Note 3: Securities

The amortized cost, unrealized gains and losses and fair values of securities classified available for sale are summarized as follows:

			Gross		Gross
	Amortized		Unrealized		Unrealized			Fair
	Cost		Gains		Losses			Value
	(dollars in thousands)
March 31, 2013:
U.S. Treasury securities	$	103,225	$	1,292	$	—		$	104,517
Obligations of U.S. government corporations and agencies	332,583		5,644		(16		)	338,211
Obligations of states and political subdivisions	276,195		5,819		(220		)	281,794
Residential mortgage-backed securities	190,989		7,105		—			198,094
Corporate debt securities	24,484		154		(10		)	24,628
Total debt securities	927,476		20,014		(246		)	947,244
Mutual funds and other equity securities	3,563		1,772		—			5,335

	$	931,039	$	21,786	$	(246	)	$	952,579

			Gross		Gross
	Amortized		Unrealized		Unrealized			Fair
	Cost		Gains		Losses			Value
	(dollars in thousands)
December 31, 2012:
U.S. Treasury securities	$	103,353	$	1,303	$	—		$	104,656
Obligations of U.S. government corporations and agencies	363,583		6,616		(5		)	370,194
Obligations of states and political subdivisions	274,350		6,176		(238		)	280,288
Residential mortgage-backed securities	210,139		7,576		—			217,715
Corporate debt securities	24,601		139		(26		)	24,714
Total debt securities	976,026		21,810		(269		)	997,567
Mutual funds and other equity securities	2,451		1,479		—			3,930

	$	978,477	$	23,289	$	(269	)	$	1,001,497

The amortized cost and fair value of debt securities available for sale as of March 31, 2013, by contractual maturity, are shown below. Mutual funds and other equity securities do not have stated maturity dates and therefore are not included in the following maturity summary. Mortgages underlying the residential mortgage-backed securities may be called or prepaid without penalties; therefore, actual maturities could differ from the contractual maturities. All residential mortgage-backed securities were issued by U.S. government agencies and corporations.

	Amortized		Fair
	Cost		Value
	(dollars in thousands)
Due in one year or less	$	143,583	$	144,951
Due after one year through five years	518,792		527,045
Due after five years through ten years	202,954		209,884
Due after ten years	62,147		65,364
	$	927,476	$	947,244

There were no realized gains and losses related to sales of securities and no tax provision related to net realized gains and losses for the three months ended March 31, 2013 and 2012.

Investment securities with carrying amounts of $418.2 million and $489.1 million on March 31, 2013 and December 31, 2012, respectively, were pledged as collateral for public deposits, securities sold under agreements to repurchase and for other purposes as required or permitted by law.

Information pertaining to securities with gross unrealized losses at March 31, 2013 and December 31, 2012 aggregated by investment category and length of time that individual securities have been in a continuous loss position follows:

	Less than 12 months				Greater than 12 months				Total
	Fair		Unrealized		Fair		Unrealized		Fair		Unrealized
	Value		Losses		Value		Losses		Value		Losses
	(dollars in thousands)
March 31, 2013:
U.S. Treasury securities(1)	$	355	$	—	$	—	$	—	$	355	$	—
Obligations of U.S. government corporations and agencies	10,144		16		—		—		10,144		16
Obligations of states and political subdivisions	26,454		164		4,282		56		30,736		220
Corporate debt securities	7,159		10		—		—		7,159		10
Total temporarily impaired securities	$	44,112	$	190	$	4,282	$	56	$	48,394	$	246

(1)Unrealized loss was less than one thousand dollars.

	Less than 12 months				Greater than 12 months				Total
	Fair		Unrealized		Fair		Unrealized		Fair		Unrealized
	Value		Losses		Value		Losses		Value		Losses
	(dollars in thousands)
December 31, 2012:
Obligations of U.S. government corporations and agencies	$	10,155	$	5	$	—	$	—	$	10,155	$	5
Obligations of states and political subdivisions	37,958		189		3,311		49		41,269		238
Corporate debt securities	15,207		26		—		—		15,207		26
Total temporarily impaired securities	$	63,320	$	220	$	3,311	$	49	$	66,631	$	269

The total number of securities in the investment portfolio in an unrealized loss position as of March 31, 2013 was 74, and represented a loss of 0.51% of the aggregate carrying value. Based upon a review of unrealized loss circumstances, the unrealized losses resulted from changes in market interest rates and liquidity, not from changes in the probability of receiving the contractual cash flows. The Company does not intend to sell the securities and it is more-likely-than-not that the Company will recover the amortized cost prior to being required to sell the securities. Full collection of the amounts due according to the contractual terms of the securities is expected; therefore, the Company does not consider these investments to be other-than-temporarily impaired at March 31, 2013.

Management evaluates securities for other-than-temporary impairment at least on a quarterly basis, and more frequently when economic or market concerns warrant such evaluation. Consideration is given to the length of time and extent to which the fair value has been less than cost, the financial condition and near-term prospects of the issuer, and whether the Company has the intent to sell the security and it is more-likely-than-not we will have to sell the security before recovery of its cost basis.