INCOME TAXES - Components of Deferred Tax Assets (Liabilities) (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Deferred tax assets:
Accrued payroll & employee benefits	$ 15.9	$ 15.1
Workers’ compensation	9.6	9.0
Share-based compensation	5.1	7.9
Legal & compliance matters	7.0	4.8
Lease liability	25.2	23.1
Provider relief fund advance (1)	15.6	0.0
Deferred social security taxes (2)	14.3	0.0
Net operating loss carryforwards	2.4	3.7
Tax credit carryforwards	2.9	3.1
Other	0.6	0.5
Gross deferred tax assets	98.6	67.2
Less: valuation allowance	(0.1)	(0.4)
Net deferred tax assets	98.5	66.8
Deferred tax liabilities:
Property and equipment	(3.8)	(4.3)
Amortization of intangible assets	(11.8)	(0.3)
Deferred revenue	(9.0)	(13.5)
Investment in partnerships	0.0	(3.3)
Right-of-use asset	(24.9)	(22.8)
Other liabilities	(1.0)	(1.2)
Gross deferred tax liabilities	(50.5)	(45.4)
Net deferred tax assets (liabilities)	$ 48.0	$ 21.4