Revenues by Client Location (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues	$ 103,800	$ 80,176	$ 198,183	$ 152,978
Reimbursable expenses and other revenues
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues	1,706	1,706	2,793	2,806
United States
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues	48,565	39,387	94,604	76,644
United Kingdom
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues	22,858	17,292	45,786	30,960
Russia
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues	9,393	10,309	18,491	19,812
Switzerland
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues	6,797	3,777	12,942	7,372
Germany
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues	3,959	1,757	7,441	3,082
Ukraine
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues	4,321	218	4,375	845
Kazakhstan
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues	1,662	1,909	3,333	3,654
Sweden
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues	1,017	1,439	2,472	2,737
Netherlands
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues	868	1,022	1,658	2,264
Other Countries
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues	$ 2,654	$ 1,360	$ 4,288	$ 2,802