Segment Information - Financial Information by Reportable Segment (Detail) - USD ($) $ in Millions	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	$ 711.4	$ 687.6	$ 2,224.6	$ 2,124.9
Segment income	108.4	101.8	323.7	292.9
Aquatic Systems
Segment Reporting Information [Line Items]
Net sales	232.7	211.8	749.3	688.0
Segment income	59.9	53.1	199.5	182.9
Filtration Solutions
Segment Reporting Information [Line Items]
Net sales	240.4	242.4	754.1	737.0
Segment income	38.4	40.4	124.4	113.4
Flow Technologies
Segment Reporting Information [Line Items]
Net sales	238.0	233.0	720.2	698.8
Segment income	36.6	39.3	119.7	112.7
Other
Segment Reporting Information [Line Items]
Net sales	0.3	0.4	1.0	1.1
Segment income	(13.1)	(12.6)	(40.7)	(40.2)
Operating Segments
Segment Reporting Information [Line Items]
Segment income	$ 121.8	$ 120.2	$ 402.9	$ 368.8