Goodwill and Other Identifiable Intangible Assets - Changes in Carrying Amount of Goodwill by Segment (Detail) $ in Millions	6 Months Ended
	Jun. 30, 2018 USD ($)
Goodwill [Roll Forward]
Beginning Balance	$ 2,112.8
Foreign currency translation/other	(24.0)
Ending Balance	2,088.8
Aquatic Systems
Goodwill [Roll Forward]
Beginning Balance	973.1
Foreign currency translation/other	4.7
Ending Balance	977.8
Filtration Solutions
Goodwill [Roll Forward]
Beginning Balance	472.1
Foreign currency translation/other	(25.1)
Ending Balance	447.0
Flow Technologies
Goodwill [Roll Forward]
Beginning Balance	667.6
Foreign currency translation/other	(3.6)
Ending Balance	$ 664.0