Derivatives and Hedge Accounting Activities (Volume of Derivative Activity) (Details) - 9 months ended Sep. 30, 2017 MMcf in Thousands		USD ($) MWh MMcf gal	EUR (€)
Fixed Price - Natural Gas - Current Derivative Contract
Derivative [Line Items]
Volume of derivative activity (bcf, Gal)	[1]	62
Fixed Price - Natural Gas - Current Derivative Contract | Virginia Electric and Power Company
Derivative [Line Items]
Volume of derivative activity (bcf, Gal)	[1]	28
Fixed Price - Natural Gas - Current Derivative Contract | Dominion Energy Gas Holdings, LLC
Derivative [Line Items]
Volume of derivative activity (bcf, Gal)		2
Fixed Price - Natural Gas - Non-current Derivative Contract
Derivative [Line Items]
Volume of derivative activity (bcf, Gal)	[1]	17
Fixed Price - Natural Gas - Non-current Derivative Contract | Virginia Electric and Power Company
Derivative [Line Items]
Volume of derivative activity (bcf, Gal)	[1]	6
Fixed Price - Natural Gas - Non-current Derivative Contract | Dominion Energy Gas Holdings, LLC
Derivative [Line Items]
Volume of derivative activity (bcf, Gal)		0
Basis - Natural Gas - Current Derivative Contract
Derivative [Line Items]
Volume of derivative activity (bcf, Gal)		165
Basis - Natural Gas - Current Derivative Contract | Virginia Electric and Power Company
Derivative [Line Items]
Volume of derivative activity (bcf, Gal)		85
Basis - Natural Gas - Current Derivative Contract | Dominion Energy Gas Holdings, LLC
Derivative [Line Items]
Volume of derivative activity (bcf, Gal)		2
Basis - Natural Gas - Non-current Derivative Contract
Derivative [Line Items]
Volume of derivative activity (bcf, Gal)		612
Basis - Natural Gas - Non-current Derivative Contract | Virginia Electric and Power Company
Derivative [Line Items]
Volume of derivative activity (bcf, Gal)		562
Basis - Natural Gas - Non-current Derivative Contract | Dominion Energy Gas Holdings, LLC
Derivative [Line Items]
Volume of derivative activity (bcf, Gal)		0
Fixed Price - Electricity - Current Derivative Contract
Derivative [Line Items]
Volume of electricity (MWh) | MWh		6,749,288
Fixed Price - Electricity - Current Derivative Contract | Virginia Electric and Power Company
Derivative [Line Items]
Volume of electricity (MWh) | MWh	[1]	1,426,093
Fixed Price - Electricity - Non-current Derivative Contract
Derivative [Line Items]
Volume of electricity (MWh) | MWh		902,069
Fixed Price - Electricity - Non-current Derivative Contract | Virginia Electric and Power Company
Derivative [Line Items]
Volume of electricity (MWh) | MWh	[1]	611,629
Financial Transmission Rights - Electricity- Current Derivative Contract
Derivative [Line Items]
Volume of electricity (MWh) | MWh		72,126,361
Financial Transmission Rights - Electricity- Current Derivative Contract | Virginia Electric and Power Company
Derivative [Line Items]
Volume of electricity (MWh) | MWh		65,673,158
Financial Transmission Rights - Electricity- Non-current Derivative Contract
Derivative [Line Items]
Volume of electricity (MWh) | MWh		0
Financial Transmission Rights - Electricity- Non-current Derivative Contract | Virginia Electric and Power Company
Derivative [Line Items]
Volume of electricity (MWh) | MWh		0
Liquids - Current Derivative Contract
Derivative [Line Items]
Volume of derivative activity (bcf, Gal) | gal	[2]	36,940,288
Liquids - Current Derivative Contract | Dominion Energy Gas Holdings, LLC
Derivative [Line Items]
Volume of derivative activity (bcf, Gal) | gal		30,514,288
Liquids - Non-current Derivative Contract
Derivative [Line Items]
Volume of derivative activity (bcf, Gal) | gal	[2]	0
Liquids - Non-current Derivative Contract | Dominion Energy Gas Holdings, LLC
Derivative [Line Items]
Volume of derivative activity (bcf, Gal) | gal		0
Foreign currency
Derivative [Line Items]
Interest rate / Foreign currency (US Dollars, Euros) | €	[3],[4]		€ 250,000,000
Foreign currency | Dominion Energy Gas Holdings, LLC
Derivative [Line Items]
Interest rate / Foreign currency (US Dollars, Euros) | €			€ 250,000,000
Foreign Exchange - Current Derivative Contract
Derivative [Line Items]
Interest rate / Foreign currency (US Dollars, Euros) | $	[3],[4]	$ 0
Foreign Exchange - Current Derivative Contract | Dominion Energy Gas Holdings, LLC
Derivative [Line Items]
Interest rate / Foreign currency (US Dollars, Euros) | $	[5]	0
Foreign Exchange - Non- Current Derivative Contract
Derivative [Line Items]
Interest rate / Foreign currency (US Dollars, Euros) | $	[3],[4]	280,000,000
Foreign Exchange - Non- Current Derivative Contract | Dominion Energy Gas Holdings, LLC
Derivative [Line Items]
Interest rate / Foreign currency (US Dollars, Euros) | $	[5]	280,000,000
Interest Rate - Current Derivative Contract
Derivative [Line Items]
Interest rate / Foreign currency (US Dollars, Euros) | $	[4]	1,100,000,000
Interest Rate - Current Derivative Contract | Virginia Electric and Power Company
Derivative [Line Items]
Interest rate / Foreign currency (US Dollars, Euros) | $	[6]	300,000,000
Interest Rate - Non-current Derivative Contract
Derivative [Line Items]
Interest rate / Foreign currency (US Dollars, Euros) | $	[4]	5,049,890,127
Interest Rate - Non-current Derivative Contract | Virginia Electric and Power Company
Derivative [Line Items]
Interest rate / Foreign currency (US Dollars, Euros) | $	[6]	$ 1,150,000,000

[1] Includes options.

[2] Includes NGLs and oil.

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

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

[5] Maturity is determined based on final settlement period. Euro equivalent volumes are €250,000,000

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