Income Taxes - Provision for Income Tax (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Current
Federal	$ 51.6	$ 37.4	$ 35.3
State and local	3.7	5.0	5.0
Foreign	0.0	2.1	2.7
Total current	55.3	44.5	43.0
Deferred
Federal	(25.3)	(2.4)	7.4
State and local	(1.3)	(0.5)	1.7
Foreign	0.9	1.0	0.1
Total deferred	(25.7)	(1.9)	9.2
Provision (benefit) for income taxes	$ 29.6	$ 42.6	$ 52.2