REVENUE (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Schedule of revenue [Line Items]
Revenue	$ 50,465	$ 121,444
Service revenue
Schedule of revenue [Line Items]
Revenue	48,080	113,176
Reimbursable expenses
Schedule of revenue [Line Items]
Revenue	2,013	7,845
Non-controlling interests
Schedule of revenue [Line Items]
Revenue	$ 372	$ 423