SECURITIES

Amortized cost and estimated fair value of securities available for sale are as follows (in thousands):



	March 31, 2018
	Amortized Cost		Unrealized Gains		Unrealized Losses		Estimated Fair Value
Obligations of U.S. Government and U.S. Government sponsored enterprises	$	15,490	$	15	$	54	$	15,451
Mortgage-backed securities, residential	216,489		87		8,757		207,819
Obligations of states and political subdivisions	52,177		44		604		51,617
Corporate bonds and notes	249		—		—		249
SBA loan pools	3,874		1		27		3,848
Total	$	288,279	$	147	$	9,442	$	278,984



	December 31, 2017
	Amortized Cost		Unrealized Gains		Unrealized Losses		Estimated Fair Value
Obligations of U.S. Government and U.S. Government sponsored enterprises	$	15,492	$	20	$	21	$	15,491
Mortgage-backed securities, residential	224,939		136		5,166		219,909
Obligations of states and political subdivisions	52,928		355		151		53,132
Corporate bonds and notes	249		2		—		251
SBA loan pools	4,339		1		32		4,308
Total	$	297,947	$	514	$	5,370	$	293,091

Amortized cost and estimated fair value of securities held to maturity are as follows (in thousands):



	March 31, 2018
	Amortized Cost		Unrealized Gains		Unrealized Losses		Estimated Fair Value
Obligations of states and political subdivisions	$	1,805	$	—	$	—	$	1,805
Time deposits with other financial institutions	1,835		—		13		1,822
Total	$	3,640	$	—	$	13	$	3,627



	December 31, 2017
	Amortized Cost		Unrealized Gains		Unrealized Losses		Estimated Fair Value
Obligations of states and political subdivisions	$	1,946	$	—	$	—	$	1,946
Time deposits with other financial institutions	1,835		—		5		1,830
Total	$	3,781	$	—	$	5	$	3,776

The amortized cost and estimated fair value of debt securities are shown below by expected 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):



	March 31, 2018
	Available for Sale				Held to Maturity
	Amortized Cost		Fair Value		Amortized Cost		Fair Value
Within one year	$	18,365	$	18,350	$	900	$	899
After one, but within five years	19,992		19,911		2,507		2,495
After five, but within ten years	28,720		28,245		233		233
After ten years	839		811		—		—
	67,916		67,317		3,640		3,627
Mortgage-backed securities, residential	216,489		207,819		—		—
SBA loan pools	3,874		3,848		—		—
Total	$	288,279	$	278,984	$	3,640	$	3,627

There were no proceeds from sales and calls of securities resulting in gains or losses for the three months ended March 31, 2018 and 2017.

The following tables summarize the investment securities available for sale with unrealized losses at March 31, 2018 and December 31, 2017 by aggregated major security type and length of time in a continuous unrealized loss position (in thousands):



	Less than 12 months				12 months or longer				Total
March 31, 2018	Fair Value		Unrealized Losses		Fair Value		Unrealized Losses		Fair Value		Unrealized Losses
Obligations of U.S. Government and U.S. Government sponsored enterprises	$	14,947	$	54	$	—	$	—	$	14,947	$	54
Mortgage-backed securities, residential	73,034		2,093		132,122		6,664		205,156		8,757
Obligations of states and political subdivisions	42,728		574		260		30		42,988		604
SBA loan pools	1,833		25		1,756		2		3,589		27
Total temporarily impaired securities	$	132,542	$	2,746	$	134,138	$	6,696	$	266,680	$	9,442



	Less than 12 months				12 months or longer				Total
December 31, 2017	Fair Value		Unrealized Losses		Fair Value		Unrealized Losses		Fair Value		Unrealized Losses
Obligations of U.S. Government and U.S. Government sponsored enterprises	$	14,982	$	21	$	—	$	—	$	14,982	$	21
Mortgage-backed securities, residential	83,562		1,013		131,165		4,153		214,727		5,166
Obligations of states and political subdivisions	20,526		133		271		18		20,797		151
SBA loan pools	3,937		32		—		—		3,937		32
Total temporarily impaired securities	$	123,007	$	1,199	$	131,436	$	4,171	$	254,443	$	5,370

Other-Than-Temporary Impairment

As of March 31, 2018, the majority of the Corporation’s unrealized losses in the investment securities portfolio related to mortgage-backed securities. At March 31, 2018, 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 it is not likely that the Corporation 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 March 31, 2018.