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



	March 31, 2016									December 31, 2015
(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	$	14,923	$	144	$	—		$	15,067	$	14,914	$	27	$	—		$	14,941
Obligations of U.S. government corporations and agencies	266,807		4,733		—			271,540		262,045		1,825		(567		)	263,303
Collateralized mortgage obligations of U.S. government corporations and agencies	134,502		2,828		—			137,330		128,458		693		(316		)	128,835
Residential mortgage-backed securities of U.S. government corporations and agencies	37,858		1,427		—			39,285		39,185		1,091		(151		)	40,125
Commercial mortgage-backed securities of U.S. government corporations and agencies	69,445		1,226		(7		)	70,664		69,697		183		(676		)	69,204
Obligations of states and political subdivisions	126,892		7,490		—			134,382		128,904		5,988		(6		)	134,886
Debt Securities	650,427		17,848		(7		)	668,268		643,203		9,807		(1,716		)	651,294
Marketable equity securities	7,579		1,374		—			8,953		7,579		2,090		—			9,669
Total	$	658,006	$	19,222	$	(7	)	$	677,221	$	650,782	$	11,897	$	(1,716	)	$	660,963

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



	March 31, 2016
	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	—	$	—	$	—	—	$	—	$	—		—	$	—	$	—
Collateralized mortgage obligations of U.S. government corporations and agencies	—	—		—		—	—		—			—	—		—
Residential mortgage-backed securities of U.S. government corporations and agencies	—	—		—		—	—		—			—	—		—
Commercial mortgage-backed securities of U.S. government corporations and agencies	—	—		—		1	9,637		(7		)	1	9,637		(7		)
Obligations of states and political subdivisions	—	—		—		—	—		—			—	—		—
Debt Securities	—	—		—		1	9,637		(7		)	1	9,637		(7		)
Total Temporarily Impaired Securities	—	$	—	$	—	1	$	9,637	$	(7	)	1	$	9,637	$	(7	)



	December 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	10	$	88,584	$	(379	)	2	$	14,542	$	(188	)	12	$	103,126	$	(567	)
Collateralized mortgage obligations of U.S. government corporations and agencies	6	61,211		(316		)	—	—		—			6	61,211		(316		)
Residential mortgage-backed securities of U.S. government corporations and agencies	1	7,993		(151		)	—	—		—			1	7,993		(151		)
Commercial mortgage-backed securities of U.S. government corporations and agencies	5	50,839		(450		)	1	9,472		(226		)	6	60,311		(676		)
Obligations of states and political subdivisions	1	5,370		(6		)	—	—		—			1	5,370		(6		)
Debt Securities	23	213,997		(1,302		)	3	24,014		(414		)	26	238,011		(1,716		)
Total Temporarily Impaired Securities	23	$	213,997	$	(1,302	)	3	$	24,014	$	(414	)	26	$	238,011	$	(1,716	)

We do not believe any individual unrealized loss as of March 31, 2016 represents an other than temporary impairment, or OTTI. As of March 31, 2016, the unrealized loss on one debt security was primarily attributable to changes in interest rates and not related to the credit quality of the security. 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 at either March 31, 2016 or December 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 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 (loss)/income, for the periods presented:



	March 31, 2016							December 31, 2015
(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	$	19,222	$	(7	)	$	19,215	$	11,897	$	(1,716	)	$	10,181
Income tax expense/(benefit)	6,728		(2		)	6,726		4,164		(601		)	3,563
Net unrealized gains/(losses), net of tax included in accumulated other comprehensive income/(loss)	$	12,494	$	(5	)	$	12,489	$	7,733	$	(1,115	)	$	6,618

The amortized cost and fair value of securities available-for-sale at March 31, 2016 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, 2016
(dollars in thousands)	Amortized Cost		Fair Value
Obligations of the U.S. Treasury, U.S. government corporations and agencies, and obligations of states and political subdivisions
Due in one year or less	$	46,963	$	47,106
Due after one year through five years	220,193		225,234
Due after five years through ten years	66,133		68,646
Due after ten years	75,333		80,003
	408,622		420,989
Collateralized mortgage obligations of U.S. government corporations and agencies	134,502		137,330
Residential mortgage-backed securities of U.S. government corporations and agencies	37,858		39,285
Commercial mortgage-backed securities of U.S. government corporations and agencies	69,445		70,664
Debt Securities	650,427		668,268
Marketable equity securities	7,579		8,953
Total	$	658,006	$	677,221

At March 31, 2016 and December 31, 2015, securities with carrying values of $297.3 million and $278.4 million were pledged for various regulatory and legal requirements.