Mortgage Loans TDRs with Sub Defaults (Details) $ in Millions	3 Months Ended	9 Months Ended
Sep. 30, 2017 USD ($) contracts	Sep. 30, 2016 USD ($) contracts	Sep. 30, 2017 USD ($) contracts	Sep. 30, 2016 USD ($) contracts
Financing Receivable, Modifications [Line Items]
Number of loans troubled debt restructurings subsequent default \| contracts	5,730	6,268	16,073	18,559
Recorded investment troubled debt restructurings subsequent default \| $	$ 816	$ 895	$ 2,296	$ 2,689
Single-family [Member]
Financing Receivable, Modifications [Line Items]
Number of loans troubled debt restructurings subsequent default \| contracts			16,072	18,559
Recorded investment troubled debt restructurings subsequent default \| $			$ 2,292	$ 2,689
Single-family [Member] \| Primary [Member]
Financing Receivable, Modifications [Line Items]
Number of loans troubled debt restructurings subsequent default \| contracts	4,900	5,268	13,617	15,377
Recorded investment troubled debt restructurings subsequent default \| $	$ 684	$ 734	$ 1,894	$ 2,174
Single-family [Member] \| Government [Member]
Financing Receivable, Modifications [Line Items]
Number of loans troubled debt restructurings subsequent default \| contracts	25	31	69	73
Recorded investment troubled debt restructurings subsequent default \| $	$ 3	$ 4	$ 8	$ 9
Single-family [Member] \| Alt-A [Member]
Financing Receivable, Modifications [Line Items]
Number of loans troubled debt restructurings subsequent default \| contracts	627	734	1,857	2,342
Recorded investment troubled debt restructurings subsequent default \| $	$ 95	$ 116	$ 288	$ 376
Single-family [Member] \| Other [Member]
Financing Receivable, Modifications [Line Items]
Number of loans troubled debt restructurings subsequent default \| contracts	178	235	529	767
Recorded investment troubled debt restructurings subsequent default \| $	$ 34	$ 41	$ 102	$ 130
Multifamily [Member]
Financing Receivable, Modifications [Line Items]
Number of loans troubled debt restructurings subsequent default \| contracts			1	0
Recorded investment troubled debt restructurings subsequent default \| $			$ 4	$ 0

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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=84173941&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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