Income Taxes - Provision/(Benefit) For Income Taxes (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Current
U.S. federal	$ 3.5	$ 0.7	$ 0.8
Foreign	14.6	36.1	49.0
State and local	0.4	1.5	1.9
Total current	18.5	38.3	51.7
Deferred
U.S. federal	7.1	78.1	4.6
Foreign	(22.6)	(11.7)	(19.8)
State and local	(4.0)	12.0	0.7
Total deferred	(19.5)	78.4	(14.5)
Income tax expense (benefit)	$ (1.0)	$ 116.7	$ 37.2