Regulatory Matters	6 Months Ended
Jun. 30, 2018
Regulated Operations [Abstract]
Regulatory Matters	Note 8. Regulatory Matters As a public utility, Questar Gas is subject to the jurisdiction of the Utah Commission and the Wyoming Commission. Natural gas sales and transportation services are provided under rate schedules approved by the two regulatory commissions. In March 2018, Questar Gas submitted a filing to the Wyoming Commission with a proposal to return the benefit of lower federal income tax rates to customers through a surcredit beginning in June 2018. Questar Gas has proposed to calculate the impact of the 2017 Tax Reform Act on excess deferred income taxes in a separate filing by the first quarter of 2019. This matter is pending. In April 2018, Questar Gas submitted a filing to the Utah Commission to return the benefit of lower federal income tax rates to customers through a surcredit effective June 2018. In May 2018, the Utah Commission approved a stipulation to reduce the cost-of-service component of rates by $14.5 million annually beginning in June 2018. In addition, in July 2018 the Utah Commission approved a stipulation for Questar Gas to return $9.5 million to customers beginning in August 2018 for the cost-of-service component of rates collected from customers during the period January through May 2018. Questar Gas has proposed to calculate the impact of the 2017 Tax Reform Act on excess deferred income taxes in a separate filing to be submitted in the first quarter of 2019. The determination of the amounts of any surcredits associated with the above mentioned March and July filings could be material to Questar Gas’ operating cash flows. Questar Gas has recorded a reasonable estimate of net income taxes refundable through future rates in the jurisdictions in which it operates. Through actions by the Utah, Wyoming or Idaho Commissions, the estimates may be subject to changes that could have a material impact on Questar Gas’ results of operations, financial condition and/or cash flows. In the second quarter of 2018, Questar Gas filed a request with the Utah Commission for pre-approval to construct an LNG peaking storage facility with a liquefaction rate of 8.2 million cubic feet per day. This pre-approval process allows Questar Gas to receive a prudency determination from the Commission before making a capital investment in the facility. Under the preapproval statute, the Utah Commission has 180 days to make a prudency determination. Based on this timeline, a determination is expected by the end of October 2018. In May 2018, Questar Gas submitted filings with both the Utah Commission and the Wyoming Commission for an approximately $86.0 million gas cost decrease reflecting forecasted decreases in commodity costs, combined with reductions in Wexpro’s operator service fee related to the 2017 Tax Reform Act. The Utah Commission and the Wyoming Commission both approved the filings in May 2018 with rates effective June 2018.

Note 8. Regulatory Matters

As a public utility, Questar Gas is subject to the jurisdiction of the Utah Commission and the Wyoming Commission. Natural gas sales and transportation services are provided under rate schedules approved by the two regulatory commissions.

In March 2018, Questar Gas submitted a filing to the Wyoming Commission with a proposal to return the benefit of lower federal income tax rates to customers through a surcredit beginning in June 2018. Questar Gas has proposed to calculate the impact of the 2017 Tax Reform Act on excess deferred income taxes in a separate filing by the first quarter of 2019. This matter is pending.

In April 2018, Questar Gas submitted a filing to the Utah Commission to return the benefit of lower federal income tax rates to customers through a surcredit effective June 2018. In May 2018, the Utah Commission approved a stipulation to reduce the cost-of-service component of rates by $14.5 million annually beginning in June 2018. In addition, in July 2018 the Utah Commission approved a stipulation for Questar Gas to return $9.5 million to customers beginning in August 2018 for the cost-of-service component of rates collected from customers during the period January through May 2018. Questar Gas has proposed to calculate the impact of the 2017 Tax Reform Act on excess deferred income taxes in a separate filing to be submitted in the first quarter of 2019.

The determination of the amounts of any surcredits associated with the above mentioned March and July filings could be material to Questar Gas’ operating cash flows. Questar Gas has recorded a reasonable estimate of net income taxes refundable through future rates in the jurisdictions in which it operates. Through actions by the Utah, Wyoming or Idaho Commissions, the estimates may be subject to changes that could have a material impact on Questar Gas’ results of operations, financial condition and/or cash flows.

In the second quarter of 2018, Questar Gas filed a request with the Utah Commission for pre-approval to construct an LNG peaking storage facility with a liquefaction rate of 8.2 million cubic feet per day. This pre-approval process allows Questar Gas to receive a prudency determination from the Commission before making a capital investment in the facility. Under the preapproval statute, the Utah Commission has 180 days to make a prudency determination. Based on this timeline, a determination is expected by the end of October 2018.

In May 2018, Questar Gas submitted filings with both the Utah Commission and the Wyoming Commission for an approximately $86.0 million gas cost decrease reflecting forecasted decreases in commodity costs, combined with reductions in Wexpro’s operator service fee related to the 2017 Tax Reform Act. The Utah Commission and the Wyoming Commission both approved the filings in May 2018 with rates effective June 2018.