FAIR VALUE (Estimated fair value financial instruments incl. carrying amounts) (Details) - USD ($) $ in Thousands	Sep. 30, 2024	Dec. 31, 2023
Securities:
Carried at fair value	$ 880,341
Held to maturity	839,623	$ 838,241
Quoted Prices in Active Markets for Identical Assets (Level 1)
Financial assets:
Cash and cash equivalents	588,394	323,013
Time deposits in other financial institutions	1,050	1,240
Securities:
Carried at fair value	7,963	32,118
Held to maturity	0	0
Other investments	0	0
Loans held for sale	0	0
Loans, net	0	0
Cash surrender value on life insurance	0	0
Derivative financial instrument	0	0
Financial liabilities:
Borrowings	0	0
Term Debt	0	0
Derivative financial instrument	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) | Demand deposits
Financial liabilities:
Deposits	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) | Savings deposits
Financial liabilities:
Deposits	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) | Time deposits
Financial liabilities:
Deposits	0	0
Significant Other Observable Inputs (Level 2)
Financial assets:
Cash and cash equivalents	0	0
Time deposits in other financial institutions	0	0
Securities:
Carried at fair value	4,049,372	4,614,773
Held to maturity	844,296	816,399
Other investments	69,511	91,277
Loans held for sale	0	5,071
Loans, net	10,730,996	11,149,694
Cash surrender value on life insurance	199,998	197,085
Derivative financial instrument	75,967	84,904
Financial liabilities:
Borrowings	546,219	622,255
Term Debt	375,240	374,017
Derivative financial instrument	88,574	84,249
Significant Other Observable Inputs (Level 2) | Demand deposits
Financial liabilities:
Deposits	4,009,218	4,500,304
Significant Other Observable Inputs (Level 2) | Savings deposits
Financial liabilities:
Deposits	8,926,192	8,805,597
Significant Other Observable Inputs (Level 2) | Time deposits
Financial liabilities:
Deposits	2,017,806	2,895,813
Significant Unobservable Inputs (Level 3)
Financial assets:
Cash and cash equivalents	0	0
Time deposits in other financial institutions	0	0
Securities:
Carried at fair value	0	0
Held to maturity	0	0
Other investments	0	0
Loans held for sale	0	0
Loans, net	40,863	59,973
Cash surrender value on life insurance	0	0
Derivative financial instrument	0	0
Financial liabilities:
Borrowings	0	0
Term Debt	0	0
Derivative financial instrument	0	0
Significant Unobservable Inputs (Level 3) | Demand deposits
Financial liabilities:
Deposits	0	0
Significant Unobservable Inputs (Level 3) | Savings deposits
Financial liabilities:
Deposits	0	0
Significant Unobservable Inputs (Level 3) | Time deposits
Financial liabilities:
Deposits	0	0
Commercial and industrial | Quoted Prices in Active Markets for Identical Assets (Level 1) | Commercial and industrial
Securities:
Loans, net	0	0
Commercial and industrial | Quoted Prices in Active Markets for Identical Assets (Level 1) | Paycheck Protection Program ("PPP")
Securities:
Loans, net	0	0
Commercial and industrial | Quoted Prices in Active Markets for Identical Assets (Level 1) | Owner occupied commercial real estate
Securities:
Loans, net	0	0
Commercial and industrial | Quoted Prices in Active Markets for Identical Assets (Level 1) | Non-owner occupied commercial real estate
Securities:
Loans, net	0	0
Commercial and industrial | Quoted Prices in Active Markets for Identical Assets (Level 1) | Real estate construction
Securities:
Loans, net	0	0
Commercial and industrial | Significant Other Observable Inputs (Level 2) | Commercial and industrial
Securities:
Loans, net	3,294,671	3,373,206
Commercial and industrial | Significant Other Observable Inputs (Level 2) | Paycheck Protection Program ("PPP")
Securities:
Loans, net	1,582	2,777
Commercial and industrial | Significant Other Observable Inputs (Level 2) | Owner occupied commercial real estate
Securities:
Loans, net	2,330,548	2,414,140
Commercial and industrial | Significant Other Observable Inputs (Level 2) | Non-owner occupied commercial real estate
Securities:
Loans, net	2,330,827	2,393,931
Commercial and industrial | Significant Other Observable Inputs (Level 2) | Real estate construction
Securities:
Loans, net	1,084,962	978,463
Commercial and industrial | Significant Unobservable Inputs (Level 3) | Commercial and industrial
Securities:
Loans, net	15,242	23,422
Commercial and industrial | Significant Unobservable Inputs (Level 3) | Paycheck Protection Program ("PPP")
Securities:
Loans, net	0	0
Commercial and industrial | Significant Unobservable Inputs (Level 3) | Owner occupied commercial real estate
Securities:
Loans, net	2,631	30,400
Commercial and industrial | Significant Unobservable Inputs (Level 3) | Non-owner occupied commercial real estate
Securities:
Loans, net	5,661	0
Commercial and industrial | Significant Unobservable Inputs (Level 3) | Real estate construction
Securities:
Loans, net	675	642
Agricultural and agricultural real estate | Quoted Prices in Active Markets for Identical Assets (Level 1)
Securities:
Loans, net	0	0
Agricultural and agricultural real estate | Significant Other Observable Inputs (Level 2)
Securities:
Loans, net	628,822	834,804
Agricultural and agricultural real estate | Significant Unobservable Inputs (Level 3)
Securities:
Loans, net	15,927	4,768
Residential real estate | Quoted Prices in Active Markets for Identical Assets (Level 1)
Securities:
Loans, net	0	0
Residential real estate | Significant Other Observable Inputs (Level 2)
Securities:
Loans, net	620,692	686,687
Residential real estate | Significant Unobservable Inputs (Level 3)
Securities:
Loans, net	727	741
Consumer | Quoted Prices in Active Markets for Identical Assets (Level 1)
Securities:
Loans, net	0	0
Consumer | Significant Other Observable Inputs (Level 2)
Securities:
Loans, net	438,892	465,686
Consumer | Significant Unobservable Inputs (Level 3)
Securities:
Loans, net	0	0
Carrying Amount
Financial assets:
Cash and cash equivalents	588,394	323,013
Time deposits in other financial institutions	1,050	1,240
Securities:
Carried at fair value	4,057,335	4,646,891
Held to maturity	839,623	838,241
Other investments	69,511	91,277
Loans held for sale	0	5,071
Loans, net	11,334,120	11,946,079
Cash surrender value on life insurance	199,998	197,085
Derivative financial instrument	75,967	84,904
Financial liabilities:
Borrowings	546,219	622,255
Term Debt	373,324	372,396
Derivative financial instrument	88,574	84,249
Carrying Amount | Demand deposits
Financial liabilities:
Deposits	4,009,218	4,500,304
Carrying Amount | Savings deposits
Financial liabilities:
Deposits	8,926,192	8,805,597
Carrying Amount | Time deposits
Financial liabilities:
Deposits	2,017,806	2,895,813
Carrying Amount | Commercial and industrial | Commercial and industrial
Securities:
Loans, net	3,479,674	3,611,368
Carrying Amount | Commercial and industrial | Paycheck Protection Program ("PPP")
Securities:
Loans, net	1,582	2,777
Carrying Amount | Commercial and industrial | Owner occupied commercial real estate
Securities:
Loans, net	2,476,446	2,621,019
Carrying Amount | Commercial and industrial | Non-owner occupied commercial real estate
Securities:
Loans, net	2,437,977	2,536,462
Carrying Amount | Commercial and industrial | Real estate construction
Securities:
Loans, net	1,084,442	982,943
Carrying Amount | Agricultural and agricultural real estate
Securities:
Loans, net	697,408	914,892
Carrying Amount | Residential real estate
Securities:
Loans, net	702,629	791,984
Carrying Amount | Consumer
Securities:
Loans, net	453,962	484,634
Estimated Fair Value
Financial assets:
Cash and cash equivalents	588,394	323,013
Time deposits in other financial institutions	1,050	1,240
Securities:
Carried at fair value	4,057,335	4,646,891
Held to maturity	844,296	816,399
Other investments	69,511	91,277
Loans held for sale	0	5,071
Loans, net	10,771,859	11,209,667
Cash surrender value on life insurance	199,998	197,085
Derivative financial instrument	75,967	84,904
Financial liabilities:
Borrowings	546,219	622,255
Term Debt	375,240	374,017
Derivative financial instrument	88,574	84,249
Estimated Fair Value | Demand deposits
Financial liabilities:
Deposits	4,009,218	4,500,304
Estimated Fair Value | Savings deposits
Financial liabilities:
Deposits	8,926,192	8,805,597
Estimated Fair Value | Time deposits
Financial liabilities:
Deposits	2,017,806	2,895,813
Estimated Fair Value | Commercial and industrial | Commercial and industrial
Securities:
Loans, net	3,309,913	3,396,628
Estimated Fair Value | Commercial and industrial | Paycheck Protection Program ("PPP")
Securities:
Loans, net	1,582	2,777
Estimated Fair Value | Commercial and industrial | Owner occupied commercial real estate
Securities:
Loans, net	2,333,179	2,444,540
Estimated Fair Value | Commercial and industrial | Non-owner occupied commercial real estate
Securities:
Loans, net	2,336,488	2,393,931
Estimated Fair Value | Commercial and industrial | Real estate construction
Securities:
Loans, net	1,085,637	979,105
Estimated Fair Value | Agricultural and agricultural real estate
Securities:
Loans, net	644,749	839,572
Estimated Fair Value | Residential real estate
Securities:
Loans, net	621,419	687,428
Estimated Fair Value | Consumer
Securities:
Loans, net	$ 438,892	$ 465,686