Schedule of Estimated Useful Lives (Detail)	12 Months Ended
	Dec. 31, 2017
Office Building
Property, Plant and Equipment [Line Items]
Estimated useful life	30 years
Residential Property
Property, Plant and Equipment [Line Items]
Estimated useful life	20 years
Computer Equipment and Software
Property, Plant and Equipment [Line Items]
Estimated useful life	3 years
Furniture, Fixtures And Other Equipment | Minimum
Property, Plant and Equipment [Line Items]
Estimated useful life	5 years
Furniture, Fixtures And Other Equipment | Maximum
Property, Plant and Equipment [Line Items]
Estimated useful life	7 years
Vehicles | Minimum
Property, Plant and Equipment [Line Items]
Estimated useful life	3 years
Vehicles | Maximum
Property, Plant and Equipment [Line Items]
Estimated useful life	5 years
Leasehold Improvements
Property, Plant and Equipment [Line Items]
Estimated useful life	Shorter of economic life or life of lease
Leasehold Land
Property, Plant and Equipment [Line Items]
Estimated useful life	Shorter of economic life or life of lease