Income Taxes - Income Tax Expense (Benefit) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Current:
Federal	$ 35.0	$ 10.4	$ 15.3
State	9.4	5.3	6.0
Foreign	0.8	0.9	1.0
Total current	45.2	16.6	22.3
Deferred:
Federal	(2.3)	(87.5)	5.0
State	(5.2)	9.1	(1.1)
Deferred Foreign Income Tax Expense (Benefit)	0.0	0.0	(0.4)
Total deferred	(7.5)	(78.4)	3.5
Total income tax expense (benefit)	$ 37.7	$ (61.8)	$ 25.8