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v2.4.0.6

Income taxes (Details 12) | 12 Months Ended
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Dec. 31, 2012
Threshold of likelihood of tax positions being realized upon ultimate settlement with a taxing authority | 50.00%

X
- Definition Threshold of likelihood that tax benefits will be realized upon ultimate settlement with a taxing authority. + References No definition available. + Details
Name: | mdu_ThresholdOfLikelihoodOfTaxPositionsBeingRealizedUponUltimateSettlementWithTaxingAuthority
Namespace Prefix: | mdu_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration