Acquisitions and Dispositions (Schedule of Capital Expenditures and Significant Noncash Items Reported As Discontinued Operations) (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Significant noncash items:
Impairment of assets and other charges (benefit)	$ 321	$ 44	$ 416	$ 812
Depreciation, depletion and amortization	$ 604	$ 578	1,212	1,156
Accrued capital expenditures			327	346
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				138
Significant noncash items:
Impairment of assets and other charges (benefit)				482
Depreciation, depletion and amortization				164
Accrued capital expenditures				28
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			15	15
Significant noncash items:
Impairment of assets and other charges (benefit)			0	1
Depreciation, depletion and amortization			0	26
Accrued capital expenditures			$ 4	$ 1