Letters of credit.

No definition available.

Name:	mdu_LettersOfCredit
Namespace Prefix:	mdu_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Long-term private shelf agreement.

+ References

No definition available.

+ Details

Name:	mdu_LongtermPrivateShelfAgreement
Namespace Prefix:	mdu_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Notes outstanding which reduce capacity under the uncommitted private shelf agreement.

+ References

No definition available.

+ Details

Name:	mdu_Notesoutstanding
Namespace Prefix:	mdu_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Ratio - EBIT to interest expense.

+ References

No definition available.

+ Details

Name:	mdu_RatioEbitToInterestExpense
Namespace Prefix:	mdu_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Ratio - EBITDA to interest expense.

+ References

No definition available.

+ Details

Name:	mdu_RatioEbitdaToInterestExpense
Namespace Prefix:	mdu_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Ratio of funded debt capitalization - Company alone, as specified in debt convenants.

+ References

No definition available.

+ Details

Name:	mdu_RatioOfFundedDebtCapitalizationCompanyAloneAsSpecifiedInDebtConvenants
Namespace Prefix:	mdu_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Ratio of funded debt to total capitalization as specified in debt convenants.

+ References

No definition available.

+ Details

Name:	mdu_RatioOfFundedDebtToTotalCapitalizationAsSpecifiedInDebtConvenants
Namespace Prefix:	mdu_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Ratio of subsidiary debt to subsidiary capitalization as specified in debt convenants.

+ References

No definition available.

+ Details

Name:	mdu_RatioOfSubsidiaryDebtToSubsidiaryCapitalizationAsSpecifiedInDebtConvenants
Namespace Prefix:	mdu_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Ratio of total debt to adjusted total capitalization as specified in debt convenants.

+ References

No definition available.

+ Details

Name:	mdu_RatioOfTotalDebtToAdjustedTotalCapitalizationAsSpecifiedInDebtConvenants
Namespace Prefix:	mdu_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Ratio of total debt to total capitalization as specified in debt convenants.

+ References

No definition available.

+ Details

Name:	mdu_RatioOfTotalDebtToTotalCapitalizationAsSpecifiedInDebtConvenants
Namespace Prefix:	mdu_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- 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_DebtInstrumentLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.19(b),22(b))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

Name:	us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Details

Name:	dei_LegalEntityAxis=mdu_MduResourcesGroupIncMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_CreditFacilityAxis=mdu_CommercialPaperRevolvingCreditAgreementMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=us-gaap_LongTermDebtMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_CreditFacilityAxis=us-gaap_RevolvingCreditFacilityMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	dei_LegalEntityAxis=mdu_MduEnergyCapitalLlcMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_CreditFacilityAxis=mdu_MasterShelfAgreementMemberMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	dei_LegalEntityAxis=mdu_CascadeNaturalGasCorporationMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	dei_LegalEntityAxis=mdu_IntermountainGasCompanyMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	dei_LegalEntityAxis=mdu_CentennialEnergyHoldingsIncMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	dei_LegalEntityAxis=mdu_WbiEnergyTransmissionIncMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_CreditFacilityAxis=mdu_UncommittedLongTermPrivateShelfAgreementMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: