Mortgage Loans Aging (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2021	Dec. 31, 2020
Financing Receivable, Past Due [Line Items]
Days delinquent	$ 121,156	$ 143,215
Current	3,624,505	3,519,496
Total recorded investment in loans	3,745,661	3,662,711
Recorded investment in loans 90 days or more delinquent and accruing interest	58,366	77,196
Recorded investment in nonaccrual loans	36,138	28,574
Table Footnote [Abstract]
Financing Receivable, Nonaccrual, No Allowance	7,830	7,455
Financing Receivable, before Allowance for Credit Loss	3,741,684	3,659,247
30 to 59 Days Delinquent [Member]
Financing Receivable, Past Due [Line Items]
Days delinquent	21,618	29,473
60 to 89 Days Delinquent [Member]
Financing Receivable, Past Due [Line Items]
Days delinquent	7,896	10,570
Seriously Delinquent [Member]
Financing Receivable, Past Due [Line Items]
Days delinquent	91,642	103,172
Single-family [Member]
Financing Receivable, Past Due [Line Items]
Days delinquent	117,130	138,387
Current	3,236,664	3,146,898
Total recorded investment in loans	3,353,794	3,285,285
Recorded investment in loans 90 days or more delinquent and accruing interest	57,962	76,586
Recorded investment in nonaccrual loans	33,985	26,505
Table Footnote [Abstract]
Financing Receivable, Nonaccrual, No Allowance	7,647	7,153
Financing Receivable, before Allowance for Credit Loss	$ 3,340,905	$ 3,271,810
Single-family [Member] | Minimum [Member]
Table Footnote [Abstract]
Serious delinquency, days past due	90 days	90 days
Single-family [Member] | 30 to 59 Days Delinquent [Member]
Financing Receivable, Past Due [Line Items]
Days delinquent	$ 20,123	$ 28,333
Single-family [Member] | 60 to 89 Days Delinquent [Member]
Financing Receivable, Past Due [Line Items]
Days delinquent	7,896	10,570
Single-family [Member] | Seriously Delinquent [Member]
Financing Receivable, Past Due [Line Items]
Days delinquent	89,111	99,484
Single-family [Member] | FixedRateResidentialMortgage15yearMember
Financing Receivable, Past Due [Line Items]
Days delinquent	6,509	7,616
Current	475,960	449,443
Total recorded investment in loans	482,469	457,059
Recorded investment in loans 90 days or more delinquent and accruing interest	3,424	4,292
Recorded investment in nonaccrual loans	945	853
Table Footnote [Abstract]
Financing Receivable, Nonaccrual, No Allowance	210	240
Financing Receivable, before Allowance for Credit Loss	482,469	457,059
Single-family [Member] | FixedRateResidentialMortgage15yearMember | 30 to 59 Days Delinquent [Member]
Financing Receivable, Past Due [Line Items]
Days delinquent	1,742	1,987
Single-family [Member] | FixedRateResidentialMortgage15yearMember | 60 to 89 Days Delinquent [Member]
Financing Receivable, Past Due [Line Items]
Days delinquent	492	601
Single-family [Member] | FixedRateResidentialMortgage15yearMember | Seriously Delinquent [Member]
Financing Receivable, Past Due [Line Items]
Days delinquent	4,275	5,028
Single-family [Member] | Other [Member]
Financing Receivable, Past Due [Line Items]
Days delinquent	5,612	6,645
Current	45,188	47,937
Total recorded investment in loans	50,800	54,582
Recorded investment in loans 90 days or more delinquent and accruing interest	2,132	2,861
Recorded investment in nonaccrual loans	2,583	2,475
Table Footnote [Abstract]
Financing Receivable, Nonaccrual, No Allowance	860	771
Financing Receivable, before Allowance for Credit Loss	37,911	41,107
Single-family [Member] | Other [Member] | 30 to 59 Days Delinquent [Member]
Financing Receivable, Past Due [Line Items]
Days delinquent	801	1,150
Single-family [Member] | Other [Member] | 60 to 89 Days Delinquent [Member]
Financing Receivable, Past Due [Line Items]
Days delinquent	317	458
Single-family [Member] | Other [Member] | Seriously Delinquent [Member]
Financing Receivable, Past Due [Line Items]
Days delinquent	4,494	5,037
Single-family [Member] | Adjustable Rate Residential Mortgage [Member]
Financing Receivable, Past Due [Line Items]
Days delinquent	1,236	1,508
Current	26,549	29,933
Total recorded investment in loans	27,785	31,441
Recorded investment in loans 90 days or more delinquent and accruing interest	735	907
Table Footnote [Abstract]
Financing Receivable, Nonaccrual, No Allowance	116	114
Financing Receivable, before Allowance for Credit Loss	27,785	31,441
Single-family [Member] | Adjustable Rate Residential Mortgage [Member] | 30 to 59 Days Delinquent [Member]
Financing Receivable, Past Due [Line Items]
Days delinquent	180	268
Single-family [Member] | Adjustable Rate Residential Mortgage [Member] | 60 to 89 Days Delinquent [Member]
Financing Receivable, Past Due [Line Items]
Days delinquent	63	97
Single-family [Member] | Adjustable Rate Residential Mortgage [Member] | Seriously Delinquent [Member]
Financing Receivable, Past Due [Line Items]
Days delinquent	993	1,143
Single-family [Member] | Fixed Rate Residential Mortgage
Financing Receivable, Past Due [Line Items]
Days delinquent	103,773	122,618
Current	2,688,967	2,619,585
Total recorded investment in loans	2,792,740	2,742,203
Recorded investment in loans 90 days or more delinquent and accruing interest	51,671	68,526
Recorded investment in nonaccrual loans	30,173	22,907
Table Footnote [Abstract]
Financing Receivable, Nonaccrual, No Allowance	6,461	6,028
Financing Receivable, before Allowance for Credit Loss	2,792,740	2,742,203
Single-family [Member] | Fixed Rate Residential Mortgage | 30 to 59 Days Delinquent [Member]
Financing Receivable, Past Due [Line Items]
Days delinquent	17,400	24,928
Single-family [Member] | Fixed Rate Residential Mortgage | 60 to 89 Days Delinquent [Member]
Financing Receivable, Past Due [Line Items]
Days delinquent	7,024	9,414
Single-family [Member] | Fixed Rate Residential Mortgage | Seriously Delinquent [Member]
Financing Receivable, Past Due [Line Items]
Days delinquent	79,349	88,276
Single-family [Member] | Government [Member]
Table Footnote [Abstract]
Financing Receivable, before Allowance for Credit Loss	12,900	13,500
Multifamily [Member]
Financing Receivable, Past Due [Line Items]
Days delinquent	4,026	4,828
Current	387,841	372,598
Total recorded investment in loans	391,867	377,426
Recorded investment in loans 90 days or more delinquent and accruing interest	404	610
Recorded investment in nonaccrual loans	2,153	2,069
Table Footnote [Abstract]
Financing Receivable, Nonaccrual, No Allowance	$ 183	302
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	$ 1,495	1,140
Multifamily [Member] | Seriously Delinquent [Member]
Financing Receivable, Past Due [Line Items]
Days delinquent	$ 2,531	$ 3,688