Regulatory Matters (Narrative) (Detail) $ in Millions		1 Months Ended									3 Months Ended		6 Months Ended
		Jul. 31, 2018 USD ($) project	Jun. 30, 2018 USD ($) kV power_station mi	May 31, 2018 USD ($) kV mi	Feb. 28, 2018 USD ($)	Oct. 31, 2017 USD ($) program	Jun. 30, 2016	Aug. 31, 2009 kV	Apr. 30, 2008	Apr. 30, 2007 kV	Jun. 30, 2018 USD ($) MMcf	Jun. 30, 2017 USD ($)	Jun. 30, 2018 USD ($) kV mi	Jun. 30, 2017 USD ($)	Dec. 31, 2017 USD ($)
Public Utilities General Disclosures [Line Items]
Regulatory assets-noncurrent			$ 2,395								$ 2,395		$ 2,395		$ 2,480	[1]
Cost of project													51	$ 280
Regulatory asset recovered through retail rates
Public Utilities General Disclosures [Line Items]
Regulatory assets-noncurrent	[2]		237								237		237		222
Virginia Regulation | Operating Segments
Public Utilities General Disclosures [Line Items]
Charge associated with legislation													215
Charge associated with legislation, after tax													160
Virginia Electric and Power Company
Public Utilities General Disclosures [Line Items]
ROE (percentage)									11.40%
Regulatory assets-noncurrent			729								729		729		810	[3]
Interim reduction in generation and distribution services on annual basis				$ 125
Cost of project													43	$ 3
Virginia Electric and Power Company | Regulatory asset recovered through retail rates
Public Utilities General Disclosures [Line Items]
Regulatory assets-noncurrent	[2]		$ 237								237		$ 237		$ 222
Virginia Electric and Power Company | Virginia Regulation
Public Utilities General Disclosures [Line Items]
Estimated recovery of fuel expenses				1,500
Proposed increase in fuel revenue				$ 222
Earnings above authorized return on equity (basis points)													0.70%
One-time bill credit, provisions for current customers													$ 200
Virginia Electric and Power Company | Virginia Regulation | Double Circuit Transmission Line Between Near Gainesville Substation And Haymarket Substation
Public Utilities General Disclosures [Line Items]
Capacity of transmission line (kV) | kV													230
Length of kV line (miles) | mi													5
Virginia Electric and Power Company | Virginia Regulation | Transmission Line Between the Chesterfield and Hopewell Substations
Public Utilities General Disclosures [Line Items]
Capacity of transmission line (kV) | kV				230
Length of kV line (miles) | mi				8
Total estimated cost of project				$ 30
Virginia Electric and Power Company | Virginia Regulation | Transmission Line Between the Chesterfield and Lakeside Substations
Public Utilities General Disclosures [Line Items]
Capacity of transmission line (kV) | kV				230
Length of kV line (miles) | mi				21
Total estimated cost of project				$ 35
Virginia Electric and Power Company | Virginia Regulation | Transmission Line Between the Landstown and Thrasher Substations
Public Utilities General Disclosures [Line Items]
Capacity of transmission line (kV) | kV			230
Length of kV line (miles) | mi			8.5
Total estimated cost of project			$ 20								20		$ 20
Virginia Electric and Power Company | Virginia Regulation | Four Separate Segments of Line # 224
Public Utilities General Disclosures [Line Items]
Capacity of transmission line (kV) | kV			230
Total estimated cost of project			$ 35								35		35
Virginia Electric and Power Company | Virginia Regulation | Operating Segments
Public Utilities General Disclosures [Line Items]
Charge associated with legislation													215
Charge associated with legislation, after tax													160
Reduction in base rate on annual basis													125
Estimated capital investment for first three years			816								816		816
Proposed operations and maintenance expenses for first three years													$ 102
Electric distribution grid transformation project duration													10 years
Proposed revenue requirement				755
Virginia Electric and Power Company | Virginia Regulation | Operating Segments | Transmission Component of Virginia Power's
Public Utilities General Disclosures [Line Items]
Proposed revenue requirement				468
Virginia Electric and Power Company | Virginia Regulation | Operating Segments | Colonial Trail West and Spring Grove 1 Solar Facilities | Subsequent Event
Public Utilities General Disclosures [Line Items]
Cost of project		$ 410
Number of solar facilities to be construct | project		2
Virginia Electric and Power Company | Virginia Regulation | Rider T1 | Operating Segments
Public Utilities General Disclosures [Line Items]
Proposed revenue requirement				287
Increase (decrease) in revenue requirement				146
Virginia Electric and Power Company | Virginia Regulation | Rider S | Operating Segments
Public Utilities General Disclosures [Line Items]
Proposed revenue requirement			220
Increase (decrease) in revenue requirement			2
Virginia Electric and Power Company | Virginia Regulation | Rider W | Operating Segments
Public Utilities General Disclosures [Line Items]
Proposed revenue requirement			107
Increase (decrease) in revenue requirement			(2)
Virginia Electric and Power Company | Virginia Regulation | Rider R | Operating Segments
Public Utilities General Disclosures [Line Items]
Proposed revenue requirement			59
Increase (decrease) in revenue requirement			(7)
Virginia Electric and Power Company | Virginia Regulation | Rider B
Public Utilities General Disclosures [Line Items]
Proposed revenue requirement					$ 54
Increase (decrease) in revenue requirement			$ 7
Number of power stations converted to biomass | power_station			3
Virginia Electric and Power Company | Virginia Regulation | Rider GV | Operating Segments
Public Utilities General Disclosures [Line Items]
Proposed revenue requirement			$ 121
Increase (decrease) in revenue requirement			39
Virginia Electric and Power Company | Virginia Regulation | Riders C1A and C2A | Operating Segments | Energy Efficiency Program
Public Utilities General Disclosures [Line Items]
Proposed revenue requirement						$ 31
Increase (decrease) in revenue requirement						$ 3
Number of new energy efficiency programs | program						1
Period for cost cap						5 years
Amount of cost recovery						$ 25
Approved revenue required				31
Virginia Electric and Power Company | Virginia Regulation | Rider BW | Operating Segments
Public Utilities General Disclosures [Line Items]
Proposed revenue requirement						132
Increase (decrease) in revenue requirement						5
Virginia Electric and Power Company | Virginia Regulation | Rider BW | Operating Segments | Subsequent Event
Public Utilities General Disclosures [Line Items]
Approved revenue required		$ 116
Virginia Electric and Power Company | Virginia Regulation | Rider US-2 | Operating Segments
Public Utilities General Disclosures [Line Items]
Proposed revenue requirement						15
Increase (decrease) in revenue requirement						$ 5
Virginia Electric and Power Company | Virginia Regulation | Rider US-2 | Operating Segments | Subsequent Event
Public Utilities General Disclosures [Line Items]
Approved revenue required		13
Virginia Electric and Power Company | Virginia Regulation | Rider US-3 | Operating Segments | Subsequent Event
Public Utilities General Disclosures [Line Items]
Proposed revenue requirement		$ 11
Virginia Electric and Power Company | Settled Litigation | Federal Energy Regulatory Commission | Order Regarding Transmission Rate Design For Allocation Of Costs Among P J M Interconnect L L C Transmission Customers | Unfavorable Regulatory Action
Public Utilities General Disclosures [Line Items]
Duration of payment under settlement agreement							10 years
Virginia Electric and Power Company | Settled Litigation | Federal Energy Regulatory Commission | Order Regarding Transmission Rate Design For Allocation Of Costs Among P J M Interconnect L L C Transmission Customers | Unfavorable Regulatory Action | Other Current Liabilities
Public Utilities General Disclosures [Line Items]
Amount of contingent liability			148								148		$ 148
Virginia Electric and Power Company | Settled Litigation | Federal Energy Regulatory Commission | Order Regarding Transmission Rate Design For Allocation Of Costs Among P J M Interconnect L L C Transmission Customers | Unfavorable Regulatory Action | Other Deferred Credits and Other Liabilities
Public Utilities General Disclosures [Line Items]
Amount of contingent liability			98								98		98
Virginia Electric and Power Company | Settled Litigation | Federal Energy Regulatory Commission | Order Regarding Transmission Rate Design For Allocation Of Costs Among P J M Interconnect L L C Transmission Customers | Unfavorable Regulatory Action | Regulatory asset recovered through retail rates
Public Utilities General Disclosures [Line Items]
Regulatory assets-noncurrent			$ 237								237		$ 237
Virginia Electric and Power Company | Minimum
Public Utilities General Disclosures [Line Items]
Facility operating capacity (kV) | kV										500
Virginia Electric and Power Company | Minimum | Judicial Ruling [Member]
Public Utilities General Disclosures [Line Items]
Facility operating capacity (kV) | kV								500
DETI | Federal Energy Regulatory Commission | Other operations and maintenance | Preliminary recommendation one
Public Utilities General Disclosures [Line Items]
Audit compliance charge recognized in connection with preliminary recommendation												$ 15
Audit compliance after-tax charge recognized in connection with preliminary recommendation												$ 9
DETI | Federal Energy Regulatory Commission | Other operations and maintenance | Other preliminary recommendation
Public Utilities General Disclosures [Line Items]
Audit compliance charge recognized in connection with preliminary recommendation											129
Audit compliance after-tax charge recognized in connection with preliminary recommendation											$ 94
Questar Gas | Cost-of-service impact of 2017 Tax Reform Act
Public Utilities General Disclosures [Line Items]
Reduction in regulatory liabilities				15
Questar Gas | Utah and Wyoming Regulation
Public Utilities General Disclosures [Line Items]
LNG peaking storage facility, liquefaction rate per day | MMcf											8.2
Number of days to make prudency determination											180 days
Proposed cost increase (decrease) amount				86
East Ohio | Ohio Regulation | Percentage of Income Payment Plan Rider
Public Utilities General Disclosures [Line Items]
Refund of over-recovery of accumulated arrearages				4
Recovery of projected deferred program costs				10
East Ohio | Ohio Regulation | UEX Rider
Public Utilities General Disclosures [Line Items]
Elimination of over-recovered balance of accumulated bad debt expense				11
Prospective bad debt expense recovered				16
Hope Gas, Inc. | West Virginia Regulation | Pipeline Infrastructure Replacement Program
Public Utilities General Disclosures [Line Items]
Amount of cost recovery				8
Projected capital investment, current year				31
Projected capital investment, next year				36
Projected capital investment, previous year				$ 28

[1] Dominion Energy’s Consolidated Balance Sheet at December 31, 2017 has been derived from the audited Consolidated Balance Sheet at that date.

[2] Reflects amounts related to the PJM transmission cost allocation matter. See Note 13 for more information.

[3] Virginia Power’s Consolidated Balance Sheet at December 31, 2017 has been derived from the audited Consolidated Balance Sheet at that date.