Risk Rating Under the Risk Rating System (Detail) (USD $) In Millions	Sep. 30, 2011	Dec. 31, 2010	Sep. 30, 2010
Credit Risk Associated With Commitments To Extend Credit [Line Items]
Commitments To Extend Credit	$ 46,019	$ 43,677	$ 43,003
Pass
Credit Risk Associated With Commitments To Extend Credit [Line Items]
Commitments To Extend Credit	45,015	42,326	41,523
Risk Level Special Mention [Member]
Credit Risk Associated With Commitments To Extend Credit [Line Items]
Commitments To Extend Credit	545	556	650
Risk Level, Substandard
Credit Risk Associated With Commitments To Extend Credit [Line Items]
Commitments To Extend Credit	443	758	774
Risk Level, Doubtful
Credit Risk Associated With Commitments To Extend Credit [Line Items]
Commitments To Extend Credit	$ 16	$ 37	$ 56