XML 20 R92.htm IDEA: XBRL DOCUMENT
v3.19.3.a.u2

Long-term borrowings (Details 3) - USD ($) $ in Thousands | Dec. 31, 2019 | Dec. 16, 2019 | Dec. 31, 2018
--- | --- | --- | ---
Long-term debt outstanding [Line Items] |  |  |
Long-term debt | $ 2,243,107 |  | $ 2,108,695
Montana-Dakota Utilities Co. [Member] |  |  |
Long-term debt outstanding [Line Items] |  |  |
Ratio of total debt to total capitalization | 52.00% |  |
Cascade Natural Gas [Member] |  |  |
Long-term debt outstanding [Line Items] |  |  |
Ratio of total debt to total capitalization | 53.00% |  |
Intermountain Gas Company |  |  |
Long-term debt outstanding [Line Items] |  |  |
Ratio of total debt to total capitalization | 50.00% |  |
Centennial Energy Holdings, Inc. |  |  |
Long-term debt outstanding [Line Items] |  |  |
Ratio of total debt to total capitalization | 34.00% |  |
WBI Energy Transmission, Inc. |  |  |
Long-term debt outstanding [Line Items] |  |  |
Ratio of total debt to total capitalization | 40.00% |  |
Senior Notes |  |  |
Long-term debt outstanding [Line Items] |  |  |
Long-term debt | $ 1,850,000 |  | $ 1,381,000
Weighted average interest rate | 4.45% |  |
Senior Notes | Montana-Dakota Utilities Co. [Member] |  |  |
Long-term debt outstanding [Line Items] |  |  |
Long-term debt | $ 200,000 |  |
Weighted average interest rate | 3.95% |  |
Ratio of total debt to total capitalization as specified in debt covenants | 65.00% |  |
Senior Notes | Cascade Natural Gas [Member] |  |  |
Long-term debt outstanding [Line Items] |  |  |
Long-term debt | $ 75,000 |  |
Weighted average interest rate | 3.93% |  |
Ratio of total debt to total capitalization as specified in debt covenants | 65.00% |  |
Senior Notes | Intermountain Gas Company |  |  |
Long-term debt outstanding [Line Items] |  |  |
Long-term debt | $ 50,000 |  |
Weighted average interest rate | 3.92% |  |
Ratio of total debt to total capitalization as specified in debt covenants | 65.00% |  |
Senior Notes | Centennial Energy Holdings, Inc. |  |  |
Long-term debt outstanding [Line Items] |  |  |
Long-term debt | $ 150,000 |  |
Weighted average interest rate | 4.60% |  |
Ratio of total debt to total capitalization as specified in debt covenants | 60.00% |  |
Senior Notes | WBI Energy Transmission, Inc. |  |  |
Long-term debt outstanding [Line Items] |  |  |
Long-term debt | $ 170,000 | $ 45,000 |
Weighted average interest rate | 4.17% |  |
Ratio of total debt to total capitalization as specified in debt covenants | 55.00% |  |
Long-term private shelf agreement issuance capacity | $ 300,000 |  |
Remaining capacity under uncommitted private shelf agreement | $ 130,000 |  |
Revolving credit facility | Montana-Dakota Utilities Co. [Member] |  |  |
Long-term debt outstanding [Line Items] |  |  |
Ratio of funded debt to total capitalization as specified in debt covenants | 65.00% |  |
Revolving credit facility | Cascade Natural Gas [Member] |  |  |
Long-term debt outstanding [Line Items] |  |  |
Ratio of total debt to total capitalization as specified in debt covenants | 65.00% |  |
Facility limit, maximum borrowing capacity | $ 100,000 |  |
Revolving credit facility | Intermountain Gas Company |  |  |
Long-term debt outstanding [Line Items] |  |  |
Ratio of total debt to total capitalization as specified in debt covenants | 65.00% |  |
Revolving credit facility | Centennial Energy Holdings, Inc. |  |  |
Long-term debt outstanding [Line Items] |  |  |
Ratio of total debt to total capitalization as specified in debt covenants | 65.00% |  |
Facility limit, maximum borrowing capacity | $ 600,000 |  |

X
- Definition Long-term private shelf agreement amended issuance capacity. + References No definition available. + Details
Name: | mdu_LongtermPrivateShelfAgreementIssuanceCapacity
Namespace Prefix: | mdu_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Ratio of funded debt to total capitalization as specified in debt convenants. + References No definition available. + Details
Name: | mdu_RatioOfFundedDebtToTotalCapitalizationAsSpecifiedInDebtConvenants
Namespace Prefix: | mdu_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant

X
- Definition Ratio of total debt to total capitalization as specified in debt convenants. + References No definition available. + Details
Name: | mdu_RatioOfTotalDebtToTotalCapitalizationAsSpecifiedInDebtConvenants
Namespace Prefix: | mdu_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant

X
- Definition Ratio of total debt to total capitalization for the current period ended. + References No definition available. + Details
Name: | mdu_RatioofTotalDebttoTotalCapitalization
Namespace Prefix: | mdu_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant

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

X
- Definition Amount of unused borrowing capacity under the long-term financing arrangement that is available to the entity as of the balance sheet date. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.22(b)) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 + Details
Name: | us-gaap_DebtInstrumentUnusedBorrowingCapacityAmount
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.19(b),22(b)) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 + Details
Name: | us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Amount, after unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 470 -SubTopic 20 -Section 50 -Paragraph 4 -Subparagraph (b)(3) -URI http://asc.fasb.org/extlink&oid=109500613&loc=SL6031897-161870 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-03(a)(16)) -URI http://asc.fasb.org/extlink&oid=119400593&loc=d3e572229-122910 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-03(16)) -URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878 Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02(22)) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 + Details
Name: | us-gaap_LongTermDebt
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Weighted average interest rate of long-term debt outstanding calculated at point in time. + References No definition available. + Details
Name: | us-gaap_LongtermDebtWeightedAverageInterestRate
Namespace Prefix: | us-gaap_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant

X
- Details
Name: | dei_LegalEntityAxis=mdu_MontanaDakotaUtilitiesCo.Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | dei_LegalEntityAxis=mdu_CascadeNaturalGasMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | dei_LegalEntityAxis=mdu_IntermountainGasCompanyMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | dei_LegalEntityAxis=mdu_CentennialEnergyHoldingsIncMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | dei_LegalEntityAxis=mdu_WbiEnergyTransmissionIncMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_LongtermDebtTypeAxis=us-gaap_SeniorNotesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_LongtermDebtTypeAxis=us-gaap_RevolvingCreditFacilityMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |