Debt Instrument, Debt To Capitalization Ratio

No definition available.

Name:	mdu_DebtInstrumentDebtToCapitalizationRatio
Namespace Prefix:	mdu_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

The option to increase borrowing capacity to the stated maximum amount, at the option of the company, on stated conditions.

+ References

No definition available.

+ Details

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

- Definition

The total amount of the contingent obligation under letters of credit outstanding as of the reporting date.

+ References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Topic 944
-SubTopic 605
-Name Accounting Standards Codification
-Section 55
-Paragraph 15
-Publisher FASB
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+ Details

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

- Definition

The carrying value as of the balance sheet date of the current and noncurrent portions of long-term obligations drawn from a line of credit, which is a bank's commitment to make loans up to a specific amount. Examples of items that might be included in the application of this element may consist of letters of credit, standby letters of credit, and revolving credit arrangements, under which borrowings can be made up to a maximum amount as of any point in time conditional on satisfaction of specified terms before, as of and after the date of drawdowns on the line. Includes short-term obligations that would normally be classified as current liabilities but for which (a) postbalance sheet date issuance of a long term obligation to refinance the short term obligation on a long term basis, or (b) the enterprise has entered into a financing agreement that clearly permits the enterprise to refinance the short-term obligation on a long term basis and the following conditions are met (1) the agreement does not expire within 1 year and is not cancelable by the lender except for violation of an objectively determinable provision, (2) no violation exists at the BS date, and (3) the lender has entered into the financing agreement is expected to be financially capable of honoring the agreement.

+ References

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+ Details

Name:	us-gaap_LineOfCredit
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
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

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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+ Details

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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/2009/role/commonPracticeRef
-Topic 210
-SubTopic 10
-Name Accounting Standards Codification
-Section S50
-Paragraph 8
-Publisher FASB
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-URI https://asc.fasb.org/1943274/2147480566/210-10-S99-1

+ Details

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

- Details

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

- Details

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

- Details

Name:	us-gaap_DebtInstrumentAxis=mdu_CreditAgreementExpiringOctober2028Member
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Balance Type:
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- Details

Name:	dei_LegalEntityAxis=mdu_CascadeNaturalGasCorporationMember
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Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=mdu_CreditAgreementExpiringJune2029Member
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Balance Type:
Period Type:

- Details

Name:	dei_LegalEntityAxis=mdu_IntermountainGasCompanyMember
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- Details

Name:	dei_LegalEntityAxis=mdu_MDUResourcesGroupInc.Member
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- Details

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Debt - Schedule of Credit Facilities (Details) - USD ($)	Jun. 30, 2026	Dec. 31, 2025	Jun. 30, 2025
Line of Credit Facility [Line Items]
Letters of credit at end of period	$ 0
Revolving Credit Facility \| Montana-Dakota Utilities Co. \| Credit Agreement Expiring October 2028
Line of Credit Facility [Line Items]
Debt-to-Total Capitalization Ratio at June 30, 2026	51.00%
Provisions for Increased Borrowings, up to a maximum of:	$ 250,000,000.0
Facility Limit	200,000,000.0
Amount outstanding, end of period	82,000,000.0	$ 132,000,000.0	$ 43,300,000
Letters of credit at end of period	$ 0
Revolving Credit Facility \| Cascade Natural Gas Corporation \| Credit Agreement Expiring June 2029
Line of Credit Facility [Line Items]
Debt-to-Total Capitalization Ratio at June 30, 2026	49.00%
Provisions for Increased Borrowings, up to a maximum of:	$ 225,000,000.0
Facility Limit	175,000,000.0
Amount outstanding, end of period	108,300,000	96,500,000	14,000,000.0
Letters of credit at end of period	$ 2,200,000
Revolving Credit Facility \| Intermountain Gas Company \| Credit Agreement Expiring June 2029
Line of Credit Facility [Line Items]
Debt-to-Total Capitalization Ratio at June 30, 2026	53.00%
Provisions for Increased Borrowings, up to a maximum of:	$ 225,000,000.0
Facility Limit	175,000,000.0
Amount outstanding, end of period	77,900,000	67,300,000	86,800,000
Letters of credit at end of period	$ 0
Revolving Credit Facility \| MDU Resources Group, Inc. \| Credit Agreement Expiring May 2028
Line of Credit Facility [Line Items]
Debt-to-Total Capitalization Ratio at June 30, 2026	47.00%
Provisions for Increased Borrowings, up to a maximum of:	$ 250,000,000.0
Facility Limit	200,000,000.0
Amount outstanding, end of period	45,000,000.0	$ 32,900,000	$ 0
Letters of credit at end of period	$ 1,000,000.0