XML 66 R49.htm IDEA: XBRL DOCUMENT
v3.4.0.3

Derivative instruments (Details) MMBTU in Millions | 3 Months Ended |  |
--- | --- | --- | ---
Mar. 31, 2016 USD ($) bbl MMBTU | Dec. 31, 2015 USD ($) bbl MMBTU | Mar. 31, 2015 USD ($) bbl MMBTU
Derivative instruments [Line Items] |  |  |
Cash flow hedge gain (loss) to be reclassified within twelve months from AOCI into earnings | $ (400,000) |  |
Oil swap and\or collar [Member] |  |  |
Derivative instruments [Line Items] |  |  |
Derivative, nonmonetary notional amount | bbl | 0 | 0 | 958,000
Natural gas swap and\or collar [Member] |  |  |
Derivative instruments [Line Items] |  |  |
Derivative, nonmonetary notional amount | MMBTU | 0.0 | 0.0 | 2.8
Interest Rate Swap [Member] |  |  |
Derivative instruments [Line Items] |  |  |
Derivative, Notional Amount | $ 0 | $ 0 | $ 0

X
- Definition Aggregate notional amount of derivative expressed in nonmonetary units. For example, the number of barrels specified in a fuel oil forward purchase contract. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Article 12 -Section 13 -Sentence Column B + Details
Name: | invest_DerivativeNonmonetaryNotionalAmount
Namespace Prefix: | invest_
Data Type: | xbrli:decimalItemType
Balance Type: | na
Period Type: | instant

X
- Definition Aggregate notional amount specified by the derivative(s). Expressed as an absolute value. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Article 12 -Section 13 -Sentence Column B + Details
Name: | invest_DerivativeNotionalAmount
Namespace Prefix: | invest_
Data Type: | xbrli:monetaryItemType
Balance Type: | na
Period Type: | instant

X
- Definition The estimated net amount of existing gains or losses on cash flow hedges at the reporting date expected to be reclassified to earnings within the next 12 months. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 30 -Section 50 -Paragraph 1 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=35736893&loc=d3e80748-113994 + Details
Name: | us-gaap_CashFlowHedgeGainLossToBeReclassifiedWithinTwelveMonths
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

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

X
- Details
Name: | us-gaap_DerivativeInstrumentRiskAxis=mdu_OilSwapAndOrCollarMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DerivativeInstrumentRiskAxis=mdu_NaturalGasSwapAndorCollarMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DerivativeInstrumentRiskAxis=us-gaap_InterestRateSwapMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |