INVESTMENT SECURITIES (Tables)

12 Months Ended

Dec. 31, 2017

Investments, Debt and Equity Securities [Abstract]

Summary of available for sale and held to maturity investment securities



	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Fair Value
	(Dollars in thousands)
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 held-to-maturity investment securities	$	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 sponsored entities	51,681		627		(761		)	51,547
Commercial-Non-government sponsored entities	135,248		2,387		(411		)	137,224
Other	564		96		—			660
Total available-for-sale investment securities	$	1,246,728	$	9,784	$	(12,665	)	$	1,243,847

A summary of our investment securities portfolio as of December 31, 2017 and 2016 is as follows:



	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Fair Value
	(Dollars in thousands)
December 31, 2017
Held-to-Maturity:
Mortgage-backed securities:
Residential-U.S. Government sponsored entities	$	100,279	$	106	$	(2,222	)	$	98,163
Commercial-U.S. Government sponsored entities	91,474		—		(436		)	91,038
Total held-to-maturity investment securities	$	191,753	$	106	$	(2,658	)	$	189,201

Available-for-Sale:
Debt securities:
States and political subdivisions	$	178,459	$	2,041	$	(719	)	$	179,781
Corporate securities	73,772		582		(76		)	74,278
U.S. Treasury obligations and direct obligations of U.S Government agencies	25,519		60		(69		)	25,510
Mortgage-backed securities:
Residential-U.S. Government sponsored entities	808,242		2,230		(9,789		)	800,683
Residential-Non-government sponsored entities	45,679		1,084		—			46,763
Commercial-U.S. Government agencies and sponsored entities	40,012		—		(287		)	39,725
Commercial-Non-government sponsored entities	135,058		2,461		(193		)	137,326
Other	686		139		—			825
Total available-for-sale investment securities	$	1,307,427	$	8,597	$	(11,133	)	$	1,304,891

Schedule of amortized cost and estimated fair value of investment securities by contractual maturity

The amortized cost and estimated fair value of our investment securities at December 31, 2017 by contractual maturity are shown below. Actual maturities may differ from contractual maturities as issuers have the right to call or prepay obligations with or without call or prepayment penalties. Securities not due at a single maturity date are shown separately.



	December 31, 2017
	Amortized Cost		Fair Value
	(Dollars in thousands)
Held-to-Maturity:
Mortgage-backed securities:
Residential-U.S. Government-sponsored entities	$	100,279	$	98,163
Commercial-U.S. Government-sponsored entities	91,474		91,038
Total held-to-maturity investment securities	$	191,753	$	189,201

Available-for-Sale:
Due in one year or less	$	8,796	$	8,799
Due after one year through five years	165,356		166,447
Due after five years through ten years	40,762		41,166
Due after ten years	62,836		63,157
Mortgage-backed securities
Residential-U.S. Government-sponsored entities	808,242		800,683
Residential-Non-government agencies	45,679		46,763
Commercial-U.S. Government agencies and sponsored entities	40,012		39,725
Commercial-Non-government agencies	135,058		137,326
Other	686		825
Total available-for-sale investment securities	$	1,307,427	$	1,304,891

Schedule of investment securities in an unrealized loss position

The following table summarizes securities which were in an unrealized or unrecognized loss position at December 31, 2017 and 2016, aggregated by major security type and length of time in a continuous unrealized or unrecognized loss position:



	Less Than 12 Months					12 Months or Longer					Total
Description of Securities	Fair Value		Unrealized Losses			Fair Value		Unrealized Losses			Fair Value		Unrealized Losses
	(Dollars in thousands)
December 31, 2017
Debt securities:
States and political subdivisions	$	53,811	$	(305	)	$	15,403	$	(414	)	$	69,214	$	(719	)
Corporate securities	—		—			5,307		(76		)	5,307		(76		)
U.S. Treasury obligations and direct obligations of U.S Government agencies	10,740		(69		)	—		—			10,740		(69		)

Mortgage-backed securities:
Residential-U.S. Government sponsored entities	335,883		(3,372		)	340,219		(8,639		)	676,102		(12,011		)
Commercial-U.S. Government sponsored entities	130,763		(723		)	—		—			130,763		(723		)
Commercial-Non-government sponsored entities	28,490		(193		)	—		—			28,490		(193		)
Total temporarily impaired securities	$	559,687	$	(4,662	)	$	360,929	$	(9,129	)	$	920,616	$	(13,791	)



	Less Than 12 Months					12 Months or Longer					Total
Description of Securities	Fair Value		Unrealized Losses			Fair Value		Unrealized Losses			Fair Value		Unrealized Losses
	(Dollars in thousands)
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 sponsored entities	30,596		(761		)	—		—			30,596		(761		)
Commercial-U.S. Government sponsored entities	92,666		(920		)	—		—			92,666		(920		)
Commercial-Non-government sponsored entities	52,880		(411		)	—		—			52,880		(411		)
Total temporarily impaired securities	$	930,710	$	(15,836	)	$	3,978	$	(223	)	$	934,688	$	(16,059	)