Property and Equipment, Net - Components of Company's Property and Equipment (Detail) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 105,857	$ 107,162
Accumulated depreciation	(70,136)	(64,800)
Property and equipment, net	35,721	42,362
Leasehold improvements [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	43,120	44,043
Office furniture, fixtures and equipment [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	24,273	24,067
Computer equipment and software [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 38,464	$ 39,052