Variable Interest Entities (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
Mar. 31, 2012
LIHTC funds [Member]
Variable Interest Entities Information
Variable Interest Entity, Carrying Amount of Assets, Consolidated VIE	$ 87
Variable Interest Entity, Carrying Amount of Assets, Unconsolidated VIE	124
Education Loan Securitization Trusts [Member]
Variable Interest Entities Information
Variable Interest Entity, Carrying Amount of Assets, Consolidated VIE	2,747
Variable Interest Entity, Carrying Amount of Liabilities, Consolidated VIE	2,542
LIHTC investments [Member]
Variable Interest Entities Information
Variable Interest Entity, Carrying Amount of Assets, Unconsolidated VIE	1,035
Maximum Exposure To Loss, Unconsolidated VIE	$ 490

The carrying amount of the variable interest entity's assets consolidated into the statement of financial position. In general, a VIE is a corporation, partnership, trust, or any other legal structure used for business purposes that either (a) does not have equity investors with voting rights or (b) has equity investors that do not provide sufficient financial resources for the entity to support its activities. A VIE often holds financial assets, including loans or receivables, real estate or other property. A VIE may be essentially passive or it may engage in research and development or other activities on behalf of another company.

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The carrying amount of the variable interest entity's liabilities consolidated into the statement of financial position. In general, a VIE is a corporation, partnership, trust, or any other legal structure used for business purposes that either (a) does not have equity investors with voting rights or (b) has equity investors that do not provide sufficient financial resources for the entity to support its activities. A VIE often holds financial assets, including loans or receivables, real estate or other property. A VIE may be essentially passive or it may engage in research and development or other activities on behalf of another company.

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