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SDPUC (Details 4)	Mar. 11, 2021 USD ($)
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

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No definition available.

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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: