Restructuring - Additional Information (Detail) $ in Millions	3 Months Ended		12 Months Ended
	Mar. 31, 2019 USD ($) Person	Mar. 31, 2018 USD ($)	Dec. 31, 2018 Person
Restructuring Cost and Reserve [Line Items]
Number of employees | Person	10		300
Total restructuring costs	$ 1.1	$ 5.6
Aquatic Systems
Restructuring Cost and Reserve [Line Items]
Total restructuring costs	0.9	1.8
Filtration Solutions
Restructuring Cost and Reserve [Line Items]
Total restructuring costs	0.4	2.0
Flow Technologies
Restructuring Cost and Reserve [Line Items]
Total restructuring costs	(0.3)	1.7
Other
Restructuring Cost and Reserve [Line Items]
Total restructuring costs	$ 0.1	$ 0.1