Business Segment Information - Net Sales and Income from Operation by Business Segment (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Segment Reporting Information [Line Items]
Net sales	$ 92,651	$ 103,175
Income from Operations	1,350	5,807
Environmental Segment [Member]
Segment Reporting Information [Line Items]
Net sales	35,929	39,122
Income from Operations	5,109	4,746
Energy Segment [Member]
Segment Reporting Information [Line Items]
Net sales	41,083	47,932
Income from Operations	1,613	5,196
Fluid Handling and Filtration Segment [Member]
Segment Reporting Information [Line Items]
Net sales	15,816	16,595
Income from Operations	3,309	3,198
Corporate and Other [Member]
Segment Reporting Information [Line Items]
Net sales	(177)	(474)
Income from Operations	(8,011)	(6,920)
Inter-segment Elimination [Member]
Segment Reporting Information [Line Items]
Income from Operations	$ (670)	$ (413)