Income and Other Taxes - Schedule of Components of Provision for Income Taxes (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Current provision:
Federal	$ 22.0	$ 46.1	$ 13.2
State and local	2.6	3.8	2.0
Foreign	0.0	0.4	0.1
Current income tax expense (benefit)	24.6	50.3	15.3
Deferred:
Federal	34.4	(1.8)	19.7
State and local	1.6	0.0	0.0
Foreign	(0.6)	(1.6)	(4.9)
Deferred income tax expense (benefit)	35.4	(3.4)	14.8
Income tax expense (benefit)	$ 60.0	$ 46.9	$ 30.1