Financial Guarantees (Details) - USD ($) $ in Millions	9 Months Ended
Sep. 30, 2026	Dec. 31, 2025
Financial Guarantees and Maximum Recovery [Line Items]
Contractual terms of our guarantees	29 years
Maximum Exposure	$ 11,086	$ 11,380
Guaranty Obligation	100	96
Maximum recovery	4,171	4,319
Unconsolidated Fannie Mae MBS \| Unconsolidated VIEs
Financial Guarantees and Maximum Recovery [Line Items]
Maximum Exposure	2,028	2,229
Guaranty Obligation	12	13
Maximum recovery	1,994	2,187
Other guaranty arrangements \| Unconsolidated VIEs
Financial Guarantees and Maximum Recovery [Line Items]
Maximum Exposure	9,058	9,151
Guaranty Obligation	88	83
Maximum recovery	2,177	2,132
Agency \| Unconsolidated VIEs
Financial Guarantees and Maximum Recovery [Line Items]
Single security, Freddie Mac issued securities backing unconsolidated Fannie Mae securities	$ 173,600	$ 184,300

[Line Items] for Financial Guarantees and Maximum Recovery [Table]

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- Definition

Portion of Freddie Mac securities backing commingled Fannie Mae-issued structured securities.

+ References

No definition available.

+ Details

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- Definition

Represents the maximum amount we could recover through available credit enhancements and recourse with third parties on guarantees recognized in our on and off balance sheets. Recoverability of such credit enhancements and recourse is subject to, among other factors, our mortgage insurers' and financial guarantors' ability to meet their obligations to us.

+ References

No definition available.

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- Definition

The current carrying amount of the liability for the freestanding or embedded guarantor's obligations under the guarantee or each group of similar guarantees.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 460
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 4
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482425/460-10-50-4

+ Details

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- Definition

Maximum potential amount of future payments (undiscounted) the guarantor could be required to make under the guarantee or each group of similar guarantees before reduction for potential recoveries under recourse or collateralization provisions.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 460
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 4
-Subparagraph (b)(1)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482425/460-10-50-4

+ Details

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- Definition

Term of guarantee or group of similar guarantees, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 460
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 4
-Subparagraph (a)(1)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482425/460-10-50-4

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