Discontinued Operations and Divestitures (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2011	Sep. 30, 2010
Net impacts of the discontinued operations on earnings
Income from Continuing Operations	$ 129.8	$ 112.3	$ 398.7	$ 328.8
Total Income from Discontinued Operations, Net of Tax	0	(0.1)	11.5	1.8
Net Income	129.8	112.2	410.2	330.6
Discontinued Operations and Divestitures (Textuals)
Ownership percentage in Edgewater Generating Unit 5 sold			25.00%
Proceeds from the sale of interest in Edgewater Generating Unit			38
Edison Sault Electric Co [Member]
Net impacts of the discontinued operations on earnings
Total Income from Discontinued Operations, Net of Tax	0	0	0	1.8
Discontinued Operations and Divestitures (Textuals)
Proceeds from Divestiture of Businesses				63.0
Other Operations [Member]
Net impacts of the discontinued operations on earnings
Total Income from Discontinued Operations, Net of Tax	$ 0	$ (0.1)	$ 11.5	$ 0