<?xml version='1.0' encoding='UTF-8'?>
<FilingSummary>
  <Version>3.3.0.814</Version>
  <ProcessingTime/>
  <ReportFormat>html</ReportFormat>
  <ContextCount>434</ContextCount>
  <ElementCount>294</ElementCount>
  <EntityCount>1</EntityCount>
  <FootnotesReported>true</FootnotesReported>
  <SegmentCount>55</SegmentCount>
  <ScenarioCount>0</ScenarioCount>
  <TuplesReported>false</TuplesReported>
  <UnitCount>4</UnitCount>
  <MyReports>
    <Report instance="cbfv-20150930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R1.htm</HtmlFileName>
      <LongName>000 - Disclosure - Document And Entity Information</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.communitybank.tv/role/DocumentAndEntityInformation</Role>
      <ShortName>Document And Entity Information</ShortName>
      <MenuCategory>Cover</MenuCategory>
      <Position>1</Position>
    </Report>
    <Report instance="cbfv-20150930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R2.htm</HtmlFileName>
      <LongName>001 - Statement - Consolidated Statement of Financial Condition (Current Period Unaudited)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.communitybank.tv/role/ConsolidatedBalanceSheet</Role>
      <ShortName>Consolidated Statement of Financial Condition (Current Period Unaudited)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>2</Position>
    </Report>
    <Report instance="cbfv-20150930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R3.htm</HtmlFileName>
      <LongName>002 - Statement - Consolidated Statement of Financial Condition (Current Period Unaudited) (Parentheticals)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.communitybank.tv/role/ConsolidatedBalanceSheet_Parentheticals</Role>
      <ShortName>Consolidated Statement of Financial Condition (Current Period Unaudited) (Parentheticals)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>3</Position>
    </Report>
    <Report instance="cbfv-20150930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R4.htm</HtmlFileName>
      <LongName>003 - Statement - Consolidated Statement of Income (Unaudited)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.communitybank.tv/role/ConsolidatedIncomeStatement</Role>
      <ShortName>Consolidated Statement of Income (Unaudited)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>4</Position>
    </Report>
    <Report instance="cbfv-20150930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R5.htm</HtmlFileName>
      <LongName>004 - Statement - Consolidated Statement of Comprehensive Income (Unaudited)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.communitybank.tv/role/ConsolidatedComprehensiveIncome</Role>
      <ShortName>Consolidated Statement of Comprehensive Income (Unaudited)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>5</Position>
    </Report>
    <Report instance="cbfv-20150930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R6.htm</HtmlFileName>
      <LongName>005 - Statement - Consolidated Statement of Comprehensive Income (Unaudited) (Parentheticals)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.communitybank.tv/role/ConsolidatedComprehensiveIncome_Parentheticals</Role>
      <ShortName>Consolidated Statement of Comprehensive Income (Unaudited) (Parentheticals)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>6</Position>
    </Report>
    <Report instance="cbfv-20150930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R7.htm</HtmlFileName>
      <LongName>006 - Statement - Consolidated Statement of Changes in Stockholders’ Equity (Unaudited)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.communitybank.tv/role/ShareholdersEquityType2or3</Role>
      <ShortName>Consolidated Statement of Changes in Stockholders’ Equity (Unaudited)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>7</Position>
    </Report>
    <Report instance="cbfv-20150930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R8.htm</HtmlFileName>
      <LongName>007 - Statement - Consolidated Statement of Changes in Stockholders’ Equity (Unaudited) (Parentheticals)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.communitybank.tv/role/ShareholdersEquityType2or3_Parentheticals</Role>
      <ShortName>Consolidated Statement of Changes in Stockholders’ Equity (Unaudited) (Parentheticals)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>8</Position>
    </Report>
    <Report instance="cbfv-20150930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R9.htm</HtmlFileName>
      <LongName>008 - Statement - Consolidated Statement of Cash Flows (Unaudited)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.communitybank.tv/role/ConsolidatedCashFlow</Role>
      <ShortName>Consolidated Statement of Cash Flows (Unaudited)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>9</Position>
    </Report>
    <Report instance="cbfv-20150930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R10.htm</HtmlFileName>
      <LongName>009 - Statement - Consolidated Statement of Cash Flows (Unaudited) (Parentheticals)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.communitybank.tv/role/ConsolidatedCashFlow_Parentheticals</Role>
      <ShortName>Consolidated Statement of Cash Flows (Unaudited) (Parentheticals)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>10</Position>
    </Report>
    <Report instance="cbfv-20150930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R11.htm</HtmlFileName>
      <LongName>010 - Disclosure - Note 1 - Summary of Significant Accounting Policies</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.communitybank.tv/role/Note1SummaryofSignificantAccountingPolicies</Role>
      <ShortName>Note 1 - Summary of Significant Accounting Policies</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>11</Position>
    </Report>
    <Report instance="cbfv-20150930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R12.htm</HtmlFileName>
      <LongName>011 - Disclosure - Note 2 - Earnings Per Share</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.communitybank.tv/role/Note2EarningsPerShare</Role>
      <ShortName>Note 2 - Earnings Per Share</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>12</Position>
    </Report>
    <Report instance="cbfv-20150930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R13.htm</HtmlFileName>
      <LongName>012 - Disclosure - Note 3 - Investment Securities</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.communitybank.tv/role/Note3InvestmentSecurities</Role>
      <ShortName>Note 3 - Investment Securities</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>13</Position>
    </Report>
    <Report instance="cbfv-20150930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R14.htm</HtmlFileName>
      <LongName>013 - Disclosure - Note 4 - Loans and Related Allowance for Loan Loss</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.communitybank.tv/role/Note4LoansandRelatedAllowanceforLoanLoss</Role>
      <ShortName>Note 4 - Loans and Related Allowance for Loan Loss</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>14</Position>
    </Report>
    <Report instance="cbfv-20150930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R15.htm</HtmlFileName>
      <LongName>014 - Disclosure - Note 5 - Deposits</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.communitybank.tv/role/Note5Deposits</Role>
      <ShortName>Note 5 - Deposits</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>15</Position>
    </Report>
    <Report instance="cbfv-20150930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R16.htm</HtmlFileName>
      <LongName>015 - Disclosure - Note 6 - Short-term Borrowings</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.communitybank.tv/role/Note6ShorttermBorrowings</Role>
      <ShortName>Note 6 - Short-term Borrowings</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>16</Position>
    </Report>
    <Report instance="cbfv-20150930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R17.htm</HtmlFileName>
      <LongName>016 - Disclosure - Note 7 - Other Borrowed Funds</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.communitybank.tv/role/Note7OtherBorrowedFunds</Role>
      <ShortName>Note 7 - Other Borrowed Funds</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>17</Position>
    </Report>
    <Report instance="cbfv-20150930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R18.htm</HtmlFileName>
      <LongName>017 - Disclosure - Note 8 - Commitments and Contingent Liabilities</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.communitybank.tv/role/Note8CommitmentsandContingentLiabilities</Role>
      <ShortName>Note 8 - Commitments and Contingent Liabilities</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>18</Position>
    </Report>
    <Report instance="cbfv-20150930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R19.htm</HtmlFileName>
      <LongName>018 - Disclosure - Note 9 - Fair Value Disclosure</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.communitybank.tv/role/Note9FairValueDisclosure</Role>
      <ShortName>Note 9 - Fair Value Disclosure</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>19</Position>
    </Report>
    <Report instance="cbfv-20150930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R20.htm</HtmlFileName>
      <LongName>019 - Disclosure - Accounting Policies, by Policy (Policies)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.communitybank.tv/role/AccountingPoliciesByPolicy</Role>
      <ShortName>Accounting Policies, by Policy (Policies)</ShortName>
      <MenuCategory>Policies</MenuCategory>
      <ParentRole>http://www.communitybank.tv/role/Note1SummaryofSignificantAccountingPolicies</ParentRole>
      <Position>20</Position>
    </Report>
    <Report instance="cbfv-20150930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R21.htm</HtmlFileName>
      <LongName>020 - Disclosure - Note 2 - Earnings Per Share (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.communitybank.tv/role/Note2EarningsPerShareTables</Role>
      <ShortName>Note 2 - Earnings Per Share (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.communitybank.tv/role/Note2EarningsPerShare</ParentRole>
      <Position>21</Position>
    </Report>
    <Report instance="cbfv-20150930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R22.htm</HtmlFileName>
      <LongName>021 - Disclosure - Note 3 - Investment Securities (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.communitybank.tv/role/Note3InvestmentSecuritiesTables</Role>
      <ShortName>Note 3 - Investment Securities (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.communitybank.tv/role/Note3InvestmentSecurities</ParentRole>
      <Position>22</Position>
    </Report>
    <Report instance="cbfv-20150930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R23.htm</HtmlFileName>
      <LongName>022 - Disclosure - Note 4 - Loans and Related Allowance for Loan Loss (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.communitybank.tv/role/Note4LoansandRelatedAllowanceforLoanLossTables</Role>
      <ShortName>Note 4 - Loans and Related Allowance for Loan Loss (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.communitybank.tv/role/Note4LoansandRelatedAllowanceforLoanLoss</ParentRole>
      <Position>23</Position>
    </Report>
    <Report instance="cbfv-20150930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R24.htm</HtmlFileName>
      <LongName>023 - Disclosure - Note 5 - Deposits (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.communitybank.tv/role/Note5DepositsTables</Role>
      <ShortName>Note 5 - Deposits (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.communitybank.tv/role/Note5Deposits</ParentRole>
      <Position>24</Position>
    </Report>
    <Report instance="cbfv-20150930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R25.htm</HtmlFileName>
      <LongName>024 - Disclosure - Note 6 - Short-term Borrowings (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.communitybank.tv/role/Note6ShorttermBorrowingsTables</Role>
      <ShortName>Note 6 - Short-term Borrowings (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.communitybank.tv/role/Note6ShorttermBorrowings</ParentRole>
      <Position>25</Position>
    </Report>
    <Report instance="cbfv-20150930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R26.htm</HtmlFileName>
      <LongName>025 - Disclosure - Note 7 - Other Borrowed Funds (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.communitybank.tv/role/Note7OtherBorrowedFundsTables</Role>
      <ShortName>Note 7 - Other Borrowed Funds (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.communitybank.tv/role/Note7OtherBorrowedFunds</ParentRole>
      <Position>26</Position>
    </Report>
    <Report instance="cbfv-20150930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R27.htm</HtmlFileName>
      <LongName>026 - Disclosure - Note 8 - Commitments and Contingent Liabilities (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.communitybank.tv/role/Note8CommitmentsandContingentLiabilitiesTables</Role>
      <ShortName>Note 8 - Commitments and Contingent Liabilities (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.communitybank.tv/role/Note8CommitmentsandContingentLiabilities</ParentRole>
      <Position>27</Position>
    </Report>
    <Report instance="cbfv-20150930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R28.htm</HtmlFileName>
      <LongName>027 - Disclosure - Note 9 - Fair Value Disclosure (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.communitybank.tv/role/Note9FairValueDisclosureTables</Role>
      <ShortName>Note 9 - Fair Value Disclosure (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.communitybank.tv/role/Note9FairValueDisclosure</ParentRole>
      <Position>28</Position>
    </Report>
    <Report instance="cbfv-20150930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R29.htm</HtmlFileName>
      <LongName>029 - Disclosure - Note 2 - Earnings Per Share (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.communitybank.tv/role/Note2EarningsPerShareDetails</Role>
      <ShortName>Note 2 - Earnings Per Share (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.communitybank.tv/role/Note2EarningsPerShareTables</ParentRole>
      <Position>29</Position>
    </Report>
    <Report instance="cbfv-20150930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R30.htm</HtmlFileName>
      <LongName>030 - Disclosure - Note 2 - Earnings Per Share (Details) - Basic and Diluted Earnings Per Common Share</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.communitybank.tv/role/BasicandDilutedEarningsPerCommonShareTable</Role>
      <ShortName>Note 2 - Earnings Per Share (Details) - Basic and Diluted Earnings Per Common Share</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.communitybank.tv/role/Note2EarningsPerShareTables</ParentRole>
      <Position>30</Position>
    </Report>
    <Report instance="cbfv-20150930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R31.htm</HtmlFileName>
      <LongName>031 - Disclosure - Note 3 - Investment Securities (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.communitybank.tv/role/Note3InvestmentSecuritiesDetails</Role>
      <ShortName>Note 3 - Investment Securities (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.communitybank.tv/role/Note3InvestmentSecuritiesTables</ParentRole>
      <Position>31</Position>
    </Report>
    <Report instance="cbfv-20150930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R32.htm</HtmlFileName>
      <LongName>032 - Disclosure - Note 3 - Investment Securities (Details) - Amortized Cost and Fair Value of Investment Securities Available-for-Sale</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.communitybank.tv/role/AmortizedCostandFairValueofInvestmentSecuritiesAvailableforSaleTable</Role>
      <ShortName>Note 3 - Investment Securities (Details) - Amortized Cost and Fair Value of Investment Securities Available-for-Sale</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.communitybank.tv/role/Note3InvestmentSecuritiesTables</ParentRole>
      <Position>32</Position>
    </Report>
    <Report instance="cbfv-20150930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R33.htm</HtmlFileName>
      <LongName>033 - Disclosure - Note 3 - Investment Securities (Details) - Amortized Cost and Fair Value of Investment Securities Held-to-maturity</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.communitybank.tv/role/AmortizedCostandFairValueofInvestmentSecuritiesHeldtomaturityTable</Role>
      <ShortName>Note 3 - Investment Securities (Details) - Amortized Cost and Fair Value of Investment Securities Held-to-maturity</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.communitybank.tv/role/Note3InvestmentSecuritiesTables</ParentRole>
      <Position>33</Position>
    </Report>
    <Report instance="cbfv-20150930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R34.htm</HtmlFileName>
      <LongName>034 - Disclosure - Note 3 - Investment Securities (Details) - Gross Unrealized Losses and Fair Value by Investment Category and Continuous Unrealized Loss Position</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.communitybank.tv/role/GrossUnrealizedLossesandFairValuebyInvestmentCategoryandContinuousUnrealizedLossPositionTable</Role>
      <ShortName>Note 3 - Investment Securities (Details) - Gross Unrealized Losses and Fair Value by Investment Category and Continuous Unrealized Loss Position</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.communitybank.tv/role/Note3InvestmentSecuritiesTables</ParentRole>
      <Position>34</Position>
    </Report>
    <Report instance="cbfv-20150930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R35.htm</HtmlFileName>
      <LongName>035 - Disclosure - Note 3 - Investment Securities (Details) - Maturities of Investment Securities Available-for-Sale and Held-to-maturity</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.communitybank.tv/role/MaturitiesofInvestmentSecuritiesAvailableforSaleandHeldtomaturityTable</Role>
      <ShortName>Note 3 - Investment Securities (Details) - Maturities of Investment Securities Available-for-Sale and Held-to-maturity</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.communitybank.tv/role/Note3InvestmentSecuritiesTables</ParentRole>
      <Position>35</Position>
    </Report>
    <Report instance="cbfv-20150930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R36.htm</HtmlFileName>
      <LongName>036 - Disclosure - Note 4 - Loans and Related Allowance for Loan Loss (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.communitybank.tv/role/Note4LoansandRelatedAllowanceforLoanLossDetails</Role>
      <ShortName>Note 4 - Loans and Related Allowance for Loan Loss (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.communitybank.tv/role/Note4LoansandRelatedAllowanceforLoanLossTables</ParentRole>
      <Position>36</Position>
    </Report>
    <Report instance="cbfv-20150930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R37.htm</HtmlFileName>
      <LongName>037 - Disclosure - Note 4 - Loans and Related Allowance for Loan Loss (Details) - Composition of Loan Portfolio</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.communitybank.tv/role/CompositionofLoanPortfolioTable</Role>
      <ShortName>Note 4 - Loans and Related Allowance for Loan Loss (Details) - Composition of Loan Portfolio</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.communitybank.tv/role/Note4LoansandRelatedAllowanceforLoanLossTables</ParentRole>
      <Position>37</Position>
    </Report>
    <Report instance="cbfv-20150930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R38.htm</HtmlFileName>
      <LongName>038 - Disclosure - Note 4 - Loans and Related Allowance for Loan Loss (Details) - Credit Quality Information</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.communitybank.tv/role/CreditQualityInformationTable</Role>
      <ShortName>Note 4 - Loans and Related Allowance for Loan Loss (Details) - Credit Quality Information</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.communitybank.tv/role/Note4LoansandRelatedAllowanceforLoanLossTables</ParentRole>
      <Position>38</Position>
    </Report>
    <Report instance="cbfv-20150930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R39.htm</HtmlFileName>
      <LongName>039 - Disclosure - Note 4 - Loans and Related Allowance for Loan Loss (Details) - Delinquencies in the Loan Portfolio</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.communitybank.tv/role/DelinquenciesintheLoanPortfolioTable</Role>
      <ShortName>Note 4 - Loans and Related Allowance for Loan Loss (Details) - Delinquencies in the Loan Portfolio</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.communitybank.tv/role/Note4LoansandRelatedAllowanceforLoanLossTables</ParentRole>
      <Position>39</Position>
    </Report>
    <Report instance="cbfv-20150930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R40.htm</HtmlFileName>
      <LongName>040 - Disclosure - Note 4 - Loans and Related Allowance for Loan Loss (Details) - Nonperforming Assets</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.communitybank.tv/role/NonperformingAssetsTable</Role>
      <ShortName>Note 4 - Loans and Related Allowance for Loan Loss (Details) - Nonperforming Assets</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.communitybank.tv/role/Note4LoansandRelatedAllowanceforLoanLossTables</ParentRole>
      <Position>40</Position>
    </Report>
    <Report instance="cbfv-20150930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R41.htm</HtmlFileName>
      <LongName>041 - Disclosure - Note 4 - Loans and Related Allowance for Loan Loss (Details) - Loans Classified as TDRs</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.communitybank.tv/role/LoansClassifiedasTDRsTable</Role>
      <ShortName>Note 4 - Loans and Related Allowance for Loan Loss (Details) - Loans Classified as TDRs</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.communitybank.tv/role/Note4LoansandRelatedAllowanceforLoanLossTables</ParentRole>
      <Position>41</Position>
    </Report>
    <Report instance="cbfv-20150930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R42.htm</HtmlFileName>
      <LongName>042 - Disclosure - Note 4 - Loans and Related Allowance for Loan Loss (Details) - Impaired Loans</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.communitybank.tv/role/ImpairedLoansTable</Role>
      <ShortName>Note 4 - Loans and Related Allowance for Loan Loss (Details) - Impaired Loans</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.communitybank.tv/role/Note4LoansandRelatedAllowanceforLoanLossTables</ParentRole>
      <Position>42</Position>
    </Report>
    <Report instance="cbfv-20150930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R43.htm</HtmlFileName>
      <LongName>043 - Disclosure - Note 4 - Loans and Related Allowance for Loan Loss (Details) - Activity in the Allowance for Loan Losses</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.communitybank.tv/role/ActivityintheAllowanceforLoanLossesTable</Role>
      <ShortName>Note 4 - Loans and Related Allowance for Loan Loss (Details) - Activity in the Allowance for Loan Losses</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.communitybank.tv/role/Note4LoansandRelatedAllowanceforLoanLossTables</ParentRole>
      <Position>43</Position>
    </Report>
    <Report instance="cbfv-20150930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R44.htm</HtmlFileName>
      <LongName>044 - Disclosure - Note 4 - Loans and Related Allowance for Loan Loss (Details) - Accretable Discount on Loans Acquired at Fair Value</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.communitybank.tv/role/AccretableDiscountonLoansAcquiredatFairValueTable</Role>
      <ShortName>Note 4 - Loans and Related Allowance for Loan Loss (Details) - Accretable Discount on Loans Acquired at Fair Value</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.communitybank.tv/role/Note4LoansandRelatedAllowanceforLoanLossTables</ParentRole>
      <Position>44</Position>
    </Report>
    <Report instance="cbfv-20150930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R45.htm</HtmlFileName>
      <LongName>045 - Disclosure - Note 4 - Loans and Related Allowance for Loan Loss (Details) - Major Classifications of Loans Summarized by Individually Evaluated for Impairment and Collectively Evaluated for Potential Losses</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.communitybank.tv/role/MajorClassificationsofLoansSummarizedbyIndividuallyEvaluatedforImpairmentandCollectivelyEvaluatedforPotentialLossesTable</Role>
      <ShortName>Note 4 - Loans and Related Allowance for Loan Loss (Details) - Major Classifications of Loans Summarized by Individually Evaluated for Impairment and Collectively Evaluated for Potential Losses</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.communitybank.tv/role/Note4LoansandRelatedAllowanceforLoanLossTables</ParentRole>
      <Position>45</Position>
    </Report>
    <Report instance="cbfv-20150930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R46.htm</HtmlFileName>
      <LongName>046 - Disclosure - Note 5 - Deposits (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.communitybank.tv/role/Note5DepositsDetails</Role>
      <ShortName>Note 5 - Deposits (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.communitybank.tv/role/Note5DepositsTables</ParentRole>
      <Position>46</Position>
    </Report>
    <Report instance="cbfv-20150930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R47.htm</HtmlFileName>
      <LongName>047 - Disclosure - Note 5 - Deposits (Details) - Maturities of Time Deposits</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.communitybank.tv/role/MaturitiesofTimeDepositsTable</Role>
      <ShortName>Note 5 - Deposits (Details) - Maturities of Time Deposits</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.communitybank.tv/role/Note5DepositsTables</ParentRole>
      <Position>47</Position>
    </Report>
    <Report instance="cbfv-20150930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R48.htm</HtmlFileName>
      <LongName>048 - Disclosure - Note 6 - Short-term Borrowings (Details) - Federal Funds Purchased and Short-term Borrowings</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.communitybank.tv/role/FederalFundsPurchasedandShorttermBorrowingsTable</Role>
      <ShortName>Note 6 - Short-term Borrowings (Details) - Federal Funds Purchased and Short-term Borrowings</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.communitybank.tv/role/Note6ShorttermBorrowingsTables</ParentRole>
      <Position>48</Position>
    </Report>
    <Report instance="cbfv-20150930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R49.htm</HtmlFileName>
      <LongName>049 - Disclosure - Note 7 - Other Borrowed Funds (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.communitybank.tv/role/Note7OtherBorrowedFundsDetails</Role>
      <ShortName>Note 7 - Other Borrowed Funds (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.communitybank.tv/role/Note7OtherBorrowedFundsTables</ParentRole>
      <Position>49</Position>
    </Report>
    <Report instance="cbfv-20150930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R50.htm</HtmlFileName>
      <LongName>050 - Disclosure - Note 7 - Other Borrowed Funds (Details) - Federal Home Loan Bank Advances</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.communitybank.tv/role/FederalHomeLoanBankAdvancesTable</Role>
      <ShortName>Note 7 - Other Borrowed Funds (Details) - Federal Home Loan Bank Advances</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.communitybank.tv/role/Note7OtherBorrowedFundsTables</ParentRole>
      <Position>50</Position>
    </Report>
    <Report instance="cbfv-20150930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R51.htm</HtmlFileName>
      <LongName>051 - Disclosure - Note 8 - Commitments and Contingent Liabilities (Details) - Unused and Available Credit Balances of Financial Instruments Whose Contracts Represent Credit Risk</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.communitybank.tv/role/UnusedandAvailableCreditBalancesofFinancialInstrumentsWhoseContractsRepresentCreditRiskTable</Role>
      <ShortName>Note 8 - Commitments and Contingent Liabilities (Details) - Unused and Available Credit Balances of Financial Instruments Whose Contracts Represent Credit Risk</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.communitybank.tv/role/Note8CommitmentsandContingentLiabilitiesTables</ParentRole>
      <Position>51</Position>
    </Report>
    <Report instance="cbfv-20150930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R52.htm</HtmlFileName>
      <LongName>052 - Disclosure - Note 9 - Fair Value Disclosure (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.communitybank.tv/role/Note9FairValueDisclosureDetails</Role>
      <ShortName>Note 9 - Fair Value Disclosure (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.communitybank.tv/role/Note9FairValueDisclosureTables</ParentRole>
      <Position>52</Position>
    </Report>
    <Report instance="cbfv-20150930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R53.htm</HtmlFileName>
      <LongName>053 - Disclosure - Note 9 - Fair Value Disclosure (Details) - Assets and Liabilities Reported Fair Value</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.communitybank.tv/role/AssetsandLiabilitiesReportedFairValueTable</Role>
      <ShortName>Note 9 - Fair Value Disclosure (Details) - Assets and Liabilities Reported Fair Value</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.communitybank.tv/role/Note9FairValueDisclosureTables</ParentRole>
      <Position>53</Position>
    </Report>
    <Report instance="cbfv-20150930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R54.htm</HtmlFileName>
      <LongName>054 - Disclosure - Note 9 - Fair Value Disclosure (Details) - Significant Unobservable Inputs Used in the Fair Value Measurements</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.communitybank.tv/role/SignificantUnobservableInputsUsedintheFairValueMeasurementsTable</Role>
      <ShortName>Note 9 - Fair Value Disclosure (Details) - Significant Unobservable Inputs Used in the Fair Value Measurements</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.communitybank.tv/role/Note9FairValueDisclosureTables</ParentRole>
      <Position>54</Position>
    </Report>
    <Report instance="cbfv-20150930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R55.htm</HtmlFileName>
      <LongName>055 - Disclosure - Note 9 - Fair Value Disclosure (Details) - Estimated Fair Values of the Company’s Financial Instruments</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.communitybank.tv/role/EstimatedFairValuesoftheCompanysFinancialInstrumentsTable</Role>
      <ShortName>Note 9 - Fair Value Disclosure (Details) - Estimated Fair Values of the Company’s Financial Instruments</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.communitybank.tv/role/Note9FairValueDisclosureTables</ParentRole>
      <Position>55</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="Info">In ''Consolidated Statement of Financial Condition (Current Period Unaudited)'', column(s) 3, 4 are contained in other reports, so were removed by flow through suppression.</Log>
    <Log type="Info">In ''Consolidated Statement of Cash Flows (Unaudited)'', column(s) 1, 2 are contained in other reports, so were removed by flow through suppression.</Log>
  </Logs>
  <InputFiles>
    <File>cbfv-20150930.xml</File>
    <File>cbfv-20150930_cal.xml</File>
    <File>cbfv-20150930_def.xml</File>
    <File>cbfv-20150930_lab.xml</File>
    <File>cbfv-20150930_pre.xml</File>
    <File>cbfv-20150930.xsd</File>
  </InputFiles>
  <SupplementalFiles/>
  <BaseTaxonomies/>
  <HasPresentationLinkbase>true</HasPresentationLinkbase>
  <HasCalculationLinkbase>true</HasCalculationLinkbase>
</FilingSummary>

