Our investment securities portfolio consists of the following: U.S. government-sponsored enterprise or agency (“Agency”) and non-agency residential mortgage-backed securities (“RMBS”), Agency commercial mortgage-backed securities (“CMBS”), U.S. Treasury securities and other securities. Agency securities include Government National Mortgage Association (“Ginnie Mae”) guaranteed securities, Federal National Mortgage Association (“Fannie Mae”) and Federal Home Loan Mortgage Corporation (“Freddie Mac”) issued securities. The carrying value of our investments in Agency and U.S. Treasury securities represented 96% of our total investment securities portfolio as of both December 31, 2020 and 2019.

In the first quarter of 2020, we adopted the CECL standard which resulted in an increase of the amortized cost basis and related allowance for credit losses of PCD securities classified as available for sale. The allowance for credit losses for these PCD securities is limited to the amount by which the amortized cost basis of the security exceeds its fair value. This limitation resulted in an increase of $11 million to our retained earnings with a corresponding decrease in AOCI at adoption. Our disclosures below reflect these adoption changes. Prior period presentation was not reclassified to conform to the current period presentation. See “Note 1—Summary of Significant Accounting Policies” for additional information.

The table below presents the amortized cost, gross unrealized gains and losses, and fair value of securities available for sale as of December 31, 2020 and 2019. Accrued interest receivable of $230 million as of December 31, 2020 is not included in the below table.


	December 31, 2020
(Dollars in millions)	Amortized Cost		Allowance for Credit Losses		Gross Unrealized Gains		Gross Unrealized Losses		Fair Value
Investment securities available for sale:
U.S. Treasury securities	$	9,302	$	0	$	16	$	0	$	9,318
RMBS:
Agency	73,248		0		2,326		(108)		75,466
Non-agency	1,035		(1)		204		(1)		1,237
Total RMBS	74,283		(1)		2,530		(109)		76,703
Agency CMBS	11,298		0		448		(11)		11,735
Other securities(1)	2,686		0		3		0		2,689
Total investment securities available for sale	$	97,569	$	(1)	$	2,997	$	(120)	$	100,445


	December 31, 2019
(Dollars in millions)	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses		Fair Value
Investment securities available for sale:
U.S. Treasury securities	$	4,122	$	6	$	(4)	$	4,124
RMBS:
Agency	62,003		1,120		(284)		62,839
Non-agency	1,235		266		(2)		1,499
Total RMBS	63,238		1,386		(286)		64,338
Agency CMBS	9,303		165		(42)		9,426
Other securities(1)	1,321		4		0		1,325
Total investment securities available for sale	$	77,984	$	1,561	$	(332)	$	79,213

(1)Includes $1.8 billion and $117 million of asset-backed securities (“ABS”) as of December 31, 2020, and 2019, respectively. The remaining amount is primarily comprised of supranational bonds and foreign government bonds.

The table below provides the gross unrealized losses and fair value of our securities available for sale aggregated by major security type and the length of time that individual securities have been in a continuous unrealized loss position as of December 31, 2020 and 2019. The amounts as of December 31, 2020 only include securities available for sale without an allowance for credit losses.


	December 31, 2020
	Less than 12 Months				12 Months or Longer				Total
(Dollars in millions)	Fair Value		Gross Unrealized Losses		Fair Value		Gross Unrealized Losses		Fair Value		Gross Unrealized Losses
Investment securities available for sale without an allowance for credit losses:
U.S. Treasury securities	$	0	$	0	$	0	$	0	$	0	$	0
RMBS:
Agency	7,424		(57)		1,791		(51)		9,215		(108)
Non-agency	12		0		0		0		12		0
Total RMBS	7,436		(57)		1,791		(51)		9,227		(108)
Agency CMBS	1,545		(7)		267		(4)		1,812		(11)
Other securities(1)	114		0		1		0		115		0
Total investment securities available for sale in a gross unrealized loss position without an allowance for credit losses(2)	$	9,095	$	(64)	$	2,059	$	(55)	$	11,154	$	(119)


	December 31, 2019
	Less than 12 Months				12 Months or Longer				Total
(Dollars in millions)	Fair Value		Gross Unrealized Losses		Fair Value		Gross Unrealized Losses		Fair Value		Gross Unrealized Losses
Investment securities available for sale:
U.S. Treasury securities	$	2,647	$	(4)	$	0	$	0	$	2,647	$	(4)
RMBS:
Agency	10,494		(92)		10,567		(192)		21,061		(284)
Non-agency	35		(1)		16		(1)		51		(2)
Total RMBS	10,529		(93)		10,583		(193)		21,112		(286)
Agency CMBS	2,580		(23)		1,563		(19)		4,143		(42)
Other securities(1)	126		0		106		0		232		0
Total investment securities available for sale in a gross unrealized loss position	$	15,882	$	(120)	$	12,252	$	(212)	$	28,134	$	(332)

The table below summarizes, by major security type, the contractual maturities and weighted-average yields of our investment securities as of December 31, 2020. Because borrowers may have the right to call or prepay certain obligations, the expected maturities of our securities are likely to differ from the scheduled contractual maturities presented below. The weighted-average yield below represents the effective yield for the investment securities and is calculated based on the amortized cost of each security.


	December 31, 2020
(Dollars in millions)	Due in 1 Year or Less			Due > 1 Year through 5 Years			Due > 5 Years through 10 Years			Due > 10 Years			Total
Fair value of securities available for sale:
U.S. Treasury securities	$	202		$	9,116		$	0		$	0		$	9,318
RMBS(1):
Agency	0			65			1,175			74,226			75,466
Non-agency	0			0			0			1,237			1,237
Total RMBS	0			65			1,175			75,463			76,703
Agency CMBS(1)	90			2,896			5,645			3,104			11,735
Other securities	340			2,073			276			0			2,689
Total securities available for sale	$	632		$	14,150		$	7,096		$	78,567		$	100,445
Amortized cost of securities available for sale	$	628		$	14,091		$	6,860		$	75,990		$	97,569
Weighted-average yield for securities available for sale	1.43		%	0.74		%	1.76		%	2.20		%	1.96		%

The following table presents the gross realized gains or losses and proceeds from the sale of securities available for sale for the years ended December 31, 2020, 2019 and 2018. We did not sell any investment securities that were classified as held to maturity in those periods where we had securities in that classification.


	Year Ended December 31,
(Dollars in millions)	2020		2019		2018
Realized gains (losses):
Gross realized gains	$	25	$	44	$	13
Gross realized losses	0		(18)		(21)
Net realized gains (losses)	$	25	$	26	$	(8)





Total proceeds from sales	$	812	$	4,780	$	6,399

We pledged investment securities totaling $16.5 billion and $14.0 billion as of December 31, 2020 and 2019, respectively. These securities are primarily pledged to secure FHLB advances and Public Funds deposits, as well as for other purposes as required or permitted by law. We accepted pledges of securities with a fair value of approximately $1 million as of both December 31, 2020 and 2019, related to our derivative transactions.