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Equity Investments - Narrative (Details) $ in Millions | 9 Months Ended
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Sep. 30, 2023 USD ($) MW
Wind Turbine Generators | Tenaska | Tenaska PPA | Minnesota Power |
Investments In ATC [Roll Forward] |
Generating capacity counterparty owned (MegaWatt) | MW | 250
Long-term contract for purchase of electric power | 20 years
ATC |
Investments In ATC [Roll Forward] |
Ownership percentage | 8.00%
Authorized return on equity | 10.02%
Authorized return on equity, including incentive adder | 10.52%
Basis point incentive adder | 0.50%
Approximate annual reduction in pretax income for FERC proposal to limit incentive adder, Allete's proportionate share | $ | $ 1
Nobles 2 |
Investments In ATC [Roll Forward] |
Ownership percentage | 49.00%

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