Earnings Per Share (Details) (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2013		Mar. 31, 2012
Earnings Per Share [Abstract]
Weighted average number of basic shares outstanding	418		418
Assumed exercise of dilutive stock options and awards	1	[1]	2	[1]
Weighted average number of diluted shares outstanding	419		420
Earnings available to FirstEnergy Corp.	$ 196		$ 306
Basic earnings per share of common stock (in dollars per share)	$ 0.47		$ 0.73
Diluted earnings per share of common stock (in dollars per share)	$ 0.47		$ 0.73

[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 ended March 31, 2013 and 2012.