Risk Rating Under the Risk Rating System (Detail) (USD $) In Millions, unless otherwise specified	Jun. 30, 2014	Dec. 31, 2013
Credit Risk Associated With Commitments To Extend Credit
Commitments To Extend Credit	$ 62,121	$ 62,050
Pass
Credit Risk Associated With Commitments To Extend Credit
Commitments To Extend Credit	61,290	61,364
Risk Level, Special Mention
Credit Risk Associated With Commitments To Extend Credit
Commitments To Extend Credit	372	369
Risk Level, Substandard
Credit Risk Associated With Commitments To Extend Credit
Commitments To Extend Credit	458	316
Risk Level, Doubtful
Credit Risk Associated With Commitments To Extend Credit
Commitments To Extend Credit	$ 1	$ 1