Intangible Assets - Accumulated Impairment, Changes in Goodwill and Other Indefinite-Lived Intangibles (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2012
Intangible Assets
Goodwill, Accumulated impairment loss			$ 606.3
Other indefinite-lived intangible assets, Accumulated impairment loss			$ 37.1
Summary of the changes in the carrying amount of goodwill and other indefinite-lived intangible assets
Goodwill, Beginning balance	$ 1,291.2	$ 1,323.1
Goodwill, Additions	324.8	24.9
Goodwill, Disposals	(4.5)	(1.7)
Goodwill, Foreign currency translation	49.0	(55.1)
Goodwill, Ending balance	1,660.5	1,291.2
Other indefinite-lived intangible assets, Beginning Balance	420.1	408.0
Other indefinite-lived intangible assets, Additions	40.8	26.2
Other indefinite-lived intangible assets, Disposals	(1.7)	(0.3)
Other indefinite-lived intangible assets, Foreign currency translation	14.8	(13.8)
Other indefinite-lived intangible assets, Ending Balance	$ 474.0	$ 420.1