Restructuring - Additional Information (Detail) $ in Millions	3 Months Ended		12 Months Ended
	Mar. 31, 2018 USD ($) Person	Mar. 31, 2017 USD ($)	Dec. 31, 2017 Person
Restructuring Cost and Reserve [Line Items]
Number of employees | Person	200		500
Total restructuring costs	$ 10.8	$ 20.9
Water Unit [Member]
Restructuring Cost and Reserve [Line Items]
Number of employees | Person	175		250
Total restructuring costs	$ 5.6	7.1
Electrical Unit [Member]
Restructuring Cost and Reserve [Line Items]
Number of employees | Person	25		250
Total restructuring costs	$ 2.8	9.3
Corporate and Other [Member]
Restructuring Cost and Reserve [Line Items]
Total restructuring costs	$ 2.4	$ 4.5