XML 66 R54.htm IDEA: XBRL DOCUMENT v3.4.0.3

Capital Requirements - Additional Information (Detail)	3 Months Ended
	Mar. 31, 2016
Regulatory Capital Requirements [Abstract]
Capital conservation buffer period	4 years

X

- Definition

Capital conservation buffer phase period.

+ References

No definition available.

+ Details

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

X

- References

No definition available.

+ Details

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