Summary of Significant Accounting Policies (Policies)	12 Months Ended
Dec. 31, 2012
Accounting Policies [Abstract]
Use of Estimates	Use of Estimates The preparation of financial statements in conformity with generally accepted accounting principles requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, disclosure of contingent assets and liabilities at the date of the financial statements, and the reported amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates.
Principles of Consolidation	Principles of Consolidation The accounts of CenterPoint Houston and its wholly owned subsidiaries are included in CenterPoint Houston’s consolidated financial statements. All intercompany transactions and balances are eliminated in consolidation. As of December 31, 2012, CenterPoint Houston had five variable interest entities (VIEs) consisting of transition and system restoration bond companies, which it consolidates. The consolidated VIEs are wholly owned bankruptcy remote special purpose entities that were formed specifically for the purpose of securitizing transition and system restoration related property. Creditors of CenterPoint Houston have no recourse to any assets or revenues of the transition and system restoration bond companies. The bonds issued by these VIEs are payable only from and secured by transition and system restoration property and the bondholders have no recourse to the general credit of CenterPoint Houston.
Revenues	Revenues CenterPoint Houston records revenue for electricity delivery under the accrual method and these revenues are recognized upon delivery to customers. Electricity deliveries not billed by month-end are accrued based on daily supply volumes, applicable rates and analyses reflecting significant historical trends and experience.
Long-Lived Assets and Intangibles	Long-Lived Assets and Intangibles CenterPoint Houston records property, plant and equipment at historical cost. CenterPoint Houston expenses repair and maintenance costs as incurred. CenterPoint Houston periodically evaluates long-lived assets, including property, plant and equipment, and specifically identifiable intangibles, when events or changes in circumstances indicate that the carrying value of these assets may not be recoverable. The determination of whether an impairment has occurred is based on an estimate of undiscounted cash flows attributable to the assets, as compared to the carrying value of the assets.
Regulatory Assets and Liabilities	Regulatory Assets and Liabilities CenterPoint Houston applies the guidance for accounting for regulated operations. CenterPoint Houston recognizes removal costs as a component of depreciation expense in accordance with regulatory treatment. As of December 31, 2011 and 2012, these removal costs of $339 million and $346 million, respectively, are classified as regulatory liabilities in CenterPoint Houston’s Consolidated Balance Sheets. A portion of the amount of removal costs that related to asset retirement obligations has been reclassified from a regulatory liability to an asset retirement liability in accordance with accounting guidance for conditional asset retirement obligations.
Depreciation and Amortization Expense	Depreciation and Amortization Expense Depreciation is computed using the straight-line method based on economic lives or a regulatory-mandated recovery period. Transition and system restoration property is being amortized over the expected life of the transition and system restoration bonds (12 to 14 years), based on estimated revenue from transition or system restoration charges, interest accruals and other expenses. Other amortization expense includes amortization of regulatory assets and other intangibles.
Allowance for Funds Used During Construction	Allowance for Funds Used During Construction Allowance for funds used during construction (AFUDC) is capitalized as a component of projects under construction and is amortized over the assets’ estimated useful lives once the assets are placed in service. AFUDC represents the composite interest cost of borrowed funds and a reasonable return on the equity funds used for construction. Although AFUDC increases both utility plant and earnings, it is realized in cash when the assets are included in rates. During 2010, 2011 and 2012, CenterPoint Houston capitalized AFUDC of $3 million, $4 million and $6 million, respectively.
Income Taxes	Income Taxes CenterPoint Houston is included in the consolidated income tax returns of CenterPoint Energy. CenterPoint Houston calculates its income tax provision on a separate return basis under a tax sharing agreement with CenterPoint Energy. CenterPoint Houston uses the asset and liability method of accounting for deferred income taxes. Deferred income tax assets and liabilities are recognized for the future tax consequences attributable to differences between the financial statement carrying amounts of existing assets and liabilities and their respective tax bases. Investment tax credits that were deferred are being amortized over the estimated lives of the related property. A valuation allowance is established against deferred tax assets for which management believes realization is not considered more likely than not. CenterPoint Houston recognizes interest and penalties as a component of income tax expense. Current federal and certain state income taxes are payable to or receivable from CenterPoint Energy.
Accounts Receivable and Allowance for Doubtful Accounts	Accounts Receivable and Allowance for Doubtful Accounts Accounts receivable are recorded at the invoiced amount and do not bear interest. It is the policy of management to review the outstanding accounts receivable monthly, as well as the bad debt write-offs experienced in the past, and establish an allowance for doubtful accounts. Account balances are charged off against the allowance when management determines it is probable the receivable will not be recovered. Accounts and notes receivable are net of an allowance for doubtful accounts of $1 million and $2 million at December 31, 2011 and 2012, respectively. The provision for doubtful accounts in CenterPoint Houston’s Statements of Consolidated Income for 2010, 2011 and 2012 was less than $1 million, $2 million and $2 million, respectively.
Inventory	Inventory Inventory consists principally of materials and supplies and is valued at the lower of average cost or market. Materials and supplies are recorded to inventory when purchased and subsequently charged to expense or capitalized to plant when installed.
Statements of Consolidated Cash Flows	Statements of Consolidated Cash Flows For purposes of reporting cash flows, CenterPoint Houston considers cash equivalents to be short-term, highly-liquid investments with maturities of three months or less from the date of purchase. In connection with the issuance of transition bonds and system restoration bonds, CenterPoint Houston was required to establish restricted cash accounts to collateralize the bonds that were issued in these financing transactions. These restricted cash accounts are not available for withdrawal until the maturity of the bonds and are not included in cash and cash equivalents. These restricted cash accounts of $42 million and $54 million at December 31, 2011 and 2012, respectively, are included in other current assets in CenterPoint Houston's Consolidated Balance Sheets. For additional information regarding transition and system restoration bonds, see Notes 4(b) and 8. Cash and cash equivalents includes $220 million and $266 million at December 31, 2011 and 2012, respectively, that is held by CenterPoint Houston’s transition and system restoration bond subsidiaries solely to support servicing the transition and system restoration bonds.
New Accounting Pronouncements, Policy [Policy Text Block]	New Accounting Pronouncements Management believes the impact of recently issued standards, which are not yet effective, will not have a material impact on CenterPoint Houston’s consolidated financial position, results of operations or cash flows upon adoption.
Other Current Liabilities [Policy Text Block]	Other Current Liabilities Included in other current liabilities in the Consolidated Balance Sheets at December 31, 2011 and 2012 was $23 million and $27 million, respectively, of customer deposits.

Summary of Significant Accounting Policies (Policies)

12 Months Ended

Dec. 31, 2012

The preparation of financial statements in conformity with generally accepted accounting principles requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, disclosure of contingent assets and liabilities at the date of the financial statements, and the reported amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates.

Principles of Consolidation

The accounts of CenterPoint Houston and its wholly owned subsidiaries are included in CenterPoint Houston’s consolidated financial statements. All intercompany transactions and balances are eliminated in consolidation. As of December 31, 2012, CenterPoint Houston had five variable interest entities (VIEs) consisting of transition and system restoration bond companies, which it consolidates. The consolidated VIEs are wholly owned bankruptcy remote special purpose entities that were formed specifically for the purpose of securitizing transition and system restoration related property. Creditors of CenterPoint Houston have no recourse to any assets or revenues of the transition and system restoration bond companies. The bonds issued by these VIEs are payable only from and secured by transition and system restoration property and the bondholders have no recourse to the general credit of CenterPoint Houston.

Revenues

CenterPoint Houston records revenue for electricity delivery under the accrual method and these revenues are recognized upon delivery to customers. Electricity deliveries not billed by month-end are accrued based on daily supply volumes, applicable rates and analyses reflecting significant historical trends and experience.

Long-Lived Assets and Intangibles

CenterPoint Houston records property, plant and equipment at historical cost. CenterPoint Houston expenses repair and maintenance costs as incurred. CenterPoint Houston periodically evaluates long-lived assets, including property, plant and equipment, and specifically identifiable intangibles, when events or changes in circumstances indicate that the carrying value of these assets may not be recoverable. The determination of whether an impairment has occurred is based on an estimate of undiscounted cash flows attributable to the assets, as compared to the carrying value of the assets.

Regulatory Assets and Liabilities

CenterPoint Houston applies the guidance for accounting for regulated operations. CenterPoint Houston recognizes removal costs as a component of depreciation expense in accordance with regulatory treatment. As of December 31, 2011 and 2012, these removal costs of $339 million and $346 million, respectively, are classified as regulatory liabilities in CenterPoint Houston’s Consolidated Balance Sheets. A portion of the amount of removal costs that related to asset retirement obligations has been reclassified from a regulatory liability to an asset retirement liability in accordance with accounting guidance for conditional asset retirement obligations.

Depreciation and Amortization Expense

Depreciation is computed using the straight-line method based on economic lives or a regulatory-mandated recovery period. Transition and system restoration property is being amortized over the expected life of the transition and system restoration bonds (12 to 14 years), based on estimated revenue from transition or system restoration charges, interest accruals and other expenses. Other amortization expense includes amortization of regulatory assets and other intangibles.

Allowance for Funds Used During Construction

Allowance for funds used during construction (AFUDC) is capitalized as a component of projects under construction and is amortized over the assets’ estimated useful lives once the assets are placed in service. AFUDC represents the composite interest cost of borrowed funds and a reasonable return on the equity funds used for construction. Although AFUDC increases both utility plant and earnings, it is realized in cash when the assets are included in rates. During 2010, 2011 and 2012, CenterPoint Houston capitalized AFUDC of $3 million, $4 million and $6 million, respectively.

Income Taxes

CenterPoint Houston is included in the consolidated income tax returns of CenterPoint Energy. CenterPoint Houston calculates its income tax provision on a separate return basis under a tax sharing agreement with CenterPoint Energy. CenterPoint Houston uses the asset and liability method of accounting for deferred income taxes. Deferred income tax assets and liabilities are recognized for the future tax consequences attributable to differences between the financial statement carrying amounts of existing assets and liabilities and their respective tax bases. Investment tax credits that were deferred are being amortized over the estimated lives of the related property. A valuation allowance is established against deferred tax assets for which management believes realization is not considered more likely than not. CenterPoint Houston recognizes interest and penalties as a component of income tax expense. Current federal and certain state income taxes are payable to or receivable from CenterPoint Energy.

Accounts Receivable and Allowance for Doubtful Accounts

Accounts receivable are recorded at the invoiced amount and do not bear interest. It is the policy of management to review the outstanding accounts receivable monthly, as well as the bad debt write-offs experienced in the past, and establish an allowance for doubtful accounts. Account balances are charged off against the allowance when management determines it is probable the receivable will not be recovered. Accounts and notes receivable are net of an allowance for doubtful accounts of $1 million and $2 million at December 31, 2011 and 2012, respectively. The provision for doubtful accounts in CenterPoint Houston’s Statements of Consolidated Income for 2010, 2011 and 2012 was less than $1 million, $2 million and $2 million, respectively.

Inventory

Inventory consists principally of materials and supplies and is valued at the lower of average cost or market. Materials and supplies are recorded to inventory when purchased and subsequently charged to expense or capitalized to plant when installed.

Statements of Consolidated Cash Flows

For purposes of reporting cash flows, CenterPoint Houston considers cash equivalents to be short-term, highly-liquid investments with maturities of three months or less from the date of purchase. In connection with the issuance of transition bonds and system restoration bonds, CenterPoint Houston was required to establish restricted cash accounts to collateralize the bonds that were issued in these financing transactions. These restricted cash accounts are not available for withdrawal until the maturity of the bonds and are not included in cash and cash equivalents. These restricted cash accounts of $42 million and $54 million at December 31, 2011 and 2012, respectively, are included in other current assets in CenterPoint Houston's Consolidated Balance Sheets. For additional information regarding transition and system restoration bonds, see Notes 4(b) and 8. Cash and cash equivalents includes $220 million and $266 million at December 31, 2011 and 2012, respectively, that is held by CenterPoint Houston’s transition and system restoration bond subsidiaries solely to support servicing the transition and system restoration bonds.

New Accounting Pronouncements, Policy [Policy Text Block]

New Accounting Pronouncements

Management believes the impact of recently issued standards, which are not yet effective, will not have a material impact on CenterPoint Houston’s consolidated financial position, results of operations or cash flows upon adoption.

Other Current Liabilities [Policy Text Block]

Other Current Liabilities

Included in other current liabilities in the Consolidated Balance Sheets at December 31, 2011 and 2012 was $23 million and $27 million, respectively, of customer deposits.