FAIR VALUE - Carrying Amounts and Fair Values of Company's Financial Instruments (Details) - USD ($) $ in Thousands	Sep. 30, 2024	Dec. 31, 2023
Financial assets:
Investments available-for-sale	$ 1,149,056	$ 1,102,681
Held-to-maturity debt securities	189,853	200,411
Loans, net of allowance	11,360,493	11,246,124
Accrued interest receivable	45,162	46,583
Financial liabilities:
Other deposits	11,737,694	10,996,538
Advances from FHLB	450,000	550,000
Subordinated debt	371,251	370,803
Carrying Amount
Financial assets:
Cash and cash equivalents	750,346	545,898
Residential mortgage loans held for sale	21,489	10,836
Investments available-for-sale	1,149,056	1,102,681
Held-to-maturity debt securities	220,296	236,165
Other investments	71,136	75,607
Loans, net of allowance	11,360,493	11,246,124
Interest rate swap agreements	11,806	15,867
Accrued interest receivable	45,162	46,583
Bank owned life insurance	170,584	158,921
Financial liabilities:
Time deposits	2,600,509	2,714,555
Other deposits	9,137,185	8,281,983
Securities sold under retail repurchase agreements and federal funds purchased	70,767	375,032
Advances from FHLB	450,000	550,000
Subordinated debt	371,251	370,803
Interest rate swap agreements	11,806	15,867
Accrued interest payable	18,483	30,367
Estimated Fair Value
Financial assets:
Cash and cash equivalents	750,346	545,898
Residential mortgage loans held for sale	21,489	10,836
Investments available-for-sale	1,149,056	1,102,681
Held-to-maturity debt securities	189,853	200,411
Other investments	71,136	75,607
Loans, net of allowance	10,794,898	10,476,059
Interest rate swap agreements	11,806	15,867
Accrued interest receivable	45,162	46,583
Bank owned life insurance	170,584	158,921
Financial liabilities:
Time deposits	2,604,437	2,704,013
Other deposits	9,137,185	8,281,983
Securities sold under retail repurchase agreements and federal funds purchased	70,767	375,032
Advances from FHLB	450,665	547,271
Subordinated debt	361,491	348,185
Interest rate swap agreements	11,806	15,867
Accrued interest payable	18,483	30,367
Quoted Prices in Active Markets for Identical Assets (Level 1) | Estimated Fair Value
Financial assets:
Cash and cash equivalents	750,346	545,898
Residential mortgage loans held for sale	0	0
Investments available-for-sale	0	0
Held-to-maturity debt securities	0	0
Other investments	0	0
Loans, net of allowance	0	0
Interest rate swap agreements	0	0
Accrued interest receivable	45,162	46,583
Bank owned life insurance	0	0
Financial liabilities:
Time deposits	0	0
Other deposits	9,137,185	8,281,983
Securities sold under retail repurchase agreements and federal funds purchased	0	0
Advances from FHLB	0	0
Subordinated debt	0	0
Interest rate swap agreements	0	0
Accrued interest payable	18,483	30,367
Significant Other Observable Inputs (Level 2) | Estimated Fair Value
Financial assets:
Cash and cash equivalents	0	0
Residential mortgage loans held for sale	21,489	10,836
Investments available-for-sale	1,149,056	1,102,681
Held-to-maturity debt securities	189,853	200,411
Other investments	71,136	75,607
Loans, net of allowance	0	0
Interest rate swap agreements	11,806	15,867
Accrued interest receivable	0	0
Bank owned life insurance	170,584	158,921
Financial liabilities:
Time deposits	2,604,437	2,704,013
Other deposits	0	0
Securities sold under retail repurchase agreements and federal funds purchased	70,767	375,032
Advances from FHLB	450,665	547,271
Subordinated debt	0	0
Interest rate swap agreements	11,806	15,867
Accrued interest payable	0	0
Significant Unobservable Inputs (Level 3) | Estimated Fair Value
Financial assets:
Cash and cash equivalents	0	0
Residential mortgage loans held for sale	0	0
Investments available-for-sale	0	0
Held-to-maturity debt securities	0	0
Other investments	0	0
Loans, net of allowance	10,794,898	10,476,059
Interest rate swap agreements	0	0
Accrued interest receivable	0	0
Bank owned life insurance	0	0
Financial liabilities:
Time deposits	0	0
Other deposits	0	0
Securities sold under retail repurchase agreements and federal funds purchased	0	0
Advances from FHLB	0	0
Subordinated debt	361,491	348,185
Interest rate swap agreements	0	0
Accrued interest payable	$ 0	$ 0