FAIR VALUES OF FINANCIAL INSTRUMENTS - Summary of Estimated Fair Values of Financial Instruments (Details) - USD ($) $ in Thousands	Mar. 31, 2026	Dec. 31, 2025
Assets:
Cash and due from banks	$ 98,083	$ 84,158
Interest-bearing deposits	175,354	196,300
Investment securities held to maturity, net of allowance for credit losses	1,660,935	1,718,287
Loans held for sale	44,883	20,079
Net loans	14,582,397	13,498,304
Federal Home Loan Bank stock	70,835	47,245
Interest receivable	97,026	93,374
Liabilities:
Deposits	16,480,319	15,295,040
Borrowings:
Federal funds purchased	170,000	40,000
Securities sold under repurchase agreements	89,452	103,747
Federal Home Loan Bank advances	1,301,261	803,396
Subordinated debentures and other borrowings	79,085	53,982
Interest payable	18,890	18,235
Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Cash and due from banks	98,083	84,158
Interest-bearing deposits	175,354	196,300
Investment securities held to maturity, net of allowance for credit losses	0	0
Loans held for sale	0	0
Net loans	0	0
Federal Home Loan Bank stock	0	0
Interest receivable	0	0
Liabilities:
Deposits	14,214,074	13,252,258
Borrowings:
Federal funds purchased	0	0
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, net of allowance for credit losses	1,657,082	1,713,872
Loans held for sale	44,883	20,079
Net loans	0	0
Federal Home Loan Bank stock	70,835	47,245
Interest receivable	97,026	93,374
Liabilities:
Deposits	2,266,245	2,042,782
Borrowings:
Federal funds purchased	170,000	40,000
Securities sold under repurchase agreements	89,452	103,747
Federal Home Loan Bank advances	1,301,261	803,396
Subordinated debentures and other borrowings	79,085	53,982
Interest payable	18,890	18,235
Significant Unobservable Inputs (Level 3)
Assets:
Cash and due from banks	0	0
Interest-bearing deposits	0	0
Investment securities held to maturity, net of allowance for credit losses	3,853	4,415
Loans held for sale	0	0
Net loans	14,582,397	13,498,304
Federal Home Loan Bank stock	0	0
Interest receivable	0	0
Liabilities:
Deposits	0	0
Borrowings:
Federal funds purchased	0	0
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	98,083	84,158
Interest-bearing deposits	175,354	196,300
Investment securities held to maturity, net of allowance for credit losses	1,937,485	1,971,539
Loans held for sale	44,883	20,079
Net loans	15,049,369	13,596,110
Federal Home Loan Bank stock	70,835	47,245
Interest receivable	97,026	93,374
Liabilities:
Deposits	16,485,617	15,294,855
Borrowings:
Federal funds purchased	170,000	40,000
Securities sold under repurchase agreements	89,458	103,755
Federal Home Loan Bank advances	1,299,192	798,549
Subordinated debentures and other borrowings	86,345	57,630
Interest payable	$ 18,890	$ 18,235