Revenue from International Customers by Geographic Areas (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Revenues from External Customers and Long-Lived Assets [Line Items]
Geographic revenue	$ 116,246	$ 111,167
Geographic revenue percentage	100.00%	100.00%
U.S.
Revenues from External Customers and Long-Lived Assets [Line Items]
Geographic revenue	68,142	55,692
Geographic revenue percentage	59.00%	50.00%
United Kingdom
Revenues from External Customers and Long-Lived Assets [Line Items]
Geographic revenue	15,439	18,138
Geographic revenue percentage	13.00%	16.00%
Europe, Other
Revenues from External Customers and Long-Lived Assets [Line Items]
Geographic revenue	19,985	17,285
Geographic revenue percentage	17.00%	16.00%
Other
Revenues from External Customers and Long-Lived Assets [Line Items]
Geographic revenue	$ 12,680	$ 20,052
Geographic revenue percentage	11.00%	18.00%