XML 109 R93.htm IDEA: XBRL DOCUMENT v3.3.1.900

Commitments and Unfunded Credits - Financial Instruments Representing Credit Risk (Detail) - First Bank [Member] - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Commitments to Extend Credit [Member]
Other Commitments [Line Items]
Contract amounts represent credit risk	$ 61,115	$ 60,019
Stand-By Letters of Credit [Member]
Other Commitments [Line Items]
Contract amounts represent credit risk	$ 7,732	$ 9,763

X

- Definition

The fair value of financial assets, which are not recognized in the financial statements (off-balance sheet) because they fail to meet some other criterion for recognition.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 50
-Paragraph 10
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=49121117&loc=d3e13433-108611

+ Details

Name:	us-gaap_FairValueDisclosureOffbalanceSheetRisksAmountAsset
Namespace Prefix:	us-gaap_
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_OtherCommitmentsLineItems
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:

X

- Details

Name:	us-gaap_FinancialInstrumentAxis=us-gaap_CommitmentsToExtendCreditMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_LossContingenciesByNatureOfContingencyAxis=us-gaap_StandbyLettersOfCreditMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: