EARNINGS PER SHARE - Reconciles Basic and Diluted Eps Attributable to FE (Details) - USD ($) $ / shares in Units, $ in Thousands, shares in Millions		3 Months Ended		9 Months Ended
		Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Earnings Per Share [Abstract]
Earnings attributable to FE - continuing operations		$ 421,000	$ 334,000	$ 948,000	$ 809,000
Earnings attributable to FE - discontinued operations, net of tax	[1]	(21,000)	0	(21,000)	0
EARNINGS ATTRIBUTABLE TO FIRSTENERGY CORP.		$ 400,000	$ 334,000	$ 927,000	$ 809,000
Share count information:
Weighted average number of basic shares outstanding (in shares)		573	571	573	571
Assumed exercise of dilutive stock options and awards (in shares)		1	1	1	1
Weighted average number of diluted shares outstanding (in shares)		574	572	574	572
EPS attributable to FE:
Basic - continuing operations (in dollars per share)		$ 0.74	$ 0.58	$ 1.66	$ 1.42
Basic - discontinued operations (in dollars per share)		(0.04)	0	(0.04)	0
Basic EPS (in dollars per share)		0.70	0.58	1.62	1.42
Diluted - continuing operations (in dollars per share)		0.73	0.58	1.65	1.41
Diluted - discontinued operations (in dollars per share)		(0.04)	0	(0.04)	0
Diluted EPS (in dollars per share)		$ 0.69	$ 0.58	$ 1.61	$ 1.41

[1] Consists of income taxes of $21 million during the three and nine months ended September 30, 2023.