Income Taxes - Unrecognized Tax Benefits (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 January 1	$ 50.9	$ 49.5	$ 48.4
Unrecognized Tax Benefits, Increase Resulting from Prior Period Tax Positions	0.9	5.1
Increases related to current year tax positions	0.0	4.4	4.8
Settlements	(7.7)	(5.5)	(1.5)
Reductions due to lapse of applicable statute of limitations	(7.3)	(2.6)	(0.7)
Balance at December 31	$ 36.8	$ 50.9	49.5
Unrecognized Tax Benefits, Decrease Resulting from Prior Period Tax Positions			$ (1.5)