Regulatory Capital Matters (Details) - USD ($) $ in Thousands	Sep. 30, 2023	Dec. 31, 2022
Common equity tier 1 capital ratio
Actual, Amount	$ 382,539	$ 403,307
Actual, Ratio	10.37%	13.71%
Requirement for Capital Adequacy Purposes, Amount	$ 166,023	$ 132,349
Requirement for Capital Adequacy Purposes, Ratio	4.50%	4.50%
Total risk based capital ratio
Actual, Amount	$ 510,292	$ 523,285
Actual, Ratio	0.1383	0.1779
Requirement for Capital Adequacy Purposes, Amount	$ 295,151	$ 235,288
Requirement for Capital Adequacy Purposes, Ratio	0.08	0.08
Tier 1 risk based capital ratio
Actual, Amount	$ 400,539	$ 421,307
Actual, Ratio	0.1086	0.1432
Requirement for Capital Adequacy Purposes, Amount	$ 221,364	$ 176,466
Requirement for Capital Adequacy Purposes, Ratio	0.06	0.06
Tier 1 leverage ratio
Actual, Amount	$ 400,539	$ 421,307
Actual, Ratio	0.0784	0.0984
Requirement for Capital Adequacy Purposes, Amount	$ 204,152	$ 171,233
Requirement for Capital Adequacy Purposes, Ratio	0.04	0.04
Farmers National Banc Corp
Common equity tier 1 capital ratio
Actual, Amount	$ 396,302	$ 372,679
Actual, Ratio	10.76%	12.71%
Requirement for Capital Adequacy Purposes, Amount	$ 165,756	$ 131,968
Requirement for Capital Adequacy Purposes, Ratio	4.50%	4.50%
To be Well Capitalized Under Prompt Corrective Action Provisions, Amount	$ 239,425	$ 190,620
To be Well Capitalized Under Prompt Corrective Action Provisions, Ratio	6.50%	6.50%
Total risk based capital ratio
Actual, Amount	$ 431,055	$ 399,657
Actual, Ratio	0.117	0.1362
Requirement for Capital Adequacy Purposes, Amount	$ 294,677	$ 234,609
Requirement for Capital Adequacy Purposes, Ratio	0.08	0.08
To be Well Capitalized Under Prompt Corrective Action Provisions, Amount	$ 368,347	$ 293,262
To be Well Capitalized Under Prompt Corrective Action Provisions, Ratio	0.10	0.10
Tier 1 risk based capital ratio
Actual, Amount	$ 396,302	$ 372,679
Actual, Ratio	0.1076	0.1271
Requirement for Capital Adequacy Purposes, Amount	$ 221,008	$ 175,957
Requirement for Capital Adequacy Purposes, Ratio	0.06	0.06
To be Well Capitalized Under Prompt Corrective Action Provisions, Amount	$ 294,677	$ 234,609
To be Well Capitalized Under Prompt Corrective Action Provisions, Ratio	0.08	0.08
Tier 1 leverage ratio
Actual, Amount	$ 396,302	$ 372,679
Actual, Ratio	0.078	0.0876
Requirement for Capital Adequacy Purposes, Amount	$ 203,317	$ 170,245
Requirement for Capital Adequacy Purposes, Ratio	0.04	0.04
To be Well Capitalized Under Prompt Corrective Action Provisions, Amount	$ 254,147	$ 212,807
To be Well Capitalized Under Prompt Corrective Action Provisions, Ratio	0.05	0.05

Tier one common capital.

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Tier one risk based common capital required for capital adequacy to risk weighted assets.

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Tier one risk based common capital required to be well capitalized.

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Amount of total capital as defined by regulatory framework.

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Amount of minimum total risk-based capital required for capital adequacy as defined by regulatory framework.

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Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 942
-SubTopic 505
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (c)(1)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480696/942-505-50-1

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 942
-SubTopic 505
-Name Accounting Standards Codification
-Section 50
-Paragraph 1B
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480696/942-505-50-1B

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