Maximum Estimated Useful Lives by Asset Classification (Detail)	12 Months Ended
	Dec. 31, 2011
Leasehold Improvements
Property Plant and Equipment Estimated Useful Lives [Line Items]
Premises and equipment, 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, maximum estimated useful life	3
Software
Property Plant and Equipment Estimated Useful Lives [Line Items]
Premises and equipment, minimum estimated useful life	3
Premises and equipment, maximum estimated useful life	7
Computer hardware
Property Plant and Equipment Estimated Useful Lives [Line Items]
Premises and equipment, minimum estimated useful life	3
Premises and equipment, maximum estimated useful life	5