XML 96 R80.htm IDEA: XBRL DOCUMENT v3.7.0.1

Funds Restrictions and Reserve Balance - Additional Information (Detail) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Aggregate amount of unrestricted funds	$ 1.9
First Bank [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Aggregate amounts of daily average required balances of reserve against its deposits	$ 6.0	$ 5.6

X

- Definition

Aggregate amount of daily average deposit.

+ References

No definition available.

+ Details

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

X

- Definition

Aggregate amount of unrestricted funds transferred from bank.

+ References

No definition available.

+ Details

Name:	fxnc_AggregateAmountOfUnrestrictedFundsTransferredFromBank
Namespace Prefix:	fxnc_
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_ComplianceWithRegulatoryCapitalRequirementsUnderBankingRegulationsLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

X

- Details

Name:	dei_LegalEntityAxis=fxnc_FirstBankMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: