Fair Value Recurring Changes in Fair Value (Details) (USD $) In Millions, unless otherwise specified	Jun. 30, 2014		Dec. 31, 2013
Fannie Mae [Member]
Liabilities [Abstract]
Long-term debt, fair value	$ 3,432		$ 1,308
Consolidated Trusts [Member]
Assets [Abstract]
Mortgage loans held for investment, at fair value	15,116		14,268
Liabilities [Abstract]
Long-term debt, fair value	16,420		14,976
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Assets [Abstract]
Trading securities	13,083		16,306
Available-for-sale securities	0		0
Mortgage loans held for investment, at fair value	0		0
Total assets at fair value	47,967		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	10,878		11,688
Available-for-sale securities	17,216		19,159
Mortgage loans held for investment, at fair value	2,649,758		2,599,667
Total assets at fair value	2,722,513		2,694,859
Other assets [Abstract]
Derivatives assets at fair value	8,022		10,430
Liabilities [Abstract]
Total liabilities at fair value	3,253,326		3,231,253
Other liabilities [Abstract]
Derivative liabilities at fair value	10,007		10,734
Significant Other Observable Inputs (Level 2) [Member] | Fannie Mae [Member]
Assets [Abstract]
Mortgage loans held for investment, at fair value	29,361		29,920
Liabilities [Abstract]
Long-term debt, fair value	398,264		463,991
Significant Other Observable Inputs (Level 2) [Member] | Consolidated Trusts [Member]
Assets [Abstract]
Mortgage loans held for investment, at fair value	2,620,397		2,569,747
Liabilities [Abstract]
Long-term debt, fair value	2,754,120		2,684,224
Significant Unobservable Inputs (Level 3) [Member]
Assets [Abstract]
Trading securities	2,669		2,774
Available-for-sale securities	16,810		19,012
Mortgage loans held for investment, at fair value	410,625		392,355
Total assets at fair value	432,006		415,630
Other assets [Abstract]
Derivatives assets at fair value	139		65
Liabilities [Abstract]
Total liabilities at fair value	20,006		19,611
Other liabilities [Abstract]
Derivative liabilities at fair value	119		105
Significant Unobservable Inputs (Level 3) [Member] | Fannie Mae [Member]
Assets [Abstract]
Mortgage loans held for investment, at fair value	219,051		215,960
Liabilities [Abstract]
Long-term debt, fair value	940		1,557
Significant Unobservable Inputs (Level 3) [Member] | Consolidated Trusts [Member]
Assets [Abstract]
Mortgage loans held for investment, at fair value	191,574		176,395
Liabilities [Abstract]
Long-term debt, fair value	15,054		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	(6,897)		(8,422)
Other assets [Abstract]
Derivatives assets at fair value	(6,897)		(8,422)
Liabilities [Abstract]
Total liabilities at fair value	(9,390)		(9,370)
Other liabilities [Abstract]
Derivative liabilities at fair value	(9,390)		(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	26,630		30,768
Available-for-sale securities	34,026		38,171
Mortgage loans held for investment, at fair value	3,060,383		2,992,022
Total assets at fair value	3,195,589		3,155,006
Other assets [Abstract]
Derivatives assets at fair value	1,264		2,073
Liabilities [Abstract]
Total liabilities at fair value	3,263,942		3,241,494
Other liabilities [Abstract]
Derivative liabilities at fair value	736		1,469
Estimated Fair Value [Member] | Fannie Mae [Member]
Assets [Abstract]
Mortgage loans held for investment, at fair value	248,412		245,880
Liabilities [Abstract]
Long-term debt, fair value	399,204		465,548
Estimated Fair Value [Member] | Consolidated Trusts [Member]
Assets [Abstract]
Mortgage loans held for investment, at fair value	2,811,971		2,746,142
Liabilities [Abstract]
Long-term debt, fair value	2,769,174		2,697,586
Recurring Fair Value Measurements [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Assets [Abstract]
Trading securities	13,083		16,306
Available-for-sale securities	0		0
Total assets at fair value	13,083		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	13,083		16,306
Recurring Fair Value Measurements [Member] | Significant Other Observable Inputs (Level 2) [Member]
Assets [Abstract]
Trading securities	10,878		11,688
Available-for-sale securities	17,216		19,159
Total assets at fair value	48,701		52,841
Other assets [Abstract]
Derivatives assets at fair value	8,022		10,430
Liabilities [Abstract]
Long-term debt, fair value	19,029		14,811
Total liabilities at fair value	29,036		25,545
Other liabilities [Abstract]
Derivative liabilities at fair value	10,007		10,734
Recurring Fair Value Measurements [Member] | Significant Other Observable Inputs (Level 2) [Member] | Swaps [Member]
Other assets [Abstract]
Derivatives assets at fair value	7,347		9,604
Other liabilities [Abstract]
Derivative liabilities at fair value	8,497		9,444
Recurring Fair Value Measurements [Member] | Significant Other Observable Inputs (Level 2) [Member] | Swaptions [Member]
Other assets [Abstract]
Derivatives assets at fair value	310		561
Other liabilities [Abstract]
Derivative liabilities at fair value	985		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	365		265
Other liabilities [Abstract]
Derivative liabilities at fair value	525		206
Recurring Fair Value Measurements [Member] | Significant Other Observable Inputs (Level 2) [Member] | Fannie Mae [Member]
Liabilities [Abstract]
Long-term debt, fair value	3,107		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	3,107		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	12,585		11,564
Liabilities [Abstract]
Long-term debt, fair value	15,922		14,458
Recurring Fair Value Measurements [Member] | Significant Other Observable Inputs (Level 2) [Member] | Fannie Mae [Member]
Assets [Abstract]
Trading securities	5,686		5,828
Available-for-sale securities	6,020		6,566
Recurring Fair Value Measurements [Member] | Significant Other Observable Inputs (Level 2) [Member] | Freddie Mac [Member]
Assets [Abstract]
Trading securities	1,766		1,837
Available-for-sale securities	6,193		6,834
Recurring Fair Value Measurements [Member] | Significant Other Observable Inputs (Level 2) [Member] | Ginnie Mae [Member]
Assets [Abstract]
Trading securities	234		407
Available-for-sale securities	528		588
Recurring Fair Value Measurements [Member] | Significant Other Observable Inputs (Level 2) [Member] | Alt-A private-label securities [Member]
Assets [Abstract]
Trading securities	551		898
Available-for-sale securities	2,964		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	2,641		2,718
Available-for-sale securities	1,508		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	3		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	2,669		2,774
Available-for-sale securities	16,810		19,012
Total assets at fair value	22,149		24,555
Other assets [Abstract]
Derivatives assets at fair value	139		65
Liabilities [Abstract]
Long-term debt, fair value	823		1,473
Total liabilities at fair value	942		1,578
Other liabilities [Abstract]
Derivative liabilities at fair value	119		105
Recurring Fair Value Measurements [Member] | Significant Unobservable Inputs (Level 3) [Member] | Swaps [Member]
Other assets [Abstract]
Derivatives assets at fair value	86		36
Other liabilities [Abstract]
Derivative liabilities at fair value	118		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	29		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	24		0
Other liabilities [Abstract]
Derivative liabilities at fair value	0		8
Recurring Fair Value Measurements [Member] | Significant Unobservable Inputs (Level 3) [Member] | Fannie Mae [Member]
Liabilities [Abstract]
Long-term debt, fair value	325		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	325		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	2,531		2,704
Liabilities [Abstract]
Long-term debt, fair value	498		518
Recurring Fair Value Measurements [Member] | Significant Unobservable Inputs (Level 3) [Member] | Fannie Mae [Member]
Assets [Abstract]
Trading securities	0		42
Available-for-sale securities	2		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	9		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	643		618
Available-for-sale securities	3,717		3,791
Recurring Fair Value Measurements [Member] | Significant Unobservable Inputs (Level 3) [Member] | Subprime private-label securities [Member]
Assets [Abstract]
Trading securities	1,282		1,448
Available-for-sale securities	5,705		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	643		565
Available-for-sale securities	4,560		5,253
Recurring Fair Value Measurements [Member] | Significant Unobservable Inputs (Level 3) [Member] | Other [Member]
Assets [Abstract]
Trading securities	101		99
Available-for-sale securities	2,817		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	(6,897)	[1]	(8,422)	[1]
Other assets [Abstract]
Derivatives assets at fair value	(6,897)	[1]	(8,422)	[1]
Liabilities [Abstract]
Long-term debt, fair value	0	[1]	0	[1]
Total liabilities at fair value	(9,390)	[1]	(9,370)	[1]
Other liabilities [Abstract]
Derivative liabilities at fair value	(9,390)	[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	(6,897)	[1]	(8,422)	[1]
Other liabilities [Abstract]
Derivative liabilities at fair value	(9,390)	[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	26,630		30,768
Available-for-sale securities	34,026		38,171
Total assets at fair value	77,036		85,280
Other assets [Abstract]
Derivatives assets at fair value	1,264		2,073
Liabilities [Abstract]
Long-term debt, fair value	19,852		16,284
Total liabilities at fair value	20,588		17,753
Other liabilities [Abstract]
Derivative liabilities at fair value	736		1,469
Recurring Fair Value Measurements [Member] | Estimated Fair Value [Member] | Swaps [Member]
Other assets [Abstract]
Derivatives assets at fair value	7,433		9,640
Other liabilities [Abstract]
Derivative liabilities at fair value	8,615		9,540
Recurring Fair Value Measurements [Member] | Estimated Fair Value [Member] | Swaptions [Member]
Other assets [Abstract]
Derivatives assets at fair value	310		562
Other liabilities [Abstract]
Derivative liabilities at fair value	985		1,084
Recurring Fair Value Measurements [Member] | Estimated Fair Value [Member] | Other [Member]
Other assets [Abstract]
Derivatives assets at fair value	29		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	(6,897)		(8,422)
Other liabilities [Abstract]
Derivative liabilities at fair value	(9,390)		(9,370)
Recurring Fair Value Measurements [Member] | Estimated Fair Value [Member] | Mortgage commitment derivatives [Member]
Other assets [Abstract]
Derivatives assets at fair value	389		265
Other liabilities [Abstract]
Derivative liabilities at fair value	525		214
Recurring Fair Value Measurements [Member] | Estimated Fair Value [Member] | Fannie Mae [Member]
Liabilities [Abstract]
Long-term debt, fair value	3,432		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	3,432		955
Recurring Fair Value Measurements [Member] | Estimated Fair Value [Member] | Consolidated Trusts [Member]
Assets [Abstract]
Mortgage loans held for investment, at fair value	15,116		14,268
Liabilities [Abstract]
Long-term debt, fair value	16,420		14,976
Recurring Fair Value Measurements [Member] | Estimated Fair Value [Member] | Fannie Mae [Member]
Assets [Abstract]
Trading securities	5,686		5,870
Available-for-sale securities	6,022		6,573
Recurring Fair Value Measurements [Member] | Estimated Fair Value [Member] | Freddie Mac [Member]
Assets [Abstract]
Trading securities	1,766		1,839
Available-for-sale securities	6,202		6,842
Recurring Fair Value Measurements [Member] | Estimated Fair Value [Member] | Ginnie Mae [Member]
Assets [Abstract]
Trading securities	234		407
Available-for-sale securities	528		588
Recurring Fair Value Measurements [Member] | Estimated Fair Value [Member] | Alt-A private-label securities [Member]
Assets [Abstract]
Trading securities	1,194		1,516
Available-for-sale securities	6,681		7,349
Recurring Fair Value Measurements [Member] | Estimated Fair Value [Member] | Subprime private-label securities [Member]
Assets [Abstract]
Trading securities	1,282		1,448
Available-for-sale securities	5,705		7,068
Recurring Fair Value Measurements [Member] | Estimated Fair Value [Member] | CMBS [Member]
Assets [Abstract]
Trading securities	2,641		2,718
Available-for-sale securities	1,508		1,606
Recurring Fair Value Measurements [Member] | Estimated Fair Value [Member] | Mortgage revenue bonds [Member]
Assets [Abstract]
Trading securities	643		565
Available-for-sale securities	4,560		5,256
Recurring Fair Value Measurements [Member] | Estimated Fair Value [Member] | Other [Member]
Assets [Abstract]
Trading securities	101		99
Available-for-sale securities	2,820		2,889
Recurring Fair Value Measurements [Member] | Estimated Fair Value [Member] | U.S. Treasury securities [Member]
Assets [Abstract]
Trading securities	$ 13,083		$ 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.