COST OF REVENUE (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
COST OF REVENUE
Compensation and benefits	$ 113,145	$ 82,548	$ 62,791
Outside fees and services	123,338	86,201	60,583
Reimbursable expenses	96,147	82,074	47,449
Technology and communications	23,404	18,772	12,548
Depreciation and amortization	10,167	6,254	5,688
Total	$ 366,201	$ 275,849	$ 189,059