Investments (Narrative) (Detail) $ in Millions		1 Months Ended		3 Months Ended		12 Months Ended
		Sep. 30, 2018 USD ($)	Sep. 30, 2014 mi Member	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Feb. 25, 2020 USD ($)
Schedule of Equity Method Investments [Line Items]
Equity in earnings on investments						$ 168	$ 197	$ 14
Distributions received from investment						112	209	419
Carrying amount of investment that exceeded share of underlying equity				$ 161		110	161
Equity method investment goodwill				49		159	49
Equity in earnings on investments						168	197	(18)
Length of natural gas pipeline (in miles) | mi			600
Other receivables	[1]			331		367	331
Contributions to equity method affiliates						209	428	370
Impairment charge						1,535	403	15
Liabilities, other deferred credits and other liabilities				$ 17,075		26,027	17,075
Income tax expense						351	$ 580	(30)
Cost to acquire equity method investments									$ 175
Blue Racer
Schedule of Equity Method Investments [Line Items]
Ownership percentage				50.00%			50.00%
Additional consideration including interest received in connection with sale						151
Wrangler Retail Gas Holdings L L C
Schedule of Equity Method Investments [Line Items]
Amount of gain from sale						$ 147
Ownership interest percentage of limited partner interests						20.00%
Limited partnership interest sale transaction, proceeds received						$ 301
Goodwill write-off						73
Income tax expense						82
Residential contract asset						41
Intial Fair value						75
Catalyst Old River Hydroelectric Limited Partnership
Schedule of Equity Method Investments [Line Items]
Ownership interest percentage of limited partner interests		25.00%
Finite Lived Equity Method Investment Basis Difference
Schedule of Equity Method Investments [Line Items]
Carrying amount of investment that exceeded share of underlying equity				$ 146	$ 15		$ 146	15
Dominion Energy Gas Holdings, LLC
Schedule of Equity Method Investments [Line Items]
Equity in earnings on investments						43	54	47
Other receivables	[2]			18		26	18
Impairment charge				219		13	163	15
Liabilities, other deferred credits and other liabilities				2,213		2,277	2,213
Income tax expense						101	124	(65)
Dominion Energy Gas Holdings, LLC | Partnership Interest
Schedule of Equity Method Investments [Line Items]
Distributions received from investment						74	64	55
Carrying amount of investment that exceeded share of underlying equity				146			146
Equity in earnings on investments						43	54	47
Trading Securities
Schedule of Equity Method Investments [Line Items]
Rabbi trust securities				111		120	111
Atlantic Coast Pipeline
Schedule of Equity Method Investments [Line Items]
Distributions received from investment							36	270
Contributions to equity method affiliates						$ 186	414	310
Ownership percentage						48.00%
Atlantic Coast Pipeline | Dominion Energy Gas Holdings, LLC
Schedule of Equity Method Investments [Line Items]
Ownership percentage									53.00%
Ownership percentage acquired									5.00%
Atlantic Coast Pipeline | DETI
Schedule of Equity Method Investments [Line Items]
Revenue						$ 103	203	129
Other receivables				$ 13		7	$ 13
Atlantic Coast Pipeline | Previous Maximum
Schedule of Equity Method Investments [Line Items]
Project cost estimates						$ 8
Atlantic Coast Pipeline | Pipelines | Jointly Owned Natural Gas Pipeline | Distribution
Schedule of Equity Method Investments [Line Items]
Ownership interest (percentage)				48.00%			48.00%
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%			47.00%
Atlantic Coast Pipeline | Pipelines | Jointly Owned Natural Gas Pipeline | Distribution | Southern Company Gas
Schedule of Equity Method Investments [Line Items]
Ownership interest (percentage)				5.00%			5.00%
Blue Racer
Schedule of Equity Method Investments [Line Items]
Amount of gain from sale							$ 546
Amount of after tax gain from sale							390
Up-front cash consideration							1,050
Additional deferred consideration, subject to increase for interest cost effective payable upon purchaser's availability of cash							150
Aggregate amount of contingent consideration, maximum				$ 300			300
NedPower Mount Storm LLC
Schedule of Equity Method Investments [Line Items]
Liabilities, other deferred credits and other liabilities				1	17		1	$ 17
NedPower Mount Storm LLC | Property, Plant and Equipment
Schedule of Equity Method Investments [Line Items]
Impairment charge					126
Impairment charge, after tax					$ 76
Fowler I Holdings LLC
Schedule of Equity Method Investments [Line Items]
Impairment charge				32
Impairment charge, after tax				20
Fair value of investment				$ 81			$ 81
Ownership percentage						50.00%
Catalyst Old River Hydroelectric Limited Partnership
Schedule of Equity Method Investments [Line Items]
Limited partnership interest sale transaction, proceeds received		$ 91
Catalyst Old River Hydroelectric Limited Partnership | Other Income
Schedule of Equity Method Investments [Line Items]
Amount of gain from sale		87
Amount of after tax gain from sale		$ 63
Iroquois
Schedule of Equity Method Investments [Line Items]
Ownership percentage						50.00%
Iroquois | Dominion Energy Gas Holdings, LLC
Schedule of Equity Method Investments [Line Items]
Ownership percentage						50.00%
Iroquois | Oil and Gas Properties
Schedule of Equity Method Investments [Line Items]
Ownership percentage				100.00%			100.00%
White River Hub LLC | Oil and Gas Properties
Schedule of Equity Method Investments [Line Items]
Ownership percentage				100.00%			100.00%
Pivotal LNG | JAX LNG LLC
Schedule of Equity Method Investments [Line Items]
Percentage of interest held									50.00%
Pivotal LNG | Dominion Energy Gas Holdings, LLC
Schedule of Equity Method Investments [Line Items]
Ownership percentage acquired									100.00%

[1] See Note 9 for amounts attributable to related parties.

[2] See Note 25 for amounts attributable to related parties.