Mortgage Loans Individually Impaired Loans (Details) (USD $) In Millions, unless otherwise specified	Jun. 30, 2012		Dec. 31, 2011
Financing Receivable, Impaired [Line Items]
Individually impaired loans with related allowance recorded: unpaid principal balance	$ 170,672		$ 170,414
Individually impaired loans with related allowance recorded: total recorded investment	160,469	[1]	159,676	[1]
Individually impaired loans with related allowance recorded: related allowance for loan losses	42,915	[2]	46,857	[2]
Individually impaired loans with no related allowance recorded: unpaid principal balance	17,281	[3]	14,890	[3]
Individually impaired loans with no related allowance recorded: total recorded investment	12,552	[1],[3]	10,164	[1],[3]
Total individually impaired loans: unpaid principal balance	187,953	[2]	185,304	[2]
Total individually impaired loans: total recorded investment	173,021	[1],[2]	169,840	[1],[2]
Interest Receivable [Member]
Financing Receivable, Impaired [Line Items]
Individually impaired loans with related allowance recorded: related allowance for loan losses	890	[2]	1,081	[2]
Single-Family [Member]
Financing Receivable, Impaired [Line Items]
Individually impaired loans with related allowance recorded: unpaid principal balance	168,197		167,582
Individually impaired loans with related allowance recorded: total recorded investment	157,971	[1]	156,821	[1]
Individually impaired loans with related allowance recorded: related allowance for loan losses	42,407		46,139
Individually impaired loans with no related allowance recorded: unpaid principal balance	15,526	[3]	13,131	[3]
Individually impaired loans with no related allowance recorded: total recorded investment	10,788	[1],[3]	8,393	[1],[3]
Table Footnote [Abstract]
Troubled debt restructuring recorded investment	165,900		161,900
Single-Family [Member] | Interest Receivable [Member]
Financing Receivable, Impaired [Line Items]
Individually impaired loans with related allowance recorded: related allowance for loan losses	877		1,049
Multifamily [Member]
Financing Receivable, Impaired [Line Items]
Individually impaired loans with related allowance recorded: unpaid principal balance	2,475		2,832
Individually impaired loans with related allowance recorded: total recorded investment	2,498	[1]	2,855	[1]
Individually impaired loans with related allowance recorded: related allowance for loan losses	508		718
Individually impaired loans with no related allowance recorded: unpaid principal balance	1,755	[3]	1,759	[3]
Individually impaired loans with no related allowance recorded: total recorded investment	1,764	[1],[3]	1,771	[1],[3]
Table Footnote [Abstract]
Troubled debt restructuring recorded investment	1,000		956
Multifamily [Member] | Interest Receivable [Member]
Financing Receivable, Impaired [Line Items]
Individually impaired loans with related allowance recorded: related allowance for loan losses	13		32
Primary [Member] | Single-Family [Member]
Financing Receivable, Impaired [Line Items]
Individually impaired loans with related allowance recorded: unpaid principal balance	117,485	[4]	116,825	[4]
Individually impaired loans with related allowance recorded: total recorded investment	110,755	[1],[4]	109,684	[1],[4]
Individually impaired loans with related allowance recorded: related allowance for loan losses	27,183	[4]	29,598	[4]
Individually impaired loans with no related allowance recorded: unpaid principal balance	11,364	[3],[4]	9,370	[3],[4]
Individually impaired loans with no related allowance recorded: total recorded investment	8,410	[1],[3],[4]	6,471	[1],[3],[4]
Primary [Member] | Single-Family [Member] | Interest Receivable [Member]
Financing Receivable, Impaired [Line Items]
Individually impaired loans with related allowance recorded: related allowance for loan losses	568	[4]	674	[4]
Government [Member] | Single-Family [Member]
Financing Receivable, Impaired [Line Items]
Individually impaired loans with related allowance recorded: unpaid principal balance	188	[5]	258	[5]
Individually impaired loans with related allowance recorded: total recorded investment	185	[1],[5]	258	[1],[5]
Individually impaired loans with related allowance recorded: related allowance for loan losses	28	[5]	67	[5]
Individually impaired loans with no related allowance recorded: unpaid principal balance	116	[3],[5]	25	[3],[5]
Individually impaired loans with no related allowance recorded: total recorded investment	112	[1],[3],[5]	17	[1],[3],[5]
Government [Member] | Single-Family [Member] | Interest Receivable [Member]
Financing Receivable, Impaired [Line Items]
Individually impaired loans with related allowance recorded: related allowance for loan losses	4	[5]	8	[5]
Alt-A [Member] | Single-Family [Member]
Financing Receivable, Impaired [Line Items]
Individually impaired loans with related allowance recorded: unpaid principal balance	34,513		34,318
Individually impaired loans with related allowance recorded: total recorded investment	31,801	[1]	31,516	[1]
Individually impaired loans with related allowance recorded: related allowance for loan losses	10,358		11,121
Individually impaired loans with no related allowance recorded: unpaid principal balance	3,297	[3]	3,056	[3]
Individually impaired loans with no related allowance recorded: total recorded investment	1,825	[1],[3]	1,538	[1],[3]
Alt-A [Member] | Single-Family [Member] | Interest Receivable [Member]
Financing Receivable, Impaired [Line Items]
Individually impaired loans with related allowance recorded: related allowance for loan losses	225		268
Other [Member] | Single-Family [Member]
Financing Receivable, Impaired [Line Items]
Individually impaired loans with related allowance recorded: unpaid principal balance	16,011	[6]	16,181	[6]
Individually impaired loans with related allowance recorded: total recorded investment	15,230	[1],[6]	15,363	[1],[6]
Individually impaired loans with related allowance recorded: related allowance for loan losses	4,838	[6]	5,353	[6]
Individually impaired loans with no related allowance recorded: unpaid principal balance	749	[3],[6]	680	[3],[6]
Individually impaired loans with no related allowance recorded: total recorded investment	441	[1],[3],[6]	367	[1],[3],[6]
Other [Member] | Single-Family [Member] | Interest Receivable [Member]
Financing Receivable, Impaired [Line Items]
Individually impaired loans with related allowance recorded: related allowance for loan losses	$ 80	[6]	$ 99	[6]

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

[2] Includes single-family loans restructured in a TDR with a recorded investment of $165.9 billion and $161.9 billion as of June 30, 2012 and December 31, 2011, respectively. Includes multifamily loans restructured in a TDR with a recorded investment of $1.0 billion and $956 million as of June 30, 2012 and December 31, 2011, respectively.

[3] The discounted cash flows or collateral value equals or exceeds the carrying value of the loan and, as such, no valuation allowance is required.

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

[5] 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.

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