Regulatory matters	3 Months Ended
Mar. 31, 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. Intermountain has requested the rates be retroactive to January 1, 2021. This matter is pending before the IPUC. MNPUC On September 27, 2019, Great Plains filed an application with the MNPUC for a natural gas rate increase of approximately $2.9 million annually or approximately 12.0 percent above current rates. The requested increase was primarily to recover investments in facilities to enhance safety and reliability and the depreciation and taxes associated with the increase in investment. On November 22, 2019, Great Plains received approval to implement an interim rate increase of approximately $2.6 million or approximately 11.0 percent, subject to refund, effective January 1, 2020. On October 26, 2020, the MNPUC issued an order authorizing an annual increase in revenues of approximately $2.6 million or approximately 11.5 percent. On February 25, 2021, the MNPUC approved implementing the rates effective April 1, 2021. 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 the Company 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. This matter is pending before the MNPUC. NDPSC On August 26, 2020, Montana-Dakota filed an application with the NDPSC for a natural gas rate increase of approximately $9.0 million annually or approximately 7.8 percent above current rates. The requested increase was primarily to recover investments in facilities to enhance system safety and reliability and the depreciation and taxes associated with the increase in investment. On December 16, 2020, Montana-Dakota received approval to implement an interim rate increase of approximately $6.9 million or approximately 6.0 percent, subject to refund, effective January 1, 2021. A hearing was held March 17 and 18, 2021. On April 9, 2021, Montana-Dakota, NDPSC Advocacy Staff and the intervener in the case filed a settlement agreement reflecting an updated increase of approximately $6.9 million annually or approximately 6.0 percent above current rates. On May 5, 2021, the NDPSC approved the settlement agreement with rates effective June 1, 2021. On March 2, 2021, Montana-Dakota filed an informational update to the generation resource recovery rider with the NDPSC 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. 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 the Company 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. This matter is pending before the NDPSC. SDPUC Montana-Dakota has a transmission cost recovery rider that allows annual updates to rates for actual costs for transmission-related projects and services. On March 1, 2021, Montana-Dakota filed an annual update to its transmission cost recovery rider to recover a revenue requirement of approximately $1.0 million annually, which reflects a true-up of the prior period adjustment, resulting in an increase in current rates of approximately $274,000. On April 30, 2021, the SDPUC approved the rates as requested with an effective date of May 1, 2021. Montana-Dakota has an infrastructure rider rate tariff that allows for annual adjustments for recent projected capital costs and related expenses for projects determined to be recoverable under the electric tariff. On February 26, 2021, Montana-Dakota filed an annual update to its infrastructure rider requesting to recover a revenue requirement of approximately $1.0 million annually, which reflects a true-up of the prior period adjustment, resulting in a decrease in current rates of approximately $236,000. On April 30, 2021, the SDPUC approved the rates as requested with an effective date of May 1, 2021. 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. 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 the Company prepares a true-up pursuant to the purchased gas cost adjustment tariff. On March 31, 2021, Montana-Dakota filed an out-of-cycle cost of gas adjustment with the SDPUC for approximately $5.5 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 April 30, 2021, the SDPUC approved the rates as requested with an effective date of May 1, 2021. 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. A hearing was held February 24, 2021, and briefs were filed with the WUTC on March 22, 2021. The WUTC has 11 months to render a final decision on the rate case. This matter is pending before the WUTC. WYPSC On May 14, 2020, Montana-Dakota filed separate requests for its electric and natural gas services with the WYPSC to use deferred accounting for costs related to the COVID-19 pandemic. Montana-Dakota determined the deferred accounting orders were no longer needed and the filings were withdrawn by Montana-Dakota on March 2, 2021. 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 the Company prepares a true-up pursuant to the purchased gas cost adjustment tariff. On March 31, 2021, Montana-Dakota filed an out-of-cycle cost of gas adjustment with the WYPSC for approximately $1.6 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 April 30, 2021, the WYPSC approved the rates as requested with an effective date of May 1, 2021.

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.

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. Intermountain has requested the rates be retroactive to January 1, 2021. This matter is pending before the IPUC.

On September 27, 2019, Great Plains filed an application with the MNPUC for a natural gas rate increase of approximately $2.9 million annually or approximately 12.0 percent above current rates. The requested increase was primarily to recover investments in facilities to enhance safety and reliability and the depreciation and taxes associated with the increase in investment. On November 22, 2019, Great Plains received approval to implement an interim rate increase of approximately $2.6 million or approximately 11.0 percent, subject to refund, effective January 1, 2020. On October 26, 2020, the MNPUC issued an order authorizing an annual increase in revenues of approximately $2.6 million or approximately 11.5 percent. On February 25, 2021, the MNPUC approved implementing the rates effective April 1, 2021.

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 the Company 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. This matter is pending before the MNPUC.

On August 26, 2020, Montana-Dakota filed an application with the NDPSC for a natural gas rate increase of approximately $9.0 million annually or approximately 7.8 percent above current rates. The requested increase was primarily to recover investments in facilities to enhance system safety and reliability and the depreciation and taxes associated with the increase in investment. On December 16, 2020, Montana-Dakota received approval to implement an interim rate increase of approximately $6.9 million or approximately 6.0 percent, subject to refund, effective January 1, 2021. A hearing was held March 17 and 18, 2021. On April 9, 2021, Montana-Dakota, NDPSC Advocacy Staff and the intervener in the case filed a settlement agreement reflecting an updated increase of approximately $6.9 million annually or approximately 6.0 percent above current rates. On May 5, 2021, the NDPSC approved the settlement agreement with rates effective June 1, 2021.

On March 2, 2021, Montana-Dakota filed an informational update to the generation resource recovery rider with the NDPSC 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.

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 the Company 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. This matter is pending before the NDPSC.

Montana-Dakota has a transmission cost recovery rider that allows annual updates to rates for actual costs for transmission-related projects and services. On March 1, 2021, Montana-Dakota filed an annual update to its transmission cost recovery rider to recover a revenue requirement of approximately $1.0 million annually, which reflects a true-up of the prior period adjustment, resulting in an increase in current rates of approximately $274,000. On April 30, 2021, the SDPUC approved the rates as requested with an effective date of May 1, 2021.

Montana-Dakota has an infrastructure rider rate tariff that allows for annual adjustments for recent projected capital costs and related expenses for projects determined to be recoverable under the electric tariff. On February 26, 2021, Montana-Dakota filed an annual update to its infrastructure rider requesting to recover a revenue requirement of approximately $1.0 million annually, which reflects a true-up of the prior period adjustment, resulting in a decrease in current rates of approximately $236,000. On April 30, 2021, the SDPUC approved the rates as requested with an effective date of May 1, 2021.

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.

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 the Company prepares a true-up pursuant to the purchased gas cost adjustment tariff. On March 31, 2021, Montana-Dakota filed an out-of-cycle cost of gas adjustment with the SDPUC for approximately $5.5 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 April 30, 2021, the SDPUC approved the rates as requested with an effective date of May 1, 2021.

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. A hearing was held February 24, 2021, and briefs were filed with the WUTC on March 22, 2021. The WUTC has 11 months to render a final decision on the rate case. This matter is pending before the WUTC.

On May 14, 2020, Montana-Dakota filed separate requests for its electric and natural gas services with the WYPSC to use deferred accounting for costs related to the COVID-19 pandemic. Montana-Dakota determined the deferred accounting orders were no longer needed and the filings were withdrawn by Montana-Dakota on March 2, 2021.