Business Segment Information - Net Sales and Income from Operation by Business Segment (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Segment Reporting Information [Line Items]
Net sales	$ 103,175	$ 80,985
Income from operations	5,807	2,979
Environmental Segment [Member]
Segment Reporting Information [Line Items]
Net sales	39,122	41,716
Income from operations	4,746	4,018
Energy Segment [Member]
Segment Reporting Information [Line Items]
Net sales	47,932	24,349
Income from operations	5,196	420
Fluid Handling and Filtration Segment [Member]
Segment Reporting Information [Line Items]
Net sales	16,595	15,194
Income from operations	3,198	2,956
Corporate and Other [Member]
Segment Reporting Information [Line Items]
Net sales	(474)	(274)
Income from operations	(6,920)	(3,817)
Inter-segment Elimination [Member]
Segment Reporting Information [Line Items]
Income from operations	$ (413)	$ (598)