Restructuring - Additional Information (Detail) $ in Millions	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2018 USD ($)	Sep. 30, 2017 USD ($)	Sep. 30, 2018 USD ($) Person	Sep. 30, 2017 USD ($)	Dec. 31, 2017 Person
Restructuring Cost and Reserve [Line Items]
Number of employees | Person			300		250
Total restructuring costs	$ 3.5	$ 1.4	$ 34.1	$ 18.9
Aquatic Systems
Restructuring Cost and Reserve [Line Items]
Total restructuring costs	0.6	0.3	3.6	1.9
Filtration Solutions
Restructuring Cost and Reserve [Line Items]
Total restructuring costs	0.9	0.2	14.4	6.9
Flow Technologies
Restructuring Cost and Reserve [Line Items]
Total restructuring costs	0.7	0.9	8.7	2.8
Other
Restructuring Cost and Reserve [Line Items]
Total restructuring costs	$ 1.3	$ 0.0	$ 7.4	$ 7.3