Income Taxes - Uncertain Tax Positions (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Unrecognized tax benefits, beginning balance	$ 347.9	$ 334.5
Positions related to the current year	39.4	46.1
Positions related to prior years	6.8	77.9
Settlements with taxing authorities	(6.5)	(11.1)
Lapse of statutes of limitation	(1.1)	(0.1)
Decrease in prior year positions(1)	(6.4)	(99.4)	[1]
Cumulative translation adjustment	(3.0)
Unrecognized tax benefits, ending balance	$ 377.1	$ 347.9

[1] (1) Represents a revision from the prior year presentation to remeasure certain attributes that offset deferred tax assets as a result of the U.S. Tax Act.