Reconciliation of Unrecognized Tax Benefits (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Income Tax Disclosure [Abstract]
Unrecognized tax benefits at January 1	$ 18.9	$ 4.7	$ 0.0
Gross increases - tax positions in current period	0.0	13.2	0.0
Gross increases - tax positions in prior period	1.6	1.4	5.1
Gross decreases - tax positions in prior period	(11.8)	(0.0)	(0.0)
Decreases due to settlements and payments	(1.4)	(0.0)	(0.0)
Lapse of statute of limitations	(0.0)	(0.4)	(0.4)
Unrecognized tax benefits at December 31	$ 7.3	$ 18.9	$ 4.7