Trading Arrangements, by Individual Trading Arrangements, by Individual [Table] Electricity Generation Plant, Non-Nuclear Electricity Generation Plant, Non-Nuclear [Member] Trading Arrangement: Trading Arrangement [Axis] Statistical Measurement [Domain] Statistical Measurement [Domain] Less accumulated depreciation Public Utilities, Property, Plant and Equipment, Accumulated Depreciation Short-term Debt, Type [Axis] Short-Term Debt, Type [Axis] Document Fiscal Year Focus Document Fiscal Year Focus Adjustment to Compensation, Amount Adjustment to Compensation Amount Alternative revenue and other Alternative and Other [Member] Alternative and Other [Member] Customer [Axis] Customer [Axis] Segment Reporting [Abstract] Segment Reporting [Abstract] Common stock — 1,000,000 shares authorized of $100 par value; 933,000 shares outstanding at June 30, 2026 and Dec. 31, 2025, respectively Common Stock, Value, Issued Depreciation and amortization Depreciation, Amortization and Accretion, Net Interest charges and other financing costs Interest Expense, Operating and Nonoperating State income taxes, net of federal tax effect (b) Effective Income Tax Rate Reconciliation, State and Local Income Taxes, Percent Benefit Plans and Other Postretirement Benefits Retirement Benefits [Text Block] Restatement Determination Date Restatement Determination Date Expected return on plan assets (a) Defined Benefit Plan, Expected Return (Loss) on Plan Assets Schedule of Effective Income Tax Rate Reconciliation [Table Text Block] Schedule of Effective Income Tax Rate Reconciliation [Table Text Block] Property, Plant and Equipment, Net Public Utility Property, Plant, and Equipment [Table Text Block] Regulatory liabilities Regulatory Liability, Noncurrent Amendment Flag Amendment Flag Consolidated Entities [Axis] Consolidated Entities [Axis] Current liabilities Liabilities, Current [Abstract] Inventory [Axis] Inventory [Axis] Entity Common Stock, Shares Outstanding Entity Common Stock, Shares Outstanding Allowance for funds used during construction — equity Public Utilities, Allowance for Funds Used During Construction, Capitalized Cost of Equity Loss Contingencies [Table] Loss Contingencies [Table] Retail Retail Distribution [Member] Retail Distribution [Member] Consolidated Entities [Domain] Consolidated Entities [Domain] Adjustment to Non-PEO NEO Compensation Footnote Adjustment to Non-PEO NEO Compensation Footnote [Text Block] Entity Address, State or Province Entity Address, State or Province Public Utility, Property, Plant and Equipment [Table] Public Utility, Property, Plant and Equipment [Table] PEO Total Compensation Amount PEO Total Compensation Amount Common stock, par value (in dollars per share) Common Stock, Par or Stated Value Per Share Inventories Schedule of Utility Inventory [Table Text Block] Retirement Benefits [Abstract] Retirement Benefits [Abstract] Outstanding Aggregate Erroneous Compensation Amount Outstanding Aggregate Erroneous Compensation Amount Fair Value, by Balance Sheet Grouping [Table] Fair Value, by Balance Sheet Grouping [Table] Regulatory assets Regulatory Asset, Noncurrent Loss Contingencies [Line Items] Loss Contingencies [Line Items] Total current liabilities Liabilities, Current Taxes (other than income taxes) Taxes, Miscellaneous Natural gas Regulated Operating Revenue, Gas Short-term Debt, Type [Domain] Short-Term Debt, Type [Domain] Revenue from contracts with customers Revenue from Contract with Customer, Including Assessed Tax Entity Address, City or Town Entity Address, City or Town Defined Benefit Plan Disclosure [Line Items] Defined Benefit Plan Disclosure [Line Items] Operating revenues Operating revenues [Abstract] Operating revenues Statement of Financial Position [Abstract] Statement of Financial Position [Abstract] Award Timing MNPI Disclosure Award Timing MNPI Disclosure [Text Block] Total revenue from contracts with customers Product [Member] Peer Group Total Shareholder Return Amount Peer Group Total Shareholder Return Amount Level 2 Fair Value, Inputs, Level 2 [Member] Total Shareholder Return Vs Peer Group Total Shareholder Return Vs Peer Group [Text Block] Line of Credit Facility, Maximum Borrowing Capacity Credit Facility Line of Credit Facility, Maximum Borrowing Capacity Non-Rule 10b5-1 Arrangement Terminated Non-Rule 10b5-1 Arrangement Terminated [Flag] Parent Company [Member] Parent Company [Member] Contribution of capital by parent Adjustments to Additional Paid in Capital, Other Schedule of Long-term Debt Instruments [Table] Schedule of Long-Term Debt Instruments [Table] Litigation Case [Axis] Litigation Case [Axis] Accrued property, plant and equipment additions Capital Expenditures Incurred but Not yet Paid Segment Reporting Segment Reporting [Table Text Block] Deferred credits and other liabilities Liabilities, Other than Long-Term Debt, Noncurrent [Abstract] Related Party, Type [Axis] Related and Nonrelated Parties [Axis] Long-term Debt, Carrying Amount Long-Term Debt Cost of identified MGP, landfill, or disposal sites under current investigation and/or remediation Cost of identified MGP, landfill, or disposal sites under current investigation and/or remediation Cost of identified MGP, landfill, or disposal sites under current investigation and/or remediation Document Period End Date Document Period End Date Changes in operating assets and liabilities: Adjustment to Reconcile Net Income to Cash Provided by (Used in) Operating Activity, Increase (Decrease) in Operating Capital [Abstract] Net cash used in investing activities Cash Provided by (Used in) Investing Activity, Including Discontinued Operation Equity Awards Adjustments, Excluding Value Reported in Compensation Table Equity Awards Adjustments, Excluding Value Reported in the Compensation Table [Member] Debt Instrument, Face Amount Debt Instrument, Face Amount Operating expenses Costs and Expenses [Abstract] Plant Public Utilities, Property, Plant and Equipment, Generation or Processing Electric Fuel and Purchased Power Electric Fuel and Purchased Power Electric Fuel and Purchased Power Entity Shell Company Entity Shell Company Consolidation Items [Domain] Consolidation Items [Domain] Other Effective Income Tax Rate Reconciliation, Other Adjustments, Amount Contributions to pension plans Payment for Pension Benefits Accrued interest Interest Payable, Current Name Outstanding Recovery, Individual Name Award Timing, How MNPI Considered Award Timing, How MNPI Considered [Text Block] Document Fiscal Period Focus Document Fiscal Period Focus Peer Group Issuers, Footnote Peer Group Issuers, Footnote [Text Block] Related Party Transaction, Electric Domestic Regulated Revenue Related Party Transaction, Electric Domestic Regulated Revenue Revenue derived from the regulated (by a federal, state, or local government or agency) generation, transmission and distribution of electricity earned from transactions between (a) a parent company and its subsidiaries; (b) subsidiaries of a common parent; (c) an entity and trusts for the benefit of employees, for example, but not limited to, pension and profit-sharing trusts that are managed by or under the trusteeship of the entity's management; (d) an entity and its principal, owners, management, or members of their immediate families; and (e) affiliates. Net periodic benefit cost Defined Benefit Plan Net Benefit Cost (Credit) Recognized Before Regulatory Adjustments The total mount of net periodic benefit cost, before regulatory adjustments, for defined benefit plans for the period. Periodic benefit costs include the following components: service cost, interest cost, expected return on plan assets, gain or loss, prior service cost or credit, transition asset or obligation, and gain or loss due to settlements or curtailments, before regulatory adjustments. Depreciation and amortization Utilities Operating Expense, Depreciation and Amortization Utilities Operating Expense, Depreciation and Amortization Prior Year End Fair Value of Equity Awards Granted in Any Prior Year that Fail to Meet Applicable Vesting Conditions During Covered Year Prior Year End Fair Value of Equity Awards Granted in Any Prior Year that Fail to Meet Applicable Vesting Conditions During Covered Year [Member] Pension Adjustments Prior Service Cost Pension Adjustments Prior Service Cost [Member] Company Selected Measure Name Company Selected Measure Name Income Tax Disclosure [Abstract] Income Tax Disclosure [Abstract] Other Effective Income Tax Rate Reconciliation, Tax Credit, Other, Amount Allowance for equity funds used during construction Allowance for equity funds used during construction Allowance for equity funds used during construction Credit Facility [Domain] Credit Facility [Domain] Operating activities Cash Provided by (Used in) Operating Activity, Including Discontinued Operation [Abstract] Compensation Amount Outstanding Recovery Compensation Amount Dividends payable to parent Dividends Payable, Current Individual: Individual [Axis] Public Utility [Axis] Public Utility [Axis] Disaggregation of Revenue [Line Items] Disaggregation of Revenue [Line Items] Accounts, Notes, Loans and Financing Receivable [Line Items] Accounts, Notes, Loans and Financing Receivable [Line Items] Entity Emerging Growth Company Entity Emerging Growth Company Equity Valuation Assumption Difference, Footnote Equity Valuation Assumption Difference, Footnote [Text Block] Pension and employee benefit obligations Liability, Defined Benefit Plan, Noncurrent Line of Credit Facility [Table] Line of Credit Facility [Table] Underlying Security Market Price Change Underlying Security Market Price Change, Percent Accrued unbilled revenues Accrued Unbilled Revenues The amount of fees and other revenue, excluding investment income receivable, earned but not yet received, which were recognized in conformity with revenue recognition criteria based on estimates or specific contractual terms. Accounts Receivable, Net Accounts Receivable, after Allowance for Credit Loss, Current [Abstract] Commercial Paper Commercial Paper [Member] Regulated Operating Revenue, Electric Regulated Operating Revenue, Electric Regulated Operating Revenue, Electric Amount outstanding at period end Short-Term Debt Natural Gas Processing Plant Natural Gas Processing Plant [Member] Revenues Revenue from Contract with Customer [Abstract] Other, net Increase (Decrease) in Other Operating Assets and Liabilities, Net Award Timing Predetermined Award Timing Predetermined [Flag] Property, plant and equipment, net Public Utilities, Property, Plant and Equipment, Net Adjustment To PEO Compensation, Footnote Adjustment To PEO Compensation, Footnote [Text Block] Effective income tax rate Effective Income Tax Rate Reconciliation, Percent Organization, Consolidation and Presentation of Financial Statements [Abstract] Organization, Consolidation and Presentation of Financial Statements [Abstract] Litigation Status [Domain] Litigation Status [Domain] Allowance for funds used during construction — debt Public Utilities, Allowance For Funds Used During Construction, Capitalized Cost Of Debt The component of the allowance for funds used during construction during the period based on an assumed rate of return on debt capital used in financing the construction of regulated assets. Regulated Electric Segment Regulated Electric Segment [Member] Regulated Electric Segment Inventory, Current [Table] Inventory, Current [Table] All Executive Categories All Executive Categories [Member] Pension Adjustments Service Cost Pension Adjustments Service Cost [Member] Long-term Debt, Fair Value Long-Term Debt, Fair Value Components of Net Periodic Benefit Cost Schedule of Net Benefit Costs [Table Text Block] Total interest charges and financing costs Interest and Debt Expense Interest and Debt Expense Interchange Interchange [Member] Related party transactions through the interchange agreement Conservation program expenses Conservation and Demand Side Management Program Expenses Costs incurred for energy conservation, weatherization and other programs to conserve or manage energy use by customers. Fair Value Disclosures [Abstract] Fair Value Disclosures [Abstract] Debt Disclosure [Abstract] Debt Disclosure [Abstract] Debt Instrument, Name [Domain] Debt Instrument, Name [Domain] Segment Information Segment Reporting [Text Block] Dividends paid to parent Payments of Ordinary Dividends, Common Stock Expiration Date Trading Arrangement Expiration Date Disaggregation of revenue Disaggregation of Revenue [Table Text Block] Non-Rule 10b5-1 Arrangement Adopted Non-Rule 10b5-1 Arrangement Adopted [Flag] Beginning Balance Ending Balance Equity, Including Portion Attributable to Noncontrolling Interest Line of Credit Facility, Expiration Period Line of Credit Facility, Expiration Period Aggregate Grant Date Fair Value of Equity Award Amounts Reported in Summary Compensation Table Aggregate Grant Date Fair Value of Equity Award Amounts Reported in Summary Compensation Table [Member] Nonrelated Party Nonrelated Party [Member] Affiliated Entity Affiliated Entity [Member] Net benefit cost recognized for financial reporting Defined Benefit Plan, Net Periodic Benefit Cost (Credit) Aggregate Pension Adjustments Service Cost Aggregate Pension Adjustments Service Cost [Member] Common stock, shares authorized (in shares) Common Stock, Shares Authorized Accounts receivable Increase (Decrease) in Accounts and Other Receivables Revenues Including Intersegment Revenues Revenues Including Intersegment Revenues Revenues Including Intersegment Revenues Series Due June 15, 2041 Series Due June 15, 2041 [Member] Series Due June 15, 2041 Exercise Price Award Exercise Price AFUDC equity Effective Income Tax Rate Reconciliation, AFUDC Equity, Amount Effective Income Tax Rate Reconciliation, AFUDC Equity, Amount Investing activities Cash Provided by (Used in) Investing Activity, Including Discontinued Operation [Abstract] Litigation Status [Axis] Litigation Status [Axis] Segment Reporting [Line Items] Segment Reporting [Line Items] Document Quarterly Report Document Quarterly Report Year-over-Year Change in Fair Value of Equity Awards Granted in Prior Years That are Outstanding and Unvested Year-over-Year Change in Fair Value of Equity Awards Granted in Prior Years That are Outstanding and Unvested [Member] Segments [Domain] Segments [Domain] Borrowings and Other Financing Instruments Debt Disclosure [Text Block] Awards Close in Time to MNPI Disclosures, Table Awards Close in Time to MNPI Disclosures [Table Text Block] Equity Component [Domain] Equity Component [Domain] PEO Actually Paid Compensation Amount PEO Actually Paid Compensation Amount Accounts receivable Accounts Receivable, before Allowance for Credit Loss, Current Total operating expenses Costs and Expenses Adoption Date Trading Arrangement Adoption Date Debt Instrument, Interest Rate, Stated Percentage Debt Instrument, Interest Rate, Stated Percentage Text Block [Abstract] Common dividends declared to parent Dividends, Common Stock, Cash Total common stockholder's equity Equity, Attributable to Parent Other MGP, Landfill, or Disposal Sites [Domain] Other MGP, Landfill, or Disposal Sites [Domain] Assets Assets [Abstract] Title Trading Arrangement, Individual Title Forgone Recovery due to Disqualification of Tax Benefits, Amount Forgone Recovery due to Disqualification of Tax Benefits, Amount Accounting Policies [Abstract] Accounting Policies [Abstract] Restatement does not require Recovery Restatement Does Not Require Recovery [Text Block] Environmental Remediation Site [Axis] Environmental Remediation Site [Axis] Insider Trading Policies and Procedures [Line Items] Less allowance for bad debts Accounts Receivable, Allowance for Credit Loss, Current Insider Trading Policies and Procedures Adopted Insider Trading Policies and Procedures Adopted [Flag] Credit Facilities Schedule of Line of Credit Facilities [Table Text Block] Prepayments and other Prepaid Expense and Other Assets, Current Deferred income taxes Deferred Income Tax Expense (Benefit) Selected Balance Sheet Data Supplemental Balance Sheet Disclosures [Text Block] Regulatory assets Regulatory Asset, Current Commitments and Contingencies Commitments and Contingencies Disclosure [Text Block] Compensation Actually Paid vs. Net Income Compensation Actually Paid vs. Net Income [Text Block] Entity Central Index Key Entity Central Index Key Components of Net Periodic Benefit Cost [Abstract] Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract] Notes Payable, Current Notes Payable, Current Additional paid in capital Additional Paid in Capital, Common Stock All Adjustments to Compensation All Adjustments to Compensation [Member] Dividends or Other Earnings Paid on Equity Awards not Otherwise Reflected in Total Compensation for Covered Year Dividends or Other Earnings Paid on Equity Awards not Otherwise Reflected in Total Compensation for Covered Year [Member] Net cash provided by operating activities Cash Provided by (Used in) Operating Activity, Including Discontinued Operation Federal statutory rate impact Effective Income Tax Rate Reconciliation at Federal Statutory Income Tax Rate, Amount Income Statement [Abstract] Income Statement [Abstract] Document Transition Report Document Transition Report Fair Value Hierarchy and NAV [Axis] Fair Value Hierarchy and NAV [Axis] Intersegment Eliminations Intersegment Eliminations [Member] Stock Appreciation Rights (SARs) Stock Appreciation Rights (SARs) [Member] City Area Code City Area Code Allowance for equity funds used during construction Allowance for Funds Used During Construction, Investing Activities All Individuals All Individuals [Member] Purchased power, affiliates Related Party Transaction, Utilities Operating Expense, Purchased Power Amount of operating expense for purchased power of regulated operation resulting from transactions (excluding transactions that are eliminated in consolidated or combined financial statements) with related party. Number Of Reportable Segments, Disclosed By Definition, Flag Number Of Reportable Segments, Disclosed By Definition, Flag Number Of Reportable Segments, Disclosed By Definition, Flag Name Forgone Recovery, Individual Name Balance Sheet Related Disclosures [Abstract] Balance Sheet Related Disclosures [Abstract] Non-GAAP Measure Description Non-GAAP Measure Description [Text Block] Statement [Line Items] Statement [Line Items] Total assets Assets Schedule of Defined Benefit Plans Disclosures [Table] Defined Benefit Plan [Table] Common and other property Public Utilities, Property, Plant And Equipment, Common And Other Property, Plant And Equipment Public Utilities, Property, Plant And Equipment, Common And Other Property, Plant And Equipment New Accounting Pronouncements and Changes in Accounting Principles [Abstract] Accounting Standards Update and Change in Accounting Principle [Abstract] Total revenues Operating Segments [Member] PEO PEO [Member] Outstanding Debt, Long-Term and Short-Term, Combined Amount Other Other Liabilities, Noncurrent Retirement Plan Type [Axis] Retirement Plan Type [Axis] Forgone Recovery due to Violation of Home Country Law, Amount Forgone Recovery due to Violation of Home Country Law, Amount Payable to Affiliates payable to affiliates [Member] payable to affiliates [Member] Retained Earnings Retained Earnings [Member] Taxes accrued Taxes Payable, Current 0 Revolving Credit Facility [Member] Other Effective Income Tax Rate Reconciliation, Tax Credit, Other, Percent Inventory transfers to property, plant and equipment Inventory transfers to plant, property and equipment Amount of increase (decrease) of plant, property and equipment reclassified from inventory. Erroneously Awarded Compensation Recovery Erroneously Awarded Compensation Recovery [Table] Increase (Decrease) in Stockholder's Equity Increase (Decrease) in Stockholders' Equity [Roll Forward] Common stock, shares outstanding (in shares) Balance (in shares) Balance (in shares) Common Stock, Shares, Outstanding Award Timing Disclosures [Line Items] Carrying Amount and Fair Value of Long-term Debt Fair Value, by Balance Sheet Grouping [Table Text Block] Entity Current Reporting Status Entity Current Reporting Status Net cash provided by financing activities Cash Provided by (Used in) Financing Activity, Including Discontinued Operation Total Shareholder Return Amount Total Shareholder Return Amount Pension and other employee benefit obligations Increase (Decrease) in Employee Related Liabilities Litigation Case [Domain] Litigation Case [Domain] Provision for bad debts Provision for Bad Debts Provision for Bad Debts Inventory [Domain] Inventory [Domain] Line of Credit Facility [Line Items] Line of Credit Facility [Line Items] Adjustments to reconcile net income to cash provided by operating activities: Adjustment to Reconcile Net Income to Cash Provided by (Used in) Operating Activity [Abstract] Loss Contingency Nature [Axis] Loss Contingency Nature [Axis] Property, plant and equipment, net Property, Plant, and Equipment, after Accumulated Depreciation, Depletion, and Amortization Financing activities Cash Provided by (Used in) Financing Activity, Including Discontinued Operation [Abstract] C&I Commercial and Industrial Customers [Member] Commercial and Industrial Customers [Member] Available Line of Credit Facility, Remaining Borrowing Capacity Other Effective Income Tax Rate Reconciliation, Other Adjustments, Percent Interest cost (a) Defined Benefit Plan, Interest Cost Equity Awards Adjustments, Footnote Equity Awards Adjustments, Footnote [Text Block] Underlying Securities Award Underlying Securities Amount Revenues Revenue from Contract with Customer [Text Block] Electric, non-affiliates Regulated Operating Revenue, Electric, Non-affiliate Regulated Operating Revenue, Electric, Non-affiliate Other current liabilities Increase (Decrease) in Other Current Liabilities Inventories Increase (Decrease) in Inventories State income taxes, net of federal tax effect (b) Effective Income Tax Rate Reconciliation, State and Local Income Taxes, Amount Segment Reporting [Table] Segment Reporting [Table] Defined Benefit Plan, Costs Not Recognized Due To Regulation Defined Benefit Plan, Costs Not Recognized Due To Regulation The decrease to a defined benefit pension plan's net benefit cost or a defined benefit postretirement plan's net benefit cost due to regulatory adjustments. Regulated Natural Gas Regulated Natural Gas [Member] The operations of the regulated natural gas utility segment consists of the transporting, storing, and distributing natural gas in certain markets serviced by the entity. Residential Residential Customers [Member] Residential Customers [Member] Commitments and Contingencies Disclosure [Abstract] Commitments and Contingencies Disclosure [Abstract] All Trading Arrangements All Trading Arrangements [Member] Other Performance Measure, Amount Other Performance Measure, Amount Award Timing MNPI Considered Award Timing MNPI Considered [Flag] Operating income Operating Income (Loss) Current Fiscal Year End Date Current Fiscal Year End Date Other Other Customers [Member] Other Customers [Member] Repayments under utility money pool arrangement Repayments Under Utility Money Pool Arrangement Repayments of amounts during the reporting period previously borrowed from the utility money pool borrowing arrangement among approved affiliates. Non-PEO NEO Average Total Compensation Amount Non-PEO NEO Average Total Compensation Amount Proceeds from long-term debt Proceeds from long-term debt Proceeds from long-term debt Change in Fair Value as of Vesting Date of Prior Year Equity Awards Vested in Covered Year Change in Fair Value as of Vesting Date of Prior Year Equity Awards Vested in Covered Year [Member] Entity File Number Entity File Number Electric fuel and purchased power, non-affiliates Electric Fuel and Purchased Power, Non-Affiliate Electric Fuel and Purchased Power, Non-Affiliate Rule 10b5-1 Arrangement Adopted Rule 10b5-1 Arrangement Adopted [Flag] Service cost Defined Benefit Plan, Service Cost Repayments of short-term borrowings, net Proceeds from (Repayments of) Short-Term Debt Recovery of Erroneously Awarded Compensation Disclosure [Line Items] Measure: Measure [Axis] Regulated Operating Revenue Regulated Operating Revenue Repayments from utility money pool arrangement Repayments From Utility Money Pool Arrangement Repayments received during the reporting period of amounts previously invested into the utility money pool borrowing arrangement among approved affiliates. Equity Components [Axis] Equity Components [Axis] Product and Service [Domain] Product and Service [Domain] Net regulatory assets and liabilities Increase (Decrease) in Regulatory Assets and Liabilities Disaggregation of Revenue [Table] Disaggregation of Revenue [Table] Capitalization Capitalization, Long-Term Debt and Equity [Abstract] Entity Interactive Data Current Entity Interactive Data Current Deferred income taxes Deferred Income Tax Liabilities, Net Compensation Actually Paid vs. Other Measure Compensation Actually Paid vs. Other Measure [Text Block] Plant related excess deferred taxes Effective Income Tax Rate Reconciliation, Plant Related Excess Deferred Taxes, Amount Effective Income Tax Rate Reconciliation, Plant Related Excess Deferred Taxes, Amount Entity Small Business Entity Small Business Total property, plant and equipment Public Utilities, Property, Plant and Equipment, Plant in Service Termination Date Trading Arrangement Termination Date Utility Plant [Domain] Utility Plant [Domain] Cost of natural sold and transported Cost of natural Gas Sold and Transported Cost of natural Gas Sold and Transported Federal statutory rate Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent Compensation Actually Paid vs. Total Shareholder Return Compensation Actually Paid vs. Total Shareholder Return [Text Block] MNPI Disclosure Timed for Compensation Value MNPI Disclosure Timed for Compensation Value [Flag] Other Other Liabilities, Current Other Other Assets, Noncurrent Document Type Document Type Fair Value as of Grant Date Award Grant Date Fair Value Materials and supplies Supplies [Member] Money Pool Money Pool [Member] Arrangement that allows for short-term investments in and borrowings between the utility subsidiaries. Summary of Significant Accounting Policies Significant Accounting Policies [Text Block] Pay vs Performance Disclosure, Table Pay vs Performance [Table Text Block] Common Stock, Shares Issued, Not Disclosed Common Stock, Shares Issued, Not Disclosed Common Stock, Shares Issued, Not Disclosed Arrangement Duration Trading Arrangement Duration Regulated Natural Gas Segment Regulated Natural Gas Segment [Member] Regulated Natural Gas Segment Statement of Stockholders' Equity [Abstract] Statement of Stockholders' Equity [Abstract] Local Phone Number Local Phone Number Customer advances Contract with Customer, Liability, Noncurrent Consolidation Items [Axis] Consolidation Items [Axis] Entity Address, Postal Zip Code Entity Address, Postal Zip Code Entity Registrant Name Entity Registrant Name Bonds Bonds [Member] Income before income taxes Income before income taxes (domestic) Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest Insider Trading Policies and Procedures Not Adopted Insider Trading Policies and Procedures Not Adopted [Text Block] Commitments and contingencies Commitments and Contingencies Total revenues Revenues Average amount outstanding Short-Term Debt, Average Outstanding Amount Changed Peer Group, Footnote Changed Peer Group, Footnote [Text Block] Borrowings under utility money pool arrangement Borrowings Payable Under Utility Money Pool Arrangement Borrowings under the utility money pool borrowing arrangement among approved affiliates, which are due in one year or less in the future. Forgone Recovery due to Expense of Enforcement, Amount Forgone Recovery due to Expense of Enforcement, Amount Executive Category: Executive Category [Axis] Liabilities and Equity Liabilities and Equity [Abstract] Inventories Total Inventories Inventory, Net All Award Types Award Type [Domain] Non-PEO NEO Average Compensation Actually Paid Amount Non-PEO NEO Average Compensation Actually Paid Amount Fair Value of Financial Assets and Liabilities Fair Value Disclosures [Text Block] Supplemental disclosure of cash flow information: Supplemental Cash Flow Information [Abstract] PEO Name PEO Name Schedule of Short-term Debt [Table] Short-Term Debt [Table] Segment Reporting, Other Segment Item, Amount Segment Reporting, Other Segment Item, Amount Weighted average interest rate, computed on a daily basis Line of Credit Facility, Interest Rate During Period Stock Price or TSR Estimation Method Stock Price or TSR Estimation Method [Text Block] Entity Tax Identification Number Entity Tax Identification Number Plant related excess deferred taxes Effective Income Tax Rate Reconciliation, Plant Related Excess Deferred Taxes, Percent Effective Income Tax Rate Reconciliation, Plant Related Excess Deferred Taxes, Percent Cash, cash equivalents and restricted cash at beginning of period Cash, cash equivalents and restricted cash at end of period Cash, Cash Equivalent, Restricted Cash, and Restricted Cash Equivalent, Continuing Operation Accounts payable Increase (Decrease) in Accounts Payable Entity Incorporation, State or Country Code Entity Incorporation, State or Country Code Aggregate Erroneous Compensation Not Yet Determined Aggregate Erroneous Compensation Not Yet Determined [Text Block] Material Terms of Trading Arrangement Material Terms of Trading Arrangement [Text Block] Non-NEOs Non-NEOs [Member] Inventories Public Utilities, Inventory Vesting Date Fair Value of Equity Awards Granted and Vested in Covered Year Vesting Date Fair Value of Equity Awards Granted and Vested in Covered Year [Member] Management's Opinion Organization, Consolidation and Presentation of Financial Statements Disclosure [Text Block] Debt Instrument [Axis] Debt Instrument [Axis] Customer [Domain] Customer [Domain] Long-Term Debt, Type [Domain] Long-Term Debt, Type [Domain] Total current assets Assets, Current Statistical Measurement [Axis] Statistical Measurement [Axis] Insider Trading Arrangements [Line Items] Award Type Award Type [Axis] Named Executive Officers, Footnote Named Executive Officers, Footnote [Text Block] Accounts receivable, net Accounts receivable, net Accounts Receivable, after Allowance for Credit Loss, Current Retained earnings Retained Earnings (Accumulated Deficit) Short-Term Borrowings Schedule of Short-Term Debt [Table Text Block] Product and Service [Axis] Product and Service [Axis] Aggregate Change in Present Value of Accumulated Benefit for All Pension Plans Reported in Summary Compensation Table Aggregate Change in Present Value of Accumulated Benefit for All Pension Plans Reported in Summary Compensation Table [Member] Awards Close in Time to MNPI Disclosures Awards Close in Time to MNPI Disclosures [Table] Pension Plan [Member] Pension Plan [Member] Short-term Debt [Line Items] Short-Term Debt [Line Items] Common stock Common Stock [Member] Borrowings under utility money pool arrangement Borrowings Under Utility Money Pool Arrangement Borrowings made during the reporting period from the utility money pool borrowing arrangement among approved affiliates. Compensation Actually Paid vs. Company Selected Measure Compensation Actually Paid vs. Company Selected Measure [Text Block] Cover [Abstract] Cover [Abstract] Regulated Electric Regulated Electric [Member] The core operations of the regulated electric utility segment consists of the generation, transmission, and distribution of electricity. In addition, this segment includes sales for resale and provides wholesale transmission service to other entities. Weighted average interest rate at period end Short-Term Debt, Weighted Average Interest Rate, at Point in Time Equity Awards Adjustments Equity Awards Adjustments [Member] Total liabilities and equity Liabilities and Equity Employee Stock Option Share-Based Payment Arrangement, Option [Member] Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] Construction work in progress Public Utilities, Property, Plant and Equipment, Construction Work in Progress Segments [Axis] Segments [Axis] Additional 402(v) Disclosure Additional 402(v) Disclosure [Text Block] Related Party, Type [Domain] Related and Nonrelated Parties [Domain] Accounts Receivable, Net Schedule of Accounts, Notes, Loans and Financing Receivable [Table Text Block] Tabular List, Table Tabular List [Table Text Block] Other expense, net Other Nonoperating Income (Expense) Name Awards Close in Time to MNPI Disclosures, Individual Name Year-end Fair Value of Equity Awards Granted in Covered Year that are Outstanding and Unvested Year-end Fair Value of Equity Awards Granted in Covered Year that are Outstanding and Unvested [Member] Other assets Assets, Noncurrent [Abstract] Operating and maintenance expenses Utilities Operating Expense, Maintenance, Operations, and Other Costs and Expenses Property, Plant, and Equipment, after Accumulated Depreciation, Depletion, and Amortization [Abstract] Property, Plant, and Equipment, after Accumulated Depreciation, Depletion, and Amortization [Abstract] Natural gas Public Utilities, Inventory, Natural Gas [Member] Capital contributions from parent Contributions from (to) parent The cash inflow from (outflow to) parent as a source of financing that is recorded as additional paid in capital. Investments in utility money pool arrangement Investments In Utility Money Pool Arrangement Investments made during the reporting period into the utility money pool borrowing arrangement among approved affiliates. Adjustment to Compensation: Adjustment to Compensation [Axis] Rule 10b5-1 Arrangement Terminated Rule 10b5-1 Arrangement Terminated [Flag] Aggregate Erroneous Compensation Amount Aggregate Erroneous Compensation Amount Prepaid taxes Prepaid Taxes Cash paid for interest (net of amounts capitalized) Interest Paid, Excluding Capitalized Interest, Operating Activity Capital/construction expenditures Payments to Acquire Productive Assets Statement of Cash Flows [Abstract] Statement of Cash Flows [Abstract] Inventory [Line Items] Inventory [Line Items] Credit Facility [Axis] Credit Facility [Axis] Aggregate Available Trading Arrangement, Securities Aggregate Available Amount Long-term debt Long-Term Debt and Lease Obligation Number of identified MGP sites under current investigation and/or remediation Number of identified MGP sites under current investigation and/or remediation The number of sites where former manufactured gas plant (MGP) activities have or may have resulted in actual site contamination and are under current investigation and/or remediation. Maximum amount outstanding Short-Term Debt, Maximum Amount Outstanding During Period Name Measure Name Income Taxes Income Tax Disclosure [Text Block] Accrued unbilled revenues Increase (Decrease) in Accrued Unbilled Revenues Increase (Decrease) in Accrued Unbilled Revenues Accounts payable Accounts Payable, Current Pay vs Performance Disclosure [Line Items] Fair Value Hierarchy and NAV [Domain] Fair Value Hierarchy and NAV [Domain] Debt Instrument [Line Items] Debt Instrument [Line Items] Other current assets Increase (Decrease) in Other Current Assets Pay vs Performance Disclosure Pay vs Performance Disclosure [Table] Retirement Plan Type [Domain] Retirement Plan Type [Domain] Additional Paid In Capital Additional Paid-in Capital [Member] Entity Filer Category Entity Filer Category Alternative revenue and other Revenue Not from Contract with Customer Name Trading Arrangement, Individual Name Cash and cash equivalents Cash and Cash Equivalent Company Selected Measure Amount Company Selected Measure Amount AFUDC equity Effective Income Tax Rate Reconciliation, AFUDC Equity, Percent Effective Income Tax Rate Reconciliation, AFUDC Equity, Percent Accounts and Financing Receivables [Table] Accounts and Financing Receivables [Table] Current assets Assets, Current [Abstract] Non-PEO NEO Non-PEO NEO [Member] Interest charges and financing costs Interest and Debt Expense [Abstract] Entity Address, Address Line One Entity Address, Address Line One Income tax expense Income tax expense Income Tax Expense (Benefit) Other Effective Income Tax Rate Reconciliation, Other Regulatory Adjustments, Percent Effective Income Tax Rate Reconciliation, Other Regulatory Adjustments, Percent Award Timing Method Award Timing Method [Text Block] Loss Contingency, Nature [Domain] Loss Contingency, Nature [Domain] Net change in cash, cash equivalents and restricted cash Cash, Cash Equivalent, Restricted Cash, and Restricted Cash Equivalent, Period Increase (Decrease), Including Exchange Rate Effect and Discontinued Operation Forgone Recovery, Explanation of Impracticability Forgone Recovery, Explanation of Impracticability [Text Block] Fuel Public Utilities, Inventory, Fuel [Member] Amortization of net loss (a) Defined Benefit Plan, Amortization of Gain (Loss) Accounting Pronouncements Accounting Standards Update and Change in Accounting Principle [Text Block] Net income Net Income (Loss) Net Income (Loss) Attributable to Parent Long-Term Debt, Type [Axis] Long-Term Debt, Type [Axis] Erroneous Compensation Analysis Erroneous Compensation Analysis [Text Block] Statement [Table] Statement [Table] Environmental Remediation Site [Domain] Environmental Remediation Site [Domain] Restatement Determination Date: Restatement Determination Date [Axis] Regulatory liabilities Regulatory Liability, Current Public Utility, Property, Plant and Equipment [Line Items] Public Utility, Property, Plant and Equipment [Line Items] Total deferred credits and other liabilities Liabilities, Other than Long-Term Debt, Noncurrent Total operating revenues Regulated and Unregulated Operating Revenue Borrowings and Other Financing Instruments [Abstract] Debt Instruments [Abstract] Total other assets Other Assets, Excluding Property, Plant and Equipment Sum of the carrying amounts as of the balance sheet date of all assets, excluding net property, plant and equipment, that are expected to be realized in cash, sold or consumed after one year or beyond the normal operating cycle, if longer. Supplemental disclosure of non-cash investing and financing transactions: Other Noncash Investing and Financing Items [Abstract] Pension Benefits Adjustments, Footnote Pension Benefits Adjustments, Footnote [Text Block]