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Fair Value Measurements - Financial Assets and Financial Liabilities Carried at Fair Value (Details) (USD $)
In Millions, unless otherwise specified
 3 Months Ended 12 Months Ended
Mar. 31, 2015
Dec. 31, 2014
Financial assets at fair value:    
Fixed maturities $ 19,141us-gaap_MarketableSecuritiesFixedMaturities $ 18,983us-gaap_MarketableSecuritiesFixedMaturities
Equity securities 182us-gaap_MarketableSecuritiesEquitySecurities 189us-gaap_MarketableSecuritiesEquitySecurities
Short-term investments 172us-gaap_OtherShortTermInvestments 163us-gaap_OtherShortTermInvestments
Fair Value, Measurements, Recurring [Member]    
Financial assets at fair value:    
Fixed maturities 19,141us-gaap_MarketableSecuritiesFixedMaturities
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember		 [1] 18,983us-gaap_MarketableSecuritiesFixedMaturities
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember		 [2]
Equity securities 182us-gaap_MarketableSecuritiesEquitySecurities
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember		 189us-gaap_MarketableSecuritiesEquitySecurities
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
Subtotal 19,323us-gaap_MarketableSecurities
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember		 19,172us-gaap_MarketableSecurities
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
Short-term investments 172us-gaap_OtherShortTermInvestments
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember		 163us-gaap_OtherShortTermInvestments
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
Total financial assets at fair value, excluding separate accounts 20,481ci_TotalFinancialAssetsAtFairValueExcludingSeparateAccounts
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember		 20,294ci_TotalFinancialAssetsAtFairValueExcludingSeparateAccounts
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
Financial liabilities at fair value:    
Total financial liabilities at fair value 948us-gaap_LiabilitiesFairValueDisclosure
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember		 930us-gaap_LiabilitiesFairValueDisclosure
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
Run-off Settlement Annuity Business [Member] | Fair Value, Measurements, Recurring [Member]    
Financial liabilities at fair value:    
Net appreciation required to adjust future policy benefits for run-off settlement annuity business included in fixed maturities 817ci_UnrealizedAppreciationSettlementAnnuity
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
/ us-gaap_StatementBusinessSegmentsAxis
= ci_RunoffSettlementAnnuityBusinessMember		 756ci_UnrealizedAppreciationSettlementAnnuity
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
/ us-gaap_StatementBusinessSegmentsAxis
= ci_RunoffSettlementAnnuityBusinessMember
Other derivatives [Member] | Fair Value, Measurements, Recurring [Member]    
Financial assets at fair value:    
Derivative assets 16us-gaap_DerivativeAssets
/ us-gaap_DerivativeInstrumentRiskAxis
= us-gaap_SwapMember
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember		 [3] 6us-gaap_DerivativeAssets
/ us-gaap_DerivativeInstrumentRiskAxis
= us-gaap_SwapMember
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember		 [4]
Financial liabilities at fair value:    
Derivative liabilities   1us-gaap_DerivativeLiabilities
/ us-gaap_DerivativeInstrumentRiskAxis
= us-gaap_SwapMember
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember		 [4]
Other derivatives [Member] | Designated as Hedging Instrument [Member] | Cash Flow Hedging [Member] | Fair Value, Measurements, Recurring [Member]    
Financial assets at fair value:    
Derivative assets 15us-gaap_DerivativeAssets
/ us-gaap_DerivativeInstrumentRiskAxis
= us-gaap_SwapMember
/ us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis
= us-gaap_CashFlowHedgingMember
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
/ us-gaap_HedgingDesignationAxis
= us-gaap_DesignatedAsHedgingInstrumentMember		 5us-gaap_DerivativeAssets
/ us-gaap_DerivativeInstrumentRiskAxis
= us-gaap_SwapMember
/ us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis
= us-gaap_CashFlowHedgingMember
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
/ us-gaap_HedgingDesignationAxis
= us-gaap_DesignatedAsHedgingInstrumentMember
Financial liabilities at fair value:    
Derivative liabilities   1us-gaap_DerivativeLiabilities
/ us-gaap_DerivativeInstrumentRiskAxis
= us-gaap_SwapMember
/ us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis
= us-gaap_CashFlowHedgingMember
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
/ us-gaap_HedgingDesignationAxis
= us-gaap_DesignatedAsHedgingInstrumentMember
Other derivatives [Member] | Designated as Hedging Instrument [Member] | Fair Value Hedging [Member] | Fair Value, Measurements, Recurring [Member]    
Financial assets at fair value:    
Derivative assets 1us-gaap_DerivativeAssets
/ us-gaap_DerivativeInstrumentRiskAxis
= us-gaap_SwapMember
/ us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis
= us-gaap_FairValueHedgingMember
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
/ us-gaap_HedgingDesignationAxis
= us-gaap_DesignatedAsHedgingInstrumentMember		 1us-gaap_DerivativeAssets
/ us-gaap_DerivativeInstrumentRiskAxis
= us-gaap_SwapMember
/ us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis
= us-gaap_FairValueHedgingMember
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
/ us-gaap_HedgingDesignationAxis
= us-gaap_DesignatedAsHedgingInstrumentMember
Other derivatives [Member] | Non designated [Member] | Fair Value, Measurements, Recurring [Member]    
Financial assets at fair value:    
Derivative assets 0us-gaap_DerivativeAssets
/ us-gaap_DerivativeInstrumentRiskAxis
= us-gaap_SwapMember
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
/ us-gaap_HedgingDesignationAxis
= us-gaap_NondesignatedMember		 0us-gaap_DerivativeAssets
/ us-gaap_DerivativeInstrumentRiskAxis
= us-gaap_SwapMember
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
/ us-gaap_HedgingDesignationAxis
= us-gaap_NondesignatedMember
Financial liabilities at fair value:    
Derivative liabilities   0us-gaap_DerivativeLiabilities
/ us-gaap_DerivativeInstrumentRiskAxis
= us-gaap_SwapMember
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
/ us-gaap_HedgingDesignationAxis
= us-gaap_NondesignatedMember
Guaranteed Minimum Income Benefit [Member]    
Financial liabilities at fair value:    
Percentage of GMIB exposure covered by retrocessional coverage 100.00%ci_PercentReinsuredExternallyGuaranteedMinimumIncomeBenefits
/ us-gaap_NetAmountAtRiskByProductAndGuaranteeGuaranteeTypeAxis
= us-gaap_GuaranteedMinimumIncomeBenefitMember		 100.00%ci_PercentReinsuredExternallyGuaranteedMinimumIncomeBenefits
/ us-gaap_NetAmountAtRiskByProductAndGuaranteeGuaranteeTypeAxis
= us-gaap_GuaranteedMinimumIncomeBenefitMember
Number of external reinsurers 3ci_CededCreditRiskNumberOfExternalReinsurers
/ us-gaap_NetAmountAtRiskByProductAndGuaranteeGuaranteeTypeAxis
= us-gaap_GuaranteedMinimumIncomeBenefitMember		 3ci_CededCreditRiskNumberOfExternalReinsurers
/ us-gaap_NetAmountAtRiskByProductAndGuaranteeGuaranteeTypeAxis
= us-gaap_GuaranteedMinimumIncomeBenefitMember
Guaranteed Minimum Income Benefit [Member] | Fair Value, Measurements, Recurring [Member]    
Financial assets at fair value:    
Derivative assets 970us-gaap_DerivativeAssets
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
/ us-gaap_NetAmountAtRiskByProductAndGuaranteeGuaranteeTypeAxis
= us-gaap_GuaranteedMinimumIncomeBenefitMember		 [5] 953us-gaap_DerivativeAssets
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
/ us-gaap_NetAmountAtRiskByProductAndGuaranteeGuaranteeTypeAxis
= us-gaap_GuaranteedMinimumIncomeBenefitMember		 [6]
Financial liabilities at fair value:    
Derivative liabilities 948us-gaap_DerivativeLiabilities
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
/ us-gaap_NetAmountAtRiskByProductAndGuaranteeGuaranteeTypeAxis
= us-gaap_GuaranteedMinimumIncomeBenefitMember		 929us-gaap_DerivativeLiabilities
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
/ us-gaap_NetAmountAtRiskByProductAndGuaranteeGuaranteeTypeAxis
= us-gaap_GuaranteedMinimumIncomeBenefitMember
Federal government and agency [Member] | Fair Value, Measurements, Recurring [Member]    
Financial assets at fair value:    
Fixed maturities 923us-gaap_MarketableSecuritiesFixedMaturities
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_USTreasuryAndGovernmentMember		 954us-gaap_MarketableSecuritiesFixedMaturities
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_USTreasuryAndGovernmentMember
State and local government [Member] | Fair Value, Measurements, Recurring [Member]    
Financial assets at fair value:    
Fixed maturities 1,832us-gaap_MarketableSecuritiesFixedMaturities
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_USStatesAndPoliticalSubdivisionsMember		 1,856us-gaap_MarketableSecuritiesFixedMaturities
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_USStatesAndPoliticalSubdivisionsMember
Foreign government [Member] | Fair Value, Measurements, Recurring [Member]    
Financial assets at fair value:    
Fixed maturities 1,956us-gaap_MarketableSecuritiesFixedMaturities
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_ForeignGovernmentDebtSecuritiesMember		 1,940us-gaap_MarketableSecuritiesFixedMaturities
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_ForeignGovernmentDebtSecuritiesMember
Corporate [Member] | Fair Value, Measurements, Recurring [Member]    
Financial assets at fair value:    
Fixed maturities 13,721us-gaap_MarketableSecuritiesFixedMaturities
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_CorporateDebtSecuritiesMember		 13,498us-gaap_MarketableSecuritiesFixedMaturities
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_CorporateDebtSecuritiesMember
Mortgage-backed [Member] | Fair Value, Measurements, Recurring [Member]    
Financial assets at fair value:    
Fixed maturities 64us-gaap_MarketableSecuritiesFixedMaturities
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesMember		 85us-gaap_MarketableSecuritiesFixedMaturities
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesMember
Other asset-backed [Member] | Fair Value, Measurements, Recurring [Member]    
Financial assets at fair value:    
Fixed maturities 645us-gaap_MarketableSecuritiesFixedMaturities
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_AssetBackedSecuritiesSecuritizedLoansAndReceivablesMember		 650us-gaap_MarketableSecuritiesFixedMaturities
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_AssetBackedSecuritiesSecuritizedLoansAndReceivablesMember
Fair Value Inputs Level 1 [Member] | Fair Value, Measurements, Recurring [Member]    
Financial assets at fair value:    
Fixed maturities 258us-gaap_MarketableSecuritiesFixedMaturities
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember		 [1] 290us-gaap_MarketableSecuritiesFixedMaturities
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember		 [2]
Equity securities 34us-gaap_MarketableSecuritiesEquitySecurities
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember		 61us-gaap_MarketableSecuritiesEquitySecurities
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
Subtotal 292us-gaap_MarketableSecurities
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember		 351us-gaap_MarketableSecurities
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
Short-term investments 0us-gaap_OtherShortTermInvestments
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember		 0us-gaap_OtherShortTermInvestments
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
Total financial assets at fair value, excluding separate accounts 292ci_TotalFinancialAssetsAtFairValueExcludingSeparateAccounts
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember		 351ci_TotalFinancialAssetsAtFairValueExcludingSeparateAccounts
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
Financial liabilities at fair value:    
Total financial liabilities at fair value 0us-gaap_LiabilitiesFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember		 0us-gaap_LiabilitiesFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
Fair Value Inputs Level 1 [Member] | Other derivatives [Member] | Fair Value, Measurements, Recurring [Member]    
Financial assets at fair value:    
Derivative assets 0us-gaap_DerivativeAssets
/ us-gaap_DerivativeInstrumentRiskAxis
= us-gaap_SwapMember
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember		 [3] 0us-gaap_DerivativeAssets
/ us-gaap_DerivativeInstrumentRiskAxis
= us-gaap_SwapMember
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember		 [4]
Financial liabilities at fair value:    
Derivative liabilities   0us-gaap_DerivativeLiabilities
/ us-gaap_DerivativeInstrumentRiskAxis
= us-gaap_SwapMember
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember		 [4]
Fair Value Inputs Level 1 [Member] | Guaranteed Minimum Income Benefit [Member] | Fair Value, Measurements, Recurring [Member]    
Financial assets at fair value:    
Derivative assets 0us-gaap_DerivativeAssets
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
/ us-gaap_NetAmountAtRiskByProductAndGuaranteeGuaranteeTypeAxis
= us-gaap_GuaranteedMinimumIncomeBenefitMember		 [5] 0us-gaap_DerivativeAssets
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
/ us-gaap_NetAmountAtRiskByProductAndGuaranteeGuaranteeTypeAxis
= us-gaap_GuaranteedMinimumIncomeBenefitMember		 [6]
Financial liabilities at fair value:    
Derivative liabilities 0us-gaap_DerivativeLiabilities
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
/ us-gaap_NetAmountAtRiskByProductAndGuaranteeGuaranteeTypeAxis
= us-gaap_GuaranteedMinimumIncomeBenefitMember		 0us-gaap_DerivativeLiabilities
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
/ us-gaap_NetAmountAtRiskByProductAndGuaranteeGuaranteeTypeAxis
= us-gaap_GuaranteedMinimumIncomeBenefitMember
Fair Value Inputs Level 1 [Member] | Federal government and agency [Member] | Fair Value, Measurements, Recurring [Member]    
Financial assets at fair value:    
Fixed maturities 258us-gaap_MarketableSecuritiesFixedMaturities
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_USTreasuryAndGovernmentMember		 290us-gaap_MarketableSecuritiesFixedMaturities
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_USTreasuryAndGovernmentMember
Fair Value Inputs Level 1 [Member] | State and local government [Member] | Fair Value, Measurements, Recurring [Member]    
Financial assets at fair value:    
Fixed maturities 0us-gaap_MarketableSecuritiesFixedMaturities
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_USStatesAndPoliticalSubdivisionsMember		 0us-gaap_MarketableSecuritiesFixedMaturities
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_USStatesAndPoliticalSubdivisionsMember
Fair Value Inputs Level 1 [Member] | Foreign government [Member] | Fair Value, Measurements, Recurring [Member]    
Financial assets at fair value:    
Fixed maturities 0us-gaap_MarketableSecuritiesFixedMaturities
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_ForeignGovernmentDebtSecuritiesMember		 0us-gaap_MarketableSecuritiesFixedMaturities
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_ForeignGovernmentDebtSecuritiesMember
Fair Value Inputs Level 1 [Member] | Corporate [Member] | Fair Value, Measurements, Recurring [Member]    
Financial assets at fair value:    
Fixed maturities 0us-gaap_MarketableSecuritiesFixedMaturities
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_CorporateDebtSecuritiesMember		 0us-gaap_MarketableSecuritiesFixedMaturities
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_CorporateDebtSecuritiesMember
Fair Value Inputs Level 1 [Member] | Mortgage-backed [Member] | Fair Value, Measurements, Recurring [Member]    
Financial assets at fair value:    
Fixed maturities 0us-gaap_MarketableSecuritiesFixedMaturities
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesMember		 0us-gaap_MarketableSecuritiesFixedMaturities
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesMember
Fair Value Inputs Level 1 [Member] | Other asset-backed [Member] | Fair Value, Measurements, Recurring [Member]    
Financial assets at fair value:    
Fixed maturities 0us-gaap_MarketableSecuritiesFixedMaturities
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_AssetBackedSecuritiesSecuritizedLoansAndReceivablesMember		 0us-gaap_MarketableSecuritiesFixedMaturities
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_AssetBackedSecuritiesSecuritizedLoansAndReceivablesMember
Fair Value Inputs Level 2 [Member] | Fair Value, Measurements, Recurring [Member]    
Financial assets at fair value:    
Fixed maturities 18,110us-gaap_MarketableSecuritiesFixedMaturities
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember		 [1] 17,879us-gaap_MarketableSecuritiesFixedMaturities
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember		 [2]
Equity securities 103us-gaap_MarketableSecuritiesEquitySecurities
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember		 85us-gaap_MarketableSecuritiesEquitySecurities
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
Subtotal 18,213us-gaap_MarketableSecurities
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember		 17,964us-gaap_MarketableSecurities
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
Short-term investments 172us-gaap_OtherShortTermInvestments
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember		 163us-gaap_OtherShortTermInvestments
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
Total financial assets at fair value, excluding separate accounts 18,401ci_TotalFinancialAssetsAtFairValueExcludingSeparateAccounts
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember		 18,133ci_TotalFinancialAssetsAtFairValueExcludingSeparateAccounts
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
Financial liabilities at fair value:    
Total financial liabilities at fair value 0us-gaap_LiabilitiesFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember		 1us-gaap_LiabilitiesFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
Fair Value Inputs Level 2 [Member] | Other derivatives [Member] | Fair Value, Measurements, Recurring [Member]    
Financial assets at fair value:    
Derivative assets 16us-gaap_DerivativeAssets
/ us-gaap_DerivativeInstrumentRiskAxis
= us-gaap_SwapMember
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember		 [3] 6us-gaap_DerivativeAssets
/ us-gaap_DerivativeInstrumentRiskAxis
= us-gaap_SwapMember
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember		 [4]
Financial liabilities at fair value:    
Derivative liabilities   1us-gaap_DerivativeLiabilities
/ us-gaap_DerivativeInstrumentRiskAxis
= us-gaap_SwapMember
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember		 [4]
Fair Value Inputs Level 2 [Member] | Guaranteed Minimum Income Benefit [Member] | Fair Value, Measurements, Recurring [Member]    
Financial assets at fair value:    
Derivative assets 0us-gaap_DerivativeAssets
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
/ us-gaap_NetAmountAtRiskByProductAndGuaranteeGuaranteeTypeAxis
= us-gaap_GuaranteedMinimumIncomeBenefitMember		 [5] 0us-gaap_DerivativeAssets
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
/ us-gaap_NetAmountAtRiskByProductAndGuaranteeGuaranteeTypeAxis
= us-gaap_GuaranteedMinimumIncomeBenefitMember		 [6]
Financial liabilities at fair value:    
Derivative liabilities 0us-gaap_DerivativeLiabilities
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
/ us-gaap_NetAmountAtRiskByProductAndGuaranteeGuaranteeTypeAxis
= us-gaap_GuaranteedMinimumIncomeBenefitMember		 0us-gaap_DerivativeLiabilities
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
/ us-gaap_NetAmountAtRiskByProductAndGuaranteeGuaranteeTypeAxis
= us-gaap_GuaranteedMinimumIncomeBenefitMember
Fair Value Inputs Level 2 [Member] | Federal government and agency [Member] | Fair Value, Measurements, Recurring [Member]    
Financial assets at fair value:    
Fixed maturities 665us-gaap_MarketableSecuritiesFixedMaturities
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_USTreasuryAndGovernmentMember		 664us-gaap_MarketableSecuritiesFixedMaturities
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_USTreasuryAndGovernmentMember
Fair Value Inputs Level 2 [Member] | State and local government [Member] | Fair Value, Measurements, Recurring [Member]    
Financial assets at fair value:    
Fixed maturities 1,832us-gaap_MarketableSecuritiesFixedMaturities
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_USStatesAndPoliticalSubdivisionsMember		 1,856us-gaap_MarketableSecuritiesFixedMaturities
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_USStatesAndPoliticalSubdivisionsMember
Fair Value Inputs Level 2 [Member] | Foreign government [Member] | Fair Value, Measurements, Recurring [Member]    
Financial assets at fair value:    
Fixed maturities 1,953us-gaap_MarketableSecuritiesFixedMaturities
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_ForeignGovernmentDebtSecuritiesMember		 1,936us-gaap_MarketableSecuritiesFixedMaturities
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_ForeignGovernmentDebtSecuritiesMember
Fair Value Inputs Level 2 [Member] | Corporate [Member] | Fair Value, Measurements, Recurring [Member]    
Financial assets at fair value:    
Fixed maturities 13,371us-gaap_MarketableSecuritiesFixedMaturities
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_CorporateDebtSecuritiesMember		 13,105us-gaap_MarketableSecuritiesFixedMaturities
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_CorporateDebtSecuritiesMember
Fair Value Inputs Level 2 [Member] | Mortgage-backed [Member] | Fair Value, Measurements, Recurring [Member]    
Financial assets at fair value:    
Fixed maturities 63us-gaap_MarketableSecuritiesFixedMaturities
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesMember		 84us-gaap_MarketableSecuritiesFixedMaturities
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesMember
Fair Value Inputs Level 2 [Member] | Other asset-backed [Member] | Fair Value, Measurements, Recurring [Member]    
Financial assets at fair value:    
Fixed maturities 226us-gaap_MarketableSecuritiesFixedMaturities
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_AssetBackedSecuritiesSecuritizedLoansAndReceivablesMember		 234us-gaap_MarketableSecuritiesFixedMaturities
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_AssetBackedSecuritiesSecuritizedLoansAndReceivablesMember
Fair Value Inputs Level 3 [Member] | Fair Value, Measurements, Recurring [Member]    
Financial assets at fair value:    
Fixed maturities 773us-gaap_MarketableSecuritiesFixedMaturities
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember		 [1] 814us-gaap_MarketableSecuritiesFixedMaturities
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember		 [2]
Equity securities 45us-gaap_MarketableSecuritiesEquitySecurities
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember		 43us-gaap_MarketableSecuritiesEquitySecurities
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
Subtotal 818us-gaap_MarketableSecurities
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember		 857us-gaap_MarketableSecurities
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
Short-term investments 0us-gaap_OtherShortTermInvestments
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember		 0us-gaap_OtherShortTermInvestments
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
Total financial assets at fair value, excluding separate accounts 1,788ci_TotalFinancialAssetsAtFairValueExcludingSeparateAccounts
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember		 1,810ci_TotalFinancialAssetsAtFairValueExcludingSeparateAccounts
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
Financial liabilities at fair value:    
Total financial liabilities at fair value 948us-gaap_LiabilitiesFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember		 929us-gaap_LiabilitiesFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
Fair Value Inputs Level 3 [Member] | Run-off Settlement Annuity Business [Member] | Fair Value, Measurements, Recurring [Member]    
Financial liabilities at fair value:    
Net appreciation required to adjust future policy benefits for run-off settlement annuity business included in fixed maturities 71ci_UnrealizedAppreciationSettlementAnnuity
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
/ us-gaap_StatementBusinessSegmentsAxis
= ci_RunoffSettlementAnnuityBusinessMember		 65ci_UnrealizedAppreciationSettlementAnnuity
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
/ us-gaap_StatementBusinessSegmentsAxis
= ci_RunoffSettlementAnnuityBusinessMember
Fair Value Inputs Level 3 [Member] | Other derivatives [Member] | Fair Value, Measurements, Recurring [Member]    
Financial assets at fair value:    
Derivative assets 0us-gaap_DerivativeAssets
/ us-gaap_DerivativeInstrumentRiskAxis
= us-gaap_SwapMember
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember		 [3] 0us-gaap_DerivativeAssets
/ us-gaap_DerivativeInstrumentRiskAxis
= us-gaap_SwapMember
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember		 [4]
Financial liabilities at fair value:    
Derivative liabilities   0us-gaap_DerivativeLiabilities
/ us-gaap_DerivativeInstrumentRiskAxis
= us-gaap_SwapMember
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember		 [4]
Fair Value Inputs Level 3 [Member] | Guaranteed Minimum Income Benefit [Member] | Fair Value, Measurements, Recurring [Member]    
Financial assets at fair value:    
Derivative assets 970us-gaap_DerivativeAssets
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
/ us-gaap_NetAmountAtRiskByProductAndGuaranteeGuaranteeTypeAxis
= us-gaap_GuaranteedMinimumIncomeBenefitMember		 [5] 953us-gaap_DerivativeAssets
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
/ us-gaap_NetAmountAtRiskByProductAndGuaranteeGuaranteeTypeAxis
= us-gaap_GuaranteedMinimumIncomeBenefitMember		 [6]
Financial liabilities at fair value:    
Derivative liabilities 948us-gaap_DerivativeLiabilities
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
/ us-gaap_NetAmountAtRiskByProductAndGuaranteeGuaranteeTypeAxis
= us-gaap_GuaranteedMinimumIncomeBenefitMember		 929us-gaap_DerivativeLiabilities
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
/ us-gaap_NetAmountAtRiskByProductAndGuaranteeGuaranteeTypeAxis
= us-gaap_GuaranteedMinimumIncomeBenefitMember
Fair Value Inputs Level 3 [Member] | Federal government and agency [Member] | Fair Value, Measurements, Recurring [Member]    
Financial assets at fair value:    
Fixed maturities 0us-gaap_MarketableSecuritiesFixedMaturities
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_USTreasuryAndGovernmentMember		 0us-gaap_MarketableSecuritiesFixedMaturities
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_USTreasuryAndGovernmentMember
Fair Value Inputs Level 3 [Member] | State and local government [Member] | Fair Value, Measurements, Recurring [Member]    
Financial assets at fair value:    
Fixed maturities 0us-gaap_MarketableSecuritiesFixedMaturities
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_USStatesAndPoliticalSubdivisionsMember		 0us-gaap_MarketableSecuritiesFixedMaturities
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_USStatesAndPoliticalSubdivisionsMember
Fair Value Inputs Level 3 [Member] | Foreign government [Member] | Fair Value, Measurements, Recurring [Member]    
Financial assets at fair value:    
Fixed maturities 3us-gaap_MarketableSecuritiesFixedMaturities
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_ForeignGovernmentDebtSecuritiesMember		 4us-gaap_MarketableSecuritiesFixedMaturities
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_ForeignGovernmentDebtSecuritiesMember
Fair Value Inputs Level 3 [Member] | Corporate [Member] | Fair Value, Measurements, Recurring [Member]    
Financial assets at fair value:    
Fixed maturities 350us-gaap_MarketableSecuritiesFixedMaturities
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_CorporateDebtSecuritiesMember		 393us-gaap_MarketableSecuritiesFixedMaturities
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_CorporateDebtSecuritiesMember
Fair Value Inputs Level 3 [Member] | Mortgage-backed [Member] | Fair Value, Measurements, Recurring [Member]    
Financial assets at fair value:    
Fixed maturities 1us-gaap_MarketableSecuritiesFixedMaturities
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesMember		 1us-gaap_MarketableSecuritiesFixedMaturities
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesMember
Fair Value Inputs Level 3 [Member] | Other asset-backed [Member] | Fair Value, Measurements, Recurring [Member]    
Financial assets at fair value:    
Fixed maturities $ 419us-gaap_MarketableSecuritiesFixedMaturities
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_AssetBackedSecuritiesSecuritizedLoansAndReceivablesMember		 $ 416us-gaap_MarketableSecuritiesFixedMaturities
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_AssetBackedSecuritiesSecuritizedLoansAndReceivablesMember
[1] Fixed maturities included $817 million of net appreciation required to adjust future policy benefits for the run-off settlement annuity business including $71 million of appreciation for securities classified in Level 3. See Note 8 for additional information.
[2] Fixed maturities included $756 million of net appreciation required to adjust future policy benefits for the run-off settlement annuity business including $65 million of appreciation for securities classified in Level 3. See Note 8 for additional information.
[3] Other derivative assets included $15 million of interest rate and foreign currency swaps qualifying as cash flow hedges and $1 million of interest rate swaps qualifying as fair value hedges. See Note 9 for additional information.
[4] Other derivative assets included $5 million of interest rate and foreign currency swaps qualifying as cash flow hedges and $1 million of interest rate swaps qualifying as fair value hedges. Other derivative liabilities reflected interest rate and foreign currency swaps qualifying as cash flow hedges. See Note 9 for additional information.
[5] The GMIB assets represent retrocessional contracts in place from three external reinsurers that cover the exposures on these contracts.
[6] The GMIB assets represented retrocessional contracts in place from three external reinsurers that cover the exposures on these contracts.