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v2.4.1.9

LOANS AND ALLOWANCE FOR LOAN LOSSES, CREDIT QUALITY INDICATOR (Details) (USD $) In Thousands, unless otherwise specified | 3 Months Ended |
--- | --- | ---
Mar. 31, 2015 | Dec. 31, 2014
Finance receivable by credit quality indicator [Abstract] |  |
Loans | $ 1,146,245 us-gaap_NotesReceivableNet | $ 1,124,354 us-gaap_NotesReceivableNet
Residential and consumer finance receivable [Abstract] |  |
Residential and consumer loans receivable | 18,836 chmg_ResidentialAndConsumerLoansReceivable | 20,066 chmg_ResidentialAndConsumerLoansReceivable
Deteriorated Loans Transferred in [Abstract] |  |
Contractually required principal and interest, opening balance | 3,621 us-gaap_CertainLoansAcquiredInTransferNotAccountedForAsDebtSecuritiesAcquiredDuringPeriodContractuallyRequiredPaymentsReceivableAtAcquisition |
Contractually required principal and interest, income accretion | 0 chmg_CertainLoansAcquiredInTransferNotAccountedForAsDebtSecuritiesContractuallyRequiredPaymentsReceivableIncomeAccretion |
Contractually required principal and interest, all other adjustments | (676)chmg_CertainLoansAcquiredInTransferNotAccountedForAsDebtSecuritiesAcquiredDuringPeriodContractuallyRequiredPaymentsReceivableOtherAdjustments |
Contractually required principal and interest, closing balance | 2,945 us-gaap_CertainLoansAcquiredInTransferNotAccountedForAsDebtSecuritiesAcquiredDuringPeriodContractuallyRequiredPaymentsReceivableAtAcquisition |
Contractual cash flows not expected to be collected (nonaccretable discount), opening balance | (570)us-gaap_CertainLoansAcquiredInTransferNonaccretableDifference |
Contractual cash flows not expected to be collected (nonaccretable discount), income accretion | 0 chmg_CertainLoansAcquiredInTransferNotAccountedForAsDebtSecuritiesCashFlowsNotExpectedToBeCollectedIncomeAccretion |
Contractual cash flows not expected to be collected (nonaccretable discount), all other adjustments | (25)chmg_CertainLoansAcquiredInTransferNotAccountedForAsDebtSecuritiesCashFlowsNotExpectedToBeCollectedOtherAdjustments |
Contractual cash flows not expected to be collected (nonaccretable discount), closing balance | (595)us-gaap_CertainLoansAcquiredInTransferNonaccretableDifference |
Cash flows expected to be collected, opening balance | 3,051 us-gaap_CertainLoansAcquiredInTransferNotAccountedForAsDebtSecuritiesAcquiredDuringPeriodCashFlowsExpectedToBeCollectedAtAcquisition |
Cash flows expected to be collected, income accretion | 0 chmg_CertainLoansAcquiredInTransferNotAccountedForAsDebtSecuritiesCashFlowsExpectedToBeCollectedIncomeAccretion |
Cash flows expected to be collected, all other adjustments | (701)chmg_CertainLoansAcquiredInTransferNotAccountedForAsDebtSecuritiesAcquiredDuringPeriodCashFlowsExpectedToBeCollectedOtherAdjustments |
Cash flows expected to be collected, closing balance | 2,350 us-gaap_CertainLoansAcquiredInTransferNotAccountedForAsDebtSecuritiesAcquiredDuringPeriodCashFlowsExpectedToBeCollectedAtAcquisition |
Interest component of expected cash flows (accretable yield), opening balance | (420)us-gaap_CertainLoansAcquiredInTransferNotAccountedForAsDebtSecuritiesAccretableYield |
Interest component of expected cash flows (accretable yield), income accretion | 63 us-gaap_CertainLoansAcquiredInTransferNotAccountedForAsDebtSecuritiesAccretableYieldAccretion |
Interest component of expected cash flows (accretable yield), all other adjustments | (24)chmg_CertainLoansAcquiredInTransferNotAccountedForAsDebtSecuritiesAccretableYieldOtherAdjustments |
Interest component of expected cash flows (accretable yield), closing balance | (333)us-gaap_CertainLoansAcquiredInTransferNotAccountedForAsDebtSecuritiesAccretableYield |
Fair value of loans acquired with deteriorating credit quality, opening balance | 2,631 us-gaap_CertainLoansAcquiredInTransferNotAccountedForAsDebtSecuritiesAcquiredDuringPeriodAtAcquisitionAtFairValue |
Fair value of loans acquired with deteriorating credit quality, income accretion | 63 chmg_CertainLoansAcquiredInTransferNotAccountedForAsDebtSecuritiesContractuallyRequiredPaymentsReceivableAtFairValueIncomeAccretion |
Fair value of loans acquired with deteriorating credit quality, all other adjustments | (677)chmg_CertainLoansAcquiredInTransferNotAccountedForAsDebtSecuritiesContractuallyRequiredPaymentsReceivableAtFairValueOtherAdjustments |
Fair value of loans acquired with deteriorating credit quality, closing balance | 2,017 us-gaap_CertainLoansAcquiredInTransferNotAccountedForAsDebtSecuritiesAcquiredDuringPeriodAtAcquisitionAtFairValue |
Commercial and Agricultural [Member] |  |
Finance receivable by credit quality indicator [Abstract] |  |
Loans | 172,227 us-gaap_NotesReceivableNet / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = chmg_CommercialAndAgriculturalPortfolioSegmentMember | 166,820 us-gaap_NotesReceivableNet / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = chmg_CommercialAndAgriculturalPortfolioSegmentMember
Commercial and Industrial [Member] |  |
Finance receivable by credit quality indicator [Abstract] |  |
Loans | 171,069 us-gaap_NotesReceivableNet / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = chmg_CommercialAndIndustrialMember | 165,797 us-gaap_NotesReceivableNet / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = chmg_CommercialAndIndustrialMember
Agricultural [Member] |  |
Finance receivable by credit quality indicator [Abstract] |  |
Loans | 1,158 us-gaap_NotesReceivableNet / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = chmg_AgriculturalMember | 1,023 us-gaap_NotesReceivableNet / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = chmg_AgriculturalMember
Commercial Mortgages [Member] |  |
Finance receivable by credit quality indicator [Abstract] |  |
Loans | 481,488 us-gaap_NotesReceivableNet / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstatePortfolioSegmentMember | 453,719 us-gaap_NotesReceivableNet / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstatePortfolioSegmentMember
Construction [Member] |  |
Finance receivable by credit quality indicator [Abstract] |  |
Loans | 49,505 us-gaap_NotesReceivableNet / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstateConstructionFinancingReceivableMember | 54,967 us-gaap_NotesReceivableNet / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstateConstructionFinancingReceivableMember
Commercial mortgages [Member] |  |
Finance receivable by credit quality indicator [Abstract] |  |
Loans | 431,983 us-gaap_NotesReceivableNet / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstateOtherReceivableMember | 398,752 us-gaap_NotesReceivableNet / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstateOtherReceivableMember
Residential mortgages [Member] |  |
Finance receivable by credit quality indicator [Abstract] |  |
Loans | 199,127 us-gaap_NotesReceivableNet / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ResidentialPortfolioSegmentMember | 197,287 us-gaap_NotesReceivableNet / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ResidentialPortfolioSegmentMember
Residential and consumer finance receivable [Abstract] |  |
Residential and consumer loans receivable | 199,127 chmg_ResidentialAndConsumerLoansReceivable / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ResidentialPortfolioSegmentMember | 197,287 chmg_ResidentialAndConsumerLoansReceivable / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ResidentialPortfolioSegmentMember
Consumer Loans [Member] |  |
Finance receivable by credit quality indicator [Abstract] |  |
Loans | 293,403 us-gaap_NotesReceivableNet / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerPortfolioSegmentMember | 306,528 us-gaap_NotesReceivableNet / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerPortfolioSegmentMember
Credit Cards [Member] |  |
Finance receivable by credit quality indicator [Abstract] |  |
Loans | 1,526 us-gaap_NotesReceivableNet / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerCreditCardFinancingReceivableMember | 1,654 us-gaap_NotesReceivableNet / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerCreditCardFinancingReceivableMember
Residential and consumer finance receivable [Abstract] |  |
Residential and consumer loans receivable | 1,526 chmg_ResidentialAndConsumerLoansReceivable / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerCreditCardFinancingReceivableMember | 1,654 chmg_ResidentialAndConsumerLoansReceivable / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerCreditCardFinancingReceivableMember
Home equity lines and loans [Member] |  |
Finance receivable by credit quality indicator [Abstract] |  |
Loans | 98,953 us-gaap_NotesReceivableNet / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = chmg_HomeEquityLinesAndLoansMember | 99,591 us-gaap_NotesReceivableNet / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = chmg_HomeEquityLinesAndLoansMember
Residential and consumer finance receivable [Abstract] |  |
Residential and consumer loans receivable | 98,953 chmg_ResidentialAndConsumerLoansReceivable / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = chmg_HomeEquityLinesAndLoansMember | 99,591 chmg_ResidentialAndConsumerLoansReceivable / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = chmg_HomeEquityLinesAndLoansMember
Indirect consumer loans [Member] |  |
Finance receivable by credit quality indicator [Abstract] |  |
Loans | 174,088 us-gaap_NotesReceivableNet / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = chmg_IndirectConsumerLoansMember | 185,217 us-gaap_NotesReceivableNet / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = chmg_IndirectConsumerLoansMember
Residential and consumer finance receivable [Abstract] |  |
Residential and consumer loans receivable | 174,088 chmg_ResidentialAndConsumerLoansReceivable / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = chmg_IndirectConsumerLoansMember | 185,217 chmg_ResidentialAndConsumerLoansReceivable / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = chmg_IndirectConsumerLoansMember
Direct consumer loans [Member] |  |
Finance receivable by credit quality indicator [Abstract] |  |
Loans | 18,836 us-gaap_NotesReceivableNet / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerOtherFinancingReceivableMember | 20,066 us-gaap_NotesReceivableNet / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerOtherFinancingReceivableMember
Not Rated [Member] |  |
Finance receivable by credit quality indicator [Abstract] |  |
Loans | 487,649 us-gaap_NotesReceivableNet / us-gaap_InternalCreditAssessmentAxis = chmg_NotRatedMember | 499,137 us-gaap_NotesReceivableNet / us-gaap_InternalCreditAssessmentAxis = chmg_NotRatedMember
Not Rated [Member] | Commercial and Industrial [Member] |  |
Finance receivable by credit quality indicator [Abstract] |  |
Loans | 0 us-gaap_NotesReceivableNet / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = chmg_CommercialAndIndustrialMember / us-gaap_InternalCreditAssessmentAxis = chmg_NotRatedMember | 0 us-gaap_NotesReceivableNet / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = chmg_CommercialAndIndustrialMember / us-gaap_InternalCreditAssessmentAxis = chmg_NotRatedMember
Not Rated [Member] | Agricultural [Member] |  |
Finance receivable by credit quality indicator [Abstract] |  |
Loans | 0 us-gaap_NotesReceivableNet / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = chmg_AgriculturalMember / us-gaap_InternalCreditAssessmentAxis = chmg_NotRatedMember | 0 us-gaap_NotesReceivableNet / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = chmg_AgriculturalMember / us-gaap_InternalCreditAssessmentAxis = chmg_NotRatedMember
Not Rated [Member] | Construction [Member] |  |
Finance receivable by credit quality indicator [Abstract] |  |
Loans | 0 us-gaap_NotesReceivableNet / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstateConstructionFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = chmg_NotRatedMember | 0 us-gaap_NotesReceivableNet / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstateConstructionFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = chmg_NotRatedMember
Not Rated [Member] | Commercial mortgages [Member] |  |
Finance receivable by credit quality indicator [Abstract] |  |
Loans | 0 us-gaap_NotesReceivableNet / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstateOtherReceivableMember / us-gaap_InternalCreditAssessmentAxis = chmg_NotRatedMember | 0 us-gaap_NotesReceivableNet / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstateOtherReceivableMember / us-gaap_InternalCreditAssessmentAxis = chmg_NotRatedMember
Not Rated [Member] | Residential mortgages [Member] |  |
Finance receivable by credit quality indicator [Abstract] |  |
Loans | 195,166 us-gaap_NotesReceivableNet / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ResidentialPortfolioSegmentMember / us-gaap_InternalCreditAssessmentAxis = chmg_NotRatedMember | 193,422 us-gaap_NotesReceivableNet / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ResidentialPortfolioSegmentMember / us-gaap_InternalCreditAssessmentAxis = chmg_NotRatedMember
Not Rated [Member] | Credit Cards [Member] |  |
Finance receivable by credit quality indicator [Abstract] |  |
Loans | 1,526 us-gaap_NotesReceivableNet / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerCreditCardFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = chmg_NotRatedMember | 1,654 us-gaap_NotesReceivableNet / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerCreditCardFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = chmg_NotRatedMember
Not Rated [Member] | Home equity lines and loans [Member] |  |
Finance receivable by credit quality indicator [Abstract] |  |
Loans | 98,298 us-gaap_NotesReceivableNet / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = chmg_HomeEquityLinesAndLoansMember / us-gaap_InternalCreditAssessmentAxis = chmg_NotRatedMember | 99,076 us-gaap_NotesReceivableNet / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = chmg_HomeEquityLinesAndLoansMember / us-gaap_InternalCreditAssessmentAxis = chmg_NotRatedMember
Not Rated [Member] | Indirect consumer loans [Member] |  |
Finance receivable by credit quality indicator [Abstract] |  |
Loans | 173,835 us-gaap_NotesReceivableNet / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = chmg_IndirectConsumerLoansMember / us-gaap_InternalCreditAssessmentAxis = chmg_NotRatedMember | 184,940 us-gaap_NotesReceivableNet / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = chmg_IndirectConsumerLoansMember / us-gaap_InternalCreditAssessmentAxis = chmg_NotRatedMember
Not Rated [Member] | Direct consumer loans [Member] |  |
Finance receivable by credit quality indicator [Abstract] |  |
Loans | 18,824 us-gaap_NotesReceivableNet / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerOtherFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = chmg_NotRatedMember | 20,045 us-gaap_NotesReceivableNet / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerOtherFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = chmg_NotRatedMember
Pass [Member] |  |
Finance receivable by credit quality indicator [Abstract] |  |
Loans | 616,783 us-gaap_NotesReceivableNet / us-gaap_InternalCreditAssessmentAxis = us-gaap_PassMember | 576,136 us-gaap_NotesReceivableNet / us-gaap_InternalCreditAssessmentAxis = us-gaap_PassMember
Pass [Member] | Commercial and Industrial [Member] |  |
Finance receivable by credit quality indicator [Abstract] |  |
Loans | 164,385 us-gaap_NotesReceivableNet / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = chmg_CommercialAndIndustrialMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_PassMember | 158,140 us-gaap_NotesReceivableNet / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = chmg_CommercialAndIndustrialMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_PassMember
Pass [Member] | Agricultural [Member] |  |
Finance receivable by credit quality indicator [Abstract] |  |
Loans | 1,158 us-gaap_NotesReceivableNet / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = chmg_AgriculturalMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_PassMember | 1,023 us-gaap_NotesReceivableNet / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = chmg_AgriculturalMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_PassMember
Pass [Member] | Construction [Member] |  |
Finance receivable by credit quality indicator [Abstract] |  |
Loans | 47,607 us-gaap_NotesReceivableNet / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstateConstructionFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_PassMember | 51,525 us-gaap_NotesReceivableNet / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstateConstructionFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_PassMember
Pass [Member] | Commercial mortgages [Member] |  |
Finance receivable by credit quality indicator [Abstract] |  |
Loans | 403,633 us-gaap_NotesReceivableNet / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstateOtherReceivableMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_PassMember | 365,448 us-gaap_NotesReceivableNet / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstateOtherReceivableMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_PassMember
Pass [Member] | Residential mortgages [Member] |  |
Finance receivable by credit quality indicator [Abstract] |  |
Loans | 0 us-gaap_NotesReceivableNet / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ResidentialPortfolioSegmentMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_PassMember | 0 us-gaap_NotesReceivableNet / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ResidentialPortfolioSegmentMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_PassMember
Pass [Member] | Credit Cards [Member] |  |
Finance receivable by credit quality indicator [Abstract] |  |
Loans | 0 us-gaap_NotesReceivableNet / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerCreditCardFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_PassMember | 0 us-gaap_NotesReceivableNet / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerCreditCardFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_PassMember
Pass [Member] | Home equity lines and loans [Member] |  |
Finance receivable by credit quality indicator [Abstract] |  |
Loans | 0 us-gaap_NotesReceivableNet / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = chmg_HomeEquityLinesAndLoansMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_PassMember | 0 us-gaap_NotesReceivableNet / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = chmg_HomeEquityLinesAndLoansMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_PassMember
Pass [Member] | Indirect consumer loans [Member] |  |
Finance receivable by credit quality indicator [Abstract] |  |
Loans | 0 us-gaap_NotesReceivableNet / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = chmg_IndirectConsumerLoansMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_PassMember | 0 us-gaap_NotesReceivableNet / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = chmg_IndirectConsumerLoansMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_PassMember
Pass [Member] | Direct consumer loans [Member] |  |
Finance receivable by credit quality indicator [Abstract] |  |
Loans | 0 us-gaap_NotesReceivableNet / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerOtherFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_PassMember | 0 us-gaap_NotesReceivableNet / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerOtherFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_PassMember
Loans Acquired with Deteriorated Credit Quality [Member] |  |
Finance receivable by credit quality indicator [Abstract] |  |
Loans | 2,017 us-gaap_NotesReceivableNet / us-gaap_InternalCreditAssessmentAxis = chmg_LoansAcquiredWithDeterioratedCreditQualityMember | 2,631 us-gaap_NotesReceivableNet / us-gaap_InternalCreditAssessmentAxis = chmg_LoansAcquiredWithDeterioratedCreditQualityMember
Loans Acquired with Deteriorated Credit Quality [Member] | Commercial and Industrial [Member] |  |
Finance receivable by credit quality indicator [Abstract] |  |
Loans | 0 us-gaap_NotesReceivableNet / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = chmg_CommercialAndIndustrialMember / us-gaap_InternalCreditAssessmentAxis = chmg_LoansAcquiredWithDeterioratedCreditQualityMember | 620 us-gaap_NotesReceivableNet / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = chmg_CommercialAndIndustrialMember / us-gaap_InternalCreditAssessmentAxis = chmg_LoansAcquiredWithDeterioratedCreditQualityMember
Loans Acquired with Deteriorated Credit Quality [Member] | Agricultural [Member] |  |
Finance receivable by credit quality indicator [Abstract] |  |
Loans | 0 us-gaap_NotesReceivableNet / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = chmg_AgriculturalMember / us-gaap_InternalCreditAssessmentAxis = chmg_LoansAcquiredWithDeterioratedCreditQualityMember | 0 us-gaap_NotesReceivableNet / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = chmg_AgriculturalMember / us-gaap_InternalCreditAssessmentAxis = chmg_LoansAcquiredWithDeterioratedCreditQualityMember
Loans Acquired with Deteriorated Credit Quality [Member] | Construction [Member] |  |
Finance receivable by credit quality indicator [Abstract] |  |
Loans | 0 us-gaap_NotesReceivableNet / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstateConstructionFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = chmg_LoansAcquiredWithDeterioratedCreditQualityMember | 0 us-gaap_NotesReceivableNet / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstateConstructionFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = chmg_LoansAcquiredWithDeterioratedCreditQualityMember
Loans Acquired with Deteriorated Credit Quality [Member] | Commercial mortgages [Member] |  |
Finance receivable by credit quality indicator [Abstract] |  |
Loans | 1,761 us-gaap_NotesReceivableNet / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstateOtherReceivableMember / us-gaap_InternalCreditAssessmentAxis = chmg_LoansAcquiredWithDeterioratedCreditQualityMember | 1,761 us-gaap_NotesReceivableNet / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstateOtherReceivableMember / us-gaap_InternalCreditAssessmentAxis = chmg_LoansAcquiredWithDeterioratedCreditQualityMember
Loans Acquired with Deteriorated Credit Quality [Member] | Residential mortgages [Member] |  |
Finance receivable by credit quality indicator [Abstract] |  |
Loans | 256 us-gaap_NotesReceivableNet / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ResidentialPortfolioSegmentMember / us-gaap_InternalCreditAssessmentAxis = chmg_LoansAcquiredWithDeterioratedCreditQualityMember | 250 us-gaap_NotesReceivableNet / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ResidentialPortfolioSegmentMember / us-gaap_InternalCreditAssessmentAxis = chmg_LoansAcquiredWithDeterioratedCreditQualityMember
Loans Acquired with Deteriorated Credit Quality [Member] | Credit Cards [Member] |  |
Finance receivable by credit quality indicator [Abstract] |  |
Loans | 0 us-gaap_NotesReceivableNet / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerCreditCardFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = chmg_LoansAcquiredWithDeterioratedCreditQualityMember | 0 us-gaap_NotesReceivableNet / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerCreditCardFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = chmg_LoansAcquiredWithDeterioratedCreditQualityMember
Loans Acquired with Deteriorated Credit Quality [Member] | Home equity lines and loans [Member] |  |
Finance receivable by credit quality indicator [Abstract] |  |
Loans | 0 us-gaap_NotesReceivableNet / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = chmg_HomeEquityLinesAndLoansMember / us-gaap_InternalCreditAssessmentAxis = chmg_LoansAcquiredWithDeterioratedCreditQualityMember | 0 us-gaap_NotesReceivableNet / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = chmg_HomeEquityLinesAndLoansMember / us-gaap_InternalCreditAssessmentAxis = chmg_LoansAcquiredWithDeterioratedCreditQualityMember
Loans Acquired with Deteriorated Credit Quality [Member] | Indirect consumer loans [Member] |  |
Finance receivable by credit quality indicator [Abstract] |  |
Loans | 0 us-gaap_NotesReceivableNet / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = chmg_IndirectConsumerLoansMember / us-gaap_InternalCreditAssessmentAxis = chmg_LoansAcquiredWithDeterioratedCreditQualityMember | 0 us-gaap_NotesReceivableNet / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = chmg_IndirectConsumerLoansMember / us-gaap_InternalCreditAssessmentAxis = chmg_LoansAcquiredWithDeterioratedCreditQualityMember
Loans Acquired with Deteriorated Credit Quality [Member] | Direct consumer loans [Member] |  |
Finance receivable by credit quality indicator [Abstract] |  |
Loans | 0 us-gaap_NotesReceivableNet / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerOtherFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = chmg_LoansAcquiredWithDeterioratedCreditQualityMember | 0 us-gaap_NotesReceivableNet / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerOtherFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = chmg_LoansAcquiredWithDeterioratedCreditQualityMember
Special Mention [Member] |  |
Finance receivable by credit quality indicator [Abstract] |  |
Loans | 14,991 us-gaap_NotesReceivableNet / us-gaap_InternalCreditAssessmentAxis = us-gaap_SpecialMentionMember | 27,858 us-gaap_NotesReceivableNet / us-gaap_InternalCreditAssessmentAxis = us-gaap_SpecialMentionMember
Special Mention [Member] | Commercial and Industrial [Member] |  |
Finance receivable by credit quality indicator [Abstract] |  |
Loans | 4,220 us-gaap_NotesReceivableNet / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = chmg_CommercialAndIndustrialMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_SpecialMentionMember | 3,695 us-gaap_NotesReceivableNet / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = chmg_CommercialAndIndustrialMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_SpecialMentionMember
Special Mention [Member] | Agricultural [Member] |  |
Finance receivable by credit quality indicator [Abstract] |  |
Loans | 0 us-gaap_NotesReceivableNet / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = chmg_AgriculturalMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_SpecialMentionMember | 0 us-gaap_NotesReceivableNet / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = chmg_AgriculturalMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_SpecialMentionMember
Special Mention [Member] | Construction [Member] |  |
Finance receivable by credit quality indicator [Abstract] |  |
Loans | 1,750 us-gaap_NotesReceivableNet / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstateConstructionFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_SpecialMentionMember | 3,292 us-gaap_NotesReceivableNet / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstateConstructionFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_SpecialMentionMember
Special Mention [Member] | Commercial mortgages [Member] |  |
Finance receivable by credit quality indicator [Abstract] |  |
Loans | 9,021 us-gaap_NotesReceivableNet / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstateOtherReceivableMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_SpecialMentionMember | 20,871 us-gaap_NotesReceivableNet / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstateOtherReceivableMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_SpecialMentionMember
Special Mention [Member] | Residential mortgages [Member] |  |
Finance receivable by credit quality indicator [Abstract] |  |
Loans | 0 us-gaap_NotesReceivableNet / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ResidentialPortfolioSegmentMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_SpecialMentionMember | 0 us-gaap_NotesReceivableNet / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ResidentialPortfolioSegmentMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_SpecialMentionMember
Special Mention [Member] | Credit Cards [Member] |  |
Finance receivable by credit quality indicator [Abstract] |  |
Loans | 0 us-gaap_NotesReceivableNet / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerCreditCardFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_SpecialMentionMember | 0 us-gaap_NotesReceivableNet / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerCreditCardFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_SpecialMentionMember
Special Mention [Member] | Home equity lines and loans [Member] |  |
Finance receivable by credit quality indicator [Abstract] |  |
Loans | 0 us-gaap_NotesReceivableNet / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = chmg_HomeEquityLinesAndLoansMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_SpecialMentionMember | 0 us-gaap_NotesReceivableNet / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = chmg_HomeEquityLinesAndLoansMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_SpecialMentionMember
Special Mention [Member] | Indirect consumer loans [Member] |  |
Finance receivable by credit quality indicator [Abstract] |  |
Loans | 0 us-gaap_NotesReceivableNet / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = chmg_IndirectConsumerLoansMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_SpecialMentionMember | 0 us-gaap_NotesReceivableNet / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = chmg_IndirectConsumerLoansMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_SpecialMentionMember
Special Mention [Member] | Direct consumer loans [Member] |  |
Finance receivable by credit quality indicator [Abstract] |  |
Loans | 0 us-gaap_NotesReceivableNet / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerOtherFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_SpecialMentionMember | 0 us-gaap_NotesReceivableNet / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerOtherFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_SpecialMentionMember
Substandard [Member] |  |
Finance receivable by credit quality indicator [Abstract] |  |
Loans | 20,426 us-gaap_NotesReceivableNet / us-gaap_InternalCreditAssessmentAxis = us-gaap_SubstandardMember | 18,150 us-gaap_NotesReceivableNet / us-gaap_InternalCreditAssessmentAxis = us-gaap_SubstandardMember
Substandard [Member] | Commercial and Industrial [Member] |  |
Finance receivable by credit quality indicator [Abstract] |  |
Loans | 2,285 us-gaap_NotesReceivableNet / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = chmg_CommercialAndIndustrialMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_SubstandardMember | 3,306 us-gaap_NotesReceivableNet / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = chmg_CommercialAndIndustrialMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_SubstandardMember
Substandard [Member] | Agricultural [Member] |  |
Finance receivable by credit quality indicator [Abstract] |  |
Loans | 0 us-gaap_NotesReceivableNet / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = chmg_AgriculturalMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_SubstandardMember | 0 us-gaap_NotesReceivableNet / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = chmg_AgriculturalMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_SubstandardMember
Substandard [Member] | Construction [Member] |  |
Finance receivable by credit quality indicator [Abstract] |  |
Loans | 148 us-gaap_NotesReceivableNet / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstateConstructionFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_SubstandardMember | 150 us-gaap_NotesReceivableNet / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstateConstructionFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_SubstandardMember
Substandard [Member] | Commercial mortgages [Member] |  |
Finance receivable by credit quality indicator [Abstract] |  |
Loans | 13,368 us-gaap_NotesReceivableNet / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstateOtherReceivableMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_SubstandardMember | 10,266 us-gaap_NotesReceivableNet / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstateOtherReceivableMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_SubstandardMember
Substandard [Member] | Residential mortgages [Member] |  |
Finance receivable by credit quality indicator [Abstract] |  |
Loans | 3,705 us-gaap_NotesReceivableNet / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ResidentialPortfolioSegmentMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_SubstandardMember | 3,615 us-gaap_NotesReceivableNet / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ResidentialPortfolioSegmentMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_SubstandardMember
Substandard [Member] | Credit Cards [Member] |  |
Finance receivable by credit quality indicator [Abstract] |  |
Loans | 0 us-gaap_NotesReceivableNet / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerCreditCardFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_SubstandardMember | 0 us-gaap_NotesReceivableNet / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerCreditCardFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_SubstandardMember
Substandard [Member] | Home equity lines and loans [Member] |  |
Finance receivable by credit quality indicator [Abstract] |  |
Loans | 655 us-gaap_NotesReceivableNet / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = chmg_HomeEquityLinesAndLoansMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_SubstandardMember | 515 us-gaap_NotesReceivableNet / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = chmg_HomeEquityLinesAndLoansMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_SubstandardMember
Substandard [Member] | Indirect consumer loans [Member] |  |
Finance receivable by credit quality indicator [Abstract] |  |
Loans | 253 us-gaap_NotesReceivableNet / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = chmg_IndirectConsumerLoansMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_SubstandardMember | 277 us-gaap_NotesReceivableNet / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = chmg_IndirectConsumerLoansMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_SubstandardMember
Substandard [Member] | Direct consumer loans [Member] |  |
Finance receivable by credit quality indicator [Abstract] |  |
Loans | 12 us-gaap_NotesReceivableNet / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerOtherFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_SubstandardMember | 21 us-gaap_NotesReceivableNet / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerOtherFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_SubstandardMember
Doubtful [Member] |  |
Finance receivable by credit quality indicator [Abstract] |  |
Loans | 4,379 us-gaap_NotesReceivableNet / us-gaap_InternalCreditAssessmentAxis = us-gaap_DoubtfulMember | 442 us-gaap_NotesReceivableNet / us-gaap_InternalCreditAssessmentAxis = us-gaap_DoubtfulMember
Doubtful [Member] | Commercial and Industrial [Member] |  |
Finance receivable by credit quality indicator [Abstract] |  |
Loans | 179 us-gaap_NotesReceivableNet / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = chmg_CommercialAndIndustrialMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_DoubtfulMember | 36 us-gaap_NotesReceivableNet / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = chmg_CommercialAndIndustrialMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_DoubtfulMember
Doubtful [Member] | Agricultural [Member] |  |
Finance receivable by credit quality indicator [Abstract] |  |
Loans | 0 us-gaap_NotesReceivableNet / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = chmg_AgriculturalMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_DoubtfulMember | 0 us-gaap_NotesReceivableNet / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = chmg_AgriculturalMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_DoubtfulMember
Doubtful [Member] | Construction [Member] |  |
Finance receivable by credit quality indicator [Abstract] |  |
Loans | 0 us-gaap_NotesReceivableNet / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstateConstructionFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_DoubtfulMember | 0 us-gaap_NotesReceivableNet / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstateConstructionFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_DoubtfulMember
Doubtful [Member] | Commercial mortgages [Member] |  |
Finance receivable by credit quality indicator [Abstract] |  |
Loans | 4,200 us-gaap_NotesReceivableNet / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstateOtherReceivableMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_DoubtfulMember | 406 us-gaap_NotesReceivableNet / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstateOtherReceivableMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_DoubtfulMember
Doubtful [Member] | Residential mortgages [Member] |  |
Finance receivable by credit quality indicator [Abstract] |  |
Loans | 0 us-gaap_NotesReceivableNet / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ResidentialPortfolioSegmentMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_DoubtfulMember | 0 us-gaap_NotesReceivableNet / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ResidentialPortfolioSegmentMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_DoubtfulMember
Doubtful [Member] | Credit Cards [Member] |  |
Finance receivable by credit quality indicator [Abstract] |  |
Loans | 0 us-gaap_NotesReceivableNet / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerCreditCardFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_DoubtfulMember | 0 us-gaap_NotesReceivableNet / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerCreditCardFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_DoubtfulMember
Doubtful [Member] | Home equity lines and loans [Member] |  |
Finance receivable by credit quality indicator [Abstract] |  |
Loans | 0 us-gaap_NotesReceivableNet / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = chmg_HomeEquityLinesAndLoansMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_DoubtfulMember | 0 us-gaap_NotesReceivableNet / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = chmg_HomeEquityLinesAndLoansMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_DoubtfulMember
Doubtful [Member] | Indirect consumer loans [Member] |  |
Finance receivable by credit quality indicator [Abstract] |  |
Loans | 0 us-gaap_NotesReceivableNet / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = chmg_IndirectConsumerLoansMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_DoubtfulMember | 0 us-gaap_NotesReceivableNet / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = chmg_IndirectConsumerLoansMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_DoubtfulMember
Doubtful [Member] | Direct consumer loans [Member] |  |
Finance receivable by credit quality indicator [Abstract] |  |
Loans | 0 us-gaap_NotesReceivableNet / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerOtherFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_DoubtfulMember | 0 us-gaap_NotesReceivableNet / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerOtherFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_DoubtfulMember
Performing [Member] |  |
Residential and consumer finance receivable [Abstract] |  |
Residential and consumer loans receivable | 18,824 chmg_ResidentialAndConsumerLoansReceivable / us-gaap_InternalCreditAssessmentAxis = us-gaap_PerformingFinancingReceivableMember | 20,036 chmg_ResidentialAndConsumerLoansReceivable / us-gaap_InternalCreditAssessmentAxis = us-gaap_PerformingFinancingReceivableMember
Performing [Member] | Residential mortgages [Member] |  |
Residential and consumer finance receivable [Abstract] |  |
Residential and consumer loans receivable | 195,422 chmg_ResidentialAndConsumerLoansReceivable / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ResidentialPortfolioSegmentMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_PerformingFinancingReceivableMember | 193,672 chmg_ResidentialAndConsumerLoansReceivable / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ResidentialPortfolioSegmentMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_PerformingFinancingReceivableMember
Performing [Member] | Credit Cards [Member] |  |
Residential and consumer finance receivable [Abstract] |  |
Residential and consumer loans receivable | 1,526 chmg_ResidentialAndConsumerLoansReceivable / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerCreditCardFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_PerformingFinancingReceivableMember | 1,654 chmg_ResidentialAndConsumerLoansReceivable / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerCreditCardFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_PerformingFinancingReceivableMember
Performing [Member] | Home equity lines and loans [Member] |  |
Residential and consumer finance receivable [Abstract] |  |
Residential and consumer loans receivable | 98,298 chmg_ResidentialAndConsumerLoansReceivable / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = chmg_HomeEquityLinesAndLoansMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_PerformingFinancingReceivableMember | 99,076 chmg_ResidentialAndConsumerLoansReceivable / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = chmg_HomeEquityLinesAndLoansMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_PerformingFinancingReceivableMember
Performing [Member] | Indirect consumer loans [Member] |  |
Residential and consumer finance receivable [Abstract] |  |
Residential and consumer loans receivable | 173,839 chmg_ResidentialAndConsumerLoansReceivable / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = chmg_IndirectConsumerLoansMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_PerformingFinancingReceivableMember | 184,892 chmg_ResidentialAndConsumerLoansReceivable / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = chmg_IndirectConsumerLoansMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_PerformingFinancingReceivableMember
Non-Performing [Member] |  |
Residential and consumer finance receivable [Abstract] |  |
Residential and consumer loans receivable | 12 chmg_ResidentialAndConsumerLoansReceivable / us-gaap_InternalCreditAssessmentAxis = us-gaap_NonperformingFinancingReceivableMember | 30 chmg_ResidentialAndConsumerLoansReceivable / us-gaap_InternalCreditAssessmentAxis = us-gaap_NonperformingFinancingReceivableMember
Non-Performing [Member] | Residential mortgages [Member] |  |
Residential and consumer finance receivable [Abstract] |  |
Residential and consumer loans receivable | 3,705 chmg_ResidentialAndConsumerLoansReceivable / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ResidentialPortfolioSegmentMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_NonperformingFinancingReceivableMember | 3,615 chmg_ResidentialAndConsumerLoansReceivable / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ResidentialPortfolioSegmentMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_NonperformingFinancingReceivableMember
Non-Performing [Member] | Credit Cards [Member] |  |
Residential and consumer finance receivable [Abstract] |  |
Residential and consumer loans receivable | 0 chmg_ResidentialAndConsumerLoansReceivable / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerCreditCardFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_NonperformingFinancingReceivableMember | 0 chmg_ResidentialAndConsumerLoansReceivable / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerCreditCardFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_NonperformingFinancingReceivableMember
Non-Performing [Member] | Home equity lines and loans [Member] |  |
Residential and consumer finance receivable [Abstract] |  |
Residential and consumer loans receivable | 655 chmg_ResidentialAndConsumerLoansReceivable / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = chmg_HomeEquityLinesAndLoansMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_NonperformingFinancingReceivableMember | 515 chmg_ResidentialAndConsumerLoansReceivable / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = chmg_HomeEquityLinesAndLoansMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_NonperformingFinancingReceivableMember
Non-Performing [Member] | Indirect consumer loans [Member] |  |
Residential and consumer finance receivable [Abstract] |  |
Residential and consumer loans receivable | $ 249 chmg_ResidentialAndConsumerLoansReceivable / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = chmg_IndirectConsumerLoansMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_NonperformingFinancingReceivableMember | $ 325 chmg_ResidentialAndConsumerLoansReceivable / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = chmg_IndirectConsumerLoansMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_NonperformingFinancingReceivableMember

X
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