Business Segment Information - Intra-Segment and Inter-Segment Revenues (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
Environmental Segment [Member]
Segment Reporting Information [Line Items]
Net sales									153,344	158,371	127,707
Energy Segment [Member]
Segment Reporting Information [Line Items]
Net sales									203,376	142,150	70,285
Fluid Handling and Filtration Segment [Member]
Segment Reporting Information [Line Items]
Net sales									61,783	67,610	65,638
Corporate and Other [Member]
Segment Reporting Information [Line Items]
Net sales									(1,492)	(709)	(413)
Intra - Segment Sales [Member]
Segment Reporting Information [Line Items]
Net sales									(9,476)	(13,897)	(14,898)
Intra - Segment Sales [Member] | Environmental Segment [Member]
Segment Reporting Information [Line Items]
Net sales									(4,256)	(6,744)	(7,089)
Intra - Segment Sales [Member] | Energy Segment [Member]
Segment Reporting Information [Line Items]
Net sales									(3,506)	(4,876)	(5,964)
Intra - Segment Sales [Member] | Fluid Handling and Filtration Segment [Member]
Segment Reporting Information [Line Items]
Net sales									(1,714)	(2,277)	(1,845)
Operating Segments [Member]
Segment Reporting Information [Line Items]
Net sales									432,566	384,992	280,404
Operating Segments [Member] | Environmental Segment [Member]
Segment Reporting Information [Line Items]
Net sales									160,959	167,247	136,544
Operating Segments [Member] | Energy Segment [Member]
Segment Reporting Information [Line Items]
Net sales									207,280	147,661	76,302
Operating Segments [Member] | Fluid Handling and Filtration Segment [Member]
Segment Reporting Information [Line Items]
Net sales									64,327	70,084	67,558
Inter-segment Elimination [Member] | Environmental Inter-Segment Sales [Member]
Segment Reporting Information [Line Items]
Net sales									(715)	(832)	(128)
Inter-segment Elimination [Member] | Energy Inter-Segment Sales [Member]
Segment Reporting Information [Line Items]
Net sales									(3,666)	(1,937)	(1,403)
Inter-segment Elimination [Member] | Fluid Handling Filtration Inter-Segment Sales [Member]
Segment Reporting Information [Line Items]
Net sales									(206)	(195)	(345)
Inter-segment Elimination [Member] | Corporate And Other Inter-Segment Sales [Member]
Segment Reporting Information [Line Items]
Net sales									(1,492)	(709)	(413)
Inter-segment Elimination [Member] | Environmental Segment [Member] | Environmental Inter-Segment Sales [Member]
Segment Reporting Information [Line Items]
Net sales										0	0
Inter-segment Elimination [Member] | Environmental Segment [Member] | Energy Inter-Segment Sales [Member]
Segment Reporting Information [Line Items]
Net sales									(3,153)	(1,937)	(1,403)
Inter-segment Elimination [Member] | Environmental Segment [Member] | Fluid Handling Filtration Inter-Segment Sales [Member]
Segment Reporting Information [Line Items]
Net sales									(206)	(195)	(345)
Inter-segment Elimination [Member] | Energy Segment [Member] | Environmental Inter-Segment Sales [Member]
Segment Reporting Information [Line Items]
Net sales									(398)	(635)	(53)
Inter-segment Elimination [Member] | Fluid Handling and Filtration Segment [Member] | Environmental Inter-Segment Sales [Member]
Segment Reporting Information [Line Items]
Net sales									(317)	(197)	(75)
Inter-segment Elimination [Member] | Fluid Handling and Filtration Segment [Member] | Energy Inter-Segment Sales [Member]
Segment Reporting Information [Line Items]
Net sales									(513)
Inter-segment Elimination [Member] | Corporate and Other [Member] | Corporate And Other Inter-Segment Sales [Member]
Segment Reporting Information [Line Items]
Net sales									$ (1,492)	$ (709)	$ (413)