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statementnote10regulatorymattersscheduleofcompliancewithregulatorycapitalrequirementsunderbankingregulationsdetails statementnote12fairvalueassetsandliabilitiesmeasuredatfairvalueonarecurringbasisdetails Federal Home Loan Bank Advances, Interest-only Single Maturity, Maturity at October 9, 2015 [Member] Represents the advances from Federal Home Loan Band Advances with interest only single maturity, and maturity at October 9, 2015. statementnote9incometaxesnetdeferredincometaxassetdetails statementnote9incometaxesscheduleofeffectiveincometaxratereconciliationdetails statementnote12fairvalueestimatedfairvaluesoffinancialinstrumentsdetails Pooled Trust Preferred Securities Subject to Mandatory Redemption [Member] Preferred securities that embody an unconditional obligation requiring the issuer to redeem the securities by transferring the assets at a specified or determinable date (or dates) or upon an event that is certain to occur, that are issued by a consolidated trust to outside investors where the trust uses the proceeds of the issuance of those securities to purchase, from the financial institution that established the trust, an equivalent amount of junior subordinated debentures or other loans having stated maturities. statementnote13parentcompanyfinancialstatementscondensedbalancesheetsdetails statementnote12fairvaluefinancialassetsandliabilitiesmeasuredatfairvalueonanonrecurringbasisdetails statementnote12fairvaluequantitativeinformationaboutlevel3fairvaluemeasurementsdetails statementnote14earningspersharescheduleofearningspersharebasicanddiluteddetails statementnote15accumulatedothercomprehensiveincomelosscomponentsofothercomprehensiveincomedetails Net increase in deposit accounts statementnote13parentcompanyfinancialstatementscondensedstatementsofincomeandcomprehensiveincomedetails statementnote13parentcompanyfinancialstatementscondensedstatementsofcashflowsdetails Notes To Financial Statements [Abstract] Data processing expenses Notes To Financial Statements Telephone and communications Commercial Mortgage Backed Securities [Member] Collateralized Mortgage Obligations [Member] Furniture and Fixtures [Member] Cash flows from financing activities: Federal Home Loan Bank Advances, Interest-only Single Maturity, Maturity at July 5, 2016 [Member] Represents the advances from Federal Home Loan Band Advances with interest only single maturity, and maturity at July 5, 2016. us-gaap_NetCashProvidedByUsedInInvestingActivities Net cash flows from investing activities Net cash flows from investing activities Federal Home Loan Bank Advances, Interest-only Single Maturity, Maturity at July 1, 2016 [Member] Represents the advances from Federal Home Loan Band Advances with interest only single maturity, and maturity at July 1, 2016. Federal Home Loan Bank Advances, Interest-only Single Maturity, Maturity at January 18, 2019 [Member] Represents the advances from Federal Home Loan Band Advances with interest only single maturity, and maturity at January 18, 2019. Occupancy and equipment Federal Home Loan Bank Advances, Principal and Interest Mortgage Matched, Maturity at April 1, 2019 [Member] Represents the advances from Federal Home Loan Bank Advances with principal and interest mortgage matched, and maturity at April 1, 2019. Federal Home Loan Bank Advances, Interest-only Putable, Maturity at December 7, 2017 [Member] Represents the advances from Federal Home Loan Bank with interest-only putable, and maturity at December 7, 2017. Federal Home Loan Bank Advances, Interest-only Single Maturity, Maturity at October 12, 2017 [Member] Represents the advances from Federal Home Loan Band Advances with interest only single maturity, and maturity at October 12, 2017. Common Stock, Dividends, Per Share, Declared (in dollars per share) Marketing and advertising Certificate of Deposits in Financial Institutions [Policy Text Block] Disclosure of accounting policy for certificate of deposits in other financial institutions. Expired and forfeited dividend reinvestment plan shares associated with restricted stock awards that were retired to treasury stock Its represent the issuance of treasury stock vested restricted stock awards. 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us-gaap_Deposits Total deposits Schedule of Effective Income Tax Rate Reconciliation [Table Text Block] Property, Plant and Equipment, Type [Domain] Schedule of Deferred Tax Assets and Liabilities [Table Text Block] Property, Plant and Equipment, Type [Axis] Schedule of Components of Income Tax Expense (Benefit) [Table Text Block] Bid Indications [Member] Represents information pertaining to bid indications valuation technique. Investments Classified by Contractual Maturity Date [Table Text Block] Property, Plant and Equipment, Policy [Policy Text Block] Market Approach Valuation Technique [Member] us-gaap_DeferredTaxLiabilities Net deferred asset (liability) Income Approach Valuation Technique [Member] Valuation Technique [Axis] Valuation Technique [Domain] Schedule of Realized Gain (Loss) [Table Text Block] us-gaap_DepositsFairValueDisclosure Demand and savings deposits Condensed Income Statement [Table Text Block] us-gaap_DeferredTaxAssetsTaxCreditCarryforwardsAlternativeMinimumTax AMT credit carryforward us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax Available-for-sale securities, gross unrealized gains Fair Value by Liability Class [Domain] us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis Available-for-sale Debt Securities, Amortized Cost Basis Liability Class [Axis] us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax Available-for-sale securities, gross unrealized losses Condensed Balance Sheet [Table Text Block] Transfers and Servicing of Financial Assets, Policy [Policy Text Block] Loan Commitments, Policy [Policy Text Block] us-gaap_OperatingLeasesFutureMinimumPaymentsDueInThreeYears 2019 us-gaap_OperatingLeasesFutureMinimumPaymentsDueInTwoYears 2018 us-gaap_DeferredTaxAssetsTaxDeferredExpenseReservesAndAccrualsProvisionForLoanLosses Allowance for loan losses us-gaap_OperatingLeasesFutureMinimumPaymentsDueInFiveYears 2021 us-gaap_OperatingLeasesFutureMinimumPaymentsDueInFourYears 2020 us-gaap_DeferredTaxAssetsTaxDeferredExpenseCompensationAndBenefits Deferred compensation Change in short-term borrowings us-gaap_OperatingLeasesFutureMinimumPaymentsDueCurrent 2017 Savings Repurchase and Resale Agreements Policy [Policy Text Block] Time Total us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments Income before income taxes Income before income taxes and equity in undistributed net income of subsidiary us-gaap_OperatingLeasesFutureMinimumPaymentsDue Total Non-interest bearing demand Interest bearing demand Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis [Table Text Block] us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPosition12MonthsOrLongerAggregateLosses Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Loss Fair Value, Assets and Liabilities Measured on Nonrecurring Basis, Valuation Techniques [Table Text Block] Marketable Securities, Policy [Policy Text Block] Schedule of Earnings Per Share, Basic and Diluted [Table Text Block] Organization, Consolidation and Presentation of Financial Statements Disclosure and Significant Accounting Policies [Text Block] Income tax expense Income Tax Expense (Benefit) us-gaap_IncomeTaxExpenseBenefit Class of Stock [Axis] Impaired Financing Receivables [Table Text Block] Troubled Debt Restructurings on Financing Receivables [Table Text Block] Reclassification, Policy [Policy Text Block] cbkm_AvailableForSaleSecuritiesIncomeTaxProvisionOnGrossRealizedGains Available-for-sale Securities Income Tax Provision on Gross Realized Gains This item represents the tax provision applicable to gross profit realized on the sale of debt or equity securities categorized neither as held-to-maturity nor trading securities. us-gaap_FinancingReceivablesImpairedTroubledDebtRestructuringWriteDown Financing Receivables, Impaired, Troubled Debt Restructuring, Write-down cbkm_AvailableforsaleSecuritiesIncomeTaxProvisionOnNetRealizedGainLoss Available-for-sale Securities Income Tax Provision on Net Realized Gain (Loss) This item represents the tax provision applicable to net realized gain or loss. us-gaap_FinancingReceivableModificationsRecordedInvestment Financing Receivable, Modifications, Recorded Investment Commercial Real Estate Other 2 [Member] Related to the second commercial real estate other loan. Dividend Restrictions [Policy Text Block] Disclosure of accounting policy for statutory restrictions on the payment of dividends as prescribed by the Office of the Comptroller of Currency or other regulatory authorities. Long-term Assets [Policy Text Block] Disclosure of accounting policy for long term assets. us-gaap_FinancingReceivableModificationsPreModificationRecordedInvestment2 Pre-Modification Outstanding Recorded Investment Cash Reserves [Policy Text Block] Disclosure of accounting policy for cash reserves for estimating its liability. us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2 Post-Modification Outstanding Recorded Investment Interest Bearing Deposits in Other Financial Institutions [Policy Text Block] Disclosure of accounting policy for Interest-bearing deposits in other financial institutions for relatively short periods of time including, for example, certificates of deposits, which are presented separately from cash on the balance sheet. Cash Surrender Value of Life Insurance [Policy Text Block] Disclosure of accounting policy for cash which could be received based on the terms of the insurance contract upon surrendering life policies owned by the entity. New Accounting Pronouncements, Policy [Policy Text Block] us-gaap_FinancingReceivableModificationsNumberOfContracts2 Financing Receivable, Modifications, Number of Contracts Federal Home Loan Bank FHLB Stock [Policy Text Block] Disclosure of accounting policy for borrowings and other factors, advances by federal home loan bank by branch. Use of Estimates, Policy [Policy Text Block] us-gaap_FinancingReceivableModificationsSubsequentDefaultNumberOfContracts1 Financing Receivable, Modifications, Subsequent Default, Number of Contracts Condensed Financial Information of Parent Company Only Disclosure [Text Block] Schedule of Share-based Compensation, Restricted Stock Units Award Activity [Table Text Block] us-gaap_AllocatedShareBasedCompensationExpense Allocated Share-based Compensation Expense us-gaap_ConcentrationRiskCreditRiskFinancialInstrumentMaximumExposure Concentration Risk, Credit Risk, Financial Instrument, Maximum Exposure cbkm_FinancingReceivableRecordedInvestmentNotPastDue Financing Receivable Recorded Investment Not Past Due Recorded investment in financing receivables that are not past due as of the balance sheet date. cbkm_RecordedInvestmentinLoans Recorded InvestmentIn Loans Amount included in the recorded investment in loans. Net increase in certificates of deposit with other financial institutions us-gaap_PaymentsForProceedsFromLoansAndLeases Net increase in loans us-gaap_FinancingReceivableCollectivelyEvaluatedForImpairment Loans collectively evaluated for impairment Residential Real Estate Non-owner Occupied Loans [Member] Represents the information pertaining to residential real estate non-owner occupied loans. Schedule of Accumulated Other Comprehensive Income (Loss) [Table Text Block] Debit card interchange income us-gaap_FinancingReceivableIndividuallyEvaluatedForImpairment Loans individually evaluated for impairment Residential Real Estate Owner Occupied Loans [Member] Represents the information pertaining to residential real estate owner occupied loans. Comprehensive Income (Loss) Note [Text Block] Other Commercial Real Estate Loans [Member] Represents the information pertaining to commercial real estate loans classified as other. Federal Home Loan Type [Domain] Operating Leases of Lessee Disclosure [Table Text Block] cbkm_PrepaymentPenaltyForAdvancesReceivedPercentageOfLostCashFlow Prepayment Penalty for Advances Received, Percentage of Lost Cash Flow The percentage of lost cash flow based upon the difference between the contract rate on the advance and the current rate on the new advance as prepayment penalty. Federal Home Loan Type [Axis] Consolidation, Policy [Policy Text Block] Service charges on deposit accounts Building And Leasehold Improvements [Member] Represents the information pertaining to building and leasehold improvements. Not Rated [Member] Represents the amount of the loans that are not rated. Loans and Leases Receivable, Related Parties Disclosure [Table Text Block] Tabular disclosure of loans and leases receivable from related parties. Schedule of Time Deposit Maturities [Table Text Block] Tabular disclosure of time deposit liability maturities. Average interest rate during the year The average effective interest rate during the reporting period. cbkm_TimeDepositsMinimumDenomination Time Deposits Minimum Denomination The aggregate amount of time deposits, each with a minimum denomination. Financing Receivables, 60 to 89 Days Past Due [Member] us-gaap_AllowanceForLoanAndLeaseLossRecoveryOfBadDebts Recoveries Current income taxes Financing Receivables, Equal to Greater than 90 Days Past Due [Member] Non-accrual Loans [Member] Represents the loans classified as non-accrual. us-gaap_FinancingReceivableRecordedInvestmentPastDue Financing Receivable, Recorded Investment, Past Due Financing Receivable, Recorded Investment, Nonaccrual Status Financing Receivable, Recorded Investment, Nonaccrual Status Past Due Financing Receivables [Table Text Block] us-gaap_NetCashProvidedByUsedInOperatingActivities Net cash flows from operating activities Net cash flows from operating activities us-gaap_IncreaseDecreaseInOperatingCapital Change in other assets and liabilities Financing Receivables, 30 to 59 Days Past Due [Member] us-gaap_IncreaseDecreaseInOtherOperatingCapitalNet Change in other assets and other liabilities Financing Receivables, Period Past Due [Axis] Financing Receivables, Period Past Due [Domain] us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized us-gaap_FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment Collectively evaluated for impairment Scenario, Unspecified [Domain] cbkm_FinancingReceivablesImpairedTroubledDebtRestructuringIncreaseToAllowance Financing Receivables, Impaired, Troubled Debt Restructuring, Increase to Allowance Reflects the amount of increase to allowance related to a troubled debt restructuring. us-gaap_FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1 Individually evaluated for impairment Scenario [Axis] cbkm_ThresholdAmountOfLoansOutstandingToPerformCreditAnalysis Threshold Amount of Loans Outstanding to Perform Credit Analysis The threshold amount of loans outstanding balance that will trigger the credit analysis. Financing Receivable, Recorded Investment, 90 Days Past Due and Still Accruing us-gaap_FinancingReceivableRecordedInvestmentCurrent Total ending loans balance Financing Receivable, Recorded Investment, Total Allowance for Credit Losses on Financing Receivables [Table Text Block] Scenario, Forecast [Member] Financing Receivable Credit Quality Indicators [Table Text Block] Principal pay downs Pass [Member] us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment Accumulated depreciation and amortization Premises and equipment, net Premises and equipment, net Cost Approach Valuation Technique [Member] Share-based Compensation, Option and Incentive Plans Policy [Policy Text Block] Pension and Other Postretirement Plans, Policy [Policy Text Block] us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1 Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period us-gaap_WeightedAverageNumberOfSharesRestrictedStock Dilutive effect of restricted stock (in shares) Repurchase Agreements Deposit Liabilities Disclosures [Text Block] Income Tax Disclosure [Text Block] Compensation and Employee Benefit Plans [Text Block] us-gaap_TimeDepositsAtOrAboveFDICInsuranceLimit Time Deposits, at or Above FDIC Insurance Limit Premises and equipment, gross us-gaap_AllowanceForLoanAndLeaseLossesWriteOffs Loans charged-off us-gaap_ConstructionInProgressGross Construction in Progress, Gross Schedule of Repurchase Agreements [Table Text Block] us-gaap_IncomeTaxReconciliationIncomeTaxExpenseBenefitAtFederalStatutoryIncomeTaxRate Income taxes computed at the statutory rate on pretax income us-gaap_StatutoryAccountingPracticesStatutoryAmountAvailableForDividendPaymentsWithoutRegulatoryApproval Statutory Accounting Practices, Statutory Amount Available for Dividend Payments without Regulatory Approval us-gaap_NetIncomeLossAvailableToCommonStockholdersDiluted Net income available to common shareholders us-gaap_NetIncomeLossAvailableToCommonStockholdersBasic Net income available to common shareholders Securities, available-for-sale Available-for-sale Securities, Debt Securities Net income Net income Net income Held-to-maturity securities, fair value Held-to-maturity Securities, Fair Value Held-to-maturity, fair value Maturities, calls and principal pay downs Maturities, calls and principal pay downs of available-for-sale securities Securities, held-to-maturity (fair value 2016 $3,619 and 2015 $3,722) Held-to-maturity Securities Held-to-maturity, amortized cost Proceeds from sales of available-for-sale securities Proceeds from sales Loan and collection expenses The aggregate amount of expenditures for loan and collection. Debit card processing expenses Expenses incurred for debit card processing services. Professional and director fees A fee charged for services from professionals such as doctors, lawyers, accountants. And also includes director fees. us-gaap_Assets Total assets Total assets Dividend Reinvestment Plan and Restricted Award Forfeited and Expired (in shares) The number of dividend reinvestment plan shares associated with forfeited restricted stock awards retired to treasury. LIABILITIES: Dividend reinvestment plan shares associated with expired and forfeited restricted stock awards retired to treasury Represents the dividend reinvestment plan shares associated with forfeited and expired restricted stock awards retired to treasury. Restricted Stock [Member] Securities held-to-maturity: us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod Restricted Stock Awards, Forfeited (in shares) Securities available-for-sale: us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber Restricted Stock Awards, Outstanding, Beginning Balance (in shares) Restricted Stock Awards, Outstanding, Ending Balance (in shares) us-gaap_PaymentsToAcquireAvailableForSaleSecuritiesDebt Purchases us-gaap_TimeDepositMaturitiesAfterYearFive Thereafter us-gaap_TimeDepositMaturitiesYearFive 2021 Residential Mortgage Backed Securities [Member] Collateralized Mortgage Backed Securities [Member] cbkm_CashReserveDepositRequiredAndMadeFederalReserveBanks Cash Reserve Deposit Required and Made Federal Reserve Banks Cash reserve deposit required and made with Federal Reserve Banks pursuant to Federal Reserve Board regulations. Pledged Financial Instruments, Securities for Repurchase Agreements Nature of Operations [Policy Text Block] Disclosure of accounting policy for nature of operations. us-gaap_PaymentsToAcquireHeldToMaturitySecurities Purchases Policy Loans Receivable, Policy [Policy Text Block] Federal bank and other restricted stocks, at cost us-gaap_PaymentsToAcquirePropertyPlantAndEquipment Acquisition of premises and equipment Comprehensive Income, Policy [Policy Text Block] Earnings Per Share, Policy [Policy Text Block] us-gaap_TimeDepositMaturitiesYearThree 2019 us-gaap_TimeDepositMaturitiesYearFour 2020 us-gaap_OtherAssets Other assets us-gaap_TimeDepositMaturitiesYearTwo 2018 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue Weighted-Average Grant Date Fair Value Per Share, Outstanding at Beginning Period (in dollars per share) Weighted-Average Grant Date Fair Value Per Share, Outstanding at Ending Period (in dollars per share) Income Tax, Policy [Policy Text Block] Weighted-Average Grant Date Fair Value Per Share, Forfeited (in dollars per share) us-gaap_TimeDepositMaturitiesYearOne 2017 us-gaap_AociTaxAttributableToParent Accumulated other comprehensive income (loss), tax Accumulated other comprehensive income (loss), tax Fair Value of Financial Instruments, Policy [Policy Text Block] Internal Credit Assessment [Axis] Internal Credit Assessment [Domain] Earnings Per Share [Text Block] Segment Reporting, Policy [Policy Text Block] us-gaap_AociBeforeTaxAttributableToParent Accumulated other comprehensive income (loss), before tax cbkm_IncomeFromFederalFundsSoldAndOtherInterestBearingDeposits Federal funds sold and interest-bearing deposits in financial institutions Interest income on federal funds sold. Federal funds sold represent the excess federal funds held by one commercial bank which it lends to another commercial bank, usually at an agreed-upon (federal funds) rate of interest. Such loans are made for legal reserve requirement purposes of the borrowing bank and generally are of short-duration (overnight). It also includes the interest income from aggregate of all domestic and foreign interest-bearing deposit. us-gaap_InterestAndDividendIncomeOperating Total interest and dividend income Supplemental disclosures of cash flow information: us-gaap_DefinedBenefitPlanOtherCosts Defined Benefit Plan, Other Costs us-gaap_LoansAndLeasesReceivableRelatedPartiesAdditions New loans us-gaap_DividendIncomeOperating Cash dividends from Bank subsidiary us-gaap_LoansAndLeasesReceivableRelatedPartiesProceeds Repayments Amendment Flag us-gaap_TreasuryStockValue Treasury stock, at cost (130,375 and 130,064 common shares at June 30, 2016 and 2015, respectively) us-gaap_DefinedBenefitPlanAssumptionsUsedCalculatingBenefitObligationDiscountRate Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation, Discount Rate us-gaap_LoansAndLeasesReceivableCommitmentsFixedRates Loans and Leases Receivable, Commitments, Fixed Rates us-gaap_LoansAndLeasesReceivableCommitmentsVariableRates Loans and Leases Receivable, Commitments, Variable Rates Noncash transactions: Interest expense: Document Fiscal Year Focus Document Fiscal Period Focus Loans, Notes, Trade and Other Receivables Disclosure [Text Block] Document Period End Date us-gaap_TierOneLeverageCapitalRequiredToBeWellCapitalizedToAverageAssets Tier One Leverage Capital Required to be Well Capitalized to Average Assets Deposits us-gaap_TierOneLeverageCapitalRequiredForCapitalAdequacyToAverageAssets Tier One Leverage Capital Required for Capital Adequacy to Average Assets Net change in unrealized gains (losses): us-gaap_LoansAndLeasesReceivableNetReportedAmount Net loans Net loans us-gaap_ShorttermDebtFairValue Short-term borrowings Unrealized gains (loss) arising during the period Current Fiscal Year End Date Cash surrender value of life insurance Cash Surrender Value of Life Insurance Total loans us-gaap_LoansAndLeasesReceivableDeferredIncome Loans and Leases Receivable, Deferred Income Less: Deferred loan fees and costs us-gaap_LoansAndLeasesReceivableImpairedCommitmentToLend Loans and Leases Receivable, Impaired, Commitment to Lend us-gaap_OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForSaleOfSecuritiesBeforeTax Reclassification adjustment for gains included in income us-gaap_LoansAndLeasesReceivableAllowance Beginning balance Total ending allowance balance Less allowance for loan losses Total ending allowance balance Allowance for loan losses Document Information [Line Items] us-gaap_DividendsCommonStockCash Cash dividends declared ($0.48 per share) Document Information [Table] Unrealized holding loss on available-for-sale securities arising during the period Entity Current Reporting Status Entity Voluntary Filers Entity Public Float Entity Filer Category Document Type us-gaap_InterestExpenseFederalHomeLoanBankAndFederalReserveBankAdvancesLongTerm Federal Home Loan Bank advances us-gaap_OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForSaleOfSecuritiesNetOfTax Amounts reclassified from accumulated other comprehensive income us-gaap_PaymentsForOriginationAndPurchasesOfLoansHeldForSale Origination of loans held for sale us-gaap_InterestExpenseShortTermBorrowings Interest Expense, Short-term Borrowings Transfer from loans to repossessed assets Doubtful [Member] us-gaap_InterestExpense Total interest expense cbkm_DeferredTaxLiabilitiesNetUnrealizedSecuritiesGain Net unrealized securities gain Amount of deferred tax liability attributable to taxable temporary differences from net unrealized securities gain. Substandard [Member] Demand and Savings Deposits [Member] Represents the information pertaining to demand and savings deposits. Special Mention [Member] us-gaap_StockholdersEquity Balance Balance Total shareholders’ equity Shareholders’ equity Collateral Dependent Loans [Member] Represents the information pertaining to collateral dependent loans. Entity Well-known Seasoned Issuer cbkm_FairValueInputRate Discount Rate It represents the interest rate used to measure fair value. us-gaap_BankOwnedLifeInsurance Bank Owned Life Insurance Proceeds from loans held for sale Time Deposits [Member] Represents the information pertaining to time deposits. us-gaap_ComprehensiveIncomeNetOfTax Total comprehensive income Comprehensive income Interest income: Statement of Financial Position [Abstract] Regulatory Capital Requirements under Banking Regulations [Text Block] us-gaap_RelatedPartyDepositLiabilities Related Party Deposit Liabilities us-gaap_CashCashEquivalentsAndFederalFundsSold Total cash and cash equivalents Reported Value Measurement [Member] Loans, including fees Statement of Comprehensive Income [Abstract] us-gaap_EffectiveIncomeTaxRateReconciliationAtFederalStatutoryIncomeTaxRate Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent us-gaap_TableTextBlock Notes Tables us-gaap_TierOneLeverageCapitalToAverageAssets Tier One Leverage Capital to Average Assets Securities, taxable us-gaap_CapitalRequiredToBeWellCapitalizedToRiskWeightedAssets Capital Required to be Well Capitalized to Risk Weighted Assets us-gaap_IncomeTaxReconciliationOtherAdjustments Other us-gaap_CapitalToRiskWeightedAssets Capital to Risk Weighted Assets us-gaap_CapitalRequiredForCapitalAdequacyToRiskWeightedAssets Capital Required for Capital Adequacy to Risk Weighted Assets us-gaap_LoansAndLeasesReceivableGrossCarryingAmount Loans Receivable, Gross us-gaap_OtherComprehensiveIncomeLossAvailableForSaleSecuritiesAdjustmentBeforeTax Net unrealized gain (loss) Securities, tax-exempt us-gaap_TierOneRiskBasedCapitalRequiredForCapitalAdequacyToRiskWeightedAssets Tier One Risk Based Capital Required for Capital Adequacy to Risk Weighted Assets Net current period other comprehensive loss us-gaap_TierOneRiskBasedCapitalRequiredToBeWellCapitalizedToRiskWeightedAssets Tier One Risk Based Capital Required to be Well Capitalized to Risk Weighted Assets us-gaap_OtherComprehensiveIncomeLossTaxPortionAttributableToParent1 Net current period other comprehensive gain Net current period other comprehensive loss us-gaap_TierOneRiskBasedCapitalToRiskWeightedAssets Tier One Risk Based Capital to Risk Weighted Assets us-gaap_CapitalRequiredToBeWellCapitalized Capital Required to be Well Capitalized us-gaap_IncomeTaxReconciliationTaxExemptIncome Tax exempt income us-gaap_Capital Capital us-gaap_CapitalRequiredForCapitalAdequacy Capital Required for Capital Adequacy Statement of Stockholders' Equity [Abstract] us-gaap_DefinedBenefitPlanAccumulatedBenefitObligation Defined Benefit Plan, Accumulated Benefit Obligation us-gaap_TierOneLeverageCapitalRequiredToBeWellCapitalized Tier One Leverage Capital Required to be Well Capitalized us-gaap_TierOneLeverageCapitalRequiredForCapitalAdequacy Tier One Leverage Capital Required for Capital Adequacy us-gaap_TierOneLeverageCapital Tier One Leverage Capital Other comprehensive loss Other comprehensive income (loss) us-gaap_OtherComprehensiveIncomeLossAvailableForSaleSecuritiesTax Income tax effect us-gaap_TierOneRiskBasedCapitalRequiredToBeWellCapitalized Tier One Risk Based Capital Required to be Well Capitalized us-gaap_TierOneRiskBasedCapitalRequiredForCapitalAdequacy Tier One Risk Based Capital Required for Capital Adequacy us-gaap_OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForSaleOfSecuritiesTax Amounts reclassified from accumulated other comprehensive income Amounts reclassified from accumulated other comprehensive income us-gaap_TierOneRiskBasedCapital Tier One Risk Based Capital Statement of Cash Flows [Abstract] us-gaap_OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodTax Unrealized holding gain on available-for-sale securities arising during the period Unrealized holding loss on available-for-sale securities arising during the period Schedule of Compliance with Regulatory Capital Requirements under Banking Regulations [Table Text Block] us-gaap_CostMethodInvestments Investment in subsidiary us-gaap_FederalHomeLoanBankAdvancesGeneralDebtObligationsDisclosuresCollateralPledged1 Federal Home Loan Bank, Advances, General Debt Obligations, Disclosures, Collateral Pledged us-gaap_TroubledDebtRestructuringDebtorSubsequentPeriodsContingentPaymentsAmount Troubled Debt Restructuring, Debtor, Subsequent Periods, Contingent Payments, Amount us-gaap_FederalHomeLoanBankAdvancesGeneralDebtObligationsDisclosuresAmountOfAvailableUnusedFunds Federal Home Loan Bank, Advances, General Debt Obligations, Amount of Available, Unused Funds us-gaap_FederalHomeLoanBankAdvancesMaturitiesSummaryDueFromOneToTwoYearsOfBalanceSheetDate 2018 Debt Instrument [Axis] Debt Instrument, Name [Domain] Maturity At 7th December 2017 [Member] Represents the information to advance maturity at December 7, 2017. Interest Maturity Date [Domain] cbkm_DebtInstrumentContractualTerm Federal Home Loan Bank Advances, Contractual Term Term of debt instrument maturity, fixed or variable. First Mortgage Loans [Member] Represents the information to first mortgage loans. Schedule of Principal Payments [Table Text Block] Tabular disclosure of federal home loan bank's principal payment schedule. cbkm_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsExpiredInPeriod Restricted Stock Awards, Expired (in shares) The number of equity-based payment instruments, excluding stock (or unit) options, that expired during the reporting period. us-gaap_AvailableForSaleSecuritiesPledgedAsCollateral Available-for-sale Securities Pledged as Collateral Weighted-Average Grant Date Fair Value Per Share, Expired (in dollars per share) The weighted average fair value at grant date for nonvested equity-based awards issued during the period on other than stock (or unit) option plans for expiration during the reporting period. Increase in cash surrender value of life insurance us-gaap_FederalHomeLoanBankAdvancesMaturitiesSummaryDueFromTwoToThreeYearsOfBalanceSheetDate 2019 Retained earnings Accumulated other comprehensive income Accumulated other comprehensive income (loss), net us-gaap_LiabilitiesAndStockholdersEquity Total liabilities and shareholders’ equity Total liabilities & shareholders’ equity Interest Only, Putable [Member] Represents the type of Federal Home Loans Bank advances, interest only, putable. Interest Maturity Date [Axis] Information by interest maturity date. cbkm_CommonEquityTierOneRiskBasedCapitalToRiskWeightedAssets Common Equity Tier One Risk Based Capital to Risk Weighted Assets Common Equity Tier 1 capital divided by risk weighted assets as defined by regulations. cbkm_CommonEquityTierOneRiskBasedCapital Common Equity Tier One Risk Based Capital Common Equity Tier 1 Risk Based Capital as defined in the regulations. Legal Entity [Axis] Entity Registrant Name cbkm_PercentageOfCapitalImplementation Percentage of Capital Implementation The during period represent capital implementation for regulatory matters. Entity Central Index Key Entity [Domain] cbkm_CommonEquityTierOneRiskBasedCapitalRequiredToBeWellCapitalizedToRiskWeightedAssets Common Equity Tier One Risk Based Capital Required to be Well Capitalized to Risk Weighted Assets The Common Equity Tier 1 capital ratio (Common Equity Tier 1 capital divided by risk weighted assets) required to be categorized as "well capitalized" under the regulatory framework for prompt corrective action. cbkm_CommonEquityTierOneRiskBasedCapitalRequiredToBeWellCapitalized Common Equity Tier One Risk Based Capital Required to be Well Capitalized The amount of Common Equity Tier 1 Risk Based Capital required to be categorized as well capitalized under the regulatory framework for prompt corrective action. cbkm_CommonEquityTierOneRiskBasedCapitalRequiredForCapitalAdequacyToRiskWeightedAssets Common Equity Tier One Risk Based Capital Required for Capital Adequacy to Risk Weighted Assets The minimum Common Equity Tier One Capital Ratio (Common Equity Tier one capital divided by risk-weighted assets) required for capital adequacy purposes under the regulatory framework for prompt corrective action. cbkm_CommonEquityTierOneRiskBasedCapitalRequiredForCapitalAdequacy Common Equity Tier One Risk Based Capital Required for Capital Adequacy The minimum amount of Common Equity Tier 1 Risk Based Capital required for capital adequacy purposes under the regulatory framework for prompt corrective action. Entity Common Stock, Shares Outstanding (in shares) cbkm_DeferredTaxAssetsDeferredIncomeFromOtherRealEstateOwned OREO deferred gain Amount before allocation of valuation allowances of deferred tax asset attributable to deductible temporary differences from deferred gain from the sale of other real estate owned. us-gaap_NotesReceivableNet Financing Receivable, Net cbkm_IncomeTaxReconciliationCashSurrenderValueIncome Cash surrender value income The portion of the difference between total income tax expense or benefit as reported in the Income Statement for the period and the expected income tax expense or benefit computed by applying the domestic federal statutory income tax rates to pretax income from continuing operations attributable to earnings or other increases in the value of the cash surrender value of bank owned life insurance policies that are exempt from income taxes under enacted tax laws. cbkm_DeferredTaxLiabilitiesFederalHomeLoanBankStockDividends FHLB stock dividends Amount of deferred tax liability attributable to taxable temporary differences from stock dividends received from the Federal Home Loan Bank. cbkm_DeferredTaxLiabilitiesLoanFees Loan fees Amount of deferred tax liability attributable to taxable temporary differences from deferred loan fees. cbkm_DeferredTaxAssetsNonAccrualLoanInterestIncome Non-accrual loan interest income Amount before allocation of valuation allowances of deferred tax asset attributable to deductible temporary differences from deferred interest income on nonaccrual loans. Loans held for sale Cash on hand and noninterest-bearing deposits in financial institutions Schedule of Federal Home Loan Bank, Advances, by Branch of FHLB Bank [Table Text Block] cbkm_IncomeLossFromContinuingOperationsBeforeEquityMethodInvestments Income before equity in undistributed net income of Bank subsidiary Sum of operating profit and nonoperating income or expense before Income or Loss from equity method investments in undistributed net income of subsidiary. Federal Home Loan Bank Advances, Disclosure [Text Block] us-gaap_CashAndCashEquivalentsAtCarryingValue Cash and cash equivalents, beginning of year Cash and cash equivalents, end of year us-gaap_DefinedBenefitPlanContributionsByEmployer Defined Benefit Plan, Contributions by Employer Trading Symbol us-gaap_Cash Cash cbkm_EquityInUndistributedEarningsOfSubsidiaries Equity in undistributed net income of subsidiary Equity in undistributed net income of Bank subsidiary The amount of undistributed earnings from subsidiaries. Federal funds sold and interest-bearing deposits in financial institutions us-gaap_UnrecognizedTaxBenefitsThatWouldImpactEffectiveTaxRate Unrecognized Tax Benefits that Would Impact Effective Tax Rate Commercial Real Estate - Other [Member] Represents the impaired commercial real estate loans classified as other. us-gaap_DefinedContributionPlanEmployersMatchingContributionAnnualVestingPercentage Defined Contribution Plan, Employers Matching Contribution, Annual Vesting Percentage Commitments with Off-Balance Sheet Risk Disclosure [Text Block] The entire disclosure of the fair value of financial instruments (as defined), including financial assets and financial liabilities (collectively, as defined) which are not recognized in the financial statements (off-balance sheet) because they fail to meet some other criterion for recognition. cbkm_LoansAndLeasesReceivableCommitmentsVariableRatesPercentage Loans and Leases Receivable Commitments Variable Rates Percentage The lowest stated interest rate within the commitments to fund advances to borrowers at variable interest rates. cbkm_LoansAndLeasesReceivableCommitmentsFixedRatesPercentage Loans and Leases Receivable Commitments Fixed Rates Percentage The lowest stated interest rate within the commitments to fund advances to borrowers at fixed interest rates. us-gaap_DefinedContributionPlanMaximumAnnualContributionsPerEmployeePercent Defined Contribution Plan, Maximum Annual Contributions Per Employee, Percent Certificate of deposits in financial institutions cbkm_CertificatesOfDepositsInOtherFinancialInstitutionsFairValueDisclosure Certificates of deposits in other financial institutions Fair value portion of certificates of deposits in other financial institutions. us-gaap_DefinedContributionPlanCostRecognized Defined Contribution Plan, Cost Recognized Settlement Contract [Member] Represents the information pertaining to settlement contract valuation technique. cbkm_AccruedInterestReceivableFairValueDisclosure Accrued interest receivable Fair value portion of accrued interest receivable. us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAfterFiveThroughTenYearsAmortizedCost Available-for-sale Securities, Debt Maturities, Year Six Through Ten, Amortized Cost Basis us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAfterOneThroughFiveYearsAmortizedCost Available-for-sale Securities, Debt Maturities, Year Two Through Five, Amortized Cost Basis us-gaap_InterestIncomeExpenseNet Net interest income us-gaap_DebtInstrumentInterestRateDuringPeriod Federal Home Loan Bank Advances, Interest Rate Available-for-sale Securities, Debt Maturities, Next Twelve Months, Amortized Cost Basis us-gaap_AccruedLiabilitiesFairValueDisclosure Accrued interest payable Loss Contingency Nature [Axis] Common Stock [Member] us-gaap_OtherIncome Other income Equity Component [Domain] ASSETS: Equity Components [Axis] us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAfterTenYearsAmortizedCost Available-for-sale Securities, Debt Maturities, after Ten Years, Amortized Cost Basis Other income: us-gaap_InterestIncomeExpenseAfterProvisionForLoanLoss Net interest income after provision for loan losses us-gaap_CashAndCashEquivalentsPeriodIncreaseDecrease Decrease in cash and cash equivalents Change in cash and cash equivalents us-gaap_AvailableForSaleSecuritiesGrossRealizedLosses Gross realized losses us-gaap_AvailableForSaleSecuritiesGrossRealizedGains Gross realized gains Loss Contingency, Nature [Domain] us-gaap_ProvisionForLoanAndLeaseLosses Provision for Loan and Lease Losses Provision for loan losses Provision for loan losses us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAfterFiveThroughTenYearsFairValue Available-for-sale Securities, Debt Maturities, Year Six Through Ten, Fair Value Retained Earnings [Member] us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAfterTenYearsFairValue Available-for-sale Securities, Debt Maturities, after Ten Years, Fair Value Treasury Stock [Member] us-gaap_AvailableForSaleSecuritiesDebtMaturitiesWithinOneYearFairValue Available-for-sale Securities, Debt Maturities, Next Twelve Months, Fair Value us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAfterOneThroughFiveYearsFairValue Available-for-sale Securities, Debt Maturities, Year Two Through Five, Fair Value us-gaap_AvailableForSaleSecuritiesDebtMaturitiesSingleMaturityDateAmortizedCostBasis Available-for-sale Securities, Debt Maturities, Single Maturity Date, Amortized Cost Basis us-gaap_AvailableForSaleSecuritiesDebtMaturitiesWithoutSingleMaturityDateAmortizedCost Available-for-sale Securities, Debt Maturities, without Single Maturity Date, Amortized Cost Basis us-gaap_HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingGain Held-to-maturity, gross unrecognized gains us-gaap_HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingLoss Held-to-maturity, gross unrecognized losses Accrued interest payable and other liabilities Available-for-sale Securities, Continuous Unrealized 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Equity Securities [Domain] Major Types of Debt and Equity Securities [Axis] us-gaap_FairValueDisclosureOffbalanceSheetRisksFaceAmountLiability Fair Value Disclosure, Off-balance Sheet Risks, Face Amount, Liability Parent Company [Member] Marketable Securities [Table Text Block] Treasury stock, shares (in shares) us-gaap_OtherThanTemporaryImpairmentLossesInvestmentsAvailableforsaleSecurities Other than Temporary Impairment Losses, Investments, Available-for-sale Securities Common shares, no par value; 3,500,000 shares authorized; 2,854,133 shares issued as of June 30, 2016 and 2015 AOCI Attributable to Parent [Member] Common shares, shares issued (in shares) US States and Political Subdivisions Debt Securities [Member] Common shares, shares authorized (in shares) Accounting Policies [Abstract] Subsequent Event Type [Domain] us-gaap_PaymentsOfDividends Dividend paid Subsequent Event Type [Axis] Cash and Cash Equivalents, Policy [Policy Text Block] Statement [Line Items] Subsequent Event [Member] us-gaap_PolicyTextBlockAbstract Accounting Policies Finance, Loan and Lease Receivables, Held-for-sale, Policy [Policy Text Block] us-gaap_PaymentsOfDividendsCommonStock Dividends paid Cash flows from operating activities: Loans and Leases Receivable, Allowance for Loan Losses Policy [Policy Text Block] Finance, Loan and Lease Receivables, Held for Investments, Foreclosed Assets Policy [Policy Text Block] Fair Value Disclosures [Text Block] us-gaap_DebtInstrumentMaturityDate Federal Home Loan Bank Advances, Maturity Date Fair Value, by Balance Sheet Grouping [Table Text Block] Proceeds from sale of other real estate owned us-gaap_LoansReceivableFairValueDisclosure Loans, net us-gaap_NetCashProvidedByUsedInFinancingActivities Net cash flows from financing activities Net cash flows from financing activities Maximum month-end balance Average balance during the year Estimate of Fair Value Measurement [Member] Weighted average rate, June 30 Measurement Basis [Axis] Fair Value Measurement [Domain] Schedule of Short-term Debt [Table Text Block] Debt Disclosure [Text Block] Federal income taxes paid Interest Adjustments to reconcile net income to net cash flows from operating activities: us-gaap_UnrecognizedTaxBenefitsIncomeTaxPenaltiesAndInterestAccrued Unrecognized Tax Benefits, Income Tax Penalties and Interest Accrued Equity Award [Domain] Award Type [Axis] Depreciation Depreciation us-gaap_FederalHomeLoanBankBorrowingsFairValueDisclosure Federal Home Loan Bank advances us-gaap_Liabilities Total liabilities Commitments and contingent liabilities us-gaap_OtherLiabilities Other liabilities Securities amortization and accretion, net Securities amortization and accretion, net us-gaap_LoansAndLeasesReceivableRelatedParties Principal balance, July 1 Principal balance, June 30 Federal Deposit Insurance Corporation assessments us-gaap_NoninterestExpense Total other expenses us-gaap_OtherNoninterestExpense Other SHAREHOLDERS’ EQUITY: Deferred income tax benefit