Variable Interest Entities - (Narrative) (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
Variable Interest Entity [Line Items]
Current liabilities held for sale	$ 1,050		$ 1,050		$ 625	[1]
Virginia Electric and Power Company
Variable Interest Entity [Line Items]
Long-term debt	12,462		12,462		13,207	[2]
Payables to affiliates	139		139		266	[2]
Variable Interest Entity, Primary Beneficiary | SBL Holdco
Variable Interest Entity [Line Items]
Current liabilities held for sale	264		264
Securities due within one year	32		32
Long-term debt					239
Variable Interest Entity, Not Primary Beneficiary | Virginia Electric and Power Company | DES
Variable Interest Entity [Line Items]
Shared Services Purchased	89	$ 81	278	$ 260
Payables to affiliates	$ 24		$ 24		$ 175

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

[2] Virginia Power’s Consolidated Balance Sheet at December 31, 2020 has been derived from the audited Consolidated Balance Sheet at that date.