Acquisitions of Businesses - Purchase Price Allocation (Details) - USD ($) $ in Millions		12 Months Ended
	Jan. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Consideration
Cash, net		$ 0.5	$ (1.3)	$ 4,600.3
Acquisition costs		4.8	33.4	122.4
Identifiable assets acquired and liabilities assumed
Goodwill		$ 4,201.2	$ 4,178.9	$ 4,021.9
OMG Malaysia
Consideration
Cash, net	$ (1.3)
Note receivable settlement	125.0
Total consideration	123.7
Acquisition costs	0.5
Identifiable assets acquired and liabilities assumed
Accounts receivable	4.3
Inventories	6.4
Other current assets	0.2
Property, plant and equipment	4.7
Identifiable intangible assets	43.9
Current liabilities	(3.5)
Non-current deferred tax liability	(11.3)
Total identifiable net assets	44.7
Goodwill	79.0
Total purchase price	$ 123.7