COST OF REVENUE (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Cost of Revenue [Abstract]
Compensation and benefits	$ 261,839	$ 255,889	$ 156,812
Outside fees and services	248,278	243,325	193,233
Reimbursable expenses	107,344	137,634	102,478
Technology and telecommunications	43,177	48,834	25,534
Depreciation and amortization	26,689	21,498	14,423
Total	$ 687,327	$ 707,180	$ 492,480