Consolidated Balance Sheets (Parenthetical) (USD $) In Millions, except Share data, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
ASSETS
Restricted cash	$ 67,919	$ 50,797
Investments in securities:
Available-for-sale, at fair value	63,181	77,582
Mortgage loans:
Loans held for sale, at lower of cost or fair value	464	311
Accrued interest receivable, net	9,176	10,000
Cash pledged as collateral included in other assets	1,222	1,109
Liabilities:
Accrued interest payable	11,303	12,648
Other liabilities	14,378	13,535
Fannie Mae stockholders’ equity (deficit):
Senior preferred stock issued, shares	1,000,000	1,000,000
Senior preferred stock outstanding, shares	1,000,000	1,000,000
Preferred stock authorized	700,000,000	700,000,000
Preferred stock issued	555,374,922	555,374,922
Preferred stock outstanding	555,374,922	555,374,922
Common stock issued	1,308,762,703	1,308,762,703
Common stock outstanding	1,158,077,970	1,157,767,400
Treasury stock, shares	150,684,733	150,995,303
Fannie Mae [Member]
Liabilities:
Debt at fair value	793	838
Consolidated Trusts [Member]
ASSETS
Restricted cash	61,976	45,900
Investments in securities:
Available-for-sale, at fair value	935	1,191
Mortgage loans:
Loans held for sale, at lower of cost or fair value	72	66
Loans at fair value included in loans held for investment, at amortized cost	10,800	3,611
Loans pledged as collateral that may be sold or repledged included in loans held for investment, at amortized cost	943	798
Accrued interest receivable, net	7,567	8,466
Liabilities:
Accrued interest payable	8,645	9,302
Debt at fair value	11,647	3,939
Other liabilities	$ 1,059	$ 629