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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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Amount of public utility's interim rate increase (decrease) allowed while waiting final decision of regulatory agency.

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Percentage of public utility's interim rate increase (decrease) allowed while waiting final decision of regulatory agency.

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Amount of public utility's amended requested rate increase (decrease) with regulatory agency.

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Percentage of public utility's amended requested rate increase (decrease) with regulatory agency.

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Amount of public utility's requested rate increase (decrease) with regulatory agency.

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- Definition

Percentage of public utility's requested rate increase (decrease) with regulatory agency.

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Percentage of public utility's requested return on equity.

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MTPSC (Details) - MTPSC - Montana-Dakota Utilities Co. [Member] - Electric - USD ($) $ in Millions	Jun. 12, 2023	Mar. 15, 2023	Feb. 01, 2023	Nov. 04, 2022
Public Utilities, General Disclosures [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amount				$ 10.5
Public Utilities, Requested Rate Increase (Decrease), Percentage				15.20%
Public Utilities, Requested Rate Increase (Decrease), Amended, Amount	$ 6.1	$ 11.5
Public Utilities, Requested Rate Increase (Decrease), Amended, Percentage	9.10%	17.00%
Public Utilities, Interim Rate Increase (Decrease), Amount			$ 1.7
Public Utilities, Interim Rate Increase (Decrease), Percentage			2.70%
Public Utilities, Requested Return on Equity, Percentage	9.65%