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v3.22.1

Note 17 - Lease Commitments (Details Textual) | Dec. 31, 2021
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Number of Leases | 8
Leases With Option to Extend the Lease [Member] |
Number of Leases | 6

X
- Definition Represents the number of leases. + References No definition available. + Details
Name: | fxnc_NumberOfLeases
Namespace Prefix: | fxnc_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | instant

X
- Details
Name: | us-gaap_LeaseContractualTermAxis=fxnc_LeasesWithOptionToExtendTheLeaseMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |