FAIR VALUES OF FINANCIAL INSTRUMENTS - Estimated Fair Values of Financial Instruments (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Assets:
Cash and due from banks	$ 112,649	$ 122,594
Investment securities held to maturity	1,870,374	1,907,865
Loans held for sale	18,934	9,094
Total Fair Value
Assets:
Cash and due from banks	112,649	122,594
Interest-bearing deposits	436,080	126,061
Investment securities available for sale	1,627,112	1,976,661
Investment securities held to maturity	1,870,374	1,907,865
Loans held for sale	18,934	9,094
Loans	11,958,301	11,156,217
Federal Home Loan Bank stock	41,769	38,525
Derivative assets	79,379	93,036
Interest receivable	97,664	85,070
Liabilities at December 31:
Deposits	14,811,957	14,356,953
Borrowings:
Federal funds purchased		171,560
Securities sold under repurchase agreements	157,265	167,396
Federal Home Loan Bank advances	707,377	615,211
Subordinated debentures and other borrowings	149,995	122,102
Derivative liabilities	79,008	92,770
Interest payable	18,912	7,530
Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Cash and due from banks	112,649	122,594
Interest-bearing deposits	436,080	126,061
Investment securities available for sale	0	2,459
Investment securities held to maturity	0	0
Loans held for sale	0	0
Loans	0	0
Federal Home Loan Bank stock	0	0
Derivative assets	0	0
Interest receivable	0	0
Liabilities at December 31:
Deposits	12,482,295	13,105,936
Borrowings:
Federal funds purchased		0
Securities sold under repurchase agreements	0	0
Federal Home Loan Bank advances	0	0
Subordinated debentures and other borrowings	0	0
Derivative liabilities	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 available for sale	1,623,802	1,970,763
Investment securities held to maturity	1,859,974	1,893,271
Loans held for sale	18,934	9,094
Loans	0	0
Federal Home Loan Bank stock	41,769	38,525
Derivative assets	79,379	93,036
Interest receivable	97,664	85,070
Liabilities at December 31:
Deposits	2,329,662	1,251,017
Borrowings:
Federal funds purchased		171,560
Securities sold under repurchase agreements	157,265	167,396
Federal Home Loan Bank advances	707,377	615,211
Subordinated debentures and other borrowings	149,995	122,102
Derivative liabilities	79,008	92,770
Interest payable	18,912	7,530
Significant Unobservable Inputs (Level 3)
Assets:
Cash and due from banks	0	0
Interest-bearing deposits	0	0
Investment securities available for sale	3,310	3,439
Investment securities held to maturity	10,400	14,594
Loans held for sale	0	0
Loans	11,958,301	11,156,217
Federal Home Loan Bank stock	0	0
Derivative assets	0	0
Interest receivable	0	0
Liabilities at December 31:
Deposits	0	0
Borrowings:
Federal funds purchased		0
Securities sold under repurchase agreements	0	0
Federal Home Loan Bank advances	0	0
Subordinated debentures and other borrowings	0	0
Derivative liabilities	0	0
Interest payable	0	0
Carrying Amount
Assets:
Cash and due from banks	112,649	122,594
Interest-bearing deposits	436,080	126,061
Investment securities available for sale	1,627,112	1,976,661
Investment securities held to maturity	2,184,252	2,287,127
Loans held for sale	18,934	9,094
Loans	12,281,093	11,780,617
Federal Home Loan Bank stock	41,769	38,525
Derivative assets	79,379	93,036
Interest receivable	97,664	85,070
Liabilities at December 31:
Deposits	14,821,453	14,382,745
Borrowings:
Federal funds purchased		171,560
Securities sold under repurchase agreements	157,280	167,413
Federal Home Loan Bank advances	712,852	823,674
Subordinated debentures and other borrowings	158,644	151,298
Derivative liabilities	79,008	92,770
Interest payable	$ 18,912	$ 7,530

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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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