Investments (Narrative) (Detail) $ in Millions		1 Months Ended	3 Months Ended		12 Months Ended
		Sep. 30, 2014 mi	Mar. 31, 2020 USD ($)	Mar. 31, 2019 USD ($)	Dec. 31, 2018	Dec. 31, 2019 USD ($)
Schedule of Equity Method Investments [Line Items]
Cost to acquire equity method investments			$ 184
Contributions to equity method affiliates			178
Other payables	[1]		1,414			$ 1,827	[2]
Investment in equity method affiliates			1,886			1,646	[3]
Revenue			4,323	$ 3,631
Other receivables	[4]		248			367	[3]
Dominion Energy Gas Holdings, LLC
Schedule of Equity Method Investments [Line Items]
Other payables	[5]		190			161	[6]
Equity in earnings on investments			15	13
Investment in equity method affiliates			312			312	[6]
Revenue			555	565
Other receivables	[5]		33			26	[6]
Dominion Energy Gas Holdings, LLC | Partnership Interest
Schedule of Equity Method Investments [Line Items]
Equity in earnings on investments			15	13
Distributions received from investment			15	15
Investment in equity method affiliates			312			312
Carrying amount of investment that exceeded share of underlying equity			$ 146			146
Pivotal LNG | Dominion Energy Gas Holdings, LLC
Schedule of Equity Method Investments [Line Items]
Ownership percentage acquired			100.00%
Atlantic Coast Pipeline
Schedule of Equity Method Investments [Line Items]
Contributions to equity method affiliates			$ 16	95
Project cost estimates			$ 8,000
Atlantic Coast Pipeline | Dominion Energy Gas Holdings, LLC
Schedule of Equity Method Investments [Line Items]
Ownership percentage acquired			5.00%
Percentage ownership in total units			53.00%
Atlantic Coast Pipeline | DETI
Schedule of Equity Method Investments [Line Items]
Other payables			$ 5			7
Revenue			20	31
Other receivables			$ 8			7
Atlantic Coast Pipeline | Pipelines | Jointly Owned Natural Gas Pipeline | Distribution
Schedule of Equity Method Investments [Line Items]
Length of natural gas pipeline (in miles) | mi		600
Duration of contract		20 years
JAX LNG LLC | Pivotal LNG
Schedule of Equity Method Investments [Line Items]
Percentage of interest held			50.00%
Blue Racer
Schedule of Equity Method Investments [Line Items]
Additional consideration including interest received in connection with sale				$ 151
Ownership interest percentage of limited partner interests					50.00%
Trading Securities
Schedule of Equity Method Investments [Line Items]
Rabbi trust securities			$ 116			$ 120

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

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

[5] See Note 19 for amounts attributable to related parties.

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