Long-Term Debt (Total Long Term Debt) (Parenthetical) (Detail) - USD ($) $ in Millions		1 Months Ended			12 Months Ended
		Jun. 30, 2020	Apr. 30, 2020	Feb. 29, 2020	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Mar. 31, 2020
Debt Instrument [Line Items]
Repayment of Debt					$ 2,879	$ 9,116	$ 5,682
Total principal	[1]				$ 35,496	31,557
DS C A N A
Debt Instrument [Line Items]
Debt instrument, maturity date, description					The notes would have otherwise matured in May 2021 and February 2022, respectively.
June2006 Hybrids
Debt Instrument [Line Items]
Repayment of Debt				$ 111
September 2006 hybrids
Debt Instrument [Line Items]
Repayment of Debt				$ 286
Debt Instrument, Face Amount						13
Term loans
Debt Instrument [Line Items]
Estimated mandatory prepayments due within one year					$ 22
Virginia Electric and Power Company
Debt Instrument [Line Items]
Repayment of Debt					427	591	$ 964
Total principal					13,314	12,414
2.45% to 8.875%, due 2022 to 2050 | Virginia Electric and Power Company | Senior Notes
Debt Instrument [Line Items]
Total principal					$ 12,689	11,789
2.45% to 8.875%, due 2022 to 2050 | Minimum | Virginia Electric and Power Company | Senior Notes
Debt Instrument [Line Items]
Interest Rate					2.45%
2.45% to 8.875%, due 2022 to 2050 | Maximum | Virginia Electric and Power Company | Senior Notes
Debt Instrument [Line Items]
Interest Rate					8.875%
0.45% to 1.90%, due 2032 to 2041 | Virginia Electric and Power Company | Tax-Exempt Financings
Debt Instrument [Line Items]
Total principal	[2]				$ 625	625
0.45% to 1.90%, due 2032 to 2041 | Minimum | Virginia Electric and Power Company | Tax-Exempt Financings
Debt Instrument [Line Items]
Interest Rate					0.45%
0.45% to 1.90%, due 2032 to 2041 | Maximum | Virginia Electric and Power Company | Tax-Exempt Financings
Debt Instrument [Line Items]
Interest Rate					1.90%
2.0% to 7.0%, due 2021 to 2049 | Senior Notes
Debt Instrument [Line Items]
Total principal	[3]				$ 9,938	7,688
2.0% to 7.0%, due 2021 to 2049 | Minimum | Senior Notes
Debt Instrument [Line Items]
Interest Rate					2.00%
2.0% to 7.0%, due 2021 to 2049 | Maximum | Senior Notes
Debt Instrument [Line Items]
Interest Rate					7.00%
2.579% to 4.104%, due 2019 to 2024 [Member]
Debt Instrument [Line Items]
Interest Rate			2.579%
Repayment of Debt			$ 7
Pre-payment of Debt		$ 993
2.579% to 4.104%, due 2019 to 2024 [Member] | Unsecured Junior Subordinated Notes
Debt Instrument [Line Items]
Total principal	[4]				$ 1,950	2,950
2.579% to 4.104%, due 2019 to 2024 [Member] | Minimum | Unsecured Junior Subordinated Notes
Debt Instrument [Line Items]
Interest Rate					2.579%
2.579% to 4.104%, due 2019 to 2024 [Member] | Maximum | Unsecured Junior Subordinated Notes
Debt Instrument [Line Items]
Interest Rate					4.104%
8.4% due 2031 | Unsecured Junior Subordinated Notes
Debt Instrument [Line Items]
Interest Rate					8.40%
Total principal					$ 10	10
5.25% and 5.75%, due 2054 and 2076 | Enhanced Junior Subordinated Notes
Debt Instrument [Line Items]
Total principal					$ 1,485	1,485
5.25% and 5.75%, due 2054 and 2076 | Minimum | Enhanced Junior Subordinated Notes
Debt Instrument [Line Items]
Interest Rate					5.25%
5.25% and 5.75%, due 2054 and 2076 | Maximum | Enhanced Junior Subordinated Notes
Debt Instrument [Line Items]
Interest Rate					5.75%
2.98% to 7.20%, due 2024 to 2051 | Minimum | Questar Gas Company
Debt Instrument [Line Items]
Interest Rate					2.98%
2.98% to 7.20%, due 2024 to 2051 | Maximum | Questar Gas Company
Debt Instrument [Line Items]
Interest Rate					7.20%
1.30% to 3.00%, due 2025 to 2050 | Minimum | East Ohio
Debt Instrument [Line Items]
Interest Rate					1.30%
1.30% to 3.00%, due 2025 to 2050 | Maximum | East Ohio
Debt Instrument [Line Items]
Interest Rate					3.00%
4.125% to 6.25%, due 2020 to 2022 | Minimum
Debt Instrument [Line Items]
Interest Rate					4.125%
4.125% to 6.25%, due 2020 to 2022 | Maximum
Debt Instrument [Line Items]
Interest Rate					6.25%
4.05% to 7.45%, due 2020 to 2047 | Minimum | PSNC
Debt Instrument [Line Items]
Interest Rate					4.05%
4.05% to 7.45%, due 2020 to 2047 | Maximum | PSNC
Debt Instrument [Line Items]
Interest Rate					7.45%
First mortgage bonds, 3.22% to 6.625%, due 2021 to 2065 | Minimum | DESC
Debt Instrument [Line Items]
Interest Rate					3.22%
First mortgage bonds, 3.22% to 6.625%, due 2021 to 2065 | Maximum | DESC
Debt Instrument [Line Items]
Interest Rate					6.625%
3.625% and 4.00%, due 2028 and 2033 | Tax-Exempt Financings
Debt Instrument [Line Items]
Total principal	[5]				$ 54	54
3.625% and 4.00%, due 2028 and 2033 | Minimum | Tax-Exempt Financings
Debt Instrument [Line Items]
Interest Rate					3.625%
3.625% and 4.00%, due 2028 and 2033 | Maximum | Tax-Exempt Financings
Debt Instrument [Line Items]
Interest Rate					4.00%
4.82%, due 2042
Debt Instrument [Line Items]
Interest Rate					4.82%
Total principal	[6]				$ 331	345
Tax-Exempt Financing, 1.7% due 2033
Debt Instrument [Line Items]
Interest Rate					1.70%
Tax-Exempt Financing, 1.7% due 2033 | Tax-Exempt Financings
Debt Instrument [Line Items]
Total principal					$ 27	$ 27
Four Point Seven Five Percent Medium Term Notes | DS C A N A
Debt Instrument [Line Items]
Interest Rate				4.75%
Debt Instrument, Face Amount				$ 183
Four Point One Two Five Percent Medium Term Notes | DS C A N A
Debt Instrument [Line Items]
Interest Rate				4.125%
Debt Instrument, Face Amount				$ 155
Floating rate senior notes | DS C A N A
Debt Instrument [Line Items]
Debt Instrument, Face Amount								$ 66
Debt instrument, maturity date, description					The notes would have otherwise matured in June 2034
Industrial Revenue Bonds
Debt Instrument [Line Items]
Total principal					$ 68

[1] Excludes amounts classified as held for sale. See Note 3.

[2] These financings relate to certain pollution control equipment at Virginia Power’s generating facilities.

[3] Includes debt assumed by Dominion Energy from the merger of its former CNG subsidiary.

[4] In April 2020, Dominion Energy purchased and canceled $7 million of its 2.579% junior subordinated notes that mature in July 2020. In June 2020, Dominion Energy prepaid the remaining balance of $993 million.

[5] Industrial revenue bonds totaling $68 million are secured by letters of credit that expire, subject to renewal, in the fourth quarter of 2021.

[6] Represents debt associated with Eagle Solar, SBL Holdco and Dominion Solar Projects III, Inc. The debt is nonrecourse to Dominion Energy and is secured by Eagle Solar’s, SBL Holdco’s and Dominion Solar Projects III, Inc’s interest in certain solar facilities.