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Regulatory Matters - Electric Rates (Details) - USD ($) $ in Millions			3 Months Ended	6 Months Ended
	Jun. 01, 2022	Nov. 01, 2021	Sep. 30, 2021	Jun. 30, 2022	Jun. 30, 2021	Dec. 31, 2021
Regulatory Matters [Line Items]
Regulatory Assets				$ 470.9		$ 511.8
MPUC [Member] | CIP Consolidated Filing Member | Minnesota Power [Member]
Regulatory Matters [Line Items]
Revenue from Cost Recovery Riders and Other Regulatory Programs			$ 2.4	1.9
PSCW | 2022 Wisconsin General Rate Review | SWL&P [Member] | Retail Customers [Member]
Regulatory Matters [Line Items]
Annual Additional Revenue Generated from Requested Final Rate Increase	$ 4.3
Requested Rate Increase Percent	3.60%
Requested Return on Equity	10.40%
Requested Equity Capital Structure	55.00%
Electric Rates [Member] | MPUC [Member] | Minnesota Cost Recovery Riders [Member] | Minnesota Power [Member] | Retail Customers [Member]
Regulatory Matters [Line Items]
Revenue from Cost Recovery Riders and Other Regulatory Programs				11.9	$ 22.1
Electric Rates [Member] | MPUC [Member] | 2022 Minnesota General Rate Review | Minnesota Power [Member] | Retail Customers [Member]
Regulatory Matters [Line Items]
Annual Additional Revenue Generated from Requested Final Rate Increase		$ 108.0
Requested Rate Increase Percent		18.00%
Interim Rate Increase		$ 80.0
Requested Return on Equity		10.25%
Requested Equity Capital Structure		53.81%
Deferred Interim Rates - Residential Customers		$ 8.0
Electric Rates [Member] | MPUC [Member] | Cost Recovery Riders [Member] | Minnesota Power [Member]
Regulatory Matters [Line Items]
Regulatory Assets				3.8
Electric Rates [Member] | MPUC [Member] | Fuel Adjustment Clause [Member] | Minnesota Power [Member]
Regulatory Matters [Line Items]
Regulatory Assets				$ 28.0		$ 56.0

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Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 980
-SubTopic 340
-Section 50
-Paragraph 1
-URI https://asc.fasb.org/extlink&oid=6499975&loc=d3e44250-110382

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