Business Segment Information - Net Sales and Income from Operation by Business Segment (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	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, 2016	Dec. 31, 2015	Dec. 31, 2014
Segment Reporting Information [Line Items]
Net sales	$ 99,982	$ 101,596	$ 112,258	$ 103,175	$ 101,246	$ 98,230	$ 86,961	$ 80,985	$ 417,011	$ 367,422	$ 263,217
(Loss) income from operations									(25,562)	4,949	21,663
Environmental Segment [Member]
Segment Reporting Information [Line Items]
Net sales									153,344	158,371	127,707
(Loss) income from operations									15,652	17,021	16,803
Energy Segment [Member]
Segment Reporting Information [Line Items]
Net sales									203,376	142,150	70,285
(Loss) income from operations									23,575	3,488	7,799
Fluid Handling and Filtration Segment [Member]
Segment Reporting Information [Line Items]
Net sales									61,783	67,610	65,638
(Loss) income from operations									(36,209)	11,741	13,188
Corporate and Other [Member]
Segment Reporting Information [Line Items]
Net sales									(1,492)	(709)	(413)
(Loss) income from operations									(26,981)	(26,592)	(14,297)
Inter-segment Elimination [Member]
Segment Reporting Information [Line Items]
(Loss) income from operations									$ (1,599)	$ (709)	$ (1,830)