Variable Interest Entities (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
Dec. 31, 2011
LIHTC funds [Member]
Variable Interest Entities Information
Variable Interest Entity, Carrying Amount of Assets, Consolidated VIE	$ 82
Variable Interest Entity, Carrying Amount of Assets, Unconsolidated VIE	125
Variable Interest Entity, Carrying Amount of Liabilities, Unconsolidated VIE	0
Maximum Exposure To Loss, Unconsolidated VIE	0
Education Loan Securitization Trusts [Member]
Variable Interest Entities Information
Variable Interest Entity, Carrying Amount of Assets, Consolidated VIE	2,761
Variable Interest Entity, Carrying Amount of Liabilities, Consolidated VIE	2,549
LIHTC investments [Member]
Variable Interest Entities Information
Variable Interest Entity, Carrying Amount of Assets, Unconsolidated VIE	993
Variable Interest Entity, Carrying Amount of Liabilities, Unconsolidated VIE	0
Maximum Exposure To Loss, Unconsolidated VIE	$ 482

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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