Earnings Per Share (Details) (USD $) In Millions, except Per Share data	3 Months Ended				9 Months Ended
	Sep. 30, 2011		Sep. 30, 2010		Sep. 30, 2011		Sep. 30, 2010
Reconciliation of basic and diluted earnings per share of common stock
Earnings available to FirstEnergy Corp.	$ 511		$ 179		$ 742		$ 599
Weighted average number of basic shares outstanding	418	[1]	304	[1]	392	[1]	304	[1]
Assumed exercise of dilutive stock options and awards	2	[2]	1	[2]	2	[2]	1	[2]
Weighted average number of diluted shares outstanding	420	[1]	305	[1]	394	[1]	305	[1]
Basic Earnings Per Share	$ 1.22		$ 0.59		$ 1.89		$ 1.97
Diluted Earnings Per Share	$ 1.22		$ 0.59		$ 1.88		$ 1.96
Earnings Per Share (Textuals)
Number of shares issued in connection with merger of Allegheny Energy					113

[1] Includes 113 million shares issued to AE shareholders for the periods subsequent to the merger date. (See Note 2)

[2] The number of potentially dilutive securities not included in the calculation of diluted shares outstanding due to their antidilutive effect were not significant for the three months and nine months ended September 30, 2011 and 2010.