Property and Equipment Estimated Useful Lives using Straight-Line Method (Detail)	12 Months Ended
	Dec. 31, 2011 Year
Computer and office equipment
Property, Plant and Equipment [Line Items]
Property, plant and equipment, minimum useful lives	3
Property, plant and equipment, maximum useful lives	5
Furniture and fixtures
Property, Plant and Equipment [Line Items]
Property, plant and equipment, useful lives	7
Leasehold improvements
Property, Plant and Equipment [Line Items]
Property, plant and equipment, useful lives	Lesser of useful life of improvement or remaining term of lease
Vehicles and other
Property, Plant and Equipment [Line Items]
Property, plant and equipment, minimum useful lives	4
Property, plant and equipment, maximum useful lives	5