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v3.25.2

Allowance for Credit Losses - Modified loans with payment default (Details) | 6 Months Ended
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Jun. 30, 2025
ALLOWANCE FOR LOAN LOSSES |
Modified loans past due period considered in payment default | 30 days

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- Definition -- None. No documentation exists for this element. -- + References No definition available. + Details
Name: | thff_AllowanceForLoanLossesDisclosureAbstract
Namespace Prefix: | thff_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

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- Definition Threshold period for when financing receivable is considered in default under modified terms, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. + References No definition available. + Details
Name: | thff_FinancingReceivableThresholdPeriodDefaultModifiedTerms
Namespace Prefix: | thff_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration