Restructuring - Additional Information (Detail) $ in Millions	12 Months Ended
	Dec. 31, 2017 USD ($) Person	Dec. 31, 2016 USD ($) Person	Dec. 31, 2015 USD ($) Person
Restructuring Cost and Reserve [Line Items]
Number of employees	500	650	500
Restructuring costs | $	$ 58.7	$ 24.5	$ 41.3
Water
Restructuring Cost and Reserve [Line Items]
Number of employees	250	300
Restructuring costs | $	$ 23.6	$ 10.5	17.4
Electrical
Restructuring Cost and Reserve [Line Items]
Number of employees	250	350
Restructuring costs | $	$ 16.8	$ 12.3	15.7
Other
Restructuring Cost and Reserve [Line Items]
Restructuring costs | $	$ 18.3	$ 1.7	$ 8.2
Water Quality Systems [Member]
Restructuring Cost and Reserve [Line Items]
Number of employees			300
Flow & Filtration Solutions [Member]
Restructuring Cost and Reserve [Line Items]
Number of employees			200