Income Taxes - Reconciliation of 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 beginning of period	$ 16.5	$ 14.0	$ 12.7
Additions for current year tax positions	1.9	2.2	1.8
(Reductions) additions for prior year tax positions	(9.3)	0.3	0.0
Reductions for settlements with tax authorities	0.0	0.0	(0.5)
Balance at end of period	$ 9.1	$ 16.5	$ 14.0