FAIR VALUE - Carrying Amounts and Fair Values of Company's Financial Instruments (Details) - USD ($) $ in Thousands	Jun. 30, 2024	Dec. 31, 2023
Financial assets:
Residential mortgage loans held for sale	$ 18,961	$ 10,836
Investments available-for-sale	1,101,846	1,102,681
Held-to-maturity debt securities	187,389	200,411
Loans, net of allowance	11,358,058	11,246,124
Accrued interest receivable	46,668	46,583
Financial liabilities:
Other deposits	11,340,228	10,996,538
Advances from FHLB	500,000	550,000
Subordinated debt	371,101	370,803
Carrying Amount
Financial assets:
Cash and cash equivalents	406,710	545,898
Residential mortgage loans held for sale	18,961	10,836
Investments available-for-sale	1,101,846	1,102,681
Held-to-maturity debt securities	226,233	236,165
Other investments	73,432	75,607
Loans, net of allowance	11,358,058	11,246,124
Interest rate swap agreements	17,527	15,867
Accrued interest receivable	46,668	46,583
Bank owned life insurance	169,288	158,921
Financial liabilities:
Time deposits	2,449,049	2,714,555
Other deposits	8,891,179	8,281,983
Federal Funds Purchased and Securities Sold under Agreements to Repurchase	75,038	375,032
Advances from FHLB	500,000	550,000
Subordinated debt	371,101	370,803
Interest rate swap agreements	17,527	15,867
Accrued interest payable	13,775	30,367
Estimated Fair Value
Financial assets:
Cash and cash equivalents	406,710	545,898
Residential mortgage loans held for sale	18,961	10,836
Investments available-for-sale	1,101,846	1,102,681
Held-to-maturity debt securities	187,389	200,411
Other investments	73,432	75,607
Loans, net of allowance	10,522,647	10,476,059
Interest rate swap agreements	17,527	15,867
Accrued interest receivable	46,668	46,583
Bank owned life insurance	169,288	158,921
Financial liabilities:
Time deposits	2,434,990	2,704,013
Other deposits	8,891,179	8,281,983
Federal Funds Purchased and Securities Sold under Agreements to Repurchase	75,038	375,032
Advances from FHLB	494,551	547,271
Subordinated debt	350,128	348,185
Interest rate swap agreements	17,527	15,867
Accrued interest payable	13,775	30,367
Quoted Prices in Active Markets for Identical Assets (Level 1) | Estimated Fair Value
Financial assets:
Cash and cash equivalents	406,710	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	46,668	46,583
Bank owned life insurance	0	0
Financial liabilities:
Time deposits	0	0
Other deposits	8,891,179	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	13,775	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	18,961	10,836
Investments available-for-sale	1,101,846	1,102,681
Held-to-maturity debt securities	187,389	200,411
Other investments	73,432	75,607
Loans, net of allowance	0	0
Interest rate swap agreements	17,527	15,867
Accrued interest receivable	0	0
Bank owned life insurance	169,288	158,921
Financial liabilities:
Time deposits	2,434,990	2,704,013
Other deposits	0	0
Federal Funds Purchased and Securities Sold under Agreements to Repurchase	75,038	375,032
Advances from FHLB	494,551	547,271
Subordinated debt	0	0
Interest rate swap agreements	17,527	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	10,522,647	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	350,128	348,185
Interest rate swap agreements	0	0
Accrued interest payable	$ 0	$ 0