Mortgage Loans TDRs with Sub Defaults (Details) $ in Millions	3 Months Ended	9 Months Ended
Sep. 30, 2016 USD ($) contracts	Sep. 30, 2015 USD ($) contracts	Sep. 30, 2016 USD ($) contracts	Sep. 30, 2015 USD ($) contracts
Financing Receivable, Modifications [Line Items]
Number of loans troubled debt restructurings subsequent default \| contracts	6,268	8,258	18,559	23,907
Recorded investment troubled debt restructurings subsequent default \| $	$ 895	$ 1,254	$ 2,689	$ 3,611
Single-family [Member]
Financing Receivable, Modifications [Line Items]
Number of loans troubled debt restructurings subsequent default \| contracts	6,268	8,258	18,559	23,904
Recorded investment troubled debt restructurings subsequent default \| $	$ 895	$ 1,254	$ 2,689	$ 3,605
Single-family [Member] \| Primary [Member]
Financing Receivable, Modifications [Line Items]
Number of loans troubled debt restructurings subsequent default \| contracts	5,268	6,847	15,377	19,726
Recorded investment troubled debt restructurings subsequent default \| $	$ 734	$ 1,003	$ 2,174	$ 2,870
Single-family [Member] \| Government [Member]
Financing Receivable, Modifications [Line Items]
Number of loans troubled debt restructurings subsequent default \| contracts	31	31	73	88
Recorded investment troubled debt restructurings subsequent default \| $	$ 4	$ 3	$ 9	$ 12
Single-family [Member] \| Alt-A [Member]
Financing Receivable, Modifications [Line Items]
Number of loans troubled debt restructurings subsequent default \| contracts	734	1,052	2,342	3,168
Recorded investment troubled debt restructurings subsequent default \| $	$ 116	$ 183	$ 376	$ 537
Single-family [Member] \| Other [Member]
Financing Receivable, Modifications [Line Items]
Number of loans troubled debt restructurings subsequent default \| contracts	235	328	767	922
Recorded investment troubled debt restructurings subsequent default \| $	$ 41	$ 65	$ 130	$ 186
Multifamily [Member]
Financing Receivable, Modifications [Line Items]
Number of loans troubled debt restructurings subsequent default \| contracts	0	0	0	3
Recorded investment troubled debt restructurings subsequent default \| $	$ 0	$ 0	$ 0	$ 6

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Number of financing receivables that have been modified by troubled debt restructurings within the previous 12 months and for which there was a payment default.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 34
-URI http://asc.fasb.org/extlink&oid=66008989&loc=SL6953682-111524

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Amount of investment related to financing receivables modified by troubled debt restructurings within the previous 12 months, for which there was a payment default.

+ References

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