Summary of Significant Accounting Policies (Policies)	3 Months Ended
Summary of Significant Accounting Policies (Policies)	Mar. 31, 2016
Accounting Policies [Abstract]
Principles of Consolidation	Principles of Consolidation: Farmers National Banc Corp. (“Company”) is a one-bank holding company registered under the Bank Holding Company Act of 1956, as amended. The Company provides full banking services through its nationally chartered subsidiary, The Farmers National Bank of Canfield (“Bank”). The Company acquired First National Bank of Orrville (“First National Bank”) a subsidiary of National Bancshares Corporation (“NBOH”) and 1^st National Community Bank (“FNCB”) a subsidiary of Tri-State 1^st Banc, Inc. (“Tri-State”) during 2015 and consolidated all activity of both acquisitions within the Bank. The consolidated financial statements also include the accounts of the Farmers National Bank of Canfield’s subsidiaries; Farmers National Insurance (“Insurance”) and Farmers of Canfield Investment Co. (“Investments”). The Company provides trust services through its subsidiary, Farmers Trust Company (“Trust”), retirement consulting services through National Associates, Inc. (“NAI”) and insurance services through the Bank’s subsidiary, Insurance. The consolidated financial statements include the accounts of the Company, the Bank and its subsidiaries, along with Trust and NAI. All significant intercompany balances and transactions have been eliminated in the consolidation.
Basis of Presentation	Basis of Presentation: The unaudited condensed consolidated financial statements have been prepared in conformity with the instructions to Form 10-Q and Article 10 of Regulation S-X. Accordingly, they do not include all of the information and footnotes required by U.S. generally accepted accounting principles (“U.S. GAAP”) for complete financial statements. The financial statements should be read in conjunction with the consolidated financial statements and notes thereto included in the Company’s 2015 Annual Report to Shareholders included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2015. The interim consolidated financial statements include all adjustments (consisting of only normal recurring items) that, in the opinion of management, are necessary for a fair presentation of the financial position and results of operations for the periods presented. The results of operations for the interim periods disclosed herein are not necessarily indicative of the results that may be expected for a full year. Certain items included in the prior period financial statements were reclassified to conform to the current period presentation. There was no effect on net income or total stockholders’ equity.
Estimates	Estimates: The preparation of financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates.
Segments	Segments: The Company provides a broad range of financial services to individuals and companies in northeastern Ohio. Operations are managed and financial performance is primarily aggregated and reported in three lines of business, the Bank segment, the Trust segment and the Retirement Consulting segment.
Comprehensive Income	Comprehensive Income: Comprehensive income consists of net income and other comprehensive income. Other comprehensive income consists of unrealized gains and losses on securities available for sale and changes in the funded status of the post-retirement health plan, which are recognized as separate components of equity, net of tax effects. For all periods presented there was no change in the funded status of the post-retirement health plan.
New Accounting Standards	New Accounting Standards: In March 2016, FASB issued Accounting Standards Update (ASU) 2016-09 - Compensation - Stock Compensation (Topic 718): Improvements to Employee Share-Based Payment Accounting. The Board is issuing this Update as part of its initiative to reduce complexity in accounting standards. The areas for simplification in this Update involve several aspects of the accounting for employee share-based payment transactions, including the income tax consequences, classification of awards as either equity or liabilities, and classification on the statement of cash flows. Some of the areas for simplification apply only to nonpublic entities. In addition, the amendments in this Update eliminate the guidance in Topic 718 that was indefinitely deferred shortly after the issuance of FASB Statement No. 123 (revised 2004), Share-Based Payment. This ASU is the final version of Proposed Accounting Standards Update—Compensation—Stock Compensation (Topic 718): Improvements to Employee Share-Based Payment Accounting, which has been deleted. Management is currently evaluating the impact of the adoption of this guidance on the Company’s consolidated financial statements. In February 2016, the FASB issued ASU 2016-02 - Leases (Topic 842). The ASU will require all organizations that lease assets to recognize on the balance sheet the assets and liabilities for the rights and obligations created by those leases. Additional qualitative and quantitative disclosures will be required so that users can understand more about the nature of an entity’s leasing activities. The amendments in this Update create Topic 842 Leases, and supersede the leases requirements in Topic 840 Leases. Topic 842 specifies the accounting for leases. The objective of Topic 842 is to establish the principles that lessees and lessors shall apply to report useful information to users of financial statements about the amount, timing, and uncertainty of cash flows arising from a lease. This ASU is the final version of Proposed Accounting Standards Update (Revised) 2013-270—Leases (Topic 842), which has been deleted. The new guidance is effective for annual reporting periods and interim reporting periods within those annual periods, beginning after December 15, 2018. Early adoption is permitted. Management is currently evaluating the impact of the adoption of this guidance on the Company’s consolidated financial statements. In January 2016, the FASB issued ASU 2016-01 - Financial Instruments - Overall (Subtopic 825-10): Recognition and Measurement of Financial Assets and Financial Liabilities. The amendments in this Update require all equity investments to be measured at fair value with changes in the fair value recognized through net income (other than those accounted for under equity method of accounting or those that result in consolidation of the investee). The amendments in this Update also require an entity to present separately in other comprehensive income the portion of the total change in the fair value of a liability resulting from a change in the instrument-specific credit risk when the entity has elected to measure the liability at fair value in accordance with the fair value option for financial instruments. In addition the amendments in this Update eliminate the requirement to disclose the fair value of financial instruments measured at amortized cost for entities that are not public business entities and the requirement for to disclose the method(s) and significant assumptions used to estimate the fair value that is required to be disclosed for financial instruments measured at amortized cost on the balance sheet for public business entities. This Accounting Standards Update is the final version of Proposed Accounting Standards Update 2013-220—Financial Instruments—Overall (Subtopic 825-10) and Proposed Accounting Standards Update 2013-221—Financial Instruments—Overall (Subtopic 825-10). The new guidance is effective for annual reporting periods and interim reporting periods within those annual periods, beginning after December 15, 2017. Management is currently evaluating the impact of the adoption of this guidance on the Company’s consolidated financial statements.