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v3.22.2.2

Loans (Details Textual) | 9 Months Ended
--- | ---
Sep. 30, 2022 USD ($)
Receivables [Abstract] |
Deferred loan payments | $ 0

X
- Definition Deferred loan payments. + References No definition available. + Details
Name: | fmnb_DeferredLoanPayments
Namespace Prefix: | fmnb_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- References No definition available. + Details
Name: | us-gaap_ReceivablesAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration