Variable Interest Entities (Narrative) (Detail) $ in Millions	3 Months Ended		12 Months Ended
	Mar. 31, 2020 USD ($)	Mar. 31, 2019 USD ($)	Dec. 31, 2019 USD ($) MW Generator
Virginia Electric and Power Company
Variable Interest Entity [Line Items]
Long term debt	$ 12,327		$ 12,325	[1]
Payables to affiliates	339		210	[1]
Dominion Energy Gas Holdings, LLC
Variable Interest Entity [Line Items]
Long term debt	4,817		4,821	[2]
Payables to affiliates	131		82	[2]
Variable Interest Entity, Primary Beneficiary | SBL Holdco
Variable Interest Entity [Line Items]
Securities due within one year	32		31
Long term debt	267		$ 267
Variable Interest Entity (VIE) or Potential VIE, Information Unavailability | Virginia Electric and Power Company
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 electric capacity		$ 13
Payment for electric energy		1
Variable Interest Entity, Not Primary Beneficiary | Virginia Electric and Power Company | DES
Variable Interest Entity [Line Items]
Shared services purchased	93	89
Payables to affiliates	180		$ 102
Variable Interest Entity, Not Primary Beneficiary | Dominion Energy Gas Holdings, LLC | DECGS
Variable Interest Entity [Line Items]
Shared services purchased	4	4
Variable Interest Entity, Not Primary Beneficiary | Dominion Energy Gas Holdings, LLC | DEQPS
Variable Interest Entity [Line Items]
Shared services purchased	7	8
Variable Interest Entity, Not Primary Beneficiary | Dominion Energy Gas Holdings, LLC | DECGS and DEQPS
Variable Interest Entity [Line Items]
Payables to affiliates	22		15
Variable Interest Entity, Not Primary Beneficiary | Dominion Energy Gas Holdings, LLC | DES
Variable Interest Entity [Line Items]
Shared services purchased	31	$ 28
Payables to affiliates	$ 39		$ 27

[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.