Risk Rating Under the Risk Rating System (Detail) (USD $) In Millions, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010
Credit Risk Associated With Commitments To Extend Credit [Line Items]
Commitments To Extend Credit	$ 47,719	$ 43,677
Pass
Credit Risk Associated With Commitments To Extend Credit [Line Items]
Commitments To Extend Credit	46,825	42,326
Risk Level Special Mention [Member]
Credit Risk Associated With Commitments To Extend Credit [Line Items]
Commitments To Extend Credit	480	556
Risk Level, Substandard
Credit Risk Associated With Commitments To Extend Credit [Line Items]
Commitments To Extend Credit	403	758
Risk Level, Doubtful
Credit Risk Associated With Commitments To Extend Credit [Line Items]
Commitments To Extend Credit	$ 11	$ 37