Financial Guarantees Financial Guarantees and Maximum Recovery (Details) - USD ($) $ in Millions	9 Months Ended
Sep. 30, 2020	Dec. 31, 2019
Financial Guarantees and Maximum Recovery [Line Items]
Contractual terms of our guarantees	32 years
Maximum Exposure	$ 16,830	$ 18,471
Guaranty Obligation	128	154
Maximum Recovery	7,090	8,098
Unconsolidated Fannie Mae MBS [Member] \| Unconsolidated VIEs [Member]
Financial Guarantees and Maximum Recovery [Line Items]
Maximum Exposure	4,880	5,801
Guaranty Obligation	18	26
Maximum Recovery	4,666	5,545
Other guaranty arrangements [Member] \| Unconsolidated VIEs [Member]
Financial Guarantees and Maximum Recovery [Line Items]
Maximum Exposure	11,950	12,670
Guaranty Obligation	110	128
Maximum Recovery	2,424	2,553
Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member] \| Unconsolidated VIEs [Member]
Financial Guarantees and Maximum Recovery [Line Items]
Single security, Freddie Mac issued securities backing unconsolidated Fannie Mae securities	$ 117,700	$ 50,100

Represents the original contractual term of guarantees.

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- Definition

[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.

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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=121555522&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=121555522&loc=d3e12069-110248

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