XML 53 R39.htm IDEA: XBRL DOCUMENT
v3.5.0.2

Basis of presentation (Details) | Jun. 27, 2016 | Feb. 07, 2013
--- | --- | ---
WBI Energy [Member] |  |
Noncontrolling Interest [Line Items] |  |
Previous percentage of ownership |  | 50.00%
Percentage of ownership acquired | 50.00% |
Calumet [Member] |  |
Noncontrolling Interest [Line Items] |  |
Previous percentage of ownership |  | 50.00%

X
- Definition Percentage of ownership acquired. + References No definition available. + Details
Name: | mdu_PercentageofOwnershipAcquired
Namespace Prefix: | mdu_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant

X
- Definition Previous percentage of ownership. + References No definition available. + Details
Name: | mdu_PreviousPercentageofOwnership
Namespace Prefix: | mdu_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant

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

X
- Details
Name: | dei_LegalEntityAxis=mdu_WBIEnergyMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | dei_LegalEntityAxis=mdu_CalumetMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |