Mortgage Loans Aging (Details) - USD ($) $ in Millions	6 Months Ended	12 Months Ended
	Jun. 30, 2015	Dec. 31, 2014
Financing Receivable, Recorded Investment, Past Due [Line Items]
30 - 59 days delinquent	$ 33,307	$ 34,867
60 - 89 days delinquent	9,148	10,352
Seriously delinquent	40,464	54,008
Total delinquent	82,919	99,227
Current	2,948,730	2,948,567
Total recorded investment in loans	3,031,649	3,047,794
Recorded investment in loans 90 days or more delinquent and accruing interest	355	374
Recorded investment in nonaccrual loans	49,921	64,645
Single-family [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30 - 59 days delinquent	33,250	34,807
60 - 89 days delinquent	9,148	10,352
Seriously delinquent	40,374	53,919
Total delinquent	82,772	99,078
Current	2,750,628	2,759,483
Total recorded investment in loans	2,833,400	2,858,561
Recorded investment in loans 90 days or more delinquent and accruing interest	355	374
Recorded investment in nonaccrual loans	$ 49,112	$ 63,822
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	$ 27,698	$ 29,130
60 - 89 days delinquent	7,352	8,396
Seriously delinquent	29,566	38,248
Total delinquent	64,616	75,774
Current	2,581,112	2,580,446
Total recorded investment in loans	2,645,728	2,656,220
Recorded investment in loans 90 days or more delinquent and accruing interest	56	55
Recorded investment in nonaccrual loans	36,842	46,556
Single-family [Member] | Government [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30 - 59 days delinquent	54	63
60 - 89 days delinquent	26	26
Seriously delinquent	287	305
Total delinquent	367	394
Current	43,192	44,927
Total recorded investment in loans	43,559	45,321
Recorded investment in loans 90 days or more delinquent and accruing interest	287	305
Recorded investment in nonaccrual loans	0	0
Single-family [Member] | Alt-A
Financing Receivable, Recorded Investment, Past Due [Line Items]
30 - 59 days delinquent	4,003	4,094
60 - 89 days delinquent	1,284	1,414
Seriously delinquent	7,918	11,603
Total delinquent	13,205	17,111
Current	90,821	95,650
Total recorded investment in loans	104,026	112,761
Recorded investment in loans 90 days or more delinquent and accruing interest	7	8
Recorded investment in nonaccrual loans	9,195	13,007
Single-family [Member] | Other [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30 - 59 days delinquent	1,495	1,520
60 - 89 days delinquent	486	516
Seriously delinquent	2,603	3,763
Total delinquent	4,584	5,799
Current	35,503	38,460
Total recorded investment in loans	40,087	44,259
Recorded investment in loans 90 days or more delinquent and accruing interest	5	6
Recorded investment in nonaccrual loans	3,075	4,259
Multifamily [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30 - 59 days delinquent	57	60
Seriously delinquent	90	89
Total delinquent	147	149
Current	198,102	189,084
Total recorded investment in loans	198,249	189,233
Recorded investment in loans 90 days or more delinquent and accruing interest	0	0
Recorded investment in nonaccrual loans	$ 809	$ 823
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