Regulatory matters	6 Months Ended
Regulatory matters	Jun. 30, 2021
Regulated Operations [Abstract]
Regulatory Matters	Regulatory matters The Company regularly reviews the need for electric and natural gas rate changes in each of the jurisdictions in which service is provided. The Company files for rate adjustments to seek recovery of operating costs and capital investments, as well as reasonable returns as allowed by regulators. Certain regulatory proceedings and cases may also contain recurring mechanisms that can have an annual true-up. Examples of these recurring mechanisms include: infrastructure riders, transmission trackers, renewable resource cost adjustment riders, as well as weather normalization and decoupling mechanisms. The following paragraphs summarize the Company's significant open regulatory proceedings and cases by jurisdiction including updates to those reported in the 2020 Annual Report. The Company is unable to predict the ultimate outcome of these matters, the timing of final decisions of the various regulators and courts, or the effect on the Company's results of operations, financial position or cash flows. IPUC On January 12, 2021, Intermountain filed an application with the IPUC for a decrease in its depreciation and amortization rates of approximately $2.9 million annually or a decrease from a combined rate of 3.0 percent to 2.6 percent. On June 3, 2021, Intermountain filed a joint settlement agreement with the IPUC Staff reflecting a revised annual decrease of approximately $3.8 million or approximately 2.4 percent. Intermountain and the IPUC Staff have requested the rates be retroactive to January 1, 2021. This matter is pending before the IPUC. MNPUC Great Plains defers the difference between the actual cost of gas spent to serve customers and that recovered from customers on a monthly basis. Annually, Great Plains prepares a true-up pursuant to the purchased gas adjustment tariff. On March 30, 2021, Great Plains filed an out-of-cycle cost of gas adjustment with the MNPUC for the recovery of approximately $11.1 million. The requested increase was for the February 2021 extreme cold weather, primarily in the central United States, and market conditions surrounding the natural gas commodity market. The length of recovery was requested at 28 months with a rate structure that is higher in the summer and lower in the winter due to the lower gas usage in the summer to mitigate the impact on customers. On June 8, 2021, the Company's request was denied; however, the MNPUC initiated its own investigation into the impact of severe weather in February 2021 on Minnesota's natural gas utility companies and consumers. The investigation will address the recovery of the extraordinary gas costs resulting from the February 2021 extreme cold weather event. MNPUC deliberations on this matter are scheduled for August 5, 2021. This matter is pending before the MNPUC. NDPSC Montana-Dakota defers the difference between the actual cost of gas spent to serve customers and that recovered from customers on a monthly basis. Annually, Montana-Dakota prepares a true-up pursuant to the purchased gas adjustment tariff. On March 31, 2021, Montana-Dakota filed an out-of-cycle cost of gas adjustment with the NDPSC for approximately $13.5 million. The requested increase was for the February 2021 extreme cold weather, primarily in the central United States, and market conditions surrounding the natural gas commodity market. The filing was made to expedite recovery of these costs and maintain the timing of annual purchased gas adjustment filings. On May 27, 2021, the NDPSC approved the requested increase with a recovery period of 16 months effective June 1, 2021. On July 15, 2021, Montana-Dakota filed an annual update to its transmission cost adjustment rider with the NDPSC requesting to recover revenues of approximately $14.5 million, which includes a true-up of the prior period adjustment, resulting in a decrease of approximately $1.1 million from current rates. This filing includes approximately $5.1 million related to transmission capital projects. This matter is pending before the NDPSC. SDPUC On March 11, 2021, Montana-Dakota filed an informational update to the infrastructure rider rate tariff with the SDPUC related to the retirement of Unit 1 at Lewis & Clark Station. The filing includes the annual revenue requirement offset by the related amortization of the accelerated depreciation on the plant, net of excess deferred income taxes, and the decommissioning costs projected to be incurred in 2021 resulting in no impact to customers. This matter is pending before the SDPUC. WUTC On June 19, 2020, Cascade filed an application with the WUTC for a natural gas rate increase of approximately $13.8 million annually or approximately 5.3 percent above current rates. The requested increase was primarily to recover investments made in infrastructure upgrades, as well as increased operation and maintenance costs. Cascade updated its filing on July 24, 2020, to approximately $14.3 million annually or approximately 5.5 percent. Cascade filed a rebuttal case on January 8, 2021, supporting an increase of approximately $7.4 million annually or approximately 2.8 percent. The revised revenue within the rebuttal case reflects several adjustments including depreciation, reduction to return on equity, delays on certain projects, adjustments to income taxes and updates to wages. On May 18, 2021, the WUTC issued a final order reflecting an overall revenue decrease of approximately $391,000 or approximately 0.2 percent. On May 25, 2021, Cascade filed a petition for reconsideration with the WUTC. On June 18, 2021, the WUTC denied Cascade's petition for reconsideration. Final rates were effective July 1, 2021. On June 1, 2021, Cascade filed its annual pipeline cost recovery mechanism requesting an increase in annual revenue of approximately $2.1 million or approximately 0.8 percent. The filing includes a proposed effective date of November 1, 2021. This filing will be updated to more accurate data prior to the effective date. This matter is pending before the WUTC.