Mortgage Loans Aging (Details) - USD ($) $ in Millions	6 Months Ended	12 Months Ended
	Jun. 30, 2019	Dec. 31, 2018
Financing Receivable, Recorded Investment, Past Due [Line Items]
Days delinquent	$ 60,277	$ 60,485
Current	3,213,518	3,194,683
Total recorded investment in loans	3,273,795	3,255,168
Recorded investment in loans 90 days or more delinquent and accruing interest	177	195
Recorded investment in nonaccrual loans	28,020	30,872
30 to 59 Days Delinquent [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Days delinquent	36,061	33,720
60 to 89 Days Delinquent [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Days delinquent	8,207	9,002
Seriously Delinquent [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Days delinquent	16,009	17,763
Single-family [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Days delinquent	60,066	60,258
Current	2,900,184	2,899,246
Total recorded investment in loans	2,960,250	2,959,504
Recorded investment in loans 90 days or more delinquent and accruing interest	177	195
Recorded investment in nonaccrual loans	27,507	30,380
Table Footnote [Abstract]
Mortgage Loans in Process of Foreclosure, Amount	$ 9,000	$ 10,100
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, Recorded Investment, Past Due [Line Items]
Days delinquent	$ 36,037	$ 33,664
Single-family [Member] | 60 to 89 Days Delinquent [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Days delinquent	8,207	9,002
Single-family [Member] | Seriously Delinquent [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Days delinquent	15,822	17,592
Single-family [Member] | Primary [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Days delinquent	53,885	53,218
Current	2,827,424	2,816,047
Total recorded investment in loans	2,881,309	2,869,265
Recorded investment in loans 90 days or more delinquent and accruing interest	22	22
Recorded investment in nonaccrual loans	24,035	26,170
Single-family [Member] | Primary [Member] | 30 to 59 Days Delinquent [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Days delinquent	33,030	30,471
Single-family [Member] | Primary [Member] | 60 to 89 Days Delinquent [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Days delinquent	7,308	7,881
Single-family [Member] | Primary [Member] | Seriously Delinquent [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Days delinquent	13,547	14,866
Single-family [Member] | Government [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Days delinquent	216	243
Current	18,691	21,887
Total recorded investment in loans	18,907	22,130
Recorded investment in loans 90 days or more delinquent and accruing interest	152	169
Recorded investment in nonaccrual loans	0	0
Single-family [Member] | Government [Member] | 30 to 59 Days Delinquent [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Days delinquent	46	57
Single-family [Member] | Government [Member] | 60 to 89 Days Delinquent [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Days delinquent	18	17
Single-family [Member] | Government [Member] | Seriously Delinquent [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Days delinquent	152	169
Single-family [Member] | Alt-A
Financing Receivable, Recorded Investment, Past Due [Line Items]
Days delinquent	4,406	4,997
Current	43,083	48,274
Total recorded investment in loans	47,489	53,271
Recorded investment in loans 90 days or more delinquent and accruing interest	1	2
Recorded investment in nonaccrual loans	2,528	3,082
Single-family [Member] | Alt-A | 30 to 59 Days Delinquent [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Days delinquent	2,228	2,332
Single-family [Member] | Alt-A | 60 to 89 Days Delinquent [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Days delinquent	645	821
Single-family [Member] | Alt-A | Seriously Delinquent [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Days delinquent	1,533	1,844
Single-family [Member] | Other [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Days delinquent	1,559	1,800
Current	10,986	13,038
Total recorded investment in loans	12,545	14,838
Recorded investment in loans 90 days or more delinquent and accruing interest	2	2
Recorded investment in nonaccrual loans	944	1,128
Single-family [Member] | Other [Member] | 30 to 59 Days Delinquent [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Days delinquent	733	804
Single-family [Member] | Other [Member] | 60 to 89 Days Delinquent [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Days delinquent	236	283
Single-family [Member] | Other [Member] | Seriously Delinquent [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Days delinquent	590	713
Multifamily [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Days delinquent	211	227
Current	313,334	295,437
Total recorded investment in loans	313,545	295,664
Recorded investment in loans 90 days or more delinquent and accruing interest	0	0
Recorded investment in nonaccrual loans	$ 513	$ 492
Multifamily [Member] | Minimum [Member]
Table Footnote [Abstract]
Serious delinquency, days past due	60 days	60 days
Multifamily [Member] | Maximum [Member]
Table Footnote [Abstract]
Serious delinquency, days past due	89 days	89 days
Multifamily [Member] | 30 to 59 Days Delinquent [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Days delinquent	$ 24	$ 56
Multifamily [Member] | Seriously Delinquent [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Days delinquent	$ 187	$ 171