Quarterly Financial Information (Unaudited) - Narrative (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, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Business Acquisition [Line Items]
Gross profit	$ 39,405	$ 39,980	$ 43,253	$ 40,424	$ 31,982	$ 38,193	$ 35,990	$ 32,377									$ 163,062	$ 138,542	$ 122,497
Net income/(loss)	13,848	10,675	13,125	11,669	4,420	12,785	10,813	9,169									$ 49,317	$ 37,187	$ 46,259
Restatement Adjustment
Business Acquisition [Line Items]
Net income/(loss)	$ (800)	$ (100)	$ (100)	$ (100)	(100)	(100)	(100)	$ (100)	$ (100)	$ (100)	$ (100)	$ (100)	$ (100)	$ (100)	$ (100)	$ (100)
Thermal/Acoustical Metals Segment | Restatement Adjustment
Business Acquisition [Line Items]
Gross profit					(900)	(400)	(500)
Net income/(loss)					$ (600)	$ (300)	$ (300)