Income Taxes - Income Tax Contingencies (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Balance at beginning of year	$ 151.3	$ 178.1	$ 264.5
Current Year [Abstract]
Additions	5.3	5.9	4.3
Prior Years [Abstract]
Additions	18.1	0.8	12.7
Reductions in unrecognized tax benefits	(52.0)	(3.3)	(33.8)
Settlements	(1.8)	(22.5)	(2.6)
Lapses in statutes of limitations	(4.9)	(7.7)	(67.0)
Balance at end of year	$ 116.0	$ 151.3	$ 178.1