Significant Accounting Policies (Narrative) (Detail)	1 Months Ended						3 Months Ended	12 Months Ended
	Jan. 31, 2022 USD ($) $ / shares	Mar. 31, 2020 USD ($)	Sep. 30, 2019 USD ($)	May 31, 2019 USD ($)	Mar. 31, 2019 USD ($) Facility MW	Jan. 31, 2019 USD ($)	Mar. 31, 2021 USD ($)	Dec. 31, 2021 USD ($) MWh $ / shares		Dec. 31, 2020 USD ($) MWh		Dec. 31, 2019 USD ($)	Jan. 01, 2019 USD ($)
Significant Accounting Policies [Line Items]
Accrued unbilled revenue								$ 779,000,000		$ 1,100,000,000
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								678,000,000		19,000,000
Margin liabilities								0		5,000,000
Capitalized interest costs and Capitalized interest costs and AFUDC								117,000,000		103,000,000		$ 78,000,000
Impairment of assets and other charges								$ 195,000,000		$ 2,105,000,000		1,520,000,000
Finite Lived Intangible Asset Useful Life								35 years
Estimated proved developed or proved gas and oil reserves rate per unit | MWh								1.92		1.97
Operating lease assets								$ 506,000,000	[1]	$ 564,000,000	[1]		$ 504,000,000
Operating lease liability								$ 508,000,000
Accounting Standards Update 2016-02
Significant Accounting Policies [Line Items]
Change in Accounting Principle, Accounting Standards Update, Adopted [true false]								true
Change in Accounting Principle, Accounting Standards Update, Adoption Date								Jan. 01, 2019
Discontinued Operations | GT&S and Q-Pipe Transactions
Significant Accounting Policies [Line Items]
Operating lease assets								$ 43,000,000
Operating lease liability								$ 43,000,000
Non-jurisdictional and Certain Nonutility Solar Generation Facilities | Subsequent Event
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								$ 0.03
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	$ (20,000,000)
Increase (decrease) in depreciation expense, after tax	$ (15,000,000)
Increase in EPS | $ / shares	$ 0.02
Impairment of Assets and Other Charges
Significant Accounting Policies [Line Items]
Impairment of assets and other charges			$ 26,000,000
Asset impairment charges after tax			19,000,000
Minimum
Significant Accounting Policies [Line Items]
Lessee Operating Lease Renewal Term								1 year
Maximum
Significant Accounting Policies [Line Items]
Lessee Operating Lease Renewal Term								70 years
Virginia Electric and Power Company
Significant Accounting Policies [Line Items]
Accrued unbilled revenue								$ 398,000,000		740,000,000
Percentage of fuel currently subject to deferred fuel accounting								86.00%
Margin deposit assets								$ 167,000,000		1,000,000
Margin liabilities								0		0
Capitalized interest costs and Capitalized interest costs and AFUDC								78,000,000		60,000,000		34,000,000
AFUDC recorded as regulatory asset								35,000,000		11,000,000		$ 11,000,000
MW Capacity | MW					1,292
Number of facilities in cold reserve units retired | Facility					6
Operating lease assets								256,000,000	[1]	185,000,000	[1]		$ 209,000,000
Operating lease liability								252,000,000
Virginia Electric and Power Company | Subsequent Event
Significant Accounting Policies [Line Items]
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								(31,000,000)
Increase (decrease) in depreciation expense, after tax								(23,000,000)
Virginia Electric and Power Company | Revision Of Estimated Useful Life | Subsequent Event
Significant Accounting Policies [Line Items]
Increase (decrease) in depreciation expense	$ (8,000,000)
Increase (decrease) in depreciation expense, after tax	$ (6,000,000)
Virginia Electric and Power Company | Electric Generation Facilities
Significant Accounting Policies [Line Items]
Charges recorded with dismantling										54,000,000
Charges recorded with dismantling after tax										40,000,000
Virginia Electric and Power Company | Impairment of Assets and Other Charges
Significant Accounting Policies [Line Items]
Impairment of assets and other charges		$ 751,000,000	17,000,000	$ 62,000,000	$ 346,000,000	$ 160,000,000	$ 76,000,000			127,000,000
Asset impairment charges after tax		$ 559,000,000	$ 12,000,000	$ 46,000,000	$ 257,000,000	$ 119,000,000	$ 56,000,000			94,000,000
Virginia Electric and Power Company | Affiliated Entity
Significant Accounting Policies [Line Items]
Income tax receivable								35,000,000
Income tax payable										19,000,000
Virginia Electric and Power Company | Affiliated Entity | Federal
Significant Accounting Policies [Line Items]
Income tax receivable								33,000,000
Income tax payable										17,000,000
Virginia Electric and Power Company | Affiliated Entity | State
Significant Accounting Policies [Line Items]
Income tax receivable								$ 2,000,000
Income tax payable										2,000,000
DESC
Significant Accounting Policies [Line Items]
Percentage of fuel currently subject to deferred fuel accounting								96.00%
Dominion Energy Gas Holdings, LLC
Significant Accounting Policies [Line Items]
Inventory under LIFO method								$ 26,000,000		2,000,000
Amount exceeded on LIFO basis								$ 74,000,000		$ 52,000,000
Cove Point | Brookfield
Significant Accounting Policies [Line Items]
Percentage of equity interest sold to noncontrolling interest owners								25.00%
Four Brothers And Three Cedars | Dominion Energy Midstream Partners, LP | Terra Nova Renewable Partners | Nonregulated Solar Projects
Significant Accounting Policies [Line Items]
Percentage of equity interest sold to noncontrolling interest owners								33.00%

[1] Included in other deferred charges and other assets in the Companies’ Consolidated Balance Sheets.