Regulatory Matters (Details) - USD ($)
$ in Thousands
Dec. 31, 2015
Dec. 31, 2014
Common equity tier 1 capital ratio    
Actual, Amount $ 165,451  
Actual, Ratio 11.59%  
Requirement for Capital Adequacy Purposes, Amount $ 64,245  
Requirement for Capital Adequacy Purposes, Ratio 4.50%  
Total risk based capital ratio    
Actual, Amount $ 176,571 $ 121,340
Actual, Ratio 12.37% 16.48%
Requirement for Capital Adequacy Purposes, Amount $ 114,214 $ 58,523
Requirement for Capital Adequacy Purposes, Ratio 8.00% 8.00%
Tier 1 risk based capital ratio    
Actual, Amount $ 167,550 $ 113,654
Actual, Ratio 11.74% 15.43%
Requirement for Capital Adequacy Purposes, Amount $ 85,660 $ 29,262
Requirement for Capital Adequacy Purposes, Ratio 6.00% 4.00%
Tier 1 leverage ratio    
Actual, Amount $ 167,550 $ 113,654
Actual, Ratio 9.21% 10.03%
Requirement for Capital Adequacy Purposes, Amount $ 72,803 $ 45,313
Requirement for Capital Adequacy Purposes, Ratio 4.00% 4.00%
Farmers National Banc Corp    
Common equity tier 1 capital ratio    
Actual, Amount $ 157,396  
Actual, Ratio 11.08%  
Requirement for Capital Adequacy Purposes, Amount $ 63,938  
Requirement for Capital Adequacy Purposes, Ratio 4.50%  
To be Well Capitalized Under Prompt Corrective Action Provisions, Amount $ 92,354  
To be Well Capitalized Under Prompt Corrective Action Provisions, Ratio 6.50%  
Total risk based capital ratio    
Actual, Amount $ 166,374 $ 114,321
Actual, Ratio 11.71% 15.56%
Requirement for Capital Adequacy Purposes, Amount $ 113,667 $ 58,773
Requirement for Capital Adequacy Purposes, Ratio 8.00% 8.00%
To be Well Capitalized Under Prompt Corrective Action Provisions, Amount $ 142,084 $ 73,466
To be Well Capitalized Under Prompt Corrective Action Provisions, Ratio 10.00% 10.00%
Tier 1 risk based capital ratio    
Actual, Amount $ 157,396 $ 106,689
Actual, Ratio 11.08% 14.52%
Requirement for Capital Adequacy Purposes, Amount $ 85,250 $ 29,386
Requirement for Capital Adequacy Purposes, Ratio 6.00% 4.00%
To be Well Capitalized Under Prompt Corrective Action Provisions, Amount $ 113,667 $ 44,079
To be Well Capitalized Under Prompt Corrective Action Provisions, Ratio 8.00% 6.00%
Tier 1 leverage ratio    
Actual, Amount $ 157,396 $ 106,689
Actual, Ratio 8.65% 9.37%
Requirement for Capital Adequacy Purposes, Amount $ 72,770 $ 45,565
Requirement for Capital Adequacy Purposes, Ratio 4.00% 4.00%
To be Well Capitalized Under Prompt Corrective Action Provisions, Amount $ 90,963 $ 56,956
To be Well Capitalized Under Prompt Corrective Action Provisions, Ratio 5.00% 5.00%