Consolidated Statement of Comprehensive Income - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Comprehensive Income [Abstract]
Net Income	$ 22.3	$ 16.9	$ 62.4	$ 50.7
Other Comprehensive Income [Abstract]
Unrealized Gain on Securities, Net of Income Taxes of $–, $0.1, $0.1 and $0.1	0.0	0.2	0.1	0.2
Unrealized Gain on Derivatives, Net of Income Taxes of $0.1, $–, $0.1 and $0.1	0.0	0.0	0.1	0.0
Defined Benefit Pension and Other Postretirement Benefit Plans, Net of Income Taxes of $0.2, $0.2, $0.4 and $0.4	0.4	0.3	0.7	0.6
Total Other Comprehensive Income	0.4	0.5	0.9	0.8
Total Comprehensive Income	22.7	17.4	63.3	51.5
Less: Non-Controlling Interest in Subsidiaries	(0.2)	0.1	0.0	0.4
Comprehensive Income Attributable to ALLETE	$ 22.9	$ 17.3	$ 63.3	$ 51.1