FAIR VALUE MEASUREMENTS - Changes in Level 3 liabilities measured at fair value (Details) - Level 3 - Recurring - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2020
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Balance at beginning of period	$ 6,911	$ 8,283
Change in fair value of contingent consideration	(2,155)	(3,282)
Contingent consideration paid	(2,085)	(2,085)
Foreign currency translation	(14)	(259)
Balance at end of period	$ 2,657	$ 2,657