PPA Counterparty Total Debt Outstanding Long-Term Contract for Purchase of Electric Power, Amount of Long-Term Debt or Lease Obligation Outstanding Payments for Purchase of Available-for-sale Securities Payments for Purchase of Available-for-sale Securities Payments for Purchase of Available-for-sale Securities Consolidated Entities [Axis] Consolidated Entities [Axis] Stock Appreciation Rights (SARs) Stock Appreciation Rights (SARs) [Member] Net Loss Attributable to Non-Controlling Interest Net Income (Loss) Attributable to Noncontrolling Interest Pay vs Performance Disclosure [Line Items] Statistical Measurement [Domain] Statistical Measurement [Domain] Changes in Operating Assets and Liabilities [Abstract] Increase (Decrease) in Operating Capital [Abstract] Underlying Security Market Price Change Underlying Security Market Price Change, Percent Retail Customers [Member] Retail Customers [Member] Retail Customers [Member] include residential customers, commercial customers and industrial customers. Transmission Services - Utility Transmission Services - Utility Transmission Services - Utility Component of Other Income (Expense) - Other [Domain] Component of Other Income (Expense) - Other [Domain] [Domain] for Component of Other Income (Expense) - Other [Axis] Regulatory Matters [Text Block] Public Utilities Disclosure [Text Block] All Award Types Award Type [Domain] Fair Value as of Grant Date Award Grant Date Fair Value Equity Method Investment [Domain] Investment, Name [Domain] Income Taxes [Member] Deferred Income Tax Charge [Member] Uncertain Tax Positions [Policy Text Block] Income Tax Uncertainties, Policy [Policy Text Block] Short-Term and Long-Term Debt [Text Block] Debt Disclosure [Text Block] Increase (Decrease) in Accounts Payable for Capital Additions to Property, Plant and Equipment Increase (Decrease) in Accounts Payable for Capital Additions to Property, Plant and Equipment Increase (Decrease) in Accounts Payable for Capital Additions to Property, Plant and Equipment Statement of Stockholders' Equity [Abstract] Statement of Stockholders' Equity [Abstract] Basis Point Incentive adder Basis Point Incentive adder Basis Point Incentive adder Cash Contributions to Defined Benefit Pension Plans Payment for Pension Benefits Goodwill, Change in Goodwill Allocation, Description Goodwill, Change in Goodwill Allocation, Description Expected Output Entitlement Long-Term Contract for Purchase of Electric Power, Share of Plant Output Being Purchased Square Butte [Member] Square Butte [Member] Square Butte [Member] Other [Member] Other [Member] Regulated Operations Other Revenue Recognized From Other Sources Immaterial For Disaggregation Equity Method Investments and Joint Ventures [Abstract] Equity Method Investments and Joint Ventures [Abstract] MNPI Disclosure Timed for Compensation Value MNPI Disclosure Timed for Compensation Value [Flag] Other [Member] ALLETE Clean Energy Other [Member] ALLETE Clean Energy Other Revenue Recognized From Other Sources Immaterial For Disaggregation [Member] Fuel Energy Related Inventory, Coal Segment Reporting [Abstract] Segment Reporting [Abstract] Accounts Payable Accounts Payable, Current Restatement Determination Date: Restatement Determination Date [Axis] Equity Method Investment [Axis] Investment, Name [Axis] Generating Capacity Subject to Tax Equity Financing Generating Capacity Subject to Tax Equity Financing Generating Capacity Subject to Tax Equity Financing Changes in Regulatory and Other Non-Current Liabilities Increase (Decrease) in Other Noncurrent Liabilities Total Other Expense Nonoperating Income (Expense) Statutory Federal Income Tax Rate Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent Expected Period for Costs of Compliance Expected Period for Costs of Compliance Expected Period for Costs of Compliance Commitments, Guarantees and Contingencies (Note 6) Commitments and Contingencies Insider Trading Policies and Procedures [Line Items] Rule 10b5-1 Arrangement Terminated Rule 10b5-1 Arrangement Terminated [Flag] Fuel Adjustment Clause 2022 Fuel Adjustment Clause 2022 [Member] Fuel Adjustment Clause 2022 Other Income (Expense) - Other [Line Items] Other Income (Expense) - Other [Line Items] [Line Items] for Other Income (Expense) - Other [Table] Restatement does not require Recovery Restatement Does Not Require Recovery [Text Block] Proceeds from Issuance of Common Stock Proceeds from Issuance of Common Stock Long-term Contract for Purchase of Electric Power, Term of Contract (Years) Long-term Contract for Purchase of Electric Power, Term of Contract (Years) Term in years of long-term contract to purchase electricity from a production plant constructed and financed by a public utility district, cooperative, or other organization. Changes in Regulatory and Other Non-Current Assets Increase (Decrease) in Other Noncurrent Assets Conservation Improvement Program Goal, Next Fiscal Year Energy Conservation and Optimization Plan Goal, Next Fiscal Year Energy Conservation and Optimization Plan Goal, Next Fiscal Year Geographical [Axis] Geographical [Axis] Minnesota Power [Member] Minnesota Power [Member] Minnesota Power [Member] Other (Member) Other Regulatory Assets (Liabilities) [Member] Income Tax Expense [Text Block] Income Tax Disclosure [Text Block] Regulatory Assets and Liabilities Disclosure [Abstract] Regulatory Assets and Liabilities Disclosure [Abstract] Other Other Accrued Liabilities, Noncurrent Current Liabilities [Abstract] Liabilities, Current [Abstract] Federal Deferred Federal Income Tax Expense (Benefit) Guarantor Obligations, Nature [Axis] Guarantor Obligations, Nature [Axis] Subsequent Event Type [Domain] Subsequent Event Type [Domain] Recurring Fair Value Measures [Table] Fair Value, Recurring and Nonrecurring [Table] Inventories – Net [Abstract] Inventory, Net [Abstract] Other [Member] Other Income (Expense) - Other [Member] Other Income (Expense) - Other [Member] Dividends on Common Stock Common Stock Dividends Payments of Ordinary Dividends, Common Stock Diluted Earnings Per Share of Common Stock Earnings Per Share, Diluted Cash Equivalents Other Restricted Assets, Noncurrent PEO Total Compensation Amount PEO Total Compensation Amount Accounts Receivable (Less Allowance of $1.6 and $1.6) Accounts Receivable, after Allowance for Credit Loss, Current Customer Refund Liability, Current Customer Refund Liability, Current Long-term Contract [Member] Long-term Contract [Member] Long-term Contract Revenue Stream [Member] Minnkota Power PSA [Member] Minnkota Sales Agreement [Member] Minnkota Sales Agreement [Member] Rate Type [Domain] Rate Type [Domain] Rate Type [Domain] Trading Arrangements, by Individual Trading Arrangements, by Individual [Table] Level 3 [Member] Fair Value, Inputs, Level 3 [Member] Line of Credit [Member] Line of Credit [Member] Proceeds from Issuance of First Mortgage Bond Proceeds from Issuance of First Mortgage Bond Current Regulatory Assets Regulatory Asset, Current Components of Net Periodic Benefit Expense (Income) [Table Text Block] Schedule of Net Benefit Costs [Table Text Block] Nobles 2 [Member] Nobles 2 [Member] Nobles 2 [Member] Components of Income Tax Expense (Benefit), Continuing Operations [Abstract] Components of Income Tax Expense (Benefit), Continuing Operations [Abstract] Other Income (Expense) [Abstract] Other Nonoperating Income (Expense) [Abstract] PSA Liability [Member] PSA Liability [Member] PSA Liability Fuel Adjustment Clause Increase (Decrease) in Regulatory Clause Revenue Trading Symbol Trading Symbol Letters of Credit Outstanding, Amount Letters of Credit Outstanding, Amount Payments for Equity Method Investments Cash Investments Payments to Acquire Equity Method Investments Non-PEO NEO Average Compensation Actually Paid Amount Non-PEO NEO Average Compensation Actually Paid Amount Guarantor Obligations, Nature [Domain] Guarantor Obligations, Nature [Domain] Power Purchase Agreements [Domain] Power Purchase Agreement - Energy and Capacity [Domain] Long-Term Contract for Purchase of Electric Power [Domain] Short-Term and Long-Term Debt - Fair Value Long-Term Debt, Fair Value Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI for Sale of Securities, Tax OCI, Debt Securities, Available-for-Sale, Gain (Loss), after Adjustment, Tax Net Income Attributable to ALLETE Net Income Attributable ALLETE Net Income Attributable to ALLETE Net Income (Loss) Total Current Liabilities Liabilities, Current Coal, Rail and Shipping Contracts [Line Items] Unrecorded Unconditional Purchase Obligation [Line Items] Fair Value Disclosures [Abstract] Fair Value Disclosures [Abstract] PPACA Income Tax Deferral [Member] Medicare Part D Regulatory Asset [Member] Discloses the amount of regulatory asset arising from the deferral of the retail portion of a tax charge taken in 2010 resulting from the Patient Protection and Affordable Care Act of 2010 (PPACA). Requested Equity Capital Structure Public Utilities, Requested Equity Capital Structure, Percentage Changed Peer Group, Footnote Changed Peer Group, Footnote [Text Block] Company Selected Measure Name Company Selected Measure Name Document and Entity Information, Document [Axis] Document Information, Document [Axis] Accrued Interest Interest Payable, Current Liabilities and Equity [Abstract] Liabilities and Equity [Abstract] Investment in ATC [Table] Investment in Nobles 2 [Table] Schedule of Equity Method Investments [Table] Equity [Abstract] Equity, Attributable to Parent [Abstract] Other Other Assets, Miscellaneous, Noncurrent Reconciliation of Basic and Diluted Earnings Per Share [Table Text Block] Schedule of Earnings Per Share, Basic and Diluted [Table Text Block] Operating and Maintenance Operating and Maintenance Operating and Maintenance Expenses Cost of Sales - Non-utility Cost of Goods and Services Sold Service Cost Defined Benefit Plan, Service Cost Rate Type [Axis] Rate Type [Axis] Rate Type [Axis] including categories like electric rates, natural gas rates, water rates, etc. Executive Category: Executive Category [Axis] Sale of Renewable Development Projects Sale of Renewable Development Projects [Member] Sale of Renewable Development Projects Revenue Streams [Axis] Contract with Customer, Sales Channel [Axis] Purchase Price Accounting Impact Purchase Price Accounting Impact Purchase Price Accounting Impact. Expense (benefit) as a result of purchase price accounting. Long-term PSA [Member] Long-term PSA [Member] Revenue Recognized From Long-term PSAs Level 1 [Member] Fair Value, Inputs, Level 1 [Member] Name Measure Name Industrial [Member] Industrial [Member] Industrial Sales Channel [Member] Name Forgone Recovery, Individual Name Estimated Obligation Guarantor Obligations, Maximum Exposure, Undiscounted Goodwill Goodwill Increase (Decrease) in Income Tax Due to: [Abstract] Increase (Decrease) in Tax [Abstract] Increase (Decrease) in Tax [Abstract] Equity Components [Axis] Equity Components [Axis] Public Utilities, Approved Equity Capital Structure, Percentage Public Utilities, Approved Equity Capital Structure, Percentage Additional 402(v) Disclosure Additional 402(v) Disclosure [Text Block] Underlying Securities Award Underlying Securities Amount Entity Small Business Entity Small Business Sale of Wind Energy Facility Sale of Wind Energy Facility [Member] Sale of Wind Energy Facility Local Phone Number Local Phone Number Recovery of Erroneously Awarded Compensation Disclosure [Line Items] Dividends Per Share of Common Stock Common Stock, Dividends, Per Share, Declared Unrealized Loss on Securities - Net of Income Tax Expense $-, $(0.2), $0.1 and $($0.2) Unrealized Loss on Securities OCI, Debt Securities, Available-for-Sale, Unrealized Holding Gain (Loss), before Adjustment, after Tax Common Stock, Par Value Common Stock, No Par Value Measurement Frequency [Axis] Measurement Frequency [Axis] Materials and Supplies Inventory, Supplies, Net of Reserves Operating Lease Liabilities Operating Lease, Liability, Noncurrent Retirement Plan Type [Domain] Retirement Plan Type [Domain] Forgone Recovery due to Violation of Home Country Law, Amount Forgone Recovery due to Violation of Home Country Law, Amount Pension and Other Postretirement Plan Costs [Member] Pension and Other Postretirement Plans Costs [Member] Equity Issuance Costs Payments of Stock Issuance Costs Debt Instrument, Name [Domain] Debt Instrument, Name [Domain] Depreciation Expense Depreciation Retirement Benefits [Abstract] Retirement Benefits [Abstract] Generating Facility Unit Name [Domain] Generating Facility Unit Name [Domain] [Domain] for Name of generating unit or facility [Axis] Defined Benefit Pension and Other Postretirement Benefit Plans Liability, Defined Benefit Plan, Noncurrent Goodwill and Intangible Assets - Net Intangible Assets, Net (Including Goodwill) Regulatory Matters [Line Items] Public Utilities, General Disclosures [Line Items] Dilutive Securities (Shares) Weighted Average Number of Shares Outstanding, Diluted, Adjustment Equity Method Investments (Table Text Block) Equity Method Investments [Table Text Block] Power Purchase Agreements [Axis] Power Purchase Agreement - Energy and Capacity [Axis] Long-Term Contract for Purchase of Electric Power [Axis] Cash and Cash Equivalents, Policy [Policy Text Block] Cash and Cash Equivalents, Policy [Policy Text Block] Other Income (Expense) - Other [Abstract] Other Income (Expense) - Other [Abstract] Other Income (Expense) - Other [Abstract] Power Purchase Agreements [Policy Text Block] Consolidation, Variable Interest Entity, Policy [Policy Text Block] Total Operating Revenue Operating Revenue Revenues Other Non-Current Assets [Abstract] Other Assets, Noncurrent [Abstract] Fair Value, by Balance Sheet Grouping [Table Text Block] Fair Value, by Balance Sheet Grouping [Table Text Block] Regulatory Assets and Liabilities [Policy Text Block] Public Utilities, Policy [Policy Text Block] Other Performance Measure, Amount Other Performance Measure, Amount Superior, WI [Member] Superior, WI [Member] Superior, WI Aggregate Available Trading Arrangement, Securities Aggregate Available Amount Inventories Increase (Decrease) in Inventories Standby Letters of Credit [Member] Standby Letters of Credit [Member] Investing Activities [Abstract] Net Cash Provided by (Used in) Investing Activities [Abstract] Common Stock [Abstract] Common Stock, Number of Shares, Par Value and Other Disclosure [Abstract] Insider Trading Policies and Procedures Not Adopted Insider Trading Policies and Procedures Not Adopted [Text Block] Business Combination, Acquisition Related Costs Business Combination, Acquisition Related Costs Award Type Award Type [Axis] Document Quarterly Report Document Quarterly Report Interest Expense Interest Expense Fair Value Hierarchy and NAV [Domain] Fair Value Hierarchy and NAV [Domain] Trading Arrangement: Trading Arrangement [Axis] Diamond Spring [Member] Diamond Spring [Member] Diamond Spring [Member] Employer Contributions to Defined Benefit Plans Defined Benefit Plan, Plan Assets, Contributions by Employer PEO Actually Paid Compensation Amount PEO Actually Paid Compensation Amount Expected Return on Plan Assets Defined Benefit Plan, Expected Return (Loss) on Plan Assets Long-Term Debt - Unamortized Debt Issuance Costs Unamortized Debt Issuance Expense, Long-Term Debt Excluding Current Maturities The remaining balance of debt issuance expenses that were capitalized and are being amortized against income over the lives of long-term debt excluding current maturities. Non-Controlling Interest Details [Line Items] Non-Controlling Interest Details [Line Items] [Line Items] for Non-Controlling Interest Details [Table] Income Tax Expense [Table Text Block] Schedule of Components of Income Tax Expense (Benefit) [Table Text Block] Entity File Number Entity File Number Non-Controlling Interest Details [Table] Non-Controlling Interest Details [Table] Non-Controlling Interest Details [Table] Operating Lease Liabilities Operating Lease, Liability, Current Entity Shell Company Entity Shell Company Manufactured Gas Plant - Current Manufactured Gas Plant - Current Manufactured Gas Plant - Current Business Acquisition, Acquiree [Domain] Business Acquisition, Acquiree [Domain] Document and Entity Information [Abstract] Document and Entity Information [Abstract] Document and Entity Information [Abstract] Restatement Determination Date Restatement Determination Date Counterparty Name [Domain] Counterparty Name [Domain] Requested Return on Equity Public Utilities, Requested Return on Equity, Percentage Electric Rates [Member] Electric Rates [Member] Electric Rates [Member] Rule 10b5-1 Arrangement Adopted Rule 10b5-1 Arrangement Adopted [Flag] Regulatory Agency [Domain] Regulatory Agency [Domain] Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents Cash, Cash Equivalents and Restricted Cash on the Consolidated Statement of Cash Flows Cash, Cash Equivalents, Restricted Cash, and Restricted Cash Equivalents Regulated Operations [Member] Regulated Operations [Member] Regulated Operations [Member] Document [Domain] Document [Domain] Stock Price or TSR Estimation Method Stock Price or TSR Estimation Method [Text Block] Common Stock, Shares Issued Common Stock, Shares, Issued PSAs Power Purchase Agreement - Current Liability The fair value adjustment for the price of power per MW at market rates compared to those at contract rate at the time of acquisition through the end of the contract term present valued to acquisition date resulting in a current liability. Customer Deposits Contract with Customer, Liability, Current PSAs Power Purchase Agreement - Noncurrent Liability The fair value adjustment for the price of power per MW at market rates compared to those at contract rate at the time of acquisition through the end of the contract term present valued to acquisition date resulting in a noncurrent liability. Authorized Return on Equity, Including Incentive Adder Equity Method Investment, Approved Return on Common Equity, Including Incentive Adder The approved percentage return on common equity, including an incentive adder for participation in a regional transmission organization dedicated to the utility plant in the investee accounted for under the equity method of accounting. Contracts with Customers - Utility Regulated Operating Revenue Name of Exchange Security Exchange Name Collateral Guarantor Obligations, Collateral Held Directly or by Third Parties, Amount Amount of any assets held either as collateral or by third parties that, upon the occurence of any triggering event or condition under the guarantee, can be obtained and liquidated to recover all or a portion of the amounts paid under the guarantee. Short-Term and Long-Term Debt - Carrying Amount Long-Term Debt Total Fair Value of Assets Assets, Fair Value Disclosure Capitalized Asset Retirement Costs Increase (Decrease) in Asset Retirement Obligations Accumulated Other Comprehensive Loss Accumulated Other Comprehensive Income (Loss), Net of Tax Employee Stock Option Employee Stock Option [Member] Effective Income Tax Rate Reconciliation, Investment Tax Credits Effective Income Tax Rate Reconciliation, Tax Credit, Investment, Amount Pro Rata Share of PPA Counterparty Interest Expense Long-Term Contract for Purchase of Electric Power, Interest Included in Contract Charges Component of Other Income (Expense) - Other [Axis] Component of Other Income (Expense) - Other [Axis] Component of Other Income (Expense) - Other [Axis] Plant Removal Obligations [Member] Removal Costs [Member] Total Operating Expenses Costs and Expenses Other Financing Activities Proceeds from (Payments for) Other Financing Activities Maximum [Member] Maximum [Member] Total Comprehensive Income Attributable to ALLETE Comprehensive Income (Loss), Net of Tax, Attributable to Parent Document Type Document Type Regulatory Agency [Axis] Regulatory Agency [Axis] Tabular List, Table Tabular List [Table Text Block] Cost of Power Purchased Utilities Operating Expense, Purchased Power under Long-Term Contracts Entity Address, Address Line One Entity Address, Address Line One Inventories – Net [Policy Text Block] Inventory, Policy [Policy Text Block] Commercial [Member] Commercial [Member] Revenue Recognized From Commercial Customers Actual Ratio of Indebtedness to Total Capitalization Debt Instrument, Actual Indebtedness to Total Capital Ratio Actual indebtedness to total capital ratio required to be maintained by most restrictive financial covenant. Other - Non-utility Amortization of PSAs Amortization of Power Purchase Agreements The amount of income recognized in the current period that reflects income associated with the reduced liability of the PPAs acquired in a business acquisition. As noncash income, this element is subtracted from net income when calculating cash provided by or used in operations using the indirect method. Federal Current Federal Tax Expense (Benefit) Change in Cash, Cash Equivalents and Restricted Cash Cash, Cash Equivalents, Restricted Cash, and Restricted Cash Equivalents, Period Increase (Decrease), Excluding Exchange Rate Effect Environmental Matters [Line Items] Environmental Matters [Line Items] [Line Items] for Environmental Matters [Table] Business Acquisition [Axis] Business Acquisition [Axis] Accrued Taxes Taxes Payable, Current Fair Value of Financial Instruments [Line Items] Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] Manufactured Gas Plant [Member] Manufactured Gas Plant [Member] Manufactured Gas Plant [Member] Accounts Receivable, Allowance Accounts Receivable, Allowance for Credit Loss, Current Subsequent Event [Member] Subsequent Event [Member] Regulatory Proceeding [Domain] Public Utilities, Regulatory Proceeding [Domain] Restricted Cash included in Other Non-Current Assets Restricted Cash, Non-Current Restricted Cash, Noncurrent State Deferred State and Local Income Tax Expense (Benefit) Other Total Other Current Liabilities Other Liabilities, Current Short-Term Debt - Principal Debt, Current, Gross Amount of short-term debt and current maturities of long-term debt before deduction of unamortized discount or premium and unamortized debt issuance costs. Income Statement [Abstract] Income Statement [Abstract] Total Debt - Principal Debt, Long-Term and Short-Term, Combined Amount, Gross Represents the aggregate of total long-term debt, including current maturities and short-term debt, before deduction of unamortized discount or premium and unamortized debt issuance expense. ALLETE Bonds 4.98% Due April 2033 ALLETE Bonds 4.98% Due April 2033 [Member] ALLETE Bonds 4.98% Due April 2033 Title of 12(b) Security Title of 12(b) Security Insider Trading Policies and Procedures Adopted Insider Trading Policies and Procedures Adopted [Flag] Components of Net Periodic Benefit Cost (Credit) [Abstract] Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract] Pension and Other Postretirement Benefit Plans [Line Items] Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] Aggregate Erroneous Compensation Not Yet Determined Aggregate Erroneous Compensation Not Yet Determined [Text Block] Fuel, Purchased Power and Gas - Utility Fuel, Purchased Power and Gas - Utility Fuel, Purchased Power and Gas - Utility Prepayments and Other Other Assets, Current Environmental Accruals [Policy Text Block] Environmental Costs, Policy [Policy Text Block] Other Power Suppliers [Member] Other Power Suppliers [Member] Other Power Suppliers Sales Channel [Member] Income Tax Disclosure [Abstract] Income Tax Disclosure [Abstract] Income Taxes Computed at Statutory Federal Rate Effective Income Tax Rate Reconciliation at Federal Statutory Income Tax Rate, Amount Forgone Recovery due to Expense of Enforcement, Amount Forgone Recovery due to Expense of Enforcement, Amount Entity Tax Identification Number Entity Tax Identification Number Available-for-sale Securities, Debt Maturities, After Three Years Through Five Years, Fair Value Available-for-sale Securities, Debt Maturities, After Three Years Through Five Years, Fair Value Amount of available-for-sale debt securities at fair value maturing after the third fiscal year through the fifth fiscal year following the latest fiscal year (maturing in three years to less than five years). Equity Investments Equity Investment Balance as of December 31, 2022 Equity Investment Balance as of June 30, 2023 Equity Investment Balance Equity Method Investments Total Debt - Total Debt, Long-Term and Short-Term, Combined Amount Inventories – Net Total Inventories – Net Inventory, Net Statistical Measurement [Axis] Statistical Measurement [Axis] Operating Revenue, Other Than Customer Revenue Revenue, Other Than Customer Revenue Non-cash Revenue Recognized From Amortization of PSAs Assumed Through Acquisitions ALLETE, Inc. [Member] ALLETE, Inc. [Member] -- None. No documentation exists for this element. -- Entity Interactive Data Current Entity Interactive Data Current Short-Term Debt - Unamortized Debt Issuance Costs Unamortized Debt Issuance Expense, Debt, Current The remaining balance of debt issuance expenses that were capitalized and are being amortized against income over the lives of short-term debt or the current maturities of long-term debt. Square Butte PPA [Member] Square Butte PPA [Member] Long-term contract with Square Butte for the purchase of electric power. New Energy New Energy [Member] New Energy Total Shareholder Return Amount Total Shareholder Return Amount Cash, Cash Equivalents and Restricted Cash [Abstract] Cash, Cash Equivalents, Restricted Cash, and Restricted Cash Equivalents [Abstract] Entity Common Stock, Shares Outstanding Entity Common Stock, Shares Outstanding Adjustment To PEO Compensation, Footnote Adjustment To PEO Compensation, Footnote [Text Block] Deferred Income Taxes Deferred Income Taxes and Other Tax Liabilities, Noncurrent Noncash Investing and Financing Activities [Abstract] Cash Flow, Noncash Investing and Financing Activities Disclosure [Abstract] Defined Benefit Pension and Other Postretirement Benefit Plans, Income Tax Expense Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, Tax Business Segments [Domain] Segments [Domain] Residential Interim Rate Adjustment Increase (Decrease) for Residential Interim Rate Adjustment Increase (Decrease) for Residential Interim Rate Adjustment Fair Value Hierarchy and NAV [Axis] Fair Value Hierarchy and NAV [Axis] Other Income [Table Text Block] Schedule of Other Nonoperating Income (Expense) [Table Text Block] Retained Earnings Retained Earnings (Accumulated Deficit) Measure: Measure [Axis] Commitments and Contingencies Disclosure [Abstract] Commitments and Contingencies Disclosure [Abstract] Name Outstanding Recovery, Individual Name State of Incorporation Entity Incorporation, State or Country Code Current Assets [Abstract] Assets, Current [Abstract] Wholesale and Retail Contra AFUDC [Member] Wholesale and Retail Contra AFUDC [Member] Wholesale and Retail Contra AFUDC [Member] Cost Recovery Riders [Member] Cost Recovery Riders [Member] Cost Recovery Riders [Member] Entity Address, State or Province Entity Address, State or Province Compensation Actually Paid vs. Total Shareholder Return Compensation Actually Paid vs. Total Shareholder Return [Text Block] Counterparty Name [Axis] Counterparty Name [Axis] North Dakota Investment Tax Credits [Member] North Dakota Investment Tax Credits Subject to Refund [Member] North Dakota Investment Tax Credits Subject to Refund [Member] Operating Activities [Abstract] Net Cash Provided by (Used in) Operating Activities [Abstract] Guarantor Obligations [Line Items] Guarantor Obligations [Line Items] Approximate Annual Reduction in Pretax Income for FERC Proposal to Limit Incentive adder, ALLETE's Proportionate Share Approximate Annual Reduction in Pretax Income for FERC Proposal to Limit Incentive adder, ALLETE's Proportionate Share Approximate Annual Reduction in Pretax Income for FERC Proposal to Limit Incentive adder, ALLETE's Proportionate Share Common Stock, Shares Outstanding Common Stock, Shares, Outstanding Wind Turbine Generators [Member] Wind Turbine Generators [Member] Wind Turbine Generators [Member] Environmental Remediation Contingency [Axis] Environmental Remediation Contingency [Axis] Interest Cost Defined Benefit Plan, Interest Cost Accounts Receivable Increase (Decrease) in Accounts and Other Receivables PEO PEO [Member] Other Receivables Other Receivables Pension and Other Postretirement Benefit Plans [Text Block] Retirement Benefits [Text Block] Tenaska [Member] Tenaska [Member] Tenaska Energy, Inc. and Tenaska Energy Holdings, LLC [Member] Contract Assets Contract with Customer, Asset, after Allowance for Credit Loss, Noncurrent State Income Taxes – Net of Federal Income Tax Benefit Effective Income Tax Rate Reconciliation, State and Local Income Taxes, Amount Generation Type [Axis] Generation Type [Axis] Generation Type [Axis] BNI Energy [Member] BNI Energy [Member] BNI Energy Available-for-sale Securities, Debt Maturities, After Five Years, Fair Value Available-for-sale Securities, Debt Maturities, After Five Years, Fair Value Amount of available-for-sale debt securities at fair value maturing in after the fifth fiscal year following the latest fiscal year (maturing in five years or more). Cash used in Investing Activities Net Cash Provided by (Used in) Investing Activities Energy Conservation and Optimization Plan Goal, Second Fiscal Year Energy Conservation and Optimization Plan Goal, Second Fiscal Year Energy Conservation and Optimization Plan Goal, Second Fiscal Year Inventories – Net [Table Text Block] Schedule of Inventory, Current [Table Text Block] Other Effective Income Tax Rate Reconciliation, Other Reconciling Items, Amount Defined Benefit Plan, Expected Future Employer Contributions, Remainder of Fiscal Year Defined Benefit Plan, Expected Future Employer Contributions, Remainder of Fiscal Year Debt Instrument [Axis] Debt Instrument [Axis] Contracts with Customers - Non-utility Unregulated Operating Revenue Outstanding Aggregate Erroneous Compensation Amount Outstanding Aggregate Erroneous Compensation Amount Effective Tax Rate Effective Income Tax Rate Reconciliation, Percent 2022 Minnesota General Rate Review 2022 Minnesota General Rate Review [Member] 2022 Minnesota General Rate Review Annual Additional Revenue Generated from Requested Final Rate Increase Public Utilities, Requested Rate Increase (Decrease), Amount Total Liabilities Liabilities Total Current Income Tax Expense Current Income Tax Expense (Benefit) Total Shareholder Return Vs Peer Group Total Shareholder Return Vs Peer Group [Text Block] Accumulated Other Comprehensive Loss [Member] AOCI Attributable to Parent [Member] Prepayments and Other Increase (Decrease) in Prepaid Expense and Other Assets Aggregate Erroneous Compensation Amount Aggregate Erroneous Compensation Amount Measurement Frequency [Domain] Measurement Frequency [Domain] All Executive Categories All Executive Categories [Member] Non-Rule 10b5-1 Arrangement Adopted Non-Rule 10b5-1 Arrangement Adopted [Flag] Reclassification of Property, Plant and Equipment to Inventory (a) Reclassification of Property, Plant and Equipment to Inventory Reclassification of Property, Plant and Equipment to Inventory Coal Combustion Residuals [Member] Coal Combustion Residuals [Member] Coal Combustion Residuals [Member] Debt Disclosure [Abstract] Debt Disclosure [Abstract] Number of Reportable Segments Number of Reportable Segments Fuel Adjustment Clause 2023 Fuel Adjustment Clause 2023 [Member] Fuel Adjustment Clause 2023 ATC [Member] ATC [Member] ATC [Member] Earnings Per Share [Abstract] Earnings Per Share [Abstract] Total Regulatory Asset [Domain] Regulatory Asset [Domain] Common Stock Without Par Value, 80.0 Shares Authorized, 57.4 and 57.2 Shares Issued and Outstanding Common Stock, Value, Issued Organization, Consolidation and Presentation of Financial Statements [Abstract] Organization, Consolidation and Presentation of Financial Statements [Abstract] Guarantee Entity and Type [Domain] Guarantee Entity and Type [Domain] [Domain] for Guarantee Entity and Type [Axis] Public Utilities, Approved Rate Increase (Decrease), Amount Public Utilities, Approved Rate Increase (Decrease), Amount Awards Close in Time to MNPI Disclosures, Table Awards Close in Time to MNPI Disclosures [Table Text Block] State Current State and Local Tax Expense (Benefit) Business Segments [Policy Text Block] Segment Reporting, Policy [Policy Text Block] Total Current Assets Assets, Current Deferred Income Tax Expense (Benefit) [Abstract] Deferred Income Tax Expense (Benefit), Continuing Operations [Abstract] Public Utilities Reserve for Interim Rates Public Utilities Reserve for Interim Rates Public Utilities Reserve for Interim Rates Net Periodic Benefit Cost (Credit) Defined Benefit Plan, Net Periodic Benefit Cost (Credit) All Individuals All Individuals [Member] Supplemental Cash Flow Information [Abstract] Supplemental Cash Flow Information [Abstract] ALLETE's Investment in ATC [Roll Forward] ALLETE's Investment in ATC [Roll Forward] ALLETE's Investment in ATC [Roll Forward] Other Total Other Income Other Nonoperating Income (Expense) Entity Filer Category Entity Filer Category Investment in ATC [Line Items] Investment in Nobles 2 [Line Items] Schedule of Equity Method Investments [Line Items] Non-PEO NEO Average Total Compensation Amount Non-PEO NEO Average Total Compensation Amount Minnkota Power [Member] Minnkota Power [Member] Minnkota Power [Member] Consolidated Statement of Equity [Table] Statement [Table] Current Fiscal Year End Date Current Fiscal Year End Date Earnings Per Share [Policy Text Block] Earnings Per Share, Policy [Policy Text Block] Reconciliation of Taxes from Federal Statutory Rate to Total Income Tax Expense [Table Text Block] Schedule of Effective Income Tax Rate Reconciliation [Table Text Block] Defined Benefit Pension and Postretirement Benefit Pension and Other Postretirement Benefits Expense (Reversal of Expense), Noncash Gross Unrecognized Tax Benefits Unrecognized Tax Benefits PEO Name PEO Name Fair Value of Financial Instruments [Table] Fair Value, by Balance Sheet Grouping [Table] Current Income Tax Expense (Benefit) [Abstract] Current Income Tax Expense (Benefit), Continuing Operations [Abstract] Interest and Investment Income (Loss) [Member] Interest and Investment Earnings [Member] Interest and Investment Earnings [Member] Restricted Cash included in Prepayments and Other Restricted Cash, Current Regulatory Liabilities Non-Current Regulatory Liabilities Regulatory Liability, Noncurrent Guarantee Entity and Type [Axis] Guarantee Entity and Type [Axis] Guarantee Entity and Type [Axis] Other Postretirement [Member] Other Postretirement Benefits Plan [Member] Uncertain Tax Positions [Abstract] Income Tax Uncertainties [Abstract] Cash provided by (used in) Operating Activities Net Cash Provided by (Used in) Operating Activities Equity Investments [Text Block] Equity Method Investments and Joint Ventures Disclosure [Text Block] Erroneously Awarded Compensation Recovery Erroneously Awarded Compensation Recovery [Table] Boswell Units 1 and 2 Net Plant and Equipment Boswell Units 1 and 2 Net Plant and Equipment [Member] Boswell Units 1 and 2 Net Plant and Equipment Other Other Accrued Liabilities, Current Amortization of Prior Service Credits Defined Benefit Plan, Amortization of Prior Service Cost (Credit) Regulatory Liability [Domain] Regulatory Liability [Domain] Regulatory Proceeding [Axis] Public Utilities, Regulatory Proceeding [Axis] Line of Credit, Current Line of Credit, Current Depreciation and Amortization Depreciation, Depletion and Amortization Loss (Gain) on Investments and Property, Plant and Equipment Gain (Loss) on Disposition of Other Assets Interest Rate Debt Instrument, Interest Rate, Stated Percentage Award Timing, How MNPI Considered Award Timing, How MNPI Considered [Text Block] Statement of Financial Position [Abstract] Statement of Financial Position [Abstract] Total ALLETE Equity Equity, Attributable to Parent Gross Unrecognized Tax Benefits That Would Favorably Impact Effective Income Tax Rate Unrecognized Tax Benefits that Would Impact Effective Tax Rate Other Postretirement Benefit Plans Other Postretirement Benefit Plans Other Postretirement Benefit Plans Deferred Revaluation – Net of Federal Income Tax Benefit Effective Income Tax Rate Reconciliation, Deferred Revaluation – Net of Federal Income Tax Benefit Effective Income Tax Rate Reconciliation, Deferred Revaluation – Net of Federal Income Tax Benefit Asset Retirement Obligations [Member] Asset Retirement Obligation Costs [Member] Income Before Income Taxes Income Before Income Taxes Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest Fair Value Measurement [Policy Text Block] Fair Value Measurement, Policy [Policy Text Block] Level 2 [Member] Fair Value, Inputs, Level 2 [Member] Entity Emerging Growth Company Entity Emerging Growth Company Unrecorded Unconditional Purchase Obligation [Table] Unrecorded Unconditional Purchase Obligation [Table] Coal, Rail and Shipping Contracts [Axis] Unrecorded Unconditional Purchase Obligation by Category of Item Purchased [Axis] Glen 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Organization, Consolidation, Basis of Presentation, Business Description and Accounting Policies [Text Block] ALLETE Properties Real Estate Investments, Net Distributed Earnings Proceeds from Equity Method Investment, Distribution Exercise Price Award Exercise Price Total Other Comprehensive Income (Loss) Other Comprehensive Income (Loss), Net of Tax Statement of Cash Flows [Abstract] Statement of Cash Flows [Abstract] Assets [Abstract] Assets [Abstract] Award Timing MNPI Disclosure Award Timing MNPI Disclosure [Text Block] Proceeds from Issuance of Short-Term and Long-Term Debt Proceeds from Issuance of Long-Term Debt Total Fair Value of Liabilities Liabilities, Fair Value Disclosure Renewable Energy Facilities Under Development Other Inventory, Gross Available-for-sale - Equity Securities Equity Securities, FV-NI, Noncurrent Liabilities [Abstract] Liabilities [Abstract] Net Income Net Income Net Income (Loss), Including Portion Attributable to Noncontrolling Interest Cash Paid for 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Termination Date Accounts Payable Increase (Decrease) in Accounts Payable Common Stock, Shares Authorized Common Stock, Shares Authorized Amortization of Other Intangible Assets and Other Assets Other Depreciation and Amortization Generation Type [Domain] Generation Type [Domain] [Domain] for Generation Type [Axis] Document and Entity Information [Table] Document Information [Table] South Peak [Member] South Peak [Member] South Peak [Member] Proceeds from Non-controlling Interest in Subsidiaries - Net Proceeds from Non-controlling Interest in Subsidiaries - Net of Issuance Costs Proceeds from Noncontrolling Interests Recurring Fair Value Measures [Abstract] Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] Production Tax Credits Effective Income Tax Rate Reconciliation, Tax Credit, Other, Amount Power Sales Agreements - Energy and Capacity [Axis] Long-term Contracts for Sale of Electric Power [Axis] Long-term Contracts for Sale of Electric 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Reconciliation of Taxes from Federal Statutory Rate to Total Income Tax Expense [Abstract] Income Tax Expense (Benefit), Effective Income Tax Rate Reconciliation, Amount [Abstract] Legal Entity [Axis] Legal Entity [Axis] Amortization of Net Loss Defined Benefit Plan, Amortization of Gain (Loss) Asset Retirement Obligation Asset Retirement Obligations, Noncurrent Cash and Cash Equivalents Cash and Cash Equivalents, at Carrying Value Payments to Acquire Businesses, Net of Cash Acquired Payments to Acquire Businesses, Net of Cash Acquired Generating Capacity Counterparty Owned (MW) Generating Capacity Counterparty Owned (MW) Generating Capacity Counterparty Owned (MW) Cash Paid for Interest – Net of Amounts Capitalized Interest Paid, Excluding Capitalized Interest, Operating Activities Total Comprehensive Income Comprehensive Income (Loss), Net of Tax, Including Portion Attributable to Noncontrolling Interest Non-Controlling Interest in Subsidiaries Effective Income Tax Rate Reconciliation, Noncontrolling Interest Income (Loss), Amount Available-for-sale Securities, Debt Maturities, After One Year Through Three Years, Fair Value Available-for-sale Securities, Debt Maturities, After One Year Through Three Years, Fair Value Amount of available-for-sale debt securities at fair value maturing after the first fiscal year through the third fiscal year following the latest fiscal year (maturing in more than one year to less than three years). 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Non-controlling Interest [Member] Noncontrolling Interest [Member] Accounts Receivable [Abstract] Accounts Receivable, after Allowance for Credit Loss, Current [Abstract]