Income Taxes - Reconciliation of Effective Income Tax Rate (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Percent and amount of pretax income
Federal statutory rate		21.00%	21.00%	35.00%
State and local income taxes, net of federal benefits		9.90%	(6.20%)	6.30%
Nondeductible expenses		4.00%	6.90%	(16.00%)
Goodwill impairment losses		14.40%	0.00%	(20.50%)
Compensation		0.30%	(3.80%)	29.50%
Contingent liability settlement		0.00%	0.00%	22.90%
Foreign		0.10%	(0.10%)	11.30%
Valuation allowance		0.00%	(20.30%)	2962.30%
Tax Act - deferred rate change		0.00%	0.00%	(1043.50%)
Other		0.20%	(1.50%)	3.30%
Total effective tax rate and income tax benefit (expense)		49.90%	(4.00%)	1990.60%
Amount of pretax income
Federal statutory rate		$ (18.1)	$ (18.9)	$ 8.8
State and local income taxes - net of federal benefits		(8.5)	5.6	1.6
Nondeductible expenses		(3.5)	(6.2)	(4.0)
Goodwill impairment		(12.4)	0.0	(5.1)
Compensation		(0.3)	3.4	7.4
Contingent liability settlement		0.0	0.0	5.7
Foreign		(0.1)	0.1	2.8
Valuation allowance	$ 22.4	0.0	18.3	741.9
Tax Act - deferred rate change		0.0	0.0	(261.3)
Other miscellaneous items		(0.1)	1.3	0.7
Total income tax benefit (expense)		$ (43.0)	$ 3.6	$ 498.5