Related-Party Transactions (Narrative) (Detail) - USD ($) shares in Millions		3 Months Ended
		Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019
Related Party Transaction [Line Items]
Derivative Asset		$ 150,000,000		$ 93,000,000
Derivative Liabilities		1,646,000,000		740,000,000
DCP | IRCA
Related Party Transaction [Line Items]
Interest charges related to others			$ 29,000,000
Virginia Electric and Power Company
Related Party Transaction [Line Items]
Derivative Asset		51,000,000		24,000,000
Derivative Liabilities		1,015,000,000		466,000,000
Payable to affiliates	[1]			107,000,000
Outstanding borrowings, net of repayments, under money pool for non-regulated subsidiaries		$ 0		0
Issuance of common stock to Dominion		0	0
Affiliated receivables		$ 3,000,000		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		810,000,000		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		303,000,000		287,000,000
Virginia Electric and Power Company | Affiliated Entity
Related Party Transaction [Line Items]
Derivative Asset		2,000,000		3,000,000
Derivative Liabilities		20,000,000		53,000,000
Virginia Electric and Power Company | Principal Owner
Related Party Transaction [Line Items]
Payable to affiliates		0		107,000,000
Dominion Energy Gas Holdings, LLC
Related Party Transaction [Line Items]
Derivative Asset				8,000,000
Derivative Liabilities		207,000,000		86,000,000
Payable to affiliates		256,000,000		260,000,000	[2]
Affiliated receivables		87,000,000		362,000,000	[2]
Merger and integration-related costs		37,000,000	$ 46,000,000
Dominion Energy Gas Holdings, LLC | IRCA | Revolving Credit Facility
Related Party Transaction [Line Items]
Payable to affiliates		256,000,000		251,000,000
Dominion Energy Gas Holdings, LLC | IRCA | Maximum | Revolving Credit Facility
Related Party Transaction [Line Items]
Interest charges related to others		1,000,000	1,000,000
Dominion Energy Gas Holdings, LLC | DCP | Revolving Credit Facility
Related Party Transaction [Line Items]
Payable to affiliates				9,000,000
Interest charges related to others		1,000,000	1,000,000
Dominion Energy Gas Holdings, LLC | Commercial Paper
Related Party Transaction [Line Items]
Payable to affiliates		1,800,000,000		1,800,000,000
Affiliated receivables		262,000,000		0
Interest income		11,000,000
Dominion Energy Gas Holdings, LLC | Commercial Paper | East Ohio and DGP | IRCA
Related Party Transaction [Line Items]
Interest income			5,000,000
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		331,000,000		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		19,000,000		17,000,000
Dominion Energy Gas Holdings, LLC | Medical Coverage for Local retirees | Unbilled Revenues [Member]
Related Party Transaction [Line Items]
Amounts due from Dominion, noncurrent		21,000,000		22,000,000
Dominion Energy Gas Holdings, LLC | Affiliated Entity | Commodity
Related Party Transaction [Line Items]
Derivative Asset		0		0
Derivative Liabilities		0		0
Cove Point | Commercial Paper | Term Loan Credit Agreement
Related Party Transaction [Line Items]
Interest income			27,000,000
East Ohio | Commercial Paper
Related Party Transaction [Line Items]
Affiliated receivables		1,700,000,000		$ 1,700,000,000
Interest income		$ 18,000,000
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			2,000,000
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.