00000677162020FYfalse00000677162020-01-012020-12-31iso4217:USD00000677162020-06-30xbrli:shares00000677162021-02-110000067716us-gaap:RegulatedOperationMember2020-01-012020-12-310000067716us-gaap:RegulatedOperationMember2019-01-012019-12-310000067716us-gaap:RegulatedOperationMember2018-01-012018-12-310000067716us-gaap:UnregulatedOperationMember2020-01-012020-12-310000067716us-gaap:UnregulatedOperationMember2019-01-012019-12-310000067716us-gaap:UnregulatedOperationMember2018-01-012018-12-3100000677162019-01-012019-12-3100000677162018-01-012018-12-31iso4217:USDxbrli:shares00000677162020-12-3100000677162019-12-310000067716srt:ParentCompanyMember2020-12-310000067716srt:ParentCompanyMember2019-12-310000067716us-gaap:CommonStockMember2017-12-310000067716us-gaap:CommonStockMembersrt:ScenarioPreviouslyReportedMember2017-12-310000067716us-gaap:AdditionalPaidInCapitalMembersrt:ScenarioPreviouslyReportedMember2017-12-310000067716us-gaap:RetainedEarningsMembersrt:ScenarioPreviouslyReportedMember2017-12-310000067716us-gaap:AccumulatedOtherComprehensiveIncomeMembersrt:ScenarioPreviouslyReportedMember2017-12-310000067716us-gaap:TreasuryStockMember2017-12-310000067716us-gaap:TreasuryStockMembersrt:ScenarioPreviouslyReportedMember2017-12-310000067716srt:ScenarioPreviouslyReportedMember2017-12-310000067716us-gaap:RetainedEarningsMembersrt:RevisionOfPriorPeriodAccountingStandardsUpdateAdjustmentMemberus-gaap:AccountingStandardsUpdate201409Member2017-12-310000067716srt:RevisionOfPriorPeriodAccountingStandardsUpdateAdjustmentMemberus-gaap:AccountingStandardsUpdate201409Member2017-12-310000067716us-gaap:AdditionalPaidInCapitalMember2017-12-310000067716us-gaap:RetainedEarningsMember2017-12-310000067716us-gaap:AccumulatedOtherComprehensiveIncomeMember2017-12-3100000677162017-12-310000067716us-gaap:RetainedEarningsMember2018-01-012018-12-310000067716us-gaap:AccumulatedOtherComprehensiveIncomeMember2018-01-012018-12-310000067716us-gaap:RetainedEarningsMembersrt:RevisionOfPriorPeriodAccountingStandardsUpdateAdjustmentMember2018-12-310000067716srt:RevisionOfPriorPeriodAccountingStandardsUpdateAdjustmentMemberus-gaap:AccumulatedOtherComprehensiveIncomeMember2018-12-310000067716srt:RevisionOfPriorPeriodAccountingStandardsUpdateAdjustmentMember2018-12-310000067716us-gaap:AdditionalPaidInCapitalMember2018-01-012018-12-310000067716us-gaap:TreasuryStockMember2018-01-012018-12-310000067716us-gaap:CommonStockMember2018-01-012018-12-310000067716us-gaap:CommonStockMember2018-12-310000067716us-gaap:AdditionalPaidInCapitalMember2018-12-310000067716us-gaap:RetainedEarningsMember2018-12-310000067716us-gaap:AccumulatedOtherComprehensiveIncomeMember2018-12-310000067716us-gaap:TreasuryStockMember2018-12-3100000677162018-12-310000067716us-gaap:RetainedEarningsMember2019-01-012019-12-310000067716us-gaap:AccumulatedOtherComprehensiveIncomeMember2019-01-012019-12-310000067716us-gaap:AdditionalPaidInCapitalMember2019-01-012019-12-310000067716us-gaap:CommonStockMember2019-01-012019-12-310000067716us-gaap:CommonStockMember2019-12-310000067716us-gaap:AdditionalPaidInCapitalMember2019-12-310000067716us-gaap:RetainedEarningsMember2019-12-310000067716us-gaap:AccumulatedOtherComprehensiveIncomeMember2019-12-310000067716us-gaap:TreasuryStockMember2019-12-310000067716us-gaap:RetainedEarningsMember2020-01-012020-12-310000067716us-gaap:AccumulatedOtherComprehensiveIncomeMember2020-01-012020-12-310000067716us-gaap:AdditionalPaidInCapitalMember2020-01-012020-12-310000067716us-gaap:CommonStockMember2020-01-012020-12-310000067716us-gaap:CommonStockMember2020-12-310000067716us-gaap:AdditionalPaidInCapitalMember2020-12-310000067716us-gaap:RetainedEarningsMember2020-12-310000067716us-gaap:AccumulatedOtherComprehensiveIncomeMember2020-12-310000067716us-gaap:TreasuryStockMember2020-12-310000067716srt:RestatementAdjustmentMember2020-03-310000067716srt:RestatementAdjustmentMember2020-01-012020-03-310000067716srt:RestatementAdjustmentMember2020-10-012020-12-310000067716srt:RestatementAdjustmentMember2020-12-310000067716mdu:ElectricMember2019-12-310000067716mdu:NaturalGasDistributionMember2019-12-310000067716mdu:PipelineandMidstreamMember2019-12-310000067716mdu:ConstructionMaterialsAndContractingMember2019-12-310000067716mdu:ConstructionServicesMember2019-12-310000067716mdu:ElectricMember2020-01-012020-12-310000067716mdu:NaturalGasDistributionMember2020-01-012020-12-310000067716mdu:PipelineandMidstreamMember2020-01-012020-12-310000067716mdu:ConstructionMaterialsAndContractingMember2020-01-012020-12-310000067716mdu:ConstructionServicesMember2020-01-012020-12-310000067716mdu:ElectricMember2020-12-310000067716mdu:NaturalGasDistributionMember2020-12-310000067716mdu:PipelineandMidstreamMember2020-12-310000067716mdu:ConstructionMaterialsAndContractingMember2020-12-310000067716mdu:ConstructionServicesMember2020-12-31utr:MMBTU0000067716us-gaap:CommodityContractMemberus-gaap:NotDesignatedAsHedgingInstrumentEconomicHedgeMember2020-01-012020-12-310000067716us-gaap:CommodityContractMemberus-gaap:NotDesignatedAsHedgingInstrumentEconomicHedgeMember2019-01-012019-12-31xbrli:pure0000067716mdu:ResidentialUtilitySalesMembermdu:ElectricMember2020-01-012020-12-310000067716mdu:ResidentialUtilitySalesMembermdu:NaturalGasDistributionMember2020-01-012020-12-310000067716mdu:ResidentialUtilitySalesMember2020-01-012020-12-310000067716mdu:ElectricMembermdu:CommercialUtilitySalesMember2020-01-012020-12-310000067716mdu:NaturalGasDistributionMembermdu:CommercialUtilitySalesMember2020-01-012020-12-310000067716mdu:CommercialUtilitySalesMember2020-01-012020-12-310000067716mdu:ElectricMembermdu:IndustrialUtilitySalesMember2020-01-012020-12-310000067716mdu:NaturalGasDistributionMembermdu:IndustrialUtilitySalesMember2020-01-012020-12-310000067716mdu:IndustrialUtilitySalesMember2020-01-012020-12-310000067716mdu:OtherUtilitySalesMembermdu:ElectricMember2020-01-012020-12-310000067716mdu:OtherUtilitySalesMembermdu:NaturalGasDistributionMember2020-01-012020-12-310000067716mdu:OtherUtilitySalesMember2020-01-012020-12-310000067716mdu:NaturalGasTransportationMembermdu:NaturalGasDistributionMember2020-01-012020-12-310000067716mdu:NaturalGasTransportationMembermdu:PipelineandMidstreamMember2020-01-012020-12-310000067716mdu:NaturalGasTransportationMember2020-01-012020-12-310000067716mdu:NaturalGasGatheringMembermdu:PipelineandMidstreamMember2020-01-012020-12-310000067716mdu:NaturalGasGatheringMember2020-01-012020-12-310000067716us-gaap:NaturalGasStorageMembermdu:PipelineandMidstreamMember2020-01-012020-12-310000067716us-gaap:NaturalGasStorageMember2020-01-012020-12-310000067716mdu:ConstructionMaterialsAndContractingMembermdu:ContractingServicesMember2020-01-012020-12-310000067716mdu:ContractingServicesMember2020-01-012020-12-310000067716mdu:ConstructionMaterialsAndContractingMembermdu:ConstructionMaterialsMember2020-01-012020-12-310000067716mdu:ConstructionMaterialsMember2020-01-012020-12-310000067716us-gaap:IntersubsegmentEliminationsMembermdu:ConstructionMaterialsAndContractingMember2020-01-012020-12-310000067716us-gaap:IntersubsegmentEliminationsMember2020-01-012020-12-310000067716mdu:ConstructionServicesMembermdu:InsideSpecialtyContractingMember2020-01-012020-12-310000067716mdu:InsideSpecialtyContractingMember2020-01-012020-12-310000067716mdu:ConstructionServicesMembermdu:OutsideSpecialtyContractingMember2020-01-012020-12-310000067716mdu:OutsideSpecialtyContractingMember2020-01-012020-12-310000067716mdu:ElectricMembermdu:OtherRevenuesMember2020-01-012020-12-310000067716mdu:NaturalGasDistributionMembermdu:OtherRevenuesMember2020-01-012020-12-310000067716mdu:PipelineandMidstreamMembermdu:OtherRevenuesMember2020-01-012020-12-310000067716mdu:ConstructionMaterialsAndContractingMembermdu:OtherRevenuesMember2020-01-012020-12-310000067716mdu:ConstructionServicesMembermdu:OtherRevenuesMember2020-01-012020-12-310000067716us-gaap:CorporateAndOtherMembermdu:OtherRevenuesMember2020-01-012020-12-310000067716mdu:OtherRevenuesMember2020-01-012020-12-310000067716us-gaap:IntersegmentEliminationMembermdu:ElectricMember2020-01-012020-12-310000067716us-gaap:IntersegmentEliminationMembermdu:NaturalGasDistributionMember2020-01-012020-12-310000067716us-gaap:IntersegmentEliminationMembermdu:PipelineandMidstreamMember2020-01-012020-12-310000067716us-gaap:IntersegmentEliminationMembermdu:ConstructionMaterialsAndContractingMember2020-01-012020-12-310000067716us-gaap:IntersegmentEliminationMembermdu:ConstructionServicesMember2020-01-012020-12-310000067716us-gaap:IntersegmentEliminationMemberus-gaap:CorporateAndOtherMember2020-01-012020-12-310000067716us-gaap:IntersegmentEliminationMember2020-01-012020-12-310000067716mdu:RevenueFromContractsWithCustomersMembermdu:ElectricMember2020-01-012020-12-310000067716mdu:RevenueFromContractsWithCustomersMembermdu:NaturalGasDistributionMember2020-01-012020-12-310000067716mdu:RevenueFromContractsWithCustomersMembermdu:PipelineandMidstreamMember2020-01-012020-12-310000067716mdu:RevenueFromContractsWithCustomersMembermdu:ConstructionMaterialsAndContractingMember2020-01-012020-12-310000067716mdu:RevenueFromContractsWithCustomersMembermdu:ConstructionServicesMember2020-01-012020-12-310000067716mdu:RevenueFromContractsWithCustomersMemberus-gaap:CorporateAndOtherMember2020-01-012020-12-310000067716mdu:RevenueFromContractsWithCustomersMember2020-01-012020-12-310000067716mdu:RevenuesOutOfScopeMembermdu:ElectricMember2020-01-012020-12-310000067716mdu:RevenuesOutOfScopeMembermdu:NaturalGasDistributionMember2020-01-012020-12-310000067716mdu:RevenuesOutOfScopeMembermdu:PipelineandMidstreamMember2020-01-012020-12-310000067716mdu:RevenuesOutOfScopeMembermdu:ConstructionMaterialsAndContractingMember2020-01-012020-12-310000067716mdu:RevenuesOutOfScopeMembermdu:ConstructionServicesMember2020-01-012020-12-310000067716mdu:RevenuesOutOfScopeMemberus-gaap:CorporateAndOtherMember2020-01-012020-12-310000067716mdu:RevenuesOutOfScopeMember2020-01-012020-12-310000067716us-gaap:CorporateAndOtherMember2020-01-012020-12-310000067716mdu:ResidentialUtilitySalesMembermdu:ElectricMember2019-01-012019-12-310000067716mdu:ResidentialUtilitySalesMembermdu:NaturalGasDistributionMember2019-01-012019-12-310000067716mdu:ResidentialUtilitySalesMember2019-01-012019-12-310000067716mdu:ElectricMembermdu:CommercialUtilitySalesMember2019-01-012019-12-310000067716mdu:NaturalGasDistributionMembermdu:CommercialUtilitySalesMember2019-01-012019-12-310000067716mdu:CommercialUtilitySalesMember2019-01-012019-12-310000067716mdu:ElectricMembermdu:IndustrialUtilitySalesMember2019-01-012019-12-310000067716mdu:NaturalGasDistributionMembermdu:IndustrialUtilitySalesMember2019-01-012019-12-310000067716mdu:IndustrialUtilitySalesMember2019-01-012019-12-310000067716mdu:OtherUtilitySalesMembermdu:ElectricMember2019-01-012019-12-310000067716mdu:OtherUtilitySalesMembermdu:NaturalGasDistributionMember2019-01-012019-12-310000067716mdu:OtherUtilitySalesMember2019-01-012019-12-310000067716mdu:NaturalGasTransportationMembermdu:NaturalGasDistributionMember2019-01-012019-12-310000067716mdu:NaturalGasTransportationMembermdu:PipelineandMidstreamMember2019-01-012019-12-310000067716mdu:NaturalGasTransportationMember2019-01-012019-12-310000067716mdu:NaturalGasGatheringMembermdu:PipelineandMidstreamMember2019-01-012019-12-310000067716mdu:NaturalGasGatheringMember2019-01-012019-12-310000067716us-gaap:NaturalGasStorageMembermdu:PipelineandMidstreamMember2019-01-012019-12-310000067716us-gaap:NaturalGasStorageMember2019-01-012019-12-310000067716mdu:ConstructionMaterialsAndContractingMembermdu:ContractingServicesMember2019-01-012019-12-310000067716mdu:ContractingServicesMember2019-01-012019-12-310000067716mdu:ConstructionMaterialsAndContractingMembermdu:ConstructionMaterialsMember2019-01-012019-12-310000067716mdu:ConstructionMaterialsMember2019-01-012019-12-310000067716us-gaap:IntersubsegmentEliminationsMembermdu:ConstructionMaterialsAndContractingMember2019-01-012019-12-310000067716us-gaap:IntersubsegmentEliminationsMember2019-01-012019-12-310000067716mdu:ConstructionServicesMembermdu:InsideSpecialtyContractingMember2019-01-012019-12-310000067716mdu:InsideSpecialtyContractingMember2019-01-012019-12-310000067716mdu:ConstructionServicesMembermdu:OutsideSpecialtyContractingMember2019-01-012019-12-310000067716mdu:OutsideSpecialtyContractingMember2019-01-012019-12-310000067716mdu:ElectricMembermdu:OtherRevenuesMember2019-01-012019-12-310000067716mdu:NaturalGasDistributionMembermdu:OtherRevenuesMember2019-01-012019-12-310000067716mdu:PipelineandMidstreamMembermdu:OtherRevenuesMember2019-01-012019-12-310000067716mdu:ConstructionMaterialsAndContractingMembermdu:OtherRevenuesMember2019-01-012019-12-310000067716mdu:ConstructionServicesMembermdu:OtherRevenuesMember2019-01-012019-12-310000067716us-gaap:CorporateAndOtherMembermdu:OtherRevenuesMember2019-01-012019-12-310000067716mdu:OtherRevenuesMember2019-01-012019-12-310000067716us-gaap:IntersegmentEliminationMembermdu:ElectricMember2019-01-012019-12-310000067716us-gaap:IntersegmentEliminationMembermdu:NaturalGasDistributionMember2019-01-012019-12-310000067716us-gaap:IntersegmentEliminationMembermdu:PipelineandMidstreamMember2019-01-012019-12-310000067716us-gaap:IntersegmentEliminationMembermdu:ConstructionMaterialsAndContractingMember2019-01-012019-12-310000067716us-gaap:IntersegmentEliminationMembermdu:ConstructionServicesMember2019-01-012019-12-310000067716us-gaap:IntersegmentEliminationMemberus-gaap:CorporateAndOtherMember2019-01-012019-12-310000067716us-gaap:IntersegmentEliminationMember2019-01-012019-12-310000067716mdu:RevenueFromContractsWithCustomersMembermdu:ElectricMember2019-01-012019-12-310000067716mdu:RevenueFromContractsWithCustomersMembermdu:NaturalGasDistributionMember2019-01-012019-12-310000067716mdu:RevenueFromContractsWithCustomersMembermdu:PipelineandMidstreamMember2019-01-012019-12-310000067716mdu:RevenueFromContractsWithCustomersMembermdu:ConstructionMaterialsAndContractingMember2019-01-012019-12-310000067716mdu:RevenueFromContractsWithCustomersMembermdu:ConstructionServicesMember2019-01-012019-12-310000067716mdu:RevenueFromContractsWithCustomersMemberus-gaap:CorporateAndOtherMember2019-01-012019-12-310000067716mdu:RevenueFromContractsWithCustomersMember2019-01-012019-12-310000067716mdu:RevenuesOutOfScopeMembermdu:ElectricMember2019-01-012019-12-310000067716mdu:RevenuesOutOfScopeMembermdu:NaturalGasDistributionMember2019-01-012019-12-310000067716mdu:RevenuesOutOfScopeMembermdu:PipelineandMidstreamMember2019-01-012019-12-310000067716mdu:RevenuesOutOfScopeMembermdu:ConstructionMaterialsAndContractingMember2019-01-012019-12-310000067716mdu:RevenuesOutOfScopeMembermdu:ConstructionServicesMember2019-01-012019-12-310000067716mdu:RevenuesOutOfScopeMemberus-gaap:CorporateAndOtherMember2019-01-012019-12-310000067716mdu:RevenuesOutOfScopeMember2019-01-012019-12-310000067716mdu:ElectricMember2019-01-012019-12-310000067716mdu:NaturalGasDistributionMember2019-01-012019-12-310000067716mdu:PipelineandMidstreamMember2019-01-012019-12-310000067716mdu:ConstructionMaterialsAndContractingMember2019-01-012019-12-310000067716mdu:ConstructionServicesMember2019-01-012019-12-310000067716us-gaap:CorporateAndOtherMember2019-01-012019-12-310000067716mdu:ResidentialUtilitySalesMembermdu:ElectricMember2018-01-012018-12-310000067716mdu:ResidentialUtilitySalesMembermdu:NaturalGasDistributionMember2018-01-012018-12-310000067716mdu:ResidentialUtilitySalesMember2018-01-012018-12-310000067716mdu:ElectricMembermdu:CommercialUtilitySalesMember2018-01-012018-12-310000067716mdu:NaturalGasDistributionMembermdu:CommercialUtilitySalesMember2018-01-012018-12-310000067716mdu:CommercialUtilitySalesMember2018-01-012018-12-310000067716mdu:ElectricMembermdu:IndustrialUtilitySalesMember2018-01-012018-12-310000067716mdu:NaturalGasDistributionMembermdu:IndustrialUtilitySalesMember2018-01-012018-12-310000067716mdu:IndustrialUtilitySalesMember2018-01-012018-12-310000067716mdu:OtherUtilitySalesMembermdu:ElectricMember2018-01-012018-12-310000067716mdu:OtherUtilitySalesMembermdu:NaturalGasDistributionMember2018-01-012018-12-310000067716mdu:OtherUtilitySalesMember2018-01-012018-12-310000067716mdu:NaturalGasTransportationMembermdu:NaturalGasDistributionMember2018-01-012018-12-310000067716mdu:NaturalGasTransportationMembermdu:PipelineandMidstreamMember2018-01-012018-12-310000067716mdu:NaturalGasTransportationMember2018-01-012018-12-310000067716mdu:NaturalGasGatheringMembermdu:PipelineandMidstreamMember2018-01-012018-12-310000067716mdu:NaturalGasGatheringMember2018-01-012018-12-310000067716us-gaap:NaturalGasStorageMembermdu:PipelineandMidstreamMember2018-01-012018-12-310000067716us-gaap:NaturalGasStorageMember2018-01-012018-12-310000067716mdu:ConstructionMaterialsAndContractingMembermdu:ContractingServicesMember2018-01-012018-12-310000067716mdu:ContractingServicesMember2018-01-012018-12-310000067716mdu:ConstructionMaterialsAndContractingMembermdu:ConstructionMaterialsMember2018-01-012018-12-310000067716mdu:ConstructionMaterialsMember2018-01-012018-12-310000067716us-gaap:IntersubsegmentEliminationsMembermdu:ConstructionMaterialsAndContractingMember2018-01-012018-12-310000067716us-gaap:IntersubsegmentEliminationsMember2018-01-012018-12-310000067716mdu:ConstructionServicesMembermdu:InsideSpecialtyContractingMember2018-01-012018-12-310000067716mdu:InsideSpecialtyContractingMember2018-01-012018-12-310000067716mdu:ConstructionServicesMembermdu:OutsideSpecialtyContractingMember2018-01-012018-12-310000067716mdu:OutsideSpecialtyContractingMember2018-01-012018-12-310000067716mdu:ElectricMembermdu:OtherRevenuesMember2018-01-012018-12-310000067716mdu:NaturalGasDistributionMembermdu:OtherRevenuesMember2018-01-012018-12-310000067716mdu:PipelineandMidstreamMembermdu:OtherRevenuesMember2018-01-012018-12-310000067716mdu:ConstructionMaterialsAndContractingMembermdu:OtherRevenuesMember2018-01-012018-12-310000067716mdu:ConstructionServicesMembermdu:OtherRevenuesMember2018-01-012018-12-310000067716us-gaap:CorporateAndOtherMembermdu:OtherRevenuesMember2018-01-012018-12-310000067716mdu:OtherRevenuesMember2018-01-012018-12-310000067716us-gaap:IntersegmentEliminationMembermdu:ElectricMember2018-01-012018-12-310000067716us-gaap:IntersegmentEliminationMembermdu:NaturalGasDistributionMember2018-01-012018-12-310000067716us-gaap:IntersegmentEliminationMembermdu:PipelineandMidstreamMember2018-01-012018-12-310000067716us-gaap:IntersegmentEliminationMembermdu:ConstructionMaterialsAndContractingMember2018-01-012018-12-310000067716us-gaap:IntersegmentEliminationMembermdu:ConstructionServicesMember2018-01-012018-12-310000067716us-gaap:IntersegmentEliminationMemberus-gaap:CorporateAndOtherMember2018-01-012018-12-310000067716us-gaap:IntersegmentEliminationMember2018-01-012018-12-310000067716mdu:RevenueFromContractsWithCustomersMembermdu:ElectricMember2018-01-012018-12-310000067716mdu:RevenueFromContractsWithCustomersMembermdu:NaturalGasDistributionMember2018-01-012018-12-310000067716mdu:RevenueFromContractsWithCustomersMembermdu:PipelineandMidstreamMember2018-01-012018-12-310000067716mdu:RevenueFromContractsWithCustomersMembermdu:ConstructionMaterialsAndContractingMember2018-01-012018-12-310000067716mdu:RevenueFromContractsWithCustomersMembermdu:ConstructionServicesMember2018-01-012018-12-310000067716mdu:RevenueFromContractsWithCustomersMemberus-gaap:CorporateAndOtherMember2018-01-012018-12-310000067716mdu:RevenueFromContractsWithCustomersMember2018-01-012018-12-310000067716mdu:RevenuesOutOfScopeMembermdu:ElectricMember2018-01-012018-12-310000067716mdu:RevenuesOutOfScopeMembermdu:NaturalGasDistributionMember2018-01-012018-12-310000067716mdu:RevenuesOutOfScopeMembermdu:PipelineandMidstreamMember2018-01-012018-12-310000067716mdu:RevenuesOutOfScopeMembermdu:ConstructionMaterialsAndContractingMember2018-01-012018-12-310000067716mdu:RevenuesOutOfScopeMembermdu:ConstructionServicesMember2018-01-012018-12-310000067716mdu:RevenuesOutOfScopeMemberus-gaap:CorporateAndOtherMember2018-01-012018-12-310000067716mdu:RevenuesOutOfScopeMember2018-01-012018-12-310000067716mdu:ElectricMember2018-01-012018-12-310000067716mdu:NaturalGasDistributionMember2018-01-012018-12-310000067716mdu:PipelineandMidstreamMember2018-01-012018-12-310000067716mdu:ConstructionMaterialsAndContractingMember2018-01-012018-12-310000067716mdu:ConstructionServicesMember2018-01-012018-12-310000067716us-gaap:CorporateAndOtherMember2018-01-012018-12-3100000677162021-01-012020-12-3100000677162022-01-012020-12-3100000677162023-01-012020-12-310000067716mdu:A2020AcquisitionMember2020-01-012020-12-310000067716mdu:A2020AcquisitionMember2020-12-310000067716mdu:A2019AcquisitionMember2019-01-012019-12-310000067716mdu:A2019AcquisitionMember2019-12-310000067716us-gaap:ElectricGenerationEquipmentMembermdu:ElectricMemberus-gaap:RegulatedOperationMember2020-12-310000067716us-gaap:ElectricGenerationEquipmentMembermdu:ElectricMemberus-gaap:RegulatedOperationMember2019-12-310000067716us-gaap:ElectricGenerationEquipmentMembermdu:ElectricMemberus-gaap:RegulatedOperationMember2020-01-012020-12-310000067716mdu:ElectricMemberus-gaap:ElectricDistributionMemberus-gaap:RegulatedOperationMember2020-12-310000067716mdu:ElectricMemberus-gaap:ElectricDistributionMemberus-gaap:RegulatedOperationMember2019-12-310000067716mdu:ElectricMemberus-gaap:ElectricDistributionMemberus-gaap:RegulatedOperationMember2020-01-012020-12-310000067716us-gaap:ElectricTransmissionMembermdu:ElectricMemberus-gaap:RegulatedOperationMember2020-12-310000067716us-gaap:ElectricTransmissionMembermdu:ElectricMemberus-gaap:RegulatedOperationMember2019-12-310000067716us-gaap:ElectricTransmissionMembermdu:ElectricMemberus-gaap:RegulatedOperationMember2020-01-012020-12-310000067716us-gaap:ConstructionInProgressMembermdu:ElectricMemberus-gaap:RegulatedOperationMember2020-12-310000067716us-gaap:ConstructionInProgressMembermdu:ElectricMemberus-gaap:RegulatedOperationMember2019-12-310000067716us-gaap:OtherCapitalizedPropertyPlantAndEquipmentMembermdu:ElectricMemberus-gaap:RegulatedOperationMember2020-12-310000067716us-gaap:OtherCapitalizedPropertyPlantAndEquipmentMembermdu:ElectricMemberus-gaap:RegulatedOperationMember2019-12-310000067716us-gaap:OtherCapitalizedPropertyPlantAndEquipmentMembermdu:ElectricMemberus-gaap:RegulatedOperationMember2020-01-012020-12-310000067716us-gaap:GasDistributionMembermdu:NaturalGasDistributionMemberus-gaap:RegulatedOperationMember2020-12-310000067716us-gaap:GasDistributionMembermdu:NaturalGasDistributionMemberus-gaap:RegulatedOperationMember2019-12-310000067716us-gaap:GasDistributionMembermdu:NaturalGasDistributionMemberus-gaap:RegulatedOperationMember2020-01-012020-12-310000067716us-gaap:GasTransmissionMembermdu:NaturalGasDistributionMemberus-gaap:RegulatedOperationMember2020-12-310000067716us-gaap:GasTransmissionMembermdu:NaturalGasDistributionMemberus-gaap:RegulatedOperationMember2019-12-310000067716us-gaap:GasTransmissionMembermdu:NaturalGasDistributionMemberus-gaap:RegulatedOperationMember2020-01-012020-12-310000067716mdu:NaturalGasDistributionMemberus-gaap:RegulatedOperationMemberus-gaap:NaturalGasStorageMember2020-12-310000067716mdu:NaturalGasDistributionMemberus-gaap:RegulatedOperationMemberus-gaap:NaturalGasStorageMember2019-12-310000067716mdu:NaturalGasDistributionMemberus-gaap:RegulatedOperationMemberus-gaap:NaturalGasStorageMember2020-01-012020-12-310000067716mdu:GeneralMembermdu:NaturalGasDistributionMemberus-gaap:RegulatedOperationMember2020-12-310000067716mdu:GeneralMembermdu:NaturalGasDistributionMemberus-gaap:RegulatedOperationMember2019-12-310000067716mdu:GeneralMembermdu:NaturalGasDistributionMemberus-gaap:RegulatedOperationMember2020-01-012020-12-310000067716us-gaap:ConstructionInProgressMembermdu:NaturalGasDistributionMemberus-gaap:RegulatedOperationMember2020-12-310000067716us-gaap:ConstructionInProgressMembermdu:NaturalGasDistributionMemberus-gaap:RegulatedOperationMember2019-12-310000067716us-gaap:OtherCapitalizedPropertyPlantAndEquipmentMembermdu:NaturalGasDistributionMemberus-gaap:RegulatedOperationMember2020-12-310000067716us-gaap:OtherCapitalizedPropertyPlantAndEquipmentMembermdu:NaturalGasDistributionMemberus-gaap:RegulatedOperationMember2019-12-310000067716us-gaap:OtherCapitalizedPropertyPlantAndEquipmentMembermdu:NaturalGasDistributionMemberus-gaap:RegulatedOperationMember2020-01-012020-12-310000067716us-gaap:GasTransmissionMembermdu:PipelineandMidstreamMemberus-gaap:RegulatedOperationMember2020-12-310000067716us-gaap:GasTransmissionMembermdu:PipelineandMidstreamMemberus-gaap:RegulatedOperationMember2019-12-310000067716us-gaap:GasTransmissionMembermdu:PipelineandMidstreamMemberus-gaap:RegulatedOperationMember2020-01-012020-12-310000067716us-gaap:GasGatheringAndProcessingEquipmentMembermdu:PipelineandMidstreamMemberus-gaap:RegulatedOperationMember2020-12-310000067716us-gaap:GasGatheringAndProcessingEquipmentMembermdu:PipelineandMidstreamMemberus-gaap:RegulatedOperationMember2019-12-310000067716mdu:PipelineandMidstreamMembermdu:GasStorageMemberus-gaap:RegulatedOperationMember2020-12-310000067716mdu:PipelineandMidstreamMembermdu:GasStorageMemberus-gaap:RegulatedOperationMember2019-12-310000067716mdu:PipelineandMidstreamMembermdu:GasStorageMemberus-gaap:RegulatedOperationMember2020-01-012020-12-310000067716us-gaap:ConstructionInProgressMembermdu:PipelineandMidstreamMemberus-gaap:RegulatedOperationMember2020-12-310000067716us-gaap:ConstructionInProgressMembermdu:PipelineandMidstreamMemberus-gaap:RegulatedOperationMember2019-12-310000067716us-gaap:OtherCapitalizedPropertyPlantAndEquipmentMembermdu:PipelineandMidstreamMemberus-gaap:RegulatedOperationMember2020-12-310000067716us-gaap:OtherCapitalizedPropertyPlantAndEquipmentMembermdu:PipelineandMidstreamMemberus-gaap:RegulatedOperationMember2019-12-310000067716us-gaap:OtherCapitalizedPropertyPlantAndEquipmentMembermdu:PipelineandMidstreamMemberus-gaap:RegulatedOperationMember2020-01-012020-12-310000067716mdu:PipelineandMidstreamMemberus-gaap:UnregulatedOperationMembermdu:GatheringandprocessingMemberDomain2020-12-310000067716mdu:PipelineandMidstreamMemberus-gaap:UnregulatedOperationMembermdu:GatheringandprocessingMemberDomain2019-12-310000067716us-gaap:ConstructionInProgressMembermdu:PipelineandMidstreamMemberus-gaap:UnregulatedOperationMember2020-12-310000067716us-gaap:ConstructionInProgressMembermdu:PipelineandMidstreamMemberus-gaap:UnregulatedOperationMember2019-12-310000067716us-gaap:OtherCapitalizedPropertyPlantAndEquipmentMembermdu:PipelineandMidstreamMemberus-gaap:UnregulatedOperationMember2020-12-310000067716us-gaap:OtherCapitalizedPropertyPlantAndEquipmentMembermdu:PipelineandMidstreamMemberus-gaap:UnregulatedOperationMember2019-12-310000067716us-gaap:OtherCapitalizedPropertyPlantAndEquipmentMembermdu:PipelineandMidstreamMemberus-gaap:UnregulatedOperationMember2020-01-012020-12-310000067716us-gaap:UnregulatedOperationMembermdu:ConstructionMaterialsAndContractingMemberus-gaap:LandMember2020-12-310000067716us-gaap:UnregulatedOperationMembermdu:ConstructionMaterialsAndContractingMemberus-gaap:LandMember2019-12-310000067716us-gaap:UnregulatedOperationMemberus-gaap:BuildingAndBuildingImprovementsMembermdu:ConstructionMaterialsAndContractingMember2020-12-310000067716us-gaap:UnregulatedOperationMemberus-gaap:BuildingAndBuildingImprovementsMembermdu:ConstructionMaterialsAndContractingMember2019-12-310000067716us-gaap:UnregulatedOperationMemberus-gaap:BuildingAndBuildingImprovementsMembermdu:ConstructionMaterialsAndContractingMember2020-01-012020-12-310000067716us-gaap:UnregulatedOperationMemberus-gaap:MachineryAndEquipmentMembermdu:ConstructionMaterialsAndContractingMember2020-12-310000067716us-gaap:UnregulatedOperationMemberus-gaap:MachineryAndEquipmentMembermdu:ConstructionMaterialsAndContractingMember2019-12-310000067716us-gaap:UnregulatedOperationMemberus-gaap:MachineryAndEquipmentMembermdu:ConstructionMaterialsAndContractingMember2020-01-012020-12-310000067716us-gaap:ConstructionInProgressMemberus-gaap:UnregulatedOperationMembermdu:ConstructionMaterialsAndContractingMember2020-12-310000067716us-gaap:ConstructionInProgressMemberus-gaap:UnregulatedOperationMembermdu:ConstructionMaterialsAndContractingMember2019-12-310000067716us-gaap:UnregulatedOperationMembermdu:AggregateReservesMembermdu:ConstructionMaterialsAndContractingMember2020-12-310000067716us-gaap:UnregulatedOperationMembermdu:AggregateReservesMembermdu:ConstructionMaterialsAndContractingMember2019-12-310000067716mdu:ConstructionServicesMemberus-gaap:UnregulatedOperationMemberus-gaap:LandMember2020-12-310000067716mdu:ConstructionServicesMemberus-gaap:UnregulatedOperationMemberus-gaap:LandMember2019-12-310000067716mdu:ConstructionServicesMemberus-gaap:UnregulatedOperationMemberus-gaap:BuildingAndBuildingImprovementsMember2020-12-310000067716mdu:ConstructionServicesMemberus-gaap:UnregulatedOperationMemberus-gaap:BuildingAndBuildingImprovementsMember2019-12-310000067716mdu:ConstructionServicesMemberus-gaap:UnregulatedOperationMemberus-gaap:BuildingAndBuildingImprovementsMember2020-01-012020-12-310000067716mdu:ConstructionServicesMemberus-gaap:UnregulatedOperationMemberus-gaap:MachineryAndEquipmentMember2020-12-310000067716mdu:ConstructionServicesMemberus-gaap:UnregulatedOperationMemberus-gaap:MachineryAndEquipmentMember2019-12-310000067716mdu:ConstructionServicesMemberus-gaap:UnregulatedOperationMemberus-gaap:MachineryAndEquipmentMember2020-01-012020-12-310000067716us-gaap:OtherCapitalizedPropertyPlantAndEquipmentMembermdu:ConstructionServicesMemberus-gaap:UnregulatedOperationMember2020-12-310000067716us-gaap:OtherCapitalizedPropertyPlantAndEquipmentMembermdu:ConstructionServicesMemberus-gaap:UnregulatedOperationMember2019-12-310000067716us-gaap:OtherCapitalizedPropertyPlantAndEquipmentMembermdu:ConstructionServicesMemberus-gaap:UnregulatedOperationMember2020-01-012020-12-310000067716us-gaap:UnregulatedOperationMemberus-gaap:CorporateAndOtherMemberus-gaap:LandMember2020-12-310000067716us-gaap:UnregulatedOperationMemberus-gaap:CorporateAndOtherMemberus-gaap:LandMember2019-12-310000067716us-gaap:OtherCapitalizedPropertyPlantAndEquipmentMemberus-gaap:UnregulatedOperationMemberus-gaap:CorporateAndOtherMember2020-12-310000067716us-gaap:OtherCapitalizedPropertyPlantAndEquipmentMemberus-gaap:UnregulatedOperationMemberus-gaap:CorporateAndOtherMember2019-12-310000067716us-gaap:OtherCapitalizedPropertyPlantAndEquipmentMemberus-gaap:UnregulatedOperationMemberus-gaap:CorporateAndOtherMember2020-01-012020-12-310000067716us-gaap:AssetRecoverableGasCostsMembersrt:MinimumMember2020-01-012020-12-310000067716us-gaap:AssetRecoverableGasCostsMember2020-12-310000067716us-gaap:AssetRecoverableGasCostsMember2019-12-310000067716us-gaap:RegulatoryClauseRevenuesUnderRecoveredMembersrt:MinimumMember2020-01-012020-12-310000067716us-gaap:RegulatoryClauseRevenuesUnderRecoveredMember2020-12-310000067716us-gaap:RegulatoryClauseRevenuesUnderRecoveredMember2019-12-310000067716us-gaap:RenewableEnergyProgramMember2020-01-012020-12-310000067716us-gaap:RenewableEnergyProgramMember2020-12-310000067716us-gaap:RenewableEnergyProgramMember2019-12-310000067716us-gaap:OtherRegulatoryAssetsLiabilitiesMembersrt:MinimumMember2020-01-012020-12-310000067716us-gaap:OtherRegulatoryAssetsLiabilitiesMember2020-12-310000067716us-gaap:OtherRegulatoryAssetsLiabilitiesMember2019-12-310000067716us-gaap:PensionAndOtherPostretirementPlansCostsMember2020-01-012020-12-310000067716us-gaap:PensionAndOtherPostretirementPlansCostsMember2020-12-310000067716us-gaap:PensionAndOtherPostretirementPlansCostsMember2019-12-310000067716us-gaap:AssetRetirementObligationCostsMember2020-01-012020-12-310000067716us-gaap:AssetRetirementObligationCostsMember2020-12-310000067716us-gaap:AssetRetirementObligationCostsMember2019-12-310000067716us-gaap:RemovalCostsMember2020-01-012020-12-310000067716us-gaap:RemovalCostsMember2020-12-310000067716us-gaap:RemovalCostsMember2019-12-310000067716us-gaap:EnvironmentalRestorationCostsMember2020-01-012020-12-310000067716us-gaap:EnvironmentalRestorationCostsMember2020-12-310000067716us-gaap:EnvironmentalRestorationCostsMember2019-12-310000067716us-gaap:AssetRecoverableGasCostsMembersrt:MaximumMember2020-01-012020-12-310000067716us-gaap:RegulatoryClauseRevenuesUnderRecoveredMembersrt:MaximumMember2020-01-012020-12-310000067716us-gaap:DeferredIncomeTaxChargesMember2020-01-012020-12-310000067716us-gaap:DeferredIncomeTaxChargesMember2020-12-310000067716us-gaap:DeferredIncomeTaxChargesMember2019-12-310000067716us-gaap:LossOnReacquiredDebtMember2020-01-012020-12-310000067716us-gaap:LossOnReacquiredDebtMember2020-12-310000067716us-gaap:LossOnReacquiredDebtMember2019-12-310000067716us-gaap:OtherRegulatoryAssetsLiabilitiesMembersrt:MaximumMember2020-01-012020-12-310000067716mdu:LiabilitiesRefundableGasCostsMember2020-01-012020-12-310000067716mdu:LiabilitiesRefundableGasCostsMember2020-12-310000067716mdu:LiabilitiesRefundableGasCostsMember2019-12-310000067716mdu:LiabilitiesElectricFuelAndPurchasedPowerDeferralMember2020-01-012020-12-310000067716mdu:LiabilitiesElectricFuelAndPurchasedPowerDeferralMember2020-12-310000067716mdu:LiabilitiesElectricFuelAndPurchasedPowerDeferralMember2019-12-310000067716us-gaap:DeferredIncomeTaxChargesMembersrt:MinimumMember2020-01-012020-12-310000067716us-gaap:DeferredIncomeTaxChargesMember2020-12-310000067716us-gaap:DeferredIncomeTaxChargesMember2019-12-310000067716us-gaap:OtherRegulatoryAssetsLiabilitiesMembersrt:MinimumMember2020-01-012020-12-310000067716us-gaap:OtherRegulatoryAssetsLiabilitiesMember2020-12-310000067716us-gaap:OtherRegulatoryAssetsLiabilitiesMember2019-12-310000067716us-gaap:DeferredIncomeTaxChargesMembersrt:MaximumMember2020-01-012020-12-310000067716us-gaap:RemovalCostsMember2020-01-012020-12-310000067716us-gaap:RemovalCostsMember2020-12-310000067716us-gaap:RemovalCostsMember2019-12-310000067716us-gaap:PensionAndOtherPostretirementPlansCostsMember2020-01-012020-12-310000067716us-gaap:PensionAndOtherPostretirementPlansCostsMember2020-12-310000067716us-gaap:PensionAndOtherPostretirementPlansCostsMember2019-12-310000067716us-gaap:OtherRegulatoryAssetsLiabilitiesMembersrt:MaximumMember2020-01-012020-12-310000067716mdu:NaturalGasDistributionMember2018-12-310000067716mdu:ConstructionMaterialsAndContractingMember2018-12-310000067716mdu:ConstructionServicesMember2018-12-310000067716us-gaap:CustomerRelationshipsMember2020-12-310000067716us-gaap:CustomerRelationshipsMember2019-12-310000067716us-gaap:NoncompeteAgreementsMember2020-12-310000067716us-gaap:NoncompeteAgreementsMember2019-12-310000067716us-gaap:OtherIntangibleAssetsMember2020-12-310000067716us-gaap:OtherIntangibleAssetsMember2019-12-310000067716us-gaap:MortgageBackedSecuritiesMember2020-12-310000067716us-gaap:USTreasurySecuritiesMember2020-12-310000067716us-gaap:MortgageBackedSecuritiesMember2019-12-310000067716us-gaap:USTreasurySecuritiesMember2019-12-310000067716us-gaap:FairValueInputsLevel2Memberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:MoneyMarketFundsMember2020-12-310000067716us-gaap:FairValueMeasurementsRecurringMemberus-gaap:MoneyMarketFundsMember2020-12-310000067716us-gaap:FairValueInputsLevel2Memberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:CashSurrenderValueMember2020-12-310000067716us-gaap:FairValueMeasurementsRecurringMemberus-gaap:CashSurrenderValueMember2020-12-310000067716us-gaap:FairValueInputsLevel2Memberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:MortgageBackedSecuritiesMember2020-12-310000067716us-gaap:FairValueMeasurementsRecurringMemberus-gaap:MortgageBackedSecuritiesMember2020-12-310000067716us-gaap:FairValueInputsLevel2Memberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:USTreasurySecuritiesMember2020-12-310000067716us-gaap:FairValueMeasurementsRecurringMemberus-gaap:USTreasurySecuritiesMember2020-12-310000067716us-gaap:FairValueInputsLevel2Memberus-gaap:FairValueMeasurementsRecurringMember2020-12-310000067716us-gaap:FairValueMeasurementsRecurringMember2020-12-310000067716us-gaap:FairValueInputsLevel2Memberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:MoneyMarketFundsMember2019-12-310000067716us-gaap:FairValueMeasurementsRecurringMemberus-gaap:MoneyMarketFundsMember2019-12-310000067716us-gaap:FairValueInputsLevel2Memberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:CashSurrenderValueMember2019-12-310000067716us-gaap:FairValueMeasurementsRecurringMemberus-gaap:CashSurrenderValueMember2019-12-310000067716us-gaap:FairValueInputsLevel2Memberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:MortgageBackedSecuritiesMember2019-12-310000067716us-gaap:FairValueMeasurementsRecurringMemberus-gaap:MortgageBackedSecuritiesMember2019-12-310000067716us-gaap:FairValueInputsLevel2Memberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:USTreasurySecuritiesMember2019-12-310000067716us-gaap:FairValueMeasurementsRecurringMemberus-gaap:USTreasurySecuritiesMember2019-12-310000067716us-gaap:FairValueInputsLevel2Memberus-gaap:FairValueMeasurementsRecurringMember2019-12-310000067716us-gaap:FairValueMeasurementsRecurringMember2019-12-3100000677162019-06-3000000677162019-04-012019-06-300000067716us-gaap:CarryingReportedAmountFairValueDisclosureMember2020-12-310000067716us-gaap:CarryingReportedAmountFairValueDisclosureMember2019-12-310000067716us-gaap:EstimateOfFairValueFairValueDisclosureMember2020-12-310000067716us-gaap:EstimateOfFairValueFairValueDisclosureMember2019-12-310000067716us-gaap:LongTermDebtMembermdu:MontanaDakotaUtilitiesCo.Membermdu:CommercialPaperRevolvingCreditAgreementMember2020-12-310000067716us-gaap:LongTermDebtMembermdu:MontanaDakotaUtilitiesCo.Membermdu:CommercialPaperRevolvingCreditAgreementMember2019-12-310000067716us-gaap:LongTermDebtMembermdu:MontanaDakotaUtilitiesCo.Membermdu:CommercialPaperRevolvingCreditAgreementMember2020-01-012020-12-310000067716us-gaap:LongTermDebtMembermdu:CascadeNaturalGasCorporationMemberus-gaap:RevolvingCreditFacilityMember2020-12-310000067716us-gaap:LongTermDebtMembermdu:CascadeNaturalGasCorporationMemberus-gaap:RevolvingCreditFacilityMember2019-12-310000067716us-gaap:LongTermDebtMembermdu:CascadeNaturalGasCorporationMemberus-gaap:RevolvingCreditFacilityMember2020-01-012020-12-310000067716us-gaap:LongTermDebtMemberus-gaap:RevolvingCreditFacilityMembermdu:IntermountainGasCompanyMember2020-12-310000067716us-gaap:LongTermDebtMemberus-gaap:RevolvingCreditFacilityMembermdu:IntermountainGasCompanyMember2019-12-310000067716us-gaap:LongTermDebtMemberus-gaap:RevolvingCreditFacilityMembermdu:IntermountainGasCompanyMember2020-01-012020-12-310000067716us-gaap:LongTermDebtMembermdu:CentennialEnergyHoldingsIncMembermdu:CommercialPaperRevolvingCreditAgreementMember2020-12-310000067716us-gaap:LongTermDebtMembermdu:CentennialEnergyHoldingsIncMembermdu:CommercialPaperRevolvingCreditAgreementMember2019-12-310000067716us-gaap:LongTermDebtMembermdu:CentennialEnergyHoldingsIncMembermdu:CommercialPaperRevolvingCreditAgreementMember2020-01-012020-12-310000067716us-gaap:LongTermDebtMembermdu:MontanaDakotaUtilitiesCo.Memberus-gaap:RevolvingCreditFacilityMember2020-12-310000067716us-gaap:LongTermDebtMembermdu:CentennialEnergyHoldingsIncMemberus-gaap:RevolvingCreditFacilityMember2020-12-310000067716mdu:MontanaDakotaUtilitiesCo.Membermdu:TermLoanAgreementMember2020-12-310000067716mdu:MontanaDakotaUtilitiesCo.Member2020-12-310000067716us-gaap:SeniorNotesMember2020-12-310000067716us-gaap:SeniorNotesMember2019-12-310000067716us-gaap:CommercialPaperMember2020-12-310000067716us-gaap:CommercialPaperMember2019-12-310000067716us-gaap:LineOfCreditMember2020-12-310000067716us-gaap:LineOfCreditMember2019-12-310000067716us-gaap:MediumTermNotesMember2020-12-310000067716us-gaap:MediumTermNotesMember2019-12-310000067716us-gaap:LoansPayableMember2020-12-310000067716us-gaap:LoansPayableMember2019-12-310000067716us-gaap:NotesPayableToBanksMember2020-12-310000067716us-gaap:NotesPayableToBanksMember2019-12-310000067716us-gaap:LongTermDebtMember2020-12-310000067716us-gaap:LongTermDebtMember2019-12-310000067716mdu:MontanaDakotaUtilitiesCo.Memberus-gaap:RevolvingCreditFacilityMember2020-12-310000067716us-gaap:RevolvingCreditFacilityMembermdu:CascadeNaturalGasMember2020-12-310000067716us-gaap:SeniorNotesMembermdu:CascadeNaturalGasMember2020-06-150000067716us-gaap:SeniorNotesMembermdu:CascadeNaturalGasMember2020-10-300000067716mdu:CascadeNaturalGasMember2020-12-310000067716us-gaap:RevolvingCreditFacilityMembermdu:IntermountainGasCompanyMember2020-12-310000067716mdu:IntermountainGasCompanyMember2020-12-310000067716mdu:CentennialEnergyHoldingsIncMemberus-gaap:RevolvingCreditFacilityMember2020-12-310000067716mdu:CentennialEnergyHoldingsIncMember2020-12-310000067716mdu:WbiEnergyTransmissionIncMemberus-gaap:SeniorNotesMember2019-07-260000067716mdu:WbiEnergyTransmissionIncMemberus-gaap:SeniorNotesMember2020-12-160000067716mdu:WbiEnergyTransmissionIncMemberus-gaap:SeniorNotesMember2020-12-310000067716mdu:WbiEnergyTransmissionIncMember2020-12-310000067716us-gaap:AssetRetirementObligationCostsMember2019-01-012019-12-310000067716us-gaap:CommonStockMember2020-01-012020-12-310000067716us-gaap:CommonStockMember2019-01-012019-12-310000067716us-gaap:CommonStockMember2018-01-012018-12-310000067716mdu:CentennialMember2020-01-012020-12-310000067716mdu:AtthemarketofferingMember2020-12-310000067716mdu:AtthemarketofferingMember2019-12-310000067716mdu:AtthemarketofferingMember2019-01-012019-12-310000067716mdu:KPlanMember2020-12-310000067716us-gaap:PreferredStockMember2020-12-310000067716us-gaap:PreferredStockMember2019-12-310000067716us-gaap:RestrictedStockUnitsRSUMember2020-12-310000067716us-gaap:RestrictedStockUnitsRSUMember2020-01-012020-12-310000067716mdu:GrantDateFebruary2019Memberus-gaap:PerformanceSharesMember2020-12-310000067716mdu:GrantDateFebruary2020Memberus-gaap:PerformanceSharesMember2020-12-310000067716mdu:MarketConditionMembersrt:MinimumMemberus-gaap:PerformanceSharesMember2020-01-012020-12-310000067716mdu:MarketConditionMemberus-gaap:PerformanceSharesMembersrt:MaximumMember2020-01-012020-12-310000067716mdu:MarketConditionMemberus-gaap:PerformanceSharesMember2020-01-012020-12-310000067716mdu:MarketConditionMemberus-gaap:PerformanceSharesMember2019-01-012019-12-310000067716mdu:MarketConditionMemberus-gaap:PerformanceSharesMember2018-01-012018-12-310000067716mdu:PerformanceConditionMembersrt:MinimumMemberus-gaap:PerformanceSharesMember2020-01-012020-12-310000067716mdu:PerformanceConditionMemberus-gaap:PerformanceSharesMembersrt:MaximumMember2020-01-012020-12-310000067716mdu:PerformanceConditionMemberus-gaap:PerformanceSharesMember2020-01-012020-12-310000067716mdu:PerformanceConditionMemberus-gaap:PerformanceSharesMember2019-01-012019-12-310000067716mdu:PerformanceConditionMemberus-gaap:PerformanceSharesMember2018-01-012018-12-310000067716us-gaap:PerformanceSharesMember2020-01-012020-12-310000067716us-gaap:PerformanceSharesMember2019-01-012019-12-310000067716us-gaap:PerformanceSharesMember2018-01-012018-12-310000067716us-gaap:PerformanceSharesMember2019-12-310000067716us-gaap:PerformanceSharesMember2020-12-310000067716us-gaap:AccumulatedNetGainLossFromDesignatedOrQualifyingCashFlowHedgesMember2018-12-310000067716us-gaap:AccumulatedDefinedBenefitPlansAdjustmentMember2018-12-310000067716us-gaap:AccumulatedNetUnrealizedInvestmentGainLossMember2018-12-310000067716us-gaap:AccumulatedNetGainLossFromDesignatedOrQualifyingCashFlowHedgesMember2019-01-012019-12-310000067716us-gaap:AccumulatedDefinedBenefitPlansAdjustmentMember2019-01-012019-12-310000067716us-gaap:AccumulatedNetUnrealizedInvestmentGainLossMember2019-01-012019-12-310000067716us-gaap:AccumulatedNetGainLossFromDesignatedOrQualifyingCashFlowHedgesMember2019-12-310000067716us-gaap:AccumulatedDefinedBenefitPlansAdjustmentMember2019-12-310000067716us-gaap:AccumulatedNetUnrealizedInvestmentGainLossMember2019-12-310000067716us-gaap:AccumulatedNetGainLossFromDesignatedOrQualifyingCashFlowHedgesMember2020-01-012020-12-310000067716us-gaap:AccumulatedDefinedBenefitPlansAdjustmentMember2020-01-012020-12-310000067716us-gaap:AccumulatedNetUnrealizedInvestmentGainLossMember2020-01-012020-12-310000067716us-gaap:AccumulatedNetGainLossFromDesignatedOrQualifyingCashFlowHedgesMember2020-12-310000067716us-gaap:AccumulatedDefinedBenefitPlansAdjustmentMember2020-12-310000067716us-gaap:AccumulatedNetUnrealizedInvestmentGainLossMember2020-12-310000067716us-gaap:InterestRateContractMemberus-gaap:AccumulatedNetGainLossFromDesignatedOrQualifyingCashFlowHedgesMemberus-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncomeMember2020-01-012020-12-310000067716us-gaap:InterestRateContractMemberus-gaap:AccumulatedNetGainLossFromDesignatedOrQualifyingCashFlowHedgesMemberus-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncomeMember2019-01-012019-12-310000067716us-gaap:AccumulatedDefinedBenefitPlansAdjustmentMemberus-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncomeMember2020-01-012020-12-310000067716us-gaap:AccumulatedDefinedBenefitPlansAdjustmentMemberus-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncomeMember2019-01-012019-12-310000067716us-gaap:AccumulatedNetUnrealizedInvestmentGainLossMemberus-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncomeMember2020-01-012020-12-310000067716us-gaap:AccumulatedNetUnrealizedInvestmentGainLossMemberus-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncomeMember2019-01-012019-12-310000067716us-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncomeMember2020-01-012020-12-310000067716us-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncomeMember2019-01-012019-12-310000067716us-gaap:StateAndLocalJurisdictionMember2020-12-310000067716us-gaap:StateAndLocalJurisdictionMember2019-12-310000067716mdu:FederalandStateTaxingAuthorityMember2020-12-310000067716mdu:FederalandStateTaxingAuthorityMember2019-12-310000067716mdu:ContinuinganddiscontinuedoperationsMember2020-01-012020-12-310000067716mdu:ContinuinganddiscontinuedoperationsMember2019-01-012019-12-310000067716mdu:ContinuinganddiscontinuedoperationsMember2018-01-012018-12-310000067716mdu:ElectricMemberus-gaap:RegulatedOperationMember2020-01-012020-12-310000067716mdu:ElectricMemberus-gaap:RegulatedOperationMember2019-01-012019-12-310000067716mdu:ElectricMemberus-gaap:RegulatedOperationMember2018-01-012018-12-310000067716mdu:NaturalGasDistributionMemberus-gaap:RegulatedOperationMember2020-01-012020-12-310000067716mdu:NaturalGasDistributionMemberus-gaap:RegulatedOperationMember2019-01-012019-12-310000067716mdu:NaturalGasDistributionMemberus-gaap:RegulatedOperationMember2018-01-012018-12-310000067716mdu:PipelineandMidstreamMemberus-gaap:RegulatedOperationMember2020-01-012020-12-310000067716mdu:PipelineandMidstreamMemberus-gaap:RegulatedOperationMember2019-01-012019-12-310000067716mdu:PipelineandMidstreamMemberus-gaap:RegulatedOperationMember2018-01-012018-12-310000067716mdu:PipelineandMidstreamMemberus-gaap:UnregulatedOperationMember2020-01-012020-12-310000067716mdu:PipelineandMidstreamMemberus-gaap:UnregulatedOperationMember2019-01-012019-12-310000067716mdu:PipelineandMidstreamMemberus-gaap:UnregulatedOperationMember2018-01-012018-12-310000067716us-gaap:UnregulatedOperationMembermdu:ConstructionMaterialsAndContractingMember2020-01-012020-12-310000067716us-gaap:UnregulatedOperationMembermdu:ConstructionMaterialsAndContractingMember2019-01-012019-12-310000067716us-gaap:UnregulatedOperationMembermdu:ConstructionMaterialsAndContractingMember2018-01-012018-12-310000067716mdu:ConstructionServicesMemberus-gaap:UnregulatedOperationMember2020-01-012020-12-310000067716mdu:ConstructionServicesMemberus-gaap:UnregulatedOperationMember2019-01-012019-12-310000067716mdu:ConstructionServicesMemberus-gaap:UnregulatedOperationMember2018-01-012018-12-310000067716us-gaap:UnregulatedOperationMemberus-gaap:CorporateAndOtherMember2020-01-012020-12-310000067716us-gaap:UnregulatedOperationMemberus-gaap:CorporateAndOtherMember2019-01-012019-12-310000067716us-gaap:UnregulatedOperationMemberus-gaap:CorporateAndOtherMember2018-01-012018-12-310000067716us-gaap:IntersegmentEliminationMembermdu:ElectricMemberus-gaap:RegulatedOperationMember2020-01-012020-12-310000067716us-gaap:IntersegmentEliminationMembermdu:ElectricMemberus-gaap:RegulatedOperationMember2019-01-012019-12-310000067716us-gaap:IntersegmentEliminationMembermdu:ElectricMemberus-gaap:RegulatedOperationMember2018-01-012018-12-310000067716us-gaap:IntersegmentEliminationMembermdu:NaturalGasDistributionMemberus-gaap:RegulatedOperationMember2020-01-012020-12-310000067716us-gaap:IntersegmentEliminationMembermdu:NaturalGasDistributionMemberus-gaap:RegulatedOperationMember2019-01-012019-12-310000067716us-gaap:IntersegmentEliminationMembermdu:NaturalGasDistributionMemberus-gaap:RegulatedOperationMember2018-01-012018-12-310000067716us-gaap:IntersegmentEliminationMembermdu:PipelineandMidstreamMemberus-gaap:RegulatedOperationMember2020-01-012020-12-310000067716us-gaap:IntersegmentEliminationMembermdu:PipelineandMidstreamMemberus-gaap:RegulatedOperationMember2019-01-012019-12-310000067716us-gaap:IntersegmentEliminationMembermdu:PipelineandMidstreamMemberus-gaap:RegulatedOperationMember2018-01-012018-12-310000067716us-gaap:IntersegmentEliminationMemberus-gaap:RegulatedOperationMember2020-01-012020-12-310000067716us-gaap:IntersegmentEliminationMemberus-gaap:RegulatedOperationMember2019-01-012019-12-310000067716us-gaap:IntersegmentEliminationMemberus-gaap:RegulatedOperationMember2018-01-012018-12-310000067716us-gaap:IntersegmentEliminationMembermdu:PipelineandMidstreamMemberus-gaap:UnregulatedOperationMember2020-01-012020-12-310000067716us-gaap:IntersegmentEliminationMembermdu:PipelineandMidstreamMemberus-gaap:UnregulatedOperationMember2019-01-012019-12-310000067716us-gaap:IntersegmentEliminationMembermdu:PipelineandMidstreamMemberus-gaap:UnregulatedOperationMember2018-01-012018-12-310000067716us-gaap:IntersegmentEliminationMemberus-gaap:UnregulatedOperationMembermdu:ConstructionMaterialsAndContractingMember2020-01-012020-12-310000067716us-gaap:IntersegmentEliminationMemberus-gaap:UnregulatedOperationMembermdu:ConstructionMaterialsAndContractingMember2019-01-012019-12-310000067716us-gaap:IntersegmentEliminationMemberus-gaap:UnregulatedOperationMembermdu:ConstructionMaterialsAndContractingMember2018-01-012018-12-310000067716us-gaap:IntersegmentEliminationMembermdu:ConstructionServicesMemberus-gaap:UnregulatedOperationMember2020-01-012020-12-310000067716us-gaap:IntersegmentEliminationMembermdu:ConstructionServicesMemberus-gaap:UnregulatedOperationMember2019-01-012019-12-310000067716us-gaap:IntersegmentEliminationMembermdu:ConstructionServicesMemberus-gaap:UnregulatedOperationMember2018-01-012018-12-310000067716us-gaap:IntersegmentEliminationMemberus-gaap:UnregulatedOperationMemberus-gaap:CorporateAndOtherMember2020-01-012020-12-310000067716us-gaap:IntersegmentEliminationMemberus-gaap:UnregulatedOperationMemberus-gaap:CorporateAndOtherMember2019-01-012019-12-310000067716us-gaap:IntersegmentEliminationMemberus-gaap:UnregulatedOperationMemberus-gaap:CorporateAndOtherMember2018-01-012018-12-310000067716us-gaap:IntersegmentEliminationMemberus-gaap:UnregulatedOperationMember2020-01-012020-12-310000067716us-gaap:IntersegmentEliminationMemberus-gaap:UnregulatedOperationMember2019-01-012019-12-310000067716us-gaap:IntersegmentEliminationMemberus-gaap:UnregulatedOperationMember2018-01-012018-12-310000067716srt:ConsolidationEliminationsMember2020-01-012020-12-310000067716srt:ConsolidationEliminationsMember2019-01-012019-12-310000067716srt:ConsolidationEliminationsMember2018-01-012018-12-310000067716mdu:ElectricMember2018-12-310000067716mdu:PipelineandMidstreamMember2018-12-310000067716us-gaap:CorporateAndOtherMember2020-12-310000067716us-gaap:CorporateAndOtherMember2019-12-310000067716us-gaap:CorporateAndOtherMember2018-12-310000067716mdu:DiscontinuedOperationsMember2020-12-310000067716mdu:DiscontinuedOperationsMember2019-12-310000067716mdu:DiscontinuedOperationsMember2018-12-310000067716us-gaap:UnderfundedPlanMemberus-gaap:QualifiedPlanMemberus-gaap:PensionPlansDefinedBenefitMember2019-12-310000067716us-gaap:UnderfundedPlanMemberus-gaap:QualifiedPlanMemberus-gaap:PensionPlansDefinedBenefitMember2018-12-310000067716us-gaap:QualifiedPlanMemberus-gaap:OverfundedPlanMemberus-gaap:OtherPostretirementBenefitPlansDefinedBenefitMember2019-12-310000067716us-gaap:QualifiedPlanMemberus-gaap:OverfundedPlanMemberus-gaap:OtherPostretirementBenefitPlansDefinedBenefitMember2018-12-310000067716us-gaap:UnderfundedPlanMemberus-gaap:QualifiedPlanMemberus-gaap:PensionPlansDefinedBenefitMember2020-01-012020-12-310000067716us-gaap:UnderfundedPlanMemberus-gaap:QualifiedPlanMemberus-gaap:PensionPlansDefinedBenefitMember2019-01-012019-12-310000067716us-gaap:QualifiedPlanMemberus-gaap:OverfundedPlanMemberus-gaap:OtherPostretirementBenefitPlansDefinedBenefitMember2020-01-012020-12-310000067716us-gaap:QualifiedPlanMemberus-gaap:OverfundedPlanMemberus-gaap:OtherPostretirementBenefitPlansDefinedBenefitMember2019-01-012019-12-310000067716us-gaap:UnderfundedPlanMemberus-gaap:QualifiedPlanMemberus-gaap:PensionPlansDefinedBenefitMember2020-12-310000067716us-gaap:QualifiedPlanMemberus-gaap:OverfundedPlanMemberus-gaap:OtherPostretirementBenefitPlansDefinedBenefitMember2020-12-310000067716us-gaap:UnderfundedPlanMemberus-gaap:QualifiedPlanMemberus-gaap:PensionPlansDefinedBenefitMember2018-01-012018-12-310000067716us-gaap:QualifiedPlanMemberus-gaap:OverfundedPlanMemberus-gaap:OtherPostretirementBenefitPlansDefinedBenefitMember2018-01-012018-12-310000067716us-gaap:UnderfundedPlanMemberus-gaap:QualifiedPlanMemberus-gaap:EquitySecuritiesMembersrt:MinimumMemberus-gaap:PensionPlansDefinedBenefitMember2020-12-310000067716us-gaap:UnderfundedPlanMemberus-gaap:QualifiedPlanMemberus-gaap:EquitySecuritiesMemberus-gaap:PensionPlansDefinedBenefitMembersrt:MaximumMember2020-12-310000067716us-gaap:UnderfundedPlanMemberus-gaap:QualifiedPlanMemberus-gaap:FixedIncomeSecuritiesMembersrt:MinimumMemberus-gaap:PensionPlansDefinedBenefitMember2020-12-310000067716us-gaap:UnderfundedPlanMemberus-gaap:QualifiedPlanMemberus-gaap:FixedIncomeSecuritiesMemberus-gaap:PensionPlansDefinedBenefitMembersrt:MaximumMember2020-12-310000067716us-gaap:QualifiedPlanMemberus-gaap:EquitySecuritiesMemberus-gaap:OverfundedPlanMemberus-gaap:OtherPostretirementBenefitPlansDefinedBenefitMember2020-12-310000067716us-gaap:QualifiedPlanMemberus-gaap:FixedIncomeSecuritiesMemberus-gaap:OverfundedPlanMemberus-gaap:OtherPostretirementBenefitPlansDefinedBenefitMember2020-12-310000067716us-gaap:QualifiedPlanMemberus-gaap:OverfundedPlanMemberus-gaap:OtherPostretirementBenefitPlansDefinedBenefitMembersrt:MinimumMember2019-12-310000067716us-gaap:QualifiedPlanMemberus-gaap:OverfundedPlanMemberus-gaap:OtherPostretirementBenefitPlansDefinedBenefitMembersrt:MaximumMember2019-12-310000067716us-gaap:QualifiedPlanMemberus-gaap:OverfundedPlanMemberus-gaap:OtherPostretirementBenefitPlansDefinedBenefitMembersrt:MaximumMember2020-01-012020-12-310000067716us-gaap:FairValueInputsLevel2Memberus-gaap:UnderfundedPlanMemberus-gaap:QualifiedPlanMemberus-gaap:PensionPlansDefinedBenefitMemberus-gaap:DefinedBenefitPlanCashAndCashEquivalentsMember2020-12-310000067716us-gaap:UnderfundedPlanMemberus-gaap:QualifiedPlanMemberus-gaap:PensionPlansDefinedBenefitMemberus-gaap:DefinedBenefitPlanCashAndCashEquivalentsMember2020-12-310000067716us-gaap:UnderfundedPlanMemberus-gaap:DefinedBenefitPlanEquitySecuritiesUsMemberus-gaap:QualifiedPlanMemberus-gaap:PensionPlansDefinedBenefitMemberus-gaap:FairValueInputsLevel1Member2020-12-310000067716us-gaap:UnderfundedPlanMemberus-gaap:DefinedBenefitPlanEquitySecuritiesUsMemberus-gaap:QualifiedPlanMemberus-gaap:PensionPlansDefinedBenefitMember2020-12-310000067716us-gaap:FairValueInputsLevel2Memberus-gaap:UnderfundedPlanMemberus-gaap:QualifiedPlanMemberus-gaap:DefinedBenefitPlanEquitySecuritiesNonUsMemberus-gaap:PensionPlansDefinedBenefitMember2020-12-310000067716us-gaap:UnderfundedPlanMemberus-gaap:QualifiedPlanMemberus-gaap:DefinedBenefitPlanEquitySecuritiesNonUsMemberus-gaap:PensionPlansDefinedBenefitMember2020-12-310000067716us-gaap:UnderfundedPlanMemberus-gaap:QualifiedPlanMemberus-gaap:PensionPlansDefinedBenefitMembermdu:CollectiveAndMutualFundsMemberus-gaap:FairValueInputsLevel1Member2020-12-310000067716us-gaap:FairValueInputsLevel2Memberus-gaap:UnderfundedPlanMemberus-gaap:QualifiedPlanMemberus-gaap:PensionPlansDefinedBenefitMembermdu:CollectiveAndMutualFundsMember2020-12-310000067716us-gaap:UnderfundedPlanMemberus-gaap:QualifiedPlanMemberus-gaap:PensionPlansDefinedBenefitMembermdu:CollectiveAndMutualFundsMember2020-12-310000067716us-gaap:FairValueInputsLevel2Memberus-gaap:CorporateDebtSecuritiesMemberus-gaap:UnderfundedPlanMemberus-gaap:QualifiedPlanMemberus-gaap:PensionPlansDefinedBenefitMember2020-12-310000067716us-gaap:CorporateDebtSecuritiesMemberus-gaap:UnderfundedPlanMemberus-gaap:QualifiedPlanMemberus-gaap:PensionPlansDefinedBenefitMember2020-12-310000067716us-gaap:FairValueInputsLevel2Memberus-gaap:UnderfundedPlanMemberus-gaap:QualifiedPlanMemberus-gaap:MunicipalBondsMemberus-gaap:PensionPlansDefinedBenefitMember2020-12-310000067716us-gaap:UnderfundedPlanMemberus-gaap:QualifiedPlanMemberus-gaap:MunicipalBondsMemberus-gaap:PensionPlansDefinedBenefitMember2020-12-310000067716us-gaap:UnderfundedPlanMemberus-gaap:QualifiedPlanMemberus-gaap:USTreasurySecuritiesMemberus-gaap:PensionPlansDefinedBenefitMemberus-gaap:FairValueInputsLevel1Member2020-12-310000067716us-gaap:FairValueInputsLevel2Memberus-gaap:UnderfundedPlanMemberus-gaap:QualifiedPlanMemberus-gaap:USTreasurySecuritiesMemberus-gaap:PensionPlansDefinedBenefitMember2020-12-310000067716us-gaap:UnderfundedPlanMemberus-gaap:QualifiedPlanMemberus-gaap:USTreasurySecuritiesMemberus-gaap:PensionPlansDefinedBenefitMember2020-12-310000067716us-gaap:UnderfundedPlanMemberus-gaap:FairValueMeasuredAtNetAssetValuePerShareMemberus-gaap:QualifiedPlanMemberus-gaap:PensionPlansDefinedBenefitMembermdu:CollectiveAndMutualFundsMember2020-12-310000067716us-gaap:UnderfundedPlanMemberus-gaap:QualifiedPlanMemberus-gaap:PensionPlansDefinedBenefitMembermdu:TotalAssetsMeasuredatFairValueMemberus-gaap:FairValueInputsLevel1Member2020-12-310000067716us-gaap:FairValueInputsLevel2Memberus-gaap:UnderfundedPlanMemberus-gaap:QualifiedPlanMemberus-gaap:PensionPlansDefinedBenefitMembermdu:TotalAssetsMeasuredatFairValueMember2020-12-310000067716us-gaap:UnderfundedPlanMemberus-gaap:QualifiedPlanMemberus-gaap:PensionPlansDefinedBenefitMembermdu:TotalAssetsMeasuredatFairValueMember2020-12-310000067716us-gaap:UnderfundedPlanMemberus-gaap:DefinedBenefitPlanEquitySecuritiesUsLargeCapMemberus-gaap:QualifiedPlanMemberus-gaap:PensionPlansDefinedBenefitMember2020-12-310000067716us-gaap:UnderfundedPlanMemberus-gaap:QualifiedPlanMemberus-gaap:OtherInvestmentsMemberus-gaap:PensionPlansDefinedBenefitMember2020-12-310000067716us-gaap:FairValueInputsLevel2Memberus-gaap:UnderfundedPlanMemberus-gaap:QualifiedPlanMemberus-gaap:PensionPlansDefinedBenefitMemberus-gaap:DefinedBenefitPlanCashAndCashEquivalentsMember2019-12-310000067716us-gaap:UnderfundedPlanMemberus-gaap:QualifiedPlanMemberus-gaap:PensionPlansDefinedBenefitMemberus-gaap:DefinedBenefitPlanCashAndCashEquivalentsMember2019-12-310000067716us-gaap:UnderfundedPlanMemberus-gaap:DefinedBenefitPlanEquitySecuritiesUsMemberus-gaap:QualifiedPlanMemberus-gaap:PensionPlansDefinedBenefitMemberus-gaap:FairValueInputsLevel1Member2019-12-310000067716us-gaap:UnderfundedPlanMemberus-gaap:DefinedBenefitPlanEquitySecuritiesUsMemberus-gaap:QualifiedPlanMemberus-gaap:PensionPlansDefinedBenefitMember2019-12-310000067716us-gaap:FairValueInputsLevel2Memberus-gaap:UnderfundedPlanMemberus-gaap:QualifiedPlanMemberus-gaap:DefinedBenefitPlanEquitySecuritiesNonUsMemberus-gaap:PensionPlansDefinedBenefitMember2019-12-310000067716us-gaap:UnderfundedPlanMemberus-gaap:QualifiedPlanMemberus-gaap:DefinedBenefitPlanEquitySecuritiesNonUsMemberus-gaap:PensionPlansDefinedBenefitMember2019-12-310000067716us-gaap:UnderfundedPlanMemberus-gaap:QualifiedPlanMemberus-gaap:PensionPlansDefinedBenefitMembermdu:CollectiveAndMutualFundsMemberus-gaap:FairValueInputsLevel1Member2019-12-310000067716us-gaap:FairValueInputsLevel2Memberus-gaap:UnderfundedPlanMemberus-gaap:QualifiedPlanMemberus-gaap:PensionPlansDefinedBenefitMembermdu:CollectiveAndMutualFundsMember2019-12-310000067716us-gaap:UnderfundedPlanMemberus-gaap:QualifiedPlanMemberus-gaap:PensionPlansDefinedBenefitMembermdu:CollectiveAndMutualFundsMember2019-12-310000067716us-gaap:FairValueInputsLevel2Memberus-gaap:CorporateDebtSecuritiesMemberus-gaap:UnderfundedPlanMemberus-gaap:QualifiedPlanMemberus-gaap:PensionPlansDefinedBenefitMember2019-12-310000067716us-gaap:CorporateDebtSecuritiesMemberus-gaap:UnderfundedPlanMemberus-gaap:QualifiedPlanMemberus-gaap:PensionPlansDefinedBenefitMember2019-12-310000067716us-gaap:FairValueInputsLevel2Memberus-gaap:UnderfundedPlanMemberus-gaap:QualifiedPlanMemberus-gaap:MunicipalBondsMemberus-gaap:PensionPlansDefinedBenefitMember2019-12-310000067716us-gaap:UnderfundedPlanMemberus-gaap:QualifiedPlanMemberus-gaap:MunicipalBondsMemberus-gaap:PensionPlansDefinedBenefitMember2019-12-310000067716us-gaap:UnderfundedPlanMemberus-gaap:QualifiedPlanMemberus-gaap:USTreasurySecuritiesMemberus-gaap:PensionPlansDefinedBenefitMemberus-gaap:FairValueInputsLevel1Member2019-12-310000067716us-gaap:FairValueInputsLevel2Memberus-gaap:UnderfundedPlanMemberus-gaap:QualifiedPlanMemberus-gaap:USTreasurySecuritiesMemberus-gaap:PensionPlansDefinedBenefitMember2019-12-310000067716us-gaap:UnderfundedPlanMemberus-gaap:QualifiedPlanMemberus-gaap:USTreasurySecuritiesMemberus-gaap:PensionPlansDefinedBenefitMember2019-12-310000067716us-gaap:UnderfundedPlanMemberus-gaap:QualifiedPlanMemberus-gaap:PensionPlansDefinedBenefitMembermdu:TotalAssetsMeasuredatFairValueMemberus-gaap:FairValueInputsLevel1Member2019-12-310000067716us-gaap:FairValueInputsLevel2Memberus-gaap:UnderfundedPlanMemberus-gaap:QualifiedPlanMemberus-gaap:PensionPlansDefinedBenefitMembermdu:TotalAssetsMeasuredatFairValueMember2019-12-310000067716us-gaap:UnderfundedPlanMemberus-gaap:QualifiedPlanMemberus-gaap:PensionPlansDefinedBenefitMembermdu:TotalAssetsMeasuredatFairValueMember2019-12-310000067716us-gaap:UnderfundedPlanMemberus-gaap:DefinedBenefitPlanEquitySecuritiesUsLargeCapMemberus-gaap:QualifiedPlanMemberus-gaap:PensionPlansDefinedBenefitMember2019-12-310000067716us-gaap:UnderfundedPlanMemberus-gaap:QualifiedPlanMemberus-gaap:OtherInvestmentsMemberus-gaap:PensionPlansDefinedBenefitMember2019-12-310000067716us-gaap:FairValueInputsLevel2Memberus-gaap:QualifiedPlanMemberus-gaap:OverfundedPlanMemberus-gaap:OtherPostretirementBenefitPlansDefinedBenefitMemberus-gaap:DefinedBenefitPlanCashAndCashEquivalentsMember2020-12-310000067716us-gaap:QualifiedPlanMemberus-gaap:OverfundedPlanMemberus-gaap:OtherPostretirementBenefitPlansDefinedBenefitMemberus-gaap:DefinedBenefitPlanCashAndCashEquivalentsMember2020-12-310000067716us-gaap:DefinedBenefitPlanEquitySecuritiesUsMemberus-gaap:QualifiedPlanMemberus-gaap:OverfundedPlanMemberus-gaap:OtherPostretirementBenefitPlansDefinedBenefitMemberus-gaap:FairValueInputsLevel1Member2020-12-310000067716us-gaap:DefinedBenefitPlanEquitySecuritiesUsMemberus-gaap:QualifiedPlanMemberus-gaap:OverfundedPlanMemberus-gaap:OtherPostretirementBenefitPlansDefinedBenefitMember2020-12-310000067716us-gaap:FairValueInputsLevel2Memberus-gaap:QualifiedPlanMemberus-gaap:OverfundedPlanMemberus-gaap:OtherPostretirementBenefitPlansDefinedBenefitMemberus-gaap:DefinedBenefitPlanEquitySecuritiesNonUsMember2020-12-310000067716us-gaap:QualifiedPlanMemberus-gaap:OverfundedPlanMemberus-gaap:OtherPostretirementBenefitPlansDefinedBenefitMemberus-gaap:DefinedBenefitPlanEquitySecuritiesNonUsMember2020-12-310000067716us-gaap:QualifiedPlanMemberus-gaap:OverfundedPlanMemberus-gaap:OtherPostretirementBenefitPlansDefinedBenefitMembermdu:CollectiveAndMutualFundsMemberus-gaap:FairValueInputsLevel1Member2020-12-310000067716us-gaap:FairValueInputsLevel2Memberus-gaap:QualifiedPlanMemberus-gaap:OverfundedPlanMemberus-gaap:OtherPostretirementBenefitPlansDefinedBenefitMembermdu:CollectiveAndMutualFundsMember2020-12-310000067716us-gaap:QualifiedPlanMemberus-gaap:OverfundedPlanMemberus-gaap:OtherPostretirementBenefitPlansDefinedBenefitMembermdu:CollectiveAndMutualFundsMember2020-12-310000067716us-gaap:FairValueInputsLevel2Memberus-gaap:QualifiedPlanMembermdu:InsuranceInvestmentContractMemberus-gaap:OverfundedPlanMemberus-gaap:OtherPostretirementBenefitPlansDefinedBenefitMember2020-12-310000067716us-gaap:QualifiedPlanMembermdu:InsuranceInvestmentContractMemberus-gaap:OverfundedPlanMemberus-gaap:OtherPostretirementBenefitPlansDefinedBenefitMember2020-12-310000067716us-gaap:FairValueMeasuredAtNetAssetValuePerShareMemberus-gaap:QualifiedPlanMemberus-gaap:OverfundedPlanMemberus-gaap:OtherPostretirementBenefitPlansDefinedBenefitMembermdu:CollectiveAndMutualFundsMember2020-12-310000067716us-gaap:QualifiedPlanMemberus-gaap:OverfundedPlanMemberus-gaap:OtherPostretirementBenefitPlansDefinedBenefitMembermdu:TotalAssetsMeasuredatFairValueMemberus-gaap:FairValueInputsLevel1Member2020-12-310000067716us-gaap:FairValueInputsLevel2Memberus-gaap:QualifiedPlanMemberus-gaap:OverfundedPlanMemberus-gaap:OtherPostretirementBenefitPlansDefinedBenefitMembermdu:TotalAssetsMeasuredatFairValueMember2020-12-310000067716us-gaap:QualifiedPlanMemberus-gaap:OverfundedPlanMemberus-gaap:OtherPostretirementBenefitPlansDefinedBenefitMembermdu:TotalAssetsMeasuredatFairValueMember2020-12-310000067716us-gaap:CorporateDebtSecuritiesMemberus-gaap:QualifiedPlanMemberus-gaap:OverfundedPlanMemberus-gaap:OtherPostretirementBenefitPlansDefinedBenefitMember2020-12-310000067716us-gaap:DefinedBenefitPlanEquitySecuritiesUsLargeCapMemberus-gaap:QualifiedPlanMemberus-gaap:OverfundedPlanMemberus-gaap:OtherPostretirementBenefitPlansDefinedBenefitMember2020-12-310000067716us-gaap:QualifiedPlanMemberus-gaap:USTreasurySecuritiesMemberus-gaap:OverfundedPlanMemberus-gaap:OtherPostretirementBenefitPlansDefinedBenefitMember2020-12-310000067716us-gaap:QualifiedPlanMemberus-gaap:OtherInvestmentsMemberus-gaap:OverfundedPlanMemberus-gaap:OtherPostretirementBenefitPlansDefinedBenefitMember2020-12-310000067716us-gaap:DefinedBenefitPlanEquitySecuritiesUsSmallCapMemberus-gaap:QualifiedPlanMemberus-gaap:OverfundedPlanMemberus-gaap:OtherPostretirementBenefitPlansDefinedBenefitMember2020-12-310000067716us-gaap:FairValueInputsLevel2Memberus-gaap:QualifiedPlanMemberus-gaap:OverfundedPlanMemberus-gaap:OtherPostretirementBenefitPlansDefinedBenefitMemberus-gaap:DefinedBenefitPlanCashAndCashEquivalentsMember2019-12-310000067716us-gaap:QualifiedPlanMemberus-gaap:OverfundedPlanMemberus-gaap:OtherPostretirementBenefitPlansDefinedBenefitMemberus-gaap:DefinedBenefitPlanCashAndCashEquivalentsMember2019-12-310000067716us-gaap:DefinedBenefitPlanEquitySecuritiesUsMemberus-gaap:QualifiedPlanMemberus-gaap:OverfundedPlanMemberus-gaap:OtherPostretirementBenefitPlansDefinedBenefitMemberus-gaap:FairValueInputsLevel1Member2019-12-310000067716us-gaap:DefinedBenefitPlanEquitySecuritiesUsMemberus-gaap:QualifiedPlanMemberus-gaap:OverfundedPlanMemberus-gaap:OtherPostretirementBenefitPlansDefinedBenefitMember2019-12-310000067716us-gaap:FairValueInputsLevel2Memberus-gaap:QualifiedPlanMemberus-gaap:OverfundedPlanMemberus-gaap:OtherPostretirementBenefitPlansDefinedBenefitMemberus-gaap:DefinedBenefitPlanEquitySecuritiesNonUsMember2019-12-310000067716us-gaap:QualifiedPlanMemberus-gaap:OverfundedPlanMemberus-gaap:OtherPostretirementBenefitPlansDefinedBenefitMemberus-gaap:DefinedBenefitPlanEquitySecuritiesNonUsMember2019-12-310000067716us-gaap:QualifiedPlanMemberus-gaap:OverfundedPlanMemberus-gaap:OtherPostretirementBenefitPlansDefinedBenefitMembermdu:CollectiveAndMutualFundsMemberus-gaap:FairValueInputsLevel1Member2019-12-310000067716us-gaap:FairValueInputsLevel2Memberus-gaap:QualifiedPlanMemberus-gaap:OverfundedPlanMemberus-gaap:OtherPostretirementBenefitPlansDefinedBenefitMembermdu:CollectiveAndMutualFundsMember2019-12-310000067716us-gaap:QualifiedPlanMemberus-gaap:OverfundedPlanMemberus-gaap:OtherPostretirementBenefitPlansDefinedBenefitMembermdu:CollectiveAndMutualFundsMember2019-12-310000067716us-gaap:FairValueInputsLevel2Memberus-gaap:QualifiedPlanMembermdu:InsuranceInvestmentContractMemberus-gaap:OverfundedPlanMemberus-gaap:OtherPostretirementBenefitPlansDefinedBenefitMember2019-12-310000067716us-gaap:QualifiedPlanMembermdu:InsuranceInvestmentContractMemberus-gaap:OverfundedPlanMemberus-gaap:OtherPostretirementBenefitPlansDefinedBenefitMember2019-12-310000067716us-gaap:QualifiedPlanMemberus-gaap:OverfundedPlanMemberus-gaap:OtherPostretirementBenefitPlansDefinedBenefitMembermdu:TotalAssetsMeasuredatFairValueMemberus-gaap:FairValueInputsLevel1Member2019-12-310000067716us-gaap:FairValueInputsLevel2Memberus-gaap:QualifiedPlanMemberus-gaap:OverfundedPlanMemberus-gaap:OtherPostretirementBenefitPlansDefinedBenefitMembermdu:TotalAssetsMeasuredatFairValueMember2019-12-310000067716us-gaap:QualifiedPlanMemberus-gaap:OverfundedPlanMemberus-gaap:OtherPostretirementBenefitPlansDefinedBenefitMembermdu:TotalAssetsMeasuredatFairValueMember2019-12-310000067716us-gaap:DefinedBenefitPlanEquitySecuritiesUsLargeCapMemberus-gaap:QualifiedPlanMemberus-gaap:OverfundedPlanMemberus-gaap:OtherPostretirementBenefitPlansDefinedBenefitMember2019-12-310000067716us-gaap:QualifiedPlanMemberus-gaap:USTreasurySecuritiesMemberus-gaap:OverfundedPlanMemberus-gaap:OtherPostretirementBenefitPlansDefinedBenefitMember2019-12-310000067716us-gaap:CorporateDebtSecuritiesMemberus-gaap:QualifiedPlanMemberus-gaap:OverfundedPlanMemberus-gaap:OtherPostretirementBenefitPlansDefinedBenefitMember2019-12-310000067716us-gaap:QualifiedPlanMemberus-gaap:OtherInvestmentsMemberus-gaap:OverfundedPlanMemberus-gaap:OtherPostretirementBenefitPlansDefinedBenefitMember2019-12-310000067716us-gaap:DefinedBenefitPlanEquitySecuritiesUsSmallCapMemberus-gaap:QualifiedPlanMemberus-gaap:OverfundedPlanMemberus-gaap:OtherPostretirementBenefitPlansDefinedBenefitMember2019-12-310000067716us-gaap:SupplementalEmployeeRetirementPlanDefinedBenefitMemberus-gaap:UnfundedPlanMemberus-gaap:NonqualifiedPlanMember2020-12-310000067716us-gaap:SupplementalEmployeeRetirementPlanDefinedBenefitMemberus-gaap:UnfundedPlanMemberus-gaap:NonqualifiedPlanMember2019-12-310000067716us-gaap:SupplementalEmployeeRetirementPlanDefinedBenefitMemberus-gaap:UnfundedPlanMemberus-gaap:NonqualifiedPlanMember2020-01-012020-12-310000067716us-gaap:SupplementalEmployeeRetirementPlanDefinedBenefitMemberus-gaap:UnfundedPlanMemberus-gaap:NonqualifiedPlanMember2019-01-012019-12-310000067716us-gaap:SupplementalEmployeeRetirementPlanDefinedBenefitMemberus-gaap:UnfundedPlanMemberus-gaap:NonqualifiedPlanMember2018-01-012018-12-310000067716us-gaap:UnfundedPlanMemberus-gaap:NonqualifiedPlanMember2020-01-012020-12-310000067716us-gaap:UnfundedPlanMemberus-gaap:NonqualifiedPlanMember2019-01-012019-12-310000067716us-gaap:UnfundedPlanMemberus-gaap:NonqualifiedPlanMember2018-01-012018-12-310000067716us-gaap:EquitySecuritiesMemberus-gaap:SupplementalEmployeeRetirementPlanDefinedBenefitMemberus-gaap:UnfundedPlanMember2020-12-310000067716us-gaap:EquitySecuritiesMemberus-gaap:SupplementalEmployeeRetirementPlanDefinedBenefitMemberus-gaap:UnfundedPlanMember2019-12-310000067716mdu:LifeInsuranceCarriedOnPlanParticipantsMemberus-gaap:SupplementalEmployeeRetirementPlanDefinedBenefitMemberus-gaap:UnfundedPlanMember2020-12-310000067716mdu:LifeInsuranceCarriedOnPlanParticipantsMemberus-gaap:SupplementalEmployeeRetirementPlanDefinedBenefitMemberus-gaap:UnfundedPlanMember2019-12-310000067716us-gaap:OtherInvestmentsMemberus-gaap:SupplementalEmployeeRetirementPlanDefinedBenefitMemberus-gaap:UnfundedPlanMember2020-12-310000067716us-gaap:OtherInvestmentsMemberus-gaap:SupplementalEmployeeRetirementPlanDefinedBenefitMemberus-gaap:UnfundedPlanMember2019-12-310000067716us-gaap:SupplementalEmployeeRetirementPlanDefinedBenefitMemberus-gaap:UnfundedPlanMember2020-12-310000067716us-gaap:SupplementalEmployeeRetirementPlanDefinedBenefitMemberus-gaap:UnfundedPlanMember2019-12-310000067716mdu:DefinedContributionPlanMember2020-01-012020-12-310000067716mdu:DefinedContributionPlanMember2019-01-012019-12-310000067716mdu:DefinedContributionPlanMember2018-01-012018-12-310000067716srt:MaximumMember2020-01-012020-12-310000067716srt:MinimumMember2020-01-012020-12-310000067716mdu:AlaskaLaborersEmployersRetirementFundMemberus-gaap:PensionPlansDefinedBenefitMember2020-01-012020-12-310000067716mdu:AlaskaLaborersEmployersRetirementFundMemberus-gaap:PensionPlansDefinedBenefitMember2019-01-012019-12-310000067716mdu:AlaskaLaborersEmployersRetirementFundMemberus-gaap:PensionPlansDefinedBenefitMember2018-01-012018-12-310000067716mdu:ConstructionIndustryandLaborersJointPensionTrustforSoNevadaPlanAMemberus-gaap:PensionPlansDefinedBenefitMember2020-01-012020-12-310000067716mdu:ConstructionIndustryandLaborersJointPensionTrustforSoNevadaPlanAMemberus-gaap:PensionPlansDefinedBenefitMember2019-01-012019-12-310000067716mdu:ConstructionIndustryandLaborersJointPensionTrustforSoNevadaPlanAMemberus-gaap:PensionPlansDefinedBenefitMember2018-01-012018-12-310000067716mdu:EdisonPensionPlanMemberus-gaap:PensionPlansDefinedBenefitMember2020-01-012020-12-310000067716mdu:EdisonPensionPlanMemberus-gaap:PensionPlansDefinedBenefitMember2019-01-012019-12-310000067716mdu:EdisonPensionPlanMemberus-gaap:PensionPlansDefinedBenefitMember2018-01-012018-12-310000067716mdu:LocalUnion212IbewPensionTrustFundMemberus-gaap:PensionPlansDefinedBenefitMember2020-01-012020-12-310000067716mdu:LocalUnion212IbewPensionTrustFundMemberus-gaap:PensionPlansDefinedBenefitMember2019-01-012019-12-310000067716mdu:LocalUnion212IbewPensionTrustFundMemberus-gaap:PensionPlansDefinedBenefitMember2018-01-012018-12-310000067716mdu:IBEWLocalNo.357PensionPlanAMemberus-gaap:PensionPlansDefinedBenefitMember2020-01-012020-12-310000067716mdu:IBEWLocalNo.357PensionPlanAMemberus-gaap:PensionPlansDefinedBenefitMember2019-01-012019-12-310000067716mdu:IBEWLocalNo.357PensionPlanAMemberus-gaap:PensionPlansDefinedBenefitMember2018-01-012018-12-310000067716us-gaap:PensionPlansDefinedBenefitMembermdu:IBEWLocalNo38Member2020-01-012020-12-310000067716us-gaap:PensionPlansDefinedBenefitMembermdu:IBEWLocalNo38Member2019-01-012019-12-310000067716us-gaap:PensionPlansDefinedBenefitMembermdu:IBEWLocalNo38Member2018-01-012018-12-310000067716mdu:IbewLocal648PensionPlanMemberus-gaap:PensionPlansDefinedBenefitMember2020-01-012020-12-310000067716mdu:IbewLocal648PensionPlanMemberus-gaap:PensionPlansDefinedBenefitMember2019-01-012019-12-310000067716mdu:IbewLocal648PensionPlanMemberus-gaap:PensionPlansDefinedBenefitMember2018-01-012018-12-310000067716us-gaap:PensionPlansDefinedBenefitMembermdu:IbewLocalNo82PensionPlanMember2020-01-012020-12-310000067716us-gaap:PensionPlansDefinedBenefitMembermdu:IbewLocalNo82PensionPlanMember2019-01-012019-12-310000067716us-gaap:PensionPlansDefinedBenefitMembermdu:IbewLocalNo82PensionPlanMember2018-01-012018-12-310000067716us-gaap:PensionPlansDefinedBenefitMembermdu:IdahoPlumbersandPipefittersPensionPlanMember2020-01-012020-12-310000067716us-gaap:PensionPlansDefinedBenefitMembermdu:IdahoPlumbersandPipefittersPensionPlanMember2019-01-012019-12-310000067716us-gaap:PensionPlansDefinedBenefitMembermdu:IdahoPlumbersandPipefittersPensionPlanMember2018-01-012018-12-310000067716mdu:MinnesotaTeamstersConstructionDivisionPensionFundMemberus-gaap:PensionPlansDefinedBenefitMember2020-01-012020-12-310000067716mdu:MinnesotaTeamstersConstructionDivisionPensionFundMemberus-gaap:PensionPlansDefinedBenefitMember2019-01-012019-12-310000067716mdu:MinnesotaTeamstersConstructionDivisionPensionFundMemberus-gaap:PensionPlansDefinedBenefitMember2018-01-012018-12-310000067716mdu:NationalAutomaticSprinklerIndustryPensionFundMemberus-gaap:PensionPlansDefinedBenefitMember2020-01-012020-12-310000067716mdu:NationalAutomaticSprinklerIndustryPensionFundMemberus-gaap:PensionPlansDefinedBenefitMember2019-01-012019-12-310000067716mdu:NationalAutomaticSprinklerIndustryPensionFundMemberus-gaap:PensionPlansDefinedBenefitMember2018-01-012018-12-310000067716mdu:NationalAutomaticSprinklerIndustryPensionFundMembersrt:MinimumMemberus-gaap:PensionPlansDefinedBenefitMember2020-01-012020-12-310000067716mdu:NationalAutomaticSprinklerIndustryPensionFundMemberus-gaap:PensionPlansDefinedBenefitMembersrt:MaximumMember2020-01-012020-12-310000067716mdu:NationalElectricalBenefitFundMemberus-gaap:PensionPlansDefinedBenefitMember2020-01-012020-12-310000067716mdu:NationalElectricalBenefitFundMemberus-gaap:PensionPlansDefinedBenefitMember2019-01-012019-12-310000067716mdu:NationalElectricalBenefitFundMemberus-gaap:PensionPlansDefinedBenefitMember2018-01-012018-12-310000067716mdu:NationalElectricalBenefitFundMembersrt:MinimumMemberus-gaap:PensionPlansDefinedBenefitMember2020-01-012020-12-310000067716mdu:NationalElectricalBenefitFundMemberus-gaap:PensionPlansDefinedBenefitMembersrt:MaximumMember2020-01-012020-12-310000067716mdu:PensionTrustFundforOperatingEngineersMemberus-gaap:PensionPlansDefinedBenefitMember2020-01-012020-12-310000067716mdu:PensionTrustFundforOperatingEngineersMemberus-gaap:PensionPlansDefinedBenefitMember2019-01-012019-12-310000067716mdu:PensionTrustFundforOperatingEngineersMemberus-gaap:PensionPlansDefinedBenefitMember2018-01-012018-12-310000067716mdu:PensionTrustFundforOperatingEngineersMembersrt:MinimumMemberus-gaap:PensionPlansDefinedBenefitMember2020-01-012020-12-310000067716mdu:PensionTrustFundforOperatingEngineersMemberus-gaap:PensionPlansDefinedBenefitMembersrt:MaximumMember2020-01-012020-12-310000067716mdu:SheetMetalWorkersPensionPlanofSouthernCAAZandNVMemberus-gaap:PensionPlansDefinedBenefitMember2020-01-012020-12-310000067716mdu:SheetMetalWorkersPensionPlanofSouthernCAAZandNVMemberus-gaap:PensionPlansDefinedBenefitMember2019-01-012019-12-310000067716mdu:SheetMetalWorkersPensionPlanofSouthernCAAZandNVMemberus-gaap:PensionPlansDefinedBenefitMember2018-01-012018-12-310000067716mdu:SouthwestMarinePensionTrustMemberus-gaap:PensionPlansDefinedBenefitMember2020-01-012020-12-310000067716mdu:SouthwestMarinePensionTrustMemberus-gaap:PensionPlansDefinedBenefitMember2019-01-012019-12-310000067716mdu:SouthwestMarinePensionTrustMemberus-gaap:PensionPlansDefinedBenefitMember2018-01-012018-12-310000067716us-gaap:PensionPlansDefinedBenefitMember2020-01-012020-12-310000067716us-gaap:PensionPlansDefinedBenefitMember2019-01-012019-12-310000067716us-gaap:PensionPlansDefinedBenefitMember2018-01-012018-12-310000067716us-gaap:OtherPostretirementBenefitPlansDefinedBenefitMember2020-01-012020-12-310000067716us-gaap:OtherPostretirementBenefitPlansDefinedBenefitMember2019-01-012019-12-310000067716us-gaap:OtherPostretirementBenefitPlansDefinedBenefitMember2018-01-012018-12-310000067716mdu:MultiemployerPlansDefinedContributionMember2020-01-012020-12-310000067716mdu:MultiemployerPlansDefinedContributionMember2019-01-012019-12-310000067716mdu:MultiemployerPlansDefinedContributionMember2018-01-012018-12-310000067716us-gaap:JointlyOwnedElectricityGenerationPlantMembermdu:BigStoneStationMember2020-12-310000067716us-gaap:JointlyOwnedElectricityGenerationPlantMembermdu:BigStoneStationMember2019-12-310000067716us-gaap:JointlyOwnedElectricityTransmissionAndDistributionSystemMembermdu:BSSEMember2020-12-310000067716us-gaap:JointlyOwnedElectricityTransmissionAndDistributionSystemMembermdu:BSSEMember2019-12-310000067716us-gaap:JointlyOwnedElectricityGenerationPlantMembermdu:CoyoteStationMember2020-12-310000067716us-gaap:JointlyOwnedElectricityGenerationPlantMembermdu:CoyoteStationMember2019-12-310000067716us-gaap:JointlyOwnedElectricityGenerationPlantMembermdu:WygenIiiMember2020-12-310000067716us-gaap:JointlyOwnedElectricityGenerationPlantMembermdu:WygenIiiMember2019-12-310000067716mdu:GreatPlainsNaturalGasCo.Membermdu:PendingRateCaseMembermdu:MNPUCMemberus-gaap:GasDistributionMember2019-09-272019-09-270000067716mdu:GreatPlainsNaturalGasCo.Membermdu:PendingRateCaseMembermdu:MNPUCMemberus-gaap:GasDistributionMember2020-01-012020-01-010000067716mdu:GreatPlainsNaturalGasCo.Membermdu:PendingRateCaseMembermdu:MNPUCMemberus-gaap:GasDistributionMember2020-10-262020-10-260000067716mdu:MTPSCMembermdu:MontanaDakotaUtilitiesCo.Memberus-gaap:GasDistributionMember2020-06-222020-06-220000067716mdu:MTPSCMembermdu:MontanaDakotaUtilitiesCo.Memberus-gaap:SubsequentEventMemberus-gaap:GasDistributionMember2021-02-012021-02-010000067716mdu:MTPSCMembermdu:MontanaDakotaUtilitiesCo.Memberus-gaap:SubsequentEventMemberus-gaap:GasDistributionMember2021-03-152021-03-150000067716mdu:MontanaDakotaUtilitiesCo.Membermdu:PendingRateCaseMembermdu:NDPSCMemberus-gaap:GasDistributionMember2020-08-262020-08-260000067716mdu:MontanaDakotaUtilitiesCo.Membermdu:PendingRateCaseMemberus-gaap:SubsequentEventMembermdu:NDPSCMemberus-gaap:GasDistributionMember2021-01-012021-01-010000067716mdu:MontanaDakotaUtilitiesCo.Memberus-gaap:ElectricityMemberus-gaap:SubsequentEventMembermdu:NDPSCMember2021-02-012021-02-010000067716mdu:OPUCMemberus-gaap:GasDistributionMembermdu:CascadeNaturalGasMember2020-03-312020-03-310000067716mdu:OPUCMemberus-gaap:GasDistributionMembermdu:CascadeNaturalGasMember2020-09-302020-09-300000067716us-gaap:SubsequentEventMembermdu:OPUCMemberus-gaap:GasDistributionMembermdu:CascadeNaturalGasMember2021-02-012021-02-010000067716mdu:PendingRateCaseMembermdu:WUTCMemberus-gaap:GasDistributionMembermdu:CascadeNaturalGasMember2020-06-192020-06-190000067716mdu:PendingRateCaseMembermdu:WUTCMemberus-gaap:GasDistributionMembermdu:CascadeNaturalGasMember2020-07-242020-07-240000067716mdu:PendingRateCaseMembermdu:WUTCMemberus-gaap:SubsequentEventMemberus-gaap:GasDistributionMembermdu:CascadeNaturalGasMember2021-01-082021-01-080000067716mdu:MontanaDakotaUtilitiesCo.Memberus-gaap:SubsequentEventMembermdu:ElectricMembermdu:MISOMember2021-01-012021-01-010000067716mdu:PortlandHarborSiteMember2020-12-310000067716mdu:MissoulaMTmanufacturedgasplantsiteMember2020-01-012020-12-310000067716mdu:MissoulaMTmanufacturedgasplantsiteMember2020-12-310000067716mdu:BremertonWAManufacturedGasPlantSiteMember2020-01-012020-12-310000067716mdu:BremertonWAManufacturedGasPlantSiteMember2020-07-012020-09-300000067716mdu:BremertonWAManufacturedGasPlantSiteMembersrt:MinimumMember2020-01-012020-12-310000067716mdu:BremertonWAManufacturedGasPlantSiteMembersrt:MaximumMember2020-01-012020-12-310000067716mdu:BremertonWAManufacturedGasPlantSiteMember2020-12-310000067716mdu:BellinghamWAManufacturedGasPlantSiteMembersrt:MinimumMember2020-01-012020-12-310000067716mdu:BellinghamWAManufacturedGasPlantSiteMembersrt:MaximumMember2020-01-012020-12-310000067716mdu:BellinghamWAManufacturedGasPlantSiteMember2020-01-012020-12-310000067716mdu:FuelContractMember2020-12-3100000677162020-01-012020-03-3100000677162020-04-012020-06-3000000677162020-07-012020-09-3000000677162020-10-012020-12-3100000677162019-01-012019-03-3100000677162019-07-012019-09-3000000677162019-10-012019-12-310000067716srt:ParentCompanyMember2020-01-012020-12-310000067716srt:ParentCompanyMember2019-01-012019-12-310000067716srt:ParentCompanyMember2018-01-012018-12-310000067716srt:ParentCompanyMember2018-12-310000067716srt:ParentCompanyMember2017-12-31

UNITED STATES
SECURITIES AND EXCHANGE COMMISSION
WASHINGTON, D.C. 20549
FORM 10-K
ANNUAL REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934
For the fiscal year ended December 31, 2020
OR
TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934
For the transition period from _____________ to ______________
Commission file number 1-03480
MDU RESOURCES GROUP INC
(Exact name of registrant as specified in its charter)
Delaware
 
30-1133956
(State or other jurisdiction of
incorporation or organization)
 
(I.R.S. Employer Identification No.)

1200 West Century Avenue
P.O. Box 5650
Bismarck, North Dakota 58506-5650
(Address of principal executive offices)
(Zip Code)
(701) 530-1000
(Registrant's telephone number, including area code)
Securities registered pursuant to Section 12(b) of the Act:
Title of each class Trading symbol(s) Name of each exchange on which registered
Common Stock, par value $1.00 per share MDU New York Stock Exchange
Securities registered pursuant to Section 12(g) of the Act: None
Indicate by check mark if the registrant is a well-known seasoned issuer, as defined in Rule 405 of the Securities Act. Yes  No .
Indicate by check mark if the registrant is not required to file reports pursuant to Section 13 or Section 15(d) of the Act. Yes  No .
Indicate by check mark whether the registrant (1) has filed all reports required to be filed by Section 13 or 15(d) of the Securities Exchange Act of 1934 during the preceding 12 months (or for such shorter period that the registrant was required to file such reports), and (2) has been subject to such filing requirements for the past 90 days. Yes  No .
Indicate by check mark whether the registrant has submitted electronically every Interactive Data File required to be submitted pursuant to Rule 405 of Regulation S-T (§ 232.405 of this chapter) during the preceding 12 months (or for such shorter period that the registrant was required to submit such files). Yes  No .
Indicate by check mark whether the registrant is a large accelerated filer, an accelerated filer, a non-accelerated filer, a smaller reporting company, or an emerging growth company. See the definitions of "large accelerated filer," "accelerated filer," "smaller reporting company," and "emerging growth company" in Rule 12b-2 of the Exchange Act.
Large accelerated filer Accelerated filer
Non-accelerated filer Smaller reporting company
Emerging growth company
If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act.
Indicate by check mark whether the registrant has filed a report on and attestation to its management's assessment of the effectiveness of its internal control over financial reporting under Section 404(b) of the Sarbanes-Oxley Act (15 U.S.C. 7262(b)) by the registered public accounting firm that prepared or issued its audit report.
Indicate by check mark whether the registrant is a shell company (as defined in Rule 12b-2 of the Act). Yes  No .
State the aggregate market value of the voting common stock held by non-affiliates of the registrant as of June 30, 2020: $4,447,584,104.
Indicate the number of shares outstanding of the registrant's common stock, as of February 11, 2021: 200,522,277 shares.
DOCUMENTS INCORPORATED BY REFERENCE
Relevant portions of the registrant's 2021 Proxy Statement, to be filed no later than 120 days from December 31, 2020, are incorporated by reference in Part III, Items 10, 11, 12, 13 and 14 of this Report.



Contents
Part I Page
7
7
7
10
13
15
16
19
Item 1A
20
Item 1B
27
Item 3
28
Item 4
28
Part II  
Item 5
29
Item 6
30
Item 7
32
Item 7A
54
55
60
61
62
63
64
65
65
66
72
75
76
77
78
79
81
83
84
84
85
86
87
88
2 MDU Resources Group, Inc. Form 10-K



Contents
Part II (continued) Page
89
92
100
101
102
Item 9
108
Item 9A
108
Item 9B
108
Part III  
Item 10
109
Item 11
109
Item 12
109
Item 13
109
Item 14
109
Part IV
Item 15
110
114
Item 16
116
117
MDU Resources Group, Inc. Form 10-K 3



Definitions
The following abbreviations and acronyms used in this Form 10-K are defined below:
Abbreviation or Acronym
AFUDC
Allowance for funds used during construction
Army Corps U.S. Army Corps of Engineers
ASC FASB Accounting Standards Codification
ASU
FASB Accounting Standards Update
Audit Committee
Audit Committee of the board of directors of the Company
Bcf Billion cubic feet
Big Stone Station 475-MW coal-fired electric generating facility near Big Stone City, South Dakota (22.7 percent ownership)
Brazilian Transmission Lines Company's former investment in companies owning three electric transmission lines in Brazil
BSSE 345-kilovolt transmission line from Ellendale, North Dakota, to Big Stone City, South Dakota (50 percent ownership)
Btu British thermal unit
CARES Act United States Coronavirus Aid, Relief, and Economic Security Act
Cascade Cascade Natural Gas Corporation, an indirect wholly owned subsidiary of MDU Energy Capital
CDC Centers for Disease Control and Prevention
Centennial Centennial Energy Holdings, Inc., a direct wholly owned subsidiary of the Company
Centennial Capital Centennial Holdings Capital LLC, a direct wholly owned subsidiary of Centennial
Centennial's Consolidated EBITDA Centennial's consolidated net income from continuing operations plus the related interest expense, taxes, depreciation, depletion, amortization of intangibles and any non-cash charge relating to asset impairment for the preceding 12-month period
Centennial Resources Centennial Energy Resources LLC, a direct wholly owned subsidiary of Centennial
CERCLA Comprehensive Environmental Response, Compensation and Liability Act
Clean Air Act Federal Clean Air Act
Clean Water Act Federal Clean Water Act
Company MDU Resources Group, Inc. (formerly known as MDUR Newco), which, as the context requires, refers to the previous MDU Resources Group, Inc. prior to January 1, 2019, and the new holding company of the same name after January 1, 2019
COVID-19 Coronavirus disease 2019
Coyote Creek Coyote Creek Mining Company, LLC, a subsidiary of The North American Coal Corporation
Coyote Station 427-MW coal-fired electric generating facility near Beulah, North Dakota (25 percent ownership)
CyROC Cyber Risk Oversight Committee
Dakota Prairie Refining Dakota Prairie Refining, LLC, a limited liability company previously owned by WBI Energy and Calumet Specialty Products Partners, L.P. (previously included in the Company's refining segment)
dk Decatherm
Dodd-Frank Act Dodd-Frank Wall Street Reform and Consumer Protection Act
EBITDA Earnings before interest, taxes, depreciation, depletion and amortization
EIN Employer Identification Number
EPA United States Environmental Protection Agency
ERISA Employee Retirement Income Security Act of 1974
ESA Endangered Species Act
Exchange Act Securities Exchange Act of 1934, as amended
FASB Financial Accounting Standards Board
FERC Federal Energy Regulatory Commission
Fidelity Fidelity Exploration & Production Company, a direct wholly owned subsidiary of WBI Holdings (previously referred to as the Company's exploration and production segment)
FIP Funding improvement plan
GAAP Accounting principles generally accepted in the United States of America
GHG Greenhouse gas
Great Plains Great Plains Natural Gas Co., a public utility division of the Company prior to the closing of the Holding Company Reorganization and a public utility division of Montana-Dakota as of January 1, 2019
GVTC Generation Verification Test Capacity
4 MDU Resources Group, Inc. Form 10-K



Definitions
Holding Company Reorganization The internal holding company reorganization completed on January 1, 2019, pursuant to the agreement and plan of merger, dated as of December 31, 2018, by and among Montana-Dakota, the Company and MDUR Newco Sub, which resulted in the Company becoming a holding company and owning all of the outstanding capital stock of Montana-Dakota.
IBEW International Brotherhood of Electrical Workers
ICWU International Chemical Workers Union
Intermountain Intermountain Gas Company, an indirect wholly owned subsidiary of MDU Energy Capital
IPUC Idaho Public Utilities Commission
Item 8 Financial Statements and Supplementary Data
Knife River Knife River Corporation, a direct wholly owned subsidiary of Centennial
Knife River - Northwest Knife River Corporation - Northwest, an indirect wholly owned subsidiary of Knife River
K-Plan Company's 401(k) Retirement Plan
kW Kilowatts
kWh Kilowatt-hour
LIBOR
London Inter-bank Offered Rate
LWG Lower Willamette Group
MD&A Management's Discussion and Analysis of Financial Condition and Results of Operations
Mdk Thousand dk
MDU Construction Services MDU Construction Services Group, Inc., a direct wholly owned subsidiary of Centennial
MDU Energy Capital MDU Energy Capital, LLC, a direct wholly owned subsidiary of the Company
MDUR Newco
MDUR Newco, Inc., a public holding company created by implementing the Holding Company Reorganization, now known as the Company
MDUR Newco Sub MDUR Newco Sub, Inc., a direct, wholly owned subsidiary of MDUR Newco, which was merged with and into Montana-Dakota in the Holding Company Reorganization
MEPP Multiemployer pension plan
MISO Midcontinent Independent System Operator, Inc.
MMBtu Million Btu
MMcf Million cubic feet
MMdk Million dk
MNPUC Minnesota Public Utilities Commission
Montana-Dakota Montana-Dakota Utilities Co. (formerly known as MDU Resources Group, Inc.), a public utility division of the Company prior to the closing of the Holding Company Reorganization and a direct wholly owned subsidiary of MDU Energy Capital as of January 1, 2019
MPPAA Multiemployer Pension Plan Amendments Act of 1980
MTDEQ Montana Department of Environmental Quality
MTPSC Montana Public Service Commission
MW Megawatt
NDDEQ North Dakota Department of Environmental Quality
NDPSC North Dakota Public Service Commission
NERC North American Electric Reliability Corporation
Non-GAAP Not in accordance with GAAP
Oil Includes crude oil and condensate
OPUC Oregon Public Utility Commission
PCBs Polychlorinated biphenyls
Proxy Statement Company's 2021 Proxy Statement to be filed no later than April 30, 2021
PRP Potentially Responsible Party
RCRA Resource Conservation and Recovery Act
RNG Renewable Natural Gas
ROD Record of Decision
RP Rehabilitation plan
SDPUC South Dakota Public Utilities Commission
SEC United States Securities and Exchange Commission
Securities Act Securities Act of 1933, as amended
Securities Act Industry Guide 7 Description of Property by Issuers Engaged or to be Engaged in Significant Mining Operations
Sheridan System A separate electric system owned by Montana-Dakota
MDU Resources Group, Inc. Form 10-K 5



Definitions
SOFR Secured Overnight Financing Rate
TCJA Tax Cuts and Jobs Act
UA United Association of Journeyman and Apprentices of the Plumbing and Pipefitting Industry of the United States and Canada
VIE Variable interest entity
Washington DOE Washington State Department of Ecology
WBI Energy WBI Energy, Inc., a direct wholly owned subsidiary of WBI Holdings
WBI Energy Transmission WBI Energy Transmission, Inc., an indirect wholly owned subsidiary of WBI Holdings
WBI Holdings WBI Holdings, Inc., a direct wholly owned subsidiary of Centennial
WUTC Washington Utilities and Transportation Commission
Wygen III 100-MW coal-fired electric generating facility near Gillette, Wyoming (25 percent ownership)
WYPSC Wyoming Public Service Commission
ZRCs Zonal resource credits - a MW of demand equivalent assigned to generators by MISO for meeting system reliability requirements
6 MDU Resources Group, Inc. Form 10-K



Part I

Forward-Looking Statements
This Form 10-K contains forward-looking statements within the meaning of Section 21E of the Exchange Act. Forward-looking statements are all statements other than statements of historical fact, including without limitation those statements that are identified by the words "anticipates," "estimates," "expects," "intends," "plans," "predicts" and similar expressions, and include statements concerning plans, objectives, goals, strategies, future events or performance, and underlying assumptions (many of which are based, in turn, upon further assumptions) and other statements that are other than statements of historical facts. From time to time, the Company may publish or otherwise make available forward-looking statements of this nature, including statements contained within Item 7 - MD&A - Business Segment Financial and Operating Data.
Forward-looking statements involve risks and uncertainties, which could cause actual results or outcomes to differ materially from those expressed. The Company's expectations, beliefs and projections are expressed in good faith and are believed by the Company to have a reasonable basis, including without limitation, the impact of COVID-19 on the Company's business, management's examination of historical operating trends, data contained in the Company's records and other data available from third parties. Nonetheless, the Company's expectations, beliefs or projections may not be achieved or accomplished.
Any forward-looking statement contained in this document speaks only as of the date on which the statement is made, and the Company undertakes no obligation to update any forward-looking statement or statements to reflect events or circumstances that occur after the date on which the statement is made or to reflect the occurrence of unanticipated events. New factors emerge from time to time and it is not possible for management to predict all of the factors, nor can it assess the effect of each factor on the Company's business or the extent to which any factor, or combination of factors, may cause actual results to differ materially from those contained in any forward-looking statement. All forward-looking statements, whether written or oral and whether made by or on behalf of the Company, are expressly qualified by the risk factors and cautionary statements in this Form 10-K, including statements contained within Item 1A - Risk Factors.
Items 1 and 2. Business and Properties
General
The Company is a regulated energy delivery and construction materials and services business. Its principal executive offices are located at 1200 West Century Avenue, P.O. Box 5650, Bismarck, North Dakota 58506-5650, telephone (701) 530-1000.

Montana-Dakota was incorporated under the state laws of Delaware in 1924. The Company was incorporated under the state laws of Delaware in 2018. On January 2, 2019, the Company announced the completion of the Holding Company Reorganization, which resulted in Montana-Dakota becoming a subsidiary of the Company. Immediately after consummation of the Holding Company Reorganization, the Company had, on a consolidated basis, the same assets, businesses and operations as immediately prior to the consummation of the Holding Company Reorganization.
The Company's strategy is to deliver superior value with a two-platform model, regulated energy delivery and construction materials and services businesses, while also pursuing organic growth opportunities and using a disciplined approach to strategic acquisitions of well-managed companies and properties.
The Company focuses on infrastructure and is Building a Strong America® by providing essential products and services through its regulated energy delivery platform and its construction materials and services platform, which are both comprised of different operating segments. Most of these segments experience seasonality related to the industries in which they operate. The two-platform approach helps balance this seasonality and the risk associated with each type of industry. Through its regulated energy delivery platform, the Company generates, transmits and distributes electricity and provides natural gas distribution, transportation and storage services. These businesses are regulated by state public service commissions and/or the FERC. The construction materials and services platform provides construction services to a variety of industries, including commercial, industrial and governmental customers, and provides construction materials through aggregate mining and marketing of related products, such as ready-mixed concrete, asphalt and asphalt oil.
The Company is organized into five reportable business segments. These business segments include: electric, natural gas distribution, pipeline, construction materials and contracting, and construction services. The Company's business segments are determined based on the Company's method of internal reporting, which generally segregates the strategic business units due to differences in products, services and regulation. The internal reporting of these segments is defined based on the reporting and review process used by the Company's chief executive officer.
The Company, through its wholly owned subsidiary, MDU Energy Capital, owns Montana-Dakota, Cascade and Intermountain. The electric segment is comprised of Montana-Dakota while the natural gas distribution segment is comprised of Montana-Dakota, Cascade and Intermountain.
The Company, through its wholly owned subsidiary, Centennial, owns WBI Holdings, Knife River, MDU Construction Services and Centennial Capital. WBI Holdings is the pipeline segment, Knife River is the construction materials and contracting segment, MDU Construction Services is the construction services segment, and Centennial Capital is reflected in the Other category.
MDU Resources Group, Inc. Form 10-K 7



Part I
The financial results and data applicable to each of the Company's business segments, as well as their financing requirements, are set forth in Item 7 - MD&A and Item 8 - Note 17.
The Company's material properties, which are of varying ages and are of different construction types, are generally in good condition, are well maintained and are generally suitable and adequate for the purposes for which they are used.
Human Capital Management At the core of Building a Strong America® is building a strong team of employees with a focus on safety and a commitment to diversity and inclusion. The Company's team consisted of 12,994 employees located in 40 states plus Washington D.C. as of December 31, 2020. The number of employees fluctuates during the year due to the seasonality and the number and size of construction projects. During 2020, the number of employees peaked at 15,668. Employees as of December 31, 2020, were as follows:
Company Number of employees
MDU Resources Group, Inc. 250 
MDU Energy Capital 1,592 
WBI Holdings 323 
Knife River 3,582 
MDU Construction Services 7,247 
Total employees 12,994 
Many of the Company's employees are represented by collective-bargaining agreements. The majority of the collective-bargaining agreements contain provisions that prohibit work stoppages or strikes and provide for binding arbitration dispute resolution in the event of an extended disagreement. The following information is as of December 31, 2020.
Company Collective- bargaining agreement Number of employees represented Agreement status
Montana-Dakota IBEW 336  Effective through April 30, 2021
Intermountain UA 129  Effective through March 31, 2023
Cascade ICWU 190  Effective through March 31, 2021
WBI Energy Transmission IBEW 67  Effective through March 31, 2022
Knife River 39 various agreements 555  2 agreements in negotiations
MDU Construction Services 103 various agreements 5,927  2 agreements in negotiations
Total 7,204 
Safety The Company is committed to safety and health in the workplace and subscribes to the principle that all injuries can be prevented. To ensure safe work environments, the Company provides training, adequate resources and appropriate follow-up on any unsafe conditions or actions.
To facilitate a strong safety culture, the Company established its Safety Leadership Council which is charged with receiving and reviewing information for the identification and adoption of best practices in the prevention of occupationally induced injuries and illness, as well as monitoring the effectiveness of the Company's safety and environmental health programs.
In addition to the Safety Leadership Council, the Company has policies and training that support safety in the workplace including training on safety matters through classroom and toolbox meetings on job sites. The Company utilizes safety compliance in the evaluation of employees, which includes management, and recognizes employee safety through safety award programs. Accident and safety statistical information is gathered for each of the business segments and regularly reported to management and the board of directors.
In response to COVID-19, the Company established a task force to monitor developments related to the pandemic and implemented procedures to protect employees. The Company adopted recommended practices from the CDC and is following directives of each state and local jurisdiction in which the Company operates. Some of these practices include, among other things, a daily COVID-19 self-assessment to access Company facilities; social distancing; telecommuting; virtual meetings; designated entrances, exits and stairwells; restricted business travel; and increased access to personal protective equipment.
Building People Employees are hired having the skills, abilities and motivation to achieve the results needed for their jobs. Each job is important and part of a coordinated team effort to accomplish the organization's objectives. The Company provides opportunities for advancement through job mobility, succession planning and promotions both within and between business segments.
The Company uses a variety of recruiting sources depending on the position, market and job requirements. All open positions across the Company's businesses are posted on the Company's website www.jobs.mdu.com. Other sources for recruiting employees include team member referrals, union workforce, direct recruitment and various forms of advertising, including social media. The Company also uses internship programs to introduce
8 MDU Resources Group, Inc. Form 10-K



Part I
individuals to the Company's business operations and provide a possible source of future employees. In markets where labor availability is tight, the Company uses telecommuting, guaranteed hours, flexible schedules and work arrangements to fill open positions.
To attract and retain employees, the Company offers:
Competitive salaries and wages based on the labor markets in which it operates.
Employee growth through training in the form of technical, professional and leadership programs. The Company also provides formal and informal mentoring and job shadowing programs to assist employees in their job and career goals.
Incentive compensation opportunities based on the Company's performance.
Comprehensive benefits including vacation, sick leave, health and wellness programs, retirement plans and discount programs.
Diversity and Inclusion To further its corporate vision, the Company is committed to an inclusive environment that respects the differences and embraces the strengths of its diverse employees. Each business segment has an appointed diversity officer who serves as a conduit for diversity-related issues by providing a voice to all employees. The Company has three strategic goals related to diversity:
Increase productivity and profitability through the creation of a work environment which values all perspectives and methods of accomplishing work.
Enhance collaboration efforts through cooperation and sharing of best practices to create new ways of meeting employee, customer and shareholder needs.
Maintain a culture of integrity, respect and safety by ensuring employees understand these essential values which are part of the Company's vision statement.
The Company provides training and has policies which speak to diversity and inclusion. Training for employees on diversity and inclusion topics include equal employment opportunity, workplace harassment, respect and unconscious bias. In 2020, the Company implemented a telecommuting policy to allow certain employees to work from home or other offsite locations. The flexibility of the policy may expand the potential applicant pool for job openings beyond the Company's traditional geographic footprint.
The Company also promotes its strategic diversity goals through the following special recognition awards:
The Einstein award recognizes the best process improvement ideas that contribute in a measurable way to improving the Company's bottom line and are vital to the Company's success.
The Community Spirit award recognizes employees who are actively involved in their community.
The Summit award recognizes employees who make the Company a better place to work.
The Environmental Integrity award recognizes an employee program, project or activity that reflects the Company's environmental policy and philosophy.
The Hero Award recognizes employees who go above and beyond the call of duty to save another's life.
Governmental Matters The operations of the Company and certain of its subsidiaries are subject to laws and regulations relating to air, water and solid waste pollution control; state facility-siting regulations; zoning and planning regulations of certain state and local authorities; federal and state health and safety regulations; and state hazard communication standards. The Company believes it is in substantial compliance with these regulations, except as to what may be ultimately determined with regard to items discussed in Environmental matters in Item 8 - Note 21. There are no pending CERCLA actions for any of the Company's material properties. However, the Company is involved in certain claims relating to the Portland, Oregon, Harbor Superfund Site and the Bremerton Gasworks Superfund Site. For more information on the Company's environmental matters, see Item 8 - Note 21.
The Company produces GHG emissions primarily from its fossil fuel electric generating facilities, as well as from natural gas pipeline and storage systems, and operations of equipment and fleet vehicles. GHG emissions also result from customer use of natural gas for heating and other uses. As interest in reductions in GHG emissions has grown, the Company has developed renewable generation with lower or no GHG emissions. Governmental legislation and regulatory initiatives regarding environmental and energy policy are continuously evolving and could negatively impact the Company's operations and financial results. Until legislation and regulation are finalized, the impact of these measures cannot be accurately predicted. The Company will continue to monitor legislative and regulatory activity related to environmental and energy policy initiatives. Disclosure regarding specific environmental matters applicable to each of the Company's businesses is set forth under each business description later. In addition, for a discussion of the Company's risks related to environmental laws and regulations, see Item 1A - Risk Factors.
Technology The Company uses technology in substantially all aspects of its business operations and requires uninterrupted operation of information technology systems and network infrastructure. These systems may be vulnerable to failures or unauthorized access. The Company has policies, procedures and processes designed to strengthen and protect these systems, which include the Company’s enterprise information technology and operation technology groups continually evaluating new tools and techniques to reduce the risk of a cyber breach.
The Company created CyROC to oversee its approach to cybersecurity. CyROC is responsible for supplying management and the Audit Committee with analyses, appraisals, recommendations and pertinent information concerning cyber defense of the Company’s electronic information and
MDU Resources Group, Inc. Form 10-K 9



Part I
information technology systems. A quarterly cybersecurity report is provided to the Audit Committee. For a discussion of the Company's risks related to cybersecurity, see Item 1A - Risk Factors.
Available Information This annual report on Form 10-K, the Company's quarterly reports on Form 10-Q and current reports on Form 8-K, and any amendments to those reports filed or furnished pursuant to Section 13(a) or 15(d) of the Exchange Act are available free of charge through the Company's website as soon as reasonably practicable after the Company has electronically filed such reports with, or furnished such reports to, the SEC. The Company's website address is www.mdu.com. The information available on the Company's website is not part of this annual report on Form 10-K. The SEC also maintains a website where the Company's filings can be obtained free of charge at www.SEC.gov.
Electric
General The Company's electric segment is operated through its wholly owned subsidiary, Montana-Dakota. Montana-Dakota provides electric service at retail, serving residential, commercial, industrial and municipal customers in 185 communities and adjacent rural areas in Montana, North Dakota, South Dakota and Wyoming. For more information on the retail customer classes served, see the table below. The material properties owned by Montana-Dakota for use in its electric operations include interests in 16 electric generating units at 11 facilities and two small portable diesel generators, as further described under System Supply, System Demand and Competition, approximately 3,400 and 4,900 miles of transmission and distribution lines, respectively, and 81 transmission and 298 distribution substations. Montana-Dakota has obtained and holds, or is in the process of renewing, valid and existing franchises authorizing it to conduct its electric operations in all of the municipalities it serves where such franchises are required. Montana-Dakota intends to protect its service area and seek renewal of all expiring franchises. At December 31, 2020, Montana-Dakota's net electric plant investment was $1.5 billion and its rate base was $1.3 billion.
The retail customers served and respective revenues by class for the electric business were as follows:
2020 2019 2018
Customers
Served
Revenues Customers
Served
Revenues Customers
Served
Revenues
(Dollars in thousands)
Residential 118,893  $ 122,545  118,563  $ 125,614  118,426  $ 126,173 
Commercial 23,050  131,207  22,948  142,062  22,756  141,961 
Industrial 230  36,736  234  37,790  236  36,081 
Other 1,609  6,601  1,601  7,454  1,604  7,882 
143,782  $ 297,089  143,346  $ 312,920  143,022  $ 312,097 
Other electric revenues, which are largely transmission-related revenues, for Montana-Dakota were $34.9 million, $38.8 million and $23.0 million for the years ended December 31, 2020, 2019 and 2018, respectively.
The percentage of electric retail revenues by jurisdiction was as follows:
2020 2019 2018
North Dakota 64  % 65  % 66  %
Montana 22  % 22  % 20  %
Wyoming 9  % % %
South Dakota 5  % % %
Retail electric rates, service, accounting and certain security issuances are subject to regulation by the MTPSC, NDPSC, SDPUC and WYPSC. The interstate transmission and wholesale electric power operations of Montana-Dakota are also subject to regulation by the FERC under provisions of the Federal Power Act, as are interconnections with other utilities and power generators, the issuance of certain securities, accounting, cybersecurity and other matters.
Through MISO, Montana-Dakota has access to wholesale energy, ancillary services and capacity markets for its interconnected system. MISO is a regional transmission organization responsible for operational control of the transmission systems of its members. MISO provides security center operations, tariff administration and operates day-ahead and real-time energy markets, ancillary services and capacity markets. As a member of MISO, Montana-Dakota's generation is sold into the MISO energy market and its energy needs are purchased from that market.
System Supply, System Demand and Competition Through an interconnected electric system, Montana-Dakota serves markets in portions of North Dakota, Montana and South Dakota. These markets are highly seasonal and sales volumes depend largely on the weather. Additionally, the average customer consumption has tended to decline due to increases in energy efficient lighting and appliances being installed. The interconnected system consists of 15 electric generating units at 10 facilities and two small portable diesel generators, which have an aggregate nameplate rating attributable to Montana-Dakota's interest of 750,318 kW and total net ZRCs of 512.3 in 2020. For 2020, Montana-Dakota's total ZRCs, including its firm purchase power contracts, were 553.2. Montana-Dakota's planning reserve margin requirement within MISO was 531.4 ZRCs for 2020. The maximum electric peak demand experienced to date attributable to Montana-Dakota's sales to retail customers on the interconnected system was 611,542 kW in August 2015. Montana-Dakota's latest forecast for its interconnected system indicates that its annual peak will continue to occur
10 MDU Resources Group, Inc. Form 10-K



Part I
during the summer. Montana-Dakota's interconnected system electric generating capability includes five steam-turbine generating units at four facilities using coal for fuel, four natural gas combustion turbine units at three facilities, three wind electric generating facilities, two natural gas-fired reciprocating internal combustion engines at one facility, a heat recovery electric generating facility and two small portable diesel generators.
Additional energy is purchased as needed, or in lieu of generation if more economical, from the MISO market, and in 2020, Montana-Dakota purchased approximately 25 percent of its net kWh needs for its interconnected system through the MISO market.
Approximately 30 percent of the electricity delivered to customers from Montana-Dakota's owned generation in 2020 was from renewable resources. Although Montana-Dakota's generation resource capacity has increased to serve the needs of its customers, the carbon dioxide emission intensity of its electric generation resource fleet has been reduced by approximately 28 percent since 2005 through the addition of renewable generation and MISO market purchases. Montana-Dakota's carbon dioxide emissions are expected to continue to decline through the retirement of aging coal-fired electric generating units.
Through the Sheridan System, Montana-Dakota serves Sheridan, Wyoming, and neighboring communities. The maximum peak demand experienced to date attributable to Montana-Dakota sales to retail customers on that system was approximately 64,129 kW in July 2020. Montana-Dakota has a power supply contract with Black Hills Power, Inc. to purchase up to 49,000 kW of capacity annually through December 31, 2023. Wygen III also serves a portion of the needs of Montana-Dakota's Sheridan-area customers.
The following table sets forth details applicable to the Company's electric generating stations:
Generating Station Type Nameplate Rating (kW) 2020 ZRCs (a)  2020 Net Generation (kWh in thousands)
Interconnected System:          
North Dakota:          
Coyote (b) Steam 103,647  92.7  552,839 
Heskett Steam 86,000  87.9  469,765 
Heskett Combustion Turbine 89,038  77.9  1,331 
Glen Ullin Heat Recovery 7,500  4.8  29,813 
Cedar Hills Wind 19,500  4.0  55,889 
Thunder Spirit Wind 155,500  24.2  600,626 
South Dakota:  
Big Stone (b) Steam 94,111  105.7  394,021 
Montana:  
Lewis & Clark Steam 44,000  —  232,433 
Lewis & Clark Reciprocating Internal Combustion Engine 18,700  17.6  1,613 
Glendive Combustion Turbine 75,522  67.6  853 
Miles City Combustion Turbine 23,150  21.2  349 
Diamond Willow Wind 30,000  5.5  98,781 
Diesel Units Oil 3,650  3.2  10 
    750,318  512.3    2,438,323 
Sheridan System:          
Wyoming:    
Wygen III (b) Steam 28,000  N/A 209,423 
    778,318  512.3    2,647,746 
(a)    Interconnected system only. MISO requires generators to obtain their summer capability through the GVTC. The GVTC is then converted to ZRCs by applying each generator's forced outage factor against its GVTC. Wind generator's ZRCs are calculated based on a wind capacity study performed annually by MISO. ZRCs are used to meet supply obligations within MISO.
(b)    Reflects Montana-Dakota's ownership interest.
Virtually all of the current fuel requirements of the Lewis & Clark and Heskett stations are met with coal supplied by wholly-owned subsidiaries of Westmoreland Mining LLC under contracts that expire in March 2021 and December 2021, respectively. The Lewis & Clark and Heskett coal supply agreements provide for the purchase of coal necessary to supply the coal requirements of these stations at contracted pricing. Montana-Dakota estimates the Lewis & Clark coal requirement to be 60,000 tons through March 2021 and in the range of 400,000 to 425,000 tons per contract year for Heskett.
In February 2019, Montana-Dakota announced the retirement of three aging coal-fired electric generating units, Unit 1 at Lewis & Clark Station and Units 1 and 2 at Heskett Station. The retirements are expected to be completed in March 2021 for Lewis & Clark Station and early 2022 for Heskett Station. Montana-Dakota also announced the intent to construct a new 88-MW simple-cycle natural gas-fired combustion turbine peaking unit at the existing Heskett Station.
MDU Resources Group, Inc. Form 10-K 11



Part I
The owners of Coyote Station, including Montana-Dakota, have a contract with Coyote Creek for coal supply to the Coyote Station that expires December 2040. Montana-Dakota estimates the Coyote Station coal supply agreement to be approximately 1.5 million tons per contract year. For more information, see Item 8 - Note 21.
The owners of Big Stone Station, including Montana-Dakota, have a coal supply agreement with Peabody COALSALES, LLC to meet all of the Big Stone Station's fuel requirements through 2022. Montana-Dakota estimates the Big Stone Station coal supply agreement to be approximately 1.5 million tons per contract year.
Montana-Dakota has a coal supply agreement with Wyodak Resources Development Corp., to supply the coal requirements of Wygen III at contracted pricing through June 1, 2060. Montana-Dakota estimates the maximum annual coal consumption of the facility to be 594,000 tons.
The average cost of coal purchased, including freight, at Montana-Dakota's electric generating stations (including the Big Stone, Coyote and Wygen III stations) was as follows:
Years ended December 31, 2020 2019 2018
Average cost of coal per MMBtu $ 2.10  $ 2.15  $ 2.00 
Average cost of coal per ton $ 30.52  $ 31.36  $ 29.08 
Montana-Dakota expects that it has secured adequate capacity available through existing baseload generating stations, renewable generation, turbine peaking stations, demand reduction programs and firm contracts to meet the peak customer demand requirements of its customers through 2025. Future capacity needs are expected to be met by constructing new generation resources or acquiring additional capacity through power purchase contracts or the MISO capacity auction.
Montana-Dakota has major interconnections with its neighboring utilities and considers these interconnections adequate for coordinated planning, emergency assistance, exchange of capacity and energy and power supply reliability.
Montana-Dakota is subject to competition resulting from customer demands, technological advances and other factors in certain areas, from rural electric cooperatives, on-site generators, co-generators and municipally owned systems. In addition, competition in varying degrees exists between electricity and alternative forms of energy such as natural gas.
Regulatory Matters and Revenues Subject to Refund In North Dakota, Montana, South Dakota and Wyoming, there are various recurring regulatory mechanisms with annual true-ups that can impact Montana-Dakota's results of operations, which also reflect monthly increases or decreases in electric fuel and purchased power costs (including demand charges). Montana-Dakota is deferring those electric fuel and purchased power costs that are greater or less than amounts presently being recovered through its existing rate schedules. Examples of these recurring mechanisms include: monthly Fuel and Purchased Power Tracking Adjustments, a fuel adjustment clause and an annual Electric Power Supply Cost Adjustment. Such mechanisms generally provide that these deferred fuel and purchased power costs are recoverable or refundable through rate adjustments which are filed annually. Montana-Dakota's results of operations reflect 95 percent of the increases or decreases from the base purchased power costs and also reflect 85 percent of the increases or decreases from the base coal price, which is also recovered through the Electric Power Supply Cost Adjustment in Wyoming. For more information on regulatory assets and liabilities, see Item 8 - Note 6.
All of Montana-Dakota's wind resources pertaining to electric operations in North Dakota are included in a renewable resource cost adjustment rider, including the North Dakota investment in the Thunder Spirit Wind project. Montana-Dakota also has a transmission tracker in North Dakota to recover transmission costs associated with MISO and the Southwest Power Pool, regional transmission organizations serving parts of Montana-Dakota's system, along with certain of the transmission investments not recovered through retail rates. The tracking mechanism has an annual true-up.
In South Dakota, Montana-Dakota recovers the South Dakota investment in the Thunder Spirit Wind project through an Infrastructure Rider tracking mechanism that is subject to an annual true-up. Montana-Dakota also has in place in South Dakota a transmission tracker to recover transmission costs associated with MISO and the Southwest Power Pool, regional transmission organizations serving parts of Montana-Dakota's system, along with certain of the transmission investments not recovered through retail rates. This tracking mechanism also has an annual true-up.
In Montana, Montana-Dakota recovers in rates, through a tracking mechanism, its allocated share of Montana property-related taxes assessed to electric operations on an after-tax basis.
For more information on regulatory matters, see Item 8 - Note 20.
Environmental Matters Montana-Dakota's electric operations are subject to federal, state and local laws and regulations providing for air, water and solid waste pollution control; state facility-siting regulations; zoning and planning regulations of certain state and local authorities; federal and state health and safety regulations; and state hazard communication standards. Montana-Dakota believes it is in substantial compliance with these regulations.
12 MDU Resources Group, Inc. Form 10-K



Part I
Montana-Dakota's electric generating facilities have Title V Operating Permits, under the Clean Air Act, issued by the states in which they operate. Each of these permits has a five-year life. Near the expiration of these permits, renewal applications are submitted. Permits continue in force beyond the expiration date, provided the application for renewal is submitted by the required date, usually six months prior to expiration. The Title V Operating Permit renewal application for Coyote Station was submitted timely to the North Dakota Department of Health in September 2017, and the permit was issued on May 27, 2020. Wygen III is allowed to operate under the facility's construction permit until the Title V Operating Permit is issued by the Wyoming Department of Environmental Quality. The Title V Operating Permit application for Wygen III was submitted timely in January 2011, with the permit issuance date not specified at this time. The Title V Operating Permit renewal application for Heskett Station was submitted timely in June 2019 to the NDDEQ and the permit was issued on February 4, 2020. The Title V Operating Permit renewal application for Lewis & Clark Station was submitted timely in December 2019 to the MTDEQ with the permit issuance date not specified at this time. The Title V Operating Permit renewal applications for Miles City and Glendive Combustion Turbine facilities were submitted timely in December 2020 to the MTDEQ with the permit issuance dates not specified at this time.
State water discharge permits issued under the requirements of the Clean Water Act are maintained for power production facilities on the Yellowstone and Missouri rivers. These permits also have five-year lives. Montana-Dakota renews these permits as necessary prior to expiration. Other permits held by these facilities may include an initial siting permit, which is typically a one-time, preconstruction permit issued by the state; state permits to dispose of combustion by-products; state authorizations to withdraw water for operations; and Army Corps permits to construct water intake structures. Montana-Dakota's Army Corps permits grant one-time permission to construct and do not require renewal. Other permit terms vary and the permits are renewed as necessary.
Montana-Dakota's electric operations are very small-quantity generators of hazardous waste and subject only to minimum regulation under the RCRA. Montana-Dakota routinely handles PCBs from its electric operations in accordance with federal requirements. PCB storage areas are registered with the EPA as required.
Montana-Dakota incurred approximately $800,000 of environmental capital expenditures in 2020, mainly for an embankment stabilization project at Lewis & Clark Station and coal ash management projects for Lewis & Clark Station and Coyote Station. Environmental capital expenditures are estimated to be $600,000, $3.9 million and $4.1 million in 2021, 2022 and 2023, respectively, for various environmental projects, including a coal ash impoundment closure project at Lewis & Clark Station and coal ash landfill closure project at Heskett Station. Montana-Dakota's capital and operational expenditures could also be affected by future environmental requirements, such as regional haze emissions reductions. For more information, see Item 1A - Risk Factors.
Natural Gas Distribution
General The Company's natural gas distribution segment is operated through its wholly owned subsidiaries, consisting of operations from Montana-Dakota, Cascade and Intermountain. These companies sell natural gas at retail, serving residential, commercial and industrial customers in 340 communities and adjacent rural areas across eight states. They also provide natural gas transportation services to certain customers on the Company's systems. For more information on the retail customer classes served, see the table below. These services are provided through distribution systems aggregating approximately 20,600 miles. The natural gas distribution operations have obtained and hold, or are in the process of renewing, valid and existing franchises authorizing them to conduct their natural gas operations in all of the municipalities they serve where such franchises are required. These operations intend to protect their service areas and seek renewal of all expiring franchises. At December 31, 2020, the natural gas distribution operations' net natural gas distribution plant investment was $2.0 billion and its rate base was $1.3 billion.
The retail customers served and respective revenues by class for the natural gas distribution operations were as follows:
2020 2019 2018
Customers
Served
Revenues Customers
Served
Revenues Customers
Served
Revenues
(Dollars in thousands)
Residential 887,429  $ 480,466  868,821  $ 479,673  850,595  $ 464,697 
Commercial 108,788  281,175  107,741  293,201  106,297  279,566 
Industrial 929  26,217  906  26,570  835  24,555 
997,146  $ 787,858  977,468  $ 799,444  957,727  $ 768,818 
Transportation and other revenues for the natural gas distribution operations were $60.3 million, $65.8 million and $54.4 million for the years ended December 31, 2020, 2019 and 2018, respectively.
MDU Resources Group, Inc. Form 10-K 13



Part I
The percentage of the natural gas distribution operations' retail sales revenues by jurisdiction was as follows:
2020 2019 2018
Idaho 30  % 29  % 30  %
Washington 30  % 28  % 26  %
North Dakota 13  % 15  % 15  %
Montana 8  % % %
Oregon 8  % % %
South Dakota 6  % % %
Minnesota 3  % % %
Wyoming 2  % % %
The natural gas distribution operations are subject to regulation by the IPUC, MNPUC, MTPSC, NDPSC, OPUC, SDPUC, WUTC and WYPSC regarding retail rates, service, accounting and certain security issuances.
System Supply, System Demand and Competition The natural gas distribution operations serve retail natural gas markets, consisting principally of residential and firm commercial space and water heating users, in portions of Idaho, Minnesota, Montana, North Dakota, Oregon, South Dakota, Washington and Wyoming. These markets are highly seasonal and sales volumes depend largely on the weather, the effects of which are mitigated in certain jurisdictions by weather normalization mechanisms discussed later in Regulatory Matters. Additionally, the average customer consumption has tended to decline as more efficient appliances and furnaces are installed and as the Company has implemented conservation programs. In addition to the residential and commercial sales, the utilities transport natural gas for larger commercial and industrial customers who purchase their own supply of natural gas.
Competition resulting from customer demands, technological advances and other factors exists between natural gas and other fuels and forms of energy. The natural gas distribution operations have established various natural gas transportation service rates for their distribution businesses to retain interruptible commercial and industrial loads. These rates have enhanced the natural gas distribution operations' competitive posture with alternative fuels, although certain customers have bypassed the distribution systems by directly accessing transmission pipelines within close proximity. These bypasses do not have a material effect on results of operations.
The natural gas distribution operations and various distribution transportation customers obtain natural gas for their system requirements directly from producers, processors and marketers. The Company's purchased natural gas is supplied by a portfolio of contracts specifying market-based pricing and is transported under transportation agreements with WBI Energy Transmission, Northern Border Pipeline Company, Northwest Pipeline LLC, South Dakota Intrastate Pipeline, Northern Natural Gas, Gas Transmission Northwest LLC, Northwestern Energy, Viking Gas Transmission Company, Enbridge Westcoast Pipeline, Inc., Ruby Pipeline LLC, Foothills Pipe Lines Ltd., NOVA Gas Transmission Ltd, TC Energy Corporation and Northwest Natural. The natural gas distribution operations have contracts for storage services to provide gas supply during the winter heating season and to meet peak day demand with various storage providers, including WBI Energy Transmission, Dominion Energy Questar Pipeline, LLC, Northwest Pipeline LLC, Northwest Natural and Northern Natural Gas. In addition, certain of the operations have entered into natural gas supply management agreements with various parties. Demand for natural gas, which is a widely traded commodity, has historically been sensitive to seasonal heating and industrial load requirements, as well as changes in market price. The Company believes supplies are adequate for the natural gas distribution operations to meet its system natural gas requirements for the next decade. This belief is based on current and projected domestic and regional supplies of natural gas and the pipeline transmission network currently available through its suppliers and pipeline service providers.
Regulatory Matters The natural gas distribution operations' retail natural gas rate schedules contain clauses permitting adjustments in rates based upon changes in natural gas commodity, transportation and storage costs. Current tariffs allow for recovery or refunds of under- or over-recovered gas costs through rate adjustments which are filed annually.
In North Dakota and South Dakota, Montana-Dakota's natural gas tariffs contain weather normalization mechanisms applicable to certain firm customers that adjust the distribution delivery charges to reflect weather fluctuations during the November 1 through May 1 billing periods.
In Montana, Montana-Dakota recovers in rates, through a tracking mechanism, its allocated share of Montana property-related taxes assessed to natural gas operations on an after-tax basis.
In Minnesota and Washington, Great Plains and Cascade recover qualifying capital investments related to the safety and integrity of the pipeline systems through cost recovery tracking mechanisms.
In Oregon, Cascade has a decoupling mechanism in place approved by the OPUC until January 1, 2025, with a review to be completed by September 30, 2024. Cascade also has an earnings sharing mechanism with respect to its Oregon jurisdictional operations as required by the OPUC.
On July 7, 2016, the WUTC approved a full decoupling mechanism where Cascade is allowed recovery of an average revenue per customer regardless of actual consumption. The mechanism also includes an earnings sharing component if Cascade earns beyond its authorized return. The decoupling mechanism is being reviewed by an outside consultant which will provide a report to the WUTC in March 2021.
14 MDU Resources Group, Inc. Form 10-K



Part I
On December 22, 2016, the MNPUC approved a request by Great Plains to implement a full revenue decoupling mechanism pilot project for three years. The decoupling mechanism reflects the period January 1 through December 31. The MNPUC has adopted the administrative law judge's recommendation to extend the initial pilot period through the end of 2021. A final determination will be made as part of its pending rate case.
On May 4, 2020, Intermountain filed an application for authority to facilitate access for RNG producers to the Company's distribution system for the purpose of moving RNG to the producer's end-use customers. The request was approved by the IPUC with an effective date of June 12, 2020. The facilitation plan treats all RNG access as non-utility business and fully insulates utility customers from any impact. It allows Intermountain to charge RNG producers for the cost of all infrastructure needed to serve the producer. It also provides a method to charge RNG producers for maintenance costs associated with the RNG projects as well as an access fee that provides a return on Intermountain's involvement. The facilitation plan will be vital in supporting the growth and development of the RNG industry in the state of Idaho.
On August 3, 2020, Intermountain filed an application for authority to implement a commercial energy efficiency program and funding mechanism. The request was approved by the IPUC with an effective date of October 1, 2020. The purpose of the program is to encourage upgrades to, or use of, high efficiency natural gas equipment. This will be achieved through the use of rebates, offered towards the purchase and installation of qualified energy-efficient natural gas equipment.
For more information on regulatory matters, see Item 8 - Note 20.
Environmental Matters The natural gas distribution operations are subject to federal, state and local environmental, facility-siting, zoning and planning laws and regulations. The Company believes its natural gas distribution operations are in substantial compliance with those regulations.
The Company's natural gas distribution operations are very small-quantity generators of hazardous waste, and subject only to minimum regulation under the RCRA. Washington state rule defines Cascade as a small-quantity generator, but regulation under the rule is similar to RCRA. Certain locations of the natural gas distribution operations routinely handle PCBs from their natural gas operations in accordance with federal requirements. PCB storage areas are registered with the EPA as required. Capital and operational expenditures for natural gas distribution operations could be affected in a variety of ways by potential new GHG legislation or regulation. In particular, such legislation or regulation would likely increase capital expenditures for energy efficiency and conservation programs and operational costs associated with GHG emissions compliance. Natural gas distribution operations expect to recover the operational and capital expenditures for GHG regulatory compliance in rates consistent with the recovery of other reasonable costs of complying with environmental laws and regulations.
The natural gas distribution operations did not incur any material environmental expenditures in 2020. Except as to what may be ultimately determined with regard to the issues described in the following paragraph, the natural gas distribution operations do not expect to incur any material capital expenditures related to environmental compliance with current laws and regulations through 2023.
Montana-Dakota has ties to six historic manufactured gas plants as a successor corporation or through direct ownership of the plant. Montana-Dakota is investigating possible soil and groundwater impacts due to the operation of two of these former manufactured gas plant sites. To the extent not covered by insurance, Montana-Dakota may seek recovery in its natural gas rates charged to customers for certain investigation and remediation costs incurred for these sites. Cascade has ties to nine historic manufactured gas plants as a successor corporation or through direct ownership of the plant. Cascade is involved in the investigation and remediation of one of these manufactured gas plants in Washington. To the extent not covered by insurance, Cascade will seek recovery of investigation and remediation costs through its natural gas rates charged to customers.
See Item 8 - Note 21 for further discussion of certain manufactured gas plant sites.
Pipeline
General WBI Energy owns and operates both regulated and non-regulated businesses. The regulated business of this segment, WBI Energy Transmission, owns and operates approximately 3,700 miles of natural gas transmission and storage lines in Minnesota, Montana, North Dakota, South Dakota and Wyoming. WBI Energy Transmission's underground storage fields provide storage services to local distribution companies, industrial customers, natural gas marketers and others, and serve to enhance system reliability. Its system is strategically located near four natural gas producing basins, making natural gas supplies available to its transportation and storage customers. The system has 13 interconnecting points with other pipeline facilities allowing for the receipt and/or delivery of natural gas to and from other regions of the country and from Canada. Under the Natural Gas Act, as amended, WBI Energy Transmission is subject to the jurisdiction of the FERC regarding certificate, rate, service and accounting matters, and at December 31, 2020, its net plant investment was $548.3 million.
The non-regulated business of this segment provides a variety of energy-related services, including cathodic protection and energy efficiency product sales and installation services to large end-users.
In 2020, the Company divested its regulated and non-regulated natural gas gathering assets. With the completion of these sales, the Company has exited the natural gas gathering business.
A majority of the pipeline business is transacted in the Rocky Mountain and northern Great Plains regions of the United States.
MDU Resources Group, Inc. Form 10-K 15



Part I
System Supply, System Demand and Competition Natural gas supplies emanate from traditional and nontraditional production activities in the region from both on-system and off-system supply sources. Incremental supply from nontraditional sources, such as the Bakken area in Montana and North Dakota, have helped offset declines in traditional regional supply sources and supports WBI Energy Transmission's transportation and storage services. In addition, off-system supply sources are available through the Company's interconnections with other pipeline systems. WBI Energy Transmission continues to look for opportunities to increase transportation and storage services through system expansion and/or other pipeline interconnections or enhancements that could provide future benefits.
WBI Energy Transmission's underground natural gas storage facilities have a certificated storage capacity of approximately 350 Bcf, including 193 Bcf of working gas capacity, 83 Bcf of cushion gas and 74 Bcf of native gas. These storage facilities enable customers to purchase natural gas throughout the year and meet winter peak requirements.
WBI Energy Transmission competes with several pipelines for its customers' transportation and storage business and at times may discount rates in an effort to retain market share; however, the strategic location of its system near four natural gas producing basins and the availability of underground storage services, along with interconnections with other pipelines, enhances its competitive position.
Although certain of WBI Energy Transmission's firm customers, including its largest firm customer Montana-Dakota, serve relatively secure residential, commercial and industrial end-users, they generally all have some price-sensitive end-users that could switch to alternate fuels.
WBI Energy Transmission transports substantially all of Montana-Dakota's natural gas, primarily utilizing firm transportation agreements, which for 2020 represented 23 percent of WBI Energy Transmission's subscribed firm transportation contract demand. The majority of the firm transportation agreements with Montana-Dakota expire in June 2022. In addition, Montana-Dakota has contracts, expiring in July 2035, with WBI Energy Transmission to provide firm storage services to facilitate meeting Montana-Dakota's winter peak requirements.
The non-regulated business of this segment competes for existing customers in the areas in which it operates. Its focus on customer service and the variety of services it offers serve to enhance its competitive position.
Environmental Matters The pipeline operations are subject to federal, state and local environmental, facility-siting, zoning and planning laws and regulations.
Administration of certain provisions of federal environmental laws is delegated to the states where WBI Energy and its subsidiaries operate. Administering agencies may issue permits with varying terms and operational compliance conditions. Permits are renewed and modified, as necessary, based on defined permit expiration dates, operational demand, facility upgrades or modifications, and/or regulatory changes. The Company believes it is in substantial compliance with these regulations.
Detailed environmental assessments and/or environmental impact statements as required by the National Environmental Policy Act are included in the FERC's environmental review process for both the construction and abandonment of WBI Energy Transmission's natural gas transmission pipelines, compressor stations and storage facilities.
The pipeline operations did not incur any material environmental expenditures in 2020 and do not expect to incur any material capital expenditures related to environmental compliance with current laws and regulations through 2023.
Construction Materials and Contracting
General Knife River operates construction materials and contracting businesses headquartered in Alaska, California, Hawaii, Idaho, Iowa, Minnesota, Montana, North Dakota, Oregon, South Dakota, Texas, Washington and Wyoming. Knife River mines, processes and sells construction aggregates (crushed stone, sand and gravel); produces and sells asphalt mix; and supplies ready-mixed concrete. These products are used in most types of construction, performed by Knife River and other companies, including roads, freeways and bridges, as well as homes, schools, shopping centers, office buildings and industrial parks. Knife River focuses on vertical integration of its contracting services with its construction materials to support the aggregate-based product lines including aggregate placement, asphalt and concrete paving, and site development and grading. Although not common to all locations, other products include the sale of cement, liquid asphalt for various commercial and roadway applications, various finished concrete products and other building materials and related contracting services.
During 2020, Knife River acquired the assets of Oldcastle Infrastructure Spokane, a prestressed-concrete business in Spokane, Washington, and McMurry Ready-Mix Co., an aggregates and concrete supplier in Casper, Wyoming. For more information on business combinations, see Item 8 - Note 4.
Competition Knife River's construction materials products and contracting services are marketed under competitive conditions. Price is the principal competitive force to which these products and services are subject, with service, quality, delivery time and proximity to the customer also being significant factors. Knife River focuses on markets located near aggregate sites to reduce transportation costs which allows Knife River to remain competitive with the pricing of aggregate products. The number and size of competitors varies in each of Knife River's principal market areas and product lines.
16 MDU Resources Group, Inc. Form 10-K



Part I
The demand for construction materials products and contracting services is significantly influenced by the cyclical nature of the construction industry. In addition, activity in certain locations may be seasonal in nature due to the effects of weather. The key economic factors affecting product demand are changes in the level of local, state and federal governmental spending on roads and infrastructure projects, general economic conditions within the market area that influence the commercial and residential sectors, and prevailing interest rates.
Knife River's customers are a diverse group which includes federal, state and municipal government agencies, commercial and residential developers, and private parties. The mix of sales by customer class varies each year depending on available work. Knife River is not dependent on any single customer or group of customers for sales of its products and services, the loss of which would have a material adverse effect on its construction materials businesses.
Reserve Information Aggregate reserve estimates are calculated based on the best available data. This data is collected from drill holes and other subsurface investigations, as well as investigations of surface features such as mine high walls and other exposures of the aggregate reserves. Mine plans, production history and geologic data are also utilized to estimate reserve quantities.
Estimates are based on analyses of the data described above by experienced internal mining engineers, operating personnel and geologists. Property setbacks and other regulatory restrictions and limitations are identified to determine the total area available for mining. Data described previously are used to calculate the thickness of aggregate materials to be recovered.
Topography associated with alluvial sand and gravel deposits is typically flat and volumes of these materials are calculated by applying the thickness of the resource over the areas available for mining. Volumes are then converted to tons by using an appropriate conversion factor. Typically, 1.5 tons per cubic yard in the ground is used for sand and gravel deposits.
Topography associated with hard rock reserves is typically much more diverse. Therefore, using available data, a final topography map is created and computer software is utilized to compute the volumes between the existing and final topographies. Volumes are then converted to tons by using an appropriate conversion factor. Typically, 2 tons per cubic yard in the ground is used for hard rock quarries.
Estimated reserves are probable reserves as defined in Securities Act Industry Guide 7. The reserve estimates include only salable tonnage and thus exclude waste materials that are generated in the crushing and processing phases of the operation. Approximately 1.0 billion tons of Knife River's 1.1 billion tons of aggregate reserves are permitted reserves. Remaining reserves are based on estimates of volumes that can be economically extracted and sold to meet current market and product applications. The remaining reserves are on properties that are expected to be permitted for mining under current regulatory requirements. The data used to calculate the remaining reserves may require revisions in the future to account for changes in customer requirements and unknown geological occurrences. The remaining reserve life (years) was calculated by dividing remaining reserves by the three-year average sales, including estimated sales from acquired reserves prior to acquisition, from 2018 through 2020. Actual useful lives of these reserves will be subject to, among other things, fluctuations in customer demand, customer specifications, geological conditions and changes in mining plans.
MDU Resources Group, Inc. Form 10-K 17



Part I
The following table sets forth details applicable to the Company's aggregate reserves under ownership or lease as of December 31, 2020, and sales for the years ended December 31, 2020, 2019 and 2018:
Number of Sites
(Crushed Stone)
Number of Sites
(Sand & Gravel)
Tons Sold (000's) Estimated Reserves
(000's tons)
Lease Expiration Reserve
Life
(years)
Production Area owned leased owned leased 2020 2019 2018
Anchorage, AK
—  —  —  817  868  725  14,363  N/A 18 
Hawaii
—  —  —  1,466  1,680  1,734  46,513  2023-2064 29 
Northern CA
—  —  2,076  1,901  1,798  38,510  2028-2046 20 
Southern CA
—  —  —  341  292  356  90,570  2035 Over 100
Portland, OR
4,085  4,868  5,402  166,311  2025-2055 35 
Eugene, OR
—  1,230  1,205  743  154,039  2021-2049 Over 100
Central OR/WA/ID
—  3,119  2,700  2,362  82,061  2028-2077 30 
Southwest OR
11  2,194  1,932  2,395  111,749  2021-2053 51 
Central MT
—  —  1,074  822  1,081  13,344  2023-2027 13 
Northwest MT
—  —  —  2,007  2,084  1,965  57,794  N/A 29 
Wyoming
—  840  837  626  104,894  2021-2085 62  *
Central MN
41  3,233  3,477  2,890  64,902  2021-2028 20 
Northern MN
—  11  483  330  369  20,046  2021-2024 51 
ND/SD
—  22  4,528  3,747  1,506  63,069  2021-2031 15  *
Eastern TX —  984  1,378  1,094  76,722  2022-2029 67 
Sales from other sources
        2,472  4,193  4,749 
30,949  32,314  29,795  1,104,887 
*    Includes estimate of three-year average sales for acquired reserves.
The 1.1 billion tons of estimated aggregate reserves at December 31, 2020, are comprised of 581 million tons on properties that are owned and 524 million tons that are leased. Approximately 40 percent of the tons under lease have lease expiration dates of 20 years or more. The weighted average years remaining on all leases containing estimated probable aggregate reserves is approximately 20 years, including options for renewal that are at Knife River's discretion. Based on a three-year average of sales from 2018 through 2020 of leased reserves, the average time necessary to produce remaining aggregate reserves from such leases is approximately 45 years. Some sites have leases that expire prior to the exhaustion of the estimated reserves. The estimated reserve life assumes, based on Knife River's experience, that leases will be renewed to allow sufficient time to fully recover these reserves.
The changes in Knife River's aggregate reserves for the years ended December 31 were as follows:
  2020 2019 2018
  (000's of tons)
Aggregate reserves:
Beginning of year 1,054,186  1,014,431  965,036 
Acquisitions (a) 114,666  71,157  81,004 
Sales volumes (b) (28,477) (28,121) (25,046)
Other (c) (35,488) (3,281) (6,563)
End of year 1,104,887  1,054,186  1,014,431 
(a)    Includes reserves from recent business combinations.
(b)    Excludes sales from other sources.
(c)    Includes property sales, revisions of previous estimates and expiring leases.
Environmental Matters Knife River's construction materials and contracting operations are subject to regulation customary for such operations, including federal, state and local environmental compliance and reclamation regulations. Except as to the issues described later, Knife River believes it is in substantial compliance with these regulations. Individual permits applicable to Knife River's various operations are managed and tracked as they relate to the statuses of the application, modification, renewal, compliance and reporting procedures.
Knife River's asphalt and ready-mixed concrete manufacturing plants and aggregate processing plants are subject to the Clean Air Act and the Clean Water Act requirements for controlling air emissions and water discharges. Some mining and construction activities are also subject to these laws. In most of the states where Knife River operates, these regulatory programs are delegated to state and local regulatory authorities. Knife River's facilities are also subject to the RCRA as it applies to the management of hazardous wastes and underground storage tank systems. These programs are generally delegated to the state and local authorities in the states where Knife River operates. Knife River's facilities must comply with requirements for managing wastes and underground storage tank systems.
18 MDU Resources Group, Inc. Form 10-K



Part I
Certain activities of Knife River are directly regulated by federal agencies. For example, certain in-water mining operations are subject to provisions of the Clean Water Act that are administered by the Army Corps. Knife River has several such operations, including gravel bar skimming and dredging operations, and Knife River has the associated required permits. The expiration dates of these permits vary, with five years generally being the longest term.
Knife River's operations are also occasionally subject to the ESA. For example, land use regulations often require environmental studies, including wildlife studies, before a permit may be granted for a new or expanded mining facility or an asphalt or concrete plant. If endangered species or their habitats are identified, ESA requirements for protection, mitigation or avoidance apply. Endangered species protection requirements are usually included as part of land use permit conditions. Typical conditions include avoidance, setbacks, restrictions on operations during certain times of the breeding or rearing season, and construction or purchase of mitigation habitat. Knife River's operations are also subject to state and federal cultural resources protection laws when new areas are disturbed for mining operations or processing plants. Land use permit applications generally require that areas proposed for mining or other surface disturbances be surveyed for cultural resources. If any are identified, they must be protected or managed in accordance with regulatory agency requirements.
The most comprehensive environmental permit requirements are usually associated with new mining operations, although requirements vary widely from state to state and even within states. In some areas, land use regulations and associated permitting requirements are minimal. However, some states and local jurisdictions have very demanding requirements for permitting new mines. Environmental impact reports are sometimes required before a mining permit application can be considered for approval. These reports can take up to several years to complete. The report can include projected impacts of the proposed project on air and water quality, wildlife, noise levels, traffic, scenic vistas and other environmental factors. The reports generally include suggested actions to mitigate the projected adverse impacts.
Provisions for public hearings and public comments are usually included in land use permit application review procedures in the counties where Knife River operates. After considering environmental, mine plan and reclamation information provided by the permittee, as well as comments from the public and other regulatory agencies, the local authority approves or denies the permit application. Denial is rare, but land use permits often include conditions that must be addressed by the permittee. Conditions may include property line setbacks, reclamation requirements, environmental monitoring and reporting, operating hour restrictions, financial guarantees for reclamation, and other requirements intended to protect the environment or address concerns submitted by the public or other regulatory agencies.
Knife River has been successful in obtaining mining and other land use permits so sufficient permitted reserves are available to support its operations. For mining operations, this often requires considerable advanced planning to ensure sufficient time is available to complete the permitting process before the newly permitted aggregate reserve is needed to support Knife River's operations.
Knife River's Gascoyne surface coal mine last produced coal in 1995 but continues to be subject to reclamation requirements of the Surface Mining Control and Reclamation Act, as well as the North Dakota Surface Mining Act. Portions of the Gascoyne Mine remain under reclamation bond until the 10-year revegetation liability period has expired. A portion of the original permit has been released from bond and additional areas are currently in the process of having the bond released. Knife River intends to request bond release as soon as it is deemed possible.
Knife River did not incur any material environmental expenditures in 2020 and, except as to what may be ultimately determined with regard to the issues described in the following paragraph, Knife River does not expect to incur any material capital expenditures related to environmental compliance with current laws and regulations through 2023.
In December 2000, Knife River - Northwest was named by the EPA as a PRP in connection with the cleanup of a commercial property site, acquired by Knife River - Northwest in 1999, and part of the Portland, Oregon, Harbor Superfund Site. For more information, see Item 8 - Note 21.
Mine Safety The Dodd-Frank Act requires disclosure of certain mine safety information. For more information, see Item 4 - Mine Safety Disclosures.
Construction Services
General MDU Construction Services provides inside and outside specialty contracting services in 44 states plus Washington D.C. Its inside services include design, construction and maintenance of electrical and communication wiring and infrastructure, fire suppression systems, and mechanical piping and services. Its outside services include design, construction and maintenance of overhead and underground electrical distribution and transmission lines, substations, external lighting, traffic signalization, and gas pipelines, as well as utility excavation and the manufacture and distribution of transmission line construction equipment. This segment also constructs and maintains renewable energy projects. These specialty contracting services are provided to utilities and large manufacturing, commercial, industrial, institutional and governmental customers.
During 2020, MDU Construction Services acquired PerLectric, Inc., an electrical construction company in Fairfax, Virginia. For more information on business combinations, see Item 8 - Note 4.
Construction and maintenance crews are active year round. However, activity in certain locations may be seasonal in nature due to the effects of weather. MDU Construction Services works with the National Electrical Contractors Association, the IBEW and other trade associations on hiring and recruiting a qualified workforce.
MDU Resources Group, Inc. Form 10-K 19



Part I
MDU Construction Services operates a fleet of owned and leased trucks and trailers, support vehicles and specialty construction equipment, such as backhoes, excavators, trenchers, generators, boring machines and cranes. In addition, as of December 31, 2020, MDU Construction Services owned or leased facilities in 17 states. This space is used for offices, equipment yards, manufacturing, warehousing, storage and vehicle shops.
Competition MDU Construction Services operates in a highly competitive business environment. Most of MDU Construction Services' work is obtained on the basis of competitive bids or by negotiation of either cost-plus or fixed-price contracts. Its workforce and equipment are highly mobile, providing greater flexibility in the size and location of MDU Construction Services' market area. Competition is based primarily on price and reputation for quality, safety and reliability. The size and location of the services provided, as well as the state of the economy, are factors in the number of competitors that MDU Construction Services will encounter on any particular project. MDU Construction Services believes the diversification of the services it provides, the markets it serves in the United States and the quality and management of its workforce enable it to effectively operate in this competitive environment.
Utilities and independent contractors represent the largest customer base for this segment. Accordingly, utility and subcontract work accounts for a significant portion of the work performed by MDU Construction Services and the amount of construction contracts is dependent on the level and timing of maintenance and construction programs undertaken by customers. MDU Construction Services relies on repeat customers and strives to maintain successful long-term relationships with its customers. The mix of sales by customer class varies each year depending on available work. MDU Construction Services is not dependent on any single customer or group of customers for sales of its products and services, the loss of which would have a material adverse effect on its business.
Environmental Matters MDU Construction Services' operations are subject to regulation customary for the industry, including federal, state and local environmental compliance. MDU Construction Services believes it is in substantial compliance with these regulations.
The nature of MDU Construction Services' operations is such that few, if any, environmental permits are required. Operational convenience supports the use of petroleum storage tanks in several locations, which are permitted under state programs authorized by the EPA. MDU Construction Services has no ongoing remediation related to releases from petroleum storage tanks. MDU Construction Services' operations are conditionally exempt small-quantity waste generators, subject to minimal regulation under the RCRA. Federal permits for specific construction and maintenance jobs that may require these permits are typically obtained by the hiring entity, and not by MDU Construction Services.
MDU Construction Services did not incur any material environmental expenditures in 2020 and does not expect to incur any material capital expenditures related to environmental compliance with current laws and regulations through 2023.
Item 1A. Risk Factors
The Company's business and financial results are subject to a number of risks and uncertainties, including those set forth below and in other documents filed with the SEC. The factors and other matters discussed herein are important factors that could cause actual results or outcomes for the Company to differ materially from those discussed in the forward-looking statements included elsewhere in this document. If any of the risks described below actually occur, the Company's business, prospects, financial condition or financial results could be materially harmed. The following are the most material risk factors applicable to the Company and are not necessarily listed in order of importance or probability of occurrence.
Economic Risks
The Company is subject to government regulations that may have a negative impact on its business and its results of operations and cash flows. Statutory and regulatory requirements also may limit another party's ability to acquire the Company or impose conditions on an acquisition of or by the Company.
The Company's electric and natural gas transmission and distribution businesses are subject to comprehensive regulation by federal, state and local regulatory agencies with respect to, among other things, allowed rates of return and recovery of investments and costs, financing, rate structures, customer service, health care coverage and costs, taxes, franchises; recovery of purchased power and purchased natural gas costs; and construction and siting of generation and transmission facilities. These governmental regulations significantly influence the Company's operating environment and may affect its ability to recover costs from its customers. The Company is unable to predict the impact on operating results from future regulatory activities of any of these agencies. Changes in regulations or the imposition of additional regulations could have an adverse impact on the Company's results of operations and cash flows.
There can be no assurance that applicable regulatory commissions will determine that the Company's electric and natural gas transmission and distribution businesses' costs have been prudent, which could result in the disallowance of costs in setting rates for customers. Also, the regulatory process of approving rates for these businesses may not allow for timely and full recovery of the costs of providing services or a return on the Company's invested capital. Changes in regulatory requirements or operating conditions may require early retirement of certain assets. While regulation typically provides rate recovery for these retirements, there is no assurance regulators will allow full recovery of all remaining costs, which could leave stranded asset costs. Rising fuel costs could increase the risk that the utility businesses will not be able to fully recover those fuel costs from customers.
Approval from federal and state regulatory agencies would be needed for acquisition of the Company, as well as for certain acquisitions by the Company. The approval process could be lengthy and the outcome uncertain, which may deter potential acquirers from approaching the Company or impact the Company's ability to pursue acquisitions.
20 MDU Resources Group, Inc. Form 10-K



Part I
Economic volatility affects the Company's operations, as well as the demand for its products and services.
Unfavorable economic conditions can negatively affect the level of public and private expenditures on projects and the timing of these projects which, in turn, can negatively affect demand for the Company's products and services, primarily at the Company's construction businesses. The level of demand for construction products and services could be adversely impacted by the economic conditions in the industries the Company serves, as well as in the general economy. State and federal budget issues affect the funding available for infrastructure spending.
Economic conditions and population growth affect the electric and natural gas distribution businesses' growth in service territory, customer base and usage demand. Economic volatility in the markets served, along with economic conditions such as increased unemployment which could impact the ability of the Company's customers to make payments, could adversely affect the Company's results of operations, cash flows and asset values. Further, any material decreases in customers' energy demand, for economic or other reasons, could have an adverse impact on the Company's earnings and results of operations.
The Company's operations involve risks that may result from catastrophic events.
The Company's operations, particularly those related to natural gas and electric transmission and distribution, include a variety of inherent hazards and operating risks, such as product leaks; explosions; mechanical failures; vandalism; fires; pandemics; social or civil unrest; protests and riots; natural disasters; acts of terrorism; and acts of war. These hazards and operating risks could result in loss of human life; personal injury; property damage; environmental pollution; impairment of operations; and substantial financial losses. The Company maintains insurance against some, but not all, of these risks and losses. A significant incident could also increase regulatory scrutiny and result in penalties and higher amounts of capital expenditures and operational costs. Losses not fully covered by insurance could have an adverse effect on the Company’s financial position, results of operations and cash flows.
A disruption of the regional electric transmission grid or interstate natural gas infrastructure could negatively impact the Company's business and reputation. Because the Company's electric and natural gas utility and pipeline systems are part of larger interconnecting systems, a disruption could result in a significant decrease in revenues and system repair costs negatively impacting the Company's financial position, results of operations and cash flows.
The Company is subject to capital market and interest rate risks.
The Company's operations, particularly its electric and natural gas transmission and distribution businesses, require significant capital investment. Consequently, the Company relies on financing sources and capital markets as sources of liquidity for capital requirements not satisfied by cash flows from operations. If the Company is not able to access capital at competitive rates, including through its "at-the-market" offering program, the ability to implement business plans, make capital expenditures or pursue acquisitions the Company would otherwise rely on for future growth may be adversely affected. Market disruptions may increase the cost of borrowing or adversely affect the Company's ability to access one or more financial markets. Such disruptions could include:
A significant economic downturn.
The financial distress of unrelated industry leaders in the same line of business.
Deterioration in capital market conditions.
Turmoil in the financial services industry.
Volatility in commodity prices.
Pandemics, including COVID-19.
Terrorist attacks.
Cyberattacks.
The issuance of a substantial amount of the Company's common stock, whether issued in connection with an acquisition or otherwise, or the perception that such an issuance could occur, could have a dilutive effect on shareholders and/or may adversely affect the market price of the Company's common stock. Higher interest rates on borrowings could also have an adverse effect on the Company's operating results.
Financial market changes could impact the Company’s pension and postretirement benefit plans and obligations.
The Company has pension and postretirement defined benefit plans for some of its employees and former employees. Assumptions regarding future costs, returns on investments, interest rates and other actuarial assumptions have a significant impact on the funding requirements and expense recorded relating to these plans. Adverse changes in economic indicators, such as consumer spending, inflation data, interest rate changes, political developments and threats of terrorism, among other things, can create volatility in the financial markets. These changes could impact the assumptions and negatively affect the value of assets held in the Company's pension and other postretirement benefit plans and may increase the amount and accelerate the timing of required funding contributions for those plans.
Significant changes in energy prices could negatively affect the Company's businesses.
Fluctuations in oil and natural gas production, supplies and prices; fluctuations in commodity price basis differentials; political and economic conditions in oil-producing countries; actions of the Organization of Petroleum Exporting Countries; demand for oil due to the economic slowdowns; and other external factors impact the development of oil and natural gas supplies and the expansion and operation of natural gas pipeline systems. The Company has benefited from associated natural gas production in the Bakken, which has provided opportunities for organic growth projects.
MDU Resources Group, Inc. Form 10-K 21



Part I
Depressed oil and natural gas prices, however, place pressure on the ability of oil exploration and production companies to meet credit requirements and will continue to be a challenge if prices remain depressed long-term. Prolonged depressed prices for oil and natural gas could negatively affect the growth, results of operations, cash flows and asset values of the Company's electric, natural gas and pipeline businesses.
If oil and natural gas prices increase significantly, customer demand could decline for utility, pipeline and construction materials, which could impact the Company's results of operations and cash flows. While the Company has fuel clause recovery mechanisms for its utility operations in all of the states where it operates, higher utility fuel costs could also significantly impact results of operations if such costs are not recovered. Delays in the collection of utility fuel cost recoveries, as compared to expenditures for fuel purchases, could also negatively impact the Company's cash flows. High oil prices also affect the cost and demand for asphalt products and related contracting services.
COVID-19 may have a negative impact on the Company's business operations, revenues, results of operations, liquidity and cash flows.
To the extent the COVID-19 pandemic adversely affects the Company's business, operations, revenues, liquidity or cash flows, it may also have the effect of heightening many of the other risks described in this section. The degree to which COVID-19 will impact the Company depends on future developments, including severity and duration of the outbreak, actions taken by governmental authorities, timing and effectiveness of vaccines being administered, and timing of when relatively normal economic and operating conditions resume.

The Company's operations have experienced some disruptions due to its employees or third-party employees being diagnosed with COVID-19 or other illnesses and required quarantine periods for those in close contact to COVID-19. Self-quarantine or actual viral health issues may have a negative impact on the Company's employees and the ability to continue its work activities under a normal course of business. Moreover, the diagnosis of COVID-19 or other illnesses could require the Company or its business partners to suspend projects, quarantine employees or institute more aggressive preventive measures including closure of job sites. Mandated healthcare protocols could lead to a shortage of employees or altered operations. If a significant percentage of the Company's workforce are unable to work because of illness, quarantine or government restrictions in connection with the COVID-19 pandemic, the Company's operations may be negatively impacted, potentially adversely affecting its business, operations, revenues, liquidity and cash flows.
A portion of the Company's workforce has been working remotely and the Company has delayed return to work processes for certain office employees due to the rise in local COVID-19 cases in some operating regions. To date, the Company has not experienced any significant delays or information technology disruptions. An increased amount of social engineering and attacks by bad actors taking advantage of the pandemic could affect the Company's ability to maintain secure operations, communications and productivity in the future.
The regulated businesses have been deemed essential service providers and have seen some impacts on their businesses; however, the Company could be materially affected if its businesses were no longer deemed essential service providers. Future actions of its regulatory commissions on accounting for the impacts of the COVID-19 pandemic may also affect the Company's future operating results and cash flows. The Company has experienced some impacts to its commercial and industrial electric and natural gas loads associated with reduced demand from those customers due to the COVID-19 pandemic.
The construction businesses have generally been deemed essential service providers and have experienced some inefficiencies and interruptions on its businesses from the pandemic; however, the Company could be materially impacted if its businesses were no longer deemed essential service providers. These businesses could be further impacted in the future by site closures, government shut-down measures, additional inefficiencies due to compliance with safety and social distancing measures, public and private sector budget changes and constraints, and the impact of overall macro and local economic conditions on future construction projects.
Other factors associated with the COVID-19 pandemic that could impact the Company's businesses and future operating results, revenues and liquidity include impacts related to the health, safety, and availability of its employees and contractors; continued flexible payment plans; counterparty credit; costs and availability of supplies; capital construction and infrastructure operation and maintenance programs; financing plans; pension valuations; travel restrictions; and legal and regulatory matters, including the potential for delayed regulatory filings and recovery of invested capital.
Reductions in the Company's credit ratings could increase financing costs.
There is no assurance the Company's current credit ratings, or those of its subsidiaries, will remain in effect or that a rating will not be lowered or withdrawn by a rating agency. Events affecting the Company's financial results may impact its cash flows and credit metrics, potentially resulting in a change in the Company's credit ratings. The Company's credit ratings may also change as a result of the differing methodologies or changes in the methodologies used by the rating agencies.
Increasing costs associated with health care plans may adversely affect the Company's results of operations.
The Company's self-insured costs of health care benefits for eligible employees continues to increase. Increasing quantities of large individual health care claims and an overall increase in total health care claims could have an adverse impact on operating results, financial position and liquidity. Legislation related to health care could also change the Company's benefit program and costs.
22 MDU Resources Group, Inc. Form 10-K



Part I
The Company is exposed to risk of loss resulting from the nonpayment and/or nonperformance by the Company's customers and counterparties.
If the Company's customers or counterparties experience financial difficulties, the Company could experience difficulty in collecting receivables. Nonpayment and/or nonperformance by the Company's customers and counterparties, particularly customers and counterparties of the Company’s construction materials and contracting and construction services businesses for large construction projects, could have a negative impact on the Company's results of operations and cash flows. The Company could also have indirect credit risk from participating in energy markets such as MISO in which credit losses are socialized to all participants.
Changes in tax law may negatively affect the Company's business.
Changes to federal, state and local tax laws have the ability to benefit or adversely affect the Company's earnings and customer costs. Significant changes to corporate tax rates could result in the impairment of deferred tax assets that are established based on existing law at the time of deferral. Changes to the value of various tax credits could change the economics of resources and the resource selection for the electric generation business. Regulation incorporates changes in tax law into the rate-setting process for the regulated energy delivery businesses which could create timing delays before the impact of changes are realized.
The Company's operations could be negatively impacted by import tariffs and/or other government mandates.
The Company operates in or provides services to capital intensive industries in which federal trade policies could significantly impact the availability and cost of materials. Imposed and proposed tariffs could significantly increase the prices and delivery lead times on raw materials and finished products that are critical to the Company and its customers, such as aluminum and steel. Prolonged lead times on the delivery of raw materials and further tariff increases on raw materials and finished products could adversely affect the Company's business, financial condition and results of operations.
Operational Risks
Significant portions of the Company’s natural gas pipelines and power generation and transmission facilities are aging. The aging infrastructure may require significant additional maintenance or replacement that could adversely affect the Company’s results of operations.
The Company’s energy delivery infrastructure is aging, which increases certain risks, including breakdown or failure of equipment, pipeline leaks and fires developing from power lines. Aging infrastructure is more prone to failure which increases maintenance costs, unplanned outages and the need to replace facilities. Even if properly maintained, reliability may ultimately deteriorate and negatively affect the Company’s ability to serve its customers, which could result in increased costs associated with regulatory oversight. The costs associated with maintaining the aging infrastructure and capital expenditures for new or replacement infrastructure could cause rate volatility and/or regulatory lag in some jurisdictions. If, at the end of its life, the investment costs of a facility have not been fully recovered, the Company may be adversely affected if commissions do not allow such costs to be recovered in rates. Such impacts of an aging infrastructure, could adversely affect the Company’s results of operations and cash flows.
Additionally, hazards from aging infrastructure could result in serious injury, loss of human life, significant damage to property, environmental impacts and impairment of operations, which in turn could lead to substantial financial losses. The location of facilities near populated areas, including residential areas, business centers, industrial sites and other public gathering places, could increase the damages resulting from these risks. A major incident involving another natural gas system could lead to additional capital expenditures, increased regulation, and fines and penalties on natural gas utilities. The occurrence of any of these events could adversely affect the Company’s results of operations, financial position and cash flows.
The Company's utility and pipeline operations are subject to planning risks.
Most electric and natural gas utility investments, including natural gas transmission pipeline investments, are made with the intent of being used for decades. In particular, electric transmission and generation resources are planned well in advance of when they are placed into service based upon resource plans using assumptions over the planning horizon including sales growth, commodity prices, equipment and construction costs, regulatory treatment, available technology and public policy. Public policy changes and technology advancements related to areas such as energy efficient appliances and buildings, renewable and distributive electric generation and storage, carbon dioxide emissions, electric vehicle penetration, restrictions on or disallowance of new or existing services, and natural gas availability and cost may significantly impact the planning assumptions. Changes in critical planning assumptions may result in excess generation, transmission and distribution resources creating increased per customer costs and downward pressure on load growth. These changes could also result in a stranded investment if the Company is unable to fully recover the costs of its investments.
The regulatory approval, permitting, construction, startup and/or operation of pipelines, power generation and transmission facilities, and aggregate reserves may involve unanticipated events, delays and unrecoverable costs.
The construction, startup and operation of natural gas pipelines and electric power generation and transmission facilities involve many risks, which may include delays; breakdown or failure of equipment; inability to obtain required governmental permits and approvals; inability to obtain or renew easements; public opposition; inability to complete financing; inability to negotiate acceptable equipment acquisition, construction, fuel supply, off-take, transmission, transportation or other material agreements; changes in markets and market prices for power; cost increases and overruns; the risk of performance below expected levels of output or efficiency; and the inability to obtain full cost recovery in regulated rates. Additionally, in a number of states in which the Company operates, it can be difficult to permit new aggregate sites or expand existing aggregate sites due to community resistance. Such unanticipated events could negatively impact the Company's business, its results of operations and cash flows.
MDU Resources Group, Inc. Form 10-K 23



Part I
Operating or other costs required to comply with current or potential pipeline safety regulations and potential new regulations under various agencies could be significant. The regulations require verification of pipeline infrastructure records by pipeline owners and operators to confirm the maximum allowable operating pressure of certain lines. Increased emphasis on pipeline safety and increased regulatory scrutiny may result in penalties and higher costs of operations. If these costs are not fully recoverable from customers, they could have an adverse effect on the Company’s results of operations and cash flows.
The backlogs at the Company's construction materials and contracting and construction services businesses may not accurately represent future revenue.
Backlog consists of the uncompleted portion of services to be performed under job-specific contracts. Contracts are subject to delay, default or cancellation, and contracts in the Company's backlog are subject to changes in the scope of services to be provided, as well as adjustments to the costs relating to the applicable contracts. Backlog may also be affected by project delays or cancellations resulting from weather conditions, external market factors and economic factors beyond the Company's control. Accordingly, there is no assurance that backlog will be realized. The timing of contract awards, duration of large new contracts and the mix of services can significantly affect backlog. Backlog at any given point in time may not accurately represent the revenue or net income that is realized in any period. Also, the backlog as of the end of the year may not be indicative of the revenue and net income expected to be earned in the following year and should not be relied upon as a stand-alone indicator of future revenues or net income.
Environmental and Regulatory Risks
The Company's operations could be adversely impacted by climate change.
Severe weather events, such as tornadoes, hurricanes, rain, ice and snowstorms and high and low temperature extremes, occur in regions in which the Company operates and maintains infrastructure. Climate change could change the frequency and severity of these weather events, which may create physical and financial risks to the Company. Such risks could have an adverse effect on the Company's financial condition, results of operations and cash flows.
Severe weather events may damage or disrupt the Company's electric and natural gas transmission and distribution facilities, which could result in disruption of service and ability to meet customer demand, increased maintenance or capital costs to repair facilities and restore customer service. The cost of providing service could increase to the extent the frequency of severe weather events increases because of climate change or otherwise. The Company may not recover all costs related to mitigating these physical risks.
Increases in severe weather conditions or extreme temperatures may cause infrastructure construction projects to be delayed or canceled and limit resources available for such projects resulting in decreased revenue or increased project costs at the construction materials and contracting and construction services businesses. In addition, drought conditions could restrict the availability of water supplies, inhibiting the ability of the construction businesses to conduct operations.
Utility customers’ energy needs vary with weather conditions, primarily temperature and humidity. For residential customers, heating and cooling represent the largest energy use. To the extent weather conditions are affected by climate change, customers’ energy use could increase or decrease. Increased energy use by its utility customers due to weather may require the Company to invest in additional generating assets, transmission and other infrastructure to serve increased load. Decreased energy use due to weather may result in decreased revenues. Extreme weather conditions, such as uncommonly long periods of high or low ambient temperature, in general require more system backup, adding to costs, and can contribute to increased system stress, including service interruptions. Weather conditions outside of the Company's service territory could also have an impact on revenues. The Company buys and sells electricity that might be generated outside its service territory, depending upon system needs and market opportunities. Extreme temperatures may create high energy demand and raise electricity prices, which could increase the cost of energy provided to customers.
Climate change may impact a region’s economic health, which could impact revenues at all of the Company's businesses. The Company's financial performance is tied to the health of the regional economies served. The Company provides natural gas and electric utility service, as well as construction materials and services, for some states and communities that are economically affected by the agriculture industry. Increases in severe weather events or significant changes in temperature and precipitation patterns could adversely affect the agriculture industry and, correspondingly, the economies of the states and communities affected by that industry.
The insurance industry may be adversely affected by severe weather events which may impact the availability of insurance coverage, insurance premiums and insurance policy terms.
The Company may be subject to litigation related to climate change. Costs of such litigation could be significant, and an adverse outcome could require substantial capital expenditures, changes in operations and possible payment of penalties or damages, which could affect the Company's results of operations and cash flows if the costs are not recoverable in rates.
The price of energy also has an impact on the economic health of communities. The cost of additional regulatory requirements to combat climate change, such as regulation of carbon dioxide emissions under the Clean Air Act, requirements to replace fossil-fuels with renewable energy or credits, or other environmental regulation or taxes could impact the availability of goods and the prices charged by suppliers, which would normally be borne by consumers through higher prices for energy and purchased goods, and could adversely impact economic conditions of areas served by the
24 MDU Resources Group, Inc. Form 10-K



Part I
Company. To the extent financial markets view climate change and emissions of GHGs as a financial risk, this could negatively affect the Company's ability to access capital markets or cause less than ideal terms and conditions.
The Company's operations are subject to environmental laws and regulations that may increase costs of operations, impact or limit business plans, or expose the Company to environmental liabilities.
The Company is subject to environmental laws and regulations affecting many aspects of its operations, including air and water quality, wastewater discharge, the generation, transmission and disposal of solid waste and hazardous substances, aggregate permitting and other environmental considerations. These laws and regulations can increase capital, operating and other costs; cause delays as a result of litigation and administrative proceedings; and create compliance, remediation, containment, monitoring and reporting obligations, particularly relating to electric generation, permitting and environmental compliance for construction material facilities, and natural gas transmission and storage operations. Environmental laws and regulations can also require the Company to install pollution control equipment at its facilities, clean up spills and other contamination and correct environmental hazards, including payment of all or part of the cost to remediate sites where the Company's past activities, or the activities of other parties, caused environmental contamination. These laws and regulations generally require the Company to obtain and comply with a variety of environmental licenses, permits, inspections and other approvals and may cause the Company to shut down existing facilities due to difficulties in assuring compliance or where the cost of compliance makes operation of the facilities uneconomical. Although the Company strives to comply with all applicable environmental laws and regulations, public and private entities and private individuals may interpret the Company's legal or regulatory requirements differently and seek injunctive relief or other remedies against the Company. The Company cannot predict the outcome, financial or operational, of any such litigation or administrative proceedings.
Existing environmental laws and regulations may be revised and new laws and regulations seeking to protect the environment may be adopted or become applicable to the Company. These laws and regulations could require the Company to limit the use or output of certain facilities; restrict the use of certain fuels; prohibit or restrict new or existing services; replace certain fuels with renewable fuels; retire and replace certain facilities; install pollution controls; remediate environmental impacts; remove or reduce environmental hazards; or forego or limit the development of resources. Revised or new laws and regulations that increase compliance costs or restrict operations, particularly if costs are not fully recoverable from customers, could adversely affect the Company's results of operations and cash flows.
Initiatives related to global climate change and to reduce GHG emissions could adversely impact the Company's operation, costs of or access to capital and impact or limit business plans.
Concern that GHG emissions contribute to global climate change has led to international, federal, state and local legislative and regulatory proposals to reduce or mitigate the effects of GHG emissions. The Company’s primary GHG emission is carbon dioxide from fossil fuels combustion at Montana-Dakota's electric generating facilities, particularly its coal-fired facilities. Approximately 46 percent of Montana-Dakota's owned generating capacity and approximately 70 percent of the electricity it generated in 2020 was from coal-fired facilities.
Treaties, legislation or regulations to reduce GHG emissions in response to climate change may be adopted that affect the Company's utility operations by requiring additional energy conservation efforts or renewable energy sources, limiting emissions, imposing carbon taxes or other compliance costs; as well as other mandates that could significantly increase capital expenditures and operating costs or reduce demand for the Company's utility services. If the Company’s utility operations do not receive timely and full recovery of GHG emission compliance costs from customers, then such costs could adversely impact the results of operations and cash flows. Significant reductions in demand for the Company's utility services as a result of increased costs or emissions limitations could also adversely impact the results of operations and cash flows.
The Company monitors, analyzes and reports GHG emissions from its other operations as required by applicable laws and regulations. The Company will continue to monitor GHG regulations and their potential impact on operations.
Due to the uncertain availability of technologies to control GHG emissions and the unknown obligations that potential GHG emission legislation or regulations may create, the Company cannot determine the potential financial impact on its operations.
There have also been recent efforts to discourage the investment community from investing in equity and debt securities of companies engaged in fossil fuel related business and pressuring lenders to limit funding to such companies. Additionally, some insurance carriers have indicated an unwillingness to insure assets and operations related to certain fossil fuels. Although the Company has not experienced difficulties in accessing the capital markets or insurance; such efforts, if successfully directed at the Company, could increase the costs of or access to capital and interfere with business operations and ability to make capital expenditures.
Other Risks
The Company's various businesses are seasonal and subject to weather conditions that can adversely affect the Company's operations, revenues and cash flows.
The Company's results of operations can be affected by changes in the weather. Weather conditions influence the demand for electricity and natural gas and affect the price of energy commodities. Utility operations have historically generated lower revenues when weather conditions are cooler than normal in the summer and warmer than normal in the winter particularly in jurisdictions that do not have weather normalization mechanisms in place. Where weather normalization mechanisms are in place, there is no assurance the Company will continue to receive such regulatory protection from adverse weather in future rates.
MDU Resources Group, Inc. Form 10-K 25



Part I
Adverse weather conditions, such as heavy or sustained rainfall or snowfall, storms, wind and colder weather may affect the demand for products and the ability to perform services at the construction businesses and affect ongoing operation and maintenance and construction activities for the electric and natural gas transmission and distribution businesses. In addition, severe weather can be destructive, causing outages and property damage, which could require additional remediation costs. The Company could also be impacted by drought conditions, which may restrict the availability of water supplies and inhibit the ability of the construction businesses to conduct operations. As a result, unusual or adverse weather conditions could negatively affect the Company's results of operations, financial position and cash flows.
Competition exists in all of the Company's businesses.
The Company's businesses are subject to competition. Construction services' competition is based primarily on price and reputation for quality, safety and reliability. Construction materials products are marketed under highly competitive conditions and are subject to competitive forces such as price, service, delivery time and proximity to the customer. The electric utility and natural gas industries also experience competitive pressures as a result of consumer demands, technological advances and other factors. The pipeline business competes with several pipelines for access to natural gas supplies and for transportation and storage business. New acquisition opportunities are subject to competitive bidding environments which impact prices the Company must pay to successfully acquire new properties to grow its business. The Company's failure to effectively compete could negatively affect the Company's results of operations, financial position and cash flows.
The Company's operations may be negatively affected if it is unable to obtain, develop and retain key personnel and skilled labor forces.
The Company must attract, develop and retain executive officers and other professional, technical and skilled labor forces with the skills and experience necessary to successfully manage, operate and grow the Company's businesses. Competition for these employees is high, and in some cases competition for these employees is on a regional or national basis. At times of low unemployment or economic downturns, it can be difficult for the Company to attract and retain qualified and affordable personnel. A shortage in the supply of skilled personnel creates competitive hiring markets, increased labor expenses, decreased productivity and potentially lost business opportunities to support the Company's operating and growth strategies. Additionally, if the Company is unable to hire employees with the requisite skills, the Company may be forced to incur significant training expenses. As a result, the Company's ability to maintain productivity, relationships with customers, competitive costs, and quality services is limited by the ability to employ, retain and train the necessary skilled personnel and could negatively affect the Company's results of operations, financial position and cash flows.
The Company's construction materials and contracting and construction services businesses may be exposed to warranty claims.
The Company, particularly its construction businesses, may provide warranties guaranteeing the work performed against defects in workmanship and material. If warranty claims occur, they may require the Company to re-perform the services or to repair or replace the warranted item, at a cost to the Company and could also result in other damages if the Company is not able to adequately satisfy warranty obligations. In addition, the Company may be required under contractual arrangements with customers to warrant any defects or failures in materials the Company purchased from third parties. While the Company generally requires suppliers to provide warranties that are consistent with those the Company provides to customers, if any of the suppliers default on their warranty obligations to the Company, the Company may nonetheless incur costs to repair or replace the defective materials. Costs incurred as a result of warranty claims could adversely affect the Company's results of operations, financial condition and cash flows.
The Company is a holding company and relies on cash from its subsidiaries to pay dividends.
The Company is a holding company as a result of the Holding Company Reorganization in 2019. The Company's investments in its subsidiaries comprise the Company's primary assets. The Company depends on earnings, cash flows and dividends from its subsidiaries to pay dividends on its common stock. Regulatory, contractual and legal limitations, as well as their capital requirements, affect the ability of the subsidiaries to pay dividends to the Company and thereby could restrict or influence the Company's ability or decision to pay dividends on its common stock, which could adversely affect the Company's stock price.
Costs related to obligations under MEPPs could have a material negative effect on the Company's results of operations and cash flows.
Various operating subsidiaries of the Company participate in approximately 68 MEPPs for employees represented by certain unions. The Company is required to make contributions to these plans in amounts established under numerous collective bargaining agreements between the operating subsidiaries and those unions.
The Company may be obligated to increase its contributions to underfunded plans that are classified as being in endangered, seriously endangered or critical status as defined by the Pension Protection Act of 2006. Plans classified as being in one of these statuses are required to adopt RPs or FIPs to improve their funded status through increased contributions, reduced benefits or a combination of the two. Based on available information, the Company believes that approximately 31 percent of the MEPPs to which it contributes are currently in endangered, seriously endangered or critical status.
The Company may also be required to increase its contributions to MEPPs if the other participating employers in such plans withdraw from the plans and are not able to contribute amounts sufficient to fund the unfunded liabilities associated with their participation in the plans. The amount and timing of any increase in the Company's required contributions to MEPPs may depend upon one or more factors including the outcome of collective bargaining; actions taken by trustees who manage the plans; actions taken by the plans' other participating employers; the industry for which contributions are made; future determinations that additional plans reach endangered, seriously endangered or critical status; newly-enacted government laws or regulations and the actual return on assets held in the plans; among others. The Company could experience increased operating
26 MDU Resources Group, Inc. Form 10-K



Part I
expenses as a result of required contributions to MEPPs, which could have an adverse effect on the Company's results of operations, financial position or cash flows.
In addition, pursuant to ERISA, as amended by MPPAA, the Company could incur a partial or complete withdrawal liability upon withdrawing from a plan, exiting a market in which it does business with a union workforce or upon termination of a plan. The Company could also incur additional withdrawal liability if its withdrawal from a plan is determined by that plan to be part of a mass withdrawal.
Information technology disruptions or cyber-attacks could adversely impact the Company's operations.
The Company uses technology in substantially all aspects of its business operations and requires uninterrupted operation of information technology systems, including disaster recovery and backup systems and network infrastructure. While the Company has policies, procedures and processes in place designed to strengthen and protect these systems, they may be vulnerable to failures or unauthorized access, due to hacking, human error, theft, sabotage, malicious software, acts of terrorism, acts of war, acts of nature or other causes. If these systems fail or become compromised, and they are not recovered in a timely manner, the Company may be unable to fulfill critical business functions. This may include interruption of electric generation, transmission and distribution facilities, natural gas storage and pipeline facilities and facilities for delivery of construction materials or other products and services, any of which could adversely affect the Company's reputation, business, cash flows and results of operations or subject the Company to legal or regulatory liabilities and increased costs. Additionally, because electric generation and transmission systems and natural gas pipelines are part of interconnected systems with other operators’ facilities, a cyber-related disruption in another operator’s system could negatively impact the Company's business.
The Company’s accounting systems and its ability to collect information and invoice customers for products and services could be disrupted. If the Company’s operations are disrupted, it could result in decreased revenues or remediation costs that could adversely affect the Company's results of operations and cash flows.
The Company is subject to cybersecurity and privacy laws and regulations of many government agencies, including FERC and NERC. NERC issues comprehensive regulations and standards surrounding the security of bulk power systems and continually updates these requirements, as well as establishing new requirements with which the utility industry must comply. As these regulations evolve, the Company may experience increased compliance costs and may be at higher risk for violating these standards. Experiencing a cybersecurity incident could cause the Company to be non-compliant with applicable laws and regulations, causing the Company to incur costs related to legal claims or proceedings and regulatory fines or penalties.
The Company, through the ordinary course of business, requires access to sensitive customer, employee and Company data. While the Company has implemented extensive security measures, a breach of its systems could compromise sensitive data and could go unnoticed for some time. Such an event could result in negative publicity and reputational harm, remediation costs, legal claims and fines that could have an adverse effect on the Company's financial results. Third-party service providers that perform critical business functions for the Company or have access to sensitive information within the Company also may be vulnerable to security breaches and information technology risks that could adversely affect the Company.
The Company’s information systems experience on-going and often sophisticated cyber-attacks by a variety of sources with the apparent aim to breach the Company's cyber-defenses. As cyber-attacks continue to increase in frequency and sophistication, the Company may be unable to prevent all such attacks in the future. The Company is continuously reevaluating the need to upgrade and/or replace systems and network infrastructure. These upgrades and/or replacements could adversely impact operations by imposing substantial capital expenditures, creating delays or outages, or experiencing difficulties transitioning to new systems. Systems implementation disruption and any other information technology disruption, if not anticipated and appropriately mitigated, could adversely affect the Company.
General risk factors that could impact the Company's businesses.
The following are additional factors that should be considered for a better understanding of the risks to the Company. These factors may negatively impact the Company's financial results in future periods.
Acquisition, disposal and impairments of assets or facilities.
Changes in present or prospective electric generation.
Population decline and demographic patterns in the Company's areas of service.
The cyclical nature of large construction projects at certain operations.
Labor negotiations or disputes.
Inability of the contract counterparties to meet their contractual obligations.
The inability to effectively integrate the operations and the internal controls of acquired companies.
Item 1B. Unresolved Staff Comments
The Company has no unresolved comments with the SEC.
MDU Resources Group, Inc. Form 10-K 27



Part I
Item 3. Legal Proceedings
SEC regulations require the Company to disclose certain information about proceedings arising under federal, state or local environmental provisions if the Company reasonably believes that such proceedings may result in monetary sanctions above a stated threshold. Pursuant to SEC regulations, the Company has adopted a threshold of $1.0 million for purposes of determining whether disclosure of any such proceedings is required.
For information regarding legal proceedings required by this item, see Item 8 - Note 21, which is incorporated herein by reference.
Item 4. Mine Safety Disclosures
For information regarding mine safety violations or other regulatory matters required by Section 1503(a) of the Dodd-Frank Act and Item 104 of Regulation S-K, see Exhibit 95 to this Form 10-K, which is incorporated herein by reference.
28 MDU Resources Group, Inc. Form 10-K



Part II

Item 5. Market for the Registrant's Common Equity, Related Stockholder Matters and Issuer Purchases of Equity Securities
The Company's common stock is listed on the New York Stock Exchange under the symbol "MDU."
As of December 31, 2020, the Company's common stock was held by approximately 10,400 stockholders of record.
The Company depends on earnings and dividends from its subsidiaries to pay dividends on common stock. The Company has paid uninterrupted dividends to stockholders for 83 consecutive years with an increase in the payout amount for the last 30 consecutive years. The declaration and payment of dividends is at the sole discretion of the board of directors, subject to limitations imposed by the Company's credit agreements, federal and state laws, and applicable regulatory limitations. For more information on factors that may limit the Company's ability to pay dividends, see Item 8 - Note 12.
The following table includes information with respect to the Company's purchase of equity securities:
ISSUER PURCHASES OF EQUITY SECURITIES
Period (a)
Total Number
of Shares
(or Units)
Purchased (1)
(b) 
Average Price Paid per Share
(or Unit)
(c)
Total Number of Shares
(or Units) Purchased
as Part of Publicly
Announced Plans
or Programs (2)
(d)
Maximum Number (or
Approximate Dollar
Value) of Shares (or
Units) that May Yet Be
Purchased Under the
Plans or Programs (2)
October 1 through October 31, 2020 —  —  —  — 
November 1 through November 30, 2020 45,273  $25.40 —  — 
December 1 through December 31, 2020 —  —  —  — 
Total 45,273  —  — 
(1)    Represents shares of common stock purchased on the open market in connection with annual stock grants made to the Company's non-employee directors.
(2)    Not applicable. The Company does not currently have in place any publicly announced plans or programs to purchase equity securities.
MDU Resources Group, Inc. Form 10-K 29



Part II
Item 6. Selected Financial Data
2020 2019 2018 2017 2016 2015
Selected Financial Data
Operating revenues (000's):
Electric
$ 332,029  $ 351,725  $ 335,123  $ 342,805  $ 322,356  $ 280,615 
Natural gas distribution
848,185  865,222  823,247  848,388  766,115  817,419 
Pipeline 143,877  140,444  128,923  122,213  141,602  154,904 
Construction materials and contracting
2,178,002  2,190,717  1,925,854  1,812,529  1,874,270  1,904,282 
Construction services
2,095,723  1,849,266  1,371,453  1,367,602  1,073,272  926,427 
Other
11,903  16,551  11,259  7,874  8,643  9,191 
Intersegment eliminations
(76,969) (77,149) (64,307) (58,060) (57,430) (78,786)
$ 5,532,750  $ 5,336,776  $ 4,531,552  $ 4,443,351  $ 4,128,828  $ 4,014,052 
Operating income (loss) (000's):
       
Electric
$ 63,434  $ 64,039  $ 65,148  $ 79,902  $ 67,929  $ 59,915 
Natural gas distribution
73,082  69,188  72,336  84,239  66,166  54,974 
Pipeline 49,436  42,796  36,128  36,004  42,864  30,218 
Construction materials and contracting
214,498  179,955  141,426  143,230  178,753  148,312 
Construction services
147,644  126,426  86,764  81,292  53,546  43,678 
Other
(3,169) (1,184) (79) (619) (349) (8,414)
Intersegment eliminations
  —  —  —  —  (2,942)
$ 544,925  $ 481,220  $ 401,723  $ 424,048  $ 408,909  $ 325,741 
Earnings (loss) on common stock (000's):        
Electric
$ 55,601  $ 54,763  $ 47,000  $ 49,366  $ 42,222  $ 35,914 
Natural gas distribution
44,049  39,517  37,732  32,225  27,102  23,607 
Pipeline 37,012  29,603  28,459  20,493  23,435  13,250 
Construction materials and contracting
147,325  120,371  92,647  123,398  102,687  89,096 
Construction services
109,721  92,998  64,309  53,306  33,945  23,762 
Other
(3,181) (2,086) (761) (1,422) (3,231) (14,941)
Intersegment eliminations
  —  —  6,849  6,251  5,016 
Earnings on common stock before income (loss) from discontinued operations 390,527  335,166  269,386  284,215  232,411  175,704 
Income (loss) from discontinued operations, net of tax* (322) 287  2,932  (3,783) (300,354) (834,080)
Loss from discontinued operations attributable to noncontrolling interest   —  —  —  (131,691) (35,256)
$ 390,205  $ 335,453  $ 272,318  $ 280,432  $ 63,748  $ (623,120)
Earnings per common share before discontinued operations - diluted $ 1.95  $ 1.69  $ 1.38  $ 1.45  $ 1.19  $ .90 
Discontinued operations attributable to the Company, net of tax
  —  .01  (.02) (.86) (4.10)
$ 1.95  $ 1.69  $ 1.39  $ 1.43  $ .33  $ (3.20)
Common Stock Statistics
       
Weighted average common shares outstanding - diluted (000's) 200,571  198,626  196,150  195,687  195,618  194,986 
Dividends declared per common share
$ .8350  $ .8150  $ .7950  $ .7750  $ .7550  $ .7350 
Book value per common share
$ 15.36  $ 14.21  $ 13.09  $ 12.44  $ 11.78  $ 12.83 
Market price per common share (year end)
$ 26.34  $ 29.71  $ 23.84  $ 26.88  $ 28.77  $ 18.32 
Market price ratios:
     
Dividend payout** 43  % 48  % 58  % 53  % 63  % 82  %
Yield 3  % % % % % %
Market value as a percent of book value 171  % 209  % 182  % 216  % 244  % 143  %
*    Reflects oil and natural gas properties noncash write-downs of $315.3 million (after tax) in 2015 and fair value impairments of assets held for sale of $157.8 million (after tax) and $475.4 million (after tax) in 2016 and 2015, respectively.
**Based on continuing operations.
30 MDU Resources Group, Inc. Form 10-K



Part II
Item 6. Selected Financial Data (continued)
  2020 2019 2018 2017 2016 2015
General
Total assets (000's)
$ 8,053,372  $ 7,683,059  $ 6,988,110  $ 6,334,666  $ 6,284,467  $ 6,565,154 
Total long-term debt (000's)
$ 2,213,130  $ 2,243,107  $ 2,108,695  $ 1,714,853  $ 1,790,159  $ 1,796,163 
Capitalization ratios:
Total equity 58  % 56  % 55  % 59  % 56  % 58  %
Total debt 42  44  45  41  44  42 
100  % 100  % 100  % 100  % 100  % 100  %
Electric        
Retail sales (thousand kWh)
3,204,523  3,314,307  3,354,401  3,306,470  3,258,537  3,316,017 
Electric system summer and firm purchase contract ZRCs (Interconnected system)
553.2  591.3  574.5  553.1  559.7  547.3 
Electric system peak demand obligation, including firm purchase contracts, planning reserve margin requirement (Interconnected system)
531.4  537.2  537.2  530.2  559.7  547.3 
All-time demand peak - kW (Interconnected system)
611,542  611,542  611,542  611,542  611,542  611,542 
Electricity produced (thousand kWh)
2,647,746  2,792,770  2,840,353  2,630,640  2,626,763  1,898,160 
Electricity purchased (thousand kWh)
890,054  891,539  831,039  955,687  904,702  1,658,002 
Average cost of electric fuel and purchased power per kWh
$ .019  $ .023  $ .022  $ .022  $ .021  $ .024 
Natural Gas Distribution      
Retail sales (Mdk)
114,543  123,675  112,566  112,551  99,296  95,559 
Transportation sales (Mdk)
160,010  166,077  149,497  144,477  147,592  154,225 
Pipeline      
Transportation (Mdk)
438,615  429,660  351,498  312,520  285,254  290,494 
Gathering (Mdk)
8,611  13,900  14,882  16,064  20,049  33,441 
Customer natural gas storage balance (Mdk)
25,451  16,223  13,928  22,397  26,403  16,600 
Construction Materials and Contracting      
Sales (000's):
Aggregates (tons) 30,949  32,314  29,795  28,213  27,580  26,959 
Asphalt (tons) 7,202  6,707  6,838  6,237  7,203  6,705 
Ready-mixed concrete (cubic yards) 4,087  4,123  3,518  3,548  3,655  3,592 
Aggregate reserves (000's tons) 1,104,887  1,054,186  1,014,431  965,036  989,084  1,022,513 

MDU Resources Group, Inc. Form 10-K 31



Part II
Item 7. Management's Discussion and Analysis of Financial Condition and Results of Operations
The Company focuses on infrastructure and is Building a Strong America® by providing essential products and services through its regulated energy delivery and construction materials and services businesses. The Company and its employees work hard to keep the economy of the United States moving with the products and services provided, which include powering and connecting homes, factories, offices and stores; and building roads, highways, data infrastructure and airports.
The Company's two-platform business model, regulated energy delivery and construction materials and services, are each comprised of different operating segments. Most of these segments experience seasonality related to the industries in which they operate. The two-platform approach helps balance this seasonality and the risks associated with each type of industry. The Company is authorized to conduct business in 45 states and during peak times has over 15,600 employees. The Company’s organic investments are strong drivers of high-quality earnings growth and continue to be an important part of the Company’s growth story. Management believes the Company is well positioned in the industries and markets in which it operates.
Impact of the COVID-19 pandemic on the Company
In March 2020, the World Health Organization declared the outbreak of COVID-19 a pandemic, and the President of the United States declared the COVID-19 outbreak as a national emergency. Most of the Company's products and services are considered essential to our country and our communities; therefore, operations have generally been permitted to proceed with increased social distancing measures and hygiene practices for its employees. While the Company has experienced some inefficiency impacts, including operation suspensions and interruptions at some locations to carry out preventative measures or in response to instances of positive tests, the impacts have not been material. For more information on specific impacts to each of the Company's business segments, see the following discussions in each business segment's Outlook section.
In March 2020, the President of the United States signed into law the CARES Act in response to the COVID-19 pandemic. The CARES Act provided economic relief and stimulus to support the national economy during the pandemic, including support for individuals and businesses affected by the pandemic and economic downturn. The CARES Act allowed businesses to defer payment of the employer portion of social security taxes incurred through the end of 2020. At December 31, 2020, the Company had deferred approximately $56.7 million in payroll taxes related to this provision. The Company is required to pay 50 percent of the payroll taxes deferred under this provision by the end of 2021 and the remaining balance by the end of 2022.
The Company evaluated its planned capital projects and delayed certain expenditures in 2020 to provide additional financial flexibility and to ensure projects will provide acceptable returns on investment. In addition, the Company established a task force to monitor developments related to the pandemic and implemented procedures to protect employees. Many employees that have the capacity to work from home continue to do so as the Company has delayed return to work processes for certain office employees due to COVID-19 cases in some operating regions. The Company has also enacted additional physical and cybersecurity measures to safeguard systems for remote work locations.
Although there have been logistical and other challenges as a result of COVID-19, there were no material adverse impacts on the Company's results of operations for the year ended December 31, 2020. The Company continues to adjust its business in response to the pandemic while positioning for an economic rebound and potential opportunities to enhance its competitive position. The situation surrounding COVID-19 remains fluid and the potential for a material adverse impact on the Company increases the longer the virus impacts the level of economic activity in the United States. Due to the uncertainty of the economic outlook resulting from the COVID-19 pandemic, the Company continues to monitor the situation closely. For more information on the possible impacts, see Item 1A - Risk Factors.
32 MDU Resources Group, Inc. Form 10-K



Part II
Consolidated Earnings Overview
The following table summarizes the contribution to the consolidated income by each of the Company's business segments.
Years ended December 31, 2020  2019  2018 
  (In millions, except per share amounts)
Electric $ 55.6  $ 54.8  $ 47.0 
Natural gas distribution 44.0  39.5  37.7 
Pipeline 37.0  29.6  28.5 
Construction materials and contracting 147.3  120.4  92.6 
Construction services 109.7  93.0  64.3 
Other (3.1) (2.1) (.7)
Income from continuing operations 390.5  335.2  269.4 
Income (loss) from discontinued operations, net of tax (.3) .3  2.9 
Net income $ 390.2  $ 335.5  $ 272.3 
Earnings per share - basic:
Income from continuing operations $ 1.95  $ 1.69  $ 1.38 
Discontinued operations, net of tax   —  .01 
Earnings per share - basic $ 1.95  $ 1.69  $ 1.39 
Earnings per share - diluted:
Income from continuing operations $ 1.95  $ 1.69  $ 1.38 
Discontinued operations, net of tax   —  .01 
Earnings per share - diluted $ 1.95  $ 1.69  $ 1.39 
2020 compared to 2019 The Company's consolidated earnings increased $54.7 million or 16 percent in 2020 as compared to 2019.
The Company's earnings were positively impacted by increased earnings across all of the Company's businesses in 2020. The construction materials and contracting business experienced an increase in gross margin, primarily resulting from favorable weather conditions and higher realized materials margins on asphalt and asphalt-related products and ready-mixed concrete, as well as most other product lines. The construction services business also experienced an increase in gross margin as a result of higher inside and outside specialty contracting workloads, partially due to the businesses acquired, as well as hospitality projects, high-tech projects and natural disaster recovery work. The pipeline business experienced increased transportation volumes and revenues, largely related to organic growth projects, as well as higher storage-related revenues as a result of stronger demand for storage services. In addition, approved rate recovery positively impacted earnings at the electric and natural gas distribution businesses.
2019 compared to 2018 The Company's consolidated earnings increased $63.2 million or 23 percent in 2019 as compared to 2018.
Positively impacting the Company's earnings was an increase in gross margin at the construction services business, largely resulting from higher inside and outside specialty contracting workloads. Also contributing to the increase in earnings was an increase in gross margin at the construction materials and contracting business as a result of strong economic environments in certain states, as well as contributions from the businesses acquired and an increase in gains recognized on asset sales. The electric business also positively impacted earnings primarily due to approved rate relief in Montana and recovery of the investment in the BSSE project placed into service in the first quarter of 2019. Higher returns on the Company's benefit plan investments also increased earnings across all businesses. At the pipeline business, increased rates and volumes of natural gas being transported through its pipeline were mostly offset by the absence of a $4.2 million income tax benefit recorded in 2018 relating to the reversal of a regulatory liability recorded in 2017 based on a FERC final accounting order and higher depreciation, depletion and amortization expense.
A discussion of key financial data from the Company's business segments follows.
Business Segment Financial and Operating Data
Following are key financial and operating data for each of the Company's business segments. Also included are highlights on key growth strategies, projections and certain assumptions for the Company and its subsidiaries and other matters of the Company's business segments. Many of these highlighted points are "forward-looking statements." For more information, see Part I - Forward-Looking Statements. There is no assurance that the Company's projections, including estimates for growth and changes in earnings, will in fact be achieved. Please refer to assumptions contained in this section, as well as the various important factors listed in Item 1A - Risk Factors. Changes in such assumptions and factors could cause actual future results to differ materially from the Company's growth and earnings projections.
For information pertinent to various commitments and contingencies, see Item 8 - Notes to Consolidated Financial Statements. For a summary of the Company's business segments, see Item 8 - Note 17.
MDU Resources Group, Inc. Form 10-K 33



Part II
Electric and Natural Gas Distribution
Strategy and challenges The electric and natural gas distribution segments provide electric and natural gas distribution services to customers, as discussed in Items 1 and 2 - Business Properties. Both segments strive to be top performing utility companies measured by integrity, employee safety and satisfaction, customer service and shareholder return, while providing safe, environmentally friendly, reliable and competitively priced energy and related services to customers. The Company is focused on cultivating organic growth while managing operating costs and monitoring opportunities for these segments to retain, grow and expand their customer base through extensions of existing operations, including building and upgrading electric generation, transmission and distribution, and natural gas systems, and through selected acquisitions of companies and properties with similar operating and growth objectives at prices that will provide stable cash flows and an opportunity to earn a competitive return on investment. The continued efforts to create operational improvements and efficiencies across both segments promotes the Company's business integration strategy. The primary factors that impact the results of these segments are the ability to earn authorized rates of return, the cost of natural gas, cost of electric fuel and purchased power, weather, competitive factors in the energy industry, population growth and economic conditions in the segments' service areas.
The electric and natural gas distribution segments are subject to extensive regulation in the jurisdictions where they conduct operations with respect to costs, timely recovery of investments and permitted returns on investment, as well as certain operational, environmental and system integrity regulations. Legislative and regulatory initiatives to increase renewable energy resources and reduce GHG emissions could impact the price and demand for electricity and natural gas, as well as increase costs to produce electricity and natural gas. The segments continue to invest in facility upgrades to be in compliance with the existing and future regulations. To assist in the reduction of regulatory lag in obtaining revenue increases to align with increased investments, tracking mechanisms have been implemented in certain jurisdictions, as further discussed in Items 1 and 2 - Business Properties and Item 8 - Note 20.
In September 2019, the Pipeline and Hazardous Materials Safety Administration issued a rule for additional regulations to strengthen the safety of natural gas transmission and storage facilities and hazardous liquid pipelines. The natural gas segment has implemented procedure changes for the initial requirements and continues to evaluate procedure changes necessary for the additional requirements effective July 1, 2021.
State implementation of pollution control plans to improve visibility at Class I areas, such as national parks, under the EPA's Regional Haze Rule could require the owners of Coyote Station to incur significant new costs. If the owners decide to incur such costs, the costs could, dependent on determination by state regulatory commissions on approval to recover such costs from customers, negatively impact the Company's results of operations, financial position and cash flows. The NDDEQ's state implementation plan is due to be submitted to the EPA by July 2021. The Company expects the NDDEQ to draft a state implementation plan and share its controls selection with federal land managers of the National Park Service and the United States Fish and Wildlife Service in early 2021. Additionally, the Company is one of four owners of Coyote Station and cannot make a unilateral decision on the plant's future. The Company could be negatively impacted by the decisions of the other owners.
The electric and natural gas distribution segments are facing increased lead times on delivery of certain raw materials used in electric transmission and natural gas pipeline projects. Long lead times are attributable to increased demand for steel products from pipeline companies as they respond to the United States Department of Transportation Pipeline System Safety and Integrity Plan, as well as delays in the manufacturing of electrical equipment as a result of the COVID-19 pandemic, including delays in trucking times and issuance of permits for large and heavy loads. The Company continues to monitor the material lead times and is working with manufacturers to proactively order such materials to help mitigate the risk of delays due to extended lead times.
The ability to grow through acquisitions is subject to significant competition and acquisition premiums. In addition, the ability of the segments to grow their service territory and customer base is affected by regulatory constraints, the economic environment of the markets served and competition from other energy providers and fuels. The construction of any new electric generating facilities, transmission lines and other service facilities is subject to increasing costs and lead times, extensive permitting procedures, and federal and state legislative and regulatory initiatives, which will likely necessitate increases in electric energy prices.
Revenues are impacted by both customer growth and usage, the latter of which is primarily impacted by weather, as well as impacts associated with commercial and industrial slow-downs, including economic recessions, and energy efficiencies. Very cold winters increase demand for natural gas and to a lesser extent, electricity, while warmer than normal summers increase demand for electricity, especially among residential and commercial customers. Average consumption among both electric and natural gas customers has tended to decline as more efficient appliances and furnaces are installed, and as the Company has implemented conservation programs. Natural gas weather normalization and decoupling mechanisms in certain jurisdictions have been implemented to largely mitigate the effect that would otherwise be caused by variations in volumes sold to these customers due to weather and changing consumption patterns on the Company's distribution margins, as further discussed in Items 1 and 2 - Business Properties.
34 MDU Resources Group, Inc. Form 10-K



Part II
Earnings overview - The following information summarizes the performance of the electric segment.
2020 vs. 2019
2019 vs. 2018
Years ended December 31, 2020 2019 2018 % change % change
  (Dollars in millions, where applicable)
Operating revenues $ 332.0  $ 351.7  $ 335.1  (5.6) % 5.0  %
Electric fuel and purchased power 66.9  86.6  80.7  (22.7) % 7.3  %
Taxes, other than income .6  .6  .7  —  % (14.3) %
Adjusted gross margin 264.5  264.5  253.7  —  % 4.3  %
Operating expenses:  
Operation and maintenance 121.3  125.7  123.0  (3.5) % 2.2  %
Depreciation, depletion and amortization 63.0  58.7  51.0  7.3  % 15.1  %
Taxes, other than income 16.8  16.1  14.5  4.3  % 11.0  %
Total operating expenses 201.1  200.5  188.5  .3  % 6.4  %
Operating income 63.4  64.0  65.2  (.9) % (1.8) %
Other income 7.2  3.4  1.2  111.8  % 183.3  %
Interest expense 26.7  25.3  25.9  5.5  % (2.3) %
Income before income taxes 43.9  42.1  40.5  4.3  % 4.0  %
Income tax benefit (11.7) (12.7) (6.5) (7.9) % 95.4  %
Net income $ 55.6  $ 54.8  $ 47.0  1.5  % 16.6  %

Operating statistics 2020 2019 2018
Retail sales (million kWh):
Residential 1,170.9  1,177.9  1,196.6 
Commercial 1,419.4  1,499.9  1,513.9 
Industrial 532.1  549.4  551.0 
Other 82.1  87.1  92.9 
3,204.5  3,314.3  3,354.4 
Average cost of electric fuel and purchased power per kWh $ .019  $ .023  $ .022 
Adjusted gross margin is a non-GAAP financial measure. For additional information and reconciliation of the non-GAAP adjusted gross margin attributable to the electric segment, see the Non-GAAP Financial Measures section later in this Item.
2020 compared to 2019 Electric earnings increased $800,000 as a result of:
Adjusted gross margin: Comparable to the prior year. The adjusted gross margin was positively impacted by higher rates of $2.8 million, including approved rate relief resulting in $2.0 million additional revenue. These increases were offset by lower retail sales volumes of 3.3 percent across all customer classes due to warmer weather and slow-downs as a result of the COVID-19 pandemic.
Operation and maintenance: Decrease of $4.4 million, largely due to lower generation station expenses of $3.5 million and lower payroll and other employee-related costs of approximately $1.5 million. Partially offsetting the decreases were increased bad debt expense of $500,000 as a result of the COVID-19 pandemic, as discussed later.
Depreciation, depletion and amortization: Increase of $4.3 million, largely from an increase in asset base driven by capital expenditures, which include transmission projects, and higher depreciation rates implemented from a Montana rate case of $1.2 million.
Taxes, other than income: Increase of $700,000, from higher property taxes in certain jurisdictions.
Other income: Increase of $3.8 million, largely attributable to an out-of-period adjustment of $2.5 million in the fourth quarter of 2020 related to previously overstated benefit plan expense, as discussed in Item 8 - Note 1, and the absence of the write-down of a non-utility investment in the second quarter of 2019 for $1.2 million, as discussed in Item 8 - Note 8. Lower 2020 pension expense also contributed to the increase in other income.
Interest expense: Increase of $1.4 million driven by higher short-term debt balances.
Income tax benefit: Decrease of $1.0 million, largely due to higher income before income taxes.
2019 compared to 2018 Electric earnings increased $7.8 million as a result of:
Adjusted gross margin: Increase of $10.8 million, primarily due to an increase in revenues. The revenue increase was driven by implemented regulatory mechanisms, which include approved Montana interim and final rates and recovery of the investment in the BSSE project placed into service in the first quarter of 2019. Also contributing to the increase was the absence in 2019 of a transmission formula rate adjustment
MDU Resources Group, Inc. Form 10-K 35



Part II
recognized in the third quarter of 2018 for decreased costs on the BSSE project. These increases were partially offset by lower retail sales volumes of 1.2 percent across all major customer classes.
Operation and maintenance: Increase of $2.7 million, primarily resulting from higher payroll-related costs, partially offset by lower material expenses across all locations.
Depreciation, depletion and amortization: Increase of $7.7 million as a result of increased property, plant and equipment balances including the BSSE project, as previously discussed, and other capital projects, as well as a reserve for certain costs related to the retirement of three aging coal-fired electric generating units, as discussed in Item 8 - Note 6, which is offset in income taxes.
Taxes, other than income: Increase of $1.6 million, primarily from higher property taxes in certain jurisdictions.
Other income: Increase of $2.2 million, largely the result of higher returns on the Company's benefit plan investments, partially offset by the write-down of a non-utility investment in the second quarter of 2019, as discussed in Item 8 - Note 8.
Interest expense: Decrease of $600,000 driven by higher AFUDC, which resulted in more interest being capitalized on regulated construction projects.
Income tax benefit: Increase of $6.2 million, largely due to increased production tax credits, as well as increased excess deferred tax amortization.
Earnings overview - The following information summarizes the performance of the natural gas distribution segment.
2020 vs. 2019
2019 vs. 2018
Years ended December 31, 2020  2019  2018  % change % change
  (Dollars in millions, where applicable)
Operating revenues $ 848.2  $ 865.2  $ 823.2  (2.0) % 5.1  %
Purchased natural gas sold 448.1  477.6  454.8  (6.2) % 5.0  %
Taxes, other than income 32.4  30.3  28.5  6.9  % 6.3  %
Adjusted gross margin 367.7  357.3  339.9  2.9  % 5.1  %
Operating expenses:
Operation and maintenance 185.4  185.0  173.4  .2  % 6.7  %
Depreciation, depletion and amortization 84.6  79.6  72.5  6.3  % 9.8  %
Taxes, other than income 24.6  23.5  21.7  4.7  % 8.3  %
Total operating expenses 294.6  288.1  267.6  2.3  % 7.7  %
Operating income 73.1  69.2  72.3  5.6  % (4.3) %
Other income 13.5  7.2  .2  87.5  % NM
Interest expense 36.8  35.5  30.7  3.7  % 15.6  %
Income before income taxes 49.8  40.9  41.8  21.8  % (2.2) %
Income tax expense 5.8  1.4  4.1  NM (65.9) %
Net income $ 44.0  $ 39.5  $ 37.7  11.4  % 4.8  %
*    NM - not meaningful

36 MDU Resources Group, Inc. Form 10-K



Part II