Income Taxes - Reconciliation of Income Tax Provision (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income Taxes
Income tax (expense) benefit, net	$ (1.5)	$ 65.1	$ 158.3
Reconciliation of the income tax provision computed at statutory tax rates to the income tax provision
Statutory federal income taxes	(8.0)	32.0	(9.5)
State income taxes	(2.1)	11.9	(1.6)
Uncertain tax positions	3.7	(0.1)	(3.2)
Tax status change & other true-ups	0.9	1.3	4.0
Other true-ups	0.8	1.0	1.2
Equity compensation	(0.3)	(1.9)
Other permanent differences	(0.4)	(0.3)	(0.5)
Goodwill impairment		(11.2)	(35.1)
Corporate Tax Reform			103.4
Change in valuation allowance	$ 3.9	$ 32.4	$ 99.6
Effective tax rate (as a percent)	21.00%	21.00%	35.00%
Temporary bonus depreciation rate (as a percent)		100.00%
Additional valuation allowance from re-measurement		$ 22.1
Deferred tax expense (benefit)		$ 125.5