XML 119 R89.htm IDEA: XBRL DOCUMENT
v3.22.4

Long-term borrowings (Details 4) - USD ($) $ in Thousands | Dec. 31, 2022 | Dec. 22, 2022 | Oct. 13, 2022 | Jun. 15, 2022 | Mar. 23, 2022 | Dec. 31, 2021
--- | --- | --- | --- | --- | --- | ---
Long-term debt outstanding [Line Items] |  |  |  |  |  |
Long-term debt | $ 2,841,425 |  |  |  |  | $ 2,741,900
Montana-Dakota Utilities Co. [Member] |  |  |  |  |  |
Long-term debt outstanding [Line Items] |  |  |  |  |  |
Ratio of total debt to total capitalization | 51.00% |  |  |  |  |
Cascade Natural Gas [Member] |  |  |  |  |  |
Long-term debt outstanding [Line Items] |  |  |  |  |  |
Ratio of total debt to total capitalization | 50.00% |  |  |  |  |
Intermountain Gas Company |  |  |  |  |  |
Long-term debt outstanding [Line Items] |  |  |  |  |  |
Ratio of total debt to total capitalization | 57.00% |  |  |  |  |
Intermountain Gas Company | Revolving credit facility | Long-term debt |  |  |  |  |  |
Long-term debt outstanding [Line Items] |  |  |  |  |  |
Facility limit, maximum borrowing capacity | $ 100,000 |  |  |  |  |
Centennial Energy Holdings, Inc. |  |  |  |  |  |
Long-term debt outstanding [Line Items] |  |  |  |  |  |
Ratio of total debt to total capitalization | 46.00% |  |  |  |  |
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 | $ 2,258,500 |  |  |  |  | $ 2,125,000
Weighted average interest rate | 4.32% |  |  |  |  |
Senior Notes | Cascade Natural Gas [Member] |  |  |  |  |  |
Long-term debt outstanding [Line Items] |  |  |  |  |  |
Long-term debt |  |  |  | $ 50,000 |  |
Weighted average interest rate |  |  |  | 4.50% |  |
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 |  |  |  | $ 40,000 |  |
Weighted average interest rate |  |  |  | 4.68% |  |
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 |  |  |  |  | 3.71% |
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 | $ 235,000 | $ 40,000 |  |  |  |
Weighted average interest rate |  | 6.67% |  |  |  |
Ratio of total debt to total capitalization as specified in debt covenants | 55.00% |  |  |  |  |
Long-term private shelf agreement issuance capacity |  | $ 350,000 |  |  |  |
Remaining capacity under uncommitted private shelf agreement | $ 115,000 |  |  |  |  |
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% |  |  |  |  |
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% |  |  |  |  |
Facility limit, maximum borrowing capacity |  |  | $ 100,000 |  |  |
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% |  |  |  |  |

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: | dtr-types: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: | dtr-types: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: | dtr-types: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 https://asc.fasb.org/extlink&oid=120391452&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 https://asc.fasb.org/extlink&oid=120391452&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, excluding unamortized premium (discount) and debt issuance cost, of long-term debt. Excludes lease obligation. + 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 https://asc.fasb.org/extlink&oid=123466204&loc=SL6031897-161870 Reference 2: http://www.xbrl.org/2003/role/exampleRef -Publisher FASB -Name Accounting Standards Codification -Topic 470 -SubTopic 20 -Section 55 -Paragraph 69C -URI https://asc.fasb.org/extlink&oid=123466577&loc=SL123495737-112612 Reference 3: 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 https://asc.fasb.org/extlink&oid=126734703&loc=d3e572229-122910 Reference 4: http://www.xbrl.org/2003/role/exampleRef -Publisher FASB -Name Accounting Standards Codification -Topic 470 -SubTopic 20 -Section 55 -Paragraph 69B -URI https://asc.fasb.org/extlink&oid=123466577&loc=SL123495735-112612 Reference 5: 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 https://asc.fasb.org/extlink&oid=126897435&loc=d3e534808-122878 Reference 6: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 470 -SubTopic 20 -Section 50 -Paragraph 1D -Subparagraph (b) -URI https://asc.fasb.org/extlink&oid=123466505&loc=SL123495340-112611 Reference 7: 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 https://asc.fasb.org/extlink&oid=120391452&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: | dtr-types: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: | us-gaap_CreditFacilityAxis=us-gaap_RevolvingCreditFacilityMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DebtInstrumentAxis=us-gaap_LongTermDebtMember
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: |