting Polici_2

Significant Accounting Policies (Policies)	9 Months Ended
	Sep. 30, 2018
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation The accompanying consolidated financial statements for the Company have been prepared in accordance with accounting principles generally accepted in the United States ("U.S. GAAP"). The consolidated financial statements include the accounts of the Company and its wholly-owned subsidiaries. All intercompany transactions have been eliminated.
Revenue Recognition	Revenue Disclosure Revenue from the sale of gypsum products is recognized when control of the promised products is transferred to the Company's customers, in an amount that reflects the consideration the Company expects to be entitled to in exchange for those products (the transaction price). A performance obligation is a promise in a contract to transfer a distinct product to a customer and is the unit of account under Financial Accounting Standards Board ("FASB") Accounting Standards Codification ("ASC") Topic 606. Control transfers to the customer at a point in time. To indicate the transfer of control, the Company must have a present right to payment, legal title must have passed to the customer and the customer must have the significant risks and rewards of ownership. Generally, the Company satisfies its performance obligations within a number of days from the time the contract is executed. The Company records estimated reductions to revenue for customer programs and incentive offerings, including promotions and other volume-based incentives, in the period in which the sale occurs. Amounts billed to a customer at the transaction price are included in net sales, and costs incurred for shipping and handling are treated as fulfillment costs and are classified as cost of goods sold in the Consolidated Statements of Operations. See Note 17, Segment reporting, for disaggregation of revenue by segment.
Recent Accounting Pronouncements	Recent Accounting Pronouncements Accounting Standards Recently Adopted In May 2014, the FASB issued ASU No. 2014-9, "Revenue from Contracts with Customers (Topic 606)," which provides accounting guidance for all revenue arising from contracts with customers and affects all entities that enter into contracts to provide goods or services to their customers. In August 2015, the FASB issued ASU No. 2015-14, "Revenue from Contracts with Customers (Topic 606): Deferral of the Effective Date," which deferred the effective date of ASU No. 2014-9 for all entities by one year to annual reporting periods beginning after December 15, 2017. The ASU requires retroactive application on either a full or modified basis. The Company adopted the standard on January 1, 2018 using the modified retrospective approach. Based on its evaluation, the Company has concluded it has one revenue stream and the adoption of this new guidance did not have a material impact on its Consolidated Financial Statements. In August 2016, the FASB issued ASU 2016-15, "Classification of Certain Cash Receipts and Cash Payments." This ASU reduces existing diversity in the classification of certain cash receipts and cash payments on the statements of cash flows. ASU 2016-15 is effective for fiscal years beginning after December 15, 2017, and for interim periods within those fiscal years. The adoption of this standard did not have a material impact on the Company's Consolidated Financial Statements. In October 2016, the FASB issued ASU 2016-16, "Intra-Entity Transfers of Assets Other Than Inventory." The new standard requires companies to recognize the income tax effects of intercompany sales or transfers of assets, other than inventory, in the income statement as income tax expense (or benefit) in the period the sales or transfer occurs. The standard requires companies to apply a modified retrospective approach with a cumulative catch-up adjustment to opening retained earnings in the period of adoption. The provisions of this standard are effective for fiscal years beginning after December 15, 2017, and early adoption is permitted. The adoption of this standard did not have a material impact on the Company's Consolidated Financial Statements. Accounting Standards Not Yet Adopted In February 2016, the FASB issued ASU 2016-02, "Leases." ASU 2016-02 requires lessees to recognize a lease liability and a right-of-use asset on the balance sheet. ASU 2016-02 is effective for fiscal years beginning after December 15, 2018, including interim periods within those fiscal years. The Company will adopt the standard on January 1, 2019. The Company will take advantage of the transition package of practical expedients permitted within the new standard, which among other things, allows companies to carryforward the historical lease classification. In addition, the Company is electing the comparative period practical expedient, which allows the Company to implement the guidance as of the effective date without having to adjust the comparative financial statements. Instead, under this expedient, companies will recognize the cumulative effect adjustment in equity. The Company will also make an accounting policy election that leases with an initial term of 12 months or less will not be recorded on the balance sheet and will result in the recognition of those lease payments in the Consolidated Statements of Operations on a straight-line basis over the lease term. While the Company is continuing to evaluate the impact of adoption, it is not expected to have a material impact on its Consolidated Financial Statements. In June 2016, the FASB issued ASU 2016-13, "Financial Instruments – Credit Losses: Measurement of Credit Losses on Financial Instruments." This ASU is intended to introduce a revised approach to the recognition and measurement of credit losses, emphasizing an updated model based on expected losses rather than incurred losses. The provisions of this standard are effective for reporting periods beginning after December 15, 2019 and early adoption is permitted. The Company is currently evaluating the impact that this guidance may have on its Consolidated Financial Statements. In August 2017, the FASB issued ASU 2017-12, "Derivatives and Hedging (Topic 815), Targeted Improvements to Accounting for Hedging Activities." This ASU expands an entity's ability to hedge non-financial and financial risk components and reduce complexity in fair value hedges of interest rate risk. The guidance eliminates the requirement to separately measure and report hedge ineffectiveness and generally requires the entire change in the fair value of a hedging instrument to be presented in the same income statement line as the hedged item. The provisions of this standard are effective in 2019 for calendar-year public business entities and in 2020 for all other calendar-year companies. Early adoption of the standard is permitted. The Company is currently evaluating the impact that this guidance may have on its Consolidated Financial Statements. In February 2018, the FASB issued ASU 2018-02, "Income Statement - Reporting Comprehensive Income (Topic 220), Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income." This ASU allows a reclassification from accumulated other comprehensive income to retained earnings for stranded tax effects resulting from the Tax Cuts and Jobs Act. The provisions of this standard are effective for reporting periods beginning after December 15, 2018 and early adoption is permitted. The Company is currently evaluating the impact that this guidance may have on its Consolidated Financial Statements. In August 2018, the FASB issued ASU 2018-13, "Fair Value Measurements (Topic 820), Changes to the Disclosure Requirements for Fair Value Measurement." This ASU eliminates certain disclosure requirements for fair value measurements for all entities, requires public entities to disclose certain new information and modifies some disclosure requirements. The provisions of this standard are effective for reporting periods beginning after December 15, 2019 and early adoption is permitted. The Company is currently evaluating the impact that this guidance may have on its Consolidated Financial Statements. In August 2018, the FASB issued ASU 2018-15, "Intangibles - Goodwill and Other - Internal-Use Software (Subtopic 350-40), Customer's Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement That Is a Service Contract." This ASU requires a customer in a cloud computing arrangement that is a service contract to follow the internal-use software guidance in Accounting Standards Codification 350-40 to determine which implementation costs to defer and recognize as an asset. The provisions of this standard are effective for reporting periods beginning after December 15, 2019 and early adoption is permitted. The Company is currently evaluating the impact that this guidance may have on its Consolidated Financial Statements.
Reclassifications	Reclassifications Certain reclassifications of prior year information were made to conform to the 2018 presentation. These reclassifications had no material impact on the Company's Consolidated Financial Statements.

Significant Accounting Polici_3

Significant Accounting Policies (Tables)	9 Months Ended
	Sep. 30, 2017
Accounting Policies [Abstract]
Schedule of Cash Flow, Supplemental Disclosures	Supplemental Cash Flow Disclosure Table 2.1: Certain Cash Transactions and Other Activity For the Nine Months Ended September 30, 2018 September 30, 2017 (in thousands) Cash paid during the period for: Interest paid on term loan, net $ 8,049 $ 7,582 Income taxes paid, net 15,903 16,338 Other activity: Amounts in accounts payable for capital expenditures 1,538 1,123

Trade Receivables, Net (Tables)

Trade Receivables, Net (Tables)	9 Months Ended
	Sep. 30, 2018
Receivables [Abstract]
Detail of Receivables, Net	Table 3: Details of Trade Receivables, Net September 30, 2018 December 31, 2017 (in thousands) Trade receivables, gross $ 40,447 $ 39,577 Allowance for cash discounts and doubtful accounts (850 ) (808 ) Trade receivables, net $ 39,597 $ 38,769

Inventories, Net (Tables)

Inventories, Net (Tables)	9 Months Ended
	Sep. 30, 2018
Inventory Disclosure [Abstract]
Composition of Inventories	Table 4: Details of Inventories, Net September 30, 2018 December 31, 2017 (in thousands) Finished products $ 8,195 $ 5,893 Raw materials 16,821 11,663 Supplies and other 7,423 7,326 Inventories, net $ 32,439 $ 24,882

Property, Plant and Equipment_2

Property, Plant and Equipment, Net (Tables)	9 Months Ended
	Sep. 30, 2018
Property, Plant and Equipment [Abstract]
Property, Plant and Equipment Details	Table 5: Details of Property, Plant and Equipment, Net September 30, 2018 December 31, 2017 (in thousands) Land $ 13,187 $ 13,187 Buildings 115,422 114,051 Plant machinery 284,151 281,786 Mobile equipment 12,828 10,366 Construction in progress 32,186 20,291 Property, plant and equipment, at cost 457,774 439,681 Accumulated depreciation (167,104 ) (145,678 ) Property, plant and equipment, net $ 290,670 $ 294,003

Customer Relationships and Ot_2

Customer Relationships and Other Intangibles, Net (Tables)	9 Months Ended
	Sep. 30, 2018
Goodwill and Intangible Assets Disclosure [Abstract]
Details of Customer Relationships and Other Intangibles, Net	Table 6.1: Details of Customer Relationships and Other Intangibles, Net September 30, 2018 December 31, 2017 Gross Accumulated Amortization Net Gross Accumulated Amortization Net (in thousands) Customer relationships $ 116,529 $ (64,041 ) $ 52,488 $ 116,711 $ (57,811 ) $ 58,900 Purchased and internally developed software 7,718 (5,340 ) 2,378 6,226 (4,871 ) 1,355 Trademarks 14,816 (5,021 ) 9,795 14,839 (4,287 ) 10,552 Total $ 139,063 $ (74,402 ) $ 64,661 $ 137,776 $ (66,969 ) $ 70,807
Future Amortization Expense of Customer Relationships and Other Intangibles	Table 6.2: Details of Future Amortization Expense of Customer Relationships and Other Intangibles As of September 30, 2018 (in thousands) October 1, 2018 through December 31, 2018 $ 2,766 2019 8,907 2020 8,150 2021 7,410 2022 6,746 Thereafter 30,682 Total $ 64,661

Accrued and Other Liabilities (

Accrued and Other Liabilities (Tables)	9 Months Ended
	Sep. 30, 2018
Payables and Accruals [Abstract]
Details of Accrued and Other Liabilities	Table 8: Details of Accrued and Other Liabilities September 30, 2018 December 31, 2017 (in thousands) Employee-related costs $ 8,471 $ 9,258 Property taxes 2,321 472 Other taxes 562 466 Other 1,885 1,744 Accrued and other liabilities $ 13,239 $ 11,940

Debt (Tables)

Debt (Tables)	9 Months Ended
	Sep. 30, 2018
Debt Disclosure [Abstract]
Details of Debt	Table 9.1: Details of Debt September 30, 2018 December 31, 2017 (in thousands) Amended and Restated Credit Agreement ( 1 ) $ 269,536 $ 271,573 Less: Original issue discount (net of amortization) (1,442 ) (1,681 ) Less: Debt issuance costs (4,024 ) (4,580 ) Total debt 264,070 265,312 Less: Current portion of long-term debt (1,670 ) (1,702 ) Long-term debt $ 262,400 $ 263,610
Future Minimum Principal Payments Due Under the Credit Agreements	Table 9.2: Details of Future Minimum Principal Payments Due Under the Amended and Restated Credit Agreement Amount Due (in thousands) October 1, 2018 through December 31, 2018 $ 679 2019 2,716 2020 2,716 2021 2,716 2022 2,716 Thereafter 257,993 Total Payments $ 269,536

Derivative Instruments (Tables)

Derivative Instruments (Tables)	9 Months Ended
	Sep. 30, 2018
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Schedule of Derivative Instruments in Statement of Financial Position, Fair Value	Table 10.1: Details of Derivatives Fair Value September 30, 2018 December 31, 2017 (in thousands) Assets Interest rate swap $ 697 $ 2,148 Commodity hedges 77 11 Total assets $ 774 $ 2,159 Liabilities Interest rate swap $ — $ — Commodity hedges 5 613 Total liabilities $ 5 $ 613
Derivative Instruments, Gain (Loss)	Table 10.2: Gains/(Losses) on Derivatives For the Three Months Ended September 30, For the Nine Months Ended September 30, 2018 2017 2018 2017 2018 2017 2018 2017 Gain/(loss) recognized in Other comprehensive income on derivatives (effective portion), net of tax Gain/(loss) reclassified from Accumulated other comprehensive loss into income (effective portion), net of tax Gain/(loss) recognized in Other comprehensive income on derivatives (effective portion), net of tax Gain/(loss) reclassified from Accumulated other comprehensive loss into income (effective portion), net of tax (in thousands) Interest rate swap $ 145 $ 37 $ 169 $ (7 ) $ 1,413 $ (318 ) $ 379 $ (133 ) Commodity hedges 7 (44 ) (9 ) (127 ) 251 (304 ) (204 ) (38 ) Total $ 152 $ (7 ) $ 160 $ (134 ) $ 1,664 $ (622 ) $ 175 $ (171 )

Treasury Stock (Tables)

Treasury Stock (Tables)	9 Months Ended
	Sep. 30, 2018
Equity [Abstract]
Treasury Stock Activity	All repurchased shares are held in treasury, reducing the number of shares of common stock outstanding and used in the Company's earnings per share calculation. Table 11: Details of Treasury Stock Activity September 30, 2018 September 30, 2017 Shares Amount (1) Average Share Price (1) Shares Amount (1) Average Share Price (1) (in thousands, except share data) For the Three Months Ended: Beginning Balance 7,664,325 $ 167,919 $ 21.91 5,648,778 $ 116,592 $ 20.64 Repurchases on open market 76,600 2,863 37.38 941,039 21,292 22.63 Ending Balance 7,740,925 $ 170,782 $ 22.06 6,589,817 $ 137,884 $ 20.92 For the Nine Months Ended: Beginning Balance 6,788,817 $ 143,357 $ 21.12 4,499,655 $ 88,756 $ 19.73 Repurchases on open market 952,108 27,425 28.80 2,090,162 49,128 23.50 Ending Balance 7,740,925 $ 170,782 $ 22.06 6,589,817 $ 137,884 $ 20.92 ( 1 ) Includes commissions paid for repurchases on open market.

Accumulated Other Comprehensi_2

Accumulated Other Comprehensive Loss (Tables)	9 Months Ended
	Sep. 30, 2018
Equity [Abstract]
Changes in Accumulated Other Comprehensive (Loss)/Income by Category	Table 13: Details of Changes in Accumulated Other Comprehensive Loss by Category Foreign currency translation adjustment Net unrealized gain on derivatives, net of tax Total (in thousands) Balance as of December 31, 2017 $ (3,636 ) $ 987 $ (2,649 ) Other comprehensive (loss)/income before reclassifications (496 ) 1,664 1,168 Amounts reclassified from accumulated other comprehensive loss — (175 ) (175 ) Net current period other comprehensive (loss)/income (496 ) 1,489 993 Balance as of September 30, 2018 $ (4,132 ) $ 2,476 $ (1,656 )

Earnings Per Share (Tables)

Earnings Per Share (Tables)	9 Months Ended
	Sep. 30, 2018
Earnings Per Share [Abstract]
Basic and Dilutive Earnings Per Share	The following table shows the weighted average number of shares used in computing earnings per share and the effect on the weighted average number of shares of potentially dilutive securities. Potentially dilutive common stock has no effect on income available to common stockholders. There were no anti-dilutive awards during the three months ended September 30, 2018 and 2017 . For the nine months ended September 30, 2018 and 2017 , awards that had an anti-dilutive impact on the Company's dilutive earnings per share computation excluded from the weighted average shares outstanding were 21,000 and 29,000 , respectively. Table 15: Details of Basic and Dilutive Earnings Per Share For the Three Months Ended For the Nine Months Ended September 30, 2018 September 30, 2017 September 30, 2018 September 30, 2017 (dollars in thousands, except for per share amounts) Net income $ 18,564 $ 10,987 $ 54,105 $ 35,612 Weighted average number of shares outstanding - basic 36,732,746 38,212,869 37,012,536 38,966,575 Effect of dilutive securities: Restricted stock awards — 6,852 1,170 7,598 Restricted stock units 89,750 48,175 72,650 54,171 Performance restricted stock units 68,384 58,199 67,231 30,853 Stock options 28,024 19,461 27,800 21,776 Total effect of dilutive securities 186,158 132,687 168,851 114,398 Weighted average number of shares outstanding - diluted 36,918,904 38,345,556 37,181,387 39,080,973 Basic earnings per share $ 0.51 $ 0.29 $ 1.46 $ 0.91 Diluted earnings per share $ 0.50 $ 0.29 $ 1.46 $ 0.91

Commitments and Contingencies (

Commitments and Contingencies (Tables)	9 Months Ended
	Sep. 30, 2018
Commitments and Contingencies Disclosure [Abstract]
Future Minimum Lease Payments Due Under Non-Cancelable Operating Leases and Purchase Commitments by Year	Table 16: Details of Future Minimum Lease Payments Due Under Noncancellable Operating Leases and Purchase Commitments Future Minimum Lease Payments Purchase Commitments (in thousands) October 1, 2018 - December 31, 2018 $ 180 $ 17,958 2019 1,658 47,287 2020 48 46,141 2021 — 28,097 2022 — 25,069 2023 — 12,284 Thereafter — 53,621 Total $ 1,886 $ 230,457

Segment Reporting (Tables)

Segment Reporting (Tables)	9 Months Ended
	Sep. 30, 2018
Segment Reporting [Abstract]
Segment Reporting	Table 17.1: Segment Reporting For the Three Months Ended For the Nine Months Ended September 30, 2018 September 30, 2017 September 30, 2018 September 30, 2017 (in thousands) Net Sales: Wallboard $ 128,101 $ 112,796 $ 376,739 $ 346,466 Other 3,133 3,730 10,565 11,305 Total net sales $ 131,234 $ 116,526 $ 387,304 $ 357,771 Operating Income: Wallboard $ 27,551 $ 19,992 $ 79,702 $ 63,402 Other (580 ) (285 ) (1,409 ) (388 ) Total operating income $ 26,971 $ 19,707 $ 78,293 $ 63,014 Adjustments: Interest expense $ (2,549 ) $ (2,988 ) $ (7,963 ) $ (8,966 ) Losses from equity investment (393 ) (204 ) (1,148 ) (29 ) Other (expense)/income, net (29 ) 146 (256 ) (633 ) Income before provision for income taxes $ 24,000 $ 16,661 $ 68,926 $ 53,386 Depreciation and Amortization: Wallboard $ 11,299 $ 11,793 $ 32,016 $ 34,992 Other 281 264 950 825 Total depreciation and amortization $ 11,580 $ 12,057 $ 32,966 $ 35,817
Net Sales By Geographic Region	Table 17.2: Details of Net Sales By Geographic Region For the Three Months Ended For the Nine Months Ended September 30, 2018 September 30, 2017 September 30, 2018 September 30, 2017 (in thousands) United States $ 125,430 $ 110,430 $ 367,917 $ 334,481 Canada 5,804 6,096 19,387 23,290 Net sales $ 131,234 $ 116,526 $ 387,304 $ 357,771
Assets By Geographic Region	Table 17.3: Details of Assets By Geographic Region Fixed Assets Total Assets September 30, 2018 December 31, 2017 September 30, 2018 December 31, 2017 (in thousands) United States $ 287,255 $ 290,324 $ 654,965 $ 622,836 Canada 3,415 3,679 17,939 19,098 Total $ 290,670 $ 294,003 $ 672,904 $ 641,934

Fair Value Disclosures (Tables)

Fair Value Disclosures (Tables)	9 Months Ended
	Sep. 30, 2018
Fair Value Disclosures [Abstract]
Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis	Table 18.1: Fair Value Hierarchy - 2018 As of September 30, 2018 Level 1 Level 2 Level 3 Balance (in thousands) Asset Interest rate swap $ — $ 697 $ — $ 697 Commodity derivatives — 77 — 77 Total assets $ — $ 774 $ — $ 774 Liabilities Interest rate swap $ — $ — $ — $ — Commodity derivatives — 5 — 5 Total liabilities $ — $ 5 $ — $ 5 Table 18.2: Fair Value Hierarchy - 2017 As of December 31, 2017 Level 1 Level 2 Level 3 Balance (in thousands) Asset Interest rate swap $ — $ 2,148 $ — $ 2,148 Commodity derivatives — 11 — 11 Total assets $ — $ 2,159 $ — $ 2,159 Liabilities Interest rate swap $ — $ — $ — $ — Commodity derivatives — 613 — 613 Total liabilities $ — $ 613 $ — $ 613

Background and Nature of Oper_2

Background and Nature of Operations - Description of Business and Acquisition (Detail) $ in Millions	Aug. 30, 2013USD ($)	Sep. 30, 2018facility
Lone Star Fund VIII (U.S.), L.P. | Lafarge N.A.
Business Acquisition [Line Items]
Total purchase price | $	$ 703
Wallboard
Business Acquisition [Line Items]
Number of operating facilities (facility)		3
Joint Compound
Business Acquisition [Line Items]
Number of operating facilities (facility)		1

Significant Accounting Polici_4

Significant Accounting Policies - Additional Information (Detail) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Accounting Policies [Abstract]
Accounts receivable	$ 39,597	$ 38,769

Significant Accounting Polici_5

Significant Accounting Policies - Certain Cash and Non-Cash Transactions (Detail) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Accounting Policies [Abstract]
Interest paid on term loan, net	$ 8,049	$ 7,582
Income taxes paid, net	15,903	16,338
Other activity:	$ 1,538	$ 1,123

Trade Receivables, Net - Detail

Trade Receivables, Net - Detail of Receivables, Net (Detail) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Receivables [Abstract]
Trade receivables, gross	$ 40,447	$ 39,577
Allowance for cash discounts and doubtful accounts	(850)	(808)
Trade receivables, net	$ 39,597	$ 38,769

Inventories, Net (Detail)

Inventories, Net (Detail) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Inventory Disclosure [Abstract]
Finished products	$ 8,195	$ 5,893
Raw materials	16,821	11,663
Supplies and other	7,423	7,326
Inventories, net	$ 32,439	$ 24,882

Property, Plant and Equipment_3

Property, Plant and Equipment, Net - Property, Plant and Equipment Details (Detail) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Property, Plant and Equipment [Line Items]
Property, plant and equipment, at cost	$ 457,774	$ 439,681
Accumulated depreciation	(167,104)	(145,678)
Property, plant and equipment, net	290,670	294,003
Land
Property, Plant and Equipment [Line Items]
Property, plant and equipment, at cost	13,187	13,187
Buildings
Property, Plant and Equipment [Line Items]
Property, plant and equipment, at cost	115,422	114,051
Plant machinery
Property, Plant and Equipment [Line Items]
Property, plant and equipment, at cost	284,151	281,786
Mobile equipment
Property, Plant and Equipment [Line Items]
Property, plant and equipment, at cost	12,828	10,366
Construction in progress
Property, Plant and Equipment [Line Items]
Property, plant and equipment, at cost	$ 32,186	$ 20,291

Property, Plant and Equipment_4

Property, Plant and Equipment, Net - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Property, Plant and Equipment [Abstract]
Depreciation expense	$ 9.1	$ 9	$ 25.4	$ 26.5

Investment in Seven Hills - Add

Investment in Seven Hills - Additional Information (Detail) - Seven Hills - Variable Interest Entity, Not Primary Beneficiary - Equity Method Investee - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Schedule of Equity Method Investments [Line Items]
Cost of paperboard	$ 12.3	$ 15.5	$ 37.4	$ 42.3
Purchase commitments			$ 29.2

Customer Relationships and Ot_3

Customer Relationships and Other Intangibles, Net - Details of Customer Relationships and Other Intangibles, Net (Detail) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Finite-Lived Intangible Assets [Line Items]
Gross	$ 139,063	$ 137,776
Accumulated Amortization	(74,402)	(66,969)
Net	64,661	70,807
Customer relationships
Finite-Lived Intangible Assets [Line Items]
Gross	116,529	116,711
Accumulated Amortization	(64,041)	(57,811)
Net	52,488	58,900
Purchased and internally developed software
Finite-Lived Intangible Assets [Line Items]
Gross	7,718	6,226
Accumulated Amortization	(5,340)	(4,871)
Net	2,378	1,355
Trademarks
Finite-Lived Intangible Assets [Line Items]
Gross	14,816	14,839
Accumulated Amortization	(5,021)	(4,287)
Net	$ 9,795	$ 10,552

Customer Relationships and Ot_4

Customer Relationships and Other Intangibles, Net - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Goodwill and Intangible Assets Disclosure [Abstract]
Amortization expense	$ 2.5	$ 3	$ 7.5	$ 9.3

Customer Relationships and Ot_5

Customer Relationships and Other Intangibles, Net - Future Amortization Expense of Customer Relationships and Other Intangibles (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Finite-Lived Intangible Assets, Net, Amortization Expense, Fiscal Year Maturity [Abstract]
October 1, 2018 through December 31, 2018	$ 2,766
2,019	8,907
2,020	8,150
2,021	7,410
2,022	6,746
Thereafter	30,682
Net	$ 64,661	$ 70,807

Accrued and Other Liabilities_2

Accrued and Other Liabilities (Detail) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Payables and Accruals [Abstract]
Employee-related costs	$ 8,471	$ 9,258
Property taxes	2,321	472
Other taxes	562	466
Other	1,885	1,744
Accrued and other liabilities	$ 13,239	$ 11,940

Debt - Details of Debt (Detail)

Debt - Details of Debt (Detail) - USD ($) $ in Thousands	Dec. 06, 2017	Feb. 21, 2017	Sep. 30, 2018	Dec. 31, 2017
Debt Instrument [Line Items]
Amended and Restated Credit Agreement			$ 269,536
Less: Original issue discount (net of amortization)			(1,442)	$ (1,681)
Less: Debt issuance costs			(4,024)	(4,580)
Total debt			264,070	265,312
Less: Current portion of long-term debt			(1,670)	(1,702)
Long-term debt			262,400	263,610
Amended and Restated Credit Agreement | London Interbank Offered Rate (LIBOR)
Debt Instrument [Line Items]
Debt, variable interest rate (as a percent)	2.25%	2.50%
Term Loan Facility | Amended and Restated Credit Agreement
Debt Instrument [Line Items]
Amended and Restated Credit Agreement			$ 269,536	$ 271,573
Term Loan Facility | Amended and Restated Credit Agreement | London Interbank Offered Rate (LIBOR)
Debt Instrument [Line Items]
Floor rate			0.75%
Debt, variable interest rate (as a percent)			2.25%

Debt - Additional Information (

Debt - Additional Information (Detail)	Dec. 06, 2017	Feb. 21, 2017	Aug. 18, 2016USD ($)	Sep. 30, 2018USD ($)covenant	Sep. 30, 2017USD ($)	Dec. 31, 2017USD ($)
Debt Instrument [Line Items]
Scheduled mandatory principal payments				$ 2,000,000	$ 2,000,000
First Lien Credit Agreement
Debt Instrument [Line Items]
Number of covenants | covenant				1
Debt covenant trigger, line of credit facility amount less letters of credit threshold				$ 22,500,000
First Lien Credit Agreement | Maximum
Debt Instrument [Line Items]
Leverage ratio (no greater than)				5
Amended and Restated Credit Agreement
Debt Instrument [Line Items]
Decrease in basis spread, percentage	25.00%	0.25%
Leverage ratio (no greater than)	1.1
Amended and Restated Credit Agreement | London Interbank Offered Rate (LIBOR)
Debt Instrument [Line Items]
Debt, variable interest rate (as a percent)	2.25%	2.50%
Debt, variable interest rate if leverage ratio met	2.00%
Term Loan Facility | First Lien Credit Agreement
Debt Instrument [Line Items]
Debt principal amount			$ 275,000,000
Effective interest rate				5.00%
Term Loan Facility | First Lien Credit Agreement | London Interbank Offered Rate (LIBOR)
Debt Instrument [Line Items]
Debt, variable interest rate (as a percent)			2.75%
Floor rate			0.75%
Term Loan Facility | Amended and Restated Credit Agreement | London Interbank Offered Rate (LIBOR)
Debt Instrument [Line Items]
Debt, variable interest rate (as a percent)				2.25%
Floor rate				0.75%
Line of Credit | First Lien Credit Agreement | Revolving Credit Facility
Debt Instrument [Line Items]
Line of credit facility borrowing capacity			$ 75,000,000
Debt, variable interest rate (as a percent)				2.25%
Outstanding amount				$ 0		$ 0
Proceeds from line of credit				$ 0	$ 0
Facility fee, basis points				0.50%
Remaining outstanding				$ 73,600,000

Debt - Future Minimum Principal

Debt - Future Minimum Principal Payments Due Under the Credit Agreements (Detail) $ in Thousands	Sep. 30, 2018USD ($)
Long-term Debt, Fiscal Year Maturity [Abstract]
October 1, 2018 through December 31, 2018	$ 679
2,019	2,716
2,018	2,716
2,020	2,716
2,021	2,716
Thereafter	257,993
Total Payments	$ 269,536

Derivative Instruments - Additi

Derivative Instruments - Additional Information (Detail)	Mar. 29, 2018USD ($)	Sep. 30, 2016USD ($)	Sep. 30, 2018USD ($)MMBTU
Derivative [Line Items]
Proceeds from derivative hedges	$ 3,200,000
Derivatives, net liability position			$ 800,000
Collateral posted with counterparties related to derivatives			$ 0
Natural Gas Swap | Cash Flow Hedging | Designated as Hedging Instrument
Derivative [Line Items]
Aggregate notional amount outstanding (in mmBTUs) | MMBTU			2,070,000
Interest rate swap | Cash Flow Hedging | Designated as Hedging Instrument
Derivative [Line Items]
Aggregate notional amount outstanding	$ 100,000,000	$ 100,000,000
Derivative instrument term (not beyond)		4 years
Average fixed rate (as a percent)	2.46%	1.323%
Interest rate swap | Cash Flow Hedging | Designated as Hedging Instrument | London Interbank Offered Rate (LIBOR)
Derivative [Line Items]
Floor rate (as a percent)	0.75%	0.75%

Derivative Instruments - Deriva

Derivative Instruments - Derivatives at Fair Value (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Derivative [Line Items]
Derivative asset	$ 774	$ 2,159
Derivative liability	5	613
Interest rate swap
Derivative [Line Items]
Derivative asset	697	2,148
Derivative liability	0	0
Commodity derivatives
Derivative [Line Items]
Derivative asset	77	11
Derivative liability	$ 5	$ 613

Derivative Instruments - Gains

Derivative Instruments - Gains (losses) on derivatives (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Derivative Instruments, Gain (Loss) [Line Items]
Gain/(loss) recognized in Other comprehensive income on derivatives (effective portion), net of tax	$ 152	$ (7)	$ 1,664	$ (622)
Gain/(loss) reclassified from Accumulated other comprehensive loss into income (effective portion), net of tax	160	(134)	175	(171)
Interest rate swap
Derivative Instruments, Gain (Loss) [Line Items]
Gain/(loss) recognized in Other comprehensive income on derivatives (effective portion), net of tax	145	37	1,413	(318)
Gain/(loss) reclassified from Accumulated other comprehensive loss into income (effective portion), net of tax	169	(7)	379	(133)
Commodity derivatives
Derivative Instruments, Gain (Loss) [Line Items]
Gain/(loss) recognized in Other comprehensive income on derivatives (effective portion), net of tax	7	(44)	251	(304)
Gain/(loss) reclassified from Accumulated other comprehensive loss into income (effective portion), net of tax	$ (9)	$ (127)	$ (204)	$ (38)

Treasury Stock - Additional Inf

Treasury Stock - Additional Information (Detail)	21 Months Ended
	Sep. 30, 2018expansion	Feb. 21, 2018USD ($)	Nov. 04, 2015USD ($)
Equity [Abstract]
Stock repurchase program authorized amount (up to) | $		$ 300,000,000	$ 50,000,000
Number of expansions to stock repurchase program | expansion	2

Treasury Stock - Treasury Stock

Treasury Stock - Treasury Stock Activity (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended				9 Months Ended		12 Months Ended
	Sep. 30, 2018	Jun. 30, 2018	Sep. 30, 2017	Jun. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017	Dec. 31, 2016
Treasury Stock [Roll Forward]
Beginning balance (shares)	7,664,325		5,648,778		6,788,817	4,499,655	4,499,655
Ending balance (shares)	7,740,925	7,664,325	6,589,817	5,648,778	7,740,925	6,589,817	6,788,817	4,499,655
Beginning balance	$ 167,919		$ 116,592		$ 143,357	$ 88,756	$ 88,756
Ending balance	$ 170,782	$ 167,919	$ 137,884	$ 116,592	$ 170,782	$ 137,884	$ 143,357	$ 88,756
Average share price (usd per share)	$ 22.06	$ 21.91	$ 20.92	$ 20.64	$ 22.06	$ 20.92	$ 21.12	$ 19.73
Repurchases on open market
Treasury Stock [Roll Forward]
Shares repurchased (shares)	76,600		941,039		952,108	2,090,162
Shares repurchased	$ 2,863		$ 21,292		$ 27,425	$ 49,128
Average share price (usd per share)	$ 37.38		$ 22.63		$ 28.80	$ 23.50

Share-Based Compensation - Addi

Share-Based Compensation - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Compensation expense	$ 0.8	$ 0.6	$ 2.5	$ 2.1
Unrecognized compensation expense	$ 5.5		$ 5.5
Unrecognized compensation expense, weighted average remaining period			2 years 3 months 20 days

Accumulated Other Comprehensi_3

Accumulated Other Comprehensive Loss (Details) $ in Thousands	9 Months Ended
	Sep. 30, 2018USD ($)
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning Balance	$ 318,026
Ending Balance	347,950
Foreign currency translation adjustment
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning Balance	(3,636)
Other comprehensive (loss)/income before reclassifications	(496)
Amounts reclassified from accumulated other comprehensive loss	0
Net current period other comprehensive (loss)/income	(496)
Ending Balance	(4,132)
Net unrealized gain on derivatives, net of tax
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning Balance	987
Other comprehensive (loss)/income before reclassifications	1,664
Amounts reclassified from accumulated other comprehensive loss	(175)
Net current period other comprehensive (loss)/income	1,489
Ending Balance	2,476
Accumulated Other Comprehensive Loss
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning Balance	(2,649)
Other comprehensive (loss)/income before reclassifications	1,168
Amounts reclassified from accumulated other comprehensive loss	(175)
Net current period other comprehensive (loss)/income	993
Ending Balance	$ (1,656)

Income Taxes - Narrative (Detai

Income Taxes - Narrative (Detail) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
	Dec. 31, 2017	Sep. 30, 2018
Income Tax Disclosure [Abstract]
Effective rate (as a percent)		22.30%
Discrete tax benefit		$ 0.6
Discrete tax benefit from stock compensation windfall		0.1
Discrete tax benefit related to re-measurement of deferred taxes		$ 0.5
Reduction in income tax expense due to Tax Cuts and Jobs Act of 2017	$ (9.2)

Earnings Per Share - Additional

Earnings Per Share - Additional Information (Details) - shares	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Share-based compensation awards
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share (shares)	0	0	21,000	29,000

Earnings Per Share (Details)

Earnings Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Net income	$ 18,564	$ 10,987	$ 54,105	$ 35,612
Weighted average number of shares outstanding- basic (shares)	36,732,746	38,212,869	37,012,536	38,966,575
Effect of dilutive securities:
Total effect of dilutive securities (shares)	186,158	132,687	168,851	114,398
Weighted average number of shares outstanding - diluted (shares)	36,918,904	38,345,556	37,181,387	39,080,973
Basic earnings per share (usd per share)	$ 0.51	$ 0.29	$ 1.46	$ 0.91
Diluted earnings per share (usd per share)	$ 0.50	$ 0.29	$ 1.46	$ 0.91
Restricted stock awards
Effect of dilutive securities:
Effect of dilutive securities (shares)	0	6,852	1,170	7,598
Restricted stock units
Effect of dilutive securities:
Effect of dilutive securities (shares)	89,750	48,175	72,650	54,171
Performance restricted stock units
Effect of dilutive securities:
Effect of dilutive securities (shares)	68,384	58,199	67,231	30,853
Stock options
Effect of dilutive securities:
Effect of dilutive securities (shares)	28,024	19,461	27,800	21,776

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Commitments and Contingencies Disclosure [Abstract]
Rent expense	$ 0.6	$ 0.8	$ 2.2	$ 2.5
Letter of Credit
Long-term Purchase Commitment [Line Items]
Outstanding amount of letters of credit	1.4		1.4		$ 1.4
Gas, Gypsum, Paper, and Other Raw Materials
Long-term Purchase Commitment [Line Items]
Non capital purchased under commitments	$ 22.7	$ 22	$ 69.5	$ 64.8

Commitments and Contingencies_2

Commitments and Contingencies - Future Minimum Lease Payments Due Under Non-Cancelable Operating Leases and Purchase Commitments by Year (Detail) $ in Thousands	Sep. 30, 2018USD ($)
Future Minimum Lease Payments
October 1, 2018 - December 31, 2018	$ 180
2,019	1,658
2,020	48
2,021	0
2,022	0
2,023	0
Thereafter	0
Total	1,886
Purchase Commitments
October 1, 2018 - December 31, 2018	17,958
2,019	47,287
2,020	46,141
2,021	28,097
2,022	25,069
2,023	12,284
Thereafter	53,621
Total	$ 230,457

Segment Reporting - Additional

Segment Reporting - Additional Information (Detail) - geographic_area	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Segment Reporting Information [Line Items]
Number of geographical areas (geographic area)	2		2
Wallboard | Sales Revenue, Net | Product Concentration Risk
Segment Reporting Information [Line Items]
Percentage of revenues	97.60%	96.80%	97.30%	96.80%

Segment Reporting - Segment Rep

Segment Reporting - Segment Reporting (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Net Sales:
Net Sales	$ 131,234	$ 116,526	$ 387,304	$ 357,771
Operating Income:
Operating income	26,971	19,707	78,293	63,014
Adjustments:
Interest expense	(2,549)	(2,988)	(7,963)	(8,966)
Losses from equity investment	(393)	(204)	(1,148)	(29)
Other (expense)/income, net	(29)	146	(256)	(633)
Income before provision for income taxes	24,000	16,661	68,926	53,386
Depreciation and Amortization
Total depreciation and amortization	11,580	12,057	32,966	35,817
Operating Segments | Wallboard
Net Sales:
Net Sales	128,101	112,796	376,739	346,466
Operating Income:
Operating income	27,551	19,992	79,702	63,402
Depreciation and Amortization
Total depreciation and amortization	11,299	11,793	32,016	34,992
Operating Segments | Other
Net Sales:
Net Sales	3,133	3,730	10,565	11,305
Operating Income:
Operating income	(580)	(285)	(1,409)	(388)
Depreciation and Amortization
Total depreciation and amortization	281	264	950	825
Adjustments
Adjustments:
Interest expense	(2,549)	(2,988)	(7,963)	(8,966)
Losses from equity investment	(393)	(204)	(1,148)	(29)
Other (expense)/income, net	$ (29)	$ 146	$ (256)	$ (633)

Segment Reporting - Net Sales b

Segment Reporting - Net Sales by Geographic Region (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Revenues from External Customers and Long-Lived Assets [Line Items]
Net sales	$ 131,234	$ 116,526	$ 387,304	$ 357,771
United States
Revenues from External Customers and Long-Lived Assets [Line Items]
Net sales	125,430	110,430	367,917	334,481
Canada
Revenues from External Customers and Long-Lived Assets [Line Items]
Net sales	$ 5,804	$ 6,096	$ 19,387	$ 23,290

Segment Reporting - Assets by G

Segment Reporting - Assets by Geographic Region (Detail) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Revenues from External Customers and Long-Lived Assets [Line Items]
Fixed Assets	$ 290,670	$ 294,003
Total Assets	672,904	641,934
United States
Revenues from External Customers and Long-Lived Assets [Line Items]
Fixed Assets	287,255	290,324
Total Assets	654,965	622,836
Canada
Revenues from External Customers and Long-Lived Assets [Line Items]
Fixed Assets	3,415	3,679
Total Assets	$ 17,939	$ 19,098

Fair Value Disclosures (Details

Fair Value Disclosures (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative asset	$ 774	$ 2,159
Derivative liability	5	613
Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative asset	774	2,159
Derivative liability	5	613
Recurring | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative asset	0	0
Derivative liability	0	0
Recurring | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative asset	774	2,159
Derivative liability	5	613
Recurring | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative asset	0	0
Derivative liability	0	0
Interest rate swap
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative asset	697	2,148
Derivative liability	0	0
Interest rate swap | Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative asset	697	2,148
Derivative liability	0	0
Interest rate swap | Recurring | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative asset	0	0
Derivative liability	0	0
Interest rate swap | Recurring | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative asset	697	2,148
Derivative liability	0	0
Interest rate swap | Recurring | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative asset	0	0
Derivative liability	0	0
Commodity derivatives
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative asset	77	11
Derivative liability	5	613
Commodity derivatives | Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative asset	77	11
Derivative liability	5	613
Commodity derivatives | Recurring | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative asset	0	0
Derivative liability	0	0
Commodity derivatives | Recurring | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative asset	77	11
Derivative liability	5	613
Commodity derivatives | Recurring | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative asset	0	0
Derivative liability	$ 0	$ 0