Earnings Per Share of Common Stock (Details) (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended				9 Months Ended
	Sep. 30, 2014		Sep. 30, 2013		Sep. 30, 2014		Sep. 30, 2013
Earnings Per Share [Abstract]
Income (loss) from continuing operations	$ 333		$ 209		$ 519		$ 233
Discontinued operations (Note 14)	0		9		86		17
EARNINGS AVAILABLE TO FIRSTENERGY CORP.	$ 333		$ 218		$ 605		$ 250
Weighted average number of basic shares outstanding	420		418		419		418
Assumed exercise of dilutive stock options and awards	1	[1]	1	[1]	1	[1]	1	[1]
Weighted average number of diluted shares outstanding	421		419		420		419
Basic earnings per share:
Income (loss) from continuing operations, in dollars per share	$ 0.79		$ 0.50		$ 1.24		$ 0.56
Discontinued operations (Note 14), in dollars per share	$ 0.00		$ 0.02		$ 0.20		$ 0.04
Basic - Earnings Available to FirstEnergy Corp., in dollars per share	$ 0.79		$ 0.52		$ 1.44		$ 0.60
Diluted earnings per share:
Income (loss) from continuing operations, in dollars per share	$ 0.79		$ 0.50		$ 1.24		$ 0.56
Discontinued operations (Note 14), in dollars per share	$ 0.00		$ 0.02		$ 0.20		$ 0.04
Diluted - Earnings Available to FirstEnergy Corp., in dollars per share	$ 0.79		$ 0.52		$ 1.44		$ 0.60
Shares excluded from the calculation of diluted shares outstanding, in shares	1		2		2		2

[1] For the three months ended September 30, 2014 and September 30, 2013, 1 million and 2 million shares, respectively, were excluded from the calculation of diluted shares outstanding, as their inclusion would be antidilutive. For the nine months ended September 30, 2014 and September 30, 2013, 2 million shares were excluded from the calculation of diluted shares outstanding, as their inclusion would be antidilutive.