REVENUE - Schedule of Disaggregation of Revenue (Details) - USD ($) $ in Millions		3 Months Ended		6 Months Ended
		Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022
Disaggregation of Revenue [Line Items]
Total revenues	[1]	$ 3,006	$ 2,818	$ 6,237	$ 5,807
Operating Segments | Regulated Distribution
Disaggregation of Revenue [Line Items]
Total revenues from contracts with customers		2,514	2,403	5,310	4,961
Total revenues		2,542	2,426	5,368	5,015
Operating Segments | Regulated Distribution | Wholesale
Disaggregation of Revenue [Line Items]
Total revenues from contracts with customers		61	159	108	249
Operating Segments | Regulated Distribution | Other Services
Disaggregation of Revenue [Line Items]
Total revenues from contracts with customers		32	29	56	55
Operating Segments | Regulated Distribution | Product and Service, Other
Disaggregation of Revenue [Line Items]
Total revenues		28	23	58	54
Operating Segments | Regulated Transmission
Disaggregation of Revenue [Line Items]
Total revenues from contracts with customers		518	440	978	891
Total revenues		520	441	981	894
Operating Segments | Regulated Transmission | Product and Service, Other
Disaggregation of Revenue [Line Items]
Total revenues		2	1	3	3
Operating Segments | Residential | Regulated Distribution
Disaggregation of Revenue [Line Items]
Total revenues from contracts with customers		1,414	1,310	3,116	2,852
Operating Segments | Commercial | Regulated Distribution
Disaggregation of Revenue [Line Items]
Total revenues from contracts with customers		627	575	1,272	1,172
Operating Segments | Industrial | Regulated Distribution
Disaggregation of Revenue [Line Items]
Total revenues from contracts with customers		353	312	706	595
Operating Segments | Other | Regulated Distribution
Disaggregation of Revenue [Line Items]
Total revenues from contracts with customers		27	18	52	38
Operating Segments | ATSI | Regulated Transmission
Disaggregation of Revenue [Line Items]
Total revenues from contracts with customers		242	217	468	434
Operating Segments | TrAIL | Regulated Transmission
Disaggregation of Revenue [Line Items]
Total revenues from contracts with customers		65	64	131	127
Operating Segments | MAIT | Regulated Transmission
Disaggregation of Revenue [Line Items]
Total revenues from contracts with customers		99	77	188	156
Operating Segments | JCP&L | Regulated Transmission
Disaggregation of Revenue [Line Items]
Total revenues from contracts with customers		57	46	100	106
Operating Segments | MP, PE and WP | Regulated Transmission
Disaggregation of Revenue [Line Items]
Total revenues from contracts with customers		55	36	91	68
Corporate/Other and Reconciling Adjustments
Disaggregation of Revenue [Line Items]
Total revenues		(56)	(49)	(112)	(102)
Corporate/Other and Reconciling Adjustments | Wholesale
Disaggregation of Revenue [Line Items]
Total revenues from contracts with customers		3	8	5	14
Corporate/Other and Reconciling Adjustments | Product and Service, Other
Disaggregation of Revenue [Line Items]
Total revenues		(13)	(12)	(26)	(26)
Corporate/Other and Reconciling Adjustments | Retail Generation and Distribution Services
Disaggregation of Revenue [Line Items]
Total revenues from contracts with customers		$ (46)	$ (45)	$ (91)	$ (90)

[1] Includes excise and gross receipts tax collections of $92 million and $91 million during the three months ended June 30, 2023 and 2022, respectively, and $201 million and $194 million during the six months ended June 30, 2023 and 2022, respectively.