Segment Information - Financial Information by Reportable Segment (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Segment Reporting Information [Line Items]
Net sales	$ 799.5	$ 780.6	$ 1,488.4	$ 1,513.2
Segment income	133.8	122.6	201.4	215.3
Aquatic Systems
Segment Reporting Information [Line Items]
Net sales	270.6	276.2	491.1	516.6
Segment income	76.8	79.6	129.2	139.6
Filtration Solutions
Segment Reporting Information [Line Items]
Net sales	285.6	262.1	524.9	513.7
Segment income	50.0	52.3	83.7	86.0
Flow Technologies
Segment Reporting Information [Line Items]
Net sales	243.0	241.9	471.7	482.2
Segment income	41.9	44.4	72.0	83.1
Other
Segment Reporting Information [Line Items]
Net sales	0.3	0.4	0.7	0.7
Segment income	(14.6)	(12.2)	(32.1)	(27.6)
Operating Segments
Segment Reporting Information [Line Items]
Segment income	$ 154.1	$ 164.1	$ 252.8	$ 281.1