INVESTMENTS

The following table presents the amortized cost, gross unrealized gains and losses and fair value of securities available for sale and held to maturity:



	September 30, 2017
(in thousands)	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Fair Value
Available for sale securities:
Obligations of U.S. Government-sponsored enterprises	$	99,866	$	271	$	(14	)	$	100,123
Obligations of states and political subdivisions	32,684		887		(229		)	33,342
Agency mortgage-backed securities	470,941		1,760		(3,045		)	469,656
Total securities available for sale	$	603,491	$	2,918	$	(3,288	)	$	603,121
Held to maturity securities:
Obligations of states and political subdivisions	$	14,704	$	159	$	(15	)	$	14,848
Agency mortgage-backed securities	61,464		93		(145		)	61,412
Total securities held to maturity	$	76,168	$	252	$	(160	)	$	76,260



	December 31, 2016
(in thousands)	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Fair Value
Available for sale securities:
Obligations of U.S. Government-sponsored enterprises	$	107,312	$	348	$	—		$	107,660
Obligations of states and political subdivisions	36,486		630		(485		)	36,631
Agency mortgage-backed securities	319,345		1,101		(3,940		)	316,506
Total securities available for sale	$	463,143	$	2,079	$	(4,425	)	$	460,797
Held to maturity securities:
Obligations of states and political subdivisions	$	14,759	$	11	$	(242	)	$	14,528
Agency mortgage-backed securities	65,704		45		(638		)	65,111
Total securities held to maturity	$	80,463	$	56	$	(880	)	$	79,639

At September 30, 2017, and December 31, 2016, there were no holdings of securities of any one issuer in an amount greater than 10% of shareholders’ equity, other than U.S. Government agencies and sponsored enterprises. The agency mortgage-backed securities are all issued by U.S. Government-sponsored enterprises. Available for sale securities having a fair value of $449.8 million and $407.3 million at September 30, 2017, and December 31, 2016, respectively, were pledged as collateral to secure deposits of public institutions and for other purposes as required by law or contract provisions.

The amortized cost and estimated fair value of debt securities at September 30, 2017, by contractual maturity, are shown below. 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. The weighted average life of the mortgage-backed securities is approximately 4 years.



	Available for sale				Held to maturity
(in thousands)	Amortized Cost		Estimated Fair Value		Amortized Cost		Estimated Fair Value
Due in one year or less	$	2,940	$	2,960	$	—	$	—
Due after one year through five years	110,538		111,122		184		194
Due after five years through ten years	15,710		16,241		12,996		13,126
Due after ten years	3,362		3,142		1,524		1,528
Agency mortgage-backed securities	470,941		469,656		61,464		61,412
	$	603,491	$	603,121	$	76,168	$	76,260

The following table represents a summary of investment securities that had an unrealized loss:



	September 30, 2017
	Less than 12 months				12 months or more				Total
(in thousands)	Fair Value		Unrealized Losses		Fair Value		Unrealized Losses		Fair Value		Unrealized Losses
Obligations of U.S. Government-sponsored enterprises	$	10,127	$	14	$	—	$	—	$	10,127	$	14
Obligations of states and political subdivisions	4,907		244		—		—		4,907		244
Agency mortgage-backed securities	332,037		2,721		11,307		469		343,344		3,190
	$	347,071	$	2,979	$	11,307	$	469	$	358,378	$	3,448

	December 31, 2016
	Less than 12 months				12 months or more				Total
(in thousands)	Fair Value		Unrealized Losses		Fair Value		Unrealized Losses		Fair Value		Unrealized Losses
Obligations of states and political subdivisions	$	21,361	$	408	$	3,553	$	320	$	24,914	$	728
Agency mortgage-backed securities	267,734		4,084		12,883		493		280,617		4,577
	$	289,095	$	4,492	$	16,436	$	813	$	305,531	$	5,305

The unrealized losses at both September 30, 2017, and December 31, 2016, were primarily attributable to changes in market interest rates since the securities were purchased. Management systematically evaluates investment securities for other-than-temporary declines in fair value on a quarterly basis. This analysis requires management to consider various factors, which include among other considerations (1) the present value of the cash flows expected to be collected compared to the amortized cost of the security, (2) duration and magnitude of the decline in value, (3) the financial condition of the issuer or issuers, (4) structure of the security, and (5) the intent to sell the security or whether it is more likely than not the Company would be required to sell the security before its anticipated recovery in market value. At September 30, 2017, management performed its quarterly analysis of all securities with an unrealized loss and concluded no individual securities were other-than-temporarily impaired.