Variable Interest Entities (Narrative) (Detail) $ in Millions	3 Months Ended
	Mar. 31, 2019 USD ($) MW Generator	Mar. 31, 2018 USD ($)	Dec. 31, 2018 USD ($)
Virginia Electric and Power Company
Variable Interest Entity [Line Items]
Securities due within one year	$ 392		$ 350	[1]
Long term debt	11,288		11,321	[1]
Payables to affiliates	104		209	[1]
Dominion Energy Gas Holdings, LLC
Variable Interest Entity [Line Items]
Securities due within one year	451		449	[2]
Long term debt	3,607		3,609	[2]
Payables to affiliates	56		65	[2]
Variable Interest Entity, Primary Beneficiary | SBL Holdco
Variable Interest Entity [Line Items]
Securities due within one year	29		31
Long term debt	$ 301		299
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
Remaining purchase commitments	$ 159
Payment for electric capacity	13	$ 13
Payment for electric energy	1	5
Variable Interest Entity, Not Primary Beneficiary | Virginia Electric and Power Company | DES
Variable Interest Entity [Line Items]
Shared services purchased	89	89
Payables to affiliates	22		107
Variable Interest Entity, Not Primary Beneficiary | Dominion Energy Gas Holdings, LLC | DES
Variable Interest Entity [Line Items]
Shared services purchased	35	$ 32
Payables to affiliates	$ 11		$ 46

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

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