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Environmental allowances and obligations (Details) $ in Millions | Sep. 30, 2023 USD ($)
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Accounting Policies [Abstract] |
Environmental Compliance Obligations | $ 36.6

X
- Definition Obligations related to emission credits + References No definition available. + Details
Name: | mdu_EnvironmentalComplianceObligations
Namespace Prefix: | mdu_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

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- References No definition available. + Details
Name: | us-gaap_AccountingPoliciesAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration