Mortgage Loans Individually Impaired Loans - 2 (Details) (USD $)	3 Months Ended				9 Months Ended
	Sep. 30, 2014		Sep. 30, 2013		Sep. 30, 2014		Sep. 30, 2013		Dec. 31, 2013
Financing Receivable, Impaired [Line Items]
Individually impaired loans with related allowance recorded: average recorded investment	$ 170,875,000,000		$ 176,883,000,000		$ 173,083,000,000		$ 178,763,000,000
Individually impaired loans with related allowance recorded: total interest income recognized	1,465,000,000	[1]	1,494,000,000	[1]	4,446,000,000	[1]	4,530,000,000	[1]
Individually impaired loans with related allowance recorded: interest income recognized on a cash basis	143,000,000		184,000,000		474,000,000		613,000,000
Individually impaired loans with no related allowance recorded: average recorded investment	19,964,000,000	[2]	17,330,000,000	[2]	18,914,000,000	[2]	15,964,000,000	[2]
Individually impaired loans with no related allowance recorded: total interest income recognized	312,000,000	[1],[2]	341,000,000	[1],[2]	853,000,000	[1],[2]	1,632,000,000	[1],[2]
Individually impaired loans with no related allowance recorded: interest income recognized on a cash basis	73,000,000	[2]	75,000,000	[2]	199,000,000	[2]	224,000,000	[2]
Impaired Financing Receivable, Interest Income, Accrual Method	1,777,000,000	[1],[3]	1,835,000,000	[1],[3]	5,299,000,000	[1],[3]	6,162,000,000	[1],[3]
Individually impaired loans: average recorded investment	190,839,000,000	[3]	194,213,000,000	[3]	191,997,000,000	[3]	194,727,000,000	[3]
Individually impaired loans: interest income recognized on a cash basis	216,000,000	[3]	259,000,000	[3]	673,000,000	[3]	837,000,000	[3]
Table Footnote [Abstract]
Individually impaired loans: total interest income recognized	1,777,000,000	[1],[3]	1,835,000,000	[1],[3]	5,299,000,000	[1],[3]	6,162,000,000	[1],[3]
Single-Family [Member]
Financing Receivable, Impaired [Line Items]
Individually impaired loans with related allowance recorded: average recorded investment	169,335,000,000		174,250,000,000		171,270,000,000		176,142,000,000
Individually impaired loans with related allowance recorded: total interest income recognized	1,448,000,000	[1]	1,462,000,000	[1]	4,383,000,000	[1]	4,431,000,000	[1]
Individually impaired loans with related allowance recorded: interest income recognized on a cash basis	143,000,000		184,000,000		474,000,000		612,000,000
Individually impaired loans with no related allowance recorded: average recorded investment	18,392,000,000	[2]	15,328,000,000	[2]	17,216,000,000	[2]	14,121,000,000	[2]
Individually impaired loans with no related allowance recorded: total interest income recognized	294,000,000	[1],[2]	316,000,000	[1],[2]	795,000,000	[1],[2]	1,560,000,000	[1],[2]
Individually impaired loans with no related allowance recorded: interest income recognized on a cash basis	73,000,000	[2]	73,000,000	[2]	199,000,000	[2]	221,000,000	[2]
Impaired Financing Receivable, Interest Income, Accrual Method	1,800,000,000		1,800,000,000		5,200,000,000		6,000,000,000
Table Footnote [Abstract]
Troubled debt restructuring recorded investment	185,900,000,000				185,900,000,000				187,600,000,000
Individually impaired loans: contractual interest income	1,400,000,000		1,400,000,000		4,300,000,000		4,300,000,000
Individually impaired loans: total interest income recognized	1,800,000,000		1,800,000,000		5,200,000,000		6,000,000,000
Individually impaired loans: effective yield adjustments	297,000,000		355,000,000		857,000,000		1,700,000,000
Single-Family [Member] | Primary [Member]
Financing Receivable, Impaired [Line Items]
Individually impaired loans with related allowance recorded: average recorded investment	121,246,000,000	[4]	123,818,000,000	[4]	122,443,000,000	[4]	125,026,000,000	[4]
Individually impaired loans with related allowance recorded: total interest income recognized	1,077,000,000	[1],[4]	1,081,000,000	[1],[4]	3,264,000,000	[1],[4]	3,276,000,000	[1],[4]
Individually impaired loans with related allowance recorded: interest income recognized on a cash basis	111,000,000	[4]	141,000,000	[4]	372,000,000	[4]	466,000,000	[4]
Individually impaired loans with no related allowance recorded: average recorded investment	14,442,000,000	[2],[4]	12,067,000,000	[2],[4]	13,514,000,000	[2],[4]	11,148,000,000	[2],[4]
Individually impaired loans with no related allowance recorded: total interest income recognized	226,000,000	[1],[2],[4]	243,000,000	[1],[2],[4]	616,000,000	[1],[2],[4]	1,167,000,000	[1],[2],[4]
Individually impaired loans with no related allowance recorded: interest income recognized on a cash basis	56,000,000	[2],[4]	58,000,000	[2],[4]	157,000,000	[2],[4]	174,000,000	[2],[4]
Single-Family [Member] | Government [Member]
Financing Receivable, Impaired [Line Items]
Individually impaired loans with related allowance recorded: average recorded investment	285,000,000	[5]	215,000,000	[5]	266,000,000	[5]	213,000,000	[5]
Individually impaired loans with related allowance recorded: total interest income recognized	3,000,000	[1],[5]	3,000,000	[1],[5]	9,000,000	[1],[5]	8,000,000	[1],[5]
Individually impaired loans with related allowance recorded: interest income recognized on a cash basis	0	[5]	0	[5]	0	[5]	0	[5]
Individually impaired loans with no related allowance recorded: average recorded investment	55,000,000	[2],[5]	114,000,000	[2],[5]	70,000,000	[2],[5]	111,000,000	[2],[5]
Individually impaired loans with no related allowance recorded: total interest income recognized	1,000,000	[1],[2],[5]	2,000,000	[1],[2],[5]	4,000,000	[1],[2],[5]	6,000,000	[1],[2],[5]
Individually impaired loans with no related allowance recorded: interest income recognized on a cash basis	0	[2],[5]	0	[2],[5]	0	[2],[5]	0	[2],[5]
Single-Family [Member] | Alt-A [Member]
Financing Receivable, Impaired [Line Items]
Individually impaired loans with related allowance recorded: average recorded investment	33,458,000,000		34,865,000,000		33,926,000,000		35,231,000,000
Individually impaired loans with related allowance recorded: total interest income recognized	268,000,000	[1]	274,000,000	[1]	805,000,000	[1]	826,000,000	[1]
Individually impaired loans with related allowance recorded: interest income recognized on a cash basis	24,000,000		31,000,000		74,000,000		105,000,000
Individually impaired loans with no related allowance recorded: average recorded investment	2,887,000,000	[2]	2,332,000,000	[2]	2,687,000,000	[2]	2,145,000,000	[2]
Individually impaired loans with no related allowance recorded: total interest income recognized	51,000,000	[1],[2]	52,000,000	[1],[2]	135,000,000	[1],[2]	282,000,000	[1],[2]
Individually impaired loans with no related allowance recorded: interest income recognized on a cash basis	14,000,000	[2]	11,000,000	[2]	34,000,000	[2]	33,000,000	[2]
Single-Family [Member] | Other [Member]
Financing Receivable, Impaired [Line Items]
Individually impaired loans with related allowance recorded: average recorded investment	14,346,000,000	[6]	15,352,000,000	[6]	14,635,000,000	[6]	15,672,000,000	[6]
Individually impaired loans with related allowance recorded: total interest income recognized	100,000,000	[1],[6]	104,000,000	[1],[6]	305,000,000	[1],[6]	321,000,000	[1],[6]
Individually impaired loans with related allowance recorded: interest income recognized on a cash basis	8,000,000	[6]	12,000,000	[6]	28,000,000	[6]	41,000,000	[6]
Individually impaired loans with no related allowance recorded: average recorded investment	1,008,000,000	[2],[6]	815,000,000	[2],[6]	945,000,000	[2],[6]	717,000,000	[2],[6]
Individually impaired loans with no related allowance recorded: total interest income recognized	16,000,000	[1],[2],[6]	19,000,000	[1],[2],[6]	40,000,000	[1],[2],[6]	105,000,000	[1],[2],[6]
Individually impaired loans with no related allowance recorded: interest income recognized on a cash basis	3,000,000	[2],[6]	4,000,000	[2],[6]	8,000,000	[2],[6]	14,000,000	[2],[6]
Multifamily [Member]
Financing Receivable, Impaired [Line Items]
Individually impaired loans with related allowance recorded: average recorded investment	1,540,000,000		2,633,000,000		1,813,000,000		2,621,000,000
Individually impaired loans with related allowance recorded: total interest income recognized	17,000,000	[1]	32,000,000	[1]	63,000,000	[1]	99,000,000	[1]
Individually impaired loans with related allowance recorded: interest income recognized on a cash basis	0		0		0		1,000,000
Individually impaired loans with no related allowance recorded: average recorded investment	1,572,000,000	[2]	2,002,000,000	[2]	1,698,000,000	[2]	1,843,000,000	[2]
Individually impaired loans with no related allowance recorded: total interest income recognized	18,000,000	[1],[2]	25,000,000	[1],[2]	58,000,000	[1],[2]	72,000,000	[1],[2]
Individually impaired loans with no related allowance recorded: interest income recognized on a cash basis	0	[2]	2,000,000	[2]	0	[2]	3,000,000	[2]
Table Footnote [Abstract]
Troubled debt restructuring recorded investment	$ 1,600,000,000				$ 1,600,000,000				$ 911,000,000

[1] Total single-family interest income recognized of $1.8 billion for the three months ended September 30, 2014 and 2013, consists of $1.4 billion of contractual interest and $297 million and $355 million of effective yield adjustments, respectively. Total single-family interest income recognized of $5.2 billion and $6.0 billion for the nine months ended September 30, 2014 and 2013, respectively, consists of $4.3 billion of contractual interest and $857 million and $1.7 billion of effective yield adjustments, respectively.

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

[3] Includes single-family loans restructured in a TDR with a recorded investment of $185.9 billion and $187.6 billion as of September 30, 2014 and December 31, 2013, respectively. Includes multifamily loans restructured in a TDR with a recorded investment of $1.6 billion and $911 million as of September 30, 2014 and December 31, 2013, respectively.

[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.