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

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- 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