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v3.20.4

Multiemployer Plans Zones (Details 18) | 12 Months Ended
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Dec. 31, 2020
Maximum |
Multiemployer Plans [Line Items] |
Multiemployer plan red zone status funded percentage | 65.00%
Mulitiemployer plan yellow status funded percentage | 80.00%
Minimum |
Multiemployer Plans [Line Items] |
Multiemployer plan yellow zone status funded percentage | 65.00%
Multiemployer plan green zone status funded percentage | 80.00%

X
- Definition Mulitiemployer plan yellow status funded percentage + References No definition available. + Details
Name: | mdu_Mulitiemployerplanyellowstatusfundedpercentage
Namespace Prefix: | mdu_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Multiemployer plan green zone status funded percentage + References No definition available. + Details
Name: | mdu_Multiemployerplangreenzonestatusfundedpercentage
Namespace Prefix: | mdu_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Multiemployer plan red zone status funded percentage + References No definition available. + Details
Name: | mdu_Multiemployerplanredzonestatusfundedpercentage
Namespace Prefix: | mdu_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Multiemployer plan yellow zone status funded percentage + References No definition available. + Details
Name: | mdu_Multiemployerplanyellowzonestatusfundedpercentage
Namespace Prefix: | mdu_
Data Type: | num:percentItemType
Balance Type: | na
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_MultiemployerPlansLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Details
Name: | srt_RangeAxis=srt_MaximumMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_RangeAxis=srt_MinimumMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |