Document and Entity Information - shares	3 Months Ended
Document and Entity Information - shares	Mar. 31, 2019	May 01, 2019
Document and Entity Information [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Mar. 31, 2019
Document Fiscal Year Focus	2018
Document Fiscal Period Focus	Q1
Trading Symbol	CBPX
Entity Registrant Name	CONTINENTAL BUILDING PRODUCTS, INC.
Entity Central Index Key	0001592480
Current Fiscal Year End Date	--12-31
Entity Current Reporting Status	Yes
Entity Filer Category	Large Accelerated Filer
Entity Emerging Growth	false
Entity Small Business	false
Entity Common Stock, Shares Outstanding		34,720,561

Consolidated Statements of Operations - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Income Statement [Abstract]
Net sales	$ 122,032	$ 116,802
Cost of goods sold	90,786	86,616
Gross profit	31,246	30,186
Selling and administrative	9,653	9,424
Gain from insurance recoveries, net	1,513	0
Operating income	23,106	20,762
Other expense, net	(36)	(140)
Interest expense, net	(2,492)	(2,720)
Income before losses from equity method investment and provision for income taxes	20,578	17,902
Losses from equity method investment	(45)	(364)
Income before provision for income taxes	20,533	17,538
Provision for income taxes	(4,607)	(3,892)
Net income	$ 15,926	$ 13,646
Net income per share:
Basic (usd per share)	$ 0.45	$ 0.36
Diluted (usd per share)	$ 0.45	$ 0.36
Weighted average shares outstanding:
Basic (shares)	35,248,280	37,432,782
Diluted (shares)	35,350,259	37,604,953

Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Statement of Comprehensive Income [Abstract]
Net income	$ 15,926	$ 13,646
Foreign currency translation adjustment	324	(481)
Derivative instrument adjustments, net of taxes	(378)	1,045
Other comprehensive (loss)/income	(54)	564
Comprehensive income	$ 15,872	$ 14,210

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

+ References + Details

Consolidated Balance Sheets - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Assets:
Cash and cash equivalents	$ 101,081	$ 102,633
Trade receivables, net	43,985	38,454
Inventories, net	37,513	32,225
Prepaid and other current assets	5,264	19,805
Total current assets	187,843	193,117
Property, plant and equipment, net	285,701	288,368
Customer relationships and other intangibles, net	60,971	62,680
Goodwill	119,945	119,945
Equity method investment	7,832	7,975
Operating lease - right of use assets	918
Debt issuance costs	252	296
Total Assets	663,462	672,381
Liabilities:
Accounts payable	34,706	48,060
Accrued and other liabilities	5,595	12,815
Debt, current portion	1,720	1,669
Operating lease liabilities, current portion	625
Total current liabilities	42,646	62,544
Deferred taxes and other long-term liabilities	19,651	20,204
Debt, non-current portion	261,420	261,886
Operating lease liabilities, non-current portion	978	0
Total Liabilities	324,695	344,634
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; 44,537,285 and 44,472,214 shares issued and 35,275,032 and 35,401,868 shares outstanding as of March 31, 2019 and December 31, 2018, respectively	44	44
Additional paid-in capital	327,668	327,515
Less: Treasury stock	(214,055)	(209,050)
Accumulated other comprehensive loss	(3,445)	(3,391)
Accumulated earnings	228,555	212,629
Total Shareholders' Equity	338,767	327,747
Total Liabilities and Shareholders' Equity	$ 663,462	$ 672,381

Consolidated Balance Sheets (Parenthetical) - $ / shares	Mar. 31, 2019	Dec. 31, 2018
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)	44,537,285	44,472,214
Common stock, shares outstanding (in shares)	35,275,032	35,401,868

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Cash flows from operating activities:
Net income	$ 15,926	$ 13,646
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	10,520	10,581
Amortization of debt issuance costs and debt discount	309	334
Gain from insurance recoveries	(1,513)	0
Losses from equity method investment	45	364
Amortization of deferred gain on terminated swaps	(288)	0
Share-based compensation	570	600
Change in assets and liabilities:
Trade receivables	(5,553)	(7,562)
Inventories	(5,244)	(2,913)
Prepaid expenses and other current assets	14,562	1,144
Accounts payable	(12,107)	(1,353)
Accrued and other current liabilities	(6,537)	(1,042)
Other long-term liabilities	(54)	(56)
Net cash provided by operating activities	10,636	13,743
Cash flows from investing activities:
Payments for property, plant and equipment	(6,656)	(5,955)
Payments for intangible assets	(701)	(482)
Proceeds from insurance recoveries	1,589	0
Capital contributions to equity method investment	(58)	(251)
Distributions from equity method investment	156	78
Net cash used in investing activities	(5,670)	(6,610)
Cash flows from financing activities:
Proceeds from exercise of stock options	118	11
Tax withholdings on share-based compensation	(1,137)	(421)
Principal payments for debt	(679)	(679)
Payments to repurchase common stock	(5,005)	(14,550)
Net cash used in financing activities	(6,703)	(15,639)
Effect of foreign exchange rates on cash and cash equivalents	185	(167)
Net change in cash and cash equivalents	(1,552)	(8,673)
Cash, beginning of period	102,633	72,521
Cash, end of period	$ 101,081	$ 63,848

Consolidated Statements of Changes in Shareholders' Equity - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-In Capital	Treasury Stock	Accumulated Other Comprehensive Loss	Accumulated Earnings
Beginning Balance at Dec. 31, 2017	$ 318,026	$ 44	$ 325,391	$ (143,357)	$ (2,649)	$ 138,597
Beginning balance (in shares) at Dec. 31, 2017		37,532,959
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	13,646					13,646
Other comprehensive income (loss), net of tax	564				564
Purchase of treasury shares	(14,550)	$ 0		(14,550)
Purchase of treasury shares ( in shares)		(530,600)
Stock option exercise	11	$ 0	11
Stock option exercise, shares		781
Share-based compensation	213	$ 0	213
Share-based compensation, shares		85,838
Ending Balance at Mar. 31, 2018	317,910	$ 44	325,615	(157,907)	(2,085)	152,243
Ending balance (in shares) at Mar. 31, 2018		37,088,978
Beginning Balance at Dec. 31, 2018	327,747	$ 44	327,515	(209,050)	(3,391)	212,629
Beginning balance (in shares) at Dec. 31, 2018		35,401,868
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	15,926					15,926
Other comprehensive income (loss), net of tax	(54)				(54)
Purchase of treasury shares	(5,005)	$ 0		(5,005)
Purchase of treasury shares ( in shares)		(191,907)
Stock option exercise	118	$ 0	118
Stock option exercise, shares		6,500
Share-based compensation	35	$ 0	35
Share-based compensation, shares		58,571
Ending Balance at Mar. 31, 2019	$ 338,767	$ 44	$ 327,668	$ (214,055)	$ (3,445)	$ 228,555
Ending balance (in shares) at Mar. 31, 2019		35,275,032

Background and Nature of Operations	3 Months Ended
Background and Nature of Operations	Mar. 31, 2019
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. 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.

Significant Accounting Policies

3 Months Ended

Mar. 31, 2019

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, 2019. 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, 2018 included in the Company's Annual Report on Form 10-K for the fiscal year then ended (the "2018 10-K"). The Company has continued to follow the accounting policies set forth in those financial statements.


(c)	Supplemental Cash Flow Disclosure



Table 2.1: Certain Cash Transactions and Other Activity
	For the Three Months Ended,
	March 31, 2019		March 31, 2018
	(in thousands)
Cash paid for amounts included in the measurement of lease liabilities:
Operating lease cash outflows	$	152	$	148
Other activity:
Acquisition of property, plant and equipment included in liabilities	$	1,813	$	3,684

(d) Recent Accounting Pronouncements

Accounting Standards Recently Adopted

The Company adopted Financial Accounting Standards Board ("FASB") Accounting Standards Update ("ASU") 2016-02, "Leases.", as of January 1, 2019. The Company elected the transition package of practical expedients permitted within ASU 2016-02, which among other things, allowed the Company to carryforward the historical lease classification. In addition, the Company elected the comparative period practical expedient, which allowed the Company to implement the guidance as of the effective date without having to adjust the comparative financial statements. Instead, under this expedient, companies recognize the cumulative effect adjustment in equity. The Company also made 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. The adoption of the standard resulted in recognition of approximately $1.0 million in right of use assets and $1.7 million in lease liabilities for operating leases on the Company's Consolidated Balance Sheet, with no impact to its retained earnings, Consolidated Statement of Operations and Consolidated Statement of Cash Flows.

The Company adopted ASU 2017-12, "Derivatives and Hedging (Topic 815), Targeted Improvements to Accounting for Hedging Activities," as of January 1, 2019. 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 adoption of the standard did not have a material impact on the Company's Consolidated Financial Statements.

Accounting Standards Not Yet Adopted

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 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.

(e) Reclassifications

Certain reclassifications of prior year information were made to conform to the 2019 presentation. These reclassifications had no material impact on the Company's Consolidated Financial Statements.

Trade Receivables, Net

3 Months Ended

Mar. 31, 2019

Receivables [Abstract]

Trade Receivables, Net

TRADE RECEIVABLES, NET



Table 3: Details of Trade Receivables, Net
	March 31, 2019			December 31, 2018
	(in thousands)
Trade receivables, gross	$	44,695		$	39,426
Allowance for cash discounts and doubtful accounts	(710		)	(972		)
Trade receivables, net	$	43,985		$	38,454

Trade receivables are recorded net of credit memos issued during the normal course of business.

Inventories, Net

3 Months Ended

Mar. 31, 2019

Inventory Disclosure [Abstract]

Inventories, Net

INVENTORIES, NET



Table 4: Details of Inventories, Net
	March 31, 2019		December 31, 2018
	(in thousands)
Finished products	$	7,760	$	6,700
Raw materials	22,297		18,388
Supplies and other	7,456		7,137
Inventories, net	$	37,513	$	32,225

Property, Plant and Equipment, Net

3 Months Ended

Mar. 31, 2019

Property, Plant and Equipment [Abstract]

Property, Plant and Equipment, Net

PROPERTY, PLANT AND EQUIPMENT, NET



Table 5: Details of Property, Plant and Equipment, Net
	March 31, 2019			December 31, 2018
	(in thousands)
Land	$	13,186		$	13,185
Buildings	120,118			118,076
Plant machinery	293,313			292,219
Mobile equipment	15,468			15,163
Construction in progress	25,520			23,566
Property, plant and equipment, at cost	467,605			462,209
Accumulated depreciation	(181,904		)	(173,841		)
Property, plant and equipment, net	$	285,701		$	288,368

Depreciation expense was $8.2 million and $8.1 million for the three months ended March 31, 2019 and 2018, respectively.

Customer Relationships and Other Intangibles, Net

3 Months Ended

Mar. 31, 2019

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
	March 31, 2019							December 31, 2018
	Gross		Accumulated Amortization			Net		Gross		Accumulated Amortization			Net
	(in thousands)
Customer relationships	$	116,310	$	(67,702	)	$	48,608	$	116,180	$	(65,738	)	$	50,442
Purchased software	8,736		(5,657		)	3,079		8,225		(5,507		)	2,718
Trademarks	14,789		(5,505		)	9,284		14,772		(5,252		)	9,520
Total	$	139,835	$	(78,864	)	$	60,971	$	139,177	$	(76,497	)	$	62,680

Amortization expense was $2.3 million and $2.5 million for the three months ended March 31, 2019 and 2018, respectively.



Table 6.2: Details of Future Amortization Expense of Customer Relationships and Other Intangibles
	As of March 31, 2019
	(in thousands)
April 1, 2019 through December 31, 2019	$	6,935
2020	8,662
2021	7,761
2022	6,987
2023	6,104
Thereafter	24,522
Total	$	60,971

Investment in Seven Hills	3 Months Ended
Investment in Seven Hills	Mar. 31, 2019
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 $13.5 million and $12.2 million for the three months ended March 31, 2019 and 2018, respectively. As of March 31, 2019, the Company had certain purchase commitments for paper totaling $35.5 million through 2022.

Accrued and Other Liabilities

3 Months Ended

Mar. 31, 2019

Payables and Accruals [Abstract]

Accrued and Other Liabilities

ACCRUED AND OTHER LIABILITIES



Table 8: Details of Accrued and Other Liabilities
	March 31, 2019		December 31, 2018
	(in thousands)
Employee-related costs	$	3,497	$	10,768
Property taxes	664		82
Other taxes	477		351
Other	957		1,614
Accrued and other liabilities	$	5,595	$	12,815

Debt

3 Months Ended

Mar. 31, 2019

Debt Disclosure [Abstract]

Debt

DEBT



Table 9.1: Details of Debt
	March 31, 2019			December 31, 2018
	(in thousands)
Amended and Restated Credit Agreement (1)	$	251,978		$	252,658
Industrial revenue bonds (2)	16,200			16,200
Less: Original issue discount (net of amortization)	(1,223		)	(1,285		)
Less: Debt issuance costs	(3,815		)	(4,018		)
Total debt	263,140			263,555
Less: Current portion of long-term debt	(1,720		)	(1,669		)
Long-term debt	$	261,420		$	261,886


(1)	As of March 31, 2019 and December 31, 2018, 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 2.00%.


(2)	As of March 31, 2019 and December 31, 2018, Industrial revenue bonds had a maturity date of December 1, 2025 and an interest rate of LIBOR plus 1.50% less an approximate 20 percent reduction in the rate related to the tax-free interest income to the bond holders.

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 existing 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 (the "Term Loan") and a $75.0 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% and allowing for a further reduction in the 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 three months ended March 31, 2019 and 2018, the Company made $0.7 million of scheduled mandatory principal payments. Because the Company attained a total leverage ratio of less than 1.1 to 1 during the fourth quarter of 2018, the interest rate was further reduced pursuant to the terms of the Amended and Restated Credit Agreement to LIBOR plus 2.00% as of December 31, 2018. As of March 31, 2019, the annual effective interest rate, including original issue discount and amortization of debt issuance costs, was 5.0%.

In December 2018, the Company completed a financing of industrial revenue bonds due 2025 with a total commitment of $28 million. The bonds were issued by the County of Campbell, Kentucky and Putnam County Development Authority, pursuant to a trust indenture between the issuers and Huntington National Bank, as trustee. Proceeds of the bonds are loaned by the issuers to the Company under a loan agreement, whereby the Company is obligated to make loan payments to the issuers sufficient to pay all debt service and expenses related to the bonds. The Company's obligations under the loan agreement and related note bear interest at a fluctuating rate based on LIBOR plus 1.50% less an approximate 20 percent reduction in the rate related to the tax-free interest income to the bond holders. The loan agreement contains restrictions and covenants on our operations that are consistent with those contained in the Amended and Restated Credit Agreement mentioned below.

There were no amounts outstanding under the Revolver as of March 31, 2019 or 2018. 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 March 31, 2019, 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
	Amount Due
	(in thousands)
April 1, 2019 through December 31, 2019	$	2,036
2020	5,326
2021	6,196
2022	6,196
2023	245,074
Thereafter	3,350
Total Payments	$	268,178

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 March 31, 2019, the total leverage ratio of no greater than 5.0 under the financial covenant was not applicable at March 31, 2019. The Company was in compliance with all applicable covenants under the Amended and Restated Credit Agreement as of March 31, 2019.

Derivative Instruments

3 Months Ended

Mar. 31, 2019

Derivative Instruments and Hedging Activities Disclosure [Abstract]

Derivative Instruments

DERIVATIVE INSTRUMENTS

Commodity Derivative Instruments

As of March 31, 2019, the Company had 2.4 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 January 31, 2020. 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 months ended March 31, 2019 and 2018.

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. During three months ended March 31, 2019, $0.2 million of unrealized gain, net of tax was amortized into interest expense. Also on March 29, 2018, 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 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 months ended March 31, 2019 and 2018.



Table 10.1: Details of Derivatives Fair Value
	March 31, 2019		December 31, 2018
	(in thousands)
Assets
Interest rate swap	$	—	$	86
Commodity hedges	101		61
Total assets	$	101	$	147
Liabilities
Interest rate swap	$	223	$	—
Commodity hedges	27		105
Total liabilities	$	250	$	105



Table 10.2: Gains/(losses) on Derivatives
	For the Three Months Ended
	March 31, 2019			March 31, 2018		March 31, 2019			March 31, 2018
	Gain/(loss) recognized in AOCI on derivatives (effective portion), net of tax					Gain/(loss) reclassified from AOCI into income (effective portion), net of tax
	(in thousands)
Interest rate swap	$	(161	)	$	831	$	303		$	70
Commodity hedges	41			241		(45		)	(97		)
Total	$	(120	)	$	1,072	$	258		$	(27	)

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 March 31, 2019, the Company's derivatives were in a $0.1 million net liability position and recorded in Other current assets and Other current liabilities. 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 March 31, 2019, the Company had no collateral posted with its counterparties related to the derivatives.

Leases Leases

3 Months Ended

Mar. 31, 2019

Leases [Abstract]

Leases

LEASES

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. Certain building leases also include options to renew, with renewal terms that can extend the lease term up to 5 years. The exercise of lease renewal options is at the Company's sole discretion.



Table 11.1: Components of lease expense
	For the Three Months Ended,
	March 31, 2019		March 31, 2018
	(in thousands)
Operating lease cost	$	101	$	99
Short term lease cost	511		735
Total lease cost	$	612	$	834



Table 11.2: Maturities of lease liabilities
	Operating leases
	(in thousands)
April 1, 2019 through December 31, 2019	$	468
2020	637
2021	600
2022	—
2023	—
Total lease payments	$	1,705
Less imputed interest	(102		)
Present value of lease liabilities	$	1,603



Table 11.3: Details of lease term and discount rate
	As of March 31, 2019
Weighted-average remaining lease term
Operating leases	3 years
Weighted-average discount rate
Operating leases	4.52	%

Treasury Stock

3 Months Ended

Mar. 31, 2019

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.

Since the initial authorization, the Company' Board of Directors has expanded and extended the 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. As of March 31, 2019, there was approximately $126.0 million of capacity remaining under this repurchase authorization.

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 12: Details of Treasury Stock Activity
	March 31, 2019					March 31, 2018
	Shares	Amount (1)		Average Share Price (1)		Shares	Amount (1)		Average Share Price (1)
	(in thousands, except share data)
Beginning Balance	9,070,346	$	209,050	$	23.05	6,788,817	$	143,357	$	21.12
Repurchases on open market	191,907	5,005		26.08		530,600	14,550		27.42
Ending Balance	9,262,253	$	214,055	$	23.11	7,319,417	$	157,907	$	21.57
(1) Includes commissions paid for repurchases on open market.

Share-Based Compensation	3 Months Ended
Share-Based Compensation	Mar. 31, 2019
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Share-Based Compensation	SHARE-BASED COMPENSATION On February 19, 2019, the Company granted certain employees 63,772 Restricted Stock Units ("RSUs") that vest ratably over four years from the grant date. All of these grants had a market price on the date of grant of $27.32. Additionally, on February 20, 2019, the Company granted an employee and members of the Board of Directors 23,936 RSUs and 17,100 RSUs, respectively, that vest ratably over a period of four years for the employee and one year for the members of the Board of Directors from the grant date and had a market price on the date of grant of $27.24. On February 19, 2019 and February 20, 2019, the Company also granted certain employees 30,172 Performance Based RSUs ("PRSUs") and 23,936 PRSUs, respectively. The PRSUs vest on December 31, 2021, with the exact number of PRSUs vesting subject to the achievement of certain performance conditions through December 31, 2020. The number of PRSUs earned will vary from 0% to 240% of the number of PRSUs awarded. The market price on February 19, 2019 was $27.32, and the market price on February 20, 2019 was $27.24. For both the three months ended March 31, 2019 and 2018, the Company recognized share-based compensation expenses of $0.6 million in expense. The expenses related to share-based compensation awards that were recorded in selling and administrative expenses. As of March 31, 2019, there was $6.9 million of total unrecognized compensation cost related to non-vested stock options, restricted stock awards, RSUs and PRSUs. This cost is expected to be recognized over a weighted average period of 2.7 years.

Accumulated Other Comprehensive Loss

3 Months Ended

Mar. 31, 2019

Equity [Abstract]

Accumulated Other Comprehensive Loss

ACCUMULATED OTHER COMPREHENSIVE LOSS



Table 14: 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, 2018	$	(5,027	)	$	1,636		$	(3,391	)
Other comprehensive income/(loss) before reclassifications	324			(120		)	204
Amounts reclassified from accumulated other comprehensive loss	—			(258		)	(258		)
Net current period other comprehensive income/(loss)	324			(378		)	(54		)
Balance as of March 31, 2019	$	(4,703	)	$	1,258		$	(3,445	)

Income Taxes	3 Months Ended
Income Taxes	Mar. 31, 2019
Income Tax Disclosure [Abstract]
Income Taxes	INCOME TAXES The Company’s estimated annual effective tax rate is 22.5%. The Company is subject to federal income taxes and various state, provincial and local income taxes. The Company is subject to audit examinations at the U.S. 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

3 Months Ended

Mar. 31, 2019

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. For the three months ended March 31, 2019 and 2018 respectively, approximately 82,253 and 62,949 share-based compensation awards were excluded from the weighted average shares outstanding because their impact would be anti-dilutive in the computation of dilutive earnings per share



Table 16: Details of Basic and Dilutive Earnings Per Share
	For the Three Months Ended
	March 31, 2019		March 31, 2018
	(dollars in thousands, except for per share amounts)
Net income	$	15,926	$	13,646

Weighted average number of shares outstanding - basic	35,248,280		37,432,782
Effect of dilutive securities:
Restricted stock awards	—		3,509
Restricted stock units	55,515		72,012
Performance restricted stock units	29,775		69,509
Stock options	16,689		27,141
Total effect of dilutive securities	101,979		172,171
Weighted average number of shares outstanding - diluted	35,350,259		37,604,953

Basic earnings per share	$	0.45	$	0.36
Diluted earnings per share	$	0.45	$	0.36

Commitments and Contingencies

3 Months Ended

Mar. 31, 2019

Commitments and Contingencies Disclosure [Abstract]

Commitments and Contingencies

COMMITMENTS AND CONTINGENCIES

Commitments

The Company has non-capital purchase commitments that primarily relate to gas, gypsum, paper and other raw materials. The total amounts purchased under such commitments were $20.4 million and $22.4 million for the three months ended March 31, 2019 and 2018, respectively.



Table 17: Details of Purchase Commitments
	As of March 31, 2019
	(in thousands)
April 1, 2019 through December 31, 2019	$	26,734
2020	36,073
2021	35,363
2022	26,832
2023	11,054
Thereafter	48,144
Total	$	184,200

Contingent obligations

Under certain circumstances, the Company provides letters of credit related to its natural gas and other supply purchases. As of March 31, 2019 and December 31, 2018, 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 March 31, 2019 and December 31, 2018, 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.

BUCHANAN PLANT OUTAGE

On January 24, 2019, Company's Buchanan, New York plant experienced a significant equipment malfunction, resulting in an outage at the plant. The plant was off-line while repairs were made through March 15, 2019. While the Buchanan plant was down, the Company increased production at its plants in Silver Grove, Kentucky and Palatka, Florida to offset a portion of the lost production from the Buchanan plant.

The Company has standard insurance coverage that is intended to cover circumstances such as these, including business interruption insurance. The Company's insurance coverage is designed to cover the direct costs of rebuilding the damaged equipment, costs incurred to re-direct products from the Company's other plants, and the lost contribution margin of the sales that otherwise would have been made if the plant was operating normally.



Details of Insurance Claims and Cash Payments Related to Buchanan Outage
	Claim Details						Cash Details
	Claim Amount		Insurance Deductible		Net recovery recorded in first quarter 2019		Cash received in first quarter 2019		Receivable Recorded as of March 31, 2019
	(in thousands)
Rebuild of property, plant and equipment damaged (a)	$	1,839	$	250	$	1,589	$	1,589	$	—
Directs costs associated with business interruption (b)	2,932		—		2,932		2,661		271
	$	4,771	$	250	$	4,521	$	4,250	$	271


(a)	The rebuild of property, plant and equipment damaged and related net recovery resulted in a net gain of $1.5 million.

(b)

Direct costs associated with the business interruption include various expenses such as additional freight to ship to customers at greater distances from other plants, additional freight costs to reroute incoming raw materials and other various costs that were incurred as a result of the Buchanan outage and are expected to be covered by the Company's insurance policy. The net recovery of direct costs associated with business interruption were netted against actual costs incurred resulting in a net impact of zero to the income statement.



Details of Gain from insurance recoveries, net
	For the Three Months Ended
	March 31, 2019
	(in thousands)
Cost to rebuild property, plant and equipment (capitalized)	$	1,839
Insurance deductible	250
Net recoveries from insurance policy	1,589
Write-off of property, plant and equipment	76
Gain from insurance recoveries, net	$	1,513

Segment Reporting

3 Months Ended

Mar. 31, 2019

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 97.5% and 96.7% of the Company's revenues for the three months ended March 31, 2019 and 2018, 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 18.1: Segment Reporting
	For the Three Months Ended
	March 31, 2019			March 31, 2018
	(in thousands)
Net Sales:
Wallboard	$	118,944		$	112,971
Other	3,088			3,831
Total net sales	$	122,032		$	116,802
Operating Income:
Wallboard	$	23,595		$	21,030
Other	(489		)	(268		)
Total operating income	$	23,106		$	20,762
Adjustments:
Interest expense	$	(2,492	)	$	(2,720	)
Losses from equity investment	(45		)	(364		)
Other expense, net	(36		)	(140		)
Income before provision for income taxes	$	20,533		$	17,538
Depreciation and Amortization:
Wallboard	$	10,276		$	10,305
Other	244			276
Total depreciation and amortization	$	10,520		$	10,581



Table 18.2: Details of Net Sales By Geographic Region
	For the Three Months Ended
	March 31, 2019		March 31, 2018
	(in thousands)
United States	$	116,712	$	109,975
Canada	5,320		6,827
Net sales	$	122,032	$	116,802



Table 18.3: Details of Assets By Geographic Region
	Fixed Assets				Total Assets
	March 31, 2019		December 31, 2018		March 31, 2019		December 31, 2018
	(in thousands)
United States	$	282,541	$	285,202	$	646,228	$	655,849
Canada	3,160		3,166		17,234		16,532
Total	$	285,701	$	288,368	$	663,462	$	672,381

Fair Value Disclosures

3 Months Ended

Mar. 31, 2019

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 March 31, 2019 and December 31, 2018, 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 March 31, 2019 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 19.1: Fair Value Hierarchy - 2019
	As of March 31, 2019
	Level 1		Level 2		Level 3		Balance
	(in thousands)
Asset
Interest rate swap	$	—	$	—	$	—	$	—
Commodity derivatives	—		101		—		101
Total assets	$	—	$	101	$	—	$	101

Liabilities
Interest rate swap	$	—	$	223	$	—	$	223
Commodity derivatives	—		27		—		27
Total liabilities	$	—	$	250	$	—	$	250



Table 19.2: Fair Value Hierarchy - 2018
	As of December 31, 2018
	Level 1		Level 2		Level 3		Balance
	(in thousands)
Asset
Interest rate swap	$	—	$	86	$	—	$	86
Commodity derivatives	—		61		—		61
Total assets	$	—	$	147	$	—	$	147

Liabilities
Interest rate swap	$	—	$	—	$	—	$	—
Commodity derivatives	—		105		—		105
Total liabilities	$	—	$	105	$	—	$	105

- 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

Buchanan Plant Outage Buchanan Plant Outage

3 Months Ended

Mar. 31, 2019

Commitments and Contingencies Disclosure [Abstract]

Buchanan Plant Outage

COMMITMENTS AND CONTINGENCIES

Commitments

The Company has non-capital purchase commitments that primarily relate to gas, gypsum, paper and other raw materials. The total amounts purchased under such commitments were $20.4 million and $22.4 million for the three months ended March 31, 2019 and 2018, respectively.



Table 17: Details of Purchase Commitments
	As of March 31, 2019
	(in thousands)
April 1, 2019 through December 31, 2019	$	26,734
2020	36,073
2021	35,363
2022	26,832
2023	11,054
Thereafter	48,144
Total	$	184,200

Contingent obligations

Under certain circumstances, the Company provides letters of credit related to its natural gas and other supply purchases. As of March 31, 2019 and December 31, 2018, 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 March 31, 2019 and December 31, 2018, 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.

BUCHANAN PLANT OUTAGE

On January 24, 2019, Company's Buchanan, New York plant experienced a significant equipment malfunction, resulting in an outage at the plant. The plant was off-line while repairs were made through March 15, 2019. While the Buchanan plant was down, the Company increased production at its plants in Silver Grove, Kentucky and Palatka, Florida to offset a portion of the lost production from the Buchanan plant.

The Company has standard insurance coverage that is intended to cover circumstances such as these, including business interruption insurance. The Company's insurance coverage is designed to cover the direct costs of rebuilding the damaged equipment, costs incurred to re-direct products from the Company's other plants, and the lost contribution margin of the sales that otherwise would have been made if the plant was operating normally.



Details of Insurance Claims and Cash Payments Related to Buchanan Outage
	Claim Details						Cash Details
	Claim Amount		Insurance Deductible		Net recovery recorded in first quarter 2019		Cash received in first quarter 2019		Receivable Recorded as of March 31, 2019
	(in thousands)
Rebuild of property, plant and equipment damaged (a)	$	1,839	$	250	$	1,589	$	1,589	$	—
Directs costs associated with business interruption (b)	2,932		—		2,932		2,661		271
	$	4,771	$	250	$	4,521	$	4,250	$	271


(a)	The rebuild of property, plant and equipment damaged and related net recovery resulted in a net gain of $1.5 million.

(b)

Direct costs associated with the business interruption include various expenses such as additional freight to ship to customers at greater distances from other plants, additional freight costs to reroute incoming raw materials and other various costs that were incurred as a result of the Buchanan outage and are expected to be covered by the Company's insurance policy. The net recovery of direct costs associated with business interruption were netted against actual costs incurred resulting in a net impact of zero to the income statement.



Details of Gain from insurance recoveries, net
	For the Three Months Ended
	March 31, 2019
	(in thousands)
Cost to rebuild property, plant and equipment (capitalized)	$	1,839
Insurance deductible	250
Net recoveries from insurance policy	1,589
Write-off of property, plant and equipment	76
Gain from insurance recoveries, net	$	1,513

Significant Accounting Policies (Policies)	3 Months Ended
Significant Accounting Policies (Policies)	Mar. 31, 2019
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.
Recent Accounting Pronouncements	Recent Accounting Pronouncements Accounting Standards Recently Adopted The Company adopted Financial Accounting Standards Board ("FASB") Accounting Standards Update ("ASU") 2016-02, "Leases.", as of January 1, 2019. The Company elected the transition package of practical expedients permitted within ASU 2016-02, which among other things, allowed the Company to carryforward the historical lease classification. In addition, the Company elected the comparative period practical expedient, which allowed the Company to implement the guidance as of the effective date without having to adjust the comparative financial statements. Instead, under this expedient, companies recognize the cumulative effect adjustment in equity. The Company also made 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. The adoption of the standard resulted in recognition of approximately $1.0 million in right of use assets and $1.7 million in lease liabilities for operating leases on the Company's Consolidated Balance Sheet, with no impact to its retained earnings, Consolidated Statement of Operations and Consolidated Statement of Cash Flows. The Company adopted ASU 2017-12, "Derivatives and Hedging (Topic 815), Targeted Improvements to Accounting for Hedging Activities," as of January 1, 2019. 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 adoption of the standard did not have a material impact on the Company's Consolidated Financial Statements. Accounting Standards Not Yet Adopted 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 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.

Significant Accounting Policies (Tables)

3 Months Ended

Mar. 31, 2018

Accounting Policies [Abstract]

Schedule of Cash Flow, Supplemental Disclosures

Supplemental Cash Flow Disclosure



Table 2.1: Certain Cash Transactions and Other Activity
	For the Three Months Ended,
	March 31, 2019		March 31, 2018
	(in thousands)
Cash paid for amounts included in the measurement of lease liabilities:
Operating lease cash outflows	$	152	$	148
Other activity:
Acquisition of property, plant and equipment included in liabilities	$	1,813	$	3,684

Trade Receivables, Net (Tables)

3 Months Ended

Mar. 31, 2019

Receivables [Abstract]

Detail of Receivables, Net



Table 3: Details of Trade Receivables, Net
	March 31, 2019			December 31, 2018
	(in thousands)
Trade receivables, gross	$	44,695		$	39,426
Allowance for cash discounts and doubtful accounts	(710		)	(972		)
Trade receivables, net	$	43,985		$	38,454

Trade receivables are recorded net of credit memos issued during the normal course of business.

- 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, Net (Tables)

3 Months Ended

Mar. 31, 2019

Inventory Disclosure [Abstract]

Composition of Inventories



Table 4: Details of Inventories, Net
	March 31, 2019		December 31, 2018
	(in thousands)
Finished products	$	7,760	$	6,700
Raw materials	22,297		18,388
Supplies and other	7,456		7,137
Inventories, net	$	37,513	$	32,225

Property, Plant and Equipment, Net (Tables)

3 Months Ended

Mar. 31, 2019

Property, Plant and Equipment [Abstract]

Property, Plant and Equipment Details



Table 5: Details of Property, Plant and Equipment, Net
	March 31, 2019			December 31, 2018
	(in thousands)
Land	$	13,186		$	13,185
Buildings	120,118			118,076
Plant machinery	293,313			292,219
Mobile equipment	15,468			15,163
Construction in progress	25,520			23,566
Property, plant and equipment, at cost	467,605			462,209
Accumulated depreciation	(181,904		)	(173,841		)
Property, plant and equipment, net	$	285,701		$	288,368

Customer Relationships and Other Intangibles, Net (Tables)

3 Months Ended

Mar. 31, 2019

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
	March 31, 2019							December 31, 2018
	Gross		Accumulated Amortization			Net		Gross		Accumulated Amortization			Net
	(in thousands)
Customer relationships	$	116,310	$	(67,702	)	$	48,608	$	116,180	$	(65,738	)	$	50,442
Purchased software	8,736		(5,657		)	3,079		8,225		(5,507		)	2,718
Trademarks	14,789		(5,505		)	9,284		14,772		(5,252		)	9,520
Total	$	139,835	$	(78,864	)	$	60,971	$	139,177	$	(76,497	)	$	62,680

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 March 31, 2019
	(in thousands)
April 1, 2019 through December 31, 2019	$	6,935
2020	8,662
2021	7,761
2022	6,987
2023	6,104
Thereafter	24,522
Total	$	60,971

Accrued and Other Liabilities (Tables)

3 Months Ended

Mar. 31, 2019

Payables and Accruals [Abstract]

Details of Accrued and Other Liabilities



Table 8: Details of Accrued and Other Liabilities
	March 31, 2019		December 31, 2018
	(in thousands)
Employee-related costs	$	3,497	$	10,768
Property taxes	664		82
Other taxes	477		351
Other	957		1,614
Accrued and other liabilities	$	5,595	$	12,815

Debt (Tables)

3 Months Ended

Mar. 31, 2019

Debt Disclosure [Abstract]

Details of Debt



Table 9.1: Details of Debt
	March 31, 2019			December 31, 2018
	(in thousands)
Amended and Restated Credit Agreement (1)	$	251,978		$	252,658
Industrial revenue bonds (2)	16,200			16,200
Less: Original issue discount (net of amortization)	(1,223		)	(1,285		)
Less: Debt issuance costs	(3,815		)	(4,018		)
Total debt	263,140			263,555
Less: Current portion of long-term debt	(1,720		)	(1,669		)
Long-term debt	$	261,420		$	261,886


(1)	As of March 31, 2019 and December 31, 2018, 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 2.00%.


(2)	As of March 31, 2019 and December 31, 2018, Industrial revenue bonds had a maturity date of December 1, 2025 and an interest rate of LIBOR plus 1.50% less an approximate 20 percent reduction in the rate related to the tax-free interest income to the bond holders.

Future Minimum Principal Payments Due Under the Credit Agreements



Table 9.2: Details of Future Minimum Principal Payments Due
	Amount Due
	(in thousands)
April 1, 2019 through December 31, 2019	$	2,036
2020	5,326
2021	6,196
2022	6,196
2023	245,074
Thereafter	3,350
Total Payments	$	268,178

- Definition

Tabular disclosure of long-debt instruments or arrangements, including identification, terms, features, collateral requirements and other information necessary to a fair presentation. These are debt arrangements that originally required repayment more than twelve months after issuance or greater than the normal operating cycle of the entity, if longer.

+ References

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+ Details

Derivative Instruments (Tables)

3 Months Ended

Mar. 31, 2019

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
	March 31, 2019		December 31, 2018
	(in thousands)
Assets
Interest rate swap	$	—	$	86
Commodity hedges	101		61
Total assets	$	101	$	147
Liabilities
Interest rate swap	$	223	$	—
Commodity hedges	27		105
Total liabilities	$	250	$	105

Derivative Instruments, Gain (Loss)



Table 10.2: Gains/(losses) on Derivatives
	For the Three Months Ended
	March 31, 2019			March 31, 2018		March 31, 2019			March 31, 2018
	Gain/(loss) recognized in AOCI on derivatives (effective portion), net of tax					Gain/(loss) reclassified from AOCI into income (effective portion), net of tax
	(in thousands)
Interest rate swap	$	(161	)	$	831	$	303		$	70
Commodity hedges	41			241		(45		)	(97		)
Total	$	(120	)	$	1,072	$	258		$	(27	)

Leases (Tables)

3 Months Ended

Mar. 31, 2019

Leases [Abstract]

Components of Lease Expense



Table 11.1: Components of lease expense
	For the Three Months Ended,
	March 31, 2019		March 31, 2018
	(in thousands)
Operating lease cost	$	101	$	99
Short term lease cost	511		735
Total lease cost	$	612	$	834

Maturities of Lease Liabilities



Table 11.2: Maturities of lease liabilities
	Operating leases
	(in thousands)
April 1, 2019 through December 31, 2019	$	468
2020	637
2021	600
2022	—
2023	—
Total lease payments	$	1,705
Less imputed interest	(102		)
Present value of lease liabilities	$	1,603

Details of Lease Term and Discount Rate



Table 11.3: Details of lease term and discount rate
	As of March 31, 2019
Weighted-average remaining lease term
Operating leases	3 years
Weighted-average discount rate
Operating leases	4.52	%

Treasury Stock (Tables)

3 Months Ended

Mar. 31, 2019

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 12: Details of Treasury Stock Activity
	March 31, 2019					March 31, 2018
	Shares	Amount (1)		Average Share Price (1)		Shares	Amount (1)		Average Share Price (1)
	(in thousands, except share data)
Beginning Balance	9,070,346	$	209,050	$	23.05	6,788,817	$	143,357	$	21.12
Repurchases on open market	191,907	5,005		26.08		530,600	14,550		27.42
Ending Balance	9,262,253	$	214,055	$	23.11	7,319,417	$	157,907	$	21.57
(1) Includes commissions paid for repurchases on open market.

Accumulated Other Comprehensive Loss (Tables)

3 Months Ended

Mar. 31, 2019

Equity [Abstract]

Changes in Accumulated Other Comprehensive (Loss)/Income by Category



Table 14: 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, 2018	$	(5,027	)	$	1,636		$	(3,391	)
Other comprehensive income/(loss) before reclassifications	324			(120		)	204
Amounts reclassified from accumulated other comprehensive loss	—			(258		)	(258		)
Net current period other comprehensive income/(loss)	324			(378		)	(54		)
Balance as of March 31, 2019	$	(4,703	)	$	1,258		$	(3,445	)

Earnings Per Share (Tables)

3 Months Ended

Mar. 31, 2019

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. For the three months ended March 31, 2019 and 2018 respectively, approximately 82,253 and 62,949 share-based compensation awards were excluded from the weighted average shares outstanding because their impact would be anti-dilutive in the computation of dilutive earnings per share



Table 16: Details of Basic and Dilutive Earnings Per Share
	For the Three Months Ended
	March 31, 2019		March 31, 2018
	(dollars in thousands, except for per share amounts)
Net income	$	15,926	$	13,646

Weighted average number of shares outstanding - basic	35,248,280		37,432,782
Effect of dilutive securities:
Restricted stock awards	—		3,509
Restricted stock units	55,515		72,012
Performance restricted stock units	29,775		69,509
Stock options	16,689		27,141
Total effect of dilutive securities	101,979		172,171
Weighted average number of shares outstanding - diluted	35,350,259		37,604,953

Basic earnings per share	$	0.45	$	0.36
Diluted earnings per share	$	0.45	$	0.36

Commitments and Contingencies (Tables)

3 Months Ended

Mar. 31, 2019

Commitments and Contingencies Disclosure [Abstract]

Future Purchase Commitments by Year



Table 17: Details of Purchase Commitments
	As of March 31, 2019
	(in thousands)
April 1, 2019 through December 31, 2019	$	26,734
2020	36,073
2021	35,363
2022	26,832
2023	11,054
Thereafter	48,144
Total	$	184,200

Segment Reporting (Tables)

3 Months Ended

Mar. 31, 2019

Segment Reporting [Abstract]

Segment Reporting



Table 18.1: Segment Reporting
	For the Three Months Ended
	March 31, 2019			March 31, 2018
	(in thousands)
Net Sales:
Wallboard	$	118,944		$	112,971
Other	3,088			3,831
Total net sales	$	122,032		$	116,802
Operating Income:
Wallboard	$	23,595		$	21,030
Other	(489		)	(268		)
Total operating income	$	23,106		$	20,762
Adjustments:
Interest expense	$	(2,492	)	$	(2,720	)
Losses from equity investment	(45		)	(364		)
Other expense, net	(36		)	(140		)
Income before provision for income taxes	$	20,533		$	17,538
Depreciation and Amortization:
Wallboard	$	10,276		$	10,305
Other	244			276
Total depreciation and amortization	$	10,520		$	10,581

Net Sales By Geographic Region



Table 18.2: Details of Net Sales By Geographic Region
	For the Three Months Ended
	March 31, 2019		March 31, 2018
	(in thousands)
United States	$	116,712	$	109,975
Canada	5,320		6,827
Net sales	$	122,032	$	116,802

Assets By Geographic Region



Table 18.3: Details of Assets By Geographic Region
	Fixed Assets				Total Assets
	March 31, 2019		December 31, 2018		March 31, 2019		December 31, 2018
	(in thousands)
United States	$	282,541	$	285,202	$	646,228	$	655,849
Canada	3,160		3,166		17,234		16,532
Total	$	285,701	$	288,368	$	663,462	$	672,381

Fair Value Disclosures (Tables)

3 Months Ended

Mar. 31, 2019

Fair Value Disclosures [Abstract]

Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis



Table 19.1: Fair Value Hierarchy - 2019
	As of March 31, 2019
	Level 1		Level 2		Level 3		Balance
	(in thousands)
Asset
Interest rate swap	$	—	$	—	$	—	$	—
Commodity derivatives	—		101		—		101
Total assets	$	—	$	101	$	—	$	101

Liabilities
Interest rate swap	$	—	$	223	$	—	$	223
Commodity derivatives	—		27		—		27
Total liabilities	$	—	$	250	$	—	$	250



Table 19.2: Fair Value Hierarchy - 2018
	As of December 31, 2018
	Level 1		Level 2		Level 3		Balance
	(in thousands)
Asset
Interest rate swap	$	—	$	86	$	—	$	86
Commodity derivatives	—		61		—		61
Total assets	$	—	$	147	$	—	$	147

Liabilities
Interest rate swap	$	—	$	—	$	—	$	—
Commodity derivatives	—		105		—		105
Total liabilities	$	—	$	105	$	—	$	105

Buchanan Plant Outage (Tables)

3 Months Ended

Mar. 31, 2019

Commitments and Contingencies Disclosure [Abstract]

Schedule of Buchanan Plant Outage



Details of Insurance Claims and Cash Payments Related to Buchanan Outage
	Claim Details						Cash Details
	Claim Amount		Insurance Deductible		Net recovery recorded in first quarter 2019		Cash received in first quarter 2019		Receivable Recorded as of March 31, 2019
	(in thousands)
Rebuild of property, plant and equipment damaged (a)	$	1,839	$	250	$	1,589	$	1,589	$	—
Directs costs associated with business interruption (b)	2,932		—		2,932		2,661		271
	$	4,771	$	250	$	4,521	$	4,250	$	271


(a)	The rebuild of property, plant and equipment damaged and related net recovery resulted in a net gain of $1.5 million.

(b)

Direct costs associated with the business interruption include various expenses such as additional freight to ship to customers at greater distances from other plants, additional freight costs to reroute incoming raw materials and other various costs that were incurred as a result of the Buchanan outage and are expected to be covered by the Company's insurance policy. The net recovery of direct costs associated with business interruption were netted against actual costs incurred resulting in a net impact of zero to the income statement.



Details of Gain from insurance recoveries, net
	For the Three Months Ended
	March 31, 2019
	(in thousands)
Cost to rebuild property, plant and equipment (capitalized)	$	1,839
Insurance deductible	250
Net recoveries from insurance policy	1,589
Write-off of property, plant and equipment	76
Gain from insurance recoveries, net	$	1,513

- Definition

Tabular disclosure of the loss contingencies that were reported in the period or disclosed as of the balance sheet date.

+ References

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+ Details

Background and Nature of Operations - Description of Business and Acquisition (Detail)	Mar. 31, 2019 facility
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 Policies - Additional Information (Detail) - USD ($) $ in Thousands	Mar. 31, 2019	Jan. 01, 2019
Property, Plant and Equipment [Line Items]
Operating lease - right of use assets	$ 918
Present value of lease liabilities	$ 1,603
Accounting Standards Update 2016-02
Property, Plant and Equipment [Line Items]
Operating lease - right of use assets		$ 1,000
Present value of lease liabilities		$ 1,700

Significant Accounting Policies - Certain Cash and Non-Cash Transactions (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Accounting Policies [Abstract]
Operating lease cash outflows	$ 152	$ 148
Acquisition of property, plant and equipment included in liabilities	$ 1,813	$ 3,684

Trade Receivables, Net - Detail of Receivables, Net (Detail) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Receivables [Abstract]
Trade receivables, gross	$ 44,695	$ 39,426
Allowance for cash discounts and doubtful accounts	(710)	(972)
Trade receivables, net	$ 43,985	$ 38,454

Inventories, Net (Detail) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Inventory Disclosure [Abstract]
Finished products	$ 7,760	$ 6,700
Raw materials	22,297	18,388
Supplies and other	7,456	7,137
Inventories, net	$ 37,513	$ 32,225

Property, Plant and Equipment, Net - Property, Plant and Equipment Details (Detail) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Property, Plant and Equipment [Line Items]
Property, plant and equipment, at cost	$ 467,605	$ 462,209
Accumulated depreciation	(181,904)	(173,841)
Property, plant and equipment, net	285,701	288,368
Land
Property, Plant and Equipment [Line Items]
Property, plant and equipment, at cost	13,186	13,185
Buildings
Property, Plant and Equipment [Line Items]
Property, plant and equipment, at cost	120,118	118,076
Plant machinery
Property, Plant and Equipment [Line Items]
Property, plant and equipment, at cost	293,313	292,219
Mobile equipment
Property, Plant and Equipment [Line Items]
Property, plant and equipment, at cost	15,468	15,163
Construction in progress
Property, Plant and Equipment [Line Items]
Property, plant and equipment, at cost	$ 25,520	$ 23,566

Property, Plant and Equipment, Net - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Property, Plant and Equipment [Abstract]
Depreciation expense	$ 8.2	$ 8.1

Investment in Seven Hills - Additional Information (Detail) - Seven Hills - Variable Interest Entity, Not Primary Beneficiary - Equity Method Investee - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Schedule of Equity Method Investments [Line Items]
Cost of paperboard	$ 13.5	$ 12.2
Purchase commitments	$ 35.5

Customer Relationships and Other Intangibles, Net - Details of Customer Relationships and Other Intangibles, Net (Detail) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Finite-Lived Intangible Assets [Line Items]
Gross	$ 139,835	$ 139,177
Accumulated Amortization	(78,864)	(76,497)
Net	60,971	62,680
Customer relationships
Finite-Lived Intangible Assets [Line Items]
Gross	116,310	116,180
Accumulated Amortization	(67,702)	(65,738)
Net	48,608	50,442
Purchased software
Finite-Lived Intangible Assets [Line Items]
Gross	8,736	8,225
Accumulated Amortization	(5,657)	(5,507)
Net	3,079	2,718
Trademarks
Finite-Lived Intangible Assets [Line Items]
Gross	14,789	14,772
Accumulated Amortization	(5,505)	(5,252)
Net	$ 9,284	$ 9,520

Customer Relationships and Other Intangibles, Net - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Goodwill and Intangible Assets Disclosure [Abstract]
Amortization expense	$ 2.3	$ 2.5

Customer Relationships and Other Intangibles, Net - Future Amortization Expense of Customer Relationships and Other Intangibles (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Finite-Lived Intangible Assets, Net, Amortization Expense, Fiscal Year Maturity [Abstract]
April 1, 2019 through December 31, 2019	$ 6,935
2020	8,662
2021	7,761
2022	6,987
2023	6,104
Thereafter	24,522
Net	$ 60,971	$ 62,680

Accrued and Other Liabilities (Detail) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Payables and Accruals [Abstract]
Employee-related costs	$ 3,497	$ 10,768
Property taxes	664	82
Other taxes	477	351
Other	957	1,614
Accrued and other liabilities	$ 5,595	$ 12,815

Debt - Details of Debt (Detail) - USD ($) $ in Thousands					3 Months Ended
Debt - Details of Debt (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 06, 2017	Feb. 21, 2017	Aug. 18, 2016	Mar. 31, 2019
Debt Instrument [Line Items]
Total debt, gross					$ 268,178
Less: Original issue discount (net of amortization)	$ (1,285)				(1,223)
Less: Debt issuance costs	(4,018)				(3,815)
Total debt	263,555				263,140
Less: Current portion of long-term debt	(1,669)				(1,720)
Long-term debt	261,886				261,420
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]
Total debt, gross	$ 252,658				$ 251,978
Term Loan Facility \| Amended and Restated Credit Agreement \| London Interbank Offered Rate (LIBOR)
Debt Instrument [Line Items]
Floor rate				0.75%	0.75%
Debt, variable interest rate (as a percent)	2.00%			2.75%	2.00%
Industrial Revenue Bonds \| Line of Credit \| Industrial revenue bonds
Debt Instrument [Line Items]
Total debt, gross	$ 16,200				$ 16,200
Industrial Revenue Bonds \| Line of Credit \| Industrial revenue bonds \| London Interbank Offered Rate (LIBOR)
Debt Instrument [Line Items]
Debt, variable interest rate (as a percent)					1.50%
Reduction in reate related to the tax-free interest income					20.00%

Debt - Additional Information (Detail)					3 Months Ended
Debt - Additional Information (Detail)	Dec. 31, 2018 USD ($)	Dec. 06, 2017	Feb. 21, 2017	Aug. 18, 2016 USD ($)	Mar. 31, 2019 USD ($) covenant	Dec. 31, 2018 USD ($)
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				1.1
Number of covenants \| covenant					1
Debt covenant trigger, line of credit facility amount less letters of credit threshold					$ 22,500,000.0
Amended and Restated Credit Agreement \| Maximum
Debt Instrument [Line Items]
Leverage ratio (no greater than)					5.0
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 \| Amended and Restated Credit Agreement
Debt Instrument [Line Items]
Debt principal amount				$ 275,000,000
Schedule principal payments					$ 700,000
Effective interest rate					5.00%
Term Loan Facility \| Amended and Restated Credit Agreement \| London Interbank Offered Rate (LIBOR)
Debt Instrument [Line Items]
Debt, variable interest rate (as a percent)	2.00%			2.75%	2.00%
Floor rate				0.75%	0.75%
Line of Credit \| Amended and Restated 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	$ 0
Facility fee, basis points					0.50%
Remaining outstanding					$ 73,600,000
Line of Credit \| Industrial revenue bonds \| Industrial Revenue Bonds
Debt Instrument [Line Items]
Line of credit facility borrowing capacity	$ 28,000,000					$ 28,000,000
Line of Credit \| Industrial revenue bonds \| Industrial Revenue Bonds \| London Interbank Offered Rate (LIBOR)
Debt Instrument [Line Items]
Debt, variable interest rate (as a percent)					1.50%
Reduction in reate related to the tax-free interest income					20.00%

Debt - Future Minimum Principal Payments Due Under the Credit Agreements (Detail) $ in Thousands	Mar. 31, 2019 USD ($)
Long-term Debt, Fiscal Year Maturity [Abstract]
April 1, 2019 through December 31, 2019	$ 2,036
2020	5,326
2021	6,196
2022	6,196
2023	245,074
Thereafter	3,350
Total Payments	$ 268,178

Derivative Instruments - Additional Information (Detail) MMBTU in Millions		1 Months Ended	3 Months Ended
	Mar. 29, 2018 USD ($)	Sep. 30, 2016 USD ($)	Mar. 31, 2019 USD ($) MMBTU
Derivative [Line Items]
Derivatives, net liability position			$ (149,000)
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			2.4
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%
Proceeds from derivative hedges	$ 3,200,000
Unrealized gain amortized into interest expense			$ 200,000
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 - Derivatives at Fair Value (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Derivative [Line Items]
Derivative asset	$ 101	$ 147
Derivative liability	250	105
Interest rate swap
Derivative [Line Items]
Derivative asset	0	86
Derivative liability	223	0
Commodity derivatives
Derivative [Line Items]
Derivative asset	101	61
Derivative liability	$ 27	$ 105

Derivative Instruments - Gains (losses) on derivatives (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Derivative Instruments, Gain (Loss) [Line Items]
Gain/(loss) recognized in AOCI on derivatives (effective portion), net of tax	$ (120)	$ 1,072
Gain/(loss) reclassified from AOCI into income (effective portion), net of tax	258	(27)
Interest rate swap
Derivative Instruments, Gain (Loss) [Line Items]
Gain/(loss) recognized in AOCI on derivatives (effective portion), net of tax	(161)	831
Gain/(loss) reclassified from AOCI into income (effective portion), net of tax	303	70
Commodity derivatives
Derivative Instruments, Gain (Loss) [Line Items]
Gain/(loss) recognized in AOCI on derivatives (effective portion), net of tax	41	241
Gain/(loss) reclassified from AOCI into income (effective portion), net of tax	$ (45)	$ (97)

Leases - Components of Lease Expense (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Leases [Abstract]
Operating lease cost	$ 101	$ 99
Short term lease cost	511	735
Total lease cost	$ 612	$ 834

Leases - Maturities of Lease Liabilities (Details) $ in Thousands	Mar. 31, 2019 USD ($)
Leases [Abstract]
April 1, 2019 through December 31, 2019	$ 468
2020	637
2021	600
Total lease payments	1,705
Less imputed interest	(102)
Present value of lease liabilities	$ 1,603

Leases - Details of Lease Term and Discount Rate (Details)	Mar. 31, 2019
Leases [Abstract]
Weighted-average remaining lease term, operating leases	3 years
Weighted-average discount rate, operating leases	4.52%

Treasury Stock - Additional Information (Detail) - USD ($)	Mar. 31, 2019	Feb. 21, 2018	Nov. 04, 2015
Equity [Abstract]
Stock repurchase program authorized amount (up to)		$ 300,000,000	$ 50,000,000
Stock repurchase program, remaining authorized amount	$ 126,000,000

Treasury Stock - Treasury Stock Activity (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018	Dec. 31, 2017
Treasury Stock [Roll Forward]
Beginning balance (shares)	9,070,346	6,788,817	6,788,817
Ending balance (shares)	9,262,253	7,319,417	9,070,346	6,788,817
Beginning balance	$ 209,050	$ 143,357	$ 143,357
Shares repurchased	5,005	14,550
Ending balance	$ 214,055	$ 157,907	$ 209,050	$ 143,357
Average share price (usd per share)	$ 23.11	$ 21.57	$ 23.05	$ 21.12
Repurchases on open market
Treasury Stock [Roll Forward]
Shares repurchased (shares)	191,907	530,600
Shares repurchased	$ 5,005	$ 14,550
Average share price (usd per share)	$ 26.08	$ 27.42

Share-Based Compensation - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Millions			3 Months Ended
	Feb. 20, 2019	Feb. 19, 2019	Mar. 31, 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation expense			$ 0.6
Unrecognized compensation expense			$ 6.9
Unrecognized compensation expense, weighted average remaining period			2 years 7 months 30 days
Restricted stock units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Awards granted (in shares)		63,772
Grant date fair value of awards granted (in shares)	$ 27.24	$ 27.32
Vesting period		4 years
Performance restricted stock units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Awards granted (in shares)	23,936	30,172
Grant date fair value of awards granted (in shares)	$ 27.24	$ 27.32
Performance restricted stock units \| Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage vesting			0.00%
Performance restricted stock units \| Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage vesting			240.00%
Employees \| Restricted stock units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Awards granted (in shares)	23,936
Vesting period	4 years
Board of Directors \| Restricted stock units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Awards granted (in shares)	17,100
Vesting period	1 year

Accumulated Other Comprehensive Loss (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2019 USD ($)
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning Balance	$ 327,747
Other comprehensive income/(loss) before reclassifications	204
Amounts reclassified from accumulated other comprehensive loss	(258)
Net current period other comprehensive income/(loss)	(54)
Ending Balance	338,767
Foreign currency translation adjustment
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning Balance	(5,027)
Other comprehensive income/(loss) before reclassifications	324
Amounts reclassified from accumulated other comprehensive loss	0
Net current period other comprehensive income/(loss)	324
Ending Balance	(4,703)
Net unrealized gain on derivatives, net of tax
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning Balance	1,636
Other comprehensive income/(loss) before reclassifications	(120)
Amounts reclassified from accumulated other comprehensive loss	(258)
Net current period other comprehensive income/(loss)	(378)
Ending Balance	1,258
Accumulated Other Comprehensive Loss
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning Balance	(3,391)
Ending Balance	$ (3,445)

Income Taxes - Narrative (Detail)	12 Months Ended
Income Taxes - Narrative (Detail)	Dec. 31, 2019
Scenario, Forecast
Income Tax Contingency [Line Items]
Effective tax rate	22.47%

Earnings Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Anti-dilutive securities (in shares)	82,253	62,949
Net income	$ 15,926	$ 13,646
Weighted average number of shares outstanding- basic (shares)	35,248,280	37,432,782
Effect of dilutive securities:
Total effect of dilutive securities (shares)	101,979	172,171
Weighted average number of shares outstanding - diluted (shares)	35,350,259	37,604,953
Basic earnings per share (usd per share)	$ 0.45	$ 0.36
Diluted earnings per share (usd per share)	$ 0.45	$ 0.36
Restricted stock awards
Effect of dilutive securities:
Effect of dilutive securities (shares)	0	3,509
Restricted stock units
Effect of dilutive securities:
Effect of dilutive securities (shares)	55,515	72,012
Performance restricted stock units
Effect of dilutive securities:
Effect of dilutive securities (shares)	29,775	69,509
Stock options
Effect of dilutive securities:
Effect of dilutive securities (shares)	16,689	27,141

Commitments and Contingencies - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018
Letter of Credit
Long-term Purchase Commitment [Line Items]
Outstanding amount of letters of credit	$ 1.4		$ 1.4
Gas, Gypsum, Paper, and Other Raw Materials
Long-term Purchase Commitment [Line Items]
Non capital purchased under commitments	$ 20.4	$ 22.4

Commitments and Contingencies - Future Minimum Lease Payments Due Under Non-Cancelable Operating Leases and Purchase Commitments by Year (Detail) $ in Thousands	Mar. 31, 2019 USD ($)
As of March 31, 2019
April 1, 2019 through December 31, 2019	$ 26,734
2020	36,073
2021	35,363
2022	26,832
2023	11,054
Thereafter	48,144
Total	$ 184,200

Segment Reporting - Additional Information (Detail) - geographic_area	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Segment Reporting Information [Line Items]
Number of geographical areas (geographic area)	2
Wallboard \| Sales Revenue, Net \| Product Concentration Risk
Segment Reporting Information [Line Items]
Percentage of revenues	97.50%	96.70%

Segment Reporting - Segment Reporting (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Net Sales:
Net Sales	$ 122,032	$ 116,802
Operating Income:
Operating income	23,106	20,762
Adjustments:
Interest expense	(2,492)	(2,720)
Losses from equity investment	(45)	(364)
Other expense, net	(36)	(140)
Income before provision for income taxes	20,533	17,538
Depreciation and Amortization
Total depreciation and amortization	10,520	10,581
Operating Segments \| Wallboard
Net Sales:
Net Sales	118,944	112,971
Operating Income:
Operating income	23,595	21,030
Depreciation and Amortization
Total depreciation and amortization	10,276	10,305
Operating Segments \| Other
Net Sales:
Net Sales	3,088	3,831
Operating Income:
Operating income	(489)	(268)
Depreciation and Amortization
Total depreciation and amortization	244	276
Adjustments
Adjustments:
Interest expense	(2,492)	(2,720)
Losses from equity investment	(45)	(364)
Other expense, net	$ (36)	$ (140)

Segment Reporting - Net Sales by Geographic Region (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Revenues from External Customers and Long-Lived Assets [Line Items]
Net sales	$ 122,032	$ 116,802
United States
Revenues from External Customers and Long-Lived Assets [Line Items]
Net sales	116,712	109,975
Canada
Revenues from External Customers and Long-Lived Assets [Line Items]
Net sales	$ 5,320	$ 6,827

Segment Reporting - Assets by Geographic Region (Detail) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Revenues from External Customers and Long-Lived Assets [Line Items]
Fixed Assets	$ 285,701	$ 288,368
Total Assets	663,462	672,381
United States
Revenues from External Customers and Long-Lived Assets [Line Items]
Fixed Assets	282,541	285,202
Total Assets	646,228	655,849
Canada
Revenues from External Customers and Long-Lived Assets [Line Items]
Fixed Assets	3,160	3,166
Total Assets	$ 17,234	$ 16,532

Fair Value Disclosures (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative asset	$ 101	$ 147
Derivative liability	250	105
Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative asset	101	147
Derivative liability	250	105
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	101	147
Derivative liability	250	105
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	0	86
Derivative liability	223	0
Interest rate swap \| Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative asset	0	86
Derivative liability	223	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	0	86
Derivative liability	223	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	101	61
Derivative liability	27	105
Commodity derivatives \| Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative asset	101	61
Derivative liability	27	105
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	101	61
Derivative liability	27	105
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

Buchanan Plant Outage - Details of Insurance Claims and Cash Payments Related to Buchanan Outage (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Loss Contingencies [Line Items]
Gain from insurance recoveries, net	$ 1,513	$ 0
Rebuild of property, plant and equipment damaged
Loss Contingencies [Line Items]
Claim Amount	1,839
Insurance Deductible	250
Net recovery recorded in first quarter 2019	1,589
Cash received in first quarter 2019	1,589
Receivable Recorded as of March 31, 2019	0
Gain from insurance recoveries, net	1,513
Directs costs associated with business interruption
Loss Contingencies [Line Items]
Claim Amount	2,932
Insurance Deductible	0
Net recovery recorded in first quarter 2019	2,932
Cash received in first quarter 2019	2,661
Receivable Recorded as of March 31, 2019	271
Total
Loss Contingencies [Line Items]
Claim Amount	4,771
Insurance Deductible	250
Net recovery recorded in first quarter 2019	4,521
Cash received in first quarter 2019	4,250
Receivable Recorded as of March 31, 2019	$ 271

Buchanan Plant Outage - Details of Gain from Insurance Recoveries, Net (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Loss Contingencies [Line Items]
Gain from insurance recoveries, net	$ 1,513	$ 0
Rebuild of property, plant and equipment damaged
Loss Contingencies [Line Items]
Loss Contingency, Loss in Period	1,839
Loss Contingency, Insurance Deductible	250
Net recoveries from insurance policy	1,589
Write-off of property, plant and equipment	76
Gain from insurance recoveries, net	$ 1,513