OPERATING SEGMENTS, Revenues by Client Location (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues	$ 140,150	$ 110,078	$ 397,532	$ 308,261
Reimbursable expenses and other revenues [Member]
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues	2,186	1,393	5,134	4,186
United States [Member]
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues	62,871	50,365	180,067	145,629
United Kingdom [Member]
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues	26,637	25,651	81,416	70,777
Switzerland [Member]
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues	13,920	8,496	33,934	21,438
Russia [Member]
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues	11,534	10,554	36,464	29,045
Canada [Member]
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues	9,162	3,270	22,980	5,816
Germany [Member]
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues	5,141	4,325	14,211	11,766
Kazakhstan [Member]
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues	2,921	2,967	7,414	6,300
Netherlands [Member]
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues	1,895	750	6,665	2,408
Sweden [Member]
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues	1,382	1,006	3,986	3,478
Spain [Member]
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues	448	387	1,689	1,109
Ukraine [Member]
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues	193	181	524	4,556
Other Countries [Member]
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues	$ 1,860	$ 733	$ 3,048	$ 1,753