Goodwill and Intangible Assets Disclosure [Abstract] Schedule of Goodwill [Table] Schedule of Goodwill [Table] Statement, Business Segments [Axis] Business Segments [Axis] Segment [Domain] Segment [Domain] Natural Gas Distribution [Member] Natural Gas Distribution [Member] Segment information for the Natural Gas Distribution segment which consists of intrastate natural gas sales to, and natural gas transportation and distribution for, residential, commercial, industrial and institutional customers. Interstate Pipelines [Member] Interstate Pipelines [Member] Segment information for the Interstate Pipelines segment which includes the interstate natural gas pipeline operations. Competitive Natural Gas Sales and Services [Member] Competitive Natural Gas Sales and Services [Member] Segment information for the Competitive Natural Gas Sales and Services segment which represents the non-rate regulated gas sales and services operations. Field Services [Member] Field Services [Member] Segment information for the Field Services business segment which includes the natural gas gathering, treating and processing operations. Other Operations [Member] Corporate and Other [Member] Goodwill [Line Items] Goodwill [Line Items] Balance at December 31, 2012 Goodwill Contributed to Midstream Partnership Goodwill, Other Changes Balance at June 30, 2013 Equity Method Investments and Joint Ventures [Abstract] Equity Method Investments and Joint Ventures Disclosure [Text Block] Equity Method Investments and Joint Ventures Disclosure [Text Block] Compensation and Retirement Disclosure [Abstract] Pension and Other Postretirement Benefits Disclosure [Text Block] Pension and Other Postretirement Benefits Disclosure [Text Block] Investment in Unconsolidated Affiliates [Abstract] Investment in Unconsolidated Affiliates [Abstract] Summary Investment Holdings [Table Text Block] Summary Investment Holdings [Table Text Block] Schedule of Equity in Earning of Unconsolidated Affiliates [Table Text Block] Schedule of Equity in Earning of Unconsolidated Affiliates [Table Text Block] Schedule of Equity in Earning of Unconsolidated Affiliates [Table Text Block] Goodwill and Intangible Assets Disclosure [Text Block] Goodwill and Intangible Assets Disclosure [Text Block] Statement of Financial Position [Abstract] Statement [Table] Statement [Table] Statement, Scenario [Axis] Scenario [Axis] Scenario, Unspecified [Domain] Scenario, Unspecified [Domain] Statement [Line Items] Statement [Line Items] ASSETS Assets [Abstract] Current Assets: Assets, Current [Abstract] Cash and cash equivalents Cash and Cash Equivalents, at Carrying Value Accounts receivable, net Accounts Receivable, Net, Current Accrued unbilled revenue Unbilled Receivables, Current Accounts and notes receivable - affiliated companies Due from Related Parties, Current Materials and supplies Inventory, Raw Materials and Supplies, Gross Natural gas inventory Energy Related Inventory, Natural Gas in Storage Non-trading derivative assets Derivative Assets, Current Prepaid expenses and other current assets Prepaid Expense and Other Assets, Current Total current assets Assets, Current Property, Plant and Equipment: Property, Plant and Equipment [Abstract] Property, plant and equipment Property, Plant and Equipment, Gross Less accumulated depreciation and amortization Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment Property, plant and equipment, net Property, Plant and Equipment, Net Other Assets: Assets, Noncurrent [Abstract] Goodwill Non-trading derivative assets Derivative Assets, Noncurrent Investment in unconsolidated affiliates Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures Notes receivable from unconsolidated affiliates Due from Affiliate, Noncurrent Other Other Assets, Noncurrent Total other assets Assets, Noncurrent Total Assets Assets LIABILITIES AND STOCKHOLDER'S EQUITY Liabilities and Equity [Abstract] Current Liabilities: Liabilities, Current [Abstract] Short-term borrowings Short-term Debt Current portion of long-term debt Long-term Debt, Current Maturities Accounts payable Accounts Payable, Current Accounts and notes payable — affiliated companies Due to Related Parties, Current Taxes accrued Taxes Payable, Current Interest accrued Interest Payable, Current Customer deposits Customer Deposits, Current Non-trading derivative liabilities Derivative Liabilities, Current Other Other Liabilities, Current Total current liabilities Liabilities, Current Other Liabilities: Liabilities, Noncurrent [Abstract] Accumulated deferred income taxes, net Deferred Tax Assets, Net, Noncurrent Non-trading derivative liabilities Derivative Liabilities, Noncurrent Benefit obligations Pension and Other Postretirement Defined Benefit Plans, Liabilities, Noncurrent Regulatory liabilities Regulatory Liability, Noncurrent Other Other Liabilities, Noncurrent Total other liabilities Liabilities, Noncurrent Long-term Debt Long-term Debt, Excluding Current Maturities Commitments and Contingencies (Note 10) Commitments and Contingencies Stockholder’s Equity: Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest [Abstract] Common stock Common Stock, Value, Issued Paid-in capital Additional Paid in Capital Retained earnings Retained Earnings (Accumulated Deficit) Accumulated other comprehensive loss Accumulated Other Comprehensive Income (Loss), Net of Tax Total stockholder’s equity Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest Total Liabilities and Stockholder's Equity Liabilities and Equity Derivative Instruments and Hedging Activities Disclosure [Abstract] Derivative Instruments Derivative Instruments and Hedging Activities Disclosure [Text Block] Related Party Transactions [Abstract] Money Pool Borrowings Money Pool Borrowings Money Pool Borrowings Interest Expense Net, Related Party Interest Income (Expense) Net, Related Party Net interest income (expense) related to affiliate investments or borrowings Corporate service charges, related party Related Party Transaction, Selling, General and Administrative Expenses from Transactions with Related Party Debt Disclosure [Abstract] Debt Instrument [Axis] Debt Instrument [Axis] Debt Instrument, Name [Domain] Debt Instrument, Name [Domain] Product Financing Arrangement [Member] Product Financing Arrangement [Member] Affiliated Entity [Member] Affiliated Entity [Member] Long-term Debt, Type [Axis] Long-term Debt, Type [Axis] Long-term Debt, Type [Domain] Long-term Debt, Type [Domain] Senior Notes Due Range 1 [Member] Senior Notes Due Range 1 [Member] Senior Notes Due Range 1 [Member] Senior Notes [Member] Senior Notes Due Range 2 [Member] Senior Notes Due Range 2 [Member] Commercial Paper [Member] Commercial Paper [Member] Line of Credit [Member] Line of Credit [Member] Legal Entity [Axis] Legal Entity [Axis] Entity [Domain] Entity [Domain] CERC Corp [Member] CERC Corp [Member] Another company which is controlled, directly or indirectly, by its parent. The usual condition for control is ownership of a majority (over 50%) of the outstanding voting stock. The power to control may also exist with a lesser percentage of ownership, for example, by contract, lease, agreement with other stockholders or by court decree. Midstream Partnership [Member] Midstream Partnership [Member] Midstream Partnership [Member] Debt repayment by affiliate Debt repayment by affiliate Debt repayment by affiliate Short-term Debt Line of Credit Facility, Maximum Borrowing Capacity Line of Credit Facility, Maximum Borrowing Capacity Revolving credit facility borrowing rate Line of Credit Facility, Interest Rate Description Loans Outstanding Line of Credit Facility, Amount Outstanding Letters Of Credit Outstanding Letters of Credit Outstanding, Amount Commercial Paper Outstanding Long-term Commercial Paper Percentage on limitation of debt to total capitalization under covenant (in hundredths) Percentage on limitation of debt to total capitalization under covenant (in hundredths) Percentage on limitation of debt to total capitalization under covenant. Extinguishment of Debt, Amount Extinguishment of Debt, Amount Debt Instrument, Interest Rate, Stated Percentage Debt Instrument, Interest Rate, Stated Percentage Extinguishment Of Debt Purchase Price Percentage Of Principal Extinguishment Of Debt Purchase Price Percentage Of Principal Repurchase price of debt obligations expressed as a percentage of principal amount Hedging Designation [Axis] Hedging Designation [Axis] Hedging Designation [Domain] Hedging Designation [Domain] Not Designated as Hedging Instrument [Member] Not Designated as Hedging Instrument [Member] Fair Value, Hierarchy [Axis] Fair Value, Hierarchy [Axis] Fair Value, Measurements, Fair Value Hierarchy [Domain] Fair Value, Measurements, Fair Value Hierarchy [Domain] Derivative Instrument Risk [Axis] Derivative Instrument Risk [Axis] Derivative Contract Type [Domain] Derivative Contract Type [Domain] Natural Gas Derivatives [Member] Commodity Contract [Member] Derivative Instruments, Gain (Loss) by Income Statement Location [Axis] Income Statement Location [Axis] Income Statement and Other Comprehensive Income (Loss) Location [Domain] Income Statement Location [Domain] Gains (Losses) in Revenue [Member] Sales [Member] Gains (Losses) in Expense: Natural Gas [Member] Cost of Sales [Member] Derivatives, Fair Value, by Balance Sheet Location [Axis] Balance Sheet Location [Axis] Balance Sheet Location [Domain] Balance Sheet Location [Domain] Current Assets [Member] Current Assets [Member] Line item in the statement of financial position in which the fair value amounts of the derivative instruments are included. Other Assets [Member] Other Assets [Member] Current Liabilities [Member] Current Liabilities [Member] Line item in the statement of financial position in which the fair value amounts of the derivative instruments are included. Other Liabilities [Member] Other Liabilities [Member] Derivatives, Fair Value [Line Items] Derivatives, Fair Value [Line Items] Derivative Instruments Physical Forwards Purchased Derivative Instruments Physical Forwards Purchased Derivative Instruments Physical Forwards Purchased Derivative Financial Instruments, Liabilities, Fair Value Disclosure Derivative Financial Instruments, Liabilities, Fair Value Disclosure Weather Hedges Term Weather Hedges Term Period of time used as the basis for weather hedges entered into by the company. Gains (losses) recognized from weather hedges Weather Hedges Gain Loss Recognized The amount of gain or loss recognized from weather hedges. Gross Amounts Recognized Derivative, Fair Value, Gross Amount Not Offset Against Collateral, Net Gross Amounts Offset in the Consolidated Balance Sheets Derivative Liability, Fair Value, Amount Offset Against Collateral Net Amount Presented in the Consolidated Balance Sheets Derivative, Fair Value, Amount Offset Against Collateral, Net Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net Derivative Assets Fair Value Derivative Asset, Fair Value, Gross Asset Derivative Liabilities Fair Value Derivative Liability, Fair Value, Gross Liability Derivative Instruments, Liabilities, Physical Forwards Purchased Derivative Instruments, Liabilities, Physical Forwards Purchased Derivative Instruments, Liabilities, Physical Forwards Purchased Derivative gross volumes on natural gas contracts (MMcf) Derivative Gross Volumes on Natural Gas Contracts Derivative Gross Volumes on Natural Gas Contracts Net long position (MMcf) Derivative Gross Volume Long Position Net long position volume amount taken by the company in its natural gas derivative contracts. Amount of net long position constituted by basis swaps (MMcf) Derivative Gross Volume Basis Swaps Long Position The amount of net long position constituted by basis swaps. Costs associated with price stabilization activities of the Natural Gas Distribution business segment included in Expenses Derivative Instruments Price Stabilization Cost Derivative activity in expenses includes costs associated with price stabilization activities of the Natural Gas Distribution business segment. Total fair value of the derivative instruments that contain credit risk contingency features that are in a net liability position Derivative, Net Liability Position, Aggregate Fair Value The aggregate fair value of assets already posted as collateral Collateral Already Posted, Aggregate Fair Value Credit Risk Contingent Feature assets Additional Collateral, Aggregate Fair Value Schedule of Defined Benefit Plans Disclosures [Table] Schedule of Defined Benefit Plans Disclosures [Table] Defined Benefit Plans and Other Postretirement Benefit Plans Disclosures [Axis] Defined Benefit Plans and Other Postretirement Benefit Plans [Axis] Defined Benefit Plans and Other Postretirement Benefit Plans [Domain] Defined Benefit Plans and Other Postretirement Benefit Plans [Domain] Other Postretirement Benefit Plans, Defined Benefit [Member] Other Postretirement Benefit Plans, Defined Benefit [Member] Defined Benefit Plan by Plan Asset Categories [Axis] Defined Benefit Plan, Asset Categories [Axis] Plan Asset Categories [Domain] Plan Asset Categories [Domain] Defined Benefit Plan Disclosure [Line Items] Defined Benefit Plan Disclosure [Line Items] Interest cost on accumulated benefit obligation Defined Benefit Plan, Interest Cost Amortization of prior service cost Defined Benefit Plan, Amortization of Prior Service Cost (Credit) Amortization of loss Defined Benefit Plan, Amortization of Gains (Losses) Net periodic cost Defined Benefit Plan, Net Periodic Benefit Cost Contribution expected in 2013 Defined Benefit Plan, Estimated Future Employer Contributions in Current Fiscal Year Contribution made in period Defined Benefit Plan, Contributions by Employer Other Current Assets and Liabilities [Abstract] Other Current Assets and Liabilities [Abstract] Class of Stock [Axis] Class of Stock [Axis] Class of Stock [Domain] Class of Stock [Domain] Margin Deposits Margin Deposit Assets Under Recovered Gas Costs Under Recovered Gas Costs Under-recovered gas costs Over Recovered Gas Costs Over Recovered Gas Costs Over-recovered gas costs Segment Reporting [Abstract] Reportable Business Segments Segment Reporting Disclosure [Text Block] Related Party Transactions Related Party Transactions Disclosure [Text Block] Schedule of Line of Credit Facilities [Table Text Block] Schedule of Line of Credit Facilities [Table Text Block] Statement of Other Comprehensive Income [Abstract] Net Income (loss) Net Income (Loss) Attributable to Parent Other comprehensive income, net of tax: Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent [Abstract] Adjustment to pension and other postretirement plans (net of tax) Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Adjustment, Net of Tax Other comprehensive income Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent Comprehensive income (loss) Comprehensive Income (Loss), Net of Tax, Attributable to Parent Income Tax Disclosure [Abstract] Income Taxes Income Tax Disclosure [Text Block] Organization, Consolidation and Presentation of Financial Statements [Abstract] Equity Method Investee, Name [Axis] Equity Method Investee, Name [Axis] Equity Method Investee, Name [Domain] Equity Method Investee, Name [Domain] Southeast Supply Header Llc [Member] Southeast Supply Header Llc [Member] The equity method investment in Southeast Supply Header LLC. Enogex LLC [Member] Enogex LLC [Member] Enogex LLC [Member] OGE [Member] OGE [Member] OGE [Member] ArcLight [Member] ArcLight [Member] ArcLight [Member] OGE ARCLIGHT [Member] OGE ARCLIGHT [Member] OGE ARCLIGHT [Member] Equity Method Investment, Ownership Percentage Equity Method Investment, Ownership Percentage Equity Interest Contributed, Percentage Equity Interest Contributed, Percentage Equity Interest Contributed, Percentage Nature of Common Ownership or Management Control Relationships Nature of Common Ownership or Management Control Relationships Incentive Distribution Right Incentive Distribution Right Incentive Distribution Right Effective Income Tax Rate Effective Income Tax Rate, Continuing Operations Unrecognized tax expenses Unrecognized tax expense The gross amount of unrecognized tax expense pertaining to uncertain tax positions taken in tax returns as of the balance sheet date. Portion of unrecognized tax expenses that, if recognized, would increase the effective income tax rate Unrecognized Tax Benefits that Would Impact Effective Tax Rate Interest accrued on unrecognized tax expenses Unrecognized tax expense, interest on income taxed accrued This element represents the amount of interest income as of the date of the statement of financial positioin for an overpayment of income taxes computed by applying the applicable statutory rate of interest to the difference between a tax position recognized for financial reporting purposes and the amount previously taken or expected to be taken in a tax return of the entity. Period of time for possible decrease in unrecognized tax benefits (in months) Period of time for possible decrease in unrecognized tax benefits (in months) Period of time for possible decrease in unrecognized tax benefits (in months) Deferred Tax Liabilities, Goodwill and Intangible Assets Deferred Tax Liabilities, Goodwill and Intangible Assets Deferred income taxes Deferred Income Tax Expense (Benefit) Background and Basis of Presentation Organization, Consolidation and Presentation of Financial Statements Disclosure [Text Block] Commitments and Contingencies Disclosure [Abstract] CenterPoint Energy [Member] CenterPoint Energy [Member] Another company which is controlled, directly or indirectly, by its parent. The usual condition for control is ownership of a majority (over 50%) of the outstanding voting stock. The power to control may also exist with a lesser percentage of ownership, for example, by contract, lease, agreement with other stockholders or by court decree. Schedule of Capital Expansion Projects, by Project [Axis] Schedule of Capital Expansion Projects, by Project [Axis] A table of capital expansion projects by project. Capital Expansion Project [Domain] Capital Expansion Project [Domain] The capital expansion projects by name. Recorded Unconditional Purchase Obligation Payment Schedule [Abstract] Recorded Unconditional Purchase Obligation, Fiscal Year Maturity Schedule [Abstract] 2013 Recorded Unconditional Purchase Obligation Due in Next Twelve Months 2014 Recorded Unconditional Purchase Obligation Due in Second Year 2015 Recorded Unconditional Purchase Obligation Due in Third Year 2016 Recorded Unconditional Purchase Obligation Due in Fourth Year 2017 Recorded Unconditional Purchase Obligation Due in Fifth Year After 2017 Recorded Unconditional Purchase Obligation Due after Fifth Year Schedule of Capital Expansion Projects [Abstract] Schedule of Capital Expansion Projects [Abstract] -- None. No documentation exists for this element. -- LegalEnvironmentalAndOtherRegulatoryMattersLegalMattersGasMarketManipulationCasesAbstract LegalEnvironmentalAndOtherRegulatoryMattersLegalMattersGasMarketManipulationCasesAbstract -- None. No documentation exists for this element. -- Recovery of compensatory damages sought by plaintiffs Loss Contingency, Damages Sought Approximate number of gas market manipulatioin lawsuits naming CenterPoint Energy and/or Reliant Energy (in number of lawsuits) Loss Contingency Total Gas Market Manipulation Cases The total amount of gas market manipulation lawsuits filed against a company. Number of gas market manipulation lawsuits pending for CenterPoint and its affiliates (in number of lawsuits) Loss Contingency Pending Gas Market Manipulation Lawsuits Number The total number of pending lawsuits related to gas market manipulation. Site Contingency Completed Remediation Site Contingency Completed Remediation Number of manufactured gas plant sites where remediation is complete, other than ongoing operations. Number of remaining sites in the Minnesota service territory (in number of sites) Site Contingency Remaining Minnesota Sites Number of other sites in the company's Minnesota service territory. Number of remaining sites in the Minnesota service territory where the company believes it has no liability (in number of sites) Site Contingency Sites Without Liability Number of sites in Minnesota where the company believes it has no liability. Amount accrued for remediation of Minnesota sites Accrual for Environmental Loss Contingencies Minimum estimated remediation costs for the Minnesota sites Site Contingency Loss Exposure Low Estimate Low-end of the range estimate of the reasonably possible loss exposure at an individual site. Maximum estimated remediation costs for the Minnesota sites Site Contingency Loss Exposure High Estimate High-end of the range estimate of the reasonably possible loss exposure at an individual site. Minimum years of remediation for the Minnesota sites (in years) Site Contingency Estimated Time Frame To Resolve Contingency Low Estimate Low-end of the range estimated time frame for remediation to continue. Maximum estimated remediation for the Minnesota sites (in years) Site Contingency Estimated Time Frame To Resolve Contingency High Estimate High-end of the range estimated time frame for remediation to continue. Annual amount included in rates to fund normal on-going remediation costs Environmental Costs Recognized, Recovery Credited to Expense Amount collected from insurance companies to be used for future environmental remediation Recorded Third-Party Environmental Recoveries, Amount Approximate amount of undiscounted maximum potential guarantee obligation Guarantor Obligations, Maximum Exposure, Undiscounted Guarantor Obligations, Current Amount Guarantor Obligations, Current Amount Guarantor Obligations, Current Amount Guarantee Obligations Maximum Amount Upon Completion Of Gathering Systems Guarantee Obligations Maximum Amount Upon Completion Of Gathering Systems Maximum amount of guarantees reduce to plus any additional amounts related to expansion of services upon completion of gathering systems. Unsecured Term Loan Facility Unsecured Debt Schedule of Goodwill [Table Text Block] Schedule of Goodwill [Table Text Block] Fair Value Disclosures [Abstract] Fair Value, Assets Measured on Recurring Basis [Table Text Block] Fair Value, Assets Measured on Recurring Basis [Table Text Block] Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Table Text Block] Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Table Text Block] Fair Value, by Balance Sheet Grouping [Table Text Block] Fair Value, by Balance Sheet Grouping [Table Text Block] Summary of Unrecognized Tax Benefits [Table Text Block] Summary of Income Tax Contingencies [Table Text Block] Fair Value of Derivative Instruments Table Schedule of Derivative Instruments in Statement of Financial Position, Fair Value [Table Text Block] Income Statement Impact of Derivative Activity Table Schedule of Derivative Instruments, Gain (Loss) in Statement of Financial Performance [Table Text Block] Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Table] Fair Value Measurements, Recurring and Nonrecurring [Table] Fair Value, Inputs, Level 1 [Member] Fair Value, Inputs, Level 1 [Member] Fair Value, Inputs, Level 2 [Member] Fair Value, Inputs, Level 2 [Member] Fair Value, Inputs, Level 3 [Member] Fair Value, Inputs, Level 3 [Member] Netting Adjustments [Member] Netting Adjustments [Member] This item represents the amount of adjustment to assets or liabilities, due to the netting arrangements as specified in master contract. Relates to derivative contracts with counterparties. Fair Value, by Balance Sheet Grouping, Disclosure Item Amounts [Axis] Fair Value, by Balance Sheet Grouping, Disclosure Item Amounts [Axis] Fair Value, Disclosure Item Amounts [Domain] Fair Value, Disclosure Item Amounts [Domain] Carrying Amount [Member] Carrying (Reported) Amount, Fair Value Disclosure [Member] Fair Value [Member] Estimate of Fair Value, Fair Value Disclosure [Member] Statement [Line Items] Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] Notes Receivable, Fair Value Disclosure Notes Receivable, Fair Value Disclosure Illiquid forward price low range Illiquid forward price low range Illiquid forward price per mmbtu - low range Illiquid forward price high range Illiquid forward price high range Illiquid forward price per mmbtu - high range Cash collateral posted with counterparties Cash collateral posted with counterparties The amount of cash that is posted, at the end of the reporting period, as collateral for derivative instruments with credit-risk-related contingent features. Option volatilities low range Option volatilities low range Option volatilities low range Option volatilities high range Option volatilities high range Option volatilities high range Corporate Equities Fair Value Assets Measured On Recurring Basis Corporate Equities This element represents a certain statement of financial position asset caption which represents a class of assets, or which may include an individual asset, measured at fair value on a recurring basis. Investments, including money market funds Investments, Fair Value Disclosure Natural gas derivatives, assets Derivative Assets Total Assets Assets, Fair Value Disclosure, Recurring Natural gas derivatives, liabilities Total liabilities Liabilities, Fair Value Disclosure, Recurring Long-term Debt Long-term Debt, Fair Value Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation Calculation Roll Forward Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward] Beginning balance Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Net Asset Liability Value This element represents the net asset/liability measured at fair value using significant unobservable inputs (Level 3) which is required for reconciliation purposes of beginning and ending balances. Total gains Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings Total settlements Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases, Sales, Issues, Settlements Transfers out of Level 3 Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers, Net Ending balance Amount Of Total Gains For Period Included In Earnings Amount Of Total Gains Losses For Period Included In Earnings This item represents the amount of the total change in unrealized (holding) gains or losses for the period which are included in the statement of income (or changes in net assets) in assets still held at reporting period. Such unrealized (holding) gains or losses relate to those assets still held at the reporting date for which fair value is measured on a recurring basis using significant unobservable inputs (Level 3). New Accounting Pronouncements and Changes in Accounting Principles [Abstract] Description of New Accounting Pronouncements Not yet Adopted [Text Block] Description of New Accounting Pronouncements Not yet Adopted [Text Block] Midstream Partnership [Abstract] Midstream Partnership [Abstract] Senior Subordinated Notes [Member] Senior Subordinated Notes [Member] Other Entity [Member] Other Entity [Member] Other Entity [Member] SESH [Member] SESH [Member] SESH [Member] Equity Method Investment, Summarized Financial Information, Revenue Equity Method Investment, Summarized Financial Information, Revenue Equity in earnings of unconsolidated affiliates Income (Loss) from Equity Method Investments Contributed Assets Contributed Assets Contributed Assets Contributed Liabilities Contributed Liabilities Contributed Liabilities Debt repayment by affiliate Term Loan of Affiliate Term Loan of Affiliate Debt of Affiliate Debt of Affiliate Debt of Affiliate Transitional Service Costs to be Reimbursed Transitional Service Costs to be Reimbursed Transitional Service Costs to be Reimbursed Equity Method Investment, Summarized Financial Information, Gross Profit (Loss) Equity Method Investment, Summarized Financial Information, Gross Profit (Loss) Equity Method Investment, Summarized Fnancial Information, Operating Income Equity Method Investment, Summarized Fnancial Information, Operating Income Equity Method Investment, Summarized Fnancial Information, Operating Income Equity Method Investment, Summarized Financial Information, Net Income (Loss) Equity Method Investment, Summarized Financial Information, Net Income (Loss) Gross equity in earnings Gross equity in earnings Gross equity in earnings Basis Difference Amortization Basis Difference Amortization Basis Difference Amortization Equity Earnings Net of Basis Difference Amortization Equity Earnings Net of Basis Difference Amortization Equity Earnings Net of Basis Difference Amortization Debt Instrument, Interest Rate, Stated Percentage Rate Range, Minimum Debt Instrument, Interest Rate, Stated Percentage Rate Range, Minimum Debt Instrument, Interest Rate, Stated Percentage Rate Range, Maximum Debt Instrument, Interest Rate, Stated Percentage Rate Range, Maximum Statement of Cash Flows [Abstract] Cash Flows from Operating Activities: Net Cash Provided by (Used in) Operating Activities [Abstract] Net Income (loss) Adjustments to reconcile net income (loss) to net cash provided by operating activities: Adjustments to Reconcile Net Income (Loss) to Cash Provided by (Used in) Operating Activities [Abstract] Depreciation and amortization Depreciation, Depletion and Amortization Amortization of deferred financing costs Amortization of Financing Costs Write-down of natural gas inventory Inventory Write-down Equity in earnings of unconsolidated affiliates, net of distributions Income (Loss) from Equity Method Investments, Net of Dividends or Distributions Changes in other assets and liabilities: Increase (Decrease) in Operating Capital [Abstract] Accounts receivable and unbilled revenues, net. Increase (Decrease) in Accounts and Other Receivables Accounts receivable/payable, affiliates companies Increase decrease in Accounts receivable payable affiliates The increase (decrease) in net accounts receivables and payables due to/from affiliates. Inventory Increase (Decrease) in Inventories Taxes receivable Increase (Decrease) in Income Taxes Receivable Accounts payable Increase (Decrease) in Accounts Payable Fuel cost recovery Increase (Decrease) in over (under) Energy Recovery Interest and taxes accrued Increase Decrease Interest and taxes accrued Increase (decrease) in interest and taxes accrued. Non-trading derivatives, net Increase (Decrease) in Commodity Contract Assets and Liabilities Margin deposits, net Increase (Decrease) in Margin Deposits Outstanding Other current assets Increase (Decrease) in Other Current Assets Other current liabilities Increase (Decrease) in Other Current Liabilities Other assets Increase (Decrease) in Other Noncurrent Assets Other liabilities Increase (Decrease) in Other Noncurrent Liabilities Other, net Increase (Decrease) in Other Operating Assets and Liabilities, Net Net cash provided by operating activities Net Cash Provided by (Used in) Operating Activities Cash Flows from Investing Activities: Net Cash Provided by (Used in) Investing Activities [Abstract] Capital expenditures, net of acquisitions Payments to Acquire Productive Assets Acquisition, net of cash acquired Payments to Acquire Assets, Investing Activities Investment in unconsolidated affiliates Payments to Acquire Interest in Joint Venture Cash contribution to Midstream Partnership Cash Contributed Cash Contributed Other, net Payments for (Proceeds from) Other Investing Activities Net cash used in investing activities Net Cash Provided by (Used in) Investing Activities Cash Flows from Financing Activities: Net Cash Provided by (Used in) Financing Activities [Abstract] Decrease in short-term borrowings, net Proceeds from (Repayments of) Short-term Debt Payments of commercial paper, net Proceeds from (Repayments of) Commercial Paper Proceeds from long-term debt Proceeds from Issuance of Long-term Debt Repayments of Long-term Debt Repayments of Long-term Debt Increase (decrease) in notes payable to affiliates Increase (Decrease) in Notes Payable, Related Parties, Current Other, net Proceeds from (Payments for) Other Financing Activities Net cash used in financing activities Net Cash Provided by (Used in) Financing Activities Net Increase in Cash and Cash Equivalents Cash and Cash Equivalents, Period Increase (Decrease) Cash and Cash Equivalents at Beginning of Period Cash and Cash Equivalents at End of Period Supplemental Disclosure of Cash Flow Information: Supplemental Cash Flow Information [Abstract] Cash Payments: Cash Payments [Abstract] -- None. No documentation exists for this element. -- Interest, net of capitalized interest Interest Paid, Net Income Taxes, Net Income Taxes Paid, Net Non-cash transactions: Noncash Investing and Financing Items [Abstract] Accounts payable related to capital expenditures Capital Expenditures Incurred but Not yet Paid Schedule of Segment Reporting Information, by Segment [Table Text Block] Schedule of Segment Reporting Information, by Segment [Table Text Block] Schedule of Segment Reporting Information, by Segment [Table] Schedule of Segment Reporting Information, by Segment [Table] CERC Remaining Interest in SESH [Member] CERC Remaining Interest in SESH [Member] CERC Remaining Interest in SESH [Member] Midstream Investments [Member] Midstream Investments [Member] Midstream Investments [Member] Reconciling Eliminations [Member] Intersegment Elimination [Member] Segment Reporting Information [Line Items] Segment Reporting Information [Line Items] Revenues Revenues Revenue from External Customers Revenue from External Customers Intersegment Revenue Segment Reporting Information, Intersegment Revenue Operating Income (Loss) Operating Income (Loss) Assets Schedule of Net Benefit Costs [Table Text Block] Schedule of Net Benefit Costs [Table Text Block] Other Current Assets and Liabilities [Text Block] Other Current Assets and Liabilities [Text Block] Other Current Assets and Liabilities [Text Block] Commitments and Contingencies Commitments and Contingencies Disclosure [Text Block] Fair Value Disclosures [Text Block] Fair Value Disclosures [Text Block] Short-term Borrowings and Long-term Debt Debt Disclosure [Text Block] Document and Entity Information [Abstract] Document and Entity Information [Abstract] Entities [Table] Entities [Table] Entity Information [Line Items] Entity Information [Line Items] Entity Registrant Name Entity Registrant Name Entity Central Index Key Entity Central Index Key Current Fiscal Year End Date Current Fiscal Year End Date Entity Filer Category Entity Filer Category Document Type Document Type Document Period End Date Document Period End Date Document Fiscal Year Focus Document Fiscal Year Focus Document Fiscal Period Focus Document Fiscal Period Focus Amendment Flag Amendment Flag Entity Common Stock, Shares Outstanding Entity Common Stock, Shares Outstanding Entity Well-known Seasoned Issuer Entity Well-known Seasoned Issuer Entity Voluntary Filers Entity Voluntary Filers Entity Current Reporting Status Entity Current Reporting Status Entity Public Float Entity Public Float Income Statement [Abstract] Scenario [Axis] Revenues Expenses: Operating Expenses [Abstract] Natural gas Cost of Natural Gas Purchases Natural gas-affiliates Cost of natural gas purchases, affiliates Cost of natural gas purchased and associated transportation and storage costs during the period from unconsolidated affiliates Operation and maintenance Operation and maintenance The amount of operating expense for the period for recurring costs associated with normal operations including general and administrative expenses, and routine plant mainentnance and repairs. Taxes other than income taxes Taxes, Miscellaneous Total Operating Expenses Operating Income Other Income (Expense): Nonoperating Income (Expense) [Abstract] Interest and other finance charges Interest and Debt Expense Other, net Other Nonoperating Income (Expense) Total Nonoperating Income (Expense) Income Before Income Taxes Income (Loss) from Continuing Operations before Income Taxes, Extraordinary Items, Noncontrolling Interest Income tax expense Income Tax Expense (Benefit) Net Income (Loss)