Mortgage Loans Non-accrual Loans (Details) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2020
Financing Receivable, Nonaccrual [Line Items]
Recorded investment in nonaccrual loans	$ 36,138		$ 28,574
Financing Receivable, Nonaccrual, Interest Income	79	$ 117
Single-family [Member]
Financing Receivable, Nonaccrual [Line Items]
Loans and Leases Receivable, Impaired, Interest Lost on Nonaccrual Loans	307	182
Recorded investment in nonaccrual loans	33,985		26,505
Financing Receivable, Nonaccrual, Interest Income	71	117
Financing Receivable, Accrued Interest, Writeoff	108	87
Single-family [Member] \| FixedRateResidentialMortgage15yearMember
Financing Receivable, Nonaccrual [Line Items]
Recorded investment in nonaccrual loans	945		853
Financing Receivable, Nonaccrual, Interest Income	2	2
Single-family [Member] \| Other [Member]
Financing Receivable, Nonaccrual [Line Items]
Recorded investment in nonaccrual loans	2,583		2,475
Financing Receivable, Nonaccrual, Interest Income	4	13
Single-family [Member] \| Adjustable Rate Loans
Financing Receivable, Nonaccrual [Line Items]
Recorded investment in nonaccrual loans	284		270
Financing Receivable, Nonaccrual, Interest Income	1	1
Single-family [Member] \| Fixed Rate Residential Mortgage
Financing Receivable, Nonaccrual [Line Items]
Recorded investment in nonaccrual loans	30,173		22,907
Financing Receivable, Nonaccrual, Interest Income	64	101
Multifamily [Member]
Financing Receivable, Nonaccrual [Line Items]
Loans and Leases Receivable, Impaired, Interest Lost on Nonaccrual Loans	14	1
Recorded investment in nonaccrual loans	2,153		$ 2,069
Financing Receivable, Nonaccrual, Interest Income	8	0
Financing Receivable, Accrued Interest, Writeoff	$ 0	$ 0

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
-URI http://asc.fasb.org/extlink&oid=121599337&loc=SL120267969-210447

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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
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Amount of financing receivable on nonaccrual status.

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Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
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-SubTopic 10
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Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
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-Topic 326
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-Section 50
-Paragraph 16
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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).

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