EMPLOYEE BENEFITS	12 Months Ended
Dec. 31, 2017
Compensation And Retirement Disclosure [Abstract]
EMPLOYEE BENEFITS	NOTE 16. EMPLOYEE BENEFITS Questar Gas participates in retirement benefit plans sponsored by Dominion Energy effective December 2017, reflecting the merger of plans previously sponsored by Dominion Energy Questar, which provides certain retirement benefits to eligible active employees, retirees and qualifying dependents of Questar Gas. Under the terms of its benefit plans, Dominion Energy reserves the right to change, modify or terminate the plans. From time to time in the past, benefits have changed, and some of these changes have reduced benefits. Pension benefits for Questar Gas employees are covered by a defined benefit pension plan sponsored by Dominion Energy that provides benefits to multiple Dominion Energy subsidiaries. Retirement benefits payable are based primarily on years of service, age and the employee's compensation. As a participating employer, Questar Gas is subject to Dominion Energy’s funding policy, which is to contribute annually an amount that is in accordance with the provisions of ERISA. During 2017, Questar Gas made $12.2 million of contributions to the pension plan. No contributions to the plan by Questar Gas are currently expected in 2018. Net periodic pension expense (credit) related to the plan was $(9.2) million, $6.4 million and $10.4 million in 2017, 2016 and 2015, respectively, recorded in other operations and maintenance expense in the Statements of Income. The funded status of various Dominion Energy subsidiary groups and employee compensation are the basis for determining the share of total pension costs for participating Dominion Energy subsidiaries. At December 31, 2017 and 2016, the amount due to Questar Gas associated with this plan, was $107.1 million and $87.8 million, respectively, recorded in pension and other postretirement benefit assets in Questar Gas' Balance Sheet. Retiree healthcare and life insurance benefits for Questar Gas employees are covered by a health and welfare plan sponsored by Dominion Energy that provides certain retiree healthcare and life insurance benefits to multiple Dominion Energy subsidiaries. Annual employee premiums are based on several factors such as retirement date and years of service. Net periodic benefit expense (credit) related to this plan was $(0.8) million, $0.8 million and $0.9 million in 2017, 2016 and 2015, respectively, recorded in other operations and maintenance expense in the Statements of Income. Employee headcount is the basis for determining the share of total other postretirement benefit costs for participating Dominion Energy subsidiaries. At December 31, 2017 and 2016 the amount due from Questar Gas associated with this plan was $14.9 million and $13.0 million, respectively, and is reflected as pension and other postretirement benefit liabilities in Questar Gas' Balance Sheet. Dominion Energy holds investments in trusts to fund employee benefit payments for the pension and other postretirement benefit plans in which Questar Gas' employees participate. Any investment-related declines in these trusts will result in future increases in the net periodic cost recognized for such employee benefit plans and will be included in the determination of the amount of cash that Questar Gas will provide to Dominion Energy for its share of employee benefit plan contributions. Defined Contribution Plan Questar Gas also participates in a Dominion Energy-sponsored defined contribution plan which covers multiple Dominion Energy subsidiaries. Questar Gas recognized $5.0 million, $4.7 million and $4.5 million of expense in other operations and maintenance expense in the Statements of Income in 2017, 2016 and 2015, respectively, as employer matching contributions to this plan. Share-based Compensation Prior to the Dominion Energy Questar Combination, Questar Gas employees participated in certain share-based compensation plans of Dominion Energy Questar. Effective with the Dominion Energy Questar Combination all such awards vested on September 16, 2016. Total share-based compensation expense amounted to $3.0 million in 2016 and $1.4 million in 2015.

NOTE 16. EMPLOYEE BENEFITS

Questar Gas participates in retirement benefit plans sponsored by Dominion Energy effective December 2017, reflecting the merger of plans previously sponsored by Dominion Energy Questar, which provides certain retirement benefits to eligible active employees, retirees and qualifying dependents of Questar Gas. Under the terms of its benefit plans, Dominion Energy reserves the right to change, modify or terminate the plans. From time to time in the past, benefits have changed, and some of these changes have reduced benefits.

Pension benefits for Questar Gas employees are covered by a defined benefit pension plan sponsored by Dominion Energy that provides benefits to multiple Dominion Energy subsidiaries. Retirement benefits payable are based primarily on years of service, age and the employee's compensation. As a participating employer, Questar Gas is subject to Dominion Energy’s funding policy, which is to contribute annually an amount that is in accordance with the provisions of ERISA. During 2017, Questar Gas made $12.2 million of contributions to the pension plan. No contributions to the plan by Questar Gas are currently expected in 2018. Net periodic pension expense (credit) related to the plan was $(9.2) million, $6.4 million and $10.4 million in 2017, 2016 and 2015, respectively, recorded in other operations and maintenance expense in the Statements of Income. The funded status of various Dominion Energy subsidiary groups and employee compensation are the basis for determining the share of total pension costs for participating Dominion Energy subsidiaries. At December 31, 2017 and 2016, the amount due to Questar Gas associated with this plan, was $107.1 million and $87.8 million, respectively, recorded in pension and other postretirement benefit assets in Questar Gas' Balance Sheet.

Retiree healthcare and life insurance benefits for Questar Gas employees are covered by a health and welfare plan sponsored by Dominion Energy that provides certain retiree healthcare and life insurance benefits to multiple Dominion Energy subsidiaries. Annual employee premiums are based on several factors such as retirement date and years of service. Net periodic benefit expense (credit) related to this plan was $(0.8) million, $0.8 million and $0.9 million in 2017, 2016 and 2015, respectively, recorded in other operations and maintenance expense in the Statements of Income. Employee headcount is the basis for determining the share of total other postretirement benefit costs for participating Dominion Energy subsidiaries. At December 31, 2017 and 2016 the amount due from Questar Gas associated with this plan was $14.9 million and $13.0 million, respectively, and is reflected as pension and other postretirement benefit liabilities in Questar Gas' Balance Sheet.

Dominion Energy holds investments in trusts to fund employee benefit payments for the pension and other postretirement benefit plans in which Questar Gas' employees participate. Any investment-related declines in these trusts will result in future increases in the net periodic cost recognized for such employee benefit plans and will be included in the determination of the amount of cash that Questar Gas will provide to Dominion Energy for its share of employee benefit plan contributions.

Defined Contribution Plan

Questar Gas also participates in a Dominion Energy-sponsored defined contribution plan which covers multiple Dominion Energy subsidiaries. Questar Gas recognized $5.0 million, $4.7 million and $4.5 million of expense in other operations and maintenance expense in the Statements of Income in 2017, 2016 and 2015, respectively, as employer matching contributions to this plan.

Share-based Compensation

Prior to the Dominion Energy Questar Combination, Questar Gas employees participated in certain share-based compensation plans of Dominion Energy Questar. Effective with the Dominion Energy Questar Combination all such awards vested on September 16, 2016. Total share-based compensation expense amounted to $3.0 million in 2016 and $1.4 million in 2015.