Mortgage Loans Aging (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2012		Dec. 31, 2011
Financing Receivable, Recorded Investment, Past Due [Line Items]
30 - 59 days delinquent	$ 47,925	[1]	$ 54,393	[1]
60 - 89 days delinquent	17,023	[1]	19,816	[1]
Seriously delinquent	99,213	[1],[2]	121,744	[1],[2]
Total delinquent	164,161	[1]	195,953	[1]
Current	2,843,310	[1]	2,782,938	[1]
Total recorded investment in loans	3,007,471	[1]	2,978,891	[1]
Recorded investment in loans 90 days or more delinquent and accruing interest	3,301	[1],[3]	548	[1]
Recorded investment in nonaccrual loans	114,293	[1]	142,612	[1]
Single-Family [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30 - 59 days delinquent	47,747	[1]	54,183	[1]
60 - 89 days delinquent	17,023	[1]	19,816	[1]
Seriously delinquent	98,785	[1],[2]	120,639	[1],[2]
Total delinquent	163,555	[1]	194,638	[1]
Current	2,652,865	[1]	2,605,032	[1]
Total recorded investment in loans	2,816,420	[1]	2,799,670	[1]
Recorded investment in loans 90 days or more delinquent and accruing interest	3,301	[1],[3]	548	[1]
Recorded investment in nonaccrual loans	112,079	[1]	139,848	[1]
Single-Family [Member] | Primary [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30 - 59 days delinquent	39,043	[1],[4]	43,516	[1],[4]
60 - 89 days delinquent	13,513	[1],[4]	15,282	[1],[4]
Seriously delinquent	67,737	[1],[2],[4]	80,712	[1],[2],[4]
Total delinquent	120,293	[1],[4]	139,510	[1],[4]
Current	2,424,022	[1],[4]	2,341,646	[1],[4]
Total recorded investment in loans	2,544,315	[1],[4],[5],[6]	2,481,156	[1],[4],[5],[6]
Recorded investment in loans 90 days or more delinquent and accruing interest	2,162	[1],[3],[4]	111	[1],[4]
Recorded investment in nonaccrual loans	78,822	[1],[4]	95,959	[1],[4]
Single-Family [Member] | Government [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30 - 59 days delinquent	82	[1],[7]	109	[1],[7]
60 - 89 days delinquent	40	[1],[7]	49	[1],[7]
Seriously delinquent	340	[1],[2],[7]	327	[1],[2],[7]
Total delinquent	462	[1],[7]	485	[1],[7]
Current	50,408	[1],[7]	51,391	[1],[7]
Total recorded investment in loans	50,870	[1],[7]	51,876	[1],[7]
Recorded investment in loans 90 days or more delinquent and accruing interest	340	[1],[3],[7]	327	[1],[7]
Recorded investment in nonaccrual loans	0	[1],[7]	0	[1],[7]
Single-Family [Member] | Alt-A [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30 - 59 days delinquent	6,009	[1]	7,155	[1]
60 - 89 days delinquent	2,417	[1]	3,054	[1]
Seriously delinquent	22,181	[1],[2]	28,323	[1],[2]
Total delinquent	30,607	[1]	38,532	[1]
Current	121,099	[1]	138,880	[1]
Total recorded investment in loans	151,706	[1],[5],[6]	177,412	[1],[5],[6]
Recorded investment in loans 90 days or more delinquent and accruing interest	502	[1],[3]	14	[1]
Recorded investment in nonaccrual loans	24,048	[1]	31,356	[1]
Single-Family [Member] | Other [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30 - 59 days delinquent	2,613	[1],[8]	3,403	[1],[8]
60 - 89 days delinquent	1,053	[1],[8]	1,431	[1],[8]
Seriously delinquent	8,527	[1],[2],[8]	11,277	[1],[2],[8]
Total delinquent	12,193	[1],[8]	16,111	[1],[8]
Current	57,336	[1],[8]	73,115	[1],[8]
Total recorded investment in loans	69,529	[1],[5],[6],[8]	89,226	[1],[5],[6],[8]
Recorded investment in loans 90 days or more delinquent and accruing interest	297	[1],[3],[8]	96	[1],[8]
Recorded investment in nonaccrual loans	9,209	[1],[8]	12,533	[1],[8]
Multifamily [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30 - 59 days delinquent	178	[1],[9]	210	[1],[9]
Seriously delinquent	428	[1],[2],[9]	1,105	[1],[2],[9]
Total delinquent	606	[1],[9]	1,315	[1],[9]
Current	190,445	[1],[9]	177,906	[1],[9]
Total recorded investment in loans	191,051	[1],[10],[9]	179,221	[1],[10],[9]
Recorded investment in loans 90 days or more delinquent and accruing interest	0	[1],[3],[9]	0	[1],[9]
Recorded investment in nonaccrual loans	2,214	[1],[9]	2,764	[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]
Financing Receivable, Recorded Investment, Past Due [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 collectibility resulting from this agreement, see “Note 20, Subsequent Events.”

[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 $50.9 billion and $51.9 billion as of December 31, 2012 and 2011, 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).