Business Segment Information - Property and Equipment Additions, Depreciation and Amortization and Identifiable Assets (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Segment Reporting Information [Line Items]
Property and equipment additions	$ 1,028	$ 5,461	$ 763
Depreciation and amortization	16,088	18,903	16,520
Identifiable assets	438,549	498,634
Environmental Segment [Member]
Segment Reporting Information [Line Items]
Property and equipment additions	166	404	166
Depreciation and amortization	3,297	3,816	4,443
Identifiable assets	107,910	118,680
Energy Segment [Member]
Segment Reporting Information [Line Items]
Property and equipment additions	438	569	429
Depreciation and amortization	7,866	9,555	5,293
Identifiable assets	217,033	257,566
Fluid Handling and Filtration Segment [Member]
Segment Reporting Information [Line Items]
Property and equipment additions	382	4,481	150
Depreciation and amortization	4,754	5,406	6,331
Identifiable assets	100,916	104,294
Corporate and Other [Member]
Segment Reporting Information [Line Items]
Property and equipment additions	42	7	18
Depreciation and amortization	171	126	$ 453
Identifiable assets	$ 12,690	$ 18,094