Acquisitions and Dispositions (Schedule of Major Classes of Assets and Liabilities Reported As Held for Sale in Discontinued Operations) (Detail) - USD ($) $ in Millions		Dec. 31, 2020		Dec. 31, 2019
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Current assets	[1]	$ 1,482		$ 535
Current liabilities		625		1,039
Dominion Energy Gas Holdings, LLC | GT&S Transaction
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Current assets	[2]			445
Equity method investments	[3]			276
Property, plant and equipment, net				10,764
Other deferred charges and other assets, including goodwill and intangible assets	[4]			1,553
Current liabilities	[5]			1,002
Long-term debt				4,401
Other deferred credits and liabilities				773
Dominion Energy Gas Holdings, LLC | Q-Pipe Transaction
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Current assets	[2]	47	[6]	49
Equity method investments	[3]	35	[6]	36
Property, plant and equipment, net		1,113	[6]	1,103
Other deferred charges and other assets, including goodwill and intangible assets	[4]	224	[6]	225
Current liabilities	[5]	30	[6]	37
Long-term debt		426	[6]	425
Other deferred credits and liabilities		$ 154	[6]	$ 155

[1] See Note 9 for amounts attributable to related parties.

[2] Includes cash and cash equivalents of $20 million as of December 31, 2019 within the GT&S Transaction and $7 million and $11 million as of December 31, 2020 and December 31, 2019, respectively, within the Q-Pipe Transaction.

[3] Comprised of equity method investments in Iroquois and JAX LNG within the GT&S Transaction and White River Hub within the Q-Pipe Transaction.

[4] Includes goodwill of $1.4 billion at December 31, 2019 within the GT&S Transaction and $191 million at both December 31, 2020 and December 31, 2019 within the Q-Pipe Transaction.

[5] Includes current portions of long-term debt of $699 million as of December 31, 2019, within the GT&S Transaction.

[6] All amounts at December 31, 2020 are classified as current in Dominion Energy’s Consolidated Balance Sheets.