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 at June 30, 2023 totaled 937, compared with 914 at December 31, 2022. The increase in the number of securities in an unrealized loss position at June 30, 2023 was due to higher current market interest rates compared to rates at December 31, 2022.


	June 30, 2023
	Amortized cost		Gross unrealized gains	Gross unrealized losses	Fair value

U.S. Treasury obligations	$	276,106	—	(29,039)	247,067
Agency obligations	31,452		301	—	31,753
Mortgage-backed securities	1,549,842		84	(203,202)	1,346,724
Asset-backed securities	34,351		379	(224)	34,506
State and municipal obligations	64,939		—	(9,214)	55,725
Corporate obligations	40,495		—	(6,381)	34,114

	$	1,997,185	764	(248,060)	1,749,889


	December 31, 2022
	Amortized cost		Gross unrealized gains	Gross unrealized losses	Fair value

U.S. Treasury obligations	$	275,620	—	(29,804)	245,816

Mortgage-backed securities	1,636,913		209	(209,983)	1,427,139
Asset-backed securities	37,706		278	(363)	37,621
State and municipal obligations	67,706		—	(10,842)	56,864
Corporate obligations	40,540		50	(4,482)	36,108

	$	2,058,485	537	(255,474)	1,803,548

The amortized cost and fair value of available for sale debt securities at June 30, 2023, 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.


	June 30, 2023
	Amortized cost		Fair value
Due in one year or less	$	—	—
Due after one year through five years	242,910		218,600
Due after five years through ten years	82,226		70,318
Due after ten years	56,404		47,988
	$	381,540	336,906

Investments which pay principal on a periodic basis totaling $1.62 billion at amortized cost and $1.41 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.

There were no sales of securities from the available for sale debt securities portfolio for the three and six months ended June 30, 2023 and 2022. For the three and six months ended June 30, 2023, there were no proceeds from calls on securities in the available for sale debt securities portfolio. For the three and six months ended June 30, 2022, proceeds from calls on securities in the available for sale debt securities portfolio totaled $5.4 million with gains of $58,000 and no losses recognized.

The number of available for sale debt securities in an unrealized loss position at June 30, 2023 totaled 464, compared with 475 at December 31, 2022. The decline in the number of securities in an unrealized loss position at June 30, 2023 was due to maturities and calls of securities in the quarter. All securities in an unrealized loss position were investment grade at June 30, 2023.

The following tables present the amortized cost, gross unrealized gains, gross unrealized losses and the estimated fair value for held to maturity debt securities at June 30, 2023 and December 31, 2022 (in thousands):


	June 30, 2023
	Amortized cost		Gross unrealized gains	Gross unrealized losses	Fair value
Agency obligations	$	12,096	—	(929)	11,167

State and municipal obligations	357,003		168	(12,510)	344,661
Corporate obligations	9,820		—	(619)	9,201
	$	378,919	168	(14,058)	365,029


	December 31, 2022
	Amortized cost		Gross unrealized gains	Gross unrealized losses	Fair value
Agency obligations	$	9,997	—	(1,033)	8,964

State and municipal obligations	366,164		268	(13,015)	353,417
Corporate obligations	11,789		1	(703)	11,087
	$	387,950	269	(14,751)	373,468

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 and six months ended June 30, 2023 and 2022. For the three and six months ended June 30, 2023, proceeds from calls on securities in the held to maturity debt securities portfolio totaled $3.5 million and $6.6 million, respectively. As to these calls on securities, for the three months ended June 30, 2023, there were gross gains of $28,000 and no gross losses, while for the six months ended June 30, 2023, gross gains totaled $24,000, with no gross losses. For the three and six months ended June 30, 2022, proceeds from calls on securities in the held to maturity debt securities portfolio totaled $10.3 million and $26.2 million, respectively. As to these calls on securities for the three and six months ended June 30, 2022, gross gains totaled $83,000 and $99,000, respectively, with no gross losses.

The amortized cost and fair value of investment securities in the held to maturity debt securities portfolio at June 30, 2023 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.


	June 30, 2023
	Amortized cost		Fair value
Due in one year or less	$	25,283	25,199
Due after one year through five years	169,684		166,605
Due after five years through ten years	153,491		148,121
Due after ten years	30,461		25,104
	$	378,919	365,029

The number of held to maturity debt securities in an unrealized loss position at June 30, 2023 totaled 473, compared with 439 at December 31, 2022. The increase in the number of securities in an unrealized loss position at June 30, 2023, was due to higher current market interest rates compared to rates at December 31, 2022.

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 at June 30, 2023 no lower than A and the Company had no securities rated BBB or worse by Moody’s Investors Service.


	June 30, 2023
Total Portfolio	AAA		AA	A	BBB	Not Rated	Total
Agency obligations	$	12,096	—	—	—	—	12,096

State and municipal obligations	47,125		166,596	142,830	—	452	357,003
Corporate obligations	505		2,073	6,146	—	1,096	9,820
	$	59,726	168,669	148,976	—	1,548	378,919

	December 31, 2022
Total Portfolio	AAA		AA	A	BBB	Not Rated	Total
Agency obligations	$	9,997	—	—	—	—	9,997

State and municipal obligations	48,453		171,934	143,829	770	1,178	366,164
Corporate obligations	507		3,592	7,415	—	275	11,789
	$	58,957	175,526	151,244	770	1,453	387,950

Credit quality indicators are metrics that provide information regarding the relative credit risk of debt securities. At June 30, 2023, the held to maturity debt securities portfolio was comprised of 16% rated AAA, 45% rated AA, 39% 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.