Mortgage Loans Aging (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Financing Receivable, Past Due [Line Items]
Days delinquent, recorded investment	$ 55,266	$ 60,485
Current, recorded investment	3,281,663	3,194,683
Total recorded investment in loans	3,336,929	3,255,168
Recorded investment in loans 90 days or more delinquent and accruing interest	164	195
Recorded investment in nonaccrual loans	27,981	30,872
30 to 59 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Days delinquent, recorded investment	31,240	33,720
60 to 89 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Days delinquent, recorded investment	8,326	9,002
Seriously Delinquent [Member]
Financing Receivable, Past Due [Line Items]
Days delinquent, recorded investment	15,700	17,763
Single-Family [Member]
Financing Receivable, Past Due [Line Items]
Days delinquent, recorded investment	55,144	60,258
Current, recorded investment	2,951,167	2,899,246
Total recorded investment in loans	3,006,311	2,959,504
Recorded investment in loans 90 days or more delinquent and accruing interest	164	195
Recorded investment in nonaccrual loans	$ 27,546	$ 30,380
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, recorded investment	$ 31,233	$ 33,664
Single-Family [Member] | 60 to 89 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Days delinquent, recorded investment	8,326	9,002
Single-Family [Member] | Seriously Delinquent [Member]
Financing Receivable, Past Due [Line Items]
Days delinquent, recorded investment	15,585	17,592
Single-Family [Member] | Primary [Member]
Financing Receivable, Past Due [Line Items]
Days delinquent, recorded investment	50,101	53,218
Current, recorded investment	2,886,520	2,816,047
Total recorded investment in loans	2,936,621	2,869,265
Recorded investment in loans 90 days or more delinquent and accruing interest	29	22
Recorded investment in nonaccrual loans	24,573	26,170
Single-Family [Member] | Primary [Member] | 30 to 59 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Days delinquent, recorded investment	28,909	30,471
Single-Family [Member] | Primary [Member] | 60 to 89 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Days delinquent, recorded investment	7,497	7,881
Single-Family [Member] | Primary [Member] | Seriously Delinquent [Member]
Financing Receivable, Past Due [Line Items]
Days delinquent, recorded investment	13,695	14,866
Single-Family [Member] | Government [Member]
Financing Receivable, Past Due [Line Items]
Days delinquent, recorded investment	198	243
Current, recorded investment	16,931	21,887
Total recorded investment in loans	17,129	22,130
Recorded investment in loans 90 days or more delinquent and accruing interest	133	169
Recorded investment in nonaccrual loans	0	0
Single-Family [Member] | Government [Member] | 30 to 59 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Days delinquent, recorded investment	44	57
Single-Family [Member] | Government [Member] | 60 to 89 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Days delinquent, recorded investment	21	17
Single-Family [Member] | Government [Member] | Seriously Delinquent [Member]
Financing Receivable, Past Due [Line Items]
Days delinquent, recorded investment	133	169
Single-Family [Member] | Alt-A [Member]
Financing Receivable, Past Due [Line Items]
Days delinquent, recorded investment	3,613	4,997
Current, recorded investment	38,642	48,274
Total recorded investment in loans	42,255	53,271
Recorded investment in loans 90 days or more delinquent and accruing interest	1	2
Recorded investment in nonaccrual loans	2,198	3,082
Single-Family [Member] | Alt-A [Member] | 30 to 59 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Days delinquent, recorded investment	1,721	2,332
Single-Family [Member] | Alt-A [Member] | 60 to 89 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Days delinquent, recorded investment	602	821
Single-Family [Member] | Alt-A [Member] | Seriously Delinquent [Member]
Financing Receivable, Past Due [Line Items]
Days delinquent, recorded investment	1,290	1,844
Single-Family [Member] | Other [Member]
Financing Receivable, Past Due [Line Items]
Days delinquent, recorded investment	1,232	1,800
Current, recorded investment	9,074	13,038
Total recorded investment in loans	10,306	14,838
Recorded investment in loans 90 days or more delinquent and accruing interest	1	2
Recorded investment in nonaccrual loans	775	1,128
Single-Family [Member] | Other [Member] | 30 to 59 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Days delinquent, recorded investment	559	804
Single-Family [Member] | Other [Member] | 60 to 89 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Days delinquent, recorded investment	206	283
Single-Family [Member] | Other [Member] | Seriously Delinquent [Member]
Financing Receivable, Past Due [Line Items]
Days delinquent, recorded investment	467	713
Multifamily [Member]
Financing Receivable, Past Due [Line Items]
Days delinquent, recorded investment	122	227
Current, recorded investment	330,496	295,437
Total recorded investment in loans	330,618	295,664
Recorded investment in loans 90 days or more delinquent and accruing interest	0	0
Recorded investment in nonaccrual loans	$ 435	$ 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 Past Due [Member]
Financing Receivable, Past Due [Line Items]
Days delinquent, recorded investment	$ 7	$ 56
Multifamily [Member] | Seriously Delinquent [Member]
Financing Receivable, Past Due [Line Items]
Days delinquent, recorded investment	$ 115	$ 171