INVESTMENT SECURITIES

A summary of held-to-maturity and available-for-sale investment securities are as follows:



(dollars in thousands)	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Estimated Fair Value
March 31, 2016
Held-to-Maturity:
Mortgage-backed securities:
Residential - U.S. Government-sponsored entities	$	146,497	$	242	$	(497	)	$	146,242
Commercial - U.S. Government-sponsored entities	95,100		1,730		—			96,830
Total	$	241,597	$	1,972	$	(497	)	$	243,072

Available-for-Sale:
Debt securities:
States and political subdivisions	$	186,878	$	5,280	$	(356	)	$	191,802
Corporate securities	107,315		2,481		—			109,796
Mortgage-backed securities:
Residential - U.S. Government-sponsored entities	782,288		10,358		(1,000		)	791,646
Residential - Non-government agencies	62,274		1,966		—			64,240
Commercial - Non-government agencies	135,392		5,578		—			140,970
Other	653		69		—			722
Total	$	1,274,800	$	25,732	$	(1,356	)	$	1,299,176



(dollars in thousands)	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Estimated Fair Value
December 31, 2015
Held-to-Maturity:
Mortgage-backed securities:
Residential - U.S. Government-sponsored entities	$	152,315	$	123	$	(2,915	)	$	149,523
Commercial - U.S. Government-sponsored entities	95,602		—		(989		)	94,613
Total	$	247,917	$	123	$	(3,904	)	$	244,136

Available-for-Sale:
Debt securities:
States and political subdivisions	$	187,552	$	3,819	$	(898	)	$	190,473
Corporate securities	107,721		1,077		(227		)	108,571
Mortgage-backed securities:
Residential - U.S. Government-sponsored entities	771,657		5,885		(5,633		)	771,909
Residential - Non-government agencies	64,286		733		(987		)	64,032
Commercial - Non-government agencies	135,439		2,033		(1,118		)	136,354
Other	848		68		—			916
Total	$	1,267,503	$	13,615	$	(8,863	)	$	1,272,255

The amortized cost and estimated fair value of investment securities at March 31, 2016 by contractual maturity are shown below. Expected maturities will 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		Estimated Fair Value
Held-to-Maturity:
Mortgage-backed securities:
Residential - U.S. Government-sponsored entities	$	146,497	$	146,242
Commercial - U.S. Government-sponsored entities	95,100		96,830
Total	$	241,597	$	243,072

Available-for-Sale:
Due in one year or less	$	21,256	$	21,454
Due after one year through five years	104,442		107,027
Due after five years through ten years	78,885		81,183
Due after ten years	89,610		91,934

Mortgage-backed securities:
Residential - U.S. Government-sponsored entities	782,288		791,646
Residential - Non-government agencies	62,274		64,240
Commercial - Non-government agencies	135,392		140,970
Other	653		722
Total	$	1,274,800	$	1,299,176

We did not sell any available-for-sale securities during the first quarter of 2016 and 2015.

Investment securities of $1.0 billion and $1.0 billion at March 31, 2016 and December 31, 2015, respectively, were pledged to secure public funds on deposit and other long-term debt and short-term borrowings.

Provided below is a summary of the 51 and 155 investment securities which were in an unrealized loss position at March 31, 2016 and December 31, 2015, respectively, segregated by continuous length of impairment.



	Less Than 12 Months					12 Months or Longer					Total
(dollars in thousands)	Fair Value		Unrealized Losses			Fair Value		Unrealized Losses			Fair Value		Unrealized Losses
March 31, 2016
Debt securities:
States and political subdivisions	$	6,786	$	(88	)	$	8,640	$	(268	)	$	15,426	$	(356	)
Mortgage-backed securities:
Residential - U.S. Government-sponsored entities	44,973		(120		)	254,673		(1,377		)	299,646		(1,497		)
Total temporarily impaired securities	$	51,759	$	(208	)	$	263,313	$	(1,645	)	$	315,072	$	(1,853	)



	Less Than 12 Months					12 Months or Longer					Total
(dollars in thousands)	Fair Value		Unrealized Losses			Fair Value		Unrealized Losses			Fair Value		Unrealized Losses
December 31, 2015
Debt securities:
States and political subdivisions	$	30,481	$	(532	)	$	12,576	$	(366	)	$	43,057	$	(898	)
Corporate securities	32,977		(227		)	—		—			32,977		(227		)
Mortgage-backed securities:
Residential - U.S. Government-sponsored entities	507,525		(6,241		)	88,271		(2,307		)	595,796		(8,548		)
Residential - Non-government agencies	37,975		(987		)	—		—			37,975		(987		)
Commercial - U.S. Government-sponsored entities	94,613		(989		)	—		—			94,613		(989		)
Commercial - Non-government agencies	62,555		(961		)	4,644		(157		)	67,199		(1,118		)
Total temporarily impaired securities	$	766,126	$	(9,937	)	$	105,491	$	(2,830	)	$	871,617	$	(12,767	)

Other-Than-Temporary Impairment (“OTTI”)

Unrealized losses for all investment securities are reviewed to determine whether the losses are deemed “other-than-temporary.” Investment securities are evaluated for OTTI on at least a quarterly basis and more frequently when economic or market conditions warrant such an evaluation to determine whether a decline in their value below amortized cost is other-than-temporary. In conducting this assessment, we evaluate a number of factors including, but not limited to:


•	The length of time and the extent to which fair value has been less than the amortized cost basis;


•	Adverse conditions specifically related to the security, an industry, or a geographic area;


•	The historical and implied volatility of the fair value of the security;


•	The payment structure of the debt security and the likelihood of the issuer being able to make payments;


•	Failure of the issuer to make scheduled interest or principal payments;


•	Any rating changes by a rating agency; and


•	Recoveries or additional declines in fair value subsequent to the balance sheet date.

The term “other-than-temporary” is not intended to indicate that the decline is permanent, but indicates that the prospects for a near-term recovery of value are not necessarily favorable, or that there is a general lack of evidence to support a realizable value equal to or greater than the carrying value of the investment. Once a decline in value is determined to be other-than-temporary, the value of the security is reduced and a corresponding charge to earnings is recognized for anticipated credit losses.

Because we have no intent to sell securities in an unrealized loss position and it is not more likely than not that we will be required to sell such securities before recovery of its amortized cost basis, we do not consider our investments to be other-than-temporarily impaired.