COST OF REVENUE (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Cost of Revenue [Abstract]
Compensation and benefits	$ 135,502	$ 200,486	$ 240,487
Outside fees and services	240,796	278,380	325,459
Cost of real estate sold	42,763	47,659	24,398
Technology and telecommunications	36,302	41,588	42,340
Reimbursable expenses	24,172	30,039	39,912
Depreciation and amortization	13,721	24,013	27,269
Total	$ 493,256	$ 622,165	$ 699,865