Income Taxes - Income Tax Expense and Income Before Income Taxes (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Income Taxes
Current income taxes (benefits): U.S. federal	$ 15.8	$ 31.9	$ (48.9)
Current income taxes (benefits): State	5.0	18.1	10.3
Current income taxes (benefits): Foreign	55.4	45.6	51.7
Current income taxes (benefits): Tax benefit of operating loss carryforwards	(3.3)	(3.0)	(13.5)
Total current income taxes (benefits)	72.9	92.6	(0.4)
Deferred income taxes (benefits): U.S. federal	143.6	108.6	224.3
Deferred income taxes (benefits): State	11.5	6.9	19.2
Deferred income taxes (benefits): Foreign	37.0	41.1	(12.4)
Total deferred income taxes (benefits)	192.1	156.6	231.1
Income taxes (benefits)	265.0	249.2	230.7
Income (loss) before income taxes
Income (loss) before income taxes - domestic	1,323.2	1,351.9	1,661.1
Income (loss) before income taxes - foreign	370.3	341.4	123.3
Income (loss) before income taxes	$ 1,693.5	$ 1,693.3	$ 1,784.4