Regulatory Capital Matters (Details Textual)	Sep. 30, 2021	Dec. 31, 2020
Regulatory Matters (Additional Textual) [Abstract]
Common equity tier 1 capital to risk-weighted assets, capital conservation buffer ratio	2.50%
Tier 1 capital to risk-weighted assets, capital conservation buffer ratio	2.50%
Total capital to risk-weighted assets, capital conservation buffer ratio	2.50%
Minimum ratio of common equity tier 1 capital to risk-weighted assets	4.50%	4.50%
Minimum ratio of tier 1 capital to risk-weighted assets	0.060	0.060
Minimum ratio of total capital to risk-weighted assets	0.080	0.080
Minimum leverage ratio	0.040	0.040
Farmers National Banc Corp
Regulatory Matters (Additional Textual) [Abstract]
Minimum ratio of common equity tier 1 capital to risk-weighted assets	4.50%	4.50%
Minimum ratio of tier 1 capital to risk-weighted assets	0.060	0.060
Minimum ratio of total capital to risk-weighted assets	0.080	0.080
Minimum leverage ratio	0.040	0.040