Mortgage Loans Individually Impaired Loans - 2 (Details) (USD $)	3 Months Ended				6 Months Ended
	Jun. 30, 2014		Jun. 30, 2013		Jun. 30, 2014		Jun. 30, 2013		Dec. 31, 2013
Financing Receivable, Impaired [Line Items]
Individually impaired loans with related allowance recorded: average recorded investment	$ 173,583,000,000		$ 179,683,000,000		$ 174,255,000,000		$ 179,754,000,000
Individually impaired loans with related allowance recorded: total interest income recognized	1,488,000,000	[1]	1,514,000,000	[1]	2,981,000,000	[1]	3,036,000,000	[1]
Individually impaired loans with related allowance recorded: interest income recognized on a cash basis	152,000,000		203,000,000		331,000,000		429,000,000
Individually impaired loans with no related allowance recorded: average recorded investment	18,700,000,000	[2]	14,712,000,000	[2]	18,375,000,000	[2]	15,318,000,000	[2]
Individually impaired loans with no related allowance recorded: total interest income recognized	283,000,000	[1],[2]	388,000,000	[1],[2]	541,000,000	[1],[2]	1,291,000,000	[1],[2]
Individually impaired loans with no related allowance recorded: interest income recognized on a cash basis	66,000,000	[2]	74,000,000	[2]	126,000,000	[2]	149,000,000	[2]
Individually impaired loans: average recorded investment	192,283,000,000	[3]	194,395,000,000	[3]	192,630,000,000	[3]	195,072,000,000	[3]
Individually impaired loans: interest income recognized on a cash basis	218,000,000	[3]	277,000,000	[3]	457,000,000	[3]	578,000,000	[3]
Table Footnote [Abstract]
Individually impaired loans: total interest income recognized	1,771,000,000	[1],[3]	1,902,000,000	[1],[3]	3,522,000,000	[1],[3]	4,327,000,000	[1],[3]
Single-Family [Member]
Financing Receivable, Impaired [Line Items]
Individually impaired loans with related allowance recorded: average recorded investment	171,770,000,000		176,979,000,000		172,288,000,000		177,126,000,000
Individually impaired loans with related allowance recorded: total interest income recognized	1,465,000,000	[1]	1,478,000,000	[1]	2,935,000,000	[1]	2,969,000,000	[1]
Individually impaired loans with related allowance recorded: interest income recognized on a cash basis	152,000,000		202,000,000		331,000,000		428,000,000
Individually impaired loans with no related allowance recorded: average recorded investment	17,032,000,000	[2]	13,046,000,000	[2]	16,617,000,000	[2]	13,518,000,000	[2]
Individually impaired loans with no related allowance recorded: total interest income recognized	263,000,000	[1],[2]	363,000,000	[1],[2]	501,000,000	[1],[2]	1,244,000,000	[1],[2]
Individually impaired loans with no related allowance recorded: interest income recognized on a cash basis	66,000,000	[2]	74,000,000	[2]	126,000,000	[2]	148,000,000	[2]
Table Footnote [Abstract]
Troubled debt restructuring recorded investment	187,100,000,000				187,100,000,000				187,600,000,000
Individually impaired loans: total interest income recognized	1,700,000,000		1,800,000,000		3,400,000,000		4,200,000,000
Individually impaired loans: contractual interest income	1,400,000,000		1,400,000,000		2,900,000,000		2,900,000,000
Individually impaired loans: effective yield adjustments	285,000,000		410,000,000		560,000,000		1,300,000,000
Single-Family [Member] | Primary [Member]
Financing Receivable, Impaired [Line Items]
Individually impaired loans with related allowance recorded: average recorded investment	122,791,000,000	[4]	125,689,000,000	[4]	123,066,000,000	[4]	125,663,000,000	[4]
Individually impaired loans with related allowance recorded: total interest income recognized	1,093,000,000	[1],[4]	1,093,000,000	[1],[4]	2,187,000,000	[1],[4]	2,195,000,000	[1],[4]
Individually impaired loans with related allowance recorded: interest income recognized on a cash basis	121,000,000	[4]	152,000,000	[4]	261,000,000	[4]	325,000,000	[4]
Individually impaired loans with no related allowance recorded: average recorded investment	13,413,000,000	[2],[4]	10,301,000,000	[2],[4]	13,055,000,000	[2],[4]	10,688,000,000	[2],[4]
Individually impaired loans with no related allowance recorded: total interest income recognized	205,000,000	[1],[2],[4]	283,000,000	[1],[2],[4]	390,000,000	[1],[2],[4]	924,000,000	[1],[2],[4]
Individually impaired loans with no related allowance recorded: interest income recognized on a cash basis	53,000,000	[2],[4]	57,000,000	[2],[4]	101,000,000	[2],[4]	116,000,000	[2],[4]
Single-Family [Member] | Government [Member]
Financing Receivable, Impaired [Line Items]
Individually impaired loans with related allowance recorded: average recorded investment	281,000,000	[5]	214,000,000	[5]	257,000,000	[5]	211,000,000	[5]
Individually impaired loans with related allowance recorded: total interest income recognized	3,000,000	[1],[5]	2,000,000	[1],[5]	6,000,000	[1],[5]	5,000,000	[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	56,000,000	[2],[5]	112,000,000	[2],[5]	76,000,000	[2],[5]	110,000,000	[2],[5]
Individually impaired loans with no related allowance recorded: total interest income recognized	2,000,000	[1],[2],[5]	2,000,000	[1],[2],[5]	3,000,000	[1],[2],[5]	4,000,000	[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	34,029,000,000		35,376,000,000		34,178,000,000		35,422,000,000
Individually impaired loans with related allowance recorded: total interest income recognized	267,000,000	[1]	275,000,000	[1]	537,000,000	[1]	552,000,000	[1]
Individually impaired loans with related allowance recorded: interest income recognized on a cash basis	22,000,000		35,000,000		50,000,000		74,000,000
Individually impaired loans with no related allowance recorded: average recorded investment	2,636,000,000	[2]	1,972,000,000	[2]	2,576,000,000	[2]	2,049,000,000	[2]
Individually impaired loans with no related allowance recorded: total interest income recognized	43,000,000	[1],[2]	55,000,000	[1],[2]	84,000,000	[1],[2]	230,000,000	[1],[2]
Individually impaired loans with no related allowance recorded: interest income recognized on a cash basis	10,000,000	[2]	12,000,000	[2]	20,000,000	[2]	22,000,000	[2]
Single-Family [Member] | Other [Member]
Financing Receivable, Impaired [Line Items]
Individually impaired loans with related allowance recorded: average recorded investment	14,669,000,000	[6]	15,700,000,000	[6]	14,787,000,000	[6]	15,830,000,000	[6]
Individually impaired loans with related allowance recorded: total interest income recognized	102,000,000	[1],[6]	108,000,000	[1],[6]	205,000,000	[1],[6]	217,000,000	[1],[6]
Individually impaired loans with related allowance recorded: interest income recognized on a cash basis	9,000,000	[6]	15,000,000	[6]	20,000,000	[6]	29,000,000	[6]
Individually impaired loans with no related allowance recorded: average recorded investment	927,000,000	[2],[6]	661,000,000	[2],[6]	910,000,000	[2],[6]	671,000,000	[2],[6]
Individually impaired loans with no related allowance recorded: total interest income recognized	13,000,000	[1],[2],[6]	23,000,000	[1],[2],[6]	24,000,000	[1],[2],[6]	86,000,000	[1],[2],[6]
Individually impaired loans with no related allowance recorded: interest income recognized on a cash basis	3,000,000	[2],[6]	5,000,000	[2],[6]	5,000,000	[2],[6]	10,000,000	[2],[6]
Multifamily [Member]
Financing Receivable, Impaired [Line Items]
Individually impaired loans with related allowance recorded: average recorded investment	1,813,000,000		2,704,000,000		1,967,000,000		2,628,000,000
Individually impaired loans with related allowance recorded: total interest income recognized	23,000,000	[1]	36,000,000	[1]	46,000,000	[1]	67,000,000	[1]
Individually impaired loans with related allowance recorded: interest income recognized on a cash basis	0		1,000,000		0		1,000,000
Individually impaired loans with no related allowance recorded: average recorded investment	1,668,000,000	[2]	1,666,000,000	[2]	1,758,000,000	[2]	1,800,000,000	[2]
Individually impaired loans with no related allowance recorded: total interest income recognized	20,000,000	[1],[2]	25,000,000	[1],[2]	40,000,000	[1],[2]	47,000,000	[1],[2]
Individually impaired loans with no related allowance recorded: interest income recognized on a cash basis	0	[2]	0	[2]	0	[2]	1,000,000	[2]
Table Footnote [Abstract]
Troubled debt restructuring recorded investment	$ 880,000,000				$ 880,000,000				$ 911,000,000

[1] Total single-family interest income recognized of $1.7 billion and $1.8 billion for the three months ended June 30, 2014 and 2013, respectively, consists of $1.4 billion of contractual interest for both periods and $285 million and $410 million of effective yield adjustments, respectively. Total single-family interest income recognized of $3.4 billion and $4.2 billion for the six months ended June 30, 2014 and 2013, respectively, consists of $2.9 billion of contractual interest for both periods and $560 million and $1.3 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 $187.1 billion and $187.6 billion as of June 30, 2014 and December 31, 2013, respectively. Includes multifamily loans restructured in a TDR with a recorded investment of $880 million and $911 million as of June 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.