Significant Accounting Policies (Policies)	3 Months Ended
Significant Accounting Policies (Policies)	Mar. 31, 2018
Accounting Policies [Abstract]
Consolidation, Policy [Policy Text Block]	Principles of Consolidation and Basis of Presentation The accompanying consolidated financial statements include the accounts of CB Financial Services, Inc. (“CB Financial”) and its wholly owned subsidiary, Community Bank (the “Bank”), and the Bank’s wholly-owned subsidiary, Exchange Underwriters, Inc. (“Exchange Underwriters” or “EU”). CB Financial and the Bank are collectively referred to as the “Company”. All intercompany transactions and balances have been eliminated in consolidation. The accompanying unaudited interim financial statements have been prepared pursuant to the rules and regulations of the Securities and Exchange Commission (“SEC”) and in conformity with accounting principles generally accepted in the United States of America (“GAAP”). Certain information and note disclosures normally included in annual financial statements prepared in accordance with GAAP have been condensed or omitted pursuant to those rules and regulations, although the Company believes that the disclosures made are adequate to make the information not misleading in any material respect. In preparing financial statements in conformity with GAAP, management is required to make estimates and assumptions that affect the reported amounts of assets and liabilities and the disclosure of contingent assets and liabilities at the date of the financial statements and income and expenses during the reporting period. Actual results could differ significantly from those estimates. Material estimates that are particularly susceptible to significant change in the near term relate to determination of the allowance for losses on loans, the valuation of real estate acquired in connection with foreclosures or in satisfaction of loans, evaluation of securities for other-than-temporary impairment including related cash flow projections, goodwill impairment, and the valuation of deferred tax assets. In the opinion of management, the accompanying unaudited interim financial statements include all adjustments considered necessary for a fair presentation of the Company’s financial position and results of operations at the dates and for the periods presented. All of these adjustments are of a normal, recurring nature, and they are the only adjustments included in the accompanying unaudited interim financial statements. These interim consolidated financial statements should be read in conjunction with the audited consolidated financial statements and notes thereto in the Company’s Annual Report on Form 10 -K for the year ended December 31, 2017. Interim results are not necessarily indicative of results for a full year. The Company evaluated subsequent events through the date the consolidated financial statements were filed with the SEC and incorporated into the consolidated financial statements the effect of all material known events determined by ASC Topic 855, Subsequent Events , to be recognizable events.
Nature of Operations [Policy Text Block]	Nature of Operations The Company derives substantially all its income from banking and bank-related services which include interest earnings on commercial, commercial mortgage, residential real estate and consumer loan financing, as well as interest earnings on investment securities and fees generated from deposit services to its customers. The Company provides banking services primarily to communities in Greene, Allegheny, Washington, Fayette, and Westmoreland Counties located in southwestern Pennsylvania. The Company also conducts insurance brokerage activities through Exchange Underwriters.
Finance, Loans and Leases Receivable, Policy [Policy Text Block]	Acquired Loans Loans that were acquired in a previous merger, were recorded at fair value with no carryover of the related allowance for credit losses. The fair value of the acquired loans was estimated by management with the assistance of a third party valuation specialist. For performing loans acquired in the merger, the excess of cash flows expected at acquisition over the estimated fair value is referred to as the accretable discount and is recognized into interest income over the remaining life of the loan. For purchased credit impaired (“PCI”) loans acquired in the merger, the difference between contractually required payments at acquisition and the cash flows expected to be collected at acquisition is referred to as the nonaccretable discount. The nonaccretable discount represents estimated future credit losses expected to be incurred over the life of the loan. Subsequent decreases to the expected cash flows require an evaluation to determine the need for an allowance for loan losses. Subsequent improvements in expected cash flows result in the reversal of a corresponding amount of the nonaccretable discount which is then reclassified as accretable discount that is recognized into interest income over the remaining life of the loan using the interest method. The evaluation of the amount of future cash flows that is expected to be collected is performed in a similar manner as that used to determine our allowance for credit losses. Charge-offs of the principal amount on acquired loans would be first applied to the nonaccretable discount portion of the fair value adjustment.
Income Tax, Policy [Policy Text Block]	Income Taxes The income tax decrease was due to the enactment of the Tax Cuts and Jobs Act reducing the corporate tax rate from 34% to 21% effective January 1, 2018, and tax-exempt bank-owned life insurance proceeds which was a discrete item and reduced the expected 2018 effective tax rate of 16.7% to 10.9% at March 31, 2018, compared to 30.0% at March 31, 2017.
Prior Period Error Recognition [Policy Text Block]	Recognition of a Prior Period Error In April 2018, the Company discovered an error with the collateral position on a commercial and industrial classified loan relationship that had occurred in April 2017. This error resulted in the loss of the Company’s first lien position, leaving the loan with insufficient collateral. The Company corrected the error by recording a specific reserve and recognizing an additional $300,000 (pre-tax) of provision for loan losses for the quarter-ended March 31, 2018. The impact of the correction of an error resulted in a decrease of $300,000 in income before income taxes, a decrease of $63,000 in income taxes, and a decrease of $237,000 (after-tax) in net income ( $0.06 earnings per share) for the quarter ended March 31, 2018. As a result of this error, the Company’s 2017 results were overstated by $237,000 and the Company’s March 31, 2018 quarterly results were understated by the same amount. Management of the Company concluded the effect of the error was immaterial to the Company’s 2017 results as well as estimated annual results for 2018.
Reclassification, Policy [Policy Text Block]	Reclassifications Certain comparative amounts for the prior year have been reclassified to conform to the current year presentation. Such reclassifications did not affect net income or stockholders’ equity.
New Accounting Pronouncements, Policy [Policy Text Block]	Recent Accounting Standards In January 2018, the FASB issued Accounting Standards Update (“ASU”) 2018 - 01, Leases (Topic 842 ), Land Easement Practical Expedient for Transition to Topic 842. ASU 2018 - 01 is intended to be effective with ASU 2016 - 02, as amended. The amendments in ASU 2018 - 01 are as follows: provide an optional transition practical expedient for the adoption of ASU 2016 - 02 that, if elected, would not require an organization to reconsider their accounting for existing land easements that are not currently accounted for under the old lease standards; and clarify that new or modified land easements should be evaluated under ASU 2016 - 02, once an entity has adopted the new standard. ASU 2016 - 02 will require lessees to recognize a right-of-use (ROU) asset for its right to use the underlying asset and a lease liability for the corresponding lease obligation for leases with terms of more than twelve months. Both the ROU asset and lease liability will initially be measured at the present value of the future minimum lease payments over the lease term. Subsequent measurement, including the presentation of expenses and cash flows, will depend on the classification of the lease as either a finance or an operating lease. Accounting by lessors will remain largely unchanged from current U.S. GAAP. ASU 2016 - 02 is effective for fiscal years beginning after December 15, 2018, and interim periods within those years, with early adoption permitted, and is to be applied as of the beginning of the earliest period presented using a modified retrospective approach. The Company is currently evaluating the provisions of ASU 2016 - 02, but expects to report increased assets and liabilities as a result of reporting additional leases on the Company's consolidated financial condition or results of operations. In September 2017, the FASB issued ASU 2017 - 13, Revenue Recognition (Topic 605 ), Revenue from Contracts with Customers (Topic 606 ), Leases (Topic 840 ), and Leases (Topic 842 ): Amendments to SEC Paragraphs Pursuant to the Staff Announcement at the July 20, 2017 EITF Meeting and Rescission of Prior SEC Staff Announcements and Observer Comments. ASU 2017 - 13 amends the early adoption date option for certain companies related to the adoption of ASU No. 2014 - 09, Revenue from Contracts with Customers (Topic 606 ) and ASU No. 2016 - 02, Leases (Topic 842 ). The SEC staff stated the SEC would not object to a public business entity that otherwise would not meet the definition of a public business entity except for a requirement to include or the inclusion of its financial statements or financial information in another entity’s filing with the SEC adopting ASC Topic 606 for annual reporting periods beginning after December 15, 2018, and interim reporting periods within annual reporting periods beginning after December 15, 2019. The SEC staff stated the SEC would not object to a public business entity that otherwise would not meet the definition of a public business entity except for a requirement to include or the inclusion of its financial statements or financial information in another entity’s filing with the SEC adopting ASC Topic 842 for fiscal years beginning after December 15, 2019, and interim periods within fiscal years beginning after December 15, 2020. The Company is evaluating the provisions of ASU 2017 - 13 but believes that its adoption will not have a material impact on the Company's consolidated financial condition or results of operations. In July 2017, the FASB issued ASU 2017 - 11, Earnings Per Share (Topic 260 ); Distinguishing Liabilities from Equity (Topic 480 ); Derivatives and Hedging (Topic 815 ): (Part I) Accounting for Certain Financial Instruments with Down Round Features, (Part II) Replacement of the Indefinite Deferral for Mandatorily Redeemable Financial Instruments of Certain Nonpublic Entities and Certain Mandatorily Redeemable Noncontrolling Interests with a Scope Exception. ASU 2017 - 11 amendments simplify the accounting for certain financial instruments with down round features. The amendments require companies to disregard the down round feature when assessing whether the instrument is indexed to its own stock, for purposes of determining liability or equity classification. Companies that provide earnings per share (EPS) data will adjust their basic EPS calculation for the effect of the feature when triggered and will also recognize the effect of the trigger within equity. ASU 2017 - 11 is effective for public business entities that are SEC filers for annual periods beginning after December 15, 2018, and interim periods within those annual periods, for public entities that are not SEC filers for annual periods beginning after December 15, 2019 and for all other entities for annual periods beginning after December 15, 2020 with early adoption permitted. The Company is evaluating the provisions of ASU 2017 - 11 but believes that its adoption will not have a material impact on the Company's consolidated financial condition or results of operations. In May 2017, the FASB issued ASU 2017 - 10, Service Concession Arrangements (Topic 853 ): Determining the Customer of the Operation Services. ASU 2017 - 10 amendments clarify that the grantor in a service concession arrangement is the customer of the operation services in all cases for those arrangements. ASU 2017 - 10 is effective for public business entities that are SEC filers for annual periods beginning after December 15, 2017, and interim periods within those annual periods, for public entities that are not SEC filers for annual periods beginning after December 15, 2018 and for all other entities for annual periods beginning after December 15, 2019 with early adoption permitted, including within an interim period, subject to specific transition requirements depending on whether an entity adopted Topic 606 before or after the issuance of ASU 2017 - 10. The Company adopted the provisions of ASU 2017 - 10 as of January 1, 2018, and its adoption did not have a material impact on the Company's consolidated financial condition or results of operations. In May 2017, the FASB issued ASU 2017 - 09, Compensation—Stock Compensation (Topic 718 ): Scope of Modification Accounting. ASU 2017 - 09 amendments provide guidance on determining which changes to the terms and conditions of share-based payment awards require an entity to apply modification accounting under ASU Topic 718. ASU 2017 - 09 is effective for all entities for annual periods, including interim periods within those annual periods beginning after December 15, 2017 with early adoption permitted. The Company adopted the provisions of ASU 2017 - 09 as of January 1, 2018, and its adoption did not have a material impact on the Company's consolidated financial condition or results of operations. In March 2017, the FASB issued ASU 2017 - 08, Receivables- Nonrefundable Fees and Other Costs (Subtopic 310 - 20 ): Premium Amortization on Purchases of Callable Debt Securities. ASU 2017 - 08 amends guidance on the amortization period of premiums on certain purchases of callable debt securities. The amendments shorten the amortization period of premiums on certain purchases of callable debt securities to the earliest call date. ASU 2017 - 08 is effective for public business entities that are SEC filers for annual periods beginning after December 15, 2018, and interim periods within those annual periods, for public entities that are not SEC filers for annual periods beginning after December 15, 2019 and for all other entities for annual periods beginning after December 15, 2020 with early adoption permitted. The Company is evaluating the provisions of ASU 2017 - 08 but believes that its adoption will not have a material impact on the Company's consolidated financial condition or results of operations. In January 2017, the FASB issued ASU 2017 - 04, Intangibles - Goodwill and Other (Topic 350 ): Simplifying the Test for Goodwill Impairment . ASU 2017 - 04 simplifies the accounting for goodwill impairments by eliminating the second step of the goodwill impairment test. Instead, an entity will apply a one -step quantitative test and record the amount of goodwill impairment as the excess of a reporting unit's carrying amount over its fair value, not to exceed the total amount of goodwill allocated to the reporting unit. The new guidance does not amend the optional qualitative assessment of goodwill impairment. ASU 2017 - 04 is effective for public business entities that are SEC filers for annual periods beginning after December 15, 2019, and interim periods within those annual periods, with early adoption permitted, and is to be applied on a prospective basis. The Company is currently evaluating the provisions of ASU 2017 - 04, but does not believe that its adoption will have a material impact on the Company's consolidated financial condition or results of operations. In August 2016, the FASB issued ASU 2016 - 15, Statement of Cash Flow (Topic 230 ): Classification of Certain Cash Receipts and Cash Payments . ASU 2016 - 15 addresses the following eight specific cash flow issues: debt prepayment or debt extinguishment costs; settlement of zero -coupon debt instruments or other debt instruments with coupon interest rates that are insignificant in relation to the effective interest rate of the borrowing; contingent consideration payments made after a business combination; proceeds from the settlement of insurance claims; proceeds from the settlement of corporate-owned life insurance policies, including bank-owned life insurance policies; distributions received from equity method investees; beneficial interests in securitization transactions; and separately identifiable cash flows and application of the predominance principle. ASU 2016 - 15 is effective for fiscal years beginning after December 15, 2017, and interim periods within those fiscal years. Early adoption is permitted and the amendments should be applied using a retrospective transition method to each period presented. The Company adopted the provisions of ASU 2016 - 15 as of January 1, 2018, and the adoption did not have a material impact on the Company's consolidated financial condition or results of operations. In June 2016, the FASB issued ASU 2016 - 13, Financial Instruments – Credit Losses (Topic 326 ): Measurement of Credit Losses on Financial Instruments . ASU 2016 - 13 amends guidance on reporting credit losses for assets held at amortized cost basis and available for sale debt securities. For assets held at amortized cost basis, ASU 2016 - 13 eliminates the probable initial recognition threshold in current GAAP; and instead requires an entity to reflect its current estimate of all expected credit losses. The allowance for credit losses is a valuation account that is deducted from the amortized cost basis of the financial assets to present the net amount expected to be collected. For available for sale debt securities, credit losses should be measured in a manner similar to current GAAP, however this ASU will require that credit losses be presented as an allowance rather than as a write-down. ASU 2016 - 13 affects companies holding financial assets and net investment in leases that are not accounted for at fair value through net income. The ASU 2016 - 13 amendments affect loans, debt securities, trade receivables, net investments in leases, off balance-sheet credit exposures, reinsurance receivables, and any other financial assets not excluded from the scope that have the contractual right to receive cash. ASU 2016 - 13 is effective for fiscal years beginning after December 15, 2019, and interim periods within those fiscal years, with early adoption permitted. The Company is currently evaluating the provisions of ASU 2016 - 13, but does not believe that its adoption will have a material impact on the Company's consolidated financial condition or results of operations. In February 2016, the FASB issued ASU 2016 - 02, Leases (Topic 842 ) , which increases the transparency and comparability among organizations by recognizing lease assets and lease liabilities on the balance sheet, and disclosing key information about leasing arrangements. ASU 2016 - 02 will require lessees to recognize a right-of-use (ROU) asset for its right to use the underlying asset and a lease liability for the corresponding lease obligation for leases with terms of more than twelve months. Both the ROU asset and lease liability will initially be measured at the present value of the future minimum lease payments over the lease term. Subsequent measurement, including the presentation of expenses and cash flows, will depend on the classification of the lease as either a finance or an operating lease. Accounting by lessors will remain largely unchanged from current U.S. GAAP. ASU 2016 - 02 is effective for fiscal years beginning after December 15, 2018, and interim periods within those years, with early adoption permitted, and is to be applied as of the beginning of the earliest period presented using a modified retrospective approach. The Company is currently evaluating the provisions of ASU 2016 - 02, but expects to report increased assets and liabilities as a result of reporting additional leases on the Company's consolidated statement of financial condition or results of operations. In January 2016, the FASB issued ASU 2016 - 01, Financial Instruments – Overall (Subtopic 825 - 10 ) , which enhances the reporting model for financial instruments regarding certain aspects of recognition, measurement, presentation, and disclosure. ASU 2016 - 01 (i) requires equity investments (except those accounted for under the equity method or that are consolidated) to be measured at fair value with changes in fair value recognized in net income; (ii) simplifies the impairment assessment of equity investments without readily determinable fair values by requiring a qualitative assessment to identify impairment; (iii) eliminates the requirement for an entity to disclose the methods and significant assumptions used to estimate the fair value of financial instruments measured at amortized cost; (iv) requires an entity to use the exit price notion when measuring the fair value of financial instruments for disclosure purposes; and (v) requires separate presentation of financial assets and financial liabilities by measurement category and form of financial asset on the balance sheet or in the accompanying notes to the financial statements. ASU 2016 - 01 is effective for fiscal years, and interim periods within those years, beginning after December 15, 2017, and is to be applied using a cumulative-effect adjustment to the balance sheet as of the beginning of the fiscal year of adoption. The Company adopted the provisions of ASU 2016 - 01 effective in the first quarter of 2018. Its adoption did not have a material impact on the Company's consolidated financial condition or results of operations. As of January 1, 2018, there was a one -time $40,000 cumulative fair value adjustment that was reclassified within the March 31, 2018, Statement of Stockholders’ Equity. As of March 31, 2018, the fair value adjustment recognized for equity securities was a loss of $25,000. This fair value adjustment will fluctuate between reporting periods and is based on market conditions. In May 2014, the FASB issued ASU 2014 - 09, Revenue from Contracts with Customers , which establishes a comprehensive revenue recognition standard for virtually all industries under GAAP, including those that previously followed industry-specific guidance, such as the real estate, construction and software industries. ASU 2014 - 09 specifies that an entity shall recognize revenue when, or as, the entity satisfies a performance obligation by transferring a promised good or service (i.e., an asset) to a customer. An asset is transferred when, or as, the customer obtains control of the asset. Entities are required to disclose qualitative and quantitative information on the nature, amount, timing and uncertainty of revenue and cash flows arising from contracts with customers. The guidance is effective for the Company’s financial statements beginning January 1, 2018. On January 1, 2018, the Company adopted ASU 2014 - 09, Revenue from Contracts with Customers and all subsequent amendments to the ASU (collectively, “ASC 606” ), which (i) creates a single framework for recognizing a gain (loss) from the transfer of nonfinancial assets, such as OREO. The Company adopted the ASC 2014 - 09 using the modified retrospective approach. The majority of the Company’s revenues are derived from interest income and other sources, including loans, leases, securities and derivatives that are outside the scope of ASC 606. The Company’s services that fall within the scope of ASC 606 are presented within non-interest income and non-interest expense, and are recognized as revenue as the Company satisfies its obligation to the customer. Services within the scope of ASC 606 include services fees on deposits accounts, interchange income, insurance commissions, other commissions, and the sale of OREO. Refer to Note 4 – Revenue Recognition from Contracts with Customers for further discussion on the Company’s accounting policies for revenue sources within the scope of ASC 606.

Disclosure of accounting policy for finance, loan and lease receivables, including those held for investment and those held for sale. This disclosure may include (1) the basis at which such receivables are carried in the entity's statements of financial position (2) how the level of the allowance for loan and lease losses is determined (3) when impairments, charge-offs or recoveries are recognized for such receivables (4) the treatment of origination fees and costs, including the amortization method for net deferred fees or costs (5) the treatment of any premiums or discounts or unearned income (6) the entity's income recognition (revenues, expenses and gains and losses arising from committing to issue, issuing, granting, collecting, terminating, modifying and holding loans) policies for such receivables, including those that are impaired, past due or placed on nonaccrual status and (7) the treatment of foreclosures or repossessions.

- Definition

Disclosure of accounting policy for income taxes, which may include its accounting policies for recognizing and measuring deferred tax assets and liabilities and related valuation allowances, recognizing investment tax credits, operating loss carryforwards, tax credit carryforwards, and other carryforwards, methodologies for determining its effective income tax rate and the characterization of interest and penalties in the financial statements.

+ References + Details