Operating Segments - Virginia Power (Narrative) (Detail) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Jun. 30, 2022	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Segment Reporting Information [Line Items]
Charge for RGGI compliance cost, after tax	$ 134
Charge in connection with comprehensive settlement agreement for fuel expenses, after-tax	142
Gain (loss) on investments		$ 474	$ (505)	$ 639
Charge for the write-off of certain previously deferred amounts		307	1,401	194
Virginia Electric and Power Company
Segment Reporting Information [Line Items]
Charge for RGGI compliance cost, after tax	134
Charge in connection with comprehensive settlement agreement for fuel expenses, after-tax	$ 142
Gain (loss) on investments		68	(66)	81
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 expenses		405	(2,400)	(316)
Charge associated with storm damage and service restoration			125
Charge associated with storm damage and service restoration, after tax			93
Gain (loss) on investments		411	(559)	568
Gain (loss) on investments, after tax		$ 305	$ (451)	$ 445
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]
Charges associated with budget process related to customer arrears				$ 77
Charges associated with budget process related to customer arrears, after tax				57
Charge associated with storm damage and service restoration			$ 117	68
Charge associated with storm damage and service restoration, after tax			87	50
Loss from unbilled revenue reduction				151
Loss from unbilled revenue reduction, after tax				112
Net charge associated with settlement of the 2021 Triennial Review				125
Net charge associated with settlement of the 2021 Triennial Review, after tax				93
Easement charge related to CVOW Commercial Project		$ 65
Easement charge related to CVOW Commercial Project, after tax		48
Amortization of regulatory asset		244	243	61
Amortization of regulatory asset after tax		182	181	45
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		59	(78)
Gain (loss) on investments, after tax		$ 43	$ (58)
Investment, Type [Extensible Enumeration]		Nuclear Decommissioning Trust Fund [Member]	Nuclear Decommissioning Trust Fund [Member]
Charges for Dismantling cost			$ 167
Charges for Dismantling cost, after tax			124
Benefit for change in CCRO reserve				130
Benefit for change in CCRO reserve, after tax				97
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
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 expenses		(166)	(1,300)	873
After- tax net expenses for specific items		251	(1,300)	991
Operating Segments | Corporate and Other | Virginia Electric and Power Company
Segment Reporting Information [Line Items]
After- tax net expenses		(232)	(793)	(201)
After- tax net expenses for specific items		$ (232)	$ (773)	$ (201)