XML 64 R53.htm IDEA: XBRL DOCUMENT
v3.24.2.u1

Regulatory assets and liabilities - Schedule of Unamortized Regulatory Assets and Liabilities (Details) - USD ($) $ in Thousands | Jun. 30, 2024 | Dec. 31, 2023 | Jun. 30, 2023
--- | --- | --- | ---
Regulatory Asset [Abstract] |  |  |
Current regulatory assets | $ 217,822 | $ 172,492 | $ 193,162
Regulatory assets | 351,334 | 447,099 | 345,185
Total regulatory assets | 569,156 | 619,591 | 538,347
Regulatory Liability [Abstract] |  |  |
Regulatory liabilities due within one year | 158,535 | 70,761 | 48,057
Regulatory liabilities | 461,366 | 521,050 | 455,877
Total regulatory liabilities | 619,901 | 591,811 | 503,934
Net regulatory position | $ (50,745) | 27,780 | 34,413
Environmental compliance programs |  |  |
Regulatory Liability [Abstract] |  |  |
Estimated Recovery or Refund Period | 1 year |  |
Regulatory liabilities due within one year | $ 72,644 | 0 | 0
Regulatory liabilities | $ 0 | 61,941 | 0
Natural gas costs refundable through rate adjustments |  |  |
Regulatory Liability [Abstract] |  |  |
Estimated Recovery or Refund Period | 1 year |  |
Regulatory liabilities due within one year | $ 60,400 | 43,161 | 17,820
Provision for rate refund |  |  |
Regulatory Liability [Abstract] |  |  |
Estimated Recovery or Refund Period | 1 year |  |
Regulatory liabilities due within one year | $ 7,767 | 6,866 | 1,227
Cost recovery mechanisms |  |  |
Regulatory Liability [Abstract] |  |  |
Regulatory liabilities due within one year | 3,841 | 6,284 | 3,304
Regulatory liabilities | $ 26,286 | 21,791 | 18,226
Conservation programs |  |  |
Regulatory Liability [Abstract] |  |  |
Estimated Recovery or Refund Period | 1 year |  |
Regulatory liabilities due within one year | $ 3,330 | 2,130 | 2,851
Margin sharing |  |  |
Regulatory Liability [Abstract] |  |  |
Estimated Recovery or Refund Period | 1 year |  |
Regulatory liabilities due within one year | $ 2,188 | 5,243 | 1,791
Taxes recoverable from customers |  |  |
Regulatory Liability [Abstract] |  |  |
Estimated Recovery or Refund Period | 1 year |  |
Regulatory liabilities due within one year | $ 2,074 | 2,149 | 1,513
Regulatory liabilities | $ 187,827 | 193,578 | 197,757
Refundable fuel and electric costs |  |  |
Regulatory Liability [Abstract] |  |  |
Estimated Recovery or Refund Period | 1 year |  |
Regulatory liabilities due within one year | $ 1,431 | 263 | 103
Electric fuel and purchased power deferral |  |  |
Regulatory Liability [Abstract] |  |  |
Estimated Recovery or Refund Period | 1 year |  |
Regulatory liabilities due within one year | $ 506 | 0 | 8,481
Other |  |  |
Regulatory Liability [Abstract] |  |  |
Regulatory liabilities due within one year | 4,354 | 4,665 | 10,967
Regulatory liabilities | 2,024 | 1,809 | 1,694
Plant removal and decommissioning costs |  |  |
Regulatory Liability [Abstract] |  |  |
Regulatory liabilities | 222,668 | 220,147 | 216,682
Accumulated deferred investment tax credit |  |  |
Regulatory Liability [Abstract] |  |  |
Regulatory liabilities | 16,518 | 15,740 | 14,398
Pension and postretirement benefits |  |  |
Regulatory Liability [Abstract] |  |  |
Regulatory liabilities | $ 6,043 | 6,044 | 7,120
Minimum | Cost recovery mechanisms |  |  |
Regulatory Liability [Abstract] |  |  |
Estimated Recovery or Refund Period | 1 year |  |
Minimum | Other |  |  |
Regulatory Liability [Abstract] |  |  |
Estimated Recovery or Refund Period | 1 year |  |
Maximum | Cost recovery mechanisms |  |  |
Regulatory Liability [Abstract] |  |  |
Estimated Recovery or Refund Period | 18 years |  |
Maximum | Other |  |  |
Regulatory Liability [Abstract] |  |  |
Estimated Recovery or Refund Period | 14 years |  |
Natural gas costs recoverable through rate adjustments |  |  |
Regulatory Asset [Abstract] |  |  |
Current regulatory assets | $ 105,064 | 98,844 | 170,249
Regulatory assets | $ 15,870 | 55,493 | 0
Natural gas costs recoverable through rate adjustments | Minimum |  |  |
Regulatory Asset [Abstract] |  |  |
Estimated Recovery or Refund Period | 1 year |  |
Natural gas costs recoverable through rate adjustments | Maximum |  |  |
Regulatory Asset [Abstract] |  |  |
Estimated Recovery or Refund Period | 2 years |  |
Environmental compliance programs |  |  |
Regulatory Asset [Abstract] |  |  |
Estimated Recovery or Refund Period | 1 year |  |
Current regulatory assets | $ 84,486 | 5,525 | 2,926
Regulatory assets | $ 2,858 | 66,806 | 20,611
Conservation programs |  |  |
Regulatory Asset [Abstract] |  |  |
Estimated Recovery or Refund Period | 1 year |  |
Current regulatory assets | $ 15,713 | 14,425 | 10,897
Cost recovery mechanisms |  |  |
Regulatory Asset [Abstract] |  |  |
Current regulatory assets | 6,074 | 9,153 | 4,758
Regulatory assets | $ 82,984 | 85,944 | 63,890
Cost recovery mechanisms | Minimum |  |  |
Regulatory Asset [Abstract] |  |  |
Estimated Recovery or Refund Period | 1 year |  |
Cost recovery mechanisms | Maximum |  |  |
Regulatory Asset [Abstract] |  |  |
Estimated Recovery or Refund Period | 25 years |  |
Electric fuel and purchased power deferral |  |  |
Regulatory Asset [Abstract] |  |  |
Current regulatory assets | $ 3,024 | 33,918 | 2,221
Regulatory assets | $ 12,160 | 0 | 0
Electric fuel and purchased power deferral | Minimum |  |  |
Regulatory Asset [Abstract] |  |  |
Estimated Recovery or Refund Period | 1 year |  |
Electric fuel and purchased power deferral | Maximum |  |  |
Regulatory Asset [Abstract] |  |  |
Estimated Recovery or Refund Period | 2 years |  |
Other |  |  |
Regulatory Asset [Abstract] |  |  |
Current regulatory assets | $ 3,461 | 10,627 | 2,111
Regulatory assets | $ 9,061 | 8,588 | 10,766
Other | Minimum |  |  |
Regulatory Asset [Abstract] |  |  |
Estimated Recovery or Refund Period | 1 year |  |
Other | Maximum |  |  |
Regulatory Asset [Abstract] |  |  |
Estimated Recovery or Refund Period | 15 years |  |
Pension and postretirement benefits |  |  |
Regulatory Asset [Abstract] |  |  |
Regulatory assets | $ 142,511 | 142,511 | 144,448
Plant costs/asset retirement obligations |  |  |
Regulatory Asset [Abstract] |  |  |
Regulatory assets | 45,342 | 46,009 | 43,855
Manufactured gas plant site remediation |  |  |
Regulatory Asset [Abstract] |  |  |
Regulatory assets | 25,704 | 26,127 | 25,764
Taxes recoverable from customers |  |  |
Regulatory Asset [Abstract] |  |  |
Regulatory assets | $ 12,311 | 12,249 | 12,099
Long-term debt refinancing costs |  |  |
Regulatory Asset [Abstract] |  |  |
Estimated Recovery or Refund Period | 36 years |  |
Regulatory assets | $ 2,306 | 2,600 | 2,894
Plant removal and decommissioning costs |  |  |
Regulatory Asset [Abstract] |  |  |
Regulatory assets | $ 227 | $ 772 | $ 20,858

X
- Definition The net amount of all regulatory assets less all regulatory liabilities as of the end of the period. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Topic 980 -SubTopic 340 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Publisher FASB -URI https://asc.fasb.org/1943274/2147478742/980-340-50-1 + Details
Name: | us-gaap_NetRegulatoryAssets
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

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

X
- Definition Amortization period for the recovery of regulatory asset, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. + References No definition available. + Details
Name: | us-gaap_RegulatoryAssetAmortizationPeriod
Namespace Prefix: | us-gaap_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | instant

X
- Definition The amount for the individual regulatory asset as itemized in a table of regulatory assets as of the end of the period. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Topic 980 -SubTopic 340 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Publisher FASB -URI https://asc.fasb.org/1943274/2147478742/980-340-50-1 + Details
Name: | us-gaap_RegulatoryAssets
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Carrying amount as of the balance sheet date of capitalized costs of regulated entities that are expected to be recovered through revenue sources within one year or the normal operating cycle, if longer. Such costs are capitalized if they meet both of the following criteria: a. It is probable that future revenue in an amount at least equal to the capitalized cost will result from inclusion of that cost in allowable costs for rate-making purposes. b. Based on available evidence, the future revenue will be provided to permit recovery of the previously incurred cost rather than to provide for expected levels of similar future costs. If the revenue will be provided through an automatic rate-adjustment clause, this criterion requires that the regulator's intent clearly be to permit recovery of the previously incurred cost. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Topic 980 -SubTopic 340 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Publisher FASB -URI https://asc.fasb.org/1943274/2147478742/980-340-50-1 + Details
Name: | us-gaap_RegulatoryAssetsCurrent
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Carrying amount as of the balance sheet date of capitalized costs of regulated entities that are not expected to be recovered through revenue sources within one year or the normal operating cycle if longer. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Topic 980 -SubTopic 340 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Publisher FASB -URI https://asc.fasb.org/1943274/2147478742/980-340-50-1 + Details
Name: | us-gaap_RegulatoryAssetsNoncurrent
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition The amount for the individual regulatory liability as itemized in a table of regulatory liabilities as of the end of the period. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Topic 980 -SubTopic 405 -Name Accounting Standards Codification -Section 25 -Paragraph 1 -Publisher FASB -URI https://asc.fasb.org/1943274/2147477571/980-405-25-1 + Details
Name: | us-gaap_RegulatoryLiabilities
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

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

X
- Definition Amortization period for the recovery of regulatory liability, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. + References No definition available. + Details
Name: | us-gaap_RegulatoryLiabilityAmortizationPeriod
Namespace Prefix: | us-gaap_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | instant

X
- Definition The amount for the individual regulatory current liability as itemized in a table of regulatory current liabilities as of the end of the period. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Topic 980 -SubTopic 405 -Name Accounting Standards Codification -Section 25 -Paragraph 1 -Publisher FASB -URI https://asc.fasb.org/1943274/2147477571/980-405-25-1 + Details
Name: | us-gaap_RegulatoryLiabilityCurrent
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition The amount for the individual regulatory noncurrent liability as itemized in a table of regulatory noncurrent liabilities as of the end of the period. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Topic 210 -SubTopic 10 -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02(24)) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480566/210-10-S99-1 + Details
Name: | us-gaap_RegulatoryLiabilityNoncurrent
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Details
Name: | us-gaap_RegulatoryLiabilityAxis=mdu_EnvironmentalComplianceProgramsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_RegulatoryLiabilityAxis=mdu_LiabilitiesRefundableGasCostsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_RegulatoryLiabilityAxis=mdu_ReserveForRefundMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_RegulatoryLiabilityAxis=mdu_RegulatoryClauseRevenuesOverRecoveredMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_RegulatoryLiabilityAxis=us-gaap_RenewableEnergyProgramMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_RegulatoryLiabilityAxis=mdu_MarginSharingMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_RegulatoryLiabilityAxis=us-gaap_DeferredIncomeTaxChargesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_RegulatoryLiabilityAxis=mdu_RefundableFuelAndElectricCostsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_RegulatoryLiabilityAxis=mdu_ElectricFuelAndPurchasedPowerDeferralMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_RegulatoryLiabilityAxis=us-gaap_OtherRegulatoryAssetsLiabilitiesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_RegulatoryLiabilityAxis=us-gaap_RemovalCostsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_RegulatoryLiabilityAxis=mdu_AccumulatedDeferredITCMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_RegulatoryLiabilityAxis=us-gaap_PensionAndOtherPostretirementPlansCostsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_RangeAxis=srt_MinimumMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_RangeAxis=srt_MaximumMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_RegulatoryAssetAxis=us-gaap_AssetRecoverableGasCostsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_RegulatoryAssetAxis=mdu_EnvironmentalComplianceProgramsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_RegulatoryAssetAxis=us-gaap_RenewableEnergyProgramMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_RegulatoryAssetAxis=us-gaap_RegulatoryClauseRevenuesUnderRecoveredMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_RegulatoryAssetAxis=mdu_ElectricFuelAndPurchasedPowerDeferralMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_RegulatoryAssetAxis=us-gaap_OtherRegulatoryAssetsLiabilitiesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_RegulatoryAssetAxis=us-gaap_PensionAndOtherPostretirementPlansCostsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_RegulatoryAssetAxis=us-gaap_AssetRetirementObligationCostsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_RegulatoryAssetAxis=us-gaap_EnvironmentalRestorationCostsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_RegulatoryAssetAxis=us-gaap_DeferredIncomeTaxChargesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_RegulatoryAssetAxis=us-gaap_LossOnReacquiredDebtMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_RegulatoryAssetAxis=us-gaap_RemovalCostsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |