1.0.0.3 false CONSOLIDATED BALANCE SHEETS (USD $) In Millions false 1 $ false false u000 Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 u001 Standard http://www.xbrl.org/2003/instance shares xbrli 0 false 2 $ false false u000 Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 4 Current Assets: 2 us-gaap_AssetsCurrentAbstract us-gaap true na duration string No definition available. false false false false false true false false false 1 false false 0 0 false false 2 false false 0 0 false false No definition available. false 5 Cash and cash equivalents 3 us-gaap_CashAndCashEquivalentsAtCarryingValue us-gaap true debit instant monetary No definition available. false false false false false false false false false 1 true true 740000000 740 false false 2 true true 167000000 167 false false No definition available. No authoritative reference available. false 6 Investment in marketable securities 3 us-gaap_MarketableSecuritiesCurrent us-gaap true debit instant monetary No definition available. false false false false false false false false false 1 false true 300000000 300 false false 2 false true 218000000 218 false false No definition available. No authoritative reference available. false 7 Accounts receivable, net 3 us-gaap_AccountsReceivableNetCurrent us-gaap true debit instant monetary No definition available. false false false false false false false false false 1 false true 790000000 790 false false 2 false true 1009000000 1009 false false No definition available. No authoritative reference available. false 8 Accrued unbilled revenues 3 cnp_AccruedUnbilledRevenues cnp false na instant monetary Estimated cycle billing accrued revenue false false false false false false false false false 1 false true 485000000 485 false false 2 false true 541000000 541 false false Estimated cycle billing accrued revenue No authoritative reference available. false 9 Inventory 3 us-gaap_InventoryNet us-gaap true debit instant monetary No definition available. false false false false false false false false false 1 false true 327000000 327 false false 2 false true 569000000 569 false false No definition available. No authoritative reference available. false 10 Non-trading derivative assets 3 us-gaap_DerivativeAssetsCurrent us-gaap true debit instant monetary No definition available. false false false false false false false false false 1 false true 39000000 39 false false 2 false true 118000000 118 false false No definition available. No authoritative reference available. false 11 Prepaid expense and other current assets 3 us-gaap_OtherAssetsCurrent us-gaap true debit instant monetary No definition available. false false false false false false false false false 1 false true 223000000 223 false false 2 false true 413000000 413 false false No definition available. No authoritative reference available. false 12 Total current assets 3 us-gaap_AssetsCurrent us-gaap true debit instant monetary No definition available. false false false false false false false false false 1 false true 2904000000 2904 false false 2 false true 3035000000 3035 false false No definition available. No authoritative reference available. false 13 Property, Plant and Equipment, net 2 us-gaap_PropertyPlantAndEquipmentNet us-gaap true debit instant monetary No definition available. false false false false false false false false false 1 false true 10788000000 10788 false false 2 false true 10296000000 10296 false false No definition available. No authoritative reference available. false 14 Other Assets: 2 us-gaap_AssetsNoncurrentAbstract us-gaap true na duration string No definition available. false false false false false true false false false 1 false false 0 0 false false 2 false false 0 0 false false No definition available. false 15 Goodwill 3 us-gaap_Goodwill us-gaap true debit instant monetary No definition available. false false false false false false false false false 1 false true 1696000000 1696 false false 2 false true 1696000000 1696 false false No definition available. No authoritative reference available. false 16 Regulatory assets 3 us-gaap_RegulatoryAssetsNoncurrent us-gaap true debit instant monetary No definition available. false false false false false false false false false 1 false true 3677000000 3677 false false 2 false true 3684000000 3684 false false No definition available. No authoritative reference available. false 17 Non-trading derivative assets 3 us-gaap_DerivativeAssetsNoncurrent us-gaap true debit instant monetary No definition available. false false false false false false false false false 1 false true 15000000 15 false false 2 false true 20000000 20 false false No definition available. No authoritative reference available. false 18 Investment in unconsolidated affiliates 3 us-gaap_InvestmentsInAffiliatesSubsidiariesAssociatesAndJointVentures us-gaap true debit instant monetary No definition available. false false false false false false false false false 1 false true 463000000 463 false false 2 false true 345000000 345 false false No definition available. No authoritative reference available. false 19 Notes receivable from unconsolidated affiliates 3 us-gaap_AdvancesToAffiliate us-gaap true debit instant monetary No definition available. false false false false false false false false false 1 false true 0 0 false false 2 false true 323000000 323 false false No definition available. No authoritative reference available. false 20 Other 3 us-gaap_OtherAssetsNoncurrent us-gaap true debit instant monetary No definition available. false false false false false false false false false 1 false true 230000000 230 false false 2 false true 277000000 277 false false No definition available. No authoritative reference available. false 21 Total other assets 3 us-gaap_AssetsNoncurrent us-gaap true debit instant monetary No definition available. false false false false false false false false false 1 false true 6081000000 6081 false false 2 false true 6345000000 6345 false false No definition available. No authoritative reference available. false 22 Total Assets 2 us-gaap_Assets us-gaap true debit instant monetary No definition available. false false false false false false false false false 1 false true 19773000000 19773 false false 2 false true 19676000000 19676 false false No definition available. No authoritative reference available. true 24 Current Liabilities: 2 us-gaap_LiabilitiesCurrentAbstract us-gaap true na duration string No definition available. false false false false false true false false false 1 false false 0 0 false false 2 false false 0 0 false false No definition available. false 25 Short-term borrowings 3 us-gaap_ShortTermBorrowings us-gaap true credit instant monetary No definition available. false false false false false false false false false 1 false true 55000000 55 false false 2 false true 153000000 153 false false No definition available. No authoritative reference available. false 26 Current portion of transition and system restoration bonds long-term debt 3 cnp_TransitionAndSystemRestorationBondsLongTermDebtCurrent cnp false na instant monetary Long-term transition and system restoration bonds are securitization bonds issued to recover qualified stranded costs and... false false false false false false false false false 1 false true 241000000 241 false false 2 false true 208000000 208 false false Long-term transition and system restoration bonds are securitization bonds issued to recover qualified stranded costs and qualified storm recovery costs. This represents the current portion. No authoritative reference available. false 27 Current portion of indexed debt 3 cnp_IndexedDebtSecuritiesDerivative cnp false na instant monetary Fair values as of the balance sheet date of the Company's 2% Zero-Premium Exchangeable Subordinated Notes (ZENS) derivative... false false false false false false false false false 1 false true 121000000 121 false false 2 false true 117000000 117 false false Fair values as of the balance sheet date of the Company's 2% Zero-Premium Exchangeable Subordinated Notes (ZENS) derivative component which represents the holder's option to receive the appreciated value of Time Warner Inc. common stock. No authoritative reference available. false 28 Current portion of other long-term debt 3 us-gaap_OtherLongTermDebtCurrent us-gaap true credit instant monetary No definition available. false false false false false false false false false 1 false true 541000000 541 false false 2 false true 8000000 8 false false No definition available. No authoritative reference available. false 29 Indexed debt securities derivative 3 cnp_IndexedDebtCurrent cnp false na instant monetary Debt component of the Company's 2% Zero-Premium Exchangeable Subordinated Nots (ZENS). false false false false false false false false false 1 false true 201000000 201 false false 2 false true 133000000 133 false false Debt component of the Company's 2% Zero-Premium Exchangeable Subordinated Nots (ZENS). No authoritative reference available. false 30 Accounts payable 3 us-gaap_AccountsPayable us-gaap true credit instant monetary No definition available. false false false false false false false false false 1 false true 648000000 648 false false 2 false true 897000000 897 false false No definition available. No authoritative reference available. false 31 Taxes accrued 3 us-gaap_TaxesPayable us-gaap true credit instant monetary No definition available. false false false false false false false false false 1 false true 148000000 148 false false 2 false true 189000000 189 false false No definition available. No authoritative reference available. false 32 Interest accrued 3 us-gaap_InterestPayable us-gaap true credit instant monetary No definition available. false false false false false false false false false 1 false true 181000000 181 false false 2 false true 180000000 180 false false No definition available. No authoritative reference available. false 33 Non-trading derivative liabilities 3 us-gaap_DerivativeLiabilitiesCurrent us-gaap true credit instant monetary No definition available. false false false false false false false false false 1 false true 51000000 51 false false 2 false true 87000000 87 false false No definition available. No authoritative reference available. false 34 Accumulated deferred income taxes, net 3 us-gaap_DeferredTaxLiabilitiesCurrent us-gaap true credit instant monetary No definition available. false false false false false false false false false 1 false true 406000000 406 false false 2 false true 372000000 372 false false No definition available. No authoritative reference available. false 35 Other 3 us-gaap_OtherLiabilitiesCurrent us-gaap true credit instant monetary No definition available. false false false false false false false false false 1 false true 445000000 445 false false 2 false true 504000000 504 false false No definition available. No authoritative reference available. false 36 Total current liabilities 3 us-gaap_LiabilitiesCurrent us-gaap true credit instant monetary No definition available. false false false false false false false false false 1 false true 3038000000 3038 false false 2 false true 2848000000 2848 false false No definition available. No authoritative reference available. false 37 Other Liabilities: 2 us-gaap_LiabilitiesNoncurrentAbstract us-gaap true na duration string No definition available. false false false false false true false false false 1 false false 0 0 false false 2 false false 0 0 false false No definition available. false 38 Accumulated deferred income taxes, net 3 us-gaap_DeferredTaxLiabilitiesNoncurrent us-gaap true credit instant monetary No definition available. false false false false false false false false false 1 false true 2776000000 2776 false false 2 false true 2608000000 2608 false false No definition available. No authoritative reference available. false 39 Unamortized investment tax credits 3 us-gaap_AccumulatedDeferredInvestmentTaxCredit us-gaap true credit instant monetary No definition available. false false false false false false false false false 1 false true 16000000 16 false false 2 false true 24000000 24 false false No definition available. No authoritative reference available. false 40 Non-trading derivative liabilities 3 us-gaap_DerivativeLiabilitiesNoncurrent us-gaap true credit instant monetary No definition available. false false false false false false false false false 1 false true 42000000 42 false false 2 false true 47000000 47 false false No definition available. No authoritative reference available. false 41 Benefit obligations 3 us-gaap_PensionAndOtherPostretirementDefinedBenefitPlansNoncurrentLiabilities us-gaap true credit instant monetary No definition available. false false false false false false false false false 1 false true 861000000 861 false false 2 false true 849000000 849 false false No definition available. No authoritative reference available. false 42 Regulatory liabilities 3 us-gaap_RegulatoryLiabilityNoncurrent us-gaap true credit instant monetary No definition available. false false false false false false false false false 1 false true 921000000 921 false false 2 false true 821000000 821 false false No definition available. No authoritative reference available. false 43 Other 3 us-gaap_OtherLiabilitiesNoncurrent us-gaap true credit instant monetary No definition available. false false false false false false false false false 1 false true 361000000 361 false false 2 false true 276000000 276 false false No definition available. No authoritative reference available. false 44 Total other liabilities 3 us-gaap_LiabilitiesNoncurrent us-gaap true credit instant monetary No definition available. false false false false false false false false false 1 false true 4977000000 4977 false false 2 false true 4625000000 4625 false false No definition available. No authoritative reference available. false 45 Long-term Debt: 2 us-gaap_LongTermDebtNoncurrentAbstract us-gaap true na duration string No definition available. false false false false false true false false false 1 false false 0 0 false false 2 false false 0 0 false false No definition available. false 46 Transition and system restoration bonds 3 cnp_TransitionAndSystemRestorationBondsLongTermDebtNonCurrent cnp false na instant monetary Long-term transition and system restoration bonds are securitization bonds issued to recover qualified stranded costs and... false false false false false false false false false 1 false true 2805000000 2805 false false 2 false true 2381000000 2381 false false Long-term transition and system restoration bonds are securitization bonds issued to recover qualified stranded costs and qualified storm recovery costs. This represents the non-current portion. No authoritative reference available. false 47 Other 3 us-gaap_OtherLongTermDebtNoncurrent us-gaap true credit instant monetary No definition available. false false false false false false false false false 1 false true 6314000000 6314 false false 2 false true 7800000000 7800 false false No definition available. No authoritative reference available. false 48 Total long-term debt 3 us-gaap_LongTermDebtNoncurrent us-gaap true credit instant monetary No definition available. false false false false false false false false false 1 false true 9119000000 9119 false false 2 false true 10181000000 10181 false false No definition available. No authoritative reference available. false 49 Commitments and C... 2 us-gaap_CommitmentsAndContingencies2009 us-gaap true na duration string No definition available. false false false false false true false false false 1 false false 0 0 false false 2 false false 0 0 false false No definition available. No authoritative reference available. false 50 Shareholders' Equity 2 us-gaap_StockholdersEquity us-gaap true credit instant monetary No definition available. false false false false false false false false false 1 false true 2639000000 2639 false false 2 false true 2022000000 2022 false false No definition available. No authoritative reference available. false 51 Total Liabilities and Shareholders' Equity 2 us-gaap_LiabilitiesAndStockholdersEquity us-gaap true credit instant monetary No definition available. false false false false false false false false false 1 true true 19773000000 19773 false false 2 true true 19676000000 19676 false false No definition available. No authoritative reference available. false false 2 47 false Millions UnKnown UnKnown false true