CONSOLIDATED STATEMENT OF COMPREHENSIVE INCOME Unaudited - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2025	Jun. 30, 2024	Jun. 30, 2025	Jun. 30, 2024
Statement of Comprehensive Income [Abstract]
Net Income	$ 6.6	$ 19.7	$ 41.3	$ 56.7
Other Comprehensive Loss
Unrealized Gain on Securities: Net of Income Tax Expense of $—, $—, $— and $—	0.0	0.0	0.0	0.0
Defined Benefit Pension and Other Postretirement Benefit Plans: Net of Income Tax Benefit of $—, $(0.3), $— and $(0.2)	0.0	0.0	0.0	(0.4)
Total Other Comprehensive Loss	0.0	0.0	0.0	(0.4)
Total Comprehensive Income	6.6	19.7	41.3	56.3
Net Loss Attributable to Non-Controlling Interest	(25.3)	(13.3)	(46.7)	(27.0)
Total Comprehensive Income Attributable to ALLETE	$ 31.9	$ 33.0	$ 88.0	$ 83.3