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SDPUC (Details 4) | Mar. 11, 2021 USD ($)
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SDPUC | Pending Rate Case [Member] | Electricity [Member] | Montana-Dakota Utilities Co. [Member] |
Public Utilities, General Disclosures [Line Items] |
Total Infrastructure Rider | $ 0

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- Definition Total Infrastructure Rider + References No definition available. + Details
Name: | mdu_TotalInfrastructureRider
Namespace Prefix: | mdu_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

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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
Name: | us-gaap_PublicUtilitiesGeneralDisclosuresLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

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- Details
Name: | us-gaap_RegulatoryAgencyAxis=mdu_SDPUCMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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- Details
Name: | us-gaap_PublicUtilitiesRegulatoryProceedingAxis=mdu_PendingRateCaseMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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- Details
Name: | us-gaap_PublicUtilityAxis=us-gaap_ElectricityMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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- Details
Name: | dei_LegalEntityAxis=mdu_MontanaDakotaUtilitiesCo.Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |