XML 17 R55.htm IDEA: XBRL DOCUMENT v2.4.0.8

Fair Value Measurements - Additional Information (Detail) (USD $) In Thousands, unless otherwise specified	6 Months Ended
	Jun. 30, 2014	Dec. 31, 2013
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Period of maturity as classifies as short-term borrowings	90 days
Fair value of loan commitments and standby letters of credit	$ 0	$ 0
Maximum [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Period under consideration for valuation of real estate collateral	12 months
Period under consideration for valuation of business equipment	1 year
Minimum [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Period under consideration for valuation of house or building in the process of construction	1 year

X

- Definition

Fair value of loan commitments and standby letters of credit.

+ References

No definition available.

+ Details

Name:	fxnc_FairValueOfLoanCommitmentsAndStandbyLettersOfCredit
Namespace Prefix:	fxnc_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

X

- Definition

Minimum period of appraisal of property to consider different method to measure fair value.

+ References

No definition available.

+ Details

Name:	fxnc_PeriodOfAppraisalOfPropertyToConsiderDifferentMethodToMeasureFairValue
Namespace Prefix:	fxnc_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

X

- Definition

Period of maturity as classifies as short term borrowing.

+ References

No definition available.

+ Details

Name:	fxnc_PeriodOfMaturityAsClassifiesAsShortTermBorrowing
Namespace Prefix:	fxnc_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

X

- Definition

Maximum period used to determine value of business equipment.

+ References

No definition available.

+ Details

Name:	fxnc_PeriodUsedToDetermineValueOfBusinessEquipment
Namespace Prefix:	fxnc_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

X

- Definition

Maximum period used to determine value of real estate collateral.

+ References

No definition available.

+ Details

Name:	fxnc_PeriodUsedToDetermineValueOfRealEstateCollateral
Namespace Prefix:	fxnc_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

X

- Details

Name:	us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration