Commitments and Contingencies Disclosure [Abstract] REGULATORY MATTERS Public Utilities Disclosure [Text Block] Leases [Abstract] Lessor, Lease, Description [Table] Lessor, Lease, Description [Table] Legal Entity [Axis] Legal Entity [Axis] Entity [Domain] Entity [Domain] MISSISSIPPI POWER CO Mississippi Power [Member] Mississippi Power. Lessor, Lease, Description [Line Items] Lessor, Lease, Description [Line Items] 2019 (remaining) Sales-type and Direct Financing Leases, Lease Receivable, Payments to be Received, Remainder of Fiscal Year 2020 Sales-type and Direct Financing Leases, Lease Receivable, Payments to be Received, Two Years 2021 Sales-type and Direct Financing Leases, Lease Receivable, Payments to be Received, Three Years 2022 Sales-type and Direct Financing Leases, Lease Receivable, Payments to be Received, Four Years 2023 Sales-type and Direct Financing Leases, Lease Receivable, Payments to be Received, Five Years Thereafter Sales-type and Direct Financing Leases, Lease Receivable, Payments to be Received, Thereafter Total undiscounted cash flows Sales-type and Direct Financing Leases, Lease Receivable, Payments to be Received Lease receivable Sales-type and Direct Financing Leases, Lease Receivable Difference between undiscounted cash flows and discounted cash flows Sales-type and Direct Financing Leases, Lease Receivable, Undiscounted Excess Amount Derivative Instruments and Hedging Activities Disclosure [Abstract] Derivative [Table] Derivative [Table] Southern Company Southern Company [Member] Southern Company [Member] ALABAMA POWER CO Alabama Power [Member] Alabama Power. GEORGIA POWER CO Georgia Power [Member] Georgia Power. SOUTHERN POWER CO Southern Power [Member] Southern Power. SOUTHERN Co GAS Southern Company Gas [Member] Southern Company Gas [Member] Variable Rate [Axis] Variable Rate [Axis] Variable Rate [Domain] Variable Rate [Domain] LIBOR London Interbank Offered Rate (LIBOR) [Member] Derivative Instrument [Axis] Derivative Instrument [Axis] Derivative Contract [Domain] Derivative Contract [Domain] Energy-related, Natural Gas Public Utilities, Inventory, Natural Gas [Member] Interest rate derivatives Interest Rate Contract [Member] Hedging Designation [Axis] Hedging Designation [Axis] Hedging Designation [Domain] Hedging Designation [Domain] Derivatives not designated as hedging instruments Not Designated as Hedging Instrument [Member] Position [Axis] Position [Axis] Position [Domain] Position [Domain] Long Long [Member] Short Short [Member] Hedging Maturity Date [Axis] Hedging Maturity Date [Axis] Hedging Maturity Date [Axis] Hedging Maturity Date [Domain] Hedging Maturity Date [Domain] Hedging Maturity Date [Domain] June 2020 Maturity Date June 2020 [Member] Maturity Date June 2020 [Member] July 2021 Maturity Date July 2021 [Member] Maturity Date July 2021 [Member] December 2019 Maturity Date December 2019 [Member] Maturity Date December 2019 [Member] Hedging Relationship [Axis] Hedging Relationship [Axis] Hedging Relationship [Domain] Hedging Relationship [Domain] Fair Value Hedges of Existing Debt Fair Value Hedges Of Existing Debt [Member] Fair Value Hedges Of Existing Debt [Member] Derivative [Line Items] Derivative [Line Items] Energy-related derivative contracts Energy Related Derivative Contracts for Registrants [Abstract] Energy-related derivative contracts for the registrants. Net Purchased mmBtu Net Quantity Purchase Of Derivatives Not Designated As Hedges Net Quantity Purchase Of Derivatives Not Designated As Hedges 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 Interest rate derivatives Notional Disclosures [Abstract] Notional Amount Derivative, Notional Amount Interest Rate Received Notional Amount of Interest Rate Derivatives Interest Rate Received Notional amount of interest rate derivatives, interest rate received. Weighted Average Interest Rate Paid Notional Amount of Interest Rate Derivatives Interest Rate Paid Notional amount of interest rate derivatives, interest rate paid. Fair Value Gain (Loss) at March 31, 2019 Fair Value Gain (Loss) Fair value gain (Loss). Fair Value Hedging Fair Value Hedging [Member] Balance Sheet Location [Axis] Balance Sheet Location [Axis] Balance Sheet Location [Domain] Balance Sheet Location [Domain] Securities due within one year Short-term Debt [Member] Long-term debt Long-term Debt [Member] Carrying Amount of the Hedged Item Derivative, Amount of Hedged Item 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 Business Combinations [Abstract] Schedule of Business Acquisitions, by Acquisition [Table] Schedule of Business Acquisitions, by Acquisition [Table] Business Acquisition [Axis] Business Acquisition [Axis] Business Acquisition, Acquiree [Domain] Business Acquisition, Acquiree [Domain] Series of Construction Projects Series of Construction Projects [Member] Series of Construction Projects [Member] Mankato expansion Mankato [Member] Mankato [Member] Range [Axis] Range [Axis] Range [Domain] Range [Domain] Minimum Minimum [Member] Maximum Maximum [Member] Public Utility [Axis] Public Utility [Axis] Utility Plant [Domain] Utility Plant [Domain] Wind Generating Facility Wind Generating Facility [Member] Wind Generating Facility [Member] Disposal Group Classification [Axis] Disposal Group Classification [Axis] Disposal Group Classification [Domain] Disposal Group Classification [Domain] Disposal Group, Held-for-sale, Not Discontinued Operations Disposal Group, Held-for-sale, Not Discontinued Operations [Member] Disposal Group Name [Axis] Disposal Group Name [Axis] Disposal Group Name [Domain] Disposal Group Name [Domain] Nacogdoches Biomass-Fueled Facility Nacogdoches Biomass-Fueled Facility [Member] Nacogdoches Biomass-Fueled Facility [Member] Subsequent Event Type [Axis] Subsequent Event Type [Axis] Subsequent Event Type [Domain] Subsequent Event Type [Domain] Subsequent Event Subsequent Event [Member] Scenario [Axis] Scenario [Axis] Scenario, Unspecified [Domain] Scenario, Unspecified [Domain] Scenario, Forecast Scenario, Forecast [Member] Lien Category [Axis] Lien Category [Axis] Lien Category [Domain] Lien Category [Domain] Lien Senior Lien [Member] Business Acquisition [Line Items] Business Acquisition [Line Items] Estimated future construction payments Estimated Future Construction Payments Estimated Future Construction Payments Construction work in progress Construction in Progress, Gross Equipment marketed for sale Assets Held-for-sale, Not Part of Disposal Group, Current Proceeds from divestiture of businesses, net of cash divested Proceeds from Divestiture of Businesses Approximate nameplate capacity (MW) Approximate Nameplate Capacity Approximate Nameplate Capacity Nacogdoches biomass-fueled facility Disposal Group, Including Discontinued Operation, Consideration Property, plant, and equipment, subject to lien Assets Revenue from Contract with Customer [Abstract] Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Table] Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Table] Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis] Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis] Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items] Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items] Revenue, remaining performance obligation Revenue, Remaining Performance Obligation, Amount Performance obligation, expected timing of satisfaction Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period Income Statement [Abstract] Statement [Table] Statement [Table] Product and Service [Axis] Product and Service [Axis] Product and Service [Domain] Product and Service [Domain] Retail electric revenues Retail [Member] Wholesale electric revenues Wholesale, Non-Affiliates [Member] Wholesale, Non-Affiliates [Member] Other electric revenues Other Electric Revenue [Member] Other electric revenue. Natural gas Natural Gas, US Regulated [Member] Other Product and Service, Other [Member] Fuel Fuel [Member] Purchased power Electricity, Purchased [Member] Wholesale revenues, affiliates Wholesale, Affiliates [Member] Wholesale, Affiliates [Member] Purchased power, affiliates Electricity, Purchased, Affiliates [Member] Electricity, Purchased, Affiliates [Member] Alternative revenue programs Alternative Energy [Member] Statement [Line Items] Statement [Line Items] Operating Revenues: Revenues [Abstract] Total operating revenues Revenues Operating Expenses: Costs and Expenses [Abstract] Total cost of natural gas Cost of Goods and Services Sold Other operations and maintenance Utilities Operating Expense, Maintenance and Operations Depreciation and amortization 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. Taxes other than income taxes Taxes, Miscellaneous Estimated loss on plants under construction Estimated Loss On Plants Under Construction Estimated Loss On Plants Under Construction Gain on dispositions, net Gain (Loss) on Disposition of Assets Goodwill impairment Goodwill, Impairment Loss Total operating expenses Costs and Expenses Operating Income (Loss) Operating Income (Loss) Other Income and (Expense): Nonoperating Income (Expense) [Abstract] Allowance for equity funds used during construction Public Utilities, Allowance for Funds Used During Construction, Capitalized Cost of Equity Earnings from equity method investments Income (Loss) from Equity Method Investments Interest expense, net of amounts capitalized Interest and Debt Expense Other income (expense), net Other Nonoperating Income (Expense) Total other income and (expense) Nonoperating Income (Expense) Earnings (Loss) Before Income Taxes Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest Income taxes Income Tax Expense (Benefit) Consolidated net income (loss) Net Income (Loss), Including Portion Attributable to Noncontrolling Interest Dividends on preferred stock of subsidiaries Preferred Stock Dividends, Income Statement Impact Net loss attributable to noncontrolling interests Net Income (Loss) Attributable to Noncontrolling Interest Net Income (Loss) Net Income (Loss) Available to Common Stockholders, Basic Common Stock Data: Common Stock Data [Abstract] Common stock data. Earnings per share - Earnings Per Share [Abstract] Basic (in dollars per share) Earnings Per Share, Basic Diluted (in dollars per share) Earnings Per Share, Diluted Average number of shares of common stock outstanding (in millions) Weighted Average Number of Shares Outstanding, Diluted [Abstract] Basic (in shares) Weighted Average Number of Shares Outstanding, Basic Diluted (in shares) Weighted Average Number of Shares Outstanding, Diluted Lessee, Lease, Description [Table] Lessee, Lease, Description [Table] Property, Plant and Equipment, Type [Axis] Property, Plant and Equipment, Type [Axis] Property, Plant and Equipment, Type [Domain] Property, Plant and Equipment, Type [Domain] Electric generating units Electric Generating Units [Member] Electric Generating Units [Member] Real estate/land Land and Building [Member] Communication towers Communication Towers [Member] Communication Towers [Member] Railcars Railcars [Member] Railcars [Member] Other Property, Plant and Equipment, Other Types [Member] Lessee, Lease, Description [Line Items] Lessee, Lease, Description [Line Items] Lease obligations Lease, Liability Lease, Liability Organization, Consolidation and Presentation of Financial Statements [Abstract] Basis of Accounting Basis of Accounting, Policy [Policy Text Block] Reclassifications Reclassification, Policy [Policy Text Block] Recently Adopted Accounting Standards New Accounting Pronouncements, Policy [Policy Text Block] Goodwill and Other Intangible Assets Goodwill and Intangible Assets, Policy [Policy Text Block] Restricted Cash Cash and Cash Equivalents, Restricted Cash and Cash Equivalents, Policy [Policy Text Block] Natural Gas For Sale Natural Gas For Sale, Policy [Policy Text Block] Natural Gas For Sale, Policy [Policy Text Block] Valuation Methodologies Fair Value Measurement, Policy [Policy Text Block] Derivatives Derivatives, Policy [Policy Text Block] Debt Disclosure [Abstract] FINANCING Debt Disclosure [Text Block] Derivative Instruments, Gain (Loss) [Table] Derivative Instruments, Gain (Loss) [Table] Energy-related derivatives Energy Related Derivative [Member] Income Statement Location [Axis] Income Statement Location [Axis] Income Statement Location [Domain] Income Statement Location [Domain] Natural gas revenues Natural Gas Revenues [Member] Natural Gas Revenues [Member] Total cost of natural gas Cost of Natural Gas [Member] Cost of Natural Gas [Member] Derivative Instruments, Gain (Loss) [Line Items] Derivative Instruments, Gain (Loss) [Line Items] Derivative instruments not designated as hedging instruments, gain (loss), net Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net Credit Arrangements by Company Schedule of Line of Credit Facilities [Table Text Block] Schedule of Long-term Debt Financing Activities Schedule of Long-term Debt Instruments [Table Text Block] 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. Retirement Benefits [Abstract] Pension Plans and Postretirement Plans Schedule of Net Benefit Costs [Table Text Block] Total operating revenues Revenue from Contract with Customer, Including Assessed Tax Excise taxes collected Excise Taxes Collected Cash Flow Hedging Cash Flow Hedging [Member] Gain (loss) on energy-related cash flow hedges Foreign currency derivatives Foreign Exchange Contract [Member] Total depreciation and amortization Depreciation and Amortization [Member] Depreciation and Amortization [Member] Total interest expense, net of amounts capitalized Interest Expense [Member] Total other income (expense), net Other Nonoperating Income (Expense) [Member] Gain (loss) on hedge Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), Reclassification, before Tax Total interest expense, net of amounts capitalized Total other income (expense), net Statement of Cash Flows [Abstract] Operating Activities: Net Cash Provided by (Used in) Operating Activities [Abstract] Net income (loss) Adjustments to reconcile net income (loss) to net cash provided from (used for) operating activities — Adjustments to Reconcile Net Income (Loss) to Cash Provided by (Used in) Operating Activities [Abstract] Depreciation and amortization, total Depreciation, Amortization and Accretion, Net Deferred income taxes Deferred Income Tax Expense (Benefit) Amortization of investment tax credits Amortization of Deferred Investment Tax Credits Amortization of deferred investment tax credits. Allowance for equity funds used during construction Pension, postretirement, and other employee benefits Pension and Other Postretirement Benefits Cost (Reversal of Cost) Settlement of asset retirement obligations Asset Retirement Obligation, Cash Paid to Settle Stock based compensation expense Stock or Unit Option Plan Expense Estimated loss on Kemper IGCC Estimated Loss On Integrated Coal Gasification Combined Cycle Project, Non-Cash Estimated Loss On Integrated Coal Gasification Combined Cycle Project, Non-Cash Mark-to-market adjustments Derivative, Gain (Loss) on Derivative, Net Gain on dispositions, net Disposal Group, Not Discontinued Operation, Gain (Loss) on Disposal Other, net Other Noncash Income (Expense) Changes in certain current assets and liabilities — Increase (Decrease) in Operating Capital [Abstract] -Receivables Increase (Decrease) in Receivables -Prepayments Increase (Decrease) in Prepaid Expense -Natural gas for sale Increase (Decrease) in Energy Related Inventory, Natural Gas in Storage Increase (Decrease) in Energy Related Inventory, Natural Gas in Storage -Materials and supplies Increase (Decrease) in Materials and Supplies -Fossil fuel stock Increase (Decrease) in Fossil Fuel Inventories -Prepaid income taxes Increase (Decrease) in Prepaid Taxes -Other current assets Increase (Decrease) in Other Operating Assets -Accounts payable Increase (Decrease) in Accounts Payable -Accrued taxes Increase Decrease in Accrued Taxes The net change during the period in the amount of cash payments due to taxing authorities for income and non income-related taxes. -Accrued compensation Increase (Decrease) in Accrued Salaries -Other current liabilities Increase (Decrease) in Other Operating Liabilities Net cash used for operating activities Net Cash Provided by (Used in) Operating Activities Investing Activities: Net Cash Provided by (Used in) Investing Activities [Abstract] Business acquisitions, net of cash acquired Payments to Acquire Businesses, Net of Cash Acquired Property additions Payments to Acquire Property, Plant, and Equipment Nuclear decommissioning trust fund purchases Payments to Acquire Investments to be Held in Decommissioning Trust Fund Nuclear decommissioning trust fund sales Proceeds from Decommissioning Trust Fund Assets Cost of removal, net of salvage Payments for Removal Costs Proceeds from asset dispositions Proceeds from Sale of Productive Assets 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. Investment in unconsolidated subsidiaries Payments to Acquire Equity Method Investments Change in construction payables, net of joint owner portion Change in Construction Payables Net of Joint Owner Portion The net change during the reporting period in the aggregate amount of construction obligations due within one year (or one business cycle) net of joint owner portion. This includes accounts payable related to construction activities. Payments pursuant to LTSAs Payments Pursuant to Long Term Service Agreements Payments pursuant to long-term service agreements. Other investing activities Payments for (Proceeds from) Other Investing Activities Net cash provided from (used for) investing activities Net Cash Provided by (Used in) Investing Activities Financing Activities: Net Cash Provided by (Used in) Financing Activities [Abstract] Increase (decrease) in notes payable, net Proceeds from (Repayments of) Short-term Debt Proceeds — Proceeds [Abstract] Proceeds. Long-term debt Proceeds from Issuance of Long-term Debt Common stock Proceeds from Issuance of Common Stock Senior notes Proceeds from Issuance of Senior Long-term Debt Short-term borrowings Proceeds from Short-term Debt FFB loan Federal Financing Bank Loan Federal Financing Bank Loan Pollution control revenue bonds Proceeds from Pollution Control Bond Capital contributions from parent company Proceeds from Contributions from Parent Redemptions and repurchases — Redemptions [Abstract] Redemptions. Long-term debt Repayments of Long-term Debt Senior notes Repayments of Senior Debt Pollution control revenue bonds Repayments of Pollution Control Bond Short-term borrowings Repayments of Short-term Debt Other long-term debt Repayments of Other Long-term Debt Distributions to noncontrolling interests Payments to Noncontrolling Interests Capital contributions from noncontrolling interests Proceeds from Noncontrolling Interests Payment of common stock dividends Payments of Ordinary Dividends, Common Stock Return of capital Return Of Paid In Capital Return Of Paid In Capital Other financing activities Proceeds from (Payments for) Other Financing Activities Net cash provided from (used for) financing activities Net Cash Provided by (Used in) Financing Activities Net Change in Cash, Cash Equivalents, and Restricted Cash Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents, Period Increase (Decrease), Including Exchange Rate Effect Cash, Cash Equivalents, and Restricted Cash at Beginning of Period Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents Cash, Cash Equivalents, and Restricted Cash at End of Period Supplemental Cash Flow Information: Supplemental Cash Flow Information [Abstract] Cash paid (received) during the period for — Cash Paid Received During Period [Abstract] Cash paid received during period. Interest, net of amounts capitalized Interest Paid, Excluding Capitalized Interest, Operating Activities Income taxes, net Income Taxes Paid, Net Noncash transactions — Accrued property additions at end of period Capital Expenditures Incurred but Not yet Paid Statement of Comprehensive Income [Abstract] Qualifying hedges: Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), after Reclassification, Tax [Abstract] Changes in fair value, tax Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), before Reclassification, Tax Reclassification adjustment for amounts included in net income, tax Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), Reclassification, Tax Pension and other postretirement benefit plans: Other Comprehensive (Income) Loss, Defined Benefit Plan, Reclassification Adjustment from AOCI, Tax [Abstract] Reclassification adjustment for amounts included in net income, tax Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss), Reclassification Adjustment from AOCI, Tax Other information Lessee Disclosure [Abstract] Cash paid for amounts included in the measurements of lease obligations: Cash Flow, Lessee [Abstract] Cash Flow, Lessee [Abstract] Operating cash flows from operating leases Operating Lease, Payments Operating cash flows from finance leases Finance Lease, Interest Payment on Liability Financing cash flows from finance leases Finance Lease, Principal Payments ROU assets obtained in exchange for new operating lease obligations Right-of-Use Asset Obtained in Exchange for Operating Lease Liability ROU assets obtained in exchange for new finance lease obligations Right-of-Use Asset Obtained in Exchange for Finance Lease Liability Weighted-average remaining lease term in years: Lease, Weighted Average Remaining Lease Term [Abstract] Lease, Weighted Average Remaining Lease Term [Abstract] Operating leases Operating Lease, Weighted Average Remaining Lease Term Finance leases Finance Lease, Weighted Average Remaining Lease Term Weighted-average discount rate: Lease, Weighted Average Discount Rate, Percent [Abstract] Lease, Weighted Average Discount Rate, Percent [Abstract] Operating leases Operating Lease, Weighted Average Discount Rate, Percent Finance leases Finance Lease, Weighted Average Discount Rate, Percent Regulated Operations [Abstract] Schedule of Equity Method Investments [Table] Schedule of Equity Method Investments [Table] Investment, Name [Axis] Investment, Name [Axis] Investment, Name [Domain] Investment, Name [Domain] SNG SNG [Member] SNG [Member] Atlantic Coast Pipeline Atlantic Coast Pipeline [Member] Represents Atlantic Coast Pipeline. PennEast Pipeline PennEast Pipeline [Member] Represents PennEast Pipeline. Other Other [Member] Other [Member] Schedule of Equity Method Investments [Line Items] Schedule of Equity Method Investments [Line Items] Investment Balance Equity Method Investments Loss Contingencies [Table] Loss Contingencies [Table] Program [Axis] Program [Axis] Program [Axis] Program [Domain] Program [Domain] [Domain] for Program [Axis] SAVE SAVE [Member] SAVE [Member] Year [Axis] Year [Axis] Year [Axis] Year [Domain] Year [Domain] [Domain] for Year [Axis] 2018 Year 2018 [Member] Year 2018 [Member] 2019 Year 2019 [Member] Year 2019 [Member] 2020 Year 2020 [Member] Year 2020 [Member] 2021 Year 2021 [Member] Year 2021 [Member] 2022 Year 2022 [Member] Year 2022 [Member] 2023 Year 2023 [Member] Year 2023 [Member] 2024 Year 2024 [Member] Year 2024 [Member] Nicor Gas Nicor Gas [Member] Nicor Gas [Member] Virginia Natural Gas Virginia Natural Gas [Member] Virginia Natural Gas [Member] Loss Contingencies [Line Items] Loss Contingencies [Line Items] Approved increase (decrease) in fuel rates amount Public Utilities, Approved Rate Increase (Decrease), Amount Public utilities, approved return on equity percentage Public Utilities, Approved Return on Equity, Percentage Regulatory equity ratio Regulatory Equity Ratio Regulatory Equity Ratio Number of intervenors Public Utilities, Number Of Intervenors Public Utilities, Number Of Intervenors Requested increase in rate amounts Public Utilities, Requested Rate Increase (Decrease), Amount Bill credits Contract With Customer, Liability, Bill Credits Contract With Customer, Liability, Bill Credits Approved investment amount Approved Infrastructure Replacement Program, Approved Investment Amount Approved Infrastructure Replacement Program, Approved Investment Amount Infrastructure replacement program, proposed investment amount Infrastructure Replacement Program, Petitioned Investment Amount Infrastructure Replacement Program, Petitioned Investment Amount Infrastructure replacement program, petitioned investment renewal term Infrastructure Replacement Program, Petitioned Investment Renewal Term Infrastructure Replacement Program, Petitioned Investment Renewal Term Infrastructure replacement program, petitioned investment term Infrastructure Replacement Program, Petitioned Investment Term Infrastructure Replacement Program, Petitioned Investment Term Infrastructure replacement program, proposed investment variance amount Infrastructure Replacement Program, Petitioned Investment Variance Amount Infrastructure Replacement Program, Petitioned Investment Variance Amount Equity Method Investments Equity Method Investments [Table Text Block] Schedule of Other Nonoperating Income, by Component Schedule of Other Nonoperating Income, by Component [Table Text Block] Major Categories of Lease Obligations Schedule Of Operating Lease, Right-Of-Use Assets [Table Text Block] Schedule Of Operating Lease, Right-Of-Use Assets [Table Text Block] Balance Sheet Amounts Recorded for Operating and Financing Leases Assets And Liabilities, Lessee [Table Text Block] Assets And Liabilities, Lessee [Table Text Block] Lease Costs and Other Information Lease, Cost [Table Text Block] Maturities of Operating Lease Liabilities Lessee, Operating Lease, Liability, Maturity [Table Text Block] Maturities of Finance Lease Liabilities Finance Lease, Liability, Maturity [Table Text Block] Lease Income, Sales-type Leases Sales-type Lease, Lease Income [Table Text Block] Lease Income, Operating Leases Operating Lease, Lease Income [Table Text Block] Undiscounted Cash Flows to be Received Under Tolling Arrangements Accounted for as Sales-type Leases Sales-type and Direct Financing Leases, Lease Receivable, Maturity [Table Text Block] Undiscounted Cash Flows to be Received Under PPAs Accounted for as Operating Leases Lessor, Operating Lease, Payments to be Received, Maturity [Table Text Block] Segment Reporting [Abstract] Schedule of Segment Reporting Information, by Segment [Table] Schedule of Segment Reporting Information, by Segment [Table] Counterparty Name [Axis] Counterparty Name [Axis] Counterparty Name [Domain] Counterparty Name [Domain] Traditional Electric Operating Companies Traditional Electric Operating Companies [Member] Traditional Electric Operating Companies [Member] Disposal Group, Disposed of by Sale, Not Discontinued Operations Disposal Group, Disposed of by Sale, Not Discontinued Operations [Member] SNG Southern Natural Gas Company, LLC [Member] Southern Natural Gas Company, LLC [Member] Dalton Pipeline Dalton Pipeline [Member] Dalton Pipeline [Member] Project [Axis] Project [Axis] Project [Domain] Project [Domain] Pipeline Pipelines [Member] Segment Reporting Information [Line Items] Segment Reporting Information [Line Items] Number of states in which entity operates Number of States in which Entity Operates Number of reportable segments Number of Reportable Segments Ownership percentage, equity method investment Equity Method Investment, Ownership Percentage Number of pipeline construction projects Number Of Pipeline Construction Projects Number Of Pipeline Construction Projects REVENUE FROM CONTRACTS WITH CUSTOMERS Revenue from Contract with Customer [Text Block] ACQUISITIONS AND DISPOSITIONS Mergers, Acquisitions and Dispositions Disclosures [Text Block] Statement of Financial Position [Abstract] Other intangible assets, amortization Finite-Lived Intangible Assets, Accumulated Amortization Restrictions on Cash and Cash Equivalents [Table] Restrictions on Cash and Cash Equivalents [Table] Restricted Cash and Cash Equivalents [Axis] Restricted Cash and Cash Equivalents [Axis] Cash and Cash Equivalents [Domain] Cash and Cash Equivalents [Domain] Restricted cash Restricted Cash [Member] Restricted Cash [Member] Other accounts and notes receivable Other Accounts And Notes Receivable [Member] Other Accounts And Notes Receivable [Member] Restricted Cash and Cash Equivalents Items [Line Items] Restricted Cash and Cash Equivalents Items [Line Items] Cash and cash equivalents Cash and Cash Equivalents, at Carrying Value Cash and cash equivalents held for sale Disposal Group, Including Discontinued Operation, Cash and Cash Equivalents Restricted cash: Restricted Cash [Abstract] Restricted cash Restricted Cash Total cash, cash equivalents, and restricted cash Disaggregation of Revenue [Table] Disaggregation of Revenue [Table] Disaggregation of Revenue [Line Items] Disaggregation of Revenue [Line Items] Receivables Accounts Receivable, Net Contract Assets Contract with Customer, Asset, Net Contract Liabilities Contract with Customer, Liability Lease cost Lease, Cost [Abstract] Operating lease cost Operating Lease, Cost Finance lease cost: Finance Lease, Cost [Abstract] Amortization of ROU assets Finance Lease, Right-of-Use Asset, Amortization Interest on lease obligations Finance Lease, Interest Expense Total finance lease cost Finance Lease, Cost Finance Lease, Cost Short-term lease costs Short-term Lease, Cost Variable lease cost Variable Lease, Cost Sublease income Sublease Income Total lease cost Lease, Cost Schedule of Defined Benefit Plans Disclosures [Table] Schedule of Defined Benefit Plans Disclosures [Table] Retirement Plan Type [Axis] Retirement Plan Type [Axis] Retirement Plan Type [Domain] Retirement Plan Type [Domain] Pension Plans Pension Plan [Member] Postretirement Benefits Other Postretirement Benefits Plan [Member] Consolidated Entities [Axis] Consolidated Entities [Axis] Consolidated Entities [Domain] Consolidated Entities [Domain] Southern Company Parent Company [Member] Defined Benefit Plan Disclosure [Line Items] Defined Benefit Plan Disclosure [Line Items] Defined benefit plan, expected future employer contributions, remainder of fiscal year Defined Benefit Plan, Expected Future Employer Contributions, Remainder of Fiscal Year Pension Plans and Postretirement Plans Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract] Service cost Defined Benefit Plan, Service Cost Interest cost Defined Benefit Plan, Interest Cost Expected return on plan assets Defined Benefit Plan, Expected Return (Loss) on Plan Assets Amortization: Defined Benefit Plan, Net Periodic Benefit Cost, Amortization [Abstract] Defined Benefit Plan, Net Periodic Benefit Cost, Amortization [Abstract] Prior service costs Defined Benefit Plan, Amortization of Prior Service Cost (Credit) Regulatory asset Amortization of Regulatory Asset Net (gain)/loss Defined Benefit Plan, Amortization of Gain (Loss) Net periodic pension cost (income) Defined Benefit Plan, Net Periodic Benefit Cost (Credit) Consolidation Items [Axis] Consolidation Items [Axis] Consolidation Items [Domain] Consolidation Items [Domain] Operating Segments Operating Segments [Member] Total retail electric and gas distribution revenues Total Retail Electric and Gas Distribution [Member] Total Retail Electric and Gas Distribution [Member] Retail electric revenues Retail Electric [Member] Retail Electric [Member] Residential Retail Electric - Residential [Member] Retail Electric - Residential [Member] Commercial Retail Electric - Commercial [Member] Retail Electric - Commercial [Member] Industrial Retail Electric - Industrial [Member] Retail Electric - Industrial [Member] Other Retail Electric - Other [Member] Retail Electric - Other [Member] Natural gas distribution revenues Natural Gas Distribution [Member] Natural Gas Distribution [Member] Residential Natural Gas Distribution - Residential [Member] Natural Gas Distribution - Residential [Member] Commercial Natural Gas Distribution - Commercial [Member] Natural Gas Distribution - Commercial [Member] Transportation Natural Gas Distribution - Transportation [Member] Natural Gas Distribution - Transportation [Member] Industrial Natural Gas Distribution - Industrial [Member] Natural Gas Distribution - Industrial [Member] Other Natural Gas Distribution - Other [Member] Natural Gas Distribution - Other [Member] Alternative revenue programs Alternative Revenue Programs [Member] Alternative Revenue Programs [Member] Wholesale energy revenues Wholesale Energy [Member] Wholesale Energy [Member] Wholesale capacity revenues Wholesale Capacity [Member] Wholesale Capacity [Member] Other natural gas revenues Other Natural Gas [Member] Other Natural Gas [Member] PPA capacity revenues PPA Capacity [Member] PPA Capacity [Member] PPA energy revenues PPA Energy [Member] PPA Energy [Member] Non-PPA revenues Non-PPA [Member] Non-PPA [Member] Gas pipeline investments Gas Pipeline Investments [Member] Gas Pipeline Investments [Member] Wholesale gas services Wholesale Gas Services [Member] Wholesale Gas Services [Member] Gas marketing services Gas Marketing Services [Member] Gas Marketing Services [Member] Other revenues Other Revenues [Member] Other Revenues [Member] Segments [Axis] Segments [Axis] Segments [Domain] Segments [Domain] Wholesale Gas Services Subsegments [Axis] Subsegments [Axis] Subsegments [Domain] Subsegments [Domain] Third Party Gross Revenues Third Party Gross Revenues [Member] Gross revenues from third parties. Revenue from leases Lease Income Increase (decrease) in revenue from cost recovery mechanisms Increase (Decrease) in Revenue from Cost Recovery Mechanisms Increase (Decrease) in Revenue from Cost Recovery Mechanisms Revenue from transactions accounted for as derivatives Revenue from Transactions Accounted for as Derivatives Revenue from Transactions Accounted for as Derivatives Revenues not accounted for under ASC 606 Other Income RETIREMENT BENEFITS Pension and Other Postretirement Benefits Disclosure [Text Block] New Accounting Pronouncements or Change in Accounting Principle [Table] New Accounting Pronouncements or Change in Accounting Principle [Table] New Accounting Pronouncements or Change in Accounting Principle [Line Items] New Accounting Pronouncements or Change in Accounting Principle [Line Items] Inventory decrement Inventory Write-down Kemper IGCC Kemper Igcc [Member] Kemper IGCC. Pre-tax charge to income Pre-Tax Charge To Income Pre-Tax Charge To Income Asset retirement obligation, liabilities incurred, net of tax Asset Retirement Obligation, Liabilities Incurred, Net Of Tax Asset Retirement Obligation, Liabilities Incurred, Net Of Tax Asset retirement obligation, expected cost Asset Retirement Obligation, Expected Cost Asset Retirement Obligation, Expected Cost Asset retirement obligation, liabilities incurred Asset Retirement Obligation, Liabilities Incurred Government grants received Government Grants Received Government Grants Received Cash Flow Hedges of Existing Debt Cash Flow Hedges Of Existing Debt [Member] Cash Flow Hedges Of Existing Debt [Member] Foreign currency derivatives June 2022 Maturity Date June 2022 [Member] Maturity Date June 2022 [Member] June 2026 Maturity Date June 2026 [Member] Maturity Date June 2026 [Member] Pay Notional Derivative Notional Amount, Pay Derivative Notional Amount, Pay Pay Rate Notional Amount Of Foreign Currency Derivatives, Pay Rate Notional Amount Of Foreign Currency Derivatives, Pay Rate Receive Notional Derivative Notional Amount, Receive Derivative Notional Amount, Receive Receive Rate Notional Amount Of Foreign Currency Derivatives, Receive Rate Notional Amount Of Foreign Currency Derivatives, Receive Rate Fair Value Disclosures [Abstract] Fair Value Option, Disclosures [Table] Fair Value Option, Disclosures [Table] Fair Value, Option, Quantitative Disclosures [Line Items] Fair Value, Option, Quantitative Disclosures [Line Items] 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 Goodwill [Table] Schedule of Goodwill [Table] Gas Distribution Operations Gas Distribution Operations [Member] Gas Distribution Operations [Member] Gas Marketing Services Goodwill [Line Items] Goodwill [Line Items] Goodwill Goodwill Income Statement Information Equity Method Investment, Summarized Financial Information, Income Statement [Abstract] Revenues Equity Method Investment, Summarized Financial Information, Revenue Operating income Equity Method Investment, Summarized Financial Information, Operating Income (Loss) Equity Method Investment, Summarized Financial Information, Operating Income (Loss) Net income Equity Method Investment, Summarized Financial Information, Net Income (Loss) SP Solar Holdings I, LP SP Solar Holdings I, LP [Member] SP Solar Holdings I, LP [Member] SP Wind SP Wind [Member] SP Wind [Member] Variable Interest Entities [Axis] Variable Interest Entities [Axis] Variable Interest Entity, Classification [Domain] Variable Interest Entity, Classification [Domain] Variable Interest Entity, Primary Beneficiary Variable Interest Entity, Primary Beneficiary [Member] Global Atlantic Global Atlantic [Member] Global Atlantic [Member] Financial Investors Financial Investors [Member] Financial Investors [Member] Assets Variable Interest Entity, Consolidated, Carrying Amount, Assets Liabilities Variable Interest Entity, Consolidated, Carrying Amount, Liabilities Noncontrolling interests related to other partners' interests Noncontrolling Interest in Variable Interest Entity 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 Number of financial investors Number Of Financial Investors Number Of Financial Investors Wild Horse Mountain Wild Horse Mountain [Member] Wild Horse Mountain [Member] Wild Horse Mountain Wildhorse [Member] Wildhorse [Member] Reading Reading [Member] Reading Ownership [Axis] Ownership [Axis] Ownership [Domain] Ownership [Domain] Class of Stock [Axis] Class of Stock [Axis] Class of Stock [Domain] Class of Stock [Domain] Class B Membership Interest Class B Membership Interest [Member] Class B Membership Interest [Member] Approximate Nameplate Capacity (MW) PPA Contract Period Life Output Of Plant The contracted life output of the plant. Ownership percentage by parent Noncontrolling Interest, Ownership Percentage by Parent Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Table] Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Table] Investment Type [Axis] Investment Type [Axis] Investments [Domain] Investments [Domain] Private equity Private Equity Funds [Member] Fair Value Hierarchy and NAV [Axis] Fair Value Hierarchy and NAV [Axis] Fair Value Hierarchy and NAV [Domain] Fair Value Hierarchy and NAV [Domain] Significant Unobservable Inputs (Level 3) Fair Value, Inputs, Level 3 [Member] Financial Instrument [Axis] Financial Instrument [Axis] Financial Instruments [Domain] Financial Instruments [Domain] Measurement Input Type [Axis] Measurement Input Type [Axis] Measurement Input Type [Domain] Measurement Input Type [Domain] Forward Price Measurement Input, Commodity Forward Price [Member] Valuation Approach and Technique [Axis] Valuation Approach and Technique [Axis] Valuation Approach and Technique [Domain] Valuation Approach and Technique [Domain] Valuation, Market Approach Valuation, Market Approach [Member] 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] Fair value Alternative Investment Unfunded commitments Fair Value, Investments, Entities that Calculate Net Asset Value Per Share, Unfunded Commitments Derivatives Derivative Liability Fair value of derivatives Derivative Assets (Liabilities), at Fair Value, Net Measurement input (usd per mmbtu) Derivative Asset (Liability) Net, Measurement Input Electric Utilities Electric Utilities [Member] Electric utilities. Eliminations Intersegment Eliminations [Member] Traditional Electric Operating Companies Traditional Operating Companies [Member] Traditional operating companies. All Other Other Segments [Member] Gas Pipeline Investments GEORGIA POWER AND MISSISSIPPI POWER CO Georgia Power And Mississippi Power [Member] Georgia Power And Mississippi Power [Member] GULF POWER CO Gulf Power [Member] Gulf Power. Pivotal Home Solutions Pivotal Home Solutions [Member] Pivotal Home Solutions [Member] Kemper County Energy Facility Kemper County Energy Facility [Member] Kemper County Energy Facility [Member] Intercompany Revenues Intercompany Revenues [Member] The amount of intercompany revenues. Total Gross Revenues Total Gross Revenues [Member] Total amount of gross revenues. Operating revenues Segment net income (loss) Goodwill Total assets Public utilities, property, plant and equipment, amount of loss (recovery) on plant abandonment Public Utilities, Property, Plant and Equipment, Amount of Loss (Recovery) on Plant Abandonment Public utilities, property, plant and equipment, amount of loss (recovery) on plant abandonment after tax Public Utilities, Property, Plant And Equipment, Amount Of Loss (Recovery) On Plant Abandonment, After Tax Public Utilities, Property, Plant And Equipment, Amount Of Loss (Recovery) On Plant Abandonment, After Tax Preliminary pre-tax gain Gain (Loss) on Disposition of Business Preliminary after-tax gain Gain (Loss) On Disposition Of Business, Net Of Tax Gain (Loss) On Disposition Of Business, Net Of Tax Number of natural gas distribution utilities disposed Disposal Group, Including Discontinued Operation, Number Of Distribution Utilities Disposal Group, Including Discontinued Operation, Number Of Distribution Utilities Operating revenues Disposal Group, Including Discontinued Operation, Revenue Less Gross Gas Costs Maturity Analysis Operating leases: Operating Lease Liabilities, Payments Due [Abstract] 2019 (remaining) Lessee, Operating Lease, Liability, Payments, Remainder of Fiscal Year 2020 Lessee, Operating Lease, Liability, Payments, Due Year Two 2021 Lessee, Operating Lease, Liability, Payments, Due Year Three 2022 Lessee, Operating Lease, Liability, Payments, Due Year Four 2023 Lessee, Operating Lease, Liability, Payments, Due Year Five Thereafter Lessee, Operating Lease, Liability, Payments, Due after Year Five Total Lessee, Operating Lease, Liability, Payments, Due Less: Present value discount Lessee, Operating Lease, Liability, Undiscounted Excess Amount Operating lease obligations, including held for sale Operating Lease, Liability, Including Held For Sale Operating Lease, Liability, Including Held For Sale Operating lease obligations Operating Lease, Liability Finance leases: Finance Lease Liabilities, Payments, Due [Abstract] 2019 (remaining) Finance Lease, Liability, Payments, Remainder of Fiscal Year 2020 Finance Lease, Liability, Payments, Due Year Two 2021 Finance Lease, Liability, Payments, Due Year Three 2022 Finance Lease, Liability, Payments, Due Year Four 2023 Finance Lease, Liability, Payments, Due Year Five Thereafter Finance Lease, Liability, Payments, Due after Year Five Total Finance Lease, Liability, Payments, Due Less: Present value discount Finance Lease, Liability, Undiscounted Excess Amount Finance lease obligations Finance Lease, Liability Assets and Liabilities Measured at Fair Value on a Recurring Basis Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis [Table Text Block] 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] 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. Fair Value of Commodity Derivative Contracts that Include a Significant Unobservable Component Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Table Text Block] Fair Value, by Balance Sheet Grouping [Table] Fair Value, by Balance Sheet Grouping [Table] Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] Long-term debt, including securities due within one year: Long-term Debt, Unclassified [Abstract] Carrying amount Long-term Debt, Gross Fair value Debt Instrument, Fair Value Disclosure Schedule of Long-term Debt Instruments [Table] Schedule of Long-term Debt Instruments [Table] Other Other Subsidiaries [Member] Other Subsidiaries. Debt Instrument [Line Items] Debt Instrument [Line Items] Senior Note Maturities, Redemptions, and Repurchases Maturities of Senior Debt Revenue Bond Issuances and Reofferings of Purchased Bonds Revenue Bond Issuances and Reofferings of Purchased Bonds Revenue Bond Issuances and Reofferings of Purchased Bonds Revenue Bond Maturities, Redemptions, and Repurchases Revenue Bond Redemptions Revenue Bond Redemptions Other Long-Term Debt Issuances Proceeds from Issuance of Long-term Debt and Capital Securities, Net Other Long-Term Debt Redemptions and Maturities Repayments of Long-term Debt, Long-term Capital Lease Obligations, and Capital Securities Operating Leases Assets And Liabilities, Operating Lease, Lessee [Abstract] Assets And Liabilities, Operating Lease, Lessee [Abstract] Operating lease ROU assets, net, including held for sale Operating Lease, Right-Of-Use Asset, Including Held For Sale Operating Lease, Right-Of-Use Asset, Including Held For Sale Operating lease ROU assets, net Operating Lease, Right-of-Use Asset Operating lease obligations - current, including held for sale Operating Lease, Liability, Including Held For Sale, Current Operating Lease, Liability, Including Held For Sale, Current Operating lease obligations - current Operating Lease, Liability, Current Operating lease obligations - non current, including held for sale Operating Lease, Liability, Including Held For Sale, Noncurrent Operating Lease, Liability, Including Held For Sale, Noncurrent Operating lease obligations - non current Operating Lease, Liability, Noncurrent Total operating lease obligations, including held for sale Total operating lease obligations Finance Leases Assets And Liabilities, Finance Lease, Lessee [Abstract] Assets And Liabilities, Finance Lease, Lessee [Abstract] Finance lease ROU assets, net Finance Lease, Right-of-Use Asset Finance lease obligations - current Finance Lease, Liability, Current Finance lease obligations - noncurrent Finance Lease, Liability, Noncurrent Total finance lease obligations Parent Company and Southern Power Parent Company and Southern Power [Member] Parent Company and Southern Power [Member] Registrants Registrants [Member] Registrants [Member] Related Party [Axis] Related Party [Axis] Related Party [Domain] Related Party [Domain] Derivative Counterparties Derivative Counterparties [Member] Derivative Counterparties [Member] 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. 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 Foreign currency cash flow hedge gain (loss) to be reclassified during next 12 months Foreign Currency Cash Flow Hedge Gain (Loss) to be Reclassified During Next 12 Months Collateral already posted, aggregate fair value Collateral Already Posted, Aggregate Fair Value Schedule of Error Corrections and Prior Period Adjustment Restatement [Table] Schedule of Error Corrections and Prior Period Adjustment Restatement [Table] Plant Gorgas Units 8, 9, and 10 Plant Gorgas Units 8, 9, And 10 [Member] Plant Gorgas Units 8, 9, And 10 [Member] Restatement [Axis] Restatement [Axis] Restatement [Domain] Restatement [Domain] Restatement Adjustment Restatement Adjustment [Member] Error Corrections and Prior Period Adjustments Restatement [Line Items] Error Corrections and Prior Period Adjustments Restatement [Line Items] Plant in service, net of depreciation Plant in Service Net of Depreciation Carrying amount at the balance sheet date for long-lived physical assets used in the normal conduct of business and not intended for resale, less depreciation. Other utility plant, net Other Utility Plant, Net Other utility plant, net. Net investment costs Public Utilities, Net Investment Costs To Be Transferred Upon Retirement Public Utilities, Net Investment Costs To Be Transferred Upon Retirement Capitalized asset retirement costs, net Capitalized Costs, Asset Retirement Costs Regulatory asset to be recovered over the units' remaining useful lives Remaining Amounts of Regulatory Assets for which No Return on Investment During Recovery Period is Provided Cost Recovery Clauses Cost Recovery Clauses [Table Text Block] [Table Text Block] for Cost Recovery Clauses [Table] Cost and Schedule Revised Cost and Schedule [Table Text Block] Revised Cost and Schedule [Table Text Block] SEGMENT AND RELATED INFORMATION Segment Reporting Disclosure [Text Block] Lease income - interest income on sales-type leases Sales-type Lease, Interest Income Lease income - operating leases Operating Lease, Lease Income Variable lease income Variable Lease, Income Total lease income Disposal Groups, Including Discontinued Operations [Table] Disposal Groups, Including Discontinued Operations [Table] Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items] Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items] Amount of indebtedness assumed at closing Disposal Group, Including Discontinued Operation, Accounts Payable and Accrued Liabilities Preliminary gain Preliminary gain, net of tax Disposal Group, Not Discontinued Operation, Gain (Loss) on Disposal, After Tax Disposal Group, Not Discontinued Operation, Gain (Loss) on Disposal, After Tax Public Utilities, Regulatory Proceeding [Axis] Public Utilities, Regulatory Proceeding [Axis] Public Utilities, Regulatory Proceeding [Domain] Public Utilities, Regulatory Proceeding [Domain] Open Access Transmission Tariff Open Access Transmission Tariff [Member] Open Access Transmission Tariff [Member] SCS SCS [Member] SCS [Member] Moratorium period Public Utilities, Moratorium Period Public Utilities, Moratorium Period Unregulated Distributed Generation Unregulated Distributed Generation [Member] Unregulated Distributed Generation [Member] Performance obligation, expected timing of satisfaction Revenue, Performance Obligation, Description of Timing Contract assets Contract liabilities Assets Held for Sale: Disposal Group, Including Discontinued Operation, Assets [Abstract] Current assets Disposal Group, Including Discontinued Operation, Assets, Current Total property, plant, and equipment Disposal Group, Including Discontinued Operation, Property, Plant and Equipment Goodwill and other intangible assets Disposal Group, Including Discontinued Operation, Goodwill and Other Intangible Assets Disposal Group, Including Discontinued Operation, Goodwill and Other Intangible Assets Other non-current assets Disposal Group, Including Discontinued Operation, Other Assets, Noncurrent Total Assets Held for Sale Disposal Group, Including Discontinued Operation, Assets Liabilities Held for Sale: Disposal Group, Including Discontinued Operation, Liabilities [Abstract] Current liabilities Disposal Group, Including Discontinued Operation, Liabilities, Current Long-term debt Disposal Group, Including Discontinued Operation, Long-term Debt Disposal Group, Including Discontinued Operation, Long-term Debt Accumulated deferred income taxes Disposal Group, Including Discontinued Operation, Deferred Tax Liabilities Other non-current liabilities Disposal Group, Including Discontinued Operation, Liabilities, Noncurrent Total Liabilities Held for Sale Disposal Group, Including Discontinued Operation, Liabilities Statement of Stockholders' Equity [Abstract] Cash dividends (in dollars per share) Common Stock, Dividends, Per Share, Cash Paid Plant Vogtle Units 3 And 4 Plant Vogtle Units 3 And 4 [Member] Plant Vogtle Units 3 And 4 [Member] Traditional Electric Operating Companies Credit Facility [Axis] Credit Facility [Axis] Credit Facility [Domain] Credit Facility [Domain] Term Loan Term Loan [Member] Term Loan [Member] 2014 FFB Credit Facility FFB Loan [Member] FFB Loan [Member] Additional FFB Credit Facility Additional FFB Credit Facility [Member] Additional FFB Credit Facility [Member] Short-term Debt, Type [Axis] Short-term Debt, Type [Axis] Short-term Debt, Type [Domain] Short-term Debt, Type [Domain] Notes Payable to Banks Notes Payable to Banks [Member] Jointly Owned Utility Plant [Axis] Jointly Owned Utility Plant [Axis] Jointly Owned Utility Plant [Domain] Jointly Owned Utility Plant [Domain] U.S. Treasury Rate U.S. Treasury Rate [Member] U.S. Treasury Rate [Member] Long-term Debt, Type [Axis] Long-term Debt, Type [Axis] Long-term Debt, Type [Domain] Long-term Debt, Type [Domain] Senior Notes Senior Notes [Member] Municipal bonds Municipal Bonds [Member] Debt Instrument [Axis] Debt Instrument [Axis] Debt Instrument, Name [Domain] Debt Instrument, Name [Domain] Uncommitted Bank Credit Arrangement Uncommitted Bank Credit Arrangement [Member] Uncommitted Bank Credit Arrangement [Member] Floating Rate Bank Term Loan Agreement Floating Rate Bank Term Loan Agreement 6 [Member] Floating Rate Bank Term Loan Agreement 6 [Member] 1.85% Notes Senior Notes 1.85% Due July 1, 2019 [Member] Senior Notes 1.85% Due July 1, 2019 [Member] Series 2014B Notes Series 2014B 2.15% Senior Notes Due September 1, 2019 [Member] Series 2014B 2.15% Senior Notes Due September 1, 2019 [Member] Series 2018A Notes Series 2018A Floating Rate Senior Notes Due February 14, 2020 [Member] Series 2018A Floating Rate Senior Notes Due February 14, 2020 [Member] Development Authority of Burke County (Georgia) Pollution Control Revenue Bonds (Georgia Power Company Plant Vogtle Project) First Series 1992 Development Authority of Burke County (Georgia) Pollution Control Revenue Bonds (Georgia Power Company Plant Vogtle Project) First Series 1992 [Member] Development Authority of Burke County (Georgia) Pollution Control Revenue Bonds (Georgia Power Company Plant Vogtle Project), First Series 1992 [Member] Development Authority of Burke County (Georgia) Pollution Control Revenue Bonds (Georgia Power Company Plant Vogtle Project), Eighth Series 1994 Development Authority of Burke County (Georgia) Pollution Control Revenue Bonds (Georgia Power Company Plant Vogtle Project), Eighth Series 1994 [Member] Development Authority of Burke County (Georgia) Pollution Control Revenue Bonds (Georgia Power Company Plant Vogtle Project), Eighth Series 1994 [Member] Development Authority of Burke County (Georgia) Pollution Control Revenue Bonds (Georgia Power Company Plant Vogtle Project), Second Series 1995 Development Authority of Burke County (Georgia) Pollution Control Revenue Bonds (Georgia Power Company Plant Vogtle Project), Second Series 1995 [Member] Development Authority of Burke County (Georgia) Pollution Control Revenue Bonds (Georgia Power Company Plant Vogtle Project), Second Series 1995 [Member] Development Authority of Bartow County (Georgia) Pollution Control Revenue Bonds (Georgia Power Company Plant Bowen Project), First Series 2009 Development Authority Of Bartow County (Georgia) Pollution Control Revenue Bonds (Georgia Power Company Plant Bowen Project), First Series 2009 [Member] Development Authority Of Bartow County (Georgia) Pollution Control Revenue Bonds (Georgia Power Company Plant Bowen Project), First Series 2009 [Member] Development Authority of Burke County (Georgia) Pollution Control Revenue Bonds (Georgia Power Company Plant Vogtle Project), First Series 2013 Development Authority Of Burke County (Georgia) Pollution Control Revenue Bonds (Georgia Power Company Plant Vogtle Project), First Series 2013 [Member] Development Authority Of Burke County (Georgia) Pollution Control Revenue Bonds (Georgia Power Company Plant Vogtle Project), First Series 2013 [Member] Development Authority of Burke County (Georgia) Pollution Control Revenue Bonds (Georgia Power Company Plant Vogtle Project), Second Series 2008 Development Authority of Burke County (Georgia) Pollution Control Revenue Bonds (Georgia Power Company Plant Vogtle Project), Second Series 2008 [Member] Development Authority of Burke County (Georgia) Pollution Control Revenue Bonds (Georgia Power Company Plant Vogtle Project), Second Series 2008 [Member] Development Authority of Burke County (Georgia) Pollution Control Revenue Bonds (Georgia Power Company Plant Vogtle Project), Fourth Series 1994 Development Authority Of Burke County (Georgia) Pollution Control Revenue Bonds (Georgia Power Company Plant Vogtle Project), Fourth Series 1994 [Member] Development Authority Of Burke County (Georgia) Pollution Control Revenue Bonds (Georgia Power Company Plant Vogtle Project), Fourth Series 1994 [Member] Development Authority of Burke County (Georgia) Pollution Control Revenue Bonds (Georgia Power Company Plant Vogtle Project), Fourth Series 1995 Development Authority Of Burke County (Georgia) Pollution Control Revenue Bonds (Georgia Power Company Plant Vogtle Project), Fourth Series 1995 [Member] Development Authority Of Burke County (Georgia) Pollution Control Revenue Bonds (Georgia Power Company Plant Vogtle Project), Fourth Series 1995 [Member] Development Authority of Burke County (Georgia) Pollution Control Revenue Bonds (Georgia Power Company Plant Vogtle Project), Ninth Series 1994 Development Authority Of Burke County (Georgia) Pollution Control Revenue Bonds (Georgia Power Company Plant Vogtle Project), Ninth Series 1994 [Member] Development Authority Of Burke County (Georgia) Pollution Control Revenue Bonds (Georgia Power Company Plant Vogtle Project), Ninth Series 1994 [Member] Development Authority of Burke County (Georgia) Pollution Control Revenue Bonds (Georgia Power Company Plant Vogtle Project), Second Series 1994 Development Authority Of Burke County (Georgia) Pollution Control Revenue Bonds (Georgia Power Company Plant Vogtle Project), Second Series 1994 [Member] Development Authority Of Burke County (Georgia) Pollution Control Revenue Bonds (Georgia Power Company Plant Vogtle Project), Second Series 1994 [Member] Mississippi Business Finance Corporation Pollution Control Revenue Refunding Bonds, Series 2002 Mississippi Business Finance Corporation Pollution Control Revenue Refunding Bonds, Series 2002 [Member] Mississippi Business Finance Corporation Pollution Control Revenue Refunding Bonds, Series 2002 [Member] 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. 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. Number of term loan facilities Number of Term Loan Facilities Number of Term Loan Facilities Eligible project costs to be reimbursed Eligible Project Costs To Be Reimbursed Eligible Project Costs To Be Reimbursed Eligible project costs to be reimbursed, percentage Line Of Credit Facility, Percent Of Eligible Project Costs To Be Reimbursed Line Of Credit Facility, Percent Of Eligible Project Costs To Be Reimbursed Amounts received under Guarantee Settlement Agreement, less Custumer Refunds Funds Received Under Guarantee Settlement Agreement, Less Customer Refunds Funds Received Under Guarantee Settlement Agreement, Less Customer Refunds Maximum borrowing capacity Line of Credit Facility, Maximum Borrowing Capacity Borrowings made Proceeds from Lines of Credit Interest rate Debt Instrument, Interest Rate, Stated Percentage Borrowings outstanding Long-term Line of Credit Undivided ownership interest Jointly Owned Utility Plant, Proportionate Ownership Share Basis spread Debt Instrument, Basis Spread on Variable Rate Amortization period for line of credit facility Amortization Period For Line Of Credit Facility Amortization Period For Line Of Credit Facility Failure to vote, percentage of ownership interests Ownership Interest Percentage Required for Voting for Continuing Construction Ownership Interest Percentage Required for Voting for Continuing Construction Repayments of short-term debt Repurchase amount Debt Instrument, Repurchase Amount Debt face amount Debt Instrument, Face Amount Repayments of debt Repayments of Debt Redeemed aggregate principal amount Debt Instrument, Repurchased Face Amount Stock-based compensation awards not included in the diluted earnings per share calculation because they were anti-dilutive (in shares) Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Table] Fair Value Measurements, Recurring and Nonrecurring [Table] Fair Value by Measurement Frequency [Axis] Measurement Frequency [Axis] Fair Value, Measurement Frequency [Domain] Fair Value, Measurement Frequency [Domain] Fair Value, Measurements, Recurring Fair Value, Measurements, Recurring [Member] Domestic equity Domestic Equity [Member] Domestic equity. Foreign equity Foreign Equity [Member] Foreign equity. U.S. Treasury and government agency securities US Treasury and Government [Member] Pooled funds – fixed income Fixed Income Funds [Member] Corporate bonds Corporate Debt Securities [Member] Mortgage and asset backed securities Asset-backed Securities [Member] Cash and cash equivalents Cash Equivalents [Member] Other Other than Securities Investment [Member] Fair Value, Measurements, Fair Value Hierarchy [Domain] Quoted Prices in Active Markets for Identical Assets (Level 1) Fair Value, Inputs, Level 1 [Member] Significant Other Observable Inputs (Level 2) Fair Value, Inputs, Level 2 [Member] Net Asset Value as a Practical Expedient (NAV) Fair Value Measured at Net Asset Value Per Share [Member] Weather Derivative Premiums and Weather Derivative [Member] Premiums and Weather Derivative [Member] 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] Assets: Assets, Fair Value Disclosure [Abstract] Derivatives Derivative Asset Non-qualified deferred compensation trusts Non-Qualified Deferred Compensation Trusts, Fair Value Disclosure Non-Qualified Deferred Compensation Trusts, Fair Value Disclosure Investments in trusts Decommissioning Fund Investments, Fair Value Cash equivalents Cash and Cash Equivalents, Fair Value Disclosure Other investments Other Assets, Fair Value Disclosure Total Assets, Fair Value Disclosure Liabilities: Liabilities, Fair Value Disclosure [Abstract] Contingent consideration Business Combination, Contingent Consideration, Liability Total Financial and Nonfinancial Liabilities, Fair Value Disclosure Assets Assets [Abstract] Current Assets: Assets, Current [Abstract] Cash and cash equivalents Restricted cash and cash equivalents Restricted Cash and Cash Equivalents, Current Receivables — Receivables, Net, Current [Abstract] Customer accounts receivable Accounts Receivable, Gross, Current Energy marketing receivables Energy Marketing Contracts Assets, Current Unbilled revenues Unbilled Revenues Current Carrying amount at the balance sheet date of revenues which have been earned but not yet billed. Under recovered fuel clause revenues Under Recovered Regulatory Clause Revenues Carrying amount at the balance sheet date of customer accounts receivable for retail and wholesale under recovered fuel costs, and other under recovered regulatory costs. Joint owner accounts receivable Joint Owner Accounts Receivable Amounts due from joint owners related to jointly-owned assets within one year of the balance sheet date. Affiliated Due from Related Parties, Current Other accounts and notes receivable Other Accounts Notes and Loans Receivable Amounts due from customers or clients, within one year of the balance sheet date (or one operating cycle, if longer), for goods or services that have been delivered or sold in the normal course of business and an amount representing an agreement for an unconditional promise by the maker to pay the entity (holder) a definite sum of money at a future date within one year of the balance sheet, not elsewhere specified in the taxonomy. Accumulated provision for uncollectible accounts Allowance for Doubtful Accounts Receivable, Current Materials and supplies Other Inventory, Supplies, Gross Fossil fuel for generation Energy Related Inventory, Other Fossil Fuel Natural gas for sale Energy Related Inventory, Natural Gas in Storage Prepaid income taxes Prepaid Taxes Prepaid expenses Prepaid Expense, Current Assets from risk management activities, net of collateral Derivative Asset, Current 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. Assets held for sale Other current assets Other Assets, Current Total current assets Assets, Current Property, Plant, and Equipment: Property, Plant and Equipment, Net [Abstract] In service Property, Plant and Equipment, Gross Less: Accumulated depreciation Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment Plant in service, net of depreciation Nuclear fuel, at amortized cost Nuclear Fuel at Amortized Cost The carrying amount as of the balance sheet of nuclear fuel held as property plant and equipment. This amount is net of amortization based on the energy produced over the life of the fuel. Total property, plant, and equipment Property, Plant and Equipment, Net Other Property and Investments: Long-term Investments [Abstract] Intangible assets, net of amortization Intangible Assets, Net (Including Goodwill) Equity investments in unconsolidated subsidiaries Other intangible assets, net of amortization Intangible Assets, Net (Excluding Goodwill) Nuclear decommissioning trusts, at fair value Decommissioning Fund Investments Leveraged leases Leveraged Leases, Balance Sheet, Investment in Leveraged Leases, Net Miscellaneous property and investments Other Long-term Investments Total other property and investments Long-term Investments Deferred Charges and Other Assets: Deferred Charges and Other Assets [Abstract] Deferred charges and other assets. Operating lease right-of-use assets, net of amortization 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. Unamortized loss on reacquired debt Unamortized Loss Reacquired Debt, Noncurrent Deferred under recovered regulatory clause revenues Deferred under Recovered Regulatory Clause Revenues Carrying amount at the balance sheet date of under recovered fuel costs allowed to be deferred by regulatory authorities, that are expected to be recoverable through rate adjustments after one year. 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. Prepaid LTSAs Prepaid Long Term Service Agreements Prepaid long-term service agreements. Accumulated deferred income taxes Deferred Income Tax Assets, Net Income taxes receivable, non-current Income Taxes Receivable, Noncurrent Assets held for sale, deferred Disposal Group, Including Discontinued Operation, Assets, Noncurrent Other deferred charges and assets Other Assets, Noncurrent 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. Total Assets Liabilities and Stockholders' Equity Liabilities and Equity [Abstract] Current Liabilities: Liabilities, Current [Abstract] Securities due within one year Long-term Debt and Capital Lease Obligations, Current Notes payable Short-term Debt Energy marketing trade payables Energy Marketing Contract Liabilities, Current Accounts payable — Accounts Payable and Accrued Liabilities, Current [Abstract] Accounts payable Accounts Payable, Current Affiliated Due to Related Parties, Current Other Accounts Payable, Other, Current Customer deposits Customer Deposits, Current1 Customer Deposits Current1 Accrued taxes — Taxes Payable, Current [Abstract] Accrued income taxes Accrued Income Taxes, Current Other accrued taxes Accrual for Taxes Other than Income Taxes, Current Accrued interest Interest Payable, Current Accrued compensation Accrued Salaries, Current Accrued plant closure costs Accrued Plant Closure Costs Accrued Plant Closure Costs Asset retirement obligations Asset Retirement Obligation, Current Liabilities from risk management activities, net of collateral Derivative Instruments and Hedges, Liabilities 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. Liabilities held for sale Operating lease obligations Other current liabilities Other Liabilities, Current Over recovered regulatory clause liabilities Over Recovered Regulatory Clause Liabilities Over recovered regulatory clause liabilities. Total current liabilities Liabilities, Current Long-term Debt Long-term Debt and Capital Lease Obligations Deferred Credits and Other Liabilities: Deferred Credits and Other Liabilities [Abstract] Accumulated deferred income taxes Deferred Income Tax Liabilities, Net 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. Accumulated deferred ITCs Accumulated Deferred Investment Tax Credit Employee benefit obligations Liability, Defined Benefit Plan, Noncurrent Operating lease obligations, deferred Asset retirement obligations, deferred Asset Retirement Obligations, Noncurrent Accrued environmental remediation Accrued Environmental Loss Contingencies, Noncurrent 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. Other regulatory liabilities, deferred Other Regulatory Liabilities Deferred Other regulatory liabilities, deferred. Liabilities held for sale, deferred Other deferred credits and liabilities Other Liabilities, Noncurrent Total deferred credits and other liabilities Deferred Credits and Other Liabilities Total Liabilities Liabilities Redeemable Preferred Stock of Subsidiaries Temporary Equity, Carrying Amount, Attributable to Parent Redeemable Preferred Stock Preferred Stock, Value, Outstanding Stockholders' Equity: Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest [Abstract] Total stockholders' equity Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest Total Liabilities and Stockholders' Equity Liabilities and Equity Geographical [Axis] Geographical [Axis] Geographical [Domain] Geographical [Domain] Location One Location One [Member] Location One [Member] Environmental remediation liability, current and former sites Environmental Exit Costs, Assets Previously Disposed, Liability for Remediation FAIR VALUE MEASUREMENTS Fair Value Disclosures [Text Block] Document and Entity Information [Abstract] Document and entity information. Document Information [Table] Document Information [Table] Document Information [Line Items] Document Information [Line Items] Entity Registrant Name Entity Registrant Name Entity Central Index Key Entity Central Index Key Document Type Document Type Document Period End Date Document Period End Date Amendment Flag Amendment Flag Document Fiscal Year Focus Document Fiscal Year Focus Document Fiscal Period Focus Document Fiscal Period Focus Current Fiscal Year End Date Current Fiscal Year End Date Entity Filer Category Entity Filer Category Entity Emerging Growth Company Entity Emerging Growth Company Entity Small Business Entity Small Business Entity Common Stock, Shares Outstanding Entity Common Stock, Shares Outstanding Disaggregation of Revenue Disaggregation of Revenue [Table Text Block] Contract with Customer, Asset and Liability and Revenue Recognized Contract with Customer, Asset and Liability [Table Text Block] Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Table Text Block] Schedule of Goodwill Schedule of Goodwill [Table Text Block] Schedule of Other Intangible Assets, Finite-Lived Schedule of Finite-Lived Intangible Assets [Table Text Block] Schedule of Other Intangible Assets, Indefinite-Lived Schedule of Indefinite-Lived Intangible Assets [Table Text Block] Finite-lived Intangible Assets Amortization Expense Finite-lived Intangible Assets Amortization Expense [Table Text Block] Schedule of Cash and Cash Equivalents Schedule of Cash and Cash Equivalents [Table Text Block] Restrictions on Cash and Cash Equivalents Restrictions on Cash and Cash Equivalents [Table Text Block] Other comprehensive income (loss): Other Comprehensive Income (Loss), Net of Tax [Abstract] Qualifying hedges: Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), after Reclassification and Tax [Abstract] Changes in fair value, net of tax Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), before Reclassification, after Tax Reclassification adjustment for amounts included in net income, net of tax Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), Reclassification, after Tax Pension and other postretirement benefit plans: Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, after Tax [Abstract] 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 Total other comprehensive income (loss) Other Comprehensive Income (Loss), Net of Tax Comprehensive Income (Loss) Comprehensive Income (Loss), Net of Tax, Including Portion Attributable to Noncontrolling Interest Less: Preferred Stock Dividends and Other Adjustments [Abstract] Comprehensive loss attributable to noncontrolling interests Comprehensive Income (Loss) Attributable to Parent Comprehensive Income (Loss), Net of Tax, Attributable to Parent Financial Data for Business Segments Schedule of Segment Reporting Information, by Segment [Table Text Block] Financial Data for Products and Services Financial data for Products and Services [Table Text Block] Financial data for products and services. Fair Values Derivatives, Balance Sheet Location, by Derivative Contract Type [Table] Fair Values Derivatives, Balance Sheet Location, by Derivative Contract Type [Table] Derivatives designated as hedging instruments for regulatory purposes Hedging Instruments for Regulatory Purposes [Member] Hedging instruments for regulatory purposes. 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. Derivatives designated as hedging instruments for regulatory purposes Designated as Hedging Instrument [Member] Other current assets Other Current Assets [Member] Under recovered fuel balance Other Current Liabilities [Member] Other deferred charges and assets Other deferred charges and assets [Member] Other deferred charges and assets. Other deferred credits and liabilities Other deferred credits and liabilities [Member] Other deferred credits and liabilities. Assets from risk management activities Assets From Risk Management Activities [Member] Assets From Risk Management Activities [Member] Liabilities from risk management activities Liabilities from risk management activities [Member] Liabilities from risk management activities. Assets held for sale, current Assets Held For Sale, Current [Member] Assets Held For Sale, Current [Member] Liabilities held for sale, current Liabilities Held For Sale, Current [Member] Liabilities Held For Sale, Current [Member] Derivatives, Fair Value [Line Items] Derivatives, Fair Value [Line Items] Derivatives, assets Derivative Asset, Fair Value, Gross Asset Derivatives, liabilities Derivative Liability, Fair Value, Gross Liability Derivative asset, Gross amounts offset Derivative Asset, Fair Value, Gross Liability Derivative liability, Gross amounts offset Derivative Liability, Fair Value, Gross Asset Derivative asset Derivative liability Weather derivative premium Weather Derivative Premium Financial instruments that can be used for risk management purposes to hedge against losses due to adverse, unpredictable weather recorded on the balance sheet based on intrinsic value, not fair value. INTRODUCTION Organization, Consolidation and Presentation of Financial Statements Disclosure [Text Block] Florida Plants Florida Plants [Member] Florida Plants [Member] Earnings before income taxes Income (Loss) from Individually Significant Component Disposed of or Held-for-sale, Excluding Discontinued Operations, Attributable to Parent, before Income Tax Schedule of Energy-Related Derivatives Schedule of Derivative Instruments [Table Text Block] Schedule of Interest Rate Derivatives Schedule of Interest Rate Derivatives [Table Text Block] Schedule of Foreign Currency Derivatives Schedule Of Foreign Exchange Contracts [Table Text Block] [Table Text Block] for Schedule Of Foreign Exchange Contracts [Table] Fair Value of Energy-Related Derivatives and Interest Rate Derivatives Schedule of Derivatives Instruments Statements of Financial Performance and Financial Position, Location [Table Text Block] Pre-tax Effects of Unrealized Derivative Gains (Losses) Arising from Energy-Related Derivative Instruments Pre tax effect of unrealized derivative gains losses [Table Text Block] Pre-tax effect of unrealized derivative gains (losses). Pre-tax Effects of Interest Rate Derivatives, Designated as Cash Flow Hedging Instruments Derivative Instruments, Gain (Loss) [Table Text Block] Schedule of Cash Flow Hedging Instruments, Statements of Financial Performance and Financial Position, Location Schedule of Cash Flow Hedging Instruments, Statements of Financial Performance and Financial Position, Location [Table Text Block] Schedule of Fair Value Hedging Instruments, Statements of Financial Performance and Financial Position, Location Schedule of Fair Value Hedging Instruments, Statements of Financial Performance and Financial Position, Location [Table Text Block] Pre-tax Effect of Interest Rate and Energy Related Derivatives Pre tax Effect of Interest Rate and Energy Related Derivatives [Table Text Block] [Table Text Block] for Pre tax Effect of Interest Rate and Energy Related Derivatives [Table] Interest capitalized Interest Paid, Capitalized, Investing Activities Martin Product Sales, LLC Litigation Martin Product Sales, LLC Litigation [Member] Martin Product Sales, LLC Litigation [Member] RE Roserock, LLC RE Roserock, LLC [Member] RE Roserock, LLC [Member] Litigation Status [Axis] Litigation Status [Axis] Litigation Status [Domain] Litigation Status [Domain] Pending Litigation Pending Litigation [Member] Litigation Case [Axis] Litigation Case [Axis] Litigation Case [Domain] Litigation Case [Domain] Putative Securities Class Action Putative Securities Class Action [Member] Putative Securities Class Action [Member] Shareholder Derivative Lawsuits Shareholder Derivative Lawsuits [Member] Shareholder Derivative Lawsuits [Member] Purported Violations Of Mississippi Consumer Protection Act Purported Violations Of Mississippi Consumer Protection Act [Member] Purported Violations Of Mississippi Consumer Protection Act [Member] Increase in the purported class period Class Action Complaint, Increase In Purported Class Period Class Action Complaint, Increase In Purported Class Period Pending number of claims Loss Contingency, Pending Claims, Number Stay period Loss Contingency, Stay Period Loss Contingency, Stay Period Number of agreements Loss Contingency, Number Of Agreements Loss Contingency, Number Of Agreements Damages sought by litigation Loss Contingency, Damages Sought, Value Number of plaintiffs Loss Contingency, Number of Plaintiffs Number of defendants Loss Contingency, Number of Defendants Withholding of construction contract payments Withholding Of Construction Contract Payments Withholding Of Construction Contract Payments Amount paid to other party Litigation Settlement, Amount Awarded to Other Party Insurance proceeds Proceeds from Insurance Settlement, Investing Activities Schedule of Finite-Lived Intangible Assets [Table] Schedule of Finite-Lived Intangible Assets [Table] Finite-Lived Intangible Assets [Line Items] Finite-Lived Intangible Assets [Line Items] Amortization of intangible assets Amortization of Intangible Assets Vogtle Owners Vogtle Owners [Member] Vogtle Owners [Member] FFB Loan Proportionate ownership share Number of construction units approved Number Of Construction Units Approved Number Of Construction Units Approved Electric generating capacity in mega watts under consortium agreement Electric Generating Capacity in Mega Watts Under Consortium Agreement Electric generating capacity in mega watts under consortium agreement. Period of notice required in the event letters of credit are not renewed Period of Notice Required in the Event Letters of Credit Are Not Renewed Period of Notice Required in the Event Letters of Credit Are Not Renewed Construction financing costs Construction Financing Costs Construction Financing Costs Base project capital cost forecast, monthly Estimated Cost To Complete, Base Project Capital Cost Forecast, Monthly Estimated Cost to Complete, Base Project Capital Cost Forecast, Monthly Monthly AFUDC Public Utilities, Allowance for Funds Used During Construction, Monthly Public Utilities, Allowance for Funds Used During Construction, Monthly Percentage of ownership interest required for voting for continuing construction Additional construction capital costs Additional Construction Capital Costs Additional Construction Capital Costs Estimated in-service capital cost Estimated In-service Capital Cost Increase Estimated In-service Capital Cost Financing costs collected, net of tax Proceeds from Recovery of Financing Costs Proceeds from Recovery of Financing Costs Cost settlement agreement revised forecast, net of payments Cost Settlement Agreement Revised Forecast, Net Of Payments Cost Settlement Agreement Revised Forecast, Net Of Payments Increase in NCCR tariff Public Utilities, Requested Tariff Increase (Decrease), Amount Public Utilities, Requested Tariff Increase (Decrease), Amount Amendment to estimated in-service capital cost Amendment To Estimated In-service Capital Cost Amendment To Estimated In-service Capital Cost Retail rate of return on common equity Retail Rate Of Return On Common Equity Retail Rate Of Return On Common Equity Public utilities, approved return on equity, monthly percentage decrease Public Utilities, Return on Equity, Potential Decrease Each Month, Percentage Public Utilities, Return on Equity, Potential Decrease Each Month, Percentage Return on equity reduction, negative impact on earnings Return On Equity Reduction, Negative Impact On Earnings Return On Equity Reduction, Negative Impact On Earnings Number of appeals Loss Contingency, Claims Dismissed, Number Requested capital construction costs Public Utilities, Requested Capital Construction Costs Public Utilities, Requested Capital Construction Costs Deferred approval of expenditures related to administrative claim Expenditures Related To Administrative Claim, Deferred Approval Expenditures Related To Administrative Claim, Deferred Approval Guarantor obligations Guarantor Obligations, Maximum Exposure, Undiscounted Customer refund Customer Refund Customer Refund Long-term line of credit DERIVATIVES Derivative Instruments and Hedging Activities Disclosure [Text Block] Income Tax Disclosure [Abstract] Income Tax Contingency [Table] Income Tax Contingency [Table] Income Tax Contingency [Line Items] Income Tax Contingency [Line Items] Effective tax (benefit) rate Effective Income Tax Rate Reconciliation, Percent Earnings from Equity Method Investments Legal Entity [Axis] Finite-Lived Intangible Assets by Major Class [Axis] Finite-Lived Intangible Assets by Major Class [Axis] Finite-Lived Intangible Assets, Major Class Name [Domain] Finite-Lived Intangible Assets, Major Class Name [Domain] Customer relationships Customer Relationships [Member] Trade names Trade Names [Member] Storage and transportation contracts Storage and Transportation Contracts [Member] Storage and Transportation Contracts [Member] PPA fair value adjustments PPA Fair Value Adjustments [Member] PPA Fair Value Adjustments [Member] Other Other Intangible Assets [Member] Other intangible assets subject to amortization: Finite-Lived Intangible Assets, Net [Abstract] Gross Carrying Amount Finite-Lived Intangible Assets, Gross Accumulated Amortization Other Intangible Assets, Net Finite-Lived Intangible Assets, Net Other intangible assets not subject to amortization: Indefinite-lived Intangible Assets (Excluding Goodwill) [Abstract] Federal Communications Commission licenses Indefinite-lived Intangible Assets (Excluding Goodwill) Total other intangible assets Intangible Assets, Net (Excluding Goodwill) [Abstract] Gross Carrying Amount Intangible Assets, Gross (Excluding Goodwill) Other Intangible Assets, Net MRA Revenue MRA Revenue [Member] MRA Revenue. Decrease in base rate under cost based electric tariff Decrease In Base Rate Under Cost Based Electric Tariff Due To Settlement Decrease In Base Rate Under Cost Based Electric Tariff Due To Settlement Concentration Risk [Table] Concentration Risk [Table] Electric Utilities' Revenues Southern Company Gas' Revenues Retail Wholesale Other Gas Distribution Operations Other Concentration Risk Benchmark [Axis] Concentration Risk Benchmark [Axis] Concentration Risk Benchmark [Domain] Concentration Risk Benchmark [Domain] Revenues Sales Revenue, Net [Member] Concentration Risk Type [Axis] Concentration Risk Type [Axis] Concentration Risk Type [Domain] Concentration Risk Type [Domain] Product Concentration Risk Product Concentration Risk [Member] Customer [Axis] Customer [Axis] Customer [Domain] Customer [Domain] Three Gas Distribution Operations Three Gas Distribution Operations [Member] Three Gas Distribution Operations [Member] Concentration Risk [Line Items] Concentration Risk [Line Items] As reported shares Effect of stock-based compensation Incremental Common Shares Attributable to Dilutive Effect of Share-based Payment Arrangements Diluted shares Schedule of Construction Projects Schedule of Construction Projects [Table Text Block] [Table Text Block] for Schedule of Construction Projects [Table] Disposal Groups, Including Discontinued Operations Disposal Groups, Including Discontinued Operations [Table Text Block] INCOME TAXES Income Tax Disclosure [Text Block] 2019 (remaining) Lessor, Operating Lease, Payments to be Received, Remainder of Fiscal Year 2020 Lessor, Operating Lease, Payments to be Received, Two Years 2021 Lessor, Operating Lease, Payments to be Received, Three Years 2022 Lessor, Operating Lease, Payments to be Received, Four Years 2023 Lessor, Operating Lease, Payments to be Received, Five Years Thereafter Lessor, Operating Lease, Payments to be Received, Thereafter Total Lessor, Operating Lease, Payments to be Received Equity Components [Axis] Equity Components [Axis] Equity Component [Domain] Equity Component [Domain] Common Stock Common Stock [Member] Treasury Treasury Stock [Member] Paid-In Capital Additional Paid-in Capital [Member] Retained Earnings Retained Earnings [Member] Accumulated Other Comprehensive Income (Loss) AOCI Attributable to Parent [Member] Total Common Stockholders' Equity Common Stockholder's Equity Not Including Noncontrolling Interest [Member] Common Stockholder's Equity Not Including Noncontrolling Interest [Member] Noncontrolling Interests Noncontrolling Interest [Member] Increase (Decrease) in Stockholders' Equity [Roll Forward] Increase (Decrease) in Stockholders' Equity [Roll Forward] Beginning balance (in shares) Shares, Issued Beginning balance Net income (loss) Other comprehensive income (loss) Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent Stock issued (in shares) Stock Issued During Period, Shares, New Issues Stock issued Stock Issued During Period, Value, New Issues Stock-based compensation Adjustments to Additional Paid in Capital, Share-based Compensation, Requisite Service Period Recognition Cash dividends on common stock Dividends, Common Stock, Cash Contributions from noncontrolling interests Noncontrolling Interest, Increase from Contributions from Noncontrolling Interest Holders Noncontrolling Interest, Increase from Contributions from Noncontrolling Interest Holders Distributions to noncontrolling interests Noncontrolling Interest, Decrease from Distributions to Noncontrolling Interest Holders Net income (loss) attributable to noncontrolling interests Noncontrolling Interest in Net Income (Loss) Other Noncontrolling Interests, Redeemable Other (in shares) Stockholders' Equity, Other Shares Other Stockholders' Equity, Other Capital contributions from parent company Capital Contributions From (To) Parent Company Capital Contributions From (To) Parent Company Ending balance (in shares) Ending balance Deferred under recovered regulatory clause revenues Deferred Under Recovered Regulatory Clause Revenues [Member] Deferred Under Recovered Regulatory Clause Revenues [Member] Customer accounts receivable Accounts Receivable [Member] Other regulatory liabilities, deferred Other regulatory liabilities deferred [Member] Other regulatory liabilities deferred. Receivables – under recovered fuel clause revenues Under Recovered Fuel Clause [Member] Under recovered fuel clause. Over recovered retail fuel costs Over Recovered Retail Fuel Costs [Member] Over Recovered Retail Fuel Costs [Member] Rate RSE Refund Liability Rate RSE Refund Liability Rate RSE Refund Liability Rate CNP Compliance Under Recovered Rate Cnp Balance Under recovered Rate CNP balance. Rate CNP PPA Rate Cnp Power Purchase Agreement Rate Cnp Power Purchase Agreement Retail Energy Cost Recovery() Retail Energy Cost Recovery Retail Energy Cost Recovery Natural Disaster Reserve Accumulated reserve balance for future storms Accumulated reserve balance for future storms. Fuel Cost Recovery Over (Under) Recovered Fuel Balance Over (Under) recovered fuel balance. Fuel Cost Recovery Over Recovered Fuel Cost Over recovered fuel cost. Line of Credit Facility [Table] Line of Credit Facility [Table] Southern Company Gas Capital Southern Company Gas Capital [Member] Southern Company Gas Capital [Member] Standby Letters of Credit Standby Letters of Credit [Member] Line of Credit Facility [Line Items] Line of Credit Facility [Line Items] Expires, 2019 Line Of Credit Expire Year One Line Of Credit Expire Year One Expires, 2020 Line Of Credit Expire Year Two Line Of Credit Expire Year Two Expires, 2022 Line Of Credit Expire Year Four Line Of Credit Expire Year Four Total Unused Line of Credit Facility, Remaining Borrowing Capacity LEASES Lessee, Operating Leases [Text Block] LEASES Lessee, Finance Leases [Text Block] LEASES Lessor, Operating Leases [Text Block] LEASES Lessor, Sales-type Leases [Text Block] CONTINGENCIES Legal Matters and Contingencies [Text Block] Other regulatory assets, current Other regulatory assets current [Member] Other regulatory assets, current. Other regulatory assets, deferred Other regulatory assets deferred [Member] Other regulatory assets, deferred. Other regulatory liabilities, current Other regulatory liabilities current [Member] Other regulatory liabilities current. Total energy-related derivative gains (losses) Regulatory Hedge Unrealized Gain Loss Regulatory hedge unrealized gain (loss). Gain (Loss) Recognized in OCI on Derivative Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), after Reclassification, before Tax Revenue from contracts with customers recognized Contract with Customer, Liability, Revenue Recognized Plant Daniel Units 1 And 2 Plant Daniel Units 1 And 2 [Member] Plant Daniel Units 1 And 2 [Member] Undivided ownership interest to be sold Undivided Ownership Interest To Be Sold Undivided Ownership Interest To Be Sold Undivided ownership interest, ownership interest in individual unit Undivided Ownership Interest, Ownership Interest In Individual Unit Undivided Ownership Interest, Ownership Interest In Individual Unit Payments to acquire business Payments to Acquire Businesses, Gross Option to purchase, period Business Combination, Option To Purchase, Period Business Combination, Option To Purchase, Period CONSOLIDATED ENTITIES AND EQUITY METHOD INVESTMENTS Noncontrolling Interest Disclosure [Text Block] Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Table] Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Table] Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward] Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward] Beginning balance Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis with Unobservable Inputs Transfers to Level 3 Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Inputs Reconciliation, Transfers into Level 3 Changes in fair value Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Inputs Reconciliation, Gain (Loss) Included in Earnings Ending balance Base project capital cost forecast Estimated Cost To Complete, Base Project Capital Cost Forecast Estimated Cost to Complete, Base Project Capital Cost Forecast Construction contingency estimate Estimated Cost to Complete, Construction Contingency Estimate Estimated Cost To Complete, Construction Contingency Estimate Total project capital cost forecast Preliminary Estimated Cost to Complete Preliminary Estimated Cost to Complete Net investment as of March 31, 2019 Public Utilities, Property, Plant and Equipment, Investment, Net Public Utilities, Property, Plant and Equipment, Investment, Net Remaining estimate to complete Guarantee Obligations of Contractor's Parent Guarantee Obligations of Contractor's Parent Expected capitalized costs Allowance for Funds Used During Construction, Capitalized Interest Real estate Building [Member] Land Land [Member] Outdoor lighting Outdoor Lighting [Member] Outdoor Lighting [Member] Fuel cells Fuel Cells [Member] Fuel Cells [Member] Affiliate Affiliated Entity [Member] Remaining terms Lease, Weighted Average Remaining Lease Term Lease, Weighted Average Remaining Lease Term Remaining terms Lessee, lease term Lessee, Lease, Term Of Contract Lessee, Lease, Term Of Contract Lessee, renewal period Lessee, Lease, Renewal Term Lessee, Lease, Renewal Term Lease obligations Lease term, lease not yet commenced Lessee, Operating Lease, Lease Not yet Commenced, Term of Contract Total estimate obligations of leases that have not yet commenced Lessee, Operating Lease, Lease Not Yet Commenced, Liability Lessee, Operating Lease, Lease Not Yet Commenced, Liability Lessor, lease term, operating lease Lessor, Operating Lease, Term of Contract Lessor, lease term, sales-type lease Lessor, Sales-type Lease, Term of Contract Lessor, remaining term Lessor, Operating Lease, Remaining Lease Term Lessor, Operating Lease, Remaining Lease Term