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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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