Regulatory matters - NDPSC (Details) - Natural gas distribution - NDPSC - Montana-Dakota Utilities Co. - Pending Rate Case - USD ($) $ in Millions	Dec. 13, 2023	Nov. 01, 2023
Public Utilities, General Disclosures [Line Items]
Public utilities, requested rate increase (decrease), amount		$ 11.6
Public utilities, requested rate increase (decrease), percentage		7.50%
Public utilities, interim rate increase (decrease), amount	$ 10.1
Public utilities, interim rate increase (decrease), percentage	6.50%

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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 requested rate increase (decrease) with regulatory agency.

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

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