REVENUE REVENUE (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Schedule of revenue [Line Items]
Revenue	$ 234,979	$ 252,745	$ 726,147	$ 758,676
Service revenue
Schedule of revenue [Line Items]
Revenue	224,308	239,782	692,254	715,386
Reimbursable expenses
Schedule of revenue [Line Items]
Revenue	9,866	12,080	31,786	41,317
Non-controlling interests
Schedule of revenue [Line Items]
Revenue	$ 805	$ 883	$ 2,107	$ 1,973