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Goodwill (Details 5) | 3 Months Ended
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Dec. 31, 2014
Accounting Policies [Abstract] |
Fair value inputs discount rate, range bottom | 5.00%mdu_FairValueInputsDiscountRatesRangeBottom
Fair value inputs, discount rate, range top | 9.00%mdu_FairValueDiscountRateRangeTop
Long-term growth rate projections | 3.00%us-gaap_FairValueInputsLongTermRevenueGrowthRate

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- Definition Interest rate used to find the present value of an amount to be paid or received in the future as an input to measure fair value, range top. + References No definition available. + Details
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- Definition Interest rate used to find the present value of an amount to be paid or received in the future as an input to measure fair value, bottom. + 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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- Definition Percentage of assumed long-term growth in revenues, used as an input to measure fair value. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (bbb) -URI http://asc.fasb.org/extlink&oid=36462937&loc=d3e19207-110258 + Details
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