Mortgage Loans TDR (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended				9 Months Ended
	Sep. 30, 2013 contracts		Sep. 30, 2012 contracts		Sep. 30, 2013 contracts		Sep. 30, 2012 contracts
Financing Receivable, Modifications [Line Items]
Average term extension of a single-family modified loan	156 months		133 months		152 months		127 months
Number of loans troubled debt restructurings activity	39,102		205,467		124,845		279,251
Recorded investment troubled debt restructurings activity	$ 6,161	[1]	$ 29,249	[1]	$ 19,819	[1]	$ 42,575	[1]
Number of loans troubled debt restructurings subsequent default	16,220		13,617		46,597		42,709
Recorded investment troubled debt restructurings subsequent default	2,629	[2]	2,388	[2]	7,603	[2]	7,701	[2]
Average interest rate reduction of a single-family modified loan	1.66%		2.08%		1.73%		2.23%
Single-Family [Member]
Financing Receivable, Modifications [Line Items]
Number of loans troubled debt restructurings activity	39,098		205,463		124,816		279,226
Recorded investment troubled debt restructurings activity	6,142	[1]	29,230	[1]	19,632	[1]	42,423	[1]
Number of loans troubled debt restructurings subsequent default	16,217		13,616		46,588		42,706
Recorded investment troubled debt restructurings subsequent default	2,585	[2]	2,379	[2]	7,539	[2]	7,689	[2]
Single-Family [Member] | Primary [Member]
Financing Receivable, Modifications [Line Items]
Number of loans troubled debt restructurings activity	32,083	[3]	165,395	[3]	101,638	[3]	224,165	[3]
Recorded investment troubled debt restructurings activity	4,831	[1],[3]	22,068	[1],[3]	15,308	[1],[3]	32,022	[1],[3]
Number of loans troubled debt restructurings subsequent default	12,591	[3]	10,870	[3]	35,971	[3]	33,446	[3]
Recorded investment troubled debt restructurings subsequent default	1,905	[2],[3]	1,798	[2],[3]	5,521	[2],[3]	5,699	[2],[3]
Single-Family [Member] | Government [Member]
Financing Receivable, Modifications [Line Items]
Number of loans troubled debt restructurings activity	73	[4]	112	[4]	253	[4]	314	[4]
Recorded investment troubled debt restructurings activity	8	[1],[4]	13	[1],[4]	29	[1],[4]	41	[1],[4]
Number of loans troubled debt restructurings subsequent default	33	[4]	51	[4]	93	[4]	150	[4]
Recorded investment troubled debt restructurings subsequent default	5	[2],[4]	8	[2],[4]	13	[2],[4]	25	[2],[4]
Single-Family [Member] | Alt-A [Member]
Financing Receivable, Modifications [Line Items]
Number of loans troubled debt restructurings activity	5,410		31,088		17,695		42,026
Recorded investment troubled debt restructurings activity	964	[1]	5,284	[1]	3,134	[1]	7,537	[1]
Number of loans troubled debt restructurings subsequent default	2,744		1,854		8,000		6,113
Recorded investment troubled debt restructurings subsequent default	491	[2]	377	[2]	1,441	[2]	1,246	[2]
Single-Family [Member] | Other [Member]
Financing Receivable, Modifications [Line Items]
Number of loans troubled debt restructurings activity	1,532	[5]	8,868	[5]	5,230	[5]	12,721	[5]
Recorded investment troubled debt restructurings activity	339	[1],[5]	1,865	[1],[5]	1,161	[1],[5]	2,823	[1],[5]
Number of loans troubled debt restructurings subsequent default	849	[5]	841	[5]	2,524	[5]	2,997	[5]
Recorded investment troubled debt restructurings subsequent default	184	[2],[5]	196	[2],[5]	564	[2],[5]	719	[2],[5]
Multifamily [Member]
Financing Receivable, Modifications [Line Items]
Number of loans troubled debt restructurings activity	4		4		29		25
Recorded investment troubled debt restructurings activity	19	[1]	19	[1]	187	[1]	152	[1]
Number of loans troubled debt restructurings subsequent default	3		1		9		3
Recorded investment troubled debt restructurings subsequent default	$ 44	[2]	$ 9	[2]	$ 64	[2]	$ 12	[2]

[1] Recorded investment consists of unpaid principal balance, unamortized premiums, discounts and other cost basis adjustments, and accrued interest receivable. Based on the nature of our modification programs, which do not include principal or past-due interest forgiveness, there is not a material difference between the recorded investment in our loans pre- and post- modification, therefore amounts represent recorded investment post-modification.

[2] Recorded investment consists of unpaid principal balance, unamortized premiums, discounts and other cost basis adjustments, and accrued interest receivable. Represents our recorded investment in the loan at time of payment default.

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

[4] 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.

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