Fair Value Recurring Changes in Fair Value (Details) (USD $) In Millions, unless otherwise specified	Sep. 30, 2014		Dec. 31, 2013
Fannie Mae [Member]
Liabilities [Abstract]
Long-term debt, fair value	$ 5,204		$ 1,308
Consolidated Trusts [Member]
Assets [Abstract]
Mortgage loans held for investment, at fair value	15,262		14,268
Liabilities [Abstract]
Long-term debt, fair value	16,598		14,976
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Assets [Abstract]
Trading securities	17,757		16,306
Available-for-sale securities	0		0
Mortgage loans held for investment, at fair value	0		0
Total assets at fair value	52,104		52,939
Other assets [Abstract]
Derivatives assets at fair value	0		0
Liabilities [Abstract]
Total liabilities at fair value	0		0
Other liabilities [Abstract]
Derivative liabilities at fair value	0		0
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Fannie Mae [Member]
Assets [Abstract]
Mortgage loans held for investment, at fair value	0		0
Liabilities [Abstract]
Long-term debt, fair value	0		0
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Consolidated Trusts [Member]
Assets [Abstract]
Mortgage loans held for investment, at fair value	0		0
Liabilities [Abstract]
Long-term debt, fair value	0		0
Significant Other Observable Inputs (Level 2) [Member]
Assets [Abstract]
Trading securities	9,959		11,688
Available-for-sale securities	16,202		19,159
Mortgage loans held for investment, at fair value	2,656,224		2,599,667
Total assets at fair value	2,734,213		2,694,859
Other assets [Abstract]
Derivatives assets at fair value	7,333		10,430
Liabilities [Abstract]
Total liabilities at fair value	3,246,990		3,231,253
Other liabilities [Abstract]
Derivative liabilities at fair value	9,349		10,734
Significant Other Observable Inputs (Level 2) [Member] | Fannie Mae [Member]
Assets [Abstract]
Mortgage loans held for investment, at fair value	30,689		29,920
Liabilities [Abstract]
Long-term debt, fair value	387,920		463,991
Significant Other Observable Inputs (Level 2) [Member] | Consolidated Trusts [Member]
Assets [Abstract]
Mortgage loans held for investment, at fair value	2,625,535		2,569,747
Liabilities [Abstract]
Long-term debt, fair value	2,752,301		2,684,224
Significant Unobservable Inputs (Level 3) [Member]
Assets [Abstract]
Trading securities	3,128		2,774
Available-for-sale securities	15,897		19,012
Mortgage loans held for investment, at fair value	389,199		392,355
Total assets at fair value	409,718		415,630
Other assets [Abstract]
Derivatives assets at fair value	125		65
Liabilities [Abstract]
Total liabilities at fair value	21,148		19,611
Other liabilities [Abstract]
Derivative liabilities at fair value	134		105
Significant Unobservable Inputs (Level 3) [Member] | Fannie Mae [Member]
Assets [Abstract]
Mortgage loans held for investment, at fair value	218,495		215,960
Liabilities [Abstract]
Long-term debt, fair value	942		1,557
Significant Unobservable Inputs (Level 3) [Member] | Consolidated Trusts [Member]
Assets [Abstract]
Mortgage loans held for investment, at fair value	170,704		176,395
Liabilities [Abstract]
Long-term debt, fair value	16,457		13,362
Netting Adjustment [Member]
Assets [Abstract]
Trading securities	0		0
Available-for-sale securities	0		0
Mortgage loans held for investment, at fair value	0		0
Total assets at fair value	(6,202)		(8,422)
Other assets [Abstract]
Derivatives assets at fair value	(6,202)		(8,422)
Liabilities [Abstract]
Total liabilities at fair value	(9,040)		(9,370)
Other liabilities [Abstract]
Derivative liabilities at fair value	(9,040)		(9,370)
Netting Adjustment [Member] | Fannie Mae [Member]
Assets [Abstract]
Mortgage loans held for investment, at fair value	0		0
Liabilities [Abstract]
Long-term debt, fair value	0		0
Netting Adjustment [Member] | Consolidated Trusts [Member]
Assets [Abstract]
Mortgage loans held for investment, at fair value	0		0
Liabilities [Abstract]
Long-term debt, fair value	0		0
Estimated Fair Value [Member]
Assets [Abstract]
Trading securities	30,844		30,768
Available-for-sale securities	32,099		38,171
Mortgage loans held for investment, at fair value	3,045,423		2,992,022
Total assets at fair value	3,189,833		3,155,006
Other assets [Abstract]
Derivatives assets at fair value	1,256		2,073
Liabilities [Abstract]
Total liabilities at fair value	3,259,098		3,241,494
Other liabilities [Abstract]
Derivative liabilities at fair value	443		1,469
Estimated Fair Value [Member] | Fannie Mae [Member]
Assets [Abstract]
Mortgage loans held for investment, at fair value	249,184		245,880
Liabilities [Abstract]
Long-term debt, fair value	388,862		465,548
Estimated Fair Value [Member] | Consolidated Trusts [Member]
Assets [Abstract]
Mortgage loans held for investment, at fair value	2,796,239		2,746,142
Liabilities [Abstract]
Long-term debt, fair value	2,768,758		2,697,586
Recurring Fair Value Measurements [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Assets [Abstract]
Trading securities	17,757		16,306
Available-for-sale securities	0		0
Total assets at fair value	17,757		16,306
Other assets [Abstract]
Derivatives assets at fair value	0		0
Liabilities [Abstract]
Long-term debt, fair value	0		0
Total liabilities at fair value	0		0
Other liabilities [Abstract]
Derivative liabilities at fair value	0		0
Recurring Fair Value Measurements [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Swaps [Member]
Other assets [Abstract]
Derivatives assets at fair value	0		0
Other liabilities [Abstract]
Derivative liabilities at fair value	0		0
Recurring Fair Value Measurements [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Swaptions [Member]
Other assets [Abstract]
Derivatives assets at fair value	0		0
Other liabilities [Abstract]
Derivative liabilities at fair value	0		0
Recurring Fair Value Measurements [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Other [Member]
Other assets [Abstract]
Derivatives assets at fair value	0		0
Other liabilities [Abstract]
Derivative liabilities at fair value	0		0
Recurring Fair Value Measurements [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Netting adjustment [Member]
Other assets [Abstract]
Derivatives assets at fair value	0		0
Other liabilities [Abstract]
Derivative liabilities at fair value	0		0
Recurring Fair Value Measurements [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Mortgage commitment derivatives [Member]
Other assets [Abstract]
Derivatives assets at fair value	0		0
Other liabilities [Abstract]
Derivative liabilities at fair value	0		0
Recurring Fair Value Measurements [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Fannie Mae [Member]
Liabilities [Abstract]
Long-term debt, fair value	0		0
Recurring Fair Value Measurements [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Fannie Mae [Member] | Senior Fixed [Member]
Liabilities [Abstract]
Long-term debt, fair value			0
Recurring Fair Value Measurements [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Fannie Mae [Member] | Senior Floating [Member]
Liabilities [Abstract]
Long-term debt, fair value	0		0
Recurring Fair Value Measurements [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Consolidated Trusts [Member]
Assets [Abstract]
Mortgage loans held for investment, at fair value	0		0
Liabilities [Abstract]
Long-term debt, fair value	0		0
Recurring Fair Value Measurements [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Fannie Mae [Member]
Assets [Abstract]
Trading securities	0		0
Available-for-sale securities	0		0
Recurring Fair Value Measurements [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Freddie Mac [Member]
Assets [Abstract]
Trading securities	0		0
Available-for-sale securities	0		0
Recurring Fair Value Measurements [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Ginnie Mae [Member]
Assets [Abstract]
Trading securities	0		0
Available-for-sale securities	0		0
Recurring Fair Value Measurements [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Alt-A private-label securities [Member]
Assets [Abstract]
Trading securities	0		0
Available-for-sale securities	0		0
Recurring Fair Value Measurements [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Subprime private-label securities [Member]
Assets [Abstract]
Trading securities	0		0
Available-for-sale securities	0		0
Recurring Fair Value Measurements [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | CMBS [Member]
Assets [Abstract]
Trading securities	0		0
Available-for-sale securities	0		0
Recurring Fair Value Measurements [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Mortgage revenue bonds [Member]
Assets [Abstract]
Trading securities	0		0
Available-for-sale securities	0		0
Recurring Fair Value Measurements [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Other [Member]
Assets [Abstract]
Trading securities	0		0
Available-for-sale securities	0		0
Recurring Fair Value Measurements [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | U.S. Treasury securities [Member]
Assets [Abstract]
Trading securities	17,757		16,306
Recurring Fair Value Measurements [Member] | Significant Other Observable Inputs (Level 2) [Member]
Assets [Abstract]
Trading securities	9,959		11,688
Available-for-sale securities	16,202		19,159
Total assets at fair value	46,885		52,841
Other assets [Abstract]
Derivatives assets at fair value	7,333		10,430
Liabilities [Abstract]
Long-term debt, fair value	20,978		14,811
Total liabilities at fair value	30,327		25,545
Other liabilities [Abstract]
Derivative liabilities at fair value	9,349		10,734
Recurring Fair Value Measurements [Member] | Significant Other Observable Inputs (Level 2) [Member] | Swaps [Member]
Other assets [Abstract]
Derivatives assets at fair value	7,068		9,604
Other liabilities [Abstract]
Derivative liabilities at fair value	8,315		9,444
Recurring Fair Value Measurements [Member] | Significant Other Observable Inputs (Level 2) [Member] | Swaptions [Member]
Other assets [Abstract]
Derivatives assets at fair value	161		561
Other liabilities [Abstract]
Derivative liabilities at fair value	894		1,084
Recurring Fair Value Measurements [Member] | Significant Other Observable Inputs (Level 2) [Member] | Other [Member]
Other assets [Abstract]
Derivatives assets at fair value	0		0
Other liabilities [Abstract]
Derivative liabilities at fair value	0		0
Recurring Fair Value Measurements [Member] | Significant Other Observable Inputs (Level 2) [Member] | Netting adjustment [Member]
Other assets [Abstract]
Derivatives assets at fair value	0		0
Other liabilities [Abstract]
Derivative liabilities at fair value	0		0
Recurring Fair Value Measurements [Member] | Significant Other Observable Inputs (Level 2) [Member] | Mortgage commitment derivatives [Member]
Other assets [Abstract]
Derivatives assets at fair value	104		265
Other liabilities [Abstract]
Derivative liabilities at fair value	140		206
Recurring Fair Value Measurements [Member] | Significant Other Observable Inputs (Level 2) [Member] | Fannie Mae [Member]
Liabilities [Abstract]
Long-term debt, fair value	4,868		353
Recurring Fair Value Measurements [Member] | Significant Other Observable Inputs (Level 2) [Member] | Fannie Mae [Member] | Senior Fixed [Member]
Liabilities [Abstract]
Long-term debt, fair value			353
Recurring Fair Value Measurements [Member] | Significant Other Observable Inputs (Level 2) [Member] | Fannie Mae [Member] | Senior Floating [Member]
Liabilities [Abstract]
Long-term debt, fair value	4,868		0
Recurring Fair Value Measurements [Member] | Significant Other Observable Inputs (Level 2) [Member] | Consolidated Trusts [Member]
Assets [Abstract]
Mortgage loans held for investment, at fair value	13,391		11,564
Liabilities [Abstract]
Long-term debt, fair value	16,110		14,458
Recurring Fair Value Measurements [Member] | Significant Other Observable Inputs (Level 2) [Member] | Fannie Mae [Member]
Assets [Abstract]
Trading securities	5,146		5,828
Available-for-sale securities	5,756		6,566
Recurring Fair Value Measurements [Member] | Significant Other Observable Inputs (Level 2) [Member] | Freddie Mac [Member]
Assets [Abstract]
Trading securities	1,500		1,837
Available-for-sale securities	5,806		6,834
Recurring Fair Value Measurements [Member] | Significant Other Observable Inputs (Level 2) [Member] | Ginnie Mae [Member]
Assets [Abstract]
Trading securities	323		407
Available-for-sale securities	498		588
Recurring Fair Value Measurements [Member] | Significant Other Observable Inputs (Level 2) [Member] | Alt-A private-label securities [Member]
Assets [Abstract]
Trading securities	440		898
Available-for-sale securities	2,673		3,558
Recurring Fair Value Measurements [Member] | Significant Other Observable Inputs (Level 2) [Member] | Subprime private-label securities [Member]
Assets [Abstract]
Trading securities	0		0
Available-for-sale securities	0		0
Recurring Fair Value Measurements [Member] | Significant Other Observable Inputs (Level 2) [Member] | CMBS [Member]
Assets [Abstract]
Trading securities	2,550		2,718
Available-for-sale securities	1,467		1,606
Recurring Fair Value Measurements [Member] | Significant Other Observable Inputs (Level 2) [Member] | Mortgage revenue bonds [Member]
Assets [Abstract]
Trading securities	0		0
Available-for-sale securities	0		3
Recurring Fair Value Measurements [Member] | Significant Other Observable Inputs (Level 2) [Member] | Other [Member]
Assets [Abstract]
Trading securities	0		0
Available-for-sale securities	2		4
Recurring Fair Value Measurements [Member] | Significant Other Observable Inputs (Level 2) [Member] | U.S. Treasury securities [Member]
Assets [Abstract]
Trading securities	0		0
Recurring Fair Value Measurements [Member] | Significant Unobservable Inputs (Level 3) [Member]
Assets [Abstract]
Trading securities	3,128		2,774
Available-for-sale securities	15,897		19,012
Total assets at fair value	21,021		24,555
Other assets [Abstract]
Derivatives assets at fair value	125		65
Liabilities [Abstract]
Long-term debt, fair value	824		1,473
Total liabilities at fair value	958		1,578
Other liabilities [Abstract]
Derivative liabilities at fair value	134		105
Recurring Fair Value Measurements [Member] | Significant Unobservable Inputs (Level 3) [Member] | Swaps [Member]
Other assets [Abstract]
Derivatives assets at fair value	97		36
Other liabilities [Abstract]
Derivative liabilities at fair value	123		96
Recurring Fair Value Measurements [Member] | Significant Unobservable Inputs (Level 3) [Member] | Swaptions [Member]
Other assets [Abstract]
Derivatives assets at fair value	0		1
Other liabilities [Abstract]
Derivative liabilities at fair value	0		0
Recurring Fair Value Measurements [Member] | Significant Unobservable Inputs (Level 3) [Member] | Other [Member]
Other assets [Abstract]
Derivatives assets at fair value	26		28
Other liabilities [Abstract]
Derivative liabilities at fair value	1		1
Recurring Fair Value Measurements [Member] | Significant Unobservable Inputs (Level 3) [Member] | Netting adjustment [Member]
Other assets [Abstract]
Derivatives assets at fair value	0		0
Other liabilities [Abstract]
Derivative liabilities at fair value	0		0
Recurring Fair Value Measurements [Member] | Significant Unobservable Inputs (Level 3) [Member] | Mortgage commitment derivatives [Member]
Other assets [Abstract]
Derivatives assets at fair value	2		0
Other liabilities [Abstract]
Derivative liabilities at fair value	10		8
Recurring Fair Value Measurements [Member] | Significant Unobservable Inputs (Level 3) [Member] | Fannie Mae [Member]
Liabilities [Abstract]
Long-term debt, fair value	336		955
Recurring Fair Value Measurements [Member] | Significant Unobservable Inputs (Level 3) [Member] | Fannie Mae [Member] | Senior Fixed [Member]
Liabilities [Abstract]
Long-term debt, fair value			0
Recurring Fair Value Measurements [Member] | Significant Unobservable Inputs (Level 3) [Member] | Fannie Mae [Member] | Senior Floating [Member]
Liabilities [Abstract]
Long-term debt, fair value	336		955
Recurring Fair Value Measurements [Member] | Significant Unobservable Inputs (Level 3) [Member] | Consolidated Trusts [Member]
Assets [Abstract]
Mortgage loans held for investment, at fair value	1,871		2,704
Liabilities [Abstract]
Long-term debt, fair value	488		518
Recurring Fair Value Measurements [Member] | Significant Unobservable Inputs (Level 3) [Member] | Fannie Mae [Member]
Assets [Abstract]
Trading securities	325		42
Available-for-sale securities	0		7
Recurring Fair Value Measurements [Member] | Significant Unobservable Inputs (Level 3) [Member] | Freddie Mac [Member]
Assets [Abstract]
Trading securities	0		2
Available-for-sale securities	6		8
Recurring Fair Value Measurements [Member] | Significant Unobservable Inputs (Level 3) [Member] | Ginnie Mae [Member]
Assets [Abstract]
Trading securities	0		0
Available-for-sale securities	0		0
Recurring Fair Value Measurements [Member] | Significant Unobservable Inputs (Level 3) [Member] | Alt-A private-label securities [Member]
Assets [Abstract]
Trading securities	695		618
Available-for-sale securities	3,496		3,791
Recurring Fair Value Measurements [Member] | Significant Unobservable Inputs (Level 3) [Member] | Subprime private-label securities [Member]
Assets [Abstract]
Trading securities	1,316		1,448
Available-for-sale securities	5,386		7,068
Recurring Fair Value Measurements [Member] | Significant Unobservable Inputs (Level 3) [Member] | CMBS [Member]
Assets [Abstract]
Trading securities	0		0
Available-for-sale securities	0		0
Recurring Fair Value Measurements [Member] | Significant Unobservable Inputs (Level 3) [Member] | Mortgage revenue bonds [Member]
Assets [Abstract]
Trading securities	693		565
Available-for-sale securities	4,266		5,253
Recurring Fair Value Measurements [Member] | Significant Unobservable Inputs (Level 3) [Member] | Other [Member]
Assets [Abstract]
Trading securities	99		99
Available-for-sale securities	2,743		2,885
Recurring Fair Value Measurements [Member] | Significant Unobservable Inputs (Level 3) [Member] | U.S. Treasury securities [Member]
Assets [Abstract]
Trading securities	0		0
Recurring Fair Value Measurements [Member] | Netting Adjustment [Member]
Assets [Abstract]
Trading securities	0	[1]	0	[1]
Available-for-sale securities	0	[1]	0	[1]
Total assets at fair value	(6,202)	[1]	(8,422)	[1]
Other assets [Abstract]
Derivatives assets at fair value	(6,202)	[1]	(8,422)	[1]
Liabilities [Abstract]
Long-term debt, fair value	0	[1]	0	[1]
Total liabilities at fair value	(9,040)	[1]	(9,370)	[1]
Other liabilities [Abstract]
Derivative liabilities at fair value	(9,040)	[1]	(9,370)	[1]
Recurring Fair Value Measurements [Member] | Netting Adjustment [Member] | Swaps [Member]
Other assets [Abstract]
Derivatives assets at fair value	0	[1]	0	[1]
Other liabilities [Abstract]
Derivative liabilities at fair value	0	[1]	0	[1]
Recurring Fair Value Measurements [Member] | Netting Adjustment [Member] | Swaptions [Member]
Other assets [Abstract]
Derivatives assets at fair value	0	[1]	0	[1]
Other liabilities [Abstract]
Derivative liabilities at fair value	0	[1]	0	[1]
Recurring Fair Value Measurements [Member] | Netting Adjustment [Member] | Other [Member]
Other assets [Abstract]
Derivatives assets at fair value	0	[1]	0	[1]
Other liabilities [Abstract]
Derivative liabilities at fair value	0	[1]	0	[1]
Recurring Fair Value Measurements [Member] | Netting Adjustment [Member] | Netting adjustment [Member]
Other assets [Abstract]
Derivatives assets at fair value	(6,202)	[1]	(8,422)	[1]
Other liabilities [Abstract]
Derivative liabilities at fair value	(9,040)	[1]	(9,370)	[1]
Recurring Fair Value Measurements [Member] | Netting Adjustment [Member] | Mortgage commitment derivatives [Member]
Other assets [Abstract]
Derivatives assets at fair value	0	[1]	0	[1]
Other liabilities [Abstract]
Derivative liabilities at fair value	0	[1]	0	[1]
Recurring Fair Value Measurements [Member] | Netting Adjustment [Member] | Fannie Mae [Member]
Liabilities [Abstract]
Long-term debt, fair value	0	[1]	0	[1]
Recurring Fair Value Measurements [Member] | Netting Adjustment [Member] | Fannie Mae [Member] | Senior Fixed [Member]
Liabilities [Abstract]
Long-term debt, fair value			0	[1]
Recurring Fair Value Measurements [Member] | Netting Adjustment [Member] | Fannie Mae [Member] | Senior Floating [Member]
Liabilities [Abstract]
Long-term debt, fair value	0	[1]	0	[1]
Recurring Fair Value Measurements [Member] | Netting Adjustment [Member] | Consolidated Trusts [Member]
Assets [Abstract]
Mortgage loans held for investment, at fair value	0	[1]	0	[1]
Liabilities [Abstract]
Long-term debt, fair value	0	[1]	0	[1]
Recurring Fair Value Measurements [Member] | Netting Adjustment [Member] | Fannie Mae [Member]
Assets [Abstract]
Trading securities	0	[1]	0	[1]
Available-for-sale securities	0	[1]	0	[1]
Recurring Fair Value Measurements [Member] | Netting Adjustment [Member] | Freddie Mac [Member]
Assets [Abstract]
Trading securities	0	[1]	0	[1]
Available-for-sale securities	0	[1]	0	[1]
Recurring Fair Value Measurements [Member] | Netting Adjustment [Member] | Ginnie Mae [Member]
Assets [Abstract]
Trading securities	0	[1]	0	[1]
Available-for-sale securities	0	[1]	0	[1]
Recurring Fair Value Measurements [Member] | Netting Adjustment [Member] | Alt-A private-label securities [Member]
Assets [Abstract]
Trading securities	0	[1]	0	[1]
Available-for-sale securities	0	[1]	0	[1]
Recurring Fair Value Measurements [Member] | Netting Adjustment [Member] | Subprime private-label securities [Member]
Assets [Abstract]
Trading securities	0	[1]	0	[1]
Available-for-sale securities	0	[1]	0	[1]
Recurring Fair Value Measurements [Member] | Netting Adjustment [Member] | CMBS [Member]
Assets [Abstract]
Trading securities	0	[1]	0	[1]
Available-for-sale securities	0	[1]	0	[1]
Recurring Fair Value Measurements [Member] | Netting Adjustment [Member] | Mortgage revenue bonds [Member]
Assets [Abstract]
Trading securities	0	[1]	0	[1]
Available-for-sale securities	0	[1]	0	[1]
Recurring Fair Value Measurements [Member] | Netting Adjustment [Member] | Other [Member]
Assets [Abstract]
Trading securities	0	[1]	0	[1]
Available-for-sale securities	0	[1]	0	[1]
Recurring Fair Value Measurements [Member] | Netting Adjustment [Member] | U.S. Treasury securities [Member]
Assets [Abstract]
Trading securities	0	[1]	0	[1]
Recurring Fair Value Measurements [Member] | Estimated Fair Value [Member]
Assets [Abstract]
Trading securities	30,844		30,768
Available-for-sale securities	32,099		38,171
Total assets at fair value	79,461		85,280
Other assets [Abstract]
Derivatives assets at fair value	1,256		2,073
Liabilities [Abstract]
Long-term debt, fair value	21,802		16,284
Total liabilities at fair value	22,245		17,753
Other liabilities [Abstract]
Derivative liabilities at fair value	443		1,469
Recurring Fair Value Measurements [Member] | Estimated Fair Value [Member] | Swaps [Member]
Other assets [Abstract]
Derivatives assets at fair value	7,165		9,640
Other liabilities [Abstract]
Derivative liabilities at fair value	8,438		9,540
Recurring Fair Value Measurements [Member] | Estimated Fair Value [Member] | Swaptions [Member]
Other assets [Abstract]
Derivatives assets at fair value	161		562
Other liabilities [Abstract]
Derivative liabilities at fair value	894		1,084
Recurring Fair Value Measurements [Member] | Estimated Fair Value [Member] | Other [Member]
Other assets [Abstract]
Derivatives assets at fair value	26		28
Other liabilities [Abstract]
Derivative liabilities at fair value	1		1
Recurring Fair Value Measurements [Member] | Estimated Fair Value [Member] | Netting adjustment [Member]
Other assets [Abstract]
Derivatives assets at fair value	(6,202)		(8,422)
Other liabilities [Abstract]
Derivative liabilities at fair value	(9,040)		(9,370)
Recurring Fair Value Measurements [Member] | Estimated Fair Value [Member] | Mortgage commitment derivatives [Member]
Other assets [Abstract]
Derivatives assets at fair value	106		265
Other liabilities [Abstract]
Derivative liabilities at fair value	150		214
Recurring Fair Value Measurements [Member] | Estimated Fair Value [Member] | Fannie Mae [Member]
Liabilities [Abstract]
Long-term debt, fair value	5,204		1,308
Recurring Fair Value Measurements [Member] | Estimated Fair Value [Member] | Fannie Mae [Member] | Senior Fixed [Member]
Liabilities [Abstract]
Long-term debt, fair value			353
Recurring Fair Value Measurements [Member] | Estimated Fair Value [Member] | Fannie Mae [Member] | Senior Floating [Member]
Liabilities [Abstract]
Long-term debt, fair value	5,204		955
Recurring Fair Value Measurements [Member] | Estimated Fair Value [Member] | Consolidated Trusts [Member]
Assets [Abstract]
Mortgage loans held for investment, at fair value	15,262		14,268
Liabilities [Abstract]
Long-term debt, fair value	16,598		14,976
Recurring Fair Value Measurements [Member] | Estimated Fair Value [Member] | Fannie Mae [Member]
Assets [Abstract]
Trading securities	5,471		5,870
Available-for-sale securities	5,756		6,573
Recurring Fair Value Measurements [Member] | Estimated Fair Value [Member] | Freddie Mac [Member]
Assets [Abstract]
Trading securities	1,500		1,839
Available-for-sale securities	5,812		6,842
Recurring Fair Value Measurements [Member] | Estimated Fair Value [Member] | Ginnie Mae [Member]
Assets [Abstract]
Trading securities	323		407
Available-for-sale securities	498		588
Recurring Fair Value Measurements [Member] | Estimated Fair Value [Member] | Alt-A private-label securities [Member]
Assets [Abstract]
Trading securities	1,135		1,516
Available-for-sale securities	6,169		7,349
Recurring Fair Value Measurements [Member] | Estimated Fair Value [Member] | Subprime private-label securities [Member]
Assets [Abstract]
Trading securities	1,316		1,448
Available-for-sale securities	5,386		7,068
Recurring Fair Value Measurements [Member] | Estimated Fair Value [Member] | CMBS [Member]
Assets [Abstract]
Trading securities	2,550		2,718
Available-for-sale securities	1,467		1,606
Recurring Fair Value Measurements [Member] | Estimated Fair Value [Member] | Mortgage revenue bonds [Member]
Assets [Abstract]
Trading securities	693		565
Available-for-sale securities	4,266		5,256
Recurring Fair Value Measurements [Member] | Estimated Fair Value [Member] | Other [Member]
Assets [Abstract]
Trading securities	99		99
Available-for-sale securities	2,745		2,889
Recurring Fair Value Measurements [Member] | Estimated Fair Value [Member] | U.S. Treasury securities [Member]
Assets [Abstract]
Trading securities	$ 17,757		$ 16,306

[1] Derivative contracts are reported on a gross basis by level. The netting adjustment represents the effect of the legal right to offset under legally enforceable master netting agreements to settle with the same counterparty on a net basis, including cash collateral posted and received.