
	2020				2019
	Amortized Cost		Estimated Fair Value		Amortized Cost		Estimated Fair Value

Mortgage-backed securities, residential	$	458,245	$	467,866	$	225,029	$	225,234

Obligations of states and political subdivisions	40,662		43,405		41,265		42,845
Corporate bonds and notes	9,000		9,035		250		250
SBA loan pools	34,455		34,305		15,712		15,761


Total	$	542,362	$	554,611	$	282,256	$	284,090


	2020				2019
	Unrealized Gains		Unrealized Losses		Unrealized Gains		Unrealized Losses

Mortgage-backed securities, residential	$	9,822	$	201	$	1,471	$	1,266

Obligations of states and political subdivisions	2,743		—		1,580		—
Corporate bonds and notes	47		12		—		—
SBA loan pools	42		192		95		46


Total	$	12,654	$	405	$	3,146	$	1,312

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, 2020
	Amortized Cost		Fair Value
Within one year
After one, but within five years	27,215		28,757
After five, but within ten years	21,688		22,875
After ten years	759		808
Mortgage-backed securities, residential	458,245		467,866

SBA loan pools	34,455		34,305
Total	$	542,362	$	554,611

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.


	2020				2019
	Amortized Cost		Estimated Fair Value		Amortized Cost		Estimated Fair Value
Obligations of states and political subdivisions	$	326	$	326	$	1,045	$	1,045
Time deposits with other financial institutions	2,143		2,175		2,070		2,094
	$	2,469	$	2,501	$	3,115	$	3,139


	2020				2019
	Unrealized Gains		Unrealized Losses		Unrealized Gains		Unrealized Losses
Obligations of states and political subdivisions	$	—	$	—	$	—	$	—
Time deposits with other financial institutions	32		—		24		—
Total	$	32	$	—	$	24	$	—


	December 31, 2020
	Amortized Cost		Fair Value
Within one year	$	856	$	863
After one, but within five years	1,613		1,638
After five, but within ten years	—		—
After ten years	—		—
Total	$	2,469	$	2,501

The following table summarizes the investment securities available for sale with unrealized losses at December 31, 2020 and December 31, 2019 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
2020
Obligations of U.S. Government and U.S. Government sponsored enterprises	$	—	$	—	$	—	$	—	$	—	$	—
Mortgage-backed securities, residential	70,037		200		970		1		71,007		201
Obligations of states and political subdivisions	—		—		—		—		—		—
Corporate bonds and notes	2,988		12		—		—		2,988		12
SBA loan pools	15,245		156		3,636		36		18,881		192
Total temporarily impaired securities	$	88,270	$	368	$	4,606	$	37	$	92,876	$	405


	Less than 12 months				12 months or longer				Total
	Fair Value		Unrealized Losses		Fair Value		Unrealized Losses		Fair Value		Unrealized Losses
2019
Obligations of U.S. Government and U.S. Government sponsored enterprises	$	—	$	—	$	—	$	—	$	—	$	—
Mortgage-backed securities, residential	71,506		791		54,343		$	475	125,849		1,266
Obligations of states and political subdivisions	—		—		—		—		—		—
Corporate bonds and notes	—		—		—		—		—		—
SBA loan pools	3,014		9		1,405		37		4,419		46
Total temporarily impaired securities	$	74,520	$	800	$	55,748	$	512	$	130,268	$	1,312

As of December 31, 2020, the majority of the Corporation’s unrealized losses in the investment securities portfolio related to mortgage-backed securities. At December 31, 2020, all of the unrealized losses related to mortgage-backed securities were 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, 2020.

The fair value of securities pledged to secure public funds on deposit or for other purposes as required by law was $180.8 million at December 31, 2020 and $205.9 million at December 31, 2019.

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, 2020 or 2019.

The Corporation has an equity investment in Cephas Capital Partners, L.P. This small business investment company was established for the purpose of providing 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. As of December 31, 2020 and 2019, this investment totaled $0.2 million and $0.3 million respectively, is included in other assets, and is accounted for under the equity method of accounting.