Organization, Consolidation and Presentation of Financial Statements (Policies)	3 Months Ended
Mar. 31, 2021
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Transfers and Servicing of Financial Assets, Policy [Policy Text Block]	Transfers of Financial AssetsWe issue Fannie Mae MBS through portfolio securitization transactions by transferring pools of mortgage loans or mortgage-related securities to one or more trusts or special purpose entities. We are considered to be the transferor when we transfer assets from our own retained mortgage portfolio in a portfolio securitization transaction.We retain interests from the transfer and sale of mortgage-related securities to unconsolidated single-class and multi-class portfolio securitization trusts.

- Definition

Disclosure of accounting policy for transfers and servicing financial assets, including securitization transactions as well as repurchase and resale agreements. This disclosure may include how the entity (1) determines whether a transaction is accounted for as a sale; (2) accounts for a sale transaction, including the initial and subsequent accounting for any interests that the entity obtains or continues to hold in the transaction, how such interests are valued, and the significant assumptions used in the valuation; (3) accounts for a transaction that does not qualify for sale treatment (that is, a financing); and (4) accounts for its servicing assets and liabilities ("servicing"), including how such servicing is measured initially and subsequently, and the methodology and significant assumptions used to value such servicing.

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