Consolidated Statement of Income (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Operating Revenue	$ 296.5	$ 263.8
Operating Expenses [Abstract]
Fuel and Purchased Power	96.2	86.5
Operating and Maintenance	119.8	104.7
Depreciation	32.2	28.2
Total Operating Expenses	248.2	219.4
Operating Income	48.3	44.4
Other Income (Expense) [Abstract]
Interest Expense	(12.8)	(12.3)
Equity Earnings in ATC	5.1	5.2
Other	2.0	2.7
Total Other Expense	(5.7)	(4.4)
Income Before Non-Controlling Interest and Income Taxes	42.6	40.0
Income Tax Expense	8.8	7.5
Net Income	33.8	32.5
Less: Non-Controlling Interest in Subsidiaries	0.3	0
Net Income Attributable to ALLETE	$ 33.5	$ 32.5
Average Shares of Common Stock [Abstract]
Basic	41.4	38.9
Diluted	41.6	39.0
Basic Earnings Per Share of Common Stock	$ 0.81	$ 0.83
Diluted Earnings Per Share of Common Stock	$ 0.80	$ 0.83
Dividends Per Share of Common Stock	$ 0.49	$ 0.475