Background and Basis of Presentation (Policies)	9 Months Ended
Sep. 30, 2021
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Basis of Presentation	Basis of Presentation. The preparation of the Registrants’ 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. The Interim Condensed Financial Statements reflect all normal recurring adjustments that are, in the opinion of management, necessary to present fairly the financial position, results of operations and cash flows for the respective periods. Amounts reported in the Condensed Statements of Consolidated Income are not necessarily indicative of amounts expected for a full-year period due to the effects of, among other things, (a) seasonal fluctuations in demand for energy, (b) changes in energy commodity prices, (c) timing of maintenance and other expenditures and (d) acquisitions and dispositions of businesses, assets and other interests. Certain prior year amounts have been reclassified to conform to the current year reportable segment presentation described in the 2020 Form 10-K and to reflect the impacts of discontinued operations.
Consolidation	The Infrastructure Services Disposal Group provided pipeline construction and repair services to CenterPoint Energy’s and CERC’s Natural Gas. In accordance with consolidation guidance in ASC 980—Regulated Operations, costs incurred by Natural Gas utilities for these pipeline construction and repair services are not eliminated in consolidation when capitalized and included in rate base by the Natural Gas utility. Amounts charged for these services that are not capitalized are included primarily in Operation and maintenance expenses.
Fair Value Measurements	Assets and liabilities that are recorded at fair value in the Registrants’ Condensed Consolidated Balance Sheets are categorized based upon the level of judgment associated with the inputs used to measure their value. Hierarchical levels, as defined below and directly related to the amount of subjectivity associated with the inputs to fair valuations of these assets and liabilities, are as follows: Level 1: Inputs are unadjusted quoted prices in active markets for identical assets or liabilities at the measurement date. The types of assets carried at Level 1 fair value generally are exchange-traded derivatives and equity securities. Level 2: Inputs, other than quoted prices included in Level 1, are observable for the asset or liability, either directly or indirectly. Level 2 inputs include quoted prices for similar instruments in active markets, quoted prices for identical or similar assets or liabilities in inactive markets, inputs other than quoted prices that are observable for the asset or liability and inputs that are derived principally from or corroborated by observable market data by correlation or other means. Fair value assets and liabilities that are generally included in this category are derivatives with fair values based on inputs from actively quoted markets. A market approach is utilized to value the Registrants’ Level 2 natural gas derivative assets or liabilities. CenterPoint Energy’s Level 2 indexed debt securities derivative is valued using an option model and a discounted cash flow model, which uses projected dividends on the ZENS-Related Securities and a discount rate as observable inputs. Level 3: Inputs are unobservable for the asset or liability, and include situations where there is little, if any, market activity for the asset or liability. Unobservable inputs reflect the Registrants’ judgments about the assumptions market participants would use in pricing the asset or liability since limited market data exists. The Registrants develop these inputs based on the best information available, including the Registrants’ own data. The Registrants determine the appropriate level for each financial asset and liability on a quarterly basis.
Earnings Per Share	The two-class method uses an earnings allocation formula that treats participating securities as having rights to earnings that otherwise would have been available only to common shareholders. Under the two-class method, income (loss) available to common shareholders from continuing operations is derived by subtracting the following from income (loss) from continuing operations: •preferred share dividend requirement; •deemed dividends for the amortization of the beneficial conversion feature recognized at issuance of the Series C Preferred Stock; and •an allocation of undistributed earnings to preferred shareholders of participating securities (Series C Preferred Stock) based on the securities’ right to receive dividends. Undistributed earnings are calculated by subtracting dividends declared on Common Stock, the preferred share dividend requirement and deemed dividends for the amortization of the beneficial conversion feature from net income. Net losses are not allocated to the Series C Preferred Stock as it does not have a contractual obligation to share in the losses of CenterPoint Energy. The Series C Preferred Stock included conversion features at a price that was below the fair value of the Common Stock on the commitment date. This beneficial conversion feature, which was approximately $32 million at issuance, represented the difference between the fair value per share of the Common Stock as of the commitment date and the conversion price, multiplied by the number of common shares issuable upon conversion. The beneficial conversion feature was recognized as a discount to Series C Preferred Stock and was amortized as a deemed dividend over the period from the issue date to the first allowable conversion date, which was November 6, 2020. Basic earnings per common share is computed by dividing income available to common shareholders from continuing operations by the basic weighted average number of common shares outstanding during the period. Participating securities are excluded from basic weighted average number of common shares outstanding. Diluted earnings per common share is computed by dividing income available to common shareholders from continuing operations by the weighted average number of common shares outstanding, including all potentially dilutive common shares, if the effect of such common shares is dilutive. Diluted earnings per share reflects the dilutive effect of potential common shares from share-based awards and convertible preferred shares. The dilutive effect of Series B Preferred Stock and Series C Preferred Stock is computed using the if-converted method, as applicable, which assumes conversion of the restricted stock, Series B Preferred Stock and Series C Preferred Stock at the beginning of the period, giving income recognition for the add-back of the preferred share dividends, amortization of beneficial conversion feature, and undistributed earnings allocated to preferred shareholders. The dilutive effect of restricted stock is computed using the treasury stock method, as applicable, which includes the incremental shares that would be hypothetically vested in excess of the number of shares assumed to be hypothetically repurchased with the assumed proceeds.
Revenues from Contract with Customers	Revenues from Contracts with Customers In accordance with ASC 606, Revenue from Contracts with Customers, revenue is recognized when a customer obtains control of promised goods or services. The amount of revenue recognized reflects the consideration to which the Registrants expect to be entitled to receive in exchange for these goods or services. The revenues and related balances in the following tables exclude operating revenues and balances from the Energy Services Disposal Group and the Infrastructure Services Disposal Group, which are reflected as discontinued operations prior to the date of closing of each transaction. See Note 3 for further information. Certain prior year amounts have been reclassified to conform to the current year reportable segment presentation described in the Registrants’ combined 2020 Form 10-K. ARPs are contracts between the utility and its regulators, not between the utility and a customer. The Registrants recognize ARP revenue as other revenues when the regulator-specified conditions for recognition have been met. Upon recovery of ARP revenue through incorporation in rates charged for utility service to customers, ARP revenue is reversed and recorded as revenue from contracts with customers. The recognition of ARP revenues and the reversal of ARP revenues upon recovery through rates charged for utility service may not occur in the same period. Revenues from Contracts with Customers Electric (CenterPoint Energy and Houston Electric). Houston Electric distributes electricity to customers over time and customers consume the electricity when delivered. Indiana Electric generates, distributes and transmits electricity to customers over time, and customers consume the electricity when delivered. Revenue, consisting of both volumetric and fixed tariff rates set by state regulators, such as the PUCT and the IURC, is recognized as electricity is delivered and represents amounts both billed and unbilled. Discretionary services requested by customers are provided at a point in time with control transferring upon the completion of the service. Revenue for discretionary services provided by Houston Electric is recognized upon completion of service based on the tariff rates set by the PUCT. Payments for electricity distribution and discretionary services are aggregated and received on a monthly basis. Houston Electric performs transmission services over time as a stand-ready obligation to provide a reliable network of transmission systems. Revenue is recognized upon time elapsed, and the monthly tariff rate set by the regulator. Payments are received on a monthly basis. Indiana Electric customers are billed monthly and payment terms, set by the regulator, require payment within a month of billing. Natural Gas (CenterPoint Energy and CERC). CenterPoint Energy and CERC distribute and transport natural gas to customers over time, and customers consume the natural gas when delivered. Revenue, consisting of both volumetric and fixed tariff rates set by the state governing agency for that service area, is recognized as natural gas is delivered and represents amounts both billed and unbilled. Discretionary services requested by the customer are satisfied at a point in time and revenue is recognized upon completion of service and the tariff rates set by the applicable state regulator. Payments of natural gas distribution, transportation and discretionary services are aggregated and received on a monthly basis. Contract Balances. When the timing of delivery of service is different from the timing of the payments made by customers and when the right to consideration is conditioned on something other than the passage of time, the Registrants recognize either a contract asset (performance precedes billing) or a contract liability (customer payment precedes performance). Those customers that prepay are represented by contract liabilities until the performance obligations are satisfied. The Registrants’ contract assets are included in Accrued unbilled revenues in their Condensed Consolidated Balance Sheets. As of September 30, 2021, CenterPoint Energy’s contract assets primarily relate to ESG contracts where revenue is recognized using the input method. The Registrants’ contract liabilities are included in Accounts payable and Other current liabilities in their Condensed Consolidated Balance Sheets. As of September 30, 2021, CenterPoint Energy’s contract liabilities primarily relate to ESG contracts where revenue is recognized using the input method.
Allowance for Credit Losses	CenterPoint Energy and CERC segregate financial assets that fall under the scope of Topic 326, primarily trade receivables due in one year or less, into portfolio segments based on shared risk characteristics, such as geographical location and regulatory environment, for evaluation of expected credit losses. Historical and current information, such as average write-offs, are applied to each portfolio segment to estimate the allowance for losses on uncollectible receivables. Additionally, the allowance for losses on uncollectible receivables is adjusted for reasonable and supportable forecasts of future economic conditions, which can include changing weather, commodity prices, regulations, and macroeconomic factors, among others. Houston Electric recognizes losses on financial assets that fall under the scope of Topic 326. Losses on financial assets are primarily recoverable through regulatory mechanisms and do not materially impact Houston Electric's allowance for credit losses.

Background and Basis of Presentation (Policies)

9 Months Ended

Sep. 30, 2021

Organization, Consolidation and Presentation of Financial Statements [Abstract]

Basis of Presentation. The preparation of the Registrants’ 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.

The Interim Condensed Financial Statements reflect all normal recurring adjustments that are, in the opinion of management, necessary to present fairly the financial position, results of operations and cash flows for the respective periods. Amounts reported in the Condensed Statements of Consolidated Income are not necessarily indicative of amounts expected for a full-year period due to the effects of, among other things, (a) seasonal fluctuations in demand for energy, (b) changes in energy commodity prices, (c) timing of maintenance and other expenditures and (d) acquisitions and dispositions of businesses, assets and other interests. Certain prior year amounts have been reclassified to conform to the current year reportable segment presentation described in the 2020 Form 10-K and to reflect the impacts of discontinued operations.

Consolidation

The Infrastructure Services Disposal Group provided pipeline construction and repair services to CenterPoint Energy’s and CERC’s Natural Gas. In accordance with consolidation guidance in ASC 980—Regulated Operations, costs incurred by Natural Gas utilities for these pipeline construction and repair services are not eliminated in consolidation when capitalized and included in rate base by the Natural Gas utility. Amounts charged for these services that are not capitalized are included primarily in Operation and maintenance expenses.

Fair Value Measurements

Assets and liabilities that are recorded at fair value in the Registrants’ Condensed Consolidated Balance Sheets are categorized based upon the level of judgment associated with the inputs used to measure their value. Hierarchical levels, as defined below and directly related to the amount of subjectivity associated with the inputs to fair valuations of these assets and liabilities, are as follows:

Level 1: Inputs are unadjusted quoted prices in active markets for identical assets or liabilities at the measurement date. The types of assets carried at Level 1 fair value generally are exchange-traded derivatives and equity securities.

Level 2: Inputs, other than quoted prices included in Level 1, are observable for the asset or liability, either directly or indirectly. Level 2 inputs include quoted prices for similar instruments in active markets, quoted prices for identical or similar assets or liabilities in inactive markets, inputs other than quoted prices that are observable for the asset or liability and inputs that are derived principally from or corroborated by observable market data by correlation or other means. Fair value assets and liabilities that are generally included in this category are derivatives with fair values based on inputs from actively quoted markets. A market approach is utilized to value the Registrants’ Level 2 natural gas derivative assets or liabilities. CenterPoint Energy’s Level 2 indexed debt securities derivative is valued using an option model and a discounted cash flow model, which uses projected dividends on the ZENS-Related Securities and a discount rate as observable inputs.

Level 3: Inputs are unobservable for the asset or liability, and include situations where there is little, if any, market activity for the asset or liability. Unobservable inputs reflect the Registrants’ judgments about the assumptions market participants would use in pricing the asset or liability since limited market data exists. The Registrants develop these inputs based on the best information available, including the Registrants’ own data.

The Registrants determine the appropriate level for each financial asset and liability on a quarterly basis.

Earnings Per Share

The two-class method uses an earnings allocation formula that treats participating securities as having rights to earnings that otherwise would have been available only to common shareholders. Under the two-class method, income (loss) available to common shareholders from continuing operations is derived by subtracting the following from income (loss) from continuing operations:

•preferred share dividend requirement;

•deemed dividends for the amortization of the beneficial conversion feature recognized at issuance of the Series C Preferred Stock; and

•an allocation of undistributed earnings to preferred shareholders of participating securities (Series C Preferred Stock) based on the securities’ right to receive dividends.

Undistributed earnings are calculated by subtracting dividends declared on Common Stock, the preferred share dividend requirement and deemed dividends for the amortization of the beneficial conversion feature from net income. Net losses are not allocated to the Series C Preferred Stock as it does not have a contractual obligation to share in the losses of CenterPoint Energy.

The Series C Preferred Stock included conversion features at a price that was below the fair value of the Common Stock on the commitment date. This beneficial conversion feature, which was approximately $32 million at issuance, represented the difference between the fair value per share of the Common Stock as of the commitment date and the conversion price, multiplied by the number of common shares issuable upon conversion. The beneficial conversion feature was recognized as a discount to Series C Preferred Stock and was amortized as a deemed dividend over the period from the issue date to the first allowable conversion date, which was November 6, 2020.

Basic earnings per common share is computed by dividing income available to common shareholders from continuing operations by the basic weighted average number of common shares outstanding during the period. Participating securities are excluded from basic weighted average number of common shares outstanding. Diluted earnings per common share is computed by dividing income available to common shareholders from continuing operations by the weighted average number of common shares outstanding, including all potentially dilutive common shares, if the effect of such common shares is dilutive.

Diluted earnings per share reflects the dilutive effect of potential common shares from share-based awards and convertible preferred shares. The dilutive effect of Series B Preferred Stock and Series C Preferred Stock is computed using the if-converted method, as applicable, which assumes conversion of the restricted stock, Series B Preferred Stock and Series C Preferred Stock at the beginning of the period, giving income recognition for the add-back of the preferred share dividends, amortization of beneficial conversion feature, and undistributed earnings allocated to preferred shareholders. The dilutive effect of restricted stock is computed using the treasury stock method, as applicable, which includes the incremental shares that would be hypothetically vested in excess of the number of shares assumed to be hypothetically repurchased with the assumed proceeds.

Revenues from Contract with Customers

Revenues from Contracts with Customers

In accordance with ASC 606, Revenue from Contracts with Customers, revenue is recognized when a customer obtains control of promised goods or services. The amount of revenue recognized reflects the consideration to which the Registrants expect to be entitled to receive in exchange for these goods or services. The revenues and related balances in the following tables exclude operating revenues and balances from the Energy Services Disposal Group and the Infrastructure Services Disposal Group, which are reflected as discontinued operations prior to the date of closing of each transaction. See Note 3 for further information. Certain prior year amounts have been reclassified to conform to the current year reportable segment presentation described in the Registrants’ combined 2020 Form 10-K.

ARPs are contracts between the utility and its regulators, not between the utility and a customer. The Registrants recognize ARP revenue as other revenues when the regulator-specified conditions for recognition have been met. Upon recovery of ARP revenue through incorporation in rates charged for utility service to customers, ARP revenue is reversed and recorded as revenue from contracts with customers. The recognition of ARP revenues and the reversal of ARP revenues upon recovery through rates charged for utility service may not occur in the same period.

Revenues from Contracts with Customers

Electric (CenterPoint Energy and Houston Electric). Houston Electric distributes electricity to customers over time and customers consume the electricity when delivered. Indiana Electric generates, distributes and transmits electricity to customers over time, and customers consume the electricity when delivered. Revenue, consisting of both volumetric and fixed tariff rates set by state regulators, such as the PUCT and the IURC, is recognized as electricity is delivered and represents amounts both billed and unbilled. Discretionary services requested by customers are provided at a point in time with control transferring upon the completion of the service. Revenue for discretionary services provided by Houston Electric is recognized upon completion of service based on the tariff rates set by the PUCT. Payments for electricity distribution and discretionary services are aggregated and received on a monthly basis. Houston Electric performs transmission services over time as a stand-ready obligation to provide a reliable network of transmission systems. Revenue is recognized upon time elapsed, and the monthly tariff rate set by the regulator. Payments are received on a monthly basis. Indiana Electric customers are billed monthly and payment terms, set by the regulator, require payment within a month of billing.

Natural Gas (CenterPoint Energy and CERC). CenterPoint Energy and CERC distribute and transport natural gas to customers over time, and customers consume the natural gas when delivered. Revenue, consisting of both volumetric and fixed tariff rates set by the state governing agency for that service area, is recognized as natural gas is delivered and represents amounts both billed and unbilled. Discretionary services requested by the customer are satisfied at a point in time and revenue is recognized upon completion of service and the tariff rates set by the applicable state regulator. Payments of natural gas distribution, transportation and discretionary services are aggregated and received on a monthly basis.

Contract Balances. When the timing of delivery of service is different from the timing of the payments made by customers and when the right to consideration is conditioned on something other than the passage of time, the Registrants recognize either a contract asset (performance precedes billing) or a contract liability (customer payment precedes performance). Those customers that prepay are represented by contract liabilities until the performance obligations are satisfied. The Registrants’ contract assets are included in Accrued unbilled revenues in their Condensed Consolidated Balance Sheets. As of September 30, 2021, CenterPoint Energy’s contract assets primarily relate to ESG contracts where revenue is recognized using the input method. The Registrants’ contract liabilities are included in Accounts payable and Other current liabilities in their Condensed Consolidated Balance Sheets. As of September 30, 2021, CenterPoint Energy’s contract liabilities primarily relate to ESG contracts where revenue is recognized using the input method.

Allowance for Credit Losses

CenterPoint Energy and CERC segregate financial assets that fall under the scope of Topic 326, primarily trade receivables due in one year or less, into portfolio segments based on shared risk characteristics, such as geographical location and regulatory environment, for evaluation of expected credit losses. Historical and current information, such as average write-offs, are applied to each portfolio segment to estimate the allowance for losses on uncollectible receivables. Additionally, the allowance for losses on uncollectible receivables is adjusted for reasonable and supportable forecasts of future economic conditions, which can include changing weather, commodity prices, regulations, and macroeconomic factors, among others. Houston Electric recognizes losses on financial assets that fall under the scope of Topic 326. Losses on financial assets are primarily recoverable through regulatory mechanisms and do not materially impact Houston Electric's allowance for credit losses.