FAIR VALUE (Estimated fair value financial instruments incl. carrying amounts) (Details) - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023
Securities:
Carried at fair value	$ 892,306
Held to maturity	841,055	$ 838,241
Deposits held for sale	596,328	0
Quoted Prices in Active Markets for Identical Assets (Level 1)
Financial assets:
Cash and cash equivalents	444,366	323,013
Time deposits in other financial institutions	1,240	1,240
Securities:
Carried at fair value	32,222	32,118
Held to maturity	0	0
Other investments	0	0
Loans held for sale	0	0
Loans, net	0	0
Deposits held for sale	0
Cash surrender value on life insurance	0	0
Derivative instruments	0	0
Financial liabilities:
Borrowings	0	0
Term Debt	0	0
Fair Value	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	4,386,000	4,614,773
Held to maturity	813,752	816,399
Other investments	68,524	91,277
Loans held for sale	352,744	5,071
Loans, net	10,768,693	11,149,694
Deposits held for sale	631,274
Cash surrender value on life insurance	197,671	197,085
Derivative instruments	120,460	84,904
Financial liabilities:
Borrowings	650,033	622,255
Term Debt	374,240	374,017
Fair Value	69,533	84,249
Significant Other Observable Inputs (Level 2) | Demand deposits
Financial liabilities:
Deposits	4,264,390	4,500,304
Significant Other Observable Inputs (Level 2) | Savings deposits
Financial liabilities:
Deposits	8,669,221	8,805,597
Significant Other Observable Inputs (Level 2) | Time deposits
Financial liabilities:
Deposits	2,368,555	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	58,414	59,973
Deposits held for sale	0
Cash surrender value on life insurance	0	0
Derivative instruments	0	0
Financial liabilities:
Borrowings	0	0
Term Debt	0	0
Fair Value	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	3,279,124	3,373,206
Commercial and industrial | Significant Other Observable Inputs (Level 2) | Paycheck Protection Program ("PPP")
Securities:
Loans, net	2,172	2,777
Commercial and industrial | Significant Other Observable Inputs (Level 2) | Owner occupied commercial real estate
Securities:
Loans, net	2,326,760	2,414,140
Commercial and industrial | Significant Other Observable Inputs (Level 2) | Non-owner occupied commercial real estate
Securities:
Loans, net	2,350,454	2,393,931
Commercial and industrial | Significant Other Observable Inputs (Level 2) | Real estate construction
Securities:
Loans, net	1,001,960	978,463
Commercial and industrial | Significant Unobservable Inputs (Level 3) | Commercial and industrial
Securities:
Loans, net	22,292	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	30,089	30,400
Commercial and industrial | Significant Unobservable Inputs (Level 3) | Non-owner occupied commercial real estate
Securities:
Loans, net	0	0
Commercial and industrial | Significant Unobservable Inputs (Level 3) | Real estate construction
Securities:
Loans, net	642	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	730,034	834,804
Agricultural and agricultural real estate | Significant Unobservable Inputs (Level 3)
Securities:
Loans, net	4,664	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	653,571	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	424,618	465,686
Consumer | Significant Unobservable Inputs (Level 3)
Securities:
Loans, net	0	0
Carrying Amount
Financial assets:
Cash and cash equivalents	444,366	323,013
Time deposits in other financial institutions	1,240	1,240
Securities:
Carried at fair value	4,418,222	4,646,891
Held to maturity	841,055	838,241
Other investments	68,524	91,277
Loans held for sale	352,744	5,071
Loans, net	11,520,707	11,946,079
Deposits held for sale	596,328
Cash surrender value on life insurance	197,671	197,085
Derivative instruments	120,460	84,904
Financial liabilities:
Borrowings	650,033	622,255
Term Debt	372,652	372,396
Fair Value	69,533	84,249
Carrying Amount | Demand deposits
Financial liabilities:
Deposits	4,264,390	4,500,304
Carrying Amount | Savings deposits
Financial liabilities:
Deposits	8,669,221	8,805,597
Carrying Amount | Time deposits
Financial liabilities:
Deposits	2,368,555	2,895,813
Carrying Amount | Commercial and industrial | Commercial and industrial
Securities:
Loans, net	3,503,946	3,611,368
Carrying Amount | Commercial and industrial | Paycheck Protection Program ("PPP")
Securities:
Loans, net	2,172	2,777
Carrying Amount | Commercial and industrial | Owner occupied commercial real estate
Securities:
Loans, net	2,530,638	2,621,019
Carrying Amount | Commercial and industrial | Non-owner occupied commercial real estate
Securities:
Loans, net	2,479,298	2,536,462
Carrying Amount | Commercial and industrial | Real estate construction
Securities:
Loans, net	1,006,658	982,943
Carrying Amount | Agricultural and agricultural real estate
Securities:
Loans, net	804,768	914,892
Carrying Amount | Residential real estate
Securities:
Loans, net	750,866	791,984
Carrying Amount | Consumer
Securities:
Loans, net	442,361	484,634
Estimated Fair Value
Financial assets:
Cash and cash equivalents	444,366	323,013
Time deposits in other financial institutions	1,240	1,240
Securities:
Carried at fair value	4,418,222	4,646,891
Held to maturity	813,752	816,399
Other investments	68,524	91,277
Loans held for sale	352,744	5,071
Loans, net	10,827,107	11,209,667
Deposits held for sale	631,274
Cash surrender value on life insurance	197,671	197,085
Derivative instruments	120,460	84,904
Financial liabilities:
Borrowings	650,033	622,255
Term Debt	374,240	374,017
Fair Value	69,533	84,249
Estimated Fair Value | Demand deposits
Financial liabilities:
Deposits	4,264,390	4,500,304
Estimated Fair Value | Savings deposits
Financial liabilities:
Deposits	8,669,221	8,805,597
Estimated Fair Value | Time deposits
Financial liabilities:
Deposits	2,368,555	2,895,813
Estimated Fair Value | Commercial and industrial | Commercial and industrial
Securities:
Loans, net	3,301,416	3,396,628
Estimated Fair Value | Commercial and industrial | Paycheck Protection Program ("PPP")
Securities:
Loans, net	2,172	2,777
Estimated Fair Value | Commercial and industrial | Owner occupied commercial real estate
Securities:
Loans, net	2,356,849	2,444,540
Estimated Fair Value | Commercial and industrial | Non-owner occupied commercial real estate
Securities:
Loans, net	2,350,454	2,393,931
Estimated Fair Value | Commercial and industrial | Real estate construction
Securities:
Loans, net	1,002,602	979,105
Estimated Fair Value | Agricultural and agricultural real estate
Securities:
Loans, net	734,698	839,572
Estimated Fair Value | Residential real estate
Securities:
Loans, net	654,298	687,428
Estimated Fair Value | Consumer
Securities:
Loans, net	$ 424,618	$ 465,686