Related-Party Transactions (Narrative) (Detail) - USD ($)	3 Months Ended			6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
Related Party Transaction [Line Items]
Derivative Asset	$ 216,000,000			$ 216,000,000		$ 93,000,000
Derivative Liabilities	1,334,000,000			1,334,000,000		740,000,000
DCP | IRCA
Related Party Transaction [Line Items]
Interest charges related to others		$ 29,000,000			$ 58,000,000
Virginia Electric and Power Company
Related Party Transaction [Line Items]
Derivative Asset	133,000,000			133,000,000		24,000,000
Derivative Liabilities	1,004,000,000			1,004,000,000		466,000,000
Payable to affiliates	340,000,000			340,000,000		107,000,000	[1]
Outstanding borrowings, net of repayments, under money pool for non-regulated subsidiaries	$ 0			$ 0		0
Issuance of common stock to Dominion	0	0		0	0
Affiliated receivables	$ 2,000,000			$ 2,000,000		27,000,000	[1]
Virginia Electric and Power Company | Pension Benefits | Amounts Associated with the Dominion Pension Plan
Related Party Transaction [Line Items]
Amounts due to Dominion, noncurrent	838,000,000			838,000,000		782,000,000
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	318,000,000			318,000,000		287,000,000
Virginia Electric and Power Company | Affiliated Entity
Related Party Transaction [Line Items]
Derivative Asset	3,000,000			3,000,000		3,000,000
Derivative Liabilities	19,000,000			19,000,000		53,000,000
Virginia Electric and Power Company | Principal Owner
Related Party Transaction [Line Items]
Payable to affiliates	340,000,000			340,000,000		107,000,000
Dominion Energy Gas Holdings, LLC
Related Party Transaction [Line Items]
Derivative Asset						8,000,000
Derivative Liabilities	204,000,000			204,000,000		86,000,000
Payable to affiliates	314,000,000			314,000,000		260,000,000	[2]
Affiliated receivables	77,000,000			77,000,000		362,000,000	[2]
Business combination acquisition related costs				1,700,000,000	$ 323,000,000
Dominion Energy Gas Holdings, LLC | IRCA | Revolving Credit Facility
Related Party Transaction [Line Items]
Payable to affiliates	314,000,000			314,000,000		251,000,000
Dominion Energy Gas Holdings, LLC | DCP | Revolving Credit Facility
Related Party Transaction [Line Items]
Payable to affiliates						9,000,000
Dominion Energy Gas Holdings, LLC | Maximum | IRCA | Revolving Credit Facility
Related Party Transaction [Line Items]
Interest charges related to others	1,000,000	$ 1,000,000		2,000,000	1,000,000
Dominion Energy Gas Holdings, LLC | Maximum | DCP | Revolving Credit Facility
Related Party Transaction [Line Items]
Interest charges related to others	1,000,000	1,000,000		1,000,000	2,000,000
Dominion Energy Gas Holdings, LLC | Commercial Paper
Related Party Transaction [Line Items]
Payable to affiliates	2,300,000,000			2,300,000,000		1,800,000,000
Affiliated receivables	263,000,000			263,000,000		0
Interest income	12,000,000			23,000,000
Dominion Energy Gas Holdings, LLC | Commercial Paper | East Ohio and DGP | IRCA
Related Party Transaction [Line Items]
Interest income		3,000,000			8,000,000
Dominion Energy Gas Holdings, LLC | Commercial Paper | Maximum
Related Party Transaction [Line Items]
Interest income	1,000,000			2,000,000
Dominion Energy Gas Holdings, LLC | Amounts Associated with the Dominion Pension Plan | Other Deferred Charges and Other Assets
Related Party Transaction [Line Items]
Amounts due from Dominion, noncurrent	334,000,000			334,000,000		326,000,000
Dominion Energy Gas Holdings, LLC | Amounts Associated with the Dominion Retiree Health and Welfare Plan | Other Deferred Charges and Other Assets
Related Party Transaction [Line Items]
Amounts due from Dominion, noncurrent	20,000,000			20,000,000		17,000,000
Dominion Energy Gas Holdings, LLC | Medical Coverage for Local retirees | Unbilled Revenues
Related Party Transaction [Line Items]
Amounts due from Dominion, noncurrent	18,000,000			18,000,000		22,000,000
Dominion Energy Gas Holdings, LLC | Affiliated Entity | Commodity
Related Party Transaction [Line Items]
Derivative Asset	0			0		0
Derivative Liabilities	0			0		0
Cove Point | Commercial Paper | Term Loan Credit Agreement
Related Party Transaction [Line Items]
Interest income		27,000,000			54,000,000
East Ohio | Commercial Paper
Related Party Transaction [Line Items]
Affiliated receivables						$ 1,700,000,000
Interest income	$ 15,000,000			$ 33,000,000
Dominion Energy Midstream Partners, LP | Commercial Paper | Term Loan Credit Agreement
Related Party Transaction [Line Items]
Payable to affiliates			$ 395,000,000
Interest charges related to others		$ 3,000,000			$ 6,000,000
Debt instrument, face amount			$ 400,000,000
Debt maturity year			2022

[1] Virginia Power’s Consolidated Balance Sheet at December 31, 2019 has been derived from the audited Consolidated Balance Sheet at that date.

[2] Dominion Energy Gas’ Consolidated Balance Sheet at December 31, 2019 has been derived from the audited Consolidated Balance Sheet at that date.