FAIR VALUES OF FINANCIAL INSTRUMENTS - Estimated Fair Values of Financial Instruments (Details) - USD ($) $ in Thousands	Mar. 31, 2025	Dec. 31, 2024
Assets:
Cash and due from banks	$ 86,113	$ 87,616
Interest-bearing deposits	331,534	298,891
Investment securities held to maturity, net	1,705,006	1,723,520
Loans held for sale	23,004	18,663
Net loans	12,641,050	12,437,523
Federal Home Loan Bank stock	45,006	41,690
Interest receivable	88,352	91,829
Liabilities:
Deposits	14,455,946	14,513,167
Borrowings:
Securities sold under repurchase agreements	122,938	142,865
Federal Home Loan Bank advances	973,038	816,786
Subordinated debentures and other borrowings	58,041	84,108
Interest payable	13,304	16,102
Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Cash and due from banks	86,113	87,616
Interest-bearing deposits	331,534	298,891
Investment securities held to maturity, net	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	12,578,429	12,502,819
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, net	1,698,685	1,716,647
Loans held for sale	23,004	18,663
Net loans	0	0
Federal Home Loan Bank stock	45,006	41,690
Interest receivable	88,352	91,829
Liabilities:
Deposits	1,877,517	2,010,348
Borrowings:
Securities sold under repurchase agreements	122,938	142,865
Federal Home Loan Bank advances	973,038	816,786
Subordinated debentures and other borrowings	58,041	84,108
Interest payable	13,304	16,102
Significant Unobservable Inputs (Level 3)
Assets:
Cash and due from banks	0	0
Interest-bearing deposits	0	0
Investment securities held to maturity, net	6,321	6,873
Loans held for sale	0	0
Net loans	12,641,050	12,437,523
Federal Home Loan Bank stock	0	0
Interest receivable	0	0
Liabilities:
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	86,113	87,616
Interest-bearing deposits	331,534	298,891
Investment securities held to maturity, net	2,048,632	2,074,220
Loans held for sale	23,004	18,663
Net loans	12,812,874	12,661,602
Federal Home Loan Bank stock	45,006	41,690
Interest receivable	88,352	91,829
Liabilities:
Deposits	14,461,978	14,521,626
Borrowings:
Securities sold under repurchase agreements	122,947	142,876
Federal Home Loan Bank advances	972,478	822,554
Subordinated debentures and other borrowings	62,619	93,529
Interest payable	$ 13,304	$ 16,102