Fair Value (Tables)

12 Months Ended

Dec. 31, 2018

Fair Value Measurement Inputs and Valuation Techniques [Line Items]

Recurring Changes in Fair Value [Table Text Block]

The following tables display our assets and liabilities measured in our consolidated balance sheets at fair value on a recurring basis subsequent to initial recognition, including instruments for which we have elected the fair value option.



	Fair Value Measurements as of December 31, 2018
	Quoted Prices in Active Markets for Identical Assets (Level 1)			Significant Other Observable Inputs (Level 2)			Significant Unobservable Inputs (Level 3)			Netting Adjustment⁽¹⁾				Estimated Fair Value
	(Dollars in millions)
Recurring fair value measurements:
Assets:
Cash equivalents⁽²⁾		$	748		$	—		$	—		$	—			$	748
Trading securities:
Mortgage-related securities:
Fannie Mae		—			1,435			32			—				1,467
Other agency		—			3,503			—			—				3,503
Private-label and other mortgage securities		—			1,305			1			—				1,306
Non-mortgage-related securities:
U.S. Treasury securities		35,502			—			—			—				35,502
Other securities		—			89			—			—				89
Total trading securities		35,502			6,332			33			—				41,867
Available-for-sale securities:
Mortgage-related securities:
Fannie Mae		—			1,645			152			—				1,797
Other agency		—			256			—			—				256
Alt-A and subprime private-label securities		—			568			24			—				592
Mortgage revenue bonds		—			—			434			—				434
Other		—			8			342			—				350
Total available-for-sale securities		—			2,477			952			—				3,429
Mortgage loans		—			7,985			937			—				8,922
Other assets:
Risk management derivatives:
Swaps		—			1,962			115			—				2,077
Swaptions		—			211			—			—				211
Netting adjustment		—			—			—			(2,266		)		(2,266		)
Mortgage commitment derivatives		—			342			37			—				379
Credit enhancement derivatives		—			—			57			—				57
Total other assets		—			2,515			209			(2,266		)		458
Total assets at fair value		$	36,250		$	19,309		$	2,131		$	(2,266	)		$	55,424



	Fair Value Measurements as of December 31, 2018
	Quoted Prices in Active Markets for Identical Assets (Level 1)			Significant Other Observable Inputs (Level 2)			Significant Unobservable Inputs (Level 3)			Netting Adjustment⁽¹⁾				Estimated Fair Value
	(Dollars in millions)
Liabilities:
Long-term debt:
Of Fannie Mae:
Senior floating		$	—		$	6,475		$	351		$	—		$	6,826
Total of Fannie Mae		—			6,475			351			—			6,826
Of consolidated trusts		—			23,552			201			—			23,753
Total long-term debt		—			30,027			552			—			30,579
Other liabilities:
Risk management derivatives:
Swaps		—			2,089			2			—			2,091
Swaptions		—			342			—			—			342
Netting adjustment		—			—			—			(2,315		)	(2,315		)
Mortgage commitment derivatives		—			646			2			—			648
Credit enhancement derivatives		—			—			11			—			11
Total other liabilities		—			3,077			15			(2,315		)	777
Total liabilities at fair value		$	—		$	33,104		$	567		$	(2,315	)	$	31,356



	Fair Value Measurements as of December 31, 2017
	Quoted Prices in Active Markets for Identical Assets (Level 1)			Significant Other Observable Inputs (Level 2)			Significant Unobservable Inputs (Level 3)			Netting Adjustment⁽¹⁾				Estimated Fair Value
	(Dollars in millions)
Assets:
Trading securities:
Mortgage-related securities:
Fannie Mae		$	—		$	2,905		$	971		$	—			$	3,876
Other agency		—			1,083			35			—				1,118
Private-label and other mortgage securities		—			268			195			—				463
Non-mortgage-related securities:
U.S. Treasury securities		29,222			—			—			—				29,222
Total trading securities		29,222			4,256			1,201			—				34,679
Available-for-sale securities:
Mortgage-related securities:
Fannie Mae		—			1,911			208			—				2,119
Other agency		—			357			—			—				357
Alt-A and subprime private-label securities		—			1,237			77			—				1,314
CMBS		—			15			—			—				15
Mortgage revenue bonds		—			—			671			—				671
Other		—			10			357			—				367
Total available-for-sale securities		—			3,530			1,313			—				4,843
Mortgage loans		—			9,480			1,116			—				10,596
Other assets:
Risk management derivatives:
Swaps		—			4,035			146			—				4,181
Swaptions		—			108			—			—				108
Netting adjustment		—			—			—			(4,272		)		(4,272		)
Mortgage commitment derivatives		—			131			1			—				132
Credit enhancement derivatives		—			—			22			—				22
Total other assets		—			4,274			169			(4,272		)		171
Total assets at fair value		$	29,222		$	21,540		$	3,799		$	(4,272	)		$	50,289



	Fair Value Measurements as of December 31, 2017
	Quoted Prices in Active Markets for Identical Assets (Level 1)			Significant Other Observable Inputs (Level 2)			Significant Unobservable Inputs (Level 3)			Netting Adjustment⁽¹⁾				Estimated Fair Value
	(Dollars in millions)
Liabilities:
Long-term debt:
Of Fannie Mae:
Senior floating		$	—		$	7,810		$	376		$	—			$	8,186
Total of Fannie Mae		—			7,810			376			—				8,186
Of consolidated trusts		—			29,911			582			—				30,493
Total long-term debt		—			37,721			958			—				38,679
Other liabilities:
Risk management derivatives:
Swaps		—			4,721			33			—				4,754
Swaptions		—			324			—			—				324
Netting adjustment		—			—			—			(4,979		)		(4,979		)
Mortgage commitment derivatives		—			227			1			—				228
Credit enhancement derivatives		—			—			1			—				1
Total other liabilities		—			5,272			35			(4,979		)		328
Total liabilities at fair value		$	—		$	42,993		$	993		$	(4,979	)		$	39,007


⁽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 arrangements to settle with the same counterparty on a net basis, including cash collateral posted and received.

⁽²⁾

Cash equivalents are comprised of U.S. Treasuries that have a maturity at the date of acquisition of three months or less.

Fair Value Measurements Using Significant Unobservable Inputs (Level 3) [Table Text Block]

The following tables display a reconciliation of all assets and liabilities measured at fair value on a recurring basis using significant unobservable inputs (Level 3). The tables also display gains and losses due to changes in fair value, including both realized and unrealized gains and losses, recognized in our consolidated statements of operations and comprehensive income for Level 3 assets and liabilities.



	Fair Value Measurements Using Significant Unobservable Inputs (Level 3)
	For the Year Ended December 31, 2018
				Total Gains (Losses) (Realized/Unrealized)																											Net Unrealized Gains (Losses) Included in Net Income Related to Assets and Liabilities Still Held as of December 31, 2018⁽⁵⁾⁽⁶⁾			Net Unrealized Gains (Losses) Included in OCI Related to Assets and Liabilities Still Held as of December 31, 2018⁽¹⁾
	Balance, December 31, 2017			Included in Net Income				Included in Total OCI Gains/(Losses)⁽¹⁾				Purchases⁽²⁾		Sales⁽²⁾			Issues⁽³⁾		Settlements⁽³⁾			Transfers out of Level 3⁽⁴⁾			Transfers into Level 3⁽⁴⁾			Balance, December 31, 2018
	(Dollars in millions)
Trading securities:
Mortgage-related:
Fannie Mae	$	971		$	163				$	—		$	1	$	(1,059	)	$	—	$	(1	)	$	(44	)	$	1		$	32		$	4		$	—
Other agency	35			(1		)			—			—		—			—		(1		)	(33		)	—			—			—			—
Private-label and other mortgage securities	195			(85		)			—			—		—			—		(5		)	(104		)	—			1			—			—
Total trading securities	$	1,201		$	77		⁽⁶⁾⁽⁷⁾		$	—		$	1	$	(1,059	)	$	—	$	(7	)	$	(181	)	$	1		$	33		$	4		$	—

Available-for-sale securities:
Mortgage-related:
Fannie Mae	$	208		$	2				$	1		$	—	$	—		$	—	$	(10	)	$	(49	)	$	—		$	152		$	—		$	—
Alt-A and subprime private-label securities	77			—					(45		)	—		—			—		(4		)	(4		)	—			24			—			1
Mortgage revenue bonds	671			—					(7		)	—		(22		)	—		(208		)	—			—			434			—			(2		)
Other	357			28					(2		)	—		—			—		(41		)	—			—			342			—			1
Total available-for-sale securities	$	1,313		$	30		⁽⁷⁾⁽⁸⁾		$	(53	)	$	—	$	(22	)	$	—	$	(263	)	$	(53	)	$	—		$	952		$	—		$	—

Mortgage loans	$	1,116		$	38		⁽⁶⁾⁽⁷⁾		$	—		$	—	$	—		$	—	$	(216	)	$	(162	)	$	161		$	937		$	14		$	—
Net derivatives	134			(38		)	⁽⁶⁾		—			—		—			—		45			53			—			194			40			—
Long-term debt:
Of Fannie Mae:
Senior floating	$	(376	)	$	25		⁽⁶⁾		$	—		$	—	$	—		$	—	$	—		$	—		$	—		$	(351	)	$	25		$	—
Of consolidated trusts	(582		)	9			⁽⁶⁾⁽⁷⁾		—			—		—			1		44			541			(214		)	(201		)	(2		)	—
Total long-term debt	$	(958	)	$	34				$	—		$	—	$	—		$	1	$	44		$	541		$	(214	)	$	(552	)	$	23		$	—



	Fair Value Measurements Using Significant Unobservable Inputs (Level 3)
	For the Year Ended December 31, 2017
				Total Gains (Losses) (Realized/Unrealized)																												Net Unrealized Gains (Losses) Included in Net Income Related to Assets and Liabilities Still Held as of December 31, 2017⁽⁵⁾⁽⁶⁾			Net Unrealized Gains (Losses) Included in OCI Related to Assets and Liabilities Still Held as of December 31, 2017⁽¹⁾
	Balance, December 31, 2016			Included in Net Income				Included in Total OCI (Loss)⁽¹⁾				Purchases⁽²⁾		Sales⁽²⁾			Issues⁽³⁾			Settlements⁽³⁾			Transfers out of Level 3⁽⁴⁾			Transfers into Level 3⁽⁴⁾			Balance, December 31, 2017
	(Dollars in millions)
Trading securities:
Mortgage-related:
Fannie Mae	$	835		$	41				$	—		$	64	$	—		$	—		$	(5	)	$	(991	)	$	1,027		$	971		$	6		$	—
Other agency	—			—					—			35		—			—			—			—			—			35			—			—
Private-label and other mortgage securities	292			18					—			—		(81		)	—			(34		)	—			—			195			5			—
Total trading securities	$	1,127		$	59		⁽⁶⁾⁽⁷⁾		$	—		$	99	$	(81	)	$	—		$	(39	)	$	(991	)	$	1,027		$	1,201		$	11		$	—

Available-for-sale securities:
Mortgage-related:
Fannie Mae	$	230		$	2				$	(1	)	$	—	$	—		$	—		$	(9	)	$	(72	)	$	58		$	208		$	—		$	—
Other agency	5			—					—			—		(1		)	—			—			(4		)	—			—			—			—
Alt-A and subprime private-label securities	217			54					(53		)	—		(105		)	—			(36		)	—			—			77			—			4
Mortgage revenue bonds	1,272			35					(11		)	—		(392		)	—			(233		)	—			—			671			—			4
Other	429			8					(11		)	—		(5		)	—			(64		)	—			—			357			—			(7		)
Total available-for-sale securities	$	2,153		$	99		⁽⁷⁾⁽⁸⁾		$	(76	)	$	—	$	(503	)	$	—		$	(342	)	$	(76	)	$	58		$	1,313		$	—		$	1

Mortgage loans	$	1,197		$	45		⁽⁶⁾⁽⁷⁾		$	—		$	5	$	—		$	—		$	(233	)	$	(70	)	$	172		$	1,116		$	25		$	—
Net derivatives	44			111			⁽⁶⁾		—			—		—			—			(22		)	6			(5		)	134			13			—
Long-term debt:
Of Fannie Mae:
Senior floating	$	(347	)	$	(29	)	⁽⁶⁾		$	—		$	—	$	—		$	—		$	—		$	—		$	—		$	(376	)	$	(29	)	$	—
Of consolidated trusts	(241		)	(9		)	⁽⁶⁾⁽⁷⁾		—			—		—			(2		)	66			388			(784		)	(582		)	(11		)	—
Total long-term debt	$	(588	)	$	(38	)			$	—		$	—	$	—		$	(2	)	$	66		$	388		$	(784	)	$	(958	)	$	(40	)	$	—



	Fair Value Measurements Using Significant Unobservable Inputs (Level 3)
	For the Year Ended December 31, 2016
				Total Gains (Losses) (Realized/Unrealized)																												Net Unrealized Gains (Losses) Included in Net Income Related to Assets and Liabilities Still Held as of December 31, 2016⁽⁵⁾⁽⁶⁾			Net Unrealized Gains (Losses) Included in OCI Related to Assets and Liabilities Still Held as of December 31, 2016⁽¹⁾
	Balance, December 31, 2015			Included in Net Income				Included in Total OCI (Loss)⁽¹⁾				Purchases⁽²⁾		Sales⁽²⁾			Issues⁽³⁾			Settlements⁽³⁾			Transfers out of Level 3⁽⁴⁾			Transfers into Level 3⁽⁴⁾			Balance, December 31, 2016
	(Dollars in millions)
Trading securities:
Mortgage-related:
Fannie Mae	$	—		$	—				$	—		$	—	$	—		$	—		$	(1	)	$	(24	)	$	860		$	835		$	—		$	—
Other agency	—			—					—			—		—			—			—			(1		)	1			—			—			—
Private-label and other mortgage securities	1,398			—					—			—		(679		)	—			(64		)	(363		)	—			292			(3		)	—
Total trading securities	$	1,398		$	—		⁽⁶⁾⁽⁷⁾		$	—		$	—	$	(679	)	$	—		$	(65	)	$	(388	)	$	861		$	1,127		$	(3	)	$	—

Available-for-sale securities:
Mortgage-related:
Fannie Mae	$	—		$	—				$	—		$	—	$	—		$	—		$	—		$	(1	)	$	231		$	230		$	—		$	—
Other agency	4			—					—			—		—			—			—			(4		)	5			5			—			—
Alt-A and subprime private-label securities	4,322			184					(233		)	—		(997		)	—			(220		)	(2,839		)	—			217			—			(5		)
Mortgage revenue bonds	2,701			132					(34		)	—		(1,129		)	—			(398		)	—			—			1,272			—			(1		)
Other	1,404			—					(12		)	—		(605		)	—			(74		)	(284		)	—			429			—			1
Total available-for-sale securities	$	8,431		$	316		⁽⁷⁾⁽⁸⁾		$	(279	)	$	—	$	(2,731	)	$	—		$	(692	)	$	(3,128	)	$	236		$	2,153		$	—		$	(5	)

Mortgage loans	$	1,477		$	129		⁽⁶⁾⁽⁷⁾		$	—		$	36	$	(392	)	$	—		$	(255	)	$	(77	)	$	279		$	1,197		$	17		$	—
Net derivatives	157			15			⁽⁶⁾		—			—		—			(8		)	(122		)	2			—			44			(132		)	—
Long-term debt:
Of Fannie Mae:
Senior floating	$	(369	)	$	22		⁽⁶⁾		$	—		$	—	$	—		$	—		$	—		$	—		$	—		$	(347	)	$	22		$	—
Of consolidated trusts	(496		)	(75		)	⁽⁶⁾⁽⁷⁾		—			—		—			(74		)	378			215			(189		)	(241		)	(9		)	—
Total long-term debt	$	(865	)	$	(53	)			$	—		$	—	$	—		$	(74	)	$	378		$	215		$	(189	)	$	(588	)	$	13		$	—


⁽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 our consolidated statements of operations and comprehensive income.


⁽²⁾	Purchases and sales include activity related to the consolidation and deconsolidation of assets of securitization trusts. For 2018, includes the dissolution of a Fannie Mae-wrapped private-label securities trust.


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

⁽⁴⁾

Transfers into and out of Level 3 consisted primarily of Fannie Mae securities backed by private-label mortgage-related securities. Prices for these securities are based on inputs that were not readily observable. Transfers out of Level 3 also occurred for Alt-A loans and subprime private-label mortgage-related securities. Prices for these securities were available from multiple third-party vendors and demonstrated an increased and sustained level of observability over time.


⁽⁵⁾	Amount represents temporary changes in fair value. Amortization, accretion and OTTI are not considered unrealized and are not included in this amount.


⁽⁶⁾	Gains (losses) are included in “Fair value gains (losses), net” in our consolidated statements of operations and comprehensive income.


⁽⁷⁾	Gains (losses) are included in “Net interest income” in our consolidated statements of operations and comprehensive income.

⁽⁸⁾

Gains (losses) are included in “Investment gains, net” in our consolidated statements of operations and comprehensive income.

Valuation Techniques and Significant Unobservable Inputs for Level 3 Assets and Liabilities [Table Text Block]

The following tables display valuation techniques and the range and the weighted average of significant unobservable inputs for our Level 3 assets and liabilities measured at fair value on a recurring basis, excluding instruments for which we have elected the fair value option. Changes in these unobservable inputs can result in significantly higher or lower fair value measurements of these assets and liabilities as of the reporting date.

Fair Value Measurements as of December 31, 2018

Fair Value

Significant Valuation Techniques

Significant Unobservable Inputs⁽¹⁾

Range⁽¹⁾

Weighted - Average⁽¹⁾⁽²⁾

(Dollars in millions)

Recurring fair value measurements:

Trading securities:

Mortgage-related securities:

Agency⁽³⁾

Various

Private-label and other mortgage securities

Various

Total trading securities



Available-for-sale securities:
Mortgage-related securities:
Agency⁽³⁾	$	152	Various
Alt-A and subprime private-label securities	24		Various
Mortgage Revenue Bonds	349		Single Vendor	Spreads (bps)	(0.5	)	-	332.8	59.0
	85		Various
Total Mortgage Revenue Bonds	434
Other	294		Discounted Cash Flow	Default Rate (%)	4.70				4.70
				Prepayment Speed (%)	8.2				8.2
				Severity (%)	70.0				70.0
				Spreads (bps)	75.4		-	390.0	389.1
	48		Various
Total other	342
Total available-for-sale securities	$	952
Net derivatives	$	113	Dealer Mark
	81		Various
Total net derivatives	$	194



	Fair Value Measurements as of December 31, 2017
	Fair Value		Significant Valuation Techniques	Significant Unobservable Inputs⁽¹⁾	Range⁽¹⁾			Weighted - Average⁽¹⁾⁽²⁾
	(Dollars in millions)
Recurring fair value measurements:
Trading securities:
Mortgage-related securities:
Agency⁽³⁾	$	971	Single Vendor	Prepayment Speed (%)	0.0	-	177.0	160.0
				Spreads (bps)	51.5	-	375.0	200.1
	35		Various
Total agency	1,006
Private-label and other mortgage securities	154		Consensus
	41		Various
Total Private-label and other mortgage securities	195
Total trading securities	$	1,201



	Fair Value Measurements as of December 31, 2017
	Fair Value		Significant Valuation Techniques	Significant Unobservable Inputs⁽¹⁾	Range⁽¹⁾				Weighted - Average⁽¹⁾⁽²⁾
	(Dollars in millions)
Available-for-sale securities:
Mortgage-related securities:
Agency⁽³⁾	$	112	Single Vendor	Prepayment Speed (%)	0.0		-	175.7	147.1
				Spreads (bps)	150.0		-	210.0	182.3
	96		Various
Total agency	208
Alt-A and subprime private-label securities	77		Various
Mortgage revenue bonds	475		Single Vendor	Spreads (bps)	(17.0	)	-	248.0	39.0
	196		Various
Total mortgage revenue bonds	671
Other	325		Discounted Cash Flow	Prepayment Speed (%)	1.6		-	2.5	2.5
				Severity (%)	50.0		-	88.0	86.6
				Spreads (bps)	84.8		-	607.0	577.9
	32		Various
Total other	357
Total available-for-sale securities	$	1,313
Net derivatives	$	113	Dealer Mark
	21		Various
Total net derivatives	$	134

⁽¹⁾

Valuation techniques for which no unobservable inputs are disclosed generally reflect the use of third-party pricing services or dealers, and the range of unobservable inputs applied by these sources is not readily available or cannot be reasonably estimated. Where we have disclosed unobservable inputs for consensus and single vendor techniques, those inputs are based on our validations performed at the security level using discounted cash flows. The prepayment speed used for available-for-sale agency securities is the Public Securities Association (“PSA”) prepayment speed, which can be greater than 100%. For all other securities, the Conditional Prepayment Rate (“CPR”) is used as the prepayment speed, which can be between 0% and 100%.


⁽²⁾	Unobservable inputs were weighted by the relative fair value of the instruments.


⁽³⁾	Includes Fannie Mae and Freddie Mac securities.

Level 3 Assets Measured on Nonrecurring Basis [Table Text Block]



Instruments	Valuation Techniques	Classification
U.S Treasury Securities	We classify securities whose values are based on quoted market prices in active markets for identical assets as Level 1 of the valuation hierarchy.	Level 1
Trading Securities and Available-for-Sale Securities	We classify securities in active markets as Level 2 of the valuation hierarchy if quoted market prices in active markets for identical assets are not available. For all valuation techniques used for securities where there is limited activity or less transparency around these inputs to the valuation, these securities are classified as Level 3 of the valuation hierarchy. Single Vendor: Uses one vendor price to estimate fair value. We generally validate these observations of fair value through the use of a discounted cash flow technique whose unobservable inputs (for example, default rates) are disclosed in the table above. Dealer Mark: Uses one dealer price to estimate fair value. We generally validate these observations of fair value through the use of a discounted cash flow technique whose unobservable inputs (for example, default rates) are disclosed in the table above. Consensus: Uses an average of two or more vendor prices for similar securities. We generally validate these observations of fair value through the use of a discounted cash flow technique whose unobservable inputs (for example, default rates) are disclosed in the table above.	Level 2 and 3
	Discounted Cash Flow: In the absence of prices provided by third-party pricing services supported by observable market data, we estimate the fair value of a portion of our securities using a discounted cash flow technique that uses inputs such as default rates, prepayment speeds, loss severity and spreads based on market assumptions where available. For private-label securities, an increase in unobservable prepayment speeds in isolation would generally result in an increase in fair value, and an increase in unobservable spreads, severity rates or default rates in isolation would generally result in a decrease in fair value. For mortgage revenue bonds classified as Level 3 of the valuation hierarchy, an increase in unobservable spreads would result in a decrease in fair value. Although we have disclosed unobservable inputs for the fair value of our recurring Level 3 securities above, interrelationships exist among these inputs such that a change in one unobservable input typically results in a change to one or more of the other inputs.
Mortgage Loans Held for Investment	Build-up: We derive the fair value of performing mortgage loans using a build-up valuation technique starting with the base value for our Fannie Mae MBS with similar characteristics and then add or subtract the fair value of the associated guaranty asset, guaranty obligation (“GO”) and master servicing arrangement. We set the GO equal to the estimated fair value we would receive if we were to issue our guaranty to an unrelated party in a stand-alone arm’s length transaction at the measurement date. The fair value of the GO is estimated based on our current guaranty pricing for loans underwritten after 2008 and our internal valuation models considering management’s best estimate of key loan characteristics for loans underwritten before 2008. Our performing loans are generally classified as Level 2 of the valuation hierarchy to the extent that significant inputs are observable. To the extent that unobservable inputs are significant, the loans are classified as Level 3 of the valuation hierarchy.	Level 2 and 3
	Consensus: Calculated through the extrapolation of indicative sample bids obtained from multiple active market participants plus the estimated value of any applicable mortgage insurance, the estimated fair value using the Consensus method represents an estimate of the prices we would receive if we were to sell these single-family nonperforming and certain reperforming loans in the whole-loan market. The fair value of any mortgage insurance is estimated by taking the loan level coverage and adjusting it by the expected claims paying ability of the associated mortgage insurer. These loans are classified as Level 3 of the valuation hierarchy because significant inputs are unobservable. We estimate the fair value for a portion of our senior-subordinated trust structures using the average of two or more vendor prices at the security level as a proxy for estimating loan fair value. These loans are classified as Level 3 of the valuation hierarchy because significant inputs are unobservable.
	Single Vendor: We estimate the fair value of our reverse mortgages using the single vendor valuation technique. Internal Model: The internal model used in this process applies one of following two approaches when valuing the collateral depending on the historical accuracy of the two approaches. (1) The comparable foreclosed property sales approach is used in the majority of the internal model valuations. The comparable foreclosed property sales approach uses various factors such as geographic distance, transaction time and the value difference. (2) The median Metropolitan Statistical Area (“MSA”) approach is based on the median of all the foreclosure sales of REOs in a specific MSA or state when there is not enough REO sales in a specific MSA. These loans are classified as Level 3 of the valuation hierarchy because significant inputs are unobservable.



Instruments	Valuation Techniques	Classification
Mortgage Loans Held for Investment	Appraisals: Uses appraisals to estimate the fair value for a portion of our multifamily loans based on either estimated replacement cost, the present value of future cash flows, or sales of similar properties. Significant unobservable inputs include estimated replacement or construction costs, property net operating income, capitalization rates, and adjustments made to sales of comparable properties based on characteristics such as financing, conditions of sale, and physical characteristics of the property. Broker Price Opinion (“BPO”): Uses BPO to estimate the fair value for a portion of our multifamily loans. This technique uses both current property value and the property value adjusted for stabilization and market conditions. The unobservable inputs used in this technique are property net operating income and market capitalization rates to estimate property value. Asset Manager Estimate (“AME”): This technique uses the net operating income and tax assessments of the specific property as well as MSA-specific market capitalization rates and average per unit sales values to estimate property fair value.	Level 2 and 3
	An increase in prepayment speeds in isolation would generally result in an increase in the fair value of our mortgage loans classified as Level 3 of the valuation hierarchy, and an increase in severity rates, default rates or spreads in isolation would generally result in a decrease in fair value. Although we have disclosed unobservable inputs for the fair value of the mortgage loans classified as Level 3 above, interrelationships exist among these inputs such that a change in one unobservable input typically results in a change to one or more of the other inputs.
Acquired Property, Net and Other Assets	Single-family acquired property valuation techniques Appraisal: An appraisal is an estimate based on recent historical data of the value of a specific property by a certified or licensed appraiser. Adjustments are made for differences between comparable properties for unobservable inputs such as square footage, location, and condition of the property. Broker Price Opinion: This technique provides an estimate of what the property is worth based upon a real estate broker’s use of specific market research and a sales comparison approach that is similar to the appraisal process. This information, all of which is unobservable, is used along with recent and pending sales and current listings of similar properties to arrive at an estimate of value.	Level 3
	Appraisal and Broker Price Opinion Walk Forwards (“Walk Forwards”): We use these techniques to adjust appraisal and broker price opinion valuations for changing market conditions by applying a walk forward factor based on local price movements since the time the third-party value was obtained. Internal Model: We use an internal model to estimate fair value for distressed properties. The valuation methodology and inputs used are described under “Mortgage Loans Held for Investment.”
	Multifamily acquired property valuation techniques Appraisals: We use this method to estimate property values for distressed properties. The valuation methodology and inputs used are described under “Mortgage Loans Held for Investment.” Broker Price Opinions: We use this method to estimate property values for distressed properties. The valuation methodology and inputs used are described under “Mortgage Loans Held for Investment.” Asset Manager Estimate (“AME”): We use this method to estimate property values for distressed properties. The valuation methodology and inputs used are described under “Mortgage Loans Held for Investment.”
Derivatives Assets and Liabilities (collectively “Derivatives”)	The valuation process for the majority of our risk management derivatives uses observable market data provided by third-party sources, resulting in Level 2 classification of the valuation hierarchy. Internal Model: We use internal models to value interest rate swaps which are valued by referencing yield curves derived from observable interest rates and spreads to project and discount swap cash flows to present value. Option-based derivatives use an internal model that projects the probability of various levels of interest rates by referencing swaption volatilities provided by market makers/dealers. The projected cash flows of the underlying swaps of these option-based derivatives are discounted to present value using yield curves derived from observable interest rates and spreads. Dealer Mark: Certain highly complex structured swaps primarily use a single dealer mark due to lack of transparency in the market and may be modeled using observable interest rates and volatility levels as well as significant unobservable assumptions, resulting in Level 3 classification of the valuation hierarchy. Mortgage commitment derivatives that use observable market data, quotes and actual transaction price levels adjusted for market movement are typically classified as Level 2 of the valuation hierarchy. To the extent mortgage commitment derivatives include adjustments for market movement that cannot be corroborated by observable market data, we classify them as Level 3 of the valuation hierarchy.	Level 2 and 3



Instruments	Valuation Techniques	Classification
Debt of Fannie Mae and Consolidated Trusts	We classify debt instruments that have quoted market prices in active markets for similar liabilities when traded as assets as Level 2 of the valuation hierarchy. For all valuation techniques used for debt instruments where there is limited activity or less transparency around these inputs to the valuation, these debt instruments are classified as Level 3 of the valuation hierarchy. Consensus: Uses an average of two or more vendor prices or dealer marks that represents estimated fair value for similar liabilities when traded as assets. Single Vendor: Uses a single vendor price that represents estimated fair value for these liabilities when traded as assets. Discounted Cash Flow: Uses spreads based on market assumptions where available. The valuation methodology and inputs used in estimating the fair value of MBS assets are described under “Trading Securities and Available-for-Sale Securities.”	Level 2 and 3

The following table displays valuation techniques for our Level 3 assets measured at fair value on a nonrecurring basis. The significant unobservable inputs related to these techniques primarily relate to collateral dependent valuations. The related ranges and weighted averages are not meaningful when aggregated as they vary significantly from property to property.



		Fair Value Measurements as of December 31,
	Valuation Techniques	2018		2017
		(Dollars in millions)
Nonrecurring fair value measurements:
Mortgage loans held for sale, at lower of cost or fair value	Consensus	$	631	$	1,113
	Single Vendor	1,119		1,880
Total mortgage loans held for sale, at lower of cost or fair value		1,750		2,993
Single-family mortgage loans held for investment, at amortized cost	Internal Model	818		1,623
Multifamily mortgage loans held for investment, at amortized cost	Asset Manager Estimate	102		163
	Various	40		32
Total multifamily mortgage loans held for investment, at amortized cost		142		195
Acquired property, net:⁽¹⁾
Single-family	Accepted Offers	151		218
	Appraisals	419		438
	Walk Forwards	181		222
	Internal Model	219		319
	Various	41		113
Total single-family		1,011		1,310
Multifamily	Various	50		19
Other assets	Various	—		2
Total nonrecurring assets at fair value		$	3,771	$	6,142

⁽¹⁾

The most commonly used techniques in our valuation of acquired property are proprietary home price model and third-party valuations (both current and walk forward). Based on the number of properties measured as of December 31, 2018, these methodologies comprised approximately 82% of our valuations, while accepted offers comprised approximately 15% of our valuations. Based on the number of properties measured as of December 31, 2017, these methodologies comprised approximately 77% of our valuations, while accepted offers comprised approximately 18% of our valuations.



	As of December 31, 2017
	Carrying Value		Quoted Price in Active Markets for Identical Assets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)		Netting Adjustment			Estimated Fair Value
	(Dollars in millions)
Financial assets:
Cash and cash equivalents and restricted cash	$	60,260	$	35,060	$	25,200	$	—	$	—		$	60,260
Federal funds sold and securities purchased under agreements to resell or similar arrangements	19,470		—		19,470		—		—			19,470
Trading securities	34,679		29,222		4,256		1,201		—			34,679
Available-for-sale securities	4,843		—		3,530		1,313		—			4,843
Mortgage loans held for sale	4,988		—		101		5,333		—			5,434
Mortgage loans held for investment, net of allowance for loan losses	3,173,537		—		2,886,470		315,719		—			3,202,189
Advances to lenders	4,938		—		4,936		2		—			4,938
Derivative assets at fair value	171		—		4,274		169		(4,272		)	171
Guaranty assets and buy-ups	149		—		—		436		—			436
Total financial assets	$	3,303,035	$	64,282	$	2,948,237	$	324,173	$	(4,272	)	$	3,332,420
Financial liabilities:
Short-term debt:
Of Fannie Mae	$	33,377	$	—	$	33,379	$	—	$	—		$	33,379
Of consolidated trusts	379		—		—		378		—			378
Long-term debt:
Of Fannie Mae	243,375		—		249,780		837		—			250,617
Of consolidated trusts	3,052,923		—		3,014,250		40,683		—			3,054,933
Derivative liabilities at fair value	328		—		5,272		35		(4,979		)	328
Guaranty obligations	258		—		—		456		—			456
Total financial liabilities	$	3,330,640	$	—	$	3,302,681	$	42,389	$	(4,979	)	$	3,340,091



Instruments	Description	Classification
Financial instruments for which fair value approximates carrying value	We hold certain financial instruments that are not carried at fair value but for which the carrying value approximates fair value due to the short-term nature and negligible credit risk inherent in them. These financial instruments include cash and cash equivalents, the majority of advances to lenders, and federal funds and securities sold/purchased under agreements to repurchase/resell.	Level 1 and 2
Federal funds and securities sold/purchased under agreements to repurchase/resell	The carrying value for the majority of these specific instruments approximates the fair value due to the short-term nature and the negligible inherent credit risk, as they involve the exchange of collateral that is easily traded. Were we to calculate the fair value of these instruments we would use observable inputs.	Level 2
Mortgage loans held for sale	Loans are reported at the lower of cost or fair value in our consolidated balance sheets. The valuation methodology and inputs used in estimating the fair value of HFS loans are the same as for our HFI loans and are described under “Fair Value Measurement—Mortgage Loans Held for Investment.” To the extent that significant inputs are unobservable, the loans are classified within Level 3 of the valuation hierarchy.	Level 2 and 3
Mortgage loans held for investment	For a description of loan valuation techniques, refer to “Fair Value Measurement—Mortgage Loans Held for Investment.” We measure the fair value of certain loans that are delivered under the Home Affordable Refinance Program (“HARP”) using a modified build-up approach while the loan is performing. Under this modified approach, we set the credit component of the consolidated loans (that is, the guaranty obligation) equal to the compensation we would currently receive for a loan delivered to us under the program because the total compensation for these loans is equal to their current exit price in the government-sponsored enterprise securitization market. We will continue to use this pricing methodology as long as the HARP program is available to market participants. If, subsequent to delivery, the refinanced loan becomes past due or is modified as a part of a troubled debt restructuring, the fair value of the guaranty obligation is then measured consistent with other loans that have similar characteristics.	Level 2 and 3
Advances to lenders	The carrying value for the majority of our advances to lenders approximates the fair value due to the short-term nature and the negligible inherent credit risk. If we were to calculate the fair value of these instruments we would use discounted cash flow models that use observable inputs such as spreads based on market assumptions, resulting in Level 2 classification. Advances to lenders also include loans that do not qualify for Fannie Mae MBS securitization and are valued using a discounted cash flow technique that uses estimated credit spreads of similar collateral and prepayment speeds that consider recent prepayment activity. We classify these valuations as Level 3 given that significant inputs are not observable or are determined by extrapolation of observable inputs.	Level 2 and 3
Guaranty assets and buy-ups	Guaranty assets related to our portfolio securitizations are recorded in our consolidated balance sheets at fair value on a recurring basis and are classified as Level 3. Guaranty assets in lender swap transactions are recorded in our consolidated balance sheets at the lower of cost or fair value. These assets, which are measured at fair value on a nonrecurring basis, are also classified as Level 3. We estimate the fair value of guaranty assets by using proprietary models to project cash flows based on management’s best estimate of key assumptions such as prepayment speeds and forward yield curves. Because guaranty assets are similar to an interest-only income stream, the projected cash flows are discounted at rates that consider the current spreads on interest-only swaps that reference Fannie Mae MBS and also liquidity considerations of the guaranty assets. The fair value of guaranty assets includes the fair value of any associated buy-ups.	Level 3
Guaranty obligations	The fair value of all guaranty obligations, measured subsequent to their initial recognition, is our estimate of a hypothetical transaction price we would receive if we were to issue our guaranty to an unrelated party in a standalone arm’s-length transaction at the measurement date. The valuation methodology and inputs used in estimating the fair value of the guaranty obligations are described under “Fair Value Measurement—Mortgage Loans Held for Investment—Build-up.”	Level 3

Fair Value of Financial Instruments [Table Text Block]

The following table displays the carrying value and estimated fair value of our financial instruments. The fair value of financial instruments we disclose includes commitments to purchase multifamily and single-family mortgage loans that we do not record in our consolidated balance sheets. The fair values of these commitments are included as “Mortgage loans held for investment, net of allowance for loan losses.” The disclosure excludes all non-financial instruments; therefore, the fair value of our financial assets and liabilities does not represent the underlying fair value of our total consolidated assets and liabilities.



	As of December 31, 2018
	Carrying Value		Quoted Price in Active Markets for Identical Assets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)		Netting Adjustment			Estimated Fair Value
	(Dollars in millions)
Financial assets:
Cash and cash equivalents and restricted cash	$	49,423	$	34,073	$	15,350	$	—	$	—		$	49,423
Federal funds sold and securities purchased under agreements to resell or similar arrangements	32,938		—		32,938		—		—			32,938
Trading securities	41,867		35,502		6,332		33		—			41,867
Available-for-sale securities	3,429		—		2,477		952		—			3,429
Mortgage loans held for sale	7,701		—		238		7,856		—			8,094
Mortgage loans held for investment, net of allowance for loan losses	3,241,694		—		2,990,104		216,404		—			3,206,508
Advances to lenders	3,356		—		3,354		2		—			3,356
Derivative assets at fair value	458		—		2,515		209		(2,266		)	458
Guaranty assets and buy-ups	147		—		—		356		—			356
Total financial assets	$	3,381,013	$	69,575	$	3,053,308	$	225,812	$	(2,266	)	$	3,346,429
Financial liabilities:
Short-term debt:
Of Fannie Mae	$	24,896	$	—	$	24,901	$	—	$	—		$	24,901
Of consolidated trusts	—		—		—		—		—			—
Long-term debt:
Of Fannie Mae	207,178		—		211,403		771		—			212,174
Of consolidated trusts	3,159,846		—		3,064,239		39,043		—			3,103,282
Derivative liabilities at fair value	777		—		3,077		15		(2,315		)	777
Guaranty obligations	160		—		—		121		—			121
Total financial liabilities	$	3,392,857	$	—	$	3,303,620	$	39,950	$	(2,315	)	$	3,341,255



	As of December 31, 2017
	Carrying Value		Quoted Price in Active Markets for Identical Assets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)		Netting Adjustment			Estimated Fair Value
	(Dollars in millions)
Financial assets:
Cash and cash equivalents and restricted cash	$	60,260	$	35,060	$	25,200	$	—	$	—		$	60,260
Federal funds sold and securities purchased under agreements to resell or similar arrangements	19,470		—		19,470		—		—			19,470
Trading securities	34,679		29,222		4,256		1,201		—			34,679
Available-for-sale securities	4,843		—		3,530		1,313		—			4,843
Mortgage loans held for sale	4,988		—		101		5,333		—			5,434
Mortgage loans held for investment, net of allowance for loan losses	3,173,537		—		2,886,470		315,719		—			3,202,189
Advances to lenders	4,938		—		4,936		2		—			4,938
Derivative assets at fair value	171		—		4,274		169		(4,272		)	171
Guaranty assets and buy-ups	149		—		—		436		—			436
Total financial assets	$	3,303,035	$	64,282	$	2,948,237	$	324,173	$	(4,272	)	$	3,332,420
Financial liabilities:
Short-term debt:
Of Fannie Mae	$	33,377	$	—	$	33,379	$	—	$	—		$	33,379
Of consolidated trusts	379		—		—		378		—			378
Long-term debt:
Of Fannie Mae	243,375		—		249,780		837		—			250,617
Of consolidated trusts	3,052,923		—		3,014,250		40,683		—			3,054,933
Derivative liabilities at fair value	328		—		5,272		35		(4,979		)	328
Guaranty obligations	258		—		—		456		—			456
Total financial liabilities	$	3,330,640	$	—	$	3,302,681	$	42,389	$	(4,979	)	$	3,340,091

Fair Value Option [Table Text Block]

The following table displays the fair value and unpaid principal balance of the financial instruments for which we have made fair value elections.



		As of December 31,
		2018									2017
	Loans⁽¹⁾			Long-Term Debt of Fannie Mae			Long-Term Debt of Consolidated Trusts			Loans⁽¹⁾			Long-Term Debt of Fannie Mae			Long-Term Debt of Consolidated Trusts
		(Dollars in millions)
Fair value		$	8,922		$	6,826		$	23,753		$	10,596		$	8,186		$	30,493
Unpaid principal balance		8,832			6,241			22,080			10,246			7,368			27,717

⁽¹⁾

Includes nonaccrual loans with a fair value of $161 million and $227 million as of December 31, 2018 and 2017, respectively. The difference between unpaid principal balance and the fair value of these nonaccrual loans as of December 31, 2018 and 2017 is $19 million and $46 million, respectively. Includes loans that are 90 days or more past due with a fair value of $102 million and $159 million as of December 31, 2018 and 2017, respectively. The difference between unpaid principal balance and the fair value of these 90 or more days past due loans as of December 31, 2018 and 2017 is $14 million and $34 million, respectively.