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Jointly-Owned Facilities and Assets - Narrative (Details) $ in Millions | 12 Months Ended |
--- | --- | ---
Dec. 31, 2023 USD ($) MW | Dec. 31, 2022
Boswell Unit 4 | Boswell Unit 4 |  |
Jointly-Owned Facilities and Assets [Line Items] |  |
% Ownership | 80.00% | 80.00%
Generating capacity jointly owned (MW) | MW | 585 |
Boswell Unit 4 | Boswell Unit 4 | Minnesota Power |  |
Jointly-Owned Facilities and Assets [Line Items] |  |
% Ownership | 80.00% |
Boswell Unit 4 | Boswell Unit 4 | WPPI Energy |  |
Jointly-Owned Facilities and Assets [Line Items] |  |
WPPI Energy ownership | 20.00% |
Nemadji Trail Energy Center |  |
Jointly-Owned Facilities and Assets [Line Items] |  |
Estimated capital expenditures, including past expenditures | $ | $ 700 |
Nemadji Trail Energy Center | Natural Gas-Fired |  |
Jointly-Owned Facilities and Assets [Line Items] |  |
Generating capacity jointly owned (MW) | MW | 600 |
Nemadji Trail Energy Center | South Shore Energy |  |
Jointly-Owned Facilities and Assets [Line Items] |  |
Capital cost spent to date | $ | $ 9 |
Nemadji Trail Energy Center | South Shore Energy | Natural Gas-Fired |  |
Jointly-Owned Facilities and Assets [Line Items] |  |
Expected output entitlement | 20.00% |

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