Mortgage Loans Non-accrual Loans (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
Jun. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019
Financing Receivable, Nonaccrual [Line Items]
Recorded investment in nonaccrual loans	$ 28,069	$ 28,069	$ 27,265	$ 27,981
Financing Receivable, Nonaccrual, Interest Income	88	257
Single-family [Member]
Financing Receivable, Nonaccrual [Line Items]
Loans and Leases Receivable, Impaired, Interest Lost on Nonaccrual Loans	246	420
Recorded investment in nonaccrual loans	27,753	27,753	27,174	27,546
Financing Receivable, Nonaccrual, Interest Income	88	256
Financing Receivable, Accrued Interest, Writeoff	45	132
Single-family [Member] \| FixedRateResidentialMortgage15yearMember
Financing Receivable, Nonaccrual [Line Items]
Recorded investment in nonaccrual loans	844	844	856	858
Financing Receivable, Nonaccrual, Interest Income	2	6
Single-family [Member] \| Other [Member]
Financing Receivable, Nonaccrual [Line Items]
Recorded investment in nonaccrual loans	2,851	2,851	2,827	2,973
Financing Receivable, Nonaccrual, Interest Income	10	27
Single-family [Member] \| Adjustable Rate Residential Mortgage [Member]
Financing Receivable, Nonaccrual [Line Items]
Financing Receivable, Nonaccrual, Interest Income	1	2
Single-family [Member] \| Adjustable Rate Loans
Financing Receivable, Nonaccrual [Line Items]
Recorded investment in nonaccrual loans	275	275	279	288
Single-family [Member] \| Fixed Rate Residential Mortgage
Financing Receivable, Nonaccrual [Line Items]
Recorded investment in nonaccrual loans	23,783	23,783	23,212	23,427
Financing Receivable, Nonaccrual, Interest Income	75	221
Multifamily [Member]
Financing Receivable, Nonaccrual [Line Items]
Loans and Leases Receivable, Impaired, Interest Lost on Nonaccrual Loans	3	3
Recorded investment in nonaccrual loans	316	316	$ 91	$ 435
Financing Receivable, Nonaccrual, Interest Income	0	1
Financing Receivable, Accrued Interest, Writeoff	$ 2	$ 2

Amount of writeoff of accrued interest on financing receivable recognized by reversing interest income.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 20
-Section 50
-Paragraph 3D
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+ 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=121599337&loc=SL82919258-210447

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Amount of financing receivable on nonaccrual status.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
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-SubTopic 10
-Section 50
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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=121599337&loc=SL82919258-210447

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Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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