Significant Accounting Policies (Narrative) (Detail 1)	1 Months Ended		3 Months Ended					12 Months Ended
	Jan. 31, 2024 USD ($) $ / shares	Jan. 31, 2022 USD ($) $ / shares	Dec. 31, 2023 USD ($) MWh $ / shares	Sep. 30, 2023 $ / shares	Jun. 30, 2023 $ / shares	Mar. 31, 2023 $ / shares	Mar. 31, 2022 USD ($) $ / shares	Dec. 31, 2023 USD ($) MWh $ / shares	Dec. 31, 2022 USD ($) MWh	Dec. 31, 2021 USD ($)
Significant Accounting Policies [Line Items]
Reversal of interest expense on uncertain tax positions effectively settled								$ 21,000,000
Reversal of penalty expense on uncertain tax positions effectively settled								7,000,000
Margin deposit assets			$ 38,000,000					38,000,000	$ 480,000,000
Margin liabilities			$ 15,000,000					15,000,000	0
Capitalized interest costs and Capitalized interest costs and AFUDC								$ 159,000,000	$ 84,000,000	$ 96,000,000
Increase in EPS | $ / shares			$ 0.07	$ (0.02)	$ (0.01)	$ (0.02)
Finite Lived Intangible Asset Useful Life			35 years					35 years
Estimated proved developed or proved gas and oil reserves rate per unit | MWh			1.73					1.73	1.67
Cost saving incentive								$ 4,000,000	$ 27,000,000	0
Non-jurisdictional and Certain Nonutility Solar Generation Facilities
Significant Accounting Policies [Line Items]
Finite Lived Intangible Asset Useful Life		35 years
Change in Depreciation Rates from New Depreciation Study
Significant Accounting Policies [Line Items]
Increase in EPS | $ / shares							$ 0.05
Revision of Estimated Useful Life | Non-jurisdictional and Certain Nonutility Solar Generation Facilities
Significant Accounting Policies [Line Items]
Increase (decrease) in depreciation expense		$ (16,000,000)						(40,000,000)
Increase (decrease) in depreciation expense, after tax		$ (12,000,000)						$ (30,000,000)
Increase in EPS | $ / shares		$ 0.02						$ 0.04
Revision of Estimated Useful Life | Non-jurisdictional and Certain Nonutility Solar Generation Facilities | Subsequent Event
Significant Accounting Policies [Line Items]
Increase (decrease) in depreciation expense	$ 15,000,000
Increase (decrease) in depreciation expense, after tax	$ 11,000,000
Increase in EPS | $ / shares	$ 0.01
Virginia Electric and Power Company
Significant Accounting Policies [Line Items]
Percentage of fuel currently subject to deferred fuel accounting								86.00%
Margin deposit assets			$ 35,000,000					$ 35,000,000	310,000,000
Margin liabilities			0					0	0
Capitalized interest costs and Capitalized interest costs and AFUDC								86,000,000	66,000,000	78,000,000
AFUDC recorded as regulatory asset									34,000,000	$ 35,000,000
Finite Lived Intangible Asset Useful Life		35 years
Virginia Electric and Power Company | Change in Depreciation Rates from New Depreciation Study
Significant Accounting Policies [Line Items]
Increase (decrease) in depreciation expense							$ (60,000,000)
Increase (decrease) in depreciation expense, after tax							$ (45,000,000)
Virginia Electric and Power Company | Revision of Estimated Useful Life
Significant Accounting Policies [Line Items]
Increase (decrease) in depreciation expense		$ (6,000,000)
Increase (decrease) in depreciation expense, after tax		$ (4,000,000)
Virginia Electric and Power Company | Electric Generation Facilities
Significant Accounting Policies [Line Items]
Charges recorded with dismantling								25,000,000	167,000,000
Charges recorded with dismantling after tax								19,000,000	124,000,000
Virginia Electric and Power Company | Maximum
Significant Accounting Policies [Line Items]
AFUDC recorded as regulatory asset			1,000,000					1,000,000
Virginia Electric and Power Company | Affiliated Entity
Significant Accounting Policies [Line Items]
Income tax receivable			40,000,000					40,000,000
Income tax payable									22,000,000
Virginia Electric and Power Company | Affiliated Entity | Federal
Significant Accounting Policies [Line Items]
Income tax receivable			45,000,000					45,000,000
Income tax payable									25,000,000
Virginia Electric and Power Company | Affiliated Entity | State
Significant Accounting Policies [Line Items]
Income tax receivable									$ 3,000,000
Income tax payable			$ 5,000,000					$ 5,000,000
DESC
Significant Accounting Policies [Line Items]
Percentage of fuel currently subject to deferred fuel accounting								96.00%