The following table summarizes the amortized cost and fair value of securities available for sale and securities held to maturity at December 31, 2019 and 2018 and the corresponding amounts of gross unrealized gains and losses:

December 31, 2019	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses		Estimated Fair Value
Available for sale:
Corporate bonds	$	19,667	$	592	$	—	$	20,259
Municipal securities		16,780		576		8		17,348
Mortgage-backed securities		83,967		550		335		84,182
Collateralized mortgage obligations		89,798		1,146		17		90,927
Total available for sale	$	210,212	$	2,864	$	360	$	212,716

Held to maturity:
Municipal securities	$	138,416	$	4,710	$	3	$	143,123
Mortgage-backed securities		14,365		198		13		14,550
Collateralized mortgage obligations		2,677		110		—		2,787
Total held to maturity	$	155,458	$	5,018	$	16	$	160,460

December 31, 2018	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses		Estimated Fair Value
Available for sale:
Corporate bonds	$	19,743	$	—	$	789	$	18,954
Municipal securities		15,778		75		260		15,593
Mortgage-backed securities		93,083		52		3,676		89,459
Collateralized mortgage obligations		111,341		—		2,372		108,969
Total available for sale	$	239,945	$	127	$	7,097	$	232,975

Held to maturity:
Municipal securities	$	141,942	$	1,156	$	1,094	$	142,004
Mortgage-backed securities		17,163		54		500		16,717
Collateralized mortgage obligations		4,059		48		28		4,079
Total held to maturity	$	163,164	$	1,258	$	1,622	$	162,800

Management evaluates securities for OTTI on at least a quarterly basis, and more frequently when economic or market concerns warrant such evaluation. Consideration is given to (1) the length of time and the extent to which the fair value has been less than cost, (2) the financial condition and near-term prospects of the issuer, and (3) the intent and ability of the Company to retain its investment in the issuer for a period of time sufficient to allow for any anticipated recovery in fair value. There were no other than temporary impairment losses on debt securities related to credit losses recognized during the years ended December 31, 2019 and 2018.

Information pertaining to securities with gross unrealized losses at December 31, 2019 and 2018, aggregated by investment category and length of time that individual securities have been in a continuous loss position, is detailed in the following tables. At December 31, 2019, the Company held 95 securities which had been in continuous loss positions over twelve months and 75 securities which had been in continuous loss position less than twelve months. Of the securities in a loss position over twelve months, 37 were classified as available for sale and 58 were classified as held to

maturity. Of the securities in a loss position less than twelve months, 13 were classified as available for sale and 62 were classified as held to maturity. The securities in a loss position were composed of tax exempt municipal bonds, corporate bonds, collateralized mortgage obligations and mortgage backed securities.

Management believes the unrealized loss on the remaining securities is a function of the movement of interest rates since the time of purchase. Based on evaluation of available evidence, including recent changes in interest rates, credit rating information and information obtained from regulatory filings, management believes the declines in fair value for these securities are temporary. Should the impairment of any of these securities become other-than-temporary, the cost basis of the investment would be reduced and the resulting loss recognized in net income in the period the other-than-temporary impairment is identified. The Company does not have the intent to sell these mortgage-backed securities and it is likely that it will not be required to sell the securities before their anticipated recovery. The Company does not consider these securities to be other-than-temporarily impaired at December 31, 2019.

The following table summarizes securities with unrealized losses at December 31, 2019 and 2018, aggregated by major security type and length of time in a continuous unrealized loss position:

	Less Than 12 Months					12 Months or Longer					Total
December 31, 2019	Gross Unrealized Losses			Estimated Fair Value		Gross Unrealized Losses			Estimated Fair Value		Gross Unrealized Losses			Estimated Fair Value
Available for sale:
Corporate bonds	$	—		$	—	$	—		$	—	$	—		$	—
Municipal securities		(8	)		1,138		—			—		(8	)		1,138
Mortgage-backed securities		(25	)		19,421		(310	)		42,116		(335	)		61,537
Collateralized mortgage obligations		—			—		(17	)		2,594		(17	)		2,594
Total available for sale	$	(33	)	$	20,559	$	(327	)	$	44,710	$	(360	)	$	65,269

Held to maturity:
Municipal securities	$	(1	)	$	1,313	$	(2	)	$	759	$	(3	)	$	2,072
Mortgage-backed securities		—			—		(13	)		7,032		(13	)		7,032
Collateralized mortgage obligations		—			—		—			—		—			—
Total held to maturity	$	(1	)	$	1,313	$	(15	)	$	7,791	$	(16	)	$	9,104

	Less Than 12 Months					12 Months or Longer					Total
December 31, 2018	Gross Unrealized Losses			Estimated Fair Value		Gross Unrealized Losses			Estimated Fair Value		Gross Unrealized Losses			Estimated Fair Value
Available for sale:
Corporate bonds	$	(453	)	$	11,236	$	(336	)	$	7,718	$	(789	)	$	18,954
Municipal securities		(17	)		2,219		(243	)		7,407		(260	)		9,626
Mortgage-backed securities		(89	)		7,173		(3,587	)		76,717		(3,676	)		83,890
Collateralized mortgage obligations		(79	)		9,232		(2,293	)		99,390		(2,372	)		108,622
Total available for sale	$	(638	)	$	29,860	$	(6,459	)	$	191,232	$	(7,097	)	$	221,092

Held to maturity:
Municipal securities	$	(512	)	$	55,793	$	(582	)	$	26,511	$	(1,094	)	$	82,304
Mortgage-backed securities		(21	)		1,478		(479	)		12,317		(500	)		13,795
Collateralized mortgage obligations		(28	)		2,171		—			—		(28	)		2,171
Total held to maturity	$	(561	)	$	59,442	$	(1,061	)	$	38,828	$	(1,622	)	$	98,270

Mortgage-backed securities and collateralized mortgage obligations are backed by pools of mortgages that are insured or guaranteed by the Federal Home Loan Mortgage Corporation (FHLMC), the Federal National Mortgage Association (FNMA) or the Government National Mortgage Association (GNMA).

As of December 31, 2019, there were no holdings of securities of any one issuer, other than the U.S. government and its agencies, in an amount greater than 10% of shareholders’ equity.

Securities with fair values of approximately $278,318 and $259,557 at December 31, 2019 and 2018, respectively, were pledged to secure public fund deposits and for other purposes as required or permitted by law.

The proceeds from sales of securities and the associated gains and losses are listed below:

During the year ended December 31, 2017, the Company sold three held to maturity securities. The Company sold these securities, which consisted of three municipal securities and two corporate bonds, based upon internal credit analysis that they had experienced significant deterioration in creditworthiness. The risk exposure presented by these securities had increased beyond acceptable levels and management determined that it was reasonably possible that all amounts due would not be collected. The credit analysis of the municipalities determined that they had been significantly impacted by the declines in market oil prices due to the fact that their tax bases are heavily reliant on the energy industry relative to other sectors of the economy. Specifically, the revenues of these municipalities had been adversely impacted by the sustained low-level of oil prices. The credit analysis of the corporate bonds, which were both a non-agency collateralized mortgage obligation bond, indicated evidence of significant deterioration in its creditworthiness. In early 2017 one bond rating agency withdrew its current rating on the bond, and prior to 2017 another rating agency had downgraded it to a ‘No Rating’ position. The Company believes the sales of these securities were merited and permissible under the applicable accounting guidelines because of the significant deterioration in the creditworthiness of the issuers.

There were no held to maturity securities sold during the years ended December 31, 2019 or 2018.

Sales of securities held to maturity were as follows for the years ended December 31:


	2019		2018		2017
Proceeds from sales	$	—	$	—	$	3,298
Amortized cost		—		—		3,140
Gross realized gains		—		—		158
Tax expense related to securities gains/losses		—		—		(44	)

Included in the amortized cost of held to maturity securities shown above for the year ended December 31, 2017 was $324 of other than temporary impairment that was recorded during 2013, as well as $499 in prior principal write-downs on corporate bonds that were sold during 2017.

The contractual maturities at December 31, 2019 of available for sale and held to maturity securities at carrying value and estimated fair value are shown below. The Company invests in mortgage-backed securities and collateralized mortgage obligations that have expected maturities that differ from their contractual maturities. These differences arise because borrowers and/or issuers may have the right to call or prepay their obligation with or without call or prepayment penalties.

	Available for Sale				Held to Maturity
December 31, 2019	Amortized Cost		Estimated Fair Value		Amortized Cost		Estimated Fair Value
Due within one year	$	1,015	$	1,019	$	2,189	$	2,200
Due after one year through five years		13,407		13,772		30,221		31,179
Due after five years through ten years		13,324		13,924		32,771		34,078
Due after ten years		8,701		8,892		73,235		75,666
Mortgage-backed securities		83,967		84,182		14,365		14,550
Collateralized mortgage obligations		89,798		90,927		2,677		2,787
Total Securities	$	210,212	$	212,716	$	155,458	$	160,460