Consolidated Balance Sheet - USD ($) $ in Millions	Sep. 30, 2022	Dec. 31, 2021
Current Assets [Abstract]
Cash and Cash Equivalents	$ 42.1	$ 45.1
Accounts Receivable (Less Allowance of $1.5 and $1.8)	120.5	123.7
Inventories – Net	472.2	97.7
Prepayments and Other	87.4	24.8
Total Current Assets	722.2	291.3
Property, Plant and Equipment – Net	5,011.0	5,100.2
Regulatory Assets	447.1	511.8
Equity Investments	320.3	318.0
Goodwill and Intangible Assets - Net	155.8	0.8
Other Non-Current Assets	201.6	212.9
Total Assets	6,858.0	6,435.0
Current Liabilities [Abstract]
Accounts Payable	124.3	111.0
Accrued Taxes	69.5	65.1
Accrued Interest	15.1	20.1
Long-Term Debt Due Within One Year	308.6	214.2
Other	188.5	133.0
Total Current Liabilities	706.0	543.4
Long-Term Debt	1,653.0	1,763.2
Deferred Income Taxes	177.0	185.7
Regulatory Liabilities	527.4	536.1
Defined Benefit Pension and Other Postretirement Benefit Plans	171.9	179.5
Other Non-Current Liabilities	268.8	280.8
Total Liabilities	3,504.1	3,488.7
Commitments, Guarantees and Contingencies (Note 7)
Equity [Abstract]
Common Stock Without Par Value, 80.0 Shares Authorized, 57.2 and 53.2 Shares Issued and Outstanding	1,777.2	1,536.7
Accumulated Other Comprehensive Loss	(23.8)	(23.8)
Retained Earnings	929.2	900.2
Total ALLETE Equity	2,682.6	2,413.1
Non-Controlling Interest in Subsidiaries	671.3	533.2
Total Equity	3,353.9	2,946.3
Total Liabilities and Equity	$ 6,858.0	$ 6,435.0