Mortgage Loans Aging (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013
Financing Receivable, Recorded Investment, Past Due [Line Items]
30 - 59 days delinquent	34,867	39,184
60 - 89 days delinquent	10,352	12,138
Seriously delinquent	54,008	69,706
Total delinquent	99,227	121,028
Current	2,948,567	2,943,641
Total recorded investment in loans	3,047,794	3,064,669
Recorded investment in loans 90 days or more delinquent and accruing interest	374	460
Recorded investment in nonaccrual loans	64,645	83,283
Government [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total recorded investment in loans	45,300	48,600
Single-Family [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30 - 59 days delinquent	34,807	39,125
60 - 89 days delinquent	10,352	12,138
Seriously delinquent	53,919	69,520
Total delinquent	99,078	120,783
Current	2,759,483	2,757,908
Total recorded investment in loans	2,858,561	2,878,691
Recorded investment in loans 90 days or more delinquent and accruing interest	374	460
Recorded investment in nonaccrual loans	63,822	81,074
Single-Family [Member] | Primary [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30 - 59 days delinquent	29,130	32,371
60 - 89 days delinquent	8,396	9,755
Seriously delinquent	38,248	48,345
Total delinquent	75,774	90,471
Current	2,580,446	2,558,826
Total recorded investment in loans	2,656,220	2,649,297
Recorded investment in loans 90 days or more delinquent and accruing interest	55	81
Recorded investment in nonaccrual loans	46,556	57,973
Single-Family [Member] | Government [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30 - 59 days delinquent	63	66
60 - 89 days delinquent	26	32
Seriously delinquent	305	346
Total delinquent	394	444
Current	44,927	48,150
Total recorded investment in loans	45,321	48,594
Recorded investment in loans 90 days or more delinquent and accruing interest	305	346
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	4,094	4,748
60 - 89 days delinquent	1,414	1,692
Seriously delinquent	11,603	15,425
Total delinquent	17,111	21,865
Current	95,650	105,644
Total recorded investment in loans	112,761	127,509
Recorded investment in loans 90 days or more delinquent and accruing interest	8	11
Recorded investment in nonaccrual loans	13,007	17,102
Single-Family [Member] | Other [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30 - 59 days delinquent	1,520	1,940
60 - 89 days delinquent	516	659
Seriously delinquent	3,763	5,404
Total delinquent	5,799	8,003
Current	38,460	45,288
Total recorded investment in loans	44,259	53,291
Recorded investment in loans 90 days or more delinquent and accruing interest	6	22
Recorded investment in nonaccrual loans	4,259	5,999
Single-Family [Member] | Minimum [Member]
Table Footnote [Abstract]
Serious Delinquency Days past due	90 days	90 days
Multifamily [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30 - 59 days delinquent	60	59
Seriously delinquent	89	186
Total delinquent	149	245
Current	189,084	185,733
Total recorded investment in loans	189,233	185,978
Recorded investment in loans 90 days or more delinquent and accruing interest	0	0
Recorded investment in nonaccrual loans	823	2,209
Multifamily [Member] | Minimum [Member]
Table Footnote [Abstract]
Serious Delinquency Days past due	60 days	60 days