Restructuring - Additional Information (Detail) $ in Millions	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2019 USD ($)	Sep. 30, 2018 USD ($)	Sep. 30, 2019 USD ($) Person	Sep. 30, 2018 USD ($)	Dec. 31, 2018 Person
Restructuring Cost and Reserve [Line Items]
Number of employees | Person			325		300
Total restructuring costs	$ 2.9	$ 3.5	$ 10.7	$ 34.1
Aquatic Systems
Restructuring Cost and Reserve [Line Items]
Total restructuring costs	0.2	0.6	3.1	3.6
Filtration Solutions
Restructuring Cost and Reserve [Line Items]
Total restructuring costs	1.5	0.9	3.1	14.4
Flow Technologies
Restructuring Cost and Reserve [Line Items]
Total restructuring costs	0.3	0.7	2.4	8.7
Other
Restructuring Cost and Reserve [Line Items]
Total restructuring costs	$ 0.9	$ 1.3	$ 2.1	$ 7.4