Business Segment Information - Intra-Segment and Inter-Segment Revenues (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Segment Reporting Information [Line Items]
Net sales	$ 101,596	$ 98,230	$ 317,029	$ 266,176
Intra - Segment Sales [Member]
Segment Reporting Information [Line Items]
Net sales	(2,128)	(3,842)	(6,726)	(10,531)
Environmental Segment [Member]
Segment Reporting Information [Line Items]
Net sales	36,606	40,644	119,939	124,158
Environmental Segment [Member] | Intra - Segment Sales [Member]
Segment Reporting Information [Line Items]
Net sales	(941)	(1,928)	(3,539)	(5,211)
Energy Segment [Member]
Segment Reporting Information [Line Items]
Net sales	50,259	40,014	151,058	91,666
Energy Segment [Member] | Intra - Segment Sales [Member]
Segment Reporting Information [Line Items]
Net sales	(874)	(1,490)	(2,019)	(3,745)
Fluid Handling and Filtration Segment [Member]
Segment Reporting Information [Line Items]
Net sales	14,866	17,136	46,874	50,075
Fluid Handling and Filtration Segment [Member] | Intra - Segment Sales [Member]
Segment Reporting Information [Line Items]
Net sales	(313)	(424)	(1,168)	(1,575)
Corporate and Other [Member]
Segment Reporting Information [Line Items]
Net sales	(135)	436	(842)	277
Operating Segments [Member]
Segment Reporting Information [Line Items]
Net sales	105,060	102,090	328,013	278,199
Operating Segments [Member] | Environmental Segment [Member]
Segment Reporting Information [Line Items]
Net sales	38,454	42,925	126,029	130,315
Operating Segments [Member] | Energy Segment [Member]
Segment Reporting Information [Line Items]
Net sales	51,155	41,511	153,476	96,037
Operating Segments [Member] | Fluid Handling and Filtration Segment [Member]
Segment Reporting Information [Line Items]
Net sales	15,451	17,654	48,508	51,847
Inter-segment Elimination [Member] | Environmental Inter-Segment Sales [Member]
Segment Reporting Information [Line Items]
Net sales	(110)	(101)	(681)	(823)
Inter-segment Elimination [Member] | Energy Inter-Segment Sales [Member]
Segment Reporting Information [Line Items]
Net sales	(1,062)	(345)	(2,529)	(938)
Inter-segment Elimination [Member] | Fluid Handling Filtration Inter-Segment Sales [Member]
Segment Reporting Information [Line Items]
Net sales	(29)	(8)	(206)	(8)
Inter-segment Elimination [Member] | Corporate And Other Inter-Segment Sales [Member]
Segment Reporting Information [Line Items]
Net sales	(135)	436	(842)	277
Inter-segment Elimination [Member] | Environmental Segment [Member] | Energy Inter-Segment Sales [Member]
Segment Reporting Information [Line Items]
Net sales	(878)	(345)	(2,345)	(938)
Inter-segment Elimination [Member] | Environmental Segment [Member] | Fluid Handling Filtration Inter-Segment Sales [Member]
Segment Reporting Information [Line Items]
Net sales	(29)	(8)	(206)	(8)
Inter-segment Elimination [Member] | Energy Segment [Member] | Environmental Inter-Segment Sales [Member]
Segment Reporting Information [Line Items]
Net sales	(22)	(7)	(399)	(626)
Inter-segment Elimination [Member] | Fluid Handling and Filtration Segment [Member] | Environmental Inter-Segment Sales [Member]
Segment Reporting Information [Line Items]
Net sales	(88)	(94)	(282)	(197)
Inter-segment Elimination [Member] | Fluid Handling and Filtration Segment [Member] | Energy Inter-Segment Sales [Member]
Segment Reporting Information [Line Items]
Net sales	(184)		(184)
Inter-segment Elimination [Member] | Corporate and Other [Member] | Corporate And Other Inter-Segment Sales [Member]
Segment Reporting Information [Line Items]
Net sales	$ (135)	$ 436	$ (842)	$ 277