Segment Reporting - Segment Reporting (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Net Sales:
Net Sales	$ 117,115	$ 110,996	$ 228,600	$ 203,172
Operating income:
Operating income	23,208	4,275	45,778	12,177
Adjustments:
Interest Expense	(3,648)	(4,184)	(7,346)	(8,405)
Loss from equity investment	(240)	(311)	(435)	(252)
Other income/(expense), net	6	31	160	(417)
Income/(loss) before (provision for)/benefit from income taxes	19,326	(189)	38,157	3,103
Depreciation and Amortization
Total depreciation and amortization	11,842	13,141	23,788	26,270
Operating Segments | Wallboard
Net Sales:
Net Sales	113,593	107,569	221,192	196,312
Operating income:
Operating income	23,216	4,418	45,620	12,196
Depreciation and Amortization
Total depreciation and amortization	11,566	12,847	23,240	25,682
Operating Segments | Other
Net Sales:
Net Sales	3,522	3,427	7,408	6,860
Operating income:
Operating income	(8)	(143)	158	(19)
Depreciation and Amortization
Total depreciation and amortization	276	294	548	588
Adjustments
Adjustments:
Interest Expense	(3,648)	(4,184)	(7,346)	(8,405)
Loss from equity investment	(240)	(311)	(435)	(252)
Other income/(expense), net	$ 6	$ 31	$ 160	$ (417)