Segment Information - Financial Information by Reportable Segment (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Segment Reporting Information [Line Items]
Net sales	$ 1,183.5	$ 1,190.0
Segment Income (Loss)	183.5	177.9
Water Unit [Member]
Segment Reporting Information [Line Items]
Net sales	682.9	665.7
Segment Income (Loss)	116.0	101.2
Electrical Unit [Member]
Segment Reporting Information [Line Items]
Net sales	502.2	524.6
Segment Income (Loss)	103.5	112.8
Other
Segment Reporting Information [Line Items]
Net sales	(1.6)	(0.3)
Segment Income (Loss)	$ (36.0)	$ (36.1)