Estimated Useful Lives (Detail)	12 Months Ended
	Dec. 31, 2012
Office Building
Property Plant and Equipment Estimated Useful Lives [Line Items]
Estimated useful life	30 years
Computer equipment and software
Property Plant and Equipment Estimated Useful Lives [Line Items]
Estimated useful life	3 years
Furniture, fixtures and other equipment
Property Plant and Equipment Estimated Useful Lives [Line Items]
Estimated useful life	7 years
Vehicles
Property Plant and Equipment Estimated Useful Lives [Line Items]
Estimated useful life	3 years
Leasehold Improvements
Property Plant and Equipment Estimated Useful Lives [Line Items]
Estimated useful life	Shorter of economic life or life of lease
Leasehold Land
Property Plant and Equipment Estimated Useful Lives [Line Items]
Estimated useful life	Shorter of economic life or life of lease