INCOME TAXES - Schedule of Tax Rate (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Amount
U.S. federal statutory income tax	$ (21.6)	$ (52.3)	$ (19.0)
Permanent items	0.3	0.2	1.2
State taxes, net of federal benefit	(3.1)	(10.1)	(3.0)
Foreign tax rate differential	2.7	(0.5)	(9.3)
Compensation related items	2.0	(3.3)	(5.1)
Change in valuation allowance	17.3	59.0	29.0
Unrecognized tax positions	0.0	6.2	2.8
Prior year true-ups	5.6	6.8	3.4
Tax Cuts and Jobs Act	0.0	(11.5)	17.3
Income tax expense (benefit)	$ 3.2	$ (5.5)	$ 17.3
Effective Rate
U.S. federal statutory income tax	21.00%	21.00%	35.00%
Permanent items	(0.30%)	(0.10%)	(2.20%)
State taxes, net of federal benefit	3.00%	4.10%	5.50%
Foreign tax rate differential	(2.60%)	0.20%	17.20%
Compensation related items	(1.90%)	1.30%	9.40%
Change in valuation allowance	(16.80%)	(23.70%)	(53.50%)
Unrecognized tax positions	0.00%	(2.50%)	(5.20%)
Prior year true-ups	(5.40%)	(2.70%)	(6.30%)
Tax Cuts and Jobs Act	0.00%	4.60%	(31.90%)
Total income tax provision (benefit)	(3.00%)	2.20%	(32.00%)