Summary of Quarterly Financial Data (Unaudited) (Details) (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Quarterly Financial Data [Line Items]
Revenues	$ 3,647	$ 4,036	$ 3,511	$ 3,723	$ 3,493	$ 4,052	$ 3,746	$ 3,982	$ 9,479	$ 9,800	$ 10,573
Other operating expenses	948	877	886	882	1,163	861	920	816	3,593	3,760	3,949
Pension and OPEB mark-to-market	(256)	0	0	0	609	0	0	0	(256)	609	507
Provision for depreciation	293	316	300	293	285	272	284	278	1,202	1,119	1,062
Impairment of long-lived assets	322	0	473	0	0	0	0	0	795	0	413
Operating Income (Loss)	401	512	46	648	(39)	902	549	740	1,607	2,152	1,677
Income (loss) from continuing operations before income taxes	208	286	(230)	306	(258)	729	307	522
Total provision for income taxes	66	77	(62)	114	(105)	307	123	220	195	545	566
Income from continuing operations	142	209	(168)	192	(153)	422	184	302	375	755	856
Discontinued operations (Note 20)	0	9	4	4	5	3	4	4	17	16	13
NET INCOME	142	218	(164)	196	(148)	425	188	306	392	771	869
Earnings (loss) available to FirstEnergy Corp.	142	218	(164)	196	(148)	425	187	306	392	770	885
Earnings per share of common stock-
Basic - Continuing Operations, in dollars per share	$ 0.34	$ 0.50	$ (0.40)	$ 0.46	$ (0.36)	$ 1.01	$ 0.44	$ 0.72	$ 0.90	$ 1.81	$ 2.19
Basic - Discontinued Operations (Note 20), in dollars per share	$ 0.00	$ 0.02	$ 0.01	$ 0.01	$ 0.01	$ 0.01	$ 0.01	$ 0.01	$ 0.04	$ 0.04	$ 0.03
Basic - Earnings Available to FirstEnergy Corp., in dollars per share	$ 0.34	$ 0.52	$ (0.39)	$ 0.47	$ (0.35)	$ 1.02	$ 0.45	$ 0.73	$ 0.94	$ 1.85	$ 2.22
Diluted - Continuing Operations, in dollars per share	$ 0.34	$ 0.50	$ (0.40)	$ 0.46	$ (0.36)	$ 1.00	$ 0.44	$ 0.72	$ 0.90	$ 1.80	$ 2.18
Diluted - Discontinued Operations (Note 20), in dollars per share	$ 0.00	$ 0.02	$ 0.01	$ 0.01	$ 0.01	$ 0.01	$ 0.01	$ 0.01	$ 0.04	$ 0.04	$ 0.03
Diluted - Earnings Available to FirstEnergy Corp., in dollars per share	$ 0.34	$ 0.52	$ (0.39)	$ 0.47	$ (0.35)	$ 1.01	$ 0.45	$ 0.73	$ 0.94	$ 1.84	$ 2.21
FES
Quarterly Financial Data [Line Items]
Revenues	1,518	1,679	1,452	1,524	1,383	1,550	1,450	1,511
Other operating expenses	382	339	387	379	328	342	392	294	1,487	1,356	1,619
Pension and OPEB mark-to-market	(81)	0	0	0	166	0	0	0	(81)	166	171
Provision for depreciation	75	80	76	75	72	70	68	62	306	272	272
Operating Income (Loss)	121	65	(39)	95	(56)	167	9	219	242	339	6
Income (loss) from continuing operations before income taxes	114	56	(117)	(1)	(74)	161	(6)	195
Total provision for income taxes	25	23	(42)	0	(36)	65	(1)	75	6	103	(16)
Income from continuing operations	89	33	(75)	(1)	(38)	96	(5)	120	46	173	(67)
Discontinued operations (Note 20)	0	7	4	3	3	5	4	2	14	14	8
NET INCOME	$ 89	$ 40	$ (71)	$ 2	$ (35)	$ 101	$ (1)	$ 122	$ 60	$ 187	$ (59)