XML 110 R93.htm IDEA: XBRL DOCUMENT
v3.19.2

FERC (Details 7) $ in Millions | May 30, 2019 USD ($)
--- | ---
Tax Cuts and Jobs Act [Member] | Natural gas rate proceeding [Member] | FERC [Member] |
Public Utilities, General Disclosures [Line Items] |
Public utilities, interim rate increase (decrease), amount | $ 4.5

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 interim rate increase (decrease) allowed while waiting final decision of regulatory agency. + References No definition available. + Details
Name: | us-gaap_PublicUtilitiesInterimRateIncreaseDecreaseAmount
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Details
Name: | us-gaap_IncomeTaxAuthorityAxis=mdu_TaxCutsandJobsActMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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

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