EQUITY INVESTMENTS - Narrative (Details) $ in Millions	6 Months Ended
	Jun. 30, 2025 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%
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%