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Regulatory matters - SDPUC (Details) - Pending Rate Case - SDPUC - Montana-Dakota Utilities Co. - USD ($) $ in Millions | Jan. 26, 2024 | Aug. 15, 2023
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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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