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Contingencies - Guarantees (Details)	Mar. 31, 2024 USD ($)
Commitments and Contingencies Disclosure [Abstract]
Guarantor obligations, maximum exposure, undiscounted	$ 329,900,000
Fixed maximum amounts guaranteed by year 2024	53,000,000
Fixed maximum amounts guaranteed by year 2025	210,700,000
Fixed maximum amounts guaranteed by year 2026	64,900,000
Fixed maximum amounts guaranteed by year 2027	1,000,000
Fixed maximum amounts guaranteed by year 2028	300,000
Fixed maximum amounts guaranteed, thereafter	0
Amount outstanding under guarantees that is reflected on balance sheet	0
Letters of credit	14,300,000
Letters of credit set to expire - 2023	12,300,000
Letters of credit set to expire - 2025	2,000,000
Outstanding letters of credit	0
Amount of surety bonds outstanding	$ 738,100,000

X

- Definition

Amount of surety bonds outstanding related to construction contracts and reclamation obligations.

+ References

No definition available.

+ Details

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Namespace Prefix:	mdu_
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Balance Type:	credit
Period Type:	instant

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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Namespace Prefix:	mdu_
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Balance Type:	credit
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- Definition

Fixed maximum amounts guaranteed by year one.

+ References

No definition available.

+ Details

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Namespace Prefix:	mdu_
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Balance Type:	credit
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- Definition

Fixed maximum amounts guaranteed by year three.

+ References

No definition available.

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
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- Definition

Fixed maximum amounts guaranteed by year two.

+ References

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- Definition

Fixed maximum amounts guaranteed, thereafter.

+ References

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Namespace Prefix:	mdu_
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Balance Type:	credit
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X

- Definition

Letters of credit.

+ References

No definition available.

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

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- Definition

Letters of credit set to expire current year.

+ References

No definition available.

+ Details

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Namespace Prefix:	mdu_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
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X

- Definition

Letters of credit set to expire in next fiscal year.

+ References

No definition available.

+ Details

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Namespace Prefix:	mdu_
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- References

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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

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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

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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.

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