SEGMENT INFORMATION - Narrative (Details) mi² in Thousands, customer in Millions, $ in Billions	3 Months Ended
	Mar. 31, 2023 USD ($) mi² customer company MW
FEV | Global Holding
Segment Reporting Information [Line Items]
Investment ownership percentage	33.30%
Regulated Distribution
Segment Reporting Information [Line Items]
Number of existing utility operating companies | company	10
Number of customers served by utility operating companies | customer	6
Number of square miles in service area | mi²	65
Megawatts of net demonstrated capacity of competitive segment	3,580
Other/Corporate | OVEC
Segment Reporting Information [Line Items]
Megawatts of net demonstrated capacity of competitive segment	67
Other/Corporate | FirstEnergy
Segment Reporting Information [Line Items]
Long-term debt and other long-term obligations | $	$ 5.7