Net Property and Equipment (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2011		Dec. 31, 2010
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	$ 57,087		$ 52,605
Less: accumulated depreciation and amortization	(36,608)		(34,066)
Property and equipment, net	20,479		18,539
Computer and office equipment
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	38,295	[1]	34,788	[1]
Furniture and fixtures
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	11,493		10,803
Leasehold improvements
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	7,193		6,708
Vehicles and other
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	$ 106		$ 306

[1] Includes $4.6 million and $4.2 million of computer and office equipment under capital lease for the years ended December 31, 2011 and 2010, respectively.