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Employee Benefit Plans Plan Assets (Details) (USD $)
In Millions, unless otherwise specified
 12 Months Ended
Dec. 31, 2014
Dec. 31, 2013
Dec. 31, 2012
Schedule Of Fair Value Of Financial Assets For Pension And Postretirement Benefits [Line Items]      
Pension plan assets, fair value $ 115us-gaap_DefinedBenefitPlanFairValueOfPlanAssets $ 114us-gaap_DefinedBenefitPlanFairValueOfPlanAssets $ 115us-gaap_DefinedBenefitPlanFairValueOfPlanAssets
Estimated future contribution to postretirement benefit plan in next fiscal year 7us-gaap_DefinedBenefitPlansEstimatedFutureEmployerContributionsInNextFiscalYear    
Postemployment Benefits, Period Expense 1us-gaap_PostemploymentBenefitsPeriodExpense 4us-gaap_PostemploymentBenefitsPeriodExpense 3us-gaap_PostemploymentBenefitsPeriodExpense
Defined Benefit Pension Plans and Defined Benefit Postretirement Plans Disclosure [Abstract]      
Benefit expense related to deferred compensation plans 1us-gaap_DeferredCompensationArrangementWithIndividualCompensationExpense 1us-gaap_DeferredCompensationArrangementWithIndividualCompensationExpense 1us-gaap_DeferredCompensationArrangementWithIndividualCompensationExpense
Equity Funds [Member]      
Schedule Of Fair Value Of Financial Assets For Pension And Postretirement Benefits [Line Items]      
Pension plan assets, fair value 115us-gaap_DefinedBenefitPlanFairValueOfPlanAssets
/ us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis
= us-gaap_EquityFundsMember		 [1] 114us-gaap_DefinedBenefitPlanFairValueOfPlanAssets
/ us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis
= us-gaap_EquityFundsMember		 [2]  
U.S. Equity [Member]      
Schedule Of Fair Value Of Financial Assets For Pension And Postretirement Benefits [Line Items]      
Defined Benefit Plan, Target Plan Asset Allocations Range Minimum 14.00%us-gaap_DefinedBenefitPlanTargetPlanAssetAllocationsRangeMinimum
/ us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis
= cehe_USEquityMember		    
Defined Benefit Plan, Target Plan Asset Allocations Range Maximum 24.00%us-gaap_DefinedBenefitPlanTargetPlanAssetAllocationsRangeMaximum
/ us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis
= cehe_USEquityMember		    
International Equity [Member]      
Schedule Of Fair Value Of Financial Assets For Pension And Postretirement Benefits [Line Items]      
Defined Benefit Plan, Target Plan Asset Allocations Range Minimum 3.00%us-gaap_DefinedBenefitPlanTargetPlanAssetAllocationsRangeMinimum
/ us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis
= cehe_InternationalEquityMember		    
Defined Benefit Plan, Target Plan Asset Allocations Range Maximum 13.00%us-gaap_DefinedBenefitPlanTargetPlanAssetAllocationsRangeMaximum
/ us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis
= cehe_InternationalEquityMember		    
Fixed Income [Member]      
Schedule Of Fair Value Of Financial Assets For Pension And Postretirement Benefits [Line Items]      
Defined Benefit Plan, Target Plan Asset Allocations Range Minimum 68.00%us-gaap_DefinedBenefitPlanTargetPlanAssetAllocationsRangeMinimum
/ us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis
= cehe_FixedIncomeMember		    
Defined Benefit Plan, Target Plan Asset Allocations Range Maximum 78.00%us-gaap_DefinedBenefitPlanTargetPlanAssetAllocationsRangeMaximum
/ us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis
= cehe_FixedIncomeMember		    
Cash and Cash Equivalents [Member]      
Schedule Of Fair Value Of Financial Assets For Pension And Postretirement Benefits [Line Items]      
Defined Benefit Plan, Target Plan Asset Allocations Range Minimum 0.00%us-gaap_DefinedBenefitPlanTargetPlanAssetAllocationsRangeMinimum
/ us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis
= us-gaap_CashAndCashEquivalentsMember		    
Defined Benefit Plan, Target Plan Asset Allocations Range Maximum 2.00%us-gaap_DefinedBenefitPlanTargetPlanAssetAllocationsRangeMaximum
/ us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis
= us-gaap_CashAndCashEquivalentsMember		    
Fair Value, Inputs, Level 1 [Member]      
Schedule Of Fair Value Of Financial Assets For Pension And Postretirement Benefits [Line Items]      
Pension plan assets, fair value 115us-gaap_DefinedBenefitPlanFairValueOfPlanAssets
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member		 114us-gaap_DefinedBenefitPlanFairValueOfPlanAssets
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member		  
Fair Value, Inputs, Level 1 [Member] | Equity Funds [Member]      
Schedule Of Fair Value Of Financial Assets For Pension And Postretirement Benefits [Line Items]      
Pension plan assets, fair value 115us-gaap_DefinedBenefitPlanFairValueOfPlanAssets
/ us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis
= us-gaap_EquityFundsMember
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member		 [1] 114us-gaap_DefinedBenefitPlanFairValueOfPlanAssets
/ us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis
= us-gaap_EquityFundsMember
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member		 [2]  
Fair Value, Inputs, Level 2 [Member]      
Schedule Of Fair Value Of Financial Assets For Pension And Postretirement Benefits [Line Items]      
Pension plan assets, fair value 0us-gaap_DefinedBenefitPlanFairValueOfPlanAssets
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member		 0us-gaap_DefinedBenefitPlanFairValueOfPlanAssets
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member		  
Fair Value, Inputs, Level 2 [Member] | Equity Funds [Member]      
Schedule Of Fair Value Of Financial Assets For Pension And Postretirement Benefits [Line Items]      
Pension plan assets, fair value 0us-gaap_DefinedBenefitPlanFairValueOfPlanAssets
/ us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis
= us-gaap_EquityFundsMember
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member		 [1] 0us-gaap_DefinedBenefitPlanFairValueOfPlanAssets
/ us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis
= us-gaap_EquityFundsMember
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member		 [2]  
Fair Value, Inputs, Level 3 [Member]      
Schedule Of Fair Value Of Financial Assets For Pension And Postretirement Benefits [Line Items]      
Pension plan assets, fair value 0us-gaap_DefinedBenefitPlanFairValueOfPlanAssets
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member		 0us-gaap_DefinedBenefitPlanFairValueOfPlanAssets
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member		  
Fair Value, Inputs, Level 3 [Member] | Equity Funds [Member]      
Schedule Of Fair Value Of Financial Assets For Pension And Postretirement Benefits [Line Items]      
Pension plan assets, fair value 0us-gaap_DefinedBenefitPlanFairValueOfPlanAssets
/ us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis
= us-gaap_EquityFundsMember
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member		 [1] 0us-gaap_DefinedBenefitPlanFairValueOfPlanAssets
/ us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis
= us-gaap_EquityFundsMember
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member		 [2]  
Other Postretirement Benefit Plans, Defined Benefit [Member]      
Expected Future Benefit Payments, Fiscal Year Maturity [Abstract]      
Postretirement benefit payments - 2014 21us-gaap_DefinedBenefitPlanExpectedFutureBenefitPaymentsNextTwelveMonths
/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis
= us-gaap_OtherPostretirementBenefitPlansDefinedBenefitMember		    
Postretirement benefit payments - 2015 22us-gaap_DefinedBenefitPlanExpectedFutureBenefitPaymentsYearTwo
/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis
= us-gaap_OtherPostretirementBenefitPlansDefinedBenefitMember		    
Postretirement benefit payments - 2016 23us-gaap_DefinedBenefitPlanExpectedFutureBenefitPaymentsYearThree
/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis
= us-gaap_OtherPostretirementBenefitPlansDefinedBenefitMember		    
Postretirement benefit payments - 2017 24us-gaap_DefinedBenefitPlanExpectedFutureBenefitPaymentsYearFour
/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis
= us-gaap_OtherPostretirementBenefitPlansDefinedBenefitMember		    
Postretirement benefit payments - 2018 26us-gaap_DefinedBenefitPlanExpectedFutureBenefitPaymentsYearFive
/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis
= us-gaap_OtherPostretirementBenefitPlansDefinedBenefitMember		    
Postretirement benefit payments - 2019-2023 139us-gaap_DefinedBenefitPlanExpectedFutureBenefitPaymentsFiveFiscalYearsThereafter
/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis
= us-gaap_OtherPostretirementBenefitPlansDefinedBenefitMember		    
Medicare Subsidy Receipts - 2014 (2)us-gaap_PrescriptionDrugSubsidyReceiptsNextTwelveMonths
/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis
= us-gaap_OtherPostretirementBenefitPlansDefinedBenefitMember		    
Medicare Subsidy Receipts - 2015 (2)us-gaap_PrescriptionDrugSubsidyReceiptsYearTwo1
/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis
= us-gaap_OtherPostretirementBenefitPlansDefinedBenefitMember		    
Medicare Subsidy Receipts - 2016 (2)us-gaap_PrescriptionDrugSubsidyReceiptsYearThree1
/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis
= us-gaap_OtherPostretirementBenefitPlansDefinedBenefitMember		    
Medicare Subsidy Receipts - 2017 (2)us-gaap_PrescriptionDrugSubsidyReceiptsYearFour1
/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis
= us-gaap_OtherPostretirementBenefitPlansDefinedBenefitMember		    
Medicare Subsidy Receipts - 2018 (3)us-gaap_PrescriptionDrugSubsidyReceiptsYearFive1
/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis
= us-gaap_OtherPostretirementBenefitPlansDefinedBenefitMember		    
Medicare Subsidy Receipts - 2019-2023 (17)us-gaap_PrescriptionDrugSubsidyReceiptsAfterYearFive
/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis
= us-gaap_OtherPostretirementBenefitPlansDefinedBenefitMember		    
International Equity [Member] | Equity Funds [Member]      
Schedule Of Fair Value Of Financial Assets For Pension And Postretirement Benefits [Line Items]      
Defined Benefit Plan, Actual Plan Asset Allocations 8.00%us-gaap_DefinedBenefitPlanWeightedAverageAssetAllocations
/ us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis
= us-gaap_EquityFundsMember
/ us-gaap_InvestmentTypeAxis
= cehe_InternationalEquityMember		 9.00%us-gaap_DefinedBenefitPlanWeightedAverageAssetAllocations
/ us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis
= us-gaap_EquityFundsMember
/ us-gaap_InvestmentTypeAxis
= cehe_InternationalEquityMember		  
Fixed Income Funds [Member] | Equity Funds [Member]      
Schedule Of Fair Value Of Financial Assets For Pension And Postretirement Benefits [Line Items]      
Defined Benefit Plan, Actual Plan Asset Allocations 73.00%us-gaap_DefinedBenefitPlanWeightedAverageAssetAllocations
/ us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis
= us-gaap_EquityFundsMember
/ us-gaap_InvestmentTypeAxis
= us-gaap_FixedIncomeFundsMember		 73.00%us-gaap_DefinedBenefitPlanWeightedAverageAssetAllocations
/ us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis
= us-gaap_EquityFundsMember
/ us-gaap_InvestmentTypeAxis
= us-gaap_FixedIncomeFundsMember		  
U.S. Equity [Member] | Equity Funds [Member]      
Schedule Of Fair Value Of Financial Assets For Pension And Postretirement Benefits [Line Items]      
Defined Benefit Plan, Actual Plan Asset Allocations 19.00%us-gaap_DefinedBenefitPlanWeightedAverageAssetAllocations
/ us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis
= us-gaap_EquityFundsMember
/ us-gaap_InvestmentTypeAxis
= cehe_USEquityMember		 18.00%us-gaap_DefinedBenefitPlanWeightedAverageAssetAllocations
/ us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis
= us-gaap_EquityFundsMember
/ us-gaap_InvestmentTypeAxis
= cehe_USEquityMember		  
Benefit Obligation [Member]      
Postemployment Benefits [Abstract]      
Postemployment benefit obligations 14us-gaap_PostemploymentBenefitsLiabilityNoncurrent
/ us-gaap_BalanceSheetLocationAxis
= cehe_BenefitObligationMember		 16us-gaap_PostemploymentBenefitsLiabilityNoncurrent
/ us-gaap_BalanceSheetLocationAxis
= cehe_BenefitObligationMember		  
Defined Benefit Pension Plans and Defined Benefit Postretirement Plans Disclosure [Abstract]      
Other non-qualified plans benefit obligations deferred compensation $ 12us-gaap_DeferredCompensationLiabilityClassifiedNoncurrent
/ us-gaap_BalanceSheetLocationAxis
= cehe_BenefitObligationMember		 $ 13us-gaap_DeferredCompensationLiabilityClassifiedNoncurrent
/ us-gaap_BalanceSheetLocationAxis
= cehe_BenefitObligationMember		  
[1] 73% of the amount invested in mutual funds is in fixed income securities; 19% is in U.S. equities and 8% is in international equities.
[2] 73% of the amount invested in mutual funds is in fixed income securities; 18% is in U.S. equities and 9% is in international equities.