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Regulatory Matters - Electric Rates (Details) - USD ($) $ in Millions					3 Months Ended		9 Months Ended
	Sep. 23, 2022	Sep. 01, 2022	Jun. 01, 2022	Nov. 01, 2021	Jun. 30, 2022	Dec. 31, 2021	Sep. 30, 2022	Sep. 30, 2021
Regulatory Matters [Line Items]
Regulatory Assets						$ 511.8	$ 447.1
MPUC [Member] | CIP Consolidated Filing Member | Minnesota Power [Member]
Regulatory Matters [Line Items]
Revenue from Cost Recovery Riders and Other Regulatory Programs					$ 1.9	2.4
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							19.5	$ 29.2
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
ALJ Recommended Rate Increase		$ 76.0
Exceptions to the ALJ Recommendations	$ 30.0
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						$ 56.0	$ 23.0

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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
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