Investments (Investments Under Equity Method of Accounting) (Detail) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2021	Dec. 31, 2020
Schedule of Equity Method Investments [Line Items]
Investment in equity method affiliates	[1]	$ 2,932	$ 2,934
Cove Point
Schedule of Equity Method Investments [Line Items]
Ownership%		50.00%
Investment in equity method affiliates		$ 2,738	2,784
Description		LNG import/export and storage facility
Atlantic Coast Pipeline
Schedule of Equity Method Investments [Line Items]
Ownership%		53.00%
Investment in equity method affiliates	[2]	$ 0
Description		Gas transmission system
Wrangler Retail Gas Holdings LLC
Schedule of Equity Method Investments [Line Items]
Ownership%	[3]	15.00%
Investment in equity method affiliates		$ 68	74
Description		Nonregulated retail energy marketing
Align RNG, LLC
Schedule of Equity Method Investments [Line Items]
Ownership%	[4]	50.00%
Investment in equity method affiliates	[4]	$ 74	25
Description	[4]	Renewable natural gas
Other Investment
Schedule of Equity Method Investments [Line Items]
Investment in equity method affiliates	[4]	$ 52	$ 51
Ownership%	[4]	various

[1] Excludes liability to Atlantic Coast Pipeline.

[2] Dominion Energy’s Consolidated Balance Sheets include a liability associated with its investment in Atlantic Coast Pipeline of $113 million and $1.1 billion at December 31, 2021 and 2020, respectively. See discussion below for additional information.

[3] Dominion Energy’s ownership interest became 15% in December 2021, following the sale of 5% of its ownership interest. See discussion below.

[4] Dominion Energy’s unfunded commitment to be made to Align RNG by the end of 2022 was $8 million and $59 million at December 31, 2021 and 2020, respectively. The commitment was fully paid in January 2022.