Segment Reporting [Abstract] Revenue from External Customers by Products and Services [Table] Revenue from External Customers by Products and Services [Table] Products and Services [Axis] Products and Services [Axis] Products and Services [Domain] Products and Services [Domain] Retail [Member] Retail [Member] Retail. Wholesale [Member] Wholesale [Member] Wholesale. Other [Member] Other Electric Revenue [Member] Other electric revenue. Revenue from External Customer [Line Items] Revenue from External Customer [Line Items] Electric Utilities' Revenues Electric Revenue Equity [Abstract] Statement [Table] Statement [Table] Equity Components [Axis] Equity Components [Axis] Equity Component [Domain] Equity Component [Domain] Number of Common shares Issued [Member] Common Stock [Member] Number of Common shares Treasury [Member] Treasury Stock [Member] Common Stockholders' Equity [Member] Parent [Member] Preferred And Preference Stock [Member] Preferred And Preference Stock [Member] Preferred And Preference Stock [Member] Noncontrolling Interest [Member] Noncontrolling Interest [Member] Stock Option Exercises Through December Two Thousand Seventeen [Member] Stock Option Exercises Through December Two Thousand Seventeen [Member] Stock Option Exercises Through December Two Thousand Seventeen [Member] Statement [Line Items] Statement [Line Items] Changes in Stockholders' Equity Increase (Decrease) in Stockholders' Equity [Roll Forward] Beginning Balance, Shares Shares, Issued Beginning Balance Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest Net income after dividends on preferred and preference stock Net Income (Loss) Available to Common Stockholders, Basic Other comprehensive income (loss) Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent Treasury stock re-issued, Shares Stock Issued During Period, Shares, Treasury Stock Reissued Treasury stock re-issued Stock Issued During Period, Value, Treasury Stock Reissued Stock issued, Shares Stock Issued During Period, Shares, New Issues Stock issued Stock Issued During Period, Value, New Issues Adjustments to Additional Paid in Capital, Share-based Compensation, Requisite Service Period Recognition Adjustments to Additional Paid in Capital, Share-based Compensation, Requisite Service Period Recognition Stock repurchased, at cost, Shares Stock Repurchased During Period, Shares Stock repurchased, at cost Stock Repurchased During Period, Value Cash dividends on common stock Dividends, Common Stock, Cash Other, Shares Stockholders' Equity, Other Shares Other Stockholders' Equity, Other Ending Balance Ending Balance, Shares Compensation and Retirement Disclosure [Abstract] Schedule of Defined Benefit Plans Disclosures [Table] Schedule of Defined Benefit Plans Disclosures [Table] Defined Benefit Plans and Other Postretirement Benefit Plans Disclosures [Axis] Defined Benefit Plans and Other Postretirement Benefit Plans [Axis] Defined Benefit Plans and Other Postretirement Benefit Plans [Domain] Defined Benefit Plan and Other Postretirement Benefit Plan [Domain] Pension Plans [Member] Pension Plan [Member] Other Postretirement Benefits [Member] Other Postretirement Benefit Plan [Member] Legal Entity [Axis] Legal Entity [Axis] Entity [Domain] Entity [Domain] Southern Company [Member] Parent Company [Member] Alabama Power [Member] Alabama Power [Member] Alabama Power. Georgia Power [Member] Georgia Power [Member] Georgia Power. Gulf Power [Member] Gulf Power [Member] Gulf Power. Mississippi Power [Member] Mississippi Power [Member] Mississippi Power. Defined Benefit Plan Disclosure [Line Items] Defined Benefit Plan Disclosure [Line Items] Pension Plans and Postretirement Plans Defined Benefit Plan, Net Periodic Benefit Cost [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 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) Net (gain)/loss Defined Benefit Plan, Amortization of Gains (Losses) Net cost Defined Benefit Plan, Net Periodic Benefit Cost Statement of Comprehensive Income [Abstract] Alabama Power [Member] Georgia Power [Member] Southern Power [Member] Southern Power [Member] Southern Power. Net Income (loss) Net Income (Loss), Including Portion Attributable to Noncontrolling Interest Other comprehensive income (loss): Other Comprehensive Income (Loss), Net of Tax [Abstract] Qualifying hedges: Other Comprehensive Income (Loss), Derivatives Qualifying as Hedges, Net of Tax [Abstract] Changes in fair value, net of tax Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, Net of Tax Reclassification adjustment for amounts included in net income, net of tax Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI on Derivatives, Net of Tax Pension and other post retirement benefit plans: Other Comprehensive (Income) Loss, Pension and Other Postretirement Benefit Plans, Adjustment, Net of Tax [Abstract] Reclassification adjustment for amounts included in net income, net of tax Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI, Pension and Other Postretirement Benefit Plans, for Net Gain (Loss), Net of Tax Total other comprehensive income (loss) Dividends on preferred and preference stock of subsidiaries Preferred Stock Dividends, Income Statement Impact Less: Comprehensive income attributable to noncontrolling interest/Dividends on preferred and preference stock of subsidiaries Net Income (Loss) Attributable to Noncontrolling Interest Comprehensive Income (Loss) Comprehensive Income (Loss), Net of Tax, Including Portion Attributable to Noncontrolling Interest Derivative Instruments and Hedging Activities Disclosure [Abstract] Derivative [Table] Derivative [Table] Southern Power [Member] Gulf Power [Member] Mississippi Power [Member] Derivative [Line Items] Derivative [Line Items] Derivatives (Textual) [Abstract] Derivatives (Textual) [Abstract] Derivatives. 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. Maximum Potential Collateral Requirements Arising from Credit Risk Related Contingent Features Maximum Potential Collateral Requirements Arising from Credit Risk Related Contingent Features Maximum potential collateral requirements arising the from credit-risk-related contingent features. DERIVATIVES Derivative Instruments and Hedging Activities Disclosure [Text Block] Fair Value Disclosures [Abstract] Fair Value, Option, Quantitative Disclosures [Table] Fair Value, Option, Quantitative Disclosures [Table] Range [Axis] Range [Axis] Range [Domain] Range [Domain] Minimum [Member] Minimum [Member] Investment Type [Axis] Investment Type [Axis] Investments [Domain] Investments [Domain] Other - commingled funds [Member] Other - commingled funds [Member] Other commingled funds Fair Value, Option, Quantitative Disclosures [Line Items] Fair Value, Option, Quantitative Disclosures [Line Items] Withdrawal Of Foreign Equity Fund Investment Withdrawal Of Foreign Equity Fund Investment Withdrawal Of Foreign Equity Fund Investment Foreign Equity Fund Investment Foreign Equity Fund Investment Foreign Equity Fund Investment Notices Of Withdrawal Foreign Equity Funds Notices Of Withdrawal Foreign Equity Funds Notices Of Withdrawal Foreign Equity Funds Maximum Number of Days Related to Dollar Weighted Average Portfolio Maturities Regarding Commingled Funds Maximum Number of Days Related to Dollar Weighted Average Portfolio Maturities Maximum number of days related to dollar weighted average portfolio maturities regarding commingled 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 Increase (decrease) in fair value of funds including reinvested interest and dividends. Statement of Financial Position [Abstract] Assets: Assets [Abstract] Current Assets: Assets, Current [Abstract] Cash and cash equivalents Cash and Cash Equivalents, at Carrying Value Receivables -- Receivables, Net, Current [Abstract] Customer accounts receivable Accounts Receivable, Gross, 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 regulatory 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. 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. Affiliated companies Due from Related Parties, Current Accumulated provision for uncollectible accounts Allowance for Doubtful Accounts Receivable, Current Fossil fuel stock, at average cost Energy Related Inventory, Other Fossil Fuel Materials and supplies, at average cost Other Inventory, Supplies, Gross Prepaid service agreements - current Prepaid Service Agreements Current Current prepaid service agreements. Vacation pay Vacation Pay Carrying amount at the balance sheet date of the regulatory asset related to vacation pay to employees. Prepaid expenses Prepaid Expense, Current Deferred income taxes, current Deferred Tax Assets, Net, Current Assets from risk management activities Derivative Asset, Current Prepaid income taxes Prepaid Taxes Other regulatory assets, current 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. 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 provision for depreciation Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment 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. 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. Construction work in progress Construction in Progress, Gross Total property, plant, and equipment Property, Plant and Equipment, Net Other Property and Investments: Long-term Investments [Abstract] Equity investments in unconsolidated subsidiaries Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures Goodwill Goodwill Other intangible assets, net of amortization of $9 and $8 at March 31, 2015 and December 31, 2014, respectively 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. Prepaid long-term service agreements Prepaid Long Term Service Agreements Prepaid long-term service agreements. Other deferred charges and assets -- affiliated Due from Other Related Parties, Noncurrent 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 debt issuance expense Unamortized Debt Issuance Expense 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. 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 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 Interest-bearing refundable deposit Interest Bearing Refundable Deposit Related to Assets Sale Interest bearing refundable deposit related to assets sale. Notes payable Short-term Debt Accounts Payable and Accrued Liabilities, Current [Abstract] Accounts Payable and Accrued Liabilities, Current [Abstract] Accounts payable Accounts Payable, Current Affiliated accounts payable Due to Related Parties, Current Other accounts payable Accounts Payable, Other, Current Customer deposits Customer Deposits, Current 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 vacation pay Accrued Vacation, Current Accrued compensation Accrued Salaries, Current Deferred capacity expense, current Deferred Capacity Expense, Other Deferred Capacity Expense, Other Other regulatory liabilities, current 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. Dividends on preferred and preference stock of subsidiaries Over recovered regulatory clause liabilities Over Recovered Regulatory Clause Liabilities Over recovered regulatory clause liabilities. Mirror CWIP Mirror Construction Work In Progress Balance Mirror Construction Work In Progress Balance Liabilities from risk management activities Derivative Instruments and Hedges, Liabilities Other current liabilities Other Liabilities, Current 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 Tax Liabilities, Net, Noncurrent 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 investment tax credits Accumulated Deferred Investment Tax Credit Deferred capacity revenues -- affiliated Deferred Capacity Revenues Affiliated The noncurrent portion of deferred revenue amount from affiliates as of balance sheet date. Deferred revenue is a liability related to a revenue producing activity for which revenue has not yet been recognized, and is not expected to be recognized in the next twelve months. Generally, an entity records deferred revenue when it receives consideration from a customer before achieving certain criteria that must be met for revenue to be recognized in conformity with GAAP. Other deferred credits and liabilities — affiliated Due to Other Related Parties, Noncurrent Employee benefit obligations Pension and Other Postretirement Defined Benefit Plans, Liabilities, Noncurrent Asset retirement obligations Asset Retirement Obligations, 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. Deferred over recovered regulatory clause revenues Deferred Over Recovered Regulatory Clause Revenues Carrying amount at the balance sheet date of over recovered fuel costs allowed to be deferred by regulatory authorities, that are expected to be recoverable through rate adjustments after one year. Deferred capacity expense Deferred Capacity Expenses Deferred Capacity Expenses 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 Redeemable Noncontrolling Interest Redeemable Noncontrolling Interest, Equity, Carrying Amount Preference Stock Preference Stock Value of all nonredeemable preference stock (or preference stock redeemable solely at the option of the issuer) held by shareholders, which is net of related treasury stock. May be all or a portion of the number of preference shares authorized. These shares represent the ownership interest of the preference shareholders. Common Stockholders' Equity: Common Stockholders Equity [Abstract] Common stockholders equity. Common stock Common Stock, Value, Issued Paid-in capital Additional Paid in Capital, Common Stock Treasury, at cost Treasury Stock, Value Retained earnings (accumulated deficit) Retained Earnings (Accumulated Deficit) Accumulated other comprehensive income (loss) Accumulated Other Comprehensive Income (Loss), Net of Tax Total common stockholders' equity Stockholders' Equity Attributable to Parent Preferred and Preference Stock of Subsidiaries Noncontrolling Interest in Preferred Unit Holders Noncontrolling Interest Nonredeemable Noncontrolling Interest Noncontrolling Interest, Total Stockholders' Equity Attributable to Noncontrolling Interest Total Stockholders' Equity Total Liabilities and Stockholders' Equity Liabilities and Equity 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 Common Stock, Shares Outstanding Entity Common Stock, Shares Outstanding Assets and liabilities measured at fair value on a recurring basis Fair Value, Assets Measured on Recurring and Nonrecurring Basis [Table Text Block] Fair value measurements of investments calculated at net asset value per share as well as the nature and risk of those investments Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [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. Income Tax Disclosure [Abstract] Income Tax Contingency [Table] Income Tax Contingency [Table] Public Utility [Axis] Public Utility [Axis] Utility Plant [Domain] Utility Plant [Domain] Kemper Igcc [Member] Kemper Igcc [Member] Kemper IGCC. Income Tax Contingency [Line Items] Income Tax Contingency [Line Items] Effective tax rate Effective Income Tax Rate Reconciliation, Percent Unrecognized tax benefit Unrecognized Tax Benefits Unrecognized tax benefit, associated interest Unrecognized Tax Benefits, Interest on Income Taxes Expense Earnings per Share Schedule of Earnings Per Share, Basic and Diluted [Table Text Block] Changes in Stockholders' Equity Schedule of Stockholders Equity [Table Text Block] EFFECTIVE TAX RATE AND UNRECOGNIZED TAX BENEFITS Income Tax Disclosure [Text Block] Fair Values Derivatives, Balance Sheet Location, by Derivative Contract Type [Table] Fair Values Derivatives, Balance Sheet Location, by Derivative Contract Type [Table] Hedging Relationship [Axis] Hedging Relationship [Axis] Hedging Relationship [Domain] Hedging Relationship [Domain] Cash Flow and Fair Value Hedging [Member] Cash Flow and Fair Value Hedging [Member] Cash flow and fair value hedging. Hedging Instruments for Regulatory Purposes [Member] Hedging Instruments for Regulatory Purposes [Member] Hedging instruments for regulatory purposes. Hedging Designation [Axis] Hedging Designation [Axis] Hedging Designation [Domain] Hedging Designation [Domain] Not Designated as Hedging Instrument [Member] Not Designated as Hedging Instrument [Member] Derivative Instrument [Axis] Derivative Instrument [Axis] Derivative Contract [Domain] Derivative Contract [Domain] Energy Related Derivative [Member] Energy Related Derivative [Member] Interest Rate Contract [Member] Interest Rate Contract [Member] Balance Sheet Location [Axis] Balance Sheet Location [Axis] Balance Sheet Location [Domain] Balance Sheet Location [Domain] Other current assets [Member] Other Current Assets [Member] Other deferred charges and assets [Member] Other deferred charges and assets [Member] Other deferred charges and assets. Other current liabilities [Member] Other Current Liabilities [Member] Other deferred credits and liabilities [Member] Other deferred credits and liabilities [Member] Other deferred credits and liabilities. Derivatives, Fair Value [Line Items] Derivatives, Fair Value [Line Items] Derivative Asset, Fair Value, Gross Asset Derivative Asset, Fair Value, Gross Asset Derivative Liability, Fair Value, Gross Liability Derivative Liability, Fair Value, Gross Liability RETIREMENT BENEFITS Pension and Other Postretirement Benefits Disclosure [Text Block] Schedule of Segment Reporting Information, by Segment [Table] Schedule of Segment Reporting Information, by Segment [Table] Segments [Axis] Segments [Axis] Segments [Domain] Segments [Domain] Traditional Operating Companies [Member] Traditional Operating Companies [Member] Traditional operating companies. Eliminations [Member] Intersegment Eliminations [Member] All Other [Member] Other Segments [Member] Electric Utilities [Member] Electric Utilities [Member] Electric utilities. Segment Reporting Information [Line Items] Segment Reporting Information [Line Items] Number of States in which Entity Operates Number of States in which Entity Operates Operating revenues Revenues Segment net income (loss) Total assets Pre-tax charge to income Pre-Tax Charge To Income Pre-Tax Charge To Income After tax charge to income After Tax Charge To Income After Tax Charge To Income Debt Disclosure [Abstract] 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] Organization, Consolidation and Presentation of Financial Statements [Abstract] Public Utility, Property, Plant and Equipment [Table] Public Utility, Property, Plant and Equipment [Table] Plant Smith Units 1 and 2 [Member] Plant Smith Units 1 and 2 [Member] Plant Smith Units 1 and 2 [Member] Public Utility, Property, Plant and Equipment [Line Items] Public Utility, Property, Plant and Equipment [Line Items] Capacity Of Units Included In Request For Decertification Of Units (in MWs) Capacity Of Units Included In Request For Decertification Of Units Capacity Of Units Included In request for decertify coal and oil-fired plants. Business Combinations [Abstract] Schedule of Business Acquisitions, by Acquisition [Table] Schedule of Business Acquisitions, by Acquisition [Table] First Solar [Member] First Solar [Member] First Solar [Member] Business Acquisition [Axis] Business Acquisition [Axis] Business Acquisition, Acquiree [Domain] Business Acquisition, Acquiree [Domain] Decatur Parkway Solar Project, LLC [Member] Decatur Parkway Solar Project, LLC [Member] Decatur Parkway Solar Project, LLC [Member] Decatur County Solar Project, LLC [Member] Decatur County Solar Project, LLC [Member] Decatur County Solar Project, LLC [Member] Decatur County Solar Projects [Member] Decatur County Solar Projects [Member] Decatur County Solar Projects [Member] Kay Wind, LLC [Member] Kay Wind, LLC [Member] Kay Wind, LLC [Member] Butler Solar LLC [Member] Butler Solar LLC [Member] Butler Solar LLC [Member] Lost Hills Blackwell Holdings, LLC [Member] Lost Hills Blackwell Holdings, LLC [Member] Lost Hills Blackwell Holdings, LLC [Member] Lost Hills Solar Facility [Member] Lost Hills Solar Facility [Member] Lost Hills Solar Facility [Member] Blackwell Solar Facility [Member] Blackwell Solar Facility [Member] Blackwell Solar Facility [Member] LS Pawpaw, LLC [Member] LS Pawpaw, LLC [Member] LS Pawpaw, LLC [Member] North Star [Member] NS Solar Holdings, LLC (North Star) [Member] NS Solar Holdings, LLC (North Star) [Member] Maximum [Member] Maximum [Member] Class of Stock [Axis] Class of Stock [Axis] Class of Stock [Domain] Class of Stock [Domain] Class A Membership Interest [Member] Class A Membership Interest [Member] Class A Membership Interest [Member] Class B Membership Interest [Member] Class B Membership Interest [Member] Class B Membership Interest [Member] Subsequent Event Type [Axis] Subsequent Event Type [Axis] Subsequent Event Type [Domain] Subsequent Event Type [Domain] Subsequent Event [Member] Subsequent Event [Member] Business Acquisition [Line Items] Business Acquisition [Line Items] Power of solar polycrystalline silicon facility (in MWs) Power of Solar Polycrystalline Silicon Facility Power of solar polycrystalline silicon facility. Beginning Year Of Output Of Constructed Plant Beginning Year Of Output Of Constructed Plant1 Beginning Year Of Output Of Constructed Plant1 Life Output Of Plant Life Output Of Plant The contracted life output of the plant. Construction Capital Costs Construction Capital Costs Construction Capital Costs Estimated Cost Estimated Cost Estimated Cost Energy From Wind-Powered Generating Facilities (in MWs) Energy From Wind-Powered Generating Facilities Energy from Wind-Powered Generating facilities. Acquisition - cash consideration Payments to Acquire Businesses, Gross Noncontrolling Interest, Ownership Percentage by Parent Noncontrolling Interest, Ownership Percentage by Parent Percentage Of Entitled Cash Distributions Percentage Of Entitled Cash Distributions Percentage Of Entitled Cash Distributions Statement of Cash Flows [Abstract] Interest paid Interest Paid Net cash paid for capitalized interest Interest Paid, Capitalized 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. Commitments and Contingencies Disclosure [Abstract] Loss Contingencies [Table] Loss Contingencies [Table] Gulf Power and Mississippi Power [Member] Gulf Power and Mississippi Power [Member] Gulf Power and Mississippi power. Kemper IGCC [Member] Plant Branch Units 1 and 3 and 4 [Member] Plant Branch Units 1 and 3 and 4 [Member] Plant Branch Units 1 and 3 and 4 [Member] Plant Yates Units 1 through 5 [Member] Plant Yates Units 1 through 5 [Member] Plant Yates Units 1 through 5 [Member] Plant McManus Units 1 and 2 [Member] Plant McManus Units 1 and 2 [Member] Plant McManus Units 1 and 2 [Member] Plant Mitchell Unit 3 [Member] Plant Mitchell Unit 3 [Member] Plant Mitchell Unit 3 [Member] Plant Vogtle Units 3 And 4 [Member] Plant Vogtle Units 3 And 4 [Member] Plant Vogtle Units 3 And 4 [Member] Electricity Generation Plant, Non-Nuclear [Member] Electricity Generation Plant, Non-Nuclear [Member] Mine [Member] Mine [Member] Mine. Property, Plant and Equipment [Member] Property, Plant and Equipment [Member] Construction in Progress [Member] Construction in Progress [Member] Current Estimate [Member] Current Estimate [Member] Current Estimate [Member] Regulatory Asset [Axis] Regulatory Asset [Axis] Regulatory Asset [Domain] Regulatory Asset [Domain] Mirror Construction Work In Progress [Member] Mirror Construction Work In Progress [Member] Mirror Construction Work In Progress [Member] Loss Contingencies [Line Items] Loss Contingencies [Line Items] Civil penalties under Clean Air Act, per day, per violation, minimum Civil Penalties under Clean Air Act Per Day Lower Range Limit Civil penalties under clean Air Act per day, lower range. Civil penalties under Clean Air Act, per day, per violation, maximum Civil Penalties under Clean Air Act Per Day Upper Range Limit Civil penalties under clean Air Act per day, upper range. Environmental Exit Costs, Assets Previously Disposed, Liability for Remediation Environmental Exit Costs, Assets Previously Disposed, Liability for Remediation Civil penalties per day violation rate Civil Penalties Per Violation Rate Civil penalties per violation rate. Number of times of punitive damages in comparison to cost incurred by Environmental Protection Agency Number of Times of Punitive Damages in Comparison to Cost Incurred by Environmental Protection Agency Number of times of punitive damages in comparison to cost incurred by Environmental Protection Agency. Claims Awarded to Companies Related to Nuclear Fuel Disposal Litigation Claims Awarded to Companies Related to Nuclear Fuel Disposal Litigation Claims awarded to companies related to nuclear fuel disposal litigation. AFUDC Cost AFUDC Cost AFUDC Cost Period To Meet Market-based Rate Standards Period To Meet Market-based Rate Standards Period to meet market-based rate standards Non-environmental Costs Non-environmental Costs Non-environmental Costs Recovery Of Non-environmental Costs Recovery Of Non-environmental Costs Recovery Of Non-environmental Costs Electric Generating Units, Capacity (in MW's) Electric Generating Units, Capacity Electric Generating Units, Capacity Fuel cost recovery balance Fuel Cost Recovery Balance Fuel Cost Recovery Balance. Additional Construction Capital Costs Additional Construction Capital Costs Additional Construction Capital Costs Percentage of Proportionate Share Owed in Consortium Agreement Percentage of Proportionate Share Owed in Consortium Agreement Percentage of proportionate share owed in consortium agreement. Reduction in projected in-service cost due to recovered cost Reduction in Projected in Service Cost due to Recovered Cost Reduction in projected in service cost due to recovered cost. Damages In Connection With Counterclaim Damages In Connection With Counterclaim Damages In Connection With Counterclaim Increase (Decrease) In Projected Certified Construction Capital Costs Increase (Decrease) In Projected Certified Construction Capital Costs Increase (Decrease) In Projected Certified Construction Capital Costs Estimated In-service Capital Cost Estimated In-service Capital Cost Increase Estimated In-service Capital Cost Delay Of Estimated In-service Date Delay Of Estimated In-service Date Delay Of Estimated In-service Date Monthly Operational Readiness Costs Monthly Operational Readiness Costs Monthly Operational Readiness Costs Monthly Financing Costs Monthly Financing Costs Monthly Financing Costs Construction Financing Costs Construction Financing Costs Construction Financing Costs Reduction In Depreciation Expense Reduction In Depreciation Expense Reduction In Depreciation Expense Reduction In Depreciation Expense Year One Reduction In Depreciation Expense Year One Reduction In Depreciation Expense Year One Number Of Regulatory Clauses Number Of Regulatory Clauses Number Of Regulatory Clauses Psc Approved Annual Property Damage Reserve Accrual Psc Approved Annual Property Damage Reserve Accrual Psc Approved Annual Property Damage Reserve Accrual Ownership percentage in scrubber project Ownership Percentage in Project One Ownership percentage in scrubber project. Estimated cost of scrubber project Estimated Cost of Project One Estimated cost of scrubber project. Scrubber project expenditures amount Project One Expenditures Amount Scrubber project expenditures amount. Allowance For Funds Used During Construction Cost Allowance For Funds Used During Construction Cost Allowance For Funds Used During Construction Cost Revenues Over Recovered Fuel Cost Over Recovered Fuel Cost Over recovered fuel cost. Under recovered regulatory clause revenues Under Recovered Fuel Cost 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. Percentage Of PSC Retail Rate Increase (Decrease) Percentage Of PSC Retail Rate Increase (Decrease) Percentage Of PSC Retail Rate Increase (Decrease) PSC Retail Rate Increase (Decrease) PSC Retail Rate Increase (Decrease) PSC Retail Rate Increase (Decrease) Plant Capacity Under Coal Gasification Combined Cycle Technology (in MWs) Plant Capacity Under Coal Gasification Combined Cycle Technology Plant capacity under coal gasification combined cycle technology. Co Two Pipeline Infrastructure (in miles) Co Two Pipeline Infrastructure Co Two pipeline infrastructure. Costs associated with CCP12 grant funds Costs Related to Grant Funding Costs related to grant funding. Loss Contingency, Estimate of Possible Loss Loss Contingency, Estimate of Possible Loss Other Property And Investments Other Property And Investments Other Property And Investments Lignite Mining Costs Lignite Mining Costs Lignite Mining Costs Materials, Supplies, and Other Materials, Supplies, and Other Cost deferred in other regulatory assets Cost Deferred in Other Regulatory Assets Cost deferred in other regulatory assets. Other deferred charges and assets Other Deferred Charges and Assets Other deferred charges and assets. Asset Retirement Obligation Asset Retirement Obligation Previously expensed Previously Expensed Previously expensed. Costs Due To Extension Of In-service Date Costs Due To Extension Of In-service Date Costs Due To Extension Of In-service Date Monthly Charge Of Allowance For Equity Funds Used During Construction Monthly Charge Of Allowance For Equity Funds Used During Construction Monthly Charge Of Allowance For Equity Funds Used During Construction Monthly Cost Regulatory Assets Deferred Monthly Cost Regulatory Assets Deferred Monthly Cost Regulatory Assets Deferred Alternate Financing Alternate Financing Alternate Financing Increase Retail Rates In Year One Increase Retail Rates In Year One Increase Retail Rates In Year One Increase Retail Rates In Year Two Increase Retail Rates In Year Two Increase Retail Rates In Year Two Settlement Agreement Collection Amount To Mitigate Rate Impact Year Two Settlement Agreement Collection Amount To Mitigate Rate Impact Year Two Settlement Agreement Collection Amount To Mitigate Rate Impact Year Two Regulatory Liabilities For Plant Construction Regulatory Liabilities For Plant Construction Regulatory Liabilities For Plant Construction Retail Rate Recovery Retail Rate Recovery Retail Rate Recovery Reduced percentage interest transferred under asset purchase agreement Reduced Percentage Interest Transferred under Asset Purchase Agreement Reduced percentage interest transferred under asset purchase agreement. Maximum Cap Construction Cost Maximum Cap Construction Cost Maximum cap construction cost. Regulatory Assets Regulatory Assets Projected Balance Of Regulatory Assets Projected Balance Of Regulatory Assets Projected Balance Of Regulatory Assets Net Regulatory Assets Net Regulatory Assets Term of Management Fee Contract Term of Management Fee Contract Term of management fee contract. Percentage of Carbon Dioxide Captured from Project Percentage of Carbon Dioxide Captured from Project Percentage of Carbon dioxide captured from project. Percentage of Contract to Purchase Carbon Dioxide from Project Percentage of Contract to Purchase Carbon Dioxide from Project Percentage of contract to purchase carbon dioxide from project. Purchase of Interest Purchase of Interest Purchase of interest. Capacity Revenues Under Power Supply Agreement Capacity Revenues Under Power Supply Agreement Capacity Revenues Under Power Supply Agreement Acquisition Period For SMEPA Acquisition Period For SMEPA Acquisition Period For SMEPA Deposit received Deposit Received Deposit received. Interest Bearing Refundable Deposit Related to Asset Sale Interest Bearing Refundable Deposit Related to Asset Sale Interest bearing refundable deposit related to asset sale. Maximum period of discretion in the event senior unsecured credit rating falls Maximum Period of Discretion Maximum period of discretion. Internal Revenue Code Section Forty Eight Tax Credits Phase I I Internal Revenue Code Section Forty Eight Tax Credits Phase I I Internal revenue code section forty eight tax credits Phase II. Tax Credit Carryforward, Amount Tax Credit Carryforward, Amount Tax Credit Carryforward Utilized Tax Credit Carryforward Utilized Tax Credit Carryforward Utilized Minimum percentage of carbon dioxide that must be capture and sequester to remain eligible for the phase II tax credits Minimum Percentage of Carbon Dioxide That Must Capture and Sequester to Remain Eligible for Tax Credits Minimum percentage of carbon dioxide that must be capture and sequester to remain eligible for the phase II tax credits. Unrecognized Tax Benefits Schedule of Asset Retirement Obligations Schedule of Asset Retirement Obligations [Table Text Block] Changes in fair value, tax Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, Tax Reclassification adjustment for amounts of qualifying hedges included in net income, tax Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI on Derivatives, Tax Reclassification adjustment for amounts of pension and other post retirement benefit plans included in net income, tax Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI, Pension and Other Postretirement Benefit Plans, for Net Gain (Loss), Tax 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 [Member] Fair Value, Measurements, Recurring [Member] Fair Value, Hierarchy [Axis] Fair Value, Hierarchy [Axis] Fair Value, Measurements, Fair Value Hierarchy [Domain] Fair Value Hierarchy [Domain] Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] Fair Value, Inputs, Level 1 [Member] Significant Other Observable Inputs (Level 2) [Member] Fair Value, Inputs, Level 2 [Member] Significant Unobservable Inputs (Level 3) [Member] Fair Value, Inputs, Level 3 [Member] Fair Value by Asset Class [Axis] Asset Class [Axis] Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, by Asset Class [Domain] Asset Class [Domain] Domestic Equity [Member] Domestic equity. Foreign equity [Member] Foreign Equity [Member] Foreign equity. U.S. Treasury and government agency securities [Member] US Treasury and Government [Member] Municipal bonds [Member] Municipal Bonds [Member] Corporate bonds [Member] Corporate Debt Securities [Member] Mortgage and asset backed securities [Member] Asset-backed Securities [Member] Other investments [Member] Other than Securities Investment [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] Interest Rate Derivative Assets, at Fair Value Interest Rate Derivative Assets, at Fair Value Nuclear decommissioning 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] Interest rate derivatives Interest Rate Derivative Liabilities, at Fair Value Total Financial and Nonfinancial Liabilities, Fair Value Disclosure Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Table] Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Table] Foreign equity funds [Member] Equity - commingled funds [Member] Equity - commingled funds [Member] Equity - commingled funds [Member] Debt - Commingled Funds [Member] Debt - Commingled Funds [Member] Debt - Commingled Funds [Member] Other - commingled funds [Member] Other - money market funds [Member] Other - money market funds [Member] Other - money market funds [Member] Trust owned life insurance [Member] Trust Owned Life Insurance [Member] Trust owned life insurance. Money market funds [Member] Money Market Funds [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 measurements of investments calculated at net asset value per share as well as the nature and risk of those investments Fair value measurements of investments calculated at net asset value per share as well as nature and risk of those investments [Abstract] Fair value measurements of investments calculated at net asset value per share as well as the nature and risk of those investments. Fair Value Alternative Investments, Fair Value Disclosure Unfunded Commitments Fair Value, Investments, Entities that Calculate Net Asset Value Per Share, Unfunded Commitments Redemption Frequency Fair Value, Investments, Entities that Calculate Net Asset Value Per Share, Investment Redemption, Frequency Redemption Notice Period Fair Value, Investments, Entities that Calculate Net Asset Value Per Share, Redemption Notice Periods Fair Value, Investments, Entities that Calculate Net Asset Value Per Share, Redemption Notice Periods Redemption Notice Period, Description Fair Value Investments Entities that Calculate Redemption Notice Period Fair Value Investments Entities that Calculate Redemption Notice Period CONTINGENCIES AND REGULATORY MATTERS Legal Matters and Contingencies [Text Block] Under Recovered Regulatory Clause Revenues [Member] Under Recovered Regulatory Clause Revenues [Member] Under Recovered Regulatory Clause Revenues [Member] Under Recovered Fuel Cost Under Recovered Purchased Power Capacity Costs Under Recovered Purchased Power Capacity Costs Under recovered purchased power capacity costs. Under Recovered Environmental Cost Under Recovered Environmental Cost Under Recovered Environmental Cost Under Recovered Energy Conservation Costs Under Recovered Energy Conservation Costs Under recovered energy conservation costs. Line of Credit Facility [Table] Line of Credit Facility [Table] Other Subsidiaries [Member] Other Subsidiaries [Member] Other Subsidiaries. Line of Credit Facility [Line Items] Line of Credit Facility [Line Items] Expires, 2015 Line of Credit Expire Year Two Line of credit expire year two. Expires, 2016 Line Of Credit Expire Year Three Line Of Credit Expire Year Three Expires, 2017 Line Of Credit Expire Year Four Line Of Credit Expire Year Four Expires, 2018 Line Of Credit Expire Year Five And Thereafter Line Of Credit Expire Year Five And Thereafter Total Line of Credit Facility, Maximum Borrowing Capacity Unused Line of Credit Facility, Remaining Borrowing Capacity Executable Term Loans, One Year Executable Term-Loans for One Year Executable term-loans for one year. Executable Term Loans, Two Years Executable Term Loans for Two Years Executable term loans for two years. Due Within One Year, Term Out Bank Credit Arrangements Term Loan Due with in One Year Bank credit arrangements term loan due with in one year. Due Within One Year, No Term Out Bank Credit Arrangements No Term Loan Due with in One Year Bank credit arrangements no term loan due with in one year. Derivative, by Nature [Axis] Derivative, by Nature [Axis] Derivative, Name [Domain] Derivative, Name [Domain] Gas [Member] Public Utilities, Inventory, Natural Gas [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] Maturity Date October 2025 [Member] Maturity Date October 2025 [Member] Maturity Date October 2025 [Member] Maturity Date May 2025 [Member] Maturity Date May 2025 [Member] Maturity Date May 2025 [Member] Maturity Date November 2025 [Member] Maturity Date November 2025 [Member] Maturity Date November 2025 [Member] Maturity Date March 2016 [Member] Maturity Date March 2016 [Member] Maturity Date March 2016 [Member] Maturity Date August 2016 [Member] Maturity Date August 2016 [Member] Maturity Date August 2016 [Member] Maturity Date August 2017 [Member] Maturity Date August 2017 [Member] Maturity Date August 2017 [Member] Maturity Date June 2018 [Member] Maturity Date June 2018 [Member] Maturity Date June 2018 [Member] Maturity Date December 2019 [Member] Maturity Date December 2019 [Member] Maturity Date December 2019 [Member] Cash Flow Hedges Of Forecasted Debt [Member] Cash Flow Hedges Of Forecasted Debt [Member] Cash Flow Hedges Of Forecasted Debt [Member] Cash Flow Hedges Of Existing Debt [Member] Cash Flow Hedges Of Existing Debt [Member] Cash Flow Hedges Of Existing Debt [Member] Fair Value Hedges Of Existing Debt [Member] Fair Value Hedges Of Existing Debt [Member] Fair Value Hedges Of Existing Debt [Member] 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. Longest Hedge Date Longest Hedge Date1 Longest Hedge Date1 Longest Non-Hedge Date Longest Non-hedge Date1 Longest Non-hedge Date1 Notional amount of interest rate derivatives Notional Disclosures [Abstract] Notional Amount Derivative, Notional Amount Interest Rate Received, Description Derivative Interest Rate Received Derivative Interest Rate Received 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. Weighted Average Interest Rate Paid, Description Notional Amount of Interest Rate Derivatives Interest Rate Paid Description Notional amount of interest rate derivatives, interest rate paid. Hedge Maturity Date Derivative, Maturity Date Fair Value Gain (Loss) at March 31, 2015 Fair Value Gain Loss Fair value gain (Loss). 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 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) Investment tax credits Investment Tax Credit Amortization of investment tax credits Amortization of Deferred Investment Tax Credits Amortization of deferred investment tax credits. Deferred revenues Recognition of Deferred Revenue Allowance for equity funds used during construction Public Utilities, Allowance for Funds Used During Construction, Capitalized Cost of Equity Retail fuel cost over recovery - long-term Retail Fuel Cost Over Recovery Long Term Retail fuel cost over recovery long term. Deferred expenses Recognition of Deferred Expenses Recognition of deferred expenses. Pension, postretirement, and other employee benefits Pension and Other Postretirement Benefit Expense Stock based compensation expense Stock or Unit Option Plan Expense Regulatory assets associated with Kemper IGCC Regulatory Assets Associated With Integrated Coal Gasification Combined Cycle Project Increase or (decrease) during reporting period of regulatory assets used in operating activities associated with the Integrated Coal Gasification Combined Cycle. Estimated loss on Kemper IGCC Estimated Loss On Integrated Coal Gasification Combined Cycle Project Estimated Loss On Integrated Coal Gasification Combined Cycle Project Other, net Other Noncash Income (Expense) Changes in certain current assets and liabilities -- Increase (Decrease) in Operating Capital [Abstract] -Receivables Increase (Decrease) in Receivables -Fossil fuel stock Increase (Decrease) in Fossil Fuel Inventories -Materials and supplies Increase (Decrease) in Raw Materials, Packaging Materials and Supplies 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 interest Increase (Decrease) in Interest Payable, Net -Accrued compensation Increase (Decrease) in Accrued Salaries -Over recovered regulatory clause revenues Over Recovered Regulatory Clause Increase or decrease in over recovered regulatory clause revenues on the cash flow. -Mirror CWIP Mirror Construction Work In Progress Mirror Construction Work In Progress -Retail fuel cost over recovery - short-term Increase (Decrease) Retail Fuel Cost Over Recovery Short Term Increase decrease retail fuel cost over recovery short-term. -Other current liabilities Increase (Decrease) in Other Operating Liabilities Net cash provided from operating activities Net Cash Provided by (Used in) Operating Activities Investing Activities: Net Cash Provided by (Used in) Investing Activities [Abstract] Property additions Payments to Acquire Property, Plant, and Equipment Distribution of restricted cash Proceeds From Distribution Of Restricted Cash Proceeds From Distribution Of Restricted Cash 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 (Proceeds from) Removal Costs Change in construction payables 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. 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. Prepaid long-term service agreement Prepaid Long-Term Service Agreement Prepaid Long-Term Service Agreement Payments pursuant to long-term service agreements 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 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 issuances Proceeds from Issuance of Long-term Debt and Capital Securities, Net Senior notes issuances Proceeds from Issuance of Senior Long-term Debt Capital contributions from parent company Proceeds from Contributions from Parent Interest-bearing refundable deposit Common stock issuances Proceeds from Issuance of Common Stock FFB loan Federal Financing Bank Loan Federal Financing Bank Loan Other long-term debt issuances Proceeds from Issuance of Other Long-term Debt Short-term borrowings Proceeds from Short-term Debt Redemptions -- Redemptions [Abstract] Redemptions. Long-term debt Repayments of Long-term Debt, Long-term Capital Lease Obligations, and Capital Securities Senior notes Repayments of Senior Debt Other long-term debt Repayments of Other Long-term Debt Common stock repurchased Payments for Repurchase of Common Stock Payment of preferred and preference stock dividends Payments of Ordinary Dividends, Preferred Stock and Preference Stock Payment of common stock dividends Payments of Ordinary Dividends, Common Stock Return of capital Return Of Paid In Capital Return Of Paid In Capital Payment of dividends on preferred and preference stock of subsidiaries Payments of Ordinary Dividends, Noncontrolling Interest FFB loan issuance costs Federal Financing Bank Loan Issuance Costs Federal Financing Bank Loan Issuance Costs 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 and Cash Equivalents Cash and Cash Equivalents, Period Increase (Decrease) Cash and Cash Equivalents at Beginning of Period Cash and Cash Equivalents 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 capitalized amounts) Interest Paid, Net Income taxes, net Income Taxes Paid, Net Noncash transactions - Accrued property additions at end of period Capital Expenditures Incurred but Not yet Paid Net Amount Of Derivatives [Member] Net Amount Of Derivatives [Member] Net Amount Of Derivatives [Member] Gross Amount Of Derivatives [Member] Gross Amount Of Derivatives [Member] Gross Amount Of Derivatives [Member] Derivative Asset, Fair Value, Amount Not Offset Against Collateral Derivative Asset, Fair Value, Amount Not Offset Against Collateral Derivative Asset, Fair Value, Amount Offset Against Collateral Derivative Asset, Fair Value, Amount Offset Against Collateral Derivative Liability, Fair Value, Amount Not Offset Against Collateral Derivative Liability, Fair Value, Amount Not Offset Against Collateral Derivative Liability, Fair Value, Amount Offset Against Collateral Derivative Liability, Fair Value, Amount Offset Against Collateral Schedule of Recovery Balance of Each Regulatory Clause Retail Regulatory Matters [Table Text Block] Retail Regulatory Matters [Table Text Block] Recovery Position of Each Regulatory Clause Cost Recovery Clauses [Table Text Block] [Table Text Block] for Cost Recovery Clauses [Table] Current And Actual Cost Estimate for Kemper IGCC Current And Actual Cost Estimate [Table Text Block] Current And Actual Cost Estimate [Table Text Block] Pension Plans and Postretirement Plans Schedule of Net Benefit Costs [Table Text Block] SEGMENT AND RELATED INFORMATION Segment Reporting Disclosure [Text Block] INTRODUCTION Organization, Consolidation and Presentation of Financial Statements Disclosure [Text Block] Deferred Under Recovered Regulatory Clause Revenues [Member] Deferred Under Recovered Regulatory Clause Revenues [Member] Deferred Under Recovered Regulatory Clause Revenues [Member] Deferred Over Recovered Regulatory Clause Revenues [Member] Deferred Over Recovered Regulatory Clause Revenues [Member] Deferred Over Recovered Regulatory Clause Revenues [Member] Other regulatory liabilities deferred [Member] Other regulatory liabilities deferred [Member] Other regulatory liabilities deferred. Under Recovered Rate Cnp Balance Under Recovered Rate Cnp Balance Under recovered Rate CNP balance. Under Recovered Rate Cnp Balance, Current Under Recovered Rate Cnp Balance, Current Under Recovered Rate Cnp Balance, Current Rate Cnp Power Purchase Agreement Rate Cnp Power Purchase Agreement Rate Cnp Power Purchase Agreement Retail Energy Cost Recovery - Over Retail Energy Cost Recovery Retail Energy Cost Recovery Accumulated reserve balance for future storms Accumulated reserve balance for future storms Accumulated reserve balance for future storms. Schedule of derivatives Schedule of Derivative Instruments [Table Text Block] Notional amount of interest rate derivatives Schedule of Interest Rate Derivatives [Table Text Block] 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] Offsetting disclosure tables Offsetting Assets And Liabilities [Table Text Block] Offsetting Assets And Liabilities [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 Schedule of Derivative Instruments, Effect on Other Comprehensive Income (Loss) [Table Text Block] Schedule of Long-term Debt Instruments [Table] Schedule of Long-term Debt Instruments [Table] Traditional Operating Companies [Member] Long-term Debt, Type [Axis] Long-term Debt, Type [Axis] Long-term Debt, Type [Domain] Long-term Debt, Type [Domain] Senior Notes [Member] Senior Notes [Member] Unsecured Debt [Member] Unsecured Debt [Member] Series DD [Member] Series DD [Member] Series DD [Member] Debt Instrument [Axis] Debt Instrument [Axis] Debt Instrument, Name [Domain] Debt Instrument, Name [Domain] Series 2015A [Member] Series 2015A [Member] Series 2015A [Member] Series 2007B [Member] Series 2007B [Member] Series 2007B [Member] Series 2015B [Member] Series 2015B [Member] Series 2015B [Member] Aggregate Stated Capital [Member] Aggregate Stated Capital [Member] Aggregate Stated Capital [Member] Second Series 2008 [Member] Second Series 2008 [Member] Second Series 2008 [Member] Maturity April First Two Thousand Sixteen [Member] Maturity April First Two Thousand Sixteen [Member] Maturity April First Two Thousand Sixteen [Member] Scenario [Axis] Scenario [Axis] Scenario, Unspecified [Domain] Scenario, Unspecified [Domain] Scenario, Plan [Member] Scenario, Forecast [Member] Five Point Two Zero Percent Class A Preferred Stock [Member] Five Point Two Zero Percent Class A Preferred Stock [Member] Five Point Two Zero Percent Class A Preferred Stock [Member] Five Point Three Zero Percent Class A Preferred Stock [Member] Five Point Three Zero Percent Class A Preferred Stock [Member] Five Point Three Zero Percent Class A Preferred Stock [Member] Five Point Six Two Five Percent Preference Stock [Member] Five Point Six Two Five Percent Preference Stock [Member] Five Point Six Two Five Percent Preference Stock [Member] Debt Instrument [Line Items] Debt Instrument [Line Items] Amount of Variable Rate Pollution Control Revenue Bonds Outstanding Requiring Liquidity Support Amount of Variable Rate Pollution Control Revenue Bonds Outstanding Requiring Liquidity Support Amount of variable rate pollution control revenue bonds outstanding requiring liquidity support. Amount of Fixed Rate Pollution Control Revenue Bonds Outstanding Requiring Liquidity Support Amount of Fixed Rate Pollution Control Revenue Bonds Outstanding Requiring Liquidity Support Amount of Fixed rate pollution control revenue bonds outstanding requiring liquidity support. Debt Instrument, Face Amount Debt Instrument, Face Amount Debt Instrument, Interest Rate, Stated Percentage Debt Instrument, Interest Rate, Stated Percentage Redemption Amount Of Principal Notes Redemption Amount Of Principal Notes Redemption Amount Of Principal Notes Long-term Pollution Control Bond Long-term Pollution Control Bond Temporary Equity, Shares Outstanding Temporary Equity, Shares Outstanding Temporary Equity, Dividend Rate Percentage Temporary Equity, Dividend Rate Percentage Temporary Equity, Dividend Rate Percentage Temporary Equity, Par or Stated Value Per Share Temporary Equity, Par or Stated Value Per Share Number Of Floating Rate Bank Loans Number Of Floating Rate Bank Loans Number Of Floating Rate Bank Loans Aggregate Principal Amount Of Floating Rate Bank Loan Aggregate Principal Amount Of Floating Rate Bank Loan Aggregate Principal Amount Of Floating Rate Bank Loan Debt Instrument, Description of Variable Rate Basis Debt Instrument, Description of Variable Rate Basis Repayment Aggregate Principal Amount Of Floating Rate Bank Loan Repayment Aggregate Principal Amount Of Floating Rate Bank Loan Repayment Aggregate Principal Amount Of Floating Rate Bank Loan Reclassification Reclassification, Policy [Policy Text Block] Recently Issued Accounting Standards New Accounting Pronouncements, Policy [Policy Text Block] Valuation Methodologies Valuation Methodologies [Policy Text Block] Valuation methodologies. Earnings per Share Earnings Per Share, Policy [Policy Text Block] Energy-Related Derivatives and Interest Rate Derivatives Derivatives, Policy [Policy Text Block] ACQUISITIONS Business Combination Disclosure [Text Block] FAIR VALUE MEASUREMENTS Fair Value Disclosures [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] Financial instruments not having carrying amount equal to fair value Financial Instruments not Having Carrying Amount Equal to Fair Value [Abstract] Financial instruments not having carrying amount equal to fair value. Long-term debt: Long-term Debt, Unclassified [Abstract] Long-term debt, Carrying Amount Long-term Debt, Gross Long-term debt, Fair Value Debt Instrument, Fair Value Disclosure Debt Redemptions [Member] Debt Redemptions [Member] Debt Redemptions [Member] Senior Note Issuances Senior Note Issuances Senior Note Issuances Senior Note Redemptions Maturities of Senior Debt Other Long-Term Debt Other Long-term Debt STOCKHOLDERS' EQUITY Stockholders' Equity Note Disclosure [Text Block] Schedule of Stock by Class [Table] Schedule of Stock by Class [Table] Class of Stock [Line Items] Class of Stock [Line Items] Earnings per Share Earnings Per Share [Abstract] As reported shares Weighted Average Number of Shares Outstanding, Basic Effect of options and performance share award units Incremental Common Shares Attributable to Dilutive Effect of Share-based Payment Arrangements Diluted shares Weighted Average Number of Shares Outstanding, Diluted Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount FINANCING Debt Disclosure [Text Block] Derivative Instruments, Gain (Loss) by Hedging Relationship, by Income Statement Location, by Derivative Instrument Risk [Table] Derivative Instruments, Gain (Loss) [Table] Other regulatory assets current [Member] Other regulatory assets current [Member] Other regulatory assets, current. Other regulatory assets deferred [Member] Other regulatory assets deferred [Member] Other regulatory assets, deferred. Other regulatory liabilities current [Member] Other regulatory liabilities current [Member] Other regulatory liabilities current. Income Statement Location [Axis] Income Statement Location [Axis] Income Statement Location [Domain] Income Statement Location [Domain] Interest Expense [Member] Interest Expense [Member] Derivative Instruments, Gain (Loss) [Line Items] Derivative Instruments, Gain (Loss) [Line Items] Regulatory Hedge Unrealized Gain (Loss) Recognized on the Balance Sheet Regulatory Hedge Unrealized Gain Loss Regulatory hedge unrealized gain (loss). Gain (Loss) Recognized in OCI on Derivative (Effective Portion) Derivative Instruments, Gain (Loss) Recognized in Other Comprehensive Income (Loss), Effective Portion, Net Gain (Loss) Reclassified from AOCI into Income (Effective Portion) Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net Other intangible assets, accumulated amortization Finite-Lived Intangible Assets, Accumulated Amortization Common stock, par value (in dollars per share) Common Stock, Par or Stated Value Per Share Common stock, no par value (in dollars per share) Common Stock, No Par Value Common stock, shares authorized Common Stock, Shares Authorized Common stock, shares issued Common Stock, Shares, Issued Common stock, shares outstanding Common Stock, Shares, Outstanding Treasury shares at cost Treasury Stock, Shares Asset Retirement Obligation Disclosure [Abstract] Property, Plant and Equipment [Table] Property, Plant and Equipment [Table] Property, Plant and Equipment [Line Items] Property, Plant and Equipment [Line Items] Income Statement [Abstract] Operating Revenues: Revenues [Abstract] Retail revenues Retail Revenues Revenues from sales of electric energy to retail regulated customers. Wholesale revenues Wholesale Revenues Revenues from sales of energy supplied by one producer or marketer to another for eventual resale to consumers. Wholesale revenues, non-affiliates Wholesale Revenues Non Affiliates Non affiliated revenues from sales of energy supplied by one producer or marketer to another for eventual resale to consumers. Wholesale revenues, affiliates Wholesale Revenues Affiliates Affiliated revenues from sales of energy supplied by one producer or marketer to another for eventual resale to consumers. Other electric revenues Other Electric Revenues Other operating revenues of electric companies not elsewhere specified in the taxonomy. Other revenues Other Revenue, Net Total operating revenues Operating Expenses: Costs and Expenses [Abstract] Fuel Utilities Operating Expense, Fuel Used Purchased power Cost of Purchased Power Purchased power, non-affiliates Cost of Purchased Power Non Affiliates Cost of electricity purchased from non-affiliates as well as fuel used to generate electricity used in operations and sold during the reporting period. Purchased power, affiliates Cost of Purchased Power Affiliates Cost of electricity purchased from affiliates as well as fuel used to generate electricity used in operations and sold during the reporting period. 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 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 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, Extraordinary Items, Noncontrolling Interest Income taxes (benefit) Income Tax Expense (Benefit) Net Income (Loss) Less: Net income attributable to noncontrolling interests Net Income (Loss) After Dividends on Preferred and Preference Stock of Subsidiaries Net income attributable to Southern Power Company Net Income (Loss) Attributable to Parent Common Stock Data: Common Stock Data [Abstract] Common stock data. Earnings per share (EPS) - Basic EPS (in dollars per share) Earnings Per Share, Basic Diluted EPS (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) Diluted (in shares) Cash dividends paid per share of common stock (in dollars per share) Common Stock, Dividends, Per Share, Cash Paid Project Estimate [Member] Project Estimate [Member] Project Estimate [Member] Cost Of Lignite Mine And Equipment Cost Of Lignite Mine And Equipment Cost Of Lignite Mine And Equipment CO2 Pipeline Facilities Cost Of CO2 Pipeline Facilities Cost Of CO2 Pipeline Facilities Cost Of AFUDC Cost Of AFUDC Cost Of AFUDC Combined Cycle And Related Assets Placed In Service, Incremental Combined Cycle And Related Assets Placed In Service, Incremental Combined Cycle And Related Assets Placed In Service, Incremental General Exceptions Plant General Exceptions Plant General Exceptions Deferred Costs Plant Regulatory Asset Plant Regulatory Asset Maximum Cap Construction Cost