Leases (Lease Assets and Liabilities Recorded in Consolidated Balance Sheets) (Detail) - USD ($) $ in Millions		Dec. 31, 2020		Dec. 31, 2019		Jan. 01, 2019
Lessee Lease Disclosure [Line Items]
Operating lease assets		$ 564	[1]	$ 462	[1]	$ 504
Operating Lease, Right-of-Use Asset, Statement of Financial Position [Extensible List]		d:DeferredChargesRegulatoryAssetsAndOtherAssetsNoncurrent		d:DeferredChargesRegulatoryAssetsAndOtherAssetsNoncurrent
Finance lease assets	[2]	$ 148		$ 134
Finance Lease, Right-of-Use Asset, Statement of Financial Position [Extensible List]		us-gaap:PropertyPlantAndEquipmentNet		us-gaap:PropertyPlantAndEquipmentNet
Total lease assets		$ 712		$ 596
Operating lease liabilities	[3]	$ 54		$ 53
Operating Lease, Liability, Current, Statement of Financial Position [Extensible List]		us-gaap:OtherLiabilitiesCurrent		us-gaap:OtherLiabilitiesCurrent
Finance lease liabilities	[4]	$ 32		$ 27
Finance Lease, Liability, Current, Statement of Financial Position [Extensible List]		us-gaap:LongTermDebtAndCapitalLeaseObligationsCurrent		us-gaap:LongTermDebtAndCapitalLeaseObligationsCurrent
Total lease liabilities - current		$ 86		$ 80
Operating lease liabilities	[5]	$ 516		$ 413
Operating Lease, Liability, Noncurrent, Statement of Financial Position [Extensible List]		us-gaap:DeferredCreditsAndOtherLiabilities		us-gaap:DeferredCreditsAndOtherLiabilities
Finance lease liabilities	[6]	$ 108		$ 100
Total lease liabilities - noncurrent		624		513
Total lease liabilities		710		593
Virginia Electric and Power Company
Lessee Lease Disclosure [Line Items]
Operating lease assets		$ 185	[1]	$ 212	[1]	$ 209
Operating Lease, Right-of-Use Asset, Statement of Financial Position [Extensible List]		d:DeferredChargesRegulatoryAssetsAndOtherAssetsNoncurrent		d:DeferredChargesRegulatoryAssetsAndOtherAssetsNoncurrent
Finance lease assets	[2]	$ 45		$ 19
Finance Lease, Right-of-Use Asset, Statement of Financial Position [Extensible List]		us-gaap:PropertyPlantAndEquipmentNet		us-gaap:PropertyPlantAndEquipmentNet
Total lease assets		$ 230		$ 231
Operating lease liabilities	[3]	$ 28		$ 30
Operating Lease, Liability, Current, Statement of Financial Position [Extensible List]		us-gaap:OtherLiabilitiesCurrent		us-gaap:OtherLiabilitiesCurrent
Finance lease liabilities	[4]	$ 8		$ 3
Finance Lease, Liability, Current, Statement of Financial Position [Extensible List]		us-gaap:LongTermDebtAndCapitalLeaseObligationsCurrent		us-gaap:LongTermDebtAndCapitalLeaseObligationsCurrent
Total lease liabilities - current		$ 36		$ 33
Operating lease liabilities	[5]	$ 155		$ 180
Operating Lease, Liability, Noncurrent, Statement of Financial Position [Extensible List]		us-gaap:DeferredCreditsAndOtherLiabilities		us-gaap:DeferredCreditsAndOtherLiabilities
Finance lease liabilities	[6]	$ 36		$ 16
Total lease liabilities - noncurrent		191		196
Total lease liabilities		$ 227		$ 229

[1] Included in other deferred charges and other assets in the Companies’ Consolidated Balance Sheets.

[2] Included in property, plant and equipment in the Companies’ Consolidated Balance Sheets, net of $50 million and $9 million of accumulated amortization at Dominion Energy and Virginia Power, respectively, at December 31, 2020 and net of $26 million and $4 million of accumulated amortization at Dominion Energy and Virginia Power, respectively, at December 31, 2019.

[3] Included in other current liabilities in the Companies’ Consolidated Balance Sheets.

[4] Included in securities due within one year in the Companies’ Consolidated Balance Sheets.

[5] Included in other deferred credits and other liabilities in the Companies’ Consolidated Balance Sheets.

[6] Included in other long-term debt in the Companies’ Consolidated Balance Sheets.