Business Segment Information - Intra-Segment and Inter-Segment Revenues (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Segment Reporting Information [Line Items]
Net sales	$ 112,258	$ 86,961	$ 215,433	$ 167,946
Intra - Segment Sales [Member]
Segment Reporting Information [Line Items]
Net sales	(1,950)	(3,735)	(4,598)	(6,689)
Environmental Segment [Member]
Segment Reporting Information [Line Items]
Net sales	44,211	41,798	83,333	83,514
Environmental Segment [Member] | Intra - Segment Sales [Member]
Segment Reporting Information [Line Items]
Net sales	(844)	(1,476)	(2,598)	(3,283)
Energy Segment [Member]
Segment Reporting Information [Line Items]
Net sales	52,867	27,303	100,799	51,652
Energy Segment [Member] | Intra - Segment Sales [Member]
Segment Reporting Information [Line Items]
Net sales	(654)	(1,560)	(1,145)	(2,255)
Fluid Handling and Filtration Segment [Member]
Segment Reporting Information [Line Items]
Net sales	15,413	17,745	32,008	32,939
Fluid Handling and Filtration Segment [Member] | Intra - Segment Sales [Member]
Segment Reporting Information [Line Items]
Net sales	(452)	(699)	(855)	(1,151)
Corporate and Other [Member]
Segment Reporting Information [Line Items]
Net sales	(233)	115	(707)	(159)
Operating Segments [Member]
Segment Reporting Information [Line Items]
Net sales	115,307	91,737	222,953	176,109
Operating Segments [Member] | Environmental Segment [Member]
Segment Reporting Information [Line Items]
Net sales	45,522	43,833	87,575	87,390
Operating Segments [Member] | Energy Segment [Member]
Segment Reporting Information [Line Items]
Net sales	53,740	29,445	102,321	54,526
Operating Segments [Member] | Fluid Handling and Filtration Segment [Member]
Segment Reporting Information [Line Items]
Net sales	16,045	18,459	33,057	34,193
Inter-segment Elimination [Member] | Environmental Inter-Segment Sales [Member]
Segment Reporting Information [Line Items]
Net sales	(399)	(597)	(571)	(722)
Inter-segment Elimination [Member] | Energy Inter-Segment Sales [Member]
Segment Reporting Information [Line Items]
Net sales	(427)	(559)	(1,467)	(593)
Inter-segment Elimination [Member] | Fluid Handling Filtration Inter-Segment Sales [Member]
Segment Reporting Information [Line Items]
Net sales	(40)		(177)
Inter-segment Elimination [Member] | Corporate And Other Inter-Segment Sales [Member]
Segment Reporting Information [Line Items]
Net sales	(233)	115	(707)	(159)
Inter-segment Elimination [Member] | Environmental Segment [Member] | Energy Inter-Segment Sales [Member]
Segment Reporting Information [Line Items]
Net sales	(427)	(559)	(1,467)	(593)
Inter-segment Elimination [Member] | Environmental Segment [Member] | Fluid Handling Filtration Inter-Segment Sales [Member]
Segment Reporting Information [Line Items]
Net sales	(40)		(177)
Inter-segment Elimination [Member] | Energy Segment [Member] | Environmental Inter-Segment Sales [Member]
Segment Reporting Information [Line Items]
Net sales	(219)	(582)	(377)	(619)
Inter-segment Elimination [Member] | Fluid Handling and Filtration Segment [Member] | Environmental Inter-Segment Sales [Member]
Segment Reporting Information [Line Items]
Net sales	(180)	(15)	(194)	(103)
Inter-segment Elimination [Member] | Corporate and Other [Member] | Corporate And Other Inter-Segment Sales [Member]
Segment Reporting Information [Line Items]
Net sales	$ (233)	$ 115	$ (707)	$ (159)