Earnings Per Share (Details) (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended				9 Months Ended
	Sep. 30, 2012		Sep. 30, 2011		Sep. 30, 2012		Sep. 30, 2011
Reconciliation of basic and diluted earnings per share of common stock
Weighted average number of basic shares outstanding	417		418		418		392
Assumed exercise of dilutive stock options and awards	2	[1]	2	[1]	1	[1]	2	[1]
Weighted average number of diluted shares outstanding	419		420		419		394
Earnings available to FirstEnergy Corp.	$ 425		$ 532		$ 918		$ 787
Basic earnings per share of common stock, in dollars per share	$ 1.02		$ 1.27		$ 2.20		$ 2.01
Diluted earnings per share of common stock, in dollars per share	$ 1.01		$ 1.27		$ 2.19		$ 2.00

[1] 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, 2012 and 2011.