Regulatory Capital Requirements (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012		Dec. 31, 2011		Dec. 31, 2010	Dec. 31, 2009
Regulatory Capital Requirements [Abstract]
Number of days of net worth deficit requiring FHFA to place us into receivership	60 days
Net worth (deficit)	$ 7,224		$ (4,571)		$ (2,517)	$ (11,983)
Core Capital	(110,350)	[1],[2]	(115,967)	[1],[2]
Statutory minimum capital requirement	30,862	[1],[3]	32,463	[1],[3]
Deficit of core capital over statutory minimum capital requirement	$ (141,212)	[1]	$ (148,430)	[1]
Component of statutory minimum capital requirement, percentage of on-balance sheet assets, except those underlying Fannie Mae MBS held by third parties	2.50%
Component of statutory minimum capital requirement, percentage of the unpaid principal balance of outstanding Fannie Mae MBS held by third parties	0.45%
Component of statutory minimum capital requirement, maximum percentage of other off-balance sheet obligations	0.45%
Component of critical capital requirement, percentage of on-balance sheet assets, except those underlying Fannie Mae MBS held by third parties	1.25%
Component of critical capital requirement, percentage of the unpaid principal balance of outstanding Fannie Mae MBS held by third parties	0.25%
Component of critical capital requirement, percentage of other off-balance sheet obligations	0.25%
Maximum deferral period of interest payment on qualifying subordinated debt	5 years
Condition of qualifying subordinated debt interest payment deferral - maximum ratio of core capital vs. critical capital requirement	1.25

[1] Amounts as of December 31, 2012 and 2011 represent estimates that we have submitted to FHFA.

[2] The sum of (a) the stated value of our outstanding common stock (common stock less treasury stock); (b) the stated value of our outstanding non-cumulative perpetual preferred stock; (c) our paid-in capital; and (d) our retained earnings (accumulated deficit). Core capital does not include: (a) accumulated other comprehensive income (loss) or (b) senior preferred stock.

[3] Generally, the sum of (a) 2.50% of on-balance sheet assets, except those underlying Fannie Mae MBS held by third parties; (b) 0.45% of the unpaid principal balance of outstanding Fannie Mae MBS held by third parties; and (c) up to 0.45% of other off-balance sheet obligations, which may be adjusted by the Director of FHFA under certain circumstances (See 12 CFR 1750.4 for existing adjustments made by the Director).