Business Segment Information - Net Sales and Income from Operation by Business Segment (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Segment Reporting Information [Line Items]
Net sales	$ 98,230	$ 63,300	$ 266,176	$ 187,111
Income (loss) from operations	(2,194)	5,245	5,273	17,925
Environmental Segment [Member]
Segment Reporting Information [Line Items]
Net sales	40,644	27,709	124,158	87,396
Income (loss) from operations	5,225	3,315	14,383	12,057
Energy Segment [Member]
Segment Reporting Information [Line Items]
Net sales	40,014	17,977	91,666	50,093
Income (loss) from operations	(1,082)	1,850	(447)	5,833
Fluid Handling and Filtration Segment [Member]
Segment Reporting Information [Line Items]
Net sales	17,136	17,584	50,075	49,729
Income (loss) from operations	4,011	4,347	11,398	10,087
Corporate and Other [Member]
Segment Reporting Information [Line Items]
Net sales	436	30	277	(107)
Income (loss) from operations	(11,170)	(3,944)	(20,061)	(8,900)
Inter-segment Elimination [Member]
Segment Reporting Information [Line Items]
Net sales	(3,842)	(3,398)	(10,531)	(9,828)
Income (loss) from operations	822	(323)		(1,152)
Inter-segment Elimination [Member] | Environmental Segment [Member]
Segment Reporting Information [Line Items]
Net sales	(1,928)	(1,634)	(5,211)	(5,124)
Inter-segment Elimination [Member] | Energy Segment [Member]
Segment Reporting Information [Line Items]
Net sales	(1,490)	(1,200)	(3,745)	(3,393)
Inter-segment Elimination [Member] | Fluid Handling and Filtration Segment [Member]
Segment Reporting Information [Line Items]
Net sales	$ (424)	$ (564)	$ (1,575)	$ (1,311)