SECURITIES

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



	March 31, 2017
	Amortized Cost		Unrealized Gains		Unrealized Losses		Estimated Fair Value
Obligations of U.S. Government and U.S. Government sponsored enterprises	$	17,295	$	145	$	—	$	17,440
Mortgage-backed securities, residential	244,049		319		4,690		239,678
Obligations of states and political subdivisions	44,007		288		140		44,155
Corporate bonds and notes	248		3		—		251
SBA loan pools	550		1		1		550
Corporate stocks	265		242		—		507
Total	$	306,414	$	998	$	4,831	$	302,581



	December 31, 2016
	Amortized Cost		Unrealized Gains		Unrealized Losses		Estimated Fair Value
Obligations of U.S. Government and U.S. Government sponsored enterprises	$	17,300	$	155	$	—	$	17,455
Mortgage-backed securities, residential	253,156		202		7,492		245,866
Obligations of states and political subdivisions	38,843		209		312		38,740
Corporate bonds and notes	249		1		—		250
SBA loan pools	568		3		1		570
Corporate stocks	285		236		—		521
Total	$	310,401	$	806	$	7,805	$	303,402

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



	March 31, 2017
	Amortized Cost		Unrealized Gains		Unrealized Losses		Estimated Fair Value
Obligations of states and political subdivisions	$	2,741	$	194	$	—	$	2,935
Time deposits with other financial institutions	980		—		3		977
Total	$	3,721	$	194	$	3	$	3,912



	December 31, 2016
	Amortized Cost		Unrealized Gains		Unrealized Losses		Estimated Fair Value
Obligations of states and political subdivisions	$	3,725	$	206	$	—	$	3,931
Time deposits with other financial institutions	980		1		—		981
Total	$	4,705	$	207	$	—	$	4,912

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, 2017
	Available for Sale				Held to Maturity
	Amortized Cost		Fair Value		Amortized Cost		Fair Value
Within one year	$	8,197	$	8,224	$	866	$	873
After one, but within five years	33,091		33,411		2,583		2,729
After five, but within ten years	17,184		17,168		272		310
After ten years	3,078		3,043		—		—
	61,550		61,846		3,721		3,912
Mortgage-backed securities, residential	244,049		239,678		—		—
SBA loan pools	550		550		—		—
Total	$	306,149	$	302,074	$	3,721	$	3,912

The proceeds from sales and calls of securities resulting in gains or losses for the three months ended March 31, 2017 and 2016 are listed below (in thousands):



	2017		2016
Proceeds	$	—	$	15,422
Gross gains	—		908
Gross losses	—		—
Tax expense	—		343

The following tables summarize the investment securities available for sale with unrealized losses at March 31, 2017 and December 31, 2016 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, 2017	Fair Value		Unrealized Losses		Fair Value		Unrealized Losses		Fair Value		Unrealized Losses
Mortgage-backed securities, residential	$	220,708	$	4,690	$	—	$	—	$	220,708	$	4,690
Obligations of states and political subdivisions	12,815		140		—		—		12,815		140
SBA loan pools	—		—		219		1		219		1
Total temporarily impaired securities	$	233,523	$	4,830	$	219	$	1	$	233,742	$	4,831



	Less than 12 months				12 months or longer				Total
December 31, 2016	Fair Value		Unrealized Losses		Fair Value		Unrealized Losses		Fair Value		Unrealized Losses
Mortgage-backed securities, residential	$	233,843	$	7,492	$	—	$	—	$	233,843	$	7,492
Obligations of states and political subdivisions	25,724		312		—		—		25,724		312
SBA loan pools	—		—		225		1		225		1
Total temporarily impaired securities	$	259,567	$	7,804	$	225	$	1	$	259,792	$	7,805

Other-Than-Temporary Impairment

As of March 31, 2017, the majority of the Corporation’s unrealized losses in the investment securities portfolio related to mortgage-backed securities. At March 31, 2017, 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, 2017.