As of March 31, 2024, the Company had $1.67 billion and $354.7 million in available for sale debt securities and held to maturity debt securities, respectively. Many factors, including lack of liquidity in the secondary market for certain securities, variations in pricing information, changes in interest rates, regulatory actions, changes in the business environment or any changes in the competitive marketplace, could have an adverse effect on the Company’s investment portfolio. The total number of available for sale and held to maturity debt securities in an unrealized loss position as of March 31, 2024 totaled 954, compared with 808 as of December 31, 2023. The increase in the number of securities in an unrealized loss position as of March 31, 2024 was due to higher current market interest rates compared to rates as of December 31, 2023.

The following tables present the amortized cost, gross unrealized gains, gross unrealized losses and the fair value for available for sale debt securities as of March 31, 2024 and December 31, 2023 (in thousands):


	March 31, 2024
	Amortized cost		Gross unrealized gains	Gross unrealized losses	Fair value

U.S. Treasury obligations	$	276,863	—	(24,476)	252,387
Agency-guaranteed obligations	22,392		1,126	—	23,518
Mortgage-backed securities	1,446,173		119	(186,411)	1,259,881
Asset-backed securities	29,978		702	(163)	30,517
State and municipal obligations	64,211		—	(8,446)	55,765
Corporate obligations	50,425		—	(6,187)	44,238

	$	1,890,042	1,947	(225,683)	1,666,306


	December 31, 2023
	Amortized cost		Gross unrealized gains	Gross unrealized losses	Fair value

U.S. Treasury obligations	$	276,618	—	(22,740)	253,878
Agency-guaranteed obligations	26,310		1,188	—	27,498
Mortgage-backed securities	1,462,159		377	(176,927)	1,285,609
Asset-backed securities	31,809		594	(168)	32,235
State and municipal obligations	64,454		—	(7,870)	56,584
Corporate obligations	40,448		—	(6,140)	34,308

	$	1,901,798	2,159	(213,845)	1,690,112

Accrued interest on available for sale debt securities, which is excluded from the amortized cost, totaled $5.2 million and $4.9 million as of March 31, 2024 and December 31, 2023, respectively, and is presented within total accrued interest receivable on the consolidated statements of financial condition.

The amortized cost and fair value of available for sale debt securities as of March 31, 2024, by contractual maturity, are shown below (in thousands). Expected maturities may differ from contractual maturities due to prepayment or early call privileges of the issuer.


	March 31, 2024
	Amortized cost		Fair value
Due in one year or less	$	—	—
Due after one year through five years	296,461		271,230
Due after five years through ten years	63,414		58,083
Due after ten years	83,994		77,112
	$	443,869	406,425

Investments which pay principal on a periodic basis totaling $1.50 billion at amortized cost and $1.31 billion at fair value are excluded from the table above as their expected lives are likely to be shorter than the contractual maturity date due to principal prepayments.

The number of available for sale debt securities in an unrealized loss position as of March 31, 2024 totaled 434, compared with 436 as of December 31, 2023. All securities in an unrealized loss position were investment grade as of March 31, 2024.

The following tables present the amortized cost, gross unrealized gains, gross unrealized losses and the estimated fair value for held to maturity debt securities as of March 31, 2024 and December 31, 2023 (in thousands):


	March 31, 2024
	Amortized cost		Gross unrealized gains	Gross unrealized losses	Fair value
Treasury Obligations	$	5,767	—	—	5,767
Agency-sponsored obligations	11,058		—	(633)	10,425

State and municipal obligations	331,292		93	(12,315)	319,070
Corporate obligations	6,571		—	(374)	6,197
	$	354,688	93	(13,322)	341,459


	December 31, 2023
	Amortized cost		Gross unrealized gains	Gross unrealized losses	Fair value
Treasury Obligations	$	5,146	1	—	5,147
Agency-sponsored obligations	11,058		—	(652)	10,406

State and municipal obligations	339,816		244	(9,700)	330,360
Corporate obligations	7,091		—	(403)	6,688
	$	363,111	245	(10,755)	352,601

The allowance for credit losses on held to maturity debt securities as of March 31, 2024 and December 31, 2023 was $17,000 and $31,000, respectively, and are excluded from amortized cost in the tables above.

Accrued interest on held to maturity debt securities, which is excluded from the amortized cost, totaled $2.4 million and $3.1 million as of March 31, 2024 and December 31, 2023, respectively, and is presented within total accrued interest receivable on the consolidated statements of financial condition.

The Company generally purchases securities for long-term investment purposes, and differences between amortized cost and fair value may fluctuate during the investment period. There were no sales of securities from the held to maturity debt securities portfolio for the three months ended March 31, 2024 and 2023. For the three months ended March 31, 2024, proceeds from calls on securities in the held to maturity debt securities portfolio totaled $1.2 million. As to these calls on securities, for the three months ended March 31, 2024, there were no gross gains and gross losses of $1,200. For the three months ended March 31, 2023, proceeds from calls on securities in the held to maturity debt securities portfolio totaled $3.1 million with no gross gains and gross losses of $5,000.

The amortized cost and fair value of investment securities in the held to maturity debt securities portfolio as of March 31, 2024 by contractual maturity are shown below (in thousands). Expected maturities may differ from contractual maturities due to prepayment or early call privileges of the issuer.


	March 31, 2024
	Amortized cost		Fair value
Due in one year or less	$	34,403	34,210
Due after one year through five years	181,204		177,227
Due after five years through ten years	114,993		110,547
Due after ten years	24,088		19,475
	$	354,688	341,459

The number of held to maturity debt securities in an unrealized loss position as of March 31, 2024 totaled 520, compared with 372 as of December 31, 2023. The increase in the number of securities in an unrealized loss position as of March 31, 2024, was due to higher current market interest rates compared to rates as of December 31, 2023.

Management measures expected credit losses on held to maturity debt securities on a collective basis by security type. Management classifies the held to maturity debt securities portfolio into the following security types:

All of the agency obligations held by the Company are issued by U.S. government entities and agencies. These securities are either explicitly or implicitly guaranteed by the U.S. government, are highly rated by major rating agencies and have a long history of no credit losses. The majority of the state and municipal and corporate obligations carry credit ratings from the rating agencies as of March 31, 2024, that were no lower than an A rating and the Company had no securities rated BBB or worse by Moody’s Investors Service.

Credit Quality Indicators. The following table provides the amortized cost of held to maturity debt securities by credit rating as of March 31, 2024 and December 31, 2023 (in thousands):


	March 31, 2024
Total Portfolio	AAA		AA	A	BBB	Not Rated	Total
Treasury obligations	$	5,767	—	—	—	—	5,767
Agency-sponsored obligations	11,058		—	—	—	—	11,058

State and municipal obligations	45,728		252,805	30,211	—	2,548	331,292
Corporate obligations	503		2,497	3,546	—	25	6,571
	$	63,056	255,302	33,757	—	2,573	354,688

	December 31, 2023
Total Portfolio	AAA		AA	A	BBB	Not Rated	Total
Treasury obligations	$	5,146	—	—	—	—	5,146
Agency-sponsored obligations	$	11,058	—	—	—	—	11,058

State and municipal obligations	43,749		156,438	137,231	—	2,398	339,816
Corporate obligations	504		2,510	4,052	—	25	7,091
	$	60,457	158,948	141,283	—	2,423	363,111

Credit quality indicators are metrics that provide information regarding the relative credit risk of debt securities. As of March 31, 2024, the held to maturity debt securities portfolio was comprised of 18% rated AAA, 72% rated AA, 10% rated A, and less than 1% either below an A rating or not rated by Moody’s Investors Service or Standard and Poor’s. Securities not explicitly rated, such as U.S. Government mortgage-backed securities, were grouped where possible under the credit rating of the issuer of the security.