
	2022				2021
	Amortized Cost		Estimated Fair Value		Amortized Cost		Estimated Fair Value
U.S. treasury notes and bonds	$	61,800	$	55,574	$	61,084	$	60,431
Mortgage-backed securities, residential	$	518,838	$	435,131	$	582,060	$	577,361

Obligations of states and political subdivisions	39,828		38,892		40,299		42,303
Corporate bonds and notes	25,750		21,970		22,750		22,848
SBA loan pools	82,982		81,022		89,216		89,083


Total	$	729,198	$	632,589	$	795,409	$	792,026

Gross unrealized gains and losses on securities available for sale at December 31, 2022 and 2021, were as follows (in thousands):


	2022				2021
	Unrealized Gains		Unrealized Losses		Unrealized Gains		Unrealized Losses
U.S. treasury notes and bonds	$	—	$	6,225	$	27	$	680
Mortgage-backed securities, residential	$	—	$	83,707	$	4,032	$	8,731

Obligations of states and political subdivisions	2		938		2,004		—
Corporate bonds and notes	—		3,780		180		82
SBA loan pools	155		2,116		344		477


Total	$	157	$	96,766	$	6,587	$	9,970

The amortized cost and estimated fair value of debt securities available for sale are shown below by contractual 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):


	December 31, 2022
	Amortized Cost		Fair Value
Within one year	$	2,576	$	2,537
After one, but within five years	106,445		97,982
After five, but within ten years	17,887		15,481
After ten years	470		436
Mortgage-backed securities, residential	518,838		435,131

SBA loan pools	82,982		81,022
Total	$	729,198	$	632,589

Actual maturities may differ from contractual maturities above because issuers may have the right to call or prepay obligations with or without call or prepayment penalties.

Amortized cost and estimated fair value of securities held to maturity at December 31, 2022 and 2021 are as follows (in thousands):


	2022				2021
	Amortized Cost		Estimated Fair Value		Amortized Cost		Estimated Fair Value
Obligations of states and political subdivisions	$	952	$	952	$	2,157	$	2,157
Time deposits with other financial institutions	1,472		1,450		1,633		1,639
	$	2,424	$	2,402	$	3,790	$	3,796

Gross unrealized gains and losses on securities held to maturity at December 31, 2022 and 2021, were as follows (in thousands):


	2022				2021
	Unrealized Gains		Unrealized Losses		Unrealized Gains		Unrealized Losses

Time deposits with other financial institutions	$	—	$	22	$	6	$	—
Total	$	—	$	22	$	6	$	—

The following table summarizes the investment securities available for sale with unrealized losses at December 31, 2022 and December 31, 2021 by aggregated major security type and length of time in a continuous unrealized position (in thousands):


	Less than 12 months				12 months or longer				Total
	Fair Value		Unrealized Losses		Fair Value		Unrealized Losses		Fair Value		Unrealized Losses
2022
U.S. treasury notes and bonds	$	1,011	$	30	$	54,563	$	6,195	$	55,574	$	6,225
Mortgage-backed securities, residential	79,891		7,621		355,240		76,086		435,131		83,707
Obligations of states and political subdivisions	37,847		938		—		—		37,847		938
Corporate bonds and notes	4,515		485		7,455		3,295		11,970		3,780
SBA loan pools	14,333		925		51,123		1,191		65,456		2,116
Total temporarily impaired securities	$	137,597	$	9,999	$	468,381	$	86,767	$	605,978	$	96,766


	Less than 12 months				12 months or longer				Total
	Fair Value		Unrealized Losses		Fair Value		Unrealized Losses		Fair Value		Unrealized Losses
2021
U.S. treasury notes and bonds	$	49,084	$	680	$	—	$	—	$	49,084	$	680
Mortgage-backed securities, residential	$	293,720	$	4,502	$	122,050	$	4,229	$	415,770	$	8,731

Corporate bonds and notes	4,928		72		1,989		10		6,917		82
SBA loan pools	51,235		296		13,769		181		65,004		477
Total temporarily impaired securities	$	398,967	$	5,550	$	137,808	$	4,420	$	536,775	$	9,970

As of December 31, 2022, the majority of the Corporation’s unrealized losses in the investment securities portfolio related to mortgage-backed securities. At December 31, 2022, the unrealized losses related to mortgage-backed were securities issued by U.S. government sponsored entities, Fannie Mae and Freddie Mac. Because the decline in fair value is attributable to changes in interest rates and not credit quality, and because the Corporation does not have the intent to sell these securities and it is not likely that it will be required to sell these securities before their anticipated recovery, the Corporation does not consider these securities to be other-than-temporarily impaired at December 31, 2022.

The fair value of securities pledged to secure public funds on deposit or for other purposes as required by law was $213.8 million at December 31, 2022 and $242.9 million at December 31, 2021.

There are no securities of a single issuer (other than securities of U.S. Government sponsored enterprises) that exceed 10% of shareholders' equity at December 31, 2022 or 2021.

Prior to December 31, 2022, the Corporation had an equity investment in Cephas Capital Partners, L.P. This small business investment company was established to provide financing to small businesses in market areas served by the Corporation, including minority-owned small businesses and those that are anticipated to create jobs for the low to moderate income levels in the targeted areas. During 2022, the Corporation received its final distribution. As of December 31, 2021, this investment totaled $0.1 million, was included in other assets, and was accounted for under the equity method of accounting.