Fair Value Level 3 Reconciliation (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2014		Mar. 31, 2013
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Total Gains or (Losses) Included in Net Income	$ 132		$ 245
Net unrealized gains (losses) included in net income related to assets still held	(115)		(202)
Interest Income [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Total Gains or (Losses) Included in Net Income	70		55
Net unrealized gains (losses) included in net income related to assets still held	0		0
Fair Value Gains, net [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Total Gains or (Losses) Included in Net Income	106		192
Net unrealized gains (losses) included in net income related to assets still held	(115)		(202)
Net Other-than-Temporary Impairments [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Total Gains or (Losses) Included in Net Income	(45)		(5)
Net unrealized gains (losses) included in net income related to assets still held	0		0
Other [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Total Gains or (Losses) Included in Net Income	1		3
Net unrealized gains (losses) included in net income related to assets still held	0		0
Trading securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	2,774		2,286
Total Gains or (Losses) Included in Net Income	139		240
Total Gains or (Losses) Included in Other Comprehensive Income (Loss)	0	[1]	0	[1]
Purchases	0	[2]	0	[2]
Sales	0	[2]	0	[2]
Issues	0	[3]	0	[3]
Settlements	(95)	[3]	(55)	[3]
Transfers out of Level 3	(117)	[4]	(44)	[4]
Transfers Into Level 3	110	[4]	325	[4]
Ending Balance	2,811		2,752
Net unrealized gains (losses) included in net income related to assets still held	138	[5]	236	[5]
Trading securities [Member] | Fannie Mae [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	42		68
Total Gains or (Losses) Included in Net Income	(1)		(3)
Total Gains or (Losses) Included in Other Comprehensive Income (Loss)	0	[1]	0	[1]
Purchases	0	[2]	0	[2]
Sales	0	[2]	0	[2]
Issues	0	[3]	0	[3]
Settlements	(2)	[3]	(4)	[3]
Transfers out of Level 3	(39)	[4]	0	[4]
Transfers Into Level 3	0	[4]	0	[4]
Ending Balance	0		61
Net unrealized gains (losses) included in net income related to assets still held	0	[5]	(2)	[5]
Trading securities [Member] | Freddie Mac [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	2		2
Total Gains or (Losses) Included in Net Income	0		0
Total Gains or (Losses) Included in Other Comprehensive Income (Loss)	0	[1]	0	[1]
Purchases	0	[2]	0	[2]
Sales	0	[2]	0	[2]
Issues	0	[3]	0	[3]
Settlements	0	[3]	0	[3]
Transfers out of Level 3	(2)	[4]	0	[4]
Transfers Into Level 3	0	[4]	0	[4]
Ending Balance	0		2
Net unrealized gains (losses) included in net income related to assets still held	0	[5]	0	[5]
Trading securities [Member] | Ginnie Mae [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance			1
Total Gains or (Losses) Included in Net Income			0
Total Gains or (Losses) Included in Other Comprehensive Income (Loss)			0	[1]
Purchases			0	[2]
Sales			0	[2]
Issues			0	[3]
Settlements			(1)	[3]
Transfers out of Level 3			0	[4]
Transfers Into Level 3			0	[4]
Ending Balance			0
Net unrealized gains (losses) included in net income related to assets still held			0	[5]
Trading securities [Member] | Alt-A private-label securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	618		104
Total Gains or (Losses) Included in Net Income	19		95
Total Gains or (Losses) Included in Other Comprehensive Income (Loss)	0	[1]	0	[1]
Purchases	0	[2]	0	[2]
Sales	0	[2]	0	[2]
Issues	0	[3]	0	[3]
Settlements	(16)	[3]	(16)	[3]
Transfers out of Level 3	(76)	[4]	(44)	[4]
Transfers Into Level 3	110	[4]	325	[4]
Ending Balance	655		464
Net unrealized gains (losses) included in net income related to assets still held	17	[5]	90	[5]
Trading securities [Member] | Subprime private-label securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	1,448		1,319
Total Gains or (Losses) Included in Net Income	76		159
Total Gains or (Losses) Included in Other Comprehensive Income (Loss)	0	[1]	0	[1]
Purchases	0	[2]	0	[2]
Sales	0	[2]	0	[2]
Issues	0	[3]	0	[3]
Settlements	(71)	[3]	(32)	[3]
Transfers out of Level 3	0	[4]	0	[4]
Transfers Into Level 3	0	[4]	0	[4]
Ending Balance	1,453		1,446
Net unrealized gains (losses) included in net income related to assets still held	76	[5]	160	[5]
Trading securities [Member] | Mortgage revenue bonds [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	565		675
Total Gains or (Losses) Included in Net Income	40		(13)
Total Gains or (Losses) Included in Other Comprehensive Income (Loss)	0	[1]	0	[1]
Purchases	0	[2]	0	[2]
Sales	0	[2]	0	[2]
Issues	0	[3]	0	[3]
Settlements	(4)	[3]	(1)	[3]
Transfers out of Level 3	0	[4]	0	[4]
Transfers Into Level 3	0	[4]	0	[4]
Ending Balance	601		661
Net unrealized gains (losses) included in net income related to assets still held	40	[5]	(13)	[5]
Trading securities [Member] | Other [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	99		117
Total Gains or (Losses) Included in Net Income	5		2
Total Gains or (Losses) Included in Other Comprehensive Income (Loss)	0	[1]	0	[1]
Purchases	0	[2]	0	[2]
Sales	0	[2]	0	[2]
Issues	0	[3]	0	[3]
Settlements	(2)	[3]	(1)	[3]
Transfers out of Level 3	0	[4]	0	[4]
Transfers Into Level 3	0	[4]	0	[4]
Ending Balance	102		118
Net unrealized gains (losses) included in net income related to assets still held	5	[5]	1	[5]
Available-for-sale securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	19,012		25,034
Total Gains or (Losses) Included in Net Income	29		55
Total Gains or (Losses) Included in Other Comprehensive Income (Loss)	526	[1]	910	[1]
Purchases	0	[2]	0	[2]
Sales	(19)	[2]	(19)	[2]
Issues	0	[3]	0	[3]
Settlements	(864)	[3]	(1,104)	[3]
Transfers out of Level 3	(611)	[4]	(1,206)	[4]
Transfers Into Level 3	390	[4]	781	[4]
Ending Balance	18,463		24,451
Net unrealized gains (losses) included in net income related to assets still held	0	[5]	0	[5]
Available-for-sale securities [Member] | Fannie Mae [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	7		29
Total Gains or (Losses) Included in Net Income	0		0
Total Gains or (Losses) Included in Other Comprehensive Income (Loss)	0	[1]	0	[1]
Purchases	0	[2]	0	[2]
Sales	0	[2]	0	[2]
Issues	0	[3]	0	[3]
Settlements	0	[3]	(3)	[3]
Transfers out of Level 3	(2)	[4]	(14)	[4]
Transfers Into Level 3	0	[4]	0	[4]
Ending Balance	5		12
Net unrealized gains (losses) included in net income related to assets still held	0	[5]	0	[5]
Available-for-sale securities [Member] | Freddie Mac [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	8		10
Total Gains or (Losses) Included in Net Income	0		0
Total Gains or (Losses) Included in Other Comprehensive Income (Loss)	0	[1]	0	[1]
Purchases	0	[2]	0	[2]
Sales	0	[2]	0	[2]
Issues	0	[3]	0	[3]
Settlements	0	[3]	(1)	[3]
Transfers out of Level 3	0	[4]	0	[4]
Transfers Into Level 3	0	[4]	0	[4]
Ending Balance	8		9
Net unrealized gains (losses) included in net income related to assets still held	0	[5]	0	[5]
Available-for-sale securities [Member] | Alt-A private-label securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	3,791		6,564
Total Gains or (Losses) Included in Net Income	13		9
Total Gains or (Losses) Included in Other Comprehensive Income (Loss)	73	[1]	218	[1]
Purchases	0	[2]	0	[2]
Sales	0	[2]	0	[2]
Issues	0	[3]	0	[3]
Settlements	(88)	[3]	(268)	[3]
Transfers out of Level 3	(609)	[4]	(1,192)	[4]
Transfers Into Level 3	390	[4]	781	[4]
Ending Balance	3,570		6,112
Net unrealized gains (losses) included in net income related to assets still held	0	[5]	0	[5]
Available-for-sale securities [Member] | Subprime private-label securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	7,068		7,447
Total Gains or (Losses) Included in Net Income	33		44
Total Gains or (Losses) Included in Other Comprehensive Income (Loss)	219	[1]	677	[1]
Purchases	0	[2]	0	[2]
Sales	0	[2]	0	[2]
Issues	0	[3]	0	[3]
Settlements	(290)	[3]	(300)	[3]
Transfers out of Level 3	0	[4]	0	[4]
Transfers Into Level 3	0	[4]	0	[4]
Ending Balance	7,030		7,868
Net unrealized gains (losses) included in net income related to assets still held	0	[5]	0	[5]
Available-for-sale securities [Member] | Mortgage revenue bonds [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	5,253		7,837
Total Gains or (Losses) Included in Net Income	(20)		(2)
Total Gains or (Losses) Included in Other Comprehensive Income (Loss)	193	[1]	(29)	[1]
Purchases	0	[2]	0	[2]
Sales	(19)	[2]	(19)	[2]
Issues	0	[3]	0	[3]
Settlements	(401)	[3]	(436)	[3]
Transfers out of Level 3	0	[4]	0	[4]
Transfers Into Level 3	0	[4]	0	[4]
Ending Balance	5,006		7,351
Net unrealized gains (losses) included in net income related to assets still held	0	[5]	0	[5]
Available-for-sale securities [Member] | Other [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	2,885		3,147
Total Gains or (Losses) Included in Net Income	3		4
Total Gains or (Losses) Included in Other Comprehensive Income (Loss)	41	[1]	44	[1]
Purchases	0	[2]	0	[2]
Sales	0	[2]	0	[2]
Issues	0	[3]	0	[3]
Settlements	(85)	[3]	(96)	[3]
Transfers out of Level 3	0	[4]	0	[4]
Transfers Into Level 3	0	[4]	0	[4]
Ending Balance	2,844		3,099
Net unrealized gains (losses) included in net income related to assets still held	0	[5]	0	[5]
Mortgage Loans [Member] | Consolidated Trusts [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	2,704		2,634
Total Gains or (Losses) Included in Net Income	25		27
Total Gains or (Losses) Included in Other Comprehensive Income (Loss)	0	[1]	0	[1]
Purchases	24	[2]	158	[2]
Sales	0	[2]	0	[2]
Issues	0	[3]	0	[3]
Settlements	(81)	[3]	(112)	[3]
Transfers out of Level 3	(148)	[4]	(38)	[4]
Transfers Into Level 3	84	[4]	213	[4]
Ending Balance	2,608		2,882
Net unrealized gains (losses) included in net income related to assets still held	11	[5]	22	[5]
Net derivatives [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	(40)		14
Total Gains or (Losses) Included in Net Income	30		(40)
Total Gains or (Losses) Included in Other Comprehensive Income (Loss)	0	[1]	0	[1]
Purchases	0	[2]	0	[2]
Sales	0	[2]	0	[2]
Issues	0	[3]	0	[3]
Settlements	(12)	[3]	23	[3]
Transfers out of Level 3	(1)	[4]	0	[4]
Transfers Into Level 3	0	[4]	(4)	[4]
Ending Balance	(23)		(7)
Net unrealized gains (losses) included in net income related to assets still held	11	[5]	(18)	[5]
Long-term debt [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	(1,473)		(1,528)
Total Gains (Losses) (Realized/Unrealized) Included in Net Loss	(91)		(37)
Total Gains or (Losses) Included in Other Comprehensive Income (Loss)	0	[1]	0	[1]
Purchases	0	[2]	0	[2]
Sales	0	[2]	0	[2]
Issues	(750)	[3]	(15)	[3]
Settlements	38	[3]	49	[3]
Transfers out of Level 3	1,484	[4]	113	[4]
Transfers Into Level 3	(24)	[4]	(42)	[4]
Ending Balance	(816)		(1,460)
Net Unrealized Gain (Loss) Included in Net Loss Related to Liabilities Still Held	(45)	[5]	(38)	[5]
Long-term debt [Member] | Consolidated Trusts [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	(518)		(1,128)
Total Gains (Losses) (Realized/Unrealized) Included in Net Loss	(1)		(54)
Total Gains or (Losses) Included in Other Comprehensive Income (Loss)	0	[1]	0	[1]
Purchases	0	[2]	0	[2]
Sales	0	[2]	0	[2]
Issues	0	[3]	(15)	[3]
Settlements	18	[3]	49	[3]
Transfers out of Level 3	19	[4]	113	[4]
Transfers Into Level 3	(24)	[4]	(42)	[4]
Ending Balance	(506)		(1,077)
Net Unrealized Gain (Loss) Included in Net Loss Related to Liabilities Still Held	(1)	[5]	(55)	[5]
Long-term debt [Member] | Senior Floating [Member] | Fannie Mae [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	(955)		(400)
Total Gains (Losses) (Realized/Unrealized) Included in Net Loss	(90)		17
Total Gains or (Losses) Included in Other Comprehensive Income (Loss)	0	[1]	0	[1]
Purchases	0	[2]	0	[2]
Sales	0	[2]	0	[2]
Issues	(750)	[3]	0	[3]
Settlements	20	[3]	0	[3]
Transfers out of Level 3	1,465	[4]	0	[4]
Transfers Into Level 3	0	[4]	0	[4]
Ending Balance	(310)		(383)
Net Unrealized Gain (Loss) Included in Net Loss Related to Liabilities Still Held	$ (44)	[5]	$ 17	[5]

[1] Gains (losses) included in other comprehensive income are included in “Changes in unrealized gains on available-for-sale securities, net of reclassification adjustments and taxes” in the condensed consolidated statements of operations and comprehensive income.

[2] Purchases and sales include activity related to the consolidation and deconsolidation of assets of securitization trusts.

[3] Issues and settlements include activity related to the consolidation and deconsolidation of liabilities of securitization trusts.

[4] Transfers out of Level 3 consisted primarily of private-label mortgage-related securities backed by Alt-A loans and credit risk sharing securities issued under our Connecticut Avenue Securities series. Prices for these securities were obtained from multiple third-party vendors or dealers supported by market observable inputs. Transfers into Level 3 consisted primarily of private-label mortgage-related securities backed by Alt-A loans. Prices for these securities are based on inputs from a single source or inputs that were not readily observable.

[5] Amount represents temporary changes in fair value. Amortization, accretion and other-than-temporary impairments are not considered unrealized and are not included in this amount.