Consolidated Statement of Comprehensive Income (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Comprehensive Income [Abstract]
Net Income	$ 40.1	$ 33.8
Other Comprehensive Income [Abstract]
Unrealized Gain on Securities, Net of Income Taxes of $0.1 and $-	0.1	0
Unrealized Gain on Derivatives, Net of Income Taxes of $- and $0.1	0.1	0
Defined Benefit Pension and Other Postretirement Benefit Plans, Net of Income Taxes of $0.2 and $0.2	0.3	0.3
Total Other Comprehensive Income	0.5	0.3
Total Comprehensive Income	40.6	34.1
Less: Non-Controlling Interest in Subsidiaries	0.2	0.3
Comprehensive Income Attributable to ALLETE	$ 40.4	$ 33.8