Note 15 - Commitments and Unfunded Credits (Details Textual) $ in Millions	Dec. 31, 2023 USD ($)
Amount of Locked Rate Commitments for Mortgage Loans	$ 1.2
Access Deposit in Other Commercial Banks	$ 1.8

Amount of locked rate commitments for mortgage loans.

No definition available.

Name:	fxnc_AmountOfLockedRateCommitmentsForMortgageLoans
Namespace Prefix:	fxnc_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant