Mortgage Loans Aging (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Dec. 31, 2019
Financing Receivable, Past Due [Line Items]
Days delinquent	$ 57,908	$ 55,266
Current	3,310,902	3,281,663
Total recorded investment in loans	3,368,810	3,336,929
Recorded investment in loans 90 days or more delinquent and accruing interest	155	164
Recorded investment in nonaccrual loans	27,265	27,981
Table Footnote [Abstract]
Nonaccrualloanswithnotallowance	8,088
30 to 59 Days Delinquent [Member]
Financing Receivable, Past Due [Line Items]
Days delinquent	34,188	31,240
60 to 89 Days Delinquent [Member]
Financing Receivable, Past Due [Line Items]
Days delinquent	7,777	8,326
Seriously Delinquent [Member]
Financing Receivable, Past Due [Line Items]
Days delinquent	15,943	15,700
Single-family [Member]
Financing Receivable, Past Due [Line Items]
Days delinquent	57,713	55,144
Current	2,973,403	2,951,167
Total recorded investment in loans	3,031,116	3,006,311
Recorded investment in loans 90 days or more delinquent and accruing interest	155	164
Recorded investment in nonaccrual loans	27,174	27,546
Table Footnote [Abstract]
Nonaccrualloanswithnotallowance	$ 8,055
Single-family [Member] | Minimum [Member]
Table Footnote [Abstract]
Serious delinquency, days past due	90 days
Single-family [Member] | 30 to 59 Days Delinquent [Member]
Financing Receivable, Past Due [Line Items]
Days delinquent	$ 34,151	31,233
Single-family [Member] | 60 to 89 Days Delinquent [Member]
Financing Receivable, Past Due [Line Items]
Days delinquent	7,777	8,326
Single-family [Member] | Seriously Delinquent [Member]
Financing Receivable, Past Due [Line Items]
Days delinquent	15,785	15,585
Single-family [Member] | Fixed Rate Residential Mortgage 30 and 20 year Member
Financing Receivable, Past Due [Line Items]
Days delinquent	49,651	47,090
Current	2,497,239	2,470,457
Total recorded investment in loans	2,546,890	2,517,547
Recorded investment in loans 90 days or more delinquent and accruing interest	23	28
Recorded investment in nonaccrual loans	23,212	23,427
Table Footnote [Abstract]
Nonaccrualloanswithnotallowance	6,653
Single-family [Member] | Fixed Rate Residential Mortgage 30 and 20 year Member | 30 to 59 Days Delinquent [Member]
Financing Receivable, Past Due [Line Items]
Days delinquent	29,663	26,882
Single-family [Member] | Fixed Rate Residential Mortgage 30 and 20 year Member | 60 to 89 Days Delinquent [Member]
Financing Receivable, Past Due [Line Items]
Days delinquent	6,665	7,126
Single-family [Member] | Fixed Rate Residential Mortgage 30 and 20 year Member | Seriously Delinquent [Member]
Financing Receivable, Past Due [Line Items]
Days delinquent	13,323	13,082
Single-family [Member] | FixedRateResidentialMortgage15yearMember
Financing Receivable, Past Due [Line Items]
Days delinquent	2,533	2,347
Current	373,012	371,740
Total recorded investment in loans	375,545	374,087
Recorded investment in loans 90 days or more delinquent and accruing interest	0	0
Recorded investment in nonaccrual loans	856	858
Table Footnote [Abstract]
Nonaccrualloanswithnotallowance	542
Single-family [Member] | FixedRateResidentialMortgage15yearMember | 30 to 59 Days Delinquent [Member]
Financing Receivable, Past Due [Line Items]
Days delinquent	1,803	1,616
Single-family [Member] | FixedRateResidentialMortgage15yearMember | 60 to 89 Days Delinquent [Member]
Financing Receivable, Past Due [Line Items]
Days delinquent	280	286
Single-family [Member] | FixedRateResidentialMortgage15yearMember | Seriously Delinquent [Member]
Financing Receivable, Past Due [Line Items]
Days delinquent	450	445
Single-family [Member] | Other [Member]
Financing Receivable, Past Due [Line Items]
Days delinquent	4,905	5,043
Current	61,288	64,726
Total recorded investment in loans	66,193	69,769
Recorded investment in loans 90 days or more delinquent and accruing interest	132	136
Recorded investment in nonaccrual loans	2,827	2,973
Table Footnote [Abstract]
Nonaccrualloanswithnotallowance	710
Single-family [Member] | Other [Member] | 30 to 59 Days Delinquent [Member]
Financing Receivable, Past Due [Line Items]
Days delinquent	2,302	2,323
Single-family [Member] | Other [Member] | 60 to 89 Days Delinquent [Member]
Financing Receivable, Past Due [Line Items]
Days delinquent	756	829
Single-family [Member] | Other [Member] | Seriously Delinquent [Member]
Financing Receivable, Past Due [Line Items]
Days delinquent	1,847	1,891
Single-family [Member] | Adjustable Rate Residential Mortgage
Financing Receivable, Past Due [Line Items]
Days delinquent	624	664
Current	41,864	44,244
Total recorded investment in loans	42,488	44,908
Recorded investment in loans 90 days or more delinquent and accruing interest	0	0
Recorded investment in nonaccrual loans		288
Table Footnote [Abstract]
Nonaccrualloanswithnotallowance	150
Single-family [Member] | Adjustable Rate Residential Mortgage | 30 to 59 Days Delinquent [Member]
Financing Receivable, Past Due [Line Items]
Days delinquent	383	412
Single-family [Member] | Adjustable Rate Residential Mortgage | 60 to 89 Days Delinquent [Member]
Financing Receivable, Past Due [Line Items]
Days delinquent	76	85
Single-family [Member] | Adjustable Rate Residential Mortgage | Seriously Delinquent [Member]
Financing Receivable, Past Due [Line Items]
Days delinquent	165	167
Multifamily [Member]
Financing Receivable, Past Due [Line Items]
Days delinquent	195	122
Current	337,499	330,496
Total recorded investment in loans	337,694	330,618
Recorded investment in loans 90 days or more delinquent and accruing interest	0	0
Recorded investment in nonaccrual loans	91	435
Table Footnote [Abstract]
Nonaccrualloanswithnotallowance	$ 33
Multifamily [Member] | Minimum [Member]
Table Footnote [Abstract]
Serious delinquency, days past due	60 days
Multifamily [Member] | Maximum [Member]
Table Footnote [Abstract]
Serious delinquency, days past due	89 days
Multifamily [Member] | 30 to 59 Days Delinquent [Member]
Financing Receivable, Past Due [Line Items]
Days delinquent	$ 37	7
Multifamily [Member] | Seriously Delinquent [Member]
Financing Receivable, Past Due [Line Items]
Days delinquent	$ 158	$ 115