REVENUE - Schedule of Components of Revenue (Details) - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2023	Mar. 31, 2022
Disaggregation of Revenue [Line Items]
Revenue	$ 39,461	$ 39,516
Service revenue
Disaggregation of Revenue [Line Items]
Revenue	37,071	37,763
Reimbursable expenses
Disaggregation of Revenue [Line Items]
Revenue	2,310	1,592
Non-controlling interests
Disaggregation of Revenue [Line Items]
Revenue	$ 80	$ 161

Amount, excluding tax collected from customer, of revenue from satisfaction of performance obligation by transferring promised good or service to customer. Tax collected from customer is tax assessed by governmental authority that is both imposed on and concurrent with specific revenue-producing transaction, including, but not limited to, sales, use, value added and excise.

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+ Details