Investment Securities

The following table shows the amortized cost and the estimated fair value of the held-to-maturity securities and available-for-sale securities at December 31, 2017 and 2016, by contractual maturity within each type:



	At December 31, 2017									At December 31, 2016
(Dollars in thousands)	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Fair Value		Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Fair Value
Securities Held-to-Maturity
U.S. government corporations and agencies:
After 1 year to 5 years	$	6,995	$	—	$	(77	)	$	6,918	$	—	$	—	$	—		$	—
	6,995		—		(77		)	6,918		—		—		—			—
Residential mortgage-backed securities:
After 5 years to 10 years	8,944		—		(51		)	8,893		—		—		—			—
Over 10 years	39,625		44		(160		)	39,509		5,071		—		(3		)	5,068
	48,569		44		(211		)	48,402		5,071		—		(3		)	5,068
Corporate bonds:
Within 1 year	—		—		—			—		19,810		2		(9		)	19,803
	—		—		—			—		19,810		2		(9		)	19,803
Total	$	55,564	$	44	$	(288	)	$	55,320	$	24,881	$	2	$	(12	)	$	24,871
Securities Available-for-Sale
U.S. government corporations and agencies:
Within 1 year	$	1,499	$	—	$	(3	)	$	1,496	$	15,000	$	20	$	—		$	15,020
After 1 year to 5 years	15,590		—		(125		)	15,465		17,265		—		(19		)	17,246
	17,089		—		(128		)	16,961		32,265		20		(19		)	32,266
State and political subdivisions:
Within 1 year	2,721		1		(6		)	2,716		964		—		(1		)	963
After 1 year to 5 years	16,787		33		(44		)	16,776		18,705		38		(75		)	18,668
After 5 years to 10 years	54,846		897		(73		)	55,670		55,541		829		(426		)	55,944
Over 10 years	3,120		15		—			3,135		12,663		226		(114		)	12,775
	77,474		946		(123		)	78,297		87,873		1,093		(616		)	88,350
Residential mortgage-backed securities:
After 1 year to 5 years	3,913		12		(26		)	3,899		6,086		—		(66		)	6,020
After 5 years to 10 years	51,428		5		(852		)	50,581		23,479		—		(622		)	22,857
Over 10 years	133,237		87		(2,383		)	130,941		174,388		99		(4,794		)	169,693
	188,578		104		(3,261		)	185,421		203,953		99		(5,482		)	198,570
Collateralized mortgage obligations:
After 5 years to 10 years	2,103		—		(82		)	2,021		—		—		—			—
Over 10 years	1,567		14		—			1,581		4,659		—		(105		)	4,554
	3,670		14		(82		)	3,602		4,659		—		(105		)	4,554
Corporate bonds:
Within 1 year	10,006		—		(5		)	10,001		250		—		—			250
After 1 year to 5 years	24,885		20		(147		)	24,758		35,923		34		(241		)	35,716
After 5 years to 10 years	16,669		71		(296		)	16,444		15,193		—		(516		)	14,677
Over 10 years	60,000		—		(4,027		)	55,973		60,000		27		(2,472		)	57,555
	111,560		91		(4,475		)	107,176		111,366		61		(3,229		)	108,198
Money market mutual funds:
No stated maturity	5,985		—		—			5,985		10,784		—		—			10,784
	5,985		—		—			5,985		10,784		—		—			10,784
Equity securities:
No stated maturity	410		667		(1		)	1,076		411		504		—			915
	410		667		(1		)	1,076		411		504		—			915
Total	$	404,766	$	1,822	$	(8,070	)	$	398,518	$	451,311	$	1,777	$	(9,451	)	$	443,637

Expected maturities may differ from contractual maturities because debt issuers may have the right to call or prepay obligations without call or prepayment penalties and mortgage-backed securities typically prepay at a rate faster than contractually due. Unrealized losses in investment securities at December 31, 2017 and 2016 do not represent other-than-temporary impairments in management's judgment.

Securities with a carrying value of $345.1 million and $356.7 million at December 31, 2017 and 2016, respectively, were pledged to secure public deposits and other contractual obligations. In addition, securities of $1.8 million and $1.4 million were pledged to secure credit derivatives and interest rate swaps at December 31, 2017 and 2016, respectively. See Note 17, "Derivative Instruments and Hedging Activities" for additional information.

The following table presents information related to sales of securities available-for-sale during the years ended December 31, 2017, 2016 and 2015:



	For the Years Ended December 31,
(Dollars in thousands)	2017		2016		2015
Securities available-for-sale:
Proceeds from sales	$	7,069	$	77,290	$	77,308
Gross realized gains on sales	74		600		1,295
Gross realized losses on sales	26		82		30
Tax expense related to net realized gains on sales	17		181		443

The Corporation did not recognize any other-than-temporary impairment charges on debt securities for the years ended December 31, 2017, 2016 and 2015. The Corporation realized other-than-temporary impairment charges to noninterest income of $0 thousand, $0 thousand, and $5 thousand on its equity portfolio during the years ended December 31, 2017, 2016 and 2015, respectively.

At December 31, 2017 and 2016, there were no investments in any single non-federal issuer representing more than 10% of shareholders’ equity.

The following table shows the fair value of securities that were in an unrealized loss position at December 31, 2017 and 2016 by the length of time those securities were in a continuous loss position. For the investment securities in an unrealized loss position, the Corporation has concluded, based on its analysis, that the unrealized losses are primarily caused by the movement of interest rates and current market conditions. The contractual terms of these investments do not permit the issuer to settle the securities at a price less than the par value of the investment. It is more likely than not that the Corporation will not be required to sell the investments before a recovery of carrying value.



	Less than Twelve Months					Twelve Months or Longer					Total
(Dollars in thousands)	Fair Value		Unrealized Losses			Fair Value		Unrealized Losses			Fair Value		Unrealized Losses
At December 31, 2017
Securities Held-to-Maturity
U.S. government corporations and agencies	$	6,919	$	(77	)	$	—	$	—		$	6,919	$	(77	)
Residential mortgage-backed securities	40,881		(211		)	—		—			40,881		(211		)
Total	$	47,800	$	(288	)	$	—	$	—		$	47,800	$	(288	)
Securities Available-for-Sale
U.S. government corporations and agencies	$	5,213	$	(38	)	$	11,749	$	(90	)	$	16,962	$	(128	)
State and political subdivisions	18,457		(91		)	6,332		(32		)	24,789		(123		)
Residential mortgage-backed securities	32,217		(210		)	141,371		(3,051		)	173,588		(3,261		)
Collateralized mortgage obligations	—		—			2,021		(82		)	2,021		(82		)
Corporate bonds	18,464		(1,016		)	71,957		(3,459		)	90,421		(4,475		)
Equity securities	—		(1		)	4		—			4		(1		)
Total	$	74,351	$	(1,356	)	$	233,434	$	(6,714	)	$	307,785	$	(8,070	)

At December 31, 2016
Securities Held-to-Maturity
Residential mortgage-backed securities	$	5,068	$	(3	)	$	—	$	—		$	5,068	$	(3	)
Corporate bonds	9,779		(9		)	—		—			9,779		(9		)
Total	$	14,847	$	(12	)	$	—	$	—		$	14,847	$	(12	)
Securities Available-for-Sale
U.S. government corporations and agencies	$	11,850	$	(19	)	$	—	$	—		$	11,850	$	(19	)
State and political subdivisions	40,771		(610		)	423		(6		)	41,194		(616		)
Residential mortgage-backed securities	192,782		(5,482		)	—		—			192,782		(5,482		)
Collateralized mortgage obligations	2,012		(26		)	2,542		(79		)	4,554		(105		)
Corporate bonds	58,535		(1,333		)	33,104		(1,896		)	91,639		(3,229		)
Total	$	305,950	$	(7,470	)	$	36,069	$	(1,981	)	$	342,019	$	(9,451	)

At December 31, 2017, gross unrealized losses for securities in an unrealized loss position for twelve months or longer, totaled $6.7 million. Four federal agency bonds, fourteen investment grade corporate bonds, 104 federal agency residential mortgage securities, and seven investment grade municipal bonds had respective unrealized loss positions of $90 thousand, $3.5 million, $3.1 million and $32 thousand, respectively. The fair value of these 129 securities fluctuate with changes in market conditions which for these underlying securities is primarily due to changes in the interest rate environment. The Corporation does not intend to sell the securities in an unrealized loss position and is unlikely to be required to sell these securities before a recovery of fair value, which may be maturity. Upon review of the attributes of the individual securities, the Corporation concluded these securities were not other-than-temporarily impaired.