Segment Information - Revenue and Operating Income (Loss), by Segment (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Revenue:
Revenue before reimbursements (net revenue)	$ 118,981	$ 117,312	$ 343,992	$ 339,903
Reimbursements	4,523	5,033	14,148	16,517
Total revenue	123,504	122,345	358,140	356,420
Operating income (loss):
Operating income before restructuring charges	8,353	10,185	14,484	20,920
Restructuring charges		0	0	(810)
Operating income before restructuring charges	8,353	10,185	14,484	20,110
Europe Segment [Member]
Operating income (loss):
Restructuring charges				(800)
Operating Segments [Member]
Operating income (loss):
Operating income before restructuring charges	21,648	23,228	50,686	56,018
Operating Segments [Member] | Americas Segment [Member]
Revenue:
Revenue before reimbursements (net revenue)	71,073	72,424	208,026	196,614
Operating income (loss):
Operating income before restructuring charges	19,279	21,293	50,733	49,146
Operating Segments [Member] | Europe Segment [Member]
Revenue:
Revenue before reimbursements (net revenue)	24,380	21,538	67,502	75,746
Operating income (loss):
Operating income before restructuring charges	59	479	(6,042)	2,964
Operating Segments [Member] | Asia Pacific Segment [Member]
Revenue:
Revenue before reimbursements (net revenue)	23,528	23,350	68,464	67,543
Operating income (loss):
Operating income before restructuring charges	2,310	1,456	5,995	3,908
Operating Segments [Member] | Corporate [Member]
Operating income (loss):
Global operations support	(13,295)	(13,043)	(36,202)	(35,098)
Segment Reconciling Items [Member]
Operating income (loss):
Restructuring charges				$ (810)