Accounting for Transfers and Servicing of Financial Assets and Variable Interest Entities (Details Textual) (USD $)	3 Months Ended	9 Months Ended
Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2011	Sep. 30, 2010	Dec. 31, 2010
Additional Accounting for Transfers and Servicing of Financial Assets and Variable Interest Entities (Textual) [Abstract]
Realized federal and state income tax credits on investments	$ 191,000,000	$ 189,000,000	$ 510,000,000	$ 500,000,000
Amortization expense recorded in tax expense on tax-advantaged investments	60,000,000	72,000,000	175,000,000	159,000,000
Amortization expense recognized in other noninterest expense on tax-advantaged investments	144,000,000	136,000,000	386,000,000	391,000,000
Short-term borrowings related to tender option bond program	5,300,000,000		5,300,000,000		5,700,000,000
Available-for-sale securities related to the tender option bond program	5,300,000,000		5,300,000,000		5,300,000,000
Minimum amount of investment in an unconsolidated VIE	1,000,000		1,000,000		1,000,000
Maximum amount of investment in an unconsolidated VIE	70,000,000		70,000,000		41,000,000
Aggregate amount of investments in unconsolidated VIEs	1,900,000,000		1,900,000,000		2,000,000,000
Company's maximum exposure to unconsolidated VIEs, including any tax implications	4,700,000,000		4,700,000,000		5,000,000,000
Company's maximum exposure to loss related to community development tax-advantaged investments	1,800,000,000		1,800,000,000		1,900,000,000
Company's maximum exposure previously recorded tax credits	2,900,000,000		2,900,000,000		3,000,000,000
Assets related to community development and tax-advantaged investment entities VIEs	5,100,000,000		5,100,000,000		3,800,000,000
Liabilities related to community development and tax-advantaged investment entities VIEs	3,700,000,000		3,700,000,000		2,600,000,000
Held-to-maturity Securities [Member]
Accounting for Transfers and Servicing of Financial Assets and Variable Interest Entities (Textual) [Abstract]
Held-to-maturity investment securities related to the conduit, in balance sheet	$ 214,000,000		$ 214,000,000		$ 400,000,000

Accounting for Transfers and Servicing of Financial Assets and Variable Interest Entities Textual Abstract.

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Additional accounting for transfers and servicing of financial assets and variable interest entities.

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Available-for-sale securities related to the tender option bond program.

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Maximum Amount Of Investment In Unconsolidated Variable Interest Entities.

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Company's maximum exposure previously recorded tax credits

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Company's maximum exposure to loss related to community development tax-advantaged investments.

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Minimum Amount Of Investment In Unconsolidated Variable Interest Entities.

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Variable Interest Carrying Amount Assets Related To Community Development And Tax Advantaged investment.

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Variable Interest Carrying Amount Liabilities related to community development and tax-advantaged investment.

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The portion of the difference between total income tax expense or benefit as reported in the Income Statement for the period and the expected income tax expense or benefit computed by applying the domestic federal statutory income tax rates to pretax income from continuing operations attributable to the different amortization methods allowed under generally accepted accounting principles and enacted tax laws.

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The portion of the difference between total income tax expense or benefit as reported in the Income Statement and the expected income tax expense or benefit computed by applying the domestic federal statutory income tax rates to pretax income from continuing operations attributable to investment tax credits generated or utilized under enacted tax laws during the period.

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This item represents the amount of amortization of purchase premium related to an investment in debt securities. The purchase premium is amortized to expense over the life (holding period) of the security to arrive at an amount of periodic interest income which results in a constant effective yield on the investment.

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The carrying amount of the consolidated Variable Interest Entity's assets included in the reporting entity's statement of financial position.

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The reporting entity's maximum amount of exposure to loss as a result of its involvement with the Variable Interest Entity (VIE).

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The net carrying amount of the assets and liabilities in the reporting entity's statement of financial position that relate to the reporting entity's variable interest in the Variable Interest Entity (VIE).

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