Acquisitions and Dispositions (Schedule of Major Classes of Assets and Liabilities Reported As Held for Sale in Discontinued Operations) (Detail) - USD ($) $ in Millions		Sep. 30, 2021	Dec. 31, 2020
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Current assets		$ 3,039	$ 1,482	[1]
Current liabilities		1,050	625	[1]
Dominion Energy Gas Holdings, LLC | Q-Pipe Group
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Current assets	[2]	47	47
Equity method investments	[3]	35	35
Property, plant and equipment, net		1,142	1,113
Other deferred charges and other assets, including goodwill and intangible assets	[4]	223	224
Current liabilities		35	30
Long-term debt		426	426
Other deferred credits and liabilities		$ 154	$ 154

[1] Dominion Energy’s Consolidated Balance Sheet at December 31, 2020 has been derived from the audited Consolidated Balance Sheet at that date.

[2] Includes cash and cash equivalents of $1 million and $7 million as of September 30, 2021 and December 31, 2020, respectively.

[3] Comprised of an equity method investment in White River Hub

[4] Includes goodwill of $191 million at both September 30, 2021 and December 31, 2020.