REVENUE (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Schedule of revenue [Line Items]
Revenue	$ 95,342	$ 196,535	$ 216,786	$ 366,470
Service revenue
Schedule of revenue [Line Items]
Revenue	91,008	190,520	204,184	355,519
Reimbursable expenses
Schedule of revenue [Line Items]
Revenue	3,840	4,775	11,685	9,271
Non-controlling interests
Schedule of revenue [Line Items]
Revenue	$ 494	$ 1,240	$ 917	$ 1,680