Revenue (Details) $ in Millions		3 Months Ended
		Mar. 31, 2018 USD ($) company MW	Mar. 31, 2017 USD ($)
Disaggregation of Revenue [Line Items]
Total revenues from contracts with customers		$ 2,892
ARP		64
Other non-customer revenue		20
Total revenues	[1]	2,976	$ 2,855
Regulated Transmission		323	313
Distribution services | Customer
Disaggregation of Revenue [Line Items]
Total revenues from contracts with customers		1,269
Retail generation | Customer
Disaggregation of Revenue [Line Items]
Total revenues from contracts with customers		1,026
Wholesale sales | Customer
Disaggregation of Revenue [Line Items]
Total revenues from contracts with customers		243
Transmission | Customer
Disaggregation of Revenue [Line Items]
Total revenues from contracts with customers		319
Other | Customer
Disaggregation of Revenue [Line Items]
Total revenues from contracts with customers		35
Derivative Revenue | Other Non-Customer Revenue
Disaggregation of Revenue [Line Items]
Total revenues		10
Regulated Distribution
Disaggregation of Revenue [Line Items]
Total revenues		2,321
Reduction in revenue		$ 72
Number of existing utility operating companies | company		10
Megawatts of net demonstrated capacity of competitive segment | MW		3,790
Utility customer payment period		30 days
Regulated Distribution | Residential
Disaggregation of Revenue [Line Items]
Total revenues		$ 1,463
Regulated Distribution | Commercial
Disaggregation of Revenue [Line Items]
Total revenues		580
Regulated Distribution | Industrial
Disaggregation of Revenue [Line Items]
Total revenues		254
Regulated Distribution | Other
Disaggregation of Revenue [Line Items]
Total revenues		24
Regulated Transmission
Disaggregation of Revenue [Line Items]
Reduction in revenue		4
Regulated Transmission		323
Regulated Transmission | JCP&L | FERC
Disaggregation of Revenue [Line Items]
Annual revenue requirement		155
Regulated Transmission | Other
Disaggregation of Revenue [Line Items]
Regulated Transmission		71
Regulated Transmission | ATSI
Disaggregation of Revenue [Line Items]
Regulated Transmission		159
Regulated Transmission | TrAIL
Disaggregation of Revenue [Line Items]
Regulated Transmission		62
Regulated Transmission | MAIT
Disaggregation of Revenue [Line Items]
Regulated Transmission		31
Operating Segments | Customer
Disaggregation of Revenue [Line Items]
Reduction in revenue		76
Operating Segments | Regulated Distribution
Disaggregation of Revenue [Line Items]
Total revenues from contracts with customers		2,479
ARP		64
Other non-customer revenue		33
Total revenues		2,576	2,500
Operating Segments | Regulated Distribution | Distribution services | Customer
Disaggregation of Revenue [Line Items]
Total revenues from contracts with customers		1,281
Operating Segments | Regulated Distribution | Retail generation | Customer
Disaggregation of Revenue [Line Items]
Total revenues from contracts with customers		1,040
Operating Segments | Regulated Distribution | Wholesale sales | Customer
Disaggregation of Revenue [Line Items]
Total revenues from contracts with customers		123
Operating Segments | Regulated Distribution | Transmission | Customer
Disaggregation of Revenue [Line Items]
Total revenues from contracts with customers		0
Operating Segments | Regulated Distribution | Other | Customer
Disaggregation of Revenue [Line Items]
Total revenues from contracts with customers		35
Operating Segments | Regulated Transmission
Disaggregation of Revenue [Line Items]
Total revenues from contracts with customers		319
ARP		0
Other non-customer revenue		4
Total revenues		323	$ 313
Operating Segments | Regulated Transmission | Distribution services | Customer
Disaggregation of Revenue [Line Items]
Total revenues from contracts with customers		0
Operating Segments | Regulated Transmission | Retail generation | Customer
Disaggregation of Revenue [Line Items]
Total revenues from contracts with customers		0
Operating Segments | Regulated Transmission | Wholesale sales | Customer
Disaggregation of Revenue [Line Items]
Total revenues from contracts with customers		0
Operating Segments | Regulated Transmission | Transmission | Customer
Disaggregation of Revenue [Line Items]
Total revenues from contracts with customers		319
Operating Segments | Regulated Transmission | Other | Customer
Disaggregation of Revenue [Line Items]
Total revenues from contracts with customers		0
Corporate/Other and Reconciling Adjustments
Disaggregation of Revenue [Line Items]
Total revenues from contracts with customers		94
ARP		0
Other non-customer revenue		(17)
Total revenues		77
Corporate/Other and Reconciling Adjustments | Distribution services | Customer
Disaggregation of Revenue [Line Items]
Total revenues from contracts with customers		(12)
Corporate/Other and Reconciling Adjustments | Retail generation | Customer
Disaggregation of Revenue [Line Items]
Total revenues from contracts with customers		(14)
Corporate/Other and Reconciling Adjustments | Wholesale sales | Customer
Disaggregation of Revenue [Line Items]
Total revenues from contracts with customers		120
Corporate/Other and Reconciling Adjustments | Transmission | Customer
Disaggregation of Revenue [Line Items]
Total revenues from contracts with customers		0
Corporate/Other and Reconciling Adjustments | Other | Customer
Disaggregation of Revenue [Line Items]
Total revenues from contracts with customers		$ 0

[1] Includes excise tax collections of $102 million and $100 million in the three months ended March 31, 2018 and 2017, respectively.