Basis of Presentation (Policies)	6 Months Ended
Jun. 30, 2018
Basis of Presentation [Abstract]
Basis of Presentation	Citizens Financial Services, Inc. (individually and collectively with its direct and indirect subsidiaries, the "Company") is a Pennsylvania corporation and the holding company of its wholly owned subsidiary, First Citizens Community Bank (the "Bank"), and of the Bank's wholly owned subsidiary, First Citizens Insurance Agency, Inc. ("First Citizens Insurance"). The accompanying consolidated financial statements have been prepared pursuant to rules and regulations of the Securities and Exchange Commission ("SEC") and in conformity with U.S. generally accepted accounting principles. Because this report is based on an interim period, certain information and footnote disclosures normally included in financial statements prepared in accordance with U.S. generally accepted accounting principles have been condensed or omitted. Certain of the prior year amounts have been reclassified to conform with the current year presentation. Such reclassifications had no effect on net income or stockholders' equity. All material inter‑company balances and transactions have been eliminated in consolidation. In the opinion of management of the Company, the accompanying interim financial statements at June 30, 2018 and for the periods ended June 30, 2018 and 2017 include all adjustments, consisting of only normal recurring adjustments, necessary for a fair presentation of the financial condition and the results of operations for the periods. In preparing the consolidated financial statements, management is required to make estimates and assumptions that affect the reported amounts of assets and liabilities as of the date of the balance sheet and revenues and expenses for the period. The financial performance reported for the Company for the six month period ended June 30, 2018 is not necessarily indicative of the results to be expected for the full year. This information should be read in conjunction with the Company's Annual Report on Form 10-K for the year ended December 31, 2017. In May 2014,the Financial Accounting Standards Board ("FASB") issued Accounting Standards Update ("ASU") 2014-09, "Revenue from Contracts with Customers" ("ASU 2014-09"), which requires an entity to recognize the amount of revenue to which it expects to be entitled for the transfer of promised goods or services to customers. The ASU replaces most existing revenue recognition guidance in GAAP. The new standard was effective for the Company on January 1, 2018. Adoption of ASU 2014-09 did not have a material impact on the Company's consolidated financial statements other than additional disclosures in note 2 as the Company's primary sources of revenues are derived from interest and dividends earned on loans, investment securities, and other financial instruments that are not within the scope of ASU 2014-09. In January 2016, the FASB finalized ASU 2016-01, Financial Instruments - Overall (Subtopic 825-10): Recognition and Measurement of Financial Assets and Financial Liabilities. This accounting standard (a) requires separate presentation of equity investments (except those accounted for under the equity method of accounting or those that result in consolidation of the investee) on the balance sheet and measured at fair value with changes in fair value recognized in net income; (b) simplifies the impairment assessment of equity investments without readily determinable fair values by requiring a qualitative assessment to identify impairment; (c) eliminates the requirement to disclose the fair value of financial instruments measured at amortized cost for entities that are not public business entities; (d) eliminates the requirement for public business entities 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; (e) requires public business entities to use the exit price notion when measuring the fair value of financial instruments for disclosure purposes; (f) requires separate presentation of financial assets and financial liabilities by measurement category and form of financial asset (that is, securities or loans and receivables) on the balance sheet or the accompanying notes to the financial statements; and (g) clarifies that an entity should evaluate the need for a valuation allowance on a deferred tax asset related to available-for-sale securities in combination with the entity's other deferred tax assets. The adoption resulted in the Company recognizing a one-time cumulative effect adjustment of $1,000 between accumulated other comprehensive income and retained earnings on the consolidated balance sheet for the fair value of equity securities included in accumulated other comprehensive income as of the beginning of the period. The adjustment had no impact on net income on any prior periods presented. The Company has adopted this standard during the reporting period. On a prospective basis, the Company implemented changes to the measurement of the fair value of financial instruments using an exit price notion for disclosure purposes included in Note 12 to the financial statements. The June 30, 2018 fair value of each class of financial instruments disclosure did utilize the exit price notion when measuring fair value and, therefore, may not be comparable to the December 3l, 2017 disclosure. In March 2017, the FASB issued ASU 2017-07, Compensation-Retirement Benefits (Topic 71S). The amendments in this Update require that an employer report the service cost component in the same line item or items as other compensation costs arising from services rendered by the pertinent employees during the period. The other components of net benefit cost are required to be presented in the income statement separately from the service cost component. The Company adopted the standard on January 1, 2018, which resulted in a reclassification of $(53)and ($100) from Salaries and employee benefits into Other noninterest expenses on the Consolidated Statement of Income for the three and six month periods ended June 30, 2017. See note 10 for additional information on the presentation of these pension cost components.

Citizens Financial Services, Inc. (individually and collectively with its direct and indirect subsidiaries, the "Company") is a Pennsylvania corporation and the holding company of its wholly owned subsidiary, First Citizens Community Bank (the "Bank"), and of the Bank's wholly owned subsidiary, First Citizens Insurance Agency, Inc. ("First Citizens Insurance").

The accompanying consolidated financial statements have been prepared pursuant to rules and regulations of the Securities and Exchange Commission ("SEC") and in conformity with U.S. generally accepted accounting principles.  Because this report is based on an interim period, certain information and footnote disclosures normally included in financial statements prepared in accordance with U.S. generally accepted accounting principles have been condensed or omitted.  Certain of the prior year amounts have been reclassified to conform with the current year presentation.  Such reclassifications had no effect on net income or stockholders' equity.  All material inter‑company balances and transactions have been eliminated in consolidation.

In the opinion of management of the Company, the accompanying interim financial statements at June 30, 2018 and for the periods ended June 30, 2018 and 2017 include all adjustments, consisting of only normal recurring adjustments, necessary for a fair presentation of the financial condition and the results of operations for the periods. In preparing the consolidated financial statements, management is required to make estimates and assumptions that affect the reported amounts of assets and liabilities as of the date of the balance sheet and revenues and expenses for the period. The financial performance reported for the Company for the six month period ended June 30, 2018 is not necessarily indicative of the results to be expected for the full year.  This information should be read in conjunction with the Company's Annual Report on Form 10-K for the year ended December 31, 2017.

In May 2014,the Financial Accounting Standards Board ("FASB") issued Accounting Standards Update ("ASU") 2014-09, "Revenue from Contracts with Customers" ("ASU 2014-09"), which requires an entity to recognize the amount of revenue to which it expects to be entitled for the transfer of promised goods or services to customers. The ASU replaces most existing revenue recognition guidance in GAAP. The new standard was effective for the Company on January 1, 2018. Adoption of ASU 2014-09 did not have a material impact on the Company's consolidated financial statements other than additional disclosures in note 2 as the Company's primary sources of revenues are derived from interest and dividends earned on loans, investment securities, and other financial instruments that are not within the scope of ASU 2014-09.

In January 2016, the FASB finalized ASU 2016-01, Financial Instruments - Overall (Subtopic 825-10): Recognition and Measurement of Financial Assets and Financial Liabilities. This accounting standard (a) requires separate presentation of equity investments (except those accounted for under the equity method of accounting or those that result in consolidation of the investee) on the balance sheet and measured at fair value with changes in fair value recognized in net income; (b) simplifies the impairment assessment of equity investments without readily determinable fair values by requiring a qualitative assessment to identify impairment; (c) eliminates the requirement to disclose the fair value of financial instruments measured at amortized cost for entities that are not public business entities; (d) eliminates the requirement for public business entities 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; (e) requires public business entities to use the exit price notion when measuring the fair value of financial instruments for disclosure purposes; (f) requires separate presentation of financial assets and financial liabilities by measurement category and form of financial asset (that is, securities or loans and receivables) on the balance sheet or the accompanying notes to the financial statements; and (g) clarifies that an entity should evaluate the need for a valuation allowance on a deferred tax asset related to available-for-sale securities in combination with the entity's other deferred tax assets.

The adoption resulted in the Company recognizing a one-time cumulative effect adjustment of $1,000 between accumulated other comprehensive income and retained earnings on the consolidated balance sheet for the fair value of equity securities included in accumulated other comprehensive income as of the beginning of the period. The adjustment had no impact on net income on any prior periods presented.

The Company has adopted this standard during the reporting period. On a prospective basis, the Company implemented changes to the measurement of the fair value of financial instruments using an exit price notion for disclosure purposes included in Note 12 to the financial statements. The June 30, 2018 fair value of each class of financial instruments disclosure did utilize the exit price notion when measuring fair value and, therefore, may not be comparable to the December 3l, 2017 disclosure.

In March 2017, the FASB issued ASU 2017-07, Compensation-Retirement Benefits (Topic 71S). The amendments in this Update require that an employer report the service cost component in the same line item or items as other compensation costs arising from services rendered by the pertinent employees during the period. The other components of net benefit cost are required to be presented in the income statement separately from the service cost component. The Company adopted the standard on January 1, 2018, which resulted in a reclassification of $(53)and ($100) from Salaries and employee benefits into Other noninterest expenses on the Consolidated Statement of Income for the three and six month periods ended June 30, 2017. See note 10 for additional information on the presentation of these pension cost components.