Income Taxes - Unrecognized Tax Benefits (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Summary of unrecognized tax benefits for the years ended
Beginning balance, January 1	$ 38.9	$ 26.0	$ 14.0
Additions	2.2	3.6	0.4
Tax positions related to prior years, additions	8.7	11.7	17.8
Tax positions related to prior years, reductions	(1.0)	(1.1)	(2.9)
Settlements with tax authorities	(0.3)	(1.2)	(2.2)
Lapses in statutes of limitation	(2.9)	(0.1)	(1.1)
Ending balance, December 31	$ 45.6	$ 38.9	$ 26.0