Significant Financing Transactions (Narrative) (Detail) - USD ($)		1 Months Ended						3 Months Ended		6 Months Ended		12 Months Ended
		Aug. 31, 2021	Jul. 31, 2021	Jun. 30, 2021	Apr. 30, 2021	Mar. 31, 2021	Mar. 31, 2020	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020		Nov. 30, 2020
Debt Instrument [Line Items]
Facility Limit	[1]			$ 6,000,000,000				$ 6,000,000,000		$ 6,000,000,000
Credit facility, amount borrowed				250,000,000				250,000,000		250,000,000
Short-term debt				$ 3,028,000,000				$ 3,028,000,000		$ 3,028,000,000		$ 895,000,000	[2]
Preferred stock shares authorized				20,000,000				20,000,000		20,000,000
Stock purchase contract liability				$ 87,000,000				$ 87,000,000		$ 87,000,000		129,000,000
Corporate units stock purchase contract liability payments										42,000,000	$ 41,000,000
Issuance of common stock										97,000,000	148,000,000
Issuance of stock								$ 49,000,000	$ 70,000,000	$ 97,000,000	$ 148,000,000
Common Stock
Debt Instrument [Line Items]
Issuance of stock (in shares)								1,000,000	1,000,000	1,000,000	2,000,000
Issuance of stock								$ 49,000,000	$ 70,000,000	$ 97,000,000	$ 148,000,000
Stock repurchase program, authorized amount														$ 1,000,000,000.0
Common Stock | Open Market Agreement
Debt Instrument [Line Items]
Stock repurchased, shares										0
Series A Preferred Stock
Debt Instrument [Line Items]
Recorded dividend								$ 7,000,000	$ 7,000,000	$ 14,000,000	$ 14,000,000
Recorded dividends per share								$ 4.375	$ 4.375	$ 8.750	$ 8.750
Series B Preferred Stock
Debt Instrument [Line Items]
Recorded dividend								$ 9,000,000	$ 9,000,000	$ 18,000,000	$ 18,000,000
Recorded dividends per share								$ 11.625	$ 11.625	$ 23.250	$ 23.250
Various Programs
Debt Instrument [Line Items]
Issuance of common stock										$ 97,000,000	$ 148,000,000
Issuance of stock (in shares)										1,000,000	2,000,000
Subsequent Event | Common Stock
Debt Instrument [Line Items]
Issuance of stock (in shares)		600,000	1,400,000
Issuance of stock		$ 45,000,000	$ 104,000,000
Floating Rate Demand Notes
Debt Instrument [Line Items]
Short-term debt				392,000,000				$ 392,000,000		$ 392,000,000		268,000,000
Floating Rate Demand Notes | Shelf Registration for Sale of Demand Notes
Debt Instrument [Line Items]
Facility Limit												3,000,000,000.0
Senior Notes Due in 2051 | PSNC
Debt Instrument [Line Items]
Total Long-term Debt						$ 150,000,000
Interest rate percentage						3.10%
Debt maturity year						2051
Senior Notes Due in 2026
Debt Instrument [Line Items]
Total Long-term Debt					$ 600,000,000
Interest rate percentage					1.45%
Debt maturity year					2026
Senior Notes Due in 2041
Debt Instrument [Line Items]
Total Long-term Debt					$ 500,000,000
Interest rate percentage					3.30%
Debt maturity year					2041
2.0% Senior Notes Due August 2021 | Subsequent Event
Debt Instrument [Line Items]
Debt maturity month and year			2021-08
Interest rate percentage			2.00%
Debt, amount redeemed			$ 400,000,000
DESC
Debt Instrument [Line Items]
Facility Limit				500,000,000				500,000,000		500,000,000
Short-term indebtedness outstanding						$ 2,200,000,000
Debt maturity month and year						2023-03
DESC | 3.22% First Mortgage Bond Due October 2021 | Subsequent Event
Debt Instrument [Line Items]
Debt maturity month and year			2021-10
Interest rate percentage			3.22%
Debt, amount redeemed			$ 30,000,000
Questar Gas
Debt Instrument [Line Items]
Facility Limit				$ 250,000,000				250,000,000		250,000,000
Questar Gas | 10-Year Senior Notes
Debt Instrument [Line Items]
Debt Instrument Term				10 years
Total Long-term Debt				$ 125,000,000				$ 125,000,000		$ 125,000,000
Interest rate percentage				2.21%				2.21%		2.21%
Questar Gas | 30-Year Senior Notes
Debt Instrument [Line Items]
Debt Instrument Term				30 years
Total Long-term Debt				$ 125,000,000				$ 125,000,000		$ 125,000,000
Interest rate percentage				3.15%				3.15%		3.15%
GESC
Debt Instrument [Line Items]
Short-term indebtedness outstanding						$ 200,000,000
Debt maturity month and year						2023-03
SBL Holdco | Credit Facilities, Maturing in December 2017 with 1 year Automatic Renewals through 2023
Debt Instrument [Line Items]
Facility Limit				$ 30,000,000				$ 30,000,000		$ 30,000,000
Automatic renewal period										1 year
Short-term debt				0				0		$ 0		0
Dominion Solar Projects III, Inc | Credit Facilities, Maturing in May 2018 with 1 year Automatic Renewals through 2024
Debt Instrument [Line Items]
Facility Limit				25,000,000				25,000,000		$ 25,000,000
Automatic renewal period										1 year
Short-term debt				$ 0				$ 0		$ 0		$ 0
Dominion Energy
Debt Instrument [Line Items]
Preferred stock shares issued				2,400,000				2,400,000		2,400,000		2,400,000
Preferred stock shares outstanding				2,400,000				2,400,000		2,400,000		2,400,000
Dominion Energy | Series A Preferred Stock
Debt Instrument [Line Items]
Preferred stock shares issued				1,600,000				1,600,000		1,600,000		1,600,000
Preferred stock shares outstanding				1,600,000				1,600,000		1,600,000		1,600,000
Dominion Energy | Series B Preferred Stock
Debt Instrument [Line Items]
Preferred stock shares issued				800,000				800,000		800,000		800,000
Preferred stock shares outstanding				800,000				800,000		800,000		800,000
New Joint Revolving Credit Facility
Debt Instrument [Line Items]
Facility Limit				$ 6,000,000,000.0				$ 6,000,000,000.0		$ 6,000,000,000.0
Letter of Credit
Debt Instrument [Line Items]
Facility Limit				2,000,000,000.0				2,000,000,000.0		2,000,000,000.0
Letter of Credit | Credit Facility, Maturing in June 2022
Debt Instrument [Line Items]
Facility Limit				30,000,000				30,000,000		30,000,000
Credit facility, amount borrowed				29,000,000				29,000,000		$ 29,000,000		$ 30,000,000
Line of credit facility, maturity date										Jun. 30, 2022
364-Day Revolving Credit Facility
Debt Instrument [Line Items]
Facility Limit							$ 900,000,000
Short-term debt												$ 225,000,000
Debt Instrument Term							364 days			364 days		364 days
Term Loan Credit Agreement | Subsequent Event
Debt Instrument [Line Items]
Facility Limit			$ 1,300,000,000
Sustainability Revolving Credit Agreement | Credit Facility, Maturing in June 2024
Debt Instrument [Line Items]
Facility Limit				900,000,000				900,000,000		$ 900,000,000
Credit facility, amount borrowed				$ 250,000,000				$ 250,000,000		$ 250,000,000
Line of credit facility, maturity date				Jun. 30, 2024

[1] This credit facility matures in June 2026, with the potential to be extended by the borrowers to June 2028, 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] Dominion Energy’s Consolidated Balance Sheet at December 31, 2020 has been derived from the audited Consolidated Balance Sheet at that date.