Property and Equipment, Net (Parenthetical) (Detail)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011
Minimum | Office and computer equipment
Property, Plant and Equipment [Line Items]
Property plant and equipment useful life	3 years	3 years
Minimum | Office furniture and fixtures
Property, Plant and Equipment [Line Items]
Property plant and equipment useful life	5 years	5 years
Minimum | Internal-use Computer Software
Property, Plant and Equipment [Line Items]
Property plant and equipment useful life	3 years	3 years
Minimum | Leasehold Improvements
Property, Plant and Equipment [Line Items]
Property plant and equipment useful life	3 years	3 years
Maximum | Office and computer equipment
Property, Plant and Equipment [Line Items]
Property plant and equipment useful life	20 years	20 years
Maximum | Office furniture and fixtures
Property, Plant and Equipment [Line Items]
Property plant and equipment useful life	10 years	10 years
Maximum | Internal-use Computer Software
Property, Plant and Equipment [Line Items]
Property plant and equipment useful life	5 years	5 years
Maximum | Leasehold Improvements
Property, Plant and Equipment [Line Items]
Property plant and equipment useful life	20 years	20 years