Business Segment Information - Property and Equipment Additions, Depreciation and Amortization and Identifiable Assets (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Dec. 31, 2016
Segment Reporting Information [Line Items]
Property and Equipment Additions	$ 410	$ 212
Depreciation and amortization	4,138	5,195
Identifiable Assets	482,304		$ 498,634
Environmental Segment [Member]
Segment Reporting Information [Line Items]
Property and Equipment Additions	9	113
Depreciation and amortization	845	967
Identifiable Assets	119,044		118,680
Energy Segment [Member]
Segment Reporting Information [Line Items]
Property and Equipment Additions	236	86
Depreciation and amortization	2,064	2,802
Identifiable Assets	240,841		257,566
Fluid Handling and Filtration Segment [Member]
Segment Reporting Information [Line Items]
Property and Equipment Additions	149	9
Depreciation and amortization	1,198	1,394
Identifiable Assets	104,007		104,294
Corporate and Other [Member]
Segment Reporting Information [Line Items]
Property and Equipment Additions	16	4
Depreciation and amortization	31	$ 32
Identifiable Assets	$ 18,412		$ 18,094