Earnings Per Share of Common Stock (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Earnings Per Share [Abstract]
Income (loss) from continuing operations	$ 187	$ 64	$ 409	$ 186
Discontinued operations	0	0	0	86
NET INCOME (LOSS)	$ 187	$ 64	$ 409	$ 272
Weighted average number of basic shares outstanding	422	420	422	419
Assumed exercise of dilutive stock options and awards	1	1	1	1
Weighted average number of diluted shares outstanding	423	421	423	420
Basic earnings per share:
Income (loss) from continuing operations, in dollars per share	$ 0.44	$ 0.16	$ 0.97	$ 0.45
Discontinued operations, in dollars per share	0.00	0.00	0.00	0.20
Basic - Net Earnings per Basic Share to FirstEnergy Corp., in dollars per share	0.44	0.16	0.97	0.65
Diluted earnings per share:
Income (loss) from continuing operations, in dollars per share	0.44	0.15	0.97	0.45
Discontinued operations, in dollars per share	0.00	0.00	0.00	0.20
Diluted - Net Earnings per Diluted Share Available to FirstEnergy Corp., in dollars per share	$ 0.44	$ 0.15	$ 0.97	$ 0.65
Shares excluded from the calculation of diluted shares outstanding, in shares	1	1	1	2