Depreciation Expense Computed Using Straight-Line Method over Useful Lives (Detail)	12 Months Ended
	Dec. 31, 2012
Computer Hardware | Minimum
Property Plant and Equipment Estimated Useful Lives [Line Items]
Property and equipment, estimated useful lives (in years)	2 years
Computer Hardware | Maximum
Property Plant and Equipment Estimated Useful Lives [Line Items]
Property and equipment, estimated useful lives (in years)	3 years
Computer Software | Minimum
Property Plant and Equipment Estimated Useful Lives [Line Items]
Property and equipment, estimated useful lives (in years)	2 years
Computer Software | Maximum
Property Plant and Equipment Estimated Useful Lives [Line Items]
Property and equipment, estimated useful lives (in years)	5 years
Furniture and Equipment
Property Plant and Equipment Estimated Useful Lives [Line Items]
Property and equipment, estimated useful lives (in years)	5 years
Leasehold Improvements | Maximum
Property Plant and Equipment Estimated Useful Lives [Line Items]
Property and equipment, estimated useful lives (in years)	5 years