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:



	March 31, 2017
(in thousands)	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Fair Value
Available for sale securities:
Obligations of U.S. Government-sponsored enterprises	$	104,979	$	262	$	(66	)	$	105,175
Obligations of states and political subdivisions	34,113		762		(365		)	34,510
Agency mortgage-backed securities	431,030		1,508		(3,537		)	429,001
U.S Treasury bills	24,998		1		—			24,999
Total securities available for sale	$	595,120	$	2,533	$	(3,968	)	$	593,685
Held to maturity securities:
Obligations of states and political subdivisions	$	14,741	$	33	$	(99	)	$	14,675
Agency mortgage-backed securities	64,495		76		(629		)	63,942
Total securities held to maturity	$	79,236	$	109	$	(728	)	$	78,617



	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 March 31, 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 $466.1 million and $407.3 million at March 31, 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 March 31, 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 5 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	$	27,529	$	27,563	$	657	$	656
Due after one year through five years	94,131		94,743		7,056		7,043
Due after five years through ten years	14,532		14,759		6,523		6,479
Due after ten years	2,900		2,620		505		497
Agency mortgage-backed securities	431,030		429,001		64,495		63,942
U.S Treasury bills	24,998		24,999		—		—
	$	595,120	$	593,685	$	79,236	$	78,617

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



	March 31, 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	$	20,110	$	66	$	—	$	—	$	20,110	$	66
Obligations of states and political subdivisions	$	14,371	$	152	$	3,559	$	312	$	17,930	$	464
Agency mortgage-backed securities	298,238		3,686		13,311		480		311,549		4,166
	$	332,719	$	3,904	$	16,870	$	792	$	349,589	$	4,696

	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 March 31, 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 March 31, 2017, management performed its quarterly analysis of all securities with an unrealized loss and concluded no individual securities were other-than-temporarily impaired.