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



	September 30, 2017									December 31, 2016
(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	$	24,930	$	2	$	(38	)	$	24,894	$	24,891	$	47	$	(127	)	$	24,811
Obligations of U.S. government corporations and agencies	195,194		1,171		(357		)	196,008		230,989		1,573		(383		)	232,179
Collateralized mortgage obligations of U.S. government corporations and agencies	115,027		476		(608		)	114,895		130,046		465		(734		)	129,777
Residential mortgage-backed securities of U.S. government corporations and agencies	34,452		896		(151		)	35,197		36,606		984		(232		)	37,358
Commercial mortgage-backed securities of U.S. government corporations and agencies	193,382		511		(1,289		)	192,604		127,311		243		(1,950		)	125,604
Obligations of states and political subdivisions	123,672		5,632		—			129,304		128,783		3,772		(46		)	132,509
Debt Securities	686,657		8,688		(2,443		)	692,902		678,626		7,084		(3,472		)	682,238
Marketable equity securities	3,815		1,237		—			5,052		7,579		3,670		—			11,249
Total	$	690,472	$	9,925	$	(2,443	)	$	697,954	$	686,205	$	10,754	$	(3,472	)	$	693,487

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



	September 30, 2017
	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
U.S. Treasury securities	2	$	14,903	$	(38	)	—	$	—	$	—		2	$	14,903	$	(38	)
Obligations of U.S. government corporations and agencies	8	72,102		(357		)	—	—		—			8	72,102		(357		)
Collateralized mortgage obligations of U.S. government corporations and agencies	8	62,408		(608		)	—	—		—			8	62,408		(608		)
Residential mortgage-backed securities of U.S. government corporations and agencies	2	9,071		(151		)	—	—		—			2	9,071		(151		)
Commercial mortgage-backed securities of U.S. government corporations and agencies	10	100,322		(1,057		)	1	7,586		(232		)	11	107,908		(1,289		)
Obligations of states and political subdivisions	—	—		—			—	—		—			—	—		—
Debt Securities	30	258,806		(2,211		)	1	7,586		(232		)	31	266,392		(2,443		)
Marketable equity securities	—	—		—			—	—		—			—	—		—
Total Temporarily Impaired Securities	30	$	258,806	$	(2,211	)	1	$	7,586	$	(232	)	31	$	266,392	$	(2,443	)



	December 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
U.S. Treasury securities	1	$	9,811	$	(127	)	—	$	—	$	—	1	$	9,811	$	(127	)
Obligations of U.S. government corporations and agencies	7	62,483		(383		)	—	—		—		7	62,483		(383		)
Collateralized mortgage obligations of U.S. government corporations and agencies	10	83,031		(734		)	—	—		—		10	83,031		(734		)
Residential mortgage-backed securities of U.S. government corporations and agencies	2	10,022		(232		)	—	—		—		2	10,022		(232		)
Commercial mortgage-backed securities of U.S. government corporations and agencies	10	96,576		(1,950		)	—	—		—		10	96,576		(1,950		)
Obligations of states and political subdivisions	1	5,577		(46		)	—	—		—		1	5,577		(46		)
Debt Securities	31	267,500		(3,472		)	—	—		—		31	267,500		(3,472		)
Marketable equity securities	—	—		—			—	—		—		—	—		—
Total Temporarily Impaired Securities	31	$	267,500	$	(3,472	)	—	$	—	$	—	31	$	267,500	$	(3,472	)

We do not believe any individual unrealized loss as of September 30, 2017 represents an other than temporary impairment, or OTTI. At September 30, 2017 and December 31, 2016 there were 31 debt securities in an unrealized loss position. There were no marketable equity securities at September 30, 2017 and December 31, 2016 with unrealized losses. The unrealized losses on debt securities were primarily 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. 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:



	September 30, 2017									December 31, 2016
(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	$	9,925		$	(2,443	)	$	7,482		$	10,754		$	(3,472	)	$	7,282
Income tax expense/(benefit)	(3,485		)	858			(2,627		)	(3,776		)	1,219			(2,557		)
Net unrealized gains/(losses), net of tax included in accumulated other comprehensive income/(loss)	$	6,440		$	(1,585	)	$	4,855		$	6,978		$	(2,253	)	$	4,725

The amortized cost and fair value of securities available-for-sale at September 30, 2017 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.



	September 30, 2017
(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	$	63,576	$	63,646
Due after one year through five years	177,864		180,087
Due after five years through ten years	56,875		58,890
Due after ten years	45,481		47,583
	343,796		350,206
Collateralized mortgage obligations of U.S. government corporations and agencies	115,027		114,895
Residential mortgage-backed securities of U.S. government corporations and agencies	34,452		35,197
Commercial mortgage-backed securities of U.S. government corporations and agencies	193,382		192,604
Debt Securities	686,657		692,902
Marketable equity securities	3,815		5,052
Total	$	690,472	$	697,954

At September 30, 2017 and December 31, 2016, securities with carrying values of $274 million and $342 million were pledged for various regulatory and legal requirements.