CBU


Line plots across dimensions of each concept
Line plots across concepts
Tables

Table of contents



us-gaap:CommonStockSharesIssued

us-gaap:CommonStockSharesAuthorized
us-gaap:StatementEquityComponents
us-gaap:CommonStockSharesOutstanding

us-gaap:WeightedAverageNumberOfDilutedSharesOutstanding

us-gaap:WeightedAverageNumberOfSharesOutstandingBasic

us-gaap:AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount

us-gaap:EarningsPerShareBasic

us-gaap:EarningsPerShareDiluted

us-gaap:TierOneRiskBasedCapitalToRiskWeightedAssets
us-gaap:ConsolidatedEntities

us-gaap:CapitalToRiskWeightedAssets
us-gaap:ConsolidatedEntities

us-gaap:ComprehensiveIncomeNetOfTax

us-gaap:IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments
us-gaap:ConsolidationItems, us-gaap:StatementBusinessSegments

us-gaap:IncomeTaxExpenseBenefit

us-gaap:IncomeTaxesPaid

us-gaap:InterestAndFeeIncomeLoansAndLeases

us-gaap:InterestExpense

us-gaap:InterestIncomeExpenseNet
us-gaap:ConsolidationItems, us-gaap:StatementBusinessSegments

us-gaap:InterestPaidNet

us-gaap:LitigationSettlementExpense

us-gaap:NetIncomeLoss
us-gaap:StatementEquityComponents

us-gaap:NetIncomeLossAvailableToCommonStockholdersBasic
us-gaap:BusinessAcquisition
us-gaap:OperatingExpenses
us-gaap:BusinessAcquisition
us-gaap:Revenues

us-gaap:Assets
dei:LegalEntity, us-gaap:ConsolidatedEntities
us-gaap:ConsolidatedEntities
us-gaap:ConsolidationItems
us-gaap:ConsolidationItems, us-gaap:StatementBusinessSegments

us-gaap:Liabilities

us-gaap:LiabilitiesAndStockholdersEquity
us-gaap:ConsolidatedEntities

us-gaap:StockholdersEquity
us-gaap:ConsolidatedEntities
us-gaap:CumulativeEffectPeriodOfAdoption
us-gaap:CumulativeEffectPeriodOfAdoption, us-gaap:AdjustmentsForNewAccountingPronouncements
us-gaap:CumulativeEffectPeriodOfAdoption, us-gaap:AdjustmentsForNewAccountingPronouncements, us-gaap:StatementEquityComponents
us-gaap:CumulativeEffectPeriodOfAdoption, us-gaap:StatementEquityComponents
us-gaap:StatementEquityComponents

us-gaap:TierOneRiskBasedCapital
us-gaap:ConsolidatedEntities

us-gaap:CashAndCashEquivalentsAtCarryingValue
dei:LegalEntity, us-gaap:ConsolidatedEntities
us-gaap:ConsolidatedEntities

us-gaap:PropertyPlantAndEquipmentGross
us-gaap:PropertyPlantAndEquipmentByType

us-gaap:AmortizationOfIntangibleAssets
us-gaap:ConsolidationItems, us-gaap:StatementBusinessSegments

us-gaap:PropertyPlantAndEquipmentNet

us-gaap:Goodwill
us-gaap:BusinessAcquisition
us-gaap:ConsolidationItems, us-gaap:StatementBusinessSegments

us-gaap:IntangibleAssetsNetExcludingGoodwill
us-gaap:ConsolidationItems, us-gaap:StatementBusinessSegments

us-gaap:FiniteLivedIntangibleAssetsNet
us-gaap:FiniteLivedIntangibleAssetsByMajorClass

us-gaap:OperatingLeaseRightOfUseAsset
us-gaap:Ownership

us-gaap:EquitySecuritiesFvNi
us-gaap:FairValueByFairValueHierarchyLevel, us-gaap:FairValueByMeasurementFrequency
us-gaap:FairValueByMeasurementFrequency

us-gaap:OtherAssets
dei:LegalEntity, us-gaap:ConsolidatedEntities
us-gaap:ConsolidatedEntities

us-gaap:TimeDepositMaturitiesYearOne
dei:LegalEntity, us-gaap:ConsolidatedEntities
us-gaap:MinorityInterest

us-gaap:LesseeOperatingLeaseLiabilityPaymentsDueYearTwo

us-gaap:LesseeOperatingLeaseLiabilityPaymentsDueYearThree

us-gaap:LesseeOperatingLeaseLiabilityPaymentsDueYearFour

us-gaap:LesseeOperatingLeaseLiabilityPaymentsDueYearFive
us-gaap:Ownership

us-gaap:LesseeOperatingLeaseLiabilityPaymentsDueAfterYearFive
us-gaap:Ownership

us-gaap:OperatingLeaseLiability
us-gaap:Ownership

us-gaap:LesseeOperatingLeaseLiabilityPaymentsDue
us-gaap:Ownership

us-gaap:LesseeOperatingLeaseLiabilityUndiscountedExcessAmount
us-gaap:Ownership

us-gaap:StockholdersEquity
us-gaap:ConsolidatedEntities
us-gaap:CumulativeEffectPeriodOfAdoption
us-gaap:CumulativeEffectPeriodOfAdoption, us-gaap:AdjustmentsForNewAccountingPronouncements
us-gaap:CumulativeEffectPeriodOfAdoption, us-gaap:AdjustmentsForNewAccountingPronouncements, us-gaap:StatementEquityComponents
us-gaap:CumulativeEffectPeriodOfAdoption, us-gaap:StatementEquityComponents
us-gaap:StatementEquityComponents

us-gaap:AdditionalPaidInCapital

us-gaap:RetainedEarningsAccumulatedDeficit
us-gaap:CumulativeEffectPeriodOfAdoption, us-gaap:AdjustmentsForNewAccountingPronouncements

us-gaap:AccumulatedOtherComprehensiveIncomeLossNetOfTax

us-gaap:TreasuryStockValue
dei:LegalEntity, us-gaap:ConsolidatedEntities
us-gaap:MinorityInterest

us-gaap:AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue
us-gaap:StatementEquityComponents

us-gaap:NetCashProvidedByUsedInOperatingActivities

us-gaap:NetCashProvidedByUsedInInvestingActivities

us-gaap:NetCashProvidedByUsedInFinancingActivities

us-gaap:IncreaseDecreaseInOtherOperatingCapitalNet

us-gaap:NetCashProvidedByUsedInOperatingActivities

us-gaap:NetIncomeLoss
us-gaap:StatementEquityComponents

us-gaap:ShareBasedCompensation

us-gaap:NetCashProvidedByUsedInInvestingActivities

us-gaap:PaymentsToAcquirePropertyPlantAndEquipment

us-gaap:NetCashProvidedByUsedInFinancingActivities

us-gaap:PaymentsOfDividendsCommonStock

us-gaap:PaymentsForRepurchaseOfCommonStock
us-gaap:AwardType
us-gaap:ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice

us-gaap:DeferredTaxLiabilities

us-gaap:DeferredTaxAssetsNet

us-gaap:UnrecognizedTaxBenefits

cbu:AccretionAmortizationOnInvestmentsLoansAndBorrowings
us-gaap:BusinessAcquisition
cbu:BusinessCombinationProvisionalInformationInitialAccountingIncompleteAdjustmentAccruedInterestAndOtherLiabilities
us-gaap:BusinessAcquisition
cbu:BusinessCombinationProvisionalInformationInitialAccountingIncompleteAdjustmentLoans
us-gaap:BusinessAcquisition
cbu:BusinessCombinationProvisionalInformationInitialAccountingIncompleteAdjustmentOtherAssets

cbu:DepositServiceFees

cbu:EmployeeBenefitServices

cbu:InterestExpenseBorrowingsExcludingJuniorSubordinatedDebentureOwedToUnconsolidatedSubsidiaryTrust

cbu:MortgageBanking

cbu:NetGainLossOnSaleOfLoansAndOtherAssets

cbu:NumberOfBorrowersRepresenting75.6MillionInOutstandingLoanBalances

cbu:NumberOfBusinessBorrowersRepresenting75.1MillionInOutstandingLoanBalances

cbu:NumberOfConsumerBorrowersRepresenting0.5MillionInOutstandingLoanBalances

cbu:OtherBankingServices

cbu:OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParentIncludingCumulativeEffectOfChangeInAccountingPrinciple

cbu:PaymentsToAcquireEquityAndOtherSecurities

cbu:PercentageOfTotalLoansOutstanding
us-gaap:Range, us-gaap:StatementScenario, us-gaap:UnusualOrInfrequentItem
cbu:PercentageOfUnemployment
us-gaap:Range, us-gaap:UnusualOrInfrequentItem
us-gaap:Ownership
cbu:ProceedsFromRedemptionOfDebenturesAndPreferredSecurities

cbu:ProvisionForLoanLeaseAndOtherLossesExcludingAcquisitionRelatedProvisionForCreditLosses
us-gaap:AdjustmentsForNewAccountingPronouncements

cbu:RepaymentsOfSubordinatedDebtHeldByUnconsolidatedSubsidiaryTrusts
us-gaap:MeasurementInputType, us-gaap:ValuationTechnique
cbu:ServicingAssetMeasurementInput2
us-gaap:Range, us-gaap:FairValueByFairValueHierarchyLevel, us-gaap:MeasurementInputType, us-gaap:ValuationTechnique

cbu:SettlementOfBankOwnedLifeInsurancePolicies
us-gaap:StatementEquityComponents
cbu:StockIssuedDuringPeriodSharesDeferredCompensationArrangements
us-gaap:StatementEquityComponents
cbu:StockIssuedDuringPeriodSharesEmployeeStockOwnershipPlanNetOfImpactOfNetSettlementOfTaxWithholdingObligations
us-gaap:StatementEquityComponents
cbu:StockIssuedDuringPeriodValueDeferredCompensationArrangements

cbu:StockIssuedDuringPeriodValueEmployeeStockOwnershipPlanNetOfImpactOfNetSettlementOfTaxWithholdingObligations
us-gaap:StatementEquityComponents

cbu:WealthManagementServices

us-gaap:AllowanceForLoanAndLeaseLossRecoveryOfBadDebts
us-gaap:AdjustmentsForNewAccountingPronouncements
us-gaap:AdjustmentsForNewAccountingPronouncements, us-gaap:CreditLossStatus
us-gaap:AdjustmentsForNewAccountingPronouncements, us-gaap:FinancingReceivablePortfolioSegment, us-gaap:FinancingReceivableRecordedInvestmentByClassOfFinancingReceivable
us-gaap:CreditLossStatus
us-gaap:FinancingReceivablePortfolioSegment, us-gaap:FinancingReceivableRecordedInvestmentByClassOfFinancingReceivable
us-gaap:AdjustmentsForNewAccountingPronouncements, us-gaap:CreditLossStatus
us-gaap:AllowanceForLoanAndLeaseLossesLoansAcquired
us-gaap:AdjustmentsForNewAccountingPronouncements, us-gaap:FinancingReceivablePortfolioSegment, us-gaap:FinancingReceivableRecordedInvestmentByClassOfFinancingReceivable

us-gaap:AllowanceForLoanAndLeaseLossesWriteOffs
us-gaap:AdjustmentsForNewAccountingPronouncements
us-gaap:AdjustmentsForNewAccountingPronouncements, us-gaap:CreditLossStatus
us-gaap:AdjustmentsForNewAccountingPronouncements, us-gaap:FinancingReceivablePortfolioSegment, us-gaap:FinancingReceivableRecordedInvestmentByClassOfFinancingReceivable
us-gaap:CreditLossStatus
us-gaap:FinancingReceivablePortfolioSegment, us-gaap:FinancingReceivableRecordedInvestmentByClassOfFinancingReceivable

us-gaap:AmortizationOfMortgageServicingRightsMSRs

us-gaap:AmountOfDilutiveSecuritiesStockOptionsAndRestrictiveStockUnits

us-gaap:BankOwnedLifeInsuranceIncome
us-gaap:BusinessAcquisition
us-gaap:BusinessAcquisitionsProFormaNetIncomeLoss
us-gaap:BusinessAcquisition
us-gaap:BusinessAcquisitionsProFormaRevenue

us-gaap:BusinessCombinationAcquisitionRelatedCosts
us-gaap:BusinessAcquisition
us-gaap:ConsolidationItems, us-gaap:StatementBusinessSegments
us-gaap:BusinessAcquisition, us-gaap:SubsequentEventType
us-gaap:BusinessCombinationConsiderationTransferred1
us-gaap:BusinessAcquisition, us-gaap:SubsequentEventType
us-gaap:BusinessCombinationConsiderationTransferredOther1
us-gaap:BusinessAcquisition
us-gaap:BusinessCombinationProvisionalInformationInitialAccountingIncompleteAdjustmentPropertyPlantAndEquipment

us-gaap:BusinessDevelopment

us-gaap:CashAcquiredFromAcquisition

us-gaap:CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseExcludingExchangeRateEffect

us-gaap:CommonStockDividendsPerShareDeclared

us-gaap:CommunicationsAndInformationTechnology
us-gaap:RetirementPlanType
us-gaap:DefinedBenefitPlanAmortizationOfGainsLosses
us-gaap:RetirementPlanType
us-gaap:DefinedBenefitPlanAmortizationOfPriorServiceCostCredit
us-gaap:RetirementPlanFundingStatus, us-gaap:RetirementPlanTaxStatus, us-gaap:RetirementPlanType
us-gaap:DefinedBenefitPlanContributionsByEmployer
us-gaap:RetirementPlanType
us-gaap:RetirementPlanType
us-gaap:DefinedBenefitPlanExpectedReturnOnPlanAssets
us-gaap:RetirementPlanType
us-gaap:DefinedBenefitPlanInterestCost
us-gaap:RetirementPlanType
us-gaap:DefinedBenefitPlanNetPeriodicBenefitCost
us-gaap:RetirementPlanType
us-gaap:DefinedBenefitPlanServiceCost

us-gaap:Depreciation

us-gaap:DividendsCommonStock
us-gaap:StatementEquityComponents

us-gaap:EquitySecuritiesFvNiUnrealizedGainLoss

us-gaap:ExcessTaxBenefitFromShareBasedCompensationFinancingActivities

us-gaap:FairValueOfAssetsAcquired

us-gaap:FinancingReceivableAllowanceForCreditLossesRecovery
us-gaap:AdjustmentsForNewAccountingPronouncements

us-gaap:FinancingReceivableAllowanceForCreditLossesWriteOffs
us-gaap:AdjustmentsForNewAccountingPronouncements

us-gaap:FinancingReceivableModificationsNumberOfContracts2
us-gaap:FinancingReceivablePortfolioSegment, us-gaap:FinancingReceivableRecordedInvestmentByClassOfFinancingReceivable

us-gaap:FinancingReceivableModificationsPostModificationRecordedInvestment2
us-gaap:FinancingReceivablePortfolioSegment, us-gaap:FinancingReceivableRecordedInvestmentByClassOfFinancingReceivable

us-gaap:FinancingReceivableSignificantPurchases
us-gaap:FinancingReceivablePortfolioSegment, us-gaap:FinancingReceivableRecordedInvestmentByClassOfFinancingReceivable

us-gaap:FinancingReceivableSignificantSales
us-gaap:FinancingReceivablePortfolioSegment, us-gaap:FinancingReceivableRecordedInvestmentByClassOfFinancingReceivable

us-gaap:GoodwillPeriodIncreaseDecrease
us-gaap:BusinessAcquisition
us-gaap:GoodwillPurchaseAccountingAdjustments

us-gaap:ImpairedFinancingReceivableAverageRecordedInvestment
us-gaap:BusinessAcquisition
us-gaap:IncreaseDecreaseInAccruedInterestReceivableNet

us-gaap:IncreaseDecreaseInDeferredCompensation

us-gaap:IncreaseDecreaseInDeposits
us-gaap:BusinessAcquisition
us-gaap:IncreaseDecreaseInFinanceReceivables
us-gaap:BusinessAcquisition
us-gaap:IncreaseDecreaseInOtherNoncurrentAssets
us-gaap:BusinessAcquisition
us-gaap:IncreaseDecreaseInOtherOperatingAssets

us-gaap:IncrementalCommonSharesAttributableToShareBasedPaymentArrangements

us-gaap:InsuranceServicesRevenue

us-gaap:InterestAndDividendIncomeOperating

us-gaap:InterestExpenseDeposits

us-gaap:InterestExpenseJuniorSubordinatedDebentures

us-gaap:InterestExpenseSubordinatedNotesAndDebentures

us-gaap:InterestIncomeExpenseAfterProvisionForLoanLoss

us-gaap:InterestIncomeSecuritiesTaxExempt

us-gaap:InterestIncomeSecuritiesTaxable

us-gaap:LaborAndRelatedExpense

us-gaap:LiabilitiesAssumed1
us-gaap:BusinessAcquisition
us-gaap:LiabilitiesFairValueAdjustment

us-gaap:MarketableSecuritiesRealizedGainLoss

us-gaap:NoninterestExpense

us-gaap:NoninterestIncome
us-gaap:ConsolidationItems
us-gaap:ConsolidationItems, us-gaap:StatementBusinessSegments

us-gaap:OccupancyNet

us-gaap:OffBalanceSheetCreditLossLiabilityCreditLossExpenseReversal
us-gaap:AdjustmentsForNewAccountingPronouncements

us-gaap:OtherComprehensiveIncomeAvailableforsaleSecuritiesAdjustmentNetOfTaxPortionAttributableToParent

us-gaap:OtherComprehensiveIncomeDefinedBenefitPlansAdjustmentNetOfTaxPortionAttributableToParent

us-gaap:OtherComprehensiveIncomeLossAmortizationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetPriorServiceCostCreditBeforeTax

us-gaap:OtherComprehensiveIncomeLossAmortizationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetPriorServiceCostCreditNetOfTax

us-gaap:OtherComprehensiveIncomeLossAmortizationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetPriorServiceCostCreditTax

us-gaap:OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent
us-gaap:StatementEquityComponents

us-gaap:OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForSaleOfSecuritiesBeforeTax

us-gaap:OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForSaleOfSecuritiesNetOfTax

us-gaap:OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForSaleOfSecuritiesTax

us-gaap:OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetGainLossBeforeTax

us-gaap:OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetGainLossNetOfTax

us-gaap:OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetGainLossTax

us-gaap:OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodBeforeTax

us-gaap:OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodNetOfTax

us-gaap:OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodTax

us-gaap:OtherCostAndExpenseOperating
us-gaap:ConsolidationItems
us-gaap:ConsolidationItems, us-gaap:StatementBusinessSegments

us-gaap:OtherNoninterestExpense

us-gaap:PaymentsForProceedsFromBusinessesAndInterestInAffiliates

us-gaap:PaymentsForProceedsFromLoansAndLeases

us-gaap:PaymentsForProceedsFromRealEstatePartnershipInvestmentNet

us-gaap:PaymentsToAcquireAvailableForSaleSecuritiesDebt
us-gaap:BusinessAcquisition
us-gaap:PaymentsToAcquireBusinessesGross

us-gaap:ProceedsFromIssuanceOfCommonStock

us-gaap:ProceedsFromMaturitiesPrepaymentsAndCallsOfAvailableForSaleSecurities

us-gaap:ProceedsFromMaturitiesPrepaymentsAndCallsOfOtherInvestments

us-gaap:ProceedsFromRepaymentsOfDebt

us-gaap:ProceedsFromSaleOfTreasuryStock

us-gaap:ProfessionalFees

us-gaap:ProvisionForLoanAndLeaseLosses
us-gaap:AdjustmentsForNewAccountingPronouncements
us-gaap:AdjustmentsForNewAccountingPronouncements, us-gaap:CreditLossStatus
us-gaap:AdjustmentsForNewAccountingPronouncements, us-gaap:FinancingReceivablePortfolioSegment
us-gaap:AdjustmentsForNewAccountingPronouncements, us-gaap:FinancingReceivablePortfolioSegment, us-gaap:FinancingReceivableRecordedInvestmentByClassOfFinancingReceivable
us-gaap:CreditLossStatus
us-gaap:FinancingReceivablePortfolioSegment
us-gaap:FinancingReceivablePortfolioSegment, us-gaap:FinancingReceivableRecordedInvestmentByClassOfFinancingReceivable

us-gaap:ProvisionForLoanLeaseAndOtherLosses
us-gaap:ConsolidationItems, us-gaap:StatementBusinessSegments

us-gaap:StockIssued1
us-gaap:StatementEquityComponents
us-gaap:StockIssuedDuringPeriodSharesAcquisitions
us-gaap:StatementEquityComponents
us-gaap:StockIssuedDuringPeriodSharesEmployeeBenefitPlan

us-gaap:StockIssuedDuringPeriodValueAcquisitions
us-gaap:StatementEquityComponents

us-gaap:StockIssuedDuringPeriodValueEmployeeBenefitPlan
us-gaap:StatementEquityComponents

us-gaap:TransferToOtherRealEstate

cbu:AccruedInterestAndOtherLiabilities
dei:LegalEntity, us-gaap:ConsolidatedEntities
us-gaap:ConsolidatedEntities

cbu:AccumulatedOtherComprehensiveIncomeLossAvailableForSaleSecuritiesAdjustmentGross

cbu:AccumulatedOtherComprehensiveIncomeLossAvailableForSaleSecuritiesAdjustmentTaxEffect
us-gaap:RetirementPlanType
cbu:AccumulatedOtherComprehensiveIncomeLossDefinedBenefitPensionAndOtherPostretirementPlansTax

cbu:AccumulatedOtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansGrossOfTax

cbu:AccumulatedOtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansTaxEffect

cbu:AggregateBankCapitalAndSurplusTransferableToCompanyMaximum

cbu:AllowanceForCreditLossesToTotalLoansRatio
us-gaap:Ownership, us-gaap:SubsequentEventType
cbu:AuthorizedAmountOfDebenturesAndAssociatedPreferredSecuritiesForRedemption

cbu:BankCapitalAndSurplusTransferableToCompanyMaximum
us-gaap:TitleOfIndividual, us-gaap:RetirementPlanType
cbu:BenefitObligationForDefinedBenefitPensionPlanBeforeRevaluation
us-gaap:BusinessAcquisition
cbu:BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAccruedInterestAndFeesReceivables
us-gaap:BusinessAcquisition
cbu:BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedDepositsAcquired
us-gaap:BusinessAcquisition
cbu:BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedLoansAcquired
us-gaap:BusinessAcquisition
cbu:BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNoncurrentLiabilitiesOtherFederalHomeLoanBankAdvances
us-gaap:BusinessAcquisition
cbu:BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedSubordinatedDebtHeldByUnconsolidatedSubsidiaryTrusts

cbu:BusinessLendingLoansHeldForSaleUnpaidPrincipalBalance
us-gaap:FairValueByFairValueHierarchyLevel
cbu:BusinessLoansHeldForSaleFairValueDisclosure
us-gaap:FairValueByFairValueHierarchyLevel, us-gaap:FairValueByMeasurementFrequency
us-gaap:FairValueByMeasurementFrequency
us-gaap:Range, us-gaap:FairValueByFairValueHierarchyLevel, us-gaap:MeasurementInputType, us-gaap:ValuationTechnique
cbu:BusinessLoansHeldForSaleMeasurementInput

cbu:CapitalRequiredForCapitalAdequacyPlusCapitalConservationBuffer
us-gaap:ConsolidatedEntities

cbu:CapitalRequiredForCapitalAdequacyPlusCapitalConservationBufferToRiskWeightedAssets
us-gaap:ConsolidatedEntities

cbu:CommonEquityTier1CapitalRequiredForCapitalAdequacyRatio
us-gaap:ConsolidatedEntities

cbu:CommonEquityTier1CapitalRequiredToBeWellCapitalizedRatio
us-gaap:ConsolidatedEntities

cbu:CommonEquityTierOneCapitalRequiredForCapitalAdequacyPlusCapitalConservationBuffer
us-gaap:ConsolidatedEntities

cbu:CommonEquityTierOneCapitalRequiredForCapitalAdequacyPlusCapitalConservationBufferRatio
us-gaap:ConsolidatedEntities

cbu:CoreDepositIntangiblesNet

cbu:CustodialEscrowBalancesMaintainedInConnectionWithLoansServicedForOthers

cbu:DebtSecuritiesAvailableForSaleAccruedInterestReceivable

cbu:DeferredTaxAssetsTaxDeferredExpenseOperatingLeaseLiabilities

cbu:DeferredTaxLiabilitiesDeferredExpenseDeferredLoanOriginationCosts

cbu:DeferredTaxLiabilitiesRightOfUseAssets

cbu:DeferredTaxLiabilitiesUnrealizedGainsOnInvestmentSecurities
us-gaap:RetirementPlanFundingStatus, us-gaap:RetirementPlanName, us-gaap:RetirementPlanTaxStatus, us-gaap:RetirementPlanType
cbu:DefinedBenefitPlanInitialProjectedBenefitObligation

cbu:EquityAndOtherSecuritiesContinuousUnrealizedLossPosition
us-gaap:FinancialInstrument

cbu:EquityAndOtherSecuritiesContinuousUnrealizedLossPositionAccumulatedLoss
us-gaap:FinancialInstrument

cbu:EquityAndOtherSecuritiesContinuousUnrealizedLossPositionLessThan12Months
us-gaap:FinancialInstrument

cbu:EquityAndOtherSecuritiesContinuousUnrealizedLossPositionLessThan12MonthsAccumulatedLoss
us-gaap:FinancialInstrument

cbu:EquitySecuritiesFvNiAccumulatedGrossUnrealizedGainBeforeTax

cbu:EquitySecuritiesFvNiAccumulatedGrossUnrealizedLossBeforeTax

cbu:FederalHomeLoanBankOvernightAdvance

cbu:FederalReserveAdvancesGeneralDebtObligationsDisclosuresAmountOfAvailableUnusedFunds

cbu:FinancingReceivableAccruedInterestReceivable
us-gaap:Range
cbu:FinancingReceivableIndividuallyEvaluatedForImpairmentThresholdBalance

cbu:FinancingReceivableModificationsNumberOfContracts
us-gaap:AccountsNotesLoansAndFinancingReceivableByReceivableType
us-gaap:AccountsNotesLoansAndFinancingReceivableByReceivableType, us-gaap:FinancingReceivablePortfolioSegment, us-gaap:FinancingReceivableRecordedInvestmentByClassOfFinancingReceivable
us-gaap:FinancingReceivablePortfolioSegment, us-gaap:FinancingReceivableRecordedInvestmentByClassOfFinancingReceivable
us-gaap:CreditScoreFico, us-gaap:FinancialInstrumentPerformanceStatus, us-gaap:FinancingReceivableRecordedInvestmentByClassOfFinancingReceivable
cbu:FinancingReceivableOriginatedFiveYearsBeforeLatestFiscalYear
us-gaap:CreditScoreFico, us-gaap:FinancingReceivableRecordedInvestmentByClassOfFinancingReceivable
us-gaap:FinancialInstrumentPerformanceStatus, us-gaap:FinancingReceivableRecordedInvestmentByClassOfFinancingReceivable
us-gaap:FinancingReceivableRecordedInvestmentByClassOfFinancingReceivable
us-gaap:FinancingReceivableRecordedInvestmentByClassOfFinancingReceivable, us-gaap:InternalCreditAssessment

cbu:FiniteLivedIntangibleAssetExpectedAmortizationAfterYearFour

cbu:ImpairedFinancingReceivableContractualBalance

cbu:ImpairedLoansFairValueDisclosure
us-gaap:FairValueByFairValueHierarchyLevel
us-gaap:FairValueByFairValueHierarchyLevel, us-gaap:FairValueByMeasurementFrequency
us-gaap:FairValueByMeasurementFrequency
us-gaap:Range, us-gaap:FairValueByFairValueHierarchyLevel, us-gaap:MeasurementInputType, us-gaap:ValuationTechnique
cbu:ImpairedLoansMeasurementInput
us-gaap:Range, us-gaap:FairValueByFairValueHierarchyLevel, us-gaap:ValuationTechnique
us-gaap:Range, us-gaap:MeasurementInputType, us-gaap:ValuationTechnique

cbu:IntangibleAssetsNet
us-gaap:ConsolidatedEntities
cbu:InvestmentAndAdvancesToBankSubsidiary
us-gaap:ConsolidatedEntities
cbu:InvestmentAndAdvancesToNonBankSubsidiaries
us-gaap:FairValueByFairValueHierarchyLevel, us-gaap:FairValueByMeasurementFrequency
cbu:MortgageLoansHeldForSalePrincipalValue

cbu:MortgageLoansServicedForOthers
us-gaap:FairValueByMeasurementBasis
cbu:OtherFederalHomeLoanBankBorrowingsFairValueDisclosure

cbu:OtherFiniteLivedIntangibleAssetsNet

cbu:OtherInvestmentAndEquitySecuritiesFairValue

cbu:OtherInvestmentsAndEquitySecuritiesAccumulatedGrossUnrealizedGainBeforeTax

cbu:OtherInvestmentsAndEquitySecuritiesAccumulatedGrossUnrealizedLossBeforeTax

cbu:OtherInvestmentsAndEquitySecuritiesAtCost
us-gaap:FinancialInstrument
cbu:OtherInvestmentsAndSecuritiesAccumulatedGrossUnrealizedGainBeforeTax
us-gaap:FinancialInstrument
cbu:OtherInvestmentsAndSecuritiesFairValue

cbu:OutstandingLoanBalancesOf11NumberOfBorrowers

cbu:OutstandingLoanBalancesOf42NumberOfBorrowers

cbu:OutstandingLoanBalancesOf47NumberOfBorrowers

cbu:OutstandingLoanBalancesOf5NumberOfConsumerBorrowers

cbu:OutstandingLoanBalancesOf63NumberOfBorrowers

cbu:OutstandingLoanBalancesOf74NumberOfBorrowers
us-gaap:FairValueByMeasurementBasis
cbu:OvernightFederalHomeLoanBankBorrowingsFairValueDisclosure

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us-gaap:ServicingAssetAtAmortizedValueFairValue
us-gaap:FairValueByFairValueHierarchyLevel
us-gaap:FairValueByFairValueHierarchyLevel, us-gaap:FairValueByMeasurementFrequency
us-gaap:FairValueByMeasurementFrequency
us-gaap:Range, us-gaap:FairValueByFairValueHierarchyLevel, us-gaap:MeasurementInputType, us-gaap:ValuationTechnique
us-gaap:ServicingAssetMeasurementInput
us-gaap:Range, us-gaap:MeasurementInputType, us-gaap:ValuationTechnique
us-gaap:AwardType
us-gaap:ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue

us-gaap:ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorized

us-gaap:ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant
us-gaap:AwardType
us-gaap:ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableWeightedAverageExercisePrice

us-gaap:ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingIntrinsicValue

us-gaap:SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsExercisableIntrinsicValue1

us-gaap:SharebasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeExercisableOptionsWeightedAverageExercisePrice1
us-gaap:ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRange

us-gaap:SharebasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeOutstandingOptionsWeightedAverageExercisePriceBeginningBalance1
us-gaap:ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRange

us-gaap:StatutoryAccountingPracticesStatutoryAmountAvailableForDividendPayments

us-gaap:StockRepurchaseProgramNumberOfSharesAuthorizedToBeRepurchased

us-gaap:TierOneLeverageCapital
us-gaap:ConsolidatedEntities

us-gaap:TierOneLeverageCapitalRequiredForCapitalAdequacy
us-gaap:ConsolidatedEntities

us-gaap:TierOneLeverageCapitalRequiredForCapitalAdequacyToAverageAssets
us-gaap:ConsolidatedEntities

us-gaap:TierOneLeverageCapitalRequiredToBeWellCapitalized
us-gaap:ConsolidatedEntities

us-gaap:TierOneLeverageCapitalRequiredToBeWellCapitalizedToAverageAssets
us-gaap:ConsolidatedEntities

us-gaap:TierOneLeverageCapitalToAverageAssets
us-gaap:ConsolidatedEntities

us-gaap:TierOneRiskBasedCapitalRequiredForCapitalAdequacy
us-gaap:ConsolidatedEntities

us-gaap:TierOneRiskBasedCapitalRequiredForCapitalAdequacyToRiskWeightedAssets
us-gaap:ConsolidatedEntities

us-gaap:TierOneRiskBasedCapitalRequiredToBeWellCapitalized
us-gaap:ConsolidatedEntities

us-gaap:TierOneRiskBasedCapitalRequiredToBeWellCapitalizedToRiskWeightedAssets
us-gaap:ConsolidatedEntities

us-gaap:TimeDepositMaturitiesAfterYearFive

us-gaap:TimeDepositMaturitiesYearFive

us-gaap:TimeDepositMaturitiesYearFour

us-gaap:TimeDepositMaturitiesYearThree

us-gaap:TimeDepositMaturitiesYearTwo

us-gaap:TimeDeposits

us-gaap:TreasuryStockShares

us-gaap:UnamortizedLoanCommitmentAndOriginationFeesAndUnamortizedDiscountsOrPremiums

us-gaap:UnbilledContractsReceivable

us-gaap:ValuationAllowanceForImpairmentOfRecognizedServicingAssetsBalance
dei:LegalEntity, us-gaap:ConsolidatedEntities
us-gaap:VariableInterestEntityEntityMaximumLossExposureAmount

Plots across concepts


IncomeStatement
Net Income Loss
Expenses
Interest Expense
Balance Sheet
Operating Lease Right Of Use Asset
Assets
Operating Lease Right Of Use Asset
Current Assets
Cash And Cash Equivalents At Carrying Value
NonCurrent Assets
Operating Lease Right Of Use Asset
PropertyPlantAndEquipmentNet
Property Plant And Equipment Net
Liabilities
Dividends Payable Current And Noncurrent
Stockholders Equity
Accumulated Other Comprehensive Income Loss Net Of Tax
Per Share
Common Stock Dividends Per Share Declared
CashFlow
Net Cash Provided By Used In Investing Activities
NetCashProvidedByUsedInOperatingActivities
Share Based Compensation
NetCashProvidedByUsedInInvestingActivities
Net Cash Provided By Used In Investing Activities
NetCashProvidedByUsedInFinancingActivities
Payments For Repurchase Of Common Stock
Shares
Treasury Stock Shares
DividendsAndRepurchase
Payments For Repurchase Of Common Stock
LesseeOperatingLeaseLiabilityPaymentsDue
Lessee Operating Lease Liability Undiscounted Excess Amount
FiniteLivedIntangibleAssets
Finite Lived Intangible Assets Net
BanksAndOrInsurance
Interest And Dividend Income Operating
LiabilitiesBanks
Long Term Debt And Capital Lease Obligations Including Current Maturities

Tables

  2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-30
us-gaap:CommonStockSharesIssued █████▇▇▇▇▇▇▇▇▇▇▇▇▅▄▄▄▄▄▃▃▃▃▃▃▃▃▂▂▂▂▂▂▂▁▁▁54.06386754.01937453.75459953.69791953.67333552.18931451.97472651.84296651.80542451.72775851.57683951.54725351.51199251.37425451.26384151.19417851.14824346.43051744.95035244.85607744.69597844.59834144.44256841.92930141.84022141.75665741.60642241.48337641.46404141.44054641.21349141.07821540.88118840.77142340.42149340.36994840.27318940.24033237.79453237.63884337.619379NA34.131289NANA
us-gaap:CommonStockSharesAuthorized NANA75.0NA75.075.075.075.075.075.075.075.075.075.075.075.075.075.075.075.075.075.075.075.075.075.075.075.075.075.075.075.075.050.050.050.050.050.050.050.050.0NA50.0NANA
 us-gaap:CommonStockSharesOutstanding us-gaap:StatementEquityComponents cbu:CommonStockOutstanding██▇▇▇▄▃▃▃▃▂▂▂▁▁53.91869553.87497953.59312753.53759353.51421652.03109251.79392351.66005451.57060851.47137151.25782451.13667651.08587450.88360350.696077NANANA44.437415NANANA43.77486NANANANANANANANANANANANANANANANANANANANANANA
us-gaap:WeightedAverageNumberOfDilutedSharesOutstanding █▁54.46954.283NA53.97452.82652.456NA52.24652.18852.061NA51.85851.72351.497NA51.28849.15145.987NA44.57844.37844.196NA41.25941.09441.064NA41.04941.05840.97NA40.62740.34140.166NA0.0398739.78739.108NA0.03704136.78433.717NANANA
us-gaap:WeightedAverageNumberOfSharesOutstandingBasic █▁54.00753.845NA53.6552.48752.036NA51.7551.65951.52NA51.2551.1450.934NA50.70348.52545.284NA44.18444.02143.863NA40.87340.6940.659NA40.59640.57440.458NA40.12139.91439.703NA0.03938439.32438.573NA0.03667936.34633.245NANANA
us-gaap:AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount █▁0.20.03NA0.50.60.2NA0.50.50.5NA0.40.40.4NA0.20.20.2NA0.00.80.6NA0.60.60.3NA0.30.30.04NA0.30.70.5NA0.60.60.3NANANA0.6NANANA
us-gaap:EarningsPerShareBasic ▄▅▄▄▃▄▄▄▄▄▄▄▄▄█▃▁▂▃▃▂▂▂▃▂▂▂▂▂▂▁▂▂▂▂▂▂▂▂▂▂▂▂▂▂0.890.980.87000000000000010.80.670.770.81999999999999980.760.870.810.78999999999999960.840.870.781.44999999999999970.690.350.580.58999999999999990.610.580.550.470.610.580.550.57000000000000030.550.580.550.37999999999999990.550.530.510.470.460.530.490.50999999999999980.540.490.480.480.520.49
us-gaap:EarningsPerShareDiluted ▄▅▄▄▃▄▄▄▄▄▄▄▄▄█▃▁▂▂▃▂▂▂▃▂▂▂▂▂▂▁▂▂▂▂▂▂▂▂▂▂▂▂▂▂0.880.970.85999999999999990.790.660.760.81999999999999980.750.860.80.78000000000000020.830.860.781.42999999999999970.680.350.570.57999999999999980.610.580.550.470.60.580.540.57000000000000030.540.570.540.37999999999999990.540.520.50.470.460.530.480.50999999999999980.540.490.480.470.510.48
us-gaap:TierOneRiskBasedCapitalToRiskWeightedAssets NANA1.899e-05NANANA1.723e-07NANANA1.8229999999999998e-07NANANA1.6639999999999998e-07NANANA1.81e-07NANANA1.709e-07NANANA1.761e-07NANANA1.642e-07NANANANANANANANANANANANANANA
 us-gaap:TierOneRiskBasedCapitalToRiskWeightedAssets us-gaap:ConsolidatedEntities srt:SubsidiariesNANA1.498e-05NANANA1.3789999999999998e-07NANANA1.535e-07NANANA1.45e-07NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
us-gaap:CapitalToRiskWeightedAssets NANA1.987e-05NANANA1.7990000000000002e-07NANANA1.906e-07NANANA1.7449999999999998e-07NANANA1.91e-07NANANA1.8079999999999998e-07NANANA1.875e-07NANANA1.757e-07NANANANANANANANANANANANANANA
 us-gaap:CapitalToRiskWeightedAssets us-gaap:ConsolidatedEntities srt:SubsidiariesNANA1.587e-05NANANA1.455e-07NANANA1.618e-07NANANA1.5310000000000001e-07NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
  2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-30
  2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-30
  2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-30
us-gaap:ComprehensiveIncomeNetOfTax ▇▁▅▅▅█▅▆▆▆▆▅▅▅▆▅▅▅▃▅▆▆▄▆▄▅▅▅▆▆▅▅▄▄▄▅▆▅▅▅▅▅▄▅▅109.501-119.18424.636.7441.835133.80430.18846.30967.15660.48957.6627.45533.348.57952.79533.77824.47928.768-31.85612.21645.60566.455-6.60152.258-6.42440.5133.18321.19946.58447.65317.33221.304-19.806-20.8817.00227.33753.24114.65824.73533.9730.66322.278-4.36622.84727.27
us-gaap:IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments ██▇▆▅▅▆▆▇▆▆▆▆▆▅▆▂▃▄▄▄▃▂▃▃▃▃▃▃▃▁▃▂▂▂▂▂▂▂▂▂▁▁▁▁62.3664.95858.73253.71344.21249.41951.73749.6956.4351.48151.49754.54154.84552.10547.61551.24624.91536.18939.62940.39938.41736.15229.8335.76434.30832.31532.46931.90833.77231.54121.54731.05829.83328.58926.62725.90629.94226.3328.10428.64824.77621.99921.8623.48622.053
us-gaap:IncomeTaxExpenseBenefit █▇▇▇▇▇▇▇▇▇▇▇▇▇▁█▇▇██▇▇▇▇▇▇▇▇▇▇▆▇▇▇▇▇▇▇▇▇▆▆▆▆▆14.41612.10812.24710.9048.9649.2858.85310.47211.4159.53510.67411.43510.23911.999-24.41116.0037.7249.93213.23713.23912.5611.7499.75910.74210.46810.0189.3369.53710.0969.3686.079.0698.7118.3487.8237.5398.8717.5049.1168.646.795.8395.9666.2245.891
us-gaap:IncomeTaxesPaid █▂▅▇▁▄▅▅▇▃▄▄▅▁▄▆▅▄▄▄▃▃▄▄▄▃▄▄▅▁▂▄▄▂▁▃▃▂▃▃▄▁19.7812.70110.87318.2460.8179.64212.30712.37517.2894.4869.5927.99312.1170.5648.04413.03311.119.0448.5229.5437.1097.0657.5578.0437.5845.7079.938.06311.30.1644.327.567.64.1680.2456.5626.5643.0916.065.0619.5650.124NANANA
us-gaap:InterestAndFeeIncomeLoansAndLeases ▇███████▇▇▇▆▆▆▆▆▅▃▃▃▃▃▂▂▂▂▂▂▂▂▂▂▂▂▂▂▂▂▃▃▂▁▁▂▁75.90779.71477.84879.64678.7278.56580.50979.93174.06773.70373.31672.25671.15269.44169.71669.49862.35152.38453.60253.70652.50951.6549.32147.0445.79145.59146.87846.88346.07345.69347.06147.60646.41247.11849.40548.5947.07747.63850.51150.70249.47142.29744.08545.09444.851
us-gaap:InterestExpense ▁▂▂▂▂▃▃▃▃▃▂▂▂▂▁▂▁▁▁▁▁▁▁▁▁▁▁▁▁▁▂▂▃▄▆▆▆▆▇█▇▇███3.2553.7114.1684.5255.2416.9417.3077.3716.0525.8225.0344.7054.1593.783.6114.0923.3932.6842.7532.8592.8042.8753.0152.9212.6522.6142.8292.8932.9393.1315.3265.5315.7089.511.98112.61912.77413.60215.27915.8515.66314.76415.87616.27316.678
us-gaap:InterestIncomeExpenseNet █████▇██▇▇▇▇▇▇▇▇▆▄▅▄▄▄▄▃▃▃▃▃▃▃▃▃▃▃▃▃▃▂▂▂▂▁▁▁▁92.10593.95493.43392.96591.95190.05492.7491.27688.386.85987.38786.19886.84684.62485.97784.39578.02967.27470.24668.46368.30666.88164.98962.36361.22859.8461.75661.39461.1760.10860.63660.60158.43258.42559.96958.77557.77153.90955.13554.56854.18745.52346.13346.32445.945
us-gaap:InterestPaidNet ▁▂▂▂▂▃▃▃▃▃▂▂▂▂▁▂▁▁▁▁▁▁▁▁▁▁▁▁▁▁▃▂▃▆▆▆▆▇██▇▇██3.2934.3514.2424.5915.4486.8886.976.736.0415.6845.0564.9744.1393.7573.6134.0823.3032.7072.7112.8682.8262.8633.0032.9282.6792.6422.8582.9012.9963.1826.2065.5776.63911.71912.18612.5812.95113.82415.59415.83615.25214.88216.3416.275NA
us-gaap:LitigationSettlementExpense NANA0.02.95NANA0.00.0NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
us-gaap:NetIncomeLoss ▅▆▅▄▃▄▄▄▅▄▄▄▅▄█▃▁▂▂▂▂▂▂▂▂▂▂▂▂▂▁▂▂▂▁▁▂▁▁▂▁▁▁▁▁47.94452.8546.48542.80935.24840.13442.88439.21845.01541.94640.82343.10644.60640.10672.02635.24317.19126.25726.39227.1625.85724.40320.07125.02223.8422.29723.13322.37123.67622.17315.47721.98921.12220.24118.80418.36721.07118.82618.98820.00817.98616.1615.89417.26216.162
us-gaap:NetIncomeLossAvailableToCommonStockholdersBasic ▅▆▅▄▃▄▄▄▅▄▄▄▄▄█▃▁▂▂▂▂▂▁▂▂▂▂▂▂▂47.81752.7246.40342.66235.12139.98842.81539.11644.86941.83740.64242.91544.41839.96571.81635.07917.10826.11926.2427.00325.70624.31419.9724.89323.74122.19723.01422.25623.55322.074NANA21.00820.16218.67718.24220.92718.72218.84919.86117.8516.029NANANA
 us-gaap:OperatingExpenses us-gaap:BusinessAcquisition cbu:KinderhookBankCorpNANA1.62.2NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
 us-gaap:OperatingExpenses us-gaap:BusinessAcquisition cbu:SteubenTrustCorporation▁█1.23.2NA1.10.3NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
 us-gaap:Revenues us-gaap:BusinessAcquisition cbu:KinderhookBankCorpNANA3.63.8NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
 us-gaap:Revenues us-gaap:BusinessAcquisition cbu:SteubenTrustCorporation█▁3.31.3NA3.80.6NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
  2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-30
  2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-30
us-gaap:Assets ██▇▇▇▆▅▆▅▅▅▅▅▅▅▅▅▄▃▃▃▃▃▃▃▃▃▃▃▂▂▂▂▂▃▃▂▂▂▂▂▁▁14801.28714620.18113931.09413845.32513444.21711808.98311410.29511597.29710745.38810916.46710607.29510659.56710633.09410966.55510746.19810850.21810884.0468913.868666.4378727.7468742.1118615.9018552.6697997.1667908.7717576.0397489.447502.6437461.3437397.2287095.8647302.0177020.7167221.0737496.87570.3737166.3316912.4586488.2756503.8546390.4855549.3725444.506NANA
us-gaap:Liabilities ██▇▇▇▅▅▅▄▄▄▄▄▅▄▅▅▃▃▃▃▃▃▂▂▂▂▂▂▂▂▂▂▂▂▂▂▁▁▁▁12740.18712648.78411826.98711746.66511362.9029832.3529555.0619756.8768935.8789159.3398893.5128991.2228976.1359335.0899110.8839256.9739311.1467617.837468.3377487.1647505.1827415.2367412.0226952.146908.4326562.6376501.5366537.1196506.3286479.0926220.0526436.3386170.6856343.7796594.0226665.7746281.2726071.7855713.6925748.2215660.414NA4837.248NANA
us-gaap:LiabilitiesAndStockholdersEquity ██▇▇▇▆▅▅▅▅▅▅▅▅▅▅▅▃▃▃▃▃▃▂▂▂▂▂▂▂▂▂▂▂▂▂▂▁▁▁▁14801.28714620.18113931.09413845.32513444.21711808.98311410.29511597.29710745.38810916.46710607.29510659.56710633.09410966.55510746.19810850.21810884.0468913.868666.4378727.7468742.1118615.9018552.6697997.1667908.7717576.0397489.447502.6437461.3437397.2287095.8647302.0177020.7167221.0737496.87570.3737166.3316912.4586488.2756503.8546390.485NA5444.506NANA
us-gaap:StockholdersEquity █▇███▇▇▇▆▆▆▆▆▆▆▅▅▄▃▄▄▃▃▃▂▂▂▂▂▂▂▂▂▂▂▂▂▂▁▁▁2061.11971.3972104.1072098.662081.3151976.6311855.2341840.4211809.511757.1281713.7831668.3451656.9591631.4661635.3151593.2451572.91296.031198.11240.5821236.9291200.6651140.6471045.0261000.3391013.402987.904965.524955.015918.136875.812865.679850.031877.294902.778904.599885.059840.673774.583755.633730.071NA607.258NANA
us-gaap:TierOneRiskBasedCapital NANA1314.864NANANA1148.336NANANA1093.166NANANA995.86NANANA858.347NANANA788.717NANANA705.163NANANA643.286NANANANANANANANANANANANANANA
 us-gaap:TierOneRiskBasedCapital us-gaap:ConsolidatedEntities srt:SubsidiariesNANA1028.285NANANA910.364NANANA912.995NANANA859.538NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
  2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-30
us-gaap:CashAndCashEquivalentsAtCarryingValue ██▆▇▅▂▁▄▄▂▁▁▁▂▁▁▁▂▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▂▁▂▁▁▂▂▁▂▁▁▁2205.9262151.3471645.8051836.5211319.88529.336205.031014.042874.836508.364211.834256.838250.154543.899221.038241.48219.695291.186173.857161.542161.634138.513153.21156.836143.047150.533138.396157.5161.903153.417149.647174.205148.573330.298228.558287.753130.902132.055324.878425.877273.693296.938211.837179.556133.967
  2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-30
us-gaap:PropertyPlantAndEquipmentGross NANA312.434NANANA297.92NANANA247.549NANANA241.575NANANA219.775NANANA214.886NANANA193.155NANANA186.512NANANA179.783NANANA176.461NANANA162.143NANA
 us-gaap:PropertyPlantAndEquipmentGross us-gaap:PropertyPlantAndEquipmentByType cbu:EquipmentAndConstructionInProgressNANA99.239NANANA89.819NANANA89.95NANANA86.059NANANA80.527NANANA80.684NANANA78.679NANANA75.523NANANA73.404NANANA75.074NANANA71.863NANA
 us-gaap:PropertyPlantAndEquipmentGross us-gaap:PropertyPlantAndEquipmentByType cbu:OperatingLeaseRightOfUseAssetsNANA34.908NANANA39.895NANANA0.0NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
 us-gaap:PropertyPlantAndEquipmentGross us-gaap:PropertyPlantAndEquipmentByType us-gaap:BuildingNANA149.217NANANA141.905NANANA133.259NANANA131.647NANANA116.663NANANA112.011NANANA96.754NANANA95.275NANANANANANANANANANANANANANA
 us-gaap:PropertyPlantAndEquipmentGross us-gaap:PropertyPlantAndEquipmentByType us-gaap:LandAndLandImprovementsNANA29.07NANANA26.301NANANA24.34NANANA23.869NANANA22.585NANANA22.191NANANA17.722NANANA15.714NANANA15.48NANANA15.069NANANA13.3NANA
us-gaap:AmortizationOfIntangibleAssets ▅▅▆▆▆▆▆▆▆▇▇▇▇███▇▄▂▂▂▂▁▁▁▁▁▁▁▂▁▁▂▂▂▂▁▁▁▂▂▁▁▂▃3.2463.3513.5253.5813.5243.6673.9623.963.9044.134.3754.4274.5554.7984.9614.9494.2632.7681.2751.3591.4031.4421.0210.8430.880.9190.9941.0511.1011.1411.0611.0891.141.1791.2641.2121.0451.0861.1311.1611.1890.9010.9721.2771.849
us-gaap:PropertyPlantAndEquipmentNet ▇▇███▇██▇▇▄▄▄▄▄▄▄▃▃▃▃▃▃▂▂▂▂▂▂▂▂▂▂▁▁▁▁▁▁▁▁161.007161.194165.655165.342167.301162.602164.638169.933154.592151.976119.988120.273120.715120.953123.393124.47122.872111.154112.318111.484112.803113.481114.43492.49192.54393.32593.63391.76290.99991.80693.63691.82691.14289.3689.93889.21584.57583.84885.95685.72486.426NA81.561NANA
us-gaap:Goodwill ████████▇▇▇▇▇▇▇▇▇▄▃▃▃▃▃▂▂▂▂▂▂▂▂▂▂▂▂▂▂▂▂▂▂▁▁794.892793.456793.708793.749792.715773.473773.81773.61733.503733.503733.503733.479733.479733.625734.43731.505733.604542.986465.142465.142465.142465.142463.252375.174375.174375.174375.174375.174375.174375.174374.991369.703369.703369.703369.703369.703345.05345.05345.05344.229345.915297.692297.692NANA
us-gaap:IntangibleAssetsNetExcludingGoodwill ▁▁▂▂▃▃▄▄▄▅▅▆▇▇█47.7849.58952.9456.46560.04659.44663.11367.07567.01270.91673.84678.22182.64886.95990.658NANANA15.702NANANANANANANANANANANANANANANANANANANANANANANANANANA
us-gaap:FiniteLivedIntangibleAssetsNet ▄▄▄▅▅▅▅▆▆▆▆▆▇▇▇██▆▂▂▂▂▂▁▁▁▁▁▁▁▁▁▁▂▂▂▁▁▁47.7849.58952.9456.46560.04659.44663.11367.07567.01270.91673.84678.22182.64886.95990.65892.8597.79975.99115.70216.97718.33619.73920.8949.35110.34110.8811.79912.79213.84414.94515.50814.03215.11216.25117.43118.69513.38514.4315.514NANANA14.022NANA
us-gaap:OperatingLeaseRightOfUseAsset NANA34.908NANANA39.89541.94837.6534.956NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
 us-gaap:OperatingLeaseRightOfUseAsset us-gaap:Ownership cbu:SevenZeroSixNorthClintonNANA4.5NANANA4.95.05.15.2NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
us-gaap:EquitySecuritiesFvNi ▅▅▃▁▂▁▄▄▃▅▂▇█0.4690.4690.4450.4230.4330.4210.4510.4610.450.4640.4320.4980.504NA0.0NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
  2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-30
us-gaap:TimeDepositMaturitiesYearOne NANA570.039NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
  2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-30
 us-gaap:MinorityInterest dei:LegalEntity,us-gaap:ConsolidatedEntities cbu:SevenZeroSixNorthClinton,us-gaap:VariableInterestEntityPrimaryBeneficiaryNANA3.0NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
us-gaap:LesseeOperatingLeaseLiabilityPaymentsDueYearTwo NANA7.505NANANA7.9529.3728.2847.967NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
us-gaap:LesseeOperatingLeaseLiabilityPaymentsDueYearThree NANA6.336NANANA6.6647.9346.7036.396NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
us-gaap:LesseeOperatingLeaseLiabilityPaymentsDueYearFour NANA4.973NANANA5.6956.6455.4075.143NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
us-gaap:LesseeOperatingLeaseLiabilityPaymentsDueYearFive NANA3.688NANANA4.5655.6744.4373.393NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
 us-gaap:LesseeOperatingLeaseLiabilityPaymentsDueYearFive us-gaap:Ownership cbu:SevenZeroSixNorthClintonNANA0.605NANANA0.5910.5910.5910.591NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
us-gaap:LesseeOperatingLeaseLiabilityPaymentsDueAfterYearFive NANA8.222NANANA11.1515.69713.91110.653NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
 us-gaap:LesseeOperatingLeaseLiabilityPaymentsDueAfterYearFive us-gaap:Ownership cbu:SevenZeroSixNorthClintonNANA2.341NANANA2.9463.5383.5383.538NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
  2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-30
us-gaap:StockholdersEquity █▇███▇▇▇▆▆▆▆▆▆▆▅▅▄▃▄▄▃▃▃▂▂▂▂▂▂▂▂▂▂▂▂▂▂▁▁▁2061.11971.3972104.1072098.662081.3151976.6311855.2341840.4211809.511757.1281713.7831668.3451656.9591631.4661635.3151593.2451572.91296.031198.11240.5821236.9291200.6651140.6471045.0261000.3391013.402987.904965.524955.015918.136875.812865.679850.031877.294902.778904.599885.059840.673774.583755.633730.071NA607.258NANA
us-gaap:AdditionalPaidInCapital █████▇▆▆▆▆▆▆▆▆▆▆▆▂▁▁▁▁▁1037.0881034.2251025.1631021.7981019.291935.924927.337921.682917.855913.917911.748907.69904.913898.036894.879889.886887.305627.015545.775540.549535.568531.357528.015NANANA409.984NANANANANANANANANANANANANANANANANANA
us-gaap:RetainedEarningsAccumulatedDeficit ██▇▇▇▇▇▆▆▆▆▅▅▅▄▄▄▄▃▃▃▃▃▃▃▃▃▂▂▂▂▂▂▂▂▂▁▁▁▁▁1015.742990.504960.183936.273915.392902.148882.851861.254843.288817.933795.563774.403750.779723.404700.557645.18627.228626.258614.692602.513589.559577.384566.591560.021547.769536.056525.985515.04504.86492.55481.732477.568466.848456.524447.018438.912431.226420.415411.805402.426391.993NA374.7NANA
us-gaap:AccumulatedOtherComprehensiveIncomeLossNetOfTax ▃▁▇███▄▅▅▄▃▃▃▄▅▅▅▅▅▇█▇▆▆▆▇▆▆▆▅▄▄▄▅▇▇▇▆▆▆▅▅▅-48.4-109.95762.07783.96290.03183.444-10.2262.47-4.621-26.762-45.305-62.142-46.491-35.226-3.69916.17717.64210.3547.84366.09181.03561.28719.23545.90718.6748.93330.7220.6721.842-1.066-26.546-28.401-27.71613.21254.33466.13657.16724.99729.16523.4189.456-3.223-9.34NANA
us-gaap:TreasuryStockValue ▁▁▁▁▁▁▁▁▂▂▃▄▄▅▆▆▇▄▄▄▄▄▅▇▇█▆▅▅▅▅▅▅▅▅▅▅▅▅▅▅5.6325.5726.1986.1316.0666.0056.8236.8758.7979.60111.52814.80315.33417.63321.01422.4423.52314.02815.1613.42813.92913.96117.63724.04425.45327.26920.39116.98216.98217.11517.11517.11517.11517.11517.40817.47317.53317.53317.68317.73117.776NA17.776NANA
 us-gaap:MinorityInterest dei:LegalEntity,us-gaap:ConsolidatedEntities cbu:SevenZeroSixNorthClinton,us-gaap:VariableInterestEntityPrimaryBeneficiaryNANA3.0NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
us-gaap:AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue ▆▆▇▅▄█▄▄▅▅▅▄▆▇▃▄▄▅▅▃▂▄▃▃▂▃▂▂▂▄▂▂▂▄▁▁▁▄▁▁1.5681.6741.7711.4151.2811.9521.2871.2411.3661.3911.4571.2111.6811.7151.1521.2551.321.411.3911.1721.0011.2191.0371.0140.9991.1510.920.9850.9061.1820.9470.9070.8871.220.8130.8190.8131.2230.7460.746NANANANANA
  2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-30
us-gaap:NetCashProvidedByUsedInOperatingActivities ▁▆▅▂▇▁█▃▅▂▅▅▅▆▅▄▄▃▂▂26.26761.8154.24629.88268.66126.69473.51639.06255.31534.60954.82754.96150.71260.90850.81846.77249.42342.66131.94333.73NANANANANANANANA29.40926.71231.25316.20134.20721.52320.25636.22623.04728.895NANANANANANANA
us-gaap:NetCashProvidedByUsedInInvestingActivities ▅▃▃▆▄▅▁▅█▅▅▅▅▅▅▅▅▅▅▅-19.232-414.982-320.541123.615-251.21249.418-708.616-65.105566.24350.42415.99-50.46220.21931.74855.78567.01837.077-28.509-18.548-10.456NANANANANANANANA-45.245-235.781495.424-246.997-48.292353.12310.302557.966-220.426-612.102-68.50448.76912.126-18.52544.7160.856NA
us-gaap:NetCashProvidedByUsedInFinancingActivities ▃▇▃▅█▄▂▄▂▄▂▃▁▄▂▂▂▃▃▃47.544858.71475.579363.144973.095248.194-173.912165.249-255.086211.497-115.8212.185-364.676230.205-127.045-92.005-157.991103.177-1.08-23.366NANANANANANANANA24.322212.839-551.235256.428-167.64-272.906-89.753-437.341196.226390.384-49.71273.207-62.68280.545-37.99318.81NA
  2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-30
us-gaap:IncreaseDecreaseInOtherOperatingCapitalNet ▇▂▃▇▁█▁▆▃▇▄▄▅▃▅▄▁▃▆▄▃▅▅▅▄▅▅▄▄▄▅▆▃▅▆▃▅▄▇▄▄▅▅▄20.981-13.396-10.00520.243-19.63126.332-22.6979.746-6.45816.864-1.483-3.2113.616-9.1745.534-1.227-22.967-7.4315.6791.093-10.1135.4652.5653.802-3.0295.4465.458-4.888-0.455-0.1054.9511.431-9.0983.96413.107-12.0263.208-3.99719.825-3.092-4.882.4164.049-1.961NA
us-gaap:NetCashProvidedByUsedInOperatingActivities ▁▆▅▂▇▁█▃▅▂▅▅▅▆▅▄▄▃▂▂26.26761.8154.24629.88268.66126.69473.51639.06255.31534.60954.82754.96150.71260.90850.81846.77249.42342.66131.94333.73NANANANANANANANA29.40926.71231.25316.20134.20721.52320.25636.22623.04728.895NANANANANANANA
us-gaap:NetIncomeLoss ▅▆▅▄▃▄▄▄▅▄▄▄▅▄█▃▁▂▂▂▂▂▂▂▂▂▂▂▂▂▁▂▂▂▁▁▂▁▁▂▁▁▁▁▁47.94452.8546.48542.80935.24840.13442.88439.21845.01541.94640.82343.10644.60640.10672.02635.24317.19126.25726.39227.1625.85724.40320.07125.02223.8422.29723.13322.37123.67622.17315.47721.98921.12220.24118.80418.36721.07118.82618.98820.00817.98616.1615.89417.26216.162
us-gaap:ShareBasedCompensation ▆▆▇▅▄█▄▄▅▅▅▄▆▇▃▄▄▅▅▃▂▄▃▃▂▃▂▂▂▄▂▂▂▄▁▁▁▄▁▁▃▄▁▁1.5681.6741.7711.4151.2811.9521.2871.2411.3661.3911.4571.2111.6811.7151.1521.2551.321.411.3911.1721.0011.2191.0371.0140.9991.1510.920.9850.9061.1820.9470.9070.8871.220.8130.8190.8131.2230.7460.7461.031.2620.7560.766NA
  2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-30
us-gaap:NetCashProvidedByUsedInInvestingActivities ▅▃▃▆▄▅▁▅█▅▅▅▅▅▅▅▅▅▅▅-19.232-414.982-320.541123.615-251.21249.418-708.616-65.105566.24350.42415.99-50.46220.21931.74855.78567.01837.077-28.509-18.548-10.456NANANANANANANANA-45.245-235.781495.424-246.997-48.292353.12310.302557.966-220.426-612.102-68.50448.76912.126-18.52544.7160.856NA
us-gaap:PaymentsToAcquirePropertyPlantAndEquipment █▇██▇▇▇▇▇▇███▇▇▇▇▇█▇▇▇▇█▇███▇▇▇██▇█▇█▇▃▇▇▇▁█4.8130.8765.6684.0861.6213.020.6611.0622.7361.2273.7433.6053.7421.5563.1182.3113.3022.0884.612.2632.932.6393.2163.3742.4893.3215.5374.0122.4321.3952.6293.8714.8532.5023.7432.9713.5720.56-16.5082.662.0982.137-27.2134.821NA
  2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-30
us-gaap:NetCashProvidedByUsedInFinancingActivities ▃▇▃▅█▄▂▄▂▄▂▃▁▄▂▂▂▃▃▃47.544858.71475.579363.144973.095248.194-173.912165.249-255.086211.497-115.8212.185-364.676230.205-127.045-92.005-157.991103.177-1.08-23.366NANANANANANANANA24.322212.839-551.235256.428-167.64-272.906-89.753-437.341196.226390.384-49.71273.207-62.68280.545-37.99318.81NA
us-gaap:PaymentsOfDividendsCommonStock ████▇▇▇▇▇▇▇▆▅▅▅▅▄▄▄▄▄▄▃▃▃▃▃▃▃▃▃▂▂▂▂▂▂▂▂▁▁▁▁▁22.60922.55322.53821.98421.34121.26821.22719.63319.57519.80619.48917.39517.3317.28117.24616.2114.66314.18614.16513.66713.61113.60512.68912.22412.18612.17412.18911.3711.32811.29111.2610.79510.72810.69910.68110.25910.2169.6099.5768.8318.0217.9767.967.955NA
us-gaap:PaymentsForRepurchaseOfCommonStock ▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▃▁▃▁▂▁▁▁▁█▄▁▁▁0.060.0680.0670.0650.0650.0740.0730.0680.0660.0790.0780.070.0690.0810.080.1483.0780.02.7540.00.7160.00.0010.00.09.1254.3680.00.00.0NANANANANANANANANANANANANANANA
  2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-30

Common Stock Shares Issued

us-gaap:CommonStockSharesIssued

us-gaap:CommonStockSharesIssued


Common
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302010-12-31
Value545453535352515151515151515151515146444444444441414141414141414140404040404037373734
Percentage of CommonStockSharesIssued100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

Common Stock Shares Authorized

us-gaap:CommonStockSharesAuthorized

us-gaap:CommonStockSharesAuthorized


Common
Period End2020-12-312020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302010-12-31
Value757575757575757575757575757575757575757575757575757575757575505050505050505050
Percentage of CommonStockSharesAuthorized100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

Common Stock Shares Outstanding

us-gaap:CommonStockSharesOutstanding us-gaap:StatementEquityComponents

us-gaap:CommonStockSharesOutstanding

cbu:CommonStockOutstanding


Common
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312016-12-312015-12-31
Value5353535353525151515151515150504443
Percentage of CommonStockSharesOutstanding100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

Weighted Average Number Of Diluted Shares Outstanding

us-gaap:WeightedAverageNumberOfDilutedSharesOutstanding

us-gaap:WeightedAverageNumberOfDilutedSharesOutstanding


Weighted
Period End2021-06-302021-03-312020-09-302020-06-302020-03-312019-09-302019-06-302019-03-312018-09-302018-06-302018-03-312017-09-302017-06-302017-03-312016-09-302016-06-302016-03-312015-09-302015-06-302015-03-312014-09-302014-06-302014-03-312013-09-302013-06-302013-03-312012-09-302012-06-302012-03-312011-09-302011-06-302011-03-31
Value54545352525252525151515149454444444141414141404040400.0398739390.0370413633
Percentage of WeightedAverageNumberOfDilutedSharesOutstanding100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

Weighted Average Number Of Shares Outstanding Basic

us-gaap:WeightedAverageNumberOfSharesOutstandingBasic

us-gaap:WeightedAverageNumberOfSharesOutstandingBasic


Weighted
Period End2021-06-302021-03-312020-09-302020-06-302020-03-312019-09-302019-06-302019-03-312018-09-302018-06-302018-03-312017-09-302017-06-302017-03-312016-09-302016-06-302016-03-312015-09-302015-06-302015-03-312014-09-302014-06-302014-03-312013-09-302013-06-302013-03-312012-09-302012-06-302012-03-312011-09-302011-06-302011-03-31
Value54535352525151515151505048454444434040404040404039390.03938439380.0366793633
Percentage of WeightedAverageNumberOfSharesOutstandingBasic100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

Antidilutive Securities Excluded From Computation Of Earnings Per Share Amount

us-gaap:AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount

us-gaap:AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount


Antidilutive
Period End2021-06-302021-03-312020-09-302020-06-302020-03-312019-09-302019-06-302019-03-312018-09-302018-06-302018-03-312017-09-302017-06-302017-03-312016-09-302016-06-302016-03-312015-09-302015-06-302015-03-312014-09-302014-06-302014-03-312013-09-302013-06-302013-03-312012-09-302012-06-302012-03-312011-03-31
Value200000.030000.0500000.0600000.0200000.0500000.0500000.0500000.0400000.0400000.0400000.0200000.0200000.0200000.00800000.0600000.0600000.0600000.0300000.0300000.0300000.040000.0300000.0700000.0500000.0600000.0600000.0300000.0600000.0
Percentage of AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.00.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

Earnings Per Share Basic

us-gaap:EarningsPerShareBasic

us-gaap:EarningsPerShareBasic


Earnings
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-30
Value0.890.980.870.80.670.770.820.760.870.810.790.840.870.781.450.690.350.580.590.610.580.550.470.610.580.550.570.550.580.550.380.550.530.510.470.460.530.490.510.540.490.480.480.520.49
Percentage of EarningsPerShareBasic100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

Earnings Per Share Diluted

us-gaap:EarningsPerShareDiluted

us-gaap:EarningsPerShareDiluted


Earnings
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-30
Value0.880.970.860.790.660.760.820.750.860.80.780.830.860.781.430.680.350.570.580.610.580.550.470.60.580.540.570.540.570.540.380.540.520.50.470.460.530.480.510.540.490.480.470.510.48
Percentage of EarningsPerShareDiluted100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

Tier One Risk Based Capital To Risk Weighted Assets

us-gaap:TierOneRiskBasedCapitalToRiskWeightedAssets

us-gaap:TierOneRiskBasedCapitalToRiskWeightedAssets


Tier
Period End2020-12-312019-12-312018-12-312017-12-312016-12-312015-12-312014-12-312013-12-31
Value18.990.17230.18230.16640.1810.17090.17610.1642
Percentage of TierOneRiskBasedCapitalToRiskWeightedAssets100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:TierOneRiskBasedCapitalToRiskWeightedAssets us-gaap:ConsolidatedEntities

srt:Subsidiaries


Tier
Period End2020-12-312019-12-312018-12-312017-12-31
Value14.980.13790.15350.145
Percentage of TierOneRiskBasedCapitalToRiskWeightedAssets78.980.084.287.1

Capital To Risk Weighted Assets

us-gaap:CapitalToRiskWeightedAssets

us-gaap:CapitalToRiskWeightedAssets


Capital
Period End2020-12-312019-12-312018-12-312017-12-312016-12-312015-12-312014-12-312013-12-31
Value19.870.17990.19060.17450.1910.18080.18750.1757
Percentage of CapitalToRiskWeightedAssets100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:CapitalToRiskWeightedAssets us-gaap:ConsolidatedEntities

srt:Subsidiaries


Capital
Period End2020-12-312019-12-312018-12-312017-12-31
Value15.870.14550.16180.1531
Percentage of CapitalToRiskWeightedAssets79.980.984.987.7

Comprehensive Income Net Of Tax

us-gaap:ComprehensiveIncomeNetOfTax

us-gaap:ComprehensiveIncomeNetOfTax


Comprehensive
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-30
Value109-119.184243641133304667605727338.57952332428-31.856124566-6.60152-6.42440332146471721-19.806-20.8817.00227531424333022-4.3662227
Percentage of ComprehensiveIncomeNetOfTax100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of InterestAndDividendIncomeOperating114.8-122.025.237.743.0137.930.246.971.265.362.430.236.69.758.938.230.141.1-43.617.164.195.3-9.780.0-10.164.951.433.072.775.426.332.2-30.9-30.79.738.375.521.735.148.243.937.0-7.036.543.5

Income Loss From Continuing Operations Before Income Taxes Minority Interest And Income Loss From Equity Method Investments

us-gaap:IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments

us-gaap:IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments


Income
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-30
Value626458534449514956515154545247512436394038362935343232313331213129282625292628282421212322
Percentage of IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of InterestAndDividendIncomeOperating65.466.560.255.145.551.051.750.459.855.555.760.060.358.953.157.930.651.754.356.654.051.843.954.853.751.750.349.652.749.932.747.046.542.137.036.342.439.039.940.735.536.535.337.535.2

us-gaap:IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments us-gaap:ConsolidationItems, us-gaap:StatementBusinessSegments

us-gaap:OperatingSegments, cbu:BankingServices


Income
Period End2021-06-302021-03-312020-06-302020-03-31
Value46493236
Percentage of IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments74.376.474.674.6
Percentage of InterestAndDividendIncomeOperating48.650.833.938.0
Percentage of InterestAndDividendIncomeOperating us-gaap:OperatingSegments cbu:BankingServices0.00.00.00.0

us-gaap:OperatingSegments, cbu:EmployeeBenefitServices


Income
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-31
Value1110109.428.3919.5418.6738.6517.8968.737.947.9226.9517.7156.6636.1895.6843.6912.6372.6032.5592.8672.8912.9422.5512.7982.9172.7772.3312.275
Percentage of IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments19.116.818.117.519.019.316.817.414.017.015.414.512.714.814.012.122.810.26.76.46.77.99.78.27.48.79.08.76.97.2
Percentage of InterestAndDividendIncomeOperating12.511.110.99.78.69.88.78.88.49.48.68.77.68.77.47.07.05.33.63.63.64.14.34.54.04.54.54.33.63.6
Percentage of InterestAndDividendIncomeOperating us-gaap:OperatingSegments cbu:EmployeeBenefitServices0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:OperatingSegments, us-gaap:AllOtherSegments


Income
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-31
Value4.1484.422.8633.2082.8253.0151.3963.3213.0332.8962.4083.3382.7431.8662.0912.282.5471.893
Percentage of IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments6.76.84.96.06.46.12.76.75.45.64.76.15.03.64.44.410.25.2
Percentage of InterestAndDividendIncomeOperating4.34.52.93.32.93.11.43.43.23.12.63.73.02.12.32.63.12.7
Percentage of InterestAndDividendIncomeOperating us-gaap:OperatingSegments us-gaap:AllOtherSegments0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:OperatingSegments, us-gaap:Banking


Income
Period End2020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-30
Value4132364137453941434542384216
Percentage of IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments76.574.674.680.575.980.677.479.979.482.381.681.683.567.0
Percentage of InterestAndDividendIncomeOperating42.133.938.041.638.248.243.044.547.649.648.143.448.320.5
Percentage of InterestAndDividendIncomeOperating us-gaap:OperatingSegments us-gaap:Banking0.00.00.00.00.00.00.00.00.00.00.00.00.00.0

Income Tax Expense Benefit

us-gaap:IncomeTaxExpenseBenefit

us-gaap:IncomeTaxExpenseBenefit


Income
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-30
Value141212108.9649.2858.85310119.53510111011-24.411167.7249.932131312119.7591010109.3369.537109.3686.079.0698.7118.3487.8237.5398.8717.5049.1168.646.795.8395.9666.2245.891
Percentage of IncomeTaxExpenseBenefit100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of InterestAndDividendIncomeOperating15.112.412.511.29.29.68.810.612.110.311.512.611.313.6-27.218.19.514.218.118.617.716.814.416.516.416.014.514.815.714.89.213.713.612.310.910.612.611.112.912.39.79.79.69.99.4

Income Taxes Paid

us-gaap:IncomeTaxesPaid

us-gaap:IncomeTaxesPaid


Income
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-31
Value192.70110180.8179.6421212174.4869.5927.993120.5648.04413119.0448.5229.5437.1097.0657.5578.0437.5845.7079.938.063110.1644.327.567.64.1680.2456.5626.5643.0916.065.0619.5650.124
Percentage of IncomeTaxesPaid100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of InterestAndDividendIncomeOperating20.72.811.118.70.89.912.312.518.34.810.48.813.30.69.014.713.612.911.713.410.010.111.112.311.99.115.412.517.60.36.511.411.86.10.39.29.34.68.67.213.70.2

Interest And Fee Income Loans And Leases

us-gaap:InterestAndFeeIncomeLoansAndLeases

us-gaap:InterestAndFeeIncomeLoansAndLeases


Interest
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-30
Value757977797878807974737372716969696252535352514947454546464645474746474948474750504942444544
Percentage of InterestAndFeeIncomeLoansAndLeases100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of InterestAndDividendIncomeOperating79.681.679.881.781.081.080.581.078.579.579.379.578.278.577.878.576.674.973.475.373.874.072.572.171.773.072.672.971.972.371.372.072.469.468.768.166.770.671.772.070.870.271.172.071.6

Interest Expense

us-gaap:InterestExpense

us-gaap:InterestExpense


Interest
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-30
Value3.2553.7114.1684.5255.2416.9417.3077.3716.0525.8225.0344.7054.1593.783.6114.0923.3932.6842.7532.8592.8042.8753.0152.9212.6522.6142.8292.8932.9393.1315.3265.5315.7089.51112121315151514151616
Percentage of InterestExpense100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of InterestAndDividendIncomeOperating3.43.84.34.65.47.27.37.56.46.35.45.24.64.34.04.64.23.83.84.03.94.14.44.54.24.24.44.54.65.08.18.48.914.016.717.718.120.121.722.522.424.525.626.026.6

Interest Income Expense Net

us-gaap:InterestIncomeExpenseNet

us-gaap:InterestIncomeExpenseNet


Interest
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-30
Value929393929190929188868786868485847867706868666462615961616160606058585958575355545445464645
Percentage of InterestIncomeExpenseNet100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of InterestAndDividendIncomeOperating96.696.295.795.494.692.892.792.593.693.794.694.895.495.796.095.495.896.296.296.096.195.995.695.595.895.895.695.595.495.091.991.691.186.083.382.381.979.978.377.577.675.574.474.073.4

us-gaap:InterestIncomeExpenseNet us-gaap:ConsolidationItems, us-gaap:StatementBusinessSegments

us-gaap:OperatingSegments, cbu:BankingServices


Interest
Period End2021-06-302021-03-312020-06-302020-03-31
Value92939189
Percentage of InterestIncomeExpenseNet99.999.999.799.7
Percentage of InterestAndDividendIncomeOperating96.596.194.392.5
Percentage of InterestAndDividendIncomeOperating us-gaap:OperatingSegments cbu:BankingServices0.00.00.00.0

us-gaap:OperatingSegments, cbu:EmployeeBenefitServices


Interest
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-31
Value0.0650.0940.2010.2560.2460.240.2170.2090.1310.1080.1120.1020.0930.070.120.1040.0940.0780.0450.0390.0380.040.030.0370.0350.0290.0250.0210.0230.023
Percentage of InterestIncomeExpenseNet0.10.10.20.30.30.30.20.20.10.10.10.10.10.10.10.10.10.10.10.10.10.10.00.10.10.00.00.00.00.0
Percentage of InterestAndDividendIncomeOperating0.10.10.20.30.30.20.20.20.10.10.10.10.10.10.10.10.10.10.10.10.10.10.00.10.10.00.00.00.00.0
Percentage of InterestAndDividendIncomeOperating us-gaap:OperatingSegments cbu:EmployeeBenefitServices0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:OperatingSegments, us-gaap:AllOtherSegments


Interest
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-31
Value0.0070.0210.0460.0670.060.0510.0490.0490.0420.0360.0370.0360.030.0240.0650.0640.0630.062
Percentage of InterestIncomeExpenseNet0.00.00.00.10.10.10.10.10.00.00.00.00.00.00.10.10.10.1
Percentage of InterestAndDividendIncomeOperating0.00.00.00.10.10.10.00.00.00.00.00.00.00.00.10.10.10.1
Percentage of InterestAndDividendIncomeOperating us-gaap:OperatingSegments us-gaap:AllOtherSegments0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:OperatingSegments, us-gaap:Banking


Interest
Period End2020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-30
Value9291899291888687868684858477
Percentage of InterestIncomeExpenseNet99.799.799.799.799.799.899.899.899.899.999.999.899.899.8
Percentage of InterestAndDividendIncomeOperating95.094.392.592.492.393.493.694.494.795.395.695.895.295.6
Percentage of InterestAndDividendIncomeOperating us-gaap:OperatingSegments us-gaap:Banking0.00.00.00.00.00.00.00.00.00.00.00.00.00.0

Interest Paid Net

us-gaap:InterestPaidNet

us-gaap:InterestPaidNet


Interest
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-30
Value3.2934.3514.2424.5915.4486.8886.976.736.0415.6845.0564.9744.1393.7573.6134.0823.3032.7072.7112.8682.8262.8633.0032.9282.6792.6422.8582.9012.9963.1826.2065.5776.6391112121213151515141616
Percentage of InterestPaidNet100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of InterestAndDividendIncomeOperating3.54.54.34.75.67.17.06.86.46.15.55.54.54.24.04.64.13.93.74.04.04.14.44.54.24.24.44.54.75.09.48.410.417.316.917.618.420.522.122.521.824.726.426.0

Litigation Settlement Expense

us-gaap:LitigationSettlementExpense

us-gaap:LitigationSettlementExpense


Litigation
Period End2020-12-312020-09-302019-12-312019-09-30
Value02950000.000
Percentage of LitigationSettlementExpense0.0100.00.00.0
Percentage of InterestAndDividendIncomeOperating0.03.00.00.0

Net Income Loss

us-gaap:NetIncomeLoss

us-gaap:NetIncomeLoss


Net
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-30
Value475246423540423945414043444072351726262725242025232223222322152121201818211818201716151716
Percentage of NetIncomeLoss100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of InterestAndDividendIncomeOperating50.354.147.643.936.341.442.939.847.745.344.247.449.045.480.439.821.137.536.238.136.435.029.538.337.335.735.834.836.935.123.533.332.929.826.125.729.927.927.028.425.726.825.627.625.8

us-gaap:NetIncomeLoss us-gaap:StatementEquityComponents

us-gaap:RetainedEarnings


Net
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-30
Value47524642354042394541404344407235172626272524202523222322232215212120181821181820
Percentage of NetIncomeLoss100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of InterestAndDividendIncomeOperating50.354.147.643.936.341.442.939.847.745.344.247.449.045.480.439.821.137.536.238.136.435.029.538.337.335.735.834.836.935.123.533.332.929.826.125.729.927.927.028.4
Percentage of InterestAndDividendIncomeOperating us-gaap:RetainedEarnings0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

Net Income Loss Available To Common Stockholders Basic

us-gaap:NetIncomeLossAvailableToCommonStockholdersBasic

us-gaap:NetIncomeLossAvailableToCommonStockholdersBasic


Net
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-31
Value47524642353942394441404244397135172626272524192423222322232221201818201818191716
Percentage of NetIncomeLossAvailableToCommonStockholdersBasic100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of InterestAndDividendIncomeOperating50.154.047.543.836.141.242.839.747.645.144.047.248.845.280.239.621.037.335.937.936.134.929.438.137.235.535.634.636.734.932.829.726.025.629.727.726.828.225.626.6

Operating Expenses

us-gaap:OperatingExpenses us-gaap:BusinessAcquisition

us-gaap:OperatingExpenses

cbu:KinderhookBankCorp


Operating
Period End2020-12-312020-09-30
Value1.62.2
Percentage of OperatingExpenses100.0100.0
Percentage of InterestAndDividendIncomeOperating1.62.3
Percentage of InterestAndDividendIncomeOperating cbu:KinderhookBankCorp0.00.0

cbu:SteubenTrustCorporation


Operating
Period End2021-06-302021-03-312020-09-302020-06-122020-06-30
Value1.23.21.17.70.3
Percentage of OperatingExpenses0.00.050.00.00.0
Percentage of InterestAndDividendIncomeOperating1.33.31.10.00.3
Percentage of InterestAndDividendIncomeOperating cbu:SteubenTrustCorporation0.00.00.00.00.0

Revenues

us-gaap:Revenues us-gaap:BusinessAcquisition

us-gaap:Revenues

cbu:KinderhookBankCorp


Revenuesus-gaap:
Period End2020-12-312020-09-30
Value3.63.8
Percentage of Revenues100.0100.0
Percentage of InterestAndDividendIncomeOperating3.73.9
Percentage of InterestAndDividendIncomeOperating cbu:KinderhookBankCorp0.00.0

cbu:SteubenTrustCorporation


Revenuesus-gaap:
Period End2021-06-302021-03-312020-09-302020-06-122020-06-30
Value3.31.33.82.60.6
Percentage of Revenues0.00.0100.00.00.0
Percentage of InterestAndDividendIncomeOperating3.51.33.90.00.6
Percentage of InterestAndDividendIncomeOperating cbu:SteubenTrustCorporation0.00.00.00.00.0

Assets

us-gaap:Assets

us-gaap:Assets


Assets
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312009-12-31
Value1480114620139311384513444118081141011597107451091610607106591063310966107461085010884891386668727874286158552799779087576748975027461739770957302702072217496757071666912648865036390554954445402
Percentage of Assets100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:Assets dei:LegalEntity, us-gaap:ConsolidatedEntities

cbu:SevenZeroSixNorthClinton, us-gaap:VariableInterestEntityPrimaryBeneficiary


Assetsdei:
Period End2020-12-312019-12-312018-12-31
Value5.9876.1256.246
Percentage of Assets0.00.10.1
Percentage of Assets0.00.10.1
Percentage of Assets cbu:SevenZeroSixNorthClinton us-gaap:VariableInterestEntityPrimaryBeneficiary100.0100.0100.0

us-gaap:Assets us-gaap:ConsolidatedEntities

srt:ParentCompany


Assetsus-gaap:
Period End2020-12-312019-12-312018-12-312017-12-31
Value2215197118331779
Percentage of Assets15.917.317.316.6
Percentage of Assets15.917.317.316.6
Percentage of Assets srt:ParentCompany100.0100.0100.0100.0

us-gaap:Assets us-gaap:ConsolidationItems

us-gaap:IntersegmentElimination


Assetsus-gaap:
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302011-12-31
Value-100.699-100.024-131.86-120.877-122.856-114.64-101.255-76.505-68.207-53.309-66.076-53.2-53.663-43.539-29.638-67.461-43.533-43.145-41.79-39.415-36.977-38.665-65.637-23.058-24.783-22.307-21.087-17.957-15.639-18.064-16.231-14.519-12.649-20.326-18.334-17.083-14.982-11.976
Percentage of Assets-0.7-0.7-0.9-0.9-0.9-1.0-0.9-0.7-0.6-0.5-0.6-0.5-0.5-0.4-0.3-0.6-0.4-0.5-0.5-0.5-0.4-0.4-0.8-0.3-0.3-0.3-0.3-0.2-0.2-0.2-0.2-0.2-0.2-0.3-0.2-0.2-0.2-0.2
Percentage of Assets-0.7-0.7-0.9-0.9-0.9-1.0-0.9-0.7-0.6-0.5-0.6-0.5-0.5-0.4-0.3-0.6-0.4-0.5-0.5-0.5-0.4-0.4-0.8-0.3-0.3-0.3-0.3-0.2-0.2-0.2-0.2-0.2-0.2-0.3-0.2-0.2-0.2-0.2
Percentage of Assets us-gaap:IntersegmentElimination100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:Assets us-gaap:ConsolidationItems, us-gaap:StatementBusinessSegments

us-gaap:OperatingSegments, cbu:BankingServices


Assetsus-gaap:
Period End2021-06-302021-03-312020-12-312020-06-302020-03-312019-12-312018-12-31
Value14588144271376213272116331122510397
Percentage of Assets98.698.798.898.798.598.498.0
Percentage of Assets98.698.798.898.798.598.498.0
Percentage of Assets us-gaap:OperatingSegments cbu:BankingServices100.0100.0100.0100.0100.0100.0100.0

us-gaap:OperatingSegments, cbu:EmployeeBenefitServices


Assetsus-gaap:
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312012-12-31
Value2352102172102162132092012061992072052072052032262172213836343835303332312927302730
Percentage of Assets1.61.41.61.51.61.81.81.71.91.82.01.91.91.91.92.12.02.50.40.40.40.40.40.40.40.40.40.40.40.40.40.4
Percentage of Assets1.61.41.61.51.61.81.81.71.91.82.01.91.91.91.92.12.02.50.40.40.40.40.40.40.40.40.40.40.40.40.40.4
Percentage of Assets us-gaap:OperatingSegments cbu:EmployeeBenefitServices100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:OperatingSegments, us-gaap:AllOtherSegments


Assetsus-gaap:
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312015-12-312014-12-31
Value788282807876767472716866646866777572717015
Percentage of Assets0.50.60.60.60.60.60.70.60.70.70.60.60.60.60.60.70.70.80.80.80.2
Percentage of Assets0.50.60.60.60.60.60.70.60.70.70.60.60.60.60.60.70.70.80.80.80.2
Percentage of Assets us-gaap:OperatingSegments us-gaap:AllOtherSegments100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:OperatingSegments, us-gaap:Banking


Assetsus-gaap:
Period End2020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302016-12-31
Value13674132721163311225113981053410699103971044010415107361050510613106358598
Percentage of Assets98.898.798.598.498.398.098.098.097.997.997.997.897.897.799.2
Percentage of Assets98.898.798.598.498.398.098.098.097.997.997.997.897.897.799.2
Percentage of Assets us-gaap:OperatingSegments us-gaap:Banking100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

Liabilities

us-gaap:Liabilities

us-gaap:Liabilities


Liabilities
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302010-12-31
Value12740126481182611746113629832955597568935915988938991897693359110925693117617746874877505741574126952690865626501653765066479622064366170634365946665628160715713574856604837
Percentage of Liabilities100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets86.186.584.984.884.583.383.784.183.283.983.884.384.485.184.885.385.585.586.285.885.986.186.786.987.486.686.887.187.287.687.788.187.987.988.088.187.687.888.188.488.688.8

Liabilities And Stockholders Equity

us-gaap:LiabilitiesAndStockholdersEquity

us-gaap:LiabilitiesAndStockholdersEquity


Liabilities
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302010-12-31
Value14801146201393113845134441180811410115971074510916106071065910633109661074610850108848913866687278742861585527997790875767489750274617397709573027020722174967570716669126488650363905444
Percentage of LiabilitiesAndStockholdersEquity100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:LiabilitiesAndStockholdersEquity us-gaap:ConsolidatedEntities

srt:ParentCompany


Liabilities
Period End2020-12-312019-12-312018-12-312017-12-31
Value2215197118331779
Percentage of LiabilitiesAndStockholdersEquity15.917.317.316.6
Percentage of Assets15.917.317.316.6
Percentage of Assets srt:ParentCompany100.0100.0100.0100.0

Stockholders Equity

us-gaap:StockholdersEquity

us-gaap:StockholdersEquity


Stockholders
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302010-12-312009-12-312008-12-31
Value20611971210420982081197618551840180917571713166816561631163515931572129611981240123612001140104510001013987965955918875865850877902904885840774755730607565544
Percentage of StockholdersEquity100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets13.913.515.115.215.516.716.315.916.816.116.215.715.614.915.214.714.514.513.814.214.113.913.313.112.613.413.212.912.812.412.311.912.112.112.011.912.412.211.911.611.411.210.50.0

us-gaap:StockholdersEquity us-gaap:ConsolidatedEntities

srt:ParentCompany


Stockholders
Period End2020-12-312019-12-312018-12-312017-12-31
Value2104185517131635
Percentage of StockholdersEquity100.0100.0100.0100.0
Percentage of Assets15.116.316.215.2
Percentage of Assets srt:ParentCompany95.094.193.591.9

us-gaap:StockholdersEquity us-gaap:CumulativeEffectPeriodOfAdoption

srt:CumulativeEffectPeriodOfAdoptionAdjustment


Stockholders
Period End2020-12-312018-12-31
Value1.140.0
Percentage of StockholdersEquity0.10.0
Percentage of Assets0.00.0
Percentage of Assets srt:CumulativeEffectPeriodOfAdoptionAdjustment0.00.0

us-gaap:StockholdersEquity us-gaap:CumulativeEffectPeriodOfAdoption, us-gaap:AdjustmentsForNewAccountingPronouncements

srt:CumulativeEffectPeriodOfAdoptionAdjustment, us-gaap:AccountingStandardsUpdate201613


Stockholders
Period End2020-09-302020-03-312019-12-31
Value1.140.530.53
Percentage of StockholdersEquity0.10.00.0
Percentage of Assets0.00.00.0
Percentage of Assets srt:CumulativeEffectPeriodOfAdoptionAdjustment us-gaap:AccountingStandardsUpdate2016130.00.00.0

us-gaap:StockholdersEquity us-gaap:CumulativeEffectPeriodOfAdoption, us-gaap:AdjustmentsForNewAccountingPronouncements, us-gaap:StatementEquityComponents

srt:CumulativeEffectPeriodOfAdoptionAdjustment, us-gaap:AccountingStandardsUpdate201613, us-gaap:RetainedEarnings


Stockholders
Period End2020-09-302020-03-312019-12-31
Value1.140.530.53
Percentage of StockholdersEquity0.10.00.0
Percentage of Assets0.00.00.0
Percentage of Assets srt:CumulativeEffectPeriodOfAdoptionAdjustment us-gaap:AccountingStandardsUpdate201613 us-gaap:RetainedEarnings0.00.00.0

us-gaap:StockholdersEquity us-gaap:CumulativeEffectPeriodOfAdoption, us-gaap:StatementEquityComponents

srt:CumulativeEffectPeriodOfAdoptionAdjustment, us-gaap:RetainedEarnings


Stockholders
Period End2020-12-312018-12-31
Value1.140.208
Percentage of StockholdersEquity0.10.0
Percentage of Assets0.00.0
Percentage of Assets srt:CumulativeEffectPeriodOfAdoptionAdjustment us-gaap:RetainedEarnings0.00.0

us-gaap:StockholdersEquity us-gaap:StatementEquityComponents

us-gaap:AccumulatedOtherComprehensiveIncome


Stockholders
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302010-12-312009-12-312008-12-31
Value-48.4-109.95762839083-10.2262.47-4.621-26.762-45.305-62.142-46.491-35.226-3.6991617107.84366816119451848302021-1.066-26.546-28.401-27.716135466572429239.456-9.34-8.784-12.864
Percentage of StockholdersEquity-2.3-5.63.04.04.34.2-0.60.1-0.3-1.5-2.6-3.7-2.8-2.2-0.21.01.10.80.75.36.65.11.74.41.94.83.12.12.3-0.1-3.0-3.3-3.31.56.07.36.53.03.83.11.3-1.5-1.6-2.4
Percentage of Assets-0.3-0.80.40.60.70.7-0.10.0-0.0-0.2-0.4-0.6-0.4-0.3-0.00.10.20.10.10.80.90.70.20.60.20.60.40.30.3-0.0-0.4-0.4-0.40.20.70.90.80.40.40.40.1-0.2-0.20.0
Percentage of Assets us-gaap:AccumulatedOtherComprehensiveIncome0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:AdditionalPaidInCapital


Stockholders
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302010-12-312009-12-312008-12-31
Value10371034102510211019935927921917913911907904898894889887627545540535531528421417413409405403402396392387383378376373372313309308225216212
Percentage of StockholdersEquity50.352.548.748.749.047.350.050.150.752.053.254.454.655.054.755.956.448.445.643.643.344.346.340.341.740.841.542.042.343.845.345.345.543.841.941.642.244.340.541.042.337.138.339.0
Percentage of Assets7.07.17.47.47.67.98.17.98.58.48.68.58.58.28.38.28.27.06.36.26.16.26.25.35.35.55.55.45.45.45.65.45.55.35.05.05.25.44.84.84.84.14.00.0
Percentage of Assets us-gaap:AdditionalPaidInCapital0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:CommonStock


Stockholders
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302010-12-312009-12-312008-12-31
Value5454535353525151515151515151515151464444444444414141414141414141404040404040373737343333
Percentage of StockholdersEquity2.62.72.62.62.62.62.82.82.92.93.03.13.13.13.13.23.33.63.83.63.63.73.94.04.24.14.24.34.34.54.74.74.84.64.54.54.64.84.95.05.25.65.96.1
Percentage of Assets0.40.40.40.40.40.40.50.40.50.50.50.50.50.50.50.50.50.50.50.50.50.50.50.50.50.60.60.60.60.60.60.60.60.60.50.50.60.60.60.60.60.60.60.0
Percentage of Assets us-gaap:CommonStock0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:DeferredCompensationShareBasedPayments


Stockholders
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302016-12-312015-12-312014-12-31
Value8.2388.1789.1279.068.9958.9310109.9799.913111111111313130.00.00.0
Percentage of StockholdersEquity0.40.40.40.40.40.50.50.50.60.60.70.70.70.70.80.80.80.00.00.0
Percentage of Assets0.10.10.10.10.10.10.10.10.10.10.10.10.10.10.10.10.10.00.00.0
Percentage of Assets us-gaap:DeferredCompensationShareBasedPayments0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:RetainedEarnings


Stockholders
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302010-12-312009-12-312008-12-31
Value1015990960936915902882861843817795774750723700645627626614602589577566560547536525515504492481477466456447438431420411402391374342329
Percentage of StockholdersEquity49.350.245.644.644.045.647.646.846.646.546.446.445.344.342.840.539.948.351.348.647.748.149.753.654.852.953.253.352.953.655.055.254.952.049.548.548.750.053.253.353.761.760.660.6
Percentage of Assets6.96.86.96.86.87.67.77.47.87.57.57.37.16.66.55.95.87.07.16.96.76.76.67.06.97.17.06.96.86.76.86.56.66.36.05.86.06.16.36.26.16.96.30.0
Percentage of Assets us-gaap:RetainedEarnings0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:TreasuryStock


Stockholders
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302010-12-312009-12-312008-12-31
Value-5.632-5.572-6.198-6.131-6.066-6.005-6.823-6.875-8.797-9.601-11.528-14.803-15.334-17.633-21.014-22.44-23.523-14.028-15.16-13.428-13.929-13.961-17.637-24.044-25.453-27.269-20.391-16.982-16.982-17.115-17.115-17.115-17.115-17.115-17.408-17.473-17.533-17.533-17.683-17.731-17.776-17.776-18.17-18.267
Percentage of StockholdersEquity-0.3-0.3-0.3-0.3-0.3-0.3-0.4-0.4-0.5-0.5-0.7-0.9-0.9-1.1-1.3-1.4-1.5-1.1-1.3-1.1-1.1-1.2-1.5-2.3-2.5-2.7-2.1-1.8-1.8-1.9-2.0-2.0-2.0-2.0-1.9-1.9-2.0-2.1-2.3-2.3-2.4-2.9-3.2-3.4
Percentage of Assets-0.0-0.0-0.0-0.0-0.0-0.1-0.1-0.1-0.1-0.1-0.1-0.1-0.1-0.2-0.2-0.2-0.2-0.2-0.2-0.2-0.2-0.2-0.2-0.3-0.3-0.4-0.3-0.2-0.2-0.2-0.2-0.2-0.2-0.2-0.2-0.2-0.2-0.3-0.3-0.3-0.3-0.3-0.30.0
Percentage of Assets us-gaap:TreasuryStock0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

Tier One Risk Based Capital

us-gaap:TierOneRiskBasedCapital

us-gaap:TierOneRiskBasedCapital


Tier
Period End2020-12-312019-12-312018-12-312017-12-312016-12-312015-12-312014-12-312013-12-31
Value131411481093995858788705643
Percentage of TierOneRiskBasedCapital100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets9.410.110.39.39.99.29.49.1

us-gaap:TierOneRiskBasedCapital us-gaap:ConsolidatedEntities

srt:Subsidiaries


Tier
Period End2020-12-312019-12-312018-12-312017-12-31
Value1028910912859
Percentage of TierOneRiskBasedCapital78.279.383.586.3
Percentage of Assets7.48.08.68.0
Percentage of Assets srt:Subsidiaries0.00.00.00.0

Cash And Cash Equivalents At Carrying Value

us-gaap:CashAndCashEquivalentsAtCarryingValue

us-gaap:CashAndCashEquivalentsAtCarryingValue


Cash
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302009-12-312008-12-31
Value220521511645183613195292051014874508211256250543221241219291173161161138153156143150138157161153149174148330228287130132324425273296211179133361213
Percentage of CashAndCashEquivalentsAtCarryingValue100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets14.914.711.813.39.84.51.88.78.14.72.02.42.45.02.12.22.03.32.01.91.81.61.82.01.82.01.82.12.22.12.12.42.14.63.03.81.81.95.06.54.35.43.90.00.06.70.0

us-gaap:CashAndCashEquivalentsAtCarryingValue dei:LegalEntity, us-gaap:ConsolidatedEntities

cbu:SevenZeroSixNorthClinton, us-gaap:VariableInterestEntityPrimaryBeneficiary


Cash
Period End2020-12-312019-12-312018-12-31
Value0.1570.1380.104
Percentage of CashAndCashEquivalentsAtCarryingValue0.00.10.0
Percentage of Assets0.00.00.0
Percentage of Assets cbu:SevenZeroSixNorthClinton us-gaap:VariableInterestEntityPrimaryBeneficiary2.62.31.7

us-gaap:CashAndCashEquivalentsAtCarryingValue us-gaap:ConsolidatedEntities

srt:ParentCompany


Cash
Period End2020-12-312019-12-312018-12-312017-12-312016-12-312015-12-31
Value1961801168415197
Percentage of CashAndCashEquivalentsAtCarryingValue11.988.154.838.286.963.5
Percentage of Assets1.41.61.10.81.71.1
Percentage of Assets srt:ParentCompany8.89.26.34.70.00.0

Property Plant And Equipment Gross

us-gaap:PropertyPlantAndEquipmentGross

us-gaap:PropertyPlantAndEquipmentGross


Property
Period End2020-12-312019-12-312018-12-312017-12-312016-12-312015-12-312014-12-312013-12-312012-12-312011-12-312010-12-31
Value312297247241219214193186179176162
Percentage of PropertyPlantAndEquipmentGross100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets2.22.62.32.22.52.52.62.62.42.73.0

us-gaap:PropertyPlantAndEquipmentGross us-gaap:PropertyPlantAndEquipmentByType

cbu:EquipmentAndConstructionInProgress


Property
Period End2020-12-312019-12-312018-12-312017-12-312016-12-312015-12-312014-12-312013-12-312012-12-312011-12-312010-12-31
Value9989898680807875737571
Percentage of PropertyPlantAndEquipmentGross31.830.136.335.636.637.540.740.540.842.544.3
Percentage of Assets0.70.80.80.80.90.91.11.11.01.21.3
Percentage of Assets cbu:EquipmentAndConstructionInProgress0.00.00.00.00.00.00.00.00.00.00.0

cbu:OperatingLeaseRightOfUseAssets


Property
Period End2020-12-312019-12-312018-12-31
Value34390.0
Percentage of PropertyPlantAndEquipmentGross11.213.40.0
Percentage of Assets0.30.30.0
Percentage of Assets cbu:OperatingLeaseRightOfUseAssets0.00.00.0

us-gaap:Building


Property
Period End2020-12-312019-12-312018-12-312017-12-312016-12-312015-12-312014-12-312013-12-31
Value1491411331311161129695
Percentage of PropertyPlantAndEquipmentGross47.847.653.854.553.152.150.151.1
Percentage of Assets1.11.21.31.21.31.31.31.3
Percentage of Assets us-gaap:Building0.00.00.00.00.00.00.00.0

us-gaap:LandAndLandImprovements


Property
Period End2020-12-312019-12-312018-12-312017-12-312016-12-312015-12-312014-12-312013-12-312012-12-312011-12-312010-12-31
Value2926242322221715151513
Percentage of PropertyPlantAndEquipmentGross9.38.89.89.910.310.39.28.48.68.58.2
Percentage of Assets0.20.20.20.20.30.30.20.20.20.20.2
Percentage of Assets us-gaap:LandAndLandImprovements0.00.00.00.00.00.00.00.00.00.00.0

Amortization Of Intangible Assets

us-gaap:AmortizationOfIntangibleAssets

us-gaap:AmortizationOfIntangibleAssets


Amortization
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-30
Value3.2463.3513.5253.5813.5243.6673.9623.963.9044.134.3754.4274.5554.7984.9614.9494.2632.7681.2751.3591.4031.4421.0210.8430.880.9190.9941.0511.1011.1411.0611.0891.141.1791.2641.2121.0451.0861.1311.1611.1890.9010.9721.2771.849
Percentage of AmortizationOfIntangibleAssets100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:AmortizationOfIntangibleAssets us-gaap:ConsolidationItems, us-gaap:StatementBusinessSegments

us-gaap:OperatingSegments, cbu:BankingServices


Amortization
Period End2021-06-302021-03-312020-06-302020-03-31
Value1.241.3241.3641.417
Percentage of AmortizationOfIntangibleAssets38.239.538.738.6
Percentage of Assets0.00.00.00.0
Percentage of Assets us-gaap:OperatingSegments cbu:BankingServices0.00.00.00.0

us-gaap:OperatingSegments, cbu:EmployeeBenefitServices


Amortization
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-31
Value1.3271.3541.411.4091.4111.4941.6651.6671.6691.7691.9681.971.9892.0882.3222.3232.3431.5910.0940.0960.1140.1160.1240.1250.1330.1330.1510.1530.1710.172
Percentage of AmortizationOfIntangibleAssets40.940.440.039.340.040.742.042.142.842.845.044.543.743.546.846.955.057.57.47.18.18.012.114.815.114.515.214.615.515.1
Percentage of Assets0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0
Percentage of Assets us-gaap:OperatingSegments cbu:EmployeeBenefitServices0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:OperatingSegments, us-gaap:AllOtherSegments


Amortization
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-31
Value0.6790.6730.760.7930.7490.7560.8430.8540.860.8780.8920.9220.9310.9660.8630.830.750.623
Percentage of AmortizationOfIntangibleAssets20.920.121.622.121.320.621.321.622.021.320.420.820.420.117.416.817.622.5
Percentage of Assets0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0
Percentage of Assets us-gaap:OperatingSegments us-gaap:AllOtherSegments0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:OperatingSegments, us-gaap:Banking


Amortization
Period End2020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-30
Value1.3791.3641.4171.4541.4391.3751.4831.5151.5351.6351.7441.7761.7961.17
Percentage of AmortizationOfIntangibleAssets38.538.738.636.736.335.235.934.634.735.936.335.836.327.4
Percentage of Assets0.00.00.00.00.00.00.00.00.00.00.00.00.00.0
Percentage of Assets us-gaap:OperatingSegments us-gaap:Banking0.00.00.00.00.00.00.00.00.00.00.00.00.00.0

Property Plant And Equipment Net

us-gaap:PropertyPlantAndEquipmentNet

us-gaap:PropertyPlantAndEquipmentNet


Property
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302010-12-31
Value16116116516516716216416915415111912012012012312412211111211111211311492929393919091939191898989848385858681
Percentage of PropertyPlantAndEquipmentNet100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets1.11.11.21.21.21.41.41.51.41.41.11.11.11.11.11.11.11.21.31.31.31.31.31.21.21.21.31.21.21.21.31.31.31.21.21.21.21.21.31.31.41.5

Goodwill

us-gaap:Goodwill

us-gaap:Goodwill


Goodwill
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-07-122019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312009-12-31
Value79479379379379277377377340733733733733733733734731733542465465465465463375375375375375375375374369369369369369345345345344345297297297
Percentage of Goodwill100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets5.45.45.75.75.96.56.86.70.06.86.76.96.96.96.76.86.76.76.15.45.35.35.45.44.74.75.05.05.05.05.15.35.15.35.14.94.94.85.05.35.35.45.45.55.5

us-gaap:Goodwill us-gaap:BusinessAcquisition

cbu:NuvantageInsuranceCorporation


Goodwillus-gaap:
Period End2021-06-30
Value1.438
Percentage of Goodwill0.2
Percentage of Assets0.0
Percentage of Assets cbu:NuvantageInsuranceCorporation0.0

cbu:NuvantageInsuranceInc.


Goodwillus-gaap:
Period End2021-06-03
Value1.5
Percentage of Goodwill0.0
Percentage of Assets0.0
Percentage of Assets cbu:NuvantageInsuranceInc.0.0

cbu:OtherAcquisitions


Goodwillus-gaap:
Period End2020-12-312019-12-312019-07-122018-12-312018-09-302018-06-302018-04-022018-03-312017-12-312017-09-30
Value0.313.750.03.753.7263.7260.313.8123.8121.65
Percentage of Goodwill0.00.50.00.50.50.50.00.50.50.2
Percentage of Assets0.00.00.00.00.00.00.00.00.00.0
Percentage of Assets cbu:OtherAcquisitions0.00.00.00.00.00.00.00.00.00.0

cbu:SteubenTrustCorporation


Goodwillus-gaap:
Period End2020-12-312020-06-12
Value2019
Percentage of Goodwill2.50.0
Percentage of Assets0.10.0
Percentage of Assets cbu:SteubenTrustCorporation0.00.0

us-gaap:Goodwill us-gaap:ConsolidationItems, us-gaap:StatementBusinessSegments

us-gaap:OperatingSegments, cbu:BankingServices


Goodwillus-gaap:
Period End2021-06-302021-03-312020-12-312020-06-302020-03-312019-12-312018-12-31
Value689689690689669670629
Percentage of Goodwill86.886.986.986.986.686.685.9
Percentage of Assets4.74.75.05.15.75.95.9
Percentage of Assets us-gaap:OperatingSegments cbu:BankingServices4.74.85.05.25.86.06.1

us-gaap:OperatingSegments, cbu:EmployeeBenefitServices


Goodwillus-gaap:
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312012-12-31
Value8383838383838383838383838383848484848.0198.0198.0188.0198.0198.0198.0198.0198.0198.0198.0198.0197.8367.836
Percentage of Goodwill10.510.510.510.510.510.810.810.811.411.411.411.411.411.411.511.511.515.51.71.71.71.71.72.12.12.12.12.12.12.12.12.1
Percentage of Assets0.60.60.60.60.60.70.70.70.80.80.80.80.80.80.80.80.80.90.10.10.10.10.10.10.10.10.10.10.10.10.10.1
Percentage of Assets us-gaap:OperatingSegments cbu:EmployeeBenefitServices35.439.638.239.538.539.039.741.340.441.840.140.540.240.541.537.239.038.020.721.823.020.822.925.923.924.925.427.128.826.128.025.8

us-gaap:OperatingSegments, us-gaap:AllOtherSegments


Goodwillus-gaap:
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312015-12-312014-12-31
Value21202020202020202020202020202017171716162.66
Percentage of Goodwill2.72.62.62.62.62.62.62.62.82.82.82.82.82.82.72.42.43.33.53.50.7
Percentage of Assets0.10.10.10.10.20.20.20.20.20.20.20.20.20.20.20.20.20.20.20.20.0
Percentage of Assets us-gaap:OperatingSegments us-gaap:AllOtherSegments27.624.724.525.226.026.526.627.427.928.629.730.531.430.030.223.023.824.722.823.117.0

us-gaap:OperatingSegments, us-gaap:Banking


Goodwillus-gaap:
Period End2020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302016-12-31
Value690689669670670629629629629629629629629631440
Percentage of Goodwill86.986.986.686.686.685.985.985.985.985.985.985.886.086.094.8
Percentage of Assets5.05.15.75.95.85.95.85.95.95.95.75.95.85.85.1
Percentage of Assets us-gaap:OperatingSegments us-gaap:Banking5.05.25.86.05.96.05.96.16.06.05.96.05.95.95.1

Intangible Assets Net Excluding Goodwill

us-gaap:IntangibleAssetsNetExcludingGoodwill

us-gaap:IntangibleAssetsNetExcludingGoodwill


Intangible
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312016-12-31
Value47495256605963676770737882869015
Percentage of IntangibleAssetsNetExcludingGoodwill100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets0.30.30.40.40.40.50.60.60.60.60.70.70.80.80.80.2

us-gaap:IntangibleAssetsNetExcludingGoodwill us-gaap:ConsolidationItems, us-gaap:StatementBusinessSegments

us-gaap:OperatingSegments, cbu:BankingServices


Intangible
Period End2021-06-302021-03-312020-12-312020-06-302020-03-312019-12-312018-12-31
Value11121316151618
Percentage of IntangibleAssetsNetExcludingGoodwill23.625.226.127.625.226.025.2
Percentage of Assets0.10.10.10.10.10.10.2
Percentage of Assets us-gaap:OperatingSegments cbu:BankingServices0.10.10.10.10.10.10.2

us-gaap:OperatingSegments, cbu:EmployeeBenefitServices


Intangible
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312016-12-31
Value2930323334363739414244464850520.666
Percentage of IntangibleAssetsNetExcludingGoodwill61.561.960.559.358.161.059.958.861.360.360.359.558.757.757.74.2
Percentage of Assets0.20.20.20.20.30.30.30.30.40.40.40.40.50.50.50.0
Percentage of Assets us-gaap:OperatingSegments cbu:EmployeeBenefitServices12.514.614.715.916.117.018.019.619.921.521.522.623.424.425.71.7

us-gaap:OperatingSegments, us-gaap:AllOtherSegments


Intangible
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312016-12-31
Value7.1436.3857.0587.8188.6118.1648.929.763101110111213137.929
Percentage of IntangibleAssetsNetExcludingGoodwill14.912.913.313.814.313.714.114.615.215.514.514.815.115.514.750.5
Percentage of Assets0.00.00.10.10.10.10.10.10.10.10.10.10.10.10.10.1
Percentage of Assets us-gaap:OperatingSegments us-gaap:AllOtherSegments9.17.88.59.711.010.711.713.214.015.515.717.419.419.820.111.1

us-gaap:OperatingSegments, us-gaap:Banking


Intangible
Period End2020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312016-12-31
Value1516151617151718202123257.107
Percentage of IntangibleAssetsNetExcludingGoodwill26.927.625.226.026.623.524.125.225.726.226.827.645.3
Percentage of Assets0.10.10.10.10.20.10.20.20.20.20.20.20.1
Percentage of Assets us-gaap:OperatingSegments us-gaap:Banking0.10.10.10.10.20.10.20.20.20.20.20.20.1

Finite Lived Intangible Assets Net

us-gaap:FiniteLivedIntangibleAssetsNet

us-gaap:FiniteLivedIntangibleAssetsNet


Finite
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312010-12-31
Value47495256605963676770737882869092977515161819209.35110101112131415141516171813141514
Percentage of FiniteLivedIntangibleAssetsNet100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets0.30.30.40.40.40.50.60.60.60.60.70.70.80.80.80.90.90.90.20.20.20.20.20.10.10.10.20.20.20.20.20.20.20.20.20.20.20.20.20.3

us-gaap:FiniteLivedIntangibleAssetsNet us-gaap:FiniteLivedIntangibleAssetsByMajorClass

us-gaap:CoreDeposits


Finite
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312010-12-31
Value11121315161516171517182021232526286.5537.1077.7138.3799.0699.7897.8948.5749.284101011121311121314159.941101110
Percentage of FiniteLivedIntangibleAssetsNet23.625.226.126.927.625.226.026.623.524.125.225.726.226.827.628.929.28.645.345.445.745.946.984.482.985.384.984.684.384.086.883.983.783.483.182.974.374.374.277.7
Percentage of Assets0.10.10.10.10.10.10.10.20.10.20.20.20.20.20.20.20.30.10.10.10.10.10.10.10.10.10.10.10.20.20.20.20.20.20.20.20.10.20.20.2
Percentage of Assets us-gaap:CoreDeposits0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:OtherIntangibleAssets


Finite
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312010-12-31
Value3637394143444649515355586163656669698.5959.2649.95710111.4571.7671.5961.7761.9762.1782.3972.0482.262.4652.6972.9393.1913.4443.7153.9953.125
Percentage of FiniteLivedIntangibleAssetsNet76.474.873.973.172.474.874.073.476.575.974.874.373.873.272.471.170.891.454.754.654.354.153.115.617.114.715.115.415.716.013.216.116.316.616.917.125.725.725.822.3
Percentage of Assets0.20.30.30.30.30.40.40.40.50.50.50.50.60.60.60.60.60.80.10.10.10.10.10.00.00.00.00.00.00.00.00.00.00.00.00.00.00.10.10.1
Percentage of Assets us-gaap:OtherIntangibleAssets0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

Operating Lease Right Of Use Asset

us-gaap:OperatingLeaseRightOfUseAsset

us-gaap:OperatingLeaseRightOfUseAsset


Operating
Period End2020-12-312019-12-312019-09-302019-06-302019-03-31
Value3439413734
Percentage of OperatingLeaseRightOfUseAsset100.0100.0100.0100.0100.0
Percentage of Assets0.30.30.40.40.3

us-gaap:OperatingLeaseRightOfUseAsset us-gaap:Ownership

cbu:SevenZeroSixNorthClinton


Operating
Period End2020-12-312019-12-312019-09-302019-06-302019-03-31
Value4.54.95.05.15.2
Percentage of OperatingLeaseRightOfUseAsset12.912.311.913.514.9
Percentage of Assets0.00.00.00.00.0
Percentage of Assets cbu:SevenZeroSixNorthClinton0.00.00.00.00.0

Equity Securities Fv Ni

us-gaap:EquitySecuritiesFvNi

us-gaap:EquitySecuritiesFvNi


Equity
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302017-12-31
Value469000.0469000.0445000.0423000.0433000.0421000.0451000.0461000.0450000.0464000.0432000.0498000.0504000.00
Percentage of EquitySecuritiesFvNi100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.00.0
Percentage of Assets0.00.00.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:EquitySecuritiesFvNi us-gaap:FairValueByFairValueHierarchyLevel, us-gaap:FairValueByMeasurementFrequency

us-gaap:FairValueInputsLevel1, us-gaap:FairValueMeasurementsRecurring


Equity
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-30
Value469000.0469000.0445000.0423000.0433000.0421000.0451000.0461000.0450000.0464000.0432000.0498000.0504000.0
Percentage of EquitySecuritiesFvNi100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets0.00.00.00.00.00.00.00.00.00.00.00.00.0
Percentage of Assets us-gaap:FairValueInputsLevel1 us-gaap:FairValueMeasurementsRecurring0.00.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:EquitySecuritiesFvNi us-gaap:FairValueByMeasurementFrequency

us-gaap:FairValueMeasurementsRecurring


Equity
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-30
Value469000.0469000.0445000.0423000.0433000.0421000.0451000.0461000.0450000.0464000.0432000.0498000.0504000.0
Percentage of EquitySecuritiesFvNi100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets0.00.00.00.00.00.00.00.00.00.00.00.00.0
Percentage of Assets us-gaap:FairValueMeasurementsRecurring0.00.00.00.00.00.00.00.00.00.00.00.00.0

Other Assets

us-gaap:OtherAssets

us-gaap:OtherAssets


Other
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302010-12-31
Value3032772812792592482432532492322232372382352492392211891801711671701701481751411401581561751521231071211171091081251079411483
Percentage of OtherAssets100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets2.01.92.02.01.92.12.12.22.32.12.12.22.22.12.32.22.02.12.12.01.92.02.01.92.21.91.92.12.12.42.11.71.51.71.61.51.51.81.71.51.81.5

us-gaap:OtherAssets dei:LegalEntity, us-gaap:ConsolidatedEntities

cbu:SevenZeroSixNorthClinton, us-gaap:VariableInterestEntityPrimaryBeneficiary


Other
Period End2020-12-312019-12-312018-12-31
Value0.0480.0420.033
Percentage of OtherAssets0.00.00.0
Percentage of Assets0.00.00.0
Percentage of Assets cbu:SevenZeroSixNorthClinton us-gaap:VariableInterestEntityPrimaryBeneficiary0.80.70.5

us-gaap:OtherAssets us-gaap:ConsolidatedEntities

srt:ParentCompany


Other
Period End2020-12-312019-12-312018-12-312017-12-31
Value15128.9579.15
Percentage of OtherAssets5.45.14.03.7
Percentage of Assets0.10.10.10.1
Percentage of Assets srt:ParentCompany0.70.60.50.5

Time Deposit Maturities Year One

us-gaap:TimeDepositMaturitiesYearOne

us-gaap:TimeDepositMaturitiesYearOne


Time
Period End2020-12-31
Value570
Percentage of TimeDepositMaturitiesYearOne100.0
Percentage of Assets4.1

Minority Interest

us-gaap:MinorityInterest dei:LegalEntity, us-gaap:ConsolidatedEntities

us-gaap:MinorityInterest

cbu:SevenZeroSixNorthClinton, us-gaap:VariableInterestEntityPrimaryBeneficiary


Minority
Period End2020-12-31
Value3000000.0
Percentage of MinorityInterest100.0
Percentage of Assets0.0
Percentage of Assets cbu:SevenZeroSixNorthClinton us-gaap:VariableInterestEntityPrimaryBeneficiary50.1

Lessee Operating Lease Liability Payments Due Year Two

us-gaap:LesseeOperatingLeaseLiabilityPaymentsDueYearTwo

us-gaap:LesseeOperatingLeaseLiabilityPaymentsDueYearTwo


Lessee
Period End2020-12-312019-12-312019-09-302019-06-302019-03-31
Value7505000.07952000.09372000.08284000.07967000.0
Percentage of LesseeOperatingLeaseLiabilityPaymentsDueYearTwo100.0100.0100.0100.0100.0
Percentage of Assets0.10.10.10.10.1

Lessee Operating Lease Liability Payments Due Year Three

us-gaap:LesseeOperatingLeaseLiabilityPaymentsDueYearThree

us-gaap:LesseeOperatingLeaseLiabilityPaymentsDueYearThree


Lessee
Period End2020-12-312019-12-312019-09-302019-06-302019-03-31
Value6336000.06664000.07934000.06703000.06396000.0
Percentage of LesseeOperatingLeaseLiabilityPaymentsDueYearThree100.0100.0100.0100.0100.0
Percentage of Assets0.00.10.10.10.1

Lessee Operating Lease Liability Payments Due Year Four

us-gaap:LesseeOperatingLeaseLiabilityPaymentsDueYearFour

us-gaap:LesseeOperatingLeaseLiabilityPaymentsDueYearFour


Lessee
Period End2020-12-312019-12-312019-09-302019-06-302019-03-31
Value4973000.05695000.06645000.05407000.05143000.0
Percentage of LesseeOperatingLeaseLiabilityPaymentsDueYearFour100.0100.0100.0100.0100.0
Percentage of Assets0.00.00.10.10.0

Lessee Operating Lease Liability Payments Due Year Five

us-gaap:LesseeOperatingLeaseLiabilityPaymentsDueYearFive

us-gaap:LesseeOperatingLeaseLiabilityPaymentsDueYearFive


Lessee
Period End2020-12-312019-12-312019-09-302019-06-302019-03-31
Value3688000.04565000.05674000.04437000.03393000.0
Percentage of LesseeOperatingLeaseLiabilityPaymentsDueYearFive100.0100.0100.0100.0100.0
Percentage of Assets0.00.00.00.00.0

us-gaap:LesseeOperatingLeaseLiabilityPaymentsDueYearFive us-gaap:Ownership

cbu:SevenZeroSixNorthClinton


Lessee
Period End2020-12-312019-12-312019-09-302019-06-302019-03-31
Value605000.0591000.0591000.0591000.0591000.0
Percentage of LesseeOperatingLeaseLiabilityPaymentsDueYearFive16.412.910.413.317.4
Percentage of Assets0.00.00.00.00.0
Percentage of Assets cbu:SevenZeroSixNorthClinton0.00.00.00.00.0

Lessee Operating Lease Liability Payments Due After Year Five

us-gaap:LesseeOperatingLeaseLiabilityPaymentsDueAfterYearFive

us-gaap:LesseeOperatingLeaseLiabilityPaymentsDueAfterYearFive


Lessee
Period End2020-12-312019-12-312019-09-302019-06-302019-03-31
Value8.22211151310
Percentage of LesseeOperatingLeaseLiabilityPaymentsDueAfterYearFive100.0100.0100.0100.0100.0
Percentage of Assets0.10.10.10.10.1

us-gaap:LesseeOperatingLeaseLiabilityPaymentsDueAfterYearFive us-gaap:Ownership

cbu:SevenZeroSixNorthClinton


Lessee
Period End2020-12-312019-12-312019-09-302019-06-302019-03-31
Value2.3412.9463.5383.5383.538
Percentage of LesseeOperatingLeaseLiabilityPaymentsDueAfterYearFive28.526.422.525.433.2
Percentage of Assets0.00.00.00.00.0
Percentage of Assets cbu:SevenZeroSixNorthClinton0.00.00.00.00.0

Operating Lease Liability

us-gaap:OperatingLeaseLiability

us-gaap:OperatingLeaseLiability


Operating
Period End2020-12-312019-12-312019-09-302019-06-302019-03-31
Value3540423835
Percentage of OperatingLeaseLiability100.0100.0100.0100.0100.0
Percentage of Assets0.30.40.40.40.3

us-gaap:OperatingLeaseLiability us-gaap:Ownership

cbu:SevenZeroSixNorthClinton


Operating
Period End2020-12-312019-12-312019-09-302019-06-302019-03-31
Value4.54.95.0395.1395.24
Percentage of OperatingLeaseLiability12.512.011.813.414.7
Percentage of Assets0.00.00.00.00.0
Percentage of Assets cbu:SevenZeroSixNorthClinton0.00.00.00.00.0

Lessee Operating Lease Liability Payments Due

us-gaap:LesseeOperatingLeaseLiabilityPaymentsDue

us-gaap:LesseeOperatingLeaseLiabilityPaymentsDue


Lessee
Period End2020-12-312019-12-312019-09-302019-06-302019-03-31
Value3945474340
Percentage of LesseeOperatingLeaseLiabilityPaymentsDue100.0100.0100.0100.0100.0
Percentage of Assets0.30.40.40.40.4

us-gaap:LesseeOperatingLeaseLiabilityPaymentsDue us-gaap:Ownership

cbu:SevenZeroSixNorthClinton


Lessee
Period End2020-12-312019-12-312019-09-302019-06-302019-03-31
Value5.315.9016.056.1976.345
Percentage of LesseeOperatingLeaseLiabilityPaymentsDue13.513.012.714.415.8
Percentage of Assets0.00.10.10.10.1
Percentage of Assets cbu:SevenZeroSixNorthClinton0.00.00.00.00.0

Lessee Operating Lease Liability Undiscounted Excess Amount

us-gaap:LesseeOperatingLeaseLiabilityUndiscountedExcessAmount

us-gaap:LesseeOperatingLeaseLiabilityUndiscountedExcessAmount


Lessee
Period End2020-12-312019-12-312019-09-302019-06-302019-03-31
Value3564000.04509000.04806000.04725000.04456000.0
Percentage of LesseeOperatingLeaseLiabilityUndiscountedExcessAmount100.0100.0100.0100.0100.0
Percentage of Assets0.00.00.00.00.0

us-gaap:LesseeOperatingLeaseLiabilityUndiscountedExcessAmount us-gaap:Ownership

cbu:SevenZeroSixNorthClinton


Lessee
Period End2020-12-312019-12-312019-09-302019-06-302019-03-31
Value791000.0964000.01011000.01058000.01105000.0
Percentage of LesseeOperatingLeaseLiabilityUndiscountedExcessAmount22.221.421.022.424.8
Percentage of Assets0.00.00.00.00.0
Percentage of Assets cbu:SevenZeroSixNorthClinton0.00.00.00.00.0

Stockholders Equity

us-gaap:StockholdersEquity

us-gaap:StockholdersEquity


Stockholders
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302010-12-312009-12-312008-12-31
Value20611971210420982081197618551840180917571713166816561631163515931572129611981240123612001140104510001013987965955918875865850877902904885840774755730607565544
Percentage of StockholdersEquity100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets13.913.515.115.215.516.716.315.916.816.116.215.715.614.915.214.714.514.513.814.214.113.913.313.112.613.413.212.912.812.412.311.912.112.112.011.912.412.211.911.611.411.210.50.0

us-gaap:StockholdersEquity us-gaap:ConsolidatedEntities

srt:ParentCompany


Stockholders
Period End2020-12-312019-12-312018-12-312017-12-31
Value2104185517131635
Percentage of StockholdersEquity100.0100.0100.0100.0
Percentage of Assets15.116.316.215.2
Percentage of Assets srt:ParentCompany95.094.193.591.9

us-gaap:StockholdersEquity us-gaap:CumulativeEffectPeriodOfAdoption

srt:CumulativeEffectPeriodOfAdoptionAdjustment


Stockholders
Period End2020-12-312018-12-31
Value1.140.0
Percentage of StockholdersEquity0.10.0
Percentage of Assets0.00.0
Percentage of Assets srt:CumulativeEffectPeriodOfAdoptionAdjustment0.00.0

us-gaap:StockholdersEquity us-gaap:CumulativeEffectPeriodOfAdoption, us-gaap:AdjustmentsForNewAccountingPronouncements

srt:CumulativeEffectPeriodOfAdoptionAdjustment, us-gaap:AccountingStandardsUpdate201613


Stockholders
Period End2020-09-302020-03-312019-12-31
Value1.140.530.53
Percentage of StockholdersEquity0.10.00.0
Percentage of Assets0.00.00.0
Percentage of Assets srt:CumulativeEffectPeriodOfAdoptionAdjustment us-gaap:AccountingStandardsUpdate2016130.00.00.0

us-gaap:StockholdersEquity us-gaap:CumulativeEffectPeriodOfAdoption, us-gaap:AdjustmentsForNewAccountingPronouncements, us-gaap:StatementEquityComponents

srt:CumulativeEffectPeriodOfAdoptionAdjustment, us-gaap:AccountingStandardsUpdate201613, us-gaap:RetainedEarnings


Stockholders
Period End2020-09-302020-03-312019-12-31
Value1.140.530.53
Percentage of StockholdersEquity0.10.00.0
Percentage of Assets0.00.00.0
Percentage of Assets srt:CumulativeEffectPeriodOfAdoptionAdjustment us-gaap:AccountingStandardsUpdate201613 us-gaap:RetainedEarnings0.00.00.0

us-gaap:StockholdersEquity us-gaap:CumulativeEffectPeriodOfAdoption, us-gaap:StatementEquityComponents

srt:CumulativeEffectPeriodOfAdoptionAdjustment, us-gaap:RetainedEarnings


Stockholders
Period End2020-12-312018-12-31
Value1.140.208
Percentage of StockholdersEquity0.10.0
Percentage of Assets0.00.0
Percentage of Assets srt:CumulativeEffectPeriodOfAdoptionAdjustment us-gaap:RetainedEarnings0.00.0

us-gaap:StockholdersEquity us-gaap:StatementEquityComponents

us-gaap:AccumulatedOtherComprehensiveIncome


Stockholders
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302010-12-312009-12-312008-12-31
Value-48.4-109.95762839083-10.2262.47-4.621-26.762-45.305-62.142-46.491-35.226-3.6991617107.84366816119451848302021-1.066-26.546-28.401-27.716135466572429239.456-9.34-8.784-12.864
Percentage of StockholdersEquity-2.3-5.63.04.04.34.2-0.60.1-0.3-1.5-2.6-3.7-2.8-2.2-0.21.01.10.80.75.36.65.11.74.41.94.83.12.12.3-0.1-3.0-3.3-3.31.56.07.36.53.03.83.11.3-1.5-1.6-2.4
Percentage of Assets-0.3-0.80.40.60.70.7-0.10.0-0.0-0.2-0.4-0.6-0.4-0.3-0.00.10.20.10.10.80.90.70.20.60.20.60.40.30.3-0.0-0.4-0.4-0.40.20.70.90.80.40.40.40.1-0.2-0.20.0
Percentage of Assets us-gaap:AccumulatedOtherComprehensiveIncome0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:AdditionalPaidInCapital


Stockholders
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302010-12-312009-12-312008-12-31
Value10371034102510211019935927921917913911907904898894889887627545540535531528421417413409405403402396392387383378376373372313309308225216212
Percentage of StockholdersEquity50.352.548.748.749.047.350.050.150.752.053.254.454.655.054.755.956.448.445.643.643.344.346.340.341.740.841.542.042.343.845.345.345.543.841.941.642.244.340.541.042.337.138.339.0
Percentage of Assets7.07.17.47.47.67.98.17.98.58.48.68.58.58.28.38.28.27.06.36.26.16.26.25.35.35.55.55.45.45.45.65.45.55.35.05.05.25.44.84.84.84.14.00.0
Percentage of Assets us-gaap:AdditionalPaidInCapital0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:CommonStock


Stockholders
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302010-12-312009-12-312008-12-31
Value5454535353525151515151515151515151464444444444414141414141414141404040404040373737343333
Percentage of StockholdersEquity2.62.72.62.62.62.62.82.82.92.93.03.13.13.13.13.23.33.63.83.63.63.73.94.04.24.14.24.34.34.54.74.74.84.64.54.54.64.84.95.05.25.65.96.1
Percentage of Assets0.40.40.40.40.40.40.50.40.50.50.50.50.50.50.50.50.50.50.50.50.50.50.50.50.50.60.60.60.60.60.60.60.60.60.50.50.60.60.60.60.60.60.60.0
Percentage of Assets us-gaap:CommonStock0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:DeferredCompensationShareBasedPayments


Stockholders
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302016-12-312015-12-312014-12-31
Value8.2388.1789.1279.068.9958.9310109.9799.913111111111313130.00.00.0
Percentage of StockholdersEquity0.40.40.40.40.40.50.50.50.60.60.70.70.70.70.80.80.80.00.00.0
Percentage of Assets0.10.10.10.10.10.10.10.10.10.10.10.10.10.10.10.10.10.00.00.0
Percentage of Assets us-gaap:DeferredCompensationShareBasedPayments0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:RetainedEarnings


Stockholders
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302010-12-312009-12-312008-12-31
Value1015990960936915902882861843817795774750723700645627626614602589577566560547536525515504492481477466456447438431420411402391374342329
Percentage of StockholdersEquity49.350.245.644.644.045.647.646.846.646.546.446.445.344.342.840.539.948.351.348.647.748.149.753.654.852.953.253.352.953.655.055.254.952.049.548.548.750.053.253.353.761.760.660.6
Percentage of Assets6.96.86.96.86.87.67.77.47.87.57.57.37.16.66.55.95.87.07.16.96.76.76.67.06.97.17.06.96.86.76.86.56.66.36.05.86.06.16.36.26.16.96.30.0
Percentage of Assets us-gaap:RetainedEarnings0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:TreasuryStock


Stockholders
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302010-12-312009-12-312008-12-31
Value-5.632-5.572-6.198-6.131-6.066-6.005-6.823-6.875-8.797-9.601-11.528-14.803-15.334-17.633-21.014-22.44-23.523-14.028-15.16-13.428-13.929-13.961-17.637-24.044-25.453-27.269-20.391-16.982-16.982-17.115-17.115-17.115-17.115-17.115-17.408-17.473-17.533-17.533-17.683-17.731-17.776-17.776-18.17-18.267
Percentage of StockholdersEquity-0.3-0.3-0.3-0.3-0.3-0.3-0.4-0.4-0.5-0.5-0.7-0.9-0.9-1.1-1.3-1.4-1.5-1.1-1.3-1.1-1.1-1.2-1.5-2.3-2.5-2.7-2.1-1.8-1.8-1.9-2.0-2.0-2.0-2.0-1.9-1.9-2.0-2.1-2.3-2.3-2.4-2.9-3.2-3.4
Percentage of Assets-0.0-0.0-0.0-0.0-0.0-0.1-0.1-0.1-0.1-0.1-0.1-0.1-0.1-0.2-0.2-0.2-0.2-0.2-0.2-0.2-0.2-0.2-0.2-0.3-0.3-0.4-0.3-0.2-0.2-0.2-0.2-0.2-0.2-0.2-0.2-0.2-0.2-0.3-0.3-0.3-0.3-0.3-0.30.0
Percentage of Assets us-gaap:TreasuryStock0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

Additional Paid In Capital

us-gaap:AdditionalPaidInCapital

us-gaap:AdditionalPaidInCapital


Additional
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312014-12-31
Value10371034102510211019935927921917913911907904898894889887627545540535531528409
Percentage of AdditionalPaidInCapital100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets7.07.17.47.47.67.98.17.98.58.48.68.58.58.28.38.28.27.06.36.26.16.26.25.5

Retained Earnings Accumulated Deficit

us-gaap:RetainedEarningsAccumulatedDeficit

us-gaap:RetainedEarningsAccumulatedDeficit


Retained
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302010-12-31
Value1015990960936915902882861843817795774750723700645627626614602589577566560547536525515504492481477466456447438431420411402391374
Percentage of RetainedEarningsAccumulatedDeficit100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets6.96.86.96.86.87.67.77.47.87.57.57.37.16.66.55.95.87.07.16.96.76.76.67.06.97.17.06.96.86.76.86.56.66.36.05.86.06.16.36.26.16.9

us-gaap:RetainedEarningsAccumulatedDeficit us-gaap:CumulativeEffectPeriodOfAdoption, us-gaap:AdjustmentsForNewAccountingPronouncements

srt:CumulativeEffectPeriodOfAdoptionAdjustment, us-gaap:AccountingStandardsUpdate201613


Retained
Period End2020-12-312019-12-31
Value1.10.5
Percentage of RetainedEarningsAccumulatedDeficit0.10.1
Percentage of Assets0.00.0
Percentage of Assets srt:CumulativeEffectPeriodOfAdoptionAdjustment us-gaap:AccountingStandardsUpdate2016130.00.0

Accumulated Other Comprehensive Income Loss Net Of Tax

us-gaap:AccumulatedOtherComprehensiveIncomeLossNetOfTax

us-gaap:AccumulatedOtherComprehensiveIncomeLossNetOfTax


Accumulated
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312009-12-31
Value-48.4-109.95762839083-10.2262.47-4.621-26.762-45.305-62.142-46.491-35.226-3.6991617107.84366816119451848302021-1.066-26.546-28.401-27.716135466572429239.456-3.223-9.34-8.784
Percentage of AccumulatedOtherComprehensiveIncomeLossNetOfTax100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets-0.3-0.80.40.60.70.7-0.10.0-0.0-0.2-0.4-0.6-0.4-0.3-0.00.10.20.10.10.80.90.70.20.60.20.60.40.30.3-0.0-0.4-0.4-0.40.20.70.90.80.40.40.40.1-0.1-0.2-0.2

Treasury Stock Value

us-gaap:TreasuryStockValue

us-gaap:TreasuryStockValue


Treasury
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302010-12-31
Value5.6325.5726.1986.1316.0666.0056.8236.8758.7979.6011114151721222314151313131724252720161617171717171717171717171717
Percentage of TreasuryStockValue100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets0.00.00.00.00.00.10.10.10.10.10.10.10.10.20.20.20.20.20.20.20.20.20.20.30.30.40.30.20.20.20.20.20.20.20.20.20.20.30.30.30.30.3

Minority Interest

us-gaap:MinorityInterest dei:LegalEntity, us-gaap:ConsolidatedEntities

us-gaap:MinorityInterest

cbu:SevenZeroSixNorthClinton, us-gaap:VariableInterestEntityPrimaryBeneficiary


Minority
Period End2020-12-31
Value3000000.0
Percentage of MinorityInterest100.0
Percentage of Assets0.0
Percentage of Assets cbu:SevenZeroSixNorthClinton us-gaap:VariableInterestEntityPrimaryBeneficiary50.1

Adjustments To Additional Paid In Capital Sharebased Compensation Requisite Service Period Recognition Value

us-gaap:AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue

us-gaap:AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue


Adjustments
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-30
Value1568000.01674000.01771000.01415000.01281000.01952000.01287000.01241000.01366000.01391000.01457000.01211000.01681000.01715000.01152000.01255000.01320000.01410000.01391000.01172000.01001000.01219000.01037000.01014000.0999000.01151000.0920000.0985000.0906000.01182000.0947000.0907000.0887000.01220000.0813000.0819000.0813000.01223000.0746000.0746000.0
Percentage of AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue us-gaap:StatementEquityComponents

us-gaap:AdditionalPaidInCapital


Adjustments
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-30
Value1568000.01674000.01771000.01415000.01281000.01952000.01287000.01241000.01366000.01391000.01457000.01211000.01681000.01715000.01152000.01255000.01320000.01410000.01391000.01172000.01001000.01219000.01037000.01014000.0999000.01151000.0920000.0985000.0906000.01182000.0947000.0907000.0887000.01220000.0813000.0819000.0813000.01223000.0746000.0746000.0
Percentage of AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0
Percentage of Assets us-gaap:AdditionalPaidInCapital0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

Net Cash Provided By Used In Operating Activities

us-gaap:NetCashProvidedByUsedInOperatingActivities

us-gaap:NetCashProvidedByUsedInOperatingActivities


Net
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-31
Value266154296826733955345454506050464942313329263116342120362328
Percentage of NetCashProvidedByUsedInOperatingActivities100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of InterestAndDividendIncomeOperating27.563.355.630.770.627.573.539.658.637.359.360.555.768.956.752.960.761.043.847.345.942.247.424.553.331.728.250.732.742.8

Net Cash Provided By Used In Investing Activities

us-gaap:NetCashProvidedByUsedInInvestingActivities

us-gaap:NetCashProvidedByUsedInInvestingActivities


Net
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-30
Value-19.232-414.982-320.541123-251.21249-708.616-65.1055665015-50.4622031556737-28.509-18.548-10.456-45.245-235.781495-246.997-48.29235310557-220.426-612.102-68.5044812-18.525440.856
Percentage of NetCashProvidedByUsedInInvestingActivities100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of InterestAndDividendIncomeOperating-20.2-424.9-328.4126.8-258.550.9-708.3-66.0600.154.417.3-55.522.235.962.375.745.5-40.8-25.4-14.7-70.6-372.8751.1-373.5-75.3519.914.3781.5-312.5-906.7-97.369.317.4-30.772.11.4

Net Cash Provided By Used In Financing Activities

us-gaap:NetCashProvidedByUsedInFinancingActivities

us-gaap:NetCashProvidedByUsedInFinancingActivities


Net
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-30
Value4785875363973248-173.912165-255.086211-115.8212.185-364.676230-127.045-92.005-157.991103-1.08-23.36624212-551.235256-167.64-272.906-89.753-437.341196390-49.71273-62.68280-37.99318
Percentage of NetCashProvidedByUsedInFinancingActivities100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of InterestAndDividendIncomeOperating49.9879.277.4372.51001.2255.9-173.8167.5-270.4228.2-125.32.4-400.7260.4-141.8-104.0-194.0147.5-1.5-32.837.9336.6-835.7387.8-261.4-401.8-124.7-612.6278.2578.3-70.6104.0-89.7133.6-61.330.0

Increase Decrease In Other Operating Capital Net

us-gaap:IncreaseDecreaseInOtherOperatingCapitalNet

us-gaap:IncreaseDecreaseInOtherOperatingCapitalNet


Increase
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-30
Value20-13.396-10.00520-19.63126-22.6979.746-6.45816-1.483-3.2113.616-9.1745.534-1.227-22.967-7.43151.093-10.1135.4652.5653.802-3.0295.4465.458-4.888-0.455-0.1054.9511-9.0983.96413-12.0263.208-3.99719-3.092-4.882.4164.049-1.961
Percentage of IncreaseDecreaseInOtherOperatingCapitalNet100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

Net Cash Provided By Used In Operating Activities

us-gaap:NetCashProvidedByUsedInOperatingActivities

us-gaap:NetCashProvidedByUsedInOperatingActivities


Net
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-31
Value266154296826733955345454506050464942313329263116342120362328
Percentage of NetCashProvidedByUsedInOperatingActivities100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of InterestAndDividendIncomeOperating27.563.355.630.770.627.573.539.658.637.359.360.555.768.956.752.960.761.043.847.345.942.247.424.553.331.728.250.732.742.8

Net Income Loss

us-gaap:NetIncomeLoss

us-gaap:NetIncomeLoss


Net
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-30
Value475246423540423945414043444072351726262725242025232223222322152121201818211818201716151716
Percentage of NetIncomeLoss100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of InterestAndDividendIncomeOperating50.354.147.643.936.341.442.939.847.745.344.247.449.045.480.439.821.137.536.238.136.435.029.538.337.335.735.834.836.935.123.533.332.929.826.125.729.927.927.028.425.726.825.627.625.8

us-gaap:NetIncomeLoss us-gaap:StatementEquityComponents

us-gaap:RetainedEarnings


Net
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-30
Value47524642354042394541404344407235172626272524202523222322232215212120181821181820
Percentage of NetIncomeLoss100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of InterestAndDividendIncomeOperating50.354.147.643.936.341.442.939.847.745.344.247.449.045.480.439.821.137.536.238.136.435.029.538.337.335.735.834.836.935.123.533.332.929.826.125.729.927.927.028.4
Percentage of InterestAndDividendIncomeOperating us-gaap:RetainedEarnings0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

Share Based Compensation

us-gaap:ShareBasedCompensation

us-gaap:ShareBasedCompensation


Share
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-30
Value1568000.01674000.01771000.01415000.01281000.01952000.01287000.01241000.01366000.01391000.01457000.01211000.01681000.01715000.01152000.01255000.01320000.01410000.01391000.01172000.01001000.01219000.01037000.01014000.0999000.01151000.0920000.0985000.0906000.01182000.0947000.0907000.0887000.01220000.0813000.0819000.0813000.01223000.0746000.0746000.01030000.01262000.0756000.0766000.0
Percentage of ShareBasedCompensation100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

Net Cash Provided By Used In Investing Activities

us-gaap:NetCashProvidedByUsedInInvestingActivities

us-gaap:NetCashProvidedByUsedInInvestingActivities


Net
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-30
Value-19.232-414.982-320.541123-251.21249-708.616-65.1055665015-50.4622031556737-28.509-18.548-10.456-45.245-235.781495-246.997-48.29235310557-220.426-612.102-68.5044812-18.525440.856
Percentage of NetCashProvidedByUsedInInvestingActivities100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of InterestAndDividendIncomeOperating-20.2-424.9-328.4126.8-258.550.9-708.3-66.0600.154.417.3-55.522.235.962.375.745.5-40.8-25.4-14.7-70.6-372.8751.1-373.5-75.3519.914.3781.5-312.5-906.7-97.369.317.4-30.772.11.4

Payments To Acquire Property Plant And Equipment

us-gaap:PaymentsToAcquirePropertyPlantAndEquipment

us-gaap:PaymentsToAcquirePropertyPlantAndEquipment


Payments
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-30
Value4.8130.8765.6684.0861.6213.020.6611.0622.7361.2273.7433.6053.7421.5563.1182.3113.3022.0884.612.2632.932.6393.2163.3742.4893.3215.5374.0122.4321.3952.6293.8714.8532.5023.7432.9713.5720.56-16.5082.662.0982.137-27.2134.821
Percentage of PaymentsToAcquirePropertyPlantAndEquipment100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

Net Cash Provided By Used In Financing Activities

us-gaap:NetCashProvidedByUsedInFinancingActivities

us-gaap:NetCashProvidedByUsedInFinancingActivities


Net
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-30
Value4785875363973248-173.912165-255.086211-115.8212.185-364.676230-127.045-92.005-157.991103-1.08-23.36624212-551.235256-167.64-272.906-89.753-437.341196390-49.71273-62.68280-37.99318
Percentage of NetCashProvidedByUsedInFinancingActivities100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of InterestAndDividendIncomeOperating49.9879.277.4372.51001.2255.9-173.8167.5-270.4228.2-125.32.4-400.7260.4-141.8-104.0-194.0147.5-1.5-32.837.9336.6-835.7387.8-261.4-401.8-124.7-612.6278.2578.3-70.6104.0-89.7133.6-61.330.0

Payments Of Dividends Common Stock

us-gaap:PaymentsOfDividendsCommonStock

us-gaap:PaymentsOfDividendsCommonStock


Payments
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-30
Value222222212121211919191917171717161414141313131212121212111111111010101010109.6099.5768.8318.0217.9767.967.955
Percentage of PaymentsOfDividendsCommonStock100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

Payments For Repurchase Of Common Stock

us-gaap:PaymentsForRepurchaseOfCommonStock

us-gaap:PaymentsForRepurchaseOfCommonStock


Payments
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-31
Value60000.068000.067000.065000.065000.074000.073000.068000.066000.079000.078000.070000.069000.081000.080000.0148000.03078000.002754000.00716000.001000.0009125000.04368000.0000
Percentage of PaymentsForRepurchaseOfCommonStock100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.00.0100.00.0100.00.0100.00.00.0100.0100.00.00.00.0

Share Based Compensation Arrangement By Share Based Payment Award Options Outstanding Weighted Average Exercise Price

us-gaap:ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice us-gaap:AwardType

us-gaap:ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice

us-gaap:EmployeeStockOption


Share
Period End2020-12-312019-12-312018-12-312017-12-312016-12-312015-12-312014-12-312013-12-312012-12-312011-12-31
Value45.4942.8238.3634.5730.8528.1525.9224.0322.8621.43
Percentage of ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

Deferred Tax Liabilities

us-gaap:DeferredTaxLiabilities

us-gaap:DeferredTaxLiabilities


Deferred
Period End2020-12-312019-12-312018-12-312017-12-312016-12-312015-12-312014-12-312013-12-312012-12-312011-12-312010-12-31
Value88665868736610156926440
Percentage of DeferredTaxLiabilities100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

Deferred Tax Assets Net

us-gaap:DeferredTaxAssetsNet

us-gaap:DeferredTaxAssetsNet


Deferred
Period End2020-12-312019-12-312018-12-312017-12-312016-12-31
Value3228171530
Percentage of DeferredTaxAssetsNet100.0100.0100.0100.0100.0

Unrecognized Tax Benefits

us-gaap:UnrecognizedTaxBenefits

us-gaap:UnrecognizedTaxBenefits


Unrecognized
Period End2020-12-312019-12-312018-12-312017-12-312016-12-312015-12-312014-12-312013-12-312012-12-312011-12-312010-12-312009-12-312008-12-31
Value00024000.092000.0127000.0162000.0138000.070000.0133000.098000.0708000.0856000.0
Percentage of UnrecognizedTaxBenefits0.00.00.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

cbu:AccretionAmortizationOnInvestmentsLoansAndBorrowings

cbu:AccretionAmortizationOnInvestmentsLoansAndBorrowings


Accretion
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-31
Value4.6027.1273.3992.0523.7892.1131.6311.0831.5181.9442.2632.3572.572.2142.2072.0671.9390.4061.1441.0211.3290.9111.1890.5950.910.595-6.4271.2990.9410.654
Percentage of AccretionAmortizationOnInvestmentsLoansAndBorrowings100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

cbu:BusinessCombinationProvisionalInformationInitialAccountingIncompleteAdjustmentAccruedInterestAndOtherLiabilities us-gaap:BusinessAcquisition

cbu:BusinessCombinationProvisionalInformationInitialAccountingIncompleteAdjustmentAccruedInterestAndOtherLiabilities

cbu:SteubenTrustCorporation


Business
Period End2020-09-30
Value1300000.0
Percentage of BusinessCombinationProvisionalInformationInitialAccountingIncompleteAdjustmentAccruedInterestAndOtherLiabilities100.0

cbu:BusinessCombinationProvisionalInformationInitialAccountingIncompleteAdjustmentLoans us-gaap:BusinessAcquisition

cbu:BusinessCombinationProvisionalInformationInitialAccountingIncompleteAdjustmentLoans

cbu:SteubenTrustCorporation


Business
Period End2020-09-30
Value200000.0
Percentage of BusinessCombinationProvisionalInformationInitialAccountingIncompleteAdjustmentLoans100.0

cbu:BusinessCombinationProvisionalInformationInitialAccountingIncompleteAdjustmentOtherAssets us-gaap:BusinessAcquisition

cbu:BusinessCombinationProvisionalInformationInitialAccountingIncompleteAdjustmentOtherAssets

cbu:SteubenTrustCorporation


Business
Period End2020-09-30
Value1700000.0
Percentage of BusinessCombinationProvisionalInformationInitialAccountingIncompleteAdjustmentOtherAssets100.0

cbu:DepositServiceFees

cbu:DepositServiceFees


Deposit
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-30
Value1414141412161616151516161819181816
Percentage of DepositServiceFees100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

cbu:EmployeeBenefitServices

cbu:EmployeeBenefitServices


Employee
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-31
Value272626252425242423242323222322202017111111121111111110101010-67.169.3979.3979.77
Percentage of EmployeeBenefitServices100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

cbu:InterestExpenseBorrowingsExcludingJuniorSubordinatedDebentureOwedToUnconsolidatedSubsidiaryTrust

cbu:InterestExpenseBorrowingsExcludingJuniorSubordinatedDebentureOwedToUnconsolidatedSubsidiaryTrust


Interest
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-31
Value253000.0268000.0289000.0292000.0430000.0558000.0451000.0347000.0429000.0621000.0621000.0796000.0446000.0480000.0
Percentage of InterestExpenseBorrowingsExcludingJuniorSubordinatedDebentureOwedToUnconsolidatedSubsidiaryTrust100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

cbu:MortgageBanking

cbu:MortgageBanking


Mortgage
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-31
Value331000.0688000.0-898000.03908000.01375000.0916000.0247000.0-138000.0213000.0201000.0
Percentage of MortgageBanking100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

cbu:NetGainLossOnSaleOfLoansAndOtherAssets

cbu:NetGainLossOnSaleOfLoansAndOtherAssets


Net
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-31
Value183000.0280000.01872000.01104000.0538000.0-9000.0-13000.021000.03000.0-22000.0-127000.061000.066000.080000.0-26000.0102000.0-310000.053000.0213000.0306000.0250000.068000.0132000.069000.0155000.0-176000.0
Percentage of NetGainLossOnSaleOfLoansAndOtherAssets100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

cbu:NumberOfBorrowersRepresenting75.6MillionInOutstandingLoanBalances

cbu:NumberOfBorrowersRepresenting75.6MillionInOutstandingLoanBalances


Number
Period End2021-06-302021-03-31
Value-35.047.0
Percentage of NumberOfBorrowersRepresenting75.6MillionInOutstandingLoanBalances100.0100.0

cbu:NumberOfBusinessBorrowersRepresenting75.1MillionInOutstandingLoanBalances

cbu:NumberOfBusinessBorrowersRepresenting75.1MillionInOutstandingLoanBalances


Number
Period End2021-06-302021-03-31
Value-34.042.0
Percentage of NumberOfBusinessBorrowersRepresenting75.1MillionInOutstandingLoanBalances100.0100.0

cbu:NumberOfConsumerBorrowersRepresenting0.5MillionInOutstandingLoanBalances

cbu:NumberOfConsumerBorrowersRepresenting0.5MillionInOutstandingLoanBalances


Number
Period End2021-06-302021-03-31
Value-1.05.0
Percentage of NumberOfConsumerBorrowersRepresenting0.5MillionInOutstandingLoanBalances100.0100.0

cbu:OtherBankingServices

cbu:OtherBankingServices


Other
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-31
Value980000.0854000.01179000.0924000.0755000.0895000.01253000.0945000.01147000.01536000.01026000.01536000.01163000.01243000.01196000.01704000.01407000.01159000.01438000.02863000.01597000.01579000.01061000.02045000.0799000.01055000.01149000.01867000.01608000.01190000.01516000.01671000.01020000.01038000.0774000.01405000.0896000.0994000.0731000.01499000.01627000.0794000.0
Percentage of OtherBankingServices100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

cbu:OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParentIncludingCumulativeEffectOfChangeInAccountingPrinciple

cbu:OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParentIncludingCumulativeEffectOfChangeInAccountingPrinciple


Other
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-30
Value61-172.034-21.885-6.0696.58793-12.6967.091221816-15.651-11.266
Percentage of OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParentIncludingCumulativeEffectOfChangeInAccountingPrinciple100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

cbu:PaymentsToAcquireEquityAndOtherSecurities

cbu:PaymentsToAcquireEquityAndOtherSecurities


Payments
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-31
Value0.0820.010.173.040.0060.0180.0580.00.120.0240.00.010.00.021
Percentage of PaymentsToAcquireEquityAndOtherSecurities100.0100.0100.0100.0100.0100.0100.00.0100.0100.00.0100.00.0100.0

cbu:PercentageOfTotalLoansOutstanding

cbu:PercentageOfTotalLoansOutstanding


Percentage
Period End2021-06-302021-03-31
Value-0.971.0
Percentage of PercentageOfTotalLoansOutstanding100.0100.0

cbu:PercentageOfUnemployment us-gaap:Range, us-gaap:StatementScenario, us-gaap:UnusualOrInfrequentItem

cbu:PercentageOfUnemployment

srt:Maximum, srt:ScenarioForecast, us-gaap:NaturalDisastersAndOtherCasualtyEvents


Percentage
Period End2021-09-30
Value0.12
Percentage of PercentageOfUnemployment100.0

srt:Minimum, srt:ScenarioForecast, us-gaap:NaturalDisastersAndOtherCasualtyEvents


Percentage
Period End2021-09-30
Value0.09
Percentage of PercentageOfUnemployment75.0

cbu:PercentageOfUnemployment us-gaap:Range, us-gaap:UnusualOrInfrequentItem

srt:Maximum, us-gaap:NaturalDisastersAndOtherCasualtyEvents


Percentage
Period End2021-06-302021-03-31
Value1.08.0
Percentage of PercentageOfUnemployment0.00.0

srt:Minimum, us-gaap:NaturalDisastersAndOtherCasualtyEvents


Percentage
Period End2021-06-302021-03-31
Value03.0
Percentage of PercentageOfUnemployment0.00.0

cbu:ProceedsFromRedemptionOfDebenturesAndPreferredSecurities us-gaap:Ownership

cbu:ProceedsFromRedemptionOfDebenturesAndPreferredSecurities

cbu:CommunityStatutoryTrust4


Proceeds
Period End2021-03-15
Value77
Percentage of ProceedsFromRedemptionOfDebenturesAndPreferredSecurities100.0

cbu:SteubenStatutoryTrust


Proceeds
Period End2020-09-15
Value2.1
Percentage of ProceedsFromRedemptionOfDebenturesAndPreferredSecurities0.0

cbu:ProvisionForLoanLeaseAndOtherLossesExcludingAcquisitionRelatedProvisionForCreditLosses

cbu:ProvisionForLoanLeaseAndOtherLossesExcludingAcquisitionRelatedProvisionForCreditLosses


Provision
Period End2021-06-302021-03-312020-09-302020-06-30
Value-4.338-5.7191.9456.573
Percentage of ProvisionForLoanLeaseAndOtherLossesExcludingAcquisitionRelatedProvisionForCreditLosses100.0100.0100.0100.0

cbu:ProvisionForLoanLeaseAndOtherLossesExcludingAcquisitionRelatedProvisionForCreditLosses us-gaap:AdjustmentsForNewAccountingPronouncements

us-gaap:AccountingStandardsUpdate201613


Provision
Period End2020-12-312020-09-302020-06-302020-03-31
Value-2.9611.9456.5735.594
Percentage of ProvisionForLoanLeaseAndOtherLossesExcludingAcquisitionRelatedProvisionForCreditLosses0.0100.0100.00.0

cbu:RepaymentsOfSubordinatedDebtHeldByUnconsolidatedSubsidiaryTrusts

cbu:RepaymentsOfSubordinatedDebtHeldByUnconsolidatedSubsidiaryTrusts


Repayments
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312018-12-31
Value0.0770.02.0620.00.00.00.0
Percentage of RepaymentsOfSubordinatedDebtHeldByUnconsolidatedSubsidiaryTrusts0.0100.00.0100.00.00.00.00.0

cbu:ServicingAssetMeasurementInput2 us-gaap:MeasurementInputType, us-gaap:ValuationTechnique

cbu:ServicingAssetMeasurementInput2

cbu:MeasurementInputAdequateCompensation, us-gaap:ValuationTechniqueDiscountedCashFlow


Servicing
Period End2020-09-302020-06-302020-03-31
Value-6993.007000.0
Percentage of ServicingAssetMeasurementInput2100.00.0100.0

cbu:ServicingAssetMeasurementInput2 us-gaap:Range, us-gaap:FairValueByFairValueHierarchyLevel, us-gaap:MeasurementInputType, us-gaap:ValuationTechnique

srt:WeightedAverage, us-gaap:FairValueInputsLevel3, us-gaap:MeasurementInputConstantPrepaymentRate, us-gaap:ValuationTechniqueDiscountedCashFlow


Servicing
Period End2021-03-31
Value15.7
Percentage of ServicingAssetMeasurementInput20.0

srt:WeightedAverage, us-gaap:FairValueInputsLevel3, us-gaap:MeasurementInputDiscountRate, us-gaap:ValuationTechniqueDiscountedCashFlow


Servicing
Period End2021-03-31
Value2.97
Percentage of ServicingAssetMeasurementInput20.0

cbu:SettlementOfBankOwnedLifeInsurancePolicies

cbu:SettlementOfBankOwnedLifeInsurancePolicies


Settlement
Period End2020-12-312019-12-312018-12-312018-09-302017-12-312017-09-302016-12-312016-09-302015-12-312015-09-30
Value000000646000.0000
Percentage of SettlementOfBankOwnedLifeInsurancePolicies0.00.00.00.00.00.0100.00.00.00.0

cbu:StockIssuedDuringPeriodSharesDeferredCompensationArrangements us-gaap:StatementEquityComponents

cbu:StockIssuedDuringPeriodSharesDeferredCompensationArrangements

cbu:CommonStockOutstanding


Stock
Period End2021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-31
Value18089.000022497.000032431.000035233.0
Percentage of StockIssuedDuringPeriodSharesDeferredCompensationArrangements100.00.00.00.0100.00.00.00.0100.00.00.00.0100.0

cbu:StockIssuedDuringPeriodSharesEmployeeStockOwnershipPlanNetOfImpactOfNetSettlementOfTaxWithholdingObligations us-gaap:StatementEquityComponents

cbu:StockIssuedDuringPeriodSharesEmployeeStockOwnershipPlanNetOfImpactOfNetSettlementOfTaxWithholdingObligations

cbu:CommonStockOutstanding


Stock
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-31
Value44493.0264780.056680.024584.0118970.0214590.0131760.037542.077666.0150920.029586.035261.0137740.0110410.0
Percentage of StockIssuedDuringPeriodSharesEmployeeStockOwnershipPlanNetOfImpactOfNetSettlementOfTaxWithholdingObligations100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

cbu:StockIssuedDuringPeriodValueDeferredCompensationArrangements us-gaap:StatementEquityComponents

cbu:StockIssuedDuringPeriodValueDeferredCompensationArrangements

us-gaap:AdditionalPaidInCapital


Stock
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-31
Value0323000.0000415000.00001064000.0
Percentage of StockIssuedDuringPeriodValueDeferredCompensationArrangements0.0100.00.00.00.0100.00.00.00.0100.0

us-gaap:DeferredCompensationShareBasedPayments


Stock
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-31
Value0-1017000.0000-1264000.0000-1894000.0000-1898000.0
Percentage of StockIssuedDuringPeriodValueDeferredCompensationArrangements0.0-314.90.00.00.0-304.60.00.00.0-178.00.00.00.00.0

us-gaap:TreasuryStock


Stock
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-31
Value0694000.0000849000.0000830000.00001898000.0
Percentage of StockIssuedDuringPeriodValueDeferredCompensationArrangements0.0214.90.00.00.0204.60.00.00.078.00.00.00.00.0

cbu:StockIssuedDuringPeriodValueEmployeeStockOwnershipPlanNetOfImpactOfNetSettlementOfTaxWithholdingObligations

cbu:StockIssuedDuringPeriodValueEmployeeStockOwnershipPlanNetOfImpactOfNetSettlementOfTaxWithholdingObligations


Stock
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-31
Value1.347.3291.6511.1186.6246.3994.4031.2912.065-0.8440.6491.154.0740.57
Percentage of StockIssuedDuringPeriodValueEmployeeStockOwnershipPlanNetOfImpactOfNetSettlementOfTaxWithholdingObligations100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

cbu:StockIssuedDuringPeriodValueEmployeeStockOwnershipPlanNetOfImpactOfNetSettlementOfTaxWithholdingObligations us-gaap:StatementEquityComponents

us-gaap:AdditionalPaidInCapital


Stock
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-31
Value1.2957.0651.5941.0926.5056.1844.2711.2541.987-0.9950.6191.1153.9360.46
Percentage of StockIssuedDuringPeriodValueEmployeeStockOwnershipPlanNetOfImpactOfNetSettlementOfTaxWithholdingObligations96.696.496.597.798.296.697.097.196.2117.995.497.096.680.7

us-gaap:CommonStock


Stock
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-31
Value0.0450.2640.0570.0260.1190.2150.1320.0370.0780.1510.030.0350.1380.11
Percentage of StockIssuedDuringPeriodValueEmployeeStockOwnershipPlanNetOfImpactOfNetSettlementOfTaxWithholdingObligations3.43.63.52.31.83.43.02.93.8-17.94.63.03.419.3

cbu:WealthManagementServices

cbu:WealthManagementServices


Wealth
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312011-09-302011-06-302010-09-302010-06-30
Value8.2278.1997.496.8896.3667.1346.5796.3636.5786.3496.4026.1686.4966.7065.9745.7075.5374.8614.7355.2264.6995.1162.9042.7822.42.666
Percentage of WealthManagementServices100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:AllowanceForLoanAndLeaseLossRecoveryOfBadDebts

us-gaap:AllowanceForLoanAndLeaseLossRecoveryOfBadDebts


Allowance
Period End2021-06-302021-03-312020-09-302020-06-302019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-30
Value1698000.01585000.01463000.01184000.01356000.01592000.01674000.01302000.01506000.01567000.01689000.01588000.01529000.01442000.01935000.01217000.01426000.01397000.01591000.01525000.01196000.01059000.01974000.01455000.01406000.01651000.01375000.01226000.01177000.01398000.01287000.01408000.01621000.01582000.01148000.0
Percentage of AllowanceForLoanAndLeaseLossRecoveryOfBadDebts100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:AllowanceForLoanAndLeaseLossRecoveryOfBadDebts us-gaap:AdjustmentsForNewAccountingPronouncements

us-gaap:AccountingStandardsUpdate201613


Allowance
Period End2020-12-312020-09-302020-06-302020-03-31
Value1545000.01463000.01184000.01497000.0
Percentage of AllowanceForLoanAndLeaseLossRecoveryOfBadDebts0.0100.0100.00.0

us-gaap:AllowanceForLoanAndLeaseLossRecoveryOfBadDebts us-gaap:AdjustmentsForNewAccountingPronouncements, us-gaap:CreditLossStatus

us-gaap:AccountingStandardsUpdate201613, us-gaap:FinancialAssetAcquiredWithCreditDeterioration


Allowance
Period End2020-12-312020-09-302020-06-302020-03-31
Value360000.032000.048000.00
Percentage of AllowanceForLoanAndLeaseLossRecoveryOfBadDebts0.02.24.10.0

us-gaap:AllowanceForLoanAndLeaseLossRecoveryOfBadDebts us-gaap:AdjustmentsForNewAccountingPronouncements, us-gaap:FinancingReceivablePortfolioSegment, us-gaap:FinancingReceivableRecordedInvestmentByClassOfFinancingReceivable

us-gaap:AccountingStandardsUpdate201613, us-gaap:CommercialPortfolioSegment, us-gaap:CommercialLoan


Allowance
Period End2020-12-312020-09-302020-06-302020-03-31
Value67000.067000.084000.0138000.0
Percentage of AllowanceForLoanAndLeaseLossRecoveryOfBadDebts0.04.67.10.0

us-gaap:AccountingStandardsUpdate201613, us-gaap:ConsumerPortfolioSegment, cbu:ConsumerInstallmentDirect


Allowance
Period End2020-12-312020-09-302020-06-302020-03-31
Value165000.0225000.0171000.0182000.0
Percentage of AllowanceForLoanAndLeaseLossRecoveryOfBadDebts0.015.414.40.0

us-gaap:AccountingStandardsUpdate201613, us-gaap:ConsumerPortfolioSegment, cbu:ConsumerInstallmentIndirect


Allowance
Period End2020-12-312020-09-302020-06-302020-03-31
Value885000.01111000.0833000.01163000.0
Percentage of AllowanceForLoanAndLeaseLossRecoveryOfBadDebts0.075.970.40.0

us-gaap:AccountingStandardsUpdate201613, us-gaap:ConsumerPortfolioSegment, cbu:HomeEquityReceivables


Allowance
Period End2020-12-312020-09-302020-06-302020-03-31
Value5000.05000.012000.06000.0
Percentage of AllowanceForLoanAndLeaseLossRecoveryOfBadDebts0.00.31.00.0

us-gaap:AccountingStandardsUpdate201613, us-gaap:ResidentialPortfolioSegment, us-gaap:ResidentialMortgage


Allowance
Period End2020-09-302020-06-302020-03-31
Value23000.036000.08000.0
Percentage of AllowanceForLoanAndLeaseLossRecoveryOfBadDebts1.63.00.0

us-gaap:AllowanceForLoanAndLeaseLossRecoveryOfBadDebts us-gaap:CreditLossStatus

us-gaap:FinancialAssetAcquiredWithCreditDeterioration


Allowance
Period End2021-06-302021-03-312020-09-302020-06-302019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-30
Value33000.027000.032000.048000.000000000000
Percentage of AllowanceForLoanAndLeaseLossRecoveryOfBadDebts1.91.72.24.10.00.00.00.00.00.00.00.00.00.00.0

us-gaap:AllowanceForLoanAndLeaseLossRecoveryOfBadDebts us-gaap:FinancingReceivablePortfolioSegment, us-gaap:FinancingReceivableRecordedInvestmentByClassOfFinancingReceivable

us-gaap:CommercialPortfolioSegment, us-gaap:CommercialLoan


Allowance
Period End2021-06-302021-03-312020-09-302020-06-302019-12-312019-09-302019-06-302019-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-30
Value255000.067000.067000.084000.0233000.0290000.0169000.0134000.0175000.0127000.0283000.071000.0105000.0220000.0156000.0136000.0162000.0107000.0527000.082000.0143000.0335000.0100000.0
Percentage of AllowanceForLoanAndLeaseLossRecoveryOfBadDebts15.04.24.67.117.218.210.110.311.48.814.65.87.415.79.88.913.510.126.75.610.220.37.3

us-gaap:ConsumerPortfolioSegment, cbu:ConsumerInstallmentDirect


Allowance
Period End2021-06-302021-03-312020-09-302020-06-302019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-30
Value213000.0231000.0225000.0171000.0143000.0167000.0221000.0179000.0195000.0223000.0167000.0222000.0201000.0221000.0182000.0245000.03463000.0246000.0238000.0221000.0156000.0174000.0199000.0193000.0169000.0239000.0226000.0
Percentage of AllowanceForLoanAndLeaseLossRecoveryOfBadDebts12.514.615.414.410.510.513.213.712.914.29.914.013.115.39.420.1242.817.615.014.513.016.410.113.312.014.516.4

us-gaap:ConsumerPortfolioSegment, cbu:ConsumerInstallmentIndirect


Allowance
Period End2021-06-302021-03-312020-09-302020-06-302019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-30
Value1183000.01246000.01111000.0833000.0884000.01095000.01239000.0962000.01186000.01190000.01347000.01151000.01137000.01058000.01452000.0869000.0-2245000.0892000.01140000.01114000.0866000.0740000.01184000.01152000.0947000.01025000.01005000.0
Percentage of AllowanceForLoanAndLeaseLossRecoveryOfBadDebts69.778.675.970.465.268.874.073.978.875.979.872.574.473.475.071.4-157.463.971.773.072.469.960.079.267.462.173.1

us-gaap:ConsumerPortfolioSegment, cbu:HomeEquityReceivables


Allowance
Period End2021-06-302021-03-312020-09-302020-06-302019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-30
Value5000.04000.05000.012000.080000.032000.031000.05000.017000.015000.07000.09000.08000.012000.07000.025000.084000.027000.019000.09000.07000.029000.019000.07000.09000.038000.032000.0
Percentage of AllowanceForLoanAndLeaseLossRecoveryOfBadDebts0.30.30.31.05.92.01.90.41.11.00.40.60.50.80.42.15.91.91.20.60.62.71.00.50.62.32.3

us-gaap:ResidentialPortfolioSegment, us-gaap:ResidentialMortgage


Allowance
Period End2021-06-302021-03-312020-09-302020-06-302019-12-312019-09-302019-06-302019-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-30
Value9000.010000.023000.036000.016000.08000.014000.022000.08000.024000.011000.07000.019000.012000.038000.045000.05000.09000.045000.021000.0138000.014000.012000.0
Percentage of AllowanceForLoanAndLeaseLossRecoveryOfBadDebts0.50.61.63.01.20.50.81.70.51.70.60.61.30.92.43.00.40.82.31.49.80.80.9

us-gaap:AllowanceForLoanAndLeaseLossesLoansAcquired us-gaap:AdjustmentsForNewAccountingPronouncements, us-gaap:CreditLossStatus

us-gaap:AllowanceForLoanAndLeaseLossesLoansAcquired

us-gaap:AccountingStandardsUpdate201613, us-gaap:FinancialAssetAcquiredWithCreditDeterioration


Allowance
Period End2020-12-312020-09-30
Value140000.00
Percentage of AllowanceForLoanAndLeaseLossesLoansAcquired100.00.0

us-gaap:AllowanceForLoanAndLeaseLossesLoansAcquired us-gaap:AdjustmentsForNewAccountingPronouncements, us-gaap:FinancingReceivablePortfolioSegment, us-gaap:FinancingReceivableRecordedInvestmentByClassOfFinancingReceivable

us-gaap:AccountingStandardsUpdate201613, us-gaap:CommercialPortfolioSegment, us-gaap:CommercialLoan


Allowance
Period End2020-12-312020-09-30
Value-140000.00
Percentage of AllowanceForLoanAndLeaseLossesLoansAcquired-100.00.0

us-gaap:AccountingStandardsUpdate201613, us-gaap:ResidentialPortfolioSegment, us-gaap:ResidentialMortgage


Allowance
Period End2020-09-30
Value0
Percentage of AllowanceForLoanAndLeaseLossesLoansAcquired0.0

us-gaap:AllowanceForLoanAndLeaseLossesWriteOffs

us-gaap:AllowanceForLoanAndLeaseLossesWriteOffs


Allowance
Period End2021-06-302021-03-312020-09-302020-06-302019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-31
Value1.1061.9662.722.0943.7253.232.8713.9014.853.2672.6224.7477.313.2243.0413.1823.6222.9242.9662.6714.712.6592.2882.4143.8692.742.8572.3484.1262.8812.0482.7764.2163.2363.284-3.446-16.3612.0262.063-2.558
Percentage of AllowanceForLoanAndLeaseLossesWriteOffs100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:AllowanceForLoanAndLeaseLossesWriteOffs us-gaap:AdjustmentsForNewAccountingPronouncements

us-gaap:AccountingStandardsUpdate201613


Allowance
Period End2020-12-312020-09-302020-06-302020-03-31
Value2.8032.722.0943.047
Percentage of AllowanceForLoanAndLeaseLossesWriteOffs0.0100.0100.00.0

us-gaap:AllowanceForLoanAndLeaseLossesWriteOffs us-gaap:AdjustmentsForNewAccountingPronouncements, us-gaap:CreditLossStatus

us-gaap:AccountingStandardsUpdate201613, us-gaap:FinancialAssetAcquiredWithCreditDeterioration


Allowance
Period End2020-12-312020-09-302020-06-302020-03-31
Value0.00.0910.0-0.0
Percentage of AllowanceForLoanAndLeaseLossesWriteOffs0.03.30.00.0

us-gaap:AllowanceForLoanAndLeaseLossesWriteOffs us-gaap:AdjustmentsForNewAccountingPronouncements, us-gaap:FinancingReceivablePortfolioSegment, us-gaap:FinancingReceivableRecordedInvestmentByClassOfFinancingReceivable

us-gaap:AccountingStandardsUpdate201613, us-gaap:CommercialPortfolioSegment, us-gaap:CommercialLoan


Allowance
Period End2020-12-312020-09-302020-06-302020-03-31
Value0.5780.7360.0070.176
Percentage of AllowanceForLoanAndLeaseLossesWriteOffs0.027.10.30.0

us-gaap:AccountingStandardsUpdate201613, us-gaap:ConsumerPortfolioSegment, cbu:ConsumerInstallmentDirect


Allowance
Period End2020-12-312020-09-302020-06-302020-03-31
Value0.4190.340.3410.533
Percentage of AllowanceForLoanAndLeaseLossesWriteOffs0.012.516.30.0

us-gaap:AccountingStandardsUpdate201613, us-gaap:ConsumerPortfolioSegment, cbu:ConsumerInstallmentIndirect


Allowance
Period End2020-12-312020-09-302020-06-302020-03-31
Value1.5911.2811.4312.079
Percentage of AllowanceForLoanAndLeaseLossesWriteOffs0.047.168.30.0

us-gaap:AccountingStandardsUpdate201613, us-gaap:ConsumerPortfolioSegment, cbu:HomeEquityReceivables


Allowance
Period End2020-12-312020-09-302020-06-302020-03-31
Value0.0210.0240.0810.073
Percentage of AllowanceForLoanAndLeaseLossesWriteOffs0.00.93.90.0

us-gaap:AccountingStandardsUpdate201613, us-gaap:ResidentialPortfolioSegment, us-gaap:ResidentialMortgage


Allowance
Period End2020-09-302020-06-302020-03-31
Value0.2480.2340.186
Percentage of AllowanceForLoanAndLeaseLossesWriteOffs9.111.20.0

us-gaap:AllowanceForLoanAndLeaseLossesWriteOffs us-gaap:CreditLossStatus

us-gaap:FinancialAssetAcquiredWithCreditDeterioration


Allowance
Period End2021-06-302021-03-312020-09-302020-06-302019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-30
Value0.00.00.091-0.00.0-0.0-0.00.00.0130.00.3230.0430.0860.00.183
Percentage of AllowanceForLoanAndLeaseLossesWriteOffs0.00.03.3-0.00.0-0.0-0.00.00.30.012.30.91.20.06.0

us-gaap:AllowanceForLoanAndLeaseLossesWriteOffs us-gaap:FinancingReceivablePortfolioSegment, us-gaap:FinancingReceivableRecordedInvestmentByClassOfFinancingReceivable

us-gaap:CommercialPortfolioSegment, us-gaap:CommercialLoan


Allowance
Period End2021-06-302021-03-312020-09-302020-06-302019-12-312019-09-302019-06-302019-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-30
Value0.0020.0510.7360.0070.560.3050.2531.2163.8970.1240.2450.6950.6090.2840.770.211.4790.2340.2990.1330.6180.4350.385
Percentage of AllowanceForLoanAndLeaseLossesWriteOffs0.22.627.10.315.09.48.831.253.33.88.121.816.89.726.07.931.48.813.15.516.015.913.5

us-gaap:ConsumerPortfolioSegment, cbu:ConsumerInstallmentDirect


Allowance
Period End2021-06-302021-03-312020-09-302020-06-302019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-30
Value0.1950.3180.340.3410.5090.4560.4450.5350.4530.4650.3640.4960.6180.5740.470.4176.3970.3950.3890.4620.4240.4270.2940.3450.3760.3070.42
Percentage of AllowanceForLoanAndLeaseLossesWriteOffs17.616.212.516.313.714.115.513.79.314.213.910.48.517.815.513.1176.613.513.117.39.016.112.814.39.711.214.7

us-gaap:ConsumerPortfolioSegment, cbu:ConsumerInstallmentIndirect


Allowance
Period End2021-06-302021-03-312020-09-302020-06-302019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-30
Value0.751.3991.2811.4312.1022.2241.4821.8232.3512.3641.3832.2842.4872.3281.6951.947-3.7332.0371.5451.8542.2931.5971.3971.4272.2111.7111.435
Percentage of AllowanceForLoanAndLeaseLossesWriteOffs67.871.247.168.356.468.951.646.748.572.452.748.134.072.255.761.2-103.169.752.169.448.760.161.159.157.162.450.2

us-gaap:ConsumerPortfolioSegment, cbu:HomeEquityReceivables


Allowance
Period End2021-06-302021-03-312020-09-302020-06-302019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-30
Value0.0170.0980.0240.0810.2220.0450.1040.0740.2190.2210.0470.0560.0560.00.190.0380.0760.0060.080.0570.0560.0660.0560.0660.3150.0740.246
Percentage of AllowanceForLoanAndLeaseLossesWriteOffs1.55.00.93.96.01.43.61.94.56.81.81.20.80.06.21.22.10.22.72.11.22.52.42.78.12.78.6

us-gaap:ResidentialPortfolioSegment, us-gaap:ResidentialMortgage


Allowance
Period End2021-06-302021-03-312020-09-302020-06-302019-12-312019-09-302019-06-302019-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-30
Value0.1420.10.2480.2340.3320.20.5870.2530.1660.1980.2580.0850.2020.2020.1560.0880.4570.2760.1990.4430.3410.2030.364
Percentage of AllowanceForLoanAndLeaseLossesWriteOffs12.85.19.111.28.96.220.46.52.36.18.52.75.66.95.33.39.710.48.718.48.87.412.7

us-gaap:AmortizationOfMortgageServicingRightsMSRs

us-gaap:AmortizationOfMortgageServicingRightsMSRs


Amortization
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-30
Value134000.0135000.0113000.0100000.084000.082000.093000.097000.090000.098000.0109000.0111000.0112000.0117000.0125000.0126000.0122000.0126000.0132000.0129000.0126000.0131000.0102000.0101000.0102000.0104000.0107000.0109000.0111000.0117000.0120000.0133000.0134000.0142000.0151000.0171000.0177000.0188000.0201000.0221000.0222000.0224000.0195000.0192000.0
Percentage of AmortizationOfMortgageServicingRightsMSRs100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:AmountOfDilutiveSecuritiesStockOptionsAndRestrictiveStockUnits

us-gaap:AmountOfDilutiveSecuritiesStockOptionsAndRestrictiveStockUnits


Amount
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-31
Value-127000.0-130000.0-82000.0-147000.0-127000.0-146000.0-69000.0-102000.0-146000.0-109000.0-181000.0-191000.0-188000.0-141000.0-210000.0-164000.0-83000.0-138000.0948000.0-157000.0-151000.0-89000.0805000.0-129000.0-99000.0-100000.0793000.0-115000.0-123000.0-99000.0748000.0-121000.0-114000.0-79000.0-871000.0125000.0144000.0-104000.0-967000.0147000.0136000.0-131000.0
Percentage of AmountOfDilutiveSecuritiesStockOptionsAndRestrictiveStockUnits100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:BankOwnedLifeInsuranceIncome

us-gaap:BankOwnedLifeInsuranceIncome


Bank
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-30
Value501000.0480000.0517000.0532000.0458000.0408000.0463000.0446000.0378000.0391000.0402000.0393000.0396000.0388000.0416000.0424000.0378000.0368000.0381000.0388000.0381000.0355000.0311000.0260000.0242000.0273000.0277000.0249000.0222000.0289000.0291000.0252000.0240000.0283000.0288000.0297000.0265000.0271000.0313000.0207000.0261000.0113000.0102000.076000.0
Percentage of BankOwnedLifeInsuranceIncome100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:BusinessAcquisitionsProFormaNetIncomeLoss us-gaap:BusinessAcquisition

us-gaap:BusinessAcquisitionsProFormaNetIncomeLoss

cbu:SteubenTrustCorporation


Business
Period End2020-09-302020-06-302019-09-302019-06-30
Value43394046
Percentage of BusinessAcquisitionsProFormaNetIncomeLoss100.0100.0100.0100.0

us-gaap:BusinessAcquisitionsProFormaRevenue us-gaap:BusinessAcquisition

us-gaap:BusinessAcquisitionsProFormaRevenue

cbu:SteubenTrustCorporation


Business
Period End2020-09-302020-06-302019-09-302019-06-30
Value152149154154
Percentage of BusinessAcquisitionsProFormaRevenue100.0100.0100.0100.0

us-gaap:BusinessCombinationAcquisitionRelatedCosts

us-gaap:BusinessCombinationAcquisitionRelatedCosts


Business
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-30
Value0.0040.0270.3960.7963.3720.3690.8196.0611.1940.5340.0-0.8320.071-0.0080.7940.58221.7161.3640.0020.2630.0775.7190.5620.3610.395-2.82.80.00.1232.110.0710.00.00.5264.7960.1640.260.1420.3813.6170.6910.6040.0570.199
Percentage of BusinessCombinationAcquisitionRelatedCosts100.0100.0100.0100.0100.0100.0100.0100.0100.0100.00.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.00.0100.0100.0100.00.00.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:BusinessCombinationAcquisitionRelatedCosts us-gaap:BusinessAcquisition

cbu:SteubenTrustCorporation


Business
Period End2020-12-312020-09-302020-06-30
Value0.50.83.3
Percentage of BusinessCombinationAcquisitionRelatedCosts126.3100.597.9

us-gaap:BusinessCombinationAcquisitionRelatedCosts us-gaap:ConsolidationItems, us-gaap:StatementBusinessSegments

us-gaap:OperatingSegments, cbu:BankingServices


Business
Period End2021-06-302021-03-312020-06-302020-03-31
Value0.0040.0273.3720.369
Percentage of BusinessCombinationAcquisitionRelatedCosts100.0100.0100.0100.0

us-gaap:OperatingSegments, cbu:EmployeeBenefitServices


Business
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-31
Value0.00.00.00.00.00.00.00.00.00.00.00.00.00.0070.0040.0110.1171.0620.4450.00.00.0
Percentage of BusinessCombinationAcquisitionRelatedCosts0.00.00.00.00.00.00.00.00.00.00.0-0.00.0-87.50.51.90.561.932.60.00.00.0

us-gaap:OperatingSegments, us-gaap:AllOtherSegments


Business
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-31
Value0.00.00.00.00.00.00.00.00.00.00.00.00.0060.00.0250.0350.050.133
Percentage of BusinessCombinationAcquisitionRelatedCosts0.00.00.00.00.00.00.00.00.00.00.0-0.08.5-0.03.16.00.27.8

us-gaap:OperatingSegments, us-gaap:Banking


Business
Period End2020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-30
Value0.7963.3720.3690.8196.0611.1940.5340.0-0.8320.065-0.0150.7650.53422
Percentage of BusinessCombinationAcquisitionRelatedCosts100.0100.0100.0100.0100.0100.0100.00.0100.091.5187.596.392.199.3

us-gaap:BusinessCombinationConsiderationTransferred1 us-gaap:BusinessAcquisition, us-gaap:SubsequentEventType

us-gaap:BusinessCombinationConsiderationTransferred1

cbu:FringeBenefitsDesignOfMinnesotaInc, us-gaap:SubsequentEvent


Business
Period End2021-07-01
Value15
Percentage of BusinessCombinationConsiderationTransferred1100.0

cbu:ThomasGregoryAssociates, us-gaap:SubsequentEvent


Business
Period End2021-08-02
Value11
Percentage of BusinessCombinationConsiderationTransferred10.0

us-gaap:BusinessCombinationConsiderationTransferredOther1 us-gaap:BusinessAcquisition, us-gaap:SubsequentEventType

us-gaap:BusinessCombinationConsiderationTransferredOther1

cbu:FringeBenefitsDesignOfMinnesotaInc, us-gaap:SubsequentEvent


Business
Period End2021-07-01
Value2700000.0
Percentage of BusinessCombinationConsiderationTransferredOther1100.0

cbu:ThomasGregoryAssociates, us-gaap:SubsequentEvent


Business
Period End2021-08-02
Value3400000.0
Percentage of BusinessCombinationConsiderationTransferredOther10.0

us-gaap:BusinessCombinationProvisionalInformationInitialAccountingIncompleteAdjustmentPropertyPlantAndEquipment us-gaap:BusinessAcquisition

us-gaap:BusinessCombinationProvisionalInformationInitialAccountingIncompleteAdjustmentPropertyPlantAndEquipment

cbu:SteubenTrustCorporation


Business
Period End2020-09-30
Value500000.0
Percentage of BusinessCombinationProvisionalInformationInitialAccountingIncompleteAdjustmentPropertyPlantAndEquipment100.0

us-gaap:BusinessDevelopment

us-gaap:BusinessDevelopment


Business
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-30
Value2.6592.032.3013.1451.5042.5132.8842.6043.142.7882.0822.5872.6542.0592.8752.5862.4512.0811.3172.0042.1492.0131.4931.8892.2581.5641.7011.7641.931.731.5591.9731.8041.4791.5591.3121.8761.1721.3971.0962.1831.2541.2421.251.731
Percentage of BusinessDevelopment100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:CashAcquiredFromAcquisition

us-gaap:CashAcquiredFromAcquisition


Cash
Period End2020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312011-12-31
Value0.00.0550.00.0900.00.00.00.00.00.0160.3390.040110.00.00.00.0810.00.00.00.00.00.00.02910.00.00.0-595.46220
Percentage of CashAcquiredFromAcquisition0.00.0100.00.00.0100.00.00.00.00.00.0100.0100.00.0100.0100.00.00.00.00.0100.00.00.00.00.00.00.00.0100.00.00.00.0100.0100.0

us-gaap:CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseExcludingExchangeRateEffect

us-gaap:CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseExcludingExchangeRateEffect


Cash
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-31
Value54505-190.716516790324-809.012139366296-45.0046.684-293.745322
Percentage of CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseExcludingExchangeRateEffect100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:CommonStockDividendsPerShareDeclared

us-gaap:CommonStockDividendsPerShareDeclared


Common
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-30
Value0.420.420.420.420.410.410.410.410.380.380.380.380.340.340.340.340.320.320.320.320.310.310.310.310.30.30.30.30.280.280.280.280.270.270.270.270.260.260.260.260.240.240.240.240.24
Percentage of CommonStockDividendsPerShareDeclared100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:CommunicationsAndInformationTechnology

us-gaap:CommunicationsAndInformationTechnology


Communications
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-30
Value1212121210101010109.3999.63110108.7429.359.313108.5218.6158.7448.7328.4128.3247.6437.4736.997.7657.4757.2516.8036.8526.9986.66.2776.2676.0785.7685.5835.2475.335.1794.7714.8675.435.309
Percentage of CommunicationsAndInformationTechnology100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:DefinedBenefitPlanAmortizationOfGainsLosses us-gaap:RetirementPlanType

us-gaap:DefinedBenefitPlanAmortizationOfGainsLosses

us-gaap:OtherPostretirementBenefitPlansDefinedBenefit


Defined
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-30
Value-11000.0-11000.0-10000.0-10000.0-10000.0-10000.0-10000.0-9000.0-9000.0-9000.0-6000.0-5000.0-5000.0-5000.0-2000.0-2000.0-2000.0-2000.01000.01000.0
Percentage of DefinedBenefitPlanAmortizationOfGainsLosses100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:PensionPlansDefinedBenefit


Defined
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-30
Value-900000.0-900000.0-809000.0-810000.0-810000.0-810000.0-642000.0-642000.0-643000.0-642000.0-298000.0-299000.0-298000.0-298000.0-148000.0-148000.0-209000.0-263000.0-377000.0-377000.0
Percentage of DefinedBenefitPlanAmortizationOfGainsLosses8181.88181.88090.08100.08100.08100.06420.07133.37144.47133.34966.75980.05960.05960.07400.07400.010450.013150.0-37700.0-37700.0

us-gaap:DefinedBenefitPlanAmortizationOfPriorServiceCostCredit us-gaap:RetirementPlanType

us-gaap:DefinedBenefitPlanAmortizationOfPriorServiceCostCredit

us-gaap:OtherPostretirementBenefitPlansDefinedBenefit


Defined
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-30
Value-44000.0-45000.0-45000.0-45000.0-44000.0-45000.0-45000.0-45000.0-45000.0-45000.0-45000.0-45000.0-44000.0-44000.0-45000.0-45000.0-45000.0-45000.0-45000.0-45000.0
Percentage of DefinedBenefitPlanAmortizationOfPriorServiceCostCredit100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:PensionPlansDefinedBenefit


Defined
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-30
Value94000.095000.061000.060000.060000.060000.016000.017000.016000.016000.0-68000.0-60000.0-83000.0-83000.012000.013000.017000.014000.010000.011000.0
Percentage of DefinedBenefitPlanAmortizationOfPriorServiceCostCredit-213.6-211.1-135.6-133.3-136.4-133.3-35.6-37.8-35.6-35.6151.1133.3188.6188.6-26.7-28.9-37.8-31.1-22.2-24.4

us-gaap:DefinedBenefitPlanContributionsByEmployer us-gaap:RetirementPlanFundingStatus, us-gaap:RetirementPlanTaxStatus, us-gaap:RetirementPlanType

us-gaap:DefinedBenefitPlanContributionsByEmployer

us-gaap:UnfundedPlan, us-gaap:NonqualifiedPlan, us-gaap:PensionPlansDefinedBenefit


Defined
Period End2020-09-302020-06-302020-03-312019-03-31
Value3.93.90.07.3
Percentage of DefinedBenefitPlanContributionsByEmployer100.0100.00.0100.0

us-gaap:DefinedBenefitPlanContributionsByEmployer us-gaap:RetirementPlanType

cbu:SteubenTrustCompanyPensionPlan


Defined
Period End2021-03-312020-09-30
Value0.093.5
Percentage of DefinedBenefitPlanContributionsByEmployer0.089.7

us-gaap:PensionPlansDefinedBenefit


Defined
Period End2021-03-312017-03-31
Value2.82.9
Percentage of DefinedBenefitPlanContributionsByEmployer0.00.0

us-gaap:DefinedBenefitPlanExpectedReturnOnPlanAssets us-gaap:RetirementPlanType

us-gaap:DefinedBenefitPlanExpectedReturnOnPlanAssets

us-gaap:PensionPlansDefinedBenefit


Defined
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-30
Value4.6954.6964.513.9323.9323.9323.5783.5783.5783.5773.7053.7053.7053.7053.3773.4483.4073.1212.962.961
Percentage of DefinedBenefitPlanExpectedReturnOnPlanAssets100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:DefinedBenefitPlanInterestCost us-gaap:RetirementPlanType

us-gaap:DefinedBenefitPlanInterestCost

us-gaap:OtherPostretirementBenefitPlansDefinedBenefit


Defined
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-30
Value11000.011000.014000.015000.014000.014000.017000.018000.018000.018000.017000.018000.017000.017000.019000.019000.019000.019000.021000.020000.0
Percentage of DefinedBenefitPlanInterestCost100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:PensionPlansDefinedBenefit


Defined
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-30
Value1259000.01259000.01589000.01356000.01356000.01356000.01566000.01566000.01565000.01566000.01425000.01422000.01415000.01415000.01452000.01453000.01449000.01361000.01406000.01406000.0
Percentage of DefinedBenefitPlanInterestCost11445.511445.511350.09040.09685.79685.79211.88700.08694.48700.08382.47900.08323.58323.57642.17647.47626.37163.26695.27030.0

us-gaap:DefinedBenefitPlanNetPeriodicBenefitCost us-gaap:RetirementPlanType

us-gaap:DefinedBenefitPlanNetPeriodicBenefitCost

us-gaap:OtherPostretirementBenefitPlansDefinedBenefit


Defined
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-30
Value-22000.0-23000.0-21000.0-20000.0-20000.0-21000.0-18000.0-18000.0-18000.0-18000.0-22000.0-22000.0-22000.0-22000.0-24000.0-24000.0-24000.0-24000.0-25000.0-26000.0
Percentage of DefinedBenefitPlanNetPeriodicBenefitCost100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:PensionPlansDefinedBenefit


Defined
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-30
Value-962000.0-962000.0-1251000.0-268000.0-268000.0-268000.0-84000.0-83000.0-84000.0-83000.0-872000.0-890000.0-954000.0-954000.0-727000.0-797000.0-665000.0-444000.0-120000.0-140000.0
Percentage of DefinedBenefitPlanNetPeriodicBenefitCost4372.74182.65957.11340.01340.01276.2466.7461.1466.7461.13963.64045.54336.44336.43029.23320.82770.81850.0480.0538.5

us-gaap:DefinedBenefitPlanServiceCost us-gaap:RetirementPlanType

us-gaap:DefinedBenefitPlanServiceCost

us-gaap:PensionPlansDefinedBenefit


Defined
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-30
Value1480000.01480000.01437000.01438000.01438000.01438000.01270000.01270000.01270000.01270000.01165000.01154000.01121000.01121000.01038000.01037000.01067000.01039000.01027000.01027000.0
Percentage of DefinedBenefitPlanServiceCost100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:Depreciation

us-gaap:Depreciation


Depreciation
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-30
Value3.984.0344.0173.9513.9164.0794.114.1013.853.833.8953.8953.9584.0013.9984.2514.1063.6693.6563.5923.5943.5563.3123.2873.2863.2473.2813.2753.243.2863.1783.1112.943.0072.9952.9362.7422.8092.7662.9492.922.7392.7722.506
Percentage of Depreciation100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:DividendsCommonStock

us-gaap:DividendsCommonStock


Dividends
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-30
Value22222222222121211919191917171717161414141313131212121212111111111010101010109.6099.575
Percentage of DividendsCommonStock100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:DividendsCommonStock us-gaap:StatementEquityComponents

us-gaap:RetainedEarnings


Dividends
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-30
Value22222222222121211919191917171717161414141313131212121212111111111010101010109.6099.575
Percentage of DividendsCommonStock100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:EquitySecuritiesFvNiUnrealizedGainLoss

us-gaap:EquitySecuritiesFvNiUnrealizedGainLoss


Equity
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-30
Value024000.024000.0-12000.012000.0-30000.0-9000.010000.0-13000.031000.0-65000.0743000.0-21000.00000
Percentage of EquitySecuritiesFvNiUnrealizedGainLoss0.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.00.00.00.00.0

us-gaap:ExcessTaxBenefitFromShareBasedCompensationFinancingActivities

us-gaap:ExcessTaxBenefitFromShareBasedCompensationFinancingActivities


Excess
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-30
Value-72000.0-1065000.0-136000.0-93000.0-93000.0-991000.0-9000.00-31000.0-3119000.0-50000.0-17000.010000.0-964000.0-44000.0-21000.0-48000.0-1320000.0862000.01301000.0334000.0594000.0756000.0478000.0367000.0696000.0592000.041000.0190000.01245000.0642000.0517000.0148000.0518000.0511000.0293000.060000.0660000.0348000.071000.0-2000.0286000.0258000.0129000.0
Percentage of ExcessTaxBenefitFromShareBasedCompensationFinancingActivities100.0100.0100.0100.0100.0100.0100.00.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:FairValueOfAssetsAcquired

us-gaap:FairValueOfAssetsAcquired


Fair
Period End2020-12-312020-09-302019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312013-12-312012-12-31
Value0.031-2.36-0.0785480.00.00.00.00.0880.027-0.4768.6961921310.00.00.00.03.6780.0
Percentage of FairValueOfAssetsAcquired100.0100.0100.0100.00.00.00.00.0100.0100.0100.0100.0100.0100.00.00.00.00.0100.00.0

us-gaap:FinancingReceivableAllowanceForCreditLossesRecovery

us-gaap:FinancingReceivableAllowanceForCreditLossesRecovery


Financing
Period End2021-06-302021-03-312020-09-302020-06-30
Value1698000.01585000.01463000.01184000.0
Percentage of FinancingReceivableAllowanceForCreditLossesRecovery100.0100.0100.0100.0

us-gaap:FinancingReceivableAllowanceForCreditLossesRecovery us-gaap:AdjustmentsForNewAccountingPronouncements

us-gaap:AccountingStandardsUpdate201613


Financing
Period End2020-12-312020-09-302020-06-302020-03-31
Value1545000.01463000.01184000.01497000.0
Percentage of FinancingReceivableAllowanceForCreditLossesRecovery0.0100.0100.00.0

us-gaap:FinancingReceivableAllowanceForCreditLossesWriteOffs

us-gaap:FinancingReceivableAllowanceForCreditLossesWriteOffs


Financing
Period End2021-06-302021-03-312020-09-302020-06-30
Value1.1061.9662.722.094
Percentage of FinancingReceivableAllowanceForCreditLossesWriteOffs100.0100.0100.0100.0

us-gaap:FinancingReceivableAllowanceForCreditLossesWriteOffs us-gaap:AdjustmentsForNewAccountingPronouncements

us-gaap:AccountingStandardsUpdate201613


Financing
Period End2020-12-312020-09-302020-06-302020-03-31
Value2.8032.722.0943.047
Percentage of FinancingReceivableAllowanceForCreditLossesWriteOffs0.0100.0100.00.0

us-gaap:FinancingReceivableModificationsNumberOfContracts2

us-gaap:FinancingReceivableModificationsNumberOfContracts2


Financing
Period End2021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-31
Value10.054954.025.07.022.020.021.015.020.013.021.016.07.026.019.013.021.07.011.020.017.037.017.09.013.012.027.026.030.031.018.023.041.0
Percentage of FinancingReceivableModificationsNumberOfContracts2100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:FinancingReceivableModificationsNumberOfContracts2 us-gaap:FinancingReceivablePortfolioSegment, us-gaap:FinancingReceivableRecordedInvestmentByClassOfFinancingReceivable

us-gaap:CommercialPortfolioSegment, us-gaap:CommercialLoan


Financing
Period End2021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-30
Value01.00003.01.02.001.0001.04.01.03.00-1.002.003.0000004.0
Percentage of FinancingReceivableModificationsNumberOfContracts20.00.00.00.00.015.04.813.30.07.70.00.014.315.45.323.10.0-14.30.010.00.08.10.00.00.00.00.015.4

us-gaap:ConsumerPortfolioSegment, cbu:ConsumerInstallmentDirect


Financing
Period End2021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-30
Value1.01.01.001.01.02.02.001.02.03.02.02.01.01.04.02.001.004.01.01.01.07.05.01.0
Percentage of FinancingReceivableModificationsNumberOfContracts210.00.04.00.04.55.09.513.30.07.79.518.828.67.75.37.719.028.60.05.00.010.85.911.17.758.318.53.8

us-gaap:ConsumerPortfolioSegment, cbu:ConsumerInstallmentIndirect


Financing
Period End2021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-30
Value6.06.014.03.014.011.010.04.011.08.014.08.04.011.08.08.08.06.09.09.012.012.012.06.07.04.016.09.0
Percentage of FinancingReceivableModificationsNumberOfContracts260.00.056.042.963.655.047.626.755.061.566.750.057.142.342.161.538.185.781.845.070.632.470.666.753.833.359.334.6

us-gaap:ConsumerPortfolioSegment, cbu:HomeEquityReceivables


Financing
Period End2021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-30
Value01.02.01.002.003.01.01.01.01.001.01.002.0003.01.05.0001.01.004.0
Percentage of FinancingReceivableModificationsNumberOfContracts20.00.08.014.30.010.00.020.05.07.74.86.20.03.85.30.09.50.00.015.05.913.50.00.07.78.30.015.4

us-gaap:ResidentialPortfolioSegment, us-gaap:ResidentialMortgage


Financing
Period End2021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-30
Value3.008.03.07.03.08.04.08.02.04.04.008.08.01.07.002.05.04.013.04.02.04.006.08.0
Percentage of FinancingReceivableModificationsNumberOfContracts230.00.032.042.931.815.038.126.740.015.419.025.00.030.842.17.733.30.018.225.023.535.123.522.230.80.022.230.8

us-gaap:FinancingReceivableModificationsPostModificationRecordedInvestment2

us-gaap:FinancingReceivableModificationsPostModificationRecordedInvestment2


Financing
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-31
Value299000.0183000.049000.0835000.0249000.0756000.0554000.01020000.0643000.0767000.0253000.0322000.0620000.0136000.0378000.0781000.0486000.0721000.0-150000.0295000.0731000.0504000.01002000.0516000.0146000.0333000.0108000.0455000.01035000.0877000.0541000.0772000.0685000.01309000.0
Percentage of FinancingReceivableModificationsPostModificationRecordedInvestment2100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:FinancingReceivableModificationsPostModificationRecordedInvestment2 us-gaap:FinancingReceivablePortfolioSegment, us-gaap:FinancingReceivableRecordedInvestmentByClassOfFinancingReceivable

us-gaap:CommercialPortfolioSegment, us-gaap:CommercialLoan


Financing
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-30
Value004000.000025000.0415000.0250000.0010000.00093000.0-2000.051000.0363000.00-29000.0051000.0067000.0000213000.00391000.0
Percentage of FinancingReceivableModificationsPostModificationRecordedInvestment20.00.08.20.00.00.04.540.738.90.04.00.00.068.4-0.56.574.70.019.30.07.00.06.70.00.00.0197.20.037.8

us-gaap:ConsumerPortfolioSegment, cbu:ConsumerInstallmentDirect


Financing
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-30
Value-7000.07000.0-2000.02000.0012000.014000.025000.06000.003000.010000.012000.02000.010000.01000.0015000.00052000.0010000.001000.04000.012000.07000.02000.0
Percentage of FinancingReceivableModificationsPostModificationRecordedInvestment2-2.33.8-4.10.20.01.62.52.50.90.01.23.11.91.52.60.10.02.1-0.00.07.10.01.00.00.71.211.11.50.2

us-gaap:ConsumerPortfolioSegment, cbu:ConsumerInstallmentIndirect


Financing
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-30
Value50000.066000.072000.0131000.047000.0127000.0158000.0116000.033000.098000.0144000.0117000.070000.041000.0167000.0181000.080000.0106000.067000.089000.0118000.0238000.086000.0112000.084000.0101000.0-22000.0165000.096000.0
Percentage of FinancingReceivableModificationsPostModificationRecordedInvestment216.736.1146.915.718.916.828.511.45.112.856.936.311.330.144.223.216.514.7-44.730.216.147.28.621.757.530.3-20.436.39.3

us-gaap:ConsumerPortfolioSegment, cbu:HomeEquityReceivables


Financing
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-30
Value0014000.056000.028000.00109000.0071000.04000.033000.0086000.00-11000.08000.0098000.02000.0073000.0050000.00015000.0-28000.00126000.0
Percentage of FinancingReceivableModificationsPostModificationRecordedInvestment20.00.028.66.711.20.019.70.011.00.513.00.013.90.0-2.91.00.013.6-1.30.010.00.05.00.00.04.5-25.90.012.2

us-gaap:ResidentialPortfolioSegment, us-gaap:ResidentialMortgage


Financing
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-30
Value256000.0110000.0-39000.0646000.0174000.0617000.0248000.0464000.0283000.0665000.063000.0195000.0452000.00214000.0540000.043000.0502000.0-190000.0206000.0437000.0266000.0789000.0404000.061000.0213000.0-67000.0283000.0420000.0
Percentage of FinancingReceivableModificationsPostModificationRecordedInvestment285.660.1-79.677.469.981.644.845.544.086.724.960.672.90.056.669.18.869.6126.769.859.852.878.778.341.864.0-62.062.240.6

us-gaap:FinancingReceivableSignificantPurchases

us-gaap:FinancingReceivableSignificantPurchases


Financing
Period End2021-06-302021-03-312020-12-312020-09-30
Value0.00.00.141-0.129
Percentage of FinancingReceivableSignificantPurchases0.00.0100.0100.0

us-gaap:FinancingReceivableSignificantPurchases us-gaap:FinancingReceivablePortfolioSegment, us-gaap:FinancingReceivableRecordedInvestmentByClassOfFinancingReceivable

us-gaap:CommercialPortfolioSegment, us-gaap:CommercialLoan


Financing
Period End2021-06-302021-03-312020-09-30
Value0.00.0-0.101
Percentage of FinancingReceivableSignificantPurchases0.00.078.3

us-gaap:ConsumerPortfolioSegment, cbu:ConsumerInstallmentDirect


Financing
Period End2021-06-302021-03-312020-09-30
Value0.00.0-0.028
Percentage of FinancingReceivableSignificantPurchases0.00.021.7

us-gaap:ConsumerPortfolioSegment, cbu:HomeEquityReceivables


Financing
Period End2021-06-302021-03-312020-09-30
Value0.00.00.012
Percentage of FinancingReceivableSignificantPurchases0.00.0-9.3

us-gaap:ResidentialPortfolioSegment, us-gaap:ResidentialMortgage


Financing
Period End2021-06-302021-03-312020-09-30
Value0.00.0-0.012
Percentage of FinancingReceivableSignificantPurchases0.00.09.3

us-gaap:FinancingReceivableSignificantSales

us-gaap:FinancingReceivableSignificantSales


Financing
Period End2021-06-302021-03-312020-12-312020-09-30
Value3.4248.2844221
Percentage of FinancingReceivableSignificantSales100.0100.0100.0100.0

us-gaap:FinancingReceivableSignificantSales us-gaap:FinancingReceivablePortfolioSegment, us-gaap:FinancingReceivableRecordedInvestmentByClassOfFinancingReceivable

us-gaap:CommercialPortfolioSegment, us-gaap:CommercialLoan


Financing
Period End2021-06-302021-03-312020-09-30
Value0.8480.00.0
Percentage of FinancingReceivableSignificantSales24.80.00.0

us-gaap:ResidentialPortfolioSegment, us-gaap:ResidentialMortgage


Financing
Period End2021-06-302021-03-312020-09-30
Value2.5768.28421
Percentage of FinancingReceivableSignificantSales75.2100.0100.0

us-gaap:GoodwillPeriodIncreaseDecrease

us-gaap:GoodwillPeriodIncreaseDecrease


Goodwill
Period End2021-06-302021-03-312016-12-312016-09-302016-06-302016-03-31
Value1.436-0.2520.00.00.01.89
Percentage of GoodwillPeriodIncreaseDecrease100.0100.00.00.00.0100.0

us-gaap:GoodwillPurchaseAccountingAdjustments us-gaap:BusinessAcquisition

us-gaap:GoodwillPurchaseAccountingAdjustments

cbu:SteubenTrustCorporation


Goodwill
Period End2021-06-302021-03-312020-09-30
Value0.00.31.1
Percentage of GoodwillPurchaseAccountingAdjustments0.0100.0100.0

us-gaap:ImpairedFinancingReceivableAverageRecordedInvestment

us-gaap:ImpairedFinancingReceivableAverageRecordedInvestment


Impaired
Period End2021-06-302021-03-312020-09-302020-06-302020-03-312019-09-302019-06-302019-03-31
Value32348.81.42.25.15.16.2
Percentage of ImpairedFinancingReceivableAverageRecordedInvestment100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:IncreaseDecreaseInAccruedInterestReceivableNet us-gaap:BusinessAcquisition

us-gaap:IncreaseDecreaseInAccruedInterestReceivableNet

cbu:KinderhookBankCorp


Increase
Period End2020-12-312020-03-312019-12-31
Value10000.0300000.010000.0
Percentage of IncreaseDecreaseInAccruedInterestReceivableNet100.0100.0100.0

us-gaap:IncreaseDecreaseInDeferredCompensation

us-gaap:IncreaseDecreaseInDeferredCompensation


Increase
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-30
Value60000.068000.067000.065000.065000.074000.073000.068000.066000.079000.078000.070000.069000.081000.080000.0148000.03078000.0000
Percentage of IncreaseDecreaseInDeferredCompensation100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.00.00.00.0

us-gaap:IncreaseDecreaseInDeposits

us-gaap:IncreaseDecreaseInDeposits


Increase
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-09-30
Value1349791042731026309-173.398111-131.457297-141.45-50.172-257.099326-161.57-19.613-159.68260-1.465119-161.2082452661-39.727191-32.067-3.964-67.593142-94.74517-104.694146-80.590.315-41.655156-43.50881-35.4838626
Percentage of IncreaseDecreaseInDeposits100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:IncreaseDecreaseInFinanceReceivables us-gaap:BusinessAcquisition

us-gaap:IncreaseDecreaseInFinanceReceivables

cbu:KinderhookBankCorp


Increase
Period End2020-09-302019-12-31
Value200000.0-50000.0
Percentage of IncreaseDecreaseInFinanceReceivables100.0100.0

us-gaap:IncreaseDecreaseInOtherNoncurrentAssets us-gaap:BusinessAcquisition

us-gaap:IncreaseDecreaseInOtherNoncurrentAssets

cbu:KinderhookBankCorp


Increase
Period End2020-09-30
Value1700000.0
Percentage of IncreaseDecreaseInOtherNoncurrentAssets100.0

us-gaap:IncreaseDecreaseInOtherOperatingAssets us-gaap:BusinessAcquisition

us-gaap:IncreaseDecreaseInOtherOperatingAssets

cbu:KinderhookBankCorp


Increase
Period End2020-09-30
Value500000.0
Percentage of IncreaseDecreaseInOtherOperatingAssets100.0

us-gaap:IncrementalCommonSharesAttributableToShareBasedPaymentArrangements

us-gaap:IncrementalCommonSharesAttributableToShareBasedPaymentArrangements


Incremental
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-31
Value462000.0438000.0-4000.0324000.0339000.0420000.0-6000.0496000.0529000.0541000.0-7000.0608000.0583000.0563000.0-13000.0585000.0626000.0703000.035000.0394000.0357000.0333000.05000.0386000.0404000.0405000.0-1000.0453000.0484000.0512000.030000.0506000.0427000.0463000.0-17.0486.0463000.0535000.0414600.0362.0438000.0472000.0
Percentage of IncrementalCommonSharesAttributableToShareBasedPaymentArrangements100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:InsuranceServicesRevenue

us-gaap:InsuranceServicesRevenue


Insurance
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-31
Value8.2098.1537.68.5318.1838.0587.4818.5278.3297.8627.2738.277.4157.3596.4416.3446.9656.45.8095.7025.7975.8412.2610.3670.3250.399
Percentage of InsuranceServicesRevenue100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:InterestAndDividendIncomeOperating

us-gaap:InterestAndDividendIncomeOperating


Interest
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-30
Value9597979797961009894929290918889888169727171696865636264646463656664677171706770706960626262
Percentage of InterestAndDividendIncomeOperating100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:InterestExpenseDeposits

us-gaap:InterestExpenseDeposits


Interest
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-31
Value2.9633.1123.3883.6554.1735.5455.9345.8594.564.1073.3812.7642.3812.1322.1132.1232.0651.731.7831.7761.8721.8941.7461.6941.7311.81.9261.9622.0682.2352.3572.532.7033.1423.8714.4024.385.5096.4726.8876.7916.006
Percentage of InterestExpenseDeposits100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:InterestExpenseJuniorSubordinatedDebentures

us-gaap:InterestExpenseJuniorSubordinatedDebentures


Interest
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-30
Value0293000.0374000.0394000.0454000.0653000.0737000.01004000.01063000.01094000.01032000.01145000.01332000.01168000.01096000.01067000.0936000.0805000.0788000.0746000.0722000.0694000.0656000.0640000.0627000.0614000.0625000.0623000.0617000.0612000.0629000.0633000.0630000.0628000.0660000.0682000.0681000.0693000.01354000.01497000.01483000.01467000.01502000.01509000.01485000.0
Percentage of InterestExpenseJuniorSubordinatedDebentures0.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:InterestExpenseSubordinatedNotesAndDebentures

us-gaap:InterestExpenseSubordinatedNotesAndDebentures


Interest
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-30
Value39000.038000.0117000.0184000.0184000.0185000.0185000.0161000.00000
Percentage of InterestExpenseSubordinatedNotesAndDebentures100.0100.0100.0100.0100.0100.0100.0100.00.00.00.00.0

us-gaap:InterestIncomeExpenseAfterProvisionForLoanLoss

us-gaap:InterestIncomeExpenseAfterProvisionForLoanLoss


Interest
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-30
Value969996918284898986848483848080827665676666656160605959595959575857575756555253535344444443
Percentage of InterestIncomeExpenseAfterProvisionForLoanLoss100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:InterestIncomeSecuritiesTaxExempt

us-gaap:InterestIncomeSecuritiesTaxExempt


Interest
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-30
Value2.6642.7762.8482.9633.0493.1013.012.8542.8582.8913.0633.2263.3363.4383.6823.7613.8964.0084.1524.2724.5854.514.6144.794.8014.8034.9415.1655.2645.0765.0825.1325.1625.5915.8676.0426.0185.5985.4165.4385.7395.7615.7125.5755.604
Percentage of InterestIncomeSecuritiesTaxExempt100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:InterestIncomeSecuritiesTaxable

us-gaap:InterestIncomeSecuritiesTaxable


Interest
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-30
Value161516141515161517161615161516151513151314131413131212121212131312151616171414141412121112
Percentage of InterestIncomeSecuritiesTaxable100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:LaborAndRelatedExpense

us-gaap:LaborAndRelatedExpense


Labor
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-30
Value575758575458565654535251525147464441363837393331313130303030303030302928262727262523222322
Percentage of LaborAndRelatedExpense100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:LiabilitiesAssumed1

us-gaap:LiabilitiesAssumed1


Liabilities
Period End2020-12-312020-09-302019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312013-12-312012-12-31
Value-0.01-1.3260.1225890.00.00.00.00.00.0310.6116.5971833300.00.00.00.03030.0
Percentage of LiabilitiesAssumed1100.0100.0100.0100.00.00.00.00.00.0100.0100.0100.0100.0100.00.00.00.00.0100.00.0

us-gaap:LiabilitiesFairValueAdjustment us-gaap:BusinessAcquisition

us-gaap:LiabilitiesFairValueAdjustment

cbu:KinderhookBankCorp


Liabilities
Period End2020-09-302020-03-312019-12-31
Value1300000.0-300000.040000.0
Percentage of LiabilitiesFairValueAdjustment100.0100.0100.0

us-gaap:MarketableSecuritiesRealizedGainLoss

us-gaap:MarketableSecuritiesRealizedGainLoss


Marketable
Period End2020-12-312020-09-302020-06-302019-12-312019-09-302019-06-302018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-31
Value0.00.00.00.00.04.8820.00.00.00.00.00.00.00.0020.00.00.00.00.00.00.00.0160.01647
Percentage of MarketableSecuritiesRealizedGainLoss0.00.00.00.00.0100.00.00.00.00.00.00.00.0100.00.00.00.00.00.00.00.00.0100.00.0100.0100.0

us-gaap:NoninterestExpense

us-gaap:NoninterestExpense


Noninterest
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-30
Value9393959690939596918887858686868310273666666674947485143444444
Percentage of NoninterestExpense100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:NoninterestIncome

us-gaap:NoninterestIncome


Noninterest
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-30
Value595857595258575760555455565753525144383938383331292929312928212727262625232322232220212222
Percentage of NoninterestIncome100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:NoninterestIncome us-gaap:ConsolidationItems

us-gaap:IntersegmentElimination


Noninterest
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-30
Value-1.707-1.889-1.867-1.454-1.374-1.519-0.775-0.669-1.213-0.769-0.834-0.763-0.7-0.695-0.823-0.684-0.687-0.664-0.658-0.623-0.595-0.566-0.694-0.526-0.472
Percentage of NoninterestIncome-2.9-3.2-3.3-2.4-2.6-2.6-1.4-1.2-2.0-1.4-1.5-1.4-1.2-1.2-1.5-1.3-1.3-1.5-1.7-1.6-1.5-1.5-2.1-1.7-1.6

us-gaap:NoninterestIncome us-gaap:ConsolidationItems, us-gaap:StatementBusinessSegments

us-gaap:OperatingSegments, cbu:BankingServices


Noninterest
Period End2021-06-302021-03-312020-06-302020-03-31
Value16161418
Percentage of NoninterestIncome27.528.128.331.9

us-gaap:OperatingSegments, cbu:EmployeeBenefitServices


Noninterest
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-30
Value27272725242525242424242323232221211712111212121111
Percentage of NoninterestIncome47.146.447.943.046.344.244.843.540.944.344.542.740.840.842.240.141.239.831.429.231.132.436.737.239.1

us-gaap:OperatingSegments, us-gaap:AllOtherSegments


Noninterest
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-31
Value161615151415141515141314141412121211
Percentage of NoninterestIncome28.328.727.226.328.026.525.126.525.025.925.726.425.025.023.523.224.925.9

us-gaap:OperatingSegments, us-gaap:Banking


Noninterest
Period End2020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-30
Value1914181817211717182020192018
Percentage of NoninterestIncome33.128.331.931.531.236.131.131.432.335.435.435.838.035.3

us-gaap:OccupancyNet

us-gaap:OccupancyNet


Occupancy
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-30
Value101110109.75410109.8019.61910109.779.437109.6229.1068.6378.1967.6337.3737.4097.6636.7026.6526.8447.3956.7246.6176.9167.6916.7826.4486.757.0656.6656.5416.136.4636.0896.1036.2536.0575.5195.5755.614
Percentage of OccupancyNet100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:OffBalanceSheetCreditLossLiabilityCreditLossExpenseReversal

us-gaap:OffBalanceSheetCreditLossLiabilityCreditLossExpenseReversal


Off
Period End2021-06-302021-03-312020-09-302020-06-30
Value-427000.0-300000.0163000.0540000.0
Percentage of OffBalanceSheetCreditLossLiabilityCreditLossExpenseReversal100.0100.0100.0100.0

us-gaap:OffBalanceSheetCreditLossLiabilityCreditLossExpenseReversal us-gaap:AdjustmentsForNewAccountingPronouncements

us-gaap:AccountingStandardsUpdate201613


Off
Period End2020-12-312020-09-302020-06-302020-03-31
Value-126000.0163000.0540000.0-340000.0
Percentage of OffBalanceSheetCreditLossLiabilityCreditLossExpenseReversal0.0100.0100.00.0

us-gaap:OtherComprehensiveIncomeAvailableforsaleSecuritiesAdjustmentNetOfTaxPortionAttributableToParent

us-gaap:OtherComprehensiveIncomeAvailableforsaleSecuritiesAdjustmentNetOfTaxPortionAttributableToParent


Other
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-31
Value60-172.764-25.99-6.7035.95293-9.2396.62211827-15.215-11.399-31.66-17.922-1.5386.0282.367-60.937-15.1551941-21.51427-30.461819-1.0982225-16.985-1.285-41.528-11.774-7.6388.55331-4.586
Percentage of OtherComprehensiveIncomeAvailableforsaleSecuritiesAdjustmentNetOfTaxPortionAttributableToParent100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:OtherComprehensiveIncomeDefinedBenefitPlansAdjustmentNetOfTaxPortionAttributableToParent

us-gaap:OtherComprehensiveIncomeDefinedBenefitPlansAdjustmentNetOfTaxPortionAttributableToParent


Other
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302013-03-312012-03-31
Value-0.73-0.73-4.105-0.634-0.635-0.6353.457-0.471-0.471-0.47110.436-0.133-0.1331.309-0.073-1.26-0.144-2.689-0.211-0.211-0.215.158-0.196-0.196-0.1969.3490.0740.0730.60.418
Percentage of OtherComprehensiveIncomeDefinedBenefitPlansAdjustmentNetOfTaxPortionAttributableToParent100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:OtherComprehensiveIncomeLossAmortizationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetPriorServiceCostCreditBeforeTax

us-gaap:OtherComprehensiveIncomeLossAmortizationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetPriorServiceCostCreditBeforeTax


Other
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-30
Value50000.050000.0-517000.015000.016000.015000.0-29000.0-28000.0-29000.0-29000.0-1039000.0-105000.0-127000.0-127000.0-768000.0-32000.0-28000.0-31000.0-35000.0-34000.0-34000.0-34000.0-43000.0-43000.0-43000.0-43000.0-1568000.0-43000.0-44000.0-44000.0-1411000.0-30000.0-30000.0-30000.0-243000.0-242000.0-243000.0
Percentage of OtherComprehensiveIncomeLossAmortizationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetPriorServiceCostCreditBeforeTax100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:OtherComprehensiveIncomeLossAmortizationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetPriorServiceCostCreditNetOfTax

us-gaap:OtherComprehensiveIncomeLossAmortizationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetPriorServiceCostCreditNetOfTax


Other
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-30
Value38000.038000.0-393000.011000.012000.012000.0-22000.0-22000.0-21000.0-22000.0-786000.0-80000.0-96000.0-96000.0-479000.0-20000.0-18000.0-19000.0-22000.0-21000.0-21000.0-21000.0-27000.0-27000.0-27000.0-27000.0-962000.0-26000.0-27000.0-27000.0-858000.0-19000.0-18000.0-18000.0-149000.0-148000.0-149000.0
Percentage of OtherComprehensiveIncomeLossAmortizationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetPriorServiceCostCreditNetOfTax100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:OtherComprehensiveIncomeLossAmortizationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetPriorServiceCostCreditTax

us-gaap:OtherComprehensiveIncomeLossAmortizationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetPriorServiceCostCreditTax


Other
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-30
Value12000.012000.0-124000.04000.04000.03000.0-7000.0-6000.0-8000.0-7000.0-253000.0-25000.0-31000.0-31000.0-289000.0-12000.0-10000.0-12000.0-13000.0-13000.0-13000.0-13000.0-16000.0-16000.0-16000.0-16000.0-606000.0-17000.0-17000.0-17000.0-553000.0-11000.0-12000.0-12000.0-94000.0-94000.0-94000.0
Percentage of OtherComprehensiveIncomeLossAmortizationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetPriorServiceCostCreditTax100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent

us-gaap:OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent


Other
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-30
Value61-172.034-21.885-6.0696.58793-12.6967.091221817-15.651-11.266-31.527-19.231-1.4657.2882.511-58.248-14.9441942-26.67227-30.2641810-1.172221.855-0.685-40.928-41.122-11.8028.9732-4.1685.74713126.118-20.265.58511
Percentage of OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent us-gaap:StatementEquityComponents

us-gaap:AccumulatedOtherComprehensiveIncome


Other
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-30
Value61-172.034-21.885-6.0696.58793-12.6967.091221816-15.651-11.057-31.527-19.231-1.4657.2882.511-58.248-14.9441942-26.672271.855-0.685-40.928-41.122-11.8028.96932-4.1685.74713
Percentage of OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent100.0100.0100.0100.0100.0100.0100.0100.0100.0100.098.8100.098.1100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForSaleOfSecuritiesBeforeTax

us-gaap:OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForSaleOfSecuritiesBeforeTax


Other
Period End2020-12-312020-09-302020-06-302019-12-312019-09-302019-06-302018-12-312018-09-302018-06-302014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-30
Value0.00.0-0.00.0-0.04.8820.0-0.0-0.00.00.00.00.0160.0-16.007470.00.2910.0
Percentage of OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForSaleOfSecuritiesBeforeTax0.00.00.00.00.0100.00.00.00.00.00.00.00.0100.00.0100.0100.00.0100.00.0

us-gaap:OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForSaleOfSecuritiesNetOfTax

us-gaap:OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForSaleOfSecuritiesNetOfTax


Other
Period End2020-12-312020-09-302020-06-302019-12-312019-09-302019-06-302018-12-312018-09-302018-06-302014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-30
Value0.00.0-0.00.0-0.03.6880.0-0.0-0.00.00.00.00.0110.09.83229-0.0110.1890.0
Percentage of OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForSaleOfSecuritiesNetOfTax0.00.00.00.00.0100.00.00.00.00.00.00.00.0100.00.0100.0100.0100.0100.00.0

us-gaap:OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForSaleOfSecuritiesTax

us-gaap:OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForSaleOfSecuritiesTax


Other
Period End2020-12-312020-09-302020-06-302019-12-312019-09-302019-06-302018-12-312018-09-302018-06-302014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-30
Value0.00.00.00.00.01.1940.00.00.00.00.00.00.05.7370.06.175170.0110.1020.0
Percentage of OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForSaleOfSecuritiesTax0.00.00.00.00.0100.00.00.00.00.00.00.00.0100.00.0100.0100.0100.0100.00.0

us-gaap:OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetGainLossBeforeTax

us-gaap:OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetGainLossBeforeTax


Other
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-30
Value-0.911-0.911-5.919-0.82-0.82-0.824.517-0.651-0.652-0.65113-0.304-0.303-0.3031.332-0.15-2.068-0.265-4.387-0.376-0.376-0.3758.326-0.363-0.363-0.363130.0790.0770.077-32.363-1.011-1.012-1.016.56-0.924-0.925
Percentage of OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetGainLossBeforeTax100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetGainLossNetOfTax

us-gaap:OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetGainLossNetOfTax


Other
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-30
Value-692000.0-692000.0-4498000.0-623000.0-623000.0-623000.03435000.0-493000.0-492000.0-492000.010249000.0-230000.0-229000.0-229000.0829000.0-93000.0-1278000.0-163000.0-2711000.0-232000.0-232000.0-231000.05131000.0-223000.0-223000.0-223000.08387000.048000.046000.048000.0-19698000.0-619000.0-618000.0-618000.04015000.0-565000.0-566000.0
Percentage of OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetGainLossNetOfTax100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetGainLossTax

us-gaap:OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetGainLossTax


Other
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-30
Value-219000.0-219000.0-1421000.0-197000.0-197000.0-197000.01082000.0-158000.0-160000.0-159000.03308000.0-74000.0-74000.0-74000.0503000.0-57000.0-790000.0-102000.0-1676000.0-144000.0-144000.0-144000.03195000.0-140000.0-140000.0-140000.05282000.031000.031000.029000.0-12665000.0-392000.0-394000.0-392000.02545000.0-359000.0-359000.0
Percentage of OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetGainLossTax100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodBeforeTax

us-gaap:OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodBeforeTax


Other
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-30
Value80-227.427-34.202-8.8217.832122-12.228.756332336-20.094-14.816-41.815-29.014-2.499.763.893-98.374-24.4653167-35.02844-49.5893130-1.8083640-8.398-1.852-50.777-18.872-12.2171451-7.017.56639198.977-31.7757.9216
Percentage of OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodBeforeTax100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodNetOfTax

us-gaap:OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodNetOfTax


Other
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-31
Value60-172.764-25.99-6.7035.95293-9.2396.62251827-15.215-11.191-31.66-17.921-1.5386.0282.367-60.937-15.1551941-21.51627-30.461819-1.0982225-4.759-1.285-31.696-41.722-7.6498.74231-4.586
Percentage of OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodNetOfTax100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodTax

us-gaap:OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodTax


Other
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-31
Value19-54.663-8.212-2.1181.8829-2.9812.1368.1895.8328.939-4.879-3.625-10.155-11.093-0.9523.7321.526-37.437-9.311225-13.51216-19.1291311-0.711315-3.639-0.567197.0984.466-5.224-19.6432.424-2.731-15.06-7.243-3.45
Percentage of OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodTax100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:OtherCostAndExpenseOperating

us-gaap:OtherCostAndExpenseOperating


Other
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-31
Value908991928489908686838381818181787569656464666355555555575454565353535554484846464942
Percentage of OtherCostAndExpenseOperating100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:OtherCostAndExpenseOperating us-gaap:ConsolidationItems

us-gaap:IntersegmentElimination


Other
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-30
Value-1.707-1.889-1.867-1.454-1.374-1.519-0.775-0.669-1.213-0.769-0.834-0.763-0.7-0.695-0.823-0.684-0.687-0.664-0.658-0.623-0.595-0.566-0.694-0.526-0.472-0.464-0.515-0.486-0.418-0.4740.068-0.527-0.584-0.4510.124-0.541-0.514
Percentage of OtherCostAndExpenseOperating-1.9-2.1-2.0-1.6-1.6-1.7-0.9-0.8-1.4-0.9-1.0-0.9-0.9-0.9-1.0-0.9-0.9-1.0-1.0-1.0-0.9-0.9-1.1-1.0-0.9-0.8-0.9-0.8-0.8-0.90.1-1.0-1.1-0.80.2-1.0-1.1

us-gaap:OtherCostAndExpenseOperating us-gaap:ConsolidationItems, us-gaap:StatementBusinessSegments

us-gaap:OperatingSegments, cbu:BankingServices


Other
Period End2021-06-302021-03-312020-06-302020-03-31
Value65655964
Percentage of OtherCostAndExpenseOperating72.272.370.471.6

us-gaap:OperatingSegments, cbu:EmployeeBenefitServices


Other
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-31
Value1415151514151514151414141413131213119.4389.029.4329.4479.1668.6448.9578.4518.2248.148.1988.297
Percentage of OtherCostAndExpenseOperating16.416.717.116.317.816.917.116.917.917.017.217.217.416.817.116.317.316.514.413.914.514.314.315.616.215.414.814.115.215.1

us-gaap:OperatingSegments, us-gaap:AllOtherSegments


Other
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-31
Value11111111111112111110101010119.7779.2179.4498.892
Percentage of OtherCostAndExpenseOperating13.313.113.112.713.513.213.412.713.112.812.812.912.914.212.011.812.512.9

us-gaap:OperatingSegments, us-gaap:Banking


Other
Period End2020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-30
Value6759646361605959575756585653
Percentage of OtherCostAndExpenseOperating72.670.471.670.471.270.471.271.070.970.569.871.872.871.2

us-gaap:OtherNoninterestExpense

us-gaap:OtherNoninterestExpense


Other
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-30
Value4.2073.4815.1024.6194.1344.567.2785.1726.2265.4146.6785.1884.0362.9385.3565.0564.0774.0525.2714.0963.6573.5293.9373.1433.13.3416.9063.7723.4563.1764.4133.6313.8073.126.1294.0463.4542.832-0.1574.5393.3132.635-1.5645.3112.708
Percentage of OtherNoninterestExpense100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:PaymentsForProceedsFromBusinessesAndInterestInAffiliates

us-gaap:PaymentsForProceedsFromBusinessesAndInterestInAffiliates


Payments
Period End2020-09-302019-09-30
Value0.03.453
Percentage of PaymentsForProceedsFromBusinessesAndInterestInAffiliates0.0100.0

us-gaap:PaymentsForProceedsFromLoansAndLeases

us-gaap:PaymentsForProceedsFromLoansAndLeases


Payments
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312011-09-302010-09-30
Value-126.87-52.297-43.104-68.638322-25.446409120-11.847-15.7566412-25.9-44.817-49.935-57.897-12.197113986229252101-70.0131.878-9.361
Percentage of PaymentsForProceedsFromLoansAndLeases100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:PaymentsForProceedsFromRealEstatePartnershipInvestmentNet

us-gaap:PaymentsForProceedsFromRealEstatePartnershipInvestmentNet


Payments
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-31
Value165000.0155000.0400000.0521000.00550000.0295000.0778000.00564000.0001118000.079000.0
Percentage of PaymentsForProceedsFromRealEstatePartnershipInvestmentNet100.0100.0100.0100.00.0100.0100.0100.00.0100.00.00.0100.0100.0

us-gaap:PaymentsToAcquireAvailableForSaleSecuritiesDebt

us-gaap:PaymentsToAcquireAvailableForSaleSecuritiesDebt


Payments
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-31
Value2125461023263034724254713
Percentage of PaymentsToAcquireAvailableForSaleSecuritiesDebt100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:PaymentsToAcquireBusinessesGross us-gaap:BusinessAcquisition

us-gaap:PaymentsToAcquireBusinessesGross

cbu:NuvantageInsuranceInc.


Payments
Period End2021-06-03
Value2.9
Percentage of PaymentsToAcquireBusinessesGross100.0

us-gaap:ProceedsFromIssuanceOfCommonStock

us-gaap:ProceedsFromIssuanceOfCommonStock


Proceeds
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312012-01-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-30
Value1.347.3291.6511.1186.6246.3994.4031.2912.065-0.8440.6491.154.0740.570.8230.9111.021.8092.9873.6742.950.9321.3862.7752.6722.9413.8740.5160.7554.8443.1674.7062.4544.9121.2721.8560.59260573.0780.4210.5281.3243.0450.325
Percentage of ProceedsFromIssuanceOfCommonStock100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:ProceedsFromMaturitiesPrepaymentsAndCallsOfAvailableForSaleSecurities

us-gaap:ProceedsFromMaturitiesPrepaymentsAndCallsOfAvailableForSaleSecurities


Proceeds
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-30
Value737866688686156544652383242274736403322373018374252363633481975456052704166361024866364021
Percentage of ProceedsFromMaturitiesPrepaymentsAndCallsOfAvailableForSaleSecurities100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:ProceedsFromMaturitiesPrepaymentsAndCallsOfOtherInvestments

us-gaap:ProceedsFromMaturitiesPrepaymentsAndCallsOfOtherInvestments


Proceeds
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-31
Value0.2652.3830.080.030.0020.4040.7370.7210.0772.46-2.4250.8842.4484.961.536181.2978.709-0.3476.049-9.296121.6180.0-6.2326.4040.001-0.0020.0030.011260.00.00.0
Percentage of ProceedsFromMaturitiesPrepaymentsAndCallsOfOtherInvestments100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.00.0100.0100.0100.0100.0100.0100.0100.00.00.00.0

us-gaap:ProceedsFromRepaymentsOfDebt

us-gaap:ProceedsFromRepaymentsOfDebt


Proceeds
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-30
Value-65.903-26.942.218112-38.523-45.041690-107.543-63.913992-97.959-81.33848-58.76411-146.212-133.7233-267.6-256.8-8.1370-142.3-5.8052410275-449.039244-54.82-414.422-0.055-429.756247182-0.054-0.105-19.704-0.075-1.047-0.049
Percentage of ProceedsFromRepaymentsOfDebt100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:ProceedsFromSaleOfTreasuryStock

us-gaap:ProceedsFromSaleOfTreasuryStock


Proceeds
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312012-12-31
Value0.00.00.00.00.0060.0790.2223.3221.4551.8855.3351.0523.6282.5462.1991.6924.0182.1511.9630.7971.1065.022111.4091.8162.2470.9590.00.00.0-0.21
Percentage of ProceedsFromSaleOfTreasuryStock0.00.00.00.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.00.00.00.0100.0

us-gaap:ProfessionalFees

us-gaap:ProfessionalFees


Professional
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-30
Value2.4993.0343.0282.3653.0613.1512.7842.5952.6842.722.5972.5222.7452.7813.782.7642.6192.4142.1531.9281.8572.5161.8611.5641.6421.7461.821.9731.5071.9471.6451.8971.5262.3992.2271.711.8042.2081.6031.641.3071.3391.7131.0141.505
Percentage of ProfessionalFees100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:ProvisionForLoanAndLeaseLosses

us-gaap:ProvisionForLoanAndLeaseLosses


Provision
Period End2021-06-302021-03-312020-09-302020-06-302019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-30
Value-3.911-5.4191.7826.0332.8571.7511.42.4222.4952.2152.4483.6795.3812.3141.4611.8282.641.792.3051.3413.3271.9060.5910.6232.5311.7471.91.03.1852.0931.3211.3932.6662.6432.1551.6441.5931.0431.051.051.9351.4
Percentage of ProvisionForLoanAndLeaseLosses100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:ProvisionForLoanAndLeaseLosses us-gaap:AdjustmentsForNewAccountingPronouncements

us-gaap:AccountingStandardsUpdate201613


Provision
Period End2020-12-312020-09-302020-06-302020-03-31
Value-2.8351.7826.0335.934
Percentage of ProvisionForLoanAndLeaseLosses0.0100.0100.00.0

us-gaap:ProvisionForLoanAndLeaseLosses us-gaap:AdjustmentsForNewAccountingPronouncements, us-gaap:CreditLossStatus

us-gaap:AccountingStandardsUpdate201613, us-gaap:FinancialAssetAcquiredWithCreditDeterioration


Provision
Period End2020-12-312020-09-302020-06-302020-03-31
Value-2.1650.045-0.061-0.026
Percentage of ProvisionForLoanAndLeaseLosses0.02.5-1.00.0

us-gaap:ProvisionForLoanAndLeaseLosses us-gaap:AdjustmentsForNewAccountingPronouncements, us-gaap:FinancingReceivablePortfolioSegment

us-gaap:AccountingStandardsUpdate201613, us-gaap:UnallocatedFinancingReceivables


Provision
Period End2020-12-312020-09-302020-06-302020-03-31
Value-0.0040.0040.228-0.228
Percentage of ProvisionForLoanAndLeaseLosses0.00.23.80.0

us-gaap:ProvisionForLoanAndLeaseLosses us-gaap:AdjustmentsForNewAccountingPronouncements, us-gaap:FinancingReceivablePortfolioSegment, us-gaap:FinancingReceivableRecordedInvestmentByClassOfFinancingReceivable

us-gaap:AccountingStandardsUpdate201613, us-gaap:CommercialPortfolioSegment, us-gaap:CommercialLoan


Provision
Period End2020-12-312020-09-302020-06-302020-03-31
Value1.7673.5392.155-0.187
Percentage of ProvisionForLoanAndLeaseLosses0.0198.635.70.0

us-gaap:AccountingStandardsUpdate201613, us-gaap:ConsumerPortfolioSegment, cbu:ConsumerInstallmentDirect


Provision
Period End2020-12-312020-09-302020-06-302020-03-31
Value-0.332-0.120.3741.476
Percentage of ProvisionForLoanAndLeaseLosses0.0-6.76.20.0

us-gaap:AccountingStandardsUpdate201613, us-gaap:ConsumerPortfolioSegment, cbu:ConsumerInstallmentIndirect


Provision
Period End2020-12-312020-09-302020-06-302020-03-31
Value-0.331-0.9632.5871.895
Percentage of ProvisionForLoanAndLeaseLosses0.0-54.042.90.0

us-gaap:AccountingStandardsUpdate201613, us-gaap:ConsumerPortfolioSegment, cbu:HomeEquityReceivables


Provision
Period End2020-12-312020-09-302020-06-302020-03-31
Value-0.309-0.1240.04-0.386
Percentage of ProvisionForLoanAndLeaseLosses0.0-7.00.70.0

us-gaap:AccountingStandardsUpdate201613, us-gaap:ResidentialPortfolioSegment, us-gaap:ResidentialMortgage


Provision
Period End2020-09-302020-06-302020-03-31
Value-0.5990.713.39
Percentage of ProvisionForLoanAndLeaseLosses-33.611.80.0

us-gaap:ProvisionForLoanAndLeaseLosses us-gaap:CreditLossStatus

us-gaap:FinancialAssetAcquiredWithCreditDeterioration


Provision
Period End2021-06-302021-03-312020-09-302020-06-302019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-30
Value-0.1440.0870.045-0.0610.0070.0010.00.122-0.0020.0150.0480.2040.181-0.0110.136
Percentage of ProvisionForLoanAndLeaseLosses3.7-1.62.5-1.00.20.10.05.0-0.10.72.05.53.4-0.59.3

us-gaap:ProvisionForLoanAndLeaseLosses us-gaap:FinancingReceivablePortfolioSegment

us-gaap:UnallocatedFinancingReceivables


Provision
Period End2021-06-302021-03-312020-09-302020-06-302019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-30
Value0.00.00.0040.2280.019-0.0530.001-0.010.089-0.159-0.014-0.0160.1020.1420.0830.122-0.2840.085-0.029-0.322-0.712-0.461-0.0090.616-0.18-0.065-0.166
Percentage of ProvisionForLoanAndLeaseLosses-0.0-0.00.23.80.7-3.00.1-0.43.6-7.2-0.6-0.41.96.15.76.7-10.84.7-1.3-24.0-21.4-24.2-1.598.9-7.1-3.7-8.7

us-gaap:ProvisionForLoanAndLeaseLosses us-gaap:FinancingReceivablePortfolioSegment, us-gaap:FinancingReceivableRecordedInvestmentByClassOfFinancingReceivable

us-gaap:CommercialPortfolioSegment, us-gaap:CommercialLoan


Provision
Period End2021-06-302021-03-312020-09-302020-06-302019-12-312019-09-302019-06-302019-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-30
Value-3.878-1.1643.5392.1551.6980.301-0.4180.8313.3470.3990.3350.2611.122-0.2830.8681.021.7280.112-0.28-0.331-0.3290.138-0.208
Percentage of ProvisionForLoanAndLeaseLosses99.221.5198.635.759.417.2-29.934.362.217.222.914.342.5-15.837.776.151.95.9-47.4-53.1-13.07.9-10.9

us-gaap:ConsumerPortfolioSegment, cbu:ConsumerInstallmentDirect


Provision
Period End2021-06-302021-03-312020-09-302020-06-302019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-30
Value-0.152-0.438-0.120.3740.3430.3830.3520.3170.1320.2990.3770.2190.4380.4260.3810.0454.250.170.2960.1190.1680.3590.207-0.052-0.040.10.405
Percentage of ProvisionForLoanAndLeaseLosses3.98.1-6.76.212.021.925.113.15.313.515.46.08.118.426.12.5161.09.512.88.95.018.835.0-8.3-1.65.721.3

us-gaap:ConsumerPortfolioSegment, cbu:ConsumerInstallmentIndirect


Provision
Period End2021-06-302021-03-312020-09-302020-06-302019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-30
Value-0.45-2.423-0.9632.5870.4931.2210.3370.7460.5621.7190.7621.3631.041.130.1651.292-2.6571.5031.2860.6521.7371.3670.569-0.0230.9091.2311.198
Percentage of ProvisionForLoanAndLeaseLosses11.544.7-54.042.917.369.724.130.822.577.631.137.019.348.811.370.7-100.684.055.848.652.271.796.3-3.735.970.563.1

us-gaap:ConsumerPortfolioSegment, cbu:HomeEquityReceivables


Provision
Period End2021-06-302021-03-312020-09-302020-06-302019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-30
Value0.265-0.585-0.1240.040.189-0.0080.109-0.0080.3120.2250.015-0.02-0.047-0.0520.066-0.027-0.140.01-0.019-0.038-0.0270.1020.0510.0211.1060.0770.256
Percentage of ProvisionForLoanAndLeaseLosses-6.810.8-7.00.76.6-0.57.8-0.312.510.20.6-0.5-0.9-2.24.5-1.5-5.30.6-0.8-2.8-0.85.48.63.443.74.413.5

us-gaap:ResidentialPortfolioSegment, us-gaap:ResidentialMortgage


Provision
Period End2021-06-302021-03-312020-09-302020-06-302019-12-312019-09-302019-06-302019-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-30
Value0.448-0.896-0.5990.710.108-0.0941.0190.4240.320.280.2950.1330.3090.305-0.177-0.0070.3040.4210.1130.3691.0350.2680.446
Percentage of ProvisionForLoanAndLeaseLosses-11.516.5-33.611.83.8-5.472.817.55.912.120.27.311.717.0-7.7-0.59.122.119.159.240.915.323.5

us-gaap:ProvisionForLoanLeaseAndOtherLosses

us-gaap:ProvisionForLoanLeaseAndOtherLosses


Provision
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-30
Value-4.338-5.719-3.1011.9459.7745.5942.8571.7511.42.4221.3932.6662.6432.1551.6441.5931.0431.051.051.9351.42.05
Percentage of ProvisionForLoanLeaseAndOtherLosses100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:ProvisionForLoanLeaseAndOtherLosses us-gaap:ConsolidationItems, us-gaap:StatementBusinessSegments

us-gaap:OperatingSegments, cbu:BankingServices


Provision
Period End2021-06-302021-03-312020-06-302020-03-31
Value-4.338-5.7199.7745.594
Percentage of ProvisionForLoanLeaseAndOtherLosses100.0100.0100.0100.0

us-gaap:OperatingSegments, us-gaap:Banking


Provision
Period End2020-09-302020-06-302020-03-312019-09-302019-06-302019-03-31
Value1.9459.7745.5941.7511.42.422
Percentage of ProvisionForLoanLeaseAndOtherLosses100.0100.0100.0100.0100.0100.0

us-gaap:StockIssued1

us-gaap:StockIssued1


Stock
Period End2020-12-312020-09-302019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-31
Value0.00.00.00.00.00.00.00.00.00.02.3950.0262780.00.00.00.0
Percentage of StockIssued10.00.00.00.00.00.00.00.00.00.0100.00.0100.0100.00.00.00.00.0

us-gaap:StockIssuedDuringPeriodSharesAcquisitions us-gaap:StatementEquityComponents

us-gaap:StockIssuedDuringPeriodSharesAcquisitions

cbu:CommonStockOutstanding


Stock
Period End2020-12-312020-09-302020-06-30
Value001363300.0
Percentage of StockIssuedDuringPeriodSharesAcquisitions0.00.0100.0

us-gaap:StockIssuedDuringPeriodSharesEmployeeBenefitPlan us-gaap:StatementEquityComponents

us-gaap:StockIssuedDuringPeriodSharesEmployeeBenefitPlan

cbu:CommonStockOutstanding


Stock
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-31
Value777.01012.03260.0-1207.0897.084.06685.051904.021571.030197.096704.015541.064533.041880.0
Percentage of StockIssuedDuringPeriodSharesEmployeeBenefitPlan100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:StockIssuedDuringPeriodValueAcquisitions

us-gaap:StockIssuedDuringPeriodValueAcquisitions


Stock
Period End2020-12-312020-09-302020-06-302017-12-312017-09-302017-06-302017-03-312011-12-312011-09-30
Value0.00.0762.3950.0262780.00.0
Percentage of StockIssuedDuringPeriodValueAcquisitions0.00.0100.0100.00.0100.0100.00.00.0

us-gaap:StockIssuedDuringPeriodValueAcquisitions us-gaap:StatementEquityComponents

us-gaap:AdditionalPaidInCapital


Stock
Period End2020-12-312020-09-302020-06-302017-12-312017-09-302017-06-302017-03-312011-12-312011-09-30
Value0.00.0752.3520.0257770.00.0
Percentage of StockIssuedDuringPeriodValueAcquisitions0.00.098.298.20.098.298.30.00.0

us-gaap:CommonStock


Stock
Period End2020-12-312020-09-302020-06-302017-12-312017-09-302017-06-302017-03-312011-12-312011-09-30
Value0.00.01.3630.0430.04.6831.3230.00.0
Percentage of StockIssuedDuringPeriodValueAcquisitions0.00.01.81.80.01.81.70.00.0

us-gaap:StockIssuedDuringPeriodValueEmployeeBenefitPlan

us-gaap:StockIssuedDuringPeriodValueEmployeeBenefitPlan


Stock
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-31
Value0.00.00.00.00.0060.0790.2223.3221.4551.8855.3351.0523.6282.546
Percentage of StockIssuedDuringPeriodValueEmployeeBenefitPlan0.00.00.00.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:StockIssuedDuringPeriodValueEmployeeBenefitPlan us-gaap:StatementEquityComponents

us-gaap:AdditionalPaidInCapital


Stock
Period End2020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-31
Value0.00.00.0020.0360.0971.3320.5850.7091.9820.4511.260.982
Percentage of StockIssuedDuringPeriodValueEmployeeBenefitPlan0.00.033.345.643.740.140.237.637.242.934.738.6

us-gaap:DeferredCompensationShareBasedPayments


Stock
Period End2021-06-302021-03-312020-09-302020-06-302020-03-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-31
Value0.060.0680.0650.0650.0740.0680.0660.079-0.220.070.0690.081
Percentage of StockIssuedDuringPeriodValueEmployeeBenefitPlan0.00.00.01083.393.72.04.54.2-4.16.71.93.2

us-gaap:TreasuryStock


Stock
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-31
Value-0.06-0.0680.204-0.065-0.061-0.0310.3381.9220.8041.0973.5730.5312.2991.483
Percentage of StockIssuedDuringPeriodValueEmployeeBenefitPlan0.00.00.00.0-1016.7-39.2152.357.955.358.267.050.563.458.2

us-gaap:TransferToOtherRealEstate

us-gaap:TransferToOtherRealEstate


Transfer
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-30
Value57000.063000.099000.0202000.0211000.0779000.0689000.0654000.0767000.0412000.0873000.0581000.0903000.0942000.01048000.0422000.01128000.0920000.0475000.01066000.0681000.0390000.01009000.01104000.01309000.0521000.0435000.0561000.0787000.0763000.03301000.01585000.01043000.02396000.02488000.0594000.0
Percentage of TransferToOtherRealEstate100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

cbu:AccruedInterestAndOtherLiabilities

cbu:AccruedInterestAndOtherLiabilities


Accrued
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302015-12-31
Value200177230246246228215259205189157152155159180213189178144173177135
Percentage of AccruedInterestAndOtherLiabilities100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

cbu:AccruedInterestAndOtherLiabilities dei:LegalEntity, us-gaap:ConsolidatedEntities

cbu:SevenZeroSixNorthClinton, us-gaap:VariableInterestEntityPrimaryBeneficiary


Accrued
Period End2020-12-312019-12-312018-12-31
Value0.00.0010.0
Percentage of AccruedInterestAndOtherLiabilities0.00.00.0

cbu:AccruedInterestAndOtherLiabilities us-gaap:ConsolidatedEntities

srt:ParentCompany


Accrued
Period End2020-12-312019-12-312018-12-312017-12-31
Value30242120
Percentage of AccruedInterestAndOtherLiabilities13.411.513.711.6

cbu:AccumulatedOtherComprehensiveIncomeLossAvailableForSaleSecuritiesAdjustmentGross

cbu:AccumulatedOtherComprehensiveIncomeLossAvailableForSaleSecuritiesAdjustmentGross


Accumulated
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-06-302012-03-312011-12-312011-03-312010-12-312009-12-31
Value-27.239-107.3131201541631553245367.676-16.229-53.04-32.692-17.875235255454114016413365100561067544469.556-31.002-3.844-1.992641311297885189.93312
Percentage of AccumulatedOtherComprehensiveIncomeLossAvailableForSaleSecuritiesAdjustmentGross100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

cbu:AccumulatedOtherComprehensiveIncomeLossAvailableForSaleSecuritiesAdjustmentTaxEffect

cbu:AccumulatedOtherComprehensiveIncomeLossAvailableForSaleSecuritiesAdjustmentTaxEffect


Accumulated
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-03-312010-12-312009-12-31
Value-6.252-25.499293739378.221109.0662.071-3.969-12.908-7.7754.149-6.006-20.295-21.247-17.515-15.989-53.426-62.734-50.732-25.317-38.826-21.847-40.976-27.603-16.176-16.886-3.402111.4280.861-24.396-49.337-53.916-48.692-29.05-31.473-6.451-3.001-4.096
Percentage of AccumulatedOtherComprehensiveIncomeLossAvailableForSaleSecuritiesAdjustmentTaxEffect100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

cbu:AccumulatedOtherComprehensiveIncomeLossDefinedBenefitPensionAndOtherPostretirementPlansTax us-gaap:RetirementPlanType

cbu:AccumulatedOtherComprehensiveIncomeLossDefinedBenefitPensionAndOtherPostretirementPlansTax

us-gaap:OtherPostretirementBenefitPlansDefinedBenefit


Accumulated
Period End2020-12-312019-12-312018-12-312017-12-312016-12-31
Value-0.094-0.155-0.21-0.296-0.614
Percentage of AccumulatedOtherComprehensiveIncomeLossDefinedBenefitPensionAndOtherPostretirementPlansTax100.0100.0100.0100.0100.0

us-gaap:PensionPlansDefinedBenefit


Accumulated
Period End2020-12-312019-12-312018-12-312017-12-312016-12-31
Value9.48811107.3411
Percentage of AccumulatedOtherComprehensiveIncomeLossDefinedBenefitPensionAndOtherPostretirementPlansTax-10093.6-7385.8-5176.2-2479.7-1892.8

cbu:AccumulatedOtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansGrossOfTax

cbu:AccumulatedOtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansGrossOfTax


Accumulated
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-03-312010-12-312009-12-31
Value3637384344454641424243282828282626282833333434252626261111111142434445383939-40.47723-23.264-23.273
Percentage of AccumulatedOtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansGrossOfTax100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

cbu:AccumulatedOtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansTaxEffect

cbu:AccumulatedOtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansTaxEffect


Accumulated
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-03-312010-12-312009-12-31
Value-8.932-9.163-9.394-10.691-10.892-11.093-11.293-10.204-10.356-10.508-10.66-7.099-6.959-7.001-7.044-10.093-10.138-10.918-11.008-12.671-12.801-12.933-13.064-9.854-9.978-10.102-10.225-4.336-4.289-4.241-4.194-16.307-16.687-17.067-17.447-14.809-15.073-15.33915-8.9048.9728.974
Percentage of AccumulatedOtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansTaxEffect100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

cbu:AggregateBankCapitalAndSurplusTransferableToCompanyMaximum

cbu:AggregateBankCapitalAndSurplusTransferableToCompanyMaximum


Aggregate
Period End2020-12-31
Value20.0
Percentage of AggregateBankCapitalAndSurplusTransferableToCompanyMaximum100.0

cbu:AllowanceForCreditLossesToTotalLoansRatio

cbu:AllowanceForCreditLossesToTotalLoansRatio


Allowance
Period End2021-06-302021-03-312020-12-312020-09-30
Value0.710.750.820.87
Percentage of AllowanceForCreditLossesToTotalLoansRatio100.0100.0100.0100.0

cbu:AuthorizedAmountOfDebenturesAndAssociatedPreferredSecuritiesForRedemption us-gaap:Ownership, us-gaap:SubsequentEventType

cbu:AuthorizedAmountOfDebenturesAndAssociatedPreferredSecuritiesForRedemption

cbu:CommunityStatutoryTrust4, us-gaap:SubsequentEvent


Authorized
Period End2021-01-20
Value77
Percentage of AuthorizedAmountOfDebenturesAndAssociatedPreferredSecuritiesForRedemption100.0

cbu:BankCapitalAndSurplusTransferableToCompanyMaximum

cbu:BankCapitalAndSurplusTransferableToCompanyMaximum


Bank
Period End2020-12-31
Value10.0
Percentage of BankCapitalAndSurplusTransferableToCompanyMaximum100.0

cbu:BenefitObligationForDefinedBenefitPensionPlanBeforeRevaluation us-gaap:TitleOfIndividual, us-gaap:RetirementPlanType

cbu:BenefitObligationForDefinedBenefitPensionPlanBeforeRevaluation

srt:ExecutiveOfficer, us-gaap:SupplementalEmployeeRetirementPlanDefinedBenefit


Benefit
Period End2020-12-312019-12-31
Value170145
Percentage of BenefitObligationForDefinedBenefitPensionPlanBeforeRevaluation100.0100.0

cbu:BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAccruedInterestAndFeesReceivables us-gaap:BusinessAcquisition

cbu:BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAccruedInterestAndFeesReceivables

cbu:NuvantageInsuranceCorporation


Business
Period End2021-06-30
Value0
Percentage of BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAccruedInterestAndFeesReceivables0.0

cbu:SteubenTrustCorporation


Business
Period End2020-12-31
Value2701000.0
Percentage of BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAccruedInterestAndFeesReceivables0.0

cbu:BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedDepositsAcquired us-gaap:BusinessAcquisition

cbu:BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedDepositsAcquired

cbu:NuvantageInsuranceCorporation


Business
Period End2021-06-30
Value0.0
Percentage of BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedDepositsAcquired0.0

cbu:SteubenTrustCorporation


Business
Period End2020-12-312020-06-12
Value516516
Percentage of BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedDepositsAcquired0.00.0

cbu:BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedLoansAcquired us-gaap:BusinessAcquisition

cbu:BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedLoansAcquired

cbu:NuvantageInsuranceCorporation


Business
Period End2021-06-30
Value0.0
Percentage of BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedLoansAcquired0.0

cbu:SteubenTrustCorporation


Business
Period End2020-12-312020-06-12
Value339339
Percentage of BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedLoansAcquired0.00.0

cbu:BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNoncurrentLiabilitiesOtherFederalHomeLoanBankAdvances us-gaap:BusinessAcquisition

cbu:BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNoncurrentLiabilitiesOtherFederalHomeLoanBankAdvances

cbu:NuvantageInsuranceCorporation


Business
Period End2021-06-30
Value0
Percentage of BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNoncurrentLiabilitiesOtherFederalHomeLoanBankAdvances0.0

cbu:BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedSubordinatedDebtHeldByUnconsolidatedSubsidiaryTrusts us-gaap:BusinessAcquisition

cbu:BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedSubordinatedDebtHeldByUnconsolidatedSubsidiaryTrusts

cbu:NuvantageInsuranceCorporation


Business
Period End2021-06-30
Value0.0
Percentage of BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedSubordinatedDebtHeldByUnconsolidatedSubsidiaryTrusts0.0

cbu:BusinessLendingLoansHeldForSaleUnpaidPrincipalBalance

cbu:BusinessLendingLoansHeldForSaleUnpaidPrincipalBalance


Business
Period End2021-03-31
Value800000.0
Percentage of BusinessLendingLoansHeldForSaleUnpaidPrincipalBalance100.0

cbu:BusinessLoansHeldForSaleFairValueDisclosure us-gaap:FairValueByFairValueHierarchyLevel

cbu:BusinessLoansHeldForSaleFairValueDisclosure

us-gaap:FairValueInputsLevel3


Business
Period End2021-03-31
Value848000.0
Percentage of BusinessLoansHeldForSaleFairValueDisclosure100.0

cbu:BusinessLoansHeldForSaleFairValueDisclosure us-gaap:FairValueByFairValueHierarchyLevel, us-gaap:FairValueByMeasurementFrequency

us-gaap:FairValueInputsLevel3, us-gaap:FairValueMeasurementsNonrecurring


Business
Period End2021-03-312020-12-31
Value848000.00
Percentage of BusinessLoansHeldForSaleFairValueDisclosure100.00.0

cbu:BusinessLoansHeldForSaleFairValueDisclosure us-gaap:FairValueByMeasurementFrequency

us-gaap:FairValueMeasurementsNonrecurring


Business
Period End2021-03-312020-12-31
Value848000.00
Percentage of BusinessLoansHeldForSaleFairValueDisclosure100.00.0

cbu:BusinessLoansHeldForSaleMeasurementInput us-gaap:Range, us-gaap:FairValueByFairValueHierarchyLevel, us-gaap:MeasurementInputType, us-gaap:ValuationTechnique

cbu:BusinessLoansHeldForSaleMeasurementInput

srt:Maximum, us-gaap:FairValueInputsLevel3, cbu:MeasurementInputEstimatedCostOfDisposalOrMarketAdjustment, cbu:ValuationTechniqueFairValueOfCollateral


Business
Period End2021-03-31
Value35.0
Percentage of BusinessLoansHeldForSaleMeasurementInput100.0

srt:Minimum, us-gaap:FairValueInputsLevel3, cbu:MeasurementInputEstimatedCostOfDisposalOrMarketAdjustment, cbu:ValuationTechniqueFairValueOfCollateral


Business
Period End2021-03-31
Value9.0
Percentage of BusinessLoansHeldForSaleMeasurementInput25.7

srt:WeightedAverage, us-gaap:FairValueInputsLevel3, cbu:MeasurementInputEstimatedCostOfDisposalOrMarketAdjustment, cbu:ValuationTechniqueFairValueOfCollateral


Business
Period End2021-03-31
Value27.9
Percentage of BusinessLoansHeldForSaleMeasurementInput79.7

cbu:CapitalRequiredForCapitalAdequacyPlusCapitalConservationBuffer

cbu:CapitalRequiredForCapitalAdequacyPlusCapitalConservationBuffer


Capital
Period End2020-12-312019-12-312018-12-312017-12-312016-12-31
Value727699592553409
Percentage of CapitalRequiredForCapitalAdequacyPlusCapitalConservationBuffer100.0100.0100.0100.0100.0

cbu:CapitalRequiredForCapitalAdequacyPlusCapitalConservationBuffer us-gaap:ConsolidatedEntities

srt:Subsidiaries


Capital
Period End2020-12-312019-12-312018-12-312017-12-31
Value720693587548
Percentage of CapitalRequiredForCapitalAdequacyPlusCapitalConservationBuffer99.199.199.299.1

cbu:CapitalRequiredForCapitalAdequacyPlusCapitalConservationBufferToRiskWeightedAssets

cbu:CapitalRequiredForCapitalAdequacyPlusCapitalConservationBufferToRiskWeightedAssets


Capital
Period End2020-12-312019-12-312018-12-312017-12-312016-12-31
Value10.50.1050.098750.09250.08625
Percentage of CapitalRequiredForCapitalAdequacyPlusCapitalConservationBufferToRiskWeightedAssets100.0100.0100.0100.0100.0

cbu:CapitalRequiredForCapitalAdequacyPlusCapitalConservationBufferToRiskWeightedAssets us-gaap:ConsolidatedEntities

srt:Subsidiaries


Capital
Period End2020-12-312019-12-312018-12-312017-12-31
Value10.50.1050.098750.0925
Percentage of CapitalRequiredForCapitalAdequacyPlusCapitalConservationBufferToRiskWeightedAssets100.0100.0100.0100.0

cbu:CommonEquityTier1CapitalRequiredForCapitalAdequacyRatio

cbu:CommonEquityTier1CapitalRequiredForCapitalAdequacyRatio


Common
Period End2020-12-312019-12-312018-12-312017-12-312016-12-312015-12-31
Value4.50.0450.0450.0450.0450.045
Percentage of CommonEquityTier1CapitalRequiredForCapitalAdequacyRatio100.0100.0100.0100.0100.0100.0

cbu:CommonEquityTier1CapitalRequiredForCapitalAdequacyRatio us-gaap:ConsolidatedEntities

srt:Subsidiaries


Common
Period End2020-12-312019-12-312018-12-312017-12-31
Value4.50.0450.0450.045
Percentage of CommonEquityTier1CapitalRequiredForCapitalAdequacyRatio100.0100.0100.0100.0

cbu:CommonEquityTier1CapitalRequiredToBeWellCapitalizedRatio

cbu:CommonEquityTier1CapitalRequiredToBeWellCapitalizedRatio


Common
Period End2020-12-312019-12-312018-12-312017-12-312016-12-312015-12-31
Value6.50.0650.0650.0650.0650.065
Percentage of CommonEquityTier1CapitalRequiredToBeWellCapitalizedRatio100.0100.0100.0100.0100.0100.0

cbu:CommonEquityTier1CapitalRequiredToBeWellCapitalizedRatio us-gaap:ConsolidatedEntities

srt:Subsidiaries


Common
Period End2020-12-312019-12-312018-12-312017-12-31
Value6.50.0650.0650.065
Percentage of CommonEquityTier1CapitalRequiredToBeWellCapitalizedRatio100.0100.0100.0100.0

cbu:CommonEquityTierOneCapitalRequiredForCapitalAdequacyPlusCapitalConservationBuffer

cbu:CommonEquityTierOneCapitalRequiredForCapitalAdequacyPlusCapitalConservationBuffer


Common
Period End2020-12-312019-12-312018-12-312017-12-312016-12-31
Value484466382344243
Percentage of CommonEquityTierOneCapitalRequiredForCapitalAdequacyPlusCapitalConservationBuffer100.0100.0100.0100.0100.0

cbu:CommonEquityTierOneCapitalRequiredForCapitalAdequacyPlusCapitalConservationBuffer us-gaap:ConsolidatedEntities

srt:Subsidiaries


Common
Period End2020-12-312019-12-312018-12-312017-12-31
Value480462379340
Percentage of CommonEquityTierOneCapitalRequiredForCapitalAdequacyPlusCapitalConservationBuffer99.199.199.299.1

cbu:CommonEquityTierOneCapitalRequiredForCapitalAdequacyPlusCapitalConservationBufferRatio

cbu:CommonEquityTierOneCapitalRequiredForCapitalAdequacyPlusCapitalConservationBufferRatio


Common
Period End2020-12-312019-12-312018-12-312017-12-312016-12-31
Value7.00.070.063750.05750.05125
Percentage of CommonEquityTierOneCapitalRequiredForCapitalAdequacyPlusCapitalConservationBufferRatio100.0100.0100.0100.0100.0

cbu:CommonEquityTierOneCapitalRequiredForCapitalAdequacyPlusCapitalConservationBufferRatio us-gaap:ConsolidatedEntities

srt:Subsidiaries


Common
Period End2020-12-312019-12-312018-12-312017-12-31
Value7.00.070.063750.0575
Percentage of CommonEquityTierOneCapitalRequiredForCapitalAdequacyPlusCapitalConservationBufferRatio100.0100.0100.0100.0

cbu:CoreDepositIntangiblesNet

cbu:CoreDepositIntangiblesNet


Core
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302010-12-31
Value11121315161516171517182021232526286.5537.1077.7138.3799.0699.7897.8948.5749.284101011121311121314159.9411011121310
Percentage of CoreDepositIntangiblesNet100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

cbu:CustodialEscrowBalancesMaintainedInConnectionWithLoansServicedForOthers

cbu:CustodialEscrowBalancesMaintainedInConnectionWithLoansServicedForOthers


Custodial
Period End2020-12-312019-12-312018-12-312017-12-312016-12-312015-12-312014-12-31
Value5583000.04596000.04982000.05363000.05603000.05700000.04320000.0
Percentage of CustodialEscrowBalancesMaintainedInConnectionWithLoansServicedForOthers100.0100.0100.0100.0100.0100.0100.0

cbu:DebtSecuritiesAvailableForSaleAccruedInterestReceivable

cbu:DebtSecuritiesAvailableForSaleAccruedInterestReceivable


Debt
Period End2020-09-30
Value14
Percentage of DebtSecuritiesAvailableForSaleAccruedInterestReceivable100.0

cbu:DeferredTaxAssetsTaxDeferredExpenseOperatingLeaseLiabilities

cbu:DeferredTaxAssetsTaxDeferredExpenseOperatingLeaseLiabilities


Deferred
Period End2020-12-312019-12-312018-12-31
Value8601000.09801000.00
Percentage of DeferredTaxAssetsTaxDeferredExpenseOperatingLeaseLiabilities100.0100.00.0

cbu:DeferredTaxLiabilitiesDeferredExpenseDeferredLoanOriginationCosts

cbu:DeferredTaxLiabilitiesDeferredExpenseDeferredLoanOriginationCosts


Deferred
Period End2020-12-312019-12-312018-12-312017-12-312016-12-312015-12-312014-12-312013-12-312012-12-312011-12-312010-12-31
Value7904000.07639000.06851000.06109000.08228000.07295000.06792000.06883000.06069000.05041000.04397000.0
Percentage of DeferredTaxLiabilitiesDeferredExpenseDeferredLoanOriginationCosts100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

cbu:DeferredTaxLiabilitiesRightOfUseAssets

cbu:DeferredTaxLiabilitiesRightOfUseAssets


Deferred
Period End2020-12-312019-12-312018-12-31
Value8384000.09566000.00
Percentage of DeferredTaxLiabilitiesRightOfUseAssets100.0100.00.0

cbu:DeferredTaxLiabilitiesUnrealizedGainsOnInvestmentSecurities

cbu:DeferredTaxLiabilitiesUnrealizedGainsOnInvestmentSecurities


Deferred
Period End2020-12-312019-12-312018-12-312017-12-312016-12-312015-12-312014-12-312013-12-312012-12-312011-12-312010-12-31
Value432114223238370.058377.487
Percentage of DeferredTaxLiabilitiesUnrealizedGainsOnInvestmentSecurities100.0100.0100.0100.0100.0100.0100.00.0100.0100.0100.0

cbu:DefinedBenefitPlanInitialProjectedBenefitObligation us-gaap:RetirementPlanFundingStatus, us-gaap:RetirementPlanName, us-gaap:RetirementPlanTaxStatus, us-gaap:RetirementPlanType

cbu:DefinedBenefitPlanInitialProjectedBenefitObligation

us-gaap:UnfundedPlan, cbu:RestorationPlan, us-gaap:NonqualifiedPlan, us-gaap:PensionPlansDefinedBenefit


Defined
Period End2020-12-312019-12-312018-12-312018-06-01
Value30000.0300000.0100000.0800000.0
Percentage of DefinedBenefitPlanInitialProjectedBenefitObligation100.0100.0100.0100.0

cbu:EquityAndOtherSecuritiesContinuousUnrealizedLossPosition

cbu:EquityAndOtherSecuritiesContinuousUnrealizedLossPosition


Equity
Period End2020-09-302020-06-302020-03-312019-03-312018-12-31
Value81000.079000.073000.098000.082000.0
Percentage of EquityAndOtherSecuritiesContinuousUnrealizedLossPosition100.0100.0100.0100.0100.0

cbu:EquityAndOtherSecuritiesContinuousUnrealizedLossPosition us-gaap:FinancialInstrument

us-gaap:EquitySecurities


Equity
Period End2020-09-302020-06-302020-03-312019-03-312018-12-31
Value81000.079000.073000.098000.082000.0
Percentage of EquityAndOtherSecuritiesContinuousUnrealizedLossPosition100.0100.0100.0100.0100.0

cbu:EquityAndOtherSecuritiesContinuousUnrealizedLossPositionAccumulatedLoss

cbu:EquityAndOtherSecuritiesContinuousUnrealizedLossPositionAccumulatedLoss


Equity
Period End2020-09-302020-06-302020-03-312019-03-312018-12-31
Value20000.022000.028000.02000.019000.0
Percentage of EquityAndOtherSecuritiesContinuousUnrealizedLossPositionAccumulatedLoss100.0100.0100