Derivatives and Hedge Accounting Activities (Schedule of Offsetting Liabilities) (Detail) - USD ($) $ in Millions		Mar. 31, 2020	Dec. 31, 2019
Offsetting Liabilities [Line Items]
Gross Liabilities Presented in the Consolidated Balance Sheet	[1]	$ 1,640	$ 735
Gross Amounts Not Offset in the Consolidated Balance Sheet, Financial Instruments		40	53
Gross Amounts Not Offset in the Consolidated Balance Sheet, Cash Collateral		24	35
Net Amounts		1,576	647
Virginia Electric and Power Company
Offsetting Liabilities [Line Items]
Gross Liabilities Presented in the Consolidated Balance Sheet	[2]	995	422
Gross Amounts Not Offset in the Consolidated Balance Sheet, Financial Instruments		1	18
Gross Amounts Not Offset in the Consolidated Balance Sheet, Cash Collateral		1	0
Net Amounts		993	404
Dominion Energy Gas Holdings, LLC
Offsetting Liabilities [Line Items]
Gross Liabilities Presented in the Consolidated Balance Sheet		207	86
Gross Amounts Not Offset in the Consolidated Balance Sheet, Financial Instruments		0	8
Gross Amounts Not Offset in the Consolidated Balance Sheet, Cash Collateral		0	0
Net Amounts		207	78
Commodity | Over-the-counter
Offsetting Liabilities [Line Items]
Gross Liabilities Presented in the Consolidated Balance Sheet	[1]	27	105
Gross Amounts Not Offset in the Consolidated Balance Sheet, Financial Instruments		3	21
Gross Amounts Not Offset in the Consolidated Balance Sheet, Cash Collateral		1	0
Net Amounts		23	84
Commodity | Over-the-counter | Virginia Electric and Power Company
Offsetting Liabilities [Line Items]
Gross Liabilities Presented in the Consolidated Balance Sheet	[2]	4	59
Gross Amounts Not Offset in the Consolidated Balance Sheet, Financial Instruments		1	18
Gross Amounts Not Offset in the Consolidated Balance Sheet, Cash Collateral		1	0
Net Amounts		2	41
Commodity | Exchange
Offsetting Liabilities [Line Items]
Gross Liabilities Presented in the Consolidated Balance Sheet	[1]	16	21
Gross Amounts Not Offset in the Consolidated Balance Sheet, Financial Instruments		16	21
Gross Amounts Not Offset in the Consolidated Balance Sheet, Cash Collateral		0	0
Net Amounts		0	0
Interest rate | Over-the-counter
Offsetting Liabilities [Line Items]
Gross Liabilities Presented in the Consolidated Balance Sheet	[1]	1,580	606
Gross Amounts Not Offset in the Consolidated Balance Sheet, Financial Instruments		21	8
Gross Amounts Not Offset in the Consolidated Balance Sheet, Cash Collateral		23	35
Net Amounts		1,536	563
Interest rate | Over-the-counter | Virginia Electric and Power Company
Offsetting Liabilities [Line Items]
Gross Liabilities Presented in the Consolidated Balance Sheet	[2]	991	363
Gross Amounts Not Offset in the Consolidated Balance Sheet, Financial Instruments		0	0
Gross Amounts Not Offset in the Consolidated Balance Sheet, Cash Collateral		0	0
Net Amounts		991	363
Interest rate | Over-the-counter | Dominion Energy Gas Holdings, LLC
Offsetting Liabilities [Line Items]
Gross Liabilities Presented in the Consolidated Balance Sheet		190	83
Gross Amounts Not Offset in the Consolidated Balance Sheet, Financial Instruments		0	5
Gross Amounts Not Offset in the Consolidated Balance Sheet, Cash Collateral		0	0
Net Amounts		190	78
Foreign currency | Over-the-counter
Offsetting Liabilities [Line Items]
Gross Liabilities Presented in the Consolidated Balance Sheet	[1]	17	3
Gross Amounts Not Offset in the Consolidated Balance Sheet, Financial Instruments		0	3
Gross Amounts Not Offset in the Consolidated Balance Sheet, Cash Collateral		0	0
Net Amounts		17	0
Foreign currency | Over-the-counter | Dominion Energy Gas Holdings, LLC
Offsetting Liabilities [Line Items]
Gross Liabilities Presented in the Consolidated Balance Sheet		17	3
Gross Amounts Not Offset in the Consolidated Balance Sheet, Financial Instruments		0	3
Gross Amounts Not Offset in the Consolidated Balance Sheet, Cash Collateral		0	0
Net Amounts		$ 17	$ 0

[1] Excludes $6 million and $5 million of derivative liabilities at March 31, 2020 and December 31, 2019, respectively, which are not subject to master netting or similar arrangements.

[2] Excludes $20 million and $44 million of derivative liabilities at March 31, 2020 and December 31, 2019, respectively, which are not subject to master netting or similar arrangements.