Business Segment Information - Intra-Segment and Inter-Segment Revenues (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Segment Reporting Information [Line Items]
Net sales	$ 88,256	$ 84,987	$ 243,485	$ 271,508
Energy Solutions Segment [Member]
Segment Reporting Information [Line Items]
Net sales	56,552	44,279	147,661	150,487
Industrial Solutions Segment [Member]
Segment Reporting Information [Line Items]
Net sales	20,258	21,638	56,379	67,737
Fluid Handling Solutions Segment [Member]
Segment Reporting Information [Line Items]
Net sales	11,446	20,105	39,445	54,269
Corporate and Other [Member]
Segment Reporting Information [Line Items]
Net sales		(1,035)		(985)
Engineered Equipment Segment [Member]
Segment Reporting Information [Line Items]
Net sales			147,661	150,487
Air Quality Segment [Member]
Segment Reporting Information [Line Items]
Net sales			56,379	67,737
Intra - Segment Sales [Member]
Segment Reporting Information [Line Items]
Net sales	(2,426)	(2,068)	(9,237)	(10,062)
Intra - Segment Sales [Member] | Energy Solutions Segment [Member]
Segment Reporting Information [Line Items]
Net sales	(1,453)	(1,102)
Intra - Segment Sales [Member] | Industrial Solutions Segment [Member]
Segment Reporting Information [Line Items]
Net sales	(574)	(396)
Intra - Segment Sales [Member] | Fluid Handling Solutions Segment [Member]
Segment Reporting Information [Line Items]
Net sales	(399)	(570)	(1,208)	(1,727)
Intra - Segment Sales [Member] | Engineered Equipment Segment [Member]
Segment Reporting Information [Line Items]
Net sales			(5,851)	(6,249)
Intra - Segment Sales [Member] | Air Quality Segment [Member]
Segment Reporting Information [Line Items]
Net sales			(2,178)	(2,086)
Operating Segments [Member]
Segment Reporting Information [Line Items]
Net sales	91,197	88,196	255,220	283,982
Operating Segments [Member] | Energy Solutions Segment [Member]
Segment Reporting Information [Line Items]
Net sales	58,561	45,387
Operating Segments [Member] | Industrial Solutions Segment [Member]
Segment Reporting Information [Line Items]
Net sales	20,800	22,041
Operating Segments [Member] | Fluid Handling Solutions Segment [Member]
Segment Reporting Information [Line Items]
Net sales	11,836	20,768	41,011	56,620
Operating Segments [Member] | Engineered Equipment Segment [Member]
Segment Reporting Information [Line Items]
Net sales			155,011	156,764
Operating Segments [Member] | Air Quality Segment [Member]
Segment Reporting Information [Line Items]
Net sales			59,198	70,598
Inter-segment Elimination [Member] | Industrial Inter-Segment Sales [Member]
Segment Reporting Information [Line Items]
Net sales	(540)	(61)
Inter-segment Elimination [Member] | Energy Inter-Segment Sales [Member]
Segment Reporting Information [Line Items]
Net sales	66	(39)	(607)	(877)
Inter-segment Elimination [Member] | Fluid Handling Filtration Inter-Segment Sales [Member]
Segment Reporting Information [Line Items]
Net sales	(41)	(6)	(46)	(45)
Inter-segment Elimination [Member] | Corporate And Other Inter-Segment Sales [Member]
Segment Reporting Information [Line Items]
Net sales		(1,035)		(985)
Inter-segment Elimination [Member] | Environmental Inter-Segment Sales [Member]
Segment Reporting Information [Line Items]
Net sales			(1,845)	(505)
Inter-segment Elimination [Member] | Energy Solutions Segment [Member] | Industrial Inter-Segment Sales [Member]
Segment Reporting Information [Line Items]
Net sales	(556)	(6)
Inter-segment Elimination [Member] | Industrial Solutions Segment [Member] | Energy Inter-Segment Sales [Member]
Segment Reporting Information [Line Items]
Net sales	73	(1)
Inter-segment Elimination [Member] | Industrial Solutions Segment [Member] | Fluid Handling Filtration Inter-Segment Sales [Member]
Segment Reporting Information [Line Items]
Net sales	(41)	(6)
Inter-segment Elimination [Member] | Fluid Handling Solutions Segment [Member] | Industrial Inter-Segment Sales [Member]
Segment Reporting Information [Line Items]
Net sales	16	(55)
Inter-segment Elimination [Member] | Fluid Handling Solutions Segment [Member] | Energy Inter-Segment Sales [Member]
Segment Reporting Information [Line Items]
Net sales	$ (7)	(38)	(7)	(147)
Inter-segment Elimination [Member] | Fluid Handling Solutions Segment [Member] | Environmental Inter-Segment Sales [Member]
Segment Reporting Information [Line Items]
Net sales			(351)	(477)
Inter-segment Elimination [Member] | Corporate and Other [Member] | Corporate And Other Inter-Segment Sales [Member]
Segment Reporting Information [Line Items]
Net sales		$ (1,035)		(985)
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			(1,494)	(28)
Inter-segment Elimination [Member] | Air Quality Segment [Member] | Energy Inter-Segment Sales [Member]
Segment Reporting Information [Line Items]
Net sales			(600)	(730)
Inter-segment Elimination [Member] | Air Quality Segment [Member] | Fluid Handling Filtration Inter-Segment Sales [Member]
Segment Reporting Information [Line Items]
Net sales			$ (41)	$ (45)