Significant Financing Transactions (Commercial Paper, Bank Loans and Letters of Credit Outstanding) (Details) - USD ($)		Sep. 30, 2017	May 31, 2017	Mar. 31, 2017
Line of Credit Facility [Line Items]
Facility Limit		$ 5,500,000,000
Outstanding Commercial Paper		3,060,000,000
Outstanding Letters of Credit		73,000,000
Facility Capacity Available		2,367,000,000
Virginia Electric and Power Company
Line of Credit Facility [Line Items]
Facility Limit	[1]	5,500,000,000
Outstanding Commercial Paper		320,000,000
Outstanding Letters of Credit		1,000,000
Dominion Energy Gas Holdings, LLC
Line of Credit Facility [Line Items]
Facility Limit	[2]	1,500,000,000
Outstanding Commercial Paper		620,000,000
Outstanding Letters of Credit		0
Credit Facility 5 Billion
Line of Credit Facility [Line Items]
Facility Limit	[3]	5,000,000,000
Outstanding Commercial Paper	[3]	3,060,000,000
Outstanding Letters of Credit	[3]	0
Facility Capacity Available	[3]	1,940,000,000
Credit Facility 5 Billion | Virginia Electric and Power Company
Line of Credit Facility [Line Items]
Facility Limit	[1]	5,000,000,000
Outstanding Commercial Paper	[1]	320,000,000
Outstanding Letters of Credit	[1]	0
Credit Facility 500 Million
Line of Credit Facility [Line Items]
Facility Limit	[3]	500,000,000
Outstanding Commercial Paper	[3]	0
Outstanding Letters of Credit	[3]	73,000,000
Facility Capacity Available	[3]	427,000,000
Credit Facility 500 Million | Virginia Electric and Power Company
Line of Credit Facility [Line Items]
Facility Limit	[1]	500,000,000
Outstanding Commercial Paper	[1]	0
Outstanding Letters of Credit	[1]	1,000,000
Credit Facility 500 Million | Dominion Energy Gas Holdings, LLC
Line of Credit Facility [Line Items]
Facility Limit	[2]	500,000,000
Outstanding Commercial Paper	[2]	0
Outstanding Letters of Credit	[2]	0
Joint Revolving Credit Facility 5 Billion and Joint Revolving Credit Facility 500 Million | Virginia Electric and Power Company
Line of Credit Facility [Line Items]
Facility Limit			$ 1,500,000,000	$ 2,000,000,000
Joint Revolving Credit Facility 5 Billion and Joint Revolving Credit Facility 500 Million | Letter of Credit
Line of Credit Facility [Line Items]
Facility Limit		2,000,000,000
Joint Revolving Credit Facility 5 Billion and Joint Revolving Credit Facility 500 Million | Letter of Credit | Virginia Electric and Power Company
Line of Credit Facility [Line Items]
Facility Limit		2,000,000,000
Credit Facility 1 Billion | Dominion Energy Gas Holdings, LLC
Line of Credit Facility [Line Items]
Facility Limit	[2]	1,000,000,000
Outstanding Commercial Paper	[2]	620,000,000
Outstanding Letters of Credit	[2]	0
Joint Revolving Credit Facility 1 Billion and Joint Revolving Credit Facility 500 Million | Dominion Energy Gas Holdings, LLC
Line of Credit Facility [Line Items]
Facility Limit		1,500,000,000
Joint Revolving Credit Facility 1 Billion and Joint Revolving Credit Facility 500 Million | Letter of Credit | Dominion Energy Gas Holdings, LLC
Line of Credit Facility [Line Items]
Facility Limit		$ 1,500,000,000
Joint Revolving Credit Facility 1 Billion and Joint Revolving Credit Facility 500 Million | Line of Credit | Dominion Energy Gas Holdings, LLC
Line of Credit Facility [Line Items]
Facility Limit			$ 750,000,000	$ 500,000,000

[1] The full amount of the facilities is available to Virginia Power, less any amounts outstanding to co-borrowers Dominion Energy, Dominion Energy Gas and Questar Gas. Sub-limits for Virginia Power are set within the facility limit but can be changed at the option of the Companies multiple times per year. In May 2017, the aggregate sub-limit for Virginia Power was decreased from $2.0 billion to $1.5 billion. If Virginia Power has liquidity needs in excess of its sub-limit, the sub-limit may be changed or such needs may be satisfied through short-term intercompany borrowings from Dominion Energy. These credit facilities mature in April 2020 and can be used to support bank borrowings and the issuance of commercial paper, as well as to support up to $2.0 billion (or the sub-limit, whichever is less) of letters of credit.

[2] A maximum of a combined $1.5 billion of the facilities is available to Dominion Energy Gas, assuming adequate capacity is available after giving effect to uses by co-borrowers Dominion Energy, Virginia Power and Questar Gas. Sub-limits for Dominion Energy Gas are set within the facility limit but can be changed at the option of the Companies multiple times per year. In May 2017, the aggregate sub-limit for Dominion Energy Gas was increased from $500 million to $750 million. If Dominion Energy Gas has liquidity needs in excess of its sub-limit, the sub-limit may be changed or such needs may be satisfied through short-term intercompany borrowings from Dominion Energy. These credit facilities mature in April 2020 and can be used to support bank borrowings and the issuance of commercial paper, as well as to support up to $1.5 billion (or the sub-limit, whichever is less) of letters of credit.

[3] These credit facilities mature in April 2020 and can be used by the Companies to support bank borrowings and the issuance of commercial paper, as well as to support up to a combined $2.0 billion of letters of credit.