Bank Premises and Equipment - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Property, Plant and Equipment [Line Items]
Depreciation and amortization expense	$ 224	$ 225	$ 227
Rental income from leased premises	19	19	16
Net occupancy expense	305	298	308
Cancelable And Noncancelable Lease Obligations
Property, Plant and Equipment [Line Items]
Net occupancy expense	$ 99	$ 98	$ 102