Consolidated Statement of Shareholders' Equity (USD $) In Millions, unless otherwise specified	Total	Retained Earnings	Accumulated Other Comprehensive Income (Loss)	Unearned ESOP Shares	Common Stock
Balance at Dec. 31, 2011	$ 1,079.3	$ 431.6	$ (28.9)	$ (29.0)	$ 705.6
Comprehensive Income
Net Income	97.1	97.1
Other Comprehensive Income - Net of Tax
Unrealized Gain (Loss) on Securities - Net	1.2		1.2
Unrealized Gain (Loss) on Derivatives - Net	(0.2)		(0.2)
Defined Benefit Pension and Other Postretirement Plans - Net	5.9		5.9
Total Comprehensive Income	104.0
Non-Controlling Interest in Subsidiaries	0
Comprehensive Income Attributable to ALLETE	104.0
Common Stock Issued - Net	79.1				79.1
Dividends Declared	(69.1)	(69.1)
ESOP Shares Earned	7.7			7.7
Balance at Dec. 31, 2012	1,201.0	459.6	(22.0)	(21.3)	784.7
Comprehensive Income
Net Income	104.7	104.7
Other Comprehensive Income - Net of Tax
Unrealized Gain (Loss) on Securities - Net	0
Unrealized Gain (Loss) on Derivatives - Net	0.1		0.1
Defined Benefit Pension and Other Postretirement Plans - Net	4.8		4.8
Total Comprehensive Income	109.6
Non-Controlling Interest in Subsidiaries	0
Comprehensive Income Attributable to ALLETE	109.6
Common Stock Issued - Net	100.5				100.5
Dividends Declared	(75.2)	(75.2)
ESOP Shares Earned	7.0			7.0
Balance at Dec. 31, 2013	1,342.9	489.1	(17.1)	(14.3)	885.2
Comprehensive Income
Net Income	125.5	125.5
Other Comprehensive Income - Net of Tax
Unrealized Gain (Loss) on Securities - Net	(0.2)		(0.2)
Unrealized Gain (Loss) on Derivatives - Net	0.2		0.2
Defined Benefit Pension and Other Postretirement Plans - Net	(4.0)		(4.0)
Total Comprehensive Income	121.5
Non-Controlling Interest in Subsidiaries	(0.7)	(0.7)
Comprehensive Income Attributable to ALLETE	120.8
Common Stock Issued - Net	222.4				222.4
Dividends Declared	(83.8)	(83.8)
ESOP Shares Earned	7.1			7.1
Balance at Dec. 31, 2014	$ 1,609.4	$ 530.1	$ (21.1)	$ (7.2)	$ 1,107.6