Trading securities are recorded at fair value with subsequent changes in fair value recorded as “Fair value gains (losses), net” in our consolidated statements of operations and comprehensive income. The following table displays our investments in trading securities.


	As of December 31,
	2020		2019
	(Dollars in millions)
Mortgage-related securities:
Fannie Mae	$	2,404	$	3,424
Other agency(1)	3,451		4,490
Private-label and other mortgage securities	158		629
Total mortgage-related securities (includes $793 million and $896 million, respectively, related to consolidated trusts)	6,013		8,543
Non-mortgage-related securities:
U.S. Treasury securities	130,456		39,501
Other securities	73		79
Total non-mortgage-related securities	130,529		39,580
Total trading securities	$	136,542	$	48,123

Our investment in U.S. Treasury securities increased as of December 31, 2020, compared with December 31, 2019 primarily driven by proceeds from significantly higher debt issuances during 2020 as well as proceeds from loan payoffs.



	For the Year Ended December 31,
	2020			2019			2018
	(Dollars in millions)
Net trading gains		$	513		$	322		$	126
Net trading gains recognized in the period related to securities still held at period end		252			238			55

We record AFS securities at fair value with unrealized gains and losses, recorded net of tax, as a component of “Other comprehensive income (loss)” and we recognize realized gains and losses from the sale of AFS securities in “Investment gains, net” in our consolidated statements of operations and comprehensive income. We define the amortized cost basis of our AFS securities as unpaid principal balance, net of unamortized premiums and discounts, and other cost basis adjustments. Pursuant to the CECL standard, we record an allowance for credit losses for AFS securities that reflects the impairment for credit losses, which are limited to the amount that fair value is less than the amortized cost. Impairment due to non-credit losses are recorded as unrealized losses within other comprehensive income.

The following tables display the amortized cost, allowance for credit losses, gross unrealized gains and losses in accumulated other comprehensive income (loss) (“AOCI”), and fair value by major security type for AFS securities.


	As of December 31, 2020
	Total Amortized Cost(1)			Allowance for Credit Losses			Gross Unrealized Gains in AOCI			Gross Unrealized Losses in AOCI			Total Fair Value(1)
	(Dollars in millions)
Fannie Mae		$	1,094		$	—		$	86		$	(12)		$	1,168
Other agency(2)		59			—			6			—			65
Alt-A and subprime private-label securities		4			—			2			—			6

Mortgage revenue bonds		211			(3)			8			—			216
Other mortgage-related securities		238			—			4			—			242
Total		$	1,606		$	(3)		$	106		$	(12)		$	1,697


	As of December 31, 2019
	Total Amortized Cost(1)(3)			Gross Unrealized Gains			Gross Unrealized Losses			Total Fair Value(1)
	(Dollars in millions)
Fannie Mae		$	1,445		$	85		$	(10)		$	1,520
Other agency(2)		183			15			—			198
Alt-A and subprime private-label securities		34			23			—			57

Mortgage revenue bonds		309			9			(3)			315
Other mortgage-related securities		310			5			(1)			314
Total		$	2,281		$	137		$	(14)		$	2,404

(1)We exclude from amortized cost and fair value accrued interest of $6 million and $10 million as of December 31, 2020 and December 31, 2019, respectively, which we record in “Other assets” in our consolidated balance sheets.

(3)Prior to our adoption of the CECL standard, total amortized cost represented the unpaid principal balance, unamortized premiums, discounts and other cost basis adjustments, as well as temporary impairments recognized in “Investment gains, net” in our consolidated statements of operations and comprehensive income.

Our Fannie Mae and other agency AFS securities consist of securities issued by us, Freddie Mac, or Ginnie Mae. The principal and interest on these securities are guaranteed by the issuing agency. We believe that the guaranty provided by the issuing agency, the support provided to the agencies by the U.S. government, the importance of the agencies to the liquidity and stability in the secondary mortgage market, and the long history of zero credit losses on agency mortgage-related securities are all indicators that there are currently no credit losses on these securities, even if the security is in an unrealized loss position. In addition, we generally hold these securities that are in an unrealized loss position to recovery. As a result, unless we intend to sell the security, we do not recognize an allowance for credit losses on agency mortgage-related securities.

As of December 31, 2020, substantially all of our non-agency mortgage-related securities were in an unrealized gain position. As a result, we have not recognized an allowance for credit losses on these securities.

The following tables display additional information regarding gross unrealized losses and fair value by major security type for AFS securities in an unrealized loss position, excluding allowance for credit losses.


	As of December 31, 2020
	Less Than 12 Consecutive Months						12 Consecutive Months or Longer
	Gross Unrealized Losses in AOCI			Fair Value			Gross Unrealized Losses in AOCI			Fair Value
	(Dollars in millions)
Fannie Mae		$	(1)		$	40		$	(11)		$	94


Mortgage revenue bonds		—			—			—			—
Other mortgage-related securities		—			—			—			—
Total		$	(1)		$	40		$	(11)		$	94

	As of December 31, 2019
	Less Than 12 Consecutive Months						12 Consecutive Months or Longer
	Gross Unrealized Losses			Fair Value			Gross Unrealized Losses			Fair Value
	(Dollars in millions)
Fannie Mae		$	—		$	—		$	(10)		$	337
Mortgage revenue bonds		—			—			(3)			3
Other mortgage-related securities		(1)			130			—			—
Total		$	(1)		$	130		$	(13)		$	340


	For the Year Ended December 31,
	2020		2019		2018
	(Dollars in millions)
Gross realized gains	$	57	$	265	$	375

Total proceeds (excludes initial sale of securities from new portfolio securitizations)	361		537		662


	As of
	December 31, 2020
	(Dollars in millions)
Net unrealized gains on AFS securities for which we have not recorded an allowance for credit losses	$	74

Other	42
Accumulated other comprehensive income	$	116


	As of
	December 31, 2019		December 31, 2018
	(Dollars in millions)
Net unrealized gains on AFS securities for which we have not recorded other-than-temporary impairment (“OTTI”)	$	97	$	52
Net unrealized gains on AFS securities for which we have recorded OTTI	—		224
Other	34		46
Accumulated other comprehensive income	$	131	$	322

Prior to our adoption of the CECL standard on January 1, 2020, we evaluated AFS securities for other-than-temporary impairment. The balance of the unrealized credit-loss component of AFS securities held by us and recognized in our consolidated statements of operations and comprehensive income was $36 million as of December 31, 2019.

The following table displays the amortized cost and fair value of our AFS securities by major security type and remaining contractual maturity, assuming no principal prepayments. The contractual maturity of mortgage-backed securities is not a reliable indicator of their expected life because borrowers generally have the right to prepay their obligations at any time.


	As of December 31, 2020
	Total Carrying Amount (1)				Total Fair Value			One Year or Less							After One Year Through Five Years							After Five Years Through Ten Years							After Ten Years
								Net Carrying Amount (1)				Fair Value			Net Carrying Amount (1)				Fair Value			Net Carrying Amount (1)				Fair Value			Net Carrying Amount (1)				Fair Value
	(Dollars in millions)
Fannie Mae		$	1,094			$	1,168		$	—			$	—		$	5			$	6		$	96			$	108		$	993			$	1,054
Other agency		59				65			—				—			—				—			9				10			50				55
Alt-A and subprime private-label securities		4				6			—				—			—				—			3				3			1				3

Mortgage revenue bonds		208				216			1				1			27				28			19				20			161				167
Other mortgage-related securities		238				242			—				—			—				—			19				21			219				221
Total		$	1,603			$	1,697		$	1			$	1		$	32			$	34		$	146			$	162		$	1,424			$	1,500
Weighted-average yield (1)		5.27		%					5.90		%					6.54		%					6.11		%					5.16		%