Mortgage Loans TDRs with Sub Defaults (Details) $ in Millions	12 Months Ended
Dec. 31, 2020 USD ($) contracts	Dec. 31, 2019 USD ($) contracts	Dec. 31, 2018 USD ($) contracts
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of loans troubled debt restructurings subsequent default \| contracts	15,586	17,851	21,744
Recorded investment troubled debt restructurings subsequent default \| $	$ 2,814	$ 2,758	$ 3,224
Single-Family [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of loans troubled debt restructurings subsequent default \| contracts	15,582	17,849	21,742
Recorded investment troubled debt restructurings subsequent default \| $	$ 2,798	$ 2,740	$ 3,221
Single-Family [Member] \| Fixed Rate Residential Mortgage [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of loans troubled debt restructurings subsequent default \| contracts	14,127	15,189	18,344
Recorded investment troubled debt restructurings subsequent default \| $	$ 2,578	$ 2,366	$ 2,675
Single-Family [Member] \| FixedRateResidentialMortgage15yearMember [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of loans troubled debt restructurings subsequent default \| contracts	148	594	206
Recorded investment troubled debt restructurings subsequent default \| $	$ 10	$ 45	$ 15
Single-Family [Member] \| Adjustable Rate Residential Mortgage [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of loans troubled debt restructurings subsequent default \| contracts	16	91	63
Recorded investment troubled debt restructurings subsequent default \| $	$ 2	$ 14	$ 8
Single-Family [Member] \| Other [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of loans troubled debt restructurings subsequent default \| contracts	1,291	1,975	3,129
Recorded investment troubled debt restructurings subsequent default \| $	$ 208	$ 315	$ 523
Multifamily [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of loans troubled debt restructurings subsequent default \| contracts	4	2	2
Recorded investment troubled debt restructurings subsequent default \| $	$ 16	$ 18	$ 3

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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=121611835&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=121611835&loc=SL6953682-111524

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