STOCK-BASED COMPENSATION (Restricted Stock and Restricted Stock Units Additional Information) (Details) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2021	Dec. 31, 2020
Service Period \| Equity Classified Award \| Equity-Settled Award \| Restricted Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Remaining unrecognized stock-based compensation cost	$ 0.7
Weighted-average remaining requisite service period	1 year 4 months 24 days
Service Period \| Equity Classified Award \| Equity-Settled Award \| Restricted stock units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Remaining unrecognized stock-based compensation cost	$ 118.9
Weighted-average remaining requisite service period	3 years 2 months 12 days
Service Period \| Liability Classified Award \| Cash-Settled Award \| Restricted stock units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Remaining unrecognized stock-based compensation cost	$ 38.1
Weighted-average remaining requisite service period	2 years 8 months 12 days
Performance Target \| Equity Classified Award \| Equity-Settled Award \| Restricted Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Remaining unrecognized stock-based compensation cost	$ 0.9
Weighted-average remaining requisite service period	2 years 4 months 24 days
Performance Target \| Equity Classified Award \| Equity-Settled Award \| Restricted stock units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Remaining unrecognized stock-based compensation cost	$ 2.9
Weighted-average remaining requisite service period	2 years 6 months
Accrued compensation and benefits expenses \| Service Period \| Liability Classified Award \| Cash-Settled Award \| Restricted stock units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Liability associated with RSUs	$ 15.3	$ 26.8

Aggregate carrying value as of the balance sheet date of the liabilities for stock option plans and other equity-based compensation arrangements payable within one year (or the operating cycle, if longer).

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
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-Paragraph 1
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Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
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-SubTopic 10
-Section 50
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