XML 121 R1.htm IDEA: XBRL DOCUMENT v3.20.1
Document And Entity Information - USD ($)
 12 Months Ended
Dec. 31, 2019
Mar. 12, 2020
Jun. 30, 2019
Document Information [Line Items]      
Entity Registrant Name FIRST NATIONAL CORP /VA/    
Entity Central Index Key 0000719402    
Trading Symbol fxnc    
Current Fiscal Year End Date --12-31    
Entity Filer Category Accelerated Filer    
Entity Current Reporting Status Yes    
Entity Voluntary Filers No    
Entity Well-known Seasoned Issuer No    
Entity Emerging Growth Company false    
Entity Small Business true    
Entity Interactive Data Current Yes    
Entity Common Stock, Shares Outstanding (in shares)   4,974,925  
Entity Public Float     $ 90,189,348
Entity Shell Company false    
Document Type 10-K    
Document Period End Date Dec. 31, 2019    
Document Fiscal Year Focus 2019    
Document Fiscal Period Focus FY    
Amendment Flag false    
Title of 12(b) Security Common stock, par value $1.25 per share