Income Taxes - Deferred Tax Asset and Liabilities (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Deferred income tax assets:
Net operating loss	$ 77.3	$ 64.8
Property, net	36.3	52.1
Insurance reserve	19.9	32.0
Stock-based compensation	19.5	23.7
Allowance for doubtful accounts	14.0	19.3
Alternative minimum tax	0.0	7.5
Carrying value of partnerships	0.0	12.9
Other accruals	20.4	26.1
Tax credits	2.8	2.6
Noncontrolling interest	26.3	14.8
Other	0.5	0.8
Total deferred income tax assets	217.0	256.6
Less: Valuation allowance	(35.8)	(27.9)
Net deferred income tax assets	181.2	228.7
Deferred income tax liabilities:
Deferred revenue	(28.9)	0.0
Intangibles	(80.0)	(113.2)
Convertible debt interest	0.0	(38.1)
Carrying value of partnerships	(6.2)	0.0
Other	(2.5)	(1.6)
Total deferred income tax liabilities	(117.6)	(152.9)
Net deferred income tax assets	$ 63.6	$ 75.8