Segment Information - Financial Information by Reportable Segment (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Segment Reporting Information [Line Items]
Net sales	$ 1,265.3	$ 1,301.2	$ 2,448.8	$ 2,491.2
Segment Income (Loss)	255.2	241.0	438.7	418.9
Water Unit [Member]
Segment Reporting Information [Line Items]
Net sales	753.7	761.7	1,436.6	1,427.4
Segment Income (Loss)	161.0	153.6	277.0	254.8
Electrical Unit [Member]
Segment Reporting Information [Line Items]
Net sales	513.2	540.6	1,015.4	1,065.2
Segment Income (Loss)	112.8	111.6	216.3	224.4
Other
Segment Reporting Information [Line Items]
Net sales	(1.6)	(1.1)	(3.2)	(1.4)
Segment Income (Loss)	$ (18.6)	$ (24.2)	$ (54.6)	$ (60.3)