REVENUE - Schedule of Components of Revenue (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Disaggregation of Revenue [Line Items]
Revenue	$ 40,421	$ 46,041	$ 79,937	$ 96,506
Service revenue
Disaggregation of Revenue [Line Items]
Revenue	37,638	43,966	75,401	92,046
Reimbursable expenses
Disaggregation of Revenue [Line Items]
Revenue	2,609	1,936	4,201	3,949
Non-controlling interests
Disaggregation of Revenue [Line Items]
Revenue	$ 174	$ 139	$ 335	$ 511