Mortgage Loans Aging (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2020	Jun. 30, 2020	Dec. 31, 2019
Financing Receivable, Past Due [Line Items]
Days delinquent	$ 163,291		$ 55,266
Current	3,390,595		3,281,663
Total recorded investment in loans	3,553,886		3,336,929
Recorded investment in loans 90 days or more delinquent and accruing interest	95,098		164
Recorded investment in nonaccrual loans	25,714	$ 28,069	27,981
Table Footnote [Abstract]
Financing Receivable, Nonaccrual, No Allowance	8,513
Financing Receivable, before Allowance for Credit Loss	3,550,734		3,336,405
30 to 59 Days Delinquent [Member]
Financing Receivable, Past Due [Line Items]
Days delinquent	31,511		31,240
60 to 89 Days Delinquent [Member]
Financing Receivable, Past Due [Line Items]
Days delinquent	15,327		8,326
Seriously Delinquent [Member]
Financing Receivable, Past Due [Line Items]
Days delinquent	116,453		15,700
Single-family [Member]
Financing Receivable, Past Due [Line Items]
Days delinquent	158,705		55,144
Current	3,035,464		2,951,167
Total recorded investment in loans	3,194,169		3,006,311
Recorded investment in loans 90 days or more delinquent and accruing interest	91,369		164
Recorded investment in nonaccrual loans	25,367	27,753	27,546
Table Footnote [Abstract]
Financing Receivable, Nonaccrual, No Allowance	8,469
Financing Receivable, before Allowance for Credit Loss	$ 3,179,241
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	$ 30,999		31,233
Single-family [Member] | 60 to 89 Days Delinquent [Member]
Financing Receivable, Past Due [Line Items]
Days delinquent	15,327		8,326
Single-family [Member] | Seriously Delinquent [Member]
Financing Receivable, Past Due [Line Items]
Days delinquent	112,379		15,585
Single-family [Member] | FixedRateResidentialMortgage15yearMember
Financing Receivable, Past Due [Line Items]
Days delinquent	9,219		2,347
Current	420,848		371,740
Total recorded investment in loans	430,067		374,087
Recorded investment in loans 90 days or more delinquent and accruing interest	5,533		0
Recorded investment in nonaccrual loans	780	844	858
Table Footnote [Abstract]
Financing Receivable, Nonaccrual, No Allowance	393
Financing Receivable, before Allowance for Credit Loss	430,067
Single-family [Member] | FixedRateResidentialMortgage15yearMember | 30 to 59 Days Delinquent [Member]
Financing Receivable, Past Due [Line Items]
Days delinquent	2,084		1,616
Single-family [Member] | FixedRateResidentialMortgage15yearMember | 60 to 89 Days Delinquent [Member]
Financing Receivable, Past Due [Line Items]
Days delinquent	965		286
Single-family [Member] | FixedRateResidentialMortgage15yearMember | Seriously Delinquent [Member]
Financing Receivable, Past Due [Line Items]
Days delinquent	6,170		445
Single-family [Member] | Other [Member]
Financing Receivable, Past Due [Line Items]
Days delinquent	7,228		5,043
Current	51,276		64,726
Total recorded investment in loans	58,504		69,769
Recorded investment in loans 90 days or more delinquent and accruing interest	3,271		136
Recorded investment in nonaccrual loans	2,438	2,851	2,973
Table Footnote [Abstract]
Financing Receivable, Nonaccrual, No Allowance	785
Financing Receivable, before Allowance for Credit Loss	43,576
Single-family [Member] | Other [Member] | 30 to 59 Days Delinquent [Member]
Financing Receivable, Past Due [Line Items]
Days delinquent	1,267		2,323
Single-family [Member] | Other [Member] | 60 to 89 Days Delinquent [Member]
Financing Receivable, Past Due [Line Items]
Days delinquent	606		829
Single-family [Member] | Other [Member] | Seriously Delinquent [Member]
Financing Receivable, Past Due [Line Items]
Days delinquent	5,355		1,891
Single-family [Member] | Adjustable Rate Residential Mortgage [Member]
Financing Receivable, Past Due [Line Items]
Days delinquent	1,844		664
Current	33,461		44,244
Total recorded investment in loans	35,305		44,908
Recorded investment in loans 90 days or more delinquent and accruing interest	1,160		0
Table Footnote [Abstract]
Financing Receivable, Nonaccrual, No Allowance	135
Financing Receivable, before Allowance for Credit Loss	35,305
Single-family [Member] | Adjustable Rate Residential Mortgage [Member] | 30 to 59 Days Delinquent [Member]
Financing Receivable, Past Due [Line Items]
Days delinquent	309		412
Single-family [Member] | Adjustable Rate Residential Mortgage [Member] | 60 to 89 Days Delinquent [Member]
Financing Receivable, Past Due [Line Items]
Days delinquent	172		85
Single-family [Member] | Adjustable Rate Residential Mortgage [Member] | Seriously Delinquent [Member]
Financing Receivable, Past Due [Line Items]
Days delinquent	1,363		167
Single-family [Member] | Fixed Rate Residential Mortgage
Financing Receivable, Past Due [Line Items]
Days delinquent	140,414		47,090
Current	2,529,879		2,470,457
Total recorded investment in loans	2,670,293		2,517,547
Recorded investment in loans 90 days or more delinquent and accruing interest	81,405		28
Recorded investment in nonaccrual loans	21,902	23,783	23,427
Table Footnote [Abstract]
Financing Receivable, Nonaccrual, No Allowance	7,156
Financing Receivable, before Allowance for Credit Loss	2,670,293
Single-family [Member] | Fixed Rate Residential Mortgage | 30 to 59 Days Delinquent [Member]
Financing Receivable, Past Due [Line Items]
Days delinquent	27,339		26,882
Single-family [Member] | Fixed Rate Residential Mortgage | 60 to 89 Days Delinquent [Member]
Financing Receivable, Past Due [Line Items]
Days delinquent	13,584		7,126
Single-family [Member] | Fixed Rate Residential Mortgage | Seriously Delinquent [Member]
Financing Receivable, Past Due [Line Items]
Days delinquent	99,491		13,082
Multifamily [Member]
Financing Receivable, Past Due [Line Items]
Days delinquent	4,586		122
Current	355,131		330,496
Total recorded investment in loans	359,717		330,618
Recorded investment in loans 90 days or more delinquent and accruing interest	3,729		0
Recorded investment in nonaccrual loans	347	$ 316	435
Table Footnote [Abstract]
Financing Receivable, Nonaccrual, No Allowance	$ 44
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	$ 512		7
Multifamily [Member] | Seriously Delinquent [Member]
Financing Receivable, Past Due [Line Items]
Days delinquent	$ 4,074		$ 115