Operating Segments - Virginia Power (Narrative) (Detail) - USD ($) $ in Millions	3 Months Ended		12 Months Ended
	Sep. 30, 2024	Mar. 31, 2024	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Segment Reporting Information [Line Items]
Gain (loss) on investments			$ 669	$ 474	$ (505)
Gain (loss) on investments, after tax	$ 132	$ 202
Investment, Type [Extensible Enumeration]	Nuclear Decommissioning Trust Fund [Member]	Nuclear Decommissioning Trust Fund [Member]
Charge for the write-off of certain previously deferred amounts			600	307	1,401
Virginia Electric and Power Company
Segment Reporting Information [Line Items]
Gain (loss) on investments			97	68	(66)
Virginia Electric and Power Company | Deferred rider costs for Virginia electric utility
Segment Reporting Information [Line Items]
Charge for the write-off of certain previously deferred amounts				36
Charge for the write-off of certain previously deferred amounts, after tax				27
Operating Segments
Segment Reporting Information [Line Items]
After- tax net income (expenses)			(132)	405	(2,400)
Charge associated with storm damage and service restoration					125
Charge associated with storm damage and service restoration, after tax					93
Gain (loss) on investments			565	411	(559)
Gain (loss) on investments, after tax			$ 434	$ 305	$ (451)
Investment, Type [Extensible Enumeration]			Nuclear Decommissioning Trust Fund [Member]	Nuclear Decommissioning Trust Fund [Member]	Nuclear Decommissioning Trust Fund [Member]
Operating Segments | Virginia Electric and Power Company
Segment Reporting Information [Line Items]
Charge associated with storm damage and service restoration					$ 117
Charge associated with storm damage and service restoration, after tax					87
Easement charge related to CVOW Commercial Project				$ 65
Easement charge related to CVOW Commercial Project, after tax				48
Amortization of regulatory asset				244	243
Amortization of regulatory asset after tax				182	181
Charge for RGGI compliance cost					213
Charge for RGGI compliance cost, after tax					159
Charge in connection with comprehensive settlement agreement for fuel expenses					191
Charge in connection with comprehensive settlement agreement for fuel expenses, after-tax					142
Gain (loss) on investments			$ 83	59	(78)
Gain (loss) on investments, after tax			$ 62	$ 43	$ (58)
Investment, Type [Extensible Enumeration]			Nuclear Decommissioning Trust Fund [Member]	Nuclear Decommissioning Trust Fund [Member]	Nuclear Decommissioning Trust Fund [Member]
Share of costs not expected to be recovered from customers on the CVOW commercial project			$ 103
Share of costs not expected to be recovered from customers on the CVOW commercial project, after tax			77
Charges for Dismantling cost			40		$ 167
Charges for Dismantling cost, after tax			30		124
Charge related to the abandonment of certain regulated solar generation facilities and other facilities				$ 25
Charge related to the abandonment of certain regulated solar generation facilities and other facilities, after tax				19
Charge for write-off of certain early stage development costs			30
Charge for write-off of certain early stage development costs after tax			22
Charge associated with an accrual for remediation costs			25
Charge associated with an accrual for remediation costs after tax			19
Operating Segments | Virginia Electric and Power Company | Deferred rider costs for Virginia electric utility
Segment Reporting Information [Line Items]
Charge for the write-off of certain previously deferred amounts				36
Charge for the write-off of certain previously deferred amounts, after tax				27
Operating Segments | Corporate and Other
Segment Reporting Information [Line Items]
After- tax net income (expenses)			(644)	(129)	(1,400)
After- tax net income (expenses) for specific items			(268)	316	(1,500)
Operating Segments | Corporate and Other | Virginia Electric and Power Company
Segment Reporting Information [Line Items]
After- tax net income (expenses)			(101)	(232)	(793)
After- tax net income (expenses) for specific items			$ (102)	$ (232)	$ (773)