XML 60 R50.htm IDEA: XBRL DOCUMENT
v3.20.2

Investment Securities - Investments in Debt and Equity Securities Reported Less than Historical Cost (Details) - USD ($) $ in Thousands | Sep. 30, 2020 | Dec. 31, 2019
--- | --- | ---
Schedule of Investments [Line Items] |  |
Fair value | $ 156,394 | $ 395,416
Investments reported at less than historical cost |  |
Schedule of Investments [Line Items] |  |
Historical cost | 157,859 | 398,172
Fair value | 156,394 | 395,416
Gross unrealized losses | $ 1,465 | $ 2,756
Percent of the Corporation's investment portfolio | 9.40% | 15.20%

X
- Definition Investment Historical Cost + References No definition available. + Details
Name: | frme_InvestmentHistoricalCost
Namespace Prefix: | frme_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Percentage of Total Investment Portfolio, Fair Value + References No definition available. + Details
Name: | frme_PercentageOfTotalInvestmentPortfolioFairValue
Namespace Prefix: | frme_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant

X
- Definition Securities Continuous Unrealized Loss Position, Accumulated Loss + References No definition available. + Details
Name: | frme_SecuritiesContinuousUnrealizedLossPositionAccumulatedLoss
Namespace Prefix: | frme_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Securities, Continuous Unrealized Loss Position, Fair Value + References No definition available. + Details
Name: | frme_SecuritiesContinuousUnrealizedLossPositionFairValue
Namespace Prefix: | frme_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References No definition available. + Details
Name: | us-gaap_ScheduleOfInvestmentsLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Details
Name: | us-gaap_FinancialInstrumentAxis=frme_InvestmentsInDebtAndEquitySecuritiesReportedAtLessThanHistoricalCostMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |