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Long-term Debt (Details) (USD $)
In Millions, unless otherwise specified
 3 Months Ended
Mar. 31, 2015
Dec. 31, 2014
Debt Instrument [Line Items]    
Line of Credit Facility, Maximum Borrowing Capacity 300us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity $ 300us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity
General mortgage bonds used as collateral 408cehe_GeneralMortgageBondsUsedAsCollateral 408cehe_GeneralMortgageBondsUsedAsCollateral
CenterPoint Energy [Member]    
Debt Instrument [Line Items]    
General mortgage bonds used as collateral 290cehe_GeneralMortgageBondsUsedAsCollateral
/ dei_LegalEntityAxis
= cehe_CenterpointEnergyMember		  
Revolving Credit Facility [Member]    
Debt Instrument [Line Items]    
Loans Outstanding 0us-gaap_LineOfCredit
/ us-gaap_CreditFacilityAxis
= us-gaap_RevolvingCreditFacilityMember		 0us-gaap_LineOfCredit
/ us-gaap_CreditFacilityAxis
= us-gaap_RevolvingCreditFacilityMember
Letter of Credit [Member]    
Debt Instrument [Line Items]    
Loans Outstanding 4us-gaap_LineOfCredit
/ us-gaap_CreditFacilityAxis
= us-gaap_LetterOfCreditMember		 $ 4us-gaap_LineOfCredit
/ us-gaap_CreditFacilityAxis
= us-gaap_LetterOfCreditMember
Line of Credit [Member]    
Debt Instrument [Line Items]    
Percentage on limitation of debt to total capitalization under covenant (in hundredths) 65.00%cehe_PercentageOnLimitationOfDebtToTotalCapitalizationUnderCovenantInHundredths
/ us-gaap_CreditFacilityAxis
= us-gaap_LineOfCreditMember		  
Line of Credit [Member] | London Interbank Offered Rate (LIBOR) [Member]    
Debt Instrument [Line Items]    
Line of Credit Facility, Interest Rate Description 1.125%us-gaap_DebtInstrumentBasisSpreadOnVariableRate1
/ us-gaap_CreditFacilityAxis
= us-gaap_LineOfCreditMember
/ us-gaap_VariableRateAxis
= us-gaap_LondonInterbankOfferedRateLIBORMember