Bank Premises and Equipment (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011 years	Dec. 31, 2010 years
Property, Plant and Equipment [Line Items]
Land and improvements	834	797
Buildings	1,623	1,593
Equipment	1,318	1,296
Leasehold improvements	394	393
Construction in Progress	140	92
Accumulated depreciation and amortization	(1,862)	(1,782)
Total	2,447	2,389
Building [Member]
Property, Plant and Equipment [Line Items]
Estimated useful life, minimum	5	5
Estimated useful life, maximum	50	50
Equipment [Member]
Property, Plant and Equipment [Line Items]
Estimated useful life, minimum	3	3
Estimated useful life, maximum	20	20
Leasehold Improvements [Member]
Property, Plant and Equipment [Line Items]
Estimated useful life, minimum	3	3
Estimated useful life, maximum	40	40