(3) Investment Securities

The amortized cost, unrealized gains and losses and estimated fair values of investments in debt and other securities at December 31, 2018 are summarized as follows:

	Amortized cost		Unrealized gains		Unrealized losses			Estimated fair value
Investment securities available-for-sale:
U.S. Treasury securities	$	50,825	$	14	$	(157	)	$	50,682
Securities of U.S. government agencies and corporations		42,215		89		(228	)		42,076
Obligations of states and political subdivisions		19,110		181		(123	)		19,168
Collateralized mortgage obligations		65,615		34		(1,850	)		63,799
Mortgage-backed securities		142,297		147		(3,532	)		138,912

Total debt securities	$	320,062	$	465	$	(5,890	)	$	314,637

The amortized cost, unrealized gains and losses and estimated fair values of investments in debt and other securities at December 31, 2017 are summarized as follows:

	Amortized cost		Unrealized gains		Unrealized losses			Estimated fair value
Investment securities available-for-sale:
U.S. Treasury Securities	$	18,589	$	—	$	(125	)	$	18,464
Securities of U.S. government agencies and corporations		21,353		—		(244	)		21,109
Obligations of states and political subdivisions		23,138		216		(146	)		23,208
Collateralized mortgage obligations		67,724		—		(1,641	)		66,083
Mortgage-backed securities		154,143		95		(2,361	)		151,877

Total debt securities	$	284,947	$	311	$	(4,517	)	$	280,741

Gross realized gains from sales and calls of available-for-sale securities were $0, $2, and $24 for the years ended December 31, 2018, 2017, and 2016, respectively. Gross realized losses from sales of available-for-sale securities were $20, $16, and $25 for the years ended December 31, 2018, 2017, and 2016, respectively.

The amortized cost and estimated fair value of debt and other securities at December 31, 2018, by contractual and expected maturity, are shown in the following table:

	Amortized cost		Estimated fair value

Maturity in years:
Due in one year or less	$	47,277	$	47,114
Due after one year through five years		58,881		58,648
Due after five years through ten years		5,462		5,628
Due after ten years		530		536
Subtotal		112,150		111,926
MBS and CMO		207,912		202,711
Total	$	320,062	$	314,637

Expected maturities may differ from contractual maturities because borrowers may have the right to call or prepay obligations with or without call or prepayment penalties. In addition, factors such as prepayments and interest rates may affect the yield on the carrying value of mortgage-related securities.

An analysis of gross unrealized losses of the available-for-sale investment securities portfolio as of December 31, 2018, follows:

	Less than 12 months					12 months or more					Total
	Fair Value		Unrealized losses			Fair Value		Unrealized losses			Fair Value		Unrealized losses
U.S. Treasury securities	$	37,805	$	(67	)	$	5,951	$	(90	)	$	43,756	$	(157	)
Securities of U.S. government agencies and corporations		16,959		(39	)		13,540		(189	)		30,499		(228	)
Obligations of states and political subdivisions		847		(2	)		9,134		(121	)		9,981		(123	)
Collateralized mortgage obligations		2,217		(6	)		53,217		(1,844	)		55,434		(1,850	)
Mortgage-backed securities		16,358		(123	)		105,361		(3,409	)		121,719		(3,532	)

Total	$	74,186	$	(237	)	$	187,203	$	(5,653	)	$	261,389	$	(5,890	)

No decline in value was considered “other-than-temporary” during 2018. Sixty-four securities, all considered investment grade, which had a fair value of $74,186 and a total unrealized loss of $237 have been in an unrealized loss position for less than twelve months as of December 31, 2018. One hundred eighty-six securities, all considered investment grade, which had a fair value of $187,203 and a total unrealized loss of $5,653, have been in an unrealized loss position for more than twelve months as of December 31, 2018. The unrealized losses on the Company's investment securities were caused by market conditions for these types of investments, particularly changes in risk-free interest rates. The Company does not intend to sell the securities and has concluded it is not more likely than not that we will be required to sell these securities prior to recovery of their anticipated cost basis. Therefore, the Company does not consider these investments to be other than temporarily impaired as of December 31, 2018.

The fair value of investment securities could decline in the future if the general economy deteriorates, inflation increases, credit ratings decline, the issuer's financial condition deteriorates, or the liquidity for securities declines. As a result, other than temporary impairments may occur in the future.

An analysis of gross unrealized losses of the available-for-sale investment securities portfolio as of December 31, 2017, follows:

	Less than 12 months					12 months or more					Total
	Fair Value		Unrealized losses			Fair Value		Unrealized losses			Fair Value		Unrealized losses
U.S. Treasury Securities	$	10,004	$	(2	)	$	8,460	$	(123	)	$	18,464	$	(125	)
Securities of U.S. government agencies and corporation		6,049		(50	)		15,060		(194	)		21,109		(244	)
Obligations of states and political subdivision		7,677		(34	)		7,116		(112	)		14,793		(146	)
Collateralized mortgage obligations		31,679		(576	)		34,404		(1,065	)		66,083		(1,641	)
Mortgage-backed securities		62,320		(650	)		76,478		(1,711	)		138,798		(2,361	)

Total	$	117,729	$	(1,312	)	$	141,518	$	(3,205	)	$	259,247	$	(4,517	)

Investment securities carried at $36,781 and $32,399 at December 31, 2018 and 2017, respectively, were pledged to secure public deposits or for other purposes as required or permitted by law.