INVESTMENTS

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



	March 31, 2013
(in thousands)	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Fair Value
Available for sale securities:
Obligations of U.S. Government-sponsored enterprises	$	130,782	$	2,765	$	—		$	133,547
Obligations of states and political subdivisions	50,402		2,113		(608		)	51,907
Residential mortgage-backed securities	292,739		5,214		(400		)	297,553
	$	473,923	$	10,092	$	(1,008	)	$	483,007

	December 31, 2012
(in thousands)	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Fair Value
Available for sale securities:
Obligations of U.S. Government-sponsored enterprises	$	149,039	$	3,329	$	—		$	152,368
Obligations of states and political subdivisions	51,202		2,279		(478		)	53,003
Residential mortgage-backed securities	427,221		7,884		(264		)	434,841
	$	627,462	$	13,492	$	(742	)	$	640,212

At March 31, 2013, and December 31, 2012, there were no holdings of securities of any one issuer in an amount greater than 10% of shareholders’ equity, other than the U.S. government agencies and sponsored enterprises. The residential mortgage-backed securities are all issued by U.S. government sponsored enterprises. Available for sale securities having a fair value of $317.8 million and $359.3 million at March 31, 2013, and December 31, 2012, 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 classified as available for sale at March 31, 2013, 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.



(in thousands)	Amortized Cost		Estimated Fair Value
Due in one year or less	$	1,594	$	1,608
Due after one year through five years	145,156		148,476
Due after five years through ten years	28,008		29,210
Due after ten years	6,426		6,160
Mortgage-backed securities	292,739		297,553
	$	473,923	$	483,007

The following table represents a summary of available-for-sale investment securities that had an unrealized loss:



	March 31, 2013
	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	$	10,042	$	259	$	3,051	$	349	$	13,093	$	608
Residential mortgage-backed securities	44,488		400		—		—		44,488		400
	$	54,530	$	659	$	3,051	$	349	$	57,581	$	1,008

	December 31, 2012
	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	6,434		122		3,389		356		9,823		478
Residential mortgage-backed securities	40,471		143		11,266		121		51,737		264
	$	46,905	$	265	$	14,655	$	477	$	61,560	$	742

The unrealized losses at both March 31, 2013, and December 31, 2012, 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 (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 that the Company would be required to sell the security before its anticipated recovery in market value. At March 31, 2013, management performed its quarterly analysis of all securities with an unrealized loss and concluded no individual securities were other-than-temporarily impaired.

The gross gains and gross losses realized from sales of available-for-sale investment securities were as follows:



	Three months ended March 31,
(in thousands)	2013			2012
Gross gains realized	$	866		$	1,075
Gross losses realized	(182		)	(53		)
Proceeds from sales	122,894			64,476