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Commitments, Guarantees and Contingencies - Environmental Matters (Details) $ in Millions |  | 12 Months Ended |  |  |
--- | --- | --- | --- | --- | ---
May 08, 2024 USD ($) | Dec. 31, 2024 USD ($) | Nov. 06, 2024 state | Sep. 29, 2023 state | Jun. 05, 2023 state
Environmental Matters [Line Items] |  |  |  |  |
Number of states contributed to downwind states’ challenges in attaining or maintaining ozone NAAQS |  |  |  |  | 23
Number of states restrictions on fossil-fuel fired power plants |  |  |  |  | 22
Number of states restricted on certain industrial sources |  |  |  |  | 20
Number of remaining covered states |  |  | 10 |  |
States were EPA issued an updated final interim rule addressing the stays |  |  |  | 5 |
Coal Combustion Residuals | Minnesota Power |  |  |  |  |
Environmental Matters [Line Items] |  |  |  |  |
Expected period for costs of compliance | 10 years | 12 years |  |  |
Coal Combustion Residuals | Minimum | Minnesota Power |  |  |  |  |
Environmental Matters [Line Items] |  |  |  |  |
Estimated costs of compliance | $ | $ 50.0 | $ 65.0 |  |  |
Coal Combustion Residuals | Maximum | Minnesota Power |  |  |  |  |
Environmental Matters [Line Items] |  |  |  |  |
Estimated costs of compliance | $ | $ 85.0 | 120.0 |  |  |
Manufactured Gas Plant | SWL&P | Superior, WI |  |  |  |  |
Environmental Matters [Line Items] |  |  |  |  |
Environmental remediation liability | $ |  | $ 0.3 |  |  |

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