BUSINESS AND SIGNIFICANT ACCOUNTING POLICIES (Details)	12 Months Ended
	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