Acquisitions and Dispositions (Schedule of Capital Expenditures and Significant Noncash Items Reported As Discontinued Operations) (Detail) - USD ($) $ in Millions		3 Months Ended		9 Months Ended
		Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Significant noncash items:
Impairment of assets and other charges (benefits)		$ (222)	$ 1,151	$ 194	$ 1,963
Depreciation, depletion and amortization		$ 621	$ 595	1,833	1,751
Accrued capital expenditures	[1]			374	461
Dominion Energy Gas Holdings, LLC | GT&S Transaction
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Capital expenditures					240
Significant noncash items:
Impairment of assets and other charges (benefits)					463
Depreciation, depletion and amortization					173
Accrued capital expenditures					43
Dominion Energy Gas Holdings, LLC | Q-Pipe Group
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Capital expenditures				26	27
Significant noncash items:
Impairment of assets and other charges (benefits)				0	0
Depreciation, depletion and amortization				0	25
Accrued capital expenditures				$ 2	$ 2

[1] See Notes 16 and 17 for noncash financing activities related to derivative restructuring and the issuance of stock associated with the settlement of litigation and noncash investing activities related to property, plant and equipment conveyed to satisfy litigation, respectively.