Goodwill and Other Identifiable Intangible Assets - Changes in Carrying Amount of Goodwill by Segment (Detail) $ in Millions	9 Months Ended
	Sep. 30, 2017 USD ($)
Goodwill [Roll Forward]
Beginning Balance	$ 4,217.4
Goodwill, Purchase Accounting Adjustments	32.6
Foreign currency translation/other	93.6
Ending Balance	4,343.6
Water Unit [Member]
Goodwill [Roll Forward]
Beginning Balance	1,994.6
Goodwill, Purchase Accounting Adjustments	27.3
Foreign currency translation/other	83.4
Ending Balance	2,105.3
Electrical Unit [Member]
Goodwill [Roll Forward]
Beginning Balance	2,222.8
Goodwill, Purchase Accounting Adjustments	5.3
Foreign currency translation/other	10.2
Ending Balance	$ 2,238.3