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, 2020		Dec. 31, 2019
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Current assets	[1]	$ 14,148		$ 535	[2]
Current liabilities		6,880		1,039	[2]
Dominion Energy Gas Holdings, LLC | Gas, Transmission & Storage
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Current assets	[4]	398	[3]	445
Equity method investments	[5]	316	[3]	276
Property, plant and equipment, net	[6]	10,449	[3]	10,764
Other deferred charges and other assets, including goodwill and intangible assets	[7]	1,544	[3]	1,553
Current liabilities	[8]	1,536	[3]	1,002
Long-term debt		3,916	[3]	4,401
Other deferred credits and liabilities		810	[3]	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	[4]	57	[3]	49
Equity method investments	[5]	35	[3]	36
Property, plant and equipment, net	[6]	1,109	[3]	1,103
Other deferred charges and other assets, including goodwill and intangible assets	[7]	224	[3]	225
Current liabilities	[8]	38	[3]	37
Long-term debt		425	[3]	425
Other deferred credits and liabilities		$ 155	[3]	$ 155

[1] See Note 10 for amounts attributable to related parties.

[2] Dominion Energy’s Consolidated Balance Sheet at December 31, 2019 has been derived from the audited Consolidated Balance Sheet at that date.

[3] All amounts at September 30, 2020 are classified as current in Dominion Energy’s Consolidated Balance Sheet

[4] Includes cash and cash equivalents of $24 million and $20 million as of September 30, 2020 and December 31, 2019, respectively, within the GT&S Transaction and $25 million and $11 million as of September 30, 2020 and December 31, 2019, respectively within the Q-Pipe Transaction.

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

[6] GT&S Transaction includes $40 million recorded at September 30, 2020 for a potential modified Supply Header Project.

[7] Includes goodwill of $1.4 billion and $191 million at both September 30, 2020 and December 31, 2019 within the GT&S Transaction and the Q-Pipe Transaction, respectively.

[8] Includes $47 million ARO recorded at September 30, 2020 related to the Supply Header Project and current portions of long-term debt of $1.2 billion and $699 million as of September 30, 2020 and December 31, 2020, respectively, within the GT&S Transaction