Segment Reporting - Segment Reporting (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Net Sales:
Net Sales	$ 131,392	$ 116,526	$ 120,630	$ 120,615	$ 118,217	$ 114,558	$ 117,115	$ 111,485	$ 489,163	$ 461,375	$ 421,682
Operating income:
Operating income	26,571	19,707	21,620	21,687	22,801	18,561	23,208	22,570	89,585	87,140	44,005
Adjustments:
Interest expense	(2,822)	(2,988)	(3,062)	(2,916)	(3,098)	(3,146)	(3,648)	(3,698)	(11,788)	(13,590)	(16,432)
Losses from equity investment	(158)	(204)	345	(170)	(10)	(291)	(240)	(195)	(187)	(736)	(750)
Other expense, net	(563)	146	(135)	(644)	(223)	(5,900)	6	154	(1,196)	(5,963)	(751)
Income before provision for income taxes	$ 23,028	$ 16,661	$ 18,768	$ 17,957	$ 19,470	$ 9,224	$ 19,326	$ 18,831	76,414	66,851	26,072
Depreciation and Amortization
Total depreciation and amortization									46,460	46,646	51,308
Operating Segments | Wallboard
Net Sales:
Net Sales									474,189	447,679	407,982
Operating income:
Operating income									90,220	87,094	44,276
Depreciation and Amortization
Total depreciation and amortization									45,368	45,561	50,150
Operating Segments | Other
Net Sales:
Net Sales									14,974	13,696	13,700
Operating income:
Operating income									(635)	46	(271)
Depreciation and Amortization
Total depreciation and amortization									1,092	1,085	1,158
Adjustments
Adjustments:
Interest expense									(11,788)	(13,590)	(16,432)
Losses from equity investment									(187)	(736)	(750)
Other expense, net									$ (1,196)	$ (5,963)	$ (751)