FAIR VALUE - Carrying Amounts and Fair Values of Company's Financial Instruments (Details) - USD ($) $ in Thousands	Jun. 30, 2023	Dec. 31, 2022
Financial assets:
Residential mortgage loans held for sale	$ 21,476	$ 11,706
Investments available-for-sale	1,143,688	1,214,538
Held-to-maturity debt securities	208,662	220,123
Loans, net of allowance	11,249,352	11,260,464
Accrued interest receivable	42,388	41,172
Financial liabilities:
Other deposits	10,958,922	10,953,421
Advances from FHLB	600,000	550,000
Subordinated debt	370,504	370,205
Carrying Amount
Financial assets:
Cash and cash equivalents	430,127	192,232
Residential mortgage loans held for sale	21,476	11,706
Investments available-for-sale	1,143,688	1,214,538
Held-to-maturity debt securities	247,814	259,452
Other investments	72,052	69,218
Loans, net of allowance	11,249,352	11,260,464
Interest rate swap agreements	18,286	18,596
Accrued interest receivable	42,388	41,172
Bank owned life insurance	156,874	153,016
Financial liabilities:
Time deposits	2,815,761	2,118,262
Other deposits	8,143,161	8,835,159
Federal Funds Purchased and Securities Sold under Agreements to Repurchase	374,510	321,967
Advances from FHLB	600,000	550,000
Subordinated debt	370,504	370,205
Interest rate swap agreements	18,286	18,596
Accrued interest payable	24,436	10,867
Estimated Fair Value
Financial assets:
Cash and cash equivalents	430,127	192,232
Residential mortgage loans held for sale	21,476	11,706
Investments available-for-sale	1,143,688	1,214,538
Held-to-maturity debt securities	208,662	220,123
Other investments	72,052	69,218
Loans, net of allowance	10,467,917	11,020,992
Interest rate swap agreements	18,286	18,596
Accrued interest receivable	42,388	41,172
Bank owned life insurance	156,874	153,016
Financial liabilities:
Time deposits	2,786,157	2,082,319
Other deposits	8,143,161	8,835,159
Federal Funds Purchased and Securities Sold under Agreements to Repurchase	374,510	321,967
Advances from FHLB	591,850	549,530
Subordinated debt	336,107	332,470
Interest rate swap agreements	18,286	18,596
Accrued interest payable	24,436	10,867
Quoted Prices in Active Markets for Identical Assets (Level 1) | Estimated Fair Value
Financial assets:
Cash and cash equivalents	430,127	192,232
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	42,388	41,172
Bank owned life insurance	0	0
Financial liabilities:
Time deposits	0	0
Other deposits	8,143,161	8,835,159
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	24,436	10,867
Significant Other Observable Inputs (Level 2) | Estimated Fair Value
Financial assets:
Cash and cash equivalents	0	0
Residential mortgage loans held for sale	21,476	11,706
Investments available-for-sale	1,143,688	1,214,538
Held-to-maturity debt securities	208,662	220,123
Other investments	72,052	69,218
Loans, net of allowance	0	0
Interest rate swap agreements	18,286	18,596
Accrued interest receivable	0	0
Bank owned life insurance	156,874	153,016
Financial liabilities:
Time deposits	2,786,157	2,082,319
Other deposits	0	0
Federal Funds Purchased and Securities Sold under Agreements to Repurchase	374,510	321,967
Advances from FHLB	591,850	549,530
Subordinated debt	0	0
Interest rate swap agreements	18,286	18,596
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	10,467,917	11,020,992
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	336,107	332,470
Interest rate swap agreements	0	0
Accrued interest payable	$ 0	$ 0