INCOME TAXES - Components of Deferred Tax Assets (Liabilities) (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Deferred tax assets:
Allowance for doubtful accounts	$ 0.0	$ 5.6
Accrued payroll & employee benefits	15.1	11.2
Workers’ compensation	9.0	8.3
Amortization of intangible assets	0.0	14.7
Share-based compensation	7.9	6.9
Compliance matters	4.8	2.2
Net operating loss carryforwards	3.7	5.9
Tax credit carryforwards	3.1	2.8
Other	0.8	0.7
Gross deferred tax assets	44.4	58.3
Less: valuation allowance	(0.4)	(0.7)
Net deferred tax assets	44.0	57.6
Deferred tax liabilities:
Property and equipment	(4.3)	(4.4)
Amortization of intangible assets - deferred tax liability	(0.3)	0.0
Deferred revenue	(13.5)	(13.5)
Investment in partnerships	(3.3)	(3.1)
Other liabilities	(1.2)	(0.8)
Gross deferred tax liabilities	(22.6)	(21.8)
Net deferred tax assets (liabilities)	$ 21.4	$ 35.8