INVESTMENTS (Tables)

6 Months Ended

Jun. 30, 2018

Investments, Debt and Equity Securities [Abstract]

Summary of Held-To-Maturity and Available-For-Sale Investment Securities

The following is a summary of held-to-maturity and available-for-sale investment securities as of June 30, 2018:

	Held-to-maturity									Available-for-sale
(Dollars in thousands)	Amortized cost		Unrecognized gain		Unrecognized loss			Fair value		Amortized cost		Unrealized gain		Unrealized loss			Fair value
U.S. Treasuries	$	0	$	0	$	0		$	0	$	98	$	0	$	(3	)	$	95
Securities of U.S. government agencies and corporations	0		0		0			0		34,896		84		(452		)	34,528
Mortgage-backed securities - residential	31,857		0		(1,515		)	30,342		644,358		1,314		(10,152		)	635,520
Mortgage-backed securities - commercial	152,906		13		(5,503		)	147,416		290,930		106		(5,059		)	285,977
Collateralized mortgage obligations	13,982		0		(675		)	13,307		873,923		965		(10,313		)	864,575
Obligations of state and other political subdivisions	245,212		936		(1,428		)	244,720		250,993		2,214		(1,910		)	251,297
Asset-backed securities	0		0		0			0		492,702		879		(1,354		)	492,227
Other securities	0		0		0			0		89,357		1,938		(605		)	90,690
Total	$	443,957	$	949	$	(9,121	)	$	435,785	$	2,677,257	$	7,500	$	(29,848	)	$	2,654,909

The following is a summary of held-to-maturity and available-for-sale investment securities as of December 31, 2017:

	Held-to-maturity									Available-for-sale
(Dollars in thousands)	Amortized cost		Unrecognized gain		Unrecognized loss			Fair value		Amortized cost		Unrealized gain		Unrealized loss			Fair value
U.S. Treasuries	$	0	$	0	$	0		$	0	$	98	$	0	$	(1	)	$	97
Securities of U.S. government agencies and corporations	11,168		0		(76		)	11,092		15,695		220		0			15,915
Mortgage-backed securities - residential	162,093		2,042		(1,535		)	162,600		290,793		849		(2,599		)	289,043
Mortgage-backed securities - commercial	255,027		1,372		(3,000		)	253,399		150,356		164		(1,417		)	149,103
Collateralized mortgage obligations	143,545		354		(1,602		)	142,297		306,095		1,158		(1,861		)	305,392
Obligations of state and other political subdivisions	82,175		1,804		(266		)	83,713		124,269		2,162		(676		)	125,755
Asset-backed securities	0		0		0			0		377,655		1,628		(306		)	378,977
Other securities	0		0		0			0		83,266		2,147		(287		)	85,126
Total	$	654,008	$	5,572	$	(6,479	)	$	653,101	$	1,348,227	$	8,328	$	(7,147	)	$	1,349,408

Summary of Investment Securities by Estimated Maturity

The following table provides a summary of investment securities by contractual maturity as of June 30, 2018, except for residential and commercial mortgage-backed securities, collateralized mortgage obligations and asset-backed securities, which are shown as single totals due to the unpredictability of the timing in principal repayments.

	Held-to-maturity				Available-for-sale
(Dollars in thousands)	Amortized cost		Fair value		Amortized cost		Fair value
By Contractual Maturity:
Due in one year or less	$	0	$	0	$	4,125	$	4,123
Due after one year through five years	275		279		70,801		70,802
Due after five years through ten years	15,799		15,778		140,577		142,222
Due after ten years	229,138		228,663		159,841		159,463
Mortgage-backed securities - residential	31,857		30,342		644,358		635,520
Mortgage-backed securities - commercial	152,906		147,416		290,930		285,977
Collateralized mortgage obligations	13,982		13,307		873,923		864,575
Asset-backed securities	0		0		492,702		492,227
Total	$	443,957	$	435,785	$	2,677,257	$	2,654,909

Age of Gross Unrealized Losses and Associated Fair Value by Investment Category

The following tables provide the fair value and gross unrealized losses on investment securities in an unrealized loss position, aggregated by investment category and the length of time the individual securities have been in a continuous loss position:

	June 30, 2018
	Less than 12 months					12 months or more					Total
(Dollars in thousands)	Fair value		Unrealized loss			Fair value		Unrealized loss			Fair value		Unrealized loss
U.S. Treasuries	$	95	$	(3	)	$	0	$	0		$	95	$	(3	)
Securities of U.S. Government agencies and corporations	19,890		(311		)	5,379		(141		)	25,269		(452		)
Mortgage-backed securities - residential	488,725		(5,650		)	129,218		(6,017		)	617,943		(11,667		)
Mortgage-backed securities - commercial	278,366		(5,414		)	88,624		(5,148		)	366,990		(10,562		)
Collateralized mortgage obligations	628,667		(6,910		)	99,142		(4,078		)	727,809		(10,988		)
Obligations of state and other political subdivisions	186,269		(2,195		)	27,441		(1,143		)	213,710		(3,338		)
Asset-backed securities	219,064		(1,215		)	13,591		(139		)	232,655		(1,354		)
Other securities	17,299		(226		)	7,571		(379		)	24,870		(605		)
Total	$	1,838,375	$	(21,924	)	$	370,966	$	(17,045	)	$	2,209,341	$	(38,969	)

	December 31, 2017
	Less than 12 months					12 months or more					Total
	Fair		Unrealized			Fair		Unrealized			Fair		Unrealized
(Dollars in thousands)	value		loss			value		loss			value		loss
U.S. Treasuries	$	97	$	(1	)	$	0	$	0		$	97	$	(1	)
Securities of U.S. Government agencies and corporations	11,092		(76		)	0		0			11,092		(76		)
Mortgage-backed securities - residential	175,183		(1,109		)	108,782		(3,025		)	283,965		(4,134		)
Mortgage-backed securities - commercial	132,818		(1,713		)	72,139		(2,704		)	204,957		(4,417		)
Collateralized mortgage obligations	164,909		(1,138		)	101,436		(2,325		)	266,345		(3,463		)
Obligations of state and other political subdivisions	38,450		(507		)	21,639		(435		)	60,089		(942		)
Asset-backed securities	44,941		(200		)	24,396		(106		)	69,337		(306		)
Other securities	2,605		(1		)	7,124		(286		)	9,729		(287		)
Total	$	570,095	$	(4,745	)	$	335,516	$	(8,881	)	$	905,611	$	(13,626	)