Regulatory matters - SDPUC (Details) - Pending Rate Case - SDPUC - Montana-Dakota Utilities Co. - USD ($) $ in Millions	Jan. 26, 2024	Aug. 15, 2023
Electric
Public Utilities, General Disclosures [Line Items]
Public utilities, requested rate increase (decrease), amount		$ 3.0
Public utilities, requested rate increase (decrease), percentage		17.30%
Natural gas distribution
Public Utilities, General Disclosures [Line Items]
Public utilities, requested rate increase (decrease), amount		$ 7.4
Public utilities, requested rate increase (decrease), percentage		11.20%
Public utilities, interim rate increase (decrease), amount	$ 2.7
Public utilities, interim rate increase (decrease), percentage	15.40%

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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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