STOCK-BASED COMPENSATION (Restricted Stock and Restricted Stock Units Additional Information) (Details) - USD ($) $ in Thousands	9 Months Ended
Sep. 30, 2020	Dec. 31, 2019
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	$ 897
Weighted-average remaining requisite service period	1 year 10 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	$ 73,991
Weighted-average remaining requisite service period	2 years 7 months 6 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	$ 34,399
Weighted-average remaining requisite service period	2 years 4 months 24 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	$ 1,137
Weighted-average remaining requisite service period	2 years 10 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	$ 4,096
Weighted-average remaining requisite service period	3 years
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	$ 18,577	$ 21,902
2020 Acquisitions \| Restricted stock units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Remaining unrecognized stock-based compensation cost	$ 698
Weighted-average remaining requisite service period	2 years 3 months 18 days
Estimated future operating results, period	2 years
Awards vesting period	3 years
Award value	$ 11,527

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