Credit Quality Indicators (Details Textual)	Jun. 30, 2015 USD ($)
Credit Quality Indicators [Abstract]
Maximum commercial loan and commercial real estate relationships	$ 750,000

Commercial loan and commercial real estate risk maximum.

No definition available.

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Namespace Prefix:	fmnb_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant