XML 159 R132.htm IDEA: XBRL DOCUMENT
v3.22.0.1

FERC (Details 5) $ in Millions | Jan. 01, 2022 USD ($)
--- | ---
MISO [Member] | Montana-Dakota Utilities Co. [Member] | Electric | Subsequent Event [Member] |
Public Utilities, General Disclosures [Line Items] |
Transmission Formula Revenue Requirement | $ 13.4

X
- Definition Transmission Formula Revenue Requirement + References No definition available. + Details
Name: | mdu_TransmissionFormulaRevenueRequirement
Namespace Prefix: | mdu_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- 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_PublicUtilitiesGeneralDisclosuresLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Details
Name: | us-gaap_RegulatoryAgencyAxis=mdu_MISOMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | dei_LegalEntityAxis=mdu_MontanaDakotaUtilitiesCo.Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_PublicUtilityAxis=mdu_ElectricMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_SubsequentEventTypeAxis=us-gaap_SubsequentEventMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |