<?xml version='1.0' encoding='utf-8'?>
<FilingSummary>
  <Version>3.23.2</Version>
  <ProcessingTime/>
  <ReportFormat>html</ReportFormat>
  <ContextCount>476</ContextCount>
  <ElementCount>368</ElementCount>
  <EntityCount>1</EntityCount>
  <FootnotesReported>false</FootnotesReported>
  <SegmentCount>84</SegmentCount>
  <ScenarioCount>0</ScenarioCount>
  <TuplesReported>false</TuplesReported>
  <UnitCount>7</UnitCount>
  <MyReports>
    <Report instance="cbfv-20230630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R1.htm</HtmlFileName>
      <LongName>0000001 - Document - Cover Page</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.communitybank.tv/role/CoverPage</Role>
      <ShortName>Cover Page</ShortName>
      <MenuCategory>Cover</MenuCategory>
      <Position>1</Position>
    </Report>
    <Report instance="cbfv-20230630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R2.htm</HtmlFileName>
      <LongName>0000002 - Statement - CONSOLIDATED STATEMENTS OF FINANCIAL CONDITION</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.communitybank.tv/role/CONSOLIDATEDSTATEMENTSOFFINANCIALCONDITION</Role>
      <ShortName>CONSOLIDATED STATEMENTS OF FINANCIAL CONDITION</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>2</Position>
    </Report>
    <Report instance="cbfv-20230630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R3.htm</HtmlFileName>
      <LongName>0000003 - Statement - CONSOLIDATED STATEMENTS OF FINANCIAL CONDITION (Parenthetical)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.communitybank.tv/role/CONSOLIDATEDSTATEMENTSOFFINANCIALCONDITIONParenthetical</Role>
      <ShortName>CONSOLIDATED STATEMENTS OF FINANCIAL CONDITION (Parenthetical)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>3</Position>
    </Report>
    <Report instance="cbfv-20230630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R4.htm</HtmlFileName>
      <LongName>0000004 - Statement - CONSOLIDATED STATEMENTS OF INCOME (UNAUDITED)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.communitybank.tv/role/CONSOLIDATEDSTATEMENTSOFINCOMEUNAUDITED</Role>
      <ShortName>CONSOLIDATED STATEMENTS OF INCOME (UNAUDITED)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>4</Position>
    </Report>
    <Report instance="cbfv-20230630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R5.htm</HtmlFileName>
      <LongName>0000005 - Statement - CONSOLIDATED STATEMENTS OF COMPREHENSIVE (LOSS) INCOME (UNAUDITED)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.communitybank.tv/role/CONSOLIDATEDSTATEMENTSOFCOMPREHENSIVELOSSINCOMEUNAUDITED</Role>
      <ShortName>CONSOLIDATED STATEMENTS OF COMPREHENSIVE (LOSS) INCOME (UNAUDITED)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>5</Position>
    </Report>
    <Report instance="cbfv-20230630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R6.htm</HtmlFileName>
      <LongName>0000006 - Statement - CONSOLIDATED STATEMENTS OF CHANGES IN STOCKHOLDERS??? EQUITY (UNAUDITED)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.communitybank.tv/role/CONSOLIDATEDSTATEMENTSOFCHANGESINSTOCKHOLDERSEQUITYUNAUDITED</Role>
      <ShortName>CONSOLIDATED STATEMENTS OF CHANGES IN STOCKHOLDERS??? EQUITY (UNAUDITED)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>6</Position>
    </Report>
    <Report instance="cbfv-20230630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R7.htm</HtmlFileName>
      <LongName>0000007 - Statement - CONSOLIDATED STATEMENTS OF CHANGES IN STOCKHOLDERS??? EQUITY (UNAUDITED) (Parenthetical)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.communitybank.tv/role/CONSOLIDATEDSTATEMENTSOFCHANGESINSTOCKHOLDERSEQUITYUNAUDITEDParenthetical</Role>
      <ShortName>CONSOLIDATED STATEMENTS OF CHANGES IN STOCKHOLDERS??? EQUITY (UNAUDITED) (Parenthetical)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>7</Position>
    </Report>
    <Report instance="cbfv-20230630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R8.htm</HtmlFileName>
      <LongName>0000008 - Statement - CONSOLIDATED STATEMENTS OF CASH FLOWS (UNAUDITED)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.communitybank.tv/role/CONSOLIDATEDSTATEMENTSOFCASHFLOWSUNAUDITED</Role>
      <ShortName>CONSOLIDATED STATEMENTS OF CASH FLOWS (UNAUDITED)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>8</Position>
    </Report>
    <Report instance="cbfv-20230630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R9.htm</HtmlFileName>
      <LongName>0000009 - Statement - CONSOLIDATED STATEMENT OF CASH FLOWS (UNAUDITED) (Parenthetical)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.communitybank.tv/role/CONSOLIDATEDSTATEMENTOFCASHFLOWSUNAUDITEDParenthetical</Role>
      <ShortName>CONSOLIDATED STATEMENT OF CASH FLOWS (UNAUDITED) (Parenthetical)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>9</Position>
    </Report>
    <Report instance="cbfv-20230630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R10.htm</HtmlFileName>
      <LongName>0000010 - Disclosure - Summary of Significant Accounting Policies</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.communitybank.tv/role/SummaryofSignificantAccountingPolicies</Role>
      <ShortName>Summary of Significant Accounting Policies</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>10</Position>
    </Report>
    <Report instance="cbfv-20230630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R11.htm</HtmlFileName>
      <LongName>0000011 - Disclosure - Earnings Per Share</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.communitybank.tv/role/EarningsPerShare</Role>
      <ShortName>Earnings Per Share</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>11</Position>
    </Report>
    <Report instance="cbfv-20230630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R12.htm</HtmlFileName>
      <LongName>0000012 - Disclosure - Securities</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.communitybank.tv/role/Securities</Role>
      <ShortName>Securities</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>12</Position>
    </Report>
    <Report instance="cbfv-20230630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R13.htm</HtmlFileName>
      <LongName>0000013 - Disclosure - Loans and Allowance for Credit Losses</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.communitybank.tv/role/LoansandAllowanceforCreditLosses</Role>
      <ShortName>Loans and Allowance for Credit Losses</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>13</Position>
    </Report>
    <Report instance="cbfv-20230630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R14.htm</HtmlFileName>
      <LongName>0000014 - Disclosure - Fair Value Disclosure</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.communitybank.tv/role/FairValueDisclosure</Role>
      <ShortName>Fair Value Disclosure</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>14</Position>
    </Report>
    <Report instance="cbfv-20230630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R15.htm</HtmlFileName>
      <LongName>0000015 - Disclosure - Commitments and Contingent Liabilities</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.communitybank.tv/role/CommitmentsandContingentLiabilities</Role>
      <ShortName>Commitments and Contingent Liabilities</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>15</Position>
    </Report>
    <Report instance="cbfv-20230630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R16.htm</HtmlFileName>
      <LongName>0000016 - Disclosure - Leases</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.communitybank.tv/role/Leases</Role>
      <ShortName>Leases</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>16</Position>
    </Report>
    <Report instance="cbfv-20230630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R17.htm</HtmlFileName>
      <LongName>0000017 - Disclosure - Other Noninterest Expense</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.communitybank.tv/role/OtherNoninterestExpense</Role>
      <ShortName>Other Noninterest Expense</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>17</Position>
    </Report>
    <Report instance="cbfv-20230630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R18.htm</HtmlFileName>
      <LongName>0000018 - Disclosure - Segment and Related Information</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.communitybank.tv/role/SegmentandRelatedInformation</Role>
      <ShortName>Segment and Related Information</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>18</Position>
    </Report>
    <Report instance="cbfv-20230630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R19.htm</HtmlFileName>
      <LongName>0000019 - Disclosure - Stock Based Compensation</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.communitybank.tv/role/StockBasedCompensation</Role>
      <ShortName>Stock Based Compensation</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>19</Position>
    </Report>
    <Report instance="cbfv-20230630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R20.htm</HtmlFileName>
      <LongName>0000020 - Disclosure - Subsequent Events</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.communitybank.tv/role/SubsequentEvents</Role>
      <ShortName>Subsequent Events</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>20</Position>
    </Report>
    <Report instance="cbfv-20230630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R21.htm</HtmlFileName>
      <LongName>995410 - Disclosure - Pay vs Performance Disclosure</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://xbrl.sec.gov/ecd/role/PvpDisclosure</Role>
      <ShortName>Pay vs Performance Disclosure</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>21</Position>
    </Report>
    <Report instance="cbfv-20230630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R22.htm</HtmlFileName>
      <LongName>9954701 - Disclosure - Summary of Significant Accounting Policies (Policies)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.communitybank.tv/role/SummaryofSignificantAccountingPoliciesPolicies</Role>
      <ShortName>Summary of Significant Accounting Policies (Policies)</ShortName>
      <MenuCategory>Policies</MenuCategory>
      <ParentRole>http://www.communitybank.tv/role/SummaryofSignificantAccountingPolicies</ParentRole>
      <Position>22</Position>
    </Report>
    <Report instance="cbfv-20230630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R23.htm</HtmlFileName>
      <LongName>9954702 - Disclosure - Earnings Per Share (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.communitybank.tv/role/EarningsPerShareTables</Role>
      <ShortName>Earnings Per Share (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.communitybank.tv/role/EarningsPerShare</ParentRole>
      <Position>23</Position>
    </Report>
    <Report instance="cbfv-20230630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R24.htm</HtmlFileName>
      <LongName>9954703 - Disclosure - Securities (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.communitybank.tv/role/SecuritiesTables</Role>
      <ShortName>Securities (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.communitybank.tv/role/Securities</ParentRole>
      <Position>24</Position>
    </Report>
    <Report instance="cbfv-20230630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R25.htm</HtmlFileName>
      <LongName>9954704 - Disclosure - Loans and Allowance for Credit Losses (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.communitybank.tv/role/LoansandAllowanceforCreditLossesTables</Role>
      <ShortName>Loans and Allowance for Credit Losses (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.communitybank.tv/role/LoansandAllowanceforCreditLosses</ParentRole>
      <Position>25</Position>
    </Report>
    <Report instance="cbfv-20230630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R26.htm</HtmlFileName>
      <LongName>9954705 - Disclosure - Fair Value Disclosure (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.communitybank.tv/role/FairValueDisclosureTables</Role>
      <ShortName>Fair Value Disclosure (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.communitybank.tv/role/FairValueDisclosure</ParentRole>
      <Position>26</Position>
    </Report>
    <Report instance="cbfv-20230630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R27.htm</HtmlFileName>
      <LongName>9954706 - Disclosure - Commitments and Contingent Liabilities (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.communitybank.tv/role/CommitmentsandContingentLiabilitiesTables</Role>
      <ShortName>Commitments and Contingent Liabilities (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.communitybank.tv/role/CommitmentsandContingentLiabilities</ParentRole>
      <Position>27</Position>
    </Report>
    <Report instance="cbfv-20230630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R28.htm</HtmlFileName>
      <LongName>9954707 - Disclosure - Leases (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.communitybank.tv/role/LeasesTables</Role>
      <ShortName>Leases (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.communitybank.tv/role/Leases</ParentRole>
      <Position>28</Position>
    </Report>
    <Report instance="cbfv-20230630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R29.htm</HtmlFileName>
      <LongName>9954708 - Disclosure - Other Noninterest Expense (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.communitybank.tv/role/OtherNoninterestExpenseTables</Role>
      <ShortName>Other Noninterest Expense (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.communitybank.tv/role/OtherNoninterestExpense</ParentRole>
      <Position>29</Position>
    </Report>
    <Report instance="cbfv-20230630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R30.htm</HtmlFileName>
      <LongName>9954709 - Disclosure - Segment and Related Information (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.communitybank.tv/role/SegmentandRelatedInformationTables</Role>
      <ShortName>Segment and Related Information (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.communitybank.tv/role/SegmentandRelatedInformation</ParentRole>
      <Position>30</Position>
    </Report>
    <Report instance="cbfv-20230630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R31.htm</HtmlFileName>
      <LongName>9954710 - Disclosure - Stock Based Compensation (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.communitybank.tv/role/StockBasedCompensationTables</Role>
      <ShortName>Stock Based Compensation (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.communitybank.tv/role/StockBasedCompensation</ParentRole>
      <Position>31</Position>
    </Report>
    <Report instance="cbfv-20230630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R32.htm</HtmlFileName>
      <LongName>9954711 - Disclosure - Summary of Significant Accounting Policies (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.communitybank.tv/role/SummaryofSignificantAccountingPoliciesDetails</Role>
      <ShortName>Summary of Significant Accounting Policies (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.communitybank.tv/role/SummaryofSignificantAccountingPoliciesPolicies</ParentRole>
      <Position>32</Position>
    </Report>
    <Report instance="cbfv-20230630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R33.htm</HtmlFileName>
      <LongName>9954712 - Disclosure - Earnings Per Share - Basic and Diluted Earnings Per Common Share (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.communitybank.tv/role/EarningsPerShareBasicandDilutedEarningsPerCommonShareDetails</Role>
      <ShortName>Earnings Per Share - Basic and Diluted Earnings Per Common Share (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>33</Position>
    </Report>
    <Report instance="cbfv-20230630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R34.htm</HtmlFileName>
      <LongName>9954713 - Disclosure - Earnings Per Share - Schedule of Computation of Diluted Earnings Per Share (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.communitybank.tv/role/EarningsPerShareScheduleofComputationofDilutedEarningsPerShareDetails</Role>
      <ShortName>Earnings Per Share - Schedule of Computation of Diluted Earnings Per Share (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>34</Position>
    </Report>
    <Report instance="cbfv-20230630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R35.htm</HtmlFileName>
      <LongName>9954714 - Disclosure - Securities - Amortized Cost and Fair Value of Investment Securities Available-for-sale (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.communitybank.tv/role/SecuritiesAmortizedCostandFairValueofInvestmentSecuritiesAvailableforsaleDetails</Role>
      <ShortName>Securities - Amortized Cost and Fair Value of Investment Securities Available-for-sale (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>35</Position>
    </Report>
    <Report instance="cbfv-20230630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R36.htm</HtmlFileName>
      <LongName>9954715 - Disclosure - Securities - Gross Unrealized Losses and Fair Value by Investment Category and Continuous Unrealized Loss Position (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.communitybank.tv/role/SecuritiesGrossUnrealizedLossesandFairValuebyInvestmentCategoryandContinuousUnrealizedLossPositionDetails</Role>
      <ShortName>Securities - Gross Unrealized Losses and Fair Value by Investment Category and Continuous Unrealized Loss Position (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>36</Position>
    </Report>
    <Report instance="cbfv-20230630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R37.htm</HtmlFileName>
      <LongName>9954716 - Disclosure - Securities - Narrative (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.communitybank.tv/role/SecuritiesNarrativeDetails</Role>
      <ShortName>Securities - Narrative (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>37</Position>
    </Report>
    <Report instance="cbfv-20230630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R38.htm</HtmlFileName>
      <LongName>9954717 - Disclosure - Securities - Maturities of Investment Securities Available-for-sale and Held-to-maturity (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.communitybank.tv/role/SecuritiesMaturitiesofInvestmentSecuritiesAvailableforsaleandHeldtomaturityDetails</Role>
      <ShortName>Securities - Maturities of Investment Securities Available-for-sale and Held-to-maturity (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>38</Position>
    </Report>
    <Report instance="cbfv-20230630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R39.htm</HtmlFileName>
      <LongName>9954718 - Disclosure - Securities - Gains (Losses) of Sales of Available-for-sale Investment Securities (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.communitybank.tv/role/SecuritiesGainsLossesofSalesofAvailableforsaleInvestmentSecuritiesDetails</Role>
      <ShortName>Securities - Gains (Losses) of Sales of Available-for-sale Investment Securities (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>39</Position>
    </Report>
    <Report instance="cbfv-20230630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R40.htm</HtmlFileName>
      <LongName>9954719 - Disclosure - Loans and Allowance for Credit Losses - Classification of Loans (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.communitybank.tv/role/LoansandAllowanceforCreditLossesClassificationofLoansDetails</Role>
      <ShortName>Loans and Allowance for Credit Losses - Classification of Loans (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>40</Position>
    </Report>
    <Report instance="cbfv-20230630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R41.htm</HtmlFileName>
      <LongName>9954720 - Disclosure - Loans and Allowance for Credit Losses - Narrative (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.communitybank.tv/role/LoansandAllowanceforCreditLossesNarrativeDetails</Role>
      <ShortName>Loans and Allowance for Credit Losses - Narrative (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>41</Position>
    </Report>
    <Report instance="cbfv-20230630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R42.htm</HtmlFileName>
      <LongName>9954721 - Disclosure - Loans and Allowance for Credit Losses - Summary of Loans by Year of Origination (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.communitybank.tv/role/LoansandAllowanceforCreditLossesSummaryofLoansbyYearofOriginationDetails</Role>
      <ShortName>Loans and Allowance for Credit Losses - Summary of Loans by Year of Origination (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>42</Position>
    </Report>
    <Report instance="cbfv-20230630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R43.htm</HtmlFileName>
      <LongName>9954722 - Disclosure - Loans and Allowance for Credit Losses - Internal Risk Rating System (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.communitybank.tv/role/LoansandAllowanceforCreditLossesInternalRiskRatingSystemDetails</Role>
      <ShortName>Loans and Allowance for Credit Losses - Internal Risk Rating System (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>43</Position>
    </Report>
    <Report instance="cbfv-20230630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R44.htm</HtmlFileName>
      <LongName>9954723 - Disclosure - Loans and Allowance for Credit Losses - Loans by Aging Categories (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.communitybank.tv/role/LoansandAllowanceforCreditLossesLoansbyAgingCategoriesDetails</Role>
      <ShortName>Loans and Allowance for Credit Losses - Loans by Aging Categories (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>44</Position>
    </Report>
    <Report instance="cbfv-20230630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R45.htm</HtmlFileName>
      <LongName>9954724 - Disclosure - Loans and Allowance for Credit Losses - Nonaccrual TDRs (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.communitybank.tv/role/LoansandAllowanceforCreditLossesNonaccrualTDRsDetails</Role>
      <ShortName>Loans and Allowance for Credit Losses - Nonaccrual TDRs (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>45</Position>
    </Report>
    <Report instance="cbfv-20230630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R46.htm</HtmlFileName>
      <LongName>9954725 - Disclosure - Loans and Allowance for Credit Losses - Activity in the Allowance for Loan Losses (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.communitybank.tv/role/LoansandAllowanceforCreditLossesActivityintheAllowanceforLoanLossesDetails</Role>
      <ShortName>Loans and Allowance for Credit Losses - Activity in the Allowance for Loan Losses (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>46</Position>
    </Report>
    <Report instance="cbfv-20230630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R47.htm</HtmlFileName>
      <LongName>9954726 - Disclosure - Loans and Allowance for Credit Losses - Schedule of Finance Receivable Allowance for Unfunded Commitments (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.communitybank.tv/role/LoansandAllowanceforCreditLossesScheduleofFinanceReceivableAllowanceforUnfundedCommitmentsDetails</Role>
      <ShortName>Loans and Allowance for Credit Losses - Schedule of Finance Receivable Allowance for Unfunded Commitments (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>47</Position>
    </Report>
    <Report instance="cbfv-20230630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R48.htm</HtmlFileName>
      <LongName>9954727 - Disclosure - Loans and Allowance for Credit Losses - Loans Summarized by Individually Evaluated for Impairment and Collectively Evaluated for Potential Losses (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.communitybank.tv/role/LoansandAllowanceforCreditLossesLoansSummarizedbyIndividuallyEvaluatedforImpairmentandCollectivelyEvaluatedforPotentialLossesDetails</Role>
      <ShortName>Loans and Allowance for Credit Losses - Loans Summarized by Individually Evaluated for Impairment and Collectively Evaluated for Potential Losses (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>48</Position>
    </Report>
    <Report instance="cbfv-20230630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R49.htm</HtmlFileName>
      <LongName>9954728 - Disclosure - Loans and Allowance for Credit Losses - Accretable Discount on Loans Acquired at Fair Value (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.communitybank.tv/role/LoansandAllowanceforCreditLossesAccretableDiscountonLoansAcquiredatFairValueDetails</Role>
      <ShortName>Loans and Allowance for Credit Losses - Accretable Discount on Loans Acquired at Fair Value (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>49</Position>
    </Report>
    <Report instance="cbfv-20230630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R50.htm</HtmlFileName>
      <LongName>9954729 - Disclosure - Loans and Allowance for Credit Losses - Impaired Loans (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.communitybank.tv/role/LoansandAllowanceforCreditLossesImpairedLoansDetails</Role>
      <ShortName>Loans and Allowance for Credit Losses - Impaired Loans (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>50</Position>
    </Report>
    <Report instance="cbfv-20230630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R51.htm</HtmlFileName>
      <LongName>9954730 - Disclosure - Fair Value Disclosure - Assets and Liabilities Reported Fair Value (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.communitybank.tv/role/FairValueDisclosureAssetsandLiabilitiesReportedFairValueDetails</Role>
      <ShortName>Fair Value Disclosure - Assets and Liabilities Reported Fair Value (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>51</Position>
    </Report>
    <Report instance="cbfv-20230630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R52.htm</HtmlFileName>
      <LongName>9954731 - Disclosure - Fair Value Disclosure - Significant Unobservable Inputs Used in the Fair Value Measurements (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.communitybank.tv/role/FairValueDisclosureSignificantUnobservableInputsUsedintheFairValueMeasurementsDetails</Role>
      <ShortName>Fair Value Disclosure - Significant Unobservable Inputs Used in the Fair Value Measurements (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>52</Position>
    </Report>
    <Report instance="cbfv-20230630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R53.htm</HtmlFileName>
      <LongName>9954732 - Disclosure - Fair Value Disclosure - Narrative (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.communitybank.tv/role/FairValueDisclosureNarrativeDetails</Role>
      <ShortName>Fair Value Disclosure - Narrative (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>53</Position>
    </Report>
    <Report instance="cbfv-20230630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R54.htm</HtmlFileName>
      <LongName>9954733 - Disclosure - Fair Value Disclosure - Estimated Fair Value of the Company's Financial Instruments (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.communitybank.tv/role/FairValueDisclosureEstimatedFairValueoftheCompanysFinancialInstrumentsDetails</Role>
      <ShortName>Fair Value Disclosure - Estimated Fair Value of the Company's Financial Instruments (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>54</Position>
    </Report>
    <Report instance="cbfv-20230630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R55.htm</HtmlFileName>
      <LongName>9954734 - Disclosure - Commitments and Contingent Liabilities - Unused and Available Credit Balances of Financial Instruments (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.communitybank.tv/role/CommitmentsandContingentLiabilitiesUnusedandAvailableCreditBalancesofFinancialInstrumentsDetails</Role>
      <ShortName>Commitments and Contingent Liabilities - Unused and Available Credit Balances of Financial Instruments (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>55</Position>
    </Report>
    <Report instance="cbfv-20230630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R56.htm</HtmlFileName>
      <LongName>9954735 - Disclosure - Leases - Narrative (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.communitybank.tv/role/LeasesNarrativeDetails</Role>
      <ShortName>Leases - Narrative (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>56</Position>
    </Report>
    <Report instance="cbfv-20230630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R57.htm</HtmlFileName>
      <LongName>9954736 - Disclosure - Leases - Operating Leases (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.communitybank.tv/role/LeasesOperatingLeasesDetails</Role>
      <ShortName>Leases - Operating Leases (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>57</Position>
    </Report>
    <Report instance="cbfv-20230630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R58.htm</HtmlFileName>
      <LongName>9954737 - Disclosure - Leases - Maturity of Operating Lease (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.communitybank.tv/role/LeasesMaturityofOperatingLeaseDetails</Role>
      <ShortName>Leases - Maturity of Operating Lease (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>58</Position>
    </Report>
    <Report instance="cbfv-20230630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R59.htm</HtmlFileName>
      <LongName>9954738 - Disclosure - Other Noninterest Expense - Components of Other Noninterest Expense (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.communitybank.tv/role/OtherNoninterestExpenseComponentsofOtherNoninterestExpenseDetails</Role>
      <ShortName>Other Noninterest Expense - Components of Other Noninterest Expense (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>59</Position>
    </Report>
    <Report instance="cbfv-20230630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R60.htm</HtmlFileName>
      <LongName>9954739 - Disclosure - Segment and Related Information - Narrative (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.communitybank.tv/role/SegmentandRelatedInformationNarrativeDetails</Role>
      <ShortName>Segment and Related Information - Narrative (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>60</Position>
    </Report>
    <Report instance="cbfv-20230630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R61.htm</HtmlFileName>
      <LongName>9954740 - Disclosure - Segment and Related Information - Reconciliation of Financial Data from Segments to Consolidated (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.communitybank.tv/role/SegmentandRelatedInformationReconciliationofFinancialDatafromSegmentstoConsolidatedDetails</Role>
      <ShortName>Segment and Related Information - Reconciliation of Financial Data from Segments to Consolidated (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>61</Position>
    </Report>
    <Report instance="cbfv-20230630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R62.htm</HtmlFileName>
      <LongName>9954741 - Disclosure - Stock Based Compensation - Stock Option Activity (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.communitybank.tv/role/StockBasedCompensationStockOptionActivityDetails</Role>
      <ShortName>Stock Based Compensation - Stock Option Activity (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>62</Position>
    </Report>
    <Report instance="cbfv-20230630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R63.htm</HtmlFileName>
      <LongName>9954742 - Disclosure - Stock Based Compensation - Nonvested Stock Option Activity (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.communitybank.tv/role/StockBasedCompensationNonvestedStockOptionActivityDetails</Role>
      <ShortName>Stock Based Compensation - Nonvested Stock Option Activity (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>63</Position>
    </Report>
    <Report instance="cbfv-20230630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R64.htm</HtmlFileName>
      <LongName>9954743 - Disclosure - Stock Based Compensation - Summary of Significant Assumptions for Newly Issued Stock Options (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.communitybank.tv/role/StockBasedCompensationSummaryofSignificantAssumptionsforNewlyIssuedStockOptionsDetails</Role>
      <ShortName>Stock Based Compensation - Summary of Significant Assumptions for Newly Issued Stock Options (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>64</Position>
    </Report>
    <Report instance="cbfv-20230630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R65.htm</HtmlFileName>
      <LongName>9954744 - Disclosure - Share Based Compensation - Restricted Stock Award Activity (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.communitybank.tv/role/ShareBasedCompensationRestrictedStockAwardActivityDetails</Role>
      <ShortName>Share Based Compensation - Restricted Stock Award Activity (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>65</Position>
    </Report>
    <Report instance="cbfv-20230630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R66.htm</HtmlFileName>
      <LongName>9954745 - Disclosure - Stock Based Compensation - Additional Information (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.communitybank.tv/role/StockBasedCompensationAdditionalInformationDetails</Role>
      <ShortName>Stock Based Compensation - Additional Information (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>66</Position>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <LongName>All Reports</LongName>
      <ReportType>Book</ReportType>
      <ShortName>All Reports</ShortName>
    </Report>
  </MyReports>
  <Logs>
    <Log type="Warning">[ix-0514-Hidden-Fact-Eligible-For-Transform] WARN: 1 fact(s) appearing in ix:hidden were eligible for transformation: cbfv:ShareBasedCompensationArrangementByShareBasedPaymentReductionOfSharesOverThreshold -  cbfv-20230630.htm 4</Log>
  </Logs>
  <InputFiles>
    <File doctype="10-Q" original="cbfv-20230630.htm">cbfv-20230630.htm</File>
    <File>cbfv-20230630.xsd</File>
    <File>cbfv-20230630_cal.xml</File>
    <File>cbfv-20230630_def.xml</File>
    <File>cbfv-20230630_lab.xml</File>
    <File>cbfv-20230630_pre.xml</File>
    <File>currentcbfv-ex311ceocertif.htm</File>
    <File>currentcbfv-ex312cfocertif.htm</File>
    <File>currentcbfv-ex321ceoandcfo.htm</File>
  </InputFiles>
  <SupplementalFiles>
    <File>cbfv-20230630_g1.jpg</File>
  </SupplementalFiles>
  <BaseTaxonomies>
    <BaseTaxonomy items="1955">http://fasb.org/us-gaap/2023</BaseTaxonomy>
    <BaseTaxonomy items="29">http://xbrl.sec.gov/dei/2023</BaseTaxonomy>
  </BaseTaxonomies>
  <HasPresentationLinkbase>true</HasPresentationLinkbase>
  <HasCalculationLinkbase>true</HasCalculationLinkbase>
</FilingSummary>
