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Exploration and Production Activities (Unaudited) Purchase and sale agreements (Details) | 12 Months Ended
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Dec. 31, 2014
Discontinued operations, disposed of by sale |
Entity Sector Industry Classifications [Line Items] |
Percent of oil and natural gas production sold | 93.00%

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Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

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- Definition Percent of oil and natural gas production sold. + References No definition available. + Details
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Namespace Prefix: | mdu_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

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- Details
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Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |