Consolidated Statement of Comprehensive Income (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Comprehensive Income (Loss) [Abstract]
Net Income	$ 14.4	$ 16.9	$ 38.8	$ 54.0
Other Comprehensive Income (Loss) [Abstract]
Unrealized Gain (Loss) on Securities, Net of Income Taxes of $(0.5), $0.2, $0.2 and $0.8	(0.5)	0.2	0.5	1.1
Unrealized Loss on Derivatives, Net of Income Taxes of $-, $-, $(0.1) and $-	(0.1)	0	(0.2)	0
Defined Benefit Pension and Other Postretirement Benefit Plans, Net of Income Taxes of $0.4, $0.2, $0.7 and $0.5	0.5	0.4	1.0	0.8
Total Other Comprehensive Income (Loss)	(0.1)	0.6	1.3	1.9
Total Comprehensive Income	14.3	17.5	40.1	55.9
Less: Non-Controlling Interest in Subsidiaries	0	(0.1)	0	(0.2)
Comprehensive Income Attributable to ALLETE	$ 14.3	$ 17.6	$ 40.1	$ 56.1