Mortgage Loans TDR (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014 contracts	Dec. 31, 2013 contracts
Financing Receivable, Modifications [Line Items]
Number of loans troubled debt restructurings activity	119,412	155,040
Recorded investment troubled debt restructurings activity	$ 18,328	$ 24,436
Number of loans troubled debt restructurings subsequent default	41,116	58,372
Recorded investment troubled debt restructurings subsequent default	6,499	9,476
Single-Family [Member]
Financing Receivable, Modifications [Line Items]
Number of loans troubled debt restructurings activity	119,393	155,007
Recorded investment troubled debt restructurings activity	17,475	24,223
Number of loans troubled debt restructurings subsequent default	41,107	58,363
Recorded investment troubled debt restructurings subsequent default	6,457	9,412
Multifamily [Member]
Financing Receivable, Modifications [Line Items]
Number of loans troubled debt restructurings activity	19	33
Recorded investment troubled debt restructurings activity	853	213
Number of loans troubled debt restructurings subsequent default	9	9
Recorded investment troubled debt restructurings subsequent default	42	64
Primary [Member]
Financing Receivable, Modifications [Line Items]
Number of loans troubled debt restructurings activity	100,956	126,998
Recorded investment troubled debt restructurings activity	14,301	19,016
Number of loans troubled debt restructurings subsequent default	33,853	45,539
Recorded investment troubled debt restructurings subsequent default	5,095	6,978
Government [Member]
Financing Receivable, Modifications [Line Items]
Number of loans troubled debt restructurings activity	365	312
Recorded investment troubled debt restructurings activity	47	35
Number of loans troubled debt restructurings subsequent default	124	130
Recorded investment troubled debt restructurings subsequent default	15	17
Alt-A [Member]
Financing Receivable, Modifications [Line Items]
Number of loans troubled debt restructurings activity	14,715	21,471
Recorded investment troubled debt restructurings activity	2,441	3,794
Number of loans troubled debt restructurings subsequent default	5,392	9,601
Recorded investment troubled debt restructurings subsequent default	960	1,732
Other [Member]
Financing Receivable, Modifications [Line Items]
Number of loans troubled debt restructurings activity	3,357	6,226
Recorded investment troubled debt restructurings activity	686	1,378
Number of loans troubled debt restructurings subsequent default	1,738	3,093
Recorded investment troubled debt restructurings subsequent default	$ 387	$ 685