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FAIR VALUE (Details) (USD $) In Thousands, unless otherwise specified | Mar. 31, 2015 | Dec. 31, 2014
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Financial Assets [Abstract] |  |
Total available for sale securities | $ 266,307 us-gaap_AvailableForSaleSecurities | $ 280,507 us-gaap_AvailableForSaleSecurities
Trading assets | 601 us-gaap_TradingSecurities | 549 us-gaap_TradingSecurities
Other real estate owned [Member] |  |
Consumer loans [Abstract] |  |
Total other real estate owned, net |  | 3,100 us-gaap_OtherRealEstateAndForeclosedAssets / us-gaap_FairValueByAssetClassAxis = chmg_OtherRealEstateOwnedMember
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] |  |
Financial Assets [Abstract] |  |
Total available for sale securities | 31,321 us-gaap_AvailableForSaleSecurities / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel1Member | 31,219 us-gaap_AvailableForSaleSecurities / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel1Member
Significant Other Observable Inputs (Level 2) [Member] |  |
Financial Assets [Abstract] |  |
Total available for sale securities | 234,986 us-gaap_AvailableForSaleSecurities / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel2Member | 249,288 us-gaap_AvailableForSaleSecurities / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel2Member
Significant Unobservable Inputs (Level 3) [Member] |  |
Financial Assets [Abstract] |  |
Total available for sale securities | 0 us-gaap_AvailableForSaleSecurities / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member | 0 us-gaap_AvailableForSaleSecurities / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member
Recurring [Member] |  |
Financial Assets [Abstract] |  |
Obligations of U.S. Government and U.S. Government sponsored enterprises | 170,447 chmg_ObligationsOfUSGovernmentAndUSGovernmentSponsoredEnterprisesFairValueDisclosure / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember | 181,673 chmg_ObligationsOfUSGovernmentAndUSGovernmentSponsoredEnterprisesFairValueDisclosure / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember
Mortgage-backed securities, residential | 59,182 us-gaap_MortgageBackedSecuritiesAvailableForSaleFairValueDisclosure / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember | 61,660 us-gaap_MortgageBackedSecuritiesAvailableForSaleFairValueDisclosure / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember
Collateralized mortgage obligations | 231 chmg_CollateralizedMortgageObligationsFairValueDisclosure / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember | 338 chmg_CollateralizedMortgageObligationsFairValueDisclosure / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember
Obligations of states and political subdivisions | 31,152 chmg_ObligationsOfStatesAndPoliticalSubdivisionsFairValueDisclosure / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember | 31,451 chmg_ObligationsOfStatesAndPoliticalSubdivisionsFairValueDisclosure / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember
Corporate bonds and notes | 1,528 chmg_CorporateBondsAndNotesFairValueDisclosure / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember | 1,533 chmg_CorporateBondsAndNotesFairValueDisclosure / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember
SBA loan pools | 1,260 chmg_SmallBusinessAdministrationPoolLoansFairValuedisclosure / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember | 1,304 chmg_SmallBusinessAdministrationPoolLoansFairValuedisclosure / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember
Trust Preferred securities | 2,024 chmg_TrustPreferredSecuritiesFairValueDisclosure / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember | 2,028 chmg_TrustPreferredSecuritiesFairValueDisclosure / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember
Corporate stocks | 483 chmg_CorporateStocksFairValueDisclosure / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember | 520 chmg_CorporateStocksFairValueDisclosure / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember
Total available for sale securities | 266,307 us-gaap_AvailableForSaleSecurities / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember | 280,507 us-gaap_AvailableForSaleSecurities / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember
Trading assets | 601 us-gaap_TradingSecurities / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember | 549 us-gaap_TradingSecurities / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember
Recurring [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] |  |
Financial Assets [Abstract] |  |
Obligations of U.S. Government and U.S. Government sponsored enterprises | 31,266 chmg_ObligationsOfUSGovernmentAndUSGovernmentSponsoredEnterprisesFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel1Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember | 31,115 chmg_ObligationsOfUSGovernmentAndUSGovernmentSponsoredEnterprisesFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel1Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember
Mortgage-backed securities, residential | 0 us-gaap_MortgageBackedSecuritiesAvailableForSaleFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel1Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember | 0 us-gaap_MortgageBackedSecuritiesAvailableForSaleFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel1Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember
Collateralized mortgage obligations | 0 chmg_CollateralizedMortgageObligationsFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel1Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember | 0 chmg_CollateralizedMortgageObligationsFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel1Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember
Obligations of states and political subdivisions | 0 chmg_ObligationsOfStatesAndPoliticalSubdivisionsFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel1Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember | 0 chmg_ObligationsOfStatesAndPoliticalSubdivisionsFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel1Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember
Corporate bonds and notes | 0 chmg_CorporateBondsAndNotesFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel1Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember | 0 chmg_CorporateBondsAndNotesFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel1Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember
SBA loan pools | 0 chmg_SmallBusinessAdministrationPoolLoansFairValuedisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel1Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember | 0 chmg_SmallBusinessAdministrationPoolLoansFairValuedisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel1Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember
Trust Preferred securities | 0 chmg_TrustPreferredSecuritiesFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel1Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember | 0 chmg_TrustPreferredSecuritiesFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel1Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember
Corporate stocks | 55 chmg_CorporateStocksFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel1Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember | 104 chmg_CorporateStocksFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel1Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember
Total available for sale securities | 31,321 us-gaap_AvailableForSaleSecurities / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel1Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember | 31,219 us-gaap_AvailableForSaleSecurities / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel1Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember
Trading assets | 601 us-gaap_TradingSecurities / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel1Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember | 549 us-gaap_TradingSecurities / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel1Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember
Recurring [Member] | Significant Other Observable Inputs (Level 2) [Member] |  |
Financial Assets [Abstract] |  |
Obligations of U.S. Government and U.S. Government sponsored enterprises | 139,181 chmg_ObligationsOfUSGovernmentAndUSGovernmentSponsoredEnterprisesFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel2Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember | 150,558 chmg_ObligationsOfUSGovernmentAndUSGovernmentSponsoredEnterprisesFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel2Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember
Mortgage-backed securities, residential | 59,182 us-gaap_MortgageBackedSecuritiesAvailableForSaleFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel2Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember | 61,660 us-gaap_MortgageBackedSecuritiesAvailableForSaleFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel2Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember
Collateralized mortgage obligations | 231 chmg_CollateralizedMortgageObligationsFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel2Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember | 338 chmg_CollateralizedMortgageObligationsFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel2Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember
Obligations of states and political subdivisions | 31,152 chmg_ObligationsOfStatesAndPoliticalSubdivisionsFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel2Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember | 31,451 chmg_ObligationsOfStatesAndPoliticalSubdivisionsFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel2Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember
Corporate bonds and notes | 1,528 chmg_CorporateBondsAndNotesFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel2Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember | 1,533 chmg_CorporateBondsAndNotesFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel2Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember
SBA loan pools | 1,260 chmg_SmallBusinessAdministrationPoolLoansFairValuedisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel2Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember | 1,304 chmg_SmallBusinessAdministrationPoolLoansFairValuedisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel2Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember
Trust Preferred securities | 2,024 chmg_TrustPreferredSecuritiesFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel2Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember | 2,028 chmg_TrustPreferredSecuritiesFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel2Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember
Corporate stocks | 428 chmg_CorporateStocksFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel2Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember | 416 chmg_CorporateStocksFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel2Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember
Total available for sale securities | 234,986 us-gaap_AvailableForSaleSecurities / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel2Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember | 249,288 us-gaap_AvailableForSaleSecurities / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel2Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember
Trading assets | 0 us-gaap_TradingSecurities / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel2Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember | 0 us-gaap_TradingSecurities / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel2Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember
Recurring [Member] | Significant Unobservable Inputs (Level 3) [Member] |  |
Financial Assets [Abstract] |  |
Obligations of U.S. Government and U.S. Government sponsored enterprises | 0 chmg_ObligationsOfUSGovernmentAndUSGovernmentSponsoredEnterprisesFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember | 0 chmg_ObligationsOfUSGovernmentAndUSGovernmentSponsoredEnterprisesFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember
Mortgage-backed securities, residential | 0 us-gaap_MortgageBackedSecuritiesAvailableForSaleFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember | 0 us-gaap_MortgageBackedSecuritiesAvailableForSaleFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember
Collateralized mortgage obligations | 0 chmg_CollateralizedMortgageObligationsFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember | 0 chmg_CollateralizedMortgageObligationsFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember
Obligations of states and political subdivisions | 0 chmg_ObligationsOfStatesAndPoliticalSubdivisionsFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember | 0 chmg_ObligationsOfStatesAndPoliticalSubdivisionsFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember
Corporate bonds and notes | 0 chmg_CorporateBondsAndNotesFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember | 0 chmg_CorporateBondsAndNotesFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember
SBA loan pools | 0 chmg_SmallBusinessAdministrationPoolLoansFairValuedisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember | 0 chmg_SmallBusinessAdministrationPoolLoansFairValuedisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember
Trust Preferred securities | 0 chmg_TrustPreferredSecuritiesFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember | 0 chmg_TrustPreferredSecuritiesFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember
Corporate stocks | 0 chmg_CorporateStocksFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember | 0 chmg_CorporateStocksFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember
Total available for sale securities | 0 us-gaap_AvailableForSaleSecurities / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember | 0 us-gaap_AvailableForSaleSecurities / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember
Trading assets | 0 us-gaap_TradingSecurities / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember | 0 us-gaap_TradingSecurities / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember
Non-recurring [Member] | Impaired Loans [Member] |  |
Impaired Loans, Fair Value Disclosure [Abstract] |  |
Commercial mortgages | 2,993 chmg_CommercialMortgageLoansOtherFairValueDisclosure / us-gaap_FairValueByAssetClassAxis = chmg_ImpairedLoansMember / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsNonrecurringMember | 3,593 chmg_CommercialMortgageLoansOtherFairValueDisclosure / us-gaap_FairValueByAssetClassAxis = chmg_ImpairedLoansMember / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsNonrecurringMember
Consumer loans [Abstract] |  |
Home equity lines and loans |  | 52 chmg_HomeEquityLinesLoans / us-gaap_FairValueByAssetClassAxis = chmg_ImpairedLoansMember / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsNonrecurringMember
Total impaired loans | 2,993 us-gaap_LoansReceivableFairValueDisclosure / us-gaap_FairValueByAssetClassAxis = chmg_ImpairedLoansMember / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsNonrecurringMember | 3,645 us-gaap_LoansReceivableFairValueDisclosure / us-gaap_FairValueByAssetClassAxis = chmg_ImpairedLoansMember / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsNonrecurringMember
Non-recurring [Member] | Other real estate owned [Member] |  |
Impaired Loans, Fair Value Disclosure [Abstract] |  |
Commercial mortgages | 2,496 chmg_CommercialMortgageLoansOtherFairValueDisclosure / us-gaap_FairValueByAssetClassAxis = chmg_OtherRealEstateOwnedMember / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsNonrecurringMember | 3,063 chmg_CommercialMortgageLoansOtherFairValueDisclosure / us-gaap_FairValueByAssetClassAxis = chmg_OtherRealEstateOwnedMember / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsNonrecurringMember
Residential mortgages | 10 chmg_CommercialMortgageLoansResidentialMortgagesFairValueDisclosure / us-gaap_FairValueByAssetClassAxis = chmg_OtherRealEstateOwnedMember / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsNonrecurringMember |
Consumer loans [Abstract] |  |
Home equity lines and loans |  | 2 chmg_HomeEquityLinesLoans / us-gaap_FairValueByAssetClassAxis = chmg_OtherRealEstateOwnedMember / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsNonrecurringMember
Total other real estate owned, net | 2,506 us-gaap_OtherRealEstateAndForeclosedAssets / us-gaap_FairValueByAssetClassAxis = chmg_OtherRealEstateOwnedMember / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsNonrecurringMember | 3,065 us-gaap_OtherRealEstateAndForeclosedAssets / us-gaap_FairValueByAssetClassAxis = chmg_OtherRealEstateOwnedMember / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsNonrecurringMember
Non-recurring [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Impaired Loans [Member] |  |
Impaired Loans, Fair Value Disclosure [Abstract] |  |
Commercial mortgages | 0 chmg_CommercialMortgageLoansOtherFairValueDisclosure / us-gaap_FairValueByAssetClassAxis = chmg_ImpairedLoansMember / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel1Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsNonrecurringMember | 0 chmg_CommercialMortgageLoansOtherFairValueDisclosure / us-gaap_FairValueByAssetClassAxis = chmg_ImpairedLoansMember / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel1Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsNonrecurringMember
Consumer loans [Abstract] |  |
Home equity lines and loans |  | 0 chmg_HomeEquityLinesLoans / us-gaap_FairValueByAssetClassAxis = chmg_ImpairedLoansMember / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel1Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsNonrecurringMember
Total impaired loans | 0 us-gaap_LoansReceivableFairValueDisclosure / us-gaap_FairValueByAssetClassAxis = chmg_ImpairedLoansMember / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel1Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsNonrecurringMember | 0 us-gaap_LoansReceivableFairValueDisclosure / us-gaap_FairValueByAssetClassAxis = chmg_ImpairedLoansMember / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel1Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsNonrecurringMember
Non-recurring [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Other real estate owned [Member] |  |
Impaired Loans, Fair Value Disclosure [Abstract] |  |
Commercial mortgages | 0 chmg_CommercialMortgageLoansOtherFairValueDisclosure / us-gaap_FairValueByAssetClassAxis = chmg_OtherRealEstateOwnedMember / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel1Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsNonrecurringMember | 0 chmg_CommercialMortgageLoansOtherFairValueDisclosure / us-gaap_FairValueByAssetClassAxis = chmg_OtherRealEstateOwnedMember / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel1Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsNonrecurringMember
Residential mortgages | 0 chmg_CommercialMortgageLoansResidentialMortgagesFairValueDisclosure / us-gaap_FairValueByAssetClassAxis = chmg_OtherRealEstateOwnedMember / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel1Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsNonrecurringMember |
Consumer loans [Abstract] |  |
Home equity lines and loans |  | 0 chmg_HomeEquityLinesLoans / us-gaap_FairValueByAssetClassAxis = chmg_OtherRealEstateOwnedMember / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel1Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsNonrecurringMember
Total other real estate owned, net | 0 us-gaap_OtherRealEstateAndForeclosedAssets / us-gaap_FairValueByAssetClassAxis = chmg_OtherRealEstateOwnedMember / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel1Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsNonrecurringMember | 0 us-gaap_OtherRealEstateAndForeclosedAssets / us-gaap_FairValueByAssetClassAxis = chmg_OtherRealEstateOwnedMember / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel1Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsNonrecurringMember
Non-recurring [Member] | Significant Other Observable Inputs (Level 2) [Member] | Impaired Loans [Member] |  |
Impaired Loans, Fair Value Disclosure [Abstract] |  |
Commercial mortgages | 0 chmg_CommercialMortgageLoansOtherFairValueDisclosure / us-gaap_FairValueByAssetClassAxis = chmg_ImpairedLoansMember / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel2Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsNonrecurringMember | 0 chmg_CommercialMortgageLoansOtherFairValueDisclosure / us-gaap_FairValueByAssetClassAxis = chmg_ImpairedLoansMember / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel2Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsNonrecurringMember
Consumer loans [Abstract] |  |
Home equity lines and loans |  | 0 chmg_HomeEquityLinesLoans / us-gaap_FairValueByAssetClassAxis = chmg_ImpairedLoansMember / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel2Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsNonrecurringMember
Total impaired loans | 0 us-gaap_LoansReceivableFairValueDisclosure / us-gaap_FairValueByAssetClassAxis = chmg_ImpairedLoansMember / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel2Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsNonrecurringMember | 0 us-gaap_LoansReceivableFairValueDisclosure / us-gaap_FairValueByAssetClassAxis = chmg_ImpairedLoansMember / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel2Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsNonrecurringMember
Non-recurring [Member] | Significant Other Observable Inputs (Level 2) [Member] | Other real estate owned [Member] |  |
Impaired Loans, Fair Value Disclosure [Abstract] |  |
Commercial mortgages | 0 chmg_CommercialMortgageLoansOtherFairValueDisclosure / us-gaap_FairValueByAssetClassAxis = chmg_OtherRealEstateOwnedMember / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel2Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsNonrecurringMember | 0 chmg_CommercialMortgageLoansOtherFairValueDisclosure / us-gaap_FairValueByAssetClassAxis = chmg_OtherRealEstateOwnedMember / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel2Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsNonrecurringMember
Residential mortgages | 0 chmg_CommercialMortgageLoansResidentialMortgagesFairValueDisclosure / us-gaap_FairValueByAssetClassAxis = chmg_OtherRealEstateOwnedMember / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel2Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsNonrecurringMember |
Consumer loans [Abstract] |  |
Home equity lines and loans |  | 0 chmg_HomeEquityLinesLoans / us-gaap_FairValueByAssetClassAxis = chmg_OtherRealEstateOwnedMember / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel2Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsNonrecurringMember
Total other real estate owned, net | 0 us-gaap_OtherRealEstateAndForeclosedAssets / us-gaap_FairValueByAssetClassAxis = chmg_OtherRealEstateOwnedMember / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel2Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsNonrecurringMember | 0 us-gaap_OtherRealEstateAndForeclosedAssets / us-gaap_FairValueByAssetClassAxis = chmg_OtherRealEstateOwnedMember / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel2Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsNonrecurringMember
Non-recurring [Member] | Significant Unobservable Inputs (Level 3) [Member] | Impaired Loans [Member] |  |
Impaired Loans, Fair Value Disclosure [Abstract] |  |
Commercial mortgages | 2,993 chmg_CommercialMortgageLoansOtherFairValueDisclosure / us-gaap_FairValueByAssetClassAxis = chmg_ImpairedLoansMember / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsNonrecurringMember | 3,593 chmg_CommercialMortgageLoansOtherFairValueDisclosure / us-gaap_FairValueByAssetClassAxis = chmg_ImpairedLoansMember / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsNonrecurringMember
Consumer loans [Abstract] |  |
Home equity lines and loans |  | 52 chmg_HomeEquityLinesLoans / us-gaap_FairValueByAssetClassAxis = chmg_ImpairedLoansMember / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsNonrecurringMember
Total impaired loans | 2,993 us-gaap_LoansReceivableFairValueDisclosure / us-gaap_FairValueByAssetClassAxis = chmg_ImpairedLoansMember / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsNonrecurringMember | 3,645 us-gaap_LoansReceivableFairValueDisclosure / us-gaap_FairValueByAssetClassAxis = chmg_ImpairedLoansMember / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsNonrecurringMember
Non-recurring [Member] | Significant Unobservable Inputs (Level 3) [Member] | Other real estate owned [Member] |  |
Impaired Loans, Fair Value Disclosure [Abstract] |  |
Commercial mortgages | 2,496 chmg_CommercialMortgageLoansOtherFairValueDisclosure / us-gaap_FairValueByAssetClassAxis = chmg_OtherRealEstateOwnedMember / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsNonrecurringMember | 3,063 chmg_CommercialMortgageLoansOtherFairValueDisclosure / us-gaap_FairValueByAssetClassAxis = chmg_OtherRealEstateOwnedMember / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsNonrecurringMember
Residential mortgages | 10 chmg_CommercialMortgageLoansResidentialMortgagesFairValueDisclosure / us-gaap_FairValueByAssetClassAxis = chmg_OtherRealEstateOwnedMember / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsNonrecurringMember |
Consumer loans [Abstract] |  |
Home equity lines and loans |  | 2 chmg_HomeEquityLinesLoans / us-gaap_FairValueByAssetClassAxis = chmg_OtherRealEstateOwnedMember / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsNonrecurringMember
Total other real estate owned, net | $ 2,506 us-gaap_OtherRealEstateAndForeclosedAssets / us-gaap_FairValueByAssetClassAxis = chmg_OtherRealEstateOwnedMember / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsNonrecurringMember | $ 3,065 us-gaap_OtherRealEstateAndForeclosedAssets / us-gaap_FairValueByAssetClassAxis = chmg_OtherRealEstateOwnedMember / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsNonrecurringMember

X
- Definition This element represents the portion of the balance sheet assertion valued at fair value by the entity whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission. This item represents collateralized mortgage obligations, as of the balance sheet date which have been categorized as available-for-sale. + References No definition available. + Details
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Namespace Prefix: | chmg_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition This element represents the portion of the balance sheet assertion valued at fair value by the entity whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission. This item represents loan receivable as presented on the statement of financial position, for the commercial mortgages loans not other wise disclosed which are due the Company as of the balance sheet date. + References No definition available. + Details
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Namespace Prefix: | chmg_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

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- Definition This element represents the portion of the balance sheet assertion valued at fair value by the entity whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission. This item represents loan receivable as presented on the statement of financial position, for the commercial mortgages loans in the Residential mortgages sector which are due the Company as of the balance sheet date. + References No definition available. + Details
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Namespace Prefix: | chmg_
Data Type: | xbrli:monetaryItemType
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- Details
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X
- Definition This element represents the portion of the balance sheet assertion valued at fair value by the entity whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission. This item represents corporate bonds and notes as of the balance sheet date which have been categorized as available-for-sale. + References No definition available. + Details
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Namespace Prefix: | chmg_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition This element represents the portion of the balance sheet assertion valued at fair value by the entity whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission. This item represents corporate stocks as of the balance sheet date which have been categorized as available-for-sale. + References No definition available. + Details
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Namespace Prefix: | chmg_
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- Definition Refers to Home equity lines & loans. + References No definition available. + Details
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Namespace Prefix: | chmg_
Data Type: | xbrli:monetaryItemType
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Period Type: | instant

X
- Details
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Namespace Prefix: | chmg_
Data Type: | xbrli:stringItemType
Balance Type: | na
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X
- Definition This element represents the portion of the balance sheet assertion valued at fair value by the entity whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission. This item represents obligations of states and political subdivisions as of the balance sheet date which have been categorized as available-for-sale. + References No definition available. + Details
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Namespace Prefix: | chmg_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition This element represents the portion of the balance sheet assertion valued at fair value by the entity whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission. This item represents investments in Obligations of U.S. Government and U.S. Government sponsored enterprises as of the balance sheet date which have been categorized as available-for-sale. + References No definition available. + Details
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Namespace Prefix: | chmg_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition This element represents the portion of the balance sheet assertion valued at fair value by the entity whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission. This item represents small business administration pool loans as of the balance sheet date which have been categorized as available-for-sale. + References No definition available. + Details
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Namespace Prefix: | chmg_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition This element represents the portion of the balance sheet assertion valued at fair value by the entity whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission. This item represents trust preferred securities as of the balance sheet date which have been categorized as available-for-sale. + References No definition available. + Details
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Namespace Prefix: | chmg_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Details
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Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 25 -Paragraph 1 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=28360136&loc=d3e22054-111558 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 5 -Subparagraph (aa) -URI http://asc.fasb.org/extlink&oid=27724398&loc=d3e27232-111563 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 45 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6871852&loc=d3e26610-111562 + Details
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Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Fair value portion of loan receivable, including, but not limited to, mortgage loans held for investment, finance receivables held for investment, policy loans on insurance contracts. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Glossary Loan -URI http://asc.fasb.org/extlink&oid=6517073 + Details
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Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

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- Definition Fair value of securitized, pay-through debt securities collateralized by real estate mortgage loans classified as available-for-sale. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Mortgage-Backed Securities -URI http://asc.fasb.org/extlink&oid=6517959 + Details
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X
- Definition Carrying amount as of the balance sheet date of other real estate and foreclosed assets. Other real estate may include real estate investments, real estate loans that qualify as investments in real estate, and premises that are no longer used in operations may also be included in real estate owned. Foreclosed assets include all assets obtained in full or partial satisfaction of a debt arrangement through foreclosure proceedings. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-03.10(4)) -URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878 + Details
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Period Type: | instant

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- Definition Amount of investments in debt and equity securities and other forms of securities that provide ownership interests classified as trading. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 45 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6871852&loc=d3e26610-111562 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 45 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=6871852&loc=d3e26626-111562 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Trading Securities -URI http://asc.fasb.org/extlink&oid=6526789 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-03.4) -URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878 + Details
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- Details
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