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 as well as 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 March 31, 2021 and December 31, 2020.

The table below presents the amortized cost, gross unrealized gains and losses, and fair value of securities available for sale as of March 31, 2021 and December 31, 2020. Accrued interest receivable of $237 million and $230 million as of March 31, 2021, and December 31, 2020, respectively, is not included in the below table.


	March 31, 2021
(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	$	9,222	$	0	$	26	$	0	$	9,248
RMBS:
Agency	73,579		0		1,649		(783)		74,445
Non-agency	973		(2)		206		0		1,177
Total RMBS	74,552		(2)		1,855		(783)		75,622
Agency CMBS	11,015		0		315		(56)		11,274
Other securities(1)	3,013		0		8		0		3,021
Total investment securities available for sale	$	97,802	$	(2)	$	2,204	$	(839)	$	99,165


	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

(1)Includes $2.1 billion and $1.8 billion of asset-backed securities (“ABS”) as of March 31, 2021, and December 31, 2020, 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 March 31, 2021 and December 31, 2020. The amounts include securities available for sale without an allowance for credit losses.


	March 31, 2021
	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:

RMBS:
Agency	$	33,027	$	(733)	$	1,558	$	(50)	$	34,585	$	(783)
Non-agency	10		0		1		0		11		0
Total RMBS	33,037		(733)		1,559		(50)		34,596		(783)
Agency CMBS	2,083		(56)		155		0		2,238		(56)
Other securities(1)	371		0		0		0		371		0
Total investment securities available for sale in a gross unrealized loss position without an allowance for credit losses(2)	$	35,491	$	(789)	$	1,714	$	(50)	$	37,205	$	(839)


	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:

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)

The table below summarizes, by major security type, the contractual maturities and weighted-average yields of our investment securities as of March 31, 2021. 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.


	March 31, 2021
(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	$	201		$	9,047		$	0		$	0		$	9,248
RMBS(1):
Agency	0			71			1,210			73,164			74,445
Non-agency	0			0			0			1,177			1,177
Total RMBS	0			71			1,210			74,341			75,622
Agency CMBS(1)	209			2,961			5,063			3,041			11,274
Other securities	542			2,214			265			0			3,021
Total securities available for sale	$	952		$	14,293		$	6,538		$	77,382		$	99,165
Amortized cost of securities available for sale	$	949		$	14,206		$	6,411		$	76,236		$	97,802
Weighted-average yield for securities available for sale	0.97		%	0.52		%	1.62		%	1.80		%	1.59		%

Total proceeds from sales of our securities were $595 million and $144 million for the three months ended March 31, 2021 and 2020, respectively. We recognized gains of $4 million and less than $1 million from the sales for the three months ended March 31, 2021 and 2020, respectively.

We pledged investment securities totaling $16.8 billion and $16.5 billion as of March 31, 2021 and December 31, 2020, 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 March 31, 2021 and December 31, 2020, related to our derivative transactions.