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INVESTMENT SECURITIES (Tables)
 3 Months Ended
Mar. 31, 2025
Investments, Debt and Equity Securities [Abstract]  
Summary of Amortized Cost, Gross Unrealized Gains and Losses and Approximate Fair Value of Investment Securities
The following tables summarize the amortized cost, gross unrealized gains and losses and approximate fair value of investment securities available for sale as of March 31, 2025 and December 31, 2024.

Amortized
Cost		Gross Unrealized
Gains		Gross Unrealized
Losses		Fair
Value
Available for sale at March 31, 2025    
U.S. Government-sponsored agency securities$93,758 $— $13,832 $79,926 
State and municipal994,697 56 149,570 845,183 
U.S. Government-sponsored mortgage-backed securities517,564 996 77,614 440,946 
Corporate obligations12,964 — 530 12,434 
Total available for sale$1,618,983 $1,052 $241,546 $1,378,489 
Amortized
Cost		Gross Unrealized
Gains		Gross Unrealized
Losses		Fair
Value
Available for sale at December 31, 2024
U.S. Government-sponsored agency securities$95,462 $— $16,081 $79,381 
State and municipal996,541 19 133,386 863,174 
U.S. Government-sponsored mortgage-backed securities519,943 403 88,724 431,622 
Corporate obligations12,960 — 662 12,298 
Total available for sale$1,624,906 $422 $238,853 $1,386,475 
The following tables summarize the amortized cost, gross unrealized gains and losses, approximate fair value and allowance for credit losses on investment securities held to maturity as of March 31, 2025 and December 31, 2024.

Amortized
Cost		Allowance for Credit LossesNet Carrying AmountGross Unrealized
Gains		Gross Unrealized
Losses		Fair
Value
Held to maturity at March 31, 2025
U.S. Government-sponsored agency securities$341,245 $— $341,245 $— $54,935 $286,310 
State and municipal1,079,688 245 1,079,443 148 200,377 879,459 
U.S. Government-sponsored mortgage-backed securities626,444 — 626,444 — 88,705 537,739 
Foreign investment1,500 — 1,500 — 2 1,498 
Total held to maturity$2,048,877 $245 $2,048,632 $148 $344,019 $1,705,006 


Amortized
Cost		Allowance for Credit LossesNet Carrying AmountGross Unrealized
Gains		Gross Unrealized
Losses		Fair
Value
Held to maturity at December 31, 2024
U.S. Government-sponsored agency securities$345,531 $— $345,531 $— $63,112 $282,419 
State and municipal1,085,921 245 1,085,676 299 185,784 900,436 
U.S. Government-sponsored mortgage-backed securities641,513 — 641,513 — 102,343 539,170 
Foreign investment1,500 — 1,500 — 5 1,495 
Total held to maturity$2,074,465 $245 $2,074,220 $299 $351,244 $1,723,520 
Summary of Amortized Cost of Investment Securities Held to Maturity Aggregated by Credit Quality Indicator
On a quarterly basis, the Corporation monitors the credit quality of investment securities held to maturity through the use of credit ratings. The following table summarizes the amortized cost of investment securities held to maturity at March 31, 2025 and December 31, 2024, aggregated by credit quality indicator.
March 31, 2025
U.S. Government-sponsored agency securities (1)
State and municipal
U.S. Government-sponsored mortgage-backed securities (1)
Foreign investmentTotal
Credit Rating:
Aaa$341,245 $120,618 $626,444 $— $1,088,307 
Aa1— 149,926 — — 149,926 
Aa2— 183,052 — — 183,052 
Aa3— 185,117 — — 185,117 
A1— 65,659 — — 65,659 
A2— 20,321 — — 20,321 
Non-rated— 354,995 — 1,500 356,495 
Total$341,245 $1,079,688 $626,444 $1,500 $2,048,877 

December 31, 2024
U.S. Government-sponsored agency securities (1)
State and municipal
U.S. Government-sponsored mortgage-backed securities (1)
Foreign investmentTotal
Credit Rating:
Aaa$345,531 $120,801 $641,513 $— $1,107,845 
Aa1— 148,923 — — 148,923 
Aa2— 184,341 — — 184,341 
Aa3— 185,166 — — 185,166 
A1— 65,665 — — 65,665 
A2— 20,317 — — 20,317 
Non-rated— 360,708 — 1,500 362,208 
Total$345,531 $1,085,921 $641,513 $1,500 $2,074,465 

(1) U.S. Government agency securities and U.S. Government mortgage-backed securities are included within the Aaa credit rating category due to their explicit or implicit government guarantees, which provide a high level of assurance regarding the timely collection of principal and interest payments.
Summary of Investment Securities in a Continuous Unrealized Loss Position
The following tables summarize, as of March 31, 2025 and December 31, 2024, investment securities available for sale in an unrealized loss position for which an allowance for credit losses has not been recorded, aggregated by security type and length of time in a continuous unrealized loss position.
Less than 12 Months12 Months or LongerTotal
Fair
Value		Gross
Unrealized
Losses		Fair
Value		Gross
Unrealized
Losses		Fair
Value		Gross
Unrealized
Losses
Investment securities available for sale at March 31, 2025
U.S. Government-sponsored agency securities$— $— $79,926 $13,832 $79,926 $13,832 
State and municipal14,702 921 828,805 148,649 843,507 149,570 
U.S. Government-sponsored mortgage-backed securities55,519 645 320,890 76,969 376,409 77,614 
Corporate obligations— — 12,402 530 12,402 530 
Total investment securities available for sale$70,221 $1,566 $1,242,023 $239,980 $1,312,244 $241,546 
Less than 12 Months12 Months or LongerTotal
Fair
Value		Gross
Unrealized
Losses		Fair
Value		Gross
Unrealized
Losses		Fair
Value		Gross
Unrealized
Losses
Investment securities available for sale at December 31, 2024
U.S. Government-sponsored agency securities$— $— $79,381 $16,081 $79,381 $16,081 
State and municipal40,398 2,115 820,663 131,271 861,061 133,386 
U.S. Government-sponsored mortgage-backed securities82,724 1,660 318,310 87,064 401,034 88,724 
Corporate obligations— — 12,268 662 12,268 662 
Total investment securities available for sale$123,122 $3,775 $1,230,622 $235,078 $1,353,744 $238,853 
The following tables summarize investment securities available for sale in an unrealized loss position for which an allowance for credit losses has not been recorded, aggregated by security type and the number of securities in the portfolio as of the dates indicated.

Gross
Unrealized
Losses		Number of Securities
Investment securities available for sale at March 31, 2025
U.S. Government-sponsored agency securities$13,832 12
State and municipal149,570 611
U.S. Government-sponsored mortgage-backed securities77,614 114
Corporate obligations530 10
Total investment securities available for sale$241,546 747 
Gross
Unrealized
Losses		Number of Securities
Investment securities available for sale at December 31, 2024
U.S. Government-sponsored agency securities$16,081 12
State and municipal133,386 611
U.S. Government-sponsored mortgage-backed securities88,724 127
Corporate obligations662 10
Total investment securities available for sale$238,853 760 
Summary of Investments in Debt and Equity Securities Reported in the Financial Statements at an Amount Less Than Their Historical Cost
Certain investment securities available for sale are reported in the financial statements at an amount less than their historical cost as indicated in the table below.
March 31, 2025December 31, 2024
Investments available for sale reported at less than historical cost:  
Historical cost$1,553,790 $1,592,597 
Fair value1,312,244 1,353,744 
Gross unrealized losses$241,546 $238,853 
Percentage of the Corporation's investment securities available for sale in an unrealized loss position95.2 %97.6 %
Summary of Amortized Cost and Fair Value of Available for Sale Securities and Held to Maturity Securities by Contractual Maturity
The amortized cost and fair value of investment securities available for sale and held to maturity at March 31, 2025 and December 31, 2024, by contractual maturity are shown below. Expected maturities will differ from contractual maturities because issuers may have the right to call or prepay obligations with or without call or prepayment penalties. Securities not due at a single maturity are shown separately.

Available for SaleHeld to Maturity
Amortized CostFair ValueAmortized CostFair Value
Maturity Distribution at March 31, 2025
Due in one year or less$1,317 $1,316 $5,268 $5,264 
Due after one through five years12,995 12,608 119,035 114,249 
Due after five through ten years178,514 159,809 187,050 165,301 
Due after ten years908,593 763,810 1,111,080 882,453 
 1,101,419 937,543 1,422,433 1,167,267 
U.S. Government-sponsored mortgage-backed securities517,564 440,946 626,444 537,739 
Total investment securities$1,618,983 $1,378,489 $2,048,877 $1,705,006 

Available for SaleHeld to Maturity
Amortized CostFair ValueAmortized CostFair Value
Maturity Distribution at December 31, 2024
Due in one year or less$1,800 $1,795 $5,268 $5,254 
Due after one through five years12,189 11,857 124,004 117,999 
Due after five through ten years168,338 151,467 174,533 154,533 
Due after ten years922,636 789,734 1,129,147 906,564 
 1,104,963 954,853 1,432,952 1,184,350 
U.S. Government-sponsored mortgage-backed securities519,943 431,622 641,513 539,170 
Total investment securities$1,624,906 $1,386,475 $2,074,465 $1,723,520 
Summary of Gross Gains and Losses on Sales and Redemptions of Available for Sale Securities
Gross gains and losses on the sales of investment securities available for sale for the three months ended March 31, 2025 and 2024 are shown below.
Three Months Ended March 31,
20252024
Sales and redemptions of investment securities available for sale:
Gross gains$— $— 
Gross losses(7)(2)
Net gains (losses) on sales and redemptions of investment securities available for sale$(7)$(2)