Income Taxes - Components of Income Tax Benefit (Provision) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Income Tax Disclosure [Abstract]
Current income tax expense	$ (0.3)	$ (1.0)
Deferred income tax benefit (expense)	34.0	(0.8)
Income tax benefit (expense)	33.7	(1.8)
Effective Income Tax Rate Reconciliation, Amount [Abstract]
Expected income tax benefit based on federal statutory rate	67.3	36.7
State income tax benefit, net of federal benefit	8.0	4.4
Non-deductible expense related to goodwill impairment	(43.4)	(43.8)
Other	1.8	0.9
Income tax benefit (expense)	$ 33.7	$ (1.8)