INCOME TAXES - Components of Deferred Tax Assets (Liabilities) (Details) - USD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020
Deferred tax assets:
Accrued payroll & employee benefits	$ 13.2	$ 15.9
Workers’ compensation	10.5	9.6
Share-based compensation	6.2	5.1
Legal & compliance matters	6.2	7.0
Lease liability	27.3	25.2
Provider relief fund advance (1)	0.0	15.6
Deferred social security taxes (2)	6.9	14.3
Net operating loss carryforwards	13.6	2.4
Tax credit carryforwards	2.5	2.9
Other assets	0.5	0.6
Gross deferred tax assets	86.9	98.6
Less: valuation allowance	(3.3)	(0.1)
Net deferred tax assets	83.6	98.5
Deferred tax liabilities:
Property and equipment	(8.1)	(3.8)
Amortization of intangible assets	(32.3)	(11.8)
Deferred revenue	(4.5)	(9.0)
Investment in partnerships	(10.8)	0.0
Right-of-use asset	(26.7)	(24.9)
Other liabilities	(0.9)	(1.0)
Gross deferred tax liabilities	(83.3)	(50.5)
Net deferred tax assets (liabilities)	$ (0.3)	$ (48.0)