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BUSINESS AND SIGNIFICANT ACCOUNTING POLICIES (Details) | 12 Months Ended
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Dec. 31, 2024 USD ($) item subsidiary | Dec. 31, 2023 USD ($) | Dec. 31, 2022 USD ($)
Property, Plant and Equipment |  |  |
Number of investment subsidiaries (subsidiary) | subsidiary | 2 |  |
Number of branches entity operates (branches) | 83 |  |
Number of loan production offices | 7 |  |
Transfer to other real estate | $ | $ 751,000 | $ 88,000 | $ 570,000
Impairment of goodwill | $ | $ 0 |  |
Repayment of deferred fees and interest in years | 10 years |  |
Expenses for deferred compensation | $ | $ 56,000 | 49,000 | 78,000
Allowance for credit losses on unfunded commitments | $ | 2,100,000 | 2,000,000 |
Compensation expense | $ | 0 | 0 | 0
Deferred compensation liability, current | $ | $ 1,000,000 | 1,100,000 |
Incentive award, payment period | 15 years |  |
Compensation liability | $ | $ 2,900,000 | 3,800,000 |
Short term portion, payment period | 75 days |  |
Vesting period | 3 years |  |
Long term portion, payment period | 75 days |  |
Officers' compensation expense | $ | $ 3,000,000 | 2,900,000 | 2,000,000
Deferred compensation liability incentive plan | $ | $ 2,000,000 | 1,800,000 |
Likelihood of unfavorable settlement (percent) | 50.00% |  |
Minimum |  |  |
Property, Plant and Equipment |  |  |
Finite-lived intangible asset, useful life | 10 years |  |
Maximum |  |  |
Property, Plant and Equipment |  |  |
Finite-lived intangible asset, useful life | 12 years |  |
Furniture and Fixtures | Minimum |  |  |
Property, Plant and Equipment |  |  |
Property, plant and equipment, estimated useful lives | 3 years |  |
Furniture and Fixtures | Maximum |  |  |
Property, Plant and Equipment |  |  |
Property, plant and equipment, estimated useful lives | 5 years |  |
Buildings And Leasehold Improvements | Minimum |  |  |
Property, Plant and Equipment |  |  |
Property, plant and equipment, estimated useful lives | 33 years |  |
Buildings And Leasehold Improvements | Maximum |  |  |
Property, Plant and Equipment |  |  |
Property, plant and equipment, estimated useful lives | 39 years |  |
Allen County, Indiana |  |  |
Property, Plant and Equipment |  |  |
Number of loan production offices | 1 |  |
Catoosa County, Georgia |  |  |
Property, Plant and Equipment |  |  |
Number of branches entity operates (branches) | 1 |  |
Walker County, Georgia |  |  |
Property, Plant and Equipment |  |  |
Number of branches entity operates (branches) | 2 |  |
Clay County, Indiana |  |  |
Property, Plant and Equipment |  |  |
Number of branches entity operates (branches) | 3 |  |
Daviess County, Indiana |  |  |
Property, Plant and Equipment |  |  |
Number of branches entity operates (branches) | 1 |  |
Greene County, Indiana |  |  |
Property, Plant and Equipment |  |  |
Number of branches entity operates (branches) | 1 |  |
Knox County, Indiana |  |  |
Property, Plant and Equipment |  |  |
Number of branches entity operates (branches) | 1 |  |
Monroe County, Indiana |  |  |
Property, Plant and Equipment |  |  |
Number of loan production offices | 1 |  |
Parke County, Indiana |  |  |
Property, Plant and Equipment |  |  |
Number of branches entity operates (branches) | 2 |  |
Putnam County, Indiana |  |  |
Property, Plant and Equipment |  |  |
Number of branches entity operates (branches) | 1 |  |
Sullivan County, Indiana |  |  |
Property, Plant and Equipment |  |  |
Number of branches entity operates (branches) | 2 |  |
Vanderburgh County, Indiana |  |  |
Property, Plant and Equipment |  |  |
Number of branches entity operates (branches) | 1 |  |
Number of loan production offices | 1 |  |
Vermillion County, Indiana |  |  |
Property, Plant and Equipment |  |  |
Number of branches entity operates (branches) | 3 |  |
Vigo County, Indiana |  |  |
Property, Plant and Equipment |  |  |
Number of branches entity operates (branches) | 7 |  |
Champaign County, Illinois |  |  |
Property, Plant and Equipment |  |  |
Number of loan production offices | 4 |  |
Clark County, Illinois |  |  |
Property, Plant and Equipment |  |  |
Number of branches entity operates (branches) | 1 |  |
Coles County, Illinois |  |  |
Property, Plant and Equipment |  |  |
Number of branches entity operates (branches) | 1 |  |
Crawford County, Illinois |  |  |
Property, Plant and Equipment |  |  |
Number of branches entity operates (branches) | 2 |  |
Franklin County, Illinois |  |  |
Property, Plant and Equipment |  |  |
Number of branches entity operates (branches) | 1 |  |
Jasper County, Illinois |  |  |
Property, Plant and Equipment |  |  |
Number of branches entity operates (branches) | 1 |  |
Lawrence County, Illinois |  |  |
Property, Plant and Equipment |  |  |
Number of branches entity operates (branches) | 1 |  |
Livingston County, Illinois |  |  |
Property, Plant and Equipment |  |  |
Number of branches entity operates (branches) | 2 |  |
Marion County, Illinois |  |  |
Property, Plant and Equipment |  |  |
Number of branches entity operates (branches) | 2 |  |
McLean County, Illinois |  |  |
Property, Plant and Equipment |  |  |
Number of branches entity operates (branches) | 2 |  |
Richland County, Illinois |  |  |
Property, Plant and Equipment |  |  |
Number of branches entity operates (branches) | 1 |  |
Vermilion County, Illinois |  |  |
Property, Plant and Equipment |  |  |
Number of branches entity operates (branches) | 5 |  |
Wayne County, Illinois |  |  |
Property, Plant and Equipment |  |  |
Number of branches entity operates (branches) | 1 |  |
Calloway County, Kentucky |  |  |
Property, Plant and Equipment |  |  |
Number of branches entity operates (branches) | 1 |  |
Breckinridge County, Kentucky |  |  |
Property, Plant and Equipment |  |  |
Number of branches entity operates (branches) | 1 |  |
Christian County, Kentucky |  |  |
Property, Plant and Equipment |  |  |
Number of branches entity operates (branches) | 3 |  |
Fulton County, Kentucky |  |  |
Property, Plant and Equipment |  |  |
Number of branches entity operates (branches) | 2 |  |
Hancock County, Kentucky |  |  |
Property, Plant and Equipment |  |  |
Number of branches entity operates (branches) | 2 |  |
Hopkins County, Kentucky |  |  |
Property, Plant and Equipment |  |  |
Number of branches entity operates (branches) | 2 |  |
Marshall County, Kentucky |  |  |
Property, Plant and Equipment |  |  |
Number of branches entity operates (branches) | 2 |  |
Todd County, Kentucky |  |  |
Property, Plant and Equipment |  |  |
Number of branches entity operates (branches) | 1 |  |
Trigg County, Kentucky |  |  |
Property, Plant and Equipment |  |  |
Number of branches entity operates (branches) | 1 |  |
Warren County, Kentucky |  |  |
Property, Plant and Equipment |  |  |
Number of branches entity operates (branches) | 1 |  |
Bradley County, Tennessee |  |  |
Property, Plant and Equipment |  |  |
Number of branches entity operates (branches) | 1 |  |
Cheatham County, Tennessee |  |  |
Property, Plant and Equipment |  |  |
Number of branches entity operates (branches) | 3 |  |
Hamilton County, Tennessee |  |  |
Property, Plant and Equipment |  |  |
Number of branches entity operates (branches) | 2 |  |
Number of loan production offices | 1 |  |
Meigs County, Tennessee |  |  |
Property, Plant and Equipment |  |  |
Number of branches entity operates (branches) | 1 |  |
Montgomery County, Tennessee |  |  |
Property, Plant and Equipment |  |  |
Number of branches entity operates (branches) | 3 |  |
Polk County, Tennessee |  |  |
Property, Plant and Equipment |  |  |
Number of branches entity operates (branches) | 1 |  |
Rhea County, Tennessee |  |  |
Property, Plant and Equipment |  |  |
Number of branches entity operates (branches) | 3 |  |
Roane County, Tennessee |  |  |
Property, Plant and Equipment |  |  |
Number of branches entity operates (branches) | 2 |  |
Hamilton County, Indiana |  |  |
Property, Plant and Equipment |  |  |
Number of loan production offices | 1 |  |
Rutherford County, Tennessee |  |  |
Property, Plant and Equipment |  |  |
Number of loan production offices | 1 |  |
Williamson County, Tennessee |  |  |
Property, Plant and Equipment |  |  |
Number of loan production offices | 1 |  |
First Financial Bank |  |  |
Property, Plant and Equipment |  |  |
Investments in subsidiaries | $ | $ 1,000,000,000 |  |
Service fees |  |  |
Property, Plant and Equipment |  |  |
Revenue within scope of ASC 606 | $ | $ 1,100,000 | $ 1,300,000 | $ 1,400,000

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