Related-Party Transactions (Detail) - USD ($) $ in Millions		3 Months Ended		9 Months Ended
		Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018
Virginia Electric and Power Company
Related Party Transaction [Line Items]
Commodity purchases from affiliates		$ 170	$ 196	$ 561	$ 733
Services provided by affiliates	[1]	107	106	387	338
Virginia Electric and Power Company | Affiliated Entity
Related Party Transaction [Line Items]
Services provided to related parties		5	6	19	17
Dominion Energy Gas Holdings, LLC
Related Party Transaction [Line Items]
Commodity purchases from affiliates		4		10	2
Services provided by affiliates	[2]	32	32	117	98
Services provided to related parties	[3]	26	53	88	166
Commodity purchases from affiliates			1
Other receivables	[4]	9		9		$ 13
Customer receivables from related parties						1
Affiliated notes receivable	[5]	13		13		16
Dominion Energy Gas Holdings, LLC | Affiliated Entity
Related Party Transaction [Line Items]
Services provided to related parties		16	$ 17	51	$ 51
Imbalances receivable from affiliates						1
Imbalances payable to affiliates	[6]	$ 1		$ 1		$ 13

[1] Includes capitalized expenditures of $33 million and $34 million for the three months ended September 30, 2019 and 2018, respectively, and $100 million and $109 million for the nine months ended September 30, 2019 and 2018, respectively.

[2] Includes capitalized expenditures of $10 million for both the three months ended September 30, 2019 and 2018 and $22 million and $27 million for the nine months ended September 30, 2019 and 2018, respectively.

[3] Amounts primarily attributable to Atlantic Coast Pipeline, a related-party VIE.

[4] Represents amounts due from Atlantic Coast Pipeline, a related-party VIE.

[5] Amounts are presented in other deferred charges and other assets in Dominion Energy Gas’ Consolidated Balance Sheets.

[6] Amounts are presented in other current liabilities in Dominion Energy Gas’ Consolidated Balance Sheets.