Income Taxes - Components of Consolidated Income Tax Provision (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Current income tax provision (benefit) -
U.S. Federal	$ 205.1	$ 185.1	$ 129.6
State and local	20.5	33.1	12.7
Foreign	0.4	0.9	0.3
Total current provision for taxes	226.0	219.1	142.6
Deferred -
U.S. Federal	(3.8)	(5.0)	(160.5)
State and local	5.6	7.6	0.3
Foreign	(0.1)	0.0	(0.1)
Total deferred provision (benefit) for taxes	1.7	2.6	(160.3)
Total provision (benefit) for taxes	$ 227.7	$ 221.7	$ (17.7)