Maximum Estimated Useful Lives by Asset Classification (Detail)	12 Months Ended
	Dec. 31, 2012
Leasehold Improvements
Property Plant and Equipment Estimated Useful Lives [Line Items]
Premises and equipment, description of estimated useful life	Lesser of lease term or asset life
Furniture and equipment
Property Plant and Equipment Estimated Useful Lives [Line Items]
Premises and equipment, description of estimated useful life	3 years
Furniture and equipment | Upper Limit
Property Plant and Equipment Estimated Useful Lives [Line Items]
Premises and equipment, estimated useful life	3 years
Software
Property Plant and Equipment Estimated Useful Lives [Line Items]
Premises and equipment, description of estimated useful life	3-7 years
Software | Lower Limit
Property Plant and Equipment Estimated Useful Lives [Line Items]
Premises and equipment, estimated useful life	3 years
Software | Upper Limit
Property Plant and Equipment Estimated Useful Lives [Line Items]
Premises and equipment, estimated useful life	7 years
Computer hardware
Property Plant and Equipment Estimated Useful Lives [Line Items]
Premises and equipment, description of estimated useful life	3-5 years
Computer hardware | Lower Limit
Property Plant and Equipment Estimated Useful Lives [Line Items]
Premises and equipment, estimated useful life	3 years
Computer hardware | Upper Limit
Property Plant and Equipment Estimated Useful Lives [Line Items]
Premises and equipment, estimated useful life	5 years