Operating Revenue (Schedule of Aggregate Amount of Transaction Price Allocated To Fixed-price Performance Obligations That Unsatisfied At End of Reporting Period And Expected To be Recognized) (Detail) $ in Millions	Dec. 31, 2018 USD ($)
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date: 2019-01-01
Revenues From Contract With Customer [Line Items]
Revenue, expected to be recognized on multi-year contracts	$ 1,643
Revenue, expected to be recognized on multi-year contracts, period	1 year
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date: 2019-01-01 | Virginia Electric and Power Company
Revenues From Contract With Customer [Line Items]
Revenue, expected to be recognized on multi-year contracts	$ 21
Revenue, expected to be recognized on multi-year contracts, period	1 year
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date: 2019-01-01 | Dominion Energy Gas Holdings, LLC
Revenues From Contract With Customer [Line Items]
Revenue, expected to be recognized on multi-year contracts	$ 600
Revenue, expected to be recognized on multi-year contracts, period	1 year
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date: 2020-01-01
Revenues From Contract With Customer [Line Items]
Revenue, expected to be recognized on multi-year contracts	$ 1,563
Revenue, expected to be recognized on multi-year contracts, period	1 year
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date: 2020-01-01 | Virginia Electric and Power Company
Revenues From Contract With Customer [Line Items]
Revenue, expected to be recognized on multi-year contracts	$ 3
Revenue, expected to be recognized on multi-year contracts, period	1 year
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date: 2020-01-01 | Dominion Energy Gas Holdings, LLC
Revenues From Contract With Customer [Line Items]
Revenue, expected to be recognized on multi-year contracts	$ 560
Revenue, expected to be recognized on multi-year contracts, period	1 year
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date: 2021-01-01
Revenues From Contract With Customer [Line Items]
Revenue, expected to be recognized on multi-year contracts	$ 1,448
Revenue, expected to be recognized on multi-year contracts, period	1 year
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date: 2021-01-01 | Virginia Electric and Power Company
Revenues From Contract With Customer [Line Items]
Revenue, expected to be recognized on multi-year contracts	$ 1
Revenue, expected to be recognized on multi-year contracts, period	1 year
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date: 2021-01-01 | Dominion Energy Gas Holdings, LLC
Revenues From Contract With Customer [Line Items]
Revenue, expected to be recognized on multi-year contracts	$ 475
Revenue, expected to be recognized on multi-year contracts, period	1 year
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date: 2022-01-01
Revenues From Contract With Customer [Line Items]
Revenue, expected to be recognized on multi-year contracts	$ 1,319
Revenue, expected to be recognized on multi-year contracts, period	1 year
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date: 2022-01-01 | Virginia Electric and Power Company
Revenues From Contract With Customer [Line Items]
Revenue, expected to be recognized on multi-year contracts	$ 0
Revenue, expected to be recognized on multi-year contracts, period	1 year
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date: 2022-01-01 | Dominion Energy Gas Holdings, LLC
Revenues From Contract With Customer [Line Items]
Revenue, expected to be recognized on multi-year contracts	$ 384
Revenue, expected to be recognized on multi-year contracts, period	1 year
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date: 2023-01-01
Revenues From Contract With Customer [Line Items]
Revenue, expected to be recognized on multi-year contracts	$ 1,154
Revenue, expected to be recognized on multi-year contracts, period	1 year
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date: 2023-01-01 | Virginia Electric and Power Company
Revenues From Contract With Customer [Line Items]
Revenue, expected to be recognized on multi-year contracts	$ 0
Revenue, expected to be recognized on multi-year contracts, period	1 year
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date: 2023-01-01 | Dominion Energy Gas Holdings, LLC
Revenues From Contract With Customer [Line Items]
Revenue, expected to be recognized on multi-year contracts	$ 268
Revenue, expected to be recognized on multi-year contracts, period	1 year
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date: 2024-01-01
Revenues From Contract With Customer [Line Items]
Revenue, expected to be recognized on multi-year contracts	$ 13,693
Revenue, expected to be recognized on multi-year contracts, period	1 year
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date: 2024-01-01 | Virginia Electric and Power Company
Revenues From Contract With Customer [Line Items]
Revenue, expected to be recognized on multi-year contracts	$ 0
Revenue, expected to be recognized on multi-year contracts, period	1 year
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date: 2024-01-01 | Dominion Energy Gas Holdings, LLC
Revenues From Contract With Customer [Line Items]
Revenue, expected to be recognized on multi-year contracts	$ 1,612
Revenue, expected to be recognized on multi-year contracts, period	1 year
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date: (nil) [Member]
Revenues From Contract With Customer [Line Items]
Revenue, expected to be recognized on multi-year contracts	$ 20,820
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date: (nil) [Member] | Virginia Electric and Power Company
Revenues From Contract With Customer [Line Items]
Revenue, expected to be recognized on multi-year contracts	25
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date: (nil) [Member] | Dominion Energy Gas Holdings, LLC
Revenues From Contract With Customer [Line Items]
Revenue, expected to be recognized on multi-year contracts	$ 3,899