Trading Arrangements, by Individual Trading Arrangements, by Individual [Table] Proceeds — Proceeds — Proceeds [Abstract] Proceeds. Trading Arrangement: Trading Arrangement [Axis] Natural gas distribution revenues Natural Gas Distribution [Member] Natural Gas Distribution [Member] Maximum Maximum [Member] Title of 12(b) Security Title of 12(b) Security Subsequent Event Subsequent Event [Member] Property damage reserve Regulatory Clause, Property Damage Reserve Regulatory Clause, Property Damage Reserve McGrau Ford Phase 1 McGrau Ford Phase 1 [Member] McGrau Ford Phase 1 Derivative Instruments, Gain (Loss) [Table] Derivative Instruments, Gain (Loss) [Table] Adjustment to Compensation, Amount Adjustment to Compensation Amount Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items] Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items] Financial Instrument [Axis] Financial Instrument [Axis] Other investments Other Assets, Fair Value Disclosure Segment Reporting [Abstract] Segment Reporting [Abstract] Laurens County Laurens County [Member] Laurens County Approved capacity increase (in MWs) Public Utilities, Approved Additional Generating Capacity Public Utilities, Approved Additional Generating Capacity Retirement Benefits Retirement Benefits [Text Block] PPA energy revenues Wholesale Electric - PPA Energy Revenues [Member] Wholesale Electric - PPA Energy Revenues [Member] Contract Assets Contract assets Contract with Customer, Asset, after Allowance for Credit Loss Derivative Instrument [Axis] Derivative Instrument [Axis] Uncommited Letter Of Credit Facility Uncommited Letter Of Credit Facility [Member] Uncommited Letter Of Credit Facility U.S. Treasury and government agency securities US Treasury and Government [Member] Derivative Counterparties Derivative Counterparties [Member] Derivative Counterparties [Member] Nuclear decommissioning trust fund sales Proceeds from Decommissioning Trust Fund Assets Consolidated Entities [Axis] Consolidated Entities [Axis] Deferred credits related to income taxes Deferred Credits Related to Income Taxes Noncurrent regulatory liabilities associated with deferred income tax liabilities. Regulatory liabilities represent probable future reductions in revenues associated with amounts that are expected to be credited to customers through the ratemaking process. These revenues are not expected to be credited within one year or the normal operating cycle if longer. FFB loan Proceeds From Federal Financing Bank Loan Proceeds From Federal Financing Bank Loan Entity Common Stock, Shares Outstanding (in shares) Entity Common Stock, Shares Outstanding Rate CNP Compliance expenses Utilities Operating Expense, Rate CNP Expenses Utilities Operating Expense, Rate CNP Expenses Approximate nameplate capacity Approximate Nameplate Capacity Approximate Nameplate Capacity Accrued taxes — Taxes Payable, Current [Abstract] Allowance for equity funds used during construction Allowance for equity funds used during construction Allowance for equity funds used during construction Public Utilities, Allowance for Funds Used During Construction, Capitalized Cost of Equity Mortgage- and asset-backed securities Asset-Backed Securities [Member] Under recovered fuel clause revenues Under Recovered Fuel Clause Revenues, Receivables, Current Under Recovered Fuel Clause Revenues, Receivables, Current Distribution made to limited partner, cash distributions paid, percentage Distribution Made To Limited Partner, Cash Distributions Paid, Percentage Distribution Made To Limited Partner, Cash Distributions Paid, Percentage Series 2016B 1.850% Senior Notes due 2026 Series 2016B 1.850% Senior Notes Due 2026 [Member] Series 2016B 1.850% Senior Notes Due 2026 [Member] Other comprehensive income (loss): Other Comprehensive Income (Loss), Net of Tax [Abstract] Recovery period Regulatory Asset, Amortization Period Consolidated Entities [Domain] Consolidated Entities [Domain] Cost, Product and Service [Extensible Enumeration] Cost, Product and Service [Extensible Enumeration] Distributions to noncontrolling interests Payments to Noncontrolling Interests Schedule of Cash and Cash Equivalents Schedule of Cash and Cash Equivalents [Table Text Block] Common stock, par value (in dollars per share) Common Stock, Par or Stated Value Per Share Other intangible assets, net of amortization Other Intangible Assets, Net Intangible Asset, Excluding Goodwill, after Accumulated Amortization Plant in service, net of depreciation Public Utilities, Other Depreciable Property, Plant And Equipment, Plant In Service Public Utilities, Other Depreciable Property, Plant And Equipment, Plant In Service Retirement Benefits [Abstract] Retirement Benefits [Abstract] Outstanding Aggregate Erroneous Compensation Amount Outstanding Aggregate Erroneous Compensation Amount Twiggs County Twiggs County [Member] Twiggs County Number of reportable segments Number of Reportable Segments Total current liabilities Liabilities, Current Customer relationships Customer Relationships [Member] Accrued compensation Increase (Decrease) in Accrued Salaries Taxes other than income taxes Taxes, Miscellaneous Gas marketing services Other Natural Gas - Gas Marketing Services [Member] Other Natural Gas - Gas Marketing Services [Member] Schedule of Energy-Related Derivatives Schedule of Derivative Instruments [Table Text Block] Liabilities from risk management activities, net of collateral Derivative Liability, Current Entity Address, City or Town Entity Address, City or Town Date One Hedging Maturity Date One [Member] Hedging Maturity Date One [Member] Statement of Financial Position [Abstract] Statement of Financial Position [Abstract] Other Intangible Assets, Net Intangible Asset, Finite-Lived, after Accumulated Amortization Peer Group Total Shareholder Return Amount Peer Group Total Shareholder Return Amount Wake Wake Wind Facility [Member] Wake Wind Facility Significant Other Observable Inputs (Level 2) Fair Value, Inputs, Level 2 [Member] Other Income and (Expense): Nonoperating Income (Expense) [Abstract] Total Shareholder Return Vs Peer Group Total Shareholder Return Vs Peer Group [Text Block] Plant Yates Unit 10 Plant Yates Unit 10 [Member] Plant Yates Unit 10 Total other comprehensive income (loss) Other comprehensive income Other Comprehensive Income (Loss), Net of Tax Non-Rule 10b5-1 Arrangement Terminated Non-Rule 10b5-1 Arrangement Terminated [Flag] Number of shares authorized (in shares) Forward Contract Indexed to Issuer's Equity, Shares Non-PPA revenues Wholesale Electric - Non-PPA Revenues [Member] Wholesale Electric - Non-PPA Revenues [Member] Wadley Wadley [Member] Wadley Subsequent Event Type [Axis] Subsequent Event Type [Axis] Schedule of Long-term Debt Instruments [Table] Schedule of Long-Term Debt Instruments [Table] Contract term Contract with Customer, Length Of Term Contract with Customer, Length Of Term Schedule of Financial Data for Business Segments Segment Reporting [Table Text Block] Municipal bonds Municipal Bonds [Member] Related Party [Axis] Related and Nonrelated Parties [Axis] Total other comprehensive income (loss) Other comprehensive income (loss) Other comprehensive income Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent Wholesale revenues, affiliates Wholesale, Affiliates [Member] Wholesale, Affiliates [Member] Document Period End Date Document Period End Date Plant Yates, Phase 1 Plant Yates, Phase 1 [Member] Plant Yates, Phase 1 SEGCO Southern Electric Generating Company [Member] Southern Electric Generating Company [Member] Capital contributions from noncontrolling interests Proceeds from Noncontrolling Interests Position [Axis] Position [Axis] Natural Gas for Sale Natural Gas For Sale, Policy [Policy Text Block] Natural Gas For Sale, Policy [Policy Text Block] Equity Method Investment, Nonconsolidated Investee [Axis] Equity Method Investment, Nonconsolidated Investee [Axis] Forward Sale Contract 2 Forward Sale Contract 2 [Member] Forward Sale Contract 2 Amortization of ITCs Amortization of Deferred Investment Tax Credits Amortization of deferred investment tax credits. Entity Shell Company Entity Shell Company Consolidation Items [Domain] Consolidation Items [Domain] Retail Customer Fixed Bill Programs Retail Customer Fixed Bill Programs [Member] Retail Customer Fixed Bill Programs Revenue, Product and Service [Extensible Enumeration] Revenue, Product and Service [Extensible Enumeration] Operating lease obligations Operating lease obligations Operating Lease, Liability, Current Earnings per share - Earnings Per Share [Abstract] Document Fiscal Period Focus Document Fiscal Period Focus Utilization of federal tax credit carryforward Investment Tax Credit, Excluding Amortization Investment Tax Credit, Excluding Amortization Total lease income Lease Income Peer Group Issuers, Footnote Peer Group Issuers, Footnote [Text Block] Total Liabilities Liabilities Liabilities Trading Symbol Trading Symbol Investments, available-for-sale: Debt Securities, Available-for-Sale, Excluding Accrued Interest Property additions Payments to Acquire Property, Plant, and Equipment Other Other [Member] Other [Member] Schedule of Interest Rate Derivatives Schedule of Interest Rate Derivatives [Table Text Block] Approved affiliate PPAs Public Utilities, Approved Number of Affiliate Power Purchase Agreements Public Utilities, Approved Number of Affiliate Power Purchase Agreements Accrued income taxes Accrued Income Taxes, Current Series 2025A 6.50% Junior Subordinated Notes due 2085 Series 2025A 6.50% Junior Subordinated Notes Due 2085 [Member] Series 2025A 6.50% Junior Subordinated Notes Due 2085 Company Selected Measure Name Company Selected Measure Name Sale of Stock [Domain] Sale of Stock [Domain] Schedule of Restrictions on Cash and Cash Equivalents Restrictions on Cash and Cash Equivalents [Table Text Block] Income Tax Disclosure [Abstract] Income Tax Disclosure [Abstract] Energy-related derivatives Energy Related Derivative [Member] Schedule of Cost Recovery Clauses Cost Recovery Clauses [Table Text Block] [Table Text Block] for Cost Recovery Clauses [Table] Credit Facility [Domain] Credit Facility [Domain] Operating Activities: Cash Provided by (Used in) Operating Activity, Including Discontinued Operation [Abstract] Other accounts and notes Other accounts and notes Other Other Receivables, Net, Current Natural gas cost over recovery Increase (Decrease) Natural Gas Cost Over Recovery Short Term Increase (Decrease) Natural Gas Cost Over Recovery Short Term Public Utility [Axis] Public Utility [Axis] Cash dividends (in dollars per share) Common Stock, Dividends, Per Share, Cash Paid Equity Valuation Assumption Difference, Footnote Equity Valuation Assumption Difference, Footnote [Text Block] Line of Credit Facility [Table] Line of Credit Facility [Table] Gas Pipeline Investments Gas Pipeline Investments [Member] Gas Pipeline Investments [Member] Dalton Pipeline Dalton Pipeline [Member] Dalton Pipeline [Member] Forward Sale Contract 7 Forward Sale Contract 7 [Member] Forward Sale Contract 7 SOUTHERN POWER CO Southern Power [Member] Southern Power. GEORGIA POWER CO Georgia Power [Member] Georgia Power. Other Other Intangible Assets [Member] Award Timing Predetermined Award Timing Predetermined [Flag] Total property, plant, and equipment Public Utilities, Property, Plant and Equipment, Net Adjustment To PEO Compensation, Footnote Adjustment To PEO Compensation, Footnote [Text Block] Stock-based compensation APIC, Share-Based Payment Arrangement, Increase for Cost Recognition Quoted Prices in Active Markets for Identical Assets (Level 1) Fair Value, Inputs, Level 1 [Member] Liability for Unpaid Claims and Claims Adjustment Expense, Net Liability for Unpaid Claims and Claims Adjustment Expense, Net Effective tax (benefit) rate Effective Income Tax Rate Reconciliation, Percent Lessor, Lease, Description [Table] Lessor, Lease, Description [Table] ARO liabilities Asset Retirement Obligation, Liabilities Incurred Effect of stock-based compensation (in shares) Incremental Common Shares Attributable to Dilutive Effect of Share-Based Payment Arrangements Other Retail Electric - Other [Member] Retail Electric - Other [Member] Number of states in which entity operates Number of States in which Entity Operates Regulated Operations [Abstract] Regulated Operations [Abstract] Electric Utilities Traditional Electric Operating Companies and Southern Power [Member] Traditional Electric Operating Companies and Southern Power Benefit plan net gain (loss), net of tax Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss) Arising During Period, after Tax Environmental remediation liability, current and former sites Environmental Exit Costs, Assets Previously Disposed, Liability for Remediation Interest expense, net of amounts capitalized Interest expense, net of amounts capitalized Interest expense(d) Interest expense Interest and Debt Expense Scenario [Domain] Scenario [Domain] Moody Moody [Member] Moody Operating lease right-of-use assets, net of amortization Operating lease ROU assets, net Operating Lease, Right-of-Use Asset Energy-related derivatives designated as hedging instruments for regulatory purposes Hedging Instruments for Regulatory Purposes [Member] Hedging instruments for regulatory purposes. Nuclear decommissioning trust fund purchases Payments to Acquire Investments to be Held in Decommissioning Trust Fund Cash flow hedge gain (loss) to be reclassified within twelve months Interest Rate Cash Flow Hedge Gain (Loss) to be Reclassified During Next 12 Months, Net Fair Value Disclosures [Abstract] Fair Value Disclosures [Abstract] Approved rate increase (decrease) Public Utilities, Approved Rate Increase (Decrease), Percentage Securities due within one year Securities due within one year Long-Term Debt and Lease Obligation, Current Payment of common stock dividends Payments of Ordinary Dividends, Common Stock Expiration Date Trading Arrangement Expiration Date Hedging Relationship [Axis] Hedging Relationship [Axis] Restricted cash Restricted Cash and Cash Equivalent Cash equivalents Cash and Cash Equivalents, Fair Value Disclosure Total Stockholders' Equity Beginning balance Ending balance Total Stockholders' Equity (See accompanying statements) Equity, Including Portion Attributable to Noncontrolling Interest Nonrelated Party Nonrelated Party [Member] Other regulatory liabilities Other Regulatory Liabilities, Current The amount for other current regulatory liabilities not elsewhere included. Regulatory liabilities represent probable future reductions in revenues associated with amounts that are expected to be credited to customers through the ratemaking process. These revenues are expected to be credited within one year. SOUTHERN Co GAS Southern Company Gas [Member] Southern Company Gas [Member] Accumulated deferred ITCs Accumulated Deferred Investment Tax Credit Aggregate Pension Adjustments Service Cost Aggregate Pension Adjustments Service Cost [Member] Derivative [Table] Derivative [Table] Common stock Proceeds from issuance of common stock Proceeds from Issuance of Common Stock Schedule of Pre-tax Effects of Unrealized Derivative Gains (Losses) Pre tax effect of unrealized derivative gains losses [Table Text Block] Pre-tax effect of unrealized derivative gains (losses). Forward Sale Contract 6 Forward Sale Contract 6 [Member] Forward Sale Contract 6 Investing Activities: Cash Provided by (Used in) Investing Activity, Including Discontinued Operation [Abstract] Segments [Domain] Segments [Domain] Financing and Leases Debt Disclosure [Text Block] Scenario [Axis] Scenario [Axis] Business Combination [Table] Business Combination [Table] Acquisitions and Dispositions Mergers, Acquisitions and Dispositions Disclosures [Text Block] PEO Actually Paid Compensation Amount PEO Actually Paid Compensation Amount Business Combination, Asset Acquisition, Transaction between Entities under Common Control, and Joint Venture Formation [Abstract] Capital contributions from parent company Capital Contributions From (To) Parent Company Capital Contributions From (To) Parent Company Total operating expenses Costs and Expenses Interest rate Debt Instrument, Interest Rate, Stated Percentage Total common stockholders' equity Beginning balance Ending balance Equity, Attributable to Parent Cash dividends on common stock Cash dividends on common stock Dividends, Common Stock, Cash Assets Assets [Abstract] Southern Company parent Southern Company [Member] Southern Company [Member] Receive Rate Notional Amount Of Foreign Currency Derivatives, Receive Rate Notional Amount Of Foreign Currency Derivatives, Receive Rate Insider Trading Policies and Procedures [Line Items] Fossil fuel for generation Fossil fuel stock Energy Related Inventory, Other Fossil Fuel Accumulated provision for uncollectible accounts Accounts Receivable, Allowance for Credit Loss, Current Deferred income taxes Deferred income taxes Deferred Income Tax Expense (Benefit) Fuel cost recovery rate adjustment period Public Utilities, Rate Adjustment Period Public Utilities, Rate Adjustment Period MISSISSIPPI POWER CO Mississippi Power Mississippi Power [Member] Mississippi Power. Number of operating segments Number of Operating Segments Goodwill Goodwill [Table Text Block] Entity Central Index Key Entity Central Index Key Regulatory asset Amortization of Regulatory Asset 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] Settlement of asset retirement obligations Asset Retirement Obligation, Cash Paid to Settle Residential Natural Gas Distribution - Residential [Member] Natural Gas Distribution - Residential [Member] Contingencies Legal Matters and Contingencies [Text Block] Other Other Stockholders' Equity, Other Ownership [Axis] Ownership [Axis] Fair Value Hierarchy and NAV [Axis] Fair Value Hierarchy and NAV [Axis] Investment, Name [Axis] Investment, Name [Axis] Energy-related derivatives designated as hedging instruments for regulatory purposes Designated as Hedging Instrument [Member] Retail fuel cost under recovery Retail fuel cost under recovery Increase (Decrease) Retail Fuel Cost Under Recovery Short Term Increase (Decrease) Retail Fuel Cost Under Recovery Short Term Southern Company, Southern Power, And Mississippi Power Southern Company, Southern Power, And Mississippi Power [Member] Southern Company, Southern Power, And Mississippi Power Debt Instrument, Basis Spread on Variable Rate Debt Instrument, Basis Spread on Variable Rate Prepayment requirement, percentage of total advances made to borrower, minimum threshold Debt Instrument, Covenant, Prepayment Requirement, Percentage Of Total Advances Made To Borrower, Minimum Threshold Debt Instrument, Covenant, Prepayment Requirement, Percentage Of Total Advances Made To Borrower, Minimum Threshold Total other property and investments Other Property and Investments Other Property and Investments Accumulated Other Comprehensive Income (Loss) AOCI Attributable to Parent [Member] All Individuals All Individuals [Member] Regulatory Liability [Domain] Regulatory Liability [Domain] Statement [Line Items] Statement [Line Items] 2026 Line Of Credit Expire Year One Line Of Credit Expire Year One Total Assets Assets Total assets Assets Schedule of Defined Benefit Plans Disclosures [Table] Defined Benefit Plan [Table] Other natural gas revenues Other Natural Gas [Member] Other Natural Gas [Member] Private equity Private Equity Funds [Member] 2026 At The Market Program 2026 At The Market Program [Member] 2026 At The Market Program Reclassification adjustment for amounts included in net income, net of tax Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss), Reclassification Adjustment from AOCI, after Tax Equity Method Investment, Nonconsolidated Investee [Domain] Equity Method Investment, Nonconsolidated Investee [Domain] Natural gas cost under recovery Deferred Gas Cost Operating Segments Operating Segments [Member] Southern Holdings Company Southern Holdings Company [Member] Southern Holdings Company Reportable Segment Reportable Segment [Member] Reportable Segment PEO PEO [Member] Mandatory prepayment, percentage of principal to be prepaid Debt Instrument, Covenant, Mandatory Prepayment, Percentage Of Principal To Be Prepaid Debt Instrument, Covenant, Mandatory Prepayment, Percentage Of Principal To Be Prepaid Prepayments Increase (Decrease) in Prepaid Expense Weighted Average Interest Rate Paid Notional Amount of Interest Rate Derivatives Interest Rate Paid Notional amount of interest rate derivatives, interest rate paid. Other deferred credits and liabilities Other Liabilities, Noncurrent Noncontrolling interests related to other partners' interests Noncontrolling Interest in Variable Interest Entity Goodwill Goodwill Goodwill 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 Date Two Hedging Maturity Date Two [Member] Hedging Maturity Date Two [Member] Millers Branch Solar Development Phase 1 Millers Branch Solar Development Phase 1 [Member] Millers Branch Solar Development Phase 1 Retained Earnings Retained Earnings Retained Earnings [Member] Operating lease obligations, deferred Operating lease obligations Operating lease obligations, deferred Operating Lease, Liability, Noncurrent Valuation Methodologies Fair Value Measurement, Policy [Policy Text Block] Beginning balance (in shares) Ending balance (in shares) Common Stock, Shares, Outstanding Increase (Decrease) in Stockholders' Equity [Roll Forward] Increase (Decrease) in Stockholders' Equity [Roll Forward] Award Timing Disclosures [Line Items] Corporate bonds Corporate Debt Securities [Member] Diluted (in dollars per share) Earnings Per Share, Diluted Capital contributions from noncontrolling interests Noncontrolling Interest, Increase from Contributions from Noncontrolling Interest Holders Noncontrolling Interest, Increase from Contributions from Noncontrolling Interest Holders Hedging Maturity Date [Domain] Hedging Maturity Date [Domain] Hedging Maturity Date [Domain] Amortization of intangible assets Intangible Asset, Finite-Lived, Amortization Expense Millers Branch Solar Development Millers Branch Solar Development [Member] Millers Branch Solar Development Intangible Asset, Finite-Lived [Line Items] Intangible Asset, Finite-Lived [Line Items] Ownership [Domain] Ownership [Domain] Reliability Reserve Liability Reliability Reserve Liability [Member] Reliability Reserve Liability Hedging Maturity Date [Axis] Hedging Maturity Date [Axis] Hedging Maturity Date [Axis] Schedule of Pre-Tax Effects of Cash Flow and Fair Value Hedging on Income Schedule of Cash Flow Hedging Instruments, Statements of Financial Performance and Financial Position, Location [Table Text Block] Unused Line of Credit Facility, Remaining Borrowing Capacity Other long-term debt Repayments of Other Long-Term Debt Schedule of Equity Method Investments Equity Method Investments [Table Text Block] Equity Awards Adjustments, Footnote Equity Awards Adjustments, Footnote [Text Block] Gross Carrying Amount Intangible Asset, Excluding Goodwill, before Accumulated Amortization Prepaid pension costs Prepaid Pension Costs Prepaid Pension Costs Issuance of common stock under dividend reinvestment plan Stock Issued Schedule of Equity Method Investments [Table] Equity Method Investment [Table] Sale of Stock [Axis] Sale of Stock [Axis] Operating Income Operating Income (Loss) Revenue, remaining performance obligation Revenue, Remaining Performance Obligation, Amount Qualifying hedges: Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), after Reclassification and Tax [Abstract] Rule 10b5-1 Arrangement Adopted Rule 10b5-1 Arrangement Adopted [Flag] Service cost Defined Benefit Plan, Service Cost Fair Value Gain (Loss) Fair Value Gain (Loss) Fair Value Gain (Loss) Fair value gain (Loss). Restricted Cash and Cash Equivalent Item [Line Items] Restricted Cash and Cash Equivalent Item [Line Items] Revision of Prior Period, Adjustment Revision of Prior Period, Adjustment [Member] Deferred under recovered fuel clause revenues Deferred Costs, Noncurrent Product and Service [Domain] Product and Service [Domain] Disaggregation of Revenue [Table] Disaggregation of Revenue [Table] Materials and supplies Materials and supplies Other Inventory, Supplies, Gross Investing In Illinois Qualifying Infrastructure Plant Investing In Illinois Qualifying Infrastructure Plant [Member] Investing In Illinois Qualifying Infrastructure Plant Accumulated deferred income taxes Deferred Income Tax Liabilities, Net Compensation Actually Paid vs. Other Measure Compensation Actually Paid vs. Other Measure [Text Block] Derivative instruments not designated as hedging instruments, gain (loss), net Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net Continuing Letter of Credit Facility A Continuing Letter Of Credit Facility A [Member] Continuing Letter Of Credit Facility A Natural gas Natural Gas, US Regulated [Member] Termination Date Trading Arrangement Termination Date Net investment in sales-type leases Sales-Type Lease, Net Investment in Lease, after Allowance for Credit Loss, Noncurrent Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Table] Fair Value, Recurring and Nonrecurring [Table] Compensation Actually Paid vs. Total Shareholder Return Compensation Actually Paid vs. Total Shareholder Return [Text Block] Energy-related derivative contracts Energy Related Derivative Contracts for Registrants [Abstract] Energy-related derivative contracts for the registrants. Other current liabilities Other Liabilities, Current Fair Value as of Grant Date Award Grant Date Fair Value Operating Activities [Axis] Operating Activities [Axis] Unbilled revenues Unbilled Revenues Current Carrying amount at the balance sheet date of revenues which have been earned but not yet billed. Schedule of Goodwill [Table] Goodwill [Table] Franklin And Wansley Natural Gas Facilities Franklin And Wansley Natural Gas Facilities [Member] Franklin And Wansley Natural Gas Facilities Forward price (in dollars per share) Forward Contract Indexed to Issuer's Equity, Forward Rate Per Share Pay vs Performance Disclosure, Table Pay vs Performance [Table Text Block] Arrangement Duration Trading Arrangement Duration Consolidation Items [Axis] Consolidation Items [Axis] Entity Address, Postal Zip Code Entity Address, Postal Zip Code Entity Registrant Name Entity Registrant Name Unamortized loss on reacquired debt Unamortized Loss Reacquired Debt, Noncurrent Insider Trading Policies and Procedures Not Adopted Insider Trading Policies and Procedures Not Adopted [Text Block] Nameplate capacity placed in service Nameplate Capacity Placed In Service Nameplate Capacity Placed In Service Gross Carrying Amount Intangible Asset, Finite-Lived, before Accumulated Amortization Total operating revenues Total operating revenues Operating revenues Revenues Earnings from equity method investments Earnings from equity method investments Income (Loss) from Equity Method Investments Fair value Alternative Investment Forgone Recovery due to Expense of Enforcement, Amount Forgone Recovery due to Expense of Enforcement, Amount Intangible Asset, Finite-Lived, Class [Domain] Intangible Asset, Finite-Lived, Class [Domain] Trade names Trade Names [Member] Schedule of Assets and Liabilities Measured at Fair Value Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis [Table Text Block] All Award Types Award Type [Domain] Storm damage cost recovery – long-term Storm Damage Cost Recovery, Noncurrent Storm Damage Cost Recovery, Noncurrent Fair Value Option, Disclosures [Table] Fair Value Option, Disclosures [Table] Fair Value Measurements Fair Value Disclosures [Text Block] Significant Unobservable Inputs (Level 3) Fair Value, Inputs, Level 3 [Member] PPA fair value adjustments PPA Fair Value Adjustments [Member] PPA Fair Value Adjustments [Member] Plant Bowen, Phase 2 Plant Bowen, Phase 2 [Member] Plant Bowen, Phase 2 Other Variable Interest Entities Other Variable Interest Entities [Member] Other Variable Interest Entities [Member] Deferred Credits and Other Liabilities: Deferred Credits and Other Liabilities [Abstract] Contract Liabilities Contract liabilities Contract with Customer, Liability Net Asset Value as a Practical Expedient (NAV) Fair Value Measured at Net Asset Value Per Share [Member] Wind Facilities Wind Facilities [Member] Wind Facilities Rate RSE expenses Utilities Operating Expense, Rate RSE Expenses Utilities Operating Expense, Rate RSE Expenses Peter P. Sena III [Member] Peter P. Sena III Legal Entity [Axis] Legal Entity [Axis] Legal Entity [Axis] Minimum annual accrual, amount Public Utilities, Approved Rate Increase (Decrease), Minimum Annual Accrual, Amount Public Utilities, Approved Rate Increase (Decrease), Minimum Annual Accrual, Amount Cash, Cash Equivalents, and Restricted Cash at Beginning of Period Cash, Cash Equivalents, and Restricted Cash at End of Period Total cash, cash equivalents, and restricted cash Cash, Cash Equivalent, Restricted Cash, and Restricted Cash Equivalent, Continuing Operation Schedule of Finite-Lived Intangible Assets [Table] Intangible Asset, Finite-Lived [Table] Non-NEOs Non-NEOs [Member] Continuing Letter of Credit Facility B Continuing Letter Of Credit Facility B [Member] Continuing Letter Of Credit Facility B Plant Wansley Plant Wansley [Member] Plant Wansley Ownership percentage, equity method investment Equity Method Investment, Ownership Percentage Investment, Name [Domain] Investment, Name [Domain] Statistical Measurement [Axis] Statistical Measurement [Axis] Other Natural Gas Distribution - Other [Member] Natural Gas Distribution - Other [Member] Plant Bowen Unit 7 Plant Bowen Unit 7 [Member] Plant Bowen Unit 7 Schedule of Pre-Tax Effects of Hedging on AOCI Derivative Instruments, Gain (Loss) [Table Text Block] Award Type Award Type [Axis] Interest rate derivatives Interest Rate Contract [Member] Named Executive Officers, Footnote Named Executive Officers, Footnote [Text Block] Lease income - interest income on sales-type leases Sales-type Lease, Interest Income 2025 Series A Corporate Units 2025 Series A Corporate Units [Member] 2025 Series A Corporate Units Product and Service [Axis] Product and Service [Axis] Awards Close in Time to MNPI Disclosures Awards Close in Time to MNPI Disclosures [Table] Pension Plans Pension Plan [Member] Common Stock, par value $0.01 per share Common Stock Common Stock [Member] Schedule of Lease Income Operating Lease, Lease Income [Table Text Block] Plant Bowen Unit 8 Plant Bowen Unit 8 [Member] Plant Bowen Unit 8 Loss from extinguishment of debt, net of tax Extinguishment of Debt, Gain (Loss), Net of Tax Capital costs Public Utilities, Requested Recovery of Construction and Capital Costs Public Utilities, Requested Recovery of Construction and Capital Costs Energy-related derivative hedge gain (loss) to be reclassified within twelve months Energy-Related Derivative, Cash Flow Hedge Gain (Loss) to be Reclassified During Next 12 Months, Net Energy-Related Derivative, Cash Flow Hedge Gain (Loss) to be Reclassified During Next 12 Months, Net Unregulated Distributed Generation Unregulated Distributed Generation [Member] Unregulated Distributed Generation [Member] Derivative Contract [Domain] Derivative Contract [Domain] Grant Plains Grant Plains Facility [Member] Grant Plains Facility Public Utilities General Disclosures [Table] Public Utilities General Disclosures [Table] Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items] Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items] Total Liabilities and Stockholders' Equity Liabilities and Equity Intangible assets, net of amortization Intangible Asset, Including Goodwill, after Accumulated Amortization Accrued compensation Accrued Salaries, Current Employee Stock Option Share-Based Payment Arrangement, Option [Member] Asset retirement obligations Asset Retirement Obligation, Current Segments [Axis] Segments [Axis] Additional 402(v) Disclosure Additional 402(v) Disclosure [Text Block] Schedule of Cumulative Basis Adjustments for Fair Value Hedges Schedule of Fair Value Hedging Instruments, Statements of Financial Performance and Financial Position, Location [Table Text Block] Related Party [Domain] Related and Nonrelated Parties [Domain] Tabular List, Table Tabular List [Table Text Block] Wholesale electric revenues Wholesale Electric Revenues [Member] Wholesale Electric Revenues [Member] Mandatory prepayment, payable period Debt Instrument, Covenant, Mandatory Prepayment, Payable Period Debt Instrument, Covenant, Mandatory Prepayment, Payable Period Millers Branch Solar Development Phase 3 Millers Branch Solar Development Phase 3 [Member] Millers Branch Solar Development Phase 3 Schedule of Construction Projects Schedule of Construction Projects [Table Text Block] [Table Text Block] for Schedule of Construction Projects [Table] Effect of convertible senior notes (in shares) Incremental Common Shares Attributable to Dilutive Effect of Conversion of Debt Securities 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] Construction costs incurred to date Construction Costs Incurred To Date Construction Costs Incurred To Date Joint owner accounts Joint Owner Accounts Receivable Amounts due from joint owners related to jointly-owned assets within one year of the balance sheet date. Property, Plant, and Equipment: Property, Plant, and Equipment, after Accumulated Depreciation, Depletion, and Amortization [Abstract] Customer refunds Increase (Decrease) In Customer Refunds Increase (Decrease) In Customer Refunds Energy-related, Natural Gas Public Utilities, Inventory, Natural Gas [Member] Adjustment to Compensation: Adjustment to Compensation [Axis] Gas marketing services Gas Marketing Services [Member] Gas Marketing Services [Member] Natural gas cost over recovery Natural Gas Cost Over Recovery Short Term Natural Gas Cost Over Recovery Short Term Rule 10b5-1 Arrangement Terminated Rule 10b5-1 Arrangement Terminated [Flag] Aggregate Erroneous Compensation Amount Aggregate Erroneous Compensation Amount Prepaid income taxes Prepaid Taxes Interest, net of amounts capitalized Interest Interest Paid, Excluding Capitalized Interest, Operating Activity Hedging Designation [Axis] Hedging Designation [Axis] Other regulatory assets, deferred Other Regulatory Assets Deferred Carrying amount of other regulatory assets (not elsewhere identified) as of the balance sheet date of capitalized costs of regulated entities that are not expected to be recovered through revenue sources within one year or the normal operating cycle if longer. Variable rate pollution control revenue bonds outstanding Amount of Variable Rate Pollution Control Revenue Bonds Outstanding Requiring Liquidity Support Amount of variable rate pollution control revenue bonds outstanding requiring liquidity support. 2024 At The Market Program 2024 At The Market Program [Member] 2024 At The Market Program Credit Facility [Axis] Credit Facility [Axis] Total Assets, Fair Value Disclosure Wholesale MRA Wholesale MRA [Member] Wholesale MRA Long-term Debt Long-Term Debt and Lease Obligation Name Measure Name Pay vs Performance Disclosure [Line Items] Fair Value, Measurements, Fair Value Hierarchy [Domain] Fair Value Hierarchy and NAV [Domain] Debt Instrument [Line Items] Debt Instrument [Line Items] McGrau Ford Phase 2 McGrau Ford Phase 2 [Member] McGrau Ford Phase 2 Paid-In Capital Additional Paid-in Capital [Member] Reliability reserve expense Reliability Reserve, Reliability-Related Transmission, Distribution, And Generation Expenses Reliability Reserve, Reliability-Related Transmission, Distribution, And Generation Expenses Other revenues Revenue Not from Contract with Customer Name Trading Arrangement, Individual Name Other Other Liabilities, Fair Value Disclosure Cash and cash equivalents Cash and Cash Equivalent Position [Domain] Position [Domain] Millers Branch Solar Development Phase 2 Millers Branch Solar Development Phase 2 [Member] Millers Branch Solar Development Phase 2 Requested revenues increase (decrease) percentage Public Utilities, Requested Rate Increase (Decrease), Percentage Remaining net book value Net Regulatory Assets Company Selected Measure Amount Company Selected Measure Amount Date Three Hedging Maturity Date Three [Member] Hedging Maturity Date Three Plant Yates Unit 8 Plant Yates Unit 8 [Member] Plant Yates Unit 8 Right-of-use assets obtained under finance leases Right-of-Use Asset Obtained in Exchange for Finance Lease Liability Non-PEO NEO Non-PEO NEO [Member] Second PPA Second PPA [Member] Second PPA Sale of investment tax credit Proceeds From Tax Credit Transfer Proceeds From Tax Credit Transfer Non-qualified deferred compensation trusts Non-Qualified Deferred Compensation Trusts, Fair Value Disclosure Non-Qualified Deferred Compensation Trusts, Fair Value Disclosure Total cost of sales Fuel and purchased power Cost of Product and Service Sold Award Timing Method Award Timing Method [Text Block] 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 Short-term borrowings Repayments of Other Short-Term Debt Other revenues Product and Service, Other [Member] Scenario, Forecast Forecast [Member] Forgone Recovery, Explanation of Impracticability Forgone Recovery, Explanation of Impracticability [Text Block] Notional Amount Derivative Liability, Notional Amount Net (gain) loss Defined Benefit Plan, Amortization of Gain (Loss) Consolidated Net Income Attributable to Southern Company Net income Net income Net Income (Loss) Attributable to Parent Erroneous Compensation Analysis Erroneous Compensation Analysis [Text Block] Plant Yates Unit 9 Plant Yates Unit 9 [Member] Plant Yates Unit 9 Balance Sheet Location [Axis] Location, Statement of Financial Position, Balance [Axis] Restatement Determination Date: Restatement Determination Date [Axis] Increase in notes payable, net Proceeds from Notes Payable Bethel Wind Facility Bethel Wind Facility [Member] Bethel Wind Facility Wholesale revenues, non-affiliates Wholesale, Non-Affiliates [Member] Wholesale, Non-Affiliates [Member] Receivables — Receivables, Net, Current [Abstract] Receivables Increase (Decrease) in Receivables Schedule of Asset Retirement Obligation [Line Items] Schedule of Asset Retirement Obligation [Line Items] [Line Items] for Schedule of Asset Retirement Obligation [Table] Gas distribution operations Gas Distribution Operations [Member] Gas Distribution Operations [Member] Natural gas for sale Energy Related Inventory, Natural Gas in Storage Return of capital to parent company Return Of Paid In Capital Return Of Paid In Capital Operating Revenues: Revenues [Abstract] Collateral already posted, assets, aggregate fair value Collateral Already Posted, Aggregate Fair Value Pension Benefits Adjustments, Footnote Pension Benefits Adjustments, Footnote [Text Block] Series 2017A 5.00% Junior Subordinated Notes due 2077 Series 2017A 5.00% Junior Subordinated Notes Due 2077 [Member] Series 2017A 5.00% Junior Subordinated Notes Due 2077 [Member] Long-term debt, including securities due within one year: Long-Term Debt, Unclassified [Abstract] Average number of shares of common stock outstanding — (in millions) Weighted Average Number of Shares Outstanding, Diluted [Abstract] Statistical Measurement [Domain] Statistical Measurement [Domain] Less: Accumulated depreciation Less: Accumulated depreciation Public Utilities, Property, Plant and Equipment, Accumulated Depreciation Forward Contract Indexed to Issuer's Equity, Type [Axis] Forward Contract Indexed to Issuer's Equity, Type [Axis] Document Fiscal Year Focus Document Fiscal Year Focus Gross amounts offset Derivative Liability, Subject to Master Netting Arrangement, Asset Offset Performance obligation, expected timing of satisfaction Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period 2031 Line Of Credit Expire Year Five Line Of Credit Expire Year Five Depreciation and amortization, total Depreciation, Amortization and Accretion, Net Registrants Registrants [Member] Registrants [Member] Public Utilities, General Disclosures [Line Items] Public Utilities, General Disclosures [Line Items] Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis] Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis] Nuclear fuel, at amortized cost Public Utilities, Property, Plant and Equipment, Fuel Forward Sale Contract 4 Forward Sale Contract 4 [Member] Forward Sale Contract 4 Restatement Determination Date Restatement Determination Date Expected return on plan assets Defined Benefit Plan, Expected Return (Loss) on Plan Assets Total energy-related derivative gains (losses) Regulatory Hedge Unrealized Gain Loss Regulatory hedge unrealized gain (loss). Series 2021B 1.875% Fixed-to-Fixed Reset Rate Junior Subordinated Notes due 2081 Series 2021B 1.875% Fixed-To-Fixed Reset Rate Junior Subordinated Notes Due 2081 [Member] Series 2021B 1.875% Fixed-To-Fixed Reset Rate Junior Subordinated Notes Due 2081 Mississippi PSC SRR Filing Mississippi PSC SRR Filing [Member] Mississippi PSC SRR Filing Not subject to amortization: Intangible Asset, Excluding Goodwill, Indefinite-Lived [Abstract] Regulatory assets – asset retirement obligations, deferred Regulatory assets – asset retirement obligations Regulatory Asset, Asset Retirement Obligation Regulatory Asset, Asset Retirement Obligation Other Property and Investments: Long-Term Investments [Abstract] Amendment Flag Amendment Flag Series 2017B 5.25% Junior Subordinated Notes due 2077 Series 2017B 5.25% Junior Subordinated Notes Due 2077 [Member] Series 2017B 5.25% Junior Subordinated Notes Due 2077 [Member] Goodwill [Line Items] Goodwill [Line Items] Current Liabilities: Liabilities, Current [Abstract] Forward Sale Contract 11 Forward Sale Contract 11 [Member] Forward Sale Contract 11 Program [Domain] Program [Domain] [Domain] for Program [Axis] Deferred Income Taxes, Excess Accumulated Amount, Period Deferred Income Taxes, Excess Accumulated Amount, Period Deferred Income Taxes, Excess Accumulated Amount, Period Loss Contingencies [Table] Loss Contingencies [Table] Mississippi PSC Mississippi PSC [Member] Mississippi PSC Affiliated and Other Accounts Payable, Other, Current Other electric revenues Other Electric Revenue [Member] Other electric revenue. Adjustment to Non-PEO NEO Compensation Footnote Adjustment to Non-PEO NEO Compensation Footnote [Text Block] Payments pursuant to LTSAs Prepaid Long-Term Service Agreement Prepaid Long-Term Service Agreement Entity Address, State or Province Entity Address, State or Province Regulatory Matters Public Utilities Disclosure [Text Block] PEO Total Compensation Amount PEO Total Compensation Amount Assets: Assets, Fair Value Disclosure [Abstract] Capital expenditures Segment Reporting, Long-Lived Asset, Expenditure for Addition Income Tax Contingency [Line Items] Income Tax Contingency [Line Items] Basic (in shares) As reported shares (in shares) Weighted Average Number of Shares Outstanding, Basic Environmental compliance expenses Utilities Environmental Compliance Expenses, ECO Plan and MRA Tariff Utilities Environmental Compliance Expenses, ECO Plan and MRA Tariff Fair Value, by Balance Sheet Grouping [Table] Fair Value, by Balance Sheet Grouping [Table] Loss Contingencies [Line Items] Loss Contingencies [Line Items] Regulatory Liability [Axis] Regulatory Liability [Axis] Total revenue from contracts with customers Operating revenues Revenue from Contract with Customer, Including Assessed Tax Long-term debt Proceeds from Issuance of Long-Term Debt and Capital Securities, Net Benefit plan net gain (loss), tax Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss) Arising During Period, Tax Defined Benefit Plan Disclosure [Line Items] Defined Benefit Plan Disclosure [Line Items] Document Information [Line Items] Document Information [Line Items] Award Timing MNPI Disclosure Award Timing MNPI Disclosure [Text Block] Basis of Accounting Basis of Accounting, Policy [Policy Text Block] Class of Stock [Axis] Class of Stock [Axis] Other Other than Securities Investment [Member] Other intangible assets, amortization Accumulated Amortization Accumulated Amortization Intangible Asset, Finite-Lived, Accumulated Amortization Total Line of credit facility, maximum borrowing capacity Line of Credit Facility, Maximum Borrowing Capacity Schedule of Financial Instruments for which Carrying Amount Did Not Equal Fair Value Financial Instruments Not Having Carrying Amount Equal to Fair Value [Table Text Block] Financial instruments not having carrying amount equal to fair value. Accrued property additions at end of period Capital Expenditures Incurred but Not yet Paid Noncontrolling Interests Noncontrolling Interest [Member] Changes in fair value, tax Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), before Reclassification, Tax Derivative nonmonetary notional amount net long short position volume Derivative Nonmonetary Notional Amount Net Long Short Position Volume Derivative Nonmonetary Notional Amount Net Long Short Position Volume Consolidated Entities and Equity Method Investments Noncontrolling Interest Disclosure [Text Block] Changes in certain current 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 for 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] Grant Grant Wind Facility [Member] Grant Wind Facility Regulatory asset balance related to storm damage Regulatory Asset Carrying Amount of the Hedged Item Derivative, Amount of Hedged Item Operating Expenses: Costs and Expenses [Abstract] Security Exchange Name Security Exchange Name Payment for PTCs Expenditures For Purchased Tax Credits Expenditures For Purchased Tax Credits Total Liabilities, Fair Value Disclosure Plant Barry Unit 5 Plant Barry Unit 5 [Member] Plant Barry Unit 5 Accrued interest Interest Payable, Current Natural gas for sale, net of temporary LIFO liquidation Increase (Decrease) in Energy Related Inventory, Natural Gas in Storage Increase (Decrease) in Energy Related Inventory, Natural Gas in Storage Finance lease ROU assets, net Finance Lease, Right-of-Use Asset, after Accumulated Amortization Statement of Comprehensive Income [Abstract] Statement of Comprehensive Income [Abstract] Name Outstanding Recovery, Individual Name Award Timing, How MNPI Considered Award Timing, How MNPI Considered [Text Block] Other revenues Other Revenues [Member] Other Revenues [Member] Prepaid LTSAs Prepaid Long Term Service Agreements Prepaid long-term service agreements. Pay Rate Notional Amount Of Foreign Currency Derivatives, Pay Rate Notional Amount Of Foreign Currency Derivatives, Pay Rate FCC licenses Intangible Asset, Excluding Goodwill, Indefinite-Lived Purchased power, affiliates Electricity, Purchased, Affiliates [Member] Electricity, Purchased, Affiliates [Member] 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] Approved rate increase (decrease) Public Utilities, Approved Rate Increase (Decrease), Amount Wholesale fuel cost over recovery Increase (Decrease) In Over Recovered Regulatory Clause Revenues Increase (Decrease) In Over Recovered Regulatory Clause Revenues Fuel and purchased power Fuel And Purchased Power [Member] Fuel And Purchased Power Pension, postretirement, and other employee benefits Pension, postretirement, and other employee benefits Pension and Other Postretirement Benefits Cost (Reversal of Cost) Miscellaneous property and investments Other Long-Term Investments Noncash transactions — Noncash Investing and Financing Items [Abstract] Commercial Natural Gas Distribution - Commercial [Member] Natural Gas Distribution - Commercial [Member] Deferred charges related to income taxes Deferred Charges Related to Income Taxes Noncurrent regulatory assets associated with deferred income tax liabilities that are expected to be recovered from customers through the ratemaking process. Carrying amount Long-Term Debt, Gross Amortization: Defined Benefit Plan, Net Periodic Benefit Cost, Amortization [Abstract] Defined Benefit Plan, Net Periodic Benefit Cost, Amortization [Abstract] First PPA First PPA [Member] First PPA Compensation Amount Outstanding Recovery Compensation Amount Individual: Individual [Axis] Diluted (in shares) Diluted (in shares) Weighted Average Number of Shares Outstanding, Diluted Disaggregation of Revenue [Line Items] Disaggregation of Revenue [Line Items] Schedule of Shares Used to Compute Diluted Earnings Per Share Earning Per Share Table Text Block [Table Text Block] Calculation of diluted shares used to determined diluted earnings per share. Entity Emerging Growth Company Entity Emerging Growth Company Employee benefit obligations Liability, Defined Benefit Plan, Noncurrent Derivatives Derivatives, Policy [Policy Text Block] Underlying Security Market Price Change Underlying Security Market Price Change, Percent Proceeds from Lines of Credit Proceeds from Lines of Credit Derivatives Derivative Instruments and Hedging Activities Disclosure [Text Block] Cost of removal, net of salvage Cost of removal, net of salvage Payments for Removal Costs Regulatory Asset [Axis] Regulatory Asset [Axis] Notes payable Notes payable Short-Term Debt Derivatives Derivative liability, gross amount recognized Derivative Liability, Subject to Master Netting Arrangement, before Offset Revenue from Contract with Customer [Abstract] Revenue from Contract with Customer [Abstract] Treasury Treasury Stock, Common [Member] Letters of credit outstanding Letters of Credit Outstanding, Amount Depreciation and amortization Depreciation and amortization(b) Depreciation and Amortization Excluding Nuclear Fuel The current period expense charged against earnings on long-lived, physical assets used in the normal conduct of business and not intended for resale to allocate or recognize the cost of assets over their useful lives; or to record the reduction in book value of an intangible asset over the benefit period of such asset. Excludes amortization of nuclear fuel. Variable lease income Variable Lease, Income Contributions in aid of construction Proceeds from Contribution in Aid of Construction, Investing Activity Organization, Consolidation and Presentation of Financial Statements [Abstract] Organization, Consolidation and Presentation of Financial Statements [Abstract] Plant Bowen, Phase 1 Plant Bowen, Phase 1 [Member] Plant Bowen, Phase 1 Schedule of Increase (Decrease) In Fair Value Of Funds Schedule Of Increase (Decrease) In Fair Value Of Funds Including Reinvested Interest And Dividends [Table Text Block] Schedule Of Increase (Decrease) In Fair Value Of Funds Including Reinvested Interest And Dividends [Table Text Block] FFB loan Repayments Of Federal Financing Bank Loan Repayments Of Federal Financing Bank Loan All Executive Categories All Executive Categories [Member] Pension Adjustments Service Cost Pension Adjustments Service Cost [Member] Schedule of Pension Plans and Postretirement Plans Schedule of Net Benefit Costs [Table Text Block] Pension and other postretirement benefit plans: Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, after Tax [Abstract] Income taxes receivable Increase (Decrease) in Income Taxes Receivable Debt Disclosure [Abstract] Debt Disclosure [Abstract] Segment and Related Information Segment Reporting [Text Block] Minimum Minimum [Member] Fossil fuel stock Increase (Decrease) in Fossil Fuel Inventories Other regulatory assets Other Regulatory Assets Current Carrying amount of other regulatory assets (not elsewhere included) as of the balance sheet date of capitalized costs of regulated entities that are expected to be recovered through revenue sources within one year or the normal operating cycle, if longer. Such costs are capitalized if they meet both of the following criteria: a. It is probable that future revenue in an amount at least equal to the capitalized cost will result from inclusion of that cost in allowable costs for rate-making purposes. b. Based on available evidence, the future revenue will be provided to permit recovery of the previously incurred cost rather than to provide for expected levels of similar future costs. If the revenue will be provided through an automatic rate-adjustment clause, this criterion requires that the regulator's intent clearly be to permit recovery of the previously incurred cost. Unfunded commitments Fair Value, Investments, Entities that Calculate Net Asset Value Per Share, Unfunded Commitments Schedule of Disaggregation of Revenue Disaggregation of Revenue [Table Text Block] Schedule of Amortization of Other Intangible Assets Intangible Asset, Finite-Lived, Amortization Expense [Table Text Block] Income Statement Location [Axis] Location, Statement of Income, Balance [Axis] Non-Rule 10b5-1 Arrangement Adopted Non-Rule 10b5-1 Arrangement Adopted [Flag] Goodwill Goodwill and Intangible Assets, Goodwill, Policy [Policy Text Block] Public Utilities, Regulatory Proceeding [Domain] Public Utilities, Regulatory Proceeding [Domain] 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] Series 2020A 4.95% Junior Subordinated Notes due 2080 Series 2020A 4.95% Junior Subordinated Notes Due 2080 [Member] Series 2020A 4.95% Junior Subordinated Notes Due 2080 [Member] Increase (decrease) in notes payable, net Repayments of Notes Payable Series 2020C 4.20% Junior Subordinated Notes due 2060 Series 2020C 4.20% Junior Subordinated Notes Due 2060 [Member] Series 2020C 4.20% Junior Subordinated Notes Due 2060 Rate ECR Retail Energy Cost Recovery Retail Energy Cost Recovery Business Combination [Line Items] Business Combination [Line Items] Requested rate increase amount Public Utilities, Requested Rate Increase (Decrease), Amount Net periodic pension income Defined Benefit Plan, Net Periodic Benefit Cost (Credit) Pooled funds – fixed income Fixed Income Funds [Member] Common stock issued to settle purchase contracts (in shares) Sale of Stock, Number of Shares Issued in Transaction Exercise Price Award Exercise Price Schedule of Equity Method Investments [Line Items] Schedule of Equity Method Investments [Line Items] Segment Reporting [Line Items] Segment Reporting [Line Items] Natural Gas Natural Gas [Member] Natural Gas 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] Accounts Receivable Accounts Receivable, after Allowance for Credit Loss Storm damage reserves Liability for Unpaid Claims and Claims Adjustment Expense, Period Increase (Decrease) Operating Activities [Domain] Operating Activities [Domain] Restricted Cash and Cash Equivalents [Axis] Restricted Cash and Cash Equivalents [Axis] Awards Close in Time to MNPI Disclosures, Table Awards Close in Time to MNPI Disclosures [Table Text Block] Equity investments in unconsolidated subsidiaries Investment Balance Equity Method Investments Equity Component [Domain] Equity Component [Domain] Prepaid pension and other postretirement benefit costs Prepaid Pension and Other Postretirement Benefit Costs Prepaid Pension and Other Postretirement Benefit Costs Foreign currency derivatives Foreign currency derivatives Foreign Exchange Contract [Member] Customer accounts Customer accounts and affiliated Customer accounts, net and Affiliated Accounts Receivable, before Allowance for Credit Loss, Current Adoption Date Trading Arrangement Adoption Date Counterparty Name [Domain] Counterparty Name [Domain] Total other income and (expense) Nonoperating Income (Expense) Accrued taxes Increase (Decrease) in Accrued Taxes Payable Short-term borrowings Proceeds from Other Short-Term Debt Forward Sale Contract 8 Forward Sale Contract 8 [Member] Forward Sale Contract 8 Title Trading Arrangement, Individual Title Forgone Recovery due to Disqualification of Tax Benefits, Amount Forgone Recovery due to Disqualification of Tax Benefits, Amount Return of capital to parent company Payments of Capital Distribution Restatement does not require Recovery Restatement Does Not Require Recovery [Text Block] Forward Contract Indexed to Issuer's Equity, Type [Domain] Forward Contract Indexed to Issuer's Equity, Type [Domain] Other financing activities Other financing activities Proceeds from (Payment for) Other Financing Activity Insider Trading Policies and Procedures Adopted Insider Trading Policies and Procedures Adopted [Flag] At The Market Program At The Market Program [Member] At The Market Program Generating capacity petitioned for decertification (at least) Public Utilities, Generating Capacity Petitioned For Decertification Public Utilities, Generating Capacity Petitioned For Decertification Increase (decrease) in fair value of funds Increase (Decrease) in Fair Value of Funds Including Reinvested Interest and Dividends Increase (decrease) in fair value of funds including reinvested interest and dividends. Schedule of Credit Arrangements Schedule of Line of Credit Facilities [Table Text Block] Derivative Instruments, Gain (Loss) [Line Items] Derivative Instruments, Gain (Loss) [Line Items] Other revenue sources Other Revenue Sources [Member] Other Revenue Sources [Member] Business Combination [Domain] Business Combination [Domain] Compensation Actually Paid vs. Net Income Compensation Actually Paid vs. Net Income [Text Block] Construction work in progress Construction in Progress, Gross 2029 Line Of Credit Expire Year Four Line Of Credit Expire Year Four Lease income - operating leases Operating Lease, Lease Income Pension Plans and Postretirement Plans Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract] All Adjustments to Compensation All Adjustments to Compensation [Member] All Other Segment Reporting, Reconciling Item, Corporate Nonsegment [Member] Business Combination [Axis] Business Combination [Axis] Return of capital to parent company Capital Distribution, Noncash Capital Distribution, Noncash Net cash provided from operating activities Cash Provided by (Used in) Operating Activity, Including Discontinued Operation Property Damage Reserve Asset Property Damage Reserve Asset [Member] Property Damage Reserve Asset 2028 Line Of Credit Expire Year Two Line Of Credit Expire Year Two Income Statement [Abstract] Income Statement [Abstract] Document Transition Report Document Transition Report Fair Value, Option, Quantitative Disclosures [Line Items] Fair Value, Option, Quantitative Disclosures [Line Items] Plant Wansley Unit 11 Plant Wansley Unit 11 [Member] Plant Wansley Unit 11 Accumulated deferred income taxes Deferred Income Tax Assets, Net Eliminations Intersegment Eliminations [Member] Stock Appreciation Rights (SARs) Stock Appreciation Rights (SARs) [Member] Schedule of Other Intangible Assets, Finite-Lived Intangible Asset, Finite-Lived [Table Text Block] Derivatives designated as hedging instruments in cash flow and fair value hedges Cash Flow and Fair Value Hedging [Member] Cash flow and fair value hedging. Lessor, Lease, Description [Line Items] Lessor, Lease, Description [Line Items] Plant Mitchell Plant Mitchell [Member] Plant Mitchell City Area Code City Area Code Forward Sale Contract 9 Forward Sale Contract 9 [Member] Forward Sale Contract 9 Alternative revenue programs Alternative Energy [Member] Document Information [Table] Document Information [Table] Fair value Debt Instrument, Fair Value Disclosure Name Forgone Recovery, Individual Name Non-GAAP Measure Description Non-GAAP Measure Description [Text Block] Additional capacity Addition To Approximate Nameplate Capacity Addition To Approximate Nameplate Capacity Entity (No default) [Domain] Entity (No default) [Domain] Entity [Domain] Collateral For Life Insurance And Long-Term Disability Insurance Collateral For Life Insurance And Long-Term Disability Insurance [Member] Collateral For Life Insurance And Long-Term Disability Insurance Plant Wansley Unit 10 Plant Wansley Unit 10 [Member] Plant Wansley Unit 10 Retail electric revenues Retail revenues Retail [Member] Prior service costs Defined Benefit Plan, Amortization of Prior Service Cost (Credit) Depreciation before tax Depreciation, Accelerated, Before Tax Depreciation, Accelerated, Before Tax ALABAMA POWER CO Alabama Power Alabama Power [Member] Alabama Power. Other current assets Increase (Decrease) in Other Operating Assets Domestic equity Domestic Equity [Member] Domestic equity. Stock issued (in shares) Stock Issued During Period, Shares, New Issues Cash and Cash Equivalents [Domain] Cash and Cash Equivalents [Domain] Other accrued taxes Accrual for Taxes Other than Income Taxes, Current Commercial Retail Electric - Commercial [Member] Retail Electric - Commercial [Member] Gross amounts offset Derivative Asset, Subject to Master Netting Arrangement, Liability Offset 2028 Line Of Credit Expire Year Three Line Of Credit Expire Year Three Utility operations and maintenance Utilities Operating Expense, Maintenance and Operations [Abstract] Regulatory assets – asset retirement obligations Regulatory assets – asset retirement obligations Regulatory Asset, Asset Retirement Obligation, Current Regulatory Asset, Asset Retirement Obligation, Current Revenue from contracts with customers recognized Contract with Customer, Liability, Revenue Recognized Robins Robins [Member] Robins Subsequent Event Type [Domain] Subsequent Event Type [Domain] Total other intangible assets Intangible Asset, Excluding Goodwill, after Accumulated Amortization [Abstract] Accrued taxes Taxes Payable, Current Revision of Prior Period [Domain] Revision of Prior Period [Domain] Alabama Property Company Alabama Property Company [Member] Alabama Property Company Under recovered retail fuel clause revenues Deferred Fuel Cost Erroneously Awarded Compensation Recovery Erroneously Awarded Compensation Recovery [Table] Mississippi PSC PEP Filing Mississippi PSC PEP Filing [Member] Mississippi PSC PEP Filing Entity Current Reporting Status Entity Current Reporting Status Net cash provided from financing activities Cash Provided by (Used in) Financing Activity, Including Discontinued Operation Total Shareholder Return Amount Total Shareholder Return Amount Cash Flow Hedging Cash Flow Hedging [Member] Liabilities: Liabilities, Fair Value Disclosure [Abstract] Fuel Fuel [Member] Interest Rate Received Notional Amount of Interest Rate Derivatives Interest Rate Received Notional amount of interest rate derivatives, interest rate received. Line of Credit Facility [Line Items] Line of Credit Facility [Line Items] Other operations and maintenance Total utility operations and maintenance Utilities Operating Expense, Maintenance and Operations Adjustments to reconcile net income to net cash provided from operating activities — Adjustment to Reconcile Net Income to Cash Provided by (Used in) Operating Activity [Abstract] Schedule of Forward Contracts Indexed to Issuer's Equity Schedule of Forward Contracts Indexed to Issuer's Equity [Table Text Block] Financing Activities: Cash Provided by (Used in) Financing Activity, Including Discontinued Operation [Abstract] Interest cost Defined Benefit Plan, Interest Cost Financial Instruments [Domain] Financial Instruments [Domain] Total deferred credits and other liabilities Deferred Credits and Other Liabilities FFB Credit Facility FFB Credit Facility [Member] FFB Credit Facility Residential Retail Electric - Residential [Member] Retail Electric - Residential [Member] Total certified amounts Public Utilities, Requested Recovery of Construction and Capital Costs, Total Certified Amount Public Utilities, Requested Recovery of Construction and Capital Costs, Total Certified Amount Derivatives Derivative asset, net amounts recognized in the balance sheets Derivative Asset Other current assets Other Current Asset [Member] Other Current Asset Intangible Asset, Finite-Lived, Class [Axis] Intangible Asset, Finite-Lived, Class [Axis] Nuclear decommissioning trusts, at fair value Decommissioning Fund Investments Underlying Securities Award Underlying Securities Amount Comprehensive income (loss) attributable to noncontrolling interests Comprehensive Income (Loss), Net of Tax, Attributable to Noncontrolling Interest Revenue from Contracts with Customers and Lease Income Revenue from Contract with Customer [Text Block] Stock issued Stock Issued During Period, Value, New Issues Redemptions and repurchases — Redemptions [Abstract] Redemptions. Fair Values Derivatives, Balance Sheet Location, by Derivative Contract Type [Table] Fair Values Derivatives, Balance Sheet Location, by Derivative Contract Type [Table] Schedule of Foreign Currency Derivatives Schedule Of Foreign Exchange Contracts [Table Text Block] [Table Text Block] for Schedule Of Foreign Exchange Contracts [Table] Prepaid expenses Prepaid Expense, Current Investments in trusts Decommissioning Fund Investments, Fair Value Southern Company Gas Capital Southern Company Gas Capital [Member] Southern Company Gas Capital [Member] Other investing activities Payment for (Proceeds from) Other Investing Activity Retail fuel cost under recovery – long-term Retail Fuel Cost Under Recovery Long Term Retail Fuel Cost Under Recovery Long Term Segment Reporting [Table] Segment Reporting [Table] Defined benefit plan, expected future employer contributions, remainder of fiscal year Defined Benefit Plan, Expected Future Employer Contributions, Remainder of Fiscal Year Other current assets Other Assets, Current 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] Qualifying hedges, reclassification adjustment, tax Reclassification adjustment for amounts included in net income, tax Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), Reclassification, Tax Current Fiscal Year End Date Current Fiscal Year End Date Non-PEO NEO Average Total Compensation Amount Non-PEO NEO Average Total Compensation Amount Derivative [Line Items] Derivative [Line Items] Fuel cost recovery Over (Under) Recovered Fuel Balance Over (Under) recovered fuel balance. Nicor Gas Nicor Gas [Member] Nicor Gas [Member] 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 Change in construction payables, net Change in Construction Payables The net change during the reporting period in the aggregate amount of construction obligations due within one year (or one business cycle). This includes accounts payable related to construction activities. Distributions to noncontrolling interests Distributions to noncontrolling interests Noncontrolling Interest, Decrease from Distributions to Noncontrolling Interest Holders Gain (loss) on hedges Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), Reclassification, before Tax Recovery of Erroneously Awarded Compensation Disclosure [Line Items] Depreciation after tax Depreciation, Accelerated, After Tax Depreciation, Accelerated, After Tax Measure: Measure [Axis] Beginning balance (in shares) Ending balance (in shares) Treasury Stock, Common, Shares Accrued environmental remediation Accrued Environmental Loss Contingencies, Noncurrent Asset retirement obligations, deferred Asset Retirement Obligations, Noncurrent Equity Components [Axis] Equity Components [Axis] Stock based compensation expense Stock or Unit Option Plan Expense Related Party Related Party [Member] Schedule of Asset Acquisitions Asset Acquisition [Table Text Block] Income taxes, net (excludes credit transfers) Income Tax Paid, after Refund Received Wholesale electric revenues Wholesale revenues Wholesale Electric [Member] Wholesale Electric Amount excluded from effectiveness testing recognized in earnings Gain (Loss) from Components Excluded from Assessment of Fair Value Hedge Effectiveness, Net Entity Interactive Data Current Entity Interactive Data Current Finance lease obligations - current Finance Lease, Liability, Current Net income (loss) attributable to noncontrolling interests Net income (loss) attributable to noncontrolling interests Net Income (Loss) Attributable to Noncontrolling Interest Capital contributions from parent company Proceeds from Contributions from Parent Thomson Thomson [Member] Thomson Entity Small Business Entity Small Business Restricted cash: Restricted Cash [Abstract] In service In service Public Utilities, Property, Plant and Equipment, Plant in Service Consolidated Comprehensive Income Attributable to Company Comprehensive Income (Loss), Net of Tax, Attributable to Parent Forward Sale Contract 5 Forward Sale Contract 5 [Member] Forward Sale Contract 5 Industrial Retail Electric - Industrial [Member] Retail Electric - Industrial [Member] Utility Plant [Domain] Utility Plant [Domain] Revenue taxes collected Excise Taxes Collected Change in par value Equity Reclassification, Change In Par Value Equity Reclassification, Change In Par Value Customer deposits Customer Deposits, Current1 Customer Deposits Current1 MNPI Disclosure Timed for Compensation Value MNPI Disclosure Timed for Compensation Value [Flag] Other deferred charges and assets Other Assets, Noncurrent Document Type Document Type Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] Loss from extinguishment of debt Gain (Loss) on Extinguishment of Debt Kay Wind Kay Wind Facility Kay Wind Facility [Member] Kay Wind Facility Short Short [Member] Schedule of Other Intangible Assets, Indefinite-Lived Intangible Asset, Indefinite-Lived [Table Text Block] Ad Valorem Tax Adjustment Ad Valorem Tax Adjustment [Member] Ad Valorem Tax Adjustment Plant McIntosh Unit 12 Plant McIntosh Unit 12 [Member] Plant McIntosh Unit 12 Cash and cash equivalents Cash and Cash Equivalents [Member] Southern Natural Gas Company, LLC Southern Natural Gas Company, LLC [Member] Southern Natural Gas Company, LLC [Member] Statement of Stockholders' Equity [Abstract] Statement of Stockholders' Equity [Abstract] Local Phone Number Local Phone Number Postretirement Benefits Other Postretirement Benefits Plan [Member] Loss on damaged equipment Loss On Damaged Equipment Loss On Damaged Equipment Fixed rate pollution control revenue bonds outstanding Amount of Fixed Rate Pollution Control Revenue Bonds Outstanding Requiring Liquidity Support Amount of Fixed rate pollution control revenue bonds outstanding requiring liquidity support. Plant Yates, Phase 2 Plant Yates, Phase 2 [Member] Plant Yates, Phase 2 Restrictions on Cash and Cash Equivalents [Table] Restrictions on Cash and Cash Equivalents [Table] Earnings Before Income Taxes Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest Reclassification adjustment for amounts included in net income, tax Reclassification adjustment for amounts included in net income, tax Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss), Reclassification Adjustment from AOCI, Tax Changed Peer Group, Footnote Changed Peer Group, Footnote [Text Block] Income Tax Contingency [Table] Income Tax Contingency [Table] Decrease in operating revenues Amortization of Other Intangible Assets Recorded as a Reduction to Operating Revenues Amortization of Other Intangible Assets Recorded as a Reduction to Operating Revenues Executive Category: Executive Category [Axis] SP Solar Holdings I, LP SP Solar Holdings I, LP [Member] SP Solar Holdings I, LP [Member] Counterparty Name [Axis] Counterparty Name [Axis] Liabilities and Stockholders' Equity Liabilities and Equity [Abstract] Expires within One Year Bank Credit Arrangements No Term Loan Due with in One Year Bank credit arrangements no term loan due with in one year. Forward Sale Contract 3 Forward Sale Contract 3 [Member] Forward Sale Contract 3 Energy Efficiency Enhancement And Upgrade Energy Efficiency Enhancement And Upgrade [Member] Energy Efficiency Enhancement And Upgrade Foreign equity Foreign Equity [Member] Foreign equity. Non-PEO NEO Average Compensation Actually Paid Amount Non-PEO NEO Average Compensation Actually Paid Amount Total deferred charges and other assets Total deferred charges and other assets Deferred Charges and Other Assets Sum of the carrying amounts as of the balance sheet date of all assets, excluding Property, Plant, and Equipment and Other Property and Investments, that are expected to be realized in cash, sold or consumed after one year or beyond the normal operating cycle, if longer. Materials and supplies Increase (Decrease) in Materials and Supplies Cumulative Amount of Fair Value Hedging Adjustment included in Carrying Amount of the Hedged Item Derivative, Cumulative Amount of Fair Value Hedging Adjustment Included in Carrying Amount Derivative, Cumulative Amount of Fair Value Hedging Adjustment Included in Carrying Amount Supplemental Cash Flow Information: Supplemental Cash Flow Information [Abstract] Reclassification adjustment for amounts included in net income, net of tax Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), Reclassification, after Tax Forward Sale Contract 10 Forward Sale Contract 10 [Member] Forward Sale Contract 10 Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Table] Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Table] PEO Name PEO Name Deferred Income Taxes, Excess Accumulated Amount Deferred Income Taxes, Excess Accumulated Amount Deferred Income Taxes, Excess Accumulated Amount Right-of-use assets obtained under operating leases Right-Of-Use Asset Obtained In Exchange For Operating And Finance Lease Liability Right-Of-Use Asset Obtained In Exchange For Operating And Finance Lease Liability Capital contributions to unconsolidated subsidiaries Payment Of Capital Contribution To Subsidiary Payment Of Capital Contribution To Subsidiary Other segment items Segment Reporting, Other Segment Item, Amount Stock Price or TSR Estimation Method Stock Price or TSR Estimation Method [Text Block] Other utility plant, net Public Utilities, Property, Plant and Equipment, Other Property, Plant and Equipment Entity Tax Identification Number Entity Tax Identification Number Purchased power Purchased power, non-affiliates Electricity, Purchased [Member] Changes in fair value, net of tax Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), before Reclassification, after Tax 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] Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Table] Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Table] Material Terms of Trading Arrangement Material Terms of Trading Arrangement [Text Block] Capital expenditures disallowed Public Utilities, Infrastructure Replacement Programs And Capital Projects, Expenditures Disallowed Public Utilities, Infrastructure Replacement Programs And Capital Projects, Expenditures Disallowed 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] Industrial Natural Gas Distribution - Industrial [Member] Natural Gas Distribution - Industrial [Member] Deferred Charges and Other Assets: Deferred Charges and Other Assets [Abstract] Deferred charges and other assets. Introduction Organization, Consolidation and Presentation of Financial Statements Disclosure [Text Block] Comprehensive Income Comprehensive Income (Loss), Net of Tax, Including Portion Attributable to Noncontrolling Interest Receive Notional Derivative Notional Amount, Receive Derivative Notional Amount, Receive Long Long [Member] Pay Notional Derivative Notional Amount, Pay Derivative Notional Amount, Pay Net cash paid for capitalized interest Interest Paid, Capitalized, Investing Activity Public Utilities, Regulatory Proceeding [Axis] Public Utilities, Regulatory Proceeding [Axis] Borrower reimbursement, maximum percentage of eligible project costs Debt Instrument, Covenant, Borrower Reimbursement, Maximum Percentage Of Eligible Project Costs Debt Instrument, Covenant, Borrower Reimbursement, Maximum Percentage Of Eligible Project Costs Forward Sale Contract 1 Forward Sale Contract 1 [Member] At-The-Market, Forward Price 1 Hammond Phase 2 Hammond Phase 2 [Member] Hammond Phase 2 South Hall South Hall [Member] South Hall Basic (in dollars per share) Earnings Per Share, Basic Total current assets Assets, Current Common Stock Data: Common Stock Data [Abstract] Common Stock Data Insider Trading Arrangements [Line Items] Long-term debt Repayment of Long-Term Debt, Long-Term Lease Obligation, and Capital Security Other Other Natural Gas - Other Natural Gas Revenues [Member] Other Natural Gas - Other Natural Gas Revenues [Member] 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] Contingent consideration Business Combination, Contingent Consideration, Liability Compensation Actually Paid vs. Company Selected Measure Compensation Actually Paid vs. Company Selected Measure [Text Block] Cover [Abstract] Cover [Abstract] Reclassifications Reclassification, Comparability Adjustment [Policy Text Block] Other long-term debt Proceeds — Other long-term debt Proceeds from Issuance of Other Long-Term Debt Wholesale MB Wholesale MB [Member] Wholesale MB Equity Awards Adjustments Equity Awards Adjustments [Member] Other regulatory liabilities, deferred Other Regulatory Liabilities Deferred Other regulatory liabilities, deferred. Hedging Relationship [Domain] Hedging Relationship [Domain] Regulatory Asset [Domain] Regulatory Asset [Domain] 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 Other current liabilities Increase (Decrease) in Other Operating Liabilities Senior notes Proceeds — Senior notes Proceeds from Issuance of Senior Long-Term Debt SNG SNG [Member] SNG [Member] Subject to amortization: Intangible Asset, Finite-Lived, after Accumulated Amortization [Abstract] Other income (expense), net Other income (expense), net Other Nonoperating Income (Expense) Redemptions - First mortgage bonds Repayments of First Mortgage Bond Total Common Stockholder's Equity Parent [Member] Redemptions — Senior notes Repayments of Senior Debt Accounts payable — Accounts Payable, Current [Abstract] Effect of forward sale contracts (in shares) Incremental Common Shares Attributable To Dilutive Effect Of Equity Forward Sale Agreements, Calculated Using The Treasury Stock Method Incremental Common Shares Attributable To Dilutive Effect Of Equity Forward Sale Agreements, Calculated Using The Treasury Stock Method Derivatives, Fair Value [Line Items] Derivatives, Fair Value [Line Items] Hammond Phase 1 Hammond Phase 1 [Member] Hammond Phase 1 Regulatory liability Regulatory Liability Hedging Designation [Domain] Hedging Designation [Domain] Class of Stock [Domain] Class of Stock [Domain] Statement of Cash Flows [Abstract] Statement of Cash Flows [Abstract] Transportation Natural Gas Distribution - Transportation [Member] Natural Gas Distribution - Transportation [Member] Net Purchased mmBtu Net Quantity Purchase Of Derivatives Not Designated As Hedges Net Quantity Purchase Of Derivatives Not Designated As Hedges Aggregate Available Trading Arrangement, Securities Aggregate Available Amount Operational expenses Utilities Operational Expenses, PEP And MRA Tariff Utilities Operational Expenses, PEP And MRA Tariff Income Taxes Income Tax Disclosure [Text Block] Accounts payable Accounts Payable, Current Expected volume of natural gas subject to option to sell back excess gas due to operational constraints Expected Volume of Natural Gas Subject to Option to Sell Back Excess Gas Due to Operational Constraints Expected volume of natural gas subject to option to sell back excess gas due to operational constraints. Plant McIntosh Plant McIntosh [Member] Plant McIntosh Other, net Other Noncash Income (Expense) Traditional Electric Operating Companies Traditional Electric Operating Companies [Member] Traditional Electric Operating Companies [Member] Schedule of Asset Retirement Obligation [Table] Schedule of Asset Retirement Obligation [Table] Schedule of Asset Retirement Obligation [Table] Schedule of Derivative Category and Balance Sheet Location Schedule of Derivatives Instruments Statements of Financial Performance and Financial Position, Location [Table Text Block] Financial Investors Financial Investors [Member] Financial Investors [Member] Pay vs Performance Disclosure Pay vs Performance Disclosure [Table] Gain (Loss) From Derivatives Recognized in OCI Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), after Reclassification, before Tax Retirement Plan Type [Domain] Retirement Plan Type [Domain] Entity Filer Category Entity Filer Category Revision of Prior Period [Axis] Revision of Prior Period [Axis] PPA Contract Period Life Output Of Plant The contracted life output of the plant. Program [Axis] Program [Axis] Program [Axis] Other cost of removal obligations Other Cost of Removal Obligations The regulatory liability as of the balance sheet date for the amount recovered from ratepayers for removal costs associated with utility plant in service which are not recognized as a liability. Energy-related derivatives not designated as hedging instruments Not Designated as Hedging Instrument [Member] Indexed shares (in shares) Forward Contract Indexed to Issuer's Equity, Indexed Shares Consolidated Net Income Consolidated Net Income Net income (loss) Net income Net Income (Loss), Including Portion Attributable to Noncontrolling Interest Current Assets: Assets, Current [Abstract] Derivatives Derivative liability, net amounts recognized in the balance sheets Derivative Liability PPA capacity revenues Wholesale Electric - PPA Capacity Revenues [Member] Wholesale Electric - PPA Capacity Revenues [Member] Entity Address, Address Line One Entity Address, Address Line One Right-of-use assets obtained under operating leases Right-of-Use Asset Obtained in Exchange for Operating Lease Liability Retail electric revenues Retail Electric [Member] Retail Electric [Member] Income taxes Income taxes (benefit) Income taxes (benefit) Income Tax Expense (Benefit) Fair Value Hedging Fair Value Hedging [Member] Variable Interest Entity, Primary Beneficiary Variable Interest Entity, Primary Beneficiary [Member] Statement [Table] Statement [Table] Schedule of Remaining Performance Obligations Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Table Text Block] Schedule of Contract Balances Contract with Customer, Contract Asset, Contract Liability, and Receivable [Table Text Block] Derivative asset, gross amount recognized Derivative Asset, Subject to Master Netting Arrangement, before Offset Plant Daniel Units 1 and 2 Plant Daniel Units 1 and 2 [Member] Plant Daniel Units 1 and 2 Fair Value Hedges of Existing Debt Fair Value Hedges Of Existing Debt [Member] Fair Value Hedges Of Existing Debt [Member] Derivative Instruments and Hedging Activities Disclosure [Abstract] Derivative Instruments and Hedging Activities Disclosure [Abstract]