Acquisitions and Dispositions (Schedule of Capital Expenditures and Significant Noncash Items Reported As Discontinued Operations) (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Significant noncash items
Depreciation, depletion and amortization	$ 608	$ 578
Accrued capital expenditures	341	343
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		73
Significant noncash items
Depreciation, depletion and amortization		82
Accrued capital expenditures		16
Dominion Energy Gas Holdings, LLC | Q-Pipe Transaction
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Capital expenditures	3	6
Significant noncash items
Depreciation, depletion and amortization	0	13
Accrued capital expenditures	$ 2	$ 0