3. 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			Fair Value
March 31, 2017
Held-to-Maturity:
Mortgage-backed securities:
Residential - U.S. Government-sponsored entities	$	118,372	$	87	$	(2,262	)	$	116,197
Commercial - U.S. Government-sponsored entities	93,054		—		(1,070		)	91,984
Total	$	211,426	$	87	$	(3,332	)	$	208,181

Available-for-Sale:
Debt securities:
States and political subdivisions	$	183,547	$	2,942	$	(1,068	)	$	185,421
Corporate securities	93,210		1,230		(105		)	94,335
Mortgage-backed securities:
Residential - U.S. Government-sponsored entities	826,491		3,466		(8,585		)	821,372
Commercial - U.S. Government agencies and sponsored entities	13,419		41		—			13,460
Residential - Non-government agencies	49,848		507		(838		)	49,517
Commercial - Non-government agencies	135,201		2,980		(79		)	138,102
Other	584		98		—			682
Total	$	1,302,300	$	11,264	$	(10,675	)	$	1,302,889



(dollars in thousands)	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Fair Value
December 31, 2016
Held-to-Maturity:
Mortgage-backed securities:
Residential - U.S. Government-sponsored entities	$	124,082	$	92	$	(2,474	)	$	121,700
Commercial - U.S. Government-sponsored entities	93,586		—		(920		)	92,666
Total	$	217,668	$	92	$	(3,394	)	$	214,366

Available-for-Sale:
Debt securities:
States and political subdivisions	$	184,836	$	2,002	$	(1,797	)	$	185,041
Corporate securities	98,596		974		(181		)	99,389
Mortgage-backed securities:
Residential - U.S. Government-sponsored entities	775,803		3,698		(9,515		)	769,986
Residential - Non-government agencies	51,681		627		(761		)	51,547
Commercial - Non-government agencies	135,248		2,387		(411		)	137,224
Other	564		96		—			660
Total	$	1,246,728	$	9,784	$	(12,665	)	$	1,243,847

The amortized cost and estimated fair value of investment securities at March 31, 2017 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, 2017
(dollars in thousands)	Amortized Cost		Fair Value
Held-to-Maturity:
Mortgage-backed securities:
Residential - U.S. Government-sponsored entities	$	118,372	$	116,197
Commercial - U.S. Government-sponsored entities	93,054		91,984
Total	$	211,426	$	208,181

Available-for-Sale:
Due in one year or less	$	6,172	$	6,241
Due after one year through five years	147,830		149,514
Due after five years through ten years	52,250		52,852
Due after ten years	70,505		71,149

Mortgage-backed securities:
Residential - U.S. Government-sponsored entities	826,491		821,372
Commercial - U.S. Government agencies and sponsored entities	13,419		13,460
Residential - Non-government agencies	49,848		49,517
Commercial - Non-government agencies	135,201		138,102
Other	584		682
Total	$	1,302,300	$	1,302,889

We did not sell any available-for-sale securities during the three months ended March 31, 2017 and 2016.

Investment securities of $1.10 billion and $1.05 billion at March 31, 2017 and December 31, 2016, 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 191 and 242 investment securities which were in an unrealized loss position at March 31, 2017 and December 31, 2016, 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, 2017
Debt securities:
States and political subdivisions	$	58,442	$	(1,068	)	$	—	$	—		$	58,442	$	(1,068	)
Corporate securities	5,353		(105		)	—		—			5,353		(105		)
Mortgage-backed securities:
Residential - U.S. Government-sponsored entities	609,420		(10,516		)	17,746		(331		)	627,166		(10,847		)
Residential - Non-government agencies	29,289		(838		)	—		—			29,289		(838		)
Commercial - U.S. Government agencies and sponsored entities	81,035		(1,070		)	—		—			81,035		(1,070		)
Commercial - Non-government agencies	28,650		(79		)	—		—			28,650		(79		)
Total temporarily impaired securities	$	812,189	$	(13,676	)	$	17,746	$	(331	)	$	829,935	$	(14,007	)



	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, 2016
Debt securities:
States and political subdivisions	$	85,288	$	(1,797	)	$	—	$	—		$	85,288	$	(1,797	)
Corporate securities	20,357		(181		)	—		—			20,357		(181		)
Mortgage-backed securities:
Residential - U.S. Government-sponsored entities	648,923		(11,766		)	3,978		(223		)	652,901		(11,989		)
Residential - Non-government agencies	30,596		(761		)	—		—			30,596		(761		)
Commercial - U.S. Government-sponsored entities	92,666		(920		)	—		—			92,666		(920		)
Commercial - Non-government agencies	52,880		(411		)	—		—			52,880		(411		)
Total temporarily impaired securities	$	930,710	$	(15,836	)	$	3,978	$	(223	)	$	934,688	$	(16,059	)

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.