Variable Interest Entities (Narrative) (Detail) $ in Millions	1 Months Ended	3 Months Ended		6 Months Ended		12 Months Ended
	May 31, 2019 USD ($)	Jun. 30, 2020 USD ($)	Jun. 30, 2019 USD ($)	Jun. 30, 2020 USD ($)	Jun. 30, 2019 USD ($)	Dec. 31, 2019 USD ($) MW Generator
Virginia Electric and Power Company
Variable Interest Entity [Line Items]
Long term debt		$ 12,328		$ 12,328		$ 12,325	[1]
Payables to affiliates		406		406		$ 210	[1]
Virginia Electric and Power Company | Variable Interest Entity (VIE) or Potential VIE, Information Unavailability
Variable Interest Entity [Line Items]
Long term capacity contract non utility generators (generators) | Generator						1
Aggregate generation capacity from long-term power and capacity contracts (MW) | MW						218
Payment for contract termination	$ 135		$ 135		$ 135
Payment for contract termination after tax			100		100
Payment for electric capacity					13
Payment for electric energy					1
Virginia Electric and Power Company | Variable Interest Entity, Not Primary Beneficiary | DES
Variable Interest Entity [Line Items]
Shared services purchased		86	129	179	218
Payables to affiliates		92		92		$ 102
Dominion Energy Gas Holdings, LLC
Variable Interest Entity [Line Items]
Long term debt		4,324		4,324		4,821	[2]
Payables to affiliates		159		159		82	[2]
Dominion Energy Gas Holdings, LLC | Variable Interest Entity, Not Primary Beneficiary | DECGS
Variable Interest Entity [Line Items]
Shared services purchased		3	5	7	9
Dominion Energy Gas Holdings, LLC | Variable Interest Entity, Not Primary Beneficiary | DEQPS
Variable Interest Entity [Line Items]
Shared services purchased		7	11	14	20
Dominion Energy Gas Holdings, LLC | Variable Interest Entity, Not Primary Beneficiary | DECGS and DEQPS
Variable Interest Entity [Line Items]
Payables to affiliates		18		18		15
Dominion Energy Gas Holdings, LLC | Variable Interest Entity, Not Primary Beneficiary | DES
Variable Interest Entity [Line Items]
Shared services purchased		27	$ 39	58	$ 67
Payables to affiliates		38		38		27
Variable Interest Entity, Primary Beneficiary | SBL Holdco
Variable Interest Entity [Line Items]
Securities due within one year		32		32		31
Long term debt		$ 258		$ 258		$ 267

[1] Virginia Power’s Consolidated Balance Sheet at December 31, 2019 has been derived from the audited Consolidated Balance Sheet at that date.

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