Business Segment Information - Intra-Segment and Inter-Segment Revenues (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Segment Reporting Information [Line Items]
Net sales	$ 81,089	$ 93,870	$ 155,229	$ 186,521
Energy Solutions Segment [Member]
Segment Reporting Information [Line Items]
Net sales	51,136	52,499	91,109	106,208
Industrial Solutions Segment [Member]
Segment Reporting Information [Line Items]
Net sales	18,324	22,796	36,121	46,099
Fluid Handling Solutions Segment [Member]
Segment Reporting Information [Line Items]
Net sales	11,791	18,348	27,999	34,164
Corporate and Other [Member]
Segment Reporting Information [Line Items]
Net sales	(162)	227		50
Engineered Equipment Segment [Member]
Segment Reporting Information [Line Items]
Net sales			91,109	106,208
Air Quality Segment [Member]
Segment Reporting Information [Line Items]
Net sales			36,121	46,099
Intra - Segment Sales [Member]
Segment Reporting Information [Line Items]
Net sales	(3,037)	(4,178)	(6,811)	(7,994)
Intra - Segment Sales [Member] | Energy Solutions Segment [Member]
Segment Reporting Information [Line Items]
Net sales	(1,929)	(2,839)
Intra - Segment Sales [Member] | Industrial Solutions Segment [Member]
Segment Reporting Information [Line Items]
Net sales	(813)	(800)
Intra - Segment Sales [Member] | Fluid Handling Solutions Segment [Member]
Segment Reporting Information [Line Items]
Net sales	(295)	(539)	(809)	(1,157)
Intra - Segment Sales [Member] | Engineered Equipment Segment [Member]
Segment Reporting Information [Line Items]
Net sales			(4,398)	(5,147)
Intra - Segment Sales [Member] | Air Quality Segment [Member]
Segment Reporting Information [Line Items]
Net sales			(1,604)	(1,690)
Operating Segments [Member]
Segment Reporting Information [Line Items]
Net sales	85,401	98,133	164,023	195,786
Operating Segments [Member] | Energy Solutions Segment [Member]
Segment Reporting Information [Line Items]
Net sales	53,322	55,338
Operating Segments [Member] | Industrial Solutions Segment [Member]
Segment Reporting Information [Line Items]
Net sales	19,670	23,635
Operating Segments [Member] | Fluid Handling Solutions Segment [Member]
Segment Reporting Information [Line Items]
Net sales	12,409	19,160	29,175	35,852
Operating Segments [Member] | Engineered Equipment Segment [Member]
Segment Reporting Information [Line Items]
Net sales			96,450	111,377
Operating Segments [Member] | Air Quality Segment [Member]
Segment Reporting Information [Line Items]
Net sales			38,398	48,557
Inter-segment Elimination [Member] | Industrial Inter-Segment Sales [Member]
Segment Reporting Information [Line Items]
Net sales	(575)	(258)
Inter-segment Elimination [Member] | Energy Inter-Segment Sales [Member]
Segment Reporting Information [Line Items]
Net sales	(533)	(15)	(673)	(838)
Inter-segment Elimination [Member] | Fluid Handling Filtration Inter-Segment Sales [Member]
Segment Reporting Information [Line Items]
Net sales	(5)	(39)	(5)	(39)
Inter-segment Elimination [Member] | Corporate And Other Inter-Segment Sales [Member]
Segment Reporting Information [Line Items]
Net sales	(162)	227		50
Inter-segment Elimination [Member] | Environmental Inter-Segment Sales [Member]
Segment Reporting Information [Line Items]
Net sales			(1,305)	(444)
Inter-segment Elimination [Member] | Energy Solutions Segment [Member] | Industrial Inter-Segment Sales [Member]
Segment Reporting Information [Line Items]
Net sales	(252)
Inter-segment Elimination [Member] | Energy Solutions Segment [Member] | Fluid Handling Filtration Inter-Segment Sales [Member]
Segment Reporting Information [Line Items]
Net sales	(5)
Inter-segment Elimination [Member] | Industrial Solutions Segment [Member] | Energy Inter-Segment Sales [Member]
Segment Reporting Information [Line Items]
Net sales	(533)
Inter-segment Elimination [Member] | Industrial Solutions Segment [Member] | Fluid Handling Filtration Inter-Segment Sales [Member]
Segment Reporting Information [Line Items]
Net sales		(39)
Inter-segment Elimination [Member] | Fluid Handling Solutions Segment [Member] | Industrial Inter-Segment Sales [Member]
Segment Reporting Information [Line Items]
Net sales	(323)	(258)
Inter-segment Elimination [Member] | Fluid Handling Solutions Segment [Member] | Energy Inter-Segment Sales [Member]
Segment Reporting Information [Line Items]
Net sales		(15)		(109)
Inter-segment Elimination [Member] | Fluid Handling Solutions Segment [Member] | Environmental Inter-Segment Sales [Member]
Segment Reporting Information [Line Items]
Net sales			(367)	(422)
Inter-segment Elimination [Member] | Corporate and Other [Member] | Corporate And Other Inter-Segment Sales [Member]
Segment Reporting Information [Line Items]
Net sales	$ (162)	$ 227		50
Inter-segment Elimination [Member] | Engineered Equipment Segment [Member] | Fluid Handling Filtration Inter-Segment Sales [Member]
Segment Reporting Information [Line Items]
Net sales			(5)
Inter-segment Elimination [Member] | Engineered Equipment Segment [Member] | Environmental Inter-Segment Sales [Member]
Segment Reporting Information [Line Items]
Net sales			(938)	(22)
Inter-segment Elimination [Member] | Air Quality Segment [Member] | Energy Inter-Segment Sales [Member]
Segment Reporting Information [Line Items]
Net sales			$ (673)	(729)
Inter-segment Elimination [Member] | Air Quality Segment [Member] | Fluid Handling Filtration Inter-Segment Sales [Member]
Segment Reporting Information [Line Items]
Net sales				$ (39)