Summary of Significant Accounting Policies	12 Months Ended
Dec. 31, 2015
Accounting Policies [Abstract]
Significant Accounting Policies [Text Block]	Summary of Significant Accounting Policies (a) 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. (b) 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, 2015, CenterPoint Houston had 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. (c) 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 actual advanced metering system data, daily supply volumes and applicable rates. (d) 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 compared to the carrying value of the assets. (e) Regulatory Assets and Liabilities CenterPoint Houston applies the guidance for accounting for regulated operations. CenterPoint Houston’s rate-regulated subsidiaries may collect revenues subject to refund pending final determination in rate proceedings. In connection with such revenues, estimated rate refund liabilities are recorded which reflect management’s current judgment of the ultimate outcomes of the proceedings. CenterPoint Houston recognizes removal costs as a component of depreciation expense in accordance with regulatory treatment. As of December 31, 2015 and 2014, these removal costs of $350 million and $353 million, respectively, are classified as regulatory liabilities in CenterPoint Houston’s Consolidated Balance Sheets. In addition, a portion of the amount of removal costs that relate to asset retirement obligations has been reclassified from a regulatory liability to an asset retirement liability in accordance with accounting guidance for asset retirement obligations. (f) 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. (g) 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 2015, 2014 and 2013, CenterPoint Houston capitalized AFUDC interest of $8 million, $10 million and $10 million, respectively. During 2015, 2014 and 2013, CenterPoint Energy recorded AFUDC equity of $12 million, $14 million and $8 million, respectively, which is included in Other Income in its Statements of Consolidated Income. (h) 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. A valuation allowance is established against deferred tax assets for which management believes realization is not considered to be 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. (i) 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. The provision for doubtful accounts in CenterPoint Houston’s Statements of Consolidated Income for 2015, 2014 and 2013 was less than $1 million, $3 million and $2 million, respectively. (j) 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. (k) 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 $35 million and $47 million as of December 31, 2015 and 2014, respectively, are included in other current assets in CenterPoint Houston’s Consolidated Balance Sheets. For additional information regarding transition and system restoration bonds, see Note 8. Cash and cash equivalents included $264 million and $290 million as of December 31, 2015 and 2014, respectively, that was held by CenterPoint Houston’s transition and system restoration bond subsidiaries solely to support servicing the transition and system restoration bonds. (l) New Accounting Pronouncements In February 2015, the Financial Accounting Standards Board (FASB) issued Accounting Standards Update No. 2015-02, Consolidation (Topic 810): Amendments to the Consolidation Analysis (ASU 2015-02). ASU 2015-02 changes the analysis that reporting organizations must perform to evaluate whether they should consolidate certain legal entities, such as limited partnerships. The changes include, among others, modification of the evaluation of whether limited partnerships and similar legal entities are variable interest entities (VIEs) or voting interest entities and elimination of the presumption that a general partner should consolidate a limited partnership. ASU 2015-02 does not amend the related party guidance for situations in which power is shared between two or more entities that hold interests in a VIE. ASU 2015-02 is effective for fiscal years, and interim periods within those years, beginning after December 15, 2015. CenterPoint Houston does not believe that ASU 2015-02 will have a material impact on its financial position, results of operations, cash flows and disclosures. In April 2015, the FASB issued Accounting Standards Update No. 2015-03, Interest-Imputation of Interest (Subtopic 835-30): Simplifying the Presentation of Debt Issuance Cost (ASU 2015-03). ASU 2015-03 requires that debt issuance costs related to a recognized debt liability be presented in the balance sheet as a direct deduction from the carrying amount of that debt liability, consistent with debt discounts. The recognition and measurement guidance for debt issuance costs are not affected by ASU 2015-03. CenterPoint Houston will adopt ASU 2015-03 retrospectively on January 1, 2016, which will result in a reduction of both other long-term assets and long-term debt on its Consolidated Balance Sheets. CenterPoint Houston had debt issuance costs of $22 million and $26 million included in other long-term assets on its Consolidated Balance Sheets as of December 31, 2015 and 2014, respectively. In April 2015, the FASB issued Accounting Standards Update No. 2015-05, Intangibles-Goodwill and Other-Internal-Use Software (Subtopic 350-40) (ASU 2015-05). ASU 2015-05 provides guidance to customers about whether a cloud computing arrangement includes a software license. If a cloud computing arrangement includes a software license, the customer should account for the software license element of the arrangement consistent with the acquisition of other software licenses. If a cloud computing arrangement does not include a software license, the customer should account for the arrangement as a service contract. The guidance will not change a customer’s accounting for service contracts. ASU 2015-05 is effective for fiscal years, and interim periods within the fiscal years, beginning after December 15, 2015 and may be adopted either prospectively or retrospectively. CenterPoint Houston will adopt ASU 2015-05 prospectively on January 1, 2016. CenterPoint Houston does not believe that ASU 2015-05 will have a material impact on its financial position, results of operations, cash flows and disclosures. In May 2014, the FASB issued Accounting Standards Update No. 2014-09, Revenue from Contracts with Customers (Topic 606) (ASU 2014-09), which supersedes most current revenue recognition guidance. ASU 2014-09 provides a comprehensive new revenue recognition model that requires revenue to be recognized in a manner that depicts the transfer of goods or services to a customer at an amount that reflects the consideration expected to be received in exchange for those goods or services. ASU 2014-09 was initially effective for fiscal years, and interim periods within those years, beginning after December 15, 2016. Early adoption is not permitted, and entities have the option of using either a full retrospective or a modified retrospective adoption approach. In August 2015, the FASB issued Accounting Standard Update No. 2015-14, Revenue from Contracts with Customers (Topic 606): Deferral of the Effective Date, which delays the effective date of ASU 2014-09 by one year. CenterPoint Houston is currently evaluating the impact that ASU 2014-09 will have on its financial position, results of operations, cash flows and disclosures, and will adopt ASU 2014-09 on January 1, 2018 as permitted by the new guidance. In July 2015, the FASB issued Accounting Standards Update No. 2015-11, Inventory (Topic 330) Simplifying the Measurement of Inventory (ASU 2015-11). ASU 2015-11 changes the subsequent measurement guidance for inventory accounted for using methods other than the last in, first out (LIFO) and Retail Inventory methods. Companies will subsequently measure inventory at the lower of cost and net realizable value. Net realizable value is the estimated selling price in the ordinary course of business, less reasonably predictable costs of completion, disposal, and transportation. Subsequent measurement is unchanged for inventory measured using LIFO or the retail inventory method. ASU 2015-11 is effective for fiscal years, and interim periods within those years, beginning after December 15, 2016, with early adoption permitted. CenterPoint Houston does not believe that ASU 2015-11 will have a material impact on its financial position, results of operations, cash flows and disclosures. In November 2015, the FASB issued Accounting Standards Update No. 2015-17, Income Taxes (Topic 740): Balance Sheet Classification of Deferred Taxes (ASU 2015-17). ASU 2015-17 requires deferred tax liabilities and assets be classified as noncurrent in a classified statement of financial position. CenterPoint Houston adopted ASU 2015-17 retrospectively starting with fiscal year 2015. As such, certain prior period amounts have been reclassified to conform to the current presentation. In the Consolidated Balance Sheet as of December 31, 2014, CenterPoint Houston reclassified $2 million from current deferred tax assets to reduce deferred income taxes within non-current liabilities. See Note 9 for additional information. Management believes that other recently issued standards, which are not yet effective, will not have a material impact on CenterPoint Energy’s consolidated financial position, results of operations or cash flows upon adoption. (m) Other Current Liabilities Included in other current liabilities in the Consolidated Balance Sheets as of December 31, 2015 and 2014 was $12 million and $24 million, respectively, of customer deposits primarily held by the transition and system restoration bond companies. (n) Environmental Costs CenterPoint Houston expenses or capitalizes environmental expenditures, as appropriate, depending on their future economic benefit. CenterPoint Houston expenses amounts that relate to an existing condition caused by past operations that do not have future economic benefit. CenterPoint Houston records undiscounted liabilities related to these future costs when environmental assessments and/or remediation activities are probable and the costs can be reasonably estimated.

Summary of Significant Accounting Policies

(a) 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.

(b) 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, 2015, CenterPoint Houston had 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.

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 actual advanced metering system data, daily supply volumes and applicable rates.

(d) 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 compared to the carrying value of the assets.

(e) Regulatory Assets and Liabilities

CenterPoint Houston applies the guidance for accounting for regulated operations. CenterPoint Houston’s rate-regulated subsidiaries may collect revenues subject to refund pending final determination in rate proceedings. In connection with such revenues, estimated rate refund liabilities are recorded which reflect management’s current judgment of the ultimate outcomes of the proceedings.

CenterPoint Houston recognizes removal costs as a component of depreciation expense in accordance with regulatory treatment. As of December 31, 2015 and 2014, these removal costs of $350 million and $353 million, respectively, are classified as regulatory liabilities in CenterPoint Houston’s Consolidated Balance Sheets. In addition, a portion of the amount of removal costs that relate to asset retirement obligations has been reclassified from a regulatory liability to an asset retirement liability in accordance with accounting guidance for asset retirement obligations.

(f) 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.

(g) 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 2015, 2014 and 2013, CenterPoint Houston capitalized AFUDC interest of $8 million, $10 million and $10 million, respectively. During 2015, 2014 and 2013, CenterPoint Energy recorded AFUDC equity of $12 million, $14 million and $8 million, respectively, which is included in Other Income in its Statements of Consolidated Income.

(h) 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. A valuation allowance is established against deferred tax assets for which management believes realization is not considered to be 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.

(i) 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. The provision for doubtful accounts in CenterPoint Houston’s Statements of Consolidated Income for 2015, 2014 and 2013 was less than $1 million, $3 million and $2 million, respectively.

(j) 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.

(k) 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 $35 million and $47 million as of December 31, 2015 and 2014, respectively, are included in other current assets in CenterPoint Houston’s Consolidated Balance Sheets. For additional information regarding transition and system restoration bonds, see Note 8. Cash and cash equivalents included $264 million and $290 million as of December 31, 2015 and 2014, respectively, that was held by CenterPoint Houston’s transition and system restoration bond subsidiaries solely to support servicing the transition and system restoration bonds.

(l) New Accounting Pronouncements

In February 2015, the Financial Accounting Standards Board (FASB) issued Accounting Standards Update No. 2015-02, Consolidation (Topic 810): Amendments to the Consolidation Analysis (ASU 2015-02). ASU 2015-02 changes the analysis that reporting organizations must perform to evaluate whether they should consolidate certain legal entities, such as limited partnerships. The changes include, among others, modification of the evaluation of whether limited partnerships and similar legal entities are variable interest entities (VIEs) or voting interest entities and elimination of the presumption that a general partner should consolidate a limited partnership. ASU 2015-02 does not amend the related party guidance for situations in which power is shared between two or more entities that hold interests in a VIE. ASU 2015-02 is effective for fiscal years, and interim periods within those years, beginning after December 15, 2015. CenterPoint Houston does not believe that ASU 2015-02 will have a material impact on its financial position, results of operations, cash flows and disclosures.

In April 2015, the FASB issued Accounting Standards Update No. 2015-03, Interest-Imputation of Interest (Subtopic 835-30): Simplifying the Presentation of Debt Issuance Cost (ASU 2015-03). ASU 2015-03 requires that debt issuance costs related to a recognized debt liability be presented in the balance sheet as a direct deduction from the carrying amount of that debt liability, consistent with debt discounts. The recognition and measurement guidance for debt issuance costs are not affected by ASU 2015-03. CenterPoint Houston will adopt ASU 2015-03 retrospectively on January 1, 2016, which will result in a reduction of both other long-term assets and long-term debt on its Consolidated Balance Sheets. CenterPoint Houston had debt issuance costs of $22 million and $26 million included in other long-term assets on its Consolidated Balance Sheets as of December 31, 2015 and 2014, respectively.

In April 2015, the FASB issued Accounting Standards Update No. 2015-05, Intangibles-Goodwill and Other-Internal-Use Software (Subtopic 350-40) (ASU 2015-05). ASU 2015-05 provides guidance to customers about whether a cloud computing arrangement includes a software license. If a cloud computing arrangement includes a software license, the customer should account for the software license element of the arrangement consistent with the acquisition of other software licenses. If a cloud computing arrangement does not include a software license, the customer should account for the arrangement as a service contract. The guidance will not change a customer’s accounting for service contracts. ASU 2015-05 is effective for fiscal years, and interim periods within the fiscal years, beginning after December 15, 2015 and may be adopted either prospectively or retrospectively. CenterPoint Houston will adopt ASU 2015-05 prospectively on January 1, 2016. CenterPoint Houston does not believe that ASU 2015-05 will have a material impact on its financial position, results of operations, cash flows and disclosures.

In May 2014, the FASB issued Accounting Standards Update No. 2014-09, Revenue from Contracts with Customers (Topic 606) (ASU 2014-09), which supersedes most current revenue recognition guidance. ASU 2014-09 provides a comprehensive new revenue recognition model that requires revenue to be recognized in a manner that depicts the transfer of goods or services to a customer at an amount that reflects the consideration expected to be received in exchange for those goods or services. ASU 2014-09 was initially effective for fiscal years, and interim periods within those years, beginning after December 15, 2016. Early adoption is not permitted, and entities have the option of using either a full retrospective or a modified retrospective adoption approach. In August 2015, the FASB issued Accounting Standard Update No. 2015-14, Revenue from Contracts with Customers (Topic 606): Deferral of the Effective Date, which delays the effective date of ASU 2014-09 by one year. CenterPoint Houston is currently evaluating the impact that ASU 2014-09 will have on its financial position, results of operations, cash flows and disclosures, and will adopt ASU 2014-09 on January 1, 2018 as permitted by the new guidance.

In July 2015, the FASB issued Accounting Standards Update No. 2015-11, Inventory (Topic 330) Simplifying the Measurement of Inventory (ASU 2015-11). ASU 2015-11 changes the subsequent measurement guidance for inventory accounted for using methods other than the last in, first out (LIFO) and Retail Inventory methods. Companies will subsequently measure inventory at the lower of cost and net realizable value. Net realizable value is the estimated selling price in the ordinary course of business, less reasonably predictable costs of completion, disposal, and transportation. Subsequent measurement is unchanged for inventory measured using LIFO or the retail inventory method. ASU 2015-11 is effective for fiscal years, and interim periods within those years, beginning after December 15, 2016, with early adoption permitted. CenterPoint Houston does not believe that ASU 2015-11 will have a material impact on its financial position, results of operations, cash flows and disclosures.

In November 2015, the FASB issued Accounting Standards Update No. 2015-17, Income Taxes (Topic 740): Balance Sheet Classification of Deferred Taxes (ASU 2015-17). ASU 2015-17 requires deferred tax liabilities and assets be classified as noncurrent in a classified statement of financial position. CenterPoint Houston adopted ASU 2015-17 retrospectively starting with fiscal year 2015. As such, certain prior period amounts have been reclassified to conform to the current presentation. In the Consolidated Balance Sheet as of December 31, 2014, CenterPoint Houston reclassified $2 million from current deferred tax assets to reduce deferred income taxes within non-current liabilities. See Note 9 for additional information.

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

(m) Other Current Liabilities

Included in other current liabilities in the Consolidated Balance Sheets as of December 31, 2015 and 2014 was $12 million and $24 million, respectively, of customer deposits primarily held by the transition and system restoration bond companies.

(n) Environmental Costs

CenterPoint Houston expenses or capitalizes environmental expenditures, as appropriate, depending on their future economic benefit. CenterPoint Houston expenses amounts that relate to an existing condition caused by past operations that do not have future economic benefit. CenterPoint Houston records undiscounted liabilities related to these future costs when environmental assessments and/or remediation activities are probable and the costs can be reasonably estimated.