FAIR VALUES OF FINANCIAL INSTRUMENTS - Estimated Fair Values of Financial Instruments (Details) - USD ($) $ in Thousands	Jun. 30, 2023	Dec. 31, 2022
Assets:
Cash and due from banks	$ 108,975	$ 122,594
Interest-bearing deposits	219,480	126,061
Investment securities available for sale	1,651,362	1,976,661
Investment securities held to maturity	1,880,683	1,907,865
Loans held for sale	27,297	9,094
Loans, net	11,576,563	11,156,217
Federal Home Loan Bank stock	41,842	38,525
Derivative assets	92,753	93,036
Interest receivable	89,784	85,070
Liabilities:
Deposits	14,558,160	14,356,953
Borrowings:
Federal funds purchased		171,560
Securities sold under repurchase agreements	152,456	167,396
Federal Home Loan Bank advances	713,622	615,211
Subordinated debentures and other borrowings	121,616	122,102
Derivative liabilities	92,219	92,770
Interest payable	13,595	7,530
Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Cash and due from banks	108,975	122,594
Interest-bearing deposits	219,480	126,061
Investment securities available for sale	2,091	2,459
Investment securities held to maturity	0	0
Loans held for sale	0	0
Loans, net	0	0
Federal Home Loan Bank stock	0	0
Derivative assets	0	0
Interest receivable	0	0
Liabilities:
Deposits	12,575,711	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	1,645,923	1,970,763
Investment securities held to maturity	1,868,970	1,893,271
Loans held for sale	27,297	9,094
Loans, net	0	0
Federal Home Loan Bank stock	41,842	38,525
Derivative assets	92,753	93,036
Interest receivable	89,784	85,070
Liabilities:
Deposits	1,982,449	1,251,017
Borrowings:
Federal funds purchased		171,560
Securities sold under repurchase agreements	152,456	167,396
Federal Home Loan Bank advances	713,622	615,211
Subordinated debentures and other borrowings	121,616	122,102
Derivative liabilities	92,219	92,770
Interest payable	13,595	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	3,348	3,439
Investment securities held to maturity	11,713	14,594
Loans held for sale	0	0
Loans, net	11,576,563	11,156,217
Federal Home Loan Bank stock	0	0
Derivative assets	0	0
Interest receivable	0	0
Liabilities:
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	108,975	122,594
Interest-bearing deposits	219,480	126,061
Investment securities available for sale	1,651,362	1,976,661
Investment securities held to maturity	2,240,129	2,287,127
Loans held for sale	27,297	9,094
Loans, net	12,049,086	11,780,617
Federal Home Loan Bank stock	41,842	38,525
Derivative assets	92,753	93,036
Interest receivable	89,784	85,070
Liabilities:
Deposits	14,581,155	14,382,745
Borrowings:
Federal funds purchased		171,560
Securities sold under repurchase agreements	152,742	167,413
Federal Home Loan Bank advances	723,480	823,674
Subordinated debentures and other borrowings	151,325	151,298
Derivative liabilities	92,219	92,770
Interest payable	$ 13,595	$ 7,530

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