EMPLOYEE BENEFITS (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total share-based compensation expense		$ 3.0	$ 1.4
Dominion Energy
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Expense recognized for defined contribution plan	$ 5.0	4.7	4.5
Dominion Energy | Pension Plan
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Amount of contributions	12.2
Net periodic pension expense (credit)	(9.2)	6.4	10.4
Amounts due to Questar Gas	107.1	87.8
Dominion Energy | Other Postretirement Benefit Plan
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Net periodic pension expense (credit)	(0.8)	0.8	$ 0.9
Amounts due from Questar Gas	$ 14.9	$ 13.0