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REGULATORY MATTERS: (Details Textual) $ in Millions | 12 Months Ended
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Dec. 31, 2020 USD ($)
Financial Services, Banking and Thrift [Abstract] |
Undistributed earnings | $ 15.5

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- Definition Financial Services, Banking and Thrift + References No definition available. + Details
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Namespace Prefix: | thff_
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Balance Type: | na
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- Definition The earnings that is allocated to common stock and participating securities to the extent that each security may share in earnings as if all of the earnings for the period had been distributed. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 260 -SubTopic 10 -Section 45 -Paragraph 66 -URI http://asc.fasb.org/extlink&oid=121326447&loc=d3e2814-109256 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 260 -SubTopic 10 -Section 45 -Paragraph 60B -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=121326447&loc=SL5780133-109256 + Details
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Data Type: | xbrli:monetaryItemType
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