Risk Rating Under the Risk Rating System (Detail) (USD $) In Millions, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013
Credit Risk Associated With Commitments To Extend Credit
Commitments To Extend Credit	$ 63,021	$ 62,050
Pass
Credit Risk Associated With Commitments To Extend Credit
Commitments To Extend Credit	62,301	61,364
Risk Level, Special Mention
Credit Risk Associated With Commitments To Extend Credit
Commitments To Extend Credit	382	369
Risk Level, Substandard
Credit Risk Associated With Commitments To Extend Credit
Commitments To Extend Credit	338	316
Risk Level, Doubtful
Credit Risk Associated With Commitments To Extend Credit
Commitments To Extend Credit		$ 1