Regulatory Capital Matters (Details Textual)	Jun. 30, 2018	Dec. 31, 2017
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%
Additional capital conservation buffer ratio	1.875%	1.25%
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	6.00%	6.00%
Minimum ratio of total capital to risk-weighted assets	8.00%	8.00%
Minimum leverage ratio	4.00%	4.00%
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	6.00%	6.00%
Minimum ratio of total capital to risk-weighted assets	8.00%	8.00%
Minimum leverage ratio	4.00%	4.00%

Additional capital conservation buffer ratio.

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Capital required for capital adequacy to risk weighted assets capital conservation buffer ratio.

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Regulatory Matters (Additional Textual) [Abstract]

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Tier one risk based capital required for capital adequacy to risk weighted assets capital conservation buffer ratio.

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No definition available.

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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 for capital adequacy to risk weighted assets capital conservation buffer ratio.

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- Definition

The minimum Total risk based capital ratio (total capital divided by risk weighted assets) required for capital adequacy purposes under the regulatory framework for prompt corrective action.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 505
-Section 50
-Paragraph 1
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-URI http://asc.fasb.org/extlink&oid=84167132&loc=SL5958568-112826

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The minimum amount of Tier 1 Leverage Capital for capital adequacy purposes divided by average assets as defined in the regulations.

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The minimum Tier One Capital Ratio (Tier one capital divided by risk-weighted assets) required for capital adequacy purposes under the regulatory framework for prompt corrective action.

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