Business Segment Information - Property and Equipment Additions, Depreciation and Amortization and Identifiable Assets (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013	Dec. 31, 2013
Segment Reporting Information [Line Items]
Property and equipment additions	$ 296	$ 183	$ 711	$ 236
Depreciation and amortization	2,619	899	5,389	1,313
Identifiable Assets	333,626		333,626		348,536
Air Pollution Control Segment [Member]
Segment Reporting Information [Line Items]
Property and equipment additions	132	42	268	94
Depreciation and amortization	383	243	778	498
Identifiable Assets	73,556		73,556		74,556
Energy Segment [Member]
Segment Reporting Information [Line Items]
Property and equipment additions	33	141	67	142
Depreciation and amortization	564	615	1,219	733
Identifiable Assets	64,232		64,232		76,960
Fluid Handling Filtration Segment [Member]
Segment Reporting Information [Line Items]
Property and equipment additions	119	0	333	0
Depreciation and amortization	1,637	8	3,325	16
Identifiable Assets	178,446		178,446		185,646
Corporate and Other [Member]
Segment Reporting Information [Line Items]
Property and equipment additions	12	0	43	0
Depreciation and amortization	35	33	67	66
Identifiable Assets	$ 17,392		$ 17,392		$ 11,374