Bank Premises and Equipment (Detail) (USD $) In Millions, unless otherwise specified			12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2012 Building [Member] Upper Limit	Dec. 31, 2012 Building [Member] Minimum [Member]	Dec. 31, 2012 Equipment [Member] Upper Limit	Dec. 31, 2012 Equipment [Member] Minimum [Member]	Dec. 31, 2012 Leasehold Improvements [Member] Upper Limit	Dec. 31, 2012 Leasehold Improvements [Member] Minimum [Member]
Property, Plant and Equipment [Line Items]
Land and improvements	$ 841	$ 834
Buildings	1,692	1,623
Equipment	1,460	1,318
Leasehold improvements	386	394
Construction in Progress	141	140
Accumulated depreciation and amortization	(1,978)	(1,862)
Total	$ 2,542	$ 2,447
Useful life			50 years	5 years	20 years	2 years	40 years	3 years