Mortgage Loans TDR (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012 contracts		Dec. 31, 2011 contracts
Financing Receivable, Modifications [Line Items]
Number of loans troubled debt restructurings activity	337,409		208,911
Recorded investment troubled debt restructurings activity	$ 52,506	[1]	$ 39,390	[1]
Number of loans troubled debt restructurings subsequent default	59,890		87,538
Recorded investment troubled debt restructurings subsequent default	10,605	[2]	16,444	[2]
Single-Family [Member]
Financing Receivable, Modifications [Line Items]
Number of loans troubled debt restructurings activity	337,363		208,864
Recorded investment troubled debt restructurings activity	52,182	[1]	39,167	[1]
Number of loans troubled debt restructurings subsequent default	59,883		87,530
Recorded investment troubled debt restructurings subsequent default	10,570	[2]	16,395	[2]
Single-Family [Member] | Primary [Member]
Financing Receivable, Modifications [Line Items]
Number of loans troubled debt restructurings activity	270,913	[3]	160,227	[3]
Recorded investment troubled debt restructurings activity	39,527	[1],[3]	28,329	[1],[3]
Number of loans troubled debt restructurings subsequent default	46,824	[3]	66,088	[3]
Recorded investment troubled debt restructurings subsequent default	7,828	[2],[3]	11,585	[2],[3]
Single-Family [Member] | Government [Member]
Financing Receivable, Modifications [Line Items]
Number of loans troubled debt restructurings activity	394	[4]	497	[4]
Recorded investment troubled debt restructurings activity	50	[1],[4]	86	[1],[4]
Number of loans troubled debt restructurings subsequent default	200	[4]	376	[4]
Recorded investment troubled debt restructurings subsequent default	33	[2],[4]	95	[2],[4]
Single-Family [Member] | Alt-A [Member]
Financing Receivable, Modifications [Line Items]
Number of loans troubled debt restructurings activity	50,572		33,416
Recorded investment troubled debt restructurings activity	9,116	[1]	7,108	[1]
Number of loans troubled debt restructurings subsequent default	8,848		14,223
Recorded investment troubled debt restructurings subsequent default	1,761	[2]	3,045	[2]
Single-Family [Member] | Other [Member]
Financing Receivable, Modifications [Line Items]
Number of loans troubled debt restructurings activity	15,484	[5]	14,724	[5]
Recorded investment troubled debt restructurings activity	3,489	[1],[5]	3,644	[1],[5]
Number of loans troubled debt restructurings subsequent default	4,011	[5]	6,843	[5]
Recorded investment troubled debt restructurings subsequent default	948	[2],[5]	1,670	[2],[5]
Multifamily [Member]
Financing Receivable, Modifications [Line Items]
Number of loans troubled debt restructurings activity	46		47
Recorded investment troubled debt restructurings activity	324	[1]	223	[1]
Number of loans troubled debt restructurings subsequent default	7		8
Recorded investment troubled debt restructurings subsequent default	$ 35	[2]	$ 49	[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.