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Contingencies - Guarantees (Details) | Sep. 30, 2024 USD ($)
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Commitments and Contingencies Disclosure [Abstract] |
Guarantor obligations, maximum exposure, undiscounted | $ 557,500,000
Fixed maximum amounts guaranteed by year 2024 | 13,300,000
Fixed maximum amounts guaranteed by year 2025 | 186,700,000
Fixed maximum amounts guaranteed by year 2026 | 312,600,000
Fixed maximum amounts guaranteed by year 2027 | 43,500,000
Fixed maximum amounts guaranteed by year 2028 | 1,000,000
Fixed maximum amounts guaranteed, thereafter | 400,000
Amount outstanding under guarantees that is reflected on balance sheet | 0
Letters of credit | 14,300,000
Letters of credit set to expire - 2024 | 12,300,000
Letters of credit set to expire - 2025 | 2,000,000
Outstanding letters of credit | 0
Amount of surety bonds outstanding | $ 848,200,000

X
- Definition Amount of surety bonds outstanding related to construction contracts and reclamation obligations. + References No definition available. + Details
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X
- Definition Fixed maximum amounts guaranteed by year five. + References No definition available. + Details
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X
- Definition Fixed maximum amounts guaranteed by year four. + References No definition available. + Details
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X
- Definition Fixed maximum amounts guaranteed by year one. + References No definition available. + Details
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- Definition Fixed maximum amounts guaranteed by year three. + References No definition available. + Details
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- Definition Fixed maximum amounts guaranteed by year two. + References No definition available. + Details
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- Definition Fixed maximum amounts guaranteed, thereafter. + References No definition available. + Details
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X
- Definition Letters of credit. + References No definition available. + Details
Name: | mdu_LettersOfCredit
Namespace Prefix: | mdu_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Letters of credit set to expire current year. + References No definition available. + Details
Name: | mdu_LettersOfCreditSetToExpireCurrentYear
Namespace Prefix: | mdu_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

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- Definition Letters of credit set to expire in next fiscal year. + References No definition available. + Details
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Namespace Prefix: | mdu_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

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- References No definition available. + Details
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- Definition The current carrying amount of the liability for the freestanding or embedded guarantor's obligations under the guarantee or each group of similar guarantees. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 460 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 4 -Subparagraph (c) -Publisher FASB -URI https://asc.fasb.org/1943274/2147482425/460-10-50-4 + Details
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- Definition Maximum potential amount of future payments (undiscounted) the guarantor could be required to make under the guarantee or each group of similar guarantees before reduction for potential recoveries under recourse or collateralization provisions. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 460 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 4 -Subparagraph (b)(1) -Publisher FASB -URI https://asc.fasb.org/1943274/2147482425/460-10-50-4 + Details
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- Definition The total amount of the contingent obligation under letters of credit outstanding as of the reporting date. + References No definition available. + Details
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