Consolidated Balance Sheets (USD $) In Millions, unless otherwise specified	Dec. 31, 2012		Dec. 31, 2011
ASSETS
Cash and cash equivalents	$ 21,117		$ 17,539
Restricted cash (includes $61,976 and $45,900, respectively, related to consolidated trusts)	67,919		50,797
Federal funds sold and securities purchased under agreements to resell or similar arrangements	32,500		46,000
Investments in securities:
Trading, at fair value	40,695		74,198
Available-for-sale, at fair value (includes $935 and $1,191, respectively, related to consolidated trusts)	63,181		77,582
Total investments in securities	103,876		151,780
Mortgage loans:
Loans held for sale, at lower of cost or fair value (includes $72 and $66, respectively, related to consolidated trusts)	464		311
Loans held for investment, at amortized cost (includes $10,800 and $3,611, respectively, at fair value and loans pledged as collateral that may be sold or repledged of $943 and $798, respectively, related to consolidated trusts)	3,007,737		2,970,466
Allowance for loan losses	(58,795)		(72,156)
Total loans held for investment, net of allowance	2,948,942		2,898,310
Total mortgage loans	2,949,406		2,898,621
Accrued interest receivable, net (includes $7,567 and $8,466, respectively, related to consolidated trusts)	9,176		10,000
Acquired property, net	10,489	[1]	11,373	[1]
Other assets (includes cash pledged as collateral of $1,222 and $1,109, respectively)	27,939		25,374
Total assets	3,222,422		3,211,484
Liabilities:
Accrued interest payable (includes $8,645 and $9,302, respectively, related to consolidated trusts)	11,303		12,648
Other liabilities (includes $1,059 and $629, respectively, related to consolidated trusts)	14,378		13,535
Total liabilities	3,215,198		3,216,055
Commitments and contingencies (Note 18)
Fannie Mae stockholders’ equity (deficit):
Senior preferred stock, 1,000,000 shares issued and outstanding	117,149		112,578
Preferred stock, 700,000,000 shares are authorized—555,374,922 shares issued and outstanding	19,130		19,130
Common stock, no par value, no maximum authorization—1,308,762,703 shares issued, 1,158,077,970 and 1,157,767,400 shares outstanding, respectively	687		687
Accumulated deficit	(122,766)		(128,381)
Accumulated other comprehensive income (loss)	384		(1,235)
Treasury stock, at cost, 150,684,733 and 150,995,303 shares, respectively	(7,401)		(7,403)
Total Fannie Mae stockholders’ equity (deficit)	7,183		(4,624)
Noncontrolling interest	41		53
Total equity (deficit)	7,224		(4,571)
Total liabilities and equity (deficit)	3,222,422		3,211,484
Fannie Mae [Member]
Mortgage loans:
Loans held for investment, at amortized cost (includes $10,800 and $3,611, respectively, at fair value and loans pledged as collateral that may be sold or repledged of $943 and $798, respectively, related to consolidated trusts)	355,544		380,134
Allowance for loan losses	(50,519)		(57,309)
Total mortgage loans	305,417		323,070
Liabilities:
Debt (includes $793 and $838, respectively, of debt of Fannie Mae and $11,647 and $3,939, respectively, of debt of consolidated trusts, at fair value)	615,864		732,444
Consolidated Trusts [Member]
ASSETS
Restricted cash (includes $61,976 and $45,900, respectively, related to consolidated trusts)	61,976		45,900
Investments in securities:
Available-for-sale, at fair value (includes $935 and $1,191, respectively, related to consolidated trusts)	935		1,191
Mortgage loans:
Loans held for sale, at lower of cost or fair value (includes $72 and $66, respectively, related to consolidated trusts)	72		66
Loans held for investment, at amortized cost (includes $10,800 and $3,611, respectively, at fair value and loans pledged as collateral that may be sold or repledged of $943 and $798, respectively, related to consolidated trusts)	2,652,193		2,590,332
Allowance for loan losses	(8,276)		(14,847)
Total mortgage loans	2,643,989		2,575,551
Accrued interest receivable, net (includes $7,567 and $8,466, respectively, related to consolidated trusts)	7,567		8,466
Liabilities:
Accrued interest payable (includes $8,645 and $9,302, respectively, related to consolidated trusts)	8,645		9,302
Debt (includes $793 and $838, respectively, of debt of Fannie Mae and $11,647 and $3,939, respectively, of debt of consolidated trusts, at fair value)	2,573,653		2,457,428
Other liabilities (includes $1,059 and $629, respectively, related to consolidated trusts)	$ 1,059		$ 629

[1] Includes valuation allowance of $669 million, $1.0 billion and $1.9 billion for the years ended December 31, 2012, 2011 and 2010, respectively.