Regulatory Matters (Narrative) (Detail) customer in Millions		1 Months Ended							3 Months Ended	12 Months Ended
		Apr. 30, 2018 USD ($) customer	Feb. 28, 2018 USD ($)	Jun. 30, 2016 USD ($)	Apr. 30, 2016	Aug. 31, 2009 kV	Apr. 30, 2008	Apr. 30, 2007 kV	Mar. 31, 2018 USD ($) kV power_station mi	Dec. 31, 2017 USD ($)
Public Utilities General Disclosures [Line Items]
Regulatory assets-noncurrent									$ 2,698,000,000	$ 2,480,000,000	[1]
Regulatory asset recovered through retail rates
Public Utilities General Disclosures [Line Items]
Regulatory assets-noncurrent	[2]								229,000,000	222,000,000
Virginia Regulation | Operating Segments
Public Utilities General Disclosures [Line Items]
Charge associated with legislation									215,000,000
Charge associated with legislation, after tax									160,000,000
Virginia Electric and Power Company
Public Utilities General Disclosures [Line Items]
ROE (percentage)							11.40%
Regulatory assets-noncurrent									1,009,000,000	810,000,000	[3]
Virginia Electric and Power Company | Regulatory asset recovered through retail rates
Public Utilities General Disclosures [Line Items]
Regulatory assets-noncurrent	[2]								$ 229,000,000	222,000,000
Virginia Electric and Power Company | Virginia Regulation
Public Utilities General Disclosures [Line Items]
Earnings above authorized return on equity (basis points)									0.70%
One-time bill credit, provisions for current customers									$ 200,000,000
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 | Operating Segments
Public Utilities General Disclosures [Line Items]
Charge associated with legislation									$ 215,000,000
Charge associated with legislation, after tax									160,000,000
Reduction in base rate on annual basis									$ 125,000,000
Virginia Electric and Power Company | Virginia Regulation | Rider B
Public Utilities General Disclosures [Line Items]
ROE (percentage)									11.20%
Number of power stations converted to biomass | power_station									3
Approved revenue required			$ 47,000,000
Proposed revenue requirement									$ 42,000,000
Virginia Electric and Power Company | Virginia Regulation | Rider U
Public Utilities General Disclosures [Line Items]
Approved revenue required									73,000,000
Phase of conversions									179,000,000
Phase of conversions not previously approved for recovery									65,000,000
Virginia Electric and Power Company | Settled Litigation | Federal Energy Regulatory Commission | Order Regarding Transmission Rate Design for Allocation of Costs among PJM Interconnect LLC Transmission Customers | Unfavorable Regulatory Action
Public Utilities General Disclosures [Line Items]
Amount required to pay under settlement agreement (in excess of $200 million)				$ 200,000,000
Duration of payment under settlement agreement				10 years
Amount of contingent liability									239,000,000
Virginia Electric and Power Company | Settled Litigation | Federal Energy Regulatory Commission | Order Regarding Transmission Rate Design for Allocation of Costs among PJM Interconnect LLC Transmission Customers | Unfavorable Regulatory Action | Regulatory asset recovered through retail rates
Public Utilities General Disclosures [Line Items]
Regulatory assets-noncurrent									229,000,000
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
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										15,000,000
Audit compliance after-tax charge recognized in connection with preliminary recommendation										9,000,000
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										0
Audit compliance after-tax charge recognized in connection with preliminary recommendation										0
East Ohio | Ohio Regulation | Pipeline Infrastructure Replacement Program
Public Utilities General Disclosures [Line Items]
Proposed revenue requirement									165,000,000
Percentage replacement of pipeline system					25.00%
Total estimated cost									$ 1,400,000,000	$ 204,000,000
East Ohio | Ohio Regulation | Automated Meter Reading Program
Public Utilities General Disclosures [Line Items]
Proposed revenue requirement		$ 5,000,000
Number of customers with automated meter reading technology | customer		1.2

[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.