Mortgage Loans Aging (Details) (USD $) In Millions, unless otherwise specified	Jun. 30, 2012		Dec. 31, 2011
Financing Receivable, Recorded Investment, Past Due [Line Items]
30 - 59 days delinquent	$ 48,441	[1]	$ 54,393	[1]
60 - 89 days delinquent	16,566	[1]	19,816	[1]
Seriously delinquent	108,829	[1],[2]	121,744	[1],[2]
Total delinquent	173,836	[1]	195,953	[1]
Current	2,818,411	[1]	2,782,938	[1]
Total	2,992,247	[1]	2,978,891	[1]
Recorded investment in loans 90 days or more delinquent and accruing interest	525	[1]	548	[1]
Recorded investment in nonaccrual loans	126,244	[1]	142,612	[1]
Single-Family [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30 - 59 days delinquent	48,272	[1]	54,183	[1]
60 - 89 days delinquent	16,566	[1]	19,816	[1]
Seriously delinquent	108,289	[1],[2]	120,639	[1],[2]
Total delinquent	173,127	[1]	194,638	[1]
Current	2,635,771	[1]	2,605,032	[1]
Total	2,808,898	[1]	2,799,670	[1]
Recorded investment in loans 90 days or more delinquent and accruing interest	525	[1]	548	[1]
Recorded investment in nonaccrual loans	124,172	[1]	139,848	[1]
Single-Family [Member] | Primary [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30 - 59 days delinquent	38,978	[1],[3]	43,516	[1],[3]
60 - 89 days delinquent	12,844	[1],[3]	15,282	[1],[3]
Seriously delinquent	73,084	[1],[2],[3]	80,712	[1],[2],[3]
Total delinquent	124,906	[1],[3]	139,510	[1],[3]
Current	2,387,341	[1],[3]	2,341,646	[1],[3]
Total	2,512,247	[1],[3],[4],[5]	2,481,156	[1],[3],[4],[5]
Recorded investment in loans 90 days or more delinquent and accruing interest	105	[1],[3]	111	[1],[3]
Recorded investment in nonaccrual loans	85,781	[1],[3]	95,959	[1],[3]
Single-Family [Member] | Government [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30 - 59 days delinquent	86	[1],[6]	109	[1],[6]
60 - 89 days delinquent	42	[1],[6]	49	[1],[6]
Seriously delinquent	328	[1],[2],[6]	327	[1],[2],[6]
Total delinquent	456	[1],[6]	485	[1],[6]
Current	50,884	[1],[6]	51,391	[1],[6]
Total	51,340	[1],[6]	51,876	[1],[6]
Recorded investment in loans 90 days or more delinquent and accruing interest	328	[1],[6]	327	[1],[6]
Recorded investment in nonaccrual loans	0	[1],[6]	0	[1],[6]
Single-Family [Member] | Alt-A [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30 - 59 days delinquent	6,297	[1]	7,155	[1]
60 - 89 days delinquent	2,522	[1]	3,054	[1]
Seriously delinquent	25,048	[1],[2]	28,323	[1],[2]
Total delinquent	33,867	[1]	38,532	[1]
Current	131,105	[1]	138,880	[1]
Total	164,972	[1],[4],[5]	177,412	[1],[4],[5]
Recorded investment in loans 90 days or more delinquent and accruing interest	16	[1]	14	[1]
Recorded investment in nonaccrual loans	27,549	[1]	31,356	[1]
Single-Family [Member] | Other [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30 - 59 days delinquent	2,911	[1],[7]	3,403	[1],[7]
60 - 89 days delinquent	1,158	[1],[7]	1,431	[1],[7]
Seriously delinquent	9,829	[1],[2],[7]	11,277	[1],[2],[7]
Total delinquent	13,898	[1],[7]	16,111	[1],[7]
Current	66,441	[1],[7]	73,115	[1],[7]
Total	80,339	[1],[4],[5],[7]	89,226	[1],[4],[5],[7]
Recorded investment in loans 90 days or more delinquent and accruing interest	76	[1],[7]	96	[1],[7]
Recorded investment in nonaccrual loans	10,842	[1],[7]	12,533	[1],[7]
Multifamily [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30 - 59 days delinquent	169	[1],[8]	210	[1],[8]
Seriously delinquent	540	[1],[2],[8]	1,105	[1],[2],[8]
Total delinquent	709	[1],[8]	1,315	[1],[8]
Current	182,640	[1],[8]	177,906	[1],[8]
Total	183,349	[1],[8],[9]	179,221	[1],[8],[9]
Recorded investment in loans 90 days or more delinquent and accruing interest	0	[1],[8]	0	[1],[8]
Recorded investment in nonaccrual loans	$ 2,072	[1],[8]	$ 2,764	[1],[8]
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

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

[4] Excludes $51.3 billion and $51.9 billion as of June 30, 2012 and December 31, 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.

[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] 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.

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

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

[9] 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).