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Income Taxes (Details) (USD $)
In Millions, unless otherwise specified
 12 Months Ended
Dec. 31, 2014
Dec. 31, 2013
Dec. 31, 2012
Current income tax expense:      
Federal $ 0us-gaap_CurrentFederalTaxExpenseBenefit $ 5us-gaap_CurrentFederalTaxExpenseBenefit $ 0us-gaap_CurrentFederalTaxExpenseBenefit
State 10us-gaap_CurrentStateAndLocalTaxExpenseBenefit 9us-gaap_CurrentStateAndLocalTaxExpenseBenefit 1us-gaap_CurrentStateAndLocalTaxExpenseBenefit
Total current expense 10us-gaap_CurrentIncomeTaxExpenseBenefit 14us-gaap_CurrentIncomeTaxExpenseBenefit 1us-gaap_CurrentIncomeTaxExpenseBenefit
Deferred income tax expense:      
Federal 171us-gaap_DeferredFederalIncomeTaxExpenseBenefit 350us-gaap_DeferredFederalIncomeTaxExpenseBenefit 198us-gaap_DeferredFederalIncomeTaxExpenseBenefit
State 7us-gaap_DeferredStateAndLocalIncomeTaxExpenseBenefit 7us-gaap_DeferredStateAndLocalIncomeTaxExpenseBenefit 47us-gaap_DeferredStateAndLocalIncomeTaxExpenseBenefit
Total deferred expense 178us-gaap_DeferredIncomeTaxExpenseBenefit 357us-gaap_DeferredIncomeTaxExpenseBenefit 245us-gaap_DeferredIncomeTaxExpenseBenefit
Total income tax expense 188us-gaap_IncomeTaxExpenseBenefit 371us-gaap_IncomeTaxExpenseBenefit 246us-gaap_IncomeTaxExpenseBenefit
Income tax reconciliation      
Income before income taxes 511us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest 435us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest 383us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest
Federal statutory income tax rate 35.00%us-gaap_EffectiveIncomeTaxRateReconciliationAtFederalStatutoryIncomeTaxRate 35.00%us-gaap_EffectiveIncomeTaxRateReconciliationAtFederalStatutoryIncomeTaxRate 35.00%us-gaap_EffectiveIncomeTaxRateReconciliationAtFederalStatutoryIncomeTaxRate
Expected federal income tax expense 179us-gaap_IncomeTaxReconciliationIncomeTaxExpenseBenefitAtFederalStatutoryIncomeTaxRate 152us-gaap_IncomeTaxReconciliationIncomeTaxExpenseBenefitAtFederalStatutoryIncomeTaxRate 134us-gaap_IncomeTaxReconciliationIncomeTaxExpenseBenefitAtFederalStatutoryIncomeTaxRate
Increase (decrease) in tax expense resulting from:      
State income tax expense, net of federal income tax 11us-gaap_IncomeTaxReconciliationStateAndLocalIncomeTaxes 23us-gaap_IncomeTaxReconciliationStateAndLocalIncomeTaxes 31us-gaap_IncomeTaxReconciliationStateAndLocalIncomeTaxes
Decrease in settled and uncertain income tax positions 0cerc_IncomeTaxReconciliationTaxSettlementsAndUncertainIncomeTaxPositions (2)cerc_IncomeTaxReconciliationTaxSettlementsAndUncertainIncomeTaxPositions (7)cerc_IncomeTaxReconciliationTaxSettlementsAndUncertainIncomeTaxPositions
Increase (decrease) in tax expense due to formation of midstream partnership 0cerc_Increasedecreaseintaxexpenseduetoformationofmidstreampartnership 198cerc_Increasedecreaseintaxexpenseduetoformationofmidstreampartnership 0cerc_Increasedecreaseintaxexpenseduetoformationofmidstreampartnership
Goodwill impairment 0us-gaap_IncomeTaxReconciliationNondeductibleExpenseImpairmentLosses 0us-gaap_IncomeTaxReconciliationNondeductibleExpenseImpairmentLosses 88us-gaap_IncomeTaxReconciliationNondeductibleExpenseImpairmentLosses
Other, net (2)us-gaap_IncomeTaxReconciliationOtherReconcilingItems 0us-gaap_IncomeTaxReconciliationOtherReconcilingItems 0us-gaap_IncomeTaxReconciliationOtherReconcilingItems
Total 9cerc_IncomeTaxReconciliationChangeInTaxExpense 219cerc_IncomeTaxReconciliationChangeInTaxExpense 112cerc_IncomeTaxReconciliationChangeInTaxExpense
Total income tax expense 188us-gaap_IncomeTaxExpenseBenefit 371us-gaap_IncomeTaxExpenseBenefit 246us-gaap_IncomeTaxExpenseBenefit
Effective tax rate 36.80%us-gaap_EffectiveIncomeTaxRateContinuingOperations 85.30%us-gaap_EffectiveIncomeTaxRateContinuingOperations 64.20%us-gaap_EffectiveIncomeTaxRateContinuingOperations
Deferred Tax Liabilities, Goodwill and Intangible Assets   225us-gaap_DeferredTaxLiabilitiesGoodwillAndIntangibleAssets  
Tax Adjustments, Settlements, and Unusual Provisions   (2)us-gaap_TaxAdjustmentsSettlementsAndUnusualProvisions (7)us-gaap_TaxAdjustmentsSettlementsAndUnusualProvisions
Goodwill impairment 0us-gaap_GoodwillImpairmentLoss 0us-gaap_GoodwillImpairmentLoss 252us-gaap_GoodwillImpairmentLoss
Other Tax Expense (Benefit)     88us-gaap_OtherTaxExpenseBenefit
Deferred Tax Assets [Abstract]      
Allowance for doubtful accounts 9us-gaap_DeferredTaxAssetsTaxDeferredExpenseReservesAndAccrualsAllowanceForDoubtfulAccounts 10us-gaap_DeferredTaxAssetsTaxDeferredExpenseReservesAndAccrualsAllowanceForDoubtfulAccounts  
Deferred gas costs 0cerc_DeferredTaxAssetsTaxDeferredExpenseReservesAndAccrualsDeferredGasCosts 7cerc_DeferredTaxAssetsTaxDeferredExpenseReservesAndAccrualsDeferredGasCosts  
Other, current deferred tax assets 8cerc_DeferredTaxAssetsCurrentOther 7cerc_DeferredTaxAssetsCurrentOther  
Total current deferred tax assets 17us-gaap_DeferredTaxAssetsGrossCurrent 24us-gaap_DeferredTaxAssetsGrossCurrent  
Employee benefits 44us-gaap_DeferredTaxAssetsTaxDeferredExpenseCompensationAndBenefitsEmployeeBenefits 41us-gaap_DeferredTaxAssetsTaxDeferredExpenseCompensationAndBenefitsEmployeeBenefits  
Loss and credit carryforwards 326cerc_DeferredTaxAssetsLossAndCreditTaxCarryforwards 193cerc_DeferredTaxAssetsLossAndCreditTaxCarryforwards  
Other, noncurrent deferred tax assets 71cerc_DeferredTaxAssetsNoncurrentOther 59cerc_DeferredTaxAssetsNoncurrentOther  
Total non-current deferred tax assets before valuation allowance 441us-gaap_DeferredTaxAssetsGrossNoncurrent 293us-gaap_DeferredTaxAssetsGrossNoncurrent  
Valuation allowance (2)us-gaap_DeferredTaxAssetsValuationAllowance (2)us-gaap_DeferredTaxAssetsValuationAllowance  
Total non-current deferred tax assets, net of valuation allowance 439us-gaap_DeferredTaxAssetsNetNoncurrent 291us-gaap_DeferredTaxAssetsNetNoncurrent  
Total deferred tax assets, net of valuation allowance 456us-gaap_DeferredTaxAssetsNet 315us-gaap_DeferredTaxAssetsNet  
Deferred Tax Liabilities [Abstract]      
Deferred gas costs 6cerc_DeferredTaxLiabilitiesDeferredGasCosts 0cerc_DeferredTaxLiabilitiesDeferredGasCosts  
Other 10cerc_DeferredTaxLiabilitiesCurrentOther 3cerc_DeferredTaxLiabilitiesCurrentOther  
Total current deferred tax liabilities 16us-gaap_DeferredTaxLiabilitiesGrossCurrent 3us-gaap_DeferredTaxLiabilitiesGrossCurrent  
Depreciation 865cerc_DeferredTaxLiabilitiesDepreciation 746cerc_DeferredTaxLiabilitiesDepreciation  
Regulatory assets, net 16us-gaap_DeferredTaxLiabilitiesRegulatoryAssetsAndLiabilities 17us-gaap_DeferredTaxLiabilitiesRegulatoryAssetsAndLiabilities  
Investment in unconsolidated affiliates (1) 1,789us-gaap_DeferredTaxLiabilitiesInvestmentInNoncontrolledAffiliates [1] 1,600us-gaap_DeferredTaxLiabilitiesInvestmentInNoncontrolledAffiliates [1]  
Other, non-current deferred tax liabilities 21cerc_DeferredTaxLiabilitiesNoncurrentOther [1] 21cerc_DeferredTaxLiabilitiesNoncurrentOther [1]  
Total non-current deferred tax liabilities (1) 2,691us-gaap_DeferredTaxLiabilitiesGrossNoncurrent [1] 2,384us-gaap_DeferredTaxLiabilitiesGrossNoncurrent [1]  
Total deferred tax liabilities (1) 2,707us-gaap_DeferredIncomeTaxLiabilities [1] 2,387us-gaap_DeferredIncomeTaxLiabilities [1]  
Accumulated deferred income taxes, net (1) 2,251us-gaap_DeferredTaxLiabilities [1] 2,072us-gaap_DeferredTaxLiabilities [1]  
Reconciliation of Unrecognized Tax Benefits (Expenses) [Roll Forward]      
Balance, beginning of year 0us-gaap_UnrecognizedTaxBenefits   8us-gaap_UnrecognizedTaxBenefits
Unrecognized tax expense   (20)cerc_UnrecognizedTaxExpense  
Tax Positions related to prior years:      
Unrecognized tax expense, increase resulting from prior period tax positions 0cerc_Unrecognizedtaxexpenseincreaseresultingfrompriorperiodtaxpositions (2)cerc_Unrecognizedtaxexpenseincreaseresultingfrompriorperiodtaxpositions 0cerc_Unrecognizedtaxexpenseincreaseresultingfrompriorperiodtaxpositions
Reductions 0us-gaap_UnrecognizedTaxBenefitsDecreasesResultingFromPriorPeriodTaxPositions 0us-gaap_UnrecognizedTaxBenefitsDecreasesResultingFromPriorPeriodTaxPositions (27)us-gaap_UnrecognizedTaxBenefitsDecreasesResultingFromPriorPeriodTaxPositions
Tax Positions related to current year:      
Unrecognized Tax Benefits, Increase Resulting from Settlements with Taxing Authorities 0us-gaap_UnrecognizedTaxBenefitsIncreasesResultingFromSettlementsWithTaxingAuthorities 22us-gaap_UnrecognizedTaxBenefitsIncreasesResultingFromSettlementsWithTaxingAuthorities  
Settlements     (1)us-gaap_UnrecognizedTaxBenefitsDecreasesResultingFromSettlementsWithTaxingAuthorities
Balance, end of year 0us-gaap_UnrecognizedTaxBenefits 0us-gaap_UnrecognizedTaxBenefits  
Unrecognized tax expense     (20)cerc_UnrecognizedTaxExpense
Income Tax Expense Benefit Related To Interest On Income Tax Positions   4cerc_IncomeTaxExpenseBenefitRelatedToInterestOnIncomeTaxPositions 3cerc_IncomeTaxExpenseBenefitRelatedToInterestOnIncomeTaxPositions
Interest Receivable on Income Tax Positions   11cerc_InterestReceivableonIncomeTaxPositions  
Federal [Member]      
Deferred Tax Liabilities [Abstract]      
Federal net operating loss carryforwards to expire in 2030 806us-gaap_OperatingLossCarryforwards
/ us-gaap_IncomeTaxAuthorityAxis
= us-gaap_InternalRevenueServiceIRSMember		    
Deferred Tax Assets, Capital Loss Carryforwards 16us-gaap_DeferredTaxAssetsCapitalLossCarryforwards
/ us-gaap_IncomeTaxAuthorityAxis
= us-gaap_InternalRevenueServiceIRSMember		    
Operating Loss Carryforwards, Expiration Dates Dec. 31, 2018    
State and Local Jurisdiction [Member]      
Deferred Tax Liabilities [Abstract]      
Federal net operating loss carryforwards to expire in 2030 723us-gaap_OperatingLossCarryforwards
/ us-gaap_IncomeTaxAuthorityAxis
= us-gaap_StateAndLocalJurisdictionMember		    
Deferred Tax Assets, Capital Loss Carryforwards 244us-gaap_DeferredTaxAssetsCapitalLossCarryforwards
/ us-gaap_IncomeTaxAuthorityAxis
= us-gaap_StateAndLocalJurisdictionMember		    
Other Tax Carryforward, Expiration Dates Dec. 31, 2017    
State capital loss carryforwards, valuation allowance net of federal tax 2cerc_OperatingLossCarryforwardsValuationAllowanceNetOfFederalTax
/ us-gaap_IncomeTaxAuthorityAxis
= us-gaap_StateAndLocalJurisdictionMember		    
General Business Tax Credit Carryforward [Member] | Federal [Member]      
Deferred Tax Liabilities [Abstract]      
Tax Credit Carryforward, Amount 4us-gaap_TaxCreditCarryforwardAmount
/ us-gaap_IncomeTaxAuthorityAxis
= us-gaap_InternalRevenueServiceIRSMember
/ us-gaap_TaxCreditCarryforwardAxis
= us-gaap_GeneralBusinessMember		    
Enable Midstream Partners [Member]      
Deferred income tax expense:      
Total deferred expense   $ (27)us-gaap_DeferredIncomeTaxExpenseBenefit
/ dei_LegalEntityAxis
= cerc_EnableMidstreamPartnersMember		  
Year From [Member] | State and Local Jurisdiction [Member]      
Deferred Tax Liabilities [Abstract]      
Operating Loss Carryforwards, Expiration Dates Dec. 31, 2015    
Year To [Member] | State and Local Jurisdiction [Member]      
Deferred Tax Liabilities [Abstract]      
Operating Loss Carryforwards, Expiration Dates Dec. 31, 2034    
[1] For tax year ended December 31, 2013, the amounts are presented after the effect of the revisions to the prior period financial statement discussed in Note 2(p).