Mortgage Loans Non-accrual Loans (Details) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2020	Dec. 31, 2019
Financing Receivable, Nonaccrual [Line Items]
Recorded investment in nonaccrual loans	$ 27,265	$ 27,981
Financing Receivable, Nonaccrual, Interest Income	117
Single-family [Member]
Financing Receivable, Nonaccrual [Line Items]
Loans and Leases Receivable, Impaired, Interest Lost on Nonaccrual Loans	182
Recorded investment in nonaccrual loans	27,174	27,546
Financing Receivable, Nonaccrual, Interest Income	117
FinancingReceivablePeriodPastDueWriteOff	87
Single-family [Member] \| Fixed Rate Residential Mortgage 30 and 20 year Member
Financing Receivable, Nonaccrual [Line Items]
Recorded investment in nonaccrual loans	23,212	23,427
Financing Receivable, Nonaccrual, Interest Income	101
Single-family [Member] \| FixedRateResidentialMortgage15yearMember
Financing Receivable, Nonaccrual [Line Items]
Recorded investment in nonaccrual loans	856	858
Financing Receivable, Nonaccrual, Interest Income	2
Single-family [Member] \| Other [Member]
Financing Receivable, Nonaccrual [Line Items]
Recorded investment in nonaccrual loans	2,827	2,973
Financing Receivable, Nonaccrual, Interest Income	13
Single-family [Member] \| AdjustableRate
Financing Receivable, Nonaccrual [Line Items]
Recorded investment in nonaccrual loans	279
Single-family [Member] \| Adjustable Rate Residential Mortgage
Financing Receivable, Nonaccrual [Line Items]
Recorded investment in nonaccrual loans		288
Financing Receivable, Nonaccrual, Interest Income	1
Multifamily [Member]
Financing Receivable, Nonaccrual [Line Items]
Loans and Leases Receivable, Impaired, Interest Lost on Nonaccrual Loans	1
Recorded investment in nonaccrual loans	91	$ 435
Financing Receivable, Nonaccrual, Interest Income	$ 0

Financing Receivable Period Past Due Write Off

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- Definition

Amount of interest income on financing receivable on nonaccrual status.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 20
-Section 50
-Paragraph 16
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=119407570&loc=SL82919258-210447

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

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- Definition

Amount of financing receivable on nonaccrual status.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 7
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=118936363&loc=d3e5111-111524

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 20
-Section 50
-Paragraph 16
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=119407570&loc=SL82919258-210447

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- Definition

Reflects the amount of additional interest income that would have been recorded if impaired or nonperforming loans were instead current, in compliance with their original terms, and outstanding throughout the reporting period or since origination (if held for part of the period).

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 40
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=118939409&loc=d3e18794-111554

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