Income Taxes - Schedule of Components of Provision for Income Taxes (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Current provision:
Federal	$ 10.1	$ 29.5	$ 33.6
State and local	3.8	3.0	3.3
Current income tax expense (benefit)	13.9	32.5	36.9
Deferred provision (benefit):
Federal	35.0	(53.0)	12.7
State and local	2.5	0.8	1.1
Foreign	(0.1)	(0.2)	0.0
Deferred income tax expense (benefit)	37.4	(52.4)	13.8
Income tax expense (benefit)	$ 51.3	$ (19.9)	$ 50.7