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Regulatory Matters - Electric Rates (Details) - USD ($) $ in Millions			3 Months Ended
	Apr. 29, 2022	Nov. 01, 2021	Mar. 31, 2022	Mar. 31, 2021	Dec. 31, 2021
Regulatory Matters [Line Items]
Regulatory Assets			$ 464.2		$ 511.8
PSCW | 2022 Wisconsin General Rate Review | SWL&P [Member] | Retail Customers [Member] | Subsequent Event [Member]
Regulatory Matters [Line Items]
Annual Additional Revenue Generated from Requested Final Rate Increase	$ 3.3
Requested Rate Increase Percent	2.70%
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			6.5	$ 9.6
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					$ 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 http://asc.fasb.org/extlink&oid=6499975&loc=d3e44250-110382

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