XML 148 R88.htm IDEA: XBRL DOCUMENT v2.4.1.9
Derivative And Credit-Related Financial Instruments (Schedule Of Derivative Instruments) (Details) (USD $)
In Millions, unless otherwise specified
Dec. 31, 2014
Dec. 31, 2013
Derivatives, Fair Value [Line Items]    
Notional/Contract Amount $ 21,562invest_DerivativeNotionalAmount [1] $ 20,538invest_DerivativeNotionalAmount [1]
Fair Value of Gross Derivative Assets 894us-gaap_DerivativeFairValueOfDerivativeAsset 500us-gaap_DerivativeFairValueOfDerivativeAsset
Fair Value of Gross Derivative Liabilities 661us-gaap_DerivativeFairValueOfDerivativeLiability 249us-gaap_DerivativeFairValueOfDerivativeLiability
Derivative Assets, Netting Adjustment - Offsetting Liabilities (133)us-gaap_DerivativeAssetFairValueGrossLiability (187)us-gaap_DerivativeAssetFairValueGrossLiability
Derivative Liabilities, Netting Adjustment - Offsetting Assets (133)us-gaap_DerivativeLiabilityFairValueGrossAsset (187)us-gaap_DerivativeLiabilityFairValueGrossAsset
Derivative Assets, Netting Adjustment - Cash Collateral Received (262)us-gaap_DerivativeAssetCollateralObligationToReturnCashOffset (2)us-gaap_DerivativeAssetCollateralObligationToReturnCashOffset
Derivative Liabilities, Netting Adjustment - Cash Collateral Posted 0us-gaap_DerivativeLiabilityCollateralRightToReclaimCashOffset (10)us-gaap_DerivativeLiabilityCollateralRightToReclaimCashOffset
Net Derivative Assets Included In Consolidated Balance Sheet 499us-gaap_DerivativeAssets [2] 311us-gaap_DerivativeAssets [2]
Net Derivative Liabilities Included In Consolidated Balance Sheet 528us-gaap_DerivativeLiabilities [2] 52us-gaap_DerivativeLiabilities [2]
Derivative Assets, Securities Pledged As Collateral (239)us-gaap_DerivativeCollateralObligationToReturnSecurities (138)us-gaap_DerivativeCollateralObligationToReturnSecurities
Derivative Liabilities, Securities Pledged As Collateral (2)us-gaap_DerivativeCollateralRightToReclaimSecurities (10)us-gaap_DerivativeCollateralRightToReclaimSecurities
Net Derivative Assets After Deducting Amounts Not Offset In Consolidated Balance Sheet 260us-gaap_DerivativeFairValueOfDerivativeAssetAmountOffsetAgainstCollateral 173us-gaap_DerivativeFairValueOfDerivativeAssetAmountOffsetAgainstCollateral
Net Derivative Liabilities After Deducting Amounts Not Offset In Consolidated Balance Sheet 526us-gaap_DerivativeFairValueOfDerivativeLiabilityAmountOffsetAgainstCollateral 42us-gaap_DerivativeFairValueOfDerivativeLiabilityAmountOffsetAgainstCollateral
Derivative Credit Risk Valuation Adjustment, Derivative Assets 2us-gaap_DerivativeCreditRiskValuationAdjustmentDerivativeAssets 2us-gaap_DerivativeCreditRiskValuationAdjustmentDerivativeAssets
Risk Management Purposes    
Derivatives, Fair Value [Line Items]    
Notional/Contract Amount 2,308invest_DerivativeNotionalAmount
/ us-gaap_DerivativeByNatureAxis
= cma_RiskManagementDerivativesMember		 [1] 1,703invest_DerivativeNotionalAmount
/ us-gaap_DerivativeByNatureAxis
= cma_RiskManagementDerivativesMember		 [1]
Fair Value of Gross Derivative Assets 179us-gaap_DerivativeFairValueOfDerivativeAsset
/ us-gaap_DerivativeByNatureAxis
= cma_RiskManagementDerivativesMember		 199us-gaap_DerivativeFairValueOfDerivativeAsset
/ us-gaap_DerivativeByNatureAxis
= cma_RiskManagementDerivativesMember
Fair Value of Gross Derivative Liabilities 0us-gaap_DerivativeFairValueOfDerivativeLiability
/ us-gaap_DerivativeByNatureAxis
= cma_RiskManagementDerivativesMember		 0us-gaap_DerivativeFairValueOfDerivativeLiability
/ us-gaap_DerivativeByNatureAxis
= cma_RiskManagementDerivativesMember
Risk Management Purposes | Designated as Hedging Instrument | Fair Value Hedging | Interest Rate Swaps    
Derivatives, Fair Value [Line Items]    
Notional/Contract Amount 1,800invest_DerivativeNotionalAmount
/ us-gaap_DerivativeByNatureAxis
= cma_RiskManagementDerivativesMember
/ us-gaap_DerivativeInstrumentRiskAxis
= us-gaap_InterestRateSwapMember
/ us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis
= us-gaap_FairValueHedgingMember
/ us-gaap_HedgingDesignationAxis
= us-gaap_DesignatedAsHedgingInstrumentMember		 [1] 1,450invest_DerivativeNotionalAmount
/ us-gaap_DerivativeByNatureAxis
= cma_RiskManagementDerivativesMember
/ us-gaap_DerivativeInstrumentRiskAxis
= us-gaap_InterestRateSwapMember
/ us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis
= us-gaap_FairValueHedgingMember
/ us-gaap_HedgingDesignationAxis
= us-gaap_DesignatedAsHedgingInstrumentMember		 [1]
Fair Value of Gross Derivative Assets 175us-gaap_DerivativeFairValueOfDerivativeAsset
/ us-gaap_DerivativeByNatureAxis
= cma_RiskManagementDerivativesMember
/ us-gaap_DerivativeInstrumentRiskAxis
= us-gaap_InterestRateSwapMember
/ us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis
= us-gaap_FairValueHedgingMember
/ us-gaap_HedgingDesignationAxis
= us-gaap_DesignatedAsHedgingInstrumentMember		 198us-gaap_DerivativeFairValueOfDerivativeAsset
/ us-gaap_DerivativeByNatureAxis
= cma_RiskManagementDerivativesMember
/ us-gaap_DerivativeInstrumentRiskAxis
= us-gaap_InterestRateSwapMember
/ us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis
= us-gaap_FairValueHedgingMember
/ us-gaap_HedgingDesignationAxis
= us-gaap_DesignatedAsHedgingInstrumentMember
Fair Value of Gross Derivative Liabilities 0us-gaap_DerivativeFairValueOfDerivativeLiability
/ us-gaap_DerivativeByNatureAxis
= cma_RiskManagementDerivativesMember
/ us-gaap_DerivativeInstrumentRiskAxis
= us-gaap_InterestRateSwapMember
/ us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis
= us-gaap_FairValueHedgingMember
/ us-gaap_HedgingDesignationAxis
= us-gaap_DesignatedAsHedgingInstrumentMember		 0us-gaap_DerivativeFairValueOfDerivativeLiability
/ us-gaap_DerivativeByNatureAxis
= cma_RiskManagementDerivativesMember
/ us-gaap_DerivativeInstrumentRiskAxis
= us-gaap_InterestRateSwapMember
/ us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis
= us-gaap_FairValueHedgingMember
/ us-gaap_HedgingDesignationAxis
= us-gaap_DesignatedAsHedgingInstrumentMember
Risk Management Purposes | Derivatives Used As Economic Hedges | Foreign Exchange Spot Forward And Swaps    
Derivatives, Fair Value [Line Items]    
Notional/Contract Amount 508invest_DerivativeNotionalAmount
/ us-gaap_DerivativeByNatureAxis
= cma_RiskManagementDerivativesMember
/ us-gaap_DerivativeInstrumentRiskAxis
= cma_ForeignExchangeSpotForwardAndSwapsMember
/ us-gaap_HedgingDesignationAxis
= cma_DerivativesUsedAsEconomicHedgesMember		 [1] 253invest_DerivativeNotionalAmount
/ us-gaap_DerivativeByNatureAxis
= cma_RiskManagementDerivativesMember
/ us-gaap_DerivativeInstrumentRiskAxis
= cma_ForeignExchangeSpotForwardAndSwapsMember
/ us-gaap_HedgingDesignationAxis
= cma_DerivativesUsedAsEconomicHedgesMember		 [1]
Fair Value of Gross Derivative Assets 4us-gaap_DerivativeFairValueOfDerivativeAsset
/ us-gaap_DerivativeByNatureAxis
= cma_RiskManagementDerivativesMember
/ us-gaap_DerivativeInstrumentRiskAxis
= cma_ForeignExchangeSpotForwardAndSwapsMember
/ us-gaap_HedgingDesignationAxis
= cma_DerivativesUsedAsEconomicHedgesMember		 1us-gaap_DerivativeFairValueOfDerivativeAsset
/ us-gaap_DerivativeByNatureAxis
= cma_RiskManagementDerivativesMember
/ us-gaap_DerivativeInstrumentRiskAxis
= cma_ForeignExchangeSpotForwardAndSwapsMember
/ us-gaap_HedgingDesignationAxis
= cma_DerivativesUsedAsEconomicHedgesMember
Fair Value of Gross Derivative Liabilities 0us-gaap_DerivativeFairValueOfDerivativeLiability
/ us-gaap_DerivativeByNatureAxis
= cma_RiskManagementDerivativesMember
/ us-gaap_DerivativeInstrumentRiskAxis
= cma_ForeignExchangeSpotForwardAndSwapsMember
/ us-gaap_HedgingDesignationAxis
= cma_DerivativesUsedAsEconomicHedgesMember		 0us-gaap_DerivativeFairValueOfDerivativeLiability
/ us-gaap_DerivativeByNatureAxis
= cma_RiskManagementDerivativesMember
/ us-gaap_DerivativeInstrumentRiskAxis
= cma_ForeignExchangeSpotForwardAndSwapsMember
/ us-gaap_HedgingDesignationAxis
= cma_DerivativesUsedAsEconomicHedgesMember
Customer-Initiated And Other Activities    
Derivatives, Fair Value [Line Items]    
Notional/Contract Amount 19,254invest_DerivativeNotionalAmount
/ us-gaap_DerivativeByNatureAxis
= cma_CustomerInitiatedAndOtherActivitiesDerivativesMember		 [1] 18,835invest_DerivativeNotionalAmount
/ us-gaap_DerivativeByNatureAxis
= cma_CustomerInitiatedAndOtherActivitiesDerivativesMember		 [1]
Fair Value of Gross Derivative Assets 715us-gaap_DerivativeFairValueOfDerivativeAsset
/ us-gaap_DerivativeByNatureAxis
= cma_CustomerInitiatedAndOtherActivitiesDerivativesMember		 301us-gaap_DerivativeFairValueOfDerivativeAsset
/ us-gaap_DerivativeByNatureAxis
= cma_CustomerInitiatedAndOtherActivitiesDerivativesMember
Fair Value of Gross Derivative Liabilities 661us-gaap_DerivativeFairValueOfDerivativeLiability
/ us-gaap_DerivativeByNatureAxis
= cma_CustomerInitiatedAndOtherActivitiesDerivativesMember		 249us-gaap_DerivativeFairValueOfDerivativeLiability
/ us-gaap_DerivativeByNatureAxis
= cma_CustomerInitiatedAndOtherActivitiesDerivativesMember
Customer-Initiated And Other Activities | Interest Rate Contracts    
Derivatives, Fair Value [Line Items]    
Notional/Contract Amount 12,328invest_DerivativeNotionalAmount
/ us-gaap_DerivativeByNatureAxis
= cma_CustomerInitiatedAndOtherActivitiesDerivativesMember
/ us-gaap_DerivativeInstrumentRiskAxis
= us-gaap_InterestRateContractMember		 [1] 11,697invest_DerivativeNotionalAmount
/ us-gaap_DerivativeByNatureAxis
= cma_CustomerInitiatedAndOtherActivitiesDerivativesMember
/ us-gaap_DerivativeInstrumentRiskAxis
= us-gaap_InterestRateContractMember		 [1]
Fair Value of Gross Derivative Assets 153us-gaap_DerivativeFairValueOfDerivativeAsset
/ us-gaap_DerivativeByNatureAxis
= cma_CustomerInitiatedAndOtherActivitiesDerivativesMember
/ us-gaap_DerivativeInstrumentRiskAxis
= us-gaap_InterestRateContractMember		 182us-gaap_DerivativeFairValueOfDerivativeAsset
/ us-gaap_DerivativeByNatureAxis
= cma_CustomerInitiatedAndOtherActivitiesDerivativesMember
/ us-gaap_DerivativeInstrumentRiskAxis
= us-gaap_InterestRateContractMember
Fair Value of Gross Derivative Liabilities 102us-gaap_DerivativeFairValueOfDerivativeLiability
/ us-gaap_DerivativeByNatureAxis
= cma_CustomerInitiatedAndOtherActivitiesDerivativesMember
/ us-gaap_DerivativeInstrumentRiskAxis
= us-gaap_InterestRateContractMember		 133us-gaap_DerivativeFairValueOfDerivativeLiability
/ us-gaap_DerivativeByNatureAxis
= cma_CustomerInitiatedAndOtherActivitiesDerivativesMember
/ us-gaap_DerivativeInstrumentRiskAxis
= us-gaap_InterestRateContractMember
Customer-Initiated And Other Activities | Interest Rate Caps And Floors Written    
Derivatives, Fair Value [Line Items]    
Notional/Contract Amount 274invest_DerivativeNotionalAmount
/ us-gaap_DerivativeByNatureAxis
= cma_CustomerInitiatedAndOtherActivitiesDerivativesMember
/ us-gaap_DerivativeInstrumentRiskAxis
= cma_InterestRateCapsAndFloorsWrittenMember		 [1] 277invest_DerivativeNotionalAmount
/ us-gaap_DerivativeByNatureAxis
= cma_CustomerInitiatedAndOtherActivitiesDerivativesMember
/ us-gaap_DerivativeInstrumentRiskAxis
= cma_InterestRateCapsAndFloorsWrittenMember		 [1]
Fair Value of Gross Derivative Assets 0us-gaap_DerivativeFairValueOfDerivativeAsset
/ us-gaap_DerivativeByNatureAxis
= cma_CustomerInitiatedAndOtherActivitiesDerivativesMember
/ us-gaap_DerivativeInstrumentRiskAxis
= cma_InterestRateCapsAndFloorsWrittenMember		 0us-gaap_DerivativeFairValueOfDerivativeAsset
/ us-gaap_DerivativeByNatureAxis
= cma_CustomerInitiatedAndOtherActivitiesDerivativesMember
/ us-gaap_DerivativeInstrumentRiskAxis
= cma_InterestRateCapsAndFloorsWrittenMember
Fair Value of Gross Derivative Liabilities 0us-gaap_DerivativeFairValueOfDerivativeLiability
/ us-gaap_DerivativeByNatureAxis
= cma_CustomerInitiatedAndOtherActivitiesDerivativesMember
/ us-gaap_DerivativeInstrumentRiskAxis
= cma_InterestRateCapsAndFloorsWrittenMember		 1us-gaap_DerivativeFairValueOfDerivativeLiability
/ us-gaap_DerivativeByNatureAxis
= cma_CustomerInitiatedAndOtherActivitiesDerivativesMember
/ us-gaap_DerivativeInstrumentRiskAxis
= cma_InterestRateCapsAndFloorsWrittenMember
Customer-Initiated And Other Activities | Interest Rate Caps and Floors Purchased    
Derivatives, Fair Value [Line Items]    
Notional/Contract Amount 274invest_DerivativeNotionalAmount
/ us-gaap_DerivativeByNatureAxis
= cma_CustomerInitiatedAndOtherActivitiesDerivativesMember
/ us-gaap_DerivativeInstrumentRiskAxis
= cma_InterestRateCapsAndFloorsPurchasedMember		 [1] 277invest_DerivativeNotionalAmount
/ us-gaap_DerivativeByNatureAxis
= cma_CustomerInitiatedAndOtherActivitiesDerivativesMember
/ us-gaap_DerivativeInstrumentRiskAxis
= cma_InterestRateCapsAndFloorsPurchasedMember		 [1]
Fair Value of Gross Derivative Assets 0us-gaap_DerivativeFairValueOfDerivativeAsset
/ us-gaap_DerivativeByNatureAxis
= cma_CustomerInitiatedAndOtherActivitiesDerivativesMember
/ us-gaap_DerivativeInstrumentRiskAxis
= cma_InterestRateCapsAndFloorsPurchasedMember		 1us-gaap_DerivativeFairValueOfDerivativeAsset
/ us-gaap_DerivativeByNatureAxis
= cma_CustomerInitiatedAndOtherActivitiesDerivativesMember
/ us-gaap_DerivativeInstrumentRiskAxis
= cma_InterestRateCapsAndFloorsPurchasedMember
Fair Value of Gross Derivative Liabilities 0us-gaap_DerivativeFairValueOfDerivativeLiability
/ us-gaap_DerivativeByNatureAxis
= cma_CustomerInitiatedAndOtherActivitiesDerivativesMember
/ us-gaap_DerivativeInstrumentRiskAxis
= cma_InterestRateCapsAndFloorsPurchasedMember		 0us-gaap_DerivativeFairValueOfDerivativeLiability
/ us-gaap_DerivativeByNatureAxis
= cma_CustomerInitiatedAndOtherActivitiesDerivativesMember
/ us-gaap_DerivativeInstrumentRiskAxis
= cma_InterestRateCapsAndFloorsPurchasedMember
Customer-Initiated And Other Activities | Interest Rate Swaps    
Derivatives, Fair Value [Line Items]    
Notional/Contract Amount 11,780invest_DerivativeNotionalAmount
/ us-gaap_DerivativeByNatureAxis
= cma_CustomerInitiatedAndOtherActivitiesDerivativesMember
/ us-gaap_DerivativeInstrumentRiskAxis
= us-gaap_InterestRateSwapMember		 [1] 11,143invest_DerivativeNotionalAmount
/ us-gaap_DerivativeByNatureAxis
= cma_CustomerInitiatedAndOtherActivitiesDerivativesMember
/ us-gaap_DerivativeInstrumentRiskAxis
= us-gaap_InterestRateSwapMember		 [1]
Fair Value of Gross Derivative Assets 153us-gaap_DerivativeFairValueOfDerivativeAsset
/ us-gaap_DerivativeByNatureAxis
= cma_CustomerInitiatedAndOtherActivitiesDerivativesMember
/ us-gaap_DerivativeInstrumentRiskAxis
= us-gaap_InterestRateSwapMember		 181us-gaap_DerivativeFairValueOfDerivativeAsset
/ us-gaap_DerivativeByNatureAxis
= cma_CustomerInitiatedAndOtherActivitiesDerivativesMember
/ us-gaap_DerivativeInstrumentRiskAxis
= us-gaap_InterestRateSwapMember
Fair Value of Gross Derivative Liabilities 102us-gaap_DerivativeFairValueOfDerivativeLiability
/ us-gaap_DerivativeByNatureAxis
= cma_CustomerInitiatedAndOtherActivitiesDerivativesMember
/ us-gaap_DerivativeInstrumentRiskAxis
= us-gaap_InterestRateSwapMember		 132us-gaap_DerivativeFairValueOfDerivativeLiability
/ us-gaap_DerivativeByNatureAxis
= cma_CustomerInitiatedAndOtherActivitiesDerivativesMember
/ us-gaap_DerivativeInstrumentRiskAxis
= us-gaap_InterestRateSwapMember
Customer-Initiated And Other Activities | Energy Contracts    
Derivatives, Fair Value [Line Items]    
Notional/Contract Amount 4,932invest_DerivativeNotionalAmount
/ us-gaap_DerivativeByNatureAxis
= cma_CustomerInitiatedAndOtherActivitiesDerivativesMember
/ us-gaap_DerivativeInstrumentRiskAxis
= us-gaap_CommodityContractMember		 [1] 5,374invest_DerivativeNotionalAmount
/ us-gaap_DerivativeByNatureAxis
= cma_CustomerInitiatedAndOtherActivitiesDerivativesMember
/ us-gaap_DerivativeInstrumentRiskAxis
= us-gaap_CommodityContractMember		 [1]
Fair Value of Gross Derivative Assets 527us-gaap_DerivativeFairValueOfDerivativeAsset
/ us-gaap_DerivativeByNatureAxis
= cma_CustomerInitiatedAndOtherActivitiesDerivativesMember
/ us-gaap_DerivativeInstrumentRiskAxis
= us-gaap_CommodityContractMember		 105us-gaap_DerivativeFairValueOfDerivativeAsset
/ us-gaap_DerivativeByNatureAxis
= cma_CustomerInitiatedAndOtherActivitiesDerivativesMember
/ us-gaap_DerivativeInstrumentRiskAxis
= us-gaap_CommodityContractMember
Fair Value of Gross Derivative Liabilities 525us-gaap_DerivativeFairValueOfDerivativeLiability
/ us-gaap_DerivativeByNatureAxis
= cma_CustomerInitiatedAndOtherActivitiesDerivativesMember
/ us-gaap_DerivativeInstrumentRiskAxis
= us-gaap_CommodityContractMember		 102us-gaap_DerivativeFairValueOfDerivativeLiability
/ us-gaap_DerivativeByNatureAxis
= cma_CustomerInitiatedAndOtherActivitiesDerivativesMember
/ us-gaap_DerivativeInstrumentRiskAxis
= us-gaap_CommodityContractMember
Customer-Initiated And Other Activities | Energy Caps and Floors Written    
Derivatives, Fair Value [Line Items]    
Notional/Contract Amount 1,218invest_DerivativeNotionalAmount
/ us-gaap_DerivativeByNatureAxis
= cma_CustomerInitiatedAndOtherActivitiesDerivativesMember
/ us-gaap_DerivativeInstrumentRiskAxis
= cma_EnergyCapsAndFloorsWrittenMember		 [1] 1,325invest_DerivativeNotionalAmount
/ us-gaap_DerivativeByNatureAxis
= cma_CustomerInitiatedAndOtherActivitiesDerivativesMember
/ us-gaap_DerivativeInstrumentRiskAxis
= cma_EnergyCapsAndFloorsWrittenMember		 [1]
Fair Value of Gross Derivative Assets 0us-gaap_DerivativeFairValueOfDerivativeAsset
/ us-gaap_DerivativeByNatureAxis
= cma_CustomerInitiatedAndOtherActivitiesDerivativesMember
/ us-gaap_DerivativeInstrumentRiskAxis
= cma_EnergyCapsAndFloorsWrittenMember		 1us-gaap_DerivativeFairValueOfDerivativeAsset
/ us-gaap_DerivativeByNatureAxis
= cma_CustomerInitiatedAndOtherActivitiesDerivativesMember
/ us-gaap_DerivativeInstrumentRiskAxis
= cma_EnergyCapsAndFloorsWrittenMember
Fair Value of Gross Derivative Liabilities 173us-gaap_DerivativeFairValueOfDerivativeLiability
/ us-gaap_DerivativeByNatureAxis
= cma_CustomerInitiatedAndOtherActivitiesDerivativesMember
/ us-gaap_DerivativeInstrumentRiskAxis
= cma_EnergyCapsAndFloorsWrittenMember		 48us-gaap_DerivativeFairValueOfDerivativeLiability
/ us-gaap_DerivativeByNatureAxis
= cma_CustomerInitiatedAndOtherActivitiesDerivativesMember
/ us-gaap_DerivativeInstrumentRiskAxis
= cma_EnergyCapsAndFloorsWrittenMember
Customer-Initiated And Other Activities | Energy Caps and Floors Purchased    
Derivatives, Fair Value [Line Items]    
Notional/Contract Amount 1,218invest_DerivativeNotionalAmount
/ us-gaap_DerivativeByNatureAxis
= cma_CustomerInitiatedAndOtherActivitiesDerivativesMember
/ us-gaap_DerivativeInstrumentRiskAxis
= cma_EnergyCapsAndFloorsPurchasedMember		 [1] 1,325invest_DerivativeNotionalAmount
/ us-gaap_DerivativeByNatureAxis
= cma_CustomerInitiatedAndOtherActivitiesDerivativesMember
/ us-gaap_DerivativeInstrumentRiskAxis
= cma_EnergyCapsAndFloorsPurchasedMember		 [1]
Fair Value of Gross Derivative Assets 173us-gaap_DerivativeFairValueOfDerivativeAsset
/ us-gaap_DerivativeByNatureAxis
= cma_CustomerInitiatedAndOtherActivitiesDerivativesMember
/ us-gaap_DerivativeInstrumentRiskAxis
= cma_EnergyCapsAndFloorsPurchasedMember		 48us-gaap_DerivativeFairValueOfDerivativeAsset
/ us-gaap_DerivativeByNatureAxis
= cma_CustomerInitiatedAndOtherActivitiesDerivativesMember
/ us-gaap_DerivativeInstrumentRiskAxis
= cma_EnergyCapsAndFloorsPurchasedMember
Fair Value of Gross Derivative Liabilities 0us-gaap_DerivativeFairValueOfDerivativeLiability
/ us-gaap_DerivativeByNatureAxis
= cma_CustomerInitiatedAndOtherActivitiesDerivativesMember
/ us-gaap_DerivativeInstrumentRiskAxis
= cma_EnergyCapsAndFloorsPurchasedMember		 1us-gaap_DerivativeFairValueOfDerivativeLiability
/ us-gaap_DerivativeByNatureAxis
= cma_CustomerInitiatedAndOtherActivitiesDerivativesMember
/ us-gaap_DerivativeInstrumentRiskAxis
= cma_EnergyCapsAndFloorsPurchasedMember
Customer-Initiated And Other Activities | Energy Swaps    
Derivatives, Fair Value [Line Items]    
Notional/Contract Amount 2,496invest_DerivativeNotionalAmount
/ us-gaap_DerivativeByNatureAxis
= cma_CustomerInitiatedAndOtherActivitiesDerivativesMember
/ us-gaap_DerivativeInstrumentRiskAxis
= cma_EnergySwapsMember		 [1] 2,724invest_DerivativeNotionalAmount
/ us-gaap_DerivativeByNatureAxis
= cma_CustomerInitiatedAndOtherActivitiesDerivativesMember
/ us-gaap_DerivativeInstrumentRiskAxis
= cma_EnergySwapsMember		 [1]
Fair Value of Gross Derivative Assets 354us-gaap_DerivativeFairValueOfDerivativeAsset
/ us-gaap_DerivativeByNatureAxis
= cma_CustomerInitiatedAndOtherActivitiesDerivativesMember
/ us-gaap_DerivativeInstrumentRiskAxis
= cma_EnergySwapsMember		 56us-gaap_DerivativeFairValueOfDerivativeAsset
/ us-gaap_DerivativeByNatureAxis
= cma_CustomerInitiatedAndOtherActivitiesDerivativesMember
/ us-gaap_DerivativeInstrumentRiskAxis
= cma_EnergySwapsMember
Fair Value of Gross Derivative Liabilities 352us-gaap_DerivativeFairValueOfDerivativeLiability
/ us-gaap_DerivativeByNatureAxis
= cma_CustomerInitiatedAndOtherActivitiesDerivativesMember
/ us-gaap_DerivativeInstrumentRiskAxis
= cma_EnergySwapsMember		 53us-gaap_DerivativeFairValueOfDerivativeLiability
/ us-gaap_DerivativeByNatureAxis
= cma_CustomerInitiatedAndOtherActivitiesDerivativesMember
/ us-gaap_DerivativeInstrumentRiskAxis
= cma_EnergySwapsMember
Customer-Initiated And Other Activities | Foreign Exchange Spot, Forwards, Options and Swaps    
Derivatives, Fair Value [Line Items]    
Notional/Contract Amount 1,994invest_DerivativeNotionalAmount
/ us-gaap_DerivativeByNatureAxis
= cma_CustomerInitiatedAndOtherActivitiesDerivativesMember
/ us-gaap_DerivativeInstrumentRiskAxis
= cma_ForeignExchangeSpotForwardsOptionsAndSwapsMember		 [1] 1,764invest_DerivativeNotionalAmount
/ us-gaap_DerivativeByNatureAxis
= cma_CustomerInitiatedAndOtherActivitiesDerivativesMember
/ us-gaap_DerivativeInstrumentRiskAxis
= cma_ForeignExchangeSpotForwardsOptionsAndSwapsMember		 [1]
Fair Value of Gross Derivative Assets 35us-gaap_DerivativeFairValueOfDerivativeAsset
/ us-gaap_DerivativeByNatureAxis
= cma_CustomerInitiatedAndOtherActivitiesDerivativesMember
/ us-gaap_DerivativeInstrumentRiskAxis
= cma_ForeignExchangeSpotForwardsOptionsAndSwapsMember		 14us-gaap_DerivativeFairValueOfDerivativeAsset
/ us-gaap_DerivativeByNatureAxis
= cma_CustomerInitiatedAndOtherActivitiesDerivativesMember
/ us-gaap_DerivativeInstrumentRiskAxis
= cma_ForeignExchangeSpotForwardsOptionsAndSwapsMember
Fair Value of Gross Derivative Liabilities $ 34us-gaap_DerivativeFairValueOfDerivativeLiability
/ us-gaap_DerivativeByNatureAxis
= cma_CustomerInitiatedAndOtherActivitiesDerivativesMember
/ us-gaap_DerivativeInstrumentRiskAxis
= cma_ForeignExchangeSpotForwardsOptionsAndSwapsMember		 $ 14us-gaap_DerivativeFairValueOfDerivativeLiability
/ us-gaap_DerivativeByNatureAxis
= cma_CustomerInitiatedAndOtherActivitiesDerivativesMember
/ us-gaap_DerivativeInstrumentRiskAxis
= cma_ForeignExchangeSpotForwardsOptionsAndSwapsMember
[1] Notional or contractual amounts, which represent the extent of involvement in the derivatives market, are used to determine the contractual cash flows required in accordance with the terms of the agreement. These amounts are typically not exchanged, significantly exceed amounts subject to credit or market risk and are not reflected in the consolidated balance sheets.
[2] Net derivative assets are included in “accrued income and other assets” and net derivative liabilities are included in “accrued expenses and other liabilities” on the consolidated balance sheets. Included in the fair value of net derivative assets and net derivative liabilities are credit valuation adjustments reflecting counterparty credit risk and credit risk of the Corporation. The fair value of net derivative assets included credit valuation adjustments for counterparty credit risk of $2 million at both December 31, 2014 and 2013.