XML 81 R64.htm IDEA: XBRL DOCUMENT
v3.19.2

Discontinued operations Noncontrolling interest (Details) | Jun. 27, 2016 | Jun. 24, 2016
--- | --- | ---
WBI Energy | Dakota Prairie Refining, LLC |  |
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items] |  |
Previous percentage of ownership | 50.00% | 50.00%

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

X
- Definition Percentage of the Variable Interest Entity's (VIE) voting interest owned by (or beneficial interest in) the reporting entity (directly or indirectly). + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 810 -SubTopic 10 -Section 50 -Paragraph 5A -Subparagraph (d) -URI http://asc.fasb.org/extlink&oid=118582676&loc=SL6759159-111685 + Details
Name: | us-gaap_VariableInterestEntityOwnershipPercentage
Namespace Prefix: | us-gaap_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

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

X
- Details
Name: | us-gaap_VariableInterestEntitiesByClassificationOfEntityAxis=mdu_DakotaPrairieRefiningLlcMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |