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Regulatory Matters - Electric Rates (Details) $ in Millions								3 Months Ended	4 Months Ended	8 Months Ended	12 Months Ended			18 Months Ended	24 Months Ended	36 Months Ended
		Jan. 23, 2023 USD ($)	Dec. 20, 2022 USD ($)	Jun. 01, 2022 USD ($)	Jan. 13, 2022 USD ($)	Nov. 01, 2021 USD ($)	Nov. 01, 2019	Jun. 30, 2021 USD ($)	Apr. 30, 2020 USD ($)	Dec. 31, 2020	Dec. 31, 2022 USD ($) Years Customers	Dec. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)	Dec. 31, 2021 USD ($)	Dec. 31, 2022 USD ($) Years Customers	Aug. 11, 2021 USD ($)
Regulatory Matters [Line Items]
Public Utilities - Reserve for Interim Rate Refund											$ 18.4	$ 0.0			$ 0.0	$ 18.4
Regulatory Assets											441.0	511.8			511.8	441.0
Regulatory Assets											$ 441.0	511.8			511.8	441.0
Cost Recovery Riders [Member]
Regulatory Matters [Line Items]
Alternative Revenue Program, Required Collection Period											2 years
Regulatory Assets	[1]										$ 41.2	63.2			63.2	41.2
Regulatory Assets	[1]										41.2	63.2			63.2	$ 41.2
MPUC [Member] | Fuel Adjustment Clause Filing [Member] | Minnesota Power [Member]
Regulatory Matters [Line Items]
Forced Outage Costs														$ 8.0
Administrative Law Judge Recommended Refund																	$ 5.0
Commission Approved Refund					$ 5.0
PSCW [Member] | 2018 Wisconsin General Rate Case [Member] | SWL&P [Member] | Retail Customers [Member]
Regulatory Matters [Line Items]
Approved Return on Common Equity																10.40%
Approved Equity Ratio																55.00%
PSCW [Member] | 2022 Wisconsin General Rate Review | SWL&P [Member] | Retail Customers [Member]
Regulatory Matters [Line Items]
Requested Average Rate Increase				3.60%
Requested Return on Equity				10.40%
Requested Equity Ratio				55.00%
Annual Additional Revenue Generated from Requested Final Rate Increase				$ 4.3
Approved Rate Increase - Amount			$ 3.3
PSCW [Member] | 2022 Wisconsin General Rate Case | SWL&P [Member] | Retail Customers [Member]
Regulatory Matters [Line Items]
Approved Return on Common Equity			10.00%
Approved Equity Ratio			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											38.8	38.9	$ 29.9
Electric Rates [Member] | MPUC [Member] | 2020 Minnesota General Rate Review [Member] | Minnesota Power [Member] | Retail Customers [Member]
Regulatory Matters [Line Items]
Requested Average Rate Increase							10.60%
Public Utilities, Interim Rate Increase (Decrease), Amount									$ 36.1
Proposed Ongoing Customer Rate Increase										4.10%
Public Utilities, Interim Rate Increase (Decrease), Percentage									5.80%
Public Utilities Reserve for Interim Rates (Recorded During Period)								$ 11.7
Electric Rates [Member] | MPUC [Member] | 2022 Minnesota General Rate Review | Minnesota Power [Member] | Retail Customers [Member]
Regulatory Matters [Line Items]
Requested Average Rate Increase						18.00%
Requested Return on Equity						10.25%
Requested Equity Ratio						53.81%
Annual Additional Revenue Generated from Requested Final Rate Increase						$ 108.0
Public Utilities, Interim Rate Increase (Decrease), Amount						80.0
Public Utility - Additional Rider Revenue											9.0
Approximate Pre-Tax Reserve for Deferred Residential Customer Interim Rates											8.0
Customer Refund Liability, Current											18.0					$ 18.0
Electric Rates [Member] | MPUC [Member] | 2022 Minnesota General Rate Review | Minnesota Power [Member] | Retail Customers [Member] | Subsequent Event [Member]
Regulatory Matters [Line Items]
Approved Return on Common Equity		9.65%
Approved Equity Ratio		52.50%
Approved Rate Increase - Amount		$ 60.0
Public Utility - Additional Rider Revenue		$ 10.0
Electric Rates [Member] | MPUC [Member] | 2022 Minnesota General Rate Review | Minnesota Power [Member] | Residential [Member]
Regulatory Matters [Line Items]
Deferred Interim Rates						$ 8.0
Electric Rates [Member] | MPUC [Member] | Cost Recovery Riders [Member] | Minnesota Power [Member]
Regulatory Matters [Line Items]
Regulatory Assets											3.8					3.8
Regulatory Assets											3.8					3.8
Electric Rates [Member] | MPUC [Member] | Fuel Adjustment Clause | Minnesota Power [Member]
Regulatory Matters [Line Items]
Regulatory Assets												56.0			56.0
Regulatory Assets												$ 56.0			$ 56.0
Electric Rates [Member] | MPUC [Member] | 2016 Minnesota General Rate Review | Minnesota Power [Member] | Retail Customers [Member]
Regulatory Matters [Line Items]
Approved Return on Common Equity															9.25%
Approved Equity Ratio															53.81%
Electric Rates [Member] | MPUC [Member] | Fuel Adjustment Clause 2022 | Minnesota Power [Member]
Regulatory Matters [Line Items]
Regulatory Assets											13.0					13.0
Regulatory Assets											$ 13.0					$ 13.0
Electric Rates [Member] | FERC [Member] | FERC-Approved Wholesale Rates [Member] | Minnesota Power [Member] | Municipal Customers [Member]
Regulatory Matters [Line Items]
Number of Customers | Customers											14					14
Notice Required to Terminate (Years) | Years											3					3
Electric Rates [Member] | FERC [Member] | FERC-Approved Wholesale Rates [Member] | Minnesota Power [Member] | Municipal Customers [Member] | Wholesale Electric Contracts (Through 2029)
Regulatory Matters [Line Items]
Number of Customers | Customers											13					13
Electric Rates [Member] | FERC [Member] | FERC-Approved Wholesale Rates [Member] | Minnesota Power [Member] | Municipal Customers [Member] | Wholesale Electric Contract (Cost-Based Formula Methodology for Entire Term) [Member]
Regulatory Matters [Line Items]
Number of Customers | Customers											2					2
[1] The cost recovery rider regulatory assets and liabilities are revenue not yet collected from our customers and cash collections from our customers in excess of the revenue recognized, respectively, primarily due to capital expenditures related to Bison and the GNTL as well as differences between production tax credits recognized and those assumed in Minnesota Power’s base rates. The cost recovery rider regulatory assets as of December 31, 2022, will be recovered within the next two years.

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