Mortgage Loans TDRs with Sub Defaults (Details) $ in Millions	3 Months Ended	9 Months Ended
Sep. 30, 2019 USD ($) contracts	Sep. 30, 2018 USD ($) contracts	Sep. 30, 2019 USD ($) contracts	Sep. 30, 2018 USD ($) contracts
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of loans troubled debt restructurings subsequent default \| contracts	4,203	4,310	13,909	14,583
Recorded investment troubled debt restructurings subsequent default \| $	$ 659	$ 624	$ 2,129	$ 2,150
Single-family [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of loans troubled debt restructurings subsequent default \| contracts	4,202	4,309	13,907	14,581
Recorded investment troubled debt restructurings subsequent default \| $	$ 646	$ 622	$ 2,110	$ 2,146
Single-family [Member] \| Primary [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of loans troubled debt restructurings subsequent default \| contracts	3,780	3,720	12,343	12,372
Recorded investment troubled debt restructurings subsequent default \| $	$ 585	$ 519	$ 1,864	$ 1,774
Single-family [Member] \| Government [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of loans troubled debt restructurings subsequent default \| contracts	28	8	56	37
Recorded investment troubled debt restructurings subsequent default \| $	$ 2	$ 0	$ 7	$ 4
Single-family [Member] \| Alt-A
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of loans troubled debt restructurings subsequent default \| contracts	307	438	1,157	1,703
Recorded investment troubled debt restructurings subsequent default \| $	$ 43	$ 74	$ 174	$ 275
Single-family [Member] \| Other [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of loans troubled debt restructurings subsequent default \| contracts	87	143	351	469
Recorded investment troubled debt restructurings subsequent default \| $	$ 16	$ 29	$ 65	$ 93
Multifamily [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of loans troubled debt restructurings subsequent default \| contracts	1	1	2	2
Recorded investment troubled debt restructurings subsequent default \| $	$ 13	$ 2	$ 19	$ 4

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Number of financing receivable contracts modified as troubled debt restructuring within previous 12 months, with subsequent payment default.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 34
-URI http://asc.fasb.org/extlink&oid=118936363&loc=SL6953682-111524

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Amount of financing receivable modified as troubled debt restructuring within previous 12 months, with subsequent payment default.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 34
-Subparagraph (a)(2)
-URI http://asc.fasb.org/extlink&oid=118936363&loc=SL6953682-111524

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