Discontinued Operations and Divestitures (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2011	Jun. 30, 2010
Net impacts of the discontinued operations on earnings
Income from Continuing Operations	$ 98.0	$ 87.5	$ 268.9	$ 216.5
Total Income from Discontinued Operations, Net of Tax	11.5	1.2	11.5	1.9
Net Income	109.5	88.7	280.4	218.4
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	1.0	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	$ 11.5	$ 0.2	$ 11.5	$ 0.1