XML 139 R115.htm IDEA: XBRL DOCUMENT
v3.3.1.900

Guarantees (Details 5) | Dec. 31, 2015 USD ($)
--- | ---
Commitments and Contingencies Disclosure [Abstract] |
Guarantor obligations, maximum exposure, undiscounted | $ 128,600,000
Fixed maximum amounts guaranteed by year 2016 | 33,100,000
Fixed maximum amounts guaranteed by year 2017 | 35,000,000
Fixed maximum amounts guaranteed by year 2018 | 600,000
Fixed maximum amounts guaranteed by year 2019 | 54,900,000
Expires on a specified number of days after the receipt of written notice | 1,000,000
Fixed maximum amounts guaranteed by year no maturity date | 4,000,000
Amount outstanding under guarantees | 0
Letters of credit | 57,300,000
Outstanding letters of credit | 4,100,000
Amount of surety bonds outstanding | $ 530,000,000

X
- Definition Amount of surety bonds outstanding related to construction contracts and reclamation obligations. + References No definition available. + Details
Name: | mdu_AmountOfSuretyBondsOutstanding
Namespace Prefix: | mdu_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition The amount outstanding under gurantees that is reflected on the balance sheet. + References No definition available. + Details
Name: | mdu_AmountOutstandingUnderGuaranteesThatIsReflectedOnBalanceSheet
Namespace Prefix: | mdu_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Fixed maximum amounts guaranteed that expires after a certain number of days written notice. + References No definition available. + Details
Name: | mdu_FixedMaximumAmountsGuaranteedByYearExpiresAfterCertainNumberOfDaysAfterWrittenNotice
Namespace Prefix: | mdu_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Fixed maximum amounts guaranteed with no maturity date. + References No definition available. + Details
Name: | mdu_FixedMaximumAmountsGuaranteedByYearNoMaturityDate
Namespace Prefix: | mdu_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Fixed maximum amounts guaranteed, due in four years. + References No definition available. + Details
Name: | mdu_FixedMaximumAmountsGuaranteedDueInFourYears
Namespace Prefix: | mdu_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Fixed maximum amounts guaranteed, due next fiscal year. + References No definition available. + Details
Name: | mdu_FixedMaximumAmountsGuaranteedDueNextFiscalYear
Namespace Prefix: | mdu_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Fixed maximum amounts guaranteed, due in three years. + References No definition available. + Details
Name: | mdu_FixedMaximumAmountsGuaranteedDueinThreeYears
Namespace Prefix: | mdu_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Fixed maximum amounts guaranteed, due in two years. + References No definition available. + Details
Name: | mdu_FixedMaximumAmountsGuaranteedDueinTwoYears
Namespace Prefix: | mdu_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Letters of credit. + References No definition available. + Details
Name: | mdu_LettersOfCredit
Namespace Prefix: | mdu_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- References No definition available. + Details
Name: | us-gaap_CommitmentsAndContingenciesDisclosureAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Maximum potential amount of future payments (undiscounted) the guarantor could be required to make under the guarantee or each group of similar guarantees before reduction for potential recoveries under recourse or collateralization provisions. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 460 -SubTopic 10 -Section 50 -Paragraph 4 -Subparagraph (b)(1) -URI http://asc.fasb.org/extlink&oid=6851643&loc=d3e12069-110248 + Details
Name: | us-gaap_GuaranteeObligationsMaximumExposure
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition The total amount of the contingent obligation under letters of credit outstanding as of the reporting date. + References No definition available. + Details
Name: | us-gaap_LettersOfCreditOutstandingAmount
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant