Income Taxes - Components of Consolidated Income Tax Provision (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Current income tax provision (benefit) -
U.S. federal	$ 123.2	$ 150.7	$ 209.3
State and local	37.0	42.9	34.9
Foreign	0.1	0.2	0.3
Total current provision for taxes	160.3	193.8	244.5
Deferred -
U.S. federal	55.3	34.7	(90.2)
State and local	5.0	4.0	5.7
Total deferred provision (benefit) for taxes	60.3	38.7	(84.5)
Total provision for taxes	$ 220.6	$ 232.5	$ 160.0