
	March 31, 2024
	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses		Allowance for Credit Losses		Estimated Fair Value
U.S. Treasury notes and bonds	$	59,828	$	—	$	4,666	$	—	$	55,162
Mortgage-backed securities, residential	467,125		7		77,425		—		389,707
Obligations of states and political subdivisions	39,415		—		1,270		—		38,145
Corporate bonds and notes	25,750		—		4,818		—		20,932
SBA loan pools	64,522		57		2,497		—		62,082

Total	$	656,640	$	64	$	90,676	$	—	$	566,028


	December 31, 2023
	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses		Allowance for Credit Losses		Estimated Fair Value
U.S. Treasury notes and bonds	$	59,812	$	—	$	4,480	$	—	$	55,332
Mortgage-backed securities, residential	476,240		6		72,422		—		403,824

Obligations of states and political subdivisions	39,503		—		817		—		38,686
Corporate bonds and notes	25,750		—		5,081		—		20,669
SBA loan pools	67,787		75		2,380		—		65,482


Total	$	669,092	$	81	$	85,180	$	—	$	583,993


	March 31, 2024
	Amortized Cost		Unrecognized Gains		Unrecognized Losses		Estimated Fair Value		Allowance for Credit Losses
Obligations of states and political subdivisions	$	785	$	—	$	—	$	785	$	—


	December 31, 2023
	Amortized Cost		Unrecognized Gains		Unrecognized Losses		Estimated Fair Value		Allowance for Credit Losses
Obligations of states and political subdivisions	$	785	$	—	$	—	$	785	$	—

The amortized cost and estimated fair value of debt securities are shown below by expected maturity. Expected maturities may differ from contractual maturities if borrowers have the right to call or prepay obligations with or without call or prepayment penalties. Securities not due at a single maturity date are shown separately (in thousands):


	March 31, 2024
	Available for Sale				Held to Maturity
	Amortized Cost		Fair Value		Amortized Cost		Fair Value
Within one year	$	8,499	$	8,297	$	—	$	—
After one, but within five years	97,948		90,687		145		145
After five, but within ten years	18,076		14,838		640		640
After ten years	470		417		—		—
	124,993		114,239		785		785
Mortgage-backed securities, residential	467,125		389,707		—		—
Collateralized mortgage obligations	—		—		—		—
SBA loan pools	64,522		62,082		—		—
Total	$	656,640	$	566,028	$	785	$	785

The following tables summarize the investment securities available for sale with unrealized losses at March 31, 2024 and December 31, 2023 by aggregated major security type and length of time in a continuous unrealized loss position (in thousands):


	Less than 12 months				12 months or longer				Total
March 31, 2024	Fair Value		Unrealized Losses		Fair Value		Unrealized Losses		Fair Value		Unrealized Losses
U.S. Treasury notes and bonds	$	—	$	—	$	55,162	$	4,666	$	55,162	$	4,666
Mortgage-backed securities, residential	—		—		388,878		77,425		388,878		77,425
Obligations of states and political subdivisions	1,154		24		36,991		1,246		38,145		1,270
Corporate bonds and notes	—		—		20,932		4,818		20,932		4,818
SBA loan pools	1,067		2		54,894		2,495		55,961		2,497

Total temporarily impaired securities	$	2,221	$	26	$	556,857	$	90,650	$	559,078	$	90,676


	Less than 12 months				12 months or longer				Total
December 31, 2023	Fair Value		Unrealized Losses		Fair Value		Unrealized Losses		Fair Value		Unrealized Losses
U.S. Treasury notes and bonds	$	—	$	—	$	55,332	$	4,480	$	55,332	$	4,480
Mortgage-backed securities, residential	—		—		402,986		72,422		402,986		72,422
Obligations of states and political subdivisions	17,891		241		20,686		576		38,577		817
Corporate bonds and notes	7,492		2,508		13,177		2,573		20,669		5,081
SBA loan pools	3,914		13		54,468		2,367		58,382		2,380
Total temporarily impaired securities	$	29,297	$	2,762	$	546,649	$	82,418	$	575,946	$	85,180

Management assesses the decline in fair value of investment securities on a regular basis. Unrealized losses on debt securities may occur from current market conditions, increases in interest rates since the time of purchase, a structural change in an investment, volatility of earnings of a specific issuer, or deterioration in credit quality of the issuer. Management evaluates both qualitative and quantitative factors to assess whether an impairment exists. The following is a discussion of the credit quality characteristics of portfolio segments carrying material unrealized losses as of March 31, 2024.

As of March 31, 2024, the majority of the Corporation’s unrealized losses in available for sale investment securities related to mortgage-backed securities, issued by government-sponsored entities and agencies. Declines in fair value are attributable to changes in interest rates and illiquidity, not credit quality. The Corporation does not have the intent, and it is not likely to be required to, sell these securities prior to their anticipated recovery. Because the Corporation considers these obligations to carry zero loss estimates, no allowance for credit losses has been recorded as of March 31, 2024.

The Corporation's corporate bonds and notes portfolio is comprised of subordinated debt issues of community and regional banks. Management considers the credit quality of these investments on an individual basis. Management reviewed the collectability of these securities, taking into consideration such factors as the financial condition of the issuers, reported regulatory capital ratios of the issuers, and credit ratings when available, among other pertinent factors. All corporate bond debt securities continue to accrue interest and make payments as expected with no defaults or deferrals on the part of the issuers. Therefore, the Corporation considers the potential credit risk of these issuers to be immaterial, and has not recorded an allowance for credit losses on its corporate bonds and notes portfolio as of March 31, 2024.