Financial Guarantees and Maximum Recovery (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2015	Dec. 31, 2014
Financial Guarantees and Maximum Recovery [Line Items]
Maximum exposure	$ 31,573	$ 35,965
Guaranty obligation	329	382
Maximum recovery	11,726	14,222
Unconsolidated VIEs [Member] \| Unconsolidated Fannie Mae MBS [Member]
Financial Guarantees and Maximum Recovery [Line Items]
Maximum exposure	15,069	17,184
Guaranty obligation	194	214
Maximum recovery	8,857	9,775
Unconsolidated VIEs [Member] \| Other guaranty arrangements [Member]
Financial Guarantees and Maximum Recovery [Line Items]
Maximum exposure	16,504	18,781
Guaranty obligation	135	168
Maximum recovery	$ 2,869	$ 4,447
Minimum [Member]
Financial Guarantees and Maximum Recovery [Line Items]
Remaining contractual terms of our guarantee	P11D
Maximum [Member]
Financial Guarantees and Maximum Recovery [Line Items]
Remaining contractual terms of our guarantee	P37Y

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

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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.

+ Details

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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/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 460
-SubTopic 10
-Section 50
-Paragraph 4
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=6851643&loc=d3e12069-110248

+ 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/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 460
-SubTopic 10
-Section 50
-Paragraph 4
-Subparagraph (b)(1)
-URI http://asc.fasb.org/extlink&oid=6851643&loc=d3e12069-110248

+ Details

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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/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 460
-SubTopic 10
-Section 50
-Paragraph 4
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=6851643&loc=d3e12069-110248

+ Details

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