Income Taxes - Federal and State Deferred Tax Assets Liabilities (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Liabilities:
Deferred cancellation of debt income	$ (11.7)	$ (36.4)
Investments in available for sale securities	(0.6)	(62.2)
Unconsolidated affiliates and investments	(19.7)	(27.9)
Accumulated depreciation and amortization	(62.8)	(65.3)
Prepaid expenses	0.0	(5.5)
Other	(3.5)	0.0
Total deferred tax liabilities	98.3	197.3
Assets:
Deferred compensation and other employee benefits	24.4	23.2
Net operating loss	14.9	8.5
Accrued liabilities	16.2	26.9
Prepaid expenses	4.4	0.0
Other	0.0	1.4
Total deferred tax assets	59.9	60.0
Valuation allowance	(7.1)	(6.0)
Net deferred tax liability	$ (45.5)	$ (143.3)