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Regulatory matters - SDPUC (Details) - Natural gas distribution - SDPUC - Subsequent Event - Montana-Dakota Utilities Co. $ in Millions | Oct. 31, 2025 USD ($)
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Public Utilities, General Disclosures [Line Items] |
Public utilities, interim rate increase (decrease), amount | $ 1.5
Public utilities, annual revenue increase (decrease) | $ 1.1

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- Definition Public Utilities, Annual Revenue Increase (Decrease) + References No definition available. + Details
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Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

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- Definition 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. + References No definition available. + Details
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- Definition Amount of public utility's interim rate increase (decrease) allowed while waiting final decision of regulatory agency. + References No definition available. + Details
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Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

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- Details
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Namespace Prefix: |
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Period Type: |

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- Details
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- Details
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- Details
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