Consolidations and Transfers of Financial Assets Qualifying Sales of Portfolio Securitizations (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Transfers and Servicing [Abstract]
Net gain on portfolio securitizations	$ 34	$ 146	$ 26
Proceeds from the initial sale of securities from portfolio securitizations	672	1,000	660
Proceeds from portfolio securitizations accounted for as secured borrowings	421	0	0
Fair value of trading securities underlying the portfolio securitizations accounted for as secured borrowings	178
Unpaid principal balance of mortgage loans of consolidated trusts underlying the portfolio securitizations accounted for as secured borrowings	$ 201

Cash Flows between a transferor and a transferee attributable to newly transferred assets related to either a securitization, asset-backed financing arrangement, or similar transfer in which the transferor has continuing involvement with the transferred financial assets underlying the transaction (including, but not limited to, servicing, recourse, and restrictions on transferor's interests in the transferred financial assets).

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Reflects, by transferred financial asset type, the amount of sales proceeds in excess of or deficient from the sum of the carrying amounts of transferred financial assets plus transaction costs, including those transactions in which the seller/transferor has continuing involvement with the financial assets that have been transferred.

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