Securities (Tables)

12 Months Ended

Dec. 31, 2023

Investments, Debt and Equity Securities [Abstract]

Schedule of Amortized Cost and Fair Value of Available-for-sale and Held-to-maturity Securities

The following table presents the fair value and amortized cost of available-for-sale and held-to-maturity debt securities:

	December 31, 2023									December 31, 2022
(in thousands)	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Estimated Fair Value		Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Estimated Fair Value
Available-for-sale debt securities
U.S. Government sponsored entities and    agencies	$	238,676	$	—	$	(30,310	)	$	208,366	$	259,418	$	2	$	(33,450	)	$	225,970
Residential mortgage-backed securities    and collateralized mortgage obligations    of government sponsored entities and    agencies		1,897,511		47		(267,874	)		1,629,684		2,144,015		25		(297,987	)		1,846,053
Commercial mortgage-backed securities    and collateralized mortgage obligations    of government sponsored entities and    agencies		274,220		11		(5,924	)		268,307		359,811		—		(10,080	)		349,731
Obligations of states and political    subdivisions		78,819		167		(2,861	)		76,125		96,081		244		(4,097	)		92,228
Corporate debt securities		11,962		—		(115	)		11,847		15,451		—		(293	)		15,158
Total available-for-sale debt securities	$	2,501,188	$	225	$	(307,084	)	$	2,194,329	$	2,874,776	$	271	$	(345,907	)	$	2,529,140
Held-to-maturity debt securities
U.S. Government sponsored entities and    agencies	$	3,587	$	—	$	(313	)	$	3,274	$	4,357	$	—	$	(416	)	$	3,941
Residential mortgage-backed securities    and collateralized mortgage obligations    of government sponsored entities and    agencies		38,893		—		(3,017	)		35,876		45,909		—		(3,809	)		42,100
Obligations of states and political    subdivisions		1,136,779		852		(127,518	)		1,010,113		1,177,986		577		(159,975	)		1,018,588
Corporate debt securities		20,268		—		(372	)		19,896		20,377		—		(616	)		19,761
Total held-to-maturity debt securities (1)	$	1,199,527	$	852	$	(131,220	)	$	1,069,159	$	1,248,629	$	577	$	(164,816	)	$	1,084,390
Total debt securities	$	3,700,715	$	1,077	$	(438,304	)	$	3,263,488	$	4,123,405	$	848	$	(510,723	)	$	3,613,530

(1) Total held-to-maturity debt securities are presented on the balance sheet net of their allowance for credit losses totaling $0.2 million at December 31, 2023 and 2022, respectively.

Schedule of Amortized Cost and Fair Value of Available-for-Sale and Held-to-Maturity Securities by Contractual Maturity

The following table presents the amortized cost and fair value of available-for-sale and held-to-maturity debt securities by contractual maturity at December 31, 2023. Actual maturities will differ from contractual maturities because borrowers may have the right to call or prepay debt obligations with or without prepayment penalties. Mortgage-backed securities and collateralized mortgage obligations are classified in the table below based on their contractual maturity date; however, regular principal payments and prepayments of principal are received on a monthly basis.

(in thousands)	Amortized Cost		Fair Value
Available-for-sale debt securities
Less than one year	$	31,309	$	30,868
1-5 years		155,156		151,367
5-10 years		321,197		304,927
Over 10 years		1,993,526		1,707,167
Total available-for-sale debt securities	$	2,501,188	$	2,194,329
Held-to-maturity debt securities
Less than one year	$	19,747	$	19,727
1-5 years		114,612		113,565
5-10 years		482,666		447,074
Over 10 years		582,502		488,793
Total held-to-maturity debt securities	$	1,199,527	$	1,069,159
Total debt securities	$	3,700,715	$	3,263,488

Schedule of Gross Realized Gains and Losses on the Sales and Calls of Securities

The following table presents the gross realized gains and losses on sales and calls of available-for-sale and held-to-maturity debt securities, as well as gains and losses on equity securities from both sales and market adjustments for the years ended December 31, 2023, 2022 and 2021, respectively. All gains and losses presented in the table below are included in the net securities gains (losses) line item of the income statement. For those equity securities relating to the key officer and director deferred compensation plan, the corresponding change in the obligation to the participant is recognized in employee benefits expense.

	For the Years Ended December 31,
(in thousands)	2023			2022			2021
Debt securities:
Gross realized gains	$	65		$	168		$	252
Gross realized losses		(302	)		(21	)		(57	)
Net (losses) gains on debt securities	$	(237	)	$	147		$	195
Equity securities:
Unrealized gains (losses) recognized on securities still held	$	1,137		$	(1,924	)	$	918
Net gains (losses) on equity securities	$	1,137		$	(1,924	)	$	918
Net securities gains (losses)	$	900		$	(1,777	)	$	1,113

Schedule of Allowance for Credit Losses on Held-to-maturity Securities

The following table provides a roll-forward of the allowance for credit losses on held-to-maturity securities for the years ended December 31, 2023, 2022 and 2021, respectively:

	Allowance for Credit Losses By Category
	For the Years Ended December 31, 2023, 2022 and 2021
	Obligations of
	state and			Corporate
	political			debt
(in thousands)	subdivisions			Securities			Total
Beginning balance at January 1, 2023	$	167		$	53		$	220
Current period provision		(7	)		(21	)		(28	)
Write-offs		—			—			—
Recoveries		—			—			—
Ending balance at December 31, 2023	$	160		$	32		$	192
Beginning balance at January 1, 2022	$	174		$	94		$	268
Current period provision		(7	)		(41	)		(48	)
Write-offs		—			—			—
Recoveries		—			—			—
Ending balance at December 31, 2022	$	167		$	53		$	220
Beginning balance at January 1, 2021	$	130		$	196		$	326
Current period provision		44			(102	)		(58	)
Write-offs		—			—			—
Recoveries		—			—			—
Ending balance at December 31, 2021	$	174		$	94		$	268

Schedule of Unrealized Losses on Investment Securities

The following tables provide information on unrealized losses on available-for-sale debt securities that have been in an unrealized loss position for less than twelve months and twelve months or more, for which an allowance for credit losses has not been recorded as of December 31, 2023 and 2022, respectively:

	December 31, 2023
	Less than 12 months							12 months or more							Total
(dollars in thousands)	Fair Value		Unrealized Losses			# of Securities		Fair Value		Unrealized Losses			# of Securities		Fair Value		Unrealized Losses			# of Securities
U.S. Government sponsored    entities and agencies	$	18	$	(1	)		1	$	208,348	$	(30,309	)		45	$	208,366	$	(30,310	)		46
Residential mortgage-backed    securities and collateralized    mortgage obligations of    government sponsored    entities and agencies		—		—			—		1,625,144		(267,874	)		467		1,625,144		(267,874	)		467
Commercial mortgage-backed    securities and collateralized    mortgage obligations of    government sponsored    entities and agencies		5,520		(31	)		1		251,765		(5,893	)		60		257,285		(5,924	)		61
Obligations of states and    political subdivisions		10,387		(86	)		19		49,002		(2,775	)		79		59,389		(2,861	)		98
Corporate debt securities		4,482		(18	)		3		7,365		(97	)		3		11,847		(115	)		6
Total temporarily impaired    securities	$	20,407	$	(136	)		24	$	2,141,624	$	(306,948	)		654	$	2,162,031	$	(307,084	)		678

	December 31, 2022
	Less than 12 months							12 months or more							Total
(dollars in thousands)	Fair Value		Unrealized Losses			# of Securities		Fair Value		Unrealized Losses			# of Securities		Fair Value		Unrealized Losses			# of Securities
U.S. Government sponsored    entities and agencies	$	107,011	$	(8,435	)		35	$	118,779	$	(25,015	)		13	$	225,790	$	(33,450	)		48
Residential mortgage-backed    securities and collateralized    mortgage obligations of    government sponsored    entities and agencies		514,789		(39,246	)		294		1,328,906		(258,741	)		202		1,843,695		(297,987	)		496
Commercial mortgage-backed    securities and collateralized    mortgage obligations of    government sponsored    entities and agencies		190,189		(5,106	)		38		159,543		(4,974	)		36		349,732		(10,080	)		74
Obligations of states and    political subdivisions		67,822		(1,815	)		128		7,812		(2,282	)		10		75,634		(4,097	)		138
Corporate debt securities		7,225		(226	)		3		4,433		(67	)		3		11,658		(293	)		6
Total temporarily impaired    securities	$	887,036	$	(54,828	)		498	$	1,619,473	$	(291,079	)		264	$	2,506,509	$	(345,907	)		762