Financial Guarantees - Financial Guarantees and Maximum Recovery (Details) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2022	Dec. 31, 2021
Financial Guarantees and Maximum Recovery [Line Items]
Contractual terms of our guarantees	31 years
Maximum Exposure	$ 13,898	$ 14,156
Guaranty Obligation	99	101
Maximum Recovery	5,575	5,743
Unconsolidated Fannie Mae MBS \| Unconsolidated VIEs
Financial Guarantees and Maximum Recovery [Line Items]
Maximum Exposure	3,570	3,733
Guaranty Obligation	15	16
Maximum Recovery	3,470	3,626
Other guaranty arrangements \| Unconsolidated VIEs
Financial Guarantees and Maximum Recovery [Line Items]
Maximum Exposure	10,328	10,423
Guaranty Obligation	84	85
Maximum Recovery	2,105	2,117
Other agency \| Unconsolidated VIEs
Financial Guarantees and Maximum Recovery [Line Items]
Single security, Freddie Mac issued securities backing unconsolidated Fannie Mae securities	$ 236,100	$ 212,300

[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.

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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.

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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://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 460
-SubTopic 10
-Section 50
-Paragraph 4
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=124440162&loc=d3e12069-110248

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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://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 460
-SubTopic 10
-Section 50
-Paragraph 4
-Subparagraph (b)(1)
-URI http://asc.fasb.org/extlink&oid=124440162&loc=d3e12069-110248

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- Definition

Describe the approximate term of the guarantee or each group of similar guarantees.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 460
-SubTopic 10
-Section 50
-Paragraph 4
-Subparagraph (a)(1)
-URI http://asc.fasb.org/extlink&oid=124440162&loc=d3e12069-110248

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