Mortgage Loans TDR (Details) (USD $)	3 Months Ended
	Mar. 31, 2013 contracts		Mar. 31, 2012 contracts		Dec. 31, 2012
Financing Receivable, Modifications [Line Items]
Number of loans troubled debt restructurings activity	47,516		33,312
Recorded investment troubled debt restructurings activity	$ 7,363,000,000	[1]	$ 6,045,000,000	[1]
Number of loans troubled debt restructurings subsequent default	15,587		15,361
Recorded investment troubled debt restructurings subsequent default	2,555,000,000	[2]	2,840,000,000	[2]
Single-Family [Member]
Financing Receivable, Modifications [Line Items]
Number of loans troubled debt restructurings activity	47,508		33,299
Recorded investment troubled debt restructurings activity	7,330,000,000	[1]	5,977,000,000	[1]
Number of loans troubled debt restructurings subsequent default	15,584		15,360
Recorded investment troubled debt restructurings subsequent default	2,540,000,000	[2]	2,838,000,000	[2]
Troubled debt restructuring recorded investment	189,200,000,000				193,400,000,000
Single-Family [Member] | Primary [Member]
Financing Receivable, Modifications [Line Items]
Number of loans troubled debt restructurings activity	38,251	[3]	26,884	[3]
Recorded investment troubled debt restructurings activity	5,644,000,000	[1],[3]	4,587,000,000	[1],[3]
Number of loans troubled debt restructurings subsequent default	12,060	[3]	11,872	[3]
Recorded investment troubled debt restructurings subsequent default	1,867,000,000	[2],[3]	2,074,000,000	[2],[3]
Single-Family [Member] | Government [Member]
Financing Receivable, Modifications [Line Items]
Number of loans troubled debt restructurings activity	90	[4]	110	[4]
Recorded investment troubled debt restructurings activity	11,000,000	[1],[4]	14,000,000	[1],[4]
Number of loans troubled debt restructurings subsequent default	29	[4]	50	[4]
Recorded investment troubled debt restructurings subsequent default	4,000,000	[2],[4]	10,000,000	[2],[4]
Single-Family [Member] | Alt-A [Member]
Financing Receivable, Modifications [Line Items]
Number of loans troubled debt restructurings activity	7,110		4,645
Recorded investment troubled debt restructurings activity	1,223,000,000	[1]	967,000,000	[1]
Number of loans troubled debt restructurings subsequent default	2,672		2,243
Recorded investment troubled debt restructurings subsequent default	484,000,000	[2]	466,000,000	[2]
Single-Family [Member] | Other [Member]
Financing Receivable, Modifications [Line Items]
Number of loans troubled debt restructurings activity	2,057	[5]	1,660	[5]
Recorded investment troubled debt restructurings activity	452,000,000	[1],[5]	409,000,000	[1],[5]
Number of loans troubled debt restructurings subsequent default	823	[5]	1,195	[5]
Recorded investment troubled debt restructurings subsequent default	185,000,000	[2],[5]	288,000,000	[2],[5]
Multifamily [Member]
Financing Receivable, Modifications [Line Items]
Number of loans troubled debt restructurings activity	8		13
Recorded investment troubled debt restructurings activity	33,000,000	[1]	68,000,000	[1]
Number of loans troubled debt restructurings subsequent default	3		1
Recorded investment troubled debt restructurings subsequent default	15,000,000	[2]	2,000,000	[2]
Troubled debt restructuring recorded investment	$ 1,100,000,000				$ 1,100,000,000

[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.