The following tables present the amortized cost and fair value of available-for-sale securities as of the dates presented:



	March 31, 2015									December 31, 2014
(dollars in thousands)	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Fair Value		Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Fair Value
U.S. Treasury securities	$	14,883	$	147	$	—		$	15,030	$	14,873	$	7	$	—		$	14,880
Obligations of U.S. government corporations and agencies	267,686		3,900		(203		)	271,383		268,029		2,334		(1,078		)	269,285
Collateralized mortgage obligations of U.S. government corporations and agencies	129,010		2,419		(25		)	131,404		116,897		1,257		(148		)	118,006
Residential mortgage-backed securities of U.S. government corporations and agencies	46,412		1,802		(49		)	48,165		45,274		1,548		(154		)	46,668
Commercial mortgage-backed securities of U.S. government corporations and agencies	39,701		517		(138		)	40,080		39,834		232		(393		)	39,673
Obligations of states and political subdivisions	134,765		5,953		(42		)	140,676		136,977		5,789		(64		)	142,702
Debt Securities	632,457		14,738		(457		)	646,738		621,884		11,167		(1,837		)	631,214
Marketable equity securities	7,579		1,512		—			9,091		7,579		1,480		—			9,059
Total	$	640,036	$	16,250	$	(457	)	$	655,829	$	629,463	$	12,647	$	(1,837	)	$	640,273

Realized gains and losses on the sale of securities are determined using the specific-identification method. The following table shows the composition of gross and net realized gains and losses for the periods presented:



	Three Months Ended March 31,
(dollars in thousands)	2015		2014
Gross realized gains	$	—	$	1
Gross realized losses	—		—
Net Realized Gains	$	—	$	1

The following tables present the fair value and the age of gross unrealized losses by investment category as of the dates presented:



	March 31, 2015
	Less Than 12 Months						12 Months or More						Total
(dollars in thousands)	Number of Securities	Fair Value		Unrealized Losses			Number of Securities	Fair Value		Unrealized Losses			Number of Securities	Fair Value		Unrealized Losses
Obligations of U.S. government corporations and agencies	3	$	23,523	$	(55	)	4	$	30,157	$	(148	)	7	$	53,680	$	(203	)
Collateralized mortgage obligations of U.S. government corporations and agencies	3	7,868		(25		)	—	—		—			3	7,868		(25		)
Residential mortgage-backed securities of U.S. government corporations and agencies	5	11,361		(49		)	—	—		—			5	11,361		(49		)
Commercial mortgage-backed securities of U.S. government corporations and agencies	—	—		—			1	9,717		(138		)	1	9,717		(138		)
Obligations of states and political subdivisions	1	5,385		(42		)	—	—		—			1	5,385		(42		)
Total Temporarily Impaired Securities	12	$	48,137	$	(171	)	5	$	39,874	$	(286	)	17	$	88,011	$	(457	)



	December 31, 2014
	Less Than 12 Months						12 Months or More						Total
(dollars in thousands)	Number of Securities	Fair Value		Unrealized Losses			Number of Securities	Fair Value		Unrealized Losses			Number of Securities	Fair Value		Unrealized Losses
Obligations of U.S. government corporations and agencies	4	$	39,745	$	(207	)	8	$	63,149	$	(871	)	12	$	102,894	$	(1,078	)
Collateralized mortgage obligations of U.S. government corporations and agencies	1	9,323		(148		)	—	—		—			1	9,323		(148		)
Residential mortgage-backed securities of U.S. government corporations and agencies	—	—		—			1	8,982		(154		)	1	8,982		(154		)
Commercial mortgage-backed securities of U.S. government corporations and agencies	1	9,998		(25		)	2	20,640		(368		)	3	30,638		(393		)
Obligations of states and political subdivisions	1	263		(1		)	2	10,756		(63		)	3	11,019		(64		)
Total Temporarily Impaired Securities	7	$	59,329	$	(381	)	13	$	103,527	$	(1,456	)	20	$	162,856	$	(1,837	)

We do not believe any individual unrealized loss as of March 31, 2015 represents an other than temporary impairment, or OTTI. As of March 31, 2015, the unrealized losses on 17 debt securities were attributable to changes in interest rates and not related to the credit quality of these securities. All debt securities are determined to be investment grade and are paying principal and interest according to the contractual terms of the security. There were no unrealized losses on marketable equity securities as of March 31, 2015. We do not intend to sell and it is not more likely than not that we will be required to sell any of the securities, referenced in the table above, in an unrealized loss position before recovery of their amortized cost.

The following table displays net unrealized gains and losses, net of tax on securities available for sale included in accumulated other comprehensive income/(loss) for the periods presented:



	March 31, 2015							December 31, 2014
(dollars in thousands)	Gross Unrealized Gains		Gross Unrealized Losses			Net Unrealized Gains/ (Losses)		Gross Unrealized Gains		Gross Unrealized Losses			Net Unrealized Gains/ (Losses)
Total unrealized gains/(losses) on securities available-for-sale	$	16,250	$	(457	)	$	15,793	$	12,647	$	(1,837	)	$	10,810
Income tax expense/(benefit)	5,688		(160		)	5,528		4,426		(643		)	3,783
Net unrealized gains/(losses), net of tax included in accumulated other comprehensive income/(loss)	$	10,562	$	(297	)	$	10,265	$	8,221	$	(1,194	)	$	7,027

The amortized cost and fair value of securities available-for-sale at March 31, 2015 by contractual maturity are included in the table below. Actual maturities may differ from contractual maturities because issuers may have the right to call or prepay obligations with or without call or prepayment penalties.



	March 31, 2015
(dollars in thousands)	Amortized Cost		Fair Value
Obligations of the U.S. Treasury and U.S. government corporations and agencies, and obligations of states and political subdivisions
Due in one year or less	$	29,757	$	30,068
Due after one year through five years	206,322		208,787
Due after five years through ten years	80,865		83,329
Due after ten years	100,390		104,905
	417,334		427,089
Collateralized mortgage obligations of U.S. government corporations and agencies	129,010		131,404
Residential mortgage-backed securities of U.S. government corporations and agencies	46,412		48,165
Commercial mortgage-backed securities of U.S. government corporations and agencies	39,701		40,080
Debt Securities	632,457		646,738
Marketable equity securities	7,579		9,091
Total	$	640,036	$	655,829

At March 31, 2015 and December 31, 2014, securities with carrying values of $334.6 million and $289.1 million were pledged for various regulatory and legal requirements.