COST OF REVENUE (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
COST OF REVENUE
Compensation and benefits	$ 156,812	$ 113,145	$ 82,548
Outside fees and services	193,233	123,338	86,201
Reimbursable expenses	102,478	96,147	82,074
Technology and telecommunications	25,534	23,404	18,772
Depreciation and amortization	14,423	10,167	6,254
Total	$ 492,480	$ 366,201	$ 275,849