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Energy Conservation and Optimization Plan Goal, Second Fiscal Year

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Energy Conservation and Optimization Plan Goal, Third Fiscal Year

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Current regulatory liabilities generally represent obligations to make refunds to customers for various reasons including overpayment.

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Percentage of public utility's approved equity to capital, including debt and equity.

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Amount of public utility's approved rate increase (decrease) by regulatory agency.

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Percentage of public utility's approved return on equity.

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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.

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Percentage of public utility's requested equity to capital, including debt and equity.

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Amount of public utility's requested rate increase (decrease) with regulatory agency.

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Percentage of public utility's requested rate increase (decrease) with regulatory agency.

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Percentage of public utility's requested return on equity.

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The amount of regulated other operating revenues recognized during the period.

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Carrying amount as of the balance sheet date of capitalized costs of regulated entities that are not expected to be recovered through revenue sources within one year or the normal operating cycle if longer.

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The amount for the individual regulatory noncurrent liability as itemized in a table of regulatory noncurrent liabilities as of the end of the period.

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Regulatory Matters - Electric Rates (Details) - USD ($) $ in Millions			3 Months Ended		6 Months Ended
	Feb. 28, 2023	Nov. 01, 2021	Sep. 30, 2023	Sep. 30, 2022	Jun. 30, 2023	Jun. 30, 2022	Dec. 31, 2022
Regulatory Matters [Line Items]
Regulatory Assets					$ 454.5		$ 441.0
Regulatory Liabilities					538.0		526.1
MPUC [Member] \| Minnesota Cost Recovery Riders [Member] \| Minnesota Power [Member] \| Retail Customers [Member] \| Electric Rates [Member]
Regulatory Matters [Line Items]
Revenue from Cost Recovery Riders and Other Regulatory Programs					31.5	$ 11.9
MPUC [Member] \| 2022 Minnesota General Rate Review \| Minnesota Power [Member] \| Retail Customers [Member] \| Electric Rates [Member]
Regulatory Matters [Line Items]
Revenue from Cost Recovery Riders and Other Regulatory Programs	$ 10.0
Annual Additional Revenue Generated from Requested Final Rate Increase		$ 108.0
Requested Rate Increase Percent		18.00%
Requested Return on Equity		10.25%
Requested Equity Capital Structure		53.81%
Customer Refund Liability, Current					31.8		18.4
Approved Return on Common Equity	9.65%
Public Utilities, Approved Equity Capital Structure, Percentage	52.50%
Public Utilities, Approved Rate Increase (Decrease), Amount	$ 60.0
MPUC [Member] \| ECO Annual Filing Member \| Minnesota Power [Member]
Regulatory Matters [Line Items]
Revenue from Cost Recovery Riders and Other Regulatory Programs				$ 1.9
MPUC [Member] \| ECO Annual Filing Member \| Minnesota Power [Member] \| Subsequent Event [Member]
Regulatory Matters [Line Items]
Revenue from Cost Recovery Riders and Other Regulatory Programs			$ 2.2
MPUC [Member] \| Fuel Adjustment Clause 2022 \| Minnesota Power [Member] \| Electric Rates [Member]
Regulatory Matters [Line Items]
Regulatory Assets					13.0		$ 13.0
MPUC [Member] \| Fuel Adjustment Clause 2023 \| Minnesota Power [Member] \| Electric Rates [Member]
Regulatory Matters [Line Items]
Regulatory Liabilities					17.8
MPUC [Member] \| ECO Triennial Filing \| Minnesota Power [Member]
Regulatory Matters [Line Items]
Conservation Improvement Program Goal, Next Fiscal Year					12.5
Energy Conservation and Optimization Plan Goal, Second Fiscal Year					12.7
Energy Conservation and Optimization Plan Goal, Third Fiscal Year					$ 12.8