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v3.10.0.1

OTHER BORROWINGS: (Tables) | 12 Months Ended
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Dec. 31, 2018
Other Borrowings Disclosure [Abstract] |
Schedule of other borrowings |
Aggregate Minimum Annual Retirements |

X
- Definition -- None. No documentation exists for this element. -- + References No definition available. + Details
Name: | thff_AggregateMinimumAnnualRetirementsOfOtherBorrowingsTableTextBlock
Namespace Prefix: | thff_
Data Type: | nonnum:textBlockItemType
Balance Type: | na
Period Type: | duration

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

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- Definition Tabular disclosure of debt arrangements (having initial terms of repayment in excess of one year or the normal operating cycle, if longer). + References No definition available. + Details
Name: | thff_ScheduleOfOtherBorrowingsTableTextBlock
Namespace Prefix: | thff_
Data Type: | nonnum:textBlockItemType
Balance Type: | na
Period Type: | duration