SHORT-TERM DEBT AND CREDIT AGREEMENTS (Details)		1 Months Ended	12 Months Ended
		Nov. 30, 2016 Facility	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)
Line Of Credit Facility [Line Items]
Facility Limit			$ 1,000,000,000	$ 1,000,000,000
Outstanding Commercial Paper	[1]		165,000,000	200,000,000
Outstanding Letters of Credit			0	0
Credit Facility $5 Billion
Line Of Credit Facility [Line Items]
Facility Limit	[2]		500,000,000	500,000,000
Outstanding Commercial Paper	[1],[2]		165,000,000	200,000,000
Outstanding Letters of Credit	[2]		0	0
Credit Facility $500 Million
Line Of Credit Facility [Line Items]
Facility Limit	[2]		500,000,000	500,000,000
Outstanding Commercial Paper	[1],[2]		0	0
Outstanding Letters of Credit	[2]		0	$ 0
Joint Revolving Credit Facilities
Line Of Credit Facility [Line Items]
Joint revolving credit facility, amount			$ 6,000,000,000
Joint revolving credit facility, maturity period			5 years
Joint Revolving Credit Facilities | Minimum
Line Of Credit Facility [Line Items]
Debt to capital ratio percentage			65.00%
Joint Revolving Credit Facilities | Maximum
Line Of Credit Facility [Line Items]
Debt to capital ratio percentage			67.50%
Joint Revolving Credit Facility $5 Billion and Joint Revolving Credit Facility $500 Million
Line Of Credit Facility [Line Items]
Number of joint revolving credit facilities | Facility		2
Facility Limit			$ 1,000,000,000
Joint Revolving Credit Facility $5 Billion and Joint Revolving Credit Facility $500 Million | Line of Credit
Line Of Credit Facility [Line Items]
Amount of note			250,000,000
Joint Revolving Credit Facility $5 Billion and Joint Revolving Credit Facility $500 Million | Letter of Credit
Line Of Credit Facility [Line Items]
Facility Limit			$ 1,000,000,000
Joint Revolving Credit Facility $5 Billion and Joint Revolving Credit Facility $500 Million | Commercial Paper
Line Of Credit Facility [Line Items]
Weighted average interest rate percentage			1.56%	1.10%

[1] The weighted-average interest rate of the outstanding commercial paper supported by these credit facilities was 1.56% and 1.10% at December 31, 2017 and 2016, respectively.

[2] A maximum of $1.0 billion of the facilities is available to Questar Gas, assuming adequate capacity is available after giving effect to uses by co-borrowers Dominion Energy, Virginia Power and Dominion Energy Gas. Sub-limits for Questar Gas are set within the facility limit but can be changed at the option of the borrowers multiple times per year. At December 31, 2017, the sub-limit for Questar Gas was $250.0 million. If Questar 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. The maturity date for these facilities is April 2020. These credit facilities can be used to support bank borrowings and the issuance of commercial paper, as well as to support up to $1.0 billion (or the sub-limit, whichever is less) of letters of credit.