XML 93 R81.htm IDEA: XBRL DOCUMENT
v3.21.2

WUTC (Details 5) - Pending Rate Case [Member] - WUTC [Member] - Cascade Natural Gas [Member] - USD ($) $ in Millions | Oct. 15, 2021 | Sep. 30, 2021 | Jun. 01, 2021
--- | --- | --- | ---
Pipeline Cost Recovery Mechanism [Member] |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |
Public Utilities, Requested Rate Increase (Decrease), Amount |  |  | $ 2.1
Public Utilities, Requested Rate Increase (Decrease), Percentage |  |  | 0.80%
Pipeline Cost Recovery Mechanism [Member] | Subsequent Event [Member] |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |
Public Utilities, Requested Rate Increase (Decrease), Amended, Amount | $ 1.7 |  |
Public Utilities, Requested Rate Increase (Decrease), Amended, Percentage | 0.60% |  |
Gas Distribution [Member] |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |
Public Utilities, Requested Rate Increase (Decrease), Amount |  | $ 13.7 |
Public Utilities, Requested Rate Increase (Decrease), Percentage |  | 5.10% |

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
- Definition Amount of public utility's amended requested rate increase (decrease) with regulatory agency. + References No definition available. + Details
Name: | us-gaap_PublicUtilitiesRequestedRateIncreaseDecreaseAmendedAmount
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Percentage of public utility's amended requested rate increase (decrease) with regulatory agency. + References No definition available. + Details
Name: | us-gaap_PublicUtilitiesRequestedRateIncreaseDecreaseAmendedPercentage
Namespace Prefix: | us-gaap_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Amount of public utility's requested rate increase (decrease) with regulatory agency. + References No definition available. + Details
Name: | us-gaap_PublicUtilitiesRequestedRateIncreaseDecreaseAmount
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Percentage of public utility's requested rate increase (decrease) with regulatory agency. + References No definition available. + Details
Name: | us-gaap_PublicUtilitiesRequestedRateIncreaseDecreasePercentage
Namespace Prefix: | us-gaap_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Details
Name: | us-gaap_PublicUtilitiesRegulatoryProceedingAxis=mdu_PendingRateCaseMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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

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

X
- Details
Name: | dei_LegalEntityAxis=mdu_CascadeNaturalGasMember
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: |

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