FAIR VALUE - Carrying Amounts and Fair Values of Company's Financial Instruments (Details) - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023
Financial assets:
Residential mortgage loans held for sale	$ 16,627	$ 10,836
Investments available-for-sale	1,100,741	1,102,681
Held-to-maturity debt securities	192,798	200,411
Loans, net of allowance	11,241,188	11,246,124
Accrued interest receivable	47,152	46,583
Financial liabilities:
Other deposits	11,227,200	10,996,538
Advances from FHLB	500,000	550,000
Subordinated debt	370,952	370,803
Carrying Amount
Financial assets:
Cash and cash equivalents	410,390	545,898
Residential mortgage loans held for sale	16,627	10,836
Investments available-for-sale	1,100,741	1,102,681
Held-to-maturity debt securities	231,354	236,165
Other investments	73,395	75,607
Loans, net of allowance	11,241,188	11,246,124
Interest rate swap agreements	17,758	15,867
Accrued interest receivable	47,152	46,583
Bank owned life insurance	163,381	158,921
Financial liabilities:
Time deposits	2,621,510	2,714,555
Other deposits	8,605,690	8,281,983
Federal Funds Purchased and Securities Sold under Agreements to Repurchase	71,529	375,032
Advances from FHLB	500,000	550,000
Subordinated debt	370,952	370,803
Interest rate swap agreements	17,758	15,867
Accrued interest payable	22,080	30,367
Estimated Fair Value
Financial assets:
Cash and cash equivalents	410,390	545,898
Residential mortgage loans held for sale	16,627	10,836
Investments available-for-sale	1,100,741	1,102,681
Held-to-maturity debt securities	192,798	200,411
Other investments	73,395	75,607
Loans, net of allowance	10,410,156	10,476,059
Interest rate swap agreements	17,758	15,867
Accrued interest receivable	47,152	46,583
Bank owned life insurance	163,381	158,921
Financial liabilities:
Time deposits	2,607,502	2,704,013
Other deposits	8,605,690	8,281,983
Federal Funds Purchased and Securities Sold under Agreements to Repurchase	71,529	375,032
Advances from FHLB	494,226	547,271
Subordinated debt	347,396	348,185
Interest rate swap agreements	17,758	15,867
Accrued interest payable	22,080	30,367
Quoted Prices in Active Markets for Identical Assets (Level 1) | Estimated Fair Value
Financial assets:
Cash and cash equivalents	410,390	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	47,152	46,583
Bank owned life insurance	0	0
Financial liabilities:
Time deposits	0	0
Other deposits	8,605,690	8,281,983
Federal Funds Purchased and Securities Sold under Agreements to Repurchase	0	0
Advances from FHLB	0	0
Subordinated debt	0	0
Interest rate swap agreements	0	0
Accrued interest payable	22,080	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	16,627	10,836
Investments available-for-sale	1,100,741	1,102,681
Held-to-maturity debt securities	192,798	200,411
Other investments	73,395	75,607
Loans, net of allowance	0	0
Interest rate swap agreements	17,758	15,867
Accrued interest receivable	0	0
Bank owned life insurance	163,381	158,921
Financial liabilities:
Time deposits	2,607,502	2,704,013
Other deposits	0	0
Federal Funds Purchased and Securities Sold under Agreements to Repurchase	71,529	375,032
Advances from FHLB	494,226	547,271
Subordinated debt	0	0
Interest rate swap agreements	17,758	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	10,410,156	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
Federal Funds Purchased and Securities Sold under Agreements to Repurchase	0	0
Advances from FHLB	0	0
Subordinated debt	347,396	348,185
Interest rate swap agreements	0	0
Accrued interest payable	$ 0	$ 0