AGREEMENT AND PLAN OF MERGER (Details) - Alloy Parent and Alloy Merger Sub $ / shares in Units, $ in Millions	May 05, 2024 USD ($) day $ / shares	Sep. 30, 2025 USD ($)
Subsequent Event [Line Items]
Conversion price, cash (in usd per share) | $ / shares	$ 67.00
Equity value of ALLETE common stock acquired	$ 3,900
Maximum conversion window | day	5
Alloy Parent | Forecast
Subsequent Event [Line Items]
Required amount to purchase of preferred stock		$ 300