Mortgage Loans Aging (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended	12 Months Ended
	Mar. 31, 2015	Dec. 31, 2014
Financing Receivable, Recorded Investment, Past Due [Line Items]
30 - 59 days delinquent	30,329	34,867
60 - 89 days delinquent	8,830	10,352
Seriously delinquent	47,131	54,008
Total delinquent	86,290	99,227
Current	2,950,277	2,948,567
Total recorded investment in loans	3,036,567	3,047,794
Recorded investment in loans 90 days or more delinquent and accruing interest	368	374
Recorded investment in nonaccrual loans	56,216	64,645
Government [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total recorded investment in loans	44,600	45,300
Single-Family [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30 - 59 days delinquent	30,231	34,807
60 - 89 days delinquent	8,830	10,352
Seriously delinquent	46,996	53,919
Total delinquent	86,057	99,078
Current	2,757,482	2,759,483
Total recorded investment in loans	2,843,539	2,858,561
Recorded investment in loans 90 days or more delinquent and accruing interest	368	374
Recorded investment in nonaccrual loans	55,409	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	25,087	29,130
60 - 89 days delinquent	7,045	8,396
Seriously delinquent	34,166	38,248
Total delinquent	66,298	75,774
Current	2,582,073	2,580,446
Total recorded investment in loans	2,648,371	2,656,220
Recorded investment in loans 90 days or more delinquent and accruing interest	56	55
Recorded investment in nonaccrual loans	41,132	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	18	26
Seriously delinquent	298	305
Total delinquent	370	394
Current	44,211	44,927
Total recorded investment in loans	44,581	45,321
Recorded investment in loans 90 days or more delinquent and accruing interest	298	305
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	3,743	4,094
60 - 89 days delinquent	1,321	1,414
Seriously delinquent	9,429	11,603
Total delinquent	14,493	17,111
Current	93,801	95,650
Total recorded investment in loans	108,294	112,761
Recorded investment in loans 90 days or more delinquent and accruing interest	7	8
Recorded investment in nonaccrual loans	10,743	13,007
Single-Family [Member] | Other [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30 - 59 days delinquent	1,347	1,520
60 - 89 days delinquent	446	516
Seriously delinquent	3,103	3,763
Total delinquent	4,896	5,799
Current	37,397	38,460
Total recorded investment in loans	42,293	44,259
Recorded investment in loans 90 days or more delinquent and accruing interest	7	6
Recorded investment in nonaccrual loans	3,534	4,259
Multifamily [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30 - 59 days delinquent	98	60
Seriously delinquent	135	89
Total delinquent	233	149
Current	192,795	189,084
Total recorded investment in loans	193,028	189,233
Recorded investment in loans 90 days or more delinquent and accruing interest	0	0
Recorded investment in nonaccrual loans	807	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