Mortgage Loans TDR (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended				9 Months Ended
	Sep. 30, 2014 contracts		Sep. 30, 2013 contracts		Sep. 30, 2014 contracts		Sep. 30, 2013 contracts
Financing Receivable, Modifications [Line Items]
Average term extension of a single-family modified loan	162 months		156 months		161 months		152 months
Average interest rate reduction of a single-family modified loan	0.89%		1.66%		1.04%		1.73%
Number of loans troubled debt restructurings activity	27,028		39,102		90,950		124,845
Recorded investment troubled debt restructurings activity	$ 4,756	[1]	$ 6,161	[1]	$ 14,241	[1]	$ 19,819	[1]
Number of loans troubled debt restructurings subsequent default	10,647		16,220		31,240		46,597
Recorded investment troubled debt restructurings subsequent default	1,664	[2]	2,629	[2]	4,961	[2]	7,603	[2]
Single-Family [Member]
Financing Receivable, Modifications [Line Items]
Number of loans troubled debt restructurings activity	27,021		39,098		90,934		124,816
Recorded investment troubled debt restructurings activity	3,945	[1]	6,142	[1]	13,392	[1]	19,632	[1]
Number of loans troubled debt restructurings subsequent default	10,646		16,217		31,234		46,588
Recorded investment troubled debt restructurings subsequent default	1,659	[2]	2,585	[2]	4,939	[2]	7,539	[2]
Single-Family [Member] | Primary [Member]
Financing Receivable, Modifications [Line Items]
Number of loans troubled debt restructurings activity	23,057	[3]	32,083	[3]	76,831	[3]	101,638	[3]
Recorded investment troubled debt restructurings activity	3,270	[1],[3]	4,831	[1],[3]	10,944	[1],[3]	15,308	[1],[3]
Number of loans troubled debt restructurings subsequent default	8,798	[3]	12,591	[3]	25,586	[3]	35,971	[3]
Recorded investment troubled debt restructurings subsequent default	1,312	[2],[3]	1,905	[2],[3]	3,873	[2],[3]	5,521	[2],[3]
Single-Family [Member] | Government [Member]
Financing Receivable, Modifications [Line Items]
Number of loans troubled debt restructurings activity	91	[4]	73	[4]	264	[4]	253	[4]
Recorded investment troubled debt restructurings activity	12	[1],[4]	8	[1],[4]	33	[1],[4]	29	[1],[4]
Number of loans troubled debt restructurings subsequent default	38	[4]	33	[4]	74	[4]	93	[4]
Recorded investment troubled debt restructurings subsequent default	6	[2],[4]	5	[2],[4]	9	[2],[4]	13	[2],[4]
Single-Family [Member] | Alt-A [Member]
Financing Receivable, Modifications [Line Items]
Number of loans troubled debt restructurings activity	3,175		5,410		11,231		17,695
Recorded investment troubled debt restructurings activity	521	[1]	964	[1]	1,875	[1]	3,134	[1]
Number of loans troubled debt restructurings subsequent default	1,372		2,744		4,212		8,000
Recorded investment troubled debt restructurings subsequent default	241	[2]	491	[2]	753	[2]	1,441	[2]
Single-Family [Member] | Other [Member]
Financing Receivable, Modifications [Line Items]
Number of loans troubled debt restructurings activity	698	[5]	1,532	[5]	2,608	[5]	5,230	[5]
Recorded investment troubled debt restructurings activity	142	[1],[5]	339	[1],[5]	540	[1],[5]	1,161	[1],[5]
Number of loans troubled debt restructurings subsequent default	438	[5]	849	[5]	1,362	[5]	2,524	[5]
Recorded investment troubled debt restructurings subsequent default	100	[2],[5]	184	[2],[5]	304	[2],[5]	564	[2],[5]
Multifamily [Member]
Financing Receivable, Modifications [Line Items]
Number of loans troubled debt restructurings activity	7		4		16		29
Recorded investment troubled debt restructurings activity	811	[1]	19	[1]	849	[1]	187	[1]
Number of loans troubled debt restructurings subsequent default	1		3		6		9
Recorded investment troubled debt restructurings subsequent default	$ 5	[2]	$ 44	[2]	$ 22	[2]	$ 64	[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.