Income Taxes - Narrative (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Tax Disclosure [Abstract]
U.S. federal statutory tax rate		21.00%	35.00%	35.00%
Remeasurement of Deferred Tax Assets due to US Tax Reform	$ 326.2
Recognition of provisional charge	326.2
Adjustment to provisional amount recorded		$ 68.0
Effective income tax rate		4.30%	42.30%	32.70%
Unrecognized tax benefits that would impact effective tax rate	$ 146.2	$ 189.5	$ 146.2	$ 107.2