Mortgage Loans Individually Impaired Loans (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended				9 Months Ended
	Sep. 30, 2013		Sep. 30, 2012		Sep. 30, 2013		Sep. 30, 2012		Dec. 31, 2012
Financing Receivable, Impaired [Line Items]
Individually impaired loans with related allowance recorded: average recorded investment	$ 176,883		$ 166,057		$ 178,763		$ 162,219
Impaired Financing Receivable, Interest Income, Accrual Method	1,835	[1],[2]	1,791	[1],[2]	6,162	[1],[2]	5,166	[1],[2]
Individually impaired loans with related allowance recorded: unpaid principal balance	187,126				187,126				190,677
Individually impaired loans with related allowance recorded: total recorded investment	177,059	[3]			177,059	[3]			180,519	[3]
Individually impaired loans with related allowance recorded: related allowance for loan losses	37,946	[1]			37,946	[1]			45,034	[1]
Individually impaired loans with no related allowance recorded: unpaid principal balance	20,305	[4]			20,305	[4]			23,594	[4]
Individually impaired loans with no related allowance recorded: total recorded investment	17,361	[3],[4]			17,361	[3],[4]			19,872	[3],[4]
Total individually impaired loans: unpaid principal balance	207,431	[1]			207,431	[1]			214,271	[1]
Total individually impaired loans: total recorded investment	194,420	[1],[3]			194,420	[1],[3]			200,391	[1],[3]
Individually impaired loans with related allowance recorded: total interest income recognized	1,494	[2]	1,417	[2]	4,530	[2]	4,154	[2]
Individually impaired loans with related allowance recorded: interest income recognized on a cash basis	184		208		613		639
Individually impaired loans with no related allowance recorded: average recorded investment	17,330	[4]	12,817	[4]	15,964	[4]	11,466	[4]
Individually impaired loans with no related allowance recorded: total interest income recognized	341	[2],[4]	374	[2],[4]	1,632	[2],[4]	1,012	[2],[4]
Individually impaired loans with no related allowance recorded: interest income recognized on a cash basis	75	[4]	79	[4]	224	[4]	236	[4]
Impaired Financing Receivable, Average Recorded Investment	194,213	[1]	178,874	[1]	194,727	[1]	173,685	[1]
Impaired Financing Receivable, Interest Income, Cash Basis Method	259	[1]	287	[1]	837	[1]	875	[1]
Interest Receivable [Member]
Financing Receivable, Impaired [Line Items]
Individually impaired loans with related allowance recorded: related allowance for loan losses	737	[1]			737	[1]			998	[1]
Single-Family [Member]
Financing Receivable, Impaired [Line Items]
Individually impaired loans with related allowance recorded: average recorded investment	174,250		163,637		176,142		159,668
Impaired Financing Receivable, Interest Income, Accrual Method	1,800		1,700		6,000		5,000
Individually impaired loans with related allowance recorded: unpaid principal balance	184,551				184,551				188,228
Individually impaired loans with related allowance recorded: total recorded investment	174,461	[3]			174,461	[3]			178,048	[3]
Individually impaired loans with related allowance recorded: related allowance for loan losses	37,548				37,548				44,545
Individually impaired loans with no related allowance recorded: unpaid principal balance	18,347	[4]			18,347	[4]			21,538	[4]
Individually impaired loans with no related allowance recorded: total recorded investment	15,395	[3],[4]			15,395	[3],[4]			17,804	[3],[4]
Individually impaired loans with related allowance recorded: total interest income recognized	1,462	[2]	1,386	[2]	4,431	[2]	4,058	[2]
Individually impaired loans with related allowance recorded: interest income recognized on a cash basis	184		207		612		637
Individually impaired loans with no related allowance recorded: average recorded investment	15,328	[4]	11,119	[4]	14,121	[4]	9,759	[4]
Individually impaired loans with no related allowance recorded: total interest income recognized	316	[2],[4]	351	[2],[4]	1,560	[2],[4]	942	[2],[4]
Individually impaired loans with no related allowance recorded: interest income recognized on a cash basis	73	[4]	79	[4]	221	[4]	235	[4]
Table Footnote [Abstract]
Troubled debt restructuring recorded investment	188,200				188,200				193,400
Single-Family [Member] | Interest Receivable [Member]
Financing Receivable, Impaired [Line Items]
Individually impaired loans with related allowance recorded: related allowance for loan losses	724				724				985
Single-Family [Member] | Primary [Member]
Financing Receivable, Impaired [Line Items]
Individually impaired loans with related allowance recorded: average recorded investment	123,818	[5]	115,042	[5]	125,026	[5]	112,050	[5]
Individually impaired loans with related allowance recorded: unpaid principal balance	130,662	[5]			130,662	[5]			132,754	[5]
Individually impaired loans with related allowance recorded: total recorded investment	124,205	[3],[5]			124,205	[3],[5]			126,106	[3],[5]
Individually impaired loans with related allowance recorded: related allowance for loan losses	24,146	[5]			24,146	[5]			28,610	[5]
Individually impaired loans with no related allowance recorded: unpaid principal balance	13,901	[4],[5]			13,901	[4],[5]			16,222	[4],[5]
Individually impaired loans with no related allowance recorded: total recorded investment	12,042	[3],[4],[5]			12,042	[3],[4],[5]			13,901	[3],[4],[5]
Individually impaired loans with related allowance recorded: total interest income recognized	1,081	[2],[5]	1,014	[2],[5]	3,276	[2],[5]	2,954	[2],[5]
Individually impaired loans with related allowance recorded: interest income recognized on a cash basis	141	[5]	157	[5]	466	[5]	479	[5]
Individually impaired loans with no related allowance recorded: average recorded investment	12,067	[4],[5]	8,709	[4],[5]	11,148	[4],[5]	7,579	[4],[5]
Individually impaired loans with no related allowance recorded: total interest income recognized	243	[2],[4],[5]	267	[2],[4],[5]	1,167	[2],[4],[5]	705	[2],[4],[5]
Individually impaired loans with no related allowance recorded: interest income recognized on a cash basis	58	[4],[5]	59	[4],[5]	174	[4],[5]	174	[4],[5]
Single-Family [Member] | Primary [Member] | Interest Receivable [Member]
Financing Receivable, Impaired [Line Items]
Individually impaired loans with related allowance recorded: related allowance for loan losses	461	[5]			461	[5]			628	[5]
Single-Family [Member] | Government [Member]
Financing Receivable, Impaired [Line Items]
Individually impaired loans with related allowance recorded: average recorded investment	215	[6]	197	[6]	213	[6]	220	[6]
Individually impaired loans with related allowance recorded: unpaid principal balance	222	[6]			222	[6]			214	[6]
Individually impaired loans with related allowance recorded: total recorded investment	217	[3],[6]			217	[3],[6]			208	[3],[6]
Individually impaired loans with related allowance recorded: related allowance for loan losses	36	[6]			36	[6]			38	[6]
Individually impaired loans with no related allowance recorded: unpaid principal balance	112	[4],[6]			112	[4],[6]			104	[4],[6]
Individually impaired loans with no related allowance recorded: total recorded investment	113	[3],[4],[6]			113	[3],[4],[6]			104	[3],[4],[6]
Individually impaired loans with related allowance recorded: total interest income recognized	3	[2],[6]	3	[2],[6]	8	[2],[6]	9	[2],[6]
Individually impaired loans with related allowance recorded: interest income recognized on a cash basis	0	[6]	0	[6]	0	[6]	0	[6]
Individually impaired loans with no related allowance recorded: average recorded investment	114	[4],[6]	102	[4],[6]	111	[4],[6]	71	[4],[6]
Individually impaired loans with no related allowance recorded: total interest income recognized	2	[2],[4],[6]	2	[2],[4],[6]	6	[2],[4],[6]	5	[2],[4],[6]
Individually impaired loans with no related allowance recorded: interest income recognized on a cash basis	0	[4],[6]	0	[4],[6]	0	[4],[6]	0	[4],[6]
Single-Family [Member] | Government [Member] | Interest Receivable [Member]
Financing Receivable, Impaired [Line Items]
Individually impaired loans with related allowance recorded: related allowance for loan losses	4	[6]			4	[6]			4	[6]
Single-Family [Member] | Alt-A [Member]
Financing Receivable, Impaired [Line Items]
Individually impaired loans with related allowance recorded: average recorded investment	34,865		32,875		35,231		32,050
Individually impaired loans with related allowance recorded: unpaid principal balance	37,637				37,637				38,387
Individually impaired loans with related allowance recorded: total recorded investment	34,767	[3]			34,767	[3]			35,620	[3]
Individually impaired loans with related allowance recorded: related allowance for loan losses	9,465				9,465				11,154
Individually impaired loans with no related allowance recorded: unpaid principal balance	3,330	[4]			3,330	[4]			3,994	[4]
Individually impaired loans with no related allowance recorded: total recorded investment	2,423	[3],[4]			2,423	[3],[4]			2,822	[3],[4]
Individually impaired loans with related allowance recorded: total interest income recognized	274	[2]	259	[2]	826	[2]	765	[2]
Individually impaired loans with related allowance recorded: interest income recognized on a cash basis	31		35		105		109
Individually impaired loans with no related allowance recorded: average recorded investment	2,332	[4]	1,865	[4]	2,145	[4]	1,703	[4]
Individually impaired loans with no related allowance recorded: total interest income recognized	52	[2],[4]	61	[2],[4]	282	[2],[4]	172	[2],[4]
Individually impaired loans with no related allowance recorded: interest income recognized on a cash basis	11	[4]	14	[4]	33	[4]	42	[4]
Single-Family [Member] | Alt-A [Member] | Interest Receivable [Member]
Financing Receivable, Impaired [Line Items]
Individually impaired loans with related allowance recorded: related allowance for loan losses	199				199				267
Single-Family [Member] | Other [Member]
Financing Receivable, Impaired [Line Items]
Individually impaired loans with related allowance recorded: average recorded investment	15,352	[7]	15,523	[7]	15,672	[7]	15,348	[7]
Individually impaired loans with related allowance recorded: unpaid principal balance	16,030	[7]			16,030	[7]			16,873	[7]
Individually impaired loans with related allowance recorded: total recorded investment	15,272	[3],[7]			15,272	[3],[7]			16,114	[3],[7]
Individually impaired loans with related allowance recorded: related allowance for loan losses	3,901	[7]			3,901	[7]			4,743	[7]
Individually impaired loans with no related allowance recorded: unpaid principal balance	1,004	[4],[7]			1,004	[4],[7]			1,218	[4],[7]
Individually impaired loans with no related allowance recorded: total recorded investment	817	[3],[4],[7]			817	[3],[4],[7]			977	[3],[4],[7]
Individually impaired loans with related allowance recorded: total interest income recognized	104	[2],[7]	110	[2],[7]	321	[2],[7]	330	[2],[7]
Individually impaired loans with related allowance recorded: interest income recognized on a cash basis	12	[7]	15	[7]	41	[7]	49	[7]
Individually impaired loans with no related allowance recorded: average recorded investment	815	[4],[7]	443	[4],[7]	717	[4],[7]	406	[4],[7]
Individually impaired loans with no related allowance recorded: total interest income recognized	19	[2],[4],[7]	21	[2],[4],[7]	105	[2],[4],[7]	60	[2],[4],[7]
Individually impaired loans with no related allowance recorded: interest income recognized on a cash basis	4	[4],[7]	6	[4],[7]	14	[4],[7]	19	[4],[7]
Single-Family [Member] | Other [Member] | Interest Receivable [Member]
Financing Receivable, Impaired [Line Items]
Individually impaired loans with related allowance recorded: related allowance for loan losses	60	[7]			60	[7]			86	[7]
Multifamily [Member]
Financing Receivable, Impaired [Line Items]
Individually impaired loans with related allowance recorded: average recorded investment	2,633		2,420		2,621		2,551
Individually impaired loans with related allowance recorded: unpaid principal balance	2,575				2,575				2,449
Individually impaired loans with related allowance recorded: total recorded investment	2,598	[3]			2,598	[3]			2,471	[3]
Individually impaired loans with related allowance recorded: related allowance for loan losses	398				398				489
Individually impaired loans with no related allowance recorded: unpaid principal balance	1,958	[4]			1,958	[4]			2,056	[4]
Individually impaired loans with no related allowance recorded: total recorded investment	1,966	[3],[4]			1,966	[3],[4]			2,068	[3],[4]
Individually impaired loans with related allowance recorded: total interest income recognized	32	[2]	31	[2]	99	[2]	96	[2]
Individually impaired loans with related allowance recorded: interest income recognized on a cash basis	0		1		1		2
Individually impaired loans with no related allowance recorded: average recorded investment	2,002	[4]	1,698	[4]	1,843	[4]	1,707	[4]
Individually impaired loans with no related allowance recorded: total interest income recognized	25	[2],[4]	23	[2],[4]	72	[2],[4]	70	[2],[4]
Individually impaired loans with no related allowance recorded: interest income recognized on a cash basis	2	[4]	0	[4]	3	[4]	1	[4]
Table Footnote [Abstract]
Troubled debt restructuring recorded investment	904				904				1,100
Multifamily [Member] | Interest Receivable [Member]
Financing Receivable, Impaired [Line Items]
Individually impaired loans with related allowance recorded: related allowance for loan losses	$ 13				$ 13				$ 13

[1] Includes single-family loans restructured in a TDR with a recorded investment of $188.2 billion and $193.4 billion as of September 30, 2013 and December 31, 2012, respectively. Includes multifamily loans restructured in a TDR with a recorded investment of $904 million and $1.1 billion as of September 30, 2013 and December 31, 2012, respectively.

[2] Total single-family interest income recognized of $1.8 billion and $1.7 billion for the three months ended September 30, 2013 and 2012, respectively, consists of $1.4 billion and $1.3 billion of contractual interest and $355 million and $444 million of effective yield adjustments. Total single-family interest income recognized of $6.0 billion and $5.0 billion for the nine months ended September 30, 2013 and 2012, respectively, consists of $4.3 billion and $3.7 billion of contractual interest and $1.7 billion and $1.3 billion of effective yield adjustments.

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

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

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

[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.

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