EARNINGS PER SHARE OF COMMON STOCK - Reconciliation of Basic and Diluted EPS Attributable to FE (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions		12 Months Ended
		Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Earnings Per Share [Abstract]
Earnings Attributable to FE - continuing operations		$ 1,123	$ 406	$ 1,239
Earnings from discontinued operations	[1]	(21)	0	44
EARNINGS ATTRIBUTABLE TO FIRSTENERGY CORP.		$ 1,102	$ 406	$ 1,283
Share Count information:
Weighted average number of basic shares outstanding (in shares)		573	571	545
Assumed exercise of dilutive share-based awards (in shares)		1	1	1
Weighted average number of diluted shares outstanding (in shares)		574	572	546
EPS Attributable to FE:
Income from continuing operations, basic (in dollars per share)		$ 1.96	$ 0.71	$ 2.27
Discontinued operations, basic (in dollars per share)		(0.04)	0	0.08
Basic - EPS (in dollars per share)		1.92	0.71	2.35
Income from continuing operations, diluted (in dollars per share)		1.96	0.71	2.27
Discontinued operations, diluted (in dollars per share)		(0.04)	0	0.08
Diluted - EPS (in dollars per share)		$ 1.92	$ 0.71	$ 2.35

[1] Net of income tax benefit (expense) of ($21 million) and $48 million in 2023 and 2021, respectively.