Mortgage Loans Aging (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Financing Receivable, Past Due [Line Items]
Days delinquent, amortized cost	$ 143,215	$ 55,266
Current, amortized cost	3,519,496	3,281,663
Total amortized cost in loans	3,662,711	3,336,929
Amortized cost in loans 90 days or more delinquent and accruing interest	77,196	164
Amortized cost in nonaccrual loans	28,574	27,981
Table Footnote [Abstract]
Financing Receivable, Nonaccrual, No Allowance	7,455
30 to 59 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Days delinquent, amortized cost	29,473	31,240
60 to 89 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Days delinquent, amortized cost	10,570	8,326
Seriously Delinquent [Member]
Financing Receivable, Past Due [Line Items]
Days delinquent, amortized cost	103,172	15,700
Single-Family [Member]
Financing Receivable, Past Due [Line Items]
Days delinquent, amortized cost	138,387	55,144
Current, amortized cost	3,146,898	2,951,167
Total amortized cost in loans	3,285,285	3,006,311
Amortized cost in loans 90 days or more delinquent and accruing interest	76,586	164
Amortized cost in nonaccrual loans	26,505	$ 27,546
Table Footnote [Abstract]
Financing Receivable, Nonaccrual, No Allowance	$ 7,153
Single-Family [Member] | Minimum [Member]
Table Footnote [Abstract]
Serious delinquency: days past due	90 days	90 days
Single-Family [Member] | 30 to 59 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Days delinquent, amortized cost	$ 28,333	$ 31,233
Single-Family [Member] | 60 to 89 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Days delinquent, amortized cost	10,570	8,326
Single-Family [Member] | Seriously Delinquent [Member]
Financing Receivable, Past Due [Line Items]
Days delinquent, amortized cost	99,484	15,585
Single-Family [Member] | Fixed Rate Residential Mortgage [Member]
Financing Receivable, Past Due [Line Items]
Days delinquent, amortized cost	122,618	47,090
Current, amortized cost	2,619,585	2,470,457
Total amortized cost in loans	2,742,203	2,517,547
Amortized cost in loans 90 days or more delinquent and accruing interest	68,526	28
Amortized cost in nonaccrual loans	22,907	23,427
Table Footnote [Abstract]
Financing Receivable, Nonaccrual, No Allowance	6,028
Single-Family [Member] | Fixed Rate Residential Mortgage [Member] | 30 to 59 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Days delinquent, amortized cost	24,928	26,882
Single-Family [Member] | Fixed Rate Residential Mortgage [Member] | 60 to 89 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Days delinquent, amortized cost	9,414	7,126
Single-Family [Member] | Fixed Rate Residential Mortgage [Member] | Seriously Delinquent [Member]
Financing Receivable, Past Due [Line Items]
Days delinquent, amortized cost	88,276	13,082
Single-Family [Member] | FixedRateResidentialMortgage15yearMember [Member]
Financing Receivable, Past Due [Line Items]
Days delinquent, amortized cost	7,616	2,347
Current, amortized cost	449,443	371,740
Total amortized cost in loans	457,059	374,087
Amortized cost in loans 90 days or more delinquent and accruing interest	4,292	0
Amortized cost in nonaccrual loans	853	858
Table Footnote [Abstract]
Financing Receivable, Nonaccrual, No Allowance	240
Single-Family [Member] | FixedRateResidentialMortgage15yearMember [Member] | 30 to 59 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Days delinquent, amortized cost	1,987	1,616
Single-Family [Member] | FixedRateResidentialMortgage15yearMember [Member] | 60 to 89 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Days delinquent, amortized cost	601	286
Single-Family [Member] | FixedRateResidentialMortgage15yearMember [Member] | Seriously Delinquent [Member]
Financing Receivable, Past Due [Line Items]
Days delinquent, amortized cost	5,028	445
Single-Family [Member] | Adjustable Rate Residential Mortgage [Member]
Financing Receivable, Past Due [Line Items]
Days delinquent, amortized cost	1,508	664
Current, amortized cost	29,933	44,244
Total amortized cost in loans	31,441	44,908
Amortized cost in loans 90 days or more delinquent and accruing interest	907	0
Table Footnote [Abstract]
Financing Receivable, Nonaccrual, No Allowance	114
Single-Family [Member] | Adjustable Rate Residential Mortgage [Member] | 30 to 59 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Days delinquent, amortized cost	268	412
Single-Family [Member] | Adjustable Rate Residential Mortgage [Member] | 60 to 89 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Days delinquent, amortized cost	97	85
Single-Family [Member] | Adjustable Rate Residential Mortgage [Member] | Seriously Delinquent [Member]
Financing Receivable, Past Due [Line Items]
Days delinquent, amortized cost	1,143	167
Single-Family [Member] | Other [Member]
Financing Receivable, Past Due [Line Items]
Days delinquent, amortized cost	6,645	5,043
Current, amortized cost	47,937	64,726
Total amortized cost in loans	54,582	69,769
Amortized cost in loans 90 days or more delinquent and accruing interest	2,861	136
Amortized cost in nonaccrual loans	2,475	2,973
Table Footnote [Abstract]
Financing Receivable, Nonaccrual, No Allowance	771
Single-Family [Member] | Other [Member] | 30 to 59 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Days delinquent, amortized cost	1,150	2,323
Single-Family [Member] | Other [Member] | 60 to 89 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Days delinquent, amortized cost	458	829
Single-Family [Member] | Other [Member] | Seriously Delinquent [Member]
Financing Receivable, Past Due [Line Items]
Days delinquent, amortized cost	5,037	1,891
Multifamily [Member]
Financing Receivable, Past Due [Line Items]
Days delinquent, amortized cost	4,828	122
Current, amortized cost	372,598	330,496
Total amortized cost in loans	377,426	330,618
Amortized cost in loans 90 days or more delinquent and accruing interest	610	0
Amortized cost in nonaccrual loans	2,069	435
Table Footnote [Abstract]
Financing Receivable, Nonaccrual, No Allowance	$ 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 Past Due [Member]
Financing Receivable, Past Due [Line Items]
Days delinquent, amortized cost	$ 1,140	7
Multifamily [Member] | Seriously Delinquent [Member]
Financing Receivable, Past Due [Line Items]
Days delinquent, amortized cost	$ 3,688	$ 115