REVENUE - Schedule of Disaggregation of Revenue (Details) - USD ($) $ in Millions		3 Months Ended		9 Months Ended
		Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Disaggregation of Revenue [Line Items]
Total revenues	[1]	$ 3,487	$ 3,475	$ 9,724	$ 9,282
Operating Segments | Regulated Distribution
Disaggregation of Revenue [Line Items]
Total revenues from contracts with customers		3,009	2,999	8,319	7,960
Total revenues		3,034	3,023	8,402	8,038
Operating Segments | Regulated Distribution | Wholesale
Disaggregation of Revenue [Line Items]
Total revenues from contracts with customers		65	159	173	408
Operating Segments | Regulated Distribution | Other revenue from contracts with customers
Disaggregation of Revenue [Line Items]
Total revenues from contracts with customers		30	27	86	82
Operating Segments | Regulated Distribution | Other revenue unrelated to contracts with customers
Disaggregation of Revenue [Line Items]
Total revenues		25	24	83	78
Operating Segments | Regulated Transmission
Disaggregation of Revenue [Line Items]
Total revenues from contracts with customers		508	502	1,486	1,393
Total revenues		509	503	1,490	1,397
Operating Segments | Regulated Transmission | Other revenue unrelated to contracts with customers
Disaggregation of Revenue [Line Items]
Total revenues		1	1	4	4
Operating Segments | Residential | Regulated Distribution
Disaggregation of Revenue [Line Items]
Total revenues from contracts with customers		1,894	1,756	5,010	4,608
Operating Segments | Commercial | Regulated Distribution
Disaggregation of Revenue [Line Items]
Total revenues from contracts with customers		698	686	1,970	1,858
Operating Segments | Industrial | Regulated Distribution
Disaggregation of Revenue [Line Items]
Total revenues from contracts with customers		296	348	1,002	943
Operating Segments | Other | Regulated Distribution
Disaggregation of Revenue [Line Items]
Total revenues from contracts with customers		26	23	78	61
Operating Segments | ATSI | Regulated Transmission
Disaggregation of Revenue [Line Items]
Total revenues from contracts with customers		244	252	712	686
Operating Segments | TrAIL | Regulated Transmission
Disaggregation of Revenue [Line Items]
Total revenues from contracts with customers		72	78	203	205
Operating Segments | MAIT | Regulated Transmission
Disaggregation of Revenue [Line Items]
Total revenues from contracts with customers		101	97	289	253
Operating Segments | JCP&L | Regulated Transmission
Disaggregation of Revenue [Line Items]
Total revenues from contracts with customers		52	45	152	151
Operating Segments | MP, PE and WP | Regulated Transmission
Disaggregation of Revenue [Line Items]
Total revenues from contracts with customers		39	30	130	98
Corporate/Other and Reconciling Adjustments
Disaggregation of Revenue [Line Items]
Total revenues		(56)	(51)	(168)	(153)
Corporate/Other and Reconciling Adjustments | Wholesale
Disaggregation of Revenue [Line Items]
Total revenues from contracts with customers		1	7	6	21
Corporate/Other and Reconciling Adjustments | Other revenue unrelated to contracts with customers
Disaggregation of Revenue [Line Items]
Total revenues		(12)	(12)	(38)	(38)
Corporate/Other and Reconciling Adjustments | Retail Generation and Distribution Services
Disaggregation of Revenue [Line Items]
Total revenues from contracts with customers		$ (45)	$ (46)	$ (136)	$ (136)

[1] Includes excise and gross receipts tax collections of $114 million and $111 million during the three months ended September 30, 2023 and 2022, respectively, and $315 million and $305 million during the nine months ended September 30, 2023 and 2022, respectively.