Consolidated Statement of Shareholders' Equity (USD $) In Millions, unless otherwise specified	Total	Retained Earnings	Accumulated Other Comprehensive Income (Loss)	Unearned ESOP Shares	Common Stock
Total Shareholders' Equity at Dec. 31, 2008	$ 827.1	$ 380.9	$ (33.0)	$ (54.9)	$ 534.1
Comprehensive Income
Net Income	60.7	60.7
Other Comprehensive Income - Net of Tax
Unrealized Gain (Loss) on Securities - Net	2.8		2.8
Unrealized Loss on Derivatives - Net	0
Defined Benefit Pension and Other Postretirement Plans	6.2		6.2
Total Comprehensive Income	69.7
Non-Controlling Interest in Subsidiaries	0.3	0.3
Comprehensive Income Attributable to ALLETE	70.0
Common Stock Issued - Net	79.3				79.3
Dividends Declared	(56.5)	(56.5)
ESOP Shares Earned	9.6			9.6
Total Shareholders' Equity at Dec. 31, 2009	929.5	385.4	(24.0)	(45.3)	613.4
Comprehensive Income
Net Income	74.8	74.8
Other Comprehensive Income - Net of Tax
Unrealized Gain (Loss) on Securities - Net	0.8		0.8
Unrealized Loss on Derivatives - Net	0
Defined Benefit Pension and Other Postretirement Plans	0
Total Comprehensive Income	75.6
Non-Controlling Interest in Subsidiaries	0.5	0.5
Comprehensive Income Attributable to ALLETE	76.1
Common Stock Issued - Net	22.7				22.7
Dividends Declared	(60.8)	(60.8)
ESOP Shares Earned	8.5			8.5
Total Shareholders' Equity at Dec. 31, 2010	976.0	399.9	(23.2)	(36.8)	636.1
Comprehensive Income
Net Income	93.6	93.6
Other Comprehensive Income - Net of Tax
Unrealized Gain (Loss) on Securities - Net	(0.3)		(0.3)
Unrealized Loss on Derivatives - Net	(0.3)		(0.3)
Defined Benefit Pension and Other Postretirement Plans	(5.1)		(5.1)
Total Comprehensive Income	87.9
Non-Controlling Interest in Subsidiaries	0.2	0.2
Comprehensive Income Attributable to ALLETE	88.1
Common Stock Issued - Net	69.5				69.5
Dividends Declared	(62.1)	(62.1)
ESOP Shares Earned	7.8			7.8
Total Shareholders' Equity at Dec. 31, 2011	$ 1,079.3	$ 431.6	$ (28.9)	$ (29.0)	$ 705.6