Fair Value Measurements (Net Change in the Assets and Liabilities Measured at Fair Value on a Recurring Basis and Included in the Level 3 Fair Value Category) (Detail) - Commodity - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Beginning balance	$ 190	$ 206	$ 86	$ 422
Total realized and unrealized gains (losses):
Included in earnings	(27)	(36)	(148)	(87)
Operating Revenue	$ 2	$ 2	$ (6)	$ 2
Fair Value, Net Derivative Asset (Liability), Recurring Basis, Unobservable Input Reconciliation, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]	Electric fuel and other energy-related purchases	Electric fuel and other energy-related purchases	Electric fuel and other energy-related purchases	Electric fuel and other energy-related purchases
Included in regulatory assets/liabilities	$ 176	$ (74)	$ 307	$ (290)
Settlements	18	36	94	71
Purchases	1		28	16
Ending balance	360	134	360	134
Virginia Electric and Power Company
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Beginning balance	(38)	55	(116)	221
Total realized and unrealized gains (losses):
Included in earnings	$ (27)	$ (36)	$ (146)	$ (88)
Fair Value, Net Derivative Asset (Liability), Recurring Basis, Unobservable Input Reconciliation, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]	Electric fuel and other energy-related purchases	Electric fuel and other energy-related purchases	Electric fuel and other energy-related purchases	Electric fuel and other energy-related purchases
Included in regulatory assets/liabilities	$ 149	$ (58)	$ 226	$ (224)
Settlements	20	36	120	72
Purchases	1		21	16
Ending balance	$ 105	$ (3)	105	$ (3)
Discontinued operations
Total realized and unrealized gains (losses):
Included in earnings			$ (1)