XML 73 R63.htm IDEA: XBRL DOCUMENT
v3.23.2

Accumulated other comprehensive loss (Details) - USD ($) $ in Thousands | 3 Months Ended | 6 Months Ended
--- | --- | ---
Jun. 30, 2023 | Mar. 31, 2023 | Jun. 30, 2022 | Mar. 31, 2022 | Jun. 30, 2023 | Jun. 30, 2022
Accumulated other comprehensive loss [Roll Forward] |  |  |  |  |  |
Balance | $ 3,575,382 | $ 3,587,129 | $ 3,360,718 | $ 3,382,874 | $ 3,587,129 | $ 3,382,874
Other comprehensive income (loss) | 363 | 217 | (2,796) | 269 | 580 | (2,527)
Amounts reclassified to accumulated other comprehensive loss from a regulatory asset, net of tax | 0 |  | (3,265) |  | 0 | (3,265)
Balance | 2,706,193 | 3,575,382 | 3,386,810 | 3,360,718 | 2,706,193 | 3,386,810
Net unrealized gain (loss) on derivative instruments qualifying as hedges |  |  |  |  |  |
Accumulated other comprehensive loss [Roll Forward] |  |  |  |  |  |
Balance | (91) | (125) | (426) | (538) | (125) | (538)
Other comprehensive loss before reclassifications | 0 | 0 | 0 | 0 |  |
Other comprehensive income (loss) | 47 | 34 | 111 | 112 |  |
Amounts reclassified to accumulated other comprehensive loss from a regulatory asset, net of tax |  |  | 0 |  |  |
Amounts reclassified from accumulated other comprehensive loss |  | 34 | 111 | 112 |  |
Amounts reclassified related to the separation of Knife River | (44) |  |  |  |  |
Balance | 0 | (91) | (315) | (426) | 0 | (315)
Postretirement liability adjustment |  |  |  |  |  |
Accumulated other comprehensive loss [Roll Forward] |  |  |  |  |  |
Balance | (29,800) | (29,900) | (40,016) | (40,461) | (29,900) | (40,461)
Other comprehensive loss before reclassifications | 0 | 0 | 0 | 0 |  |
Other comprehensive income (loss) | 387 | 100 | (2,804) | 445 |  |
Amounts reclassified to accumulated other comprehensive loss from a regulatory asset, net of tax |  |  | (3,265) |  |  |
Amounts reclassified from accumulated other comprehensive loss |  | 100 | 461 | 445 |  |
Amounts reclassified related to the separation of Knife River | (12,262) |  |  |  |  |
Balance | (17,151) | (29,800) | (42,820) | (40,016) | (17,151) | (42,820)
Net unrealized gain (loss) on available-for-sale investments |  |  |  |  |  |
Accumulated other comprehensive loss [Roll Forward] |  |  |  |  |  |
Balance | (475) | (558) | (293) | (5) | (558) | (5)
Other comprehensive loss before reclassifications |  | 70 | (128) | (320) |  |
Other comprehensive income (loss) | (71) | 83 | (103) | (288) |  |
Amounts reclassified to accumulated other comprehensive loss from a regulatory asset, net of tax |  |  | 0 |  |  |
Amounts reclassified from accumulated other comprehensive loss |  | 13 | 25 | 32 |  |
Amounts reclassified related to the separation of Knife River | 0 |  |  |  |  |
Balance | (546) | (475) | (396) | (293) | (546) | (396)
Total accumulated other comprehensive loss |  |  |  |  |  |
Accumulated other comprehensive loss [Roll Forward] |  |  |  |  |  |
Balance | (30,366) | (30,583) | (40,735) | (41,004) | (30,583) | (41,004)
Other comprehensive loss before reclassifications | (84) | 70 | (128) | (320) |  |
Other comprehensive income (loss) | 363 | 217 | (2,796) | 269 |  |
Amounts reclassified to accumulated other comprehensive loss from a regulatory asset, net of tax |  |  | (3,265) |  |  |
Amounts reclassified from accumulated other comprehensive loss | 447 | 147 | 597 | 589 |  |
Amounts reclassified related to the separation of Knife River | (12,306) |  |  |  |  |
Balance | $ (17,697) | $ (30,366) | $ (43,531) | $ (40,735) | $ (17,697) | $ (43,531)

X
- Definition Amounts reclassified related to the separation of Knife River + References No definition available. + Details
Name: | mdu_AmountsReclassifiedRelatedToTheSeparationOfKnifeRiver
Namespace Prefix: | mdu_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Other Comprehensive (Income) Loss, Reclassification Adjustment to AOCI, Postretirement Liability Adjustment From Regulatory Asset , Net of Tax + References No definition available. + Details
Name: | mdu_OtherComprehensiveIncomeLossReclassificationAdjustmentToAOCIPostretirementLiabilityAdjustmentFromRegulatoryAssetNetOfTax
Namespace Prefix: | mdu_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Amount after tax, before reclassification adjustments of other comprehensive income (loss). + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Name Accounting Standards Codification -Topic 220 -SubTopic 10 -Section 45 -Paragraph 14A -Publisher FASB -URI https://asc.fasb.org//1943274/2147482790/220-10-45-14A Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Topic 220 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 5 -Publisher FASB -URI https://asc.fasb.org//1943274/2147482765/220-10-50-5 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Topic 830 -SubTopic 30 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Publisher FASB -URI https://asc.fasb.org//1943274/2147481674/830-30-50-1 Reference 4: http://www.xbrl.org/2003/role/disclosureRef -Topic 830 -SubTopic 30 -Name Accounting Standards Codification -Section 45 -Paragraph 17 -Publisher FASB -URI https://asc.fasb.org//1943274/2147481694/830-30-45-17 Reference 5: http://www.xbrl.org/2003/role/disclosureRef -Topic 830 -SubTopic 30 -Name Accounting Standards Codification -Section 45 -Paragraph 20 -Subparagraph (b) -Publisher FASB -URI https://asc.fasb.org//1943274/2147481694/830-30-45-20 Reference 6: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 220 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 4 -Publisher FASB -URI https://asc.fasb.org//1943274/2147482765/220-10-50-4 Reference 7: http://fasb.org/us-gaap/role/ref/legacyRef -Name Accounting Standards Codification -Section 55 -Paragraph 15 -SubTopic 10 -Topic 220 -Publisher FASB -URI https://asc.fasb.org//1943274/2147482739/220-10-55-15 + Details
Name: | us-gaap_OtherComprehensiveIncomeLossBeforeReclassificationsNetOfTax
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Amount after tax and reclassification adjustments of other comprehensive income (loss). + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Name Accounting Standards Codification -Section 50 -Paragraph 2 -SubTopic 10 -Topic 505 -Publisher FASB -URI https://asc.fasb.org//1943274/2147481112/505-10-50-2 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Topic 830 -SubTopic 30 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Publisher FASB -URI https://asc.fasb.org//1943274/2147481674/830-30-50-1 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Topic 830 -SubTopic 30 -Name Accounting Standards Codification -Section 45 -Paragraph 17 -Publisher FASB -URI https://asc.fasb.org//1943274/2147481694/830-30-45-17 Reference 4: http://www.xbrl.org/2003/role/disclosureRef -Topic 944 -SubTopic 220 -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-04(19)) -Publisher FASB -URI https://asc.fasb.org//1943274/2147483586/944-220-S99-1 Reference 5: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 220 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 4 -Publisher FASB -URI https://asc.fasb.org//1943274/2147482765/220-10-50-4 Reference 6: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 220 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 5 -Publisher FASB -URI https://asc.fasb.org//1943274/2147482765/220-10-50-5 Reference 7: http://www.xbrl.org/2003/role/disclosureRef -Topic 830 -SubTopic 30 -Name Accounting Standards Codification -Section 45 -Paragraph 20 -Publisher FASB -URI https://asc.fasb.org//1943274/2147481694/830-30-45-20 Reference 8: http://www.xbrl.org/2003/role/disclosureRef -Topic 220 -SubTopic 10 -Name Accounting Standards Codification -Section S99 -Paragraph 2 -Subparagraph (SX 210.5-03(21)) -Publisher FASB -URI https://asc.fasb.org//1943274/2147483621/220-10-S99-2 Reference 9: http://www.xbrl.org/2003/role/disclosureRef -Topic 942 -SubTopic 220 -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-04(23)) -Publisher FASB -URI https://asc.fasb.org//1943274/2147483589/942-220-S99-1 Reference 10: http://www.xbrl.org/2003/role/disclosureRef -Topic 220 -SubTopic 10 -Name Accounting Standards Codification -Section 45 -Paragraph 1B -Subparagraph (b) -Publisher FASB -URI https://asc.fasb.org//1943274/2147482790/220-10-45-1B Reference 11: http://fasb.org/us-gaap/role/ref/legacyRef -Name Accounting Standards Codification -Section 55 -Paragraph 15 -SubTopic 10 -Topic 220 -Publisher FASB -URI https://asc.fasb.org//1943274/2147482739/220-10-55-15 Reference 12: http://www.xbrl.org/2003/role/disclosureRef -Topic 220 -SubTopic 10 -Name Accounting Standards Codification -Section 45 -Paragraph 1A -Subparagraph (b) -Publisher FASB -URI https://asc.fasb.org//1943274/2147482790/220-10-45-1A + Details
Name: | us-gaap_OtherComprehensiveIncomeLossNetOfTax
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Amount after tax of reclassification adjustments of other comprehensive income (loss). + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Name Accounting Standards Codification -Topic 220 -SubTopic 10 -Section 45 -Paragraph 14A -Publisher FASB -URI https://asc.fasb.org//1943274/2147482790/220-10-45-14A Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Topic 220 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 5 -Publisher FASB -URI https://asc.fasb.org//1943274/2147482765/220-10-50-5 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Topic 830 -SubTopic 30 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Publisher FASB -URI https://asc.fasb.org//1943274/2147481674/830-30-50-1 Reference 4: http://www.xbrl.org/2003/role/disclosureRef -Topic 830 -SubTopic 30 -Name Accounting Standards Codification -Section 45 -Paragraph 17 -Publisher FASB -URI https://asc.fasb.org//1943274/2147481694/830-30-45-17 Reference 5: http://www.xbrl.org/2003/role/disclosureRef -Topic 830 -SubTopic 30 -Name Accounting Standards Codification -Section 45 -Paragraph 20 -Subparagraph (d) -Publisher FASB -URI https://asc.fasb.org//1943274/2147481694/830-30-45-20 Reference 6: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 220 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 4 -Publisher FASB -URI https://asc.fasb.org//1943274/2147482765/220-10-50-4 Reference 7: http://fasb.org/us-gaap/role/ref/legacyRef -Name Accounting Standards Codification -Section 55 -Paragraph 15 -SubTopic 10 -Topic 220 -Publisher FASB -URI https://asc.fasb.org//1943274/2147482739/220-10-55-15 + Details
Name: | us-gaap_ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTax
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period. + References No definition available. + Details
Name: | us-gaap_ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTaxAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Amount of equity (deficit) attributable to parent. Excludes temporary equity and equity attributable to noncontrolling interest. + References Reference 1: http://www.xbrl.org/2003/role/exampleRef -Topic 852 -SubTopic 10 -Name Accounting Standards Codification -Section 55 -Paragraph 10 -Publisher FASB -URI https://asc.fasb.org//1943274/2147481372/852-10-55-10 Reference 2: http://www.xbrl.org/2003/role/exampleRef -Topic 946 -SubTopic 830 -Name Accounting Standards Codification -Section 55 -Paragraph 12 -Publisher FASB -URI https://asc.fasb.org//1943274/2147480167/946-830-55-12 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Topic 946 -SubTopic 210 -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SX 210.6-04(19)) -Publisher FASB -URI https://asc.fasb.org//1943274/2147479617/946-210-S99-1 Reference 4: http://www.xbrl.org/2003/role/disclosureRef -Topic 946 -SubTopic 210 -Name Accounting Standards Codification -Section S99 -Paragraph 2 -Subparagraph (SX 210.6-05(4)) -Publisher FASB -URI https://asc.fasb.org//1943274/2147479617/946-210-S99-2 Reference 5: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 946 -SubTopic 220 -Name Accounting Standards Codification -Section S99 -Paragraph 3 -Subparagraph (SX 210.6-09(4)(b)) -Publisher FASB -URI https://asc.fasb.org//1943274/2147483575/946-220-S99-3 Reference 6: http://www.xbrl.org/2003/role/disclosureRef -Topic 946 -SubTopic 220 -Name Accounting Standards Codification -Section S99 -Paragraph 3 -Subparagraph (SX 210.6-09(6)) -Publisher FASB -URI https://asc.fasb.org//1943274/2147483575/946-220-S99-3 Reference 7: http://www.xbrl.org/2003/role/disclosureRef -Topic 946 -SubTopic 220 -Name Accounting Standards Codification -Section S99 -Paragraph 3 -Subparagraph (SX 210.6-09(7)) -Publisher FASB -URI https://asc.fasb.org//1943274/2147483575/946-220-S99-3 Reference 8: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 235 -SubTopic 10 -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SX 210.4-08(g)(1)(ii)) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480678/235-10-S99-1 Reference 9: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 323 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 3 -Subparagraph (c) -Publisher FASB -URI https://asc.fasb.org//1943274/2147481687/323-10-50-3 Reference 10: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 825 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 28 -Subparagraph (f) -Publisher FASB -URI https://asc.fasb.org//1943274/2147482907/825-10-50-28 Reference 11: 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(29)) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480566/210-10-S99-1 Reference 12: 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(31)) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480566/210-10-S99-1 Reference 13: 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(30)) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480566/210-10-S99-1 Reference 14: http://fasb.org/us-gaap/role/ref/legacyRef -Topic 310 -SubTopic 10 -Name Accounting Standards Codification -Section S99 -Paragraph 2 -Subparagraph (SAB Topic 4.E) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480418/310-10-S99-2 + Details
Name: | us-gaap_StockholdersEquity
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Details
Name: | us-gaap_StatementEquityComponentsAxis=us-gaap_AccumulatedNetGainLossFromDesignatedOrQualifyingCashFlowHedgesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_StatementEquityComponentsAxis=us-gaap_AccumulatedDefinedBenefitPlansAdjustmentMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_StatementEquityComponentsAxis=us-gaap_AccumulatedNetUnrealizedInvestmentGainLossMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_StatementEquityComponentsAxis=us-gaap_AccumulatedOtherComprehensiveIncomeMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |