Consolidated Statement of Income (USD $) In Millions, except Per Share data	3 Months Ended		6 Months Ended
	Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2011	Jun. 30, 2010
Income Statement [Abstract]
Operating Revenue	$ 219.9	$ 211.2	$ 462.1	$ 444.8
Operating Expenses
Fuel and Purchased Power	76.0	74.3	155.0	154.1
Operating and Maintenance	95.7	85.4	185.8	173.1
Depreciation	22.1	19.8	44.4	39.8
Total Operating Expenses	193.8	179.5	385.2	367.0
Operating Income	26.1	31.7	76.9	77.8
Other Income (Expense)
Interest Expense	(11.0)	(9.5)	(21.7)	(18.4)
Equity Earnings in ATC	4.6	4.4	9.0	8.9
Other	1.0	2.2	1.8	3.2
Total Other Expense	(5.4)	(2.9)	(10.9)	(6.3)
Income Before Non-Controlling Interest and Income Taxes	20.7	28.8	66.0	71.5
Income Tax Expense	3.8	9.4	12.0	29.3
Net Income	16.9	19.4	54.0	42.2
Less: Non-Controlling Interest in Subsidiaries	(0.1)	0	(0.2)	(0.2)
Net Income (Loss) Attributable to ALLETE	$ 17.0	$ 19.4	$ 54.2	$ 42.4
Average Shares of Common Stock
Basic	35.0	34.1	34.8	34.0
Diluted	35.1	34.2	34.9	34.1
Basic Earnings Per Share of Common Stock	$ 0.49	$ 0.57	$ 1.56	$ 1.25
Diluted Earnings Per Share of Common Stock	$ 0.48	$ 0.57	$ 1.55	$ 1.25
Dividends Per Share of Common Stock	$ 0.445	$ 0.44	$ 0.89	$ 0.88