Debt Securities Available for Sale: The amortized cost, unrealized gains, unrealized losses and estimated fair values of debt securities available for sale at September 30, 2020 and December 31, 2019 are summarized as follows:


	September 30, 2020
	Amortized		Unrealized				Estimated
Dollars in thousands	Cost		Gains		Losses		Fair Value
Available for Sale (carried at estimated fair value)
Taxable debt securities
U.S. Government and agencies and corporations	$	36,818	$	366	$	418	$	36,766
Residential mortgage-backed securities:
Government-sponsored agencies	60,678		2,072		399		62,351
Nongovernment-sponsored entities	15,255		187		252		15,190
State and political subdivisions
General obligations	12,756		749		—		13,505
Water and sewer revenues	9,602		667		—		10,269
Lease revenues	5,837		344		3		6,178
Income tax revenues	5,055		435		—		5,490


Other revenues	15,550		1,309		1		16,858
Corporate debt securities	26,438		42		524		25,956
Asset-backed securities	47,291		14		1,270		46,035
Total taxable debt securities	235,280		6,185		2,867		238,598
Tax-exempt debt securities
State and political subdivisions
General obligations	29,149		2,828		17		31,960
Water and sewer revenues	8,290		669		—		8,959
Lease revenues	7,283		743		—		8,026







Other revenues	9,725		733		12		10,446
Total tax-exempt debt securities	54,447		4,973		29		59,391

Total available for sale securities	$	289,727	$	11,158	$	2,896	$	297,989


	December 31, 2019
	Amortized		Unrealized				Estimated
Dollars in thousands	Cost		Gains		Losses		Fair Value
Available for Sale (carried at estimated fair value)
Taxable debt securities
U.S. Government and agencies and corporations	$	21,036	$	212	$	384	$	20,864
Residential mortgage-backed securities:
Government-sponsored agencies	70,379		1,031		435		70,975
Nongovernment-sponsored entities	10,253		17		41		10,229
State and political subdivisions
General obligations	12,603		25		171		12,457
Water and sewer revenues	7,170		71		114		7,127
Lease revenues	5,310		25		77		5,258
University revenues	5,917		164		16		6,065
Other revenues	18,831		344		109		19,066
Corporate debt securities	18,268		81		149		18,200
Asset-backed securities	33,826		—		812		33,014
Total taxable debt securities	203,593		1,970		2,308		203,255
Tax-exempt debt securities
State and political subdivisions
General obligations	36,673		2,526		—		39,199
Water and sewer revenues	9,565		633		—		10,198
Lease revenues	8,455		598		—		9,053





Other revenues	13,929		728		7		14,650
Total tax-exempt debt securities	68,622		4,485		7		73,100

Total available for sale securities	$	272,215	$	6,455	$	2,315	$	276,355

The below information is relative to the five states where issuers with the highest volume of state and political subdivision securities held in our available for sale portfolio are located. We own no such securities of any single issuer which we deem to be a concentration.


	September 30, 2020
	Amortized		Unrealized				Estimated
Dollars in thousands	Cost		Gains		Losses		Fair Value


California	$	15,323	$	1,426	$	—	$	16,749
New York	10,455		959		—		11,414
Texas	9,887		844		—		10,731

Illinois	9,248		636		18		9,866
Florida	8,497		669		—		9,166


Dollars in thousands	Amortized Cost		Estimated Fair Value
Due in one year or less	$	32,295	$	32,637
Due from one to five years	84,789		86,143
Due from five to ten years	67,999		68,841
Due after ten years	104,644		110,368

Total	$	289,727	$	297,989

The proceeds from sales, calls and maturities of securities available for sale, including principal payments received on mortgage-backed obligations, and the related gross gains and losses realized, for the nine months ended September 30, 2020 and 2019 are as follows:


		Proceeds from						Gross realized
Dollars in thousands		Sales		Calls and Maturities		Principal Payments		Gains		Losses
For the Nine Months Ended September 30,
2020
	Securities available for sale	$	105,597	$	2,810	$	17,952	$	2,560	$	—

2019
	Securities available for sale	$	133,174	$	1,766	$	18,501	$	1,867	$	332


	September 30, 2020
		Less than 12 months				12 months or more				Total
Dollars in thousands	# of securities in loss position	Estimated Fair Value		Unrealized Loss		Estimated Fair Value		Unrealized Loss		Estimated Fair Value		Unrealized Loss
Taxable debt securities
U.S. Government agencies and corporations	34	$	15,995	$	61	$	12,427	$	357	$	28,422	$	418
Residential mortgage-backed securities:
Government-sponsored agencies	12	6,031		49		9,327		350		15,358		399
Nongovernment-sponsored entities	4	3,492		22		2,726		230		6,218		252
State and political subdivisions:


Lease revenues	1	1,515		3		—		—		1,515		3

Other revenues	1	1,513		1		—		—		1,513		1
Corporate debt securities	10	8,381		410		1,886		114		10,267		524
Asset-backed securities	21	11,391		204		31,930		1,066		43,321		1,270
Tax-exempt debt securities
State and political subdivisions:
General obligations	1	972		17		—		—		972		17








Other revenues	1	145		12		—		—		145		12
Total	85	$	49,435	$	779	$	58,296	$	2,117	$	107,731	$	2,896


	December 31, 2019
		Less than 12 months				12 months or more				Total
Dollars in thousands	# of securities in loss position	Estimated Fair Value		Unrealized Loss		Estimated Fair Value		Unrealized Loss		Estimated Fair Value		Unrealized Loss
Taxable debt securities
U.S. Government agencies and corporations	15	$	—	$	—	$	14,903	$	384	$	14,903	$	384
Residential mortgage-backed securities:
Government-sponsored agencies	21	12,298		96		15,174		339		27,472		435
Nongovernment-sponsored entities	4	8,323		41		—		—		8,323		41
State and political subdivisions:
General obligations	10	10,581		171		—		—		10,581		171
Water and sewer revenues	4	4,421		114		—		—		4,421		114
Lease revenues	4	4,235		77		—		—		4,235		77
University revenues	1	1,307		16		—		—		1,307		16
Other revenues	6	6,517		109		—		—		6,517		109
Corporate debt securities	6	1,686		3		3,739		146		5,425		149
Asset-backed securities	15	3,441		34		29,573		778		33,014		812
Tax-exempt debt securities
State and political subdivisions:







Other revenues	2	1,183		7		—		—		1,183		7
Total	88	$	53,992	$	668	$	63,389	$	1,647	$	117,381	$	2,315

We do not intend to sell the above securities, and it is more likely than not that we will not be required to sell these securities before recovery of their amortized cost bases. We believe that this decline in value is primarily attributable to changes in market interest rates, and in some cases limited market liquidity and is not due to credit quality as none of these securities are in default and all carry above investment grade ratings. Accordingly, no allowance for credit losses has been recognized relative to these securities.


	September 30, 2020
	Amortized		Unrealized				Estimated
Dollars in thousands	Cost		Gains		Losses		Fair Value
Held to Maturity (carried at amortized cost)
















Tax-exempt debt securities
State and political subdivisions
General obligations	$	69,731	$	1,081	$	37	$	70,775
Water and sewer revenues	7,181		104		8		7,277



Sales tax revenues	4,665		28		45		4,648




Other revenues	10,023		154		91		10,086
Total tax-exempt debt securities	91,600		1,367		181		92,786

Total	$	91,600	$	1,367	$	181	$	92,786

The below information is relative to the five states where issuers with the highest volume of state and political subdivision securities held in our held to maturity portfolio are located. We own no such securities of any single issuer which we deem to be a concentration.


	September 30, 2020
	Amortized		Unrealized				Estimated
Dollars in thousands	Cost		Gains		Losses		Fair Value
Texas	$	14,528	$	182	$	—	$	14,710
California	10,132		216		8		10,340
Pennsylvania	8,823		41		8		8,856
Michigan	7,191		25		43		7,173
Nevada	6,976		—		6		6,970


Dollars in thousands	Amortized Cost		Estimated Fair Value
Due in one year or less	$	—	$	—
Due from one to five years	—		—
Due from five to ten years	2,048		2,090
Due after ten years	89,552		90,696

Held to Maturity	$	91,600	$	92,786

The proceeds from sales, calls and maturities of held to maturity securities, including principal payments received on mortgage-backed obligations, and the related gross gains and losses realized, for the nine months ended September 30, 2020 are as follows:

In accordance with ASC 326, an allowance for credit losses on held to maturity securities is a contra-asset valuation account, that is deducted from the amortized cost basis of securities carried at amortized cost to present management's best estimate of the net amount expected to be collected. Held to maturity securities are charged-off against the allowance when deemed uncollectible by management. Adjustments to the allowance are reported in our income statement as a component of the provision for credit losses. Management measures expected credit losses on held to maturity securities on a collective basis by major security type with each type sharing similar risk characteristics, and considers historical credit loss information that is adjusted for current conditions and reasonable and supportable forecasts. Management has made the accounting policy election to exclude accrued interest receivable on held to maturity securities from the estimate of credit losses. At September 30, 2020, no allowance for credit losses on held to maturity securities has been recognized.