Derivatives and Hedge Accounting Activities (Volume of Derivative Activity) (Detail)	3 Months Ended
	Mar. 31, 2019 USD ($) MWh Bcf gal
Fixed Price - Natural Gas - Current Derivative Contract
Derivative [Line Items]
Volume of derivative activity | Bcf	78	[1]
Fixed Price - Natural Gas - Current Derivative Contract | Virginia Electric and Power Company
Derivative [Line Items]
Volume of derivative activity | Bcf	20	[1]
Fixed Price - Natural Gas - Non-current Derivative Contract
Derivative [Line Items]
Volume of derivative activity | Bcf	61	[1]
Fixed Price - Natural Gas - Non-current Derivative Contract | Virginia Electric and Power Company
Derivative [Line Items]
Volume of derivative activity | Bcf	26	[1]
Basis - Natural Gas - Current Derivative Contract
Derivative [Line Items]
Volume of derivative activity | Bcf	277
Basis - Natural Gas - Current Derivative Contract | Virginia Electric and Power Company
Derivative [Line Items]
Volume of derivative activity | Bcf	182
Basis - Natural Gas - Non-current Derivative Contract
Derivative [Line Items]
Volume of derivative activity | Bcf	547
Basis - Natural Gas - Non-current Derivative Contract | Virginia Electric and Power Company
Derivative [Line Items]
Volume of derivative activity | Bcf	473
Fixed Price - Electricity - Current Derivative Contract
Derivative [Line Items]
Volume of electricity | MWh	7,915,870
Fixed Price - Electricity - Non-current Derivative Contract
Derivative [Line Items]
Volume of electricity | MWh	1,100,600
Financial Transmission Rights - Electricity- Current Derivative Contract
Derivative [Line Items]
Volume of electricity | MWh	18,146,928
Financial Transmission Rights - Electricity- Current Derivative Contract | Virginia Electric and Power Company
Derivative [Line Items]
Volume of electricity | MWh	18,146,928
Financial Transmission Rights - Electricity- Non-current Derivative Contract
Derivative [Line Items]
Volume of electricity | MWh	0
Financial Transmission Rights - Electricity- Non-current Derivative Contract | Virginia Electric and Power Company
Derivative [Line Items]
Volume of electricity | MWh	0
NGLs - Current Derivative Contract
Derivative [Line Items]
Volume of derivative activity | gal	25,074,000
NGLs - Current Derivative Contract | Dominion Energy Gas Holdings, LLC
Derivative [Line Items]
Volume of derivative activity | gal	25,074,000
NGLs - Non-current Derivative Contract
Derivative [Line Items]
Volume of derivative activity | gal	0
NGLs - Non-current Derivative Contract | Dominion Energy Gas Holdings, LLC
Derivative [Line Items]
Volume of derivative activity | gal	0
Interest Rate - Current Derivative Contract
Derivative [Line Items]
Interest rate / Foreign currency (US Dollars, Euros)	$ 2,554,400,000	[2]
Interest Rate - Current Derivative Contract | Virginia Electric and Power Company
Derivative [Line Items]
Interest rate / Foreign currency (US Dollars, Euros)	850,000,000	[2]
Interest Rate - Current Derivative Contract | Dominion Energy Gas Holdings, LLC
Derivative [Line Items]
Interest rate / Foreign currency (US Dollars, Euros)	300,000,000	[3]
Interest Rate - Non-current Derivative Contract
Derivative [Line Items]
Interest rate / Foreign currency (US Dollars, Euros)	5,001,010,256	[2]
Interest Rate - Non-current Derivative Contract | Virginia Electric and Power Company
Derivative [Line Items]
Interest rate / Foreign currency (US Dollars, Euros)	1,200,000,000	[2]
Interest Rate - Non-current Derivative Contract | Dominion Energy Gas Holdings, LLC
Derivative [Line Items]
Interest rate / Foreign currency (US Dollars, Euros)	1,000,000,000	[3]
Foreign Exchange - Current Derivative Contract
Derivative [Line Items]
Interest rate / Foreign currency (US Dollars, Euros)	0	[2],[4]
Foreign Exchange - Current Derivative Contract | Dominion Energy Gas Holdings, LLC
Derivative [Line Items]
Interest rate / Foreign currency (US Dollars, Euros)	0	[3],[5]
Foreign Exchange - Non- Current Derivative Contract
Derivative [Line Items]
Interest rate / Foreign currency (US Dollars, Euros)	280,000,000	[2],[4]
Foreign Exchange - Non- Current Derivative Contract | Dominion Energy Gas Holdings, LLC
Derivative [Line Items]
Interest rate / Foreign currency (US Dollars, Euros)	$ 280,000,000	[3],[5]

[1] Includes options.

[2] Maturity is determined based on final settlement period.

[3] Maturity is based on final settlement period.

[4] Euro equivalent volumes are €250,000,000.

[5] Euro equivalent volumes are €250,000,000.