Revenue from International Clients by Geographic Areas (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Revenues from External Customers and Long-Lived Assets [Line Items]
Geographic revenue	$ 142,985	$ 117,315	$ 283,449	$ 233,561
Geographic revenue percentage	100.00%	100.00%	100.00%	100.00%
U.S.
Revenues from External Customers and Long-Lived Assets [Line Items]
Geographic revenue	70,411	62,313	152,428	130,455
Geographic revenue percentage	49.00%	53.00%	54.00%	56.00%
Other Americas
Revenues from External Customers and Long-Lived Assets [Line Items]
Geographic revenue	5,464	6,449	9,304	10,211
Geographic revenue percentage	4.00%	6.00%	3.00%	4.00%
United Kingdom
Revenues from External Customers and Long-Lived Assets [Line Items]
Geographic revenue	24,643	21,228	53,557	36,667
Geographic revenue percentage	17.00%	18.00%	19.00%	16.00%
Other EMEA
Revenues from External Customers and Long-Lived Assets [Line Items]
Geographic revenue	34,008	21,530	50,308	41,628
Geographic revenue percentage	24.00%	18.00%	18.00%	18.00%
Asia Pacific
Revenues from External Customers and Long-Lived Assets [Line Items]
Geographic revenue	$ 8,459	$ 5,795	$ 17,852	$ 14,600
Geographic revenue percentage	6.00%	5.00%	6.00%	6.00%