Segment Information - Financial Information by Reportable Segment (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Segment Reporting Information [Line Items]
Net sales	$ 713.6	$ 711.4	$ 2,202.0	$ 2,224.6
Segment income	108.8	108.4	310.2	323.7
Aquatic Systems
Segment Reporting Information [Line Items]
Net sales	218.7	232.7	709.8	749.3
Segment income	54.8	59.9	184.0	199.5
Filtration Solutions
Segment Reporting Information [Line Items]
Net sales	273.5	240.4	798.4	754.1
Segment income	45.1	38.4	128.8	124.4
Flow Technologies
Segment Reporting Information [Line Items]
Net sales	221.0	238.0	692.7	720.2
Segment income	37.9	36.6	109.9	119.7
Other
Segment Reporting Information [Line Items]
Net sales	0.4	0.3	1.1	1.0
Segment income	(15.0)	(13.1)	(47.1)	(40.7)
Operating Segments
Segment Reporting Information [Line Items]
Segment income	$ 122.8	$ 121.8	$ 375.6	$ 402.9