Investments (Investments Under Equity Method of Accounting) (Detail) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2020		Dec. 31, 2019
Schedule of Equity Method Investments [Line Items]
Investment in equity method affiliates		$ 2,934	[1]	$ 1,334
Cove Point
Schedule of Equity Method Investments [Line Items]
Ownership%	[2]	50.00%
Investment in equity method affiliates		$ 2,784		0
Description		LNG import/export and storage facility
Atlantic Coast Pipeline
Schedule of Equity Method Investments [Line Items]
Ownership%	[3]	53.00%
Investment in equity method affiliates		$ 0	[4]	1,123
Description		Gas transmission system
Wrangler Retail Gas Holdings LLC
Schedule of Equity Method Investments [Line Items]
Ownership%		20.00%
Investment in equity method affiliates		$ 74		77
Description		Nonregulated retail energy marketing
Fowler Ridge
Schedule of Equity Method Investments [Line Items]
Ownership%	[5]	50.00%
Investment in equity method affiliates		$ 0		74
Description		Wind-powered nonregulated generation facility
Other Investment
Schedule of Equity Method Investments [Line Items]
Investment in equity method affiliates	[6]	$ 76		$ 60
Ownership%	[6]	various

[1] Excludes liability to Atlantic Coast Pipeline.

[2] Effective November 2020, following the completion of the GT&S Transaction, Dominion Energy began accounting for its 50% noncontrolling interest in Cove Point as an equity method investment.  See discussion below and Note 3 for additional information.

[3] Dominion Energy owned 53% and 48% of Atlantic Coast Pipeline at December 31, 2020 and 2019, respectively. See discussion below for additional information.

[4] Dominion Energy’s Consolidated Balance Sheet at December 31, 2020 includes a $1.1 billion liability associated with its investment in Atlantic Coast Pipeline. See discussion below for additional information.

[5] Dominion Energy sold its 50% noncontrolling interest in Fowler Ridge in September 2020.  See discussion below for additional information.

[6] Dominion Energy has an $59 million unfunded commitment to be made to Align RNG by the end of 2022.