Carrying Amount of Covered Assets (Detail) (USD $) In Millions, unless otherwise specified	Sep. 30, 2012		Dec. 31, 2011
Covered Assets [Line Items]
Purchased Impaired Loans	$ 5,384		$ 5,854
Purchased Non-impaired Loans	5,235		6,407
Other Assets	1,737		2,800
Total	12,356		15,061
Commercial
Covered Assets [Line Items]
Purchased Impaired Loans	15		68
Purchased Non-impaired Loans	144		137
Total	159		205
Commercial Real Estate
Covered Assets [Line Items]
Purchased Impaired Loans	1,519		1,956
Purchased Non-impaired Loans	3,104		4,037
Total	4,623		5,993
Residential Mortgages
Covered Assets [Line Items]
Purchased Impaired Loans	3,850		3,830
Purchased Non-impaired Loans	1,184		1,360
Total	5,034		5,190
Credit Card
Covered Assets [Line Items]
Purchased Non-impaired Loans	5		6
Total	5		6
Other Retail
Covered Assets [Line Items]
Purchased Non-impaired Loans	798		867
Total	798		867
Losses reimbursable by FDIC
Covered Assets [Line Items]
Other Assets	1,539	[1]	2,526	[1]
Total	1,539	[1]	2,526	[1]
Covered Loans
Covered Assets [Line Items]
Purchased Impaired Loans	5,384		5,854
Purchased Non-impaired Loans	5,235		6,407
Other Assets	1,539		2,526
Total	12,158		14,787
Foreclosed real estate
Covered Assets [Line Items]
Other Assets	198		274
Total	$ 198		$ 274

[1] Relates to loss sharing agreements with remaining terms from 2 to 7 years.