FAIR VALUE MEASUREMENTS - Schedule of reconciliation of opening and closing balances for fair value measurements categorized within Level 3 (Details) - Contingent Consideration Liabilities - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Convertible Note Derivative Liability
Beginning balance	$ 7,300	$ 7,689
Payments	(100)	(100)
Accretion expense	0	247
Valuation adjustment	77	0
Reclassification to other current and long-term liabilities	(7,277)	0
Ending balance	$ 0	$ 7,836