Investments (Narrative) (Detail) $ in Millions		1 Months Ended	3 Months Ended				12 Months Ended
		Sep. 30, 2014 member mi	Mar. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)		Mar. 31, 2018 USD ($)	Dec. 31, 2021 USD ($)	Dec. 31, 2018 USD ($)
Schedule of Equity Method Investments [Line Items]
Contributions to equity method affiliates			$ 69			$ 87
Investment in equity method affiliates			1,433	$ 1,278	[1]			$ 1,278	[1]
Other receivables	[2]		203	331	[1]			$ 331	[1]
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%
Dominion Energy Gas Holdings, LLC
Schedule of Equity Method Investments [Line Items]
Other receivables	[3]		17	17	[4]			$ 17	[4]
Equity in earnings on investments			6			9
Dominion Energy Gas Holdings, LLC | Partnership Interest
Schedule of Equity Method Investments [Line Items]
Investment in equity method affiliates			90	91				91
Equity in earnings on investments			6			9
Distributions received from investment			7			7
Carrying amount of investment that exceeded share of underlying equity			8	8				8
Atlantic Coast Pipeline
Schedule of Equity Method Investments [Line Items]
Contributions to equity method affiliates			95			78
Atlantic Coast Pipeline | Previous Minimum
Schedule of Equity Method Investments [Line Items]
Project cost estimates				6,000
Atlantic Coast Pipeline | Previous Maximum
Schedule of Equity Method Investments [Line Items]
Project cost estimates				6,500
Atlantic Coast Pipeline | Current Minimum
Schedule of Equity Method Investments [Line Items]
Project cost estimates				7,000
Atlantic Coast Pipeline | Current Maximum
Schedule of Equity Method Investments [Line Items]
Project cost estimates				7,500
Atlantic Coast Pipeline | Scenario Forecast
Schedule of Equity Method Investments [Line Items]
Project cost estimates increase							$ 250
Atlantic Coast Pipeline | Minimum | Scenario Forecast
Schedule of Equity Method Investments [Line Items]
Project cost estimates							7,250
Atlantic Coast Pipeline | Maximum [Member] | Scenario Forecast
Schedule of Equity Method Investments [Line Items]
Project cost estimates							$ 7,750
Atlantic Coast Pipeline | DETI
Schedule of Equity Method Investments [Line Items]
Revenue			31			$ 46
Other receivables			11	13				13
Atlantic Coast Pipeline | Current Liabilities
Schedule of Equity Method Investments [Line Items]
Investment in equity method affiliates			$ 32
Atlantic Coast Pipeline | Pipelines | Jointly Owned Natural Gas Pipeline | Distribution
Schedule of Equity Method Investments [Line Items]
Ownership interest (percentage)			48.00%
Length of natural gas pipeline (in miles) | mi		600
Number of members | member		3
Duration of contract		20 years
Atlantic Coast Pipeline | Pipelines | Jointly Owned Natural Gas Pipeline | Distribution | Duke Energy
Schedule of Equity Method Investments [Line Items]
Ownership interest (percentage)			47.00%
Atlantic Coast Pipeline | Pipelines | Jointly Owned Natural Gas Pipeline | Distribution | Southern Company Gas [Member]
Schedule of Equity Method Investments [Line Items]
Ownership interest (percentage)			5.00%
Trading Securities
Schedule of Equity Method Investments [Line Items]
Rabbi trust securities			$ 112	$ 111				$ 111

[1] Dominion Energy’s Consolidated Balance Sheet at December 31, 2018 has been derived from the audited Consolidated Balance Sheet at that date.

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

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

[4] Dominion Energy Gas’ Consolidated Balance Sheet at December 31, 2018 has been derived from the audited Consolidated Balance Sheet at that date.