Asset Sales, Divestitures And Discontinued Operations (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012		Dec. 31, 2011		Dec. 31, 2010
Net impacts of the discontinued operations on earnings
Income from Continuing Operations	$ 546.3		$ 512.8		$ 454.4
Income from Discontinued Operations, Net of Tax	0		13.4		2.1
Net Income	546.3		526.2		456.5
Asset Sales, Divestitures and Discontinued Operations (Textuals) [Abstract]
Ownership percentage in Edgewater Generating Unit 5 sold			25.00%
Proceeds From Sale Of Interest In Unit			38
Edison Sault [Member]
Net impacts of the discontinued operations on earnings
Income from Discontinued Operations, Net of Tax	0		0		0.7
Income Statement Balance Sheet and Additional Disclosures By Disposal Groups Including Discontinued Operations (Textuals) [Abstract]
Proceeds from sale of unit of operations					63.0
Other Operations [Member]
Net impacts of the discontinued operations on earnings
Income from Discontinued Operations, Net of Tax	$ 0	[1]	$ 13.4	[1]	$ 1.4	[1]

[1] Primarily relates to the favorable resolution of uncertain state and federal tax positions associated with our previously discontinued manufacturing business.