Balance Sheet Parentheticals [Abstract] Balance Sheet Parentheticals [Abstract] Statement [Table] Statement [Table] Statement, Scenario [Axis] Statement, Scenario [Axis] Scenario, Unspecified [Domain] Scenario, Unspecified [Domain] Class of Stock [Axis] Class of Stock [Axis] Class of Stock [Domain] Class of Stock [Domain] Statement [Line Items] Statement [Line Items] Current Assets: Assets, Current [Abstract] Cash and cash equivalents, VIE Cash And Cash Equivalents Variable Interest Entities Cash And Cash Equivalents, Variable Interest Entities Accounts receivable, net, VIE Accounts Receivable Net Variable Interest Entities Accounts Receivable, Net, Variable Interest Entities Prepaid expenses and other current assets, VIE Prepaid Expenses And Other Current Assets Variable Interest Entities Prepaid Expenses And Other Current Assets, Variable Interest Entities Other Assets: Assets, Noncurrent [Abstract] Regulatory assets, VIE Regulatory Assets Variable Interest Entities Regulatory Assets Variable Interest Entities Common stock, shares outstanding Common Stock, Shares, Outstanding Entities [Table] Legal Entity [Axis] Legal Entity [Axis] Entity [Domain] Entity [Domain] 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 Comprehensive Income Phantoms [Abstract] Comprehensive Income Phantoms [Abstract] Tax effects on adjustment to pension and other postretirement plans Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Tax Tax effect on reclassification of deferred loss from cash flow hedges realized in net income Other Comprehensive Income (Loss), Reclassification Adjustment on Derivatives Included in Net Income, Tax Condensed Consolidated Balance Sheets (Unaudited) [Abstract] -- None. No documentation exists for this element. -- Cash and cash equivalents ($220 and $236 related to VIEs at December 31, 2011 and June 30, 2012, respectively) Cash and Cash Equivalents, at Carrying Value Investment in marketable securities Marketable Securities, Current Accounts receivable, net ($52 and $95 related to VIEs at December 31, 2011 and June 30, 2012, respectively) Accounts Receivable, Net, Current Accrued unbilled revenues Accrued unbilled revenues Estimated cycle billing accrued revenue. Natural gas inventory Energy Related Inventory, Natural Gas in Storage Materials and supplies Inventory, Raw Materials and Supplies Non-trading derivative assets Derivative Assets, Current Taxes receivable Income Taxes Receivable, Current Prepaid expenses and other current assets ($42 and $55 related to VIEs at December 31, 2011 and June 30, 2012, respectively) 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 Goodwill Goodwill Regulatory assets ($2,289 and $3,778 related to VIEs at December 31, 2011 and June 30, 2012, respectively) Regulatory Assets, Noncurrent Non-trading derivative assets Derivative Assets, Noncurrent Investment in unconsolidated affiliates Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures Other Other Assets, Noncurrent Total other assets Assets, Noncurrent Total Assets Assets Current Liabilities: Liabilities, Current [Abstract] Short-term borrowings Short-term Debt Current portion of VIE transition and system restoration bonds long-term debt Transition And System Restoration Bonds Long Term Debt Current 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. Current portion of indexed debt Indexed Debt Current -- None. No documentation exists for this element. -- Current portion of other long-term debt Other Long-term Debt, Current Indexed debt securities derivative Indexed debt securities derivative -- None. No documentation exists for this element. -- Accounts payable Accounts Payable, Current Taxes accrued Taxes Payable, Current Interest accrued Interest Payable, Current Non-trading derivative liabilities Derivative Liabilities, Current Accumulated deferred income taxes, net Deferred Tax Liabilities, Current Other Other Liabilities, Current Total current liabilities Liabilities, Current Other Liabilities: Liabilities, Noncurrent [Abstract] Accumulated deferred income taxes, net Deferred Tax Liabilities, 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 [Abstract] VIE transition and system restoration bonds Transition And System Restoration Bonds Long Term Debt Non Current -- None. No documentation exists for this element. -- Other Other Long-term Debt, Noncurrent Total long-term debt Long-term Debt, Excluding Current Maturities Commitments and Contingencies (Note 11) Commitments and Contingencies Shareholders' Equity: Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest [Abstract] Common stock (426,030,345 shares and 427,385,879 shares outstanding at December 31, 2011 and June 30, 2012, respectively) Common Stock, Value, Issued Additional 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 shareholders' equity Stockholders' Equity Attributable to Parent Total Liabilities and Shareholders' Equity Liabilities and Equity Fair Value Measurements - (Tables) [Abstract] -- None. No documentation exists for this element. -- Fair value, assets measured on a recurring basis Fair Value, Assets Measured on Recurring Basis [Table Text Block] Assets and liabilities measured at fair value on a recurring basis using significant unobservable inputs Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Table Text Block] Estimated fair value of financial instruments, debt instruments Fair Value, by Balance Sheet Grouping [Table Text Block] Earnings Per Share [Abstract] Schedule of Earnings Per Share, Basic and Diluted [Table Text Block] Schedule of Earnings Per Share, Basic and Diluted [Table Text Block] Derivative Instruments [Abstract] -- None. No documentation exists for this element. -- Derivative Instrument Risk [Axis] Derivative Contract Type [Domain] Derivative Contract Type [Domain] Natural Gas Derivatives [Member] Commodity Contract [Member] Indexed Debt Securities Derivative [Member] Other Contract [Member] Derivatives, Fair Value, by Balance Sheet Location [Axis] Derivatives, Fair Value, by 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] Derivative Instruments, Gain (Loss) by Income Statement Location [Axis] Income Statement and Other Comprehensive Income Location [Domain] Income Statement and Other Comprehensive Income (Loss) Location [Domain] Gains (Losses) in Revenue [Member] Sales [Member] Gains (Losses) in Expense: Natural Gas [Member] Cost of Sales [Member] Gains (losses) in Other Income (Expense) [Member] Other Expense [Member] Derivatives, Fair Value [Line Items] Derivatives, Fair Value [Line Items] Derivatives, Fair Value [Abstract] Derivatives, Fair Value [Abstract] Derivative assets fair value Derivative Asset, Fair Value, Gross Asset Derivative liability fair value Derivative Liability, Fair Value, Gross Liability Derivative gross volumes (Bcf) Description of Derivative Activity Volume Net long position (Bcf) 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 (Bcf) Derivative Gross Volume Basis Swaps Long Position The amount of net long position constituted by basis swaps. Amount of net long position comprised of price stabilization activities of the Natural Gas Distribution business segment (Bcf) Derivative Gross Volume Segment Long Position The amount of net long position comprised of price stabilization activities of the Natural Gas Distribution business segment. Total non-trading derivative assets and liabilities net of collateral Derivative, Fair Value, Amount Offset Against Collateral, Net Collateral netting Collateral Netting Amount of collateral netted with derivative contracts. Total fair value of the derivative instruments that contain credit risk contingent 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 Features assets Additional Collateral, Aggregate Fair Value Derivative Instruments, Gain (Loss) [Abstract] Derivative Instruments, Gain (Loss) [Abstract] Derivative gains and (losses) in the Statements of Consolidated Income Derivative gains and (losses) in the Statements of Consolidated Income Realized and unrealized gains (losses) recognized on derivatives during the period. 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. Increased (decreased) natural gas revenues from the unrealized net gains (losses) of derivative instruments Sales Revenue From Natural Gas Derivatives Unrealized Gains Losses Revenue derived from natural gas derivatives unrealized gains and losses. Increased (decreased) natural gas expense from the unrealized net (gains) losses of derivative instruments Expense From Natural Gas Derivatives Unrealized Losses Gains Expense derived from natural gas derivatives unrealized losses and gains. Net unrealized gain (loss) from derivative instruments Unrealized Gain (Loss) on Commodity Contracts Term of normal weather used as the basis for weather hedges (in years) 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. Commitments and Contingencies [Abstract] -- None. No documentation exists for this element. -- Commitments and Contingencies Commitments and Contingencies Disclosure [Text Block] Goodwill [Abstract] -- None. No documentation exists for this element. -- Goodwill and Intangible Assets Disclosure [Text Block] Goodwill and Intangible Assets Disclosure [Text Block] Regulatory Accounting [Abstract] regulatory accounting [Abstract] regulatory accounting [Abstract] Amount of allowed equity return on the true-up balance that has not been recognized Unrecognized Amount Of Allowed Equity Return Amount of allowed equity return on the true-up balance that has not been recognized as it will be recognized as it is recovered in rates. Amount of allowed equity return on the true-up balance that was recognized in the period Amount Of Allowed Equity Return Recognized In Period Amount of allowed equity return on the true-up balance that was recognized in the period Regulatory Matters [Abstract] -- None. No documentation exists for this element. -- Organization, Consolidation and Presentation of Financial Statements [Abstract] Background and Basis of Presentation Organization, Consolidation and Presentation of Financial Statements Disclosure [Text Block] Short-term Borrowings and Long-term Debt [Abstract] -- None. No documentation exists for this element. -- Short-term Borrowings and Long-term Debt [Text Block] Debt Disclosure [Text Block] Regulatory Matters Public Utilities Disclosure [Text Block] Capital Stock [Abstract] -- None. No documentation exists for this element. -- Capital Stock Stockholders' Equity Note Disclosure [Text Block] Fair Value Measurements [Abstract] -- None. No documentation exists for this element. -- Fair Value Disclosures [Text Block] Fair Value Disclosures [Text Block] Income Taxes [Abstract] -- None. No documentation exists for this element. -- Income Taxes Income Tax Disclosure [Text Block] New Accounting Pronouncements [Abstract] -- None. No documentation exists for this element. -- Description of New Accounting Pronouncements Not yet Adopted [Text Block] Description of New Accounting Pronouncements Not yet Adopted [Text Block] Subsequent Events [Abstract] Subsequent Events [Text Block] Subsequent Events [Text Block] Subsequent Events Schedule of Subsequent Events [Table Text Block] Reportable Business Segments [Abstract] -- None. No documentation exists for this element. -- Reportable Business Segments Segment Reporting Disclosure [Text Block] Schedule of Line of Credit Facilities [Table Text Block] Schedule of Line of Credit Facilities [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] Background and Basis of Presentation [Abstract] -- None. No documentation exists for this element. -- Number Of Vies Consolidated In Financial Statements Number Of Vies Consolidated In Financial Statements The number of variable interest entities (VIE's) consolidated in the financials. Income Statement [Abstract] Condensed Statements of Consolidated Income (Unaudited) [Abstract] -- None. No documentation exists for this element. -- Revenues Revenues Expenses: Operating Expenses [Abstract] Natural gas Cost of Natural Gas Purchases 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. Depreciation and amortization Depreciation, Depletion and Amortization, Nonproduction Taxes other than income taxes Taxes, Miscellaneous Total Operating Expenses Operating Income Operating Income (Loss) Other Income (Expense): Nonoperating Income (Expense) [Abstract] Gain on marketable securities Marketable Securities, Gain (Loss) Gain (loss) on indexed debt securities Gain (loss) on Indexed Debt Securities Gain (loss) on Indexed Debt Securities. Interest and other finance charges Interest and Debt Expense Interest on transition and system restoration bonds Interest on Transition and System Restoration Bonds Interest on Transition and System Restoration Bonds. Equity in earnings of unconsolidated affiliates Income (Loss) from Equity Method Investments Return on true-up balance Return on true-up balance Return on true-up balance 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) Income Before Extraordinary Item Income (Loss) from Operations before Extraordinary Items Extraordinary Item, net of tax Extraordinary Item, Gain (Loss), Net of Tax, Attributable to Parent Net Income Net Income (Loss) Attributable to Parent Basic Earnings Per Share: Earnings Per Share, Basic [Abstract] Income Before Extraordinary Item Income (Loss) from Operations before Extraordinary Items, Per Basic Share Extraordinary Item, net of tax Income (Loss) from Extraordinary Items, Net of Tax, Per Basic Share Basic Earnings Per Share Earnings Per Share, Basic Diluted earnings per share: Earnings Per Share, Diluted [Abstract] Income Before Extraordinary Item Income (Loss) from Operations before Extraordinary Items, Per Diluted Share Extraordinary Item, net of tax Income (Loss) from Extraordinary Items, Net of Tax, Per Diluted Share Diluted Earnings Per Share Earnings Per Share, Diluted Dividends Declared Per Share Common Stock, Dividends, Per Share, Declared Weighted Average Shares Outstanding, Basic Weighted Average Number of Shares Outstanding, Basic Weighted Average Shares Outstanding, Diluted Weighted Average Number of Shares Outstanding, Diluted Employee Benefit Plans [Abstract] -- None. No documentation exists for this element. -- Employee Benefit Plans Pension and Other Postretirement Benefits Disclosure [Text Block] Goodwill - (Tables) [Abstract] -- None. No documentation exists for this element. -- Goodwill Schedule [Table] Goodwill Schedule [Table] -- None. No documentation exists for this element. -- Statement, Business Segments [Axis] Statement, Business Segments [Axis] Segment [Domain] Segment [Domain] 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] Segment information for the Interstate Pipelines segment which includes the interstate natural gas pipeline operations. 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, which consist of three operational functions: wholesale, retail and intrastate pipelines. Field Services [Member] Segment information for the Field Services business segment which includes the natural gas gathering, treating and processing operations. Other Operations [Member] Segment information for the Other Operations segment which consists primarily of other corporate operations which support all of the business operations. Goodwill Reporting Information [Axis] Goodwill Reporting Information [Axis] Disclosure of goodwill for each reportable segment. Reporting Segments [Domain] Reporting Segments [Domain] A component of an entity for which there is an accounting requirement to report separate financial information on that component in the entity's financial statements. Natural Gas Distribution [Member] Interstate Pipelines [Member] Competitive Natural Gas Sales and Services [Member] Field Services [Member] Other Operations [Member] Goodwill Schedule [Line Items] Goodwill Schedule [Line Items] -- None. No documentation exists for this element. -- Goodwill Employee Benefit Plans - (Tables) [Abstract] -- None. No documentation exists for this element. -- Schedule of Defined Benefit Plans Disclosures [Table Text Block] Schedule of Defined Benefit Plans Disclosures [Table Text Block] Subsequent Events - (Details) [Abstract] -- None. No documentation exists for this element. -- Subsequent Event [Table] Subsequent Event [Table] Debt Instrument [Axis] Debt Instrument [Axis] Debt Instrument, Name [Domain] Debt Instrument, Name [Domain] Bonds General Mortgage Due 2013 [Member] Bonds General Mortgage Due 2013 [Member] Bonds General Mortgage Due 2013 [Member] Bonds General Mortgage Due January 2014 [Member] Bonds General Mortgage Due January 2014 [Member] Bonds General Mortgage Due January 2014 [Member] CenterPoint Houston [Member] CenterPoint Houston [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. Bonds General Mortgage Due 2014 [Member] Bonds General Mortgage Due 2014 [Member] Bonds General Mortgage Due 2014 [Member] Bonds General Mortgage Due March 2014 [Member] Bonds General Mortgage Due March 2014 [Member] Bonds General Mortgage Due March 2014 [Member] Subsequent Event Type [Axis] Subsequent Event Type [Axis] Subsequent Event Type [Domain] Subsequent Event Type [Domain] Dividend Declared [Member] Dividend Declared [Member] Subsequent Event [Line Items] Subsequent Event [Line Items] Subsequent Event, Date Subsequent Event, Date Subsequent Event, Amount Subsequent Event, Amount Dividends Payable, Date to be Paid, Day, Month and Year Dividends Payable, Date to be Paid, Day, Month and Year Dividends Payable, Date of Record, Day, Month and Year Dividends Payable, Date of Record, Day, Month and Year Ownership Interest In Waskom Percentage Of Ownership Interest In Affiliate 2 The percentage of ownership interest in Waskom Gas Processing Company. Remaining Ownership Interest in Waskom Acquired Percentage of Ownership in Affiliate 2 Acquired The remaining ownership percentage of Waskom Gas Processing Company acquired. Total Cash Consideration Business Acquisition, Cost of Acquired Entity, Cash Paid Business Acquisition, Purchase Price Allocation, Remaining Interest Business Acquisition, Purchase Price Allocation, Remaining Interest The amount of purchase price allocated to the acquistion of the remaining 50% interest in Waskom. Purchase Price Allocated to Other Gathering Assets Business Acquisition, Purchase Price Allocation, Assets Acquired Pre-tax Gain from Remeasuring Original Waskom Investment Business Combination, Step Acquisition, Equity Interest in Acquiree, Remeasurement Gain Number of general mortgage bond series called for redemption Number of general mortgage bond series called for redemption Number of general mortgage bond series called for redemption Aggregate Principal Amount Debt Instrument, Face Amount Interest Rate, Percentage Debt Instrument, Interest Rate, Stated Percentage Maturity Date Debt Instrument, Maturity Date Redemption Date Redemption Date Redemption Date Redemption Premium Redemption Premium Long-term Debt To Be Issued, Aggregate Principal Amount Long-term Debt To Be Issued, Aggregate Principal Amount Long-term Debt To Be Issued, Aggregate Principal Amount Schedule of Defined Benefit Plans Disclosures [Table] Schedule of Defined Benefit Plans Disclosures [Table] Defined Benefit Plans Disclosures, Defined Benefit Plans [Axis] Defined Benefit Plans and Other Postretirement Benefit Plans Disclosures [Axis] Defined Benefit Plans [Domain] Defined Benefit Plans and Other Postretirement Benefit Plans [Domain] Pension Plans, Defined Benefit [Member] Pension Plans, Defined Benefit [Member] Other Postretirement Benefit Plans, Defined Benefit [Member] Other Postretirement Benefit Plans, Defined Benefit [Member] Defined Benefit Plan Disclosure [Line Items] Defined Benefit Plan Disclosure [Line Items] Service cost Defined Benefit Plan, Service Cost Interest cost Defined Benefit Plan, Interest Cost Expected return on plan assets Defined Benefit Plan, Expected Return on Plan Assets Amortization of prior service credit Defined Benefit Plan, Amortization of Prior Service Cost (Credit) Amortization of net loss Defined Benefit Plan, Amortization of Gains (Losses) Amortization of transition obligation Defined Benefit Plan, Amortization of Transition Obligations (Assets) Net periodic cost Defined Benefit Plan, Net Periodic Benefit Cost Amount of pension and other postemployment benefits deferred as a regulatory asset Amount of Pension and Postemployment Benefits Deferred as Regulatory Asset Amount of pension and postemployment benefits deferred as regulatory assets. Estimated future contribution in the next fiscal year Defined Benefit Plan, Estimated Future Employer Contributions in Next Fiscal Year Total contributions to the plans during the period Defined Benefit Plan, Contributions by Employer Pension Contributions Pension Contributions Expected contribution to pension plans in the third quarter Expected contribution to pension plans in next period The anticipated contribution to the pension plan in the next reporting period. Defined Benefit Plan, Estimated Future Employer Contributions in Current Fiscal Year Defined Benefit Plan, Estimated Future Employer Contributions in Current Fiscal Year Summary of unrecognized tax benefits Summary of unrecognized tax benefits [Text Block] Summary of unrecognized tax benefits including (1) portion of unrecognized tax benefits that, if recognized, would reduce the effective income tax rate, and (2) interest accrued on unrecognized tax benefits. Significant Change in Unrecognized Tax Benefits is Reasonably Possible [Table] Significant Change in Unrecognized Tax Benefits is Reasonably Possible [Table] Reasonably Possible Significant Change in Unrecognized Tax Benefits by Item [Axis] Reasonably Possible Significant Change in Unrecognized Tax Benefits by Item [Axis] Significant Change in Unrecognized Tax Benefits is Reasonably Possible, Nature of Uncertainty [Domain] Significant Change in Unrecognized Tax Benefits is Reasonably Possible, Nature of Uncertainty [Domain] Significant Change in Unrecognized Tax Benefits is Reasonably Possible [Line Items] Significant Change in Unrecognized Tax Benefits is Reasonably Possible [Line Items] Summary of Unrecognized Tax Benefits [Table Text Block] Summary of Unrecognized Tax Benefits [Table Text Block] Summary of Unrecognized Tax Benefits [Table Text Block] Fair Value Measurements - (Details) [Abstract] -- None. No documentation exists for this element. -- Fair Value, Assets Measured on Recurring Basis [Table] Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Table] Fair Value, Assets Measured on Recurring Basis, Disclosure Items [Axis] Fair Value, Hierarchy [Axis] Fair Value, Assets Measured on Recurring Basis, Disclosure Items [Domain] Fair Value, Measurements, Fair Value Hierarchy [Domain] 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] Fair Value, Assets Measured on Recurring Basis, Financial Statement Captions [Line Items] Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] Illiquid forward price low range (per mmbtu) Illiquid forward price low range Illiquid forward price per mmbtu - low range Illiquid forward price high range (per mmbtu) Illiquid forward price high range Illiquid forward price per mmbtu - high range Assets Assets [Abstract] 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 Fair Value Assets Measured On Recurring Basis Assets Total This element represents a certain statement of financial position asset caption which represents all assets, measured at fair value on a recurring basis. Liabilities Liabilities [Abstract] Natural gas derivatives, liabilities Derivative Financial Instruments, Liabilities, Fair Value Disclosure Total liabilities Fair Value Liabilities Measured On Recurring Basis Liabilities Total This element represents a certain statement of financial position liability caption which represents all liabilities, measured at fair value on a recurring basis. 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 Long-term Debt Long-term Debt, Fair Value Fair value measurement using significant unobservable input (level 3) reconciliation [Roll Forward] Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation Calculation Roll Forward A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period. 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 unrealized 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, Issuances, 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 the period included in earnings Amount Of Total Gains 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). Derivative Instruments Derivative Instruments and Hedging Activities Disclosure [Text Block] Recorded Unconditional Purchase Obligation [Table] Recorded Unconditional Purchase Obligation [Table] 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. Magnolia Gathering System [Member] Magnolia Gathering System [Member] Information on the Magnolia Gathering System which is the result of an agreement between CenterPoint Energy Field Services, Inc., an indirect wholly-owned subsidiary of Encana Corporation, and a wholly-owned subsidiary of Royal Dutch Shell plc. The agreement is to provide gathering and treating services for natural gas production from certain Haynesville Shale and Bossier Shale formations in Louisiana. Olympia Gathering System [Member] Olympia Gathering System [Member] Additional long term agreement between CenterPoint Energy Field Services, Inc., a wholly-owned subsidiary of Encana Corporation, and an indirect wholly-owned subsidiary of Dutch Shell plc to provide gathering and treating services for their natural gas production from certain Haynesville and Bossier Shale formations in Texas and Louisiana. Long-Term Gas Gathering and Treating Agreements [Member] Long-Term Gas Gathering and Treating Agreements [Member] Long-Term Gas Gathering and Treating Agreements [Member] Recorded Unconditional Purchase Obligation by Category of Item Purchased [Axis] Recorded Unconditional Purchase Obligation by Category of Item Purchased [Axis] Unconditional Purchase Obligation, Category of Goods or Services Acquired [Domain] Unconditional Purchase Obligation, Category of Goods or Services Acquired [Domain] Natural Gas supply commitments [Member] Natural Gas supply commitments [Member] Details minimum payment obligations for natural gas supply commitments. Recorded Unconditional Purchase Obligation [Line Items] Recorded Unconditional Purchase Obligation [Line Items] Recorded Unconditional Purchase Obligation Recorded Unconditional Purchase Obligation [Abstract] -- None. No documentation exists for this element. -- 2012 Recorded Unconditional Purchase Obligation Due within One Year 2013 Recorded Unconditional Purchase Obligation Due in Second Year 2014 Recorded Unconditional Purchase Obligation Due in Third Year 2015 Recorded Unconditional Purchase Obligation Due in Fourth Year 2016 Recorded Unconditional Purchase Obligation Due in Fifth Year After 2016 Recorded Unconditional Purchase Obligation Due after Fifth Year Schedule of Capital Expansion Projects Schedule of Capital Expansion Projects [Abstract] -- None. No documentation exists for this element. -- Expanded natural gas capacity per day (in million cubic feet) Natural Gas Plant Capacity The total volume, in million cubic feet, of natural gas that can flow through a gathering and treating facility per day. Amount spent on original project scope for expansion Amount Spent On Original Project Scope For Gathering System Expansion Amount spent to date on original project scope for expansion, including the purchase of the original facilities. Number of years lapsed under volumne commitment Number of years lapsed under volumne commitment Number of years lapsed under volumne commitment Years of volume commitment (in number of years) Years of volume commitment (in number of years) Number of years under volume commitment, in order to permit the system to gather and treat natural gas, under existing long-term agreements as of balance sheet date. Additional natural gas capacity per day under the expansion election (in million cubic feet) Additional Natural Gas Plant Capacity Per Expansion Election The additional volume, in million cubic feet, of natural gas that can flow through a gathering and treating facility per day due to the expansion election. Total capacity per day of system after expansion (in million cubic feet) Total Capacity Of System After Expansion The total volume, in million cubic feet, of natural gas that can flow through a gathering facility and treating per day due to the expansion. Total costs of additional expansion Estimated Total Capital Expenditures For Expansion The estimated total capital expenditures for the expansion election. Potential additional natural gas capacity per day under potential additional expansion election (in million cubic feet) Potential Additional Natural Gas Plant Capacity Under Potential Additional Expansion Election Potential additional natural gas capacity per day under potential additional expansion election (in million cubic feet). Total capacity per day of system after potential additional expansion (in billion cubic feet) Total Capacity Of System After Potential Additional Expansion Total capacity per day of system after potential additional expansion (in billion cubic feet) Total estimatted costs of potential additional expansion Estimated Total Capital Expenditures For Potential Additonal Expansion Total costs of potential additional expansion Estimated remaining costs to complete expansion Estimated Remaining Amount To Complete Original Scope Of Gathering System Estimated remaining costs to complete expansion. Legal Environmental And Other Regulatory Matters Legal Matters Gas Market Manipulation Cases Abstract LegalEnvironmentalAndOtherRegulatoryMattersLegalMattersGasMarketManipulationCasesAbstract -- None. No documentation exists for this element. -- Recovery of compensatory damages sought by plaintiffs Loss Contingency, Damages Sought Approximate number of gas market manipulation lawsuits naming CenterPoint 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. Number of gas market mismeasurement lawsuits pending for CenterPoint and its affiliates (in number of lawsuits) Loss Contingency Pending Natural Gas Measurement Lawsuits Number The total number of pending lawsuits related to natural gas measurement. Approximate number of pipeline companies named in the mismeasurement lawsuits (in number of companies) Loss Contingency Kansas Gas Measurement Lawsuit Defendants The number of gas measurement lawsuit defendants named with the company in a pair of Kansas lawsuits. Number of gas measurement lawsuits seeking class certification and has four amendments (in number of cases) Loss Contingency Pending Measurement Lawsuit Number of gas measurement lawsuits requesting class certification and has been amended four times. Number of times gas measurement lawsuit was amended (in number of amendments) Loss Contingency Lawsuit Amendments The number of times a lawsuit has been amended. Number of years the plaintiffs claim the defendants have engaged in the systematic mismeasurement of natural gas (in years) Loss Contingency Term Of Allegations Number of years during which the defendant is alleged to have mismeasured natural gas. Number of CenterPoint subsidiaries dismissed from the claims of the plaintiff (in number of claims) Loss Contingency Defendants Dismissed Number of defendants dismissed from the claims of the plaintiffs. Number of sites where remediation is complete, other than ongoing operations (in number of sites) 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 the 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 (in number of 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 years of 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 Site Contingency Remediation Costs Included In Rates Annual amount received from customers used to fund normal on-going remediation costs. Amount collected from insurance companies to be used for future environmental remediation Recorded Third-Party Environmental Recoveries, Amount Approximate amount of undiscounted maximum potential demand charges under the transportation contracts Guarantee Obligations Demand Charges The value of demand charges included in transportation contracts. Approximate amount of collateral posted as security on transportation contracts Guarantee Obligations Collateral Posted Approximate amount of collateral posted as security on transportation contracts Effective tax rate (in hundredths) Effective Income Tax Rate, Continuing Operations Effective rate decrease (in hundredths) Effective rate decrease (in hundredths) Effective rate decrease for the period (in hundredths) Amount of non-cash recorded to income tax expense as result of change in tax law Amount of non-cash recorded to income tax expense as result of change in tax law The increase in total income tax expense for the period as result of change in tax law. Decrease in accrued interest for tax reserves related to potential normalization violation Decrease in accrued interest for tax reserves related to potential normalization violation Decrease in accrued interest for tax reserves related to potential normalization violation Amount of reduction to deferred tax assets due to actuarially determined net present value of lost future health care deductions Amount of reduction to deferred tax assets due to actuarially determined net present value of lost future health care deductions The tax effect as of the balance sheet date of the amount of the estimated future tax deductions arising from actuarially determined net present value of lost future health care deductions, which can only be deducted for tax purposes when actual costs are incurred, and which can only be realized if sufficient tax-basis income is generated in future periods to enable the deduction to be taken. Amount of adjustment to regulatory assets due to actuarially determined net present value of lost future health care deductions Deferred Tax Assets, Regulatory Assets and Liabilities Range of change possible in unrecognized tax benefits over the next 12 months, maximum Significant Change in Unrecognized Tax Benefits is Reasonably Possible, Estimated Range of Change, Maximum For a tax position taken for which it is reasonably possible that the total amount of unrecognized tax benefit will significantly increase or decrease within twelve months of the balance sheet date, provide an estimate of the range of the reasonably possible change. This is the maximum anticipated amount. Unrecognized tax benefits (expense) Unrecognized Tax Benefits Portion of unrecognized tax benefits that, if recognized, would reduce the effective income tax rate Unrecognized Tax Benefits that Would Impact Effective Tax Rate Interest accrued on unrecognized tax benefits Unrecognized Tax Benefits, Interest on Income Taxes Accrued Decrease in unrecognized tax benefits reltated to potential normalization violaton Decrease in unrecognized tax benefits reltated to potential normalization violaton Decrease in unrecognized tax benefits reltated to potential normalization violaton Reduction to liability for unrecognized tax benefits recorded Reduction to liability for unrecognized tax benefits recorded Reduction to liability for unrecognized tax benefits recorded Reduction in unrecognized tax benefits related to balance as of 12/31/2010 Reduction in unrecognized tax benefits related to balance as of 12/31/2010 Reduction in unrecognized tax benefits related to balance as of 12/31/2010 Reduction in unrecognized tax benefits related to balance as of 6/30/2011 Reduction in unrecognized tax benefits related to balance as of 6/30/2011 Reduction in unrecognized tax benefits related to balance as of 6/30/2011 Increase in deferred tax liability Increase in deferred tax liability Increase in deferred tax liability Decrease in income tax expense for the release of accrued interest expense Decrease in income tax expense for the release of accrued interest expense Decrease in income tax expense for the release of accrued interest expense Significant Change in Unrecognized Tax Benefits is Reasonably Possible, Estimated Range of Change, Lower Bound Significant Change in Unrecognized Tax Benefits is Reasonably Possible, Estimated Range of Change, Lower Bound Significant Change in Unrecognized Tax Benefits is Reasonably Possible, Estimated Range of Change, Upper Bound Significant Change in Unrecognized Tax Benefits is Reasonably Possible, Estimated Range of Change, Upper Bound 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) Reduction In Liability For Uncertain Tax Positions Reduction In Liability For Uncertain Tax Positions Represents the reduction in the liability for uncertain tax positions. Schedule of Goodwill [Table] Schedule of Goodwill [Table] Goodwill [Line Items] Goodwill [Line Items] Schedule of Goodwill [Table Text Block] Schedule of Goodwill [Table Text Block] Capital Stock (Details) [Abstract] -- None. No documentation exists for this element. -- Capital stock shares authorized (in shares) Capital Stock Shares Authorized The maximum number of capital shares permitted to be issued by an entity's charter and bylaws. Common stock shares authorized (in shares) Common Stock, Shares Authorized Common stock shares par value (in dollars per share) Common Stock, Par or Stated Value Per Share Cumulative preferred stock shares authorized (in shares) Preferred Stock, Shares Authorized Cumulative preferred stock par value (in dollars per share) Preferred Stock, Par or Stated Value Per Share Total common stock issued (in shares) Common Stock, Shares, Issued Total common stock outstanding (in shares) Treasury stock (in shares) Treasury Stock, Shares Schedule of Segment Reporting Information, by Segment [Table] Schedule of Segment Reporting Information, by Segment [Table] Segment Reporting Information [Line Items] Segment Reporting Information [Line Items] Financial data for business segments Schedule of Segment Reporting Information, by Segment [Table Text Block] Earnings Per Share Earnings Per Share [Text Block] Schedule of Long-term Debt Instruments [Table] Schedule of Long-term Debt Instruments [Table] CERC Corp. receivables facility [Member] CERC Corp. receivables facility [Member] An arrangement that in form is a sale with full right of return but in substance is a financing in that the financier is not the end customer, is not at risk other than credit risk similar to any other form of lending arrangement, and typically is repaid from collections of sales made to actual customers including an amount that constitutes interest. Product Financing Arrangement [Member] Product Financing Arrangement [Member] Senior notes issued, due 2021 (CERC Corp. senior notes) [Member] Senior notes issued, due 2021 (CERC Corp. senior notes) [Member] Senior notes, due 2021, issued for extinguishment of another existing senior notes. Senior notes are notes with the highest claim on the assets of the issuer in case of bankruptcy or liquidation (with maturities initially due after one year or beyond the operating cycle if longer), excluding current portion. Senior note holders are paid off in full before any payments are made to junior note holders. Senior notes issued, due 2011 (CERC Corp. senior notes) [Member] Senior notes issued, due 2011 (CERC Corp. senior notes) [Member] Senior notes, due 2011. Senior notes are notes with the highest claim on the assets of the issuer in case of bankruptcy or liquidation (with maturities initially due after one year or beyond the operating cycle if longer), excluding current portion. Senior note holders are paid off in full before any payments are made to junior note holders. Senior notes issued, due 2041 (CERC Corp. senior notes) [Member] Senior notes issued, due 2041 (CERC Corp. senior notes) [Member] Senior notes, due 2041, issued for extinguishment of another existing senior notes. Senior notes are notes with the highest claim on the assets of the issuer in case of bankruptcy or liquidation (with maturities initially due after one year or beyond the operating cycle if longer), excluding current portion. Senior note holders are paid off in full before any payments are made to junior note holders. Senior notes issued, due 2021 (CERC exchange offer) [Member] Senior notes issued, due 2021 (CERC exchange offer) [Member] Senior notes, due 2021, issued to replace another existing senior notes. Senior notes are notes with the highest claim on the assets of the issuer in case of bankruptcy or liquidation (with maturities initially due after one year or beyond the operating cycle if longer), excluding current portion. Senior note holders are paid off in full before any payments are made to junior note holders. Senior notes 2013 to 2037 [Member] Notes with the highest claim on the assets of the issuer in case of bankruptcy or liquidation (with maturities initially due after one year or beyond the operating cycle if longer), excluding current portion. Senior note holders are paid off in full before any payments are made to junior note holders. Long-term Debt, Type [Axis] Long-term Debt, Type [Axis] Long-term Debt, Type [Domain] Long-term Debt, Type [Domain] Commercial Paper [Member] Commercial Paper [Member] Bank loans due 2016 [Member] Line of Credit [Member] Senior notes 2013 to 2037 [Member] 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. 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. Debt Instrument [Line Items] Debt Instrument [Line Items] Length of revolving credit facility (in years) Length of revolving credit facility (in years) Length of revolving credit facility (in years) Receivables facility range, minimum Receivables facility range, minimum Reflects the minimum availability under the receivables facility Receivables facility range, maximum Receivables facility range, maximum Reflects the maximum availability under the receivables facility Receivable facility maximum advance capacity Receivables Facility Advance Capacity Reflects the available capacity under the receivables facility at the balance sheet date. Total short term borrowings Long-term Debt [Abstract] Long-term Debt, by Current and Noncurrent [Abstract] Total credit facility amount Line of Credit Facility, Maximum Borrowing Capacity Loans Outstanding Line of Credit Facility, Amount Outstanding Letters of Credit outstanding Letters Of Credit Outstanding Amount of letters of credit outstanding Commercial Paper Outstanding Long-term Commercial Paper Long term debt Long term debt, Current Portion Long-term Commercial Paper, Current Expiration date of the revolving credit facilities Line of Credit Facility, Expiration Date Revolving credit facility borrowing rate Line of Credit Facility, Interest Rate Description Debt to EBITDA covenant ratio, before amendment Debt Covenant Debt To Ebitda Total debt to earnings before interest, taxes, depreciation and amortization permitted ratio under covenant. Debt to EBITDA covenant ratio, amendment Debt Covenant Debt To Ebitda Amended Total debt to earnings before interest, taxes, depreciation and amortization temporary permitted ratio under covenant. System restoration costs threshold for increase in permitted debt to EBITDA covenant ratio Restoration Cost Expected Cost The minimum amount of estimated restoration cost in a calendar year in order for a temporary increase in debt to EBITDA covenant Consecutive Period for System Restoration Costs to Exceed $100 million (in months) Consecutive Period for System Restoration Costs to Exceed $100 million (in months) Consecutive Period for System Restoration Costs to Exceed $100 million (in months) 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, principal amount Extinguishment of Debt, Amount Utilization fee on borrowings exceeding fifty percent of total credit facility (in hundredths) Line of Credit Facility Utilization Fee Reflects the fee charge for borrowings exceeding 50% of credit facility at anytime. Percentage of utilization of credit facility (in hundredths) Percentage of Utilization of Credit facility Percentage of utilization of credit facility before an additional utilization fee will be applied to borrowings. Amount of senior notes issued (CERC Corp. senior notes) Debt Instrument, Interest Rate, Stated Percentage (in hundredths) Amount of cash consideration provided related to CERC exchange offer Repayments of Senior Debt Unamortized debt issuance cost Unamortized Debt Issuance Expense Amount Of Transition Bonds Issued To Recover Additional True Up Costs Amount Of Transition Bonds Issued To Recover Additional True Up Costs Amount of transition bonds issued to recover additional true-up costs as allowed by the Texas electric restructuring law Number of tranches of transition bonds Number of tranches of transition bonds Number of tranches of transition bonds Minimum Interest Rate On Transition Bonds Minimum Interest Rate On Transition Bonds Minimum interest rate on transition bonds issued. Maximum Interest Rate On Transition Bonds Maximum Interest Rate On Transition Bonds Maximum interest rate on transition bonds issued. Repayments of Long-term Debt Repayments of Long-term Debt 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 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 Condensed Statements of Cash Flows (Unaudited) [Abstract] -- None. No documentation exists for this element. -- Cash Flows from Operating Activities: Net Cash Provided by (Used in) Operating Activities [Abstract] Net income Adjustments to reconcile net income to net cash provided by operating activities: Adjustments to Reconcile Net Income (Loss) to Cash Provided by (Used in) Operating Activities [Abstract] Amortization of deferred financing costs Amortization of Financing Costs Deferred income taxes Deferred Income Tax Expense (Benefit) Extraordinary Item, net of tax Return on true-up balance Unrealized gain on marketable securities Marketable Securities, Unrealized Gain (Loss) Unrealized loss on indexed debt securities Unrealized Loss Gain on Indexed Debt Securities Unrealized Loss Gain on Indexed Debt Securities. 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 Pension contributions Changes in other assets and liabilities: Increase (Decrease) in Operating Capital [Abstract] Accounts receivable and unbilled revenues, net Accounts receivable and unbilled revenues, net Accounts receivable and unbilled revenues, net. 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 Non-trading derivatives, net Increase (Decrease) in Commodity Contract Assets and Liabilities Margin deposits, net Margin deposits, net Margin deposits, net. Interest and taxes accrued Interest and taxes accrued Interest and taxes accrued. Net regulatory assets and liabilities Increase (Decrease) in Regulatory Assets and Liabilities 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 Acquisitions Payments to Acquire Assets, Investing Activities Increase in restricted cash of transition and system restoration bonds companies Increase (Decrease) in Restricted Cash Investment in unconsolidated affiliates Payments to Acquire Interest in Joint Venture Cash received from U.S Department of Energy grant Cash received from DOE grant Cash received from DOE grant. 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 Increase Decrease in Short Term Borrowings Net Increase (decrease) in Short Term Borrowings Net. Payments of commercial paper, net Proceeds from Issuance of Commercial Paper Proceeds from long-term debt Proceeds from Issuance of Long-term Debt Payments of long-term debt Cash paid for debt exchange Cash paid for debt exchange The cash outflow for exchanged debt. Debt issuance costs Payments of Debt Issuance Costs Payment of common stock dividends Payments of Dividends, Common Stock Proceeds from issuance of common stock, net Proceeds from Issuance of Common Stock Other, net Proceeds from (Payments for) Other Financing Activities Net cash provided by (used in) financing activities Net Cash Provided by (Used in) Financing Activities Net Increase (Decrease) 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 (refunds), net Income Taxes Paid, Net Non-cash transactions: Non Cash Transactions [Abstract] -- None. No documentation exists for this element. -- Accounts payable related to capital expenditures Capital Expenditures Incurred but Not yet Paid Comprehensive Income [Abstract] -- None. No documentation exists for this element. -- Other comprehensive income: Comprehensive Income (Loss), Net of Tax, Attributable to Parent [Abstract] Adjustment related to pension and other postretirement plans (net of tax of $1, $2, $3 and $4) Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Adjustment, Net of Tax Total Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent Comprehensive income Comprehensive Income (Loss), Net of Tax, Attributable to Parent Basic earnings per share calculation: [Abstract] Basic earnings per share calculation: [Abstract] Basic earnings per share calculation: [Abstract] Income (Loss) from Operations before Extraordinary Items Weighted average shares outstanding Net Income Diluted earnings per share calculation: [Abstract] diluted earnings per share calculation: [Abstract] diluted earnings per share calculation: [Abstract] Plus: Incremental shares from assumed conversions: Weighted Average Number Diluted Shares Outstanding Adjustment [Abstract] Stock Options Incremental Common Shares Attributable to Share-based Payment Arrangements Restricted stock Incremental Common Shares Attributable To Restricted Stock Restricted shares whose issuance is contingent upon certain conditions and shall be considered outstanding and included in the computation of diluted Earnings Per Share. Weighted average shares assuming dilution Net Income Outstanding shares with the options to purchase not included in the computation of diluted earnings per share (in shares) Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount Reportable Business Segments - (Details) [Abstract] -- None. No documentation exists for this element. -- Segment Reporting Information, by Segment [Axis] Reporting Segment [Domain] Electric Transmission and Distribution [Member] Electric Transmission and Distribution [Member] Reconciling Eliminations [Member] Reconciling Eliminations [Member] Eliminating entries used in business segment consolidation. Revenues from External Customers Intersegment Revenues Segment Reporting Information, Intersegment Revenue Operating Income Total Assets Sales to subsidiaries of NRG Energy, Inc. Sales to subsidiaries of Customer 1 Sales to subsidiaries of NRG Energy, Inc. Sales to subsidiaries of Energy Future Holdings Corp. Sales to subsidiaries of Customer 2 Sales to subsidiaries of Energy Future Holdings Corp. Pension and other postemployment related regulatory assets included in total assets of Other Operations Segment Reporting Pension Plan Assets This represents the assets recognized in the Other Operations segment that are associated with the defined benefit plans.