Income Taxes - Reconciliation between Benefit for Income Taxes and Expected Tax Provision (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Amount computed using statutory rates	$ (5.7)	$ 3.0	$ (1.0)
State income taxes, net of Federal benefit	(4.1)	(1.8)	(3.3)
Benefit from stock option exercises	(2.4)	0.0	0.0
Acquisition related costs	1.9	0.0	0.0
Net effect of changes in tax rates	0.0	0.0	(0.3)
Uncertain tax positions and interest	(28.1)	0.5	0.5
Nondeductible expenses	1.6	0.5	1.5
Net effect of change in U.S. Tax Law	0.0	0.0	(40.4)
Other	0.2	0.2	0.6
Valuation allowance	16.2	2.2	1.2
(Benefit) expense from income taxes	$ (20.4)	$ 4.6	$ (41.2)