75000 - Document - Document and Entity Information
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75010 - Statement - Consolidated Statements of Income (Unaudited)
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75020 - Statement - Consolidated Statements of Cash Flows (Unaudited)
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75030 - Statement - Consolidated Balance Sheets (Unaudited)
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75040 - Statement - Consolidated Balance Sheets (Unaudited) (Parentheticals)
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75050 - Statement - MGE Energy Inc Consolidated Statements of Common Equity (Unaudited)
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75060 - Statement - Consolidated Statements of Common Equity (Unaudited) (Parentheticals)
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75070 - Statement - Madison Gas and Electric Company Consolidated Statements of Common Equity (Unaudited)
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75080 - Disclosure - Summary of Significant Accounting Policies
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75090 - Disclosure - New Accounting Standards
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75100 - Disclosure - Investment in ATC and ATC Holdco
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75110 - Disclosure - Taxes
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75120 - Disclosure - Pension and Other Postretirement Plans
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75130 - Disclosure - Equity and Financing Arrangements
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75140 - Disclosure - Share-Based Compensation
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75150 - Disclosure - Commitments and Contingencies
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75160 - Disclosure - Rate Matters
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75170 - Disclosure - Derivative and Hedging Instruments
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75180 - Disclosure - Fair Value of Financial Instruments
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75190 - Disclosure - Joint Plant Ownership
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75200 - Disclosure - Asset Retirement Obligations
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75210 - Disclosure - Revenue
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75220 - Disclosure - Segment Information
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75230 - Disclosure - Subsequent Events
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995455 - Disclosure - Significant Accounting Policies (Policies)
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995465 - Disclosure - Summary of Significant Accounting Principles (Tables)
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995475 - Disclosure - Investment in ATC and ATC Holdco (Tables)
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995485 - Disclosure - Taxes (Tables)
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995495 - Disclosure - Pension and Other Postretirement Plans (Tables)
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995505 - Disclosure - Equity and Financing Arrangements (Tables)
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995515 - Disclosure - Commitments and Contingencies (Tables)
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995525 - Disclosure - Rate Matters (Tables)
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995535 - Disclosure - Derivative and Hedging Instruments (Tables)
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995545 - Disclosure - Fair Value of Financial Instruments (Tables)
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995555 - Disclosure - Joint Plant (Tables)
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995565 - Disclosure - Revenue (Tables)
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995575 - Disclosure - Segment Information (Tables)
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995585 - Disclosure - Summary of Significant Accounting Principles (Details-1)
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995595 - Disclosure - Summary of Significant Accounting Principles (Details-2)
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995605 - Disclosure - New Accounting Standards (Details-1)
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995615 - Disclosure - Investment in ATC and ATC Holdco (Details-1)
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995625 - Disclosure - Investment in ATC and ATC Holdco (Details-2)
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995635 - Disclosure - Investment in ATC and ATC Holdco (Details-3)
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995645 - Disclosure - Taxes (Details)
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995655 - Disclosure - Pension and Other Postretirement Plans (Details)
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995665 - Disclosure - Pension and Other Postretirement Plans (Details) 2
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995675 - Disclosure - Equity and Financing Arrangements (Details-1)
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995685 - Disclosure - Equity and Financing Arrangements (Details-2)
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995695 - Disclosure - Share Based Compensation (Details)
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995705 - Disclosure - Commitments and Contingencies (Details-1)
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995715 - Disclosure - Commitments and Contingencies (Details-2)
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995725 - Disclosure - Rate Matters (Details)
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995735 - Disclosure - Derivative and Hedging Instruments (Details-1)
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995745 - Disclosure - Derivative and Hedging Instruments (Details-2)
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995755 - Disclosure - Derivative and Hedging Instruments (Details-3)
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995765 - Disclosure - Derivative and Hedging Instruments (Details-4)
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995775 - Disclosure - Derivative and Hedging Instruments (Details-5)
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995785 - Disclosure - Fair Value of Financial Instruments (Details-1)
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995795 - Disclosure - Fair Value of Financial Instruments (Details-2)
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995805 - Disclosure - Fair Value of Financial Instruments (Details-3)
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995815 - Disclosure - Fair Value of Financial Instruments (Details-4)
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995825 - Disclosure - Fair Value of Financial Instruments (Details-5)
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995835 - Disclosure - Joint Plant Ownership (Details)
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995845 - Disclosure - Asset Retirement Obligations (Details)
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995855 - Disclosure - Revenue (Details-1)
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995865 - Disclosure - Segment Information (Details)
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Exchange-traded investments
Equity Securities, FV-NI
Equity Securities, FV-NI, Total
Electric revenues
Regulated Operating Revenue, Electric, Non-Nuclear
Regulated Operating Revenue, Electric, Non-Nuclear, Total
Nontaxable Municipal Bonds [Member]
Retirement Plan Type [Axis]
Segments [Domain]
Tabular disclosure of deferred electric fuel-related costs.
Deferred Fuel Rules [Table Text Block]
Deferred Fuel Rules
Ending balance,
Beginning balance,
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis with Unobservable Inputs
Entity Incorporation, State or Country Code
Statement of Financial Position Location, Balance [Domain]
Operating Revenues:
Regulated and Unregulated Operating Revenue [Abstract]
Renewable Tax Credits Transferred [Member]
Renewable Tax Credits Transferred [Member]
Increase (Decrease) in Accounts Payable, Total
Increase (Decrease) in Accounts Payable
Accounts payable
Significant noncash investing activities:
Cash Flow, Noncash Investing and Financing Activities Disclosure [Abstract]
Long-term debt
Long-Term Debt, Excluding Current Maturities
Long-term Debt, Excluding Current Maturities, Total
Plan Name [Axis]
Public Utilities General Disclosures [Table]
Equity-based compensation plans and other - Shares
Stockholders' Equity, Other Shares
Equity [Abstract]
Entity Current Reporting Status
Level 2 [Member]
Fair Value, Inputs, Level 2 [Member]
West Riverside Energy Center is a natural gas-fired facility located in Beloit, WI. MGE has a 6.9% ownership interest in West Riverside for a total of 50 MW.
West Riverside Energy Center [Member]
West Riverside [Member]
Commitments and Contingencies
Commitments and Contingencies Disclosure [Text Block]
Cash Flow Hedging [Member]
Common Stock, Shares Authorized
Cash and Cash Equivalents, Unrestricted Cash and Cash Equivalents, Policy [Policy Text Block]
Cash and Cash Equivalents
Contractual obligation to purchase power through the Osceola Windpower LLC agreement over a ten year period.
Purchase Power Agreement, Osceola Windpower II, LLC [Member]
Asset Retirement Obligations
Asset Retirement Obligation [Policy Text Block]
Investments - ATC and ATC Holdco
Investment, Policy [Policy Text Block]
Capitalization:
Capitalization, Long-Term Debt and Equity [Abstract]
Product and Service [Axis]
Document Fiscal Period Focus
Other Noncurrent Liabilities [Member]
Other Deferred Liabilities and Other [Member]
Interest rate
Debt Instrument, Interest Rate, Stated Percentage
Revenue from Contract with Customer [Abstract]
Entity Shell Company
Transmission investment member.
Transmission Investment [Member]
Good Oak [Member]
Good Oak [Member]
Common stock dividends declared
Dividends, Common Stock, Cash
Cash and cash equivalents
Cash and Cash Equivalents, at Carrying Value, Total
Cash and Cash Equivalent
Cash and cash equivalents at end of period
Cash and cash equivalents at beginning of period
Distributions to parent from noncontrolling interest
Noncontrolling Interest, Decrease from Distributions to Noncontrolling Interest Holders
Regulatory Agency [Domain]
Fuel Rules Credit Year [Axis]
Fuel Rules Credit Year
Fuel Rules Credit Year [Axis]
Deferred Savings From Current Year Employee Benefit Costs
Deferred savings from current year employee benefit plan costs
MGE deferred savings from employee benefit plan costs and recorded as a regulatory liability.
Common Stock, Shares, Issued
Common Stock, Shares, Issued, Total
The amount of over-collection of normalized excess deferred taxes that has been returned in customer via bill credits.
Public Utilities Return Of Normalized Excess Deferred Taxes
Return of tax credit, total
Statement [Table]
Regulatory Liability [Axis]
Fuel Rules Credit Year [Domain]
Fuel Rules Credit Year
Fuel Rules Credit Year [Domain]
Long-Term Purchase Commitment, Category of Item Purchased [Domain]
Guarantor Obligations, Nature [Domain]
Offsetting Assets [Table]
Electric Fuel Monitored Costs Year
Electric Fuel Monitored Costs Year [Axis]
Asset Retirement Obligation, Ending Balance
Asset Retirement Obligation, Total
Asset Retirement Obligation, Beginning Balance
Asset Retirement Obligation
Statement [Line Items]
Entity Filer Category
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Gain (Loss) Due to Settlement
Settlement cost
Settlement cost
Derivative, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]
Total Liabilities and Capitalization
Liabilities and Equity
Debt Instrument [Line Items]
Long-term Debt, Current Maturities, Total
Long-term debt due within one year
Long-Term Debt, Current Maturities
Retrospective Adjustments to Cash Flows
Accounting Standards Update and Change in Accounting Principle [Table Text Block]
PPA [Member]
Purchased power agreement.
Purchased Power Agreement [Member]
Fuel Rules Refund, 2020 [Member]
Fuel Rules refund 2020 [Member]
Fuel Rules refund 2020 [Member]
Deficient Deferred Taxes, Tax Cuts And Jobs Act [Member]
Deficient Deferred Taxes, Tax Cuts And Jobs Act [Member]
Estimated Fair Market Value of Financial Instruments
Fair Value, by Balance Sheet Grouping [Table Text Block]
Proposed equity capital structure, percentage
Public Utilities, Requested Equity Capital Structure, Percentage
Hedging Relationship [Axis]
Renewable energy [Member]
Cash and cash equivalents
Cash and Cash Equivalents, Fair Value Disclosure
Fuel Rules Refund approved by the PSCW for 2017 electric fuel savings to be returned over a one-month period.
Fuel Rules Refund 2017 [Member]
Fuel Rules Refund, 2017 [Member]
Statutory federal income tax rate
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent
Five Point Ninety One Senior Notes Due 2053 Member
Five Point Ninety One Senior Notes Due 2053 [Member]
Debt issuance, 5.91% due 2053
Other [Member]
Other operating revenues.
Other Revenues [Member]
Joint Owners Member
Joint Owners [Member]
Other Noncash Income (Expense)
Other Noncash Income (Expense), Total
Other, net
Amount of net periodic benefit cost for pension and postretirement deferred (recognized prior year deferral) for the difference between estimated costs included in the rate settlement and actual costs incurred
Deferred (recognized) pension and OPEB costs
Defined Benefit Plan Deferred Net Periodic Benefit Cost
Effective income tax rate
Effective income tax rate
Effective Income Tax Rate Reconciliation, Percent
Income Tax Jurisdiction [Axis]
Restricted Cash
Cash and Cash Equivalents, Restricted Cash and Cash Equivalents, Policy [Policy Text Block]
MaximumAggregateSalesOfCommonStockThroughATMProgram
Maximum Aggregate Sales Of Common Stock Through ATM Program
Proposed rate increase (decrease), percentage
Public Utilities, Requested Rate Increase (Decrease), Percentage
Paris is a solar-battery park located in the Town of Paris in Kenosha County. MGE has a 10% ownership interest in Paris for a total of 31 MW.
Paris Units [Member]
Segment, Expenditure, Addition to Long-Lived Assets
ATM [Member]
At-the-market offering
Electricity [Member]
Liabilities:
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
SharesIssuedAtTheMarketOfferingProgram
At-the-market offering program
Shares Issued At The Market Offering Program
Contractual obligation to provide natural gas over periods that initially exceed one year or the normal operating cycle, if longer.
Natural Gas [Member]
Gross amounts offset in balance sheet
Derivative Asset, Subject to Master Netting Arrangement, Liability Offset
Fair Value Net Derivative Asset Liability Measured On Recurring Basis Unobservable Inputs Reconciliation Gain Loss Abstract
Realized and unrealized gains (losses):
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Inputs Reconciliation, Gain (Loss) [Abstract]
Purchase Obligation, to be Paid, Remainder of Fiscal Year
Purchase obligation, 2026
Stock Issued During Period, Value, Dividend Reinvestment Plan
Significant Accounting Policies [Text Block]
Summary of Significant Accounting Principles
Regulatory assets - current
Regulatory Asset, Current
Notional amount, power measure (in MW)
Nominal power measure used to calculate payments on a derivative instrument.
Derivative, Nonmonetary Notional Amount, Power Measure
Approximate Costs For Environmental Regulation
Approximate Costs For Environmental Regulation
Guarantor Obligations, Nature [Axis]
Disaggregation of Revenue [Table]
Fuel for electric generation
Fuel For Electric Generation Purchased Power [Member]
Property, Plant, and Equipment:
Property, Plant and Equipment, Net [Abstract]
Investment, Name [Axis]
Share-Based Payment Arrangement [Member]
Earnings Per Share, Basic, Total
Earnings per share of Common Stock - Basic
Earnings Per Share, Basic
Disaggregation of Revenue
Disaggregation of Revenue [Table Text Block]
Repayments of long-term debt
Repayments of Long-Term Debt
Repayments of Long-term Debt, Total
Pension and Other Postretirement Plans
Retirement Benefits [Text Block]
Assets not allocated member.
Assets Not Allocated [Member]
Operating expense purchase contracts [Abstract]
Purchase Obligation, Fiscal Year Maturity [Abstract]
Contractual obligation to provide natural gas supply over periods that initially exceed one year or the normal operating cycle, if longer.
Natual Gas, Supply [Member]
Retirement Plan Type [Domain]
Total Current Liabilities
Liabilities, Current
Regulatory assets
Regulatory Asset, Noncurrent
Short-term debt - commercial paper
Fair value portion of commercial paper.
Commercial Paper, Fair Value Disclosure
Columbia Energy Dome [Member]
Columbia Energy Dome is a storage project located near the Columbia Energy Center in Columbia County.
Total operating revenue.
Total Operating Revenue [Member]
Ursa [Member]
Ursa Solar Park is a solar park in Columbia County, Wisconsin.
Fuel Rules credit of $0.00256 per kWh approved by the PSCW for 2015 and 2016 electric fuel savings to be returned over 2015 and 2016.
Fuel Rules Credit ($0.00256/kWh), 2015/2016 [Member]
Fuel Rules Credit ($0.00256/kWh), 2015/2016 [Member]
Number of counterparties in default
Number of counterparites in default as of the balance sheet date.
Counterparties In Default
Income Tax Paid, Federal, after Refund Received
Income Tax Paid, Federal, after Refund Received, Total
Income tax receipts, net - US Federal
Contractual obligation to purchase power over periods that initially exceed one year or the normal operating cycle, if longer.
Purchase Power [Member]
Purchase Obligation, to be Paid, Year Two
Purchase obligation, 2028
Parent Company [Member]
Components of net periodic benefit cost:
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Debt Issuance, 5.43% due 2032
Five Point Forty Three Senior Notes Due 2032 [Member]
Five Point Forty Three Senior Notes Due 2032
Accounting Standards Update [Axis]
Common Stock
Stockholders' Equity, Policy [Policy Text Block]
Consolidation Items [Domain]
Entity Small Business
Gas Rate Proceeding [Member]
Gas Rate Proceeding
Gas Rate Proceeding [Member]
Regulated Operations [Abstract]
Gross Notional Volume of Open Derivatives
Schedule of Notional Amounts of Outstanding Derivative Positions [Table Text Block]
Commodity Contract [Member]
Utilities Operating Expense Fuel and Purchased Power
Amount of operating expense for fuel purchased for electric generation and cost of gas sold.
Fuel and purchased power
Fuel and purchased power
Gas member.
Gas [Member]
Gas [Member]
Columbia Energy Center Member
Columbia Energy Center [Member]
Commercial operating revenue.
Commercial [Member]
Commercial and Industrial operating revenue.
Commercial/Industrial [Member]
Commercial And Industrial [Member]
Other Current Assets [Member]
Other Current Assets/Liabilities
Share-Based Compensation
Share-Based Payment Arrangement [Text Block]
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Shares included in diluted earnings per share
Weighted Average Number of Shares Outstanding, Diluted, Adjustment
Weighted Average Number Diluted Shares Outstanding Adjustment, Total
Amendment Flag
Product and Service [Domain]
Solar Generation Source [Member]
Solar as a renewable energy generation source.
Solar
Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.
Income Tax Disclosure [Line Items]
Liabilities and Equity [Abstract]
Entity Address, Postal Zip Code
Cash Provided by Operating Activities
Cash Provided by Operating Activities
Cash Provided by (Used in) Operating Activity, Including Discontinued Operation
Notional amount, energy measures (in MWh)
Derivative, Nonmonetary Notional Amount, Energy Measure
Depreciation and amortization
Depreciation and amortization
Utilities Operating Expense, Depreciation and Amortization
Common Stock [Member]
Accounting Standards Update and Change in Accounting Principle [Table]
Disclosure of accounting policy for any over or under recovery of the electric fuel-related costs that fall outside a symmetrical cost tolerance band.
Wisconsin Fuel Rules
Wisconsin Fuel Rules, Policy [Policy Text Block]
The Company's projected costs for the current renewable projects.
Projected Renewable Project Costs
Projected renewable project costs
Total Operating Revenues
Regulated and Unregulated Operating Revenue
Operating revenues
Fair Value Inputs Counterparty Fuel Mix Abstract
Counterparty fuel mix:
Fair Value Inputs Counterparty Fuel Mix [Abstract]
Hedging Relationship [Domain]
Pension benefit asset
Assets for Plan Benefits, Defined Benefit Plan
Fair Value of Derivative Instruments on the Balance Sheet
Schedule of Derivative Instruments in Statement of Financial Position, Fair Value [Table Text Block]
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Inputs Reconciliation, Gain (Loss) Included In Regulatory Assets
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Inputs Reconciliation, Gain (Loss) Included In Regulatory Assets
Included in regulatory assets
Fairvalueinputsbasisadjustmentabstract
Basis adjustment:
Fair Value Inputs, Basis Adjustment [Abstract]
Portion at Fair Value Measurement [Member] [Default]
Portion at Fair Value Measurement [Member]
Entity Address, Address Line One
Authorized return on equity, percentage
Public Utilities, Approved Return on Equity, Percentage
Investment maturity period used in deferred compensation interest calculation.
Investment interest calculation, investment maturity period (26 weeks)
Deferred Compensation Arrangement With Individual, Investment Interest Calculation, Investment Maturity Period
Fair Value Hierarchy and NAV [Axis]
Supplemental Cash Flow Information [Abstract]
Derivatives Other Current Assets [Member]
Derivatives Other Current Assets [Member]
Other Current Assets
Maximum term of derivative hedging contract
Maximum term of derivative hedging contract.
Derivative, Maximum Term Of Hedging Contract
Receivable - margin account
Margin Deposit Assets
Derivative Asset
Derivative assets, net
Net amount presented in balance sheet
Five Point Twelve Senior Notes Due 2036 [Member]
Five Point Twelve Senior Notes Due 2036
Debt issuance, 5.12% due 2036
Increase (Decrease) in Regulatory Assets and Liabilities
Regulatory assets and liabilities, net
Regulatory assets and liabilities, net
Fuel rules, bandwidth
Pursuant to the provisions of the rate order, the fuel rules bandwidth will be plus or minus this percentage.
Fuel Rules, Bandwidth
Statement of Financial Position Location, Balance [Axis]
Investment Type [Axis]
Financial transmission rights.
Financial Transmission Rights [Member]
Less Net Income Attributable to Noncontrolling Interest, net of tax
Net Income (Loss) Attributable to Noncontrolling Interest
Net Income (Loss) Attributable to Noncontrolling Interest, Total
Net income attributable to noncontrolling interest, net of tax
Cash, Cash Equivalents, and Restricted Cash
Tabular disclosure of the components of cash and cash equivalents, including restricted amounts.
Cash, Cash Equivalents, and Restricted Cash [Table Text Block]
Included in current assets
This element represents total gains or losses for the period (realized and unrealized), arising from assets measured at fair value on a recurring basis using unobservable inputs (Level 3), which are included in current assets.
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Inputs Reconciliation, Gain (Loss) Included In Current Assets
Document Type
Income Taxes Paid, Net
Income Taxes Paid, Net, Total
Income taxes paid (receipts), net
Entity Central Index Key
Reserve for uncollectible accounts receivable
Accounts Receivable, Allowance for Credit Loss, Current
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Inputs Reconciliation, Transfers, Net, Total
Transfers in and/or out of level 3
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Inputs Reconciliation, Transfers, Net
Change in cash, cash equivalents, and restricted cash
Change in cash, cash equivalents, and restricted cash
Cash, Cash Equivalent, Restricted Cash, and Restricted Cash Equivalent, Period Increase (Decrease), Including Exchange Rate Effect and Discontinued Operation
Koshkonong Units [Member]
Koshkonong Solar Energy Center is a solar power generation facility in the towns of Christiana and Deerfield in Dane County, Wisconsin. MGE has a 10% ownership interest in Koshkonong for a total of 46.5 MW.
Subsequent Event Type [Domain]
Electricity, Generation [Member]
Guarantor Obligations, Liquidation Proceeds, Monetary Amount
Impairment of long-lived assets
Public Utilities, Property, Plant and Equipment, Amount of Loss (Recovery) on Plant Abandonment
Common Stock, Par or Stated Value Per Share
Accounting Standards Update [Domain]
Operating Costs and Expenses, Total
Operating Costs and Expenses
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Amortization of Prior Service Cost (Credit), Statement of Income or Comprehensive Income [Extensible Enumeration]
Equity contribution received by noncontrolling interest
Noncontrolling Interest, Increase from Subsidiary Equity Issuance
All Others [Member]
Corporate Segment and Other Operating Segment [Member]
Indemnification Agreement [Member]
Included are impacts of the Tax Cuts and Jobs Act for the regulated utility for excess deferred taxes recognized using a normalization method of accounting. The amount and timing of the cash impacts will depend on the period over which certain income tax benefits are provided to customers, determined by the PSCW.
Excess deferred tax - Income statement effect
Excess Deferred Tax Income Statement Effect
This element represents the portion of the balance sheet assertion valued at fair value by the entity whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission. This item represents deferred compensation obligations meeting the definition of a liability which should be reported as of the balance sheet date.
Deferred compensation
Deferred Compensation Fair Value Disclosure
Net book value of property, plant, and equipment
Public Utilities, Property, Plant and Equipment, Present Value of Regulated Asset for Plant Abandonment
The actual number of performance units that will be paid out upon vesting is dependent upon actual performance and may range from zero to 200% of the target number of units.
Awards to be granted as percentage of target units
Performance Units To Be Paid As Percentage Of Target Units
Fair Value [Member]
Estimate of Fair Value Measurement [Member]
Assets:
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Current Fiscal Year End Date
Schedule of Long-Term Debt Instruments [Table]
Purchase obligation, Thereafter
Purchase Obligation, to be Paid, after Year Five
Regulatory Liability [Domain]
Schedule of Jointly Owned Utility Plants
Schedule of Jointly Owned Utility Plants [Table Text Block]
Document Quarterly Report
Derivative, right to reclaim collateral (receivable)
Derivative collateral
Derivative Liability, Subject to Master Netting Arrangement, Collateral, Right to Reclaim Cash Not Offset
Minimum collateral that may be required to be posted.
Minimum collateral that may be required to be posted
Derivative, Collateral Required To Post, Minimum
Receivables [Abstract]
Fair Value, by Balance Sheet Grouping [Table]
Entity Address, State or Province
Payments to Acquire Interest in Subsidiaries and Affiliates, Total
Capital contributions to investments
Payments to Acquire Interest in Subsidiaries and Affiliates
Capital contributions to investments
The set of legal entities associated with a report
MGE [Member]
MGE [Member]
Collateral Already Posted, Aggregate Fair Value
Proceeds from (Repayments of) Short-term Debt, Total
Proceeds from (Repayments of) Short-Term Debt
(Repayments of) proceeds from short-term debt
Proceeds from short-term debt
Percentage increase compounded monthly used in deferred compensation interest calculation.
Investment interest calculation, monthly compounding rate
Deferred Compensation Arrangement With Individual, Investment Interest Calculation, Monthly Compounding Rate
Cash payments distributed related to awards previously granted and now payable
Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Share-Based Liabilities Paid
Estimate of counterparty's internal generation as a portion of their fuel mix, used as an input to measure fair value.
Internal generation
Fair Value Inputs Counterparty Fuel Mix Internal Generation
Investment, Name [Domain]
Fuel Rules Refund approved by the PSCW for 2019 electric fuel savings to either be deferred as part of the settlement of MGE's 2021 rate case or be returned over a one-month period.
Fuel Rules Refund, 2019 [Member]
Fuel Rules Refund 2019 [Member]
Common stock to be issued with plan
Common Stock, Capital Shares Reserved for Future Issuance
Derivative Collateral Required To Post Abstract
Derivative collateral required to be posted for PPA [Abstract]
Derivative, Collateral Required To Post [Abstract]
Fair Value, Net Derivative Asset (Liability), Recurring Basis, Unobservable Input Reconciliation, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]
Inventory [Axis]
Five Point Sixty One Senior Notes Due 2034 Member
Five Point Sixty One Senior Notes Due 2034 [Member]
Debt Issuance, 5.61% due 2034
Asset Retirement Obligation Disclosure [Abstract]
Noncontrolling interest
Equity, Attributable to Noncontrolling Interest
Stockholders' Equity Attributable to Noncontrolling Interest, Total
Stockholders' Equity Attributable to Noncontrolling Interest, Beginning Balance
Stockholders' Equity Attributable to Noncontrolling Interest, Ending Balance
In the first quarter of 2023, cash payments were distributed related to awards that were granted in 2020 under the 2013 Director Incentive Plan, 2018 under the 2006 Performance Unit Plan, and 2020 under the 2020 Performance Unit Plan.
Performance Unit Plans and Director Incentive Plan [Member]
2006 Performance Unit Plan, 2020 Performance Unit Plan, and 2013 Director Incentive Plan [Member]
Five Point Fifty Nine Senior Notes Due 2054 [Member]
Five Point Fifty Nine Senior Notes Due 2054 [Member]
Debt issuance, 5.59% due 2054
Other [Member]
Contractual obligation to provide commitments other than those specifically stated over periods that initially exceed one year or the normal operating cycle, if longer.
Other Long Term Purchase Commitments [Member]
Performance Shares [Member]
Increase (Decrease) in Deferred Income Taxes
Deferred income taxes
Postretirement Benefits [Member]
Other Postretirement Benefits Plan [Member]
Long-term debt
Long-Term Debt, Fair Value
Subsequent Event [Member]
Equity Method Investment, Nonconsolidated Investee [Domain]
Effects of The Inflation Reduction Act [Abstract]
Effects of The Inflation Reduction Act [Abstract]
Interest Expense, Operating
Interest Expense, Operating, Total
Interest expense
Other deferred assets and other
Other Assets, Noncurrent, Total
Other Assets, Noncurrent
Unamortized discount and debt issuance costs, net
Debt Instrument, Unamortized Discount (Premium) and Debt Issuance Costs, Net
Debt Instrument, Unamortized Discount (Premium) and Debt Issuance Costs, Net, Total
Fair Value Measurement Inputs and Valuation Techniques [Table]
Additional Cash Flow Elements and Supplemental Cash Flow Information [Abstract]
Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Vested in Period, Fair Value
Accumulated Other Comprehensive Income/(Loss) [Member]
AOCI Attributable to Parent [Member]
Derivative liabilities, net
Net amount presented in balance sheet
Derivative Liability
Amount of Public Utility's approved surcharge by regulatory agency.
Fuel surcharge effect on electric revenues ($)
Public Utilities Fuel Surcharge Amount
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Minimum [Member]
Derivative Asset, Fair Value, Gross Asset, Total
Derivative Asset, Subject to Master Netting Arrangement, before Offset
Derivative Asset, Fair Value, Gross Asset
Current Assets:
Assets, Current [Abstract]
Change In Derivative Fair Value Roll Forward
Change In Derivative Fair Value [Roll Forward]
Equity Method Investments Financial Data
Equity Method Investments [Table Text Block]
Regulatory Assets and Liabilities Disclosure [Abstract]
Fuel Rules, Electric Fuel Deferred Costs, Upper Threshold
Under fuel rules, the amount in which MGE would defer if actual electric fuel costs exceeded allowed electric fuel costs in latest rate order.
Fuel rules, electric fuel deferred costs upper threshold
Fair Value, Inputs, Level 3 [Member]
Level 3 [Member]
Liabilities:
Liabilities, Fair Value Disclosure [Abstract]
Segment Reporting [Abstract]
Estimate of counterparty's purchased power as a portion of their fuel mix, used as an input to measure fair value.
Purchased power
Fair Value Inputs Counterparty Fuel Mix Purchased Power
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]
Public Utilities, Requested Return on Equity, Percentage
Proposed return on equity, percentage
Supplemental Cash Flow [Line Items]
Supplemental Cash Flow Line Items
Total Capitalization
Capitalization, Long-Term Debt and Equity
Revenue from CNG fuel servicing.
CNG Vehicle Fuel Servicing Revenue
CNG Vehicle Fuel Servicing
Current Liabilities:
Liabilities, Current [Abstract]
Three Point Zero Nine Percent Notes Due2023 Member
3.09%, due 2023
Three Point Zero Nine Percent Notes Due 2023 [Member]
Regulatory Asset [Axis]
Dividend in kind to parent
Dividends, Paid-in-kind
Dividends, Paid-in-kind, Total
Purchase Obligation, to be Paid, Year Three
Purchase obligation, 2029
Stored natural gas, at average cost
Energy Related Inventory, Gas Stored Underground
Accounts receivable, less reserves
Accounts Receivable, after Allowance for Credit Loss, Current
Accounts Receivable, after Allowance for Credit Loss, Current, Total
Regulatory liabilities - current
Regulatory Liability, Current
Regulatory Liability, Current, Total
MGE has requested recovery of incremental uncollectible costs deferred from the periods 2020 through 2023.
Deferred Expenditures [Member]
Type of construction project.
Construction Project [Domain]
Deferred COVID Expenditures [Member]
Costs related to PSCW issued order authorizing deferral of expenditures, late payment charges, and cash deposits necessary to ensure the provision of safe, reliable and affordable access to utility services during the COVID-19 pandemic.
Deferred Covid Nineteen Expenditures [Member]
Commitments and contingencies (see Footnote 8)
Commitments and Contingencies
Badger Hollow [Member]
Badger Hollow [Member]
Service cost
Defined Benefit Plan, Service Cost
Shares Issued, Shares, Share-Based Payment Arrangement, after Forfeiture
Shares Issued, Shares, Share-Based Payment Arrangement, after Forfeiture, Total
Stock-based compensation
Provision for doubtful receivables
Accounts Receivable, Credit Loss Expense (Reversal)
Approved Rate Matters For Future Periods [Member]
Rate Matters For Future Periods [Member]
Forecast [Member]
Short-term debt
Short-term Debt, Total
Short-Term Debt
US Treasury Bills [Member]
US Treasury Bill Securities [Member]
Commodity Contracts and Financial Transimission Rights [Member]
Commodity Contracts And Financial Transimission Rights [Member]
Saratoga [Member]
Saratoga Solar Energy Center is a solar-battery park in Wood County, Wisconsin.
Issuances
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Inputs Reconciliation, Issues
Category of Item Purchased [Axis]
Other Credits:
Liabilities, Noncurrent [Abstract]
Reserve for uncollectible other accounts receivable
Allowance for Doubtful Accounts, Premiums and Other Receivables
Interest expense, net
Interest (expense) income, net
Net Interest Expense
Interest (expense) income, net
Interest expense, net
Net Interest Expense
Interest Income (Expense), Operating
Accrued capital expenditures
Capital Expenditures Incurred but Not yet Paid
Net Income Including Noncontrolling Interest
Net Income
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest
The entire disclosure for equity and financing arrangements.
Equity and Financing Arrangements
Equity and Financing Arragements [Text Block]
Notes Payable, Other Payables [Member]
Long-Term Debt, Type [Domain]
Columbia Units [Line Items]
Elm Road Units ownership [Line Items]
Jointly Owned Utility Plant Interests [Line Items]
Weighted Average Shares Outstanding - Basic
Weighted Average Number of Shares Outstanding, Basic
Weighted Average Number of Shares Outstanding, Basic, Total
Scenario [Axis]
Deferred expenditures related to COVID-19
Regulatory Asset
Regulatory Assets, Total
Equity-based compensation plans and other
Stockholders' Equity, Other
Increase (decrease) in current liabilities
Other current liabilities
Effective Tax Rate Reconciliation
Schedule of Effective Income Tax Rate Reconciliation [Table Text Block]
Schedule of Share-Based Compensation Arrangements by Share-Based Payment Award [Table]
Segments [Axis]
Liabilities incurred
Asset Retirement Obligation, Liabilities Incurred
Authorized rate increase (decrease), percentage
Public Utilities, Approved Rate Increase (Decrease), Percentage
Subsequent Events [Text Block]
Darien Solar Energy Center is a solar power generation facility in Walworth and Rock Counties, Wisconsin. MGE has a 10% ownership interest in Darien for a total of 32.5 MW.
Darien Units [Member]
Defined Benefit Plan, Net Periodic Benefit (Cost) Credit, Amortization of Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]
Transition obligation
Defined Benefit Plan, Amortization of Transition Asset (Obligation)
Total Common Shareholders Equity
Equity, Attributable to Parent
Ending balance, value
Beginning balance, value
Common shareholders equity
Whitetail [Member]
Whitetail Wind Energy Center is a wind energy project in Grant County, Wisconsin.
Document And Entity Information Line Items
Document And Entity Information [Line Items]
Statement of Stockholders' Equity [Abstract]
Derivative Unrealized Realized Gains Losses On Balance Sheet Line Items
Unrealized and realized gains (losses) on balance sheet [Line Items]
Derivative Unrealized Realized Gains Losses On Balance Sheet [Line Items]
Equity Method Investments
Amount capitalized of allowance for funds used during construction and the component of the allowance for funds used during construction during the period based on an assumed rate of return on equity funds used in financing the construction of regulated assets.
AFUDC
Public Utilities Allowance For Funds Used During Construction Capitalized Interest And Cost Of Equity
Equity Method Investment [Table]
Change in fuel rules monitored costs
This amount represents the change in fuel rules monitored costs approved by the PSCW.
Change in fuel rules monitored costs
Components of net periodic benefit cost [Line Items]
Defined Benefit Plan Disclosure [Line Items]
Return of tax credit
The amount of income tax expense over-collection approved by the PSCW for a tax credit to be returned to customers via a bill credit.
Public Utilities Return Of Tax Credit
Fair Value of Financial Instruments
Fair Value Disclosures [Text Block]
Dividend receivable from ATC
Dividends Receivable
Financial statement tax effects of the Tax Cuts and Jobs Act.
Effects Of The Tax Cuts And Jobs Act [Abstract]
Public Utilities, Regulatory Proceeding [Domain]
Noncontrolling Interest [Member]
Other noncurrent items, net
Increase (Decrease) in Other Noncurrent Assets and Liabilities, Net
Supplemental Cash Flow Information [Table Text Block]
Tabular disclosure of supplemental cash flow information.
Supplemental Cash Flow Information
Debt Instrument, Name [Domain]
Regulatory Asset [Domain]
Other Assets, Current
Other current assets
Accumulated Deferred Investment Tax Credit
Investment tax credit - deferred
Income (Loss) from Equity Method Investments, Total
Equity earnings in investments
Equity earnings from investment
Equity in earnings of investment
Equity earnings in ATC
Income (Loss) from Equity Method Investments
In January 2021, cash payments were distributed related to awards that were granted under the plans in 2018, for the 2013 Director Incentive Plan, and in 2016, for the 2006 Performance Unit Plan.
2006 Performance Unit Plan and 2013 Director Incentive Plan [Member]
Performance Unit Plan And Director Incentive Plan [Member]
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Fuel Rules Refund approved by the PSCW for 2018 electric fuel savings to be returned over a one-month period.
Fuel Rules Refund, 2018 [Member]
Fuel Rules Refund 2018 [Member]
Segment Reporting, Other Segment Item, Amount
Other segment items
Plan Name [Domain]
Included in earnings
Included in earnings
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Inputs Reconciliation, Gain (Loss) Included in Earnings
Asset Retirement Obligation
Asset Retirement Obligation Disclosure [Text Block]
Contractual obligation to provide transportation and storage of natural gas over periods that initially exceed one year or the normal operating cycle, if longer.
Natural Gas, Transportation and Storage [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trade Receivables, Allowance for Credit Losses, and Concentration Risk
Receivable [Policy Text Block]
Entity [Domain]
Equity Method Investment, Ownership Percentage
Minimum threshold percentage that MGEE must hold of the outstanding voting equity interest in MGE.
Debt covenant, MGEE's outstanding voting equity interest in MGE
Debt Instrument Covenant Terms Voting Equity Interest Ownership Threshold
Other Deferred Charges [Member]
Other Noncurrent Assets [Member]
Proceeds from Issuance of Common Stock, Dividend Reinvestment Plan
Related and Nonrelated Parties [Axis]
Pension Benefits [Member]
Pension Plan [Member]
Maximum collateral that may be required to be posted.
Maximum collateral that may be required to be posted
Derivative, Collateral Required To Post, Maximum
Entity Address, City or Town
Number of Reportable Segments
Security Exchange Name
Regulatory Agency [Axis]
Long-Term Debt, Gross
Effective Income Tax Rate Reconciliation, Other Adjustments, Percent
Other, net, individually insignificant
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Interest Cost, Statement of Income or Comprehensive Income [Extensible Enumeration]
Public Utilities General Disclosures [Table Text Block]
Rate Proceedings
Intersegment Eliminations [Member]
Consolidation Elimination Entries [Member]
Basis adjustment between delivery points for off peak electric future prices. Used as an input to measure fair value.
Basis adjustment - off peak
Fair Value Inputs Delivery Points Basis Adjustment Off Peak
Sales
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Inputs Reconciliation, Sales
Deferred compensation plan [Abstract]
Deferred Compensation Arrangements [Abstract]
Measurement Basis [Axis]
Statistical Measurement [Domain]
Total Current Assets
Assets, Current
Compensation expense
Share-Based Payment Arrangement, Expense
Storage for Renewable Energy [Member]
Energy storage project.
Storage
Document Period End Date
Equity Method Investments and Joint Ventures [Abstract]
Electricfuelmonitoredcosts2016 Member
Electric Fuel Monitored Costs, 2016
Electric Fuel Monitored Costs, 2016 [Member]
Fair Value Hierarchy and NAV [Domain]
Regulated Operation, Jointly Owned Utility Plant [Table]
Change in realized derivative gains and losses deferred.
Realized (loss) gain reclassified to a deferred account
Derivative, Realized Gain (Loss), Deferred
Long-Term Purchase Commitment [Line Items]
Natural Gas [Member]
Public Utilities, Inventory, Natural Gas [Member]
Statement of Financial Position [Abstract]
Restricted Units [Member]
Restricted Stock Units (RSUs) [Member]
Effective rate, including composite rate, of cost of financing additions to qualifying regulated assets, commonly called allowance for funds used during construction on 100 percent of Construction Work in Progress. This PSCW authorized rate is on significant projects. Projects that fit this description are: Saratoga Wind, Badger Hollow I, Two Creeks, its customer information billing project, and on certain environmental costs for Columbia.
Authorized AFUDC rate - Signficiant projects (100%)
Public Utilities Allowance For Funds Used During Construction Rate One Hundred Percent
Receivables, Net
Receivables, Net, Current [Abstract]
Revenue Recognition
Revenue [Policy Text Block]
Public Utilities, Regulatory Proceeding [Axis]
The amount of net income or net loss before taxes reported by an equity method investment of the entity.
Earnings before members' income taxes
Equity Method Investment, Summarized Financial Information, Net Income (Loss) Before Taxes
Regulated gas revenues.
Regulated Gas Revenues [Member]
Class of Stock [Axis]
Forward Wind units.
Forward Wind Units [Member]
The amount of other income or expenses reported by an equity method investment of the entity.
Other income, net
Equity Method Investment, Summarized Financial Information, Other Income (Expense)
Other Receivables
Amortization of utility excess deferred tax - tax reform
Effective Income Tax Rate Reconciliation, Change in Enacted Tax Rate, Percent
Amortization of utility excess deferred tax - tax reform
Fair Values Derivatives, Balance Sheet Location, by Derivative Contract Type [Table]
Collection of unprotected deficient deferred taxes
Public Utilities Collection of Tax Cuts And Jobs Act Unprotected Deficient Deferred Taxes
The amount of deficient deferred taxes related to Tax Cuts and Jobs Act not governed by IRS normalization rules to be factored in rates.
Operating Costs and Expenses [Abstract]
Battery storage as a source for renewable energy.
Battery Storage For Renewable Energy [Member]
Battery storage
Collateral posted against derivative positions
Derivative Liability, Subject to Master Netting Arrangement, Collateral, Right to Reclaim Cash Offset
Derivative, right to reclaim collateral
Counterparties in a net liability position.
Counterparties in net liability position
Counterparties In Net Liability Position
Residential operating revenue.
Residential [Member]
Asset Retirement Obligations, Noncurrent
Asset Retirement Obligations, Noncurrent, Total
Asset retirement obligations
Jointly Owned Utility Plant [Axis]
Capital contributions from parent
Proceeds from Contributions from Parent
Dilutive Securities, Effect on Basic Earnings Per Share
Dilutive Securities, Effect on Basic Earnings Per Share, Total
Derivative Liability, Statement of Financial Position [Extensible Enumeration]
Expected return on assets
Defined Benefit Plan, Expected Return (Loss) on Plan Assets
Derivative Instruments, Gain (Loss) [Line Items]
Jointly Owned Utility Plant [Domain]
Utilities Operating Expense, Gas and Petroleum Purchased
Purchased gas costs
Purchased gas costs
Purchased power
Utilities Operating Expense, Purchased Power
Weighted Average Shares Outstanding - Diluted
Weighted Average Number of Shares Outstanding, Diluted
Weighted Average Number of Shares Outstanding, Diluted, Total
Notional amount, decatherm measure (in Dth)
Nominal decatherm measure used to calculate payments on a derivative instrument.
Derivative, Nonmonetary Notional Amount, Decatherm Measure
MGE Transco
MGE Transco [Member]
Securities Act File Number
Cash dividends paid on common stock
Payments of Ordinary Dividends, Common Stock
Other, net, individually significant
Other, net, individually significant
Effective Income Tax Rate Reconciliation, Other Reconciling Items, Percent
Effective Income Tax Rate Reconciliation, Other Reconciling Items, Percent, Total
Derivative Gains and Losses in Income Statement
Derivative Instruments, Gain (Loss) [Table Text Block]
Cover [Abstract]
Red Barn Units [Member]
Red Barn is a wind farm located in the Towns of Wingville and Clifton in Grant County. MGE has a 10% ownership interest in Red Barn for a total of 9.16 MW.
Tabular disclosure of changes in Level 3 assets and liabilities measured at fair value on a recurring basis.
Changes in Level 3 Assets and Liabilities Measured at Fair Value on a Recurring Basis
Fair Value, Assets And Liabilities Measured On Recurring Basis, Unobservable Input Reconciliation [Table Text Block]
Investments [Domain]
Offsetting Assets [Line Items]
Derivative, Gain (Loss) on Derivative, Net
Derivative, Gain (Loss) on Derivative, Net, Total
Realized (loss) gain reclassified to income statement
Realized losses (gains) on income statement
Derivative, net liability position of counterparties
Derivative, Net Liability Position, Aggregate Fair Value
Supplemental Cash Flow [Table]
Supplemental Cash Flow Table
Awards forfeited during period, value
The value of equity-based payment instruments, excluding stock (or unit) options, that were forfeited during the reporting period.
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Forfeitures in Period
Scenario [Domain]
Public Utilities, General Disclosures [Line Items]
Segment Information
Segment Reporting Disclosure [Text Block]
Collateral posted against derivative positions
Collateral posted against derivative positions
Derivative Asset, Subject to Master Netting Arrangement, Collateral, Obligation to Return Cash, Offset Against Derivative Asset
Adjustment to Reconcile Net Income to Cash Provided by (Used in) Operating Activity, Noncash Item [Abstract]
Adjustments to reconcile net income to cash provided by operating activities
Revenues recognized from contracts with customers
Revenue from Contract with Customer, Including Assessed Tax
Total gains (losses) included in earnings attributed to the change in unrealized gains (losses) related to assets and liabilities
Fair Value, Net Derivative Asset (Liability), Recurring Basis, Still Held, Unrealized Gain (Loss)
Effect of New Accounting Principle on Prior Period Presentation
The effect of ASU 2017-07 reclass on prior period presentation of Statements of Income.
Effect Of New Accounting Principle On Prior Period Presentation
Short-Term Debt, Type [Domain]
Current And Long Term Reg Asset or Liability [Member]
Current And Long Term Reg Asset Liability [Member]
Current and Long-Term Regulatory Asset (Liability)
Accrued interest and taxes
Carrying value as of the balance sheet date of accrued interest and accrued taxes.
Accrued Interest and Taxes
Gross amounts offset in balance sheet
Derivative Liability, Subject to Master Netting Arrangement, Asset Offset
Short-Term Debt, Type [Axis]
New Accounting Pronouncement Disclosure
New Accounting Pronouncements, Policy [Policy Text Block]
Derivative Instruments, Gain (Loss) [Table]
Share-Based Compensation Arrangement by Share-Based Payment Award, Award Vesting Period
Approved equity capital structure, percentage
Public Utilities, Approved Equity Capital Structure, Percentage
Fuel Rules Abstract
Fuel Rules [Abstract]
Jointly owned utility plant, ownership interest
Jointly Owned Utility Plant, Proportionate Ownership Share
Asset Retirement Obligation, Liabilities Settled
Income before income taxes
Income (Loss) from Continuing Operations before Income Taxes, Domestic
Carrying Amount [Member]
Reported Value Measurement [Member]
Issuance of long-term debt
Proceeds from Issuance of Long-Term Debt
Proceeds from Issuance of Long-term Debt, Total
Other accounts receivables, less reserves
Other Receivables, Net, Current, Total
Other Receivables, Net, Current
Reportable Segment, Aggregation before Other Operating Segment [Member]
Total Reportable Segments
Common Stock, Shares, Outstanding
Common Stock, Shares, Outstanding, Ending Balance
Common Stock, Shares, Outstanding, Beginning Balance
Common stock shares outstanding at beginning of period
Electric fuel credit (per kWh)
The approved amount ($/kWh) for an electric fuel credit to be returned to customers via a bill credit.
Electric fuel credit per kWh
Contractual Obligation, Fiscal Year Maturity Schedule
Contractual Obligation, Fiscal Year Maturity [Table Text Block]
Prior service credit
Defined Benefit Plan, Amortization of Prior Service Cost (Credit)
Document Transition Report
Amortized investment tax credits
Effective Income Tax Rate Reconciliation, Tax Credit, Investment, Percent
Deferred tax effects of the Tax Cuts and Jobs Act (excess).
Excess Deferred Taxes, Tax Cuts And Jobs Act [Member]
Cost of Revenue, Total
Operating expenses
Cost of Revenue
MGEE Transco [Member]
MGEE Transco.
Property, plant, and equipment, total
Property Plant And Equipment Net Before Construction In Progress
Amount, net of accumulated depreciation, depletion and amortization, of long-lived physical assets used in the normal conduct of business and not intended for resale. This amount does not include constrcution work in progress. Examples include, but are not limited to, land, buildings, machinery and equipment, office equipment, furniture and fixtures, and computer equipment.
Property, plant, and equipment, net
Accrued pension and other postretirement benefits
Liability, Defined Benefit Plan, Noncurrent, Total
Liability, Defined Benefit Plan, Noncurrent
Unrealized Gain (Loss) on Derivatives
Unrealized loss
Statement of Cash Flows [Abstract]
Assets:
Assets, Fair Value Disclosure [Abstract]
Derivative Asset, Statement of Financial Position [Extensible Enumeration]
Pension and Other Postretirement Benefit Plan Assets
Pension and Other Postretirement Plans, Policy [Policy Text Block]
Ending balance, shares
Beginning balance, shares
Shares, Issued
Net Income
Minimum future capital commitments
Long-Term Purchase Commitment, Amount
Fuel for electric generation, at average cost
Energy Related Inventory, Other Fossil Fuel
Accounting Changes and Error Corrections [Abstract]
Five Point Thirty Senior Notes Due 2039 [Member]
Five Point Thirty Senior Notes Due 2039 [Member]
Debt issuance, 5.30% due 2039
Offsetting Liabilities
Offsetting Liabilities [Table Text Block]
Cash contributions to pension and other postretirement plans
Payment for Pension and Other Postretirement Benefits
Payment for Pension and Other Postretirement Benefits, Total
Other
Proceeds from (Payment for) Other Financing Activity
AFUDC - equity funds
Public Utilities, Allowance for Funds Used During Construction, Capitalized Cost of Equity
Rate Matters
Public Utilities Disclosure [Text Block]
Derivative instruments at fair value on the balance sheet [Line Items]
Derivatives, Fair Value [Line Items]
Revisions in estimated cash flows
Asset Retirement Obligation, Revision of Estimate
Assets [Abstract]
Exchange Traded [Member]
Cash Cash Equivalents And Restricted Cash Abstract
Cash, Cash Equivalents, And Restricted Cash [Abstract]
Document Fiscal Year Focus
Gains and Losses Included in Income for Level 3 Assets and Liabilities Measured at Fair Value on a Recurring Basis
Fair Value, Measured on Recurring Basis, Gain (Loss) Included in Earnings [Table Text Block]
Investing Activities:
Cash Provided by (Used in) Investing Activity, Including Discontinued Operation [Abstract]
Retirement Benefits [Abstract]
Paris, Darien, Koshkonong, High Noon, and Columbia Energy Dome Units [Member]
Paris, Darien, Koshkonong, High Noon, and Columbia Energy Dome Units [Member]
Accounts payable
Accounts Payable, Current
Accounts Payable, Current, Total
Schedule of Net Periodic Benefit Costs
Schedule of Net Benefit Costs [Table Text Block]
Accounting Standards Update and Change in Accounting Principle [Abstract]
Transaction Type [Axis]
Fuel for electric generation
Utilities Operating Expense, Fuel Used
Two Creeks units.
Two Creeks Units [Member]
Purchase Obligation, to be Paid, Year One
Purchase obligation, 2027
Deconsolidation of noncontrolling interest
Noncontrolling Interest, Decrease from Deconsolidation
Returned Savings From Prior Year Employee Benefit Costs
During 2022, MGE returned savings from 2021 employee benefit plan costs.
Returned savings from prior year employee benefit costs
Authorized rate increase (decrease), amount
Public Utilities, Approved Rate Increase (Decrease), Amount
Fair Value Disclosures [Abstract]
Commitments and Contingencies Disclosure [Abstract]
Derivative Hedging
Derivatives, Methods of Accounting, Hedging Derivatives [Policy Text Block]
Offsetting Assets
Offsetting Assets [Table Text Block]
Debt Instrument [Axis]
Derivative Instrument [Axis]
Interest cost
Defined Benefit Plan, Interest Cost
Share-Based Payment Arrangement [Abstract]
Total Assets
Assets, Fair Value Disclosure
Assets, Fair Value Disclosure, Total
Coal [Member]
Coal [Member]
Investment in ATC and ATC Holdco
Equity Method Investments and Joint Ventures Disclosure [Text Block]
Operating revenues
Revenues
Revenues, Total
Identifies type of construction project.
Construction Project [Axis]
Cash Used for Investing Activities
Cash Used for Investing Activities
Cash Provided by (Used in) Investing Activity, Including Discontinued Operation
Debt Issuance, 5.53% due 2035
Five Point Fifty Three Senior Notes Due 2035 [Member]
Five Point Fifty Three Senior Notes Due 2035
Jointly Owned Electric Utility Plant
Describes significant information about our ongoing solar generation projects: Two Creeks and Bager Hollow I and II.
Joint Plant Ownership
Security 12(b) Title
Title of 12(b) Security
Schedule of Segment Reporting Information, by Segment [Table]
Derivative and Hedging Instruments
Derivative Instruments and Hedging Activities Disclosure [Text Block]
Related and Nonrelated Parties [Domain]
Taxes
Income Tax Disclosure [Text Block]
Defined Benefit Plan, Net Periodic Benefit (Cost) Credit, Expected Return (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Document Information [Table]
Other deferred liabilities and other
Other Liabilities, Noncurrent, Total
Other Liabilities, Noncurrent
Consolidated Entities [Axis]
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Inputs Reconciliation, Gain (Loss) Included In Regulatory Liabilities
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Inputs Reconciliation, Gain (Loss) Included In Regulatory Liabilities
Included in regulatory liability
Legal Entity [Axis]
Adjustment to Reconcile Net Income to Cash Provided by (Used in) Operating Activity, Increase (Decrease) in Operating Capital [Abstract]
Changes in assets and liabilities
Purchase Obligation, to be Paid, Year Four
Purchase obligation, 2030
Income Tax Disclosure [Abstract]
Fair Value, Recurring and Nonrecurring [Table]
Public Utilities, Property, Plant and Equipment [Abstract]
Additional Paid-in Capital [Member]
Other long-term receivables
Financing Receivable, after Allowance for Credit Loss, Noncurrent, Total
Financing Receivable, after Allowance for Credit Loss, Noncurrent
Fuel Rules Refund approved by the PSCW for 2015 and 2016 electric fuel savings to be returned over a one-month period.
Fuel Rules Refund, 2015/2016 [Member]
Fuel Rules Refund, 2015/2016 [Member]
Counterparties In Net Liability Position Or Default Abstract
Counterparties in net liability position or default [Abstract]
Counterparties In Net Liability Position Or Default [Abstract]
Measurement Frequency [Domain]
Statement of Income Location, Balance [Axis]
Adoption of Accounting Principles and Recently Issued Accounting Pronouncements [Line Items]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
2006 Performance Unit Plan and 2021 Long Term Incentive Plan
Performance Unit Plan And Long Term Incentive Plan [Member]
In the first quarter of 2024, cash payments were distributed related to awards that were granted in 2019 under the 2006 Performance Unit Plan and in 2021 under the 2021 Long Term Incentive Plan.
Trading Symbol
Related Party Transaction [Table]
Electric [Member]
Electric [Member]
Electric member.
Subsequent Event Type [Axis]
Electric Fuel Monitored Costs Year
Electric Fuel Monitored Costs Year [Domain]
Accrued payroll related items
Employee-related Liabilities, Current
Employee-related Liabilities, Current, Total
Financing Activities:
Cash Provided by (Used in) Financing Activity, Including Discontinued Operation [Abstract]
Recurring [Member]
Fair Value, Recurring [Member]
Equity method investments [Line Items]
Schedule of Equity Method Investments [Line Items]
Basis adjustment:
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Distributions to parent from noncontrolling interest
The cash outflow for distributions to parent company from noncontrolling interest.
Payments for Distributions to Parent from Noncontrolling Interest
Revenue Subject to Refund [Member]
Columbia Environmental Project, CCR [Member]
Columbia Environmental Project, CCR [Member]
Gross Notional Volume of Open Derivatives [Abstract]
Notional Disclosures [Abstract]
Equity Components [Axis]
Segment Reporting Information Assets And Capital Expenditures [Abstract]
Segment Reporting Information Assets And Capital Expenditures Abstract
PSCW [Member]
Public Service Commission of Wisconsin
Public Service Commission of Wisconsin [Member]
Other income, net
Nonoperating Income (Expense)
Other (expense) income, net
Total Other Income and Deductions
Natural Gas, US Regulated [Member]
Natural gas
Equity Component [Domain]
Cash in lieu of fractional shares related to stock split
Cash paid in lieu of fractional shares related to a stock split.
Stockholders' Equity, Value, Cash in Lieu of Fractional Shares Related to Stock Split
Defined Benefit Plan, Net Periodic Benefit (Cost) Credit, Amortization of Transition Asset (Obligation), Statement of Income or Comprehensive Income [Extensible Enumeration]
Class of Stock Disclosures [Abstract]
Investments
Investments, Total
Projected costs for environmental regulations.
Projected costs for enviornmental regulations
Projected Costs For Environmental Regulation
Increase (Decrease) in Other Current Assets
Current assets
Beginning balance,
Derivative, Fair Value, Net
Derivative, Fair Value, Net, Total
Ending balance,
Debt issuance, 5.76% due 2055
Five Point Seventy Six Senior Notes Due 2055 [Member]
Five Point Seventy Six Senior Notes Due 2055
Fair Value Inputs Delivery Points Basis Adjustment On Peak
Basis adjustment between delivery points for on peak electric future prices. Used as an input to measure fair value.
Basis adjustment - on peak
Plan for 2021 Long Term Incentive Plan as decribed in our report.
2021 Long Term Incentive Plan [Member]
Long Term Incentive Plan 2021 [Member]
Dawn Harvest [Member]
Dawn Harvest [Member]
Other operations and maintenance
Utilities Operating Expense, Maintenance and Operations
Utilities Operating Expense, Maintenance and Operations, Total
Equity Method Investment, Nonconsolidated Investee [Axis]
Solar Farm Project Costs Year to Date
Public Utilities, Property, Plant and Equipment, Construction Work in Progress
Maximum [Member]
Total liabilities
Liabilities, Fair Value Disclosure
Statistical Measurement [Axis]
Rate Proceedings [Abstract]
Public Utilities, Rate Matters [Abstract]
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Total Retail [Member]
Total retail operating revenue.
Beginning balance, value
Ending balance, value
Total Equity
Equity, Including Portion Attributable to Noncontrolling Interest
Derivative fair values [Abstract]
Derivative, Fair Value, Net [Abstract]
Settlements
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Inputs Reconciliation, Settlements
State income taxes, net of federal benefit
Effective Income Tax Rate Reconciliation, State and Local Income Taxes, Percent
The total operating capacity (in megawatts) of the jointly owned utility plant.
Jointly owned utility plant, plant capacity (in MW)
Forward Wind Plant Capacity
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Inputs Reconciliation, Purchases
Purchases
Energy Related Commodity Contract [Member]
Energy Related Commodity Contract [Member]
Entity Public Float
Operating Expenses:
Utilities Operating Expense [Abstract]
Electric Rate Proceeding [Member]
Electric Rate Proceeding
Electric Rate Proceeding [Member]
Badger Hollow I and II solar farm.
Badger Hollow I and II [Member]
Other general taxes
Utilities Operating Expense, Taxes
Inventory [Domain]
Fair value and carrying value of financial instruments [Line Items]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Revenue from Contract with Customer
Revenue from Contract with Customer [Text Block]
Entity Registrant Name
Minimum annual rate compounded monthly used in deferred compensation interest calculation.
Investment interest calculation, minimum annual rate compounded monthly
Deferred Compensation Arrangement With Individual Investment Interest Calculation, Minimum Annual Rate Compounded Monthly
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Table]
The amount of interest reported by an equity method investment of the entity.
Interest expense, net
Equity Method Investment, Summarized Financial Information, Interest Income (Expense)
Columbia units.
Columbia Units [Member]
Subsequent Events [Abstract]
Retail and municipal operating revenue.
Other-retail/municipal
OtherRetailAndMunicipal [Member]
Consolidated Entities [Domain]
Sales to the market operating revenue
Sales To The Market [Member]
Industrial operating revenue.
Industrial [Member]
Income tax provision
Income Tax Expense (Benefit), Total
Income tax (provision) benefit
Income Tax Expense (Benefit)
Income tax (provision) benefit
Measurement Frequency [Axis]
Dividends per share of common stock
Common Stock, Dividends, Per Share, Cash Paid
High Noon [Member]
High Noon Solar Project is a solar-battery park in Columbia County, Wisconsin.
Issuance of common stock, net
Proceeds from Issuance of Common Stock
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Significant Unobservable Inputs
Fair Value Measurement Inputs and Valuation Techniques [Table Text Block]
Entity Common Stock, Shares Outstanding
Accumulated Other Comprehensive Income (Loss), Net of Tax, Total
Accumulated Other Comprehensive Income (Loss), Net of Tax
Consolidation Items [Axis]
Disallowable percent ownership of trading stock by an outside party that would result in repurchase of notes at par value.
Debt covenant, ownership interest by outside party resulting in repurchase of notes at par value
Debt Instrument, Covenant Terms, Ownership Interest by Outside Party Resulting in Repurchase of Notes at Par Value
Payments to Acquire Property, Plant, and Equipment, Total
Capital expenditures
Payments to Acquire Property, Plant, and Equipment
Wind as a renewable energy generation source.
Wind Generation Source [Member]
Wind
Other
Payment for (Proceeds from) Other Investing Activity
Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Grants in Period
Return of electric fuel credit, total
The amount of electric fuel-related savings that has been returned in customer bill credits.
Public Utilities, Return Of Fuel Rules Credit
Assets
Total Assets
Assets
Income Statement [Abstract]
Debt to total capitalization ratio
Ratio of Indebtedness to Net Capital
Adjustments to operating revenue
Adjustments To Revenues [Member]
Recurring Fair Value Measurements
Fair Value of Financial Instruments, Policy [Policy Text Block]
Electric fuel credit ($)
The amount of fuel savings approved by the PSCW for an electric fuel credit to be returned to customers via a bill credit.
Electric fuel credit
Comprehensive Income [Member]
Share-Based Payment Arrangement [Policy Text Block]
Defined Benefit Plan, Amortization of Gain (Loss)
Actuarial (gain) loss
Deferred fuel rules monitored costs
The amount of electric fuel rules monitored costs which have been deferred outside the symmetrical cost tolerance band authorized by a regulatory agency.
Deferred fuel rules monitored costs
Deferred fuel rules monitored costs
Deferred income taxes
Deferred income taxes
Deferred Income Tax Expense (Benefit)
Deferred Income Tax Expense (Benefit), Total
Weighted Average [Member]
Gristmill [Member]
Gristmill [Member]
Other types of long-term debt not otherwise specified in the taxonomy
Other Long-Term Debt [Member]
Plan for 2020 Performance Unit Agreement as decribed in our report.
2020 Performance Unit Plan [Member]
Performance Unit Plan 2020 [Member]
Stock Issued During Period, Shares, New Issues
Consolidation, Variable Interest Entity, Policy [Policy Text Block]
Variable Interest Entities
Elm Road, a coal-fired generating facility.
Elm Road Units [Member]
Earnings Per Share, Diluted, Total
Earnings per share of Common Stock - Diluted
Earnings Per Share, Diluted
2017 Tax reform bill signed by congress.
Tax Cuts and Jobs Act [Member]
Segment Information
Schedule of Segment Reporting Information, by Segment [Table Text Block]
Operating Segments [Member]
Long-Term Purchase Commitment [Table]
Effective Income Tax Rate [Line Items]
Effective Income Tax Rate Reconciliation, Percent [Abstract]
Schedule Of Income Tax Disclosures Table
Schedule of Income Tax Disclosures [Table]
City Area Code
Other comprehensive income (loss)
Total comprehensive income
Other Comprehensive Income (Loss), Net of Tax
Restricted Cash and Cash Equivalent, Current
Restricted Cash and Cash Equivalents, Current, Total
Restricted cash
Finance lease liabilities - long term, Finance lease liabilities
Finance lease liabilities
Finance Lease, Liability, Noncurrent
Face amount
Debt Instrument, Face Amount
Equity And Financing Arrangements Disclosure Abstract
Equity and Financing Arrangements Disclosure [Abstract]
Defined Benefit Plan [Table]
Completed Renewable Projects Member
Completed Renewable Projects [Member]
Tangible Asset Impairment Charges [Abstract]
Impairment of Long-Lived Assets
Atcholdcoequitymethodinvestee Member
ATC Holdco [Member]
Segment Reporting Information [Line Items]
Realized and unrealized gains (losses) included in income for level 3 instruments [Line Items]
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Oil and Gas [Member]
Effective Income Tax Rate Reconciliation, Tax Credit, Other, Percent
Credit for electricity from renewable energy
Derivative Liability, Fair Value, Gross Liability, Total
Derivative Liability, Subject to Master Netting Arrangement, before Offset
Derivative Liability, Fair Value, Gross Liability
Dividends from MGE Transco
Proceeds from Equity Method Investment, Distribution
Dividends from investments
Derivative liabilities
Other current liabilities
Derivative Liability, Current
Property, Plant and Equipment, Net, Beginning Balance
Property, Plant and Equipment, Net, Ending Balance
Total Property, Plant, and Equipment
Property, Plant and Equipment, Net
Regulatory liabilities
Regulatory Liability, Noncurrent
Regulatory Liability, Noncurrent, Total
Included in other comprehensive income
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Inputs Reconciliation, Gain (Loss) Included in Other Comprehensive Income (Loss)
Cash, cash equivalents, and restricted cash
Cash, Cash Equivalent, Restricted Cash, and Restricted Cash Equivalent, Including Discontinued Operation
Cash, cash equivalents, and restricted cash at end of period
Cash, cash equivalents, and restricted cash at beginning of period
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents, Including Disposal Group and Discontinued Operations, Total
Operating Income
Operating income (loss)
Operating Income
Operating Income (Loss)
Other types of long-term debt expected to be funded in the future. Note Purchase Agreement commited to, but funding expected in August 2021 (after filing).
Other Long Term Debt Expected In Future Periods [Member]
2006 Performance Unit Plan [Member]
Plan for 2006 Performance Unit Agreement as described in out report.
Performance Unit Plan [Member]
Derivative Netting
Derivatives, Offsetting Fair Value Amounts, Policy [Policy Text Block]
Gas transportation operating revenue.
Gas Transportation [Member]
Retained Earnings [Member]
Entity Address, Country
Receivable Margin Account
Margin Deposit Assets Policy [Text Block]
Disclosure of accounting policy for restricted receivable margin account.
Plan for Director Incentive Agreement as described in our report.
Director Incentive Agreement [Member]
Transaction [Domain]
Amortization of:
Amortization [Abstract]
Payments of Stock Issuance Costs
Total Other Credits
Liabilities, Noncurrent
Level 1 [Member]
Fair Value, Inputs, Level 1 [Member]
Class of Stock [Line Items]
Cash Used for Financing Activities
Cash Provided by (Used in) Financing Activity, Including Discontinued Operation
Cash Provided by (Used for) Financing Activities
Gas revenue
Regulated Operating Revenue, Gas
Deferred income taxes
Deferred Income Tax Liabilities, Net
Deferred Income Tax Liabilities, Net, Total
Derivative liabilities
Other deferred liabilities
Derivative Liability, Noncurrent
Derivative Contract [Domain]
West Riverside Energy Center II [Member]
West Riverside Energy Center is a natural gas-fired facility located in Beloit, WI. This tag is specific to MGE's second purchase of 25 MW in 2024.
Three Point Seventy Five Industrial Reveue Bond Due 2027
Three Point Seventy Five Industrial Reveue Bond Due 2027 [Member]
3.75%, 2027 Series, Industrial Revenue Bonds
Income Tax Jurisdiction [Domain]
Entity Interactive Data Current
Statement of Income Location, Balance [Domain]
Fair Value Measurement [Domain]
Operating Activities:
Cash Provided by (Used in) Operating Activity, Including Discontinued Operation [Abstract]
Badger Hollow II Units [Member]
Badger Hollow II units.
New Accounting Pronouncements
Accounting Standards Update and Change in Accounting Principle [Text Block]
Tabular disclsoure of the location and amount of gains and losses reported in the statement of financial position on derivative instruments designated and qualifying as hedging instruments.
Derivative Gains and Losses in Balance Sheet
Schedule Of Derivative Instruments, Gain (Loss) in Statement of Financial Position [Table Text Block]
Fuel Rules, Electric Fuel Deferred Costs, Lower Threshold
Under fuel rules, the amount in which MGE is required to defer the benefit of lower costs if actual electric fuel costs were less than the allowed electric fuel costs in latest rate order.
Fuel rules, electric fuel deferred costs lower threshold
Unbilled revenues
Unbilled Receivables, Current
Dilutive Shares Calculation [Abstract]
Dilutive Securities, Effect on Basic Earnings Per Share [Abstract]
Entity Tax Identification Number
Schedule of Common Stock Outstanding Roll Forward [Table Text Block]
Prepaid taxes
Prepaid Taxes
Long-Term Debt, Type [Axis]
Short-Term Debt [Abstract]
Badger Hollow I units.
Badger Hollow I Units [Member]
Pension and Other Postretirement Benefits Cost (Reversal of Cost)
Pension and Other Postretirement Benefits Cost (Reversal of Cost), Total
Employee benefit plan credit
Other Inventory, Supplies, Gross
Materials and supplies, at average cost
Term
Debt Instrument, Term
Cash dividends paid to parent by MGE
Cash dividends paid to parent by MGE
SEC Schedule, 12-04, Cash Dividends Paid to Registrant, Consolidated Subsidiaries
Operating expenses
Total Operating Expenses
Utilities Operating Expense
Total Operating Expenses
Offsetting Liabilities [Table]
The amount of excess deferred taxes related to the Tax Cuts and Jobs Act not governed by IRS normalization rules to be factored in rates.
Return of unprotected excess deferred taxes
Public Utilities Return Of Tax Cuts And Jobs Act Unprotected Excess Deferred Taxes
Allowance for Funds Used During Construction
Public Utilities, Allowance for Funds Used During Construction, Net Increase [Abstract]
Construction work in progress
Construction in Progress, Gross
Percentage of Public Utility's approved surcharge by regulatory agency.
Fuel surcharge effect on electric revenues (%)
Public Utilities Fuel Surcharge Percentage
Local Phone Number
Purchased power expense member.
Purchased Power Expense [Member]
Net periodic benefit (credit) cost
Defined Benefit Plan, Net Periodic Benefit Cost (Credit)
Other current liabilities
Other Liabilities, Current, Total
Other Liabilities, Current
Share-Based Compensation Arrangement by Share-Based Payment Award, Non-Option Equity Instruments, Forfeitures
A T Cequitymethodinvesteemember Member
ATC [Member]
ATC [Member]
AFUDC equity, net
Effective Income Tax Rate Reconciliation, Deduction, Other, Percent
Disclosure of accounting policy for capitalized software assets in a hosting arragement.
Capitalized Software Assets Hosting Arrangements
Capitalized Software Assets Hosting Arrangements Policy [Text Block]
Definedbenefitplandeferredpension And Other Postretirementbenefit Plan Costs Recovered Abstract
Defined Benefit Plan Deferred Pension And Other Postretirement Benefit Plan Costs Recovered [Abstract]
Accounting Policies [Abstract]
Darien, Paris, and Koshkonong Units [Member]
Darien, Paris, and Koshkonong Units [Member]
Common Stock, Number of Shares, Par Value and Other Disclosure [Abstract]
Other current liabilities [Member]
Other Current Liabilities [Member]
Stock Issued During Period, Shares, Dividend Reinvestment Plan
Stock plan
Disaggregation of Revenue [Line Items]
Offsetting Liabilities [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amount
Non-regulated energy member.
Non Regulated Energy [Member]
Non Regulated Energy Revenues [Member]
Non Regulated Energy [Member]
Class of Stock [Domain]
Cost of gas sold expense.
Cost Of Gas Sold Expense [Member]
The cost of gas sold charged against earnings for the period.
Cost of gas sold
Utilities Operating Expense, Cost of Gas Sold
Affiliated Entity [Member]
Stock, Class of Stock [Table]
Entity Emerging Growth Company
Debt Issuance, 5.43% due 2033
Five Point Forty Three Senior Notes Due 2033 [Member]
Five Point Forty Three Senior Notes Due 2033