Mortgage Loans Aging (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2013		Dec. 31, 2012
Aging Analysis [Line Items]
30 - 59 days delinquent	$ 42,311	[1]	$ 47,925	[1]
60 - 89 days delinquent	13,470	[1]	17,023	[1]
Seriously delinquent	90,132	[1],[2]	99,213	[1],[2]
Total delinquent	145,913	[1]	164,161	[1]
Current	2,866,522	[1]	2,843,310	[1]
Total recorded investment	3,012,435	[1]	3,007,471	[1]
Recorded investment in loans 90 days or more delinquent and accruing interest	496	[1]	3,301	[1],[3]
Recorded investment in nonaccrual loans	104,748	[1]	114,293	[1]
Single-Family [Member]
Aging Analysis [Line Items]
30 - 59 days delinquent	42,171	[1]	47,747	[1]
60 - 89 days delinquent	13,470	[1]	17,023	[1]
Seriously delinquent	89,310	[1],[2]	98,785	[1],[2]
Total delinquent	144,951	[1]	163,555	[1]
Current	2,677,262	[1]	2,652,865	[1]
Total recorded investment	2,822,213	[1]	2,816,420	[1]
Recorded investment in loans 90 days or more delinquent and accruing interest	495	[1]	3,301	[1],[3]
Recorded investment in nonaccrual loans	102,139	[1]	112,079	[1]
Single-Family [Member] | Primary [Member]
Aging Analysis [Line Items]
30 - 59 days delinquent	34,276	[1],[4]	39,043	[1],[4]
60 - 89 days delinquent	10,678	[1],[4]	13,513	[1],[4]
Seriously delinquent	61,396	[1],[2],[4]	67,737	[1],[2],[4]
Total delinquent	106,350	[1],[4]	120,293	[1],[4]
Current	2,456,907	[1],[4]	2,424,022	[1],[4]
Total recorded investment	2,563,257	[1],[4],[5],[6]	2,544,315	[1],[4],[5],[6]
Recorded investment in loans 90 days or more delinquent and accruing interest	104	[1],[4]	2,162	[1],[3],[4]
Recorded investment in nonaccrual loans	71,918	[1],[4]	78,822	[1],[4]
Single-Family [Member] | Government [Member]
Aging Analysis [Line Items]
30 - 59 days delinquent	74	[1],[7]	82	[1],[7]
60 - 89 days delinquent	31	[1],[7]	40	[1],[7]
Seriously delinquent	339	[1],[2],[7]	340	[1],[2],[7]
Total delinquent	444	[1],[7]	462	[1],[7]
Current	50,152	[1],[7]	50,408	[1],[7]
Total recorded investment	50,596	[1],[7]	50,870	[1],[7]
Recorded investment in loans 90 days or more delinquent and accruing interest	339	[1],[7]	340	[1],[3],[7]
Recorded investment in nonaccrual loans	0	[1],[7]	0	[1],[7]
Single-Family [Member] | Alt-A [Member]
Aging Analysis [Line Items]
30 - 59 days delinquent	5,477	[1]	6,009	[1]
60 - 89 days delinquent	1,948	[1]	2,417	[1]
Seriously delinquent	20,056	[1],[2]	22,181	[1],[2]
Total delinquent	27,481	[1]	30,607	[1]
Current	116,657	[1]	121,099	[1]
Total recorded investment	144,138	[1],[5],[6]	151,706	[1],[5],[6]
Recorded investment in loans 90 days or more delinquent and accruing interest	16	[1]	502	[1],[3]
Recorded investment in nonaccrual loans	21,977	[1]	24,048	[1]
Single-Family [Member] | Other [Member]
Aging Analysis [Line Items]
30 - 59 days delinquent	2,344	[1],[8]	2,613	[1],[8]
60 - 89 days delinquent	813	[1],[8]	1,053	[1],[8]
Seriously delinquent	7,519	[1],[2],[8]	8,527	[1],[2],[8]
Total delinquent	10,676	[1],[8]	12,193	[1],[8]
Current	53,546	[1],[8]	57,336	[1],[8]
Total recorded investment	64,222	[1],[5],[6],[8]	69,529	[1],[5],[6],[8]
Recorded investment in loans 90 days or more delinquent and accruing interest	36	[1],[8]	297	[1],[3],[8]
Recorded investment in nonaccrual loans	8,244	[1],[8]	9,209	[1],[8]
Multifamily [Member]
Aging Analysis [Line Items]
30 - 59 days delinquent	140	[1],[9]	178	[1],[9]
Seriously delinquent	822	[1],[2],[9]	428	[1],[2],[9]
Total delinquent	962	[1],[9]	606	[1],[9]
Current	189,260	[1],[9]	190,445	[1],[9]
Total recorded investment	190,222	[1],[10],[9]	191,051	[1],[10],[9]
Recorded investment in loans 90 days or more delinquent and accruing interest	1	[1],[9]	0	[1],[3],[9]
Recorded investment in nonaccrual loans	2,609	[1],[9]	2,214	[1],[9]
Minimum [Member] | Single-Family [Member]
Table Footnote [Abstract]
Serious delinquency, days past due	90 days		90 days
Minimum [Member] | Multifamily [Member]
Table Footnote [Abstract]
Serious delinquency, days past due	60 days		60 days
Repurchase Request Resolution Agreement [Member] | Bank of America [Member]
Aging Analysis [Line Items]
Recorded investment in loans 90 days or more delinquent and accruing interest			$ 2,800

[1] Recorded investment consists of unpaid principal balance, unamortized premiums, discounts and other cost basis adjustments, and accrued interest receivable.

[2] Single-family seriously delinquent loans are loans that are 90 days or more past due or in the foreclosure process. Multifamily seriously delinquent loans are loans that are 60 days or more past due.

[3] Includes loans with a recorded investment of $2.8 billion, which were repurchased in January 2013 pursuant to our resolution agreement with Bank of America. These loans were returned to accrual status to reflect the change in our assessment of collectability resulting from this agreement.

[4] Consists of mortgage loans that are not included in other loan classes.

[5] The aggregate estimated mark-to-market LTV ratio is based on the unpaid principal balance of the loan as of the end of each reported period divided by the estimated current value of the property, which we calculate using an internal valuation model that estimates periodic changes in home value.

[6] Excludes $50.6 billion and $50.9 billion as of March 31, 2013 and December 31, 2012, respectively, of mortgage loans guaranteed or insured, in whole or in part, by the U.S. government or one of its agencies that are not Alt-A loans. The segment class is primarily reverse mortgages for which we do not calculate an estimated mark-to-market LTV.

[7] Consists of mortgage loans guaranteed or insured, in whole or in part, by the U.S. government or one of its agencies that are not Alt-A. Primarily consists of reverse mortgages which due to their nature are not aged and are included in the current column.

[8] Includes loans with higher-risk loan characteristics, such as interest-only loans and negative-amortizing loans that are neither government nor Alt-A.

[9] Multifamily loans 60-89 days delinquent are included in the seriously delinquent column.

[10] Green (loan with acceptable risk); yellow (loan with signs of potential weakness); orange (loan with a well defined weakness that may jeopardize the timely full repayment); and red (loan with a weakness that makes timely collection or liquidation in full more questionable based on existing conditions and values).