Income Taxes (Provision for Income Taxes) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Current:
Federal	$ 46.1	$ 128.9	$ 358.3
State	40.5	46.9	48.4
Deferred:
Federal	151.8	121.5	(388.1)
State	18.9	30.6	9.1
State deferred benefit - change in valuation allowance	(4.6)	(4.5)	9.6
Uncertain tax positions and interest, and other	(30.7)	(40.1)	(34.2)
Provision for income taxes	$ 222.0	$ 283.3	$ 3.1