Significant Financing Transactions (Narrative) (Detail) - USD ($)		1 Months Ended			3 Months Ended		12 Months Ended
		Apr. 30, 2021	Mar. 31, 2021	Mar. 31, 2020	Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2020		Nov. 30, 2020
Debt Instrument [Line Items]
Facility Limit	[1]		$ 6,000,000,000		$ 6,000,000,000
Short-term debt			$ 2,815,000,000		$ 2,815,000,000		$ 895,000,000	[2]
Preferred stock shares authorized			20,000,000		20,000,000
Stock purchase contract liability			$ 108,000,000		$ 108,000,000		$ 129,000,000
Corporate units stock purchase contract liability payments					21,000,000	$ 20,000,000
Issuance of common stock					48,000,000	$ 78,000,000
Common Stock
Debt Instrument [Line Items]
Issuance of stock (in shares)						1,000,000
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
Recorded dividends per share					$ 4.375	$ 4.375
Series B Preferred Stock
Debt Instrument [Line Items]
Recorded dividend					$ 9,000,000	$ 9,000,000
Recorded dividends per share					$ 11.625	$ 11.625
Various Programs
Debt Instrument [Line Items]
Issuance of common stock					$ 48,000,000	$ 78,000,000
Issuance of stock (in shares)						1,000,000
Various Programs | Maximum
Debt Instrument [Line Items]
Issuance of stock (in shares)					1,000,000
Floating Rate Demand Notes
Debt Instrument [Line Items]
Short-term debt			338,000,000		$ 338,000,000		$ 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		$ 150,000,000
Interest rate percentage			3.10%		3.10%
Debt maturity year			2051
Senior Notes Due in 2026 | Subsequent Event
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 | Subsequent Event
Debt Instrument [Line Items]
Total Long-term Debt		$ 500,000,000
Interest rate percentage		3.30%
Debt maturity year		2041
Letter of Credit
Debt Instrument [Line Items]
Facility Limit			$ 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
Credit facility, outstanding amount			30,000,000		$ 30,000,000		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		$ 900,000,000
Short-term debt							225,000,000
Debt Instrument, Term				364 days
DESC
Debt Instrument [Line Items]
Facility Limit			500,000,000		$ 500,000,000
Short-term indebtedness outstanding					$ 2,200,000,000
Debt maturity month and year					2023-03
Questar Gas
Debt Instrument [Line Items]
Facility Limit			250,000,000		$ 250,000,000
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
Automatic renewal period					1 year
Short-term debt			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
Automatic renewal period					1 year
Short-term debt			$ 0		$ 0		$ 0
Dominion Energy
Debt Instrument [Line Items]
Preferred stock shares issued			2,400,000		2,400,000		2,400,000
Preferred stock shares outstanding			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
Preferred stock shares outstanding			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
Preferred stock shares outstanding			800,000		800,000		800,000

[1] This credit facility matures in March 2023 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.