Related-Party Transactions (Narrative) (Detail) - USD ($)			1 Months Ended	2 Months Ended	12 Months Ended
		Feb. 01, 2020	May 31, 2019	Feb. 28, 2019	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Nov. 30, 2019	Sep. 30, 2019	Mar. 31, 2019	Dec. 31, 2016
Related Party Transaction [Line Items]
Derivative Asset					$ 93,000,000	$ 294,000,000
Derivative Liabilities					740,000,000	279,000,000
Interest income							$ 11,000,000
Debt maximum borrowing capacity	[1]				6,000,000,000	6,000,000,000
Interest income from bonds					101,000,000	84,000,000	82,000,000
Capital expenditures					4,980,000,000	4,254,000,000	5,504,000,000
DESC Ratepayer Case
Related Party Transaction [Line Items]
Litigation settlement		$ 520,000,000
Portion of Litigation Settlement		$ 320,000,000
Commercial Paper | DMLPHCII
Related Party Transaction [Line Items]
Interest Rate											2.75%
Debt Instrument, Face Amount											$ 15,000,000.0
Term Loan Credit Agreement
Related Party Transaction [Line Items]
Credit facility, outstanding amount						3,000,000,000.0			$ 3,000,000,000.0
Revolving Credit Facility
Related Party Transaction [Line Items]
Debt maximum borrowing capacity										$ 700,000,000
Dominion Energy Gas Holdings, LLC
Related Party Transaction [Line Items]
Derivative Asset					8,000,000	31,000,000
Derivative Liabilities					86,000,000	19,000,000
Payable to affiliates					260,000,000	3,097,000,000
Affiliated receivables					362,000,000	319,000,000
Business Combination, Acquisition Related Costs					603,000,000	230,000,000	239,000,000
Debt maximum borrowing capacity	[2]				1,500,000,000	1,500,000,000
Interest income from bonds					105,000,000	26,000,000	4,000,000
Capital expenditures					704,000,000	1,109,000,000	1,815,000,000
Dominion Energy Gas Holdings, LLC | DGP
Related Party Transaction [Line Items]
Capital expenditures						704,000,000
Dominion Energy Gas Holdings, LLC | Commercial Paper
Related Party Transaction [Line Items]
Payable to affiliates					$ 1,800,000,000
Interest Rate					2.50%
Interest income					$ 5,000,000
Dominion Energy Gas Holdings, LLC | Commercial Paper | Maximum
Related Party Transaction [Line Items]
Debt maximum borrowing capacity								$ 3,000,000,000.0
Dominion Energy Gas Holdings, LLC | IRCA
Related Party Transaction [Line Items]
Interest income from bonds					14,000,000	15,000,000	5,000,000
Dominion Energy Gas Holdings, LLC | IRCA | DCP
Related Party Transaction [Line Items]
Payable to affiliates						$ 2,800,000,000
Weighted- average interest rate percentage						3.43%
Interest charges related to others					94,000,000	$ 96,000,000	82,000,000
Dominion Energy Gas Holdings, LLC | Revolving Credit Facility | DCP
Related Party Transaction [Line Items]
Payable to affiliates					$ 9,000,000	$ 57,000,000
Weighted- average interest rate percentage					3.85%	3.45%
Interest charges related to others					$ 3,000,000	$ 1,000,000	1,000,000
Dominion Energy Gas Holdings, LLC | Revolving Credit Facility | IRCA
Related Party Transaction [Line Items]
Payable to affiliates					$ 251,000,000	$ 218,000,000
Weighted- average interest rate percentage					2.02%	2.78%
Interest charges related to others					$ 3,000,000	$ 1,000,000
Dominion Energy Gas Holdings, LLC | Revolving Credit Facility | IRCA | DMLPHCII
Related Party Transaction [Line Items]
Payable to affiliates						$ 22,000,000
Weighted- average interest rate percentage						3.43%
Dominion Energy Gas Holdings, LLC | Revolving Credit Facility | IRCA | Maximum | DMLPHCII
Related Party Transaction [Line Items]
Interest charges related to others						$ 1,000,000
Dominion Energy Gas Holdings, LLC | Pension Benefits | Amounts Associated with the Dominion Pension Plan
Related Party Transaction [Line Items]
Amounts due from Dominion, noncurrent					326,000,000	319,000,000
Dominion Energy Gas Holdings, LLC | Medical Coverage for Local retirees | Unbilled Revenues [Member]
Related Party Transaction [Line Items]
Amounts due from Dominion, noncurrent					22,000,000	7,000,000
Dominion Energy Gas Holdings, LLC | Medical Coverage for Local retirees | Amounts Associated with the Dominion Retiree Health and Welfare Plan
Related Party Transaction [Line Items]
Amounts due from Dominion, noncurrent					17,000,000	13,000,000
Virginia Electric and Power Company
Related Party Transaction [Line Items]
Derivative Asset					24,000,000	93,000,000
Derivative Liabilities					466,000,000	103,000,000
Payable to affiliates					107,000,000	224,000,000
Affiliated receivables					27,000,000	101,000,000
Interest income							11,000,000
Debt maximum borrowing capacity	[3]				6,000,000,000	6,000,000,000
Interest income from bonds					11,000,000	10,000,000	19,000,000
Capital expenditures					2,642,000,000	2,228,000,000	$ 2,496,000,000
Litigation settlement			$ 7,000,000
Virginia Electric and Power Company | Affiliated Entity
Related Party Transaction [Line Items]
Derivative Asset					3,000,000	26,000,000
Derivative Liabilities					53,000,000	10,000,000
Virginia Electric and Power Company | Principal Owner
Related Party Transaction [Line Items]
Payable to affiliates					$ 107,000,000	$ 224,000,000
Weighted- average interest rate percentage					3.22%	2.94%
Virginia Electric and Power Company | Amounts Associated with the Dominion Pension Plan
Related Party Transaction [Line Items]
Amounts due to Dominion, noncurrent					$ 782,000,000	$ 632,000,000
Virginia Electric and Power Company | Medical Coverage for Local retirees | Amounts Associated with the Dominion Retiree Health and Welfare Plan
Related Party Transaction [Line Items]
Amounts due from Dominion, noncurrent					287,000,000	254,000,000
East Ohio | Commercial Paper
Related Party Transaction [Line Items]
Affiliated receivables					1,700,000,000	1,400,000,000
Interest income					$ 72,000,000	64,000,000
East Ohio | Commercial Paper | Maximum
Related Party Transaction [Line Items]
Interest Rate					4.90%
East Ohio | Commercial Paper | Minimum
Related Party Transaction [Line Items]
Interest Rate					3.67%
Dominion Energy Midstream Partners, LP
Related Party Transaction [Line Items]
Credit facility, outstanding amount				$ 73,000,000
Dominion Energy Midstream Partners, LP | Term Loan Credit Agreement | Commercial Paper
Related Party Transaction [Line Items]
Interest Rate				3.50%
Interest charges related to others					$ 10,000,000
Debt Instrument, Face Amount				$ 400,000,000
Proceeds from issuance of medium term notes				$ 395,000,000
Cove Point | Term Loan Credit Agreement | Commercial Paper
Related Party Transaction [Line Items]
Credit facility, outstanding amount						$ 3,000,000,000.0
Interest Rate						3.60%
Interest income					$ 82	$ 21,000,000

[1] This credit facility matures in March 2023 and can be used by the borrowers under the credit facility to support bank borrowings and the issuance of commercial paper, as well as to support up to a combined $2.0 billion of letters of credit.

[2] A maximum of $1.5 billion of the facility is available to Dominion Energy Gas, assuming adequate capacity is available after giving effect to uses by co-borrowers Dominion Energy, Virginia Power, Questar Gas and DESC. The sub-limit for Dominion Energy Gas is set within the facility limit but can be changed at the option of the borrowers under the credit facility multiple times per year. At December 31, 2019, the sub-limit for Dominion Energy Gas was $750 million. If Dominion Energy Gas has liquidity needs in excess of its sub-limit, the sub-limit may be changed or such needs may be satisfied through short-term intercompany borrowings from Dominion Energy. This credit facility matures in March 2023 and can be used to support bank borrowings and the issuance of commercial paper, as well as to support up to $1.5 billion (or the sub-limit, whichever is less) of letters of credit.

[3] The full amount of the facility is available to Virginia Power, less any amounts outstanding to co-borrowers Dominion Energy, Dominion Energy Gas, Questar Gas and DESC. The sub-limit for Virginia Power is set within the facility limit but can be changed at the option of the borrowers under the credit facility multiple times per year. At December 31, 2019, the sub-limit for Virginia Power was $1.5 billion. If Virginia Power has liquidity needs in excess of its sub-limit, the sub-limit may be changed or such needs may be satisfied through short-term intercompany borrowings from Dominion Energy. This credit facility matures in March 2023 and can be used to support bank borrowings and the issuance of commercial paper, as well as to support up to $2.0 billion (or the sub-limit, whichever is less) of letters of credit.