Commitments and Contingencies (Guarantees, Surety Bonds and Letters of Credit) (Detail) - USD ($)		1 Months Ended	6 Months Ended
		Oct. 31, 2017	Jun. 30, 2018
Guarantee Obligations [Line Items]
Maximum Exposure	[1]		$ 5,455,000,000
Commodity Transactions
Guarantee Obligations [Line Items]
Maximum Exposure	[2]		2,142,000,000
Nuclear Obligations
Guarantee Obligations [Line Items]
Maximum Exposure	[3]		200,000,000
Cove Point
Guarantee Obligations [Line Items]
Maximum Exposure	[4]		1,900,000,000
Financial Guarantee [Member] | Equity Method Investee [Member]
Guarantee Obligations [Line Items]
Maximum Exposure			48,000,000
Financial Guarantee [Member] | Affiliated Entity
Guarantee Obligations [Line Items]
Maximum Exposure			10,000,000
Financial Guarantee [Member] | Affiliated Entity | Minimum
Guarantee Obligations [Line Items]
Maximum annual future contributions			4,000,000
Financial Guarantee [Member] | Affiliated Entity | Maximum
Guarantee Obligations [Line Items]
Maximum annual future contributions			6,000,000
Financial Guarantee [Member] | Atlantic Coast Pipeline | Revolving Credit Facility
Guarantee Obligations [Line Items]
Facility Limit		$ 3,400,000,000
Revolving credit facility stated maturity date		Oct. 31, 2021
Maximum potential loss exposure, limited guarantee percentage		48.00%
Guarantee liability			30,000,000
Guarantee recorded amount			877,000,000
Solar
Guarantee Obligations [Line Items]
Maximum Exposure	[5]		636,000,000
Other
Guarantee Obligations [Line Items]
Maximum Exposure	[6]		577,000,000
Surety Bond [Member]
Guarantee Obligations [Line Items]
Maximum Exposure			165,000,000
Surety Bond [Member] | Virginia Electric and Power Company
Guarantee Obligations [Line Items]
Maximum Exposure			70,000,000
Surety Bond [Member] | Dominion Energy Gas Holdings, LLC
Guarantee Obligations [Line Items]
Maximum Exposure			24,000,000
Financial Standby Letter of Credit [Member]
Guarantee Obligations [Line Items]
Maximum Exposure			$ 72,000,000

[1] Excludes Dominion Energy's guarantee for the construction of a new corporate office property as discussed in Note 22 to the Consolidated Financial Statements in the Companies’ Annual Report on Form 10-K for the year ended December 31, 2017, as updated in Current Report on Form 8-K, filed June 6, 2018.

[2] Guarantees related to commodity commitments of certain subsidiaries. These guarantees were provided to counterparties in order to facilitate physical and financial transaction-related commodities and services.

[3] Guarantees related to certain DGI subsidiaries regarding all aspects of running a nuclear facility.

[4] Guarantees related to Cove Point, in support of terminal services, transportation and construction.

[5] Includes guarantees to facilitate the development of solar projects. Also includes guarantees entered into by DGI on behalf of certain subsidiaries to facilitate the acquisition and development of solar projects.

[6] Guarantees related to other miscellaneous contractual obligations such as leases, environmental obligations, construction projects and insurance programs. Due to the uncertainty of workers’ compensation claims, the parental guarantee has no stated limit. Also included are guarantees related to certain DGI subsidiaries’ obligations for equity capital contributions and energy generation associated with Fowler Ridge and NedPower. As of June 30, 2018, Dominion Energy's maximum remaining cumulative exposure under these equity funding agreements is $10 million through 2019 and its maximum annual future contributions could range from approximately $4 million to $6 million.