Regulatory Matters	9 Months Ended
Sep. 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. In October 2018, the Wyoming Commission approved Questar Gas’ request to return $0.5 million per year through a surcredit beginning November 1, 2018. The surcredit will remain in effect until rates become effective in the next Wyoming general rate case. 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. 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. In October 2018, the Utah Commission denied Questar Gas’ request for pre-approval. Questar Gas is reviewing the order and assessing its options, which could include filing supplemental information with the Utah Commission for reconsideration. 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. In September 2018, Questar Gas submitted a filing with the Utah Commission to increase customer rates by $3.5 million annually to recover costs related to Questar Gas’ infrastructure replacement program. The Utah Commission approved the filing with rates effective October 1, 2018. In October 2018, Questar Gas submitted filings with both the Utah Commission and the Wyoming Commission for an approximately $47.6 million gas cost decrease reflecting forecasted decreases in commodity costs. The Utah Commission and the Wyoming Commission both approved the filings in October 2018 with rates effective November 2018. In October 2018, Questar Gas submitted filings with both the Utah Commission and the Wyoming Commission for an approximately $9.3 million non-gas cost decrease relating to the CET and an approximately $5.9 million non-gas cost increase relating to the EEP. These matters are pending.

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. In October 2018, the Wyoming Commission approved Questar Gas’ request to return $0.5 million per year through a surcredit beginning November 1, 2018. The surcredit will remain in effect until rates become effective in the next Wyoming general rate case. 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.

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. In October 2018, the Utah Commission denied Questar Gas’ request for pre-approval. Questar Gas is reviewing the order and assessing its options, which could include filing supplemental information with the Utah Commission for reconsideration.

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.

In September 2018, Questar Gas submitted a filing with the Utah Commission to increase customer rates by $3.5 million annually to recover costs related to Questar Gas’ infrastructure replacement program. The Utah Commission approved the filing with rates effective October 1, 2018.

In October 2018, Questar Gas submitted filings with both the Utah Commission and the Wyoming Commission for an approximately $47.6 million gas cost decrease reflecting forecasted decreases in commodity costs. The Utah Commission and the Wyoming Commission both approved the filings in October 2018 with rates effective November 2018.

In October 2018, Questar Gas submitted filings with both the Utah Commission and the Wyoming Commission for an approximately $9.3 million non-gas cost decrease relating to the CET and an approximately $5.9 million non-gas cost increase relating to the EEP. These matters are pending.