Mortgage Loans TDRs with Sub Defaults (Details) $ in Millions	3 Months Ended	6 Months Ended
Jun. 30, 2018 USD ($) contracts	Jun. 30, 2017 USD ($) contracts	Jun. 30, 2018 USD ($) contracts	Jun. 30, 2017 USD ($) contracts
Financing Receivable, Modifications [Line Items]
Number of loans troubled debt restructurings subsequent default \| contracts	4,568	5,029	10,273	10,343
Recorded investment troubled debt restructurings subsequent default \| $	$ 674	$ 719	$ 1,526	$ 1,480
Single-family [Member]
Financing Receivable, Modifications [Line Items]
Number of loans troubled debt restructurings subsequent default \| contracts			10,272	10,342
Recorded investment troubled debt restructurings subsequent default \| $			$ 1,524	$ 1,476
Single-family [Member] \| Primary [Member]
Financing Receivable, Modifications [Line Items]
Number of loans troubled debt restructurings subsequent default \| contracts	3,834	4,238	8,652	8,717
Recorded investment troubled debt restructurings subsequent default \| $	$ 554	$ 589	$ 1,255	$ 1,210
Single-family [Member] \| Government [Member]
Financing Receivable, Modifications [Line Items]
Number of loans troubled debt restructurings subsequent default \| contracts	15	25	29	44
Recorded investment troubled debt restructurings subsequent default \| $	$ 2	$ 3	$ 4	$ 5
Single-family [Member] \| Alt-A [Member]
Financing Receivable, Modifications [Line Items]
Number of loans troubled debt restructurings subsequent default \| contracts	588	616	1,265	1,230
Recorded investment troubled debt restructurings subsequent default \| $	$ 92	$ 97	$ 201	$ 193
Single-family [Member] \| Other [Member]
Financing Receivable, Modifications [Line Items]
Number of loans troubled debt restructurings subsequent default \| contracts	131	150	326	351
Recorded investment troubled debt restructurings subsequent default \| $	$ 26	$ 30	$ 64	$ 68
Multifamily [Member]
Financing Receivable, Modifications [Line Items]
Number of loans troubled debt restructurings subsequent default \| contracts			1	1
Recorded investment troubled debt restructurings subsequent default \| $			$ 2	$ 4

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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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