FAIR VALUES OF FINANCIAL INSTRUMENTS - Estimated Fair Values of Financial Instruments (Details) - USD ($) $ in Thousands	Dec. 31, 2024	Dec. 31, 2023
Assets:
Cash and due from banks	$ 87,616	$ 112,649
Investment securities held to maturity	1,723,520	1,870,374
Loans held for sale	18,663	18,934
Total Fair Value
Assets:
Cash and due from banks	87,616	112,649
Interest-bearing deposits	298,891	436,080
Investment securities held to maturity	1,723,520	1,870,374
Loans held for sale	18,663	18,934
Loans	12,437,523	11,958,301
Federal Home Loan Bank stock	41,690	41,769
Interest receivable	91,829	97,664
Liabilities at December 31:
Deposits	14,513,167	14,811,957
Borrowings:
Securities sold under repurchase agreements	142,865	157,265
Federal Home Loan Bank advances	816,786	707,377
Subordinated debentures and other borrowings	84,108	149,995
Interest payable	16,102	18,912
Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Cash and due from banks	87,616	112,649
Interest-bearing deposits	298,891	436,080
Investment securities held to maturity	0	0
Loans held for sale	0	0
Loans	0	0
Federal Home Loan Bank stock	0	0
Interest receivable	0	0
Liabilities at December 31:
Deposits	12,502,819	12,482,295
Borrowings:
Securities sold under repurchase agreements	0	0
Federal Home Loan Bank advances	0	0
Subordinated debentures and other borrowings	0	0
Interest payable	0	0
Significant Other Observable Inputs (Level 2)
Assets:
Cash and due from banks	0	0
Interest-bearing deposits	0	0
Investment securities held to maturity	1,716,647	1,859,974
Loans held for sale	18,663	18,934
Loans	0	0
Federal Home Loan Bank stock	41,690	41,769
Interest receivable	91,829	97,664
Liabilities at December 31:
Deposits	2,010,348	2,329,662
Borrowings:
Securities sold under repurchase agreements	142,865	157,265
Federal Home Loan Bank advances	816,786	707,377
Subordinated debentures and other borrowings	84,108	149,995
Interest payable	16,102	18,912
Significant Unobservable Inputs (Level 3)
Assets:
Cash and due from banks	0	0
Interest-bearing deposits	0	0
Investment securities held to maturity	6,873	10,400
Loans held for sale	0	0
Loans	12,437,523	11,958,301
Federal Home Loan Bank stock	0	0
Interest receivable	0	0
Liabilities at December 31:
Deposits	0	0
Borrowings:
Securities sold under repurchase agreements	0	0
Federal Home Loan Bank advances	0	0
Subordinated debentures and other borrowings	0	0
Interest payable	0	0
Carrying Amount
Assets:
Cash and due from banks	87,616	112,649
Interest-bearing deposits	298,891	436,080
Investment securities held to maturity	2,074,220	2,184,252
Loans held for sale	18,663	18,934
Loans	12,661,602	12,281,093
Federal Home Loan Bank stock	41,690	41,769
Interest receivable	91,829	97,664
Liabilities at December 31:
Deposits	14,521,626	14,821,453
Borrowings:
Securities sold under repurchase agreements	142,876	157,280
Federal Home Loan Bank advances	822,554	712,852
Subordinated debentures and other borrowings	93,529	158,644
Interest payable	$ 16,102	$ 18,912

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For banks and other depository institutions: Includes cash on hand (currency and coin), cash items in process of collection, noninterest bearing deposits due from other financial institutions (including corporate credit unions), and noninterest bearing balances with the Federal Reserve Banks, Federal Home Loan Banks and central banks.

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Fair value portion of deposit liabilities held by the entity, including, but not limited to, foreign and domestic, interest and noninterest bearing, demand deposits, saving deposits, negotiable orders of withdrawal (NOW) and time deposits.

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Fair value of investment in debt security measured at amortized cost (held-to-maturity).

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Fair value portion of loan receivable, including, but not limited to, mortgage loans held for investment, finance receivables held for investment, policy loans on insurance contracts.

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Amount, before valuation allowance, of financing receivable classified as held-for-sale.

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Fair value portion of other liabilities.

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