INVESTMENTS (Tables)

3 Months Ended

Mar. 31, 2022

Investments, Debt and Equity Securities [Abstract]

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

The following is a summary of HTM and AFS investment securities as of March 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	$	34,967	$	1	$	(2,244)	$	32,724
Securities of U.S. government agencies and corporations	0		0		0		0		79,338		0		(5,665)		73,673
Mortgage-backed securities - residential	0		0		0		0		709,888		602		(43,418)		667,072
Mortgage-backed securities - commercial	42,211		0		(1,403)		40,808		754,978		355		(17,903)		737,430
Collateralized mortgage obligations	10,780		0		(287)		10,493		621,240		1,277		(27,662)		594,855
Obligations of state and other political subdivisions	8,356		317		0		8,673		1,071,171		10,441		(49,260)		1,032,352
Asset-backed securities	0		0		0		0		713,587		361		(21,321)		692,627
Other securities	31,250		0		(1,223)		30,027		128,000		710		(1,561)		127,149
Total	$	92,597	$	317	$	(2,913)	$	90,001	$	4,113,169	$	13,747	$	(169,034)	$	3,957,882

The following is a summary of HTM and AFS investment securities as of December 31, 2021:

	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	$	34,961	$	4	$	(189)	$	34,776
Securities of U.S. government agencies and corporations	0		0		0		0		78,998		248		(129)		79,117
Mortgage-backed securities - residential	0		0		0		0		728,050		6,635		(10,548)		724,137
Mortgage-backed securities - commercial	46,362		651		0		47,013		729,948		4,294		(2,352)		731,890
Collateralized mortgage obligations	11,882		221		0		12,103		696,258		7,979		(6,497)		697,740
Obligations of state and other political subdivisions	8,926		915		0		9,841		1,058,735		35,591		(8,594)		1,085,732
Asset-backed securities	0		0		0		0		720,638		1,521		(2,578)		719,581
Other securities	31,250		176		(485)		30,941		133,001		2,114		(242)		134,873
Total	$	98,420	$	1,963	$	(485)	$	99,898	$	4,180,589	$	58,386	$	(31,129)	$	4,207,846

Summary of Investment Securities by Estimated Maturity

The following table provides a summary of investment securities by contractual maturity as of March 31, 2022, 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	$	11,539	$	11,556
Due after one year through five years	1,072		1,092		89,910		89,562
Due after five years through ten years	36,271		35,340		357,140		348,300
Due after ten years	2,263		2,268		854,887		816,480
Mortgage-backed securities - residential	0		0		709,888		667,072
Mortgage-backed securities - commercial	42,211		40,808		754,978		737,430
Collateralized mortgage obligations	10,780		10,493		621,240		594,855
Asset-backed securities	0		0		713,587		692,627
Total	$	92,597	$	90,001	$	4,113,169	$	3,957,882

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 for which an ACL has not been recorded, aggregated by investment category and the length of time the individual securities have been in a continuous loss position:

	March 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	$	32,624	$	(2,244)	$	0	$	0	$	32,624	$	(2,244)
Securities of U.S. Government agencies and corporations	73,673		(5,665)		0		0		73,673		(5,665)
Mortgage-backed securities - residential	388,740		(26,406)		187,705		(17,012)		576,445		(43,418)
Mortgage-backed securities - commercial	636,688		(16,831)		28,585		(2,475)		665,273		(19,306)
Collateralized mortgage obligations	449,683		(22,616)		52,838		(5,333)		502,521		(27,949)
Obligations of state and other political subdivisions	496,869		(38,448)		132,317		(10,812)		629,186		(49,260)
Asset-backed securities	625,241		(19,707)		22,710		(1,614)		647,951		(21,321)
Other securities	98,897		(2,103)		11,569		(681)		110,466		(2,784)
Total	$	2,802,415	$	(134,020)	$	435,724	$	(37,927)	$	3,238,139	$	(171,947)

	December 31, 2021
	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	$	24,755	$	(190)	$	0	$	0	$	24,755	$	(190)
Securities of U.S. Government agencies and corporations	17,382		(128)		0		0		17,382		(128)
Mortgage-backed securities - residential	459,098		(8,375)		78,090		(2,173)		537,188		(10,548)
Mortgage-backed securities - commercial	205,520		(2,149)		13,818		(203)		219,338		(2,352)
Collateralized mortgage obligations	369,318		(6,110)		12,485		(387)		381,803		(6,497)
Obligations of state and other political subdivisions	380,735		(7,543)		55,568		(1,051)		436,303		(8,594)
Asset-backed securities	482,118		(2,578)		0		0		482,118		(2,578)
Other securities	31,896		(354)		11,877		(373)		43,773		(727)
Total	$	1,970,822	$	(27,427)	$	171,838	$	(4,187)	$	2,142,660	$	(31,614)