Regulatory matters	3 Months Ended
Regulatory matters	Mar. 31, 2023
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 2022 Annual Report and should be read in conjunction with previous filings. 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 Intermountain filed a request with the IPUC for a natural gas general rate increase on December 1, 2022. The request was for an increase of $11.3 million annually or 3.2 percent above current rates, which was revised on March 9, 2023, to $6.8 million annually or 1.9 percent above current rates. The requested increase is primarily to recover investments made since the last rate case in 2016 and the depreciation, operation and maintenance expenses and taxes associated with the increased investments. A settlement in principle has been reached and is expected to be filed with the IPUC no later than May 15, 2023. This matter is pending before the IPUC. MTPSC On November 4, 2022, Montana-Dakota filed an application with the MTPSC for an electric general rate increase of approximately $10.5 million annually or 15.2 percent above current rates, which was revised on March 15, 2023, to $11.5 million annually or 17.0 percent above current rates to reflect the loss of a large industrial customer. The requested increase is primarily to recover investments made since the last rate case, including Heskett Unit 4, increases in operation and maintenance expenses, and increases in property taxes. On January 24, 2023, the MTPSC approved Montana-Dakota's request for an interim increase of approximately $1.7 million or 2.7 percent above current rates, subject to refund, effective February 1, 2023. The MTPSC has 9 months to render a final decision on the rate case. The matter is pending before the MTPSC with a hearing scheduled for June 20, 2023. NDPSC On May 16, 2022, Montana-Dakota filed an application with the NDPSC for an electric general rate increase of approximately $25.4 million annually or 12.3 percent above current rates. The requested increase is primarily to recover investments in production, transmission and distribution facilities and the associated depreciation, operation and maintenance expenses and taxes associated with the increased investment. On July 14, 2022, the NDPSC approved an interim rate increase of approximately $10.9 million annually or 5.3 percent above current rates, subject to refund, for service rendered on and after July 15, 2022. The lower interim rate increase is largely due to excluding the recovery of Heskett Unit 4 from interim rates due to not being in service until summer of 2023. On April 26, 2023, the Company filed with the NDPSC an all-party settlement reflecting an annual revenue increase of $15.3 million or 7.4 percent overall. The reduction from the original filing includes a return on equity of 9.75 percent and maintaining depreciation expense at current levels. A hearing was held May 2, 2023. The matter is pending before the NDPSC. WUTC On March 24, 2022, Cascade filed a request for tariff revision with the WUTC to rectify an inadvertent IRS normalization violation resulting from its tariff established in 2018 that passes back to customers the reversal of plant-related excess deferred income taxes through an annual rate adjustment. This request was made in response to the issuances of an IRS private letter ruling to another Washington utility with the same annual rate adjustment tariff, which addressed its normalization violations. The private letter ruling concluded the tariff to refund excess deferred income taxes without corresponding adjustments for other components of rate base or changes in depreciation or income tax expense, is an impermissible methodology under the IRS normalization and consistency rules. Cascade's request proposed a similar remedy through the tariff to recover the excess amounts refunded to customers while this tariff has been in place, and revised the method going forward to reflect excess deferred income taxes in rates in the same manner as other components of rate base from its most recent general rate case. Cascade requested recovery of the excess refunded to customers of approximately $3.3 million and elimination of the currently deferred, but not yet refunded balance. A multi-party settlement was filed with the WUTC on October 21, 2022. On January 23, 2023, the WUTC denied recovery of the excess refunded to customers, but approved the tariff revision going forward to rectify the inadvertent normalization violation. On February 1, 2023, Cascade filed a motion for clarification with the WUTC on the currently deferred but not yet refunded balance. A clarifying conference was held on February 27, 2023, resulting in approval to reverse the currently deferred but not yet refunded balance of approximately $1.1 million. On February 28, 2023, this matter was finalized by the WUTC with rates effective March 1, 2023. FERC On January 27, 2023, WBI Energy Transmission filed a general rate case with the FERC for increases in its transportation and storage services rates that also includes a Greenhouse Gas Cost Recovery Mechanism for anticipated future costs. New rates, which are pending FERC approval, will be in effect August 1, 2023.