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, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Quarterly Financial Data [Line Items]
Revenues	$ 3,483	$ 3,888	$ 3,496	$ 4,182	$ 3,633	$ 4,032	$ 3,507	$ 3,720	$ 9,871	$ 9,451	$ 9,782
Other operating expenses	901	858	1,021	1,182	948	877	886	882	3,962	3,593	3,760
Pension and OPEB mark-to-market	835	0	0	0	(256)	0	0	0	835	(256)	609
Provision for depreciation	316	308	302	294	293	316	300	293	1,220	1,202	1,119
Impairment of long-lived assets	0	0	0	0	322	0	473	0	0	795	0
Operating Income (Loss)	(337)	716	292	391	387	508	42	645	1,062	1,582	2,134
Income (loss) from continuing operations before income taxes (benefits)	(574)	485	90	170	208	286	(230)	306
Total provision for income taxes	(268)	152	26	48	66	77	(62)	114	(42)	195	545
Income (loss) from continuing operations	(306)	333	64	122	142	209	(168)	192	213	375	755
Discontinued operations (net of income taxes of $69, $9 and $8, respectively) (Note 19)	0	0	0	86	0	9	4	4	86	17	16
NET INCOME (LOSS)	(306)	333	64	208	142	218	(164)	196	299	392	771
Earnings per share of common stock-
Basic - Continuing Operations, in dollars per share	$ (0.73)	$ 0.79	$ 0.16	$ 0.29	$ 0.34	$ 0.50	$ (0.40)	$ 0.46	$ 0.51	$ 0.90	$ 1.81
Basic - Discontinued Operations, in dollars per share	$ 0.00	$ 0.00	$ 0.00	$ 0.21	$ 0.00	$ 0.02	$ 0.01	$ 0.01	$ 0.20	$ 0.04	$ 0.04
Basic - Earnings Available to FirstEnergy Corp., in dollars per share	$ (0.73)	$ 0.79	$ 0.16	$ 0.50	$ 0.34	$ 0.52	$ (0.39)	$ 0.47	$ 0.71	$ 0.94	$ 1.85
Diluted - Continuing Operations, in dollars per share	$ (0.73)	$ 0.79	$ 0.15	$ 0.29	$ 0.34	$ 0.50	$ (0.40)	$ 0.46	$ 0.51	$ 0.90	$ 1.80
Diluted - Discontinued Operations, in dollars per share	$ 0.00	$ 0.00	$ 0.00	$ 0.20	$ 0.00	$ 0.02	$ 0.01	$ 0.01	$ 0.20	$ 0.04	$ 0.04
Diluted - Earnings Available to FirstEnergy Corp., in dollars per share	$ (0.73)	$ 0.79	$ 0.15	$ 0.49	$ 0.34	$ 0.52	$ (0.39)	$ 0.47	$ 0.71	$ 0.94	$ 1.84
Adjustments from prior periods	16								(25)
FES
Quarterly Financial Data [Line Items]
Revenues	1,342	1,521	1,452	1,829	1,518	1,679	1,452	1,524
Other operating expenses	359	356	468	452	382	339	387	379	1,635	1,487	1,356
Pension and OPEB mark-to-market	297	0	0	0	(81)	0	0	0	297	(81)	166
Provision for depreciation	83	83	79	74	75	80	76	75	319	306	272
Operating Income (Loss)	(321)	90	(151)	(148)	121	65	(39)	95	(530)	242	339
Income (loss) from continuing operations before income taxes (benefits)	(347)	72	(154)	(159)	114	56	(117)	(1)
Total provision for income taxes	(133)	28	(67)	(56)	25	23	(42)	0	(228)	6	103
Income (loss) from continuing operations	(214)	44	(87)	(103)	89	33	(75)	(1)	(360)	46	173
Discontinued operations (net of income taxes of $69, $9 and $8, respectively) (Note 19)	0	0	0	116	0	7	4	3	116	14	14
NET INCOME (LOSS)	$ (214)	$ 44	$ (87)	$ 13	$ 89	$ 40	$ (71)	$ 2	$ (244)	$ 60	$ 187