Bank Premises and Equipment - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Property, Plant and Equipment [Line Items]
Depreciation and amortization expense	$ 233	$ 224	$ 225
Rental income from leased premises	17	19	19
Bank premises and equipment impairment	(21)
Other noninterest income	other noninterest income
Cancelable And Noncancelable Lease Obligations
Property, Plant and Equipment [Line Items]
Occupancy Costs	$ 99	$ 99	$ 98