COST OF REVENUE (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Cost of Revenue [Abstract]
Compensation and benefits	$ 240,487	$ 264,796	$ 261,839
Outside fees and services	325,459	301,116	248,278
Cost of real estate sold	24,398	1,040	0
Reimbursable expenses	39,912	52,011	107,344
Technology and telecommunications	42,340	44,295	43,177
Depreciation and amortization	27,269	26,787	26,689
Total	$ 699,865	$ 690,045	$ 687,327