Mortgage Loans Aging (Details) - USD ($) $ in Millions	6 Months Ended	12 Months Ended
	Jun. 30, 2016	Dec. 31, 2015
Financing Receivable, Recorded Investment, Past Due [Line Items]
30 - 59 days delinquent	$ 33,861	$ 34,814
60 - 89 days delinquent	8,560	9,717
Seriously delinquent	29,272	35,061
Total delinquent	71,693	79,592
Current	2,972,068	2,956,120
Total recorded investment in loans	3,043,761	3,035,712
Recorded investment in loans 90 days or more delinquent and accruing interest	321	349
Recorded investment in nonaccrual loans	42,424	44,846
Single-family [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30 - 59 days delinquent	33,781	34,791
60 - 89 days delinquent	8,560	9,717
Seriously delinquent	29,171	34,938
Total delinquent	71,512	79,446
Current	2,759,490	2,756,092
Total recorded investment in loans	2,831,002	2,835,538
Recorded investment in loans 90 days or more delinquent and accruing interest	321	349
Recorded investment in nonaccrual loans	$ 41,949	$ 44,255
Single-family [Member] | Minimum [Member]
Table Footnote [Abstract]
Serious delinquency, days past due	90 days	90 days
Single-family [Member] | Primary [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30 - 59 days delinquent	$ 28,547	$ 29,154
60 - 89 days delinquent	7,002	7,937
Seriously delinquent	22,221	26,346
Total delinquent	57,770	63,437
Current	2,611,816	2,598,756
Total recorded investment in loans	2,669,586	2,662,193
Recorded investment in loans 90 days or more delinquent and accruing interest	41	46
Recorded investment in nonaccrual loans	32,854	34,216
Single-family [Member] | Government [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30 - 59 days delinquent	56	58
60 - 89 days delinquent	22	24
Seriously delinquent	268	291
Total delinquent	346	373
Current	38,831	40,461
Total recorded investment in loans	39,177	40,834
Recorded investment in loans 90 days or more delinquent and accruing interest	268	291
Recorded investment in nonaccrual loans	0	0
Single-family [Member] | Alt-A [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30 - 59 days delinquent	3,725	4,085
60 - 89 days delinquent	1,111	1,272
Seriously delinquent	4,925	6,141
Total delinquent	9,761	11,498
Current	79,383	84,603
Total recorded investment in loans	89,144	96,101
Recorded investment in loans 90 days or more delinquent and accruing interest	6	6
Recorded investment in nonaccrual loans	6,684	7,407
Single-family [Member] | Other [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30 - 59 days delinquent	1,453	1,494
60 - 89 days delinquent	425	484
Seriously delinquent	1,757	2,160
Total delinquent	3,635	4,138
Current	29,460	32,272
Total recorded investment in loans	33,095	36,410
Recorded investment in loans 90 days or more delinquent and accruing interest	6	6
Recorded investment in nonaccrual loans	2,411	2,632
Multifamily [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30 - 59 days delinquent	80	23
Seriously delinquent	101	123
Total delinquent	181	146
Current	212,578	200,028
Total recorded investment in loans	212,759	200,174
Recorded investment in loans 90 days or more delinquent and accruing interest	0	0
Recorded investment in nonaccrual loans	$ 475	$ 591
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