INVESTMENTS (Tables)

12 Months Ended

Dec. 31, 2023

Investments, Debt and Equity Securities [Abstract]

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

The following is table a summary of HTM and AFS investment securities as of December 31, 2023:

	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	$	34,904	$	0	$	(3,661)	$	31,243
Securities of U.S. government agencies and corporations	0		0		0		0		81,790		0		(12,010)		69,780
Mortgage-backed securities - residential	0		0		0		0		744,546		2,034		(85,532)		661,048
Mortgage-backed securities - commercial	32,926		0		(4,628)		28,298		543,134		7		(35,911)		507,230
Collateralized mortgage obligations	7,970		0		(539)		7,431		478,744		181		(60,277)		418,648
Obligations of state and other political subdivisions	8,175		130		(215)		8,090		765,223		1,614		(114,320)		652,517
Asset-backed securities	0		0		0		0		600,055		6		(39,813)		560,248
Other securities	31,250		0		(3,381)		27,869		134,208		0		(13,796)		120,412
Total	$	80,321	$	130	$	(8,763)	$	71,688	$	3,382,604	$	3,842	$	(365,320)	$	3,021,126

The following is a summary of HTM and AFS investment securities as of December 31, 2022:

	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	$	37,312	$	0	$	(4,616)	$	32,696
Securities of U.S. government agencies and corporations	0		0		0		0		80,382		0		(13,914)		66,468
Mortgage-backed securities - residential	0		0		0		0		747,478		47		(97,462)		650,063
Mortgage-backed securities - commercial	35,363		0		(4,114)		31,249		676,934		2		(47,374)		629,562
Collateralized mortgage obligations	9,280		0		(827)		8,453		538,970		181		(61,439)		477,712
Obligations of state and other political subdivisions	8,128		105		(201)		8,032		832,066		565		(124,168)		708,463
Asset-backed securities	0		0		0		0		772,261		39		(60,975)		711,325
Other securities	31,250		0		(2,499)		28,751		142,015		0		(8,656)		133,359
Total	$	84,021	$	105	$	(7,641)	$	76,485	$	3,827,418	$	834	$	(418,604)	$	3,409,648

Summary of Investment Securities by Estimated Maturity

The following table provides a summary of investment securities by contractual maturity as of December 31, 2023, 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
Due in one year or less	$	0	$	0	$	4,729	$	4,721
Due after one year through five years	4,595		4,690		161,803		148,088
Due after five years through ten years	33,130		29,781		225,993		195,230
Due after ten years	1,700		1,488		623,600		525,913
Mortgage-backed securities - residential	0		0		744,546		661,048
Mortgage-backed securities - commercial	32,926		28,298		543,134		507,230
Collateralized mortgage obligations	7,970		7,431		478,744		418,648
Asset-backed securities	0		0		600,055		560,248
Total	$	80,321	$	71,688	$	3,382,604	$	3,021,126

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

The following tables provide the fair value and gross unrealized losses on AFS investment securities in an unrealized loss position for which an allowance for credit losses was not recorded, aggregated by investment category and the length of time the individual securities have been in a continuous loss position:

	December 31, 2023
	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	$	0	$	0	$	31,243	$	(3,661)	$	31,243	$	(3,661)
Securities of U.S. government agencies and corporations	0		0		69,780		(12,010)		69,780		(12,010)
Mortgage-backed securities - residential	31,892		(483)		538,863		(85,049)		570,755		(85,532)
Mortgage-backed securities - commercial	1,772		(11)		495,451		(35,900)		497,223		(35,911)
Collateralized mortgage obligations	10,699		(157)		393,884		(60,120)		404,583		(60,277)
Obligations of state and other political subdivisions	15,155		(132)		562,740		(114,188)		577,895		(114,320)
Asset-backed securities	6,853		(15)		542,029		(39,798)		548,882		(39,813)
Other securities	14,605		(396)		105,807		(13,400)		120,412		(13,796)
Total	$	80,976	$	(1,194)	$	2,739,797	$	(364,126)	$	2,820,773	$	(365,320)

	December 31, 2022
	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	$	2,383	$	(46)	$	30,313	$	(4,570)	$	32,696	$	(4,616)
Securities of U.S. Government agencies and corporations	0		0		66,468		(13,914)		66,468		(13,914)
Mortgage-backed securities - residential	195,972		(10,413)		443,415		(87,049)		639,387		(97,462)
Mortgage-backed securities - commercial	440,207		(18,823)		175,530		(28,551)		615,737		(47,374)
Collateralized mortgage obligations	199,138		(12,453)		269,242		(48,986)		468,380		(61,439)
Obligations of state and other political subdivisions	295,913		(31,196)		368,673		(92,972)		664,586		(124,168)
Asset-backed securities	250,946		(9,410)		422,090		(51,565)		673,036		(60,975)
Other securities	118,262		(6,865)		9,959		(1,791)		128,221		(8,656)
Total	$	1,502,821	$	(89,206)	$	1,785,690	$	(329,398)	$	3,288,511	$	(418,604)

The following tables provide the fair value and gross unrealized losses on HTM investment securities in an unrealized loss position for which an allowance for credit losses was not recorded, aggregated by investment category and the length of time the individual securities have been in a continuous loss position:

	December 31, 2023
	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	$	0	$	0	$	0	$	0	$	0	$	0
Securities of U.S. government agencies and corporations	0		0		0		0		0		0
Mortgage-backed securities - residential	0		0		0		0		0		0
Mortgage-backed securities - commercial	0		0		28,298		(4,628)		28,298		(4,628)
Collateralized mortgage obligations	0		0		7,431		(539)		7,431		(539)
Obligations of state and other political subdivisions	1,128		(3)		1,488		(212)		2,616		(215)
Asset-backed securities	0		0		0		0		0		0
Other securities	0		0		27,869		(3,381)		27,869		(3,381)
Total	$	1,128	$	(3)	$	65,086	$	(8,760)	$	66,214	$	(8,763)

	December 31, 2022
	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	$	0	$	0	$	0	$	0	$	0	$	0
Securities of U.S. government agencies and corporations	0		0		0		0		0		0
Mortgage-backed securities - residential	0		0		0		0		0		0
Mortgage-backed securities - commercial	17,656		(2,197)		13,593		(1,917)		31,249		(4,114)
Collateralized mortgage obligations	6,317		(606)		2,136		(221)		8,453		(827)
Obligations of state and other political subdivisions	5,160		(201)		0		0		5,160		(201)
Asset-backed securities	0		0		0		0		0		0
Other securities	7,081		(418)		21,670		(2,081)		28,751		(2,499)
Total	$	36,214	$	(3,422)	$	37,399	$	(4,219)	$	73,613	$	(7,641)