CLF


Line plots across dimensions of each concept
Line plots across concepts
Tables

Table of contents


us-gaap:StatementClassOfStock
us-gaap:CommonStockParOrStatedValuePerShare

us-gaap:CommonStockSharesIssued
us-gaap:SubsequentEventType
us-gaap:StatementEquityComponents
us-gaap:CommonStockSharesOutstanding

us-gaap:WeightedAverageNumberOfDilutedSharesOutstanding

us-gaap:WeightedAverageNumberOfSharesOutstandingBasic
us-gaap:AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecurities
us-gaap:AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount

us-gaap:EarningsPerShareBasic

us-gaap:EarningsPerShareDiluted

us-gaap:IncomeLossFromContinuingOperationsPerBasicShare

us-gaap:IncomeLossFromContinuingOperationsPerDilutedShare

us-gaap:ComprehensiveIncomeNetOfTax

us-gaap:ComprehensiveIncomeNetOfTaxAttributableToNoncontrollingInterest

us-gaap:ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterest
us-gaap:StatementEquityComponents

us-gaap:CostOfGoodsAndServicesSold

us-gaap:CostsAndExpenses

us-gaap:GainsLossesOnExtinguishmentOfDebt
clf:EBITDACalculation
us-gaap:DebtInstrument

us-gaap:IncomeLossFromContinuingOperations

us-gaap:IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments

us-gaap:IncomeLossFromContinuingOperationsIncludingPortionAttributableToNoncontrollingInterest

us-gaap:IncomeTaxExpenseBenefit
clf:EBITDACalculation

us-gaap:IncomeTaxesPaid

us-gaap:InterestIncomeExpenseNonoperatingNet
clf:EBITDACalculation

us-gaap:InterestPaidNet

us-gaap:NetIncomeLoss
us-gaap:BusinessAcquisition

us-gaap:NetIncomeLossAttributableToNoncontrollingInterest
clf:EBITDACalculation
dei:LegalEntity, us-gaap:ConsolidatedEntities

us-gaap:NetIncomeLossAvailableToCommonStockholdersBasic

us-gaap:NonoperatingIncomeExpense

us-gaap:OperatingIncomeLoss

us-gaap:OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationAdjustmentNetOfTax

us-gaap:OtherComprehensiveIncomeLossNetOfTax

us-gaap:OtherNonoperatingIncomeExpense

us-gaap:ProfitLoss

us-gaap:Revenues
us-gaap:BusinessAcquisition
us-gaap:ConsolidationItems, us-gaap:StatementBusinessSegments
us-gaap:EquitySecuritiesByIndustry, us-gaap:StatementBusinessSegments
us-gaap:ProductOrService, us-gaap:StatementBusinessSegments
us-gaap:StatementBusinessSegments
us-gaap:StatementGeographical

us-gaap:SellingGeneralAndAdministrativeExpense

us-gaap:Assets
us-gaap:ConsolidatedEntities
us-gaap:ConsolidationItems
us-gaap:ConsolidationItems, us-gaap:StatementBusinessSegments
us-gaap:StatementBusinessSegments

us-gaap:Liabilities

us-gaap:LiabilitiesAndStockholdersEquity

us-gaap:StockholdersEquity

us-gaap:AssetsCurrent

us-gaap:CashAndCashEquivalentsAtCarryingValue
dei:LegalEntity, us-gaap:ConsolidatedEntities

us-gaap:CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents

us-gaap:AccountsReceivableNetCurrent

us-gaap:InventoryNet
dei:LegalEntity, us-gaap:ConsolidatedEntities

us-gaap:OtherAssetsCurrent

us-gaap:Land

us-gaap:PropertyPlantAndEquipmentGross
us-gaap:PropertyPlantAndEquipmentByType

us-gaap:AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment

us-gaap:AmortizationOfIntangibleAssets

us-gaap:PropertyPlantAndEquipmentNet
dei:LegalEntity, us-gaap:ConsolidatedEntities
us-gaap:StatementGeographical
us-gaap:BalanceSheetLocation
us-gaap:InvestmentsInAffiliatesSubsidiariesAssociatesAndJointVentures

us-gaap:Goodwill
us-gaap:BusinessAcquisition
us-gaap:StatementBusinessSegments

us-gaap:IntangibleAssetsNetExcludingGoodwill

us-gaap:FiniteLivedIntangibleAssetsNet
us-gaap:FiniteLivedIntangibleAssetsByMajorClass

us-gaap:DeferredTaxAssetsLiabilitiesNet

us-gaap:OperatingLeaseRightOfUseAsset

us-gaap:OtherAssetsNoncurrent

us-gaap:AccountsPayableCurrent
dei:LegalEntity, us-gaap:ConsolidatedEntities

us-gaap:AccruedLiabilitiesCurrent
us-gaap:BalanceSheetLocation
us-gaap:ContractWithCustomerLiabilityCurrent

us-gaap:DividendsPayableCurrent

us-gaap:LiabilitiesCurrent

us-gaap:LongTermDebtCurrent

us-gaap:OperatingLeaseLiabilityCurrent

us-gaap:OtherAccruedLiabilitiesCurrent

us-gaap:OtherLiabilitiesCurrent

us-gaap:TaxesPayableCurrent

us-gaap:LongTermDebt
dei:LegalEntity, us-gaap:DebtInstrument
dei:LegalEntity, us-gaap:LongtermDebtType

us-gaap:LongTermDebtNoncurrent

us-gaap:PensionAndOtherPostretirementDefinedBenefitPlansLiabilitiesNoncurrent
us-gaap:RetirementPlanType

us-gaap:MinorityInterest
dei:LegalEntity, us-gaap:ConsolidatedEntities

us-gaap:OtherLiabilitiesNoncurrent

us-gaap:OperatingLeaseLiabilityNoncurrent

us-gaap:OperatingLeaseLiability

us-gaap:LesseeOperatingLeaseLiabilityPaymentsDue

us-gaap:LesseeOperatingLeaseLiabilityUndiscountedExcessAmount

us-gaap:StockholdersEquity

us-gaap:StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest
us-gaap:StatementEquityComponents

us-gaap:AdditionalPaidInCapital

us-gaap:RetainedEarningsAccumulatedDeficit

us-gaap:AccumulatedOtherComprehensiveIncomeLossNetOfTax
us-gaap:StatementEquityComponents

us-gaap:TreasuryStockValue

us-gaap:MinorityInterest
dei:LegalEntity, us-gaap:ConsolidatedEntities

us-gaap:StockIssuedDuringPeriodValueNewIssues
us-gaap:StatementEquityComponents
us-gaap:StatementEquityComponents
us-gaap:AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue

us-gaap:MinorityInterestDecreaseFromDistributionsToNoncontrollingInterestHolders
us-gaap:StatementEquityComponents

us-gaap:NetCashProvidedByUsedInOperatingActivities

us-gaap:NetCashProvidedByUsedInInvestingActivities

us-gaap:NetCashProvidedByUsedInFinancingActivities

us-gaap:CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect

us-gaap:DeferredIncomeTaxExpenseBenefit

us-gaap:DepreciationDepletionAndAmortization
clf:EBITDACalculation

us-gaap:IncreaseDecreaseInInventories

us-gaap:NetCashProvidedByUsedInOperatingActivities

us-gaap:NetIncomeLoss
us-gaap:BusinessAcquisition

us-gaap:ProfitLoss

us-gaap:NetCashProvidedByUsedInInvestingActivities

us-gaap:PaymentsToAcquirePropertyPlantAndEquipment

us-gaap:NetCashProvidedByUsedInFinancingActivities

us-gaap:RepaymentsOfLongTermDebt

us-gaap:PaymentsOfDividends
dei:LegalEntity, us-gaap:DebtInstrument
us-gaap:DebtInstrumentInterestRateStatedPercentage

us-gaap:EffectiveIncomeTaxRateContinuingOperations

us-gaap:ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice

us-gaap:DeferredTaxLiabilities

us-gaap:DeferredTaxAssetsNet

us-gaap:UnrecognizedTaxBenefits
us-gaap:BalanceSheetLocation

us-gaap:DeferredTaxAssetsValuationAllowance
us-gaap:ValuationAllowanceByDeferredTaxAsset
clf:EBITDACalculation
clf:AcquisitionRelatedLossOnEquityMethodInvestment

clf:AdjustedEBITDAEarningsLoss
us-gaap:StatementBusinessSegments

clf:AmortizationofIntangibleLiability

clf:AmortizationofInventoryStepup
clf:EBITDACalculation
us-gaap:BusinessAcquisition

clf:AssetRetirementObligationIncreaseDecreaseInLiabilitiesAssumedAcquisition

clf:AssetRetirementObligationLiabilitiesAssumedAcquisition
us-gaap:BusinessAcquisition
clf:BusinessAcquisitionProFormaIncomeTaxExpenseBenefit
us-gaap:BusinessAcquisition
clf:BusinessCombinationProvisionalInformationInitialAccountingIncompleteAdjustmentAccountsPayable
us-gaap:BusinessAcquisition
clf:BusinessCombinationProvisionalInformationInitialAccountingIncompleteAdjustmentAccountsReceivable
us-gaap:BusinessAcquisition
clf:BusinessCombinationProvisionalInformationInitialAccountingIncompleteAdjustmentAccruedEmploymentCost
us-gaap:BusinessAcquisition
clf:BusinessCombinationProvisionalInformationInitialAccountingIncompleteAdjustmentCashAndCashEquivalents
us-gaap:BusinessAcquisition
clf:BusinessCombinationProvisionalInformationInitialAccountingIncompleteAdjustmentDeferredIncomeTaxes
us-gaap:BusinessAcquisition
clf:BusinessCombinationProvisionalInformationInitialAccountingIncompleteAdjustmentNetIdentifiableAssets
us-gaap:BusinessAcquisition
clf:BusinessCombinationProvisionalInformationInitialAccountingIncompleteAdjustmentNoncontrllingInterest
us-gaap:BusinessAcquisition
clf:BusinessCombinationProvisionalInformationInitialAccountingIncompleteAdjustmentOtherCurrentAssets
us-gaap:BusinessAcquisition
clf:BusinessCombinationProvisionalInformationInitialAccountingIncompleteAdjustmentOtherCurrentLiabilities
us-gaap:BusinessAcquisition
clf:BusinessCombinationProvisionalInformationInitialAccountingIncompleteAdjustmentOtherNoncurrentAssets
us-gaap:BusinessAcquisition
clf:BusinessCombinationProvisionalInformationInitialAccountingIncompleteAdjustmentOtherNoncurrentLiabilities
us-gaap:BusinessAcquisition
clf:BusinessCombinationProvisionalInformationInitialAccountingIncompleteAdjustmentRetirementBenefitLiabilitiesCurrent
us-gaap:BusinessAcquisition
clf:BusinessCombinationProvisionalInformationInitialAccountingIncompleteAdjustmentRetirementBenefitLiabilitiesNoncurrent
us-gaap:BusinessAcquisition
clf:BusinessCombinationSeparatelyRecognizedTransactionsSettlementOfPreexistingRelationship

clf:CapitalExpendituresIncurredbutNotyetPaidIncreaseDecreaseInPeriod
us-gaap:BusinessAcquisition
clf:CashConsiderationReceivableFromBusinessCombination
us-gaap:BalanceSheetLocation
clf:ContractWithCustomerLiabilityPeriodIncreaseDecrease

clf:DepreciationDepletionandAmortizationAttributabletoNoncontrollingInterests
clf:EBITDACalculation

clf:EBITDAEarningsLoss
clf:EBITDACalculation
clf:EBITDAofNoncontrollingInterests

clf:NoncontrollingInterestIncreaseDecreaseFromBusinessCombinationMeasurementPeriodAdjustments
us-gaap:StatementEquityComponents
us-gaap:BusinessAcquisition
clf:PaymentsToAcquireBusinessesPurchaseOfJVInterest
us-gaap:BusinessAcquisition
clf:PaymentsToAcquireBusinessesPursuantToTransactionAgreement

clf:PercentageOfRelatedPartyRevenue

clf:RevenuesExcludingDeferredRevenueRevenueRecognized
us-gaap:ConsolidationItems, us-gaap:StatementBusinessSegments
clf:SalesVolumeLongTons
us-gaap:ProductOrService, us-gaap:StatementBusinessSegments
us-gaap:StatementBusinessSegments
us-gaap:ProductOrService, us-gaap:StatementBusinessSegments
clf:SalesVolumeNetTons
us-gaap:StatementBusinessSegments

us-gaap:AllowanceForDoubtfulAccountsReceivablePeriodIncreaseDecrease

us-gaap:AssetRetirementObligationAccretionExpense

us-gaap:AssetRetirementObligationLiabilitiesSettled
us-gaap:BusinessAcquisition
us-gaap:BusinessAcquisitionsProFormaNetIncomeLoss
us-gaap:BusinessAcquisition, us-gaap:NonrecurringAdjustment
us-gaap:BusinessAcquisition
us-gaap:BusinessAcquisitionsProFormaRevenue
us-gaap:ConsolidationItems, us-gaap:BusinessAcquisition

us-gaap:BusinessCombinationAcquisitionRelatedCosts
clf:EBITDACalculation
us-gaap:BusinessAcquisition
us-gaap:BusinessAcquisition
us-gaap:BusinessCombinationConsiderationTransferred1
us-gaap:StatementScenario, us-gaap:BusinessAcquisition
us-gaap:BusinessAcquisition, us-gaap:StatementClassOfStock
us-gaap:BusinessCombinationConsiderationTransferredEquityInterestsIssuedAndIssuable
us-gaap:StatementClassOfStock
us-gaap:IncomeStatementLocation
us-gaap:BusinessCombinationProvisionalInformationInitialAccountingIncompleteAdjustmentEquityInterests
us-gaap:BalanceSheetLocation, us-gaap:BusinessAcquisition
us-gaap:BusinessCombinationProvisionalInformationInitialAccountingIncompleteAdjustmentFinancialAssets
us-gaap:BalanceSheetLocation, us-gaap:BusinessAcquisition
us-gaap:BusinessCombinationProvisionalInformationInitialAccountingIncompleteAdjustmentFinancialLiabilities
us-gaap:BalanceSheetLocation, us-gaap:BusinessAcquisition
us-gaap:BusinessCombinationProvisionalInformationInitialAccountingIncompleteAdjustmentIntangibles
us-gaap:BalanceSheetLocation, us-gaap:BusinessAcquisition
us-gaap:BusinessCombinationProvisionalInformationInitialAccountingIncompleteAdjustmentInventory
us-gaap:BusinessAcquisition
us-gaap:BusinessAcquisition
us-gaap:BusinessCombinationProvisionalInformationInitialAccountingIncompleteAdjustmentPropertyPlantAndEquipment
us-gaap:BusinessAcquisition, us-gaap:IncomeStatementLocation
us-gaap:BusinessCombinationProvisionalInformationInitialAccountingIncompleteAdjustmentsRelatedToPreviousPeriod

us-gaap:DeferredRevenueRevenueRecognized1
us-gaap:RetirementPlanType
us-gaap:DefinedBenefitPlanAmortizationOfGainsLosses
us-gaap:RetirementPlanType
us-gaap:DefinedBenefitPlanAmortizationOfPriorServiceCostCredit
us-gaap:RetirementPlanType
us-gaap:DefinedBenefitPlanExpectedReturnOnPlanAssets
us-gaap:RetirementPlanType
us-gaap:DefinedBenefitPlanInterestCost
us-gaap:RetirementPlanType
us-gaap:DefinedBenefitPlanNetPeriodicBenefitCost
us-gaap:RetirementPlanType
us-gaap:DefinedBenefitPlanServiceCost

us-gaap:Depreciation
us-gaap:DerivativeInstrumentRisk, us-gaap:HedgingDesignation
us-gaap:DerivativeInstrumentsGainLossReclassificationFromAccumulatedOCIToIncomeEstimatedNetAmountToBeTransferred

us-gaap:DerivativeInstrumentsNotDesignatedAsHedgingInstrumentsGainLossNet
us-gaap:DerivativeInstrumentRisk, us-gaap:IncomeStatementLocation
us-gaap:DerivativeInstrumentRisk, us-gaap:HedgingDesignation
us-gaap:DerivativeNonmonetaryNotionalAmountEnergyMeasure

us-gaap:EffectiveIncomeTaxRateReconciliationAtFederalStatutoryIncomeTaxRate

us-gaap:ExtinguishmentOfDebtAmount
dei:LegalEntity, us-gaap:DebtInstrument, us-gaap:SubsequentEventType
us-gaap:DebtInstrument

us-gaap:FairValueAssetsMeasuredOnRecurringBasisChangeInUnrealizedGainLoss

us-gaap:FairValueLiabilitiesMeasuredOnRecurringBasisChangeInUnrealizedGainLoss

us-gaap:FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInEarnings1

us-gaap:FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetSettlements

us-gaap:FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityGainLossIncludedInEarnings

us-gaap:FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilitySettlements
us-gaap:BusinessAcquisition
us-gaap:FinitelivedIntangibleAssetsAcquired1
us-gaap:BusinessAcquisition, us-gaap:FiniteLivedIntangibleAssetsByMajorClass
us-gaap:StatementBusinessSegments
us-gaap:GoodwillPeriodIncreaseDecrease
us-gaap:BusinessAcquisition
us-gaap:GoodwillPurchaseAccountingAdjustments

us-gaap:IncomeLossFromDiscontinuedOperationsNetOfTaxAttributableToReportingEntity
clf:EBITDACalculation

us-gaap:IncomeTaxReconciliationOtherReconcilingItems

us-gaap:IncreaseDecreaseInAccountsPayableAndAccruedLiabilities

us-gaap:IncreaseDecreaseInAccountsReceivableAndOtherOperatingAssets

us-gaap:IncreaseDecreaseInDeferredRevenue

us-gaap:IncrementalCommonSharesAttributableToConversionOfDebtSecurities

us-gaap:IncrementalCommonSharesAttributableToShareBasedPaymentArrangements

us-gaap:InterestCostsCapitalized

us-gaap:NetCashProvidedByUsedInContinuingOperations

us-gaap:NetCashProvidedByUsedInDiscontinuedOperations

us-gaap:NetPeriodicDefinedBenefitsExpenseReversalOfExpenseExcludingServiceCostComponent
us-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncome
us-gaap:OtherComprehensiveIncomeLossAmortizationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetPriorServiceCostCreditBeforeTax

us-gaap:OtherComprehensiveIncomeLossBeforeReclassificationsNetOfTax
us-gaap:StatementEquityComponents

us-gaap:OtherComprehensiveIncomeLossCashFlowHedgeGainLossReclassificationAfterTax
us-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncome
us-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncome
us-gaap:OtherComprehensiveIncomeLossCashFlowHedgeGainLossReclassificationBeforeTax
us-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncome
us-gaap:OtherComprehensiveIncomeLossCashFlowHedgeGainLossReclassificationTax

us-gaap:OtherComprehensiveIncomeLossDerivativesQualifyingAsHedgesNetOfTax

us-gaap:OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax
us-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncome
us-gaap:OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansBeforeTax
us-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncome
us-gaap:OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetGainLossBeforeTax
us-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncome
us-gaap:OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansNetOfTax
us-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncome
us-gaap:OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansTax

us-gaap:OtherNoncashIncomeExpense

us-gaap:OtherOperatingIncomeExpenseNet

us-gaap:OtherPostretirementBenefitsPayments
us-gaap:AwardType
us-gaap:OtherSignificantNoncashTransactionValueOfConsiderationGiven1
us-gaap:StatementEquityComponents

us-gaap:PaymentsForProceedsFromOtherInvestingActivities

us-gaap:PaymentsOfDebtIssuanceCosts

us-gaap:PaymentsToAcquireBusinessesGross
us-gaap:BusinessAcquisition
us-gaap:StatementScenario, us-gaap:BusinessAcquisition

us-gaap:PaymentsToAcquireBusinessesNetOfCashAcquired

us-gaap:PensionAndOtherPostretirementBenefitContributions
us-gaap:RetirementPlanType
us-gaap:PensionContributions

us-gaap:ProceedsFromIncomeTaxRefunds

us-gaap:ProceedsFromIssuanceOfCommonStock

us-gaap:ProceedsFromIssuanceOfSeniorLongTermDebt

us-gaap:ProceedsFromLinesOfCredit

us-gaap:ProceedsFromPaymentsForOtherFinancingActivities

us-gaap:PropertyPlantAndEquipmentAdditions
us-gaap:ConsolidatedEntities
us-gaap:StatementBusinessSegments
us-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncome
us-gaap:ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTax
us-gaap:StatementEquityComponents

us-gaap:ReclassificationFromAociCurrentPeriodNetOfTaxAttributableToParent
us-gaap:StatementEquityComponents

us-gaap:RelatedPartyTransactionPurchasesFromRelatedParty

us-gaap:RepaymentsOfLinesOfCredit

us-gaap:RevenueFromRelatedParties

us-gaap:RightOfUseAssetObtainedInExchangeForFinanceLeaseLiability
clf:EBITDACalculation
us-gaap:SeveranceCosts1
us-gaap:BusinessAcquisition
us-gaap:BusinessAcquisition, us-gaap:StatementClassOfStock
us-gaap:StockIssuedDuringPeriodSharesAcquisitions
us-gaap:StatementEquityComponents
us-gaap:StockIssuedDuringPeriodSharesNewIssues
us-gaap:StatementEquityComponents
us-gaap:StockIssuedDuringPeriodSharesShareBasedCompensation

us-gaap:StockIssuedDuringPeriodValueShareBasedCompensation
us-gaap:StatementEquityComponents
us-gaap:StatementClassOfStock, us-gaap:SubsequentEventType
us-gaap:StockRedeemedOrCalledDuringPeriodValue

us-gaap:UndistributedEarningsLossAllocatedToParticipatingSecuritiesBasic

us-gaap:UnrealizedGainLossOnDerivativesAndCommodityContracts

clf:BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentAssetsIncomeTaxReceivable
us-gaap:BusinessAcquisition
us-gaap:BusinessAcquisition
clf:BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentLiabilitiesAccruedEmploymentCosts
us-gaap:BusinessAcquisition
clf:BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentLiabilitiesPensionAndOPEBLiabilities
us-gaap:BusinessAcquisition
clf:BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentLiabilitiesStateAndLocalTaxes
us-gaap:BusinessAcquisition
clf:BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNonCurrentLiabilitiesPensionAndOPEBLiabilities
us-gaap:BusinessAcquisition
clf:BusinessCombinationRecognizedIdentifiableAssetsAcquiredandLiabilitiesAssumedAssetRetirementObligations
us-gaap:BusinessAcquisition
clf:BusinessCombinationRecognizedIdentifiableAssetsAcquiredandLiabilitiesAssumedCurrentLiabilitiesAcruedLiabilities
us-gaap:BusinessAcquisition
clf:BusinessCombinationRecognizedIdentifiableAssetsAcquiredandLiabilitiesAssumedDeferredIncomeTaxes
us-gaap:BusinessAcquisition
clf:BusinessCombinationRecognizedIdentifiableAssetsAcquiredandLiabilitiesAssumedIntangibleLiability
us-gaap:BusinessAcquisition
clf:BusinessCombinationRecognizedIdentifiableAssetsAcquiredandLiabilitiesAssumedOperatingLeaseLiabilityNoncurrent
us-gaap:BusinessAcquisition
clf:BusinessCombinationRecognizedIdentifiableAssetsAcquiredandLiabilitiesAssumedPensionandOPEBLiabilities
us-gaap:BusinessAcquisition
clf:BusinessCombinationRecognizedIdentifiableAssetsAcquiredandLiabilitiesAssumedRightofuseAssetOperatingLease
us-gaap:BusinessAcquisition
clf:BusinessCombinationSeparatelyRecognizedTransactionsAccountsReceivable
us-gaap:SubsequentEventType
clf:CommonStockSharesOptionToPurchaseAdditionalShares
dei:LegalEntity
clf:CommonStockSharesSold
dei:LegalEntity, us-gaap:SubsequentEventType
us-gaap:StatementScenario, us-gaap:BusinessAcquisition
clf:Costsynergies

clf:EstimatedProjectCapitalExpenditures
us-gaap:Range, us-gaap:BalanceSheetLocation, us-gaap:DerivativeInstrumentRisk, us-gaap:FairValueByFairValueHierarchyLevel, us-gaap:HedgingDesignation, us-gaap:MeasurementInputType, us-gaap:ValuationTechnique
clf:FairValueMeasurementWithUnobservableInputsRange

clf:FiniteLivedIntangibleLiabilitiesAmortizationCreditNextTwelveMonths

clf:FiniteLivedIntangibleLiabilitiesAmortizationCreditRemainderofFiscalYear

clf:FiniteLivedIntangibleLiabilitiesAmortizationCreditYearFive

clf:FiniteLivedIntangibleLiabilitiesAmortizationCreditYearFour

clf:FiniteLivedIntangibleLiabilitiesAmortizationCreditYearThree

clf:FiniteLivedIntangibleLiabilitiesAmortizationCreditYearTwo

clf:FiniteLivedIntangibleLiabilityAccumulatedAmortization

clf:FiniteLivedIntangibleLiabilityGross

clf:FiniteLivedIntangibleLiabilityNet
us-gaap:BusinessAcquisition
clf:FinitelivedIntangibleLiabilityAssumed

clf:IntangibleLiabilityNet
us-gaap:CreditFacility, us-gaap:LongtermDebtType
clf:LineOfCreditFacilityMaximumBorrowingCapacityTrancheA
dei:LegalEntity, us-gaap:ConsolidatedEntities
clf:OtherAssetsLiabilitiesNet
us-gaap:DefinedBenefitPlanByPlanAssetCategories, us-gaap:RetirementPlanType
clf:ReserveForInvestmentCommitments

us-gaap:AccountsPayableRelatedPartiesCurrent

us-gaap:AccountsReceivableRelatedPartiesCurrent

us-gaap:AccrualForEnvironmentalLossContingencies

us-gaap:AccruedEnvironmentalLossContingenciesCurrent

us-gaap:AccruedEnvironmentalLossContingenciesNoncurrent

us-gaap:AccumulatedOtherComprehensiveIncomeLossBeforeTax1
us-gaap:StatementEquityComponents

us-gaap:AccumulatedOtherComprehensiveIncomeLossCumulativeChangesInNetGainLossFromCashFlowHedgesEffectNetOfTax

us-gaap:AccumulatedOtherComprehensiveIncomeLossDefinedBenefitPensionAndOtherPostretirementPlansNetOfTax

us-gaap:AccumulatedOtherComprehensiveIncomeLossForeignCurrencyTranslationAdjustmentNetOfTax

us-gaap:AllowanceForDoubtfulAccountsReceivable

us-gaap:AociIncludingPortionAttributableToNoncontrollingInterestTax
us-gaap:StatementEquityComponents

us-gaap:AssetRetirementObligation
us-gaap:ConsolidationItems

us-gaap:AssetRetirementObligationCurrent

us-gaap:AssetRetirementObligationsNoncurrent

us-gaap:AssetsFairValueDisclosure
us-gaap:FairValueByFairValueHierarchyLevel
us-gaap:BusinessAcquisition, us-gaap:StatementClassOfStock
us-gaap:BusinessAcquisitionSharePrice
us-gaap:BusinessAcquisition
us-gaap:BusinessCombinationAcquisitionOfLessThan100PercentNoncontrollingInterestFairValue
us-gaap:BusinessAcquisition
us-gaap:BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCashAndEquivalents
us-gaap:BusinessAcquisition
us-gaap:BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentAssetsOther
us-gaap:BusinessAcquisition
us-gaap:BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentAssetsReceivables
us-gaap:BusinessAcquisition
us-gaap:BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentLiabilitiesAccountsPayable
us-gaap:BusinessAcquisition
us-gaap:BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentLiabilitiesOther
us-gaap:BusinessAcquisition
us-gaap:BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedIntangibleAssetsOtherThanGoodwill
us-gaap:BusinessAcquisition
us-gaap:BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedInventory
us-gaap:BusinessAcquisition
us-gaap:BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNet
us-gaap:BusinessAcquisition
us-gaap:BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNoncurrentLiabilitiesOther
us-gaap:BusinessAcquisition
us-gaap:BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedOtherNoncurrentAssets
us-gaap:BusinessAcquisition
us-gaap:BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedPropertyPlantAndEquipment
us-gaap:BusinessAcquisition
us-gaap:BusinessCombinationRecognizedIdentifiableAssetsAcquiredGoodwillAndLiabilitiesAssumedLessNoncontrollingInterest
us-gaap:BusinessAcquisition
us-gaap:BusinessCombinationSeparatelyRecognizedTransactionsAssetsRecognized

us-gaap:CommonStockValueOutstanding

us-gaap:DebtInstrumentCarryingAmount
dei:LegalEntity
dei:LegalEntity, us-gaap:DebtInstrument
dei:LegalEntity, us-gaap:DebtInstrument, us-gaap:SubsequentEventType
dei:LegalEntity, us-gaap:LongtermDebtType
us-gaap:DebtInstrument
us-gaap:DebtInstrumentConvertibleCarryingAmountOfTheEquityComponent
us-gaap:DebtInstrument
us-gaap:DebtInstrumentConvertibleConversionPrice1
dei:LegalEntity
us-gaap:DebtInstrumentInterestRateEffectivePercentage
dei:LegalEntity, us-gaap:DebtInstrument
dei:LegalEntity, us-gaap:LongtermDebtType
dei:LegalEntity, us-gaap:DebtInstrument
us-gaap:DebtInstrumentUnamortizedDiscount
dei:LegalEntity, us-gaap:DebtInstrument
us-gaap:DebtInstrumentUnamortizedPremium
dei:LegalEntity, us-gaap:LongtermDebtType

us-gaap:DeferredIncomeTaxAssetsNet

us-gaap:DeferredTaxAssetInterestCarryforward

us-gaap:DeferredTaxAssetsGross

us-gaap:DeferredTaxAssetsOperatingLossCarryforwards

us-gaap:DeferredTaxAssetsOperatingLossCarryforwardsDomestic

us-gaap:DeferredTaxAssetsOperatingLossCarryforwardsForeign

us-gaap:DeferredTaxAssetsStateTaxes

us-gaap:DeferredTaxAssetsTaxCreditCarryforwardsForeign

us-gaap:DeferredTaxAssetsTaxDeferredExpenseCompensationAndBenefitsPensions

us-gaap:DeferredTaxAssetsTaxDeferredExpenseReservesAndAccrualsOther

us-gaap:DeferredTaxLiabilitiesInvestments

us-gaap:DeferredTaxLiabilitiesOther

us-gaap:DeferredTaxLiabilitiesPropertyPlantAndEquipment

us-gaap:DefinedBenefitPlanAccumulatedBenefitObligation
us-gaap:RetirementPlanType
us-gaap:DefinedBenefitPlanAccumulatedOtherComprehensiveIncomeBeforeTax
us-gaap:RetirementPlanType
us-gaap:DefinedBenefitPlanAccumulatedOtherComprehensiveIncomeNetGainsLossesBeforeTax
us-gaap:RetirementPlanType
us-gaap:DefinedBenefitPlanAccumulatedOtherComprehensiveIncomeNetPriorServiceCostCreditBeforeTax
us-gaap:RetirementPlanType
us-gaap:DefinedBenefitPlanAmountsRecognizedInBalanceSheet
us-gaap:RetirementPlanType
us-gaap:DefinedBenefitPlanAssetsForPlanBenefitsNoncurrent
us-gaap:RetirementPlanType
us-gaap:DefinedBenefitPlanAssumptionsUsedCalculatingBenefitObligationDiscountRate
us-gaap:RetirementPlanType
us-gaap:DefinedBenefitPlanAssumptionsUsedCalculatingBenefitObligationRateOfCompensationIncrease
us-gaap:RetirementPlanType
us-gaap:DefinedBenefitPlanAssumptionsUsedCalculatingBenefitObligationWeightedAverageInterestCreditingRate
us-gaap:RetirementPlanType
us-gaap:DefinedBenefitPlanBenefitObligation

us-gaap:DefinedBenefitPlanExpectedAmortizationOfGainLossNextFiscalYear
us-gaap:RetirementPlanType
us-gaap:RetirementPlanType
us-gaap:DefinedBenefitPlanExpectedFutureBenefitPaymentsFiveFiscalYearsThereafter
us-gaap:RetirementPlanType
us-gaap:DefinedBenefitPlanExpectedFutureBenefitPaymentsNextTwelveMonths
us-gaap:RetirementPlanType
us-gaap:DefinedBenefitPlanExpectedFutureBenefitPaymentsYearFive
us-gaap:RetirementPlanType
us-gaap:DefinedBenefitPlanExpectedFutureBenefitPaymentsYearFour
us-gaap:RetirementPlanType
us-gaap:DefinedBenefitPlanExpectedFutureBenefitPaymentsYearThree
us-gaap:RetirementPlanType
us-gaap:DefinedBenefitPlanExpectedFutureBenefitPaymentsYearTwo
us-gaap:RetirementPlanName, us-gaap:RetirementPlanType
us-gaap:DefinedBenefitPlanExpectedFutureEmployerContributionsNextFiscalYear
us-gaap:RetirementPlanType
us-gaap:RetirementPlanType
us-gaap:DefinedBenefitPlanFundedStatusOfPlan

us-gaap:DefinedBenefitPlanHealthCareCostTrendRateAssumedNextFiscalYear
us-gaap:DefinedBenefitPlanByPlanAssetCategories, us-gaap:RetirementPlanType
us-gaap:DefinedBenefitPlanPlanAssetsTargetAllocationPercentage
us-gaap:RetirementPlanType

us-gaap:DefinedBenefitPlanUltimateHealthCareCostTrendRate1
us-gaap:DefinedBenefitPlanByPlanAssetCategories, us-gaap:RetirementPlanType
us-gaap:DefinedBenefitPlanWeightedAverageAssetAllocations
us-gaap:RetirementPlanType
us-gaap:BalanceSheetLocation, us-gaap:DerivativeInstrumentRisk
us-gaap:DerivativeAssets
us-gaap:BalanceSheetLocation, us-gaap:DerivativeInstrumentRisk, us-gaap:FairValueByFairValueHierarchyLevel
us-gaap:BalanceSheetLocation, us-gaap:DerivativeInstrumentRisk, us-gaap:HedgingDesignation
us-gaap:BalanceSheetLocation, us-gaap:DerivativeInstrumentRisk
us-gaap:DerivativeLiabilities
us-gaap:BalanceSheetLocation, us-gaap:DerivativeInstrumentRisk, us-gaap:FairValueByFairValueHierarchyLevel
us-gaap:BalanceSheetLocation, us-gaap:DerivativeInstrumentRisk, us-gaap:HedgingDesignation
us-gaap:DerivativeInstrumentRisk, us-gaap:HedgingDesignation
us-gaap:DerivativeNonmonetaryNotionalAmount
us-gaap:Currency, us-gaap:DerivativeInstrumentRisk, us-gaap:HedgingDesignation
us-gaap:DerivativeNotionalAmount
us-gaap:BalanceSheetLocation
us-gaap:DueFromRelatedPartiesCurrent
us-gaap:BalanceSheetLocation
us-gaap:DueToRelatedPartiesCurrent

us-gaap:EmployeeRelatedLiabilitiesCurrent

us-gaap:EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized
us-gaap:ScheduleOfEquityMethodInvestmentEquityMethodInvesteeName
us-gaap:EquityMethodInvestmentDifferenceBetweenCarryingAmountAndUnderlyingEquity
us-gaap:ScheduleOfEquityMethodInvestmentEquityMethodInvesteeName
us-gaap:EquityMethodInvestmentOwnershipPercentage
us-gaap:ScheduleOfEquityMethodInvestmentEquityMethodInvesteeName, us-gaap:BusinessAcquisition
us-gaap:ScheduleOfEquityMethodInvestmentEquityMethodInvesteeName, us-gaap:RelatedPartyTransactionsByRelatedParty

us-gaap:ExcessOfReplacementOrCurrentCostsOverStatedLIFOValue

us-gaap:FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue

us-gaap:FairValueMeasurementWithUnobservableInputsReconciliationsRecurringBasisLiabilityValue

us-gaap:FinanceLeaseLiability

us-gaap:FinanceLeaseLiabilityCurrent

us-gaap:FinanceLeaseLiabilityNoncurrent

us-gaap:FinanceLeaseLiabilityPaymentsDue

us-gaap:FinanceLeaseLiabilityPaymentsDueInNextRollingTwelveMonths

us-gaap:FinanceLeaseLiabilityPaymentsDueInRollingAfterYearFive

us-gaap:FinanceLeaseLiabilityPaymentsDueInRollingYearFive

us-gaap:FinanceLeaseLiabilityPaymentsDueInRollingYearFour

us-gaap:FinanceLeaseLiabilityPaymentsDueInRollingYearThree

us-gaap:FinanceLeaseLiabilityPaymentsDueInRollingYearTwo

us-gaap:FinanceLeaseLiabilityUndiscountedExcessAmount

us-gaap:FinanceLeaseRightOfUseAsset

us-gaap:FinanceLeaseWeightedAverageDiscountRatePercent

us-gaap:FinancialLiabilitiesFairValueDisclosure
us-gaap:FairValueByFairValueHierarchyLevel

us-gaap:FiniteLivedIntangibleAssetsAccumulatedAmortization
us-gaap:FiniteLivedIntangibleAssetsByMajorClass

us-gaap:FiniteLivedIntangibleAssetsAmortizationExpenseRemainderOfFiscalYear

us-gaap:FiniteLivedIntangibleAssetsGross
us-gaap:FiniteLivedIntangibleAssetsByMajorClass

us-gaap:IncomeTaxesReceivable

us-gaap:InterestPayableCurrent

us-gaap:InventoryFinishedGoodsAndWorkInProcessNetOfReserves

us-gaap:InventoryFinishedGoodsNetOfReserves

us-gaap:InventoryRawMaterialsNetOfReserves

us-gaap:InventorySuppliesNetOfReserves

us-gaap:InventoryValuationReserves

us-gaap:InventoryWorkInProcessNetOfReserves

us-gaap:LesseeOperatingLeaseLiabilityPaymentsDueAfterRollingYearFive

us-gaap:LesseeOperatingLeaseLiabilityPaymentsDueInRollingYearFive

us-gaap:LesseeOperatingLeaseLiabilityPaymentsDueInRollingYearFour

us-gaap:LesseeOperatingLeaseLiabilityPaymentsDueInRollingYearThree

us-gaap:LesseeOperatingLeaseLiabilityPaymentsDueInRollingYearTwo

us-gaap:LesseeOperatingLeaseLiabilityPaymentsDueNextRollingTwelveMonths
dei:LegalEntity, us-gaap:DebtInstrument
us-gaap:LineOfCredit
dei:LegalEntity, us-gaap:LongtermDebtType
us-gaap:DebtInstrument
us-gaap:DebtInstrument
us-gaap:LineOfCreditFacilityCurrentBorrowingCapacity

us-gaap:LineOfCreditFacilityMaximumBorrowingCapacity
dei:LegalEntity, us-gaap:LongtermDebtType
us-gaap:DebtInstrument
us-gaap:DebtInstrument
us-gaap:LineOfCreditFacilityRemainingBorrowingCapacity
us-gaap:DebtInstrument, us-gaap:FairValueByFairValueHierarchyLevel, us-gaap:FairValueByMeasurementBasis, us-gaap:LongtermDebtType
us-gaap:LongTermDebtFairValue
us-gaap:FairValueByFairValueHierarchyLevel, us-gaap:FairValueByMeasurementBasis, us-gaap:LongtermDebtType
us-gaap:FairValueByMeasurementBasis

us-gaap:LongTermDebtMaturitiesRepaymentsOfPrincipalAfterYearFive

us-gaap:LongTermDebtMaturitiesRepaymentsOfPrincipalInNextTwelveMonths

us-gaap:LongTermDebtMaturitiesRepaymentsOfPrincipalInYearFive

us-gaap:LongTermDebtMaturitiesRepaymentsOfPrincipalInYearFour

us-gaap:LongTermDebtMaturitiesRepaymentsOfPrincipalInYearThree

us-gaap:LongTermDebtMaturitiesRepaymentsOfPrincipalInYearTwo
us-gaap:DebtInstrument
us-gaap:LongTermLineOfCredit

us-gaap:MineralPropertiesAccumulatedDepletion

us-gaap:MineralPropertiesGross

us-gaap:MineralPropertiesNet

us-gaap:OperatingLeaseWeightedAverageDiscountRatePercent
us-gaap:RetirementPlanType
us-gaap:PensionAndOtherPostretirementDefinedBenefitPlansCurrentLiabilities

us-gaap:PostemploymentBenefitsLiabilityCurrent
us-gaap:AwardType
us-gaap:ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue

us-gaap:ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorized

us-gaap:ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableWeightedAverageExercisePrice

us-gaap:ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingIntrinsicValue

us-gaap:SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsExercisableIntrinsicValue1
us-gaap:StatementClassOfStock
us-gaap:SharesIssuedPricePerShare
us-gaap:StatementClassOfStock, us-gaap:SubsequentEventType
dei:LegalEntity, us-gaap:DebtInstrument
us-gaap:UnamortizedDebtIssuanceExpense
us-gaap:BalanceSheetLocation
us-gaap:UnrecognizedTaxBenefitsIncomeTaxPenaltiesAndInterestAccrued
us-gaap:UnrecordedUnconditionalPurchaseObligationByCategoryOfItemPurchased
us-gaap:UnrecordedUnconditionalPurchaseObligationBalanceSheetAmount

Plots across concepts


IncomeStatement
Other Comprehensive Income Loss Net Of Tax
Expenses
Other Nonoperating Income Expense
Balance Sheet
Cash And Cash Equivalents At Carrying Value
Assets
Cash And Cash Equivalents At Carrying Value
Current Assets
Cash And Cash Equivalents At Carrying Value
NonCurrent Assets
Intangible Assets Net Excluding Goodwill
PropertyPlantAndEquipmentNet
Accumulated Depreciation Depletion And Amortization Property Plant And Equipment
Liabilities
Operating Lease Liability
Current Liabilities
Long Term Debt Current
Noncurrent Liabilities
Operating Lease Liability Noncurrent
Stockholders Equity
Retained Earnings Accumulated Deficit
CashFlow
Net Cash Provided By Used In Financing Activities
NetCashProvidedByUsedInOperatingActivities
Increase Decrease In Inventories
NetCashProvidedByUsedInInvestingActivities
Net Cash Provided By Used In Investing Activities
NetCashProvidedByUsedInFinancingActivities
Net Cash Provided By Used In Financing Activities
Shares
Common Stock Shares Issued
OperatingLeaseLiability
Operating Lease Liability Current
NonoperatingIncomeExpense
Nonoperating Income Expense
LesseeOperatingLeaseLiabilityPaymentsDue
Lessee Operating Lease Liability Undiscounted Excess Amount
FiniteLivedIntangibleAssets
Finite Lived Intangible Assets Accumulated Amortization
InventoryNet
Inventory Work In Process Net Of Reserves

Tables

  2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-31
 us-gaap:CommonStockParOrStatedValuePerShare us-gaap:StatementClassOfStock us-gaap:CommonStockNANA1.25e-07NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
us-gaap:CommonStockSharesIssued NANANANA428.645866428.645866301.886794301.886794301.886794301.886794301.886794301.886794301.886794301.886794301.886794301.886794301.886794301.886794238.636794236.346794189.622349187.822349159.546224159.546224159.546224159.546224159.546224159.546224159.546224159.546224159.546224159.545469159.545469159.545469149.195469149.195469149.195469149.195469149.195469149.195469149.195469138.845469
 us-gaap:CommonStockSharesIssued us-gaap:SubsequentEventType us-gaap:SubsequentEventNANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
 us-gaap:CommonStockSharesOutstanding us-gaap:StatementEquityComponents us-gaap:CommonStock██▇▅▅▅▁▁▁▁▂▂▂▂▂500.0499.0478.0399.2399.2398.6270.1270.1270.0282.8292.6298.0297.8297.7297.4NANANA233.1NANANA153.5NANANA153.2NANANA153.2NANANA142.5NANANA142.0NANANA
us-gaap:WeightedAverageNumberOfDilutedSharesOutstanding █▁585.0571.0NA399.399399.088297.515NA276.578285.479289.525NA310.203301.275297.266NA301.1300.7265.2NA206.3184.557171.962NA153.237153.232178.696NA153.108153.087153.04NA178.459178.428148.081NA142.895142.814142.709NA144.989139.783136.191
us-gaap:WeightedAverageNumberOfSharesOutstandingBasic █▁500.0490.0NA399.399399.088297.515NA269.96275.769289.525NA297.878297.618297.266NA296.1296.1265.2NA206.3182.33171.677NA153.237153.232153.185NA153.108153.087153.04NA153.029153.011147.827NA142.396142.38142.226NA144.203139.0135.486
 us-gaap:AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount us-gaap:AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecurities us-gaap:StockCompensationPlanNANANA1.81.81.6NANA0.04.2NANANA3.8NANANANANANANANANANANANANANANANANANANANANANANANANANANANA
us-gaap:EarningsPerShareBasic █▇▇▇▇▇▇▇▇▇██▇▇▇▇▇▇▇▇▇▇▇▇▇▆▆▁▇▇▇▇▇▇▅▇██████1.40.080.19-0.02-0.31-0.180.230.340.59-0.082.061.470.55-0.291.040.180.1-0.110.35-0.120.070.62-0.39-0.10.39-5.04-8.48-38.49-0.01-0.540.20.680.870.66-11.360.61.812.641.34.092.933.12
us-gaap:EarningsPerShareDiluted █▇▇▇▇▇▇▇▇▇██▇▇█▇▇▇▇▇▇▇▇▇▇▇▆▁▇▇▇▇▇▇▅▇██████1.330.070.19-0.02-0.31-0.180.230.330.57-0.081.981.410.55-0.291.030.180.11-0.110.34-0.120.070.62-0.39-0.10.39-4.26-8.48-38.49-0.01-0.540.20.660.820.66-11.360.591.812.631.34.072.923.11
us-gaap:IncomeLossFromContinuingOperationsPerBasicShare █▇▇▇▇▇▇▇▇▇█▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▆▁▇▇▇▇▇▇▅▇██████1.4e-068e-081.9e-07-2e-08-3.1e-07-1.8e-072.3000000000000002e-073.4000000000000003e-075.9e-07-8e-082.1099999999999997e-066.7e-077.7e-07-2.9e-071.06e-067e-082.6e-07-1.1e-074.3e-07-1.1e-077e-086.1e-07-2.4e-071.9e-07-2.8e-071.02e-06-8.48e-06-3.849e-05-1e-08-5.4e-072.0000000000000002e-076.7e-078.7e-076.6e-07-1.158e-056.2e-071.81e-062.64e-061.3e-064.21e-062.95e-063.12e-06
us-gaap:IncomeLossFromContinuingOperationsPerDilutedShare █▇▇▇▇▇▇▇▇▇█▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▆▁▇▇▇▇▇▇▅▇██████1.33e-067e-081.9e-07-2e-08-3.1e-07-1.8e-072.3000000000000002e-073.3e-075.699999999999999e-07-8e-082.0299999999999996e-066.4e-077.6e-07-2.9e-071.0500000000000001e-067e-082.6e-07-1.1e-074.2e-07-1.1e-077e-086.1e-07-2.4e-071.9e-07-2.8e-079.399999999999999e-07-8.48e-06-3.849e-05-1e-08-5.4e-072.0000000000000002e-076.5e-078.2e-076.6e-07-1.158e-056.1e-071.81e-062.63e-061.3e-064.1900000000000005e-062.9300000000000003e-063.11e-06
  2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-31
  2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-31
 TTM Greenblatt ROC _ _█▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▆▁▇▇▇▇▇▇▆▇▇▇▇███1067.0177.0107.238.0-208.4-78.881.7121.6226.8-0.8163.2225.5254.2-40.097.4129.7114.681.9131.734.774.7-0.324.529.225.771.9-1623.8-7759.1-11.7-50.716.7224.0262.0168.3-970.176.3365.3231.1367.9820.3616.9541.2
  2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-31
us-gaap:ComprehensiveIncomeNetOfTax █▄▅▄▃▄▄▄▅▄▇▅▅▃▅▄▄▄▄▄▄▄▄▄▄▁834.054.0213.213.9-112.7-50.410.097.1164.5-13.7569.0216.6174.2-76.6301.755.736.7-31.159.0-18.016.1113.7-53.214.469.5-552.2NANANANANANANANANANANANA341.1434.3433.7447.5
us-gaap:ComprehensiveIncomeNetOfTaxAttributableToNoncontrollingInterest ▇█▅▆█▁15.016.09.811.915.83.5NANA0.00.0NANANANANANANANANA0.90.70.64.70.70.8-10.8-6.40.50.60.527.30.91.11.23.11.51.51.517.1-0.40.40.5
us-gaap:ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterest █▂▃▂▁▁▂▂▃▂849.070.0223.025.8-96.9-46.910.097.1164.5-13.7NA216.6174.2-76.6301.760.935.4-37.858.0-19.133.5123.1-46.110.575.3-564.9-1519.0-6967.950.0-12.478.6176.0-45.8126.2-1872.3118.9256.8414.6-1655.1597.2453.9447.9
us-gaap:CostOfGoodsAndServicesSold ██▅▄▃▁▂▂▂▁▂▂▂▁▂▂▂▁▂▂▂▁▂▂▂▁▃▃▃▂▃▃▃▂▃▃▃▃▃▃▃▂3848.03761.02013.11525.41207.5356.0407.2400.7480.2126.1494.3480.2429.8242.6500.2538.2424.2365.9572.5467.9404.7274.6432.7538.1440.8365.21116.01170.71008.8876.81221.31197.91220.3902.61297.41346.61176.7961.21168.81279.51075.0584.5
us-gaap:CostsAndExpenses ██▅▄▃▂▂▂▂▁3978.03872.02149.01608.01301.1437.9452.8434.0516.4157.8NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
us-gaap:GainsLossesOnExtinguishmentOfDebt ▂▁▂▃▅▃▃▃▂▃▂▃▃▃▃▁▂▁▃▂▃▆▃▄▃█▃▃▃▃-22.0-66.0-2.60.0129.43.20.00.0-17.9-0.3-7.00.00.20.00.0-88.6-4.9-71.92.2-18.33.6178.80.079.20.0313.716.20.00.00.0NANANANANANANANANANANANA
 us-gaap:GainsLossesOnExtinguishmentOfDebt clf:EBITDACalculation clf:AdjustedEBITDACalculation█▁-22.0-66.0NA0.0129.43.2NA0.0-17.9-0.3NA0.0NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
 us-gaap:GainsLossesOnExtinguishmentOfDebt us-gaap:DebtInstrument clf:A1.502025ConvertibleSeniorNotesNANA-0.30.01.3NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
 us-gaap:GainsLossesOnExtinguishmentOfDebt us-gaap:DebtInstrument clf:A4.8752024SeniorSecuredNotes█▁0.0-14.0NA0.00.5NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
 us-gaap:GainsLossesOnExtinguishmentOfDebt us-gaap:DebtInstrument clf:A5.752025SeniorNotes-17.0NA-0.30.016.3NA-0.10.0-12.9NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
 us-gaap:GainsLossesOnExtinguishmentOfDebt us-gaap:DebtInstrument clf:A5.8752027SeniorNotesNANA0.30.048.7NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
 us-gaap:GainsLossesOnExtinguishmentOfDebt us-gaap:DebtInstrument clf:A6.252040SeniorNotesNANA0.10.012.9NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
 us-gaap:GainsLossesOnExtinguishmentOfDebt us-gaap:DebtInstrument clf:A6.3752025SeniorNotes▃▁▃▃█0.0-7.0-0.30.021.3NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
 us-gaap:GainsLossesOnExtinguishmentOfDebt us-gaap:DebtInstrument clf:A63752025AKSeniorNotes█▁0.0-3.0NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
 us-gaap:GainsLossesOnExtinguishmentOfDebt us-gaap:DebtInstrument clf:A7.002027SeniorNotesNANA-1.40.028.4NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
 us-gaap:GainsLossesOnExtinguishmentOfDebt us-gaap:DebtInstrument clf:A7.502023AKSeniorNotesNANA0.20.00.02.8NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
 us-gaap:GainsLossesOnExtinguishmentOfDebt us-gaap:DebtInstrument clf:A7.6252021AKSeniorNotesNANANA0.00.00.4NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
 us-gaap:GainsLossesOnExtinguishmentOfDebt us-gaap:DebtInstrument clf:A98752025SeniorSecuredNotes█▁-5.0-42.0NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
us-gaap:IncomeLossFromContinuingOperations █▇▇▇▇▇▇▇▇▇█▇▇▇█▇▇▇▇▇▇▇▇▇▇▇▆▁▇▇▇▇▇▇▅▇▇█▇███779.041.063.0-9.7-123.6-52.763.491.8161.4-22.1624.1199.8229.4-84.8315.021.178.2-28.698.4-23.113.2105.5-37.254.5-43.2168.7-1285.1-5879.610.9-70.343.3115.2146.0107.0-1649.187.8258.0375.9185.3618.7407.7423.4
us-gaap:IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments █▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▆▁▇▇▇▇▇▇▆▇▇▇▇███1010.066.060.3-20.2-132.5-100.657.996.6183.4-25.8134.5200.3227.6-69.169.413.079.1-32.189.6-32.227.8121.8-35.446.6-40.0341.9-1657.8-7799.4-54.3-92.2-27.6178.1218.5120.3-1028.432.4317.7187.6322.6765.5589.2562.3
us-gaap:IncomeLossFromContinuingOperationsIncludingPortionAttributableToNoncontrollingInterest █▇▇▇▇▇▇▇▇▇█▇▇▇█▇▇▇▇▇▇▇▇▇▇▇▇▁▇▇▇▇▇▇▆▇██▇███794.057.072.82.2-107.8-49.263.491.8161.4-22.1624.1199.8229.4-84.8315.020.676.5-30.3100.1-25.129.9114.3-34.849.9-38.2166.8170.0-6887.290.969.7-14.2111.9141.3120.8-1901.681.1274.3391.5221.7758.8428.1423.8
us-gaap:IncomeTaxExpenseBenefit ▇▆▆▅▅▅▆▆▆▆▃▆▆▆▄▆▆▆▆▆▆▆▆▆▆▆▄▁▅▅▅▆▆▆█▅▆▅▆▆▆▆216.09.0-12.5-22.4-24.7-51.4-5.54.822.0-3.7-489.60.5-1.815.7-245.6-7.62.6-1.8-10.5-7.1-2.17.5-0.6-3.4-1.8175.1-289.7-921.4-69.1-21.8-13.965.79.3-6.0491.1-64.042.9-210.8107.817.8151.9142.0
us-gaap:IncomeTaxesPaid █▅▄▅▁▁▁▁▁▁5.03.01.83.00.10.10.10.00.00.1NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
us-gaap:InterestIncomeExpenseNonoperatingNet ▂▁▃▃▃▇██████-85.0-92.0-70.1-68.2-68.7-31.0-24.7-25.3-26.1-25.1-25.8-29.5NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
 us-gaap:InterestIncomeExpenseNonoperatingNet clf:EBITDACalculation clf:EBITDACalculation█▁-85.0-92.0NA-68.2-68.6-31.1NA-25.4-26.3-25.1NA-29.7NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
us-gaap:InterestPaidNet ██▇▄▃▃▂▂▁▄73.075.064.043.033.329.725.718.714.039.2NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
us-gaap:NetIncomeLoss █▇▇▇▇▇▇▇▇▇██▇▇█▇▇▇▇▇▇▇▇▇▇▆▆▁▇▇▇▇▇▇▅▇▇█▇███780.041.064.0-10.0-123.9-52.163.290.9160.8-22.1609.5437.8165.1-84.3309.953.431.8-28.179.1-25.812.8108.0-60.310.660.2-759.8-1285.1-5879.610.9-70.343.3117.2146.0107.0-1618.385.1258.0375.8185.4589.5407.7423.4
us-gaap:NetIncomeLossAttributableToNoncontrollingInterest ▇█▅▆█▁15.016.09.811.915.83.5NANA0.00.00.00.00.00.00.0-0.5-1.7-1.71.7-2.016.78.82.4-4.65.0-1.9-83.0-1007.63.6-0.4-57.5-3.3-4.713.8-252.4-6.716.315.623.4151.818.3NA
us-gaap:NetIncomeLossAvailableToCommonStockholdersBasic █▂▂▂▁▂▂▃▃▂▇▅▃▁780.041.064.0-10.0-123.9-52.163.290.9160.8-22.1609.5437.8165.1-84.3NA53.431.8-28.179.1-25.812.8108.0-60.3-15.060.2-772.6-1297.9-5892.4-1.9-83.130.5104.3133.197.1-1618.485.1258.0375.8NANANANA
us-gaap:NonoperatingIncomeExpense ▂▁▂▂▄▃▃▃▂▃▃▃▃▃▃▁▂▁▂▂▂▅▂▃▂█▂▂▂▂▂▂▂▂▂▂▂▂▂▂▃▃-57.0-111.0-46.9-58.275.9-21.8-23.8-25.0-43.4-25.0-28.7-25.2-26.6-29.1-28.0-116.7-35.5-114.0-42.1-66.9-46.9122.1-59.917.4-65.7270.0-34.0-40.3-42.6-41.5-44.3-45.9-43.5-48.0-58.3-43.9-47.6-43.5-45.3-54.8-27.721.1
us-gaap:OperatingIncomeLoss █▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▆▁▇▇▇▇▇▇▆▇▇▇▇███1067.0177.0107.238.0-208.4-78.881.7121.6226.8-0.8163.2225.5254.2-40.097.4129.7114.681.9131.734.774.7-0.324.529.225.771.9-1623.8-7759.1-11.7-50.716.7224.0262.0168.3-970.176.3365.3231.1367.9820.3616.9541.2
us-gaap:OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationAdjustmentNetOfTax ▅▅▅▅▅▅▅▅▅▅▅▁▅▅▅▅▅▅▅▅▅▅▅▅▅█▄▄▅▆▄▅▂▅▅▅▅▅▆▃▆0.0-1.01.61.60.7-0.90.00.00.00.00.0-228.32.20.7-0.30.5-1.4-12.716.00.9-2.74.4-1.5-11.40.5168.0-36.6-65.919.740.5-83.722.8-151.03.3-8.418.6-17.410.972.6-132.242.9NA
us-gaap:OtherComprehensiveIncomeLossNetOfTax ▆▅▇▅▅▅▄▅▅▅▄▁▅▅▅▅▅▅▄▅▅▅▅▅▅█▂▃▅▆▆▆▂▅▅▅▄▅▄▂▅54.013.0149.223.911.21.7-53.26.23.78.4-40.5-221.29.17.7-8.28.05.3-8.0-22.88.74.06.311.84.510.1196.8-150.8-80.735.558.392.862.1-187.15.4-1.540.3-17.523.2-51.4-155.626.4NA
us-gaap:OtherNonoperatingIncomeExpense 4.0NA25.810.015.29.20.90.30.60.14.14.34.44.40.90.80.80.70.00.10.20.10.4-0.1-2.1-0.816.37.12.21.23.8-1.2-2.81.1-3.53.3-0.51.5-1.3-1.70.50.5
us-gaap:ProfitLoss █▇▇▇▇▇▇▇▇▇██▇▇█▇▇▇▇▇▇▇▇▇▇▇▆▁▇▇▇▇▇▇▆▇██▇███795.057.073.81.9-108.1-48.663.290.9160.8-22.1609.5437.8165.1-84.3309.952.930.1-29.880.8-27.829.5116.8-57.96.065.2-761.7-1368.2-6887.214.5-70.7-14.2113.9141.3120.8-1870.878.4274.3391.4221.9741.3426.0423.3
us-gaap:Revenues █▇▄▃▂▁▂▂▂▁▂▂▂▁▂▂▂▁▂▂▁▁▁▂▁▁▃▃▂▂▃▃▃▂▃▃▃▃▃▄▃▂5045.04049.02256.21646.01092.7359.1534.1555.6743.2157.0696.3741.8714.3239.0600.9698.4569.3461.6754.0553.3496.2305.5476.0593.2498.1446.01284.71298.21100.8940.01515.81546.61488.51140.51535.91544.91626.01264.71662.52142.81805.81183.2
us-gaap:SellingGeneralAndAdministrativeExpense █▇▇▄▄▁▂▁▂▁▂▂▁▁▁▁▁▁▂▂▁▁▁▁▂▂▃▄▄▃▅▅▃▃▆▅▆▄▆▆▅▃104.095.094.859.662.126.137.225.530.628.135.430.126.227.728.024.627.525.736.031.122.528.227.822.430.829.142.462.752.551.163.770.648.948.479.963.983.563.081.078.369.550.7
  2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-31
  2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-31
us-gaap:Assets ███▄▄▄▂▂▂▂▂▂▂▁▂▁▁▁▁▁▁▁▁▁▁▁▂▂▆▆▆▆▆▆▆▇▇▇▇▆▆▄17746.017215.016771.08480.98490.78912.33503.83491.23393.23306.33529.63125.03051.52862.92953.41923.32030.11925.71923.91772.91851.01886.32135.52271.52609.42702.63164.04811.213102.413202.813121.913566.713594.913821.913574.915296.815194.314893.314541.713945.313671.78952.3
us-gaap:Liabilities ███▄▄▄▁▁▁▁▁▁▁▁▁▁▁▁▁▁▂▂▂▂▂▂▂▂▃▃▃▄▄▄▄▄▄▄▄▄▄▂13467.013758.013692.07357.27372.57681.33145.93131.33107.63044.63105.43211.23357.83347.73397.52756.42696.82628.73254.43173.43529.93583.03947.14031.04349.64484.74898.34988.56272.86367.26237.66632.16811.16962.97814.07607.67586.87459.47502.07093.57151.74678.4
us-gaap:LiabilitiesAndStockholdersEquity ███▄▄▄▂▂▂▂▂▂▂▁▂▁▁▁▁▁▁▁▁▁▁▁▂▂▆▆▆▆▆▆▆▇▇▇▇▆▆▄17746.017215.016771.08480.98490.78912.33503.83491.23393.23306.33529.63125.03051.52862.92953.41923.32030.11925.71923.91772.91851.01886.32135.52271.52609.42702.63164.04811.213102.413202.813121.913566.713594.913821.913574.915296.815194.314893.314541.713945.313671.78952.3
us-gaap:StockholdersEquity ▅▅▄▃▃▃▃▃▃▃▃▃▂▂▂▂▂▂▁▁▁▁▁▁▁▁▁▃████▇▇▇████▇▇▆3233.02389.02018.0810.6792.9903.2357.9359.9285.6261.7424.2-86.2-306.3-485.0-444.3-833.3-789.1-830.1-1464.3-1544.3-1830.7-1859.4-1981.4-1932.0-1923.8-1995.7-1431.330.76027.66019.56069.55779.75631.25704.64632.76336.86295.06140.05785.05723.45546.24273.0
  2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-31
us-gaap:AssetsCurrent █▇▆▃▃▄▁▁▂▂▂▂▂▂▂▁▁▁▁▁▁▁▁▁▂▂▂▂▂▂▂▂▂▂▂▂▂▂▂▂▂▅6574.05861.05298.02628.82642.33065.6897.91064.61119.41126.01479.61650.61546.91412.41544.6791.1908.3813.2824.6699.6779.2792.0982.71075.91382.21524.41448.91360.61663.81672.31560.01669.61665.91823.91650.01665.41742.61587.31790.71904.81688.33713.9
us-gaap:CashAndCashEquivalentsAtCarryingValue ▁▁▁▁▁▁▂▂▂▂▃▄▃▃▄▂▂▂▂▁▁▁▂▂▂▂▂▂▂▂▂▂▂▂▁▁▁▁▃▃▂█73.0110.0112.056.073.7186.9352.6399.3377.2430.2823.2897.1802.5786.61007.7260.8321.5295.3323.4132.2108.259.9285.2270.2276.2355.7290.9244.0359.9364.0335.5298.8263.3287.2195.236.3159.2122.3521.6545.1238.12267.7
us-gaap:CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents ▁▂▂▁▁▄▇██73.0110.0112.056.073.7187.0352.6399.3377.2NA823.2NANANA978.0NANANANANANANANANANANANANANANANANANANANANANANANANANANA
us-gaap:AccountsReceivableNetCurrent █▇▅▃▃▃▁▁▂▁▂▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▂▂▂▁▂▂▂▂▂▂▂▂▂▂▂▃2062.01659.01169.0653.7482.2560.894.0164.9193.120.1226.7141.4152.647.2140.663.976.761.1128.749.261.541.940.253.449.287.1205.6166.2198.3130.6270.0291.7259.1272.3329.0285.9310.8247.2304.2364.8317.2506.5
us-gaap:InventoryNet █▇▇▄▄▄▁4280.03932.03828.01795.11933.62148.8317.4NA219.0312.787.9187.9256.4324.4183.4207.7287.6250.8178.4317.3391.2406.3329.6351.7487.1408.5326.7516.7648.8609.8391.4438.4529.2630.1436.5526.7741.0695.9475.7528.2605.3496.4
us-gaap:OtherAssetsCurrent ▄▄▄▃▂▃▁▁▁▁▁▁▁▁▁▁▂▂▂▂▂▁▁▃▃▄▅▅▅█▅▇▇▇▅▇▅▅▄▄▄▃159.0160.0165.0115.090.2107.429.540.742.341.027.418.826.828.528.024.888.876.654.147.645.326.030.3138.1140.3190.0192.8206.1221.4363.0236.4310.6316.3297.9216.2322.1219.8192.5168.3144.0152.1137.6
us-gaap:Land NANA361.0NANANA12.4NANANA12.4NANANA12.4NANANA11.6NANANA11.6NANANA31.9NANANA46.3NANANA46.4NANANA37.3NANANA
  2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-31
us-gaap:PropertyPlantAndEquipmentGross ▆▆▆▃▃▃▂▂▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▂███████▇▇▇▇10878.010702.010217.05958.05885.85812.23027.42851.72658.02451.62308.42152.92071.32091.12079.42006.32006.11980.91941.31924.11953.91947.01970.31932.91929.71872.02217.74174.513710.013664.613570.913525.813216.013207.113044.712683.712477.812244.711881.5NANANA
us-gaap:AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment █▆▅▄▄▃▂▂▂▂▂▂▁▂▂▂▂▁▁▁▁1896.01688.01474.01407.31337.91262.41098.41081.81060.71041.31022.41008.1990.01043.81028.41012.51007.0985.9956.9934.0960.8NA911.3NANANANANA2705.22578.62417.52171.02026.41970.81837.41653.01595.71478.01356.9NANANA
us-gaap:AmortizationOfIntangibleAssets ▆█▆▇▆▃▂▁▁▁2.03.02.02.52.41.10.40.20.20.2NANA0.2NANANA0.2NANANANANANANANANANANANANANANANANANA4.84.5NANA3.34.7NA
us-gaap:PropertyPlantAndEquipmentNet ▆▆▆▃▃▃▂▂▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▃██████████▇▇▇▃8982.09014.08743.04550.74547.94549.81929.01769.91597.31410.31286.01144.81081.31047.31051.0993.8999.1995.0984.4990.1993.11009.61059.01052.61077.21047.21414.93207.911004.811086.011153.411354.811189.611236.311207.311030.710882.110766.710524.69835.39802.44021.5
 us-gaap:InvestmentsInAffiliatesSubsidiariesAssociatesAndJointVentures us-gaap:BalanceSheetLocation us-gaap:OtherNoncurrentAssets██▁116.0116.0105.0NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
us-gaap:Goodwill ▆▆█▂▂▂▁1070.0994.01406.0144.0139.3143.32.1NANANANANANANANANANANANANANANA2.02.02.02.02.02.078.677.374.5158.6157.2167.6167.41167.21166.11166.91152.11237.71227.3197.3
us-gaap:IntangibleAssetsNetExcludingGoodwill NANANA190.1192.6210.048.1NANANANANANANANANANANANANANANANANANANANANANANANA110.8115.0124.5129.0133.8137.9143.0147.0149.3159.5171.7
us-gaap:FiniteLivedIntangibleAssetsNet ▁▂▂▃▃█183.0185.0188.0190.1192.6210.0NANANANANANANANANANANA53.653.854.955.857.158.258.960.361.262.777.491.693.895.4110.8115.0124.5129.0133.8137.9143.0147.0149.3159.5171.7
us-gaap:DeferredTaxAssetsLiabilitiesNet NANA492.0NANANA459.5NANANA464.8NANANA0.0NANANA0.0NANANA0.0NANANA124.8NANANA-1074.5NANANA-1006.6NANANA-831.0NANANA
us-gaap:OperatingLeaseRightOfUseAsset NANANA207.7213.0238.011.7NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
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  2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-31
us-gaap:AccountsPayableCurrent ██▇▄▃▄▁▂▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▂▂▂▂▂▂▂▂▃▂▂▂▂▂▂▂1665.01743.01575.0710.7504.8825.3193.2212.8188.1171.7186.8140.8119.099.5127.7102.0111.791.1107.681.391.977.2106.3102.3140.0114.3272.1295.8266.0329.2345.5350.8306.6299.9555.5422.1385.2394.5380.3370.1306.9266.9
us-gaap:AccruedLiabilitiesCurrent NANANA279.4288.3299.8126.3NANANA158.995.185.194.433.7109.4112.8102.941.1134.2141.1111.185.7149.8175.5167.1255.3325.5338.0363.5206.4404.7425.4470.5258.9485.2402.1380.6165.0359.9361.6257.1
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us-gaap:DividendsPayableCurrent NANANA1.01.124.917.8NANANA15.0NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
us-gaap:LiabilitiesCurrent ███▃▃▄▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▂▂▂▂▃▃▃▃▃▃▃▃▄▅▄▄▄▄▃▃2986.02933.02929.01214.11038.01370.8409.4458.5437.4394.0468.2380.7474.9424.9452.2417.5413.3309.3391.1323.5376.1439.8581.7669.9758.4846.5958.61118.31037.51043.11085.51060.51154.61101.41381.51714.31534.31384.61493.31299.41191.01107.2
us-gaap:LongTermDebtCurrent NANA34.0NANANANANANANANANANANANANANANANANANANANANA0.00.021.8234.7161.196.920.97.90.00.094.1369.7369.787.274.8NANANA
us-gaap:OperatingLeaseLiabilityCurrent NANA53.0NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
us-gaap:OtherAccruedLiabilitiesCurrent NANANA50.061.969.59.4NANANA14.2NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
us-gaap:OtherLiabilitiesCurrent █▇█▃▃▃▁▂▂▂▁▁▁▂▁▂▂▂▁▂▂▂▁▃▃▄▂▄▄▃▃▃▃▃▃▃▃▃▂▃▃▂620.0574.0596.0224.0244.9245.752.0121.7115.5113.483.361.366.2104.356.0125.1108.195.691.4102.3137.7138.887.3235.6246.0300.1150.7262.3272.4253.5203.0188.6206.1226.6225.1197.8204.7175.7148.1185.7178.5131.7
us-gaap:TaxesPayableCurrent NANA147.0NANANA37.9NANANA35.5NANANA30.2NANANA28.3NANANA35.2NANANA52.5NANANA61.7NANANA65.9NANANANANANANA
  2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-31
us-gaap:LongTermDebt NANA5424.0NANANANANANANANANANANA2304.2NANANA2192.62195.92489.72499.12699.42721.62887.42880.92984.13247.23454.13291.73043.53327.5NANA4054.8NANANANANANANA
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 us-gaap:LongTermDebt dei:LegalEntity,us-gaap:DebtInstrument clf:ClevelandCliffsInc.,clf:A6.752026SeniorSecuredNotes█████▁819.0818.0816.0814.6813.0695.9NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
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 us-gaap:LongTermDebt dei:LegalEntity,us-gaap:DebtInstrument clf:ClevelandCliffsInc.,clf:A98752025SeniorSecuredNotes▁▂█588.0612.0922.0NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
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us-gaap:LongTermDebtNoncurrent ▇█▇▆▆▆▂▂▂▂▂▂▂▂▂▁▁▁▂▂▂▃▃▃▃▃▃▃▄▄▃▄▄▄▅▄▄▄▄▅▅▂5368.05734.05390.04309.84451.64357.12113.82109.12104.52087.02092.92300.02297.02308.22304.21689.41611.81642.92175.12195.92489.72499.12699.42721.62887.42880.92962.33012.53293.03194.83022.63319.63323.33433.03960.73514.33614.13583.83608.73883.53898.82412.5
us-gaap:PensionAndOtherPostretirementDefinedBenefitPlansLiabilitiesNoncurrent ███▃▃▃▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▂▂▂▂▂▂▂▂▁▂▂3841.03916.04113.01130.61159.61171.6311.5233.2239.3244.2248.7225.0245.0251.4257.7254.3276.1279.1280.5198.5206.4213.8221.0209.1244.8250.2395.2230.0276.6285.0294.0556.1586.9600.0618.3603.3634.2635.6665.8462.4490.9494.0
us-gaap:MinorityInterest ██████▁308.0330.0323.0313.1325.3327.80.0NANANA0.00.00.00.20.20.2122.4127.1133.8143.8151.8162.7169.8172.5183.6213.6-303.0-208.0802.0816.1814.81154.91152.61154.41128.21352.41312.51293.91254.71128.4973.80.9
us-gaap:OtherLiabilitiesNoncurrent █▇█▂▂▂▁▁▁▁▁▁▁▁▁▁▁▂▂▂▂▂▂▂▂▂▂▂▂▂▃▃▃▃▃▂▂▃▂▂▂▂1272.01175.01260.0280.7278.4263.5146.3151.4149.7145.0115.3121.8158.3182.0186.9189.8193.7199.2213.8235.3240.3216.0213.8218.5244.1216.3274.9296.3326.9347.9379.3395.9412.3473.7492.6318.6330.6371.3338.0273.6328.3248.1
us-gaap:OperatingLeaseLiabilityNoncurrent NANA211.0174.1191.5201.210.5NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
  2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-31
us-gaap:StockholdersEquity ▅▅▄▃▃▃▃▃▃▃▃▃▂▂▂▂▂▂▁▁▁▁▁▁▁▁▁▃████▇▇▇████▇▇▆3233.02389.02018.0810.6792.9903.2357.9359.9285.6261.7424.2-86.2-306.3-485.0-444.3-833.3-789.1-830.1-1464.3-1544.3-1830.7-1859.4-1981.4-1932.0-1923.8-1995.7-1431.330.76027.66019.56069.55779.75631.25704.64632.76336.86295.06140.05785.05723.45546.24273.0
us-gaap:StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest ▅▄▄▃▃▃▃▃▃▃▃▂▂▂▂▂▂▂▁▁▁▁▁▁▁▁▁▂▇▇▇▇▇▇▇████▇▇▅3541.02719.02341.01123.71118.21231.0357.9359.9285.6261.7424.2-86.2-306.3-484.8-444.1-833.1-666.7-703.0-1330.5-1400.5-1678.9-1696.7-1811.6-1759.5-1740.2-1782.1-1734.3-177.36829.66835.66884.36934.66783.86859.05760.97689.27607.57433.97039.76851.86520.04273.9
us-gaap:AdditionalPaidInCapital ███▆▆▆▆▆▆▆▆▆▆▆▆▆▆▆▅▅▄▄▃▃▃▃▃▃▃▃▃▃▃▃▂▂▂▂▂▂▂▁5491.05487.05431.04446.34443.64450.23872.13867.73863.63860.23916.73913.33918.23918.03933.93913.23999.74000.13347.03336.03037.53032.52298.92307.62304.62308.12309.82312.22318.02321.12329.52029.82024.32020.91774.71766.21759.61755.11770.81766.11760.3903.3
us-gaap:RetainedEarningsAccumulatedDeficit ▃▂▂▂▂▂▂▂▂▂▂▂▁▁▁▁▁▁▁▁▁▁▁▁▁▁▂▃▇▇▇▇▇▇▇█████▇▇-2168.0-2948.0-2989.0-3052.5-3042.5-2918.5-2842.4-2889.0-2952.6-3096.8-3060.2-3654.7-4092.5-4257.6-4207.3-4517.2-4570.6-4602.4-4574.3-4653.4-4627.4-4640.4-4748.4-4688.1-4673.1-4733.2-3960.7-2639.63276.03300.93407.33483.33401.93291.73217.74925.74929.44760.34424.34266.23717.73328.8
us-gaap:AccumulatedOtherComprehensiveIncomeLossNetOfTax ▅▄▄▂▁▁▁▂▂▂▂▂▆▆▆▆▆▆▆▆▆▆▆▆▆▆▂▅▆▅▄▃▂▆▅▆▅▅▅▅██-66.0-120.0-133.0-282.0-305.9-317.1-318.8-265.6-271.8-275.5-283.9-243.4-22.2-31.3-39.0-30.8-19.4-24.3-21.3-1.2-9.0-12.3-18.0-25.1-28.9-38.2-245.8-101.4-20.2-55.1-112.9-178.4-239.6-51.4-55.6-51.0-89.9-70.9-92.6-59.395.970.0
 us-gaap:AccumulatedOtherComprehensiveIncomeLossNetOfTax us-gaap:StatementEquityComponents us-gaap:AccumulatedDefinedBenefitPlansAdjustmentIncludingPortionAttributableToNoncontrollingInterest█▄▁-121.0-128.0-135.0NA-304.0-310.0-316.0NANANA-281.0NANANA264.0NANANANANANANANANANANANANANANANANANANANANANANANANANANA
 us-gaap:AccumulatedOtherComprehensiveIncomeLossNetOfTax us-gaap:StatementEquityComponents us-gaap:AccumulatedForeignCurrencyAdjustmentIncludingPortionAttributableToNoncontrollingInterest▁▁█2.02.03.0NANA-1.0NANANANANANANANA225.0NANANANANANANANANANANANANANANANANANANANANANANANANANANA
 us-gaap:AccumulatedOtherComprehensiveIncomeLossNetOfTax us-gaap:StatementEquityComponents us-gaap:AccumulatedGainLossCashFlowHedgeIncludingNoncontrollingInterest█▂▁53.06.0-1.0NA-2.0-6.0-3.0NANANA-3.0NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
us-gaap:TreasuryStockValue ▂▂▇▇▇▇███▅▄▃▃▃▄▅▅▅▅▅▅▅▅▆▆▆▆▆▆▆▆▆▆▆▇▇▇▇▇▆▁▁87.093.0354.0354.8355.9365.0390.7390.9391.3263.9186.1139.1147.5151.8169.6236.2236.5241.2245.5255.2255.5262.7265.0277.5277.5283.5285.7291.6297.3298.5305.5306.1306.5307.7322.6322.6322.6323.0336.0268.246.346.4
us-gaap:MinorityInterest ██████▁308.0330.0323.0313.1325.3327.80.0NANANA0.00.00.00.20.20.2122.4127.1133.8143.8151.8162.7169.8172.5183.6213.6-303.0-208.0802.0816.1814.81154.91152.61154.41128.21352.41312.51293.91254.71128.4973.80.9
us-gaap:StockIssuedDuringPeriodValueNewIssues NA322.0NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA0.00.0NANA
 us-gaap:StockIssuedDuringPeriodValueNewIssues us-gaap:StatementEquityComponents us-gaap:AdditionalPaidInCapitalNA78.0NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
 us-gaap:StockIssuedDuringPeriodValueNewIssues us-gaap:StatementEquityComponents us-gaap:TreasuryStockNA244.0NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
 us-gaap:AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue us-gaap:StatementEquityComponents us-gaap:AdditionalPaidInCapital█▁4.0-22.0NANA-7.0-24.0NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
us-gaap:MinorityInterestDecreaseFromDistributionsToNoncontrollingInterestHolders █▁24.08.0NA24.118.35.5NANANANANANANANANA132.7NANA8.77.424.417.0-11.0NANANANANANANANANANANANANANANANANANANA
  2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-31
us-gaap:NetCashProvidedByUsedInOperatingActivities ▆▁▂▅▂▂▄▅▅▃▅▅▄▂▄▄▄▃▅▄▄▂▄▄▃▂▅▅▃▃▆▅▆▃▅▅▄▂██▇▄511.0-379.0-207.8246.0-138.7-160.5174.4237.0262.3-111.2289.8238.093.6-142.9131.4138.992.9-25.1230.991.4107.2-126.597.4188.7-20.0-228.2254.9227.9-41.9-82.0460.0297.0414.3-25.4239.0308.396.2-129.0743.1820.7618.1106.9
us-gaap:NetCashProvidedByUsedInInvestingActivities ██▇██▆██████████████████████████▇██▇▇▇▇█▁█-107.0-135.0-801.8-87.8-144.9-1007.5-194.9-157.1-166.8-125.6-99.4-73.9-28.4-71.4-71.6-36.1-20.9-27.4-18.4-25.2-9.4-4.9-46.0-23.2-18.3-15.7104.3-59.6-57.6-90.7-76.9-234.1-271.9-228.4-177.1-263.8-268.9-252.0-385.8-197.8-4683.4-37.4
us-gaap:NetCashProvidedByUsedInFinancingActivities ▁▄▅▂▃▅▂▂▂▂▁▂▂▂▄▂▂▂▂▂▂▂▂▂▂▃▁▁▃▃▁▂▂▃▃▂▃▂▁▁█▄-441.0512.01064.8-176.9166.01005.1-27.2-59.0-150.1-157.8-267.5-82.0-18.7-7.0687.5-164.8-46.823.0-20.4-43.5-49.1-93.4-37.2-170.2-41.6310.0-305.7-273.392.8197.9-333.9-31.3-152.6345.992.4-164.4212.8-21.2-391.5-292.82032.0627.4
us-gaap:CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect ▅▆█▆▃▁▅▇-37.0-2.055.2-18.7-114.5-166.0-46.720.9NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
  2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-31
us-gaap:DeferredIncomeTaxExpenseBenefit █▆▆▆▆▅▆▆▆▆▁215.010.0-11.1-17.4-25.0-47.5-5.94.522.3-4.1-460.5NANANANANANANA0.00.00.00.0-0.2-2.6-3.2165.8-73.2-941.7-154.115.1-98.682.0-75.2-46.3479.5-93.3-10.7-248.5-52.5-90.061.714.2
us-gaap:DepreciationDepletionAndAmortization ██▅▃▃▂▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▂▂▂▁▁▃▅▅▅▆▆▅▅▅▅▅▄▅▄▄▃208.0217.0124.172.477.134.422.022.221.019.920.419.225.523.921.421.521.623.226.526.826.935.234.935.630.533.073.6144.0145.3141.1155.3153.1144.3140.6143.5132.9132.1117.3124.0117.7105.479.8
us-gaap:IncreaseDecreaseInInventories █▅▅▂▂▆▃▃▂▆▂▃▃▆▃▂▄▄▂▂▃▄▃▂▄▅▁▂▄▆▃▂▂▆▂▁▄▆▃▃▃▆385.0172.0141.8-121.9-118.0244.16.9-1.7-93.7224.8-100.0-68.5-67.4193.0-24.3-80.536.670.0-136.2-73.8-13.966.1-14.2-141.262.5154.9-167.0-122.537.2214.5-41.6-95.0-88.2194.0-110.3-195.546.9219.0-54.0-68.3-32.7229.5
us-gaap:NetCashProvidedByUsedInOperatingActivities ▆▁▂▅▂▂▄▅▅▃▅▅▄▂▄▄▄▃▅▄▄▂▄▄▃▂▅▅▃▃▆▅▆▃▅▅▄▂██▇▄511.0-379.0-207.8246.0-138.7-160.5174.4237.0262.3-111.2289.8238.093.6-142.9131.4138.992.9-25.1230.991.4107.2-126.597.4188.7-20.0-228.2254.9227.9-41.9-82.0460.0297.0414.3-25.4239.0308.396.2-129.0743.1820.7618.1106.9
us-gaap:NetIncomeLoss █▇▇▇▇▇▇▇▇▇██▇▇█▇▇▇▇▇▇▇▇▇▇▆▆▁▇▇▇▇▇▇▅▇▇█▇███780.041.064.0-10.0-123.9-52.163.290.9160.8-22.1609.5437.8165.1-84.3309.953.431.8-28.179.1-25.812.8108.0-60.310.660.2-759.8-1285.1-5879.610.9-70.343.3117.2146.0107.0-1618.385.1258.0375.8185.4589.5407.7423.4
us-gaap:ProfitLoss █▇▇▇▇▇▇▇▇▇██▇▇█▇▇▇▇▇▇▇▇▇▇▇▆▁▇▇▇▇▇▇▆▇██▇███795.057.073.81.9-108.1-48.663.290.9160.8-22.1609.5437.8165.1-84.3309.952.930.1-29.880.8-27.829.5116.8-57.96.065.2-761.7-1368.2-6887.214.5-70.7-14.2113.9141.3120.8-1870.878.4274.3391.4221.9741.3426.0423.3
  2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-31
us-gaap:NetCashProvidedByUsedInInvestingActivities ██▇██▆██████████████████████████▇██▇▇▇▇█▁█-107.0-135.0-801.8-87.8-144.9-1007.5-194.9-157.1-166.8-125.6-99.4-73.9-28.4-71.4-71.6-36.1-20.9-27.4-18.4-25.2-9.4-4.9-46.0-23.2-18.3-15.7104.3-59.6-57.6-90.7-76.9-234.1-271.9-228.4-177.1-263.8-268.9-252.0-385.8-197.8-4683.4-37.4
us-gaap:PaymentsToAcquirePropertyPlantAndEquipment ▄▃▄▃▄▃▄▄▆▁▁▁▁▂▂▁▁▁▁▁▁▁▁▁▁▁▂▂▂▃▃▅▆▅▇▆▆▅█▅▄▂162.0136.0146.196.0144.8138.1191.1153.5293.01.44.211.013.359.072.829.521.527.923.325.69.810.422.923.518.515.950.968.961.0103.3119.4241.0270.8230.4333.9276.6275.9241.1401.8234.4178.865.7
  2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-31
us-gaap:NetCashProvidedByUsedInFinancingActivities ▁▄▅▂▃▅▂▂▂▂▁▂▂▂▄▂▂▂▂▂▂▂▂▂▂▃▁▁▃▃▁▂▂▃▃▂▃▂▁▁█▄-441.0512.01064.8-176.9166.01005.1-27.2-59.0-150.1-157.8-267.5-82.0-18.7-7.0687.5-164.8-46.823.0-20.4-43.5-49.1-93.4-37.2-170.2-41.6310.0-305.7-273.392.8197.9-333.9-31.3-152.6345.992.4-164.4212.8-21.2-391.5-292.82032.0627.4
us-gaap:RepaymentsOfLongTermDebt ▄█▁▁▅▄▁▁▇▁▃▁437.0902.023.50.0569.6429.90.00.0719.010.3218.21.0NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
us-gaap:PaymentsOfDividends NANA0.20.023.916.927.016.214.114.80.00.00.00.0NANANANANANANANANANANANANANANANANANANANANANANANANANANANA
  2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-31
 us-gaap:DebtInstrumentInterestRateStatedPercentage dei:LegalEntity,us-gaap:DebtInstrument clf:AKSteel,clf:A63752025AKSeniorNotesNANA6.375e-06NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
 us-gaap:DebtInstrumentInterestRateStatedPercentage dei:LegalEntity,us-gaap:DebtInstrument clf:AKSteel,clf:A7.502023AKSeniorNotesNANA7.5e-06NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
 us-gaap:DebtInstrumentInterestRateStatedPercentage dei:LegalEntity,us-gaap:DebtInstrument clf:AKSteel,clf:A7.6252021AKSeniorNotesNANA7.625e-06NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
 us-gaap:DebtInstrumentInterestRateStatedPercentage dei:LegalEntity,us-gaap:DebtInstrument clf:ClevelandCliffsInc.,clf:A4.8752024SeniorSecuredNotesNANA4.875e-06NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
 us-gaap:DebtInstrumentInterestRateStatedPercentage dei:LegalEntity,us-gaap:DebtInstrument clf:ClevelandCliffsInc.,clf:A6.3752025SeniorNotesNANA6.375e-06NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA

Common Stock Par Or Stated Value Per Share

us-gaap:CommonStockParOrStatedValuePerShare us-gaap:StatementClassOfStock

us-gaap:CommonStockParOrStatedValuePerShare

us-gaap:CommonStock


Common
Period End2020-12-31
Value0.125
Percentage of CommonStockParOrStatedValuePerShare100.0

Common Stock Shares Issued

us-gaap:CommonStockSharesIssued

us-gaap:CommonStockSharesIssued


Common
Period End2021-02-112020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-06-132011-03-312010-12-312009-12-31
Value2042842830130130130130130130130130130130130123823618918715915915915915915915915915915915915914914914914914914914910138138134
Percentage of CommonStockSharesIssued100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:CommonStockSharesIssued us-gaap:SubsequentEventType

us-gaap:SubsequentEvent


Common
Period End2021-02-11
Value20
Percentage of CommonStockSharesIssued100.0

Common Stock Shares Outstanding

us-gaap:CommonStockSharesOutstanding us-gaap:StatementEquityComponents

us-gaap:CommonStockSharesOutstanding

us-gaap:CommonStock


Common
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312016-12-312015-12-312014-12-312013-12-312012-12-312011-12-312010-12-312009-12-312008-12-312007-12-31
Value50049947839939939827027027028229229829729729723315315315314214213513111387
Percentage of CommonStockSharesOutstanding100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

Weighted Average Number Of Diluted Shares Outstanding

us-gaap:WeightedAverageNumberOfDilutedSharesOutstanding

us-gaap:WeightedAverageNumberOfDilutedSharesOutstanding


Weighted
Period End2021-06-302021-03-312020-09-302020-06-302020-03-312019-09-302019-06-302019-03-312018-09-302018-06-302018-03-312017-09-302017-06-302017-03-312016-09-302016-06-302016-03-312015-09-302015-06-302015-03-312014-09-302014-06-302014-03-312013-09-302013-06-302013-03-312012-09-302012-06-302012-03-312011-09-302011-06-302011-03-312010-09-302010-06-302010-03-31
Value585571399399297276285289310301297301300265206184171153153178153153153178178148142142142144139136136136135
Percentage of WeightedAverageNumberOfDilutedSharesOutstanding100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

Weighted Average Number Of Shares Outstanding Basic

us-gaap:WeightedAverageNumberOfSharesOutstandingBasic

us-gaap:WeightedAverageNumberOfSharesOutstandingBasic


Weighted
Period End2021-06-302021-03-312020-09-302020-06-302020-03-312019-09-302019-06-302019-03-312018-09-302018-06-302018-03-312017-09-302017-06-302017-03-312016-09-302016-06-302016-03-312015-09-302015-06-302015-03-312014-09-302014-06-302014-03-312013-09-302013-06-302013-03-312012-09-302012-06-302012-03-312011-09-302011-06-302011-03-312010-09-302010-06-302010-03-31
Value500490399399297269275289297297297296296265206182171153153153153153153153153147142142142144139135135135135
Percentage of WeightedAverageNumberOfSharesOutstandingBasic100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

Antidilutive Securities Excluded From Computation Of Earnings Per Share Amount

us-gaap:AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount us-gaap:AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecurities

us-gaap:AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount

us-gaap:StockCompensationPlan


Antidilutive
Period End2020-09-302020-06-302020-03-312019-06-302019-03-312018-03-31
Value1.81.81.60.04.23.8
Percentage of AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount100.0100.0100.00.0100.0100.0

Earnings Per Share Basic

us-gaap:EarningsPerShareBasic

us-gaap:EarningsPerShareBasic


Earnings
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-312009-12-312009-09-302009-06-302009-03-31
Value1.40.080.19-0.02-0.31-0.180.230.340.59-0.082.061.470.55-0.291.040.180.1-0.110.35-0.120.070.62-0.39-0.10.39-5.04-8.48-38.49-0.01-0.540.20.680.870.66-11.360.61.812.641.34.092.933.122.842.21.930.570.830.450.36-0.07
Percentage of EarningsPerShareBasic100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

Earnings Per Share Diluted

us-gaap:EarningsPerShareDiluted

us-gaap:EarningsPerShareDiluted


Earnings
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-312009-12-312009-09-302009-06-302009-03-31
Value1.330.070.19-0.02-0.31-0.180.230.330.57-0.081.981.410.55-0.291.030.180.11-0.110.34-0.120.070.62-0.39-0.10.39-4.26-8.48-38.49-0.01-0.540.20.660.820.66-11.360.591.812.631.34.072.923.112.822.181.920.570.820.450.36-0.07
Percentage of EarningsPerShareDiluted100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

Income Loss From Continuing Operations Per Basic Share

us-gaap:IncomeLossFromContinuingOperationsPerBasicShare

us-gaap:IncomeLossFromContinuingOperationsPerBasicShare


Income
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-31
Value1.40.080.19-0.02-0.31-0.180.230.340.59-0.082.110.670.77-0.291.060.070.26-0.110.43-0.110.070.61-0.240.19-0.281.02-8.48-38.49-0.01-0.540.20.670.870.66-11.580.621.812.641.34.212.953.122.852.21.930.58
Percentage of IncomeLossFromContinuingOperationsPerBasicShare100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

Income Loss From Continuing Operations Per Diluted Share

us-gaap:IncomeLossFromContinuingOperationsPerDilutedShare

us-gaap:IncomeLossFromContinuingOperationsPerDilutedShare


Income
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-31
Value1.330.070.19-0.02-0.31-0.180.230.330.57-0.082.030.640.76-0.291.050.070.26-0.110.42-0.110.070.61-0.240.19-0.280.94-8.48-38.49-0.01-0.540.20.650.820.66-11.580.611.812.631.34.192.933.112.832.191.920.57
Percentage of IncomeLossFromContinuingOperationsPerDilutedShare100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

Comprehensive Income Net Of Tax

us-gaap:ComprehensiveIncomeNetOfTax

us-gaap:ComprehensiveIncomeNetOfTax


Comprehensive
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-31
Value8345421313-112.7-50.410.097164-13.7569216174-76.63015536-31.159-18.016113-53.21469-552.2341434433447412457185133
Percentage of ComprehensiveIncomeNetOfTax100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of RevenueFromRelatedParties2382.970.10.04.7-40.0-466.70.033.139.6-33.30.055.242.6-123.30.021.016.1-26.20.0-8.16.7110.00.06.946.5-500.20.0193.1489.0142.70.00.00.00.0

Comprehensive Income Net Of Tax Attributable To Noncontrolling Interest

us-gaap:ComprehensiveIncomeNetOfTaxAttributableToNoncontrollingInterest

us-gaap:ComprehensiveIncomeNetOfTaxAttributableToNoncontrollingInterest


Comprehensive
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-06-302019-03-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-31
Value15169.811153.50.00.00.90.70.64.70.70.8-10.8-6.40.50.60.5270.91.11.23.11.51.51.517-0.40.40.5
Percentage of ComprehensiveIncomeNetOfTaxAttributableToNoncontrollingInterest100.0100.0100.0100.0100.0100.00.00.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of RevenueFromRelatedParties42.920.80.04.05.632.40.00.00.40.30.60.00.30.5-9.80.00.10.20.20.00.20.20.40.00.30.30.50.0-0.20.50.2

Comprehensive Income Net Of Tax Including Portion Attributable To Noncontrolling Interest

us-gaap:ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterest

us-gaap:ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterest


Comprehensive
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-31
Value8497022325-96.9-46.910.097164-13.7216174-76.63016035-37.858-19.133123-46.11075-564.9-1519.0-6967.950-12.478176-45.8126-1872.3118256414-1655.1597453447
Percentage of ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterest100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of RevenueFromRelatedParties2425.790.90.08.7-34.4-434.30.033.139.6-33.355.242.6-123.30.022.915.6-31.90.0-8.513.9119.10.05.050.3-511.70.0-1786.615.5-5.70.038.6-10.143.70.025.055.2124.90.0265.5511.7142.8

us-gaap:ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterest us-gaap:StatementEquityComponents

us-gaap:AccumulatedOtherComprehensiveIncome


Comprehensive
Period End2021-06-302021-03-312020-09-302020-06-302020-03-312019-09-302019-06-302019-03-31
Value541323111.76.23.78.4
Percentage of ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterest6.418.692.6-11.6-3.66.42.2-61.3
Percentage of RevenueFromRelatedParties154.316.98.14.015.72.10.920.4
Percentage of RevenueFromRelatedParties us-gaap:AccumulatedOtherComprehensiveIncome0.00.00.00.00.00.00.00.0

us-gaap:NoncontrollingInterest


Comprehensive
Period End2021-06-302021-03-312020-09-302020-06-302020-03-312012-06-302012-03-312011-06-302011-03-31
Value151611153.51717180.4
Percentage of ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterest1.822.946.1-16.3-7.56.94.14.10.1
Percentage of RevenueFromRelatedParties42.920.84.05.632.43.85.221.20.1
Percentage of RevenueFromRelatedParties us-gaap:NoncontrollingInterest0.00.00.00.00.00.00.00.00.0

us-gaap:RetainedEarnings


Comprehensive
Period End2021-06-302021-03-312020-09-302020-06-302020-03-312019-09-302019-06-302019-03-31
Value78041-10.0-123.9-52.190160-22.1
Percentage of ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterest91.958.6-38.8127.9111.193.697.8161.3
Percentage of RevenueFromRelatedParties2228.653.2-3.4-44.0-482.431.038.7-53.8
Percentage of RevenueFromRelatedParties us-gaap:RetainedEarnings0.00.00.00.00.00.00.00.0

Cost Of Goods And Services Sold

us-gaap:CostOfGoodsAndServicesSold

us-gaap:CostOfGoodsAndServicesSold


Cost
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-31
Value38483761201315251207356407400480126494480429242500538424365572467404274432538440365111611701008876122111971220902129713461176961116812791075584943868769577
Percentage of CostOfGoodsAndServicesSold100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of RevenueFromRelatedParties10994.34884.40.0517.3428.53296.30.0136.5115.5306.80.0122.4105.0390.70.0202.7186.5308.80.0209.4167.5265.60.0258.7294.7330.80.0300.2313.2404.20.0263.0268.2312.80.0282.8252.8289.60.0568.91212.0186.40.00.00.00.0

Costs And Expenses

us-gaap:CostsAndExpenses

us-gaap:CostsAndExpenses


Costs
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-31
Value39783872214916081301437452434516157
Percentage of CostsAndExpenses100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of RevenueFromRelatedParties11365.75028.60.0545.3461.74054.60.0147.9124.2383.9

Gains Losses On Extinguishment Of Debt

us-gaap:GainsLossesOnExtinguishmentOfDebt

us-gaap:GainsLossesOnExtinguishmentOfDebt


Gains
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-31
Value-22.0-66.0-2.60.01293.20.00.0-17.9-0.3-7.00.00.20.00.0-88.6-4.9-71.92.2-18.33.61780.0790.0313160.00.00.0
Percentage of GainsLossesOnExtinguishmentOfDebt100.0100.0100.00.0100.0100.00.00.0100.0100.0100.00.0100.00.00.0100.0100.0100.0100.0100.0100.0100.00.0100.00.0100.0100.00.00.00.0
Percentage of RevenueFromRelatedParties-62.9-85.70.00.045.929.60.00.0-4.3-0.70.00.00.00.00.0-33.4-2.2-60.70.0-8.21.5172.90.038.10.0284.10.00.00.00.0

us-gaap:GainsLossesOnExtinguishmentOfDebt clf:EBITDACalculation

clf:AdjustedEBITDACalculation


Gains
Period End2021-06-302021-03-312020-09-302020-06-302020-03-312019-09-302019-06-302019-03-312018-09-30
Value-22.0-66.00.01293.20.0-17.9-0.30.0
Percentage of GainsLossesOnExtinguishmentOfDebt100.0100.00.0100.0100.00.0100.0100.00.0
Percentage of RevenueFromRelatedParties-62.9-85.70.045.929.60.0-4.3-0.70.0
Percentage of RevenueFromRelatedParties clf:AdjustedEBITDACalculation0.00.00.00.00.00.00.00.00.0

us-gaap:GainsLossesOnExtinguishmentOfDebt us-gaap:DebtInstrument

clf:A1.502025ConvertibleSeniorNotes


Gains
Period End2020-12-312020-09-302020-06-30
Value-0.30.01.3
Percentage of GainsLossesOnExtinguishmentOfDebt11.50.01.0
Percentage of RevenueFromRelatedParties0.00.00.5
Percentage of RevenueFromRelatedParties clf:A1.502025ConvertibleSeniorNotes0.00.00.0

clf:A4.8752024SeniorSecuredNotes


Gains
Period End2021-06-302021-03-312020-09-302020-06-30
Value0.0-14.00.00.5
Percentage of GainsLossesOnExtinguishmentOfDebt-0.021.20.00.4
Percentage of RevenueFromRelatedParties0.0-18.20.00.2
Percentage of RevenueFromRelatedParties clf:A4.8752024SeniorSecuredNotes0.00.00.00.0

clf:A5.752025SeniorNotes


Gains
Period End2021-06-302020-12-312020-09-302020-06-302019-12-312019-09-302019-06-30
Value-17.0-0.30.016-0.10.0-12.9
Percentage of GainsLossesOnExtinguishmentOfDebt77.311.50.012.60.00.072.1
Percentage of RevenueFromRelatedParties-48.60.00.05.80.00.0-3.1
Percentage of RevenueFromRelatedParties clf:A5.752025SeniorNotes0.00.00.00.00.00.00.0

clf:A5.8752027SeniorNotes


Gains
Period End2020-12-312020-09-302020-06-30
Value0.30.048
Percentage of GainsLossesOnExtinguishmentOfDebt-11.50.037.6
Percentage of RevenueFromRelatedParties0.00.017.3
Percentage of RevenueFromRelatedParties clf:A5.8752027SeniorNotes0.00.00.0

clf:A6.252040SeniorNotes


Gains
Period End2020-12-312020-09-302020-06-30
Value0.10.012
Percentage of GainsLossesOnExtinguishmentOfDebt-3.80.010.0
Percentage of RevenueFromRelatedParties0.00.04.6
Percentage of RevenueFromRelatedParties clf:A6.252040SeniorNotes0.00.00.0

clf:A6.3752025SeniorNotes


Gains
Period End2021-06-302021-03-312020-12-312020-09-302020-06-30
Value0.0-7.0-0.30.021
Percentage of GainsLossesOnExtinguishmentOfDebt-0.010.611.50.016.5
Percentage of RevenueFromRelatedParties0.0-9.10.00.07.6
Percentage of RevenueFromRelatedParties clf:A6.3752025SeniorNotes0.00.00.00.00.0

clf:A63752025AKSeniorNotes


Gains
Period End2021-06-302021-03-31
Value0.0-3.0
Percentage of GainsLossesOnExtinguishmentOfDebt-0.04.5
Percentage of RevenueFromRelatedParties0.0-3.9
Percentage of RevenueFromRelatedParties clf:A63752025AKSeniorNotes0.00.0

clf:A7.002027SeniorNotes


Gains
Period End2020-12-312020-09-302020-06-30
Value-1.40.028
Percentage of GainsLossesOnExtinguishmentOfDebt53.80.021.9
Percentage of RevenueFromRelatedParties0.00.010.1
Percentage of RevenueFromRelatedParties clf:A7.002027SeniorNotes0.00.00.0

clf:A7.502023AKSeniorNotes


Gains
Period End2020-12-312020-09-302020-06-302020-03-31
Value0.20.00.02.8
Percentage of GainsLossesOnExtinguishmentOfDebt-7.70.00.087.5
Percentage of RevenueFromRelatedParties0.00.00.025.9
Percentage of RevenueFromRelatedParties clf:A7.502023AKSeniorNotes0.00.00.00.0

clf:A7.6252021AKSeniorNotes


Gains
Period End2020-09-302020-06-302020-03-31
Value0.00.00.4
Percentage of GainsLossesOnExtinguishmentOfDebt0.00.012.5
Percentage of RevenueFromRelatedParties0.00.03.7
Percentage of RevenueFromRelatedParties clf:A7.6252021AKSeniorNotes0.00.00.0

clf:A98752025SeniorSecuredNotes


Gains
Period End2021-06-302021-03-31
Value-5.0-42.0
Percentage of GainsLossesOnExtinguishmentOfDebt22.763.6
Percentage of RevenueFromRelatedParties-14.3-54.5
Percentage of RevenueFromRelatedParties clf:A98752025SeniorSecuredNotes0.00.0

Income Loss From Continuing Operations

us-gaap:IncomeLossFromContinuingOperations

us-gaap:IncomeLossFromContinuingOperations


Income
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-31
Value7794163-9.7-123.6-52.76391161-22.1624199229-84.83152178-28.698-23.113105-37.254-43.2168-1285.1-5879.610-70.343115146107-1649.18725837518561840742338529826077
Percentage of IncomeLossFromContinuingOperations100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of RevenueFromRelatedParties2225.753.20.0-3.3-43.9-488.00.031.338.8-53.80.050.956.0-136.60.07.934.4-24.10.0-10.35.5102.00.026.2-28.9152.80.0-1507.63.4-32.40.025.332.137.10.018.455.4113.30.0275.1459.6135.00.00.00.00.0

Income Loss From Continuing Operations Before Income Taxes Minority Interest And Income Loss From Equity Method Investments

us-gaap:IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments

us-gaap:IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments


Income
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-31
Value10106660-20.2-132.5-100.65796183-25.8134200227-69.1691379-32.189-32.227121-35.446-40.0341-1657.8-7799.4-54.3-92.2-27.6178218120-1028.432317187322765589562386410351147
Percentage of IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of RevenueFromRelatedParties2885.785.70.0-6.8-47.0-931.50.032.944.1-62.80.051.055.6-111.30.04.934.8-27.10.0-14.411.5117.80.022.4-26.7309.70.0-1999.8-16.9-42.50.039.148.041.70.06.868.356.50.0340.4664.3179.30.00.00.00.0

Income Loss From Continuing Operations Including Portion Attributable To Noncontrolling Interest

us-gaap:IncomeLossFromContinuingOperationsIncludingPortionAttributableToNoncontrollingInterest

us-gaap:IncomeLossFromContinuingOperationsIncludingPortionAttributableToNoncontrollingInterest


Income
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-30
Value79457722.2-107.8-49.26391161-22.1624199229-84.83152076-30.3100-25.129114-34.849-38.2166170-6887.29069-14.2111141120-1901.681274391221758428423385298
Percentage of IncomeLossFromContinuingOperationsIncludingPortionAttributableToNoncontrollingInterest100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of RevenueFromRelatedParties2268.674.00.00.7-38.3-455.60.031.338.8-53.80.050.956.0-136.60.07.833.6-25.60.0-11.212.4110.50.024.0-25.5151.10.0-1765.928.232.10.024.631.141.90.017.058.9118.00.0337.4482.6135.10.00.0

Income Tax Expense Benefit

us-gaap:IncomeTaxExpenseBenefit

us-gaap:IncomeTaxExpenseBenefit


Income
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-31
Value2169.0-12.5-22.4-24.7-51.4-5.54.822-3.7-489.60.5-1.815-245.6-7.62.6-1.8-10.5-7.1-2.17.5-0.6-3.4-1.8175-289.7-921.4-69.1-21.8-13.9659.3-6.0491-64.042-210.8107171511429.51169966
Percentage of IncomeTaxExpenseBenefit100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of RevenueFromRelatedParties617.111.70.0-7.6-8.8-475.90.01.65.3-9.00.00.1-0.425.30.0-2.91.1-1.50.0-3.2-0.97.30.0-1.6-1.2158.60.0-236.3-21.5-10.10.014.42.0-2.10.0-13.49.2-63.50.07.9171.345.30.00.00.00.0

us-gaap:IncomeTaxExpenseBenefit clf:EBITDACalculation

clf:EBITDACalculation


Income
Period End2021-06-302021-03-312020-09-302020-06-302020-03-312019-09-302019-06-302019-03-312018-09-302018-06-302018-03-312017-09-302017-06-30
Value2169.0-22.4-24.7-51.4-4.8-22.03.7-0.51.8-15.77.6-2.6
Percentage of IncomeTaxExpenseBenefit100.0100.0100.0100.0100.0-100.0-100.0-100.0-100.0-100.0-100.0-100.0-100.0
Percentage of RevenueFromRelatedParties617.111.7-7.6-8.8-475.9-1.6-5.39.0-0.10.4-25.32.9-1.1
Percentage of RevenueFromRelatedParties clf:EBITDACalculation0.00.00.00.00.00.00.00.00.00.00.00.00.0

Income Taxes Paid

us-gaap:IncomeTaxesPaid

us-gaap:IncomeTaxesPaid


Income
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-31
Value5.03.01.83.00.10.10.10.00.00.1
Percentage of IncomeTaxesPaid100.0100.0100.0100.0100.0100.0100.00.00.0100.0
Percentage of RevenueFromRelatedParties14.33.90.01.00.00.90.00.00.00.2

Interest Income Expense Nonoperating Net

us-gaap:InterestIncomeExpenseNonoperatingNet

us-gaap:InterestIncomeExpenseNonoperatingNet


Interest
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-30
Value-85000000.0-92000000.0-70100000.0-68200000.0-68700000.0-31000000.0-24700000.0-25300000.0-26100000.0-25100000.0-25800000.0-29500000.0
Percentage of InterestIncomeExpenseNonoperatingNet100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of RevenueFromRelatedParties-242.9-119.50.0-23.1-24.4-287.00.0-8.6-6.3-61.10.0-7.5

us-gaap:InterestIncomeExpenseNonoperatingNet clf:EBITDACalculation

clf:EBITDACalculation


Interest
Period End2021-06-302021-03-312020-09-302020-06-302020-03-312019-09-302019-06-302019-03-312018-09-30
Value-85000000.0-92000000.0-68200000.0-68600000.0-31100000.0-25400000.0-26300000.0-25100000.0-29700000.0
Percentage of InterestIncomeExpenseNonoperatingNet100.0100.0100.099.9100.3100.4100.8100.0100.7
Percentage of RevenueFromRelatedParties-242.9-119.5-23.1-24.3-288.0-8.7-6.3-61.1-7.6
Percentage of RevenueFromRelatedParties clf:EBITDACalculation0.00.00.00.00.00.00.00.00.0

Interest Paid Net

us-gaap:InterestPaidNet

us-gaap:InterestPaidNet


Interest
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-31
Value73756443332925181439
Percentage of InterestPaidNet100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of RevenueFromRelatedParties208.697.40.014.611.8275.00.06.43.495.4

Net Income Loss

us-gaap:NetIncomeLoss

us-gaap:NetIncomeLoss


Net
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-312009-12-312009-09-302009-06-302009-03-31
Value7804164-10.0-123.9-52.16390160-22.1609437165-84.33095331-28.179-25.812108-60.31060-759.8-1285.1-5879.610-70.343117146107-1618.385258375185589407423384297260771085845-7.4
Percentage of NetIncomeLoss100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of RevenueFromRelatedParties2228.653.20.0-3.4-44.0-482.40.031.038.7-53.80.0111.640.3-135.70.020.114.0-23.70.0-11.55.3104.40.05.140.2-688.20.0-1507.63.4-32.40.025.732.137.10.017.955.4113.20.0262.1459.6135.00.00.00.00.00.00.00.00.0

us-gaap:NetIncomeLoss us-gaap:BusinessAcquisition

clf:AKSteelHoldingCorporation


Net
Period End2020-09-302020-06-302020-03-31
Value-30.4-206.5-55.1
Percentage of NetIncomeLoss304.0166.7105.8
Percentage of RevenueFromRelatedParties-10.3-73.30.0
Percentage of RevenueFromRelatedParties clf:AKSteelHoldingCorporation0.00.00.0

clf:ArcelorMittalUSA


Net
Period End2020-12-09
Value-40.0
Percentage of NetIncomeLoss0.0
Percentage of RevenueFromRelatedParties0.0
Percentage of RevenueFromRelatedParties clf:ArcelorMittalUSA0.0

Net Income Loss Attributable To Noncontrolling Interest

us-gaap:NetIncomeLossAttributableToNoncontrollingInterest

us-gaap:NetIncomeLossAttributableToNoncontrollingInterest


Net
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302010-06-30
Value15169.811153.50.00.00.00.00.00.00.0-0.5-1.7-1.71.7-2.0168.82.4-4.65.0-1.9-83.0-1007.63.6-0.4-57.5-3.3-4.713-252.4-6.716152315118-0.1
Percentage of NetIncomeLossAttributableToNoncontrollingInterest100.0100.0100.0100.0100.0100.00.00.00.00.00.00.00.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of RevenueFromRelatedParties42.920.80.04.05.632.40.00.00.00.00.00.00.0-0.2-0.7-1.40.0-0.96.98.50.0-2.23.3-1.70.0-258.41.1-0.20.0-0.7-1.04.80.0-1.43.54.70.067.520.60.0

us-gaap:NetIncomeLossAttributableToNoncontrollingInterest clf:EBITDACalculation

clf:AdjustedEBITDACalculation


Net
Period End2021-06-302020-06-30
Value1516
Percentage of NetIncomeLossAttributableToNoncontrollingInterest100.0101.3
Percentage of RevenueFromRelatedParties42.95.7
Percentage of RevenueFromRelatedParties clf:AdjustedEBITDACalculation0.00.0

us-gaap:NetIncomeLossAttributableToNoncontrollingInterest dei:LegalEntity, us-gaap:ConsolidatedEntities

clf:SunCokeMiddletown, us-gaap:VariableInterestEntityPrimaryBeneficiary


Net
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-31
Value15179.711164.0
Percentage of NetIncomeLossAttributableToNoncontrollingInterest100.0106.299.099.2101.3114.3
Percentage of RevenueFromRelatedParties42.922.10.04.05.737.0
Percentage of RevenueFromRelatedParties clf:SunCokeMiddletown us-gaap:VariableInterestEntityPrimaryBeneficiary0.00.00.00.00.00.0

Net Income Loss Available To Common Stockholders Basic

us-gaap:NetIncomeLossAvailableToCommonStockholdersBasic

us-gaap:NetIncomeLossAvailableToCommonStockholdersBasic


Net
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-31
Value7804164-10.0-123.9-52.16390160-22.1609437165-84.35331-28.179-25.812108-60.3-15.060-772.6-1297.9-5892.4-1.9-83.13010413397-1618.485258375
Percentage of NetIncomeLossAvailableToCommonStockholdersBasic100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of RevenueFromRelatedParties2228.653.20.0-3.4-44.0-482.40.031.038.7-53.80.0111.640.3-135.720.114.0-23.70.0-11.55.3104.40.0-7.240.2-699.80.0-1510.9-0.6-38.30.022.929.333.60.017.955.4113.2

Nonoperating Income Expense

us-gaap:NonoperatingIncomeExpense

us-gaap:NonoperatingIncomeExpense


Nonoperating
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-31
Value-57.0-111.0-46.9-58.275-21.8-23.8-25.0-43.4-25.0-28.7-25.2-26.6-29.1-28.0-116.7-35.5-114.0-42.1-66.9-46.9122-59.917-65.7270-34.0-40.3-42.6-41.5-44.3-45.9-43.5-48.0-58.3-43.9-47.6-43.5-45.3-54.8-27.721-6.620-14.133
Percentage of NonoperatingIncomeExpense100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of RevenueFromRelatedParties-162.9-144.20.0-19.726.9-201.90.0-8.5-10.4-60.80.0-6.4-6.5-46.90.0-44.0-15.6-96.20.0-29.9-19.4118.10.08.4-43.9244.60.0-10.3-13.2-19.10.0-10.1-9.6-16.60.0-9.2-10.2-13.10.0-24.4-31.26.70.00.00.00.0

Operating Income Loss

us-gaap:OperatingIncomeLoss

us-gaap:OperatingIncomeLoss


Operating
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-31
Value106717710738-208.4-78.881121226-0.8163225254-40.097129114811313474-0.324292571-1623.8-7759.1-11.7-50.716224262168-970.176365231367820616541393390365113
Percentage of OperatingIncomeLoss100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of RevenueFromRelatedParties3048.6229.90.012.9-74.0-729.60.041.454.5-1.90.057.562.1-64.40.048.950.469.10.015.530.9-0.30.014.017.265.10.0-1989.5-3.6-23.40.049.257.658.30.016.078.569.60.0364.7695.5172.60.00.00.00.0

Other Comprehensive Income Loss Foreign Currency Transaction And Translation Adjustment Net Of Tax

us-gaap:OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationAdjustmentNetOfTax

us-gaap:OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationAdjustmentNetOfTax


Other
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-30
Value0.0-1.01.61.60.7-0.90.00.00.00.00.0-228.32.20.7-0.30.5-1.4-12.7160.9-2.74.4-1.5-11.40.5168-36.6-65.91940-83.722-151.03.3-8.418-17.41072-132.242
Percentage of OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationAdjustmentNetOfTax0.0100.0100.0100.0100.0100.00.00.00.00.00.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of RevenueFromRelatedParties0.0-1.30.00.50.2-8.30.00.00.00.00.0-58.20.51.10.00.2-0.6-10.70.00.4-1.14.30.0-5.50.3152.20.0-16.96.118.70.05.0-33.21.10.03.9-3.73.30.0-58.848.4

Other Comprehensive Income Loss Net Of Tax

us-gaap:OtherComprehensiveIncomeLossNetOfTax

us-gaap:OtherComprehensiveIncomeLossNetOfTax


Other
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-30
Value541314923111.7-53.26.23.78.4-40.5-221.29.17.7-8.28.05.3-8.0-22.88.74.06.3114.510196-150.8-80.735589262-187.15.4-1.540-17.523-51.4-155.626
Percentage of OtherComprehensiveIncomeLossNetOfTax100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of RevenueFromRelatedParties154.316.90.08.14.015.70.02.10.920.40.0-56.42.212.40.03.02.3-6.80.03.91.76.10.02.26.8178.30.0-20.711.026.90.013.6-41.11.90.08.5-3.87.00.0-69.229.8

Other Nonoperating Income Expense

us-gaap:OtherNonoperatingIncomeExpense

us-gaap:OtherNonoperatingIncomeExpense


Other
Period End2021-06-302020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-31
Value4.02510.0159.20.90.30.60.14.14.34.44.40.90.80.80.70.00.10.20.10.4-0.1-2.1-0.8167.12.21.23.8-1.2-2.81.1-3.53.3-0.51.5-1.3-1.70.50.56.8-0.36.50.7
Percentage of OtherNonoperatingIncomeExpense100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.00.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of RevenueFromRelatedParties11.40.03.45.485.20.00.10.10.20.01.11.17.10.00.30.40.60.00.00.10.10.0-0.0-1.4-0.70.01.80.70.60.0-0.3-0.60.40.00.7-0.10.50.0-0.80.60.20.00.00.00.0

Profit Loss

us-gaap:ProfitLoss

us-gaap:ProfitLoss


Profit
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-31
Value79557731.9-108.1-48.66390160-22.1609437165-84.33095230-29.880-27.829116-57.96.065-761.7-1368.2-6887.214-70.7-14.2113141120-1870.87827439122174142642338429726077
Percentage of ProfitLoss100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of RevenueFromRelatedParties2271.474.00.00.6-38.4-450.00.031.038.7-53.80.0111.640.3-135.70.019.913.2-25.10.0-12.412.2113.00.02.943.6-689.90.0-1765.94.5-32.60.025.031.141.90.016.558.9117.90.0329.6480.3135.00.00.00.00.0

Revenues

us-gaap:Revenues

us-gaap:Revenues


Revenues
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-312009-12-312009-09-302009-06-302009-03-31
Value50454049225616461092359534555743157696741714239600698569461754553496305476593498446128412981100940151515461488114015351544162612641662214218051183142413461184727820666390464
Percentage of Revenues100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of RevenueFromRelatedParties14414.35258.40.0558.2387.83325.00.0189.3178.7382.00.0189.0174.5384.90.0263.1250.2389.50.0247.7205.4295.50.0285.2333.0404.00.0332.9341.8433.40.0339.5327.1395.20.0324.5349.4381.00.0952.82035.9377.30.00.00.00.00.00.00.00.0

us-gaap:Revenues us-gaap:BusinessAcquisition

clf:AKSteelHoldingCorporation


Revenuesus-gaap:
Period End2020-09-302020-06-302020-03-31
Value1261715217
Percentage of Revenues76.765.460.6
Percentage of RevenueFromRelatedParties427.8253.80.0
Percentage of RevenueFromRelatedParties clf:AKSteelHoldingCorporation0.00.00.0

clf:ArcelorMittalUSA


Revenuesus-gaap:
Period End2020-12-09
Value446
Percentage of Revenues0.0
Percentage of RevenueFromRelatedParties0.0
Percentage of RevenueFromRelatedParties clf:ArcelorMittalUSA0.0

us-gaap:Revenues us-gaap:ConsolidationItems, us-gaap:StatementBusinessSegments

us-gaap:IntersegmentElimination, clf:MiningandPelletizing


Revenuesus-gaap:
Period End2020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-31
Value-136.0-111.4-87.8-40.3-35.0-4.00.0
Percentage of Revenues-8.3-10.2-24.5-7.5-6.3-0.50.0
Percentage of RevenueFromRelatedParties-46.1-39.5-813.00.0-11.9-1.00.0
Percentage of RevenueFromRelatedParties us-gaap:IntersegmentElimination clf:MiningandPelletizing0.00.00.00.00.00.00.0

us-gaap:OperatingSegments, clf:MiningandPelletizing


Revenuesus-gaap:
Period End2020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-31
Value520489229574590747157
Percentage of Revenues31.644.863.9107.5106.3100.5100.0
Percentage of RevenueFromRelatedParties176.4173.52124.10.0201.2179.7382.0
Percentage of RevenueFromRelatedParties us-gaap:OperatingSegments clf:MiningandPelletizing0.00.00.00.00.00.00.0

us-gaap:Revenues us-gaap:EquitySecuritiesByIndustry, us-gaap:StatementBusinessSegments

clf:Automotive, clf:OtherBusinesses


Revenuesus-gaap:
Period End2021-06-302021-03-312020-06-302020-03-31
Value961054916
Percentage of Revenues1.92.64.54.5
Percentage of RevenueFromRelatedParties274.3136.417.4148.1
Percentage of RevenueFromRelatedParties clf:Automotive clf:OtherBusinesses0.00.00.00.0

clf:Automotive, clf:SteelandManufacturing


Revenuesus-gaap:
Period End2020-09-302020-06-302020-03-312019-06-302019-03-31
Value9203631200.00.0
Percentage of Revenues55.933.333.50.00.0
Percentage of RevenueFromRelatedParties312.0129.11113.00.00.0
Percentage of RevenueFromRelatedParties clf:Automotive clf:SteelandManufacturing0.00.00.00.00.0

clf:Automotive, clf:Steelmaking


Revenuesus-gaap:
Period End2021-06-302021-03-312020-06-302020-03-31
Value11301287309102
Percentage of Revenues22.431.828.328.4
Percentage of RevenueFromRelatedParties3228.61671.4109.7944.4
Percentage of RevenueFromRelatedParties clf:Automotive clf:Steelmaking0.00.00.00.0

clf:DistributorsAndConverters, clf:OtherBusinesses


Revenuesus-gaap:
Period End2021-06-302021-03-312020-06-302020-03-31
Value16158.02.0
Percentage of Revenues0.30.40.70.6
Percentage of RevenueFromRelatedParties45.719.52.818.5
Percentage of RevenueFromRelatedParties clf:DistributorsAndConverters clf:OtherBusinesses0.00.00.00.0

clf:DistributorsAndConverters, clf:Steelmaking


Revenuesus-gaap:
Period End2021-06-302021-03-312020-06-302020-03-31
Value1948124813952
Percentage of Revenues38.630.812.714.5
Percentage of RevenueFromRelatedParties5565.71620.849.3481.5
Percentage of RevenueFromRelatedParties clf:DistributorsAndConverters clf:Steelmaking0.00.00.00.0

clf:DistributorsandConverters, clf:SteelandManufacturing


Revenuesus-gaap:
Period End2020-09-302020-06-302020-03-312019-06-302019-03-31
Value142147530.00.0
Percentage of Revenues8.713.514.80.00.0
Percentage of RevenueFromRelatedParties48.552.5493.50.00.0
Percentage of RevenueFromRelatedParties clf:DistributorsandConverters clf:SteelandManufacturing0.00.00.00.00.0

clf:InfrastructureAndManufacturing, clf:OtherBusinesses


Revenuesus-gaap:
Period End2021-06-302021-03-312020-06-302020-03-31
Value1110.0134.0
Percentage of Revenues0.20.21.21.1
Percentage of RevenueFromRelatedParties31.413.04.637.0
Percentage of RevenueFromRelatedParties clf:InfrastructureAndManufacturing clf:OtherBusinesses0.00.00.00.0

clf:InfrastructureAndManufacturing, clf:Steelmaking


Revenuesus-gaap:
Period End2021-06-302021-03-312020-06-302020-03-31
Value131295419139
Percentage of Revenues26.023.617.510.9
Percentage of RevenueFromRelatedParties3748.61239.067.8361.1
Percentage of RevenueFromRelatedParties clf:InfrastructureAndManufacturing clf:Steelmaking0.00.00.00.0

clf:InfrastructureandManufacturing, clf:SteelandManufacturing


Revenuesus-gaap:
Period End2020-09-302020-06-302020-03-312019-06-302019-03-31
Value198203440.00.0
Percentage of Revenues12.118.612.30.00.0
Percentage of RevenueFromRelatedParties67.472.2407.40.00.0
Percentage of RevenueFromRelatedParties clf:InfrastructureandManufacturing clf:SteelandManufacturing0.00.00.00.00.0

clf:SteelProducers, clf:MiningandPelletizing


Revenuesus-gaap:
Period End2020-09-302020-06-302020-03-312019-09-302019-06-302019-03-31
Value384377141555743157
Percentage of Revenues23.334.639.4100.0100.0100.0
Percentage of RevenueFromRelatedParties130.3134.01311.1189.3178.7382.0
Percentage of RevenueFromRelatedParties clf:SteelProducers clf:MiningandPelletizing0.00.00.00.00.00.0

clf:SteelProducers, clf:Steelmaking


Revenuesus-gaap:
Period End2021-06-302021-03-312020-06-302020-03-31
Value532430384144
Percentage of Revenues10.510.635.140.1
Percentage of RevenueFromRelatedParties1520.0558.4136.31333.3
Percentage of RevenueFromRelatedParties clf:SteelProducers clf:Steelmaking0.00.00.00.0

us-gaap:Revenues us-gaap:ProductOrService, us-gaap:StatementBusinessSegments

clf:CarbonSteel, clf:SteelandManufacturing


Revenuesus-gaap:
Period End2020-09-302020-06-302020-03-312019-06-302019-03-31
Value8214311380.00.0
Percentage of Revenues49.939.538.60.00.0
Percentage of RevenueFromRelatedParties278.5153.21283.30.00.0
Percentage of RevenueFromRelatedParties clf:CarbonSteel clf:SteelandManufacturing0.00.00.00.00.0

clf:CoatedSteel, clf:Steelmaking


Revenuesus-gaap:
Period End2021-06-302021-03-312020-06-302020-03-31
Value1379130830190
Percentage of Revenues27.332.327.525.1
Percentage of RevenueFromRelatedParties3940.01698.7106.8833.3
Percentage of RevenueFromRelatedParties clf:CoatedSteel clf:Steelmaking0.00.00.00.0

clf:ColdRolledSteel, clf:Steelmaking


Revenuesus-gaap:
Period End2021-06-302021-03-312020-06-302020-03-31
Value7736328828
Percentage of Revenues15.315.68.17.8
Percentage of RevenueFromRelatedParties2208.6820.831.2259.3
Percentage of RevenueFromRelatedParties clf:ColdRolledSteel clf:Steelmaking0.00.00.00.0

clf:HotRolledSteel, clf:Steelmaking


Revenuesus-gaap:
Period End2021-06-302021-03-312020-06-302020-03-31
Value14858954219
Percentage of Revenues29.422.13.85.3
Percentage of RevenueFromRelatedParties4242.91162.314.9175.9
Percentage of RevenueFromRelatedParties clf:HotRolledSteel clf:Steelmaking0.00.00.00.0

clf:IronOre, clf:MiningandPelletizing


Revenuesus-gaap:
Period End2020-09-302020-06-302020-03-312019-09-302019-06-302019-03-31
Value357349131515697145
Percentage of Revenues21.732.036.692.793.892.6
Percentage of RevenueFromRelatedParties121.1124.11215.7175.5167.7353.8
Percentage of RevenueFromRelatedParties clf:IronOre clf:MiningandPelletizing0.00.00.00.00.00.0

clf:IronProducts, clf:Steelmaking


Revenuesus-gaap:
Period End2021-06-302021-03-312020-06-302020-03-31
Value15570377142
Percentage of Revenues3.11.734.539.5
Percentage of RevenueFromRelatedParties442.990.9133.81314.8
Percentage of RevenueFromRelatedParties clf:IronProducts clf:Steelmaking0.00.00.00.0

clf:Other, clf:OtherBusinesses


Revenuesus-gaap:
Period End2021-06-302021-03-312020-06-302020-03-31
Value1231307022
Percentage of Revenues2.43.26.46.1
Percentage of RevenueFromRelatedParties351.4168.824.8203.7
Percentage of RevenueFromRelatedParties clf:Other clf:OtherBusinesses0.00.00.00.0

clf:Other, clf:Steelmaking


Revenuesus-gaap:
Period End2021-06-302021-03-312020-06-302020-03-31
Value671187.02.0
Percentage of Revenues1.32.90.60.6
Percentage of RevenueFromRelatedParties191.4153.22.518.5
Percentage of RevenueFromRelatedParties clf:Other clf:Steelmaking0.00.00.00.0

clf:OtherProductLines, clf:SteelandManufacturing


Revenuesus-gaap:
Period End2020-09-302020-06-302020-03-312019-06-302019-03-31
Value13760190.00.0
Percentage of Revenues8.35.65.40.00.0
Percentage of RevenueFromRelatedParties46.621.6180.60.00.0
Percentage of RevenueFromRelatedParties clf:OtherProductLines clf:SteelandManufacturing0.00.00.00.00.0

clf:OtherSteelProducts, clf:Steelmaking


Revenuesus-gaap:
Period End2021-06-302021-03-31
Value345289
Percentage of Revenues6.87.1
Percentage of RevenueFromRelatedParties985.7375.3
Percentage of RevenueFromRelatedParties clf:OtherSteelProducts clf:Steelmaking0.00.0

clf:PlateSteel, clf:Steelmaking


Revenuesus-gaap:
Period End2021-06-302021-03-31
Value321244
Percentage of Revenues6.46.0
Percentage of RevenueFromRelatedParties917.1316.9
Percentage of RevenueFromRelatedParties clf:PlateSteel clf:Steelmaking0.00.0

clf:StainlessAndElectricalSteel, clf:Steelmaking


Revenuesus-gaap:
Period End2021-06-302021-03-312020-06-302020-03-31
Value39736320856
Percentage of Revenues7.99.019.015.6
Percentage of RevenueFromRelatedParties1134.3471.473.8518.5
Percentage of RevenueFromRelatedParties clf:StainlessAndElectricalSteel clf:Steelmaking0.00.00.00.0

clf:StainlessandElectricalSteel, clf:SteelandManufacturing


Revenuesus-gaap:
Period End2020-09-302020-06-302020-03-312019-06-302019-03-31
Value303222590.00.0
Percentage of Revenues18.420.416.50.00.0
Percentage of RevenueFromRelatedParties102.879.0550.00.00.0
Percentage of RevenueFromRelatedParties clf:StainlessandElectricalSteel clf:SteelandManufacturing0.00.00.00.00.0

us-gaap:CargoAndFreight, clf:MiningandPelletizing


Revenuesus-gaap:
Period End2020-09-302020-06-302020-03-312019-09-302019-06-302019-03-31
Value272710404511
Percentage of Revenues1.72.62.97.36.27.4
Percentage of RevenueFromRelatedParties9.29.995.413.811.028.2
Percentage of RevenueFromRelatedParties us-gaap:CargoAndFreight clf:MiningandPelletizing0.00.00.00.00.00.0

us-gaap:Revenues us-gaap:StatementBusinessSegments

clf:MiningandPelletizing


Revenuesus-gaap:
Period End2020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-31
Value384377141534555743157696741714180
Percentage of Revenues23.334.639.4100.0100.0100.0100.0100.0100.0100.075.3
Percentage of RevenueFromRelatedParties130.3134.01311.10.0189.3178.7382.00.0189.0174.5289.9
Percentage of RevenueFromRelatedParties clf:MiningandPelletizing0.00.00.00.00.00.00.00.00.00.00.0

clf:OtherBusinesses


Revenuesus-gaap:
Period End2021-06-302021-03-312020-06-302020-03-31
Value1231307022
Percentage of Revenues2.43.26.46.1
Percentage of RevenueFromRelatedParties351.4168.824.8203.7
Percentage of RevenueFromRelatedParties clf:OtherBusinesses0.00.00.00.0

clf:SteelandManufacturing


Revenuesus-gaap:
Period End2020-09-302020-06-302020-03-312019-06-302019-03-31
Value12617152170.00.0
Percentage of Revenues76.765.460.60.00.0
Percentage of RevenueFromRelatedParties427.8253.82013.90.00.0
Percentage of RevenueFromRelatedParties clf:SteelandManufacturing0.00.00.00.00.0

clf:Steelmaking


Revenuesus-gaap:
Period End2021-06-302021-03-312020-06-302020-03-31
Value492239191023337
Percentage of Revenues97.696.893.693.8
Percentage of RevenueFromRelatedParties14062.95089.6363.03120.4
Percentage of RevenueFromRelatedParties clf:Steelmaking0.00.00.00.0

us-gaap:Revenues us-gaap:StatementGeographical

us-gaap:NonUs


Revenuesus-gaap:
Period End2020-09-302020-06-302020-03-312019-09-302019-06-302019-03-31
Value2651764613813643
Percentage of Revenues16.116.113.025.018.427.4
Percentage of RevenueFromRelatedParties89.962.5432.447.332.8104.6
Percentage of RevenueFromRelatedParties us-gaap:NonUs0.00.00.00.00.00.0

Selling General And Administrative Expense

us-gaap:SellingGeneralAndAdministrativeExpense

us-gaap:SellingGeneralAndAdministrativeExpense


Selling
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-31
Value104959459622637253028353026272824272536312228272230294262525163704848796383638178695095574244
Percentage of SellingGeneralAndAdministrativeExpense100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of RevenueFromRelatedParties297.1123.40.020.222.0241.70.08.77.468.40.07.76.444.60.09.312.121.70.013.99.327.30.010.820.626.40.016.116.323.60.015.510.716.80.013.417.919.00.034.878.416.20.00.00.00.0

Assets

us-gaap:Assets

us-gaap:Assets


Assets
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312009-12-31
Value177461721516771848084908912350334913393330635293125305128622953192320301925192317721851188621352271260927023164481113102132021312113566135941382113574152961519414893145411394513671895277784639
Percentage of Assets100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:Assets us-gaap:ConsolidatedEntities

us-gaap:CorporateNonSegment


Assetsus-gaap:
Period End2021-06-302021-03-312020-12-31
Value456649683
Percentage of Assets2.63.84.1
Percentage of Assets2.63.84.1
Percentage of Assets us-gaap:CorporateNonSegment100.0100.0100.0

us-gaap:Assets us-gaap:ConsolidationItems

us-gaap:OperatingSegments


Assetsus-gaap:
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302019-12-31
Value172901656616088798978862556
Percentage of Assets97.496.295.994.292.973.0
Percentage of Assets97.496.295.994.292.973.0
Percentage of Assets us-gaap:OperatingSegments100.0100.0100.0100.0100.0100.0

us-gaap:Assets us-gaap:ConsolidationItems, us-gaap:StatementBusinessSegments

us-gaap:OperatingSegments, clf:MiningandPelletizing


Assetsus-gaap:
Period End2020-09-302020-06-302019-12-31
Value164316851643
Percentage of Assets19.419.846.9
Percentage of Assets19.419.846.9
Percentage of Assets us-gaap:OperatingSegments clf:MiningandPelletizing100.0100.0100.0

us-gaap:OperatingSegments, clf:OtherBusinesses


Assetsus-gaap:
Period End2021-06-302021-03-312020-12-31
Value324295239
Percentage of Assets1.81.71.4
Percentage of Assets1.81.71.4
Percentage of Assets us-gaap:OperatingSegments clf:OtherBusinesses100.0100.0100.0

us-gaap:OperatingSegments, clf:SteelandManufacturing


Assetsus-gaap:
Period End2020-09-302020-06-302019-12-31
Value63456201913
Percentage of Assets74.873.026.1
Percentage of Assets74.873.026.1
Percentage of Assets us-gaap:OperatingSegments clf:SteelandManufacturing100.0100.0100.0

us-gaap:OperatingSegments, clf:Steelmaking


Assetsus-gaap:
Period End2021-06-302021-03-312020-12-312019-12-31
Value1696616271158492557
Percentage of Assets95.694.594.573.0
Percentage of Assets95.694.594.573.0
Percentage of Assets us-gaap:OperatingSegments clf:Steelmaking100.0100.0100.0100.0

us-gaap:Assets us-gaap:StatementBusinessSegments

clf:CorporateandOtherSegments


Assetsus-gaap:
Period End2020-12-312020-09-302020-06-302020-03-312019-12-31
Value683491604717947
Percentage of Assets4.15.87.18.127.0
Percentage of Assets4.15.87.18.127.0
Percentage of Assets clf:CorporateandOtherSegments100.0100.0100.0100.0100.0

Liabilities

us-gaap:Liabilities

us-gaap:Liabilities


Liabilities
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312009-12-31
Value13467137581369273577372768131453131310730443105321133573347339727562696262832543173352935833947403143494484489849886272636762376632681169627814760775867459750270937151467839392102
Percentage of Liabilities100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets75.979.981.686.886.886.289.889.791.692.188.0102.8110.0116.9115.0143.3132.8136.5169.2179.0190.7189.9184.8177.5166.7165.9154.8103.747.948.247.548.950.150.457.649.749.950.151.650.952.352.350.645.3

Liabilities And Stockholders Equity

us-gaap:LiabilitiesAndStockholdersEquity

us-gaap:LiabilitiesAndStockholdersEquity


Liabilities
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312009-12-31
Value177461721516771848084908912350334913393330635293125305128622953192320301925192317721851188621352271260927023164481113102132021312113566135941382113574152961519414893145411394513671895277784639
Percentage of LiabilitiesAndStockholdersEquity100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

Stockholders Equity

us-gaap:StockholdersEquity

us-gaap:StockholdersEquity


Stockholders
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312009-12-31
Value323323892018810792903357359285261424-86.2-306.3-485.0-444.3-833.3-789.1-830.1-1464.3-1544.3-1830.7-1859.4-1981.4-1932.0-1923.8-1995.7-1431.3306027601960695779563157044632633662956140578557235546427338452542
Percentage of StockholdersEquity100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets18.213.912.09.69.310.110.210.38.47.912.0-2.8-10.0-16.9-15.0-43.3-38.9-43.1-76.1-87.1-98.9-98.6-92.8-85.1-73.7-73.8-45.20.646.045.646.342.641.441.334.141.441.441.239.841.040.647.749.454.8

Assets Current

us-gaap:AssetsCurrent

us-gaap:AssetsCurrent


Assets
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312009-12-31
Value65745861529826282642306589710641119112614791650154614121544791908813824699779792982107513821524144813601663167215601669166518231650166517421587179019041688371325831161
Percentage of AssetsCurrent100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets37.034.031.631.031.134.425.630.533.034.141.952.850.749.352.341.144.742.242.939.542.142.046.047.453.056.445.828.312.712.711.912.312.313.212.210.911.510.712.313.712.341.533.225.0

Cash And Cash Equivalents At Carrying Value

us-gaap:CashAndCashEquivalentsAtCarryingValue

us-gaap:CashAndCashEquivalentsAtCarryingValue


Cash
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-312009-12-312008-12-312007-12-31
Value7311011256731863523993774308238978027861007260321295323132108592852702763552902443593643352982632871953615912252154523822671566969527550502179157
Percentage of CashAndCashEquivalentsAtCarryingValue100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets0.40.60.70.70.92.110.111.411.113.023.328.726.327.534.113.615.815.316.87.55.83.213.411.910.613.29.25.12.72.82.62.21.92.11.40.21.00.83.63.91.725.320.10.00.00.010.80.00.0

us-gaap:CashAndCashEquivalentsAtCarryingValue dei:LegalEntity, us-gaap:ConsolidatedEntities

clf:SunCokeMiddletown, us-gaap:VariableInterestEntityPrimaryBeneficiary


Cash
Period End2021-03-312020-12-312020-09-302020-06-30
Value4.05.00.31.0
Percentage of CashAndCashEquivalentsAtCarryingValue3.64.50.51.4
Percentage of Assets0.00.00.00.0
Percentage of Assets clf:SunCokeMiddletown us-gaap:VariableInterestEntityPrimaryBeneficiary0.00.00.00.0

Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents

us-gaap:CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents

us-gaap:CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents


Cash
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302018-12-312017-12-31
Value731101125673187352399377823978
Percentage of CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets0.40.60.70.70.92.110.111.411.123.333.1

Accounts Receivable Net Current

us-gaap:AccountsReceivableNetCurrent

us-gaap:AccountsReceivableNetCurrent


Accounts
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312009-12-31
Value20621659116965348256094164193202261411524714063766112849614140534987205166198130270291259272329285310247304364317506359103
Percentage of AccountsReceivableNetCurrent100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets11.69.67.07.75.76.32.74.75.70.66.44.55.01.64.83.33.83.26.72.83.32.21.92.41.93.26.53.51.51.02.12.21.92.02.41.92.01.72.12.62.35.74.62.2

Inventory Net

us-gaap:InventoryNet

us-gaap:InventoryNet


Inventory
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312009-12-31
Value42803932382817951933214831721931287187256324183207287250178317391406329351487408326516648609391438529630436526741695475528605496269272
Percentage of InventoryNet100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets24.122.822.821.222.824.19.16.59.52.56.08.411.36.210.814.213.09.317.921.121.515.415.518.715.110.310.75.04.63.03.23.94.63.23.44.94.73.33.84.45.53.55.9

us-gaap:InventoryNet dei:LegalEntity, us-gaap:ConsolidatedEntities

clf:SunCokeMiddletown, us-gaap:VariableInterestEntityPrimaryBeneficiary


Inventory
Period End2021-06-302021-03-312020-12-312020-09-302020-06-30
Value2222212221
Percentage of InventoryNet0.50.60.51.31.1
Percentage of Assets0.10.10.10.30.2
Percentage of Assets clf:SunCokeMiddletown us-gaap:VariableInterestEntityPrimaryBeneficiary0.00.00.00.00.0

Other Assets Current

us-gaap:OtherAssetsCurrent

us-gaap:OtherAssetsCurrent


Other
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312009-12-31
Value15916016511590107294042412718262828248876544745263013814019019220622136323631031629721632221919216814415213711466
Percentage of OtherAssetsCurrent100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets0.90.91.01.41.11.20.81.21.21.20.80.60.91.00.91.34.44.02.82.72.41.41.46.15.47.06.14.31.72.71.82.32.32.21.62.11.41.31.21.01.11.51.51.4

Land

us-gaap:Land

us-gaap:Land


Land
Period End2020-12-312019-12-312018-12-312017-12-312016-12-312015-12-312014-12-312013-12-312012-12-312011-12-31
Value361121212111131464637
Percentage of Land100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets2.20.40.40.40.60.51.00.40.30.3

Property Plant And Equipment Gross

us-gaap:PropertyPlantAndEquipmentGross

us-gaap:PropertyPlantAndEquipmentGross


Property
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312010-12-312009-12-31
Value1087810702102175958588558123027285126582451230821522071209120792006200619801941192419531947197019321929187222174174137101366413570135251321613207130441268312477122441188149363258
Percentage of PropertyPlantAndEquipmentGross100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets61.362.260.970.369.365.286.481.778.374.165.468.967.973.070.4104.398.8102.9100.9108.5105.6103.292.385.174.069.370.186.8104.6103.5103.499.797.295.696.182.982.182.281.763.570.2

us-gaap:PropertyPlantAndEquipmentGross us-gaap:PropertyPlantAndEquipmentByType

clf:Landlandimprovementsandmineralrights


Property
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302019-12-31
Value127412411213653653582
Percentage of PropertyPlantAndEquipmentGross11.711.611.911.011.119.2
Percentage of Assets7.27.27.27.77.716.6
Percentage of Assets clf:Landlandimprovementsandmineralrights0.00.00.00.00.00.0

clf:MiningandPelletizingEquipment


Property
Period End2020-09-302020-06-302020-03-312019-12-31
Value1455144814311413
Percentage of PropertyPlantAndEquipmentGross24.424.624.646.7
Percentage of Assets17.217.116.140.3
Percentage of Assets clf:MiningandPelletizingEquipment0.00.00.00.0

clf:SteelandManufacturingEquipment


Property
Period End2020-09-302020-06-302020-03-312019-12-31
Value21282147214042
Percentage of PropertyPlantAndEquipmentGross35.736.536.81.4
Percentage of Assets25.125.324.01.2
Percentage of Assets clf:SteelandManufacturingEquipment0.00.00.00.0

us-gaap:Building


Property
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-31
Value86510047034544544521571019587878484858680716867616060606060596588307269255214184190162143144138132
Percentage of PropertyPlantAndEquipmentGross8.09.46.97.67.77.85.23.53.63.63.83.94.14.14.24.03.63.53.53.23.13.13.13.13.13.23.02.12.22.01.91.61.41.41.21.11.21.11.1
Percentage of Assets4.95.84.25.45.45.14.52.92.82.62.52.72.83.02.94.23.53.63.53.43.33.22.82.62.32.22.11.82.32.01.91.61.41.41.20.91.00.90.9
Percentage of Assets us-gaap:Building0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:ConstructionInProgress


Property
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-31
Value43040713641145105810117306685013922841681024835351969423743424034252051948928969911049113110131123844667682615
Percentage of PropertyPlantAndEquipmentGross4.03.813.419.218.017.424.123.518.916.012.37.84.92.31.71.81.03.52.22.02.22.22.01.81.31.12.32.36.56.67.37.88.67.78.66.75.35.65.2
Percentage of Assets2.42.48.113.512.511.320.819.214.811.98.15.43.31.71.21.81.03.62.22.12.32.31.91.51.00.81.62.06.86.87.67.78.37.38.35.54.44.64.2
Percentage of Assets us-gaap:ConstructionInProgress0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:Equipment


Property
Period End2021-06-302021-03-312020-12-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-31
Value810478776786581577575568548538531594594585600595592598596597594583589584732139921991624160015541401134212901318112313941323
Percentage of PropertyPlantAndEquipmentGross74.573.666.419.220.221.723.223.825.025.628.428.629.229.930.130.531.130.530.730.130.230.631.233.033.516.011.911.811.510.610.29.910.49.011.411.1
Percentage of Assets45.745.840.516.616.517.017.215.517.217.420.720.130.429.630.930.833.832.231.727.825.722.621.623.229.116.812.312.211.510.39.79.58.67.49.49.1
Percentage of Assets us-gaap:Equipment0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:MachineryAndEquipment


Property
Period End2020-12-312019-12-31
Value67861456
Percentage of PropertyPlantAndEquipmentGross66.448.1
Percentage of Assets40.541.6
Percentage of Assets us-gaap:MachineryAndEquipment0.00.0

us-gaap:OtherAssets


Property
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-31
Value20517315112112312327292725252525303030282828282829289910054606589941049137533931327343
Percentage of PropertyPlantAndEquipmentGross1.91.61.52.02.12.10.91.01.01.01.11.21.21.41.51.51.41.41.41.51.41.51.45.25.22.92.71.60.70.70.80.70.30.40.30.30.30.60.4
Percentage of Assets1.21.00.91.41.51.40.80.80.80.80.70.80.81.11.01.61.41.51.51.61.51.51.34.43.82.01.91.40.70.70.80.70.30.40.30.20.20.50.3
Percentage of Assets us-gaap:OtherAssets0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:OtherCapitalizedPropertyPlantAndEquipment


Property
Period End2020-12-312019-12-31
Value151101
Percentage of PropertyPlantAndEquipmentGross1.53.3
Percentage of Assets0.92.9
Percentage of Assets us-gaap:OtherCapitalizedPropertyPlantAndEquipment0.00.0

Accumulated Depreciation Depletion And Amortization Property Plant And Equipment

us-gaap:AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment

us-gaap:AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment


Accumulated
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302015-12-312014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312010-12-312009-12-31
Value189616881474140713371262109810811060104110221008990104310281012100798595693496091127052578241721712026197018371653159514781356957665
Percentage of AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets10.79.88.816.615.814.231.331.031.331.529.032.332.436.534.852.649.651.249.752.751.942.720.619.518.416.014.914.313.510.810.59.99.312.314.3

Amortization Of Intangible Assets

us-gaap:AmortizationOfIntangibleAssets

us-gaap:AmortizationOfIntangibleAssets


Amortization
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-06-302017-06-302012-09-302012-06-302011-09-302011-06-30
Value2.03.02.02.52.41.10.40.20.20.20.20.24.84.53.34.7
Percentage of AmortizationOfIntangibleAssets100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

Property Plant And Equipment Net

us-gaap:PropertyPlantAndEquipmentNet

us-gaap:PropertyPlantAndEquipmentNet


Property
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312009-12-31
Value8982901487434550454745491929176915971410128611441081104710519939999959849909931009105910521077104714143207110041108611153113541118911236112071103010882107661052498359802402139792592
Percentage of PropertyPlantAndEquipmentNet100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets50.652.452.153.753.651.155.150.747.142.736.436.635.436.635.651.749.251.751.255.853.753.549.646.341.338.744.766.784.084.085.083.782.381.382.672.171.672.372.470.571.744.951.255.9

us-gaap:PropertyPlantAndEquipmentNet dei:LegalEntity, us-gaap:ConsolidatedEntities

clf:SunCokeMiddletown, us-gaap:VariableInterestEntityPrimaryBeneficiary


Property
Period End2021-06-302021-03-312020-12-312020-09-302020-06-30
Value302304308305309
Percentage of PropertyPlantAndEquipmentNet3.43.43.56.76.8
Percentage of Assets1.71.81.83.63.6
Percentage of Assets clf:SunCokeMiddletown us-gaap:VariableInterestEntityPrimaryBeneficiary0.00.00.00.00.0

us-gaap:PropertyPlantAndEquipmentNet us-gaap:StatementGeographical

clf:OtherCountries


Property
Period End2020-12-31
Value5.0
Percentage of PropertyPlantAndEquipmentNet0.1
Percentage of Assets0.0
Percentage of Assets clf:OtherCountries0.0

country:CA


Property
Period End2020-12-312014-12-312013-12-312012-12-31
Value9124876807369
Percentage of PropertyPlantAndEquipmentNet1.017.668.965.8
Percentage of Assets0.57.958.554.3
Percentage of Assets country:CA0.00.00.00.0

country:US


Property
Period End2020-12-312019-12-312018-12-312017-12-312016-12-312015-12-312014-12-312013-12-312012-12-31
Value86471929128610339611012109327212795
Percentage of PropertyPlantAndEquipmentNet98.9100.0100.098.497.695.677.324.424.9
Percentage of Assets51.655.136.435.050.047.434.620.720.6
Percentage of Assets country:US0.00.00.00.00.00.00.00.00.0

Investments In Affiliates Subsidiaries Associates And Joint Ventures

us-gaap:InvestmentsInAffiliatesSubsidiariesAssociatesAndJointVentures us-gaap:BalanceSheetLocation

us-gaap:InvestmentsInAffiliatesSubsidiariesAssociatesAndJointVentures

us-gaap:OtherNoncurrentAssets


Investments
Period End2021-06-302021-03-312020-12-31
Value116116105
Percentage of InvestmentsInAffiliatesSubsidiariesAssociatesAndJointVentures100.0100.0100.0
Percentage of Assets0.70.70.6
Percentage of Assets us-gaap:OtherNoncurrentAssets0.00.00.0

Goodwill

us-gaap:Goodwill

us-gaap:Goodwill


Goodwill
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312009-12-312008-12-31
Value107099414061441391432.12.02.02.02.02.02.0787774158157167167116711661166115212371227197196742.0
Percentage of Goodwill100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets6.05.88.41.71.61.60.10.10.10.10.10.10.00.60.60.61.21.21.21.27.67.77.87.98.99.02.22.51.60.0

us-gaap:Goodwill us-gaap:BusinessAcquisition

clf:AKSteel


Goodwillus-gaap:
Period End2021-03-312020-12-312020-03-13
Value174174141
Percentage of Goodwill17.512.40.0
Percentage of Assets1.01.00.0
Percentage of Assets clf:AKSteel0.00.00.0

clf:AKSteelHoldingCorporation


Goodwillus-gaap:
Period End2020-09-302020-06-302020-03-31
Value141137141
Percentage of Goodwill98.598.598.5
Percentage of Assets1.71.61.6
Percentage of Assets clf:AKSteelHoldingCorporation0.00.00.0

clf:ArcelorMittalUSA


Goodwillus-gaap:
Period End2021-06-302021-03-312020-12-312020-12-09
Value89481812301230
Percentage of Goodwill83.682.387.50.0
Percentage of Assets5.04.87.30.0
Percentage of Assets clf:ArcelorMittalUSA0.00.00.00.0

us-gaap:Goodwill us-gaap:StatementBusinessSegments

clf:SteelandManufacturing


Goodwillus-gaap:
Period End2020-09-302020-06-302020-03-31
Value141137141
Percentage of Goodwill98.598.598.5
Percentage of Assets1.71.61.6
Percentage of Assets clf:SteelandManufacturing0.00.02.2

clf:Steelmaking


Goodwillus-gaap:
Period End2021-06-302021-03-312020-12-312019-12-31
Value89682012322.0
Percentage of Goodwill83.782.587.695.2
Percentage of Assets5.04.87.30.1
Percentage of Assets clf:Steelmaking0.00.00.00.0

Intangible Assets Net Excluding Goodwill

us-gaap:IntangibleAssetsNetExcludingGoodwill

us-gaap:IntangibleAssetsNetExcludingGoodwill


Intangible
Period End2020-09-302020-06-302020-03-312019-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312009-12-31
Value19019221048110115124129133137143147149159171175114
Percentage of IntangibleAssetsNetExcludingGoodwill100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets2.22.32.41.40.80.80.91.00.90.91.01.01.11.21.92.32.5

Finite Lived Intangible Assets Net

us-gaap:FiniteLivedIntangibleAssetsNet

us-gaap:FiniteLivedIntangibleAssetsNet


Finite
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312009-12-31
Value1831851881901922105353545557585860616277919395110115124129133137143147149159171175114
Percentage of FiniteLivedIntangibleAssetsNet100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets1.01.11.12.22.32.42.82.83.13.03.02.72.62.32.32.01.60.70.70.70.80.80.91.00.90.91.01.01.11.21.92.32.5

us-gaap:FiniteLivedIntangibleAssetsNet us-gaap:FiniteLivedIntangibleAssetsByMajorClass

clf:MiningPermits


Finite
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-31
Value47474747474748
Percentage of FiniteLivedIntangibleAssetsNet25.725.425.025.024.822.80.0
Percentage of Assets0.30.30.30.60.60.51.4
Percentage of Assets clf:MiningPermits0.00.00.00.00.00.00.0

us-gaap:CustomerRelationships


Finite
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-31
Value717274747590
Percentage of FiniteLivedIntangibleAssetsNet38.838.939.439.139.243.1
Percentage of Assets0.40.40.40.90.91.0
Percentage of Assets us-gaap:CustomerRelationships0.00.00.00.00.00.0

us-gaap:TechnologyBasedIntangibleAssets


Finite
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-31
Value555657575860
Percentage of FiniteLivedIntangibleAssetsNet30.130.330.330.530.528.9
Percentage of Assets0.30.30.30.70.70.7
Percentage of Assets us-gaap:TechnologyBasedIntangibleAssets0.00.00.00.00.00.0

us-gaap:TradeNames


Finite
Period End2020-12-31
Value10.0
Percentage of FiniteLivedIntangibleAssetsNet5.3
Percentage of Assets0.1
Percentage of Assets us-gaap:TradeNames0.0

us-gaap:TrademarksAndTradeNames


Finite
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-31
Value10.010.010.0101010
Percentage of FiniteLivedIntangibleAssetsNet5.55.45.35.45.55.2
Percentage of Assets0.10.10.10.10.10.1
Percentage of Assets us-gaap:TrademarksAndTradeNames0.00.00.00.00.00.0

Deferred Tax Assets Liabilities Net

us-gaap:DeferredTaxAssetsLiabilitiesNet

us-gaap:DeferredTaxAssetsLiabilitiesNet


Deferred
Period End2020-12-312019-12-312018-12-312017-12-312016-12-312015-12-312014-12-312013-12-312012-12-312011-12-312010-12-312009-12-31
Value4924594640.00.00.0124-1074.5-1006.6-831.078142
Percentage of DeferredTaxAssetsLiabilitiesNet100.0100.0100.00.00.00.0100.0100.0100.0100.0100.0100.0
Percentage of Assets2.913.113.20.00.00.03.9-8.2-7.4-5.71.03.1

Operating Lease Right Of Use Asset

us-gaap:OperatingLeaseRightOfUseAsset

us-gaap:OperatingLeaseRightOfUseAsset


Operating
Period End2020-09-302020-06-302020-03-312019-12-31
Value20721323811
Percentage of OperatingLeaseRightOfUseAsset100.0100.0100.0100.0
Percentage of Assets2.42.52.70.3

Other Assets Noncurrent

us-gaap:OtherAssetsNoncurrent

us-gaap:OtherAssetsNoncurrent


Other
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312009-12-31
Value78778478724024521515411411811394121117109122138122117114837884931431501311432424334444081961952001931702121861912222301964592
Percentage of OtherAssetsNoncurrent100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets4.44.64.72.82.92.44.43.33.53.42.73.93.93.84.17.26.06.16.04.74.34.54.46.35.74.84.55.03.33.43.11.41.41.51.41.11.41.31.31.61.72.20.62.0

Accounts Payable Current

us-gaap:AccountsPayableCurrent

us-gaap:AccountsPayableCurrent


Accounts
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312009-12-31
Value1665174315757105048251932121881711861401199912710211191107819177106102140114272295266329345350306299555422385394380370306266266178
Percentage of AccountsPayableCurrent100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets9.410.19.48.45.99.35.56.15.55.25.34.53.93.54.35.35.54.75.64.65.04.15.04.55.44.28.66.12.02.52.62.62.32.24.12.82.52.62.62.72.23.03.43.9

us-gaap:AccountsPayableCurrent dei:LegalEntity, us-gaap:ConsolidatedEntities

clf:SunCokeMiddletown, us-gaap:VariableInterestEntityPrimaryBeneficiary


Accounts
Period End2021-06-302021-03-312020-12-312020-09-302020-06-30
Value11121510.05.6
Percentage of AccountsPayableCurrent0.70.71.01.41.1
Percentage of Assets0.10.10.10.10.1
Percentage of Assets clf:SunCokeMiddletown us-gaap:VariableInterestEntityPrimaryBeneficiary0.00.00.00.00.0

Accrued Liabilities Current

us-gaap:AccruedLiabilitiesCurrent

us-gaap:AccruedLiabilitiesCurrent


Accrued
Period End2020-09-302020-06-302020-03-312019-12-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312009-12-31
Value27928829912615895859433109112102411341411118514917516725532533836320640442547025848540238016535936125713677
Percentage of AccruedLiabilitiesCurrent100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets3.33.43.43.64.53.02.83.31.15.75.65.32.17.67.65.94.06.66.76.28.16.82.62.81.63.03.13.41.93.22.62.61.12.62.62.91.81.7

Contract With Customer Liability Current

us-gaap:ContractWithCustomerLiabilityCurrent us-gaap:BalanceSheetLocation

us-gaap:ContractWithCustomerLiabilityCurrent

us-gaap:OtherCurrentLiabilities


Contract
Period End2020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-01-012017-12-31
Value7.02.34.90.32218151821162323
Percentage of ContractWithCustomerLiabilityCurrent100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets0.00.00.10.00.60.50.50.50.60.50.80.8
Percentage of Assets us-gaap:OtherCurrentLiabilities0.00.00.00.00.00.00.00.00.00.00.00.0

Dividends Payable Current

us-gaap:DividendsPayableCurrent

us-gaap:DividendsPayableCurrent


Dividends
Period End2020-09-302020-06-302020-03-312019-12-312018-12-31
Value1.01.1241715
Percentage of DividendsPayableCurrent100.0100.0100.0100.0100.0
Percentage of Assets0.00.00.30.50.4

Liabilities Current

us-gaap:LiabilitiesCurrent

us-gaap:LiabilitiesCurrent


Liabilities
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312009-12-31
Value2986293329291214103813704094584373944683804744244524174133093913233764395816697588469581118103710431085106011541101138117141534138414931299119111071028570
Percentage of LiabilitiesCurrent100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets16.817.017.514.312.215.411.713.112.911.913.312.215.614.815.321.720.416.120.318.220.323.327.229.529.131.330.323.27.97.98.37.88.58.010.211.210.19.310.39.38.712.413.212.3

Long Term Debt Current

us-gaap:LongTermDebtCurrent

us-gaap:LongTermDebtCurrent


Long
Period End2020-12-312015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-31
Value340.00.02123416196207.90.00.0943693698774
Percentage of LongTermDebtCurrent100.00.00.0100.0100.0100.0100.0100.0100.00.00.0100.0100.0100.0100.0100.0
Percentage of Assets0.20.00.00.74.91.20.70.20.10.00.00.72.42.40.60.5

Operating Lease Liability Current

us-gaap:OperatingLeaseLiabilityCurrent

us-gaap:OperatingLeaseLiabilityCurrent


Operating
Period End2020-12-31
Value53
Percentage of OperatingLeaseLiabilityCurrent100.0
Percentage of Assets0.3

Other Accrued Liabilities Current

us-gaap:OtherAccruedLiabilitiesCurrent

us-gaap:OtherAccruedLiabilitiesCurrent


Other
Period End2020-09-302020-06-302020-03-312019-12-312018-12-31
Value5061699.414
Percentage of OtherAccruedLiabilitiesCurrent100.0100.0100.0100.0100.0
Percentage of Assets0.60.70.80.30.4

Other Liabilities Current

us-gaap:OtherLiabilitiesCurrent

us-gaap:OtherLiabilitiesCurrent


Other
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312009-12-31
Value62057459622424424552121115113836166104561251089591102137138872352463001502622722532031882062262251972041751481851781318059
Percentage of OtherLiabilitiesCurrent100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets3.53.33.62.62.92.81.53.53.43.42.42.02.23.61.96.55.35.04.85.87.47.44.110.49.411.14.85.52.11.91.51.41.51.61.71.31.31.21.01.31.31.51.01.3

Taxes Payable Current

us-gaap:TaxesPayableCurrent

us-gaap:TaxesPayableCurrent


Taxes
Period End2020-12-312019-12-312018-12-312018-01-012017-12-312016-12-312015-12-312014-12-312013-12-312012-12-31
Value147373530302835526165
Percentage of TaxesPayableCurrent100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets0.91.11.01.01.01.51.61.70.50.5

Long Term Debt

us-gaap:LongTermDebt

us-gaap:LongTermDebt


Long
Period End2020-12-312017-12-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302012-12-31
Value54242304219221952489249926992721288728802984324734543291304333274054
Percentage of LongTermDebt100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets32.378.0114.0123.9134.5132.5126.4119.8110.7106.694.367.526.424.923.224.529.9

us-gaap:LongTermDebt dei:LegalEntity, us-gaap:DebtInstrument

clf:AKSteel, clf:A63752025AKSeniorNotes


Long
Period End2020-12-31
Value27
Percentage of LongTermDebt0.5
Percentage of Assets0.2
Percentage of Assets clf:AKSteel clf:A63752025AKSeniorNotes0.0

clf:AKSteel, clf:A7.502023AKSeniorNotes


Long
Period End2020-12-31
Value13
Percentage of LongTermDebt0.2
Percentage of Assets0.1
Percentage of Assets clf:AKSteel clf:A7.502023AKSeniorNotes0.0

clf:AKSteel, clf:A7.6252021AKSeniorNotes


Long
Period End2020-12-31
Value34
Percentage of LongTermDebt0.6
Percentage of Assets0.2
Percentage of Assets clf:AKSteel clf:A7.6252021AKSeniorNotes0.0

clf:AKSteel, clf:A7002027AKSeniorNotes


Long
Period End2021-06-302021-03-312020-12-31
Value515050
Percentage of LongTermDebt0.00.00.9
Percentage of Assets0.30.30.3
Percentage of Assets clf:AKSteel clf:A7002027AKSeniorNotes0.00.00.0

clf:AKSteel, clf:A76252021AKSeniorNotes


Long
Period End2020-12-31
Value34
Percentage of LongTermDebt0.6
Percentage of Assets0.2
Percentage of Assets clf:AKSteel clf:A76252021AKSeniorNotes0.0

clf:AKSteelHoldingCorporation, clf:A6.3752025AKSeniorNotes


Long
Period End2020-09-302020-06-302020-03-31
Value353535
Percentage of LongTermDebt0.00.00.0
Percentage of Assets0.40.40.4
Percentage of Assets clf:AKSteelHoldingCorporation clf:A6.3752025AKSeniorNotes0.00.00.0

clf:AKSteelHoldingCorporation, clf:A7.002027AKSeniorNotes


Long
Period End2020-09-302020-06-302020-03-31
Value505049
Percentage of LongTermDebt0.00.00.0
Percentage of Assets0.60.60.6
Percentage of Assets clf:AKSteelHoldingCorporation clf:A7.002027AKSeniorNotes0.00.00.0

clf:AKSteelHoldingCorporation, clf:IndustrialRevenueBonds


Long
Period End2020-09-302020-06-302020-03-31
Value9494101
Percentage of LongTermDebt0.00.00.0
Percentage of Assets1.11.11.1
Percentage of Assets clf:AKSteelHoldingCorporation clf:IndustrialRevenueBonds0.00.00.0

clf:ClevelandCliffsInc., clf:A1.502025ConvertibleSeniorNotes


Long
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-31
Value248246243239236249246
Percentage of LongTermDebt0.00.04.50.00.00.00.0
Percentage of Assets1.41.41.42.82.82.87.0
Percentage of Assets clf:ClevelandCliffsInc. clf:A1.502025ConvertibleSeniorNotes0.00.00.00.00.00.00.0

clf:ClevelandCliffsInc., clf:A4.8752024SeniorSecuredNotes


Long
Period End2020-12-312020-09-302020-06-302020-03-312019-12-31
Value391389388394393
Percentage of LongTermDebt7.20.00.00.00.0
Percentage of Assets2.34.64.64.411.2
Percentage of Assets clf:ClevelandCliffsInc. clf:A4.8752024SeniorSecuredNotes0.00.00.00.00.0

clf:ClevelandCliffsInc., clf:A46252029SeniorNotes


Long
Period End2021-06-302021-03-31
Value492491
Percentage of LongTermDebt0.00.0
Percentage of Assets2.82.9
Percentage of Assets clf:ClevelandCliffsInc. clf:A46252029SeniorNotes0.00.0

clf:ClevelandCliffsInc., clf:A48752024SeniorSecuredNotes


Long
Period End2020-12-312019-12-31
Value391393
Percentage of LongTermDebt7.20.0
Percentage of Assets2.311.2
Percentage of Assets clf:ClevelandCliffsInc. clf:A48752024SeniorSecuredNotes0.00.0

clf:ClevelandCliffsInc., clf:A5.752025SeniorNotes


Long
Period End2021-03-312020-12-312020-09-302020-06-302020-03-312019-12-31
Value390389389389464464
Percentage of LongTermDebt0.07.20.00.00.00.0
Percentage of Assets2.32.34.64.65.213.2
Percentage of Assets clf:ClevelandCliffsInc. clf:A5.752025SeniorNotes0.00.00.00.00.00.0

clf:ClevelandCliffsInc., clf:A5.8752027SeniorNotes


Long
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-31
Value535535534532532717716
Percentage of LongTermDebt0.00.09.80.00.00.00.0
Percentage of Assets3.03.13.26.36.38.020.4
Percentage of Assets clf:ClevelandCliffsInc. clf:A5.8752027SeniorNotes0.00.00.00.00.00.00.0

clf:ClevelandCliffsInc., clf:A6.252040SeniorNotes


Long
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-31
Value258258258258258293292
Percentage of LongTermDebt0.00.04.80.00.00.00.0
Percentage of Assets1.51.51.53.03.03.38.4
Percentage of Assets clf:ClevelandCliffsInc. clf:A6.252040SeniorNotes0.00.00.00.00.00.00.0

clf:ClevelandCliffsInc., clf:A6.3752025SeniorNotes


Long
Period End2020-12-312020-09-302020-06-302020-03-31
Value605959213
Percentage of LongTermDebt1.10.00.00.0
Percentage of Assets0.40.70.72.4
Percentage of Assets clf:ClevelandCliffsInc. clf:A6.3752025SeniorNotes0.00.00.00.0

clf:ClevelandCliffsInc., clf:A6.752026SeniorSecuredNotes


Long
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-31
Value819818816814813695
Percentage of LongTermDebt0.00.015.00.00.00.0
Percentage of Assets4.64.84.99.69.67.8
Percentage of Assets clf:ClevelandCliffsInc. clf:A6.752026SeniorSecuredNotes0.00.00.00.00.00.0

clf:ClevelandCliffsInc., clf:A6752026SeniorSecuredNotes


Long
Period End2020-12-31
Value816
Percentage of LongTermDebt15.0
Percentage of Assets4.9
Percentage of Assets clf:ClevelandCliffsInc. clf:A6752026SeniorSecuredNotes0.0

clf:ClevelandCliffsInc., clf:A7.002027SeniorNotes


Long
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-31
Value6666657877295
Percentage of LongTermDebt0.00.01.20.00.00.0
Percentage of Assets0.40.40.40.90.93.3
Percentage of Assets clf:ClevelandCliffsInc. clf:A7.002027SeniorNotes0.00.00.00.00.00.0

clf:ClevelandCliffsInc., clf:A9.8752025SeniorSecuredNotes


Long
Period End2020-09-302020-06-30
Value921919
Percentage of LongTermDebt0.00.0
Percentage of Assets10.910.8
Percentage of Assets clf:ClevelandCliffsInc. clf:A9.8752025SeniorSecuredNotes0.00.0

clf:ClevelandCliffsInc., clf:A98752025SeniorSecuredNotes


Long
Period End2021-06-302021-03-312020-12-31
Value588612922
Percentage of LongTermDebt0.00.017.0
Percentage of Assets3.33.65.5
Percentage of Assets clf:ClevelandCliffsInc. clf:A98752025SeniorSecuredNotes0.00.00.0

us-gaap:LongTermDebt dei:LegalEntity, us-gaap:LongtermDebtType

clf:AKSteel, clf:IndustrialRevenueBonds


Long
Period End2020-12-31
Value94
Percentage of LongTermDebt1.7
Percentage of Assets0.6
Percentage of Assets clf:AKSteel clf:IndustrialRevenueBonds0.0

Long Term Debt Noncurrent

us-gaap:LongTermDebtNoncurrent

us-gaap:LongTermDebtNoncurrent


Long
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-31
Value5368573453904309445143572113210921042087209223002297230823041689161116422175219524892499269927212887288029623012329331943022331933233433396035143614358336083883389824121713
Percentage of LongTermDebtNoncurrent100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets30.233.332.150.852.448.960.360.462.063.159.373.675.380.678.087.879.485.3113.1123.9134.5132.5126.4119.8110.7106.693.662.625.124.223.024.524.424.829.223.023.824.124.827.828.526.922.0

Pension And Other Postretirement Defined Benefit Plans Liabilities Noncurrent

us-gaap:PensionAndOtherPostretirementDefinedBenefitPlansLiabilitiesNoncurrent

us-gaap:PensionAndOtherPostretirementDefinedBenefitPlansLiabilitiesNoncurrent


Pension
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312009-12-31
Value384139164113113011591171311233239244248225245251257254276279280198206213221209244250395230276285294556586600618603634635665462490494528445
Percentage of PensionAndOtherPostretirementDefinedBenefitPlansLiabilitiesNoncurrent100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets21.622.724.513.313.713.18.96.77.17.47.07.28.08.88.713.213.614.514.611.211.211.310.39.29.49.312.54.82.12.22.24.14.34.34.63.94.24.34.63.33.65.56.89.6

us-gaap:PensionAndOtherPostretirementDefinedBenefitPlansLiabilitiesNoncurrent us-gaap:RetirementPlanType

us-gaap:OtherPostretirementBenefitPlansDefinedBenefit


Pension
Period End2020-12-312019-12-312018-12-312017-12-312016-12-31
Value288939303434
Percentage of PensionAndOtherPostretirementDefinedBenefitPlansLiabilitiesNoncurrent70.212.812.213.512.4
Percentage of Assets17.21.10.91.21.8
Percentage of Assets us-gaap:OtherPostretirementBenefitPlansDefinedBenefit0.00.00.00.00.0

us-gaap:PensionPlansDefinedBenefit


Pension
Period End2020-12-312019-12-312018-12-312017-12-312016-12-31
Value1224271218222245
Percentage of PensionAndOtherPostretirementDefinedBenefitPlansLiabilitiesNoncurrent29.887.287.886.587.6
Percentage of Assets7.37.86.27.512.8
Percentage of Assets us-gaap:PensionPlansDefinedBenefit0.00.00.00.00.0

Minority Interest

us-gaap:MinorityInterest

us-gaap:MinorityInterest


Minority
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312009-12-31
Value3083303233133253270.00.00.00.00.20.20.2122127133143151162169172183213-303.0-208.08028168141154115211541128135213121293125411289730.97.25.8
Percentage of MinorityInterest100.0100.0100.0100.0100.0100.00.00.00.00.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets1.71.91.93.73.83.70.00.00.00.00.00.00.06.06.67.08.18.28.68.07.67.07.9-9.6-4.36.16.26.28.58.58.48.38.88.68.78.68.17.10.00.10.1

us-gaap:MinorityInterest dei:LegalEntity, us-gaap:ConsolidatedEntities

clf:SunCokeMiddletown, us-gaap:VariableInterestEntityPrimaryBeneficiary


Minority
Period End2021-06-302021-03-312020-12-312020-09-302020-06-30
Value307319309312324
Percentage of MinorityInterest99.796.795.799.899.8
Percentage of Assets1.71.91.83.73.8
Percentage of Assets clf:SunCokeMiddletown us-gaap:VariableInterestEntityPrimaryBeneficiary0.00.00.00.00.0

Other Liabilities Noncurrent

us-gaap:OtherLiabilitiesNoncurrent

us-gaap:OtherLiabilitiesNoncurrent


Other
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312009-12-31
Value127211751260280278263146151149145115121158182186189193199213235240216213218244216274296326347379395412473492318330371338273328248256212
Percentage of OtherLiabilitiesNoncurrent100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets7.26.87.53.33.33.04.24.34.44.43.33.95.26.46.39.99.510.311.113.313.011.510.09.69.48.08.76.22.52.62.92.93.03.43.62.12.22.52.32.02.42.83.34.6

Operating Lease Liability Noncurrent

us-gaap:OperatingLeaseLiabilityNoncurrent

us-gaap:OperatingLeaseLiabilityNoncurrent


Operating
Period End2020-12-312020-09-302020-06-302020-03-312019-12-31
Value21117419120110
Percentage of OperatingLeaseLiabilityNoncurrent100.0100.0100.0100.0100.0
Percentage of Assets1.32.12.32.30.3

Operating Lease Liability

us-gaap:OperatingLeaseLiability

us-gaap:OperatingLeaseLiability


Operating
Period End2020-12-31
Value264
Percentage of OperatingLeaseLiability100.0
Percentage of Assets1.6

Lessee Operating Lease Liability Payments Due

us-gaap:LesseeOperatingLeaseLiabilityPaymentsDue

us-gaap:LesseeOperatingLeaseLiabilityPaymentsDue


Lessee
Period End2020-12-31
Value363
Percentage of LesseeOperatingLeaseLiabilityPaymentsDue100.0
Percentage of Assets2.2

Lessee Operating Lease Liability Undiscounted Excess Amount

us-gaap:LesseeOperatingLeaseLiabilityUndiscountedExcessAmount

us-gaap:LesseeOperatingLeaseLiabilityUndiscountedExcessAmount


Lessee
Period End2020-12-31
Value99
Percentage of LesseeOperatingLeaseLiabilityUndiscountedExcessAmount100.0
Percentage of Assets0.6

Stockholders Equity

us-gaap:StockholdersEquity

us-gaap:StockholdersEquity


Stockholders
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312009-12-31
Value323323892018810792903357359285261424-86.2-306.3-485.0-444.3-833.3-789.1-830.1-1464.3-1544.3-1830.7-1859.4-1981.4-1932.0-1923.8-1995.7-1431.3306027601960695779563157044632633662956140578557235546427338452542
Percentage of StockholdersEquity100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets18.213.912.09.69.310.110.210.38.47.912.0-2.8-10.0-16.9-15.0-43.3-38.9-43.1-76.1-87.1-98.9-98.6-92.8-85.1-73.7-73.8-45.20.646.045.646.342.641.441.334.141.441.441.239.841.040.647.749.454.8

Stockholders Equity Including Portion Attributable To Noncontrolling Interest

us-gaap:StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest

us-gaap:StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest


Stockholders
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312009-12-312008-12-312007-12-31
Value354127192341112311181231357359285261424-86.2-306.3-484.8-444.1-833.1-666.7-703.0-1330.5-1400.5-1678.9-1696.7-1811.6-1759.5-1740.2-1782.1-1734.3-177.3682968356884693467836859576076897607743370396851652042733838253717531281
Percentage of StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets20.015.814.013.213.213.810.210.38.47.912.0-2.8-10.0-16.9-15.0-43.3-32.8-36.5-69.2-79.0-90.7-89.9-84.8-77.5-66.7-65.9-54.8-3.752.151.852.551.149.949.642.450.350.149.948.449.147.747.749.454.70.00.0

us-gaap:StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest us-gaap:StatementEquityComponents

us-gaap:AccumulatedOtherComprehensiveIncome


Stockholders
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312013-12-312012-12-312011-12-312010-12-312009-12-312008-12-312007-12-31
Value-66.0-120.0-133.0-282.0-305.9-317.1-318.8-265.6-271.8-275.5-283.9-243.4-22.2-31.3-39.0-30.8-19.4-24.3-21.3-1.2-9.0-12.3-18.0-25.1-28.9-38.2-245.8-112.9-55.6-92.645-122.6-394.6-30.3
Percentage of StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest-1.9-4.4-5.7-25.1-27.4-25.8-89.1-73.8-95.2-105.3-66.9282.47.26.58.83.72.93.51.60.10.50.71.01.41.72.114.2-1.6-1.0-1.31.2-4.8-22.5-2.4
Percentage of Assets-0.4-0.7-0.8-3.3-3.6-3.6-9.1-7.6-8.0-8.3-8.0-7.8-0.7-1.1-1.3-1.6-1.0-1.3-1.1-0.1-0.5-0.7-0.8-1.1-1.1-1.4-7.8-0.9-0.4-0.60.6-2.60.00.0
Percentage of Assets us-gaap:AccumulatedOtherComprehensiveIncome0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:AdditionalPaidInCapital


Stockholders
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312016-12-312015-12-312014-12-312013-12-312012-12-312011-12-312010-12-312009-12-312008-12-312007-12-31
Value549154875431444644434450387238673863386039163913391839183933334722982309232917741770896695442116
Percentage of StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest155.1201.8232.0395.7397.4361.51081.91074.71352.81475.0923.3-4539.8-1279.2-808.2-885.8-251.6-126.9-133.233.830.825.223.327.425.29.1
Percentage of Assets30.931.932.452.452.349.9110.5110.8113.9116.8111.0125.2128.4136.9133.2174.0107.773.017.813.112.211.515.00.00.0
Percentage of Assets us-gaap:AdditionalPaidInCapital0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:CommonStock


Stockholders
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312016-12-312015-12-312014-12-312013-12-312012-12-312011-12-312010-12-312009-12-312008-12-312007-12-31
Value63636353535337373737373737373729191919181817161616
Percentage of StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest1.82.32.74.84.84.410.510.513.214.48.9-43.7-12.3-7.8-8.5-2.2-1.1-1.10.30.30.30.50.71.01.3
Percentage of Assets0.40.40.40.60.60.61.11.11.11.11.11.21.21.31.31.50.90.60.20.10.10.20.40.00.0
Percentage of Assets us-gaap:CommonStock0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:NoncontrollingInterest


Stockholders
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312018-12-312018-09-302018-06-302018-03-312017-12-312016-12-312015-12-312014-12-312013-12-312012-12-312012-06-302012-03-312011-12-312011-06-302011-03-312010-12-312009-12-312008-12-312007-12-31
Value3083303233133253270.00.00.00.00.20.2133169-303.081411281312129312549730.9-7.2-5.83.3117
Percentage of StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest8.712.113.827.929.126.60.00.0-0.0-0.0-0.0-0.0-10.1-9.417.511.819.617.317.417.814.90.0-0.2-0.20.29.2
Percentage of Assets1.71.91.93.73.83.70.00.00.00.00.00.07.08.0-9.66.28.38.68.78.67.10.0-0.1-0.10.00.0
Percentage of Assets us-gaap:NoncontrollingInterest0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:RetainedEarnings


Stockholders
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312016-12-312015-12-312014-12-312013-12-312012-12-312011-12-312010-12-312009-12-312008-12-312007-12-31
Value-2168.0-2948.0-2989.0-3052.5-3042.5-2918.5-2842.4-2889.0-2952.6-3096.8-3060.2-3654.7-4092.5-4257.6-4207.3-4574.3-4748.4-3960.73407321744242924197317991316
Percentage of StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest-61.2-108.4-127.7-271.6-272.1-237.1-794.2-802.7-1033.8-1183.3-721.44239.81336.1878.2947.4343.8262.1228.449.555.962.876.277.8102.6102.7
Percentage of Assets-12.2-17.1-17.8-36.0-35.8-32.7-81.1-82.8-87.0-93.7-86.7-117.0-134.1-148.7-142.5-237.8-222.4-125.226.023.730.437.642.50.00.0
Percentage of Assets us-gaap:RetainedEarnings0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:TreasuryStock


Stockholders
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312016-12-312015-12-312014-12-312013-12-312012-12-312011-12-312010-12-312009-12-312008-12-312007-12-31
Value-87.0-93.0-354.0-354.8-355.9-365.0-390.7-390.9-391.3-263.9-186.1-139.1-147.6-151.9-169.6-245.5-265.0-285.7-305.5-322.6-336.0-37.7-19.9-113.8-255.6
Percentage of StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest-2.5-3.4-15.1-31.6-31.8-29.7-109.2-108.6-137.0-100.8-43.9161.448.231.338.218.514.616.5-4.4-5.6-4.8-1.0-0.8-6.5-19.9
Percentage of Assets-0.5-0.5-2.1-4.2-4.2-4.1-11.2-11.2-11.5-8.0-5.3-4.5-4.8-5.3-5.7-12.8-12.4-9.0-2.3-2.4-2.3-0.5-0.40.00.0
Percentage of Assets us-gaap:TreasuryStock0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

Additional Paid In Capital

us-gaap:AdditionalPaidInCapital

us-gaap:AdditionalPaidInCapital


Additional
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312009-12-31
Value54915487543144464443445038723867386338603916391339183918393339133999400033473336303730322298230723042308230923122318232123292029202420201774176617591755177017661760903896695
Percentage of AdditionalPaidInCapital100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets30.931.932.452.452.349.9110.5110.8113.9116.8111.0125.2128.4136.9133.2203.5197.0207.7174.0188.2164.1160.8107.7101.688.385.473.048.117.717.617.815.014.914.613.111.511.611.812.212.712.910.111.515.0

Retained Earnings Accumulated Deficit

us-gaap:RetainedEarningsAccumulatedDeficit

us-gaap:RetainedEarningsAccumulatedDeficit


Retained
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312009-12-31
Value-2168.0-2948.0-2989.0-3052.5-3042.5-2918.5-2842.4-2889.0-2952.6-3096.8-3060.2-3654.7-4092.5-4257.6-4207.3-4517.2-4570.6-4602.4-4574.3-4653.4-4627.4-4640.4-4748.4-4688.1-4673.1-4733.2-3960.7-2639.63276330034073483340132913217492549294760442442663717332829241973
Percentage of RetainedEarningsAccumulatedDeficit100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets-12.2-17.1-17.8-36.0-35.8-32.7-81.1-82.8-87.0-93.7-86.7-117.0-134.1-148.7-142.5-234.9-225.1-239.0-237.8-262.5-250.0-246.0-222.4-206.4-179.1-175.1-125.2-54.925.025.026.025.725.023.823.732.232.432.030.430.627.237.237.642.5

Accumulated Other Comprehensive Income Loss Net Of Tax

us-gaap:AccumulatedOtherComprehensiveIncomeLossNetOfTax

us-gaap:AccumulatedOtherComprehensiveIncomeLossNetOfTax


Accumulated
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312009-12-312008-12-31
Value-66.0-120.0-133.0-282.0-305.9-317.1-318.8-265.6-271.8-275.5-283.9-243.4-22.2-31.3-39.0-30.8-19.4-24.3-21.3-1.2-9.0-12.3-18.0-25.1-28.9-38.2-245.8-101.4-20.2-55.1-112.9-178.4-239.6-51.4-55.6-51.0-89.9-70.9-92.6-59.3957045-122.6-394.6
Percentage of AccumulatedOtherComprehensiveIncomeLossNetOfTax100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets-0.4-0.7-0.8-3.3-3.6-3.6-9.1-7.6-8.0-8.3-8.0-7.8-0.7-1.1-1.3-1.6-1.0-1.3-1.1-0.1-0.5-0.7-0.8-1.1-1.1-1.4-7.8-2.1-0.2-0.4-0.9-1.3-1.8-0.4-0.4-0.3-0.6-0.5-0.6-0.40.70.80.6-2.60.0

us-gaap:AccumulatedOtherComprehensiveIncomeLossNetOfTax us-gaap:StatementEquityComponents

us-gaap:AccumulatedDefinedBenefitPlansAdjustmentIncludingPortionAttributableToNoncontrollingInterest


Accumulated
Period End2021-06-302021-03-312020-12-312020-06-302020-03-312019-12-312018-12-312017-12-31
Value-121.0-128.0-135.0-304.0-310.0-316.0-281.0264
Percentage of AccumulatedOtherComprehensiveIncomeLossNetOfTax183.3106.7101.599.497.899.199.0-676.9
Percentage of Assets-0.7-0.7-0.8-3.6-3.5-9.0-8.08.9
Percentage of Assets us-gaap:AccumulatedDefinedBenefitPlansAdjustmentIncludingPortionAttributableToNoncontrollingInterest0.00.00.00.00.00.00.00.0

us-gaap:AccumulatedForeignCurrencyAdjustmentIncludingPortionAttributableToNoncontrollingInterest


Accumulated
Period End2021-06-302021-03-312020-12-312020-03-312017-12-31
Value2.02.03.0-1.0225
Percentage of AccumulatedOtherComprehensiveIncomeLossNetOfTax-3.0-1.7-2.30.3-576.9
Percentage of Assets0.00.00.0-0.07.6
Percentage of Assets us-gaap:AccumulatedForeignCurrencyAdjustmentIncludingPortionAttributableToNoncontrollingInterest0.00.00.00.00.0

us-gaap:AccumulatedGainLossCashFlowHedgeIncludingNoncontrollingInterest


Accumulated
Period End2021-06-302021-03-312020-12-312020-06-302020-03-312019-12-312018-12-31
Value536.0-1.0-2.0-6.0-3.0-3.0
Percentage of AccumulatedOtherComprehensiveIncomeLossNetOfTax-80.3-5.00.80.71.90.91.1
Percentage of Assets0.30.0-0.0-0.0-0.1-0.1-0.1
Percentage of Assets us-gaap:AccumulatedGainLossCashFlowHedgeIncludingNoncontrollingInterest0.00.00.00.00.00.00.0

Treasury Stock Value

us-gaap:TreasuryStockValue

us-gaap:TreasuryStockValue


Treasury
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312009-12-31
Value879335435435536539039039126318613914715116923623624124525525526226527727728328529129729830530630630732232232232333626846463719
Percentage of TreasuryStockValue100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets0.50.52.14.24.24.111.211.211.58.05.34.54.85.35.712.311.612.512.814.413.813.912.412.210.610.59.06.12.32.32.32.32.32.22.42.12.12.22.31.90.30.50.50.4

Minority Interest

us-gaap:MinorityInterest

us-gaap:MinorityInterest


Minority
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312009-12-31
Value3083303233133253270.00.00.00.00.20.20.2122127133143151162169172183213-303.0-208.08028168141154115211541128135213121293125411289730.97.25.8
Percentage of MinorityInterest100.0100.0100.0100.0100.0100.00.00.00.00.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets1.71.91.93.73.83.70.00.00.00.00.00.00.06.06.67.08.18.28.68.07.67.07.9-9.6-4.36.16.26.28.58.58.48.38.88.68.78.68.17.10.00.10.1

us-gaap:MinorityInterest dei:LegalEntity, us-gaap:ConsolidatedEntities

clf:SunCokeMiddletown, us-gaap:VariableInterestEntityPrimaryBeneficiary


Minority
Period End2021-06-302021-03-312020-12-312020-09-302020-06-30
Value307319309312324
Percentage of MinorityInterest99.796.795.799.899.8
Percentage of Assets1.71.91.83.73.8
Percentage of Assets clf:SunCokeMiddletown us-gaap:VariableInterestEntityPrimaryBeneficiary0.00.00.00.00.0

Stock Issued During Period Value New Issues

us-gaap:StockIssuedDuringPeriodValueNewIssues

us-gaap:StockIssuedDuringPeriodValueNewIssues


Stock
Period End2021-03-312011-12-312011-09-30
Value3220.00.0
Percentage of StockIssuedDuringPeriodValueNewIssues100.00.00.0
Percentage of Assets0.00.00.0

us-gaap:StockIssuedDuringPeriodValueNewIssues us-gaap:StatementEquityComponents

us-gaap:AdditionalPaidInCapital


Stock
Period End2021-03-31
Value78
Percentage of StockIssuedDuringPeriodValueNewIssues24.2
Percentage of Assets0.0
Percentage of Assets us-gaap:AdditionalPaidInCapital0.0

us-gaap:TreasuryStock


Stock
Period End2021-03-31
Value244
Percentage of StockIssuedDuringPeriodValueNewIssues75.8
Percentage of Assets0.0
Percentage of Assets us-gaap:TreasuryStock0.0

Adjustments To Additional Paid In Capital Sharebased Compensation Requisite Service Period Recognition Value

us-gaap:AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue us-gaap:StatementEquityComponents

us-gaap:AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue

us-gaap:AdditionalPaidInCapital


Adjustments
Period End2021-06-302021-03-312020-06-302020-03-31
Value4.0-22.0-7.0-24.0
Percentage of AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue100.0100.0100.0100.0
Percentage of Assets0.00.00.00.0
Percentage of Assets us-gaap:AdditionalPaidInCapital0.00.00.00.0

Minority Interest Decrease From Distributions To Noncontrolling Interest Holders

us-gaap:MinorityInterestDecreaseFromDistributionsToNoncontrollingInterestHolders

us-gaap:MinorityInterestDecreaseFromDistributionsToNoncontrollingInterestHolders


Minority
Period End2021-06-302021-03-312020-09-302020-06-302020-03-312017-09-302016-12-312016-09-302016-06-302016-03-312015-12-31
Value248.024185.51328.77.42417-11.0
Percentage of MinorityInterestDecreaseFromDistributionsToNoncontrollingInterestHolders100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets0.00.00.00.00.00.00.00.00.00.00.0

us-gaap:MinorityInterestDecreaseFromDistributionsToNoncontrollingInterestHolders us-gaap:StatementEquityComponents

us-gaap:NoncontrollingInterest


Minority
Period End2021-06-302021-03-312020-09-302020-06-302020-03-312017-09-302016-12-312016-09-302016-06-302016-03-312015-12-31
Value248.024185.5-116.78.77.42417-11.0
Percentage of MinorityInterestDecreaseFromDistributionsToNoncontrollingInterestHolders100.0100.0100.0100.0100.0-87.9100.0100.0100.0100.0100.0
Percentage of Assets0.00.00.00.00.00.00.00.00.00.00.0
Percentage of Assets us-gaap:NoncontrollingInterest0.00.00.00.00.00.00.00.00.00.00.0

Net Cash Provided By Used In Operating Activities

us-gaap:NetCashProvidedByUsedInOperatingActivities

us-gaap:NetCashProvidedByUsedInOperatingActivities


Net
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-31
Value511-379.0-207.8246-138.7-160.5174237262-111.228923893-142.913113892-25.123091107-126.597188-20.0-228.2254227-41.9-82.0460297414-25.423930896-129.074382061810668939516174
Percentage of NetCashProvidedByUsedInOperatingActivities100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of RevenueFromRelatedParties1460.0-492.20.083.4-49.2-1486.10.080.763.1-270.60.060.722.9-230.10.052.340.8-21.20.040.944.4-122.30.090.7-13.4-206.70.058.4-13.0-37.80.065.291.1-8.80.064.820.7-38.90.0364.9696.834.10.00.00.00.0

Net Cash Provided By Used In Investing Activities

us-gaap:NetCashProvidedByUsedInInvestingActivities

us-gaap:NetCashProvidedByUsedInInvestingActivities


Net
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-31
Value-107.0-135.0-801.8-87.8-144.9-1007.5-194.9-157.1-166.8-125.6-99.4-73.9-28.4-71.4-71.6-36.1-20.9-27.4-18.4-25.2-9.4-4.9-46.0-23.2-18.3-15.7104-59.6-57.6-90.7-76.9-234.1-271.9-228.4-177.1-263.8-268.9-252.0-385.8-197.8-4683.4-37.4-75.1-935.4-155.0-202.2
Percentage of NetCashProvidedByUsedInInvestingActivities100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of RevenueFromRelatedParties-305.7-175.30.0-29.8-51.4-9328.70.0-53.5-40.1-305.60.0-18.8-6.9-115.00.0-13.6-9.2-23.10.0-11.3-3.9-4.70.0-11.2-12.2-14.20.0-15.3-17.9-41.80.0-51.4-59.8-79.10.0-55.4-57.8-75.90.0-88.0-5280.0-11.90.00.00.00.0

Net Cash Provided By Used In Financing Activities

us-gaap:NetCashProvidedByUsedInFinancingActivities

us-gaap:NetCashProvidedByUsedInFinancingActivities


Net
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-31
Value-441.05121064-176.91661005-27.2-59.0-150.1-157.8-267.5-82.0-18.7-7.0687-164.8-46.823-20.4-43.5-49.1-93.4-37.2-170.2-41.6310-305.7-273.392197-333.9-31.3-152.634592-164.4212-21.2-391.5-292.82032627-25.0964-26.5174
Percentage of NetCashProvidedByUsedInFinancingActivities100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of RevenueFromRelatedParties-1260.0664.90.0-60.058.99306.50.0-20.1-36.1-383.90.0-20.9-4.6-11.30.0-62.1-20.619.40.0-19.5-20.3-90.30.0-81.8-27.8280.80.0-70.128.891.20.0-6.9-33.5119.90.0-34.545.7-6.40.0-130.22290.9200.10.00.00.00.0

Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents Period Increase Decrease Including Exchange Rate Effect

us-gaap:CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect

us-gaap:CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect


Cash
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-30
Value-37000000.0-2000000.055200000.0-18700000.0-114500000.0-166000000.0-46700000.020900000.0
Percentage of CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of RevenueFromRelatedParties-105.7-2.60.0-6.3-40.6-1537.00.07.1

Deferred Income Tax Expense Benefit

us-gaap:DeferredIncomeTaxExpenseBenefit

us-gaap:DeferredIncomeTaxExpenseBenefit


Deferred
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-31
Value21510.0-11.1-17.4-25.0-47.5-5.94.522-4.1-460.50.00.00.00.0-0.2-2.6-3.2165-73.2-941.7-154.115-98.682-75.2-46.3479-93.3-10.7-248.5-52.5-90.06114-56.6162232
Percentage of DeferredIncomeTaxExpenseBenefit100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.00.00.00.00.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

Depreciation Depletion And Amortization

us-gaap:DepreciationDepletionAndAmortization

us-gaap:DepreciationDepletionAndAmortization


Depreciation
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-31
Value2082171247277342222211920192523212121232626263534353033731441451411551531441401431321321171241171057982848866
Percentage of DepreciationDepletionAndAmortization100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:DepreciationDepletionAndAmortization clf:EBITDACalculation

clf:EBITDACalculation


Depreciation
Period End2021-06-302021-03-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-30
Value20821772773422222119201925232121212326262635233-35.6-30.5-33.0-73.6-144.0-145.3-141.1-155.3-153.1
Percentage of DepreciationDepletionAndAmortization100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0667.9-100.0-100.0-100.0-100.0-100.0-100.0-100.0-100.0-100.0

Increase Decrease In Inventories

us-gaap:IncreaseDecreaseInInventories

us-gaap:IncreaseDecreaseInInventories


Increase
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-31
Value385172141-121.9-118.02446.9-1.7-93.7224-100.0-68.5-67.4193-24.3-80.53670-136.2-73.8-13.966-14.2-141.262154-167.0-122.537214-41.6-95.0-88.2194-110.3-195.546219-54.0-68.3-32.7229-46.0-90.25.569
Percentage of IncreaseDecreaseInInventories100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

Net Cash Provided By Used In Operating Activities

us-gaap:NetCashProvidedByUsedInOperatingActivities

us-gaap:NetCashProvidedByUsedInOperatingActivities


Net
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-31
Value511-379.0-207.8246-138.7-160.5174237262-111.228923893-142.913113892-25.123091107-126.597188-20.0-228.2254227-41.9-82.0460297414-25.423930896-129.074382061810668939516174
Percentage of NetCashProvidedByUsedInOperatingActivities100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of RevenueFromRelatedParties1460.0-492.20.083.4-49.2-1486.10.080.763.1-270.60.060.722.9-230.10.052.340.8-21.20.040.944.4-122.30.090.7-13.4-206.70.058.4-13.0-37.80.065.291.1-8.80.064.820.7-38.90.0364.9696.834.10.00.00.00.0

Net Income Loss

us-gaap:NetIncomeLoss

us-gaap:NetIncomeLoss


Net
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-312009-12-312009-09-302009-06-302009-03-31
Value7804164-10.0-123.9-52.16390160-22.1609437165-84.33095331-28.179-25.812108-60.31060-759.8-1285.1-5879.610-70.343117146107-1618.385258375185589407423384297260771085845-7.4
Percentage of NetIncomeLoss100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of RevenueFromRelatedParties2228.653.20.0-3.4-44.0-482.40.031.038.7-53.80.0111.640.3-135.70.020.114.0-23.70.0-11.55.3104.40.05.140.2-688.20.0-1507.63.4-32.40.025.732.137.10.017.955.4113.20.0262.1459.6135.00.00.00.00.00.00.00.00.0

us-gaap:NetIncomeLoss us-gaap:BusinessAcquisition

clf:AKSteelHoldingCorporation


Net
Period End2020-09-302020-06-302020-03-31
Value-30.4-206.5-55.1
Percentage of NetIncomeLoss304.0166.7105.8
Percentage of RevenueFromRelatedParties-10.3-73.30.0
Percentage of RevenueFromRelatedParties clf:AKSteelHoldingCorporation0.00.00.0

clf:ArcelorMittalUSA


Net
Period End2020-12-09
Value-40.0
Percentage of NetIncomeLoss0.0
Percentage of RevenueFromRelatedParties0.0
Percentage of RevenueFromRelatedParties clf:ArcelorMittalUSA0.0

Profit Loss

us-gaap:ProfitLoss

us-gaap:ProfitLoss


Profit
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-31
Value79557731.9-108.1-48.66390160-22.1609437165-84.33095230-29.880-27.829116-57.96.065-761.7-1368.2-6887.214-70.7-14.2113141120-1870.87827439122174142642338429726077
Percentage of ProfitLoss100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of RevenueFromRelatedParties2271.474.00.00.6-38.4-450.00.031.038.7-53.80.0111.640.3-135.70.019.913.2-25.10.0-12.412.2113.00.02.943.6-689.90.0-1765.94.5-32.60.025.031.141.90.016.558.9117.90.0329.6480.3135.00.00.00.00.0

Net Cash Provided By Used In Investing Activities

us-gaap:NetCashProvidedByUsedInInvestingActivities

us-gaap:NetCashProvidedByUsedInInvestingActivities


Net
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-31
Value-107.0-135.0-801.8-87.8-144.9-1007.5-194.9-157.1-166.8-125.6-99.4-73.9-28.4-71.4-71.6-36.1-20.9-27.4-18.4-25.2-9.4-4.9-46.0-23.2-18.3-15.7104-59.6-57.6-90.7-76.9-234.1-271.9-228.4-177.1-263.8-268.9-252.0-385.8-197.8-4683.4-37.4-75.1-935.4-155.0-202.2
Percentage of NetCashProvidedByUsedInInvestingActivities100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of RevenueFromRelatedParties-305.7-175.30.0-29.8-51.4-9328.70.0-53.5-40.1-305.60.0-18.8-6.9-115.00.0-13.6-9.2-23.10.0-11.3-3.9-4.70.0-11.2-12.2-14.20.0-15.3-17.9-41.80.0-51.4-59.8-79.10.0-55.4-57.8-75.90.0-88.0-5280.0-11.90.00.00.00.0

Payments To Acquire Property Plant And Equipment

us-gaap:PaymentsToAcquirePropertyPlantAndEquipment

us-gaap:PaymentsToAcquirePropertyPlantAndEquipment


Payments
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-31
Value162136146961441381911532931.44.21113597229212723259.8102223181550686110311924127023033327627524140123417865116874418
Percentage of PaymentsToAcquirePropertyPlantAndEquipment100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

Net Cash Provided By Used In Financing Activities

us-gaap:NetCashProvidedByUsedInFinancingActivities

us-gaap:NetCashProvidedByUsedInFinancingActivities


Net
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-31
Value-441.05121064-176.91661005-27.2-59.0-150.1-157.8-267.5-82.0-18.7-7.0687-164.8-46.823-20.4-43.5-49.1-93.4-37.2-170.2-41.6310-305.7-273.392197-333.9-31.3-152.634592-164.4212-21.2-391.5-292.82032627-25.0964-26.5174
Percentage of NetCashProvidedByUsedInFinancingActivities100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of RevenueFromRelatedParties-1260.0664.90.0-60.058.99306.50.0-20.1-36.1-383.90.0-20.9-4.6-11.30.0-62.1-20.619.40.0-19.5-20.3-90.30.0-81.8-27.8280.80.0-70.128.891.20.0-6.9-33.5119.90.0-34.545.7-6.40.0-130.22290.9200.10.00.00.00.0

Repayments Of Long Term Debt

us-gaap:RepaymentsOfLongTermDebt

us-gaap:RepaymentsOfLongTermDebt


Repayments
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-30
Value437902230.05694290.00.0719102181.0
Percentage of RepaymentsOfLongTermDebt100.0100.0100.00.0100.0100.00.00.0100.0100.0100.0100.0

Payments Of Dividends

us-gaap:PaymentsOfDividends

us-gaap:PaymentsOfDividends


Payments
Period End2020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-31
Value0.20.02316271614140.00.00.00.0
Percentage of PaymentsOfDividends100.00.0100.0100.0100.0100.0100.0100.00.00.00.00.0

Debt Instrument Interest Rate Stated Percentage

us-gaap:DebtInstrumentInterestRateStatedPercentage dei:LegalEntity, us-gaap:DebtInstrument

us-gaap:DebtInstrumentInterestRateStatedPercentage

clf:AKSteel, clf:A63752025AKSeniorNotes


Debt
Period End2020-12-31
Value6.375
Percentage of DebtInstrumentInterestRateStatedPercentage100.0
Percentage of LongTermDebtAndCapitalLeaseObligations0.0
Percentage of LongTermDebtAndCapitalLeaseObligations clf:AKSteel clf:A63752025AKSeniorNotes0.0

clf:AKSteel, clf:A7.502023AKSeniorNotes


Debt
Period End2020-12-31
Value7.5
Percentage of DebtInstrumentInterestRateStatedPercentage117.6
Percentage of LongTermDebtAndCapitalLeaseObligations0.0
Percentage of LongTermDebtAndCapitalLeaseObligations clf:AKSteel clf:A7.502023AKSeniorNotes0.0

clf:AKSteel, clf:A7.6252021AKSeniorNotes


Debt
Period End2020-12-31
Value7.625
Percentage of DebtInstrumentInterestRateStatedPercentage119.6
Percentage of LongTermDebtAndCapitalLeaseObligations0.0
Percentage of LongTermDebtAndCapitalLeaseObligations clf:AKSteel clf:A7.6252021AKSeniorNotes0.0

clf:ClevelandCliffsInc., clf:A4.8752024SeniorSecuredNotes


Debt
Period End2020-12-31
Value4.875
Percentage of DebtInstrumentInterestRateStatedPercentage76.5
Percentage of LongTermDebtAndCapitalLeaseObligations0.0
Percentage of LongTermDebtAndCapitalLeaseObligations clf:ClevelandCliffsInc. clf:A4.8752024SeniorSecuredNotes0.0

clf:ClevelandCliffsInc., clf:A6.3752025SeniorNotes


Debt
Period End2020-12-31
Value6.375
Percentage of DebtInstrumentInterestRateStatedPercentage100.0
Percentage of LongTermDebtAndCapitalLeaseObligations0.0
Percentage of LongTermDebtAndCapitalLeaseObligations clf:ClevelandCliffsInc. clf:A6.3752025SeniorNotes0.0

Effective Income Tax Rate Continuing Operations

us-gaap:EffectiveIncomeTaxRateContinuingOperations

us-gaap:EffectiveIncomeTaxRateContinuingOperations


Effective
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312012-03-312011-12-312011-09-302011-06-302011-03-312010-09-30
Value2.019.021.535.189-0.1630.474-0.039-0.025-0.0080.129-0.842000.0010.367-0.03-0.0410.0540.346-0.027-0.0370.0680.329-1.1240.188-0.0930.0020.253-0.022
Percentage of EffectiveIncomeTaxRateContinuingOperations100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.00.00.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

Share Based Compensation Arrangement By Share Based Payment Award Options Outstanding Weighted Average Exercise Price

us-gaap:ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice

us-gaap:ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice


Share
Period End2020-12-312019-12-312018-12-312017-12-31
Value11.610.4210.4210.25
Percentage of ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice100.0100.0100.0100.0

Deferred Tax Liabilities

us-gaap:DeferredTaxLiabilities

us-gaap:DeferredTaxLiabilities


Deferred
Period End2020-12-312019-12-312018-12-312017-12-312016-12-312015-12-312014-12-312013-12-312012-12-312011-12-312010-12-312009-12-31
Value458150622650265265-371.6178517541670462312
Percentage of DeferredTaxLiabilities100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

Deferred Tax Assets Net

us-gaap:DeferredTaxAssetsNet

us-gaap:DeferredTaxAssetsNet


Deferred
Period End2020-12-312019-12-312018-12-312017-12-312016-12-312015-12-312014-12-312013-12-312012-12-312011-12-312010-12-312009-12-31
Value9506101087650265265496710747839541455
Percentage of DeferredTaxAssetsNet100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

Unrecognized Tax Benefits

us-gaap:UnrecognizedTaxBenefits

us-gaap:UnrecognizedTaxBenefits


Unrecognized
Period End2020-12-312019-12-312018-12-312017-12-312016-12-312015-12-312014-12-312013-12-312012-12-312011-12-312010-12-312009-12-312008-12-312007-12-31
Value1072929333015674745510279755315
Percentage of UnrecognizedTaxBenefits100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:UnrecognizedTaxBenefits us-gaap:BalanceSheetLocation

us-gaap:OtherCurrentLiabilities


Unrecognized
Period End2020-12-31
Value9.0
Percentage of UnrecognizedTaxBenefits8.4

us-gaap:OtherLiabilities


Unrecognized
Period End2020-12-312019-12-312018-12-312017-12-312016-12-312015-12-312014-12-312013-12-312012-12-312011-12-31
Value114.44.26.18.32125257.045
Percentage of UnrecognizedTaxBenefits10.315.114.518.227.013.833.734.812.644.7

us-gaap:OtherNoncurrentAssets


Unrecognized
Period End2020-12-312019-12-312018-12-312017-12-312016-12-312015-12-312014-12-31
Value962424272213449
Percentage of UnrecognizedTaxBenefits89.784.985.581.873.086.266.1

us-gaap:OtherNoncurrentLiabilities


Unrecognized
Period End2020-12-312019-12-31
Value2.04.0
Percentage of UnrecognizedTaxBenefits1.913.7

Deferred Tax Assets Valuation Allowance

us-gaap:DeferredTaxAssetsValuationAllowance

us-gaap:DeferredTaxAssetsValuationAllowance


Deferred
Period End2020-12-312019-12-312018-12-312017-12-312016-12-312015-12-312014-12-312013-12-312012-12-312011-12-312010-12-312009-12-31
Value8364411287223833343372-2224.586485822317289
Percentage of DeferredTaxAssetsValuationAllowance100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:DeferredTaxAssetsValuationAllowance us-gaap:ValuationAllowanceByDeferredTaxAsset

us-gaap:StateAndLocalJurisdiction


Deferred
Period End2020-12-312019-12-312018-12-31
Value983838
Percentage of DeferredTaxAssetsValuationAllowance11.78.73.0

clf:AcquisitionRelatedLossOnEquityMethodInvestment clf:EBITDACalculation

clf:AcquisitionRelatedLossOnEquityMethodInvestment

clf:AdjustedEBITDACalculation


Acquisition
Period End2021-06-30
Value-18000000.0
Percentage of AcquisitionRelatedLossOnEquityMethodInvestment100.0

clf:AdjustedEBITDAEarningsLoss

clf:AdjustedEBITDAEarningsLoss


Adjusted
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-30
Value1360513286126-82.023111144248
Percentage of AdjustedEBITDAEarningsLoss100.0100.0100.0100.0100.0100.0100.0100.0100.0

clf:AdjustedEBITDAEarningsLoss us-gaap:StatementBusinessSegments

clf:CorporateandOtherSegments


Adjusted
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-30
Value-43.0-35.033-52.3-60.4-23.0-18.0-36.5-31.0
Percentage of AdjustedEBITDAEarningsLoss-3.2-6.811.8-41.473.7-100.0-16.2-25.3-12.5

clf:MiningandPelletizing


Adjusted
Period End2020-09-302020-06-302019-09-302019-06-30
Value14582182280
Percentage of AdjustedEBITDAEarningsLoss115.0-100.5126.8112.9

clf:OtherBusinesses


Adjusted
Period End2021-06-302021-03-312020-06-302020-03-31
Value8.0112.02.0
Percentage of AdjustedEBITDAEarningsLoss0.62.1-2.48.7

clf:SteelandManufacturing


Adjusted
Period End2020-09-302020-06-302019-09-302019-06-30
Value33-104.0-2.1-1.1
Percentage of AdjustedEBITDAEarningsLoss26.4126.8-1.5-0.4

clf:Steelmaking


Adjusted
Period End2021-06-302021-03-312020-06-302020-03-31
Value1395537-54.044
Percentage of AdjustedEBITDAEarningsLoss102.6104.765.9191.3

clf:AmortizationofIntangibleLiability

clf:AmortizationofIntangibleLiability


Amortizationof
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-31
Value2000000.01000000.02400000.01900000.0600000.02000000.0
Percentage of AmortizationofIntangibleLiability100.0100.0100.0100.0100.0100.0

clf:AmortizationofInventoryStepup

clf:AmortizationofInventoryStepup


Amortizationof
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-31
Value378122143623
Percentage of AmortizationofInventoryStepup100.0100.0100.0100.0100.0100.0

clf:AmortizationofInventoryStepup clf:EBITDACalculation

clf:AdjustedEBITDACalculation


Amortizationof
Period End2021-06-302021-03-312020-09-302020-06-302020-03-312019-06-30
Value37811436230.0
Percentage of AmortizationofInventoryStepup100.0100.0100.099.5100.00.0

clf:AmortizationofInventoryStepup us-gaap:BusinessAcquisition

clf:AKSteelHoldingCorporation


Amortizationof
Period End2020-09-302020-06-30
Value1436
Percentage of AmortizationofInventoryStepup100.099.5

clf:ArcelorMittalUSA


Amortizationof
Period End2020-12-09
Value21
Percentage of AmortizationofInventoryStepup0.0

clf:AssetRetirementObligationIncreaseDecreaseInLiabilitiesAssumedAcquisition

clf:AssetRetirementObligationIncreaseDecreaseInLiabilitiesAssumedAcquisition


Asset
Period End2021-06-302021-03-312020-06-302020-03-31
Value91-34.00.014
Percentage of AssetRetirementObligationIncreaseDecreaseInLiabilitiesAssumedAcquisition100.0100.00.0100.0

clf:AssetRetirementObligationLiabilitiesAssumedAcquisition

clf:AssetRetirementObligationLiabilitiesAssumedAcquisition


Asset
Period End2020-12-312020-09-30
Value1552.8
Percentage of AssetRetirementObligationLiabilitiesAssumedAcquisition100.0100.0

clf:BusinessAcquisitionProFormaIncomeTaxExpenseBenefit us-gaap:BusinessAcquisition

clf:BusinessAcquisitionProFormaIncomeTaxExpenseBenefit

clf:AKSteelHoldingCorporation


Business
Period End2020-09-302020-06-302020-03-312019-09-302019-06-302019-03-31
Value-5.6-1.611-2.18.018
Percentage of BusinessAcquisitionProFormaIncomeTaxExpenseBenefit100.0100.0100.0100.0100.0100.0

clf:BusinessCombinationProvisionalInformationInitialAccountingIncompleteAdjustmentAccountsPayable us-gaap:BusinessAcquisition

clf:BusinessCombinationProvisionalInformationInitialAccountingIncompleteAdjustmentAccountsPayable

clf:AKSteel


Business
Period End2021-03-31
Value0.0
Percentage of BusinessCombinationProvisionalInformationInitialAccountingIncompleteAdjustmentAccountsPayable0.0

clf:ArcelorMittalUSA


Business
Period End2021-06-302021-03-31
Value232.0
Percentage of BusinessCombinationProvisionalInformationInitialAccountingIncompleteAdjustmentAccountsPayable0.00.0

clf:BusinessCombinationProvisionalInformationInitialAccountingIncompleteAdjustmentAccountsReceivable us-gaap:BusinessAcquisition

clf:BusinessCombinationProvisionalInformationInitialAccountingIncompleteAdjustmentAccountsReceivable

clf:AKSteel


Business
Period End2021-03-31
Value0
Percentage of BusinessCombinationProvisionalInformationInitialAccountingIncompleteAdjustmentAccountsReceivable0.0

clf:BusinessCombinationProvisionalInformationInitialAccountingIncompleteAdjustmentAccruedEmploymentCost us-gaap:BusinessAcquisition

clf:BusinessCombinationProvisionalInformationInitialAccountingIncompleteAdjustmentAccruedEmploymentCost

clf:AKSteel


Business
Period End2021-03-31
Value0
Percentage of BusinessCombinationProvisionalInformationInitialAccountingIncompleteAdjustmentAccruedEmploymentCost0.0

clf:ArcelorMittalUSA


Business
Period End2021-06-302021-03-31
Value-2000000.03000000.0
Percentage of BusinessCombinationProvisionalInformationInitialAccountingIncompleteAdjustmentAccruedEmploymentCost0.00.0

clf:BusinessCombinationProvisionalInformationInitialAccountingIncompleteAdjustmentCashAndCashEquivalents us-gaap:BusinessAcquisition

clf:BusinessCombinationProvisionalInformationInitialAccountingIncompleteAdjustmentCashAndCashEquivalents

clf:AKSteel


Business
Period End2021-03-31
Value0
Percentage of BusinessCombinationProvisionalInformationInitialAccountingIncompleteAdjustmentCashAndCashEquivalents0.0

clf:BusinessCombinationProvisionalInformationInitialAccountingIncompleteAdjustmentDeferredIncomeTaxes us-gaap:BusinessAcquisition

clf:BusinessCombinationProvisionalInformationInitialAccountingIncompleteAdjustmentDeferredIncomeTaxes

clf:AKSteel


Business
Period End2021-03-31
Value39
Percentage of BusinessCombinationProvisionalInformationInitialAccountingIncompleteAdjustmentDeferredIncomeTaxes100.0

clf:BusinessCombinationProvisionalInformationInitialAccountingIncompleteAdjustmentNetIdentifiableAssets us-gaap:BusinessAcquisition

clf:BusinessCombinationProvisionalInformationInitialAccountingIncompleteAdjustmentNetIdentifiableAssets

clf:AKSteel


Business
Period End2021-03-31
Value0.0
Percentage of BusinessCombinationProvisionalInformationInitialAccountingIncompleteAdjustmentNetIdentifiableAssets0.0

clf:ArcelorMittalUSA


Business
Period End2021-06-302021-03-31
Value-72.0416
Percentage of BusinessCombinationProvisionalInformationInitialAccountingIncompleteAdjustmentNetIdentifiableAssets0.00.0

clf:BusinessCombinationProvisionalInformationInitialAccountingIncompleteAdjustmentNoncontrllingInterest us-gaap:BusinessAcquisition

clf:BusinessCombinationProvisionalInformationInitialAccountingIncompleteAdjustmentNoncontrllingInterest

clf:AKSteel


Business
Period End2021-03-31
Value0.0
Percentage of BusinessCombinationProvisionalInformationInitialAccountingIncompleteAdjustmentNoncontrllingInterest0.0

clf:ArcelorMittalUSA


Business
Period End2021-06-302021-03-31
Value121.0
Percentage of BusinessCombinationProvisionalInformationInitialAccountingIncompleteAdjustmentNoncontrllingInterest0.00.0

clf:BusinessCombinationProvisionalInformationInitialAccountingIncompleteAdjustmentOtherCurrentAssets us-gaap:BusinessAcquisition

clf:BusinessCombinationProvisionalInformationInitialAccountingIncompleteAdjustmentOtherCurrentAssets

clf:AKSteel


Business
Period End2021-03-31
Value0.0
Percentage of BusinessCombinationProvisionalInformationInitialAccountingIncompleteAdjustmentOtherCurrentAssets0.0

clf:ArcelorMittalUSA


Business
Period End2021-06-302021-03-31
Value-1.05.0
Percentage of BusinessCombinationProvisionalInformationInitialAccountingIncompleteAdjustmentOtherCurrentAssets0.00.0

clf:BusinessCombinationProvisionalInformationInitialAccountingIncompleteAdjustmentOtherCurrentLiabilities us-gaap:BusinessAcquisition

clf:BusinessCombinationProvisionalInformationInitialAccountingIncompleteAdjustmentOtherCurrentLiabilities

clf:AKSteel


Business
Period End2021-03-31
Value4000000.0
Percentage of BusinessCombinationProvisionalInformationInitialAccountingIncompleteAdjustmentOtherCurrentLiabilities100.0

clf:ArcelorMittalUSA


Business
Period End2021-06-302021-03-31
Value5000000.02000000.0
Percentage of BusinessCombinationProvisionalInformationInitialAccountingIncompleteAdjustmentOtherCurrentLiabilities0.050.0

clf:BusinessCombinationProvisionalInformationInitialAccountingIncompleteAdjustmentOtherNoncurrentAssets us-gaap:BusinessAcquisition

clf:BusinessCombinationProvisionalInformationInitialAccountingIncompleteAdjustmentOtherNoncurrentAssets

clf:AKSteel


Business
Period End2021-03-31
Value1000000.0
Percentage of BusinessCombinationProvisionalInformationInitialAccountingIncompleteAdjustmentOtherNoncurrentAssets100.0

clf:ArcelorMittalUSA


Business
Period End2021-06-302021-03-31
Value-2000000.08000000.0
Percentage of BusinessCombinationProvisionalInformationInitialAccountingIncompleteAdjustmentOtherNoncurrentAssets0.0800.0

clf:BusinessCombinationProvisionalInformationInitialAccountingIncompleteAdjustmentOtherNoncurrentLiabilities us-gaap:BusinessAcquisition

clf:BusinessCombinationProvisionalInformationInitialAccountingIncompleteAdjustmentOtherNoncurrentLiabilities

clf:AKSteel


Business
Period End2021-03-31
Value0.0
Percentage of BusinessCombinationProvisionalInformationInitialAccountingIncompleteAdjustmentOtherNoncurrentLiabilities0.0

clf:ArcelorMittalUSA


Business
Period End2021-06-302021-03-31
Value4535
Percentage of BusinessCombinationProvisionalInformationInitialAccountingIncompleteAdjustmentOtherNoncurrentLiabilities0.00.0

clf:BusinessCombinationProvisionalInformationInitialAccountingIncompleteAdjustmentRetirementBenefitLiabilitiesCurrent us-gaap:BusinessAcquisition

clf:BusinessCombinationProvisionalInformationInitialAccountingIncompleteAdjustmentRetirementBenefitLiabilitiesCurrent

clf:AKSteel


Business
Period End2021-03-31
Value0
Percentage of BusinessCombinationProvisionalInformationInitialAccountingIncompleteAdjustmentRetirementBenefitLiabilitiesCurrent0.0

clf:BusinessCombinationProvisionalInformationInitialAccountingIncompleteAdjustmentRetirementBenefitLiabilitiesNoncurrent us-gaap:BusinessAcquisition

clf:BusinessCombinationProvisionalInformationInitialAccountingIncompleteAdjustmentRetirementBenefitLiabilitiesNoncurrent

clf:AKSteel


Business
Period End2021-03-31
Value0
Percentage of BusinessCombinationProvisionalInformationInitialAccountingIncompleteAdjustmentRetirementBenefitLiabilitiesNoncurrent0.0

clf:BusinessCombinationSeparatelyRecognizedTransactionsSettlementOfPreexistingRelationship us-gaap:BusinessAcquisition

clf:BusinessCombinationSeparatelyRecognizedTransactionsSettlementOfPreexistingRelationship

clf:ArcelorMittalUSA


Business
Period End2020-12-09
Value237
Percentage of BusinessCombinationSeparatelyRecognizedTransactionsSettlementOfPreexistingRelationship100.0

clf:CapitalExpendituresIncurredbutNotyetPaidIncreaseDecreaseInPeriod

clf:CapitalExpendituresIncurredbutNotyetPaidIncreaseDecreaseInPeriod


Capital
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-31
Value-7.0232.43.2-81.3-10.3-11.12215-11.5
Percentage of CapitalExpendituresIncurredbutNotyetPaidIncreaseDecreaseInPeriod100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

clf:CashConsiderationReceivableFromBusinessCombination us-gaap:BusinessAcquisition

clf:CashConsiderationReceivableFromBusinessCombination

clf:ArcelorMittalUSA


Cash
Period End2020-12-09
Value56
Percentage of CashConsiderationReceivableFromBusinessCombination100.0

clf:ContractWithCustomerLiabilityPeriodIncreaseDecrease us-gaap:BalanceSheetLocation

clf:ContractWithCustomerLiabilityPeriodIncreaseDecrease

us-gaap:OtherCurrentLiabilities


Contract
Period End2020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-31
Value4800000.0-2600000.04600000.0-21800000.03800000.02800000.0-2600000.0-2900000.04900000.0-3900000.0-11000000.07200000.0
Percentage of ContractWithCustomerLiabilityPeriodIncreaseDecrease100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:OtherNoncurrentLiabilities


Contract
Period End2020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-31
Value-300000.000-25700000.0-4300000.0-4300000.0-4200000.00-4300000.0-4300000.0-4300000.00
Percentage of ContractWithCustomerLiabilityPeriodIncreaseDecrease-6.2-0.00.0117.9-113.2-153.6161.5-0.0-87.8110.339.10.0

clf:DepreciationDepletionandAmortizationAttributabletoNoncontrollingInterests

clf:DepreciationDepletionandAmortizationAttributabletoNoncontrollingInterests


Depreciation
Period End2021-03-312020-12-312020-09-302020-06-302020-03-31
Value6.04.94.34.71.0
Percentage of DepreciationDepletionandAmortizationAttributabletoNoncontrollingInterests100.0100.0100.0100.0100.0

clf:DepreciationDepletionandAmortizationAttributabletoNoncontrollingInterests clf:EBITDACalculation

clf:AdjustedEBITDACalculation


Depreciation
Period End2021-06-302020-06-30
Value6.05.0
Percentage of DepreciationDepletionandAmortizationAttributabletoNoncontrollingInterests0.0106.4

clf:EBITDAEarningsLoss

clf:EBITDAEarningsLoss


E
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-30
Value130437525512012-34.0104143230
Percentage of EBITDAEarningsLoss100.0100.0100.0100.0100.0100.0100.0100.0100.0

clf:EBITDAofNoncontrollingInterests clf:EBITDACalculation

clf:EBITDAofNoncontrollingInterests

clf:AdjustedEBITDACalculation


E
Period End2021-06-302021-03-312020-09-302020-06-302020-03-312019-06-302019-03-31
Value212216204.60.00.0
Percentage of EBITDAofNoncontrollingInterests100.0100.0100.0100.0100.00.00.0

clf:NoncontrollingInterestIncreaseDecreaseFromBusinessCombinationMeasurementPeriodAdjustments

clf:NoncontrollingInterestIncreaseDecreaseFromBusinessCombinationMeasurementPeriodAdjustments


Noncontrolling
Period End2021-06-302021-03-31
Value-13000000.0-1000000.0
Percentage of NoncontrollingInterestIncreaseDecreaseFromBusinessCombinationMeasurementPeriodAdjustments100.0100.0

clf:NoncontrollingInterestIncreaseDecreaseFromBusinessCombinationMeasurementPeriodAdjustments us-gaap:StatementEquityComponents

us-gaap:NoncontrollingInterest


Noncontrolling
Period End2021-06-302021-03-31
Value-13000000.0-1000000.0
Percentage of NoncontrollingInterestIncreaseDecreaseFromBusinessCombinationMeasurementPeriodAdjustments100.0100.0

clf:PaymentsToAcquireBusinessesPurchaseOfJVInterest us-gaap:BusinessAcquisition

clf:PaymentsToAcquireBusinessesPurchaseOfJVInterest

clf:ArcelorMittalUSA


Payments
Period End2020-12-09
Value182
Percentage of PaymentsToAcquireBusinessesPurchaseOfJVInterest100.0

clf:PaymentsToAcquireBusinessesPursuantToTransactionAgreement us-gaap:BusinessAcquisition

clf:PaymentsToAcquireBusinessesPursuantToTransactionAgreement

clf:ArcelorMittalUSA


Payments
Period End2020-12-09
Value505
Percentage of PaymentsToAcquireBusinessesPursuantToTransactionAgreement100.0

clf:PercentageOfRelatedPartyRevenue

clf:PercentageOfRelatedPartyRevenue


Percentage
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-31
Value1.02.0-2.317.90.2580.0350.4710.5090.5960.2830.0020.5730.6090.281-0.0020.4230.4440.287-0.0250.4390.5340.3750.0320.3830.3290.2760.0230.3280.3160.2520.0030.3130.3270.267-0.0110.3290.3010.276-0.0370.420.3580.277
Percentage of PercentageOfRelatedPartyRevenue100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

clf:RevenuesExcludingDeferredRevenueRevenueRecognized

clf:RevenuesExcludingDeferredRevenueRevenueRecognized


Revenues
Period End2020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-31
Value225516461092324534555743157
Percentage of RevenuesExcludingDeferredRevenueRevenueRecognized100.0100.0100.0100.0100.0100.0100.0100.0

clf:SalesVolumeLongTons us-gaap:ConsolidationItems, us-gaap:StatementBusinessSegments

clf:SalesVolumeLongTons

us-gaap:IntersegmentElimination, clf:MiningandPelletizing


Sales
Period End2020-09-302020-06-302020-03-312019-09-302019-06-302019-03-31
Value-1.204-1.041-0.783-0.346-0.0380.0
Percentage of SalesVolumeLongTons100.0100.0100.0100.0100.00.0

us-gaap:OperatingSegments, clf:MiningandPelletizing


Sales
Period End2020-09-302020-06-302020-03-312019-09-302019-06-302019-03-31
Value4.9074.7592.1345.756.2271.55
Percentage of SalesVolumeLongTons-407.6-457.2-272.5-1661.8-16386.80.0

clf:SalesVolumeLongTons us-gaap:ProductOrService, us-gaap:StatementBusinessSegments

clf:IronProducts, clf:Steelmaking


Sales
Period End2021-06-302021-03-312020-06-302020-03-31
Value0.8490.63.7181.351
Percentage of SalesVolumeLongTons0.00.0-357.2-172.5

clf:SalesVolumeLongTons us-gaap:StatementBusinessSegments

clf:MiningandPelletizing


Sales
Period End2020-09-302020-06-302020-03-312019-09-302019-06-302019-03-31
Value3.7033.7181.3515.4046.1891.55
Percentage of SalesVolumeLongTons-307.6-357.2-172.5-1561.8-16286.80.0

clf:SalesVolumeNetTons us-gaap:ProductOrService, us-gaap:StatementBusinessSegments

clf:SalesVolumeNetTons

clf:CoatedSteel, clf:Steelmaking


Sales
Period End2021-06-302021-03-312020-06-302020-03-31
Value1247000.01369000.0333000.099000.0
Percentage of SalesVolumeNetTons100.0100.0100.0100.0

clf:ColdRolledSteel, clf:Steelmaking


Sales
Period End2021-06-302021-03-312020-06-302020-03-31
Value720000.0748000.0123000.040000.0
Percentage of SalesVolumeNetTons57.754.636.940.4

clf:HotRolledSteel, clf:Steelmaking


Sales
Period End2021-06-302021-03-312020-06-302020-03-31
Value1386000.01182000.063000.031000.0
Percentage of SalesVolumeNetTons111.186.318.931.3

clf:OtherSteelProducts, clf:Steelmaking


Sales
Period End2021-06-302021-03-31
Value411000.0403000.0
Percentage of SalesVolumeNetTons33.029.4

clf:PlateSteel, clf:Steelmaking


Sales
Period End2021-06-302021-03-31
Value273000.0275000.0
Percentage of SalesVolumeNetTons21.920.1

clf:StainlessAndElectricalSteel, clf:Steelmaking


Sales
Period End2021-06-302021-03-312020-06-302020-03-31
Value168000.0167000.095000.027000.0
Percentage of SalesVolumeNetTons13.512.228.527.3

clf:SalesVolumeNetTons us-gaap:StatementBusinessSegments

clf:SteelandManufacturing


Sales
Period End2020-09-302020-06-302020-03-312019-06-302019-03-31
Value1117000.0619000.0199000.000
Percentage of SalesVolumeNetTons0.0185.9201.00.00.0

us-gaap:AllowanceForDoubtfulAccountsReceivablePeriodIncreaseDecrease

us-gaap:AllowanceForDoubtfulAccountsReceivablePeriodIncreaseDecrease


Allowance
Period End2021-03-312020-12-312020-09-302020-06-302020-03-312019-06-302019-03-31
Value1000000.0-200000.0900000.03100000.01200000.000
Percentage of AllowanceForDoubtfulAccountsReceivablePeriodIncreaseDecrease100.0100.0100.0100.0100.00.00.0

us-gaap:AssetRetirementObligationAccretionExpense

us-gaap:AssetRetirementObligationAccretionExpense


Asset
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-31
Value5.03.06.22.92.32.62.52.52.52.62.42.42.02.73.84.03.53.65.62.63.32.5-2.0-2.0-1.3-1.2-3.6-3.7-3.6-3.6-4.5-4.6-4.5-4.5-4.4-4.3-13.44.54.34.13.93.813
Percentage of AssetRetirementObligationAccretionExpense100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:AssetRetirementObligationLiabilitiesSettled

us-gaap:AssetRetirementObligationLiabilitiesSettled


Asset
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312013-12-312013-09-302013-06-302013-03-312011-12-312011-09-30
Value9000000.01000000.05600000.02600000.0400000.0400000.0300000.0100000.0300000.0100000.0100000.0600000.0200000.0100000.02400000.02400000.0500000.0300000.0-300000.00200000.0100000.000
Percentage of AssetRetirementObligationLiabilitiesSettled100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.00.0100.0100.00.00.0

us-gaap:BusinessAcquisitionsProFormaNetIncomeLoss us-gaap:BusinessAcquisition

us-gaap:BusinessAcquisitionsProFormaNetIncomeLoss

clf:AKSteelHoldingCorporation


Business
Period End2020-09-302020-06-302019-09-302019-06-30
Value-6.0-125.384184
Percentage of BusinessAcquisitionsProFormaNetIncomeLoss100.0100.0100.0100.0

us-gaap:BusinessAcquisitionsProFormaNetIncomeLoss us-gaap:BusinessAcquisition, us-gaap:NonrecurringAdjustment

clf:AKSteelHoldingCorporation, clf:OtherAdjustments


Business
Period End2020-09-302020-06-302019-09-302019-06-30
Value-10.0-12.3-1.1-4.0
Percentage of BusinessAcquisitionsProFormaNetIncomeLoss166.79.8-1.3-2.2

clf:AKSteelHoldingCorporation, us-gaap:AcquisitionRelatedCosts


Business
Period End2020-09-302020-06-30
Value0.71.8
Percentage of BusinessAcquisitionsProFormaNetIncomeLoss-11.7-1.4

clf:AKSteelHoldingCorporation, us-gaap:FairValueAdjustmentToInventory


Business
Period End2020-09-302020-06-302019-09-302019-06-30
Value1436-0.218
Percentage of BusinessAcquisitionsProFormaNetIncomeLoss-243.3-28.9-0.210.0

us-gaap:BusinessAcquisitionsProFormaRevenue us-gaap:BusinessAcquisition

us-gaap:BusinessAcquisitionsProFormaRevenue

clf:AKSteelHoldingCorporation


Business
Period End2020-09-302020-06-302019-09-302019-06-30
Value164697919372233
Percentage of BusinessAcquisitionsProFormaRevenue100.0100.0100.0100.0

us-gaap:BusinessAcquisitionsProFormaRevenue us-gaap:ConsolidationItems, us-gaap:BusinessAcquisition

us-gaap:IntersegmentElimination, clf:AKSteelHoldingCorporation


Business
Period End2020-09-302020-06-302019-09-302019-06-30
Value135113153189
Percentage of BusinessAcquisitionsProFormaRevenue8.211.67.98.5

us-gaap:BusinessCombinationAcquisitionRelatedCosts

us-gaap:BusinessCombinationAcquisitionRelatedCosts


Business
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-06-302019-03-312012-12-312012-09-302011-12-312011-09-302011-06-30
Value1.013217.518420.00.00.00.00.42.118
Percentage of BusinessCombinationAcquisitionRelatedCosts100.0100.0100.0100.0100.0100.00.00.00.00.0100.0100.0100.0

us-gaap:BusinessCombinationAcquisitionRelatedCosts clf:EBITDACalculation

clf:AdjustedEBITDACalculation


Business
Period End2021-06-302021-03-312020-09-302020-06-302020-03-312019-06-30
Value0.02.05.11.8230.0
Percentage of BusinessCombinationAcquisitionRelatedCosts0.015.468.09.854.10.0

us-gaap:BusinessCombinationAcquisitionRelatedCosts us-gaap:BusinessAcquisition

clf:AKSteelHoldingCorporation


Business
Period End2020-09-302020-06-30
Value0.61.8
Percentage of BusinessCombinationAcquisitionRelatedCosts8.09.8

clf:ArcelorMittalUSA


Business
Period End2021-06-302021-03-31
Value0.02.0
Percentage of BusinessCombinationAcquisitionRelatedCosts0.015.4

us-gaap:BusinessCombinationConsiderationTransferred1 us-gaap:BusinessAcquisition

us-gaap:BusinessCombinationConsiderationTransferred1

clf:ArcelorMittalUSA


Business
Period End2020-12-09
Value2596
Percentage of BusinessCombinationConsiderationTransferred1100.0

us-gaap:BusinessCombinationConsiderationTransferred1 us-gaap:StatementScenario, us-gaap:BusinessAcquisition

srt:ScenarioForecast, clf:ArcelorMittalUSA


Business
Period End2020-12-31
Value1400
Percentage of BusinessCombinationConsiderationTransferred10.0

us-gaap:BusinessCombinationConsiderationTransferredEquityInterestsIssuedAndIssuable us-gaap:BusinessAcquisition, us-gaap:StatementClassOfStock

us-gaap:BusinessCombinationConsiderationTransferredEquityInterestsIssuedAndIssuable

clf:ArcelorMittalUSA, us-gaap:CommonStock


Business
Period End2020-12-09
Value990
Percentage of BusinessCombinationConsiderationTransferredEquityInterestsIssuedAndIssuable100.0

clf:ArcelorMittalUSA, us-gaap:SeriesBPreferredStock


Business
Period End2020-12-09
Value738
Percentage of BusinessCombinationConsiderationTransferredEquityInterestsIssuedAndIssuable74.5

us-gaap:BusinessCombinationConsiderationTransferredEquityInterestsIssuedAndIssuable us-gaap:StatementClassOfStock

us-gaap:SeriesBPreferredStock


Business
Period End2020-12-09
Value738
Percentage of BusinessCombinationConsiderationTransferredEquityInterestsIssuedAndIssuable74.5

us-gaap:BusinessCombinationProvisionalInformationInitialAccountingIncompleteAdjustmentEquityInterests us-gaap:IncomeStatementLocation

us-gaap:BusinessCombinationProvisionalInformationInitialAccountingIncompleteAdjustmentEquityInterests

us-gaap:OtherOperatingIncomeExpense


Business
Period End2021-06-30
Value18
Percentage of BusinessCombinationProvisionalInformationInitialAccountingIncompleteAdjustmentEquityInterests100.0

us-gaap:BusinessCombinationProvisionalInformationInitialAccountingIncompleteAdjustmentFinancialAssets us-gaap:BalanceSheetLocation, us-gaap:BusinessAcquisition

us-gaap:BusinessCombinationProvisionalInformationInitialAccountingIncompleteAdjustmentFinancialAssets

clf:Rightofuseassetoperatinglease, clf:AKSteelHoldingCorporation


Business
Period End2020-09-302020-06-30
Value0.0-16.3
Percentage of BusinessCombinationProvisionalInformationInitialAccountingIncompleteAdjustmentFinancialAssets0.0100.0

us-gaap:AccountsReceivable, clf:AKSteelHoldingCorporation


Business
Period End2020-09-302020-06-30
Value0.1-3.2
Percentage of BusinessCombinationProvisionalInformationInitialAccountingIncompleteAdjustmentFinancialAssets0.019.6

us-gaap:CashAndCashEquivalents, clf:AKSteelHoldingCorporation


Business
Period End2020-09-302020-06-30
Value0.02.0
Percentage of BusinessCombinationProvisionalInformationInitialAccountingIncompleteAdjustmentFinancialAssets0.0-12.3

us-gaap:OtherCurrentAssets, clf:AKSteelHoldingCorporation


Business
Period End2020-09-302020-06-30
Value-0.9-14.5
Percentage of BusinessCombinationProvisionalInformationInitialAccountingIncompleteAdjustmentFinancialAssets0.089.0

us-gaap:OtherNoncurrentAssets, clf:AKSteelHoldingCorporation


Business
Period End2020-09-302020-06-30
Value0.325
Percentage of BusinessCombinationProvisionalInformationInitialAccountingIncompleteAdjustmentFinancialAssets0.0-158.9

us-gaap:BusinessCombinationProvisionalInformationInitialAccountingIncompleteAdjustmentFinancialLiabilities us-gaap:BalanceSheetLocation, us-gaap:BusinessAcquisition

us-gaap:BusinessCombinationProvisionalInformationInitialAccountingIncompleteAdjustmentFinancialLiabilities

clf:AssetRetirementObligation, clf:AKSteelHoldingCorporation


Business
Period End2020-09-302020-06-30
Value2000000.00
Percentage of BusinessCombinationProvisionalInformationInitialAccountingIncompleteAdjustmentFinancialLiabilities100.00.0

clf:Deferredincometaxes, clf:AKSteelHoldingCorporation


Business
Period End2020-09-302020-06-30
Value-1500000.01700000.0
Percentage of BusinessCombinationProvisionalInformationInitialAccountingIncompleteAdjustmentFinancialLiabilities-75.00.0

clf:Operatingleaseliabilitynoncurrent, clf:AKSteelHoldingCorporation


Business
Period End2020-09-302020-06-30
Value-12700000.00
Percentage of BusinessCombinationProvisionalInformationInitialAccountingIncompleteAdjustmentFinancialLiabilities-635.00.0

clf:PensionandOPEBliabilities, clf:AKSteelHoldingCorporation


Business
Period End2020-09-302020-06-30
Value-2100000.00
Percentage of BusinessCombinationProvisionalInformationInitialAccountingIncompleteAdjustmentFinancialLiabilities-105.00.0

us-gaap:AccountsPayable, clf:AKSteelHoldingCorporation


Business
Period End2020-09-302020-06-30
Value3200000.02900000.0
Percentage of BusinessCombinationProvisionalInformationInitialAccountingIncompleteAdjustmentFinancialLiabilities160.00.0

us-gaap:AccruedLiabilities, clf:AKSteelHoldingCorporation


Business
Period End2020-09-302020-06-30
Value-2200000.02100000.0
Percentage of BusinessCombinationProvisionalInformationInitialAccountingIncompleteAdjustmentFinancialLiabilities-110.00.0

us-gaap:OtherCurrentLiabilities, clf:AKSteelHoldingCorporation


Business
Period End2020-09-302020-06-30
Value400000.0-7000000.0
Percentage of BusinessCombinationProvisionalInformationInitialAccountingIncompleteAdjustmentFinancialLiabilities20.00.0

us-gaap:OtherNoncurrentLiabilities, clf:AKSteelHoldingCorporation


Business
Period End2020-09-302020-06-30
Value-3400000.05700000.0
Percentage of BusinessCombinationProvisionalInformationInitialAccountingIncompleteAdjustmentFinancialLiabilities-170.00.0

us-gaap:BusinessCombinationProvisionalInformationInitialAccountingIncompleteAdjustmentIntangibles us-gaap:BalanceSheetLocation, us-gaap:BusinessAcquisition

us-gaap:BusinessCombinationProvisionalInformationInitialAccountingIncompleteAdjustmentIntangibles

clf:Intangibleliabilities, clf:AKSteelHoldingCorporation


Business
Period End2020-09-302020-06-30
Value4.565
Percentage of BusinessCombinationProvisionalInformationInitialAccountingIncompleteAdjustmentIntangibles100.0100.0

us-gaap:FiniteLivedIntangibleAssets, clf:AKSteelHoldingCorporation


Business
Period End2020-09-302020-06-30
Value0.0-15.0
Percentage of BusinessCombinationProvisionalInformationInitialAccountingIncompleteAdjustmentIntangibles0.0-23.1

us-gaap:BusinessCombinationProvisionalInformationInitialAccountingIncompleteAdjustmentInventory us-gaap:BalanceSheetLocation, us-gaap:BusinessAcquisition

us-gaap:BusinessCombinationProvisionalInformationInitialAccountingIncompleteAdjustmentInventory

us-gaap:Inventories, clf:AKSteelHoldingCorporation


Business
Period End2020-09-302020-06-30
Value-2.0-37.8
Percentage of BusinessCombinationProvisionalInformationInitialAccountingIncompleteAdjustmentInventory100.0100.0

us-gaap:BusinessCombinationProvisionalInformationInitialAccountingIncompleteAdjustmentInventory us-gaap:BusinessAcquisition

clf:AKSteel


Business
Period End2021-03-31
Value0.0
Percentage of BusinessCombinationProvisionalInformationInitialAccountingIncompleteAdjustmentInventory0.0

clf:ArcelorMittalUSA


Business
Period End2021-06-302021-03-31
Value0.014
Percentage of BusinessCombinationProvisionalInformationInitialAccountingIncompleteAdjustmentInventory0.00.0

us-gaap:BusinessCombinationProvisionalInformationInitialAccountingIncompleteAdjustmentPropertyPlantAndEquipment us-gaap:BusinessAcquisition

us-gaap:BusinessCombinationProvisionalInformationInitialAccountingIncompleteAdjustmentPropertyPlantAndEquipment

clf:AKSteel


Business
Period End2021-03-31
Value-38.0
Percentage of BusinessCombinationProvisionalInformationInitialAccountingIncompleteAdjustmentPropertyPlantAndEquipment100.0

clf:ArcelorMittalUSA


Business
Period End2021-06-302021-03-31
Value13366
Percentage of BusinessCombinationProvisionalInformationInitialAccountingIncompleteAdjustmentPropertyPlantAndEquipment0.0-963.2

us-gaap:BusinessCombinationProvisionalInformationInitialAccountingIncompleteAdjustmentsRelatedToPreviousPeriod us-gaap:BusinessAcquisition, us-gaap:IncomeStatementLocation

us-gaap:BusinessCombinationProvisionalInformationInitialAccountingIncompleteAdjustmentsRelatedToPreviousPeriod

clf:AKSteelHoldingCorporation, us-gaap:CostOfSales


Business
Period End2020-09-30
Value200000.0
Percentage of BusinessCombinationProvisionalInformationInitialAccountingIncompleteAdjustmentsRelatedToPreviousPeriod100.0

us-gaap:DeferredRevenueRevenueRecognized1

us-gaap:DeferredRevenueRevenueRecognized1


Deferred
Period End2020-12-312020-09-302020-06-302020-03-312019-06-302019-03-31
Value0.40.00.0340.00.0
Percentage of DeferredRevenueRevenueRecognized1100.00.00.0100.00.00.0

us-gaap:DefinedBenefitPlanAmortizationOfGainsLosses us-gaap:RetirementPlanType

us-gaap:DefinedBenefitPlanAmortizationOfGainsLosses

us-gaap:OtherPostretirementBenefitPlansDefinedBenefit


Defined
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-30
Value-1.0-1.0-0.8-0.8-0.7-0.7-1.3-1.3-1.2-1.3-1.2-1.3-1.3-1.2-1.1-0.9-1.3-1.2-1.5-1.7
Percentage of DefinedBenefitPlanAmortizationOfGainsLosses100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:PensionPlansDefinedBenefit


Defined
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-30
Value-8.0-8.0-6.4-7.3-6.6-6.7-5.8-5.9-5.9-5.9-5.3-5.3-5.3-5.3-5.6-6.1-5.3-5.3-5.2-5.4
Percentage of DefinedBenefitPlanAmortizationOfGainsLosses800.0800.0800.0912.5942.9957.1446.2453.8491.7453.8441.7407.7407.7441.7509.1677.8407.7441.7346.7317.6

us-gaap:DefinedBenefitPlanAmortizationOfPriorServiceCostCredit us-gaap:RetirementPlanType

us-gaap:DefinedBenefitPlanAmortizationOfPriorServiceCostCredit

us-gaap:OtherPostretirementBenefitPlansDefinedBenefit


Defined
Period End2020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-30
Value-500000.0-500000.0-500000.0-500000.0-500000.0-500000.0-500000.0-500000.0-800000.0-700000.0-700000.0-800000.0-700000.0-800000.0-800000.0-700000.0-900000.0-900000.0
Percentage of DefinedBenefitPlanAmortizationOfPriorServiceCostCredit100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:PensionPlansDefinedBenefit


Defined
Period End2020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-30
Value300000.0200000.0300000.0200000.0300000.0300000.0300000.0300000.0500000.0600000.0600000.0500000.0700000.0600000.0700000.0600000.0600000.0500000.0
Percentage of DefinedBenefitPlanAmortizationOfPriorServiceCostCredit-60.0-40.0-60.0-40.0-60.0-60.0-60.0-60.0-62.5-85.7-85.7-62.5-100.0-75.0-87.5-85.7-66.7-55.6

us-gaap:DefinedBenefitPlanExpectedReturnOnPlanAssets us-gaap:RetirementPlanType

us-gaap:DefinedBenefitPlanExpectedReturnOnPlanAssets

us-gaap:OtherPostretirementBenefitPlansDefinedBenefit


Defined
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-30
Value10.010.06.44.54.64.54.24.24.24.24.64.64.64.64.44.44.54.44.34.3
Percentage of DefinedBenefitPlanExpectedReturnOnPlanAssets100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:PensionPlansDefinedBenefit


Defined
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-30
Value9090483636181313131315151515131313131313
Percentage of DefinedBenefitPlanExpectedReturnOnPlanAssets900.0900.0751.6815.6797.8411.1323.8326.2326.2323.8326.1326.1326.1326.1309.1313.6302.2306.8318.6316.3

us-gaap:DefinedBenefitPlanInterestCost us-gaap:RetirementPlanType

us-gaap:DefinedBenefitPlanInterestCost

us-gaap:OtherPostretirementBenefitPlansDefinedBenefit


Defined
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-30
Value19188.14.44.32.22.52.32.42.32.12.12.02.12.11.92.22.12.32.3
Percentage of DefinedBenefitPlanInterestCost100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:PensionPlansDefinedBenefit


Defined
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-30
Value26262119148.28.78.98.68.77.67.67.57.67.67.97.57.57.67.8
Percentage of DefinedBenefitPlanInterestCost136.8144.4263.0445.5346.5372.7348.0387.0358.3378.3361.9361.9375.0361.9361.9415.8340.9357.1330.4339.1

us-gaap:DefinedBenefitPlanNetPeriodicBenefitCost us-gaap:RetirementPlanType

us-gaap:DefinedBenefitPlanNetPeriodicBenefitCost

us-gaap:OtherPostretirementBenefitPlansDefinedBenefit


Defined
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-30
Value22226.71.61.3-1.6-0.5-0.6-0.7-0.7-1.5-1.3-1.5-1.6-1.4-2.1-1.3-1.3-1.0-0.8
Percentage of DefinedBenefitPlanNetPeriodicBenefitCost100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:PensionPlansDefinedBenefit


Defined
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-30
Value-42.0-42.0-19.1-4.2-9.61.95.76.05.35.43.43.23.03.14.54.24.64.74.14.3
Percentage of DefinedBenefitPlanNetPeriodicBenefitCost-190.9-190.9-285.1-262.5-738.5-118.8-1140.0-1000.0-757.1-771.4-226.7-246.2-200.0-193.8-321.4-200.0-353.8-361.5-410.0-537.5

us-gaap:DefinedBenefitPlanServiceCost us-gaap:RetirementPlanType

us-gaap:DefinedBenefitPlanServiceCost

us-gaap:OtherPostretirementBenefitPlansDefinedBenefit


Defined
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-30
Value12134.71.41.40.50.40.50.40.40.60.60.50.50.50.30.50.50.40.4
Percentage of DefinedBenefitPlanServiceCost100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:PensionPlansDefinedBenefit


Defined
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-30
Value14147.05.45.35.34.44.64.24.14.74.74.64.74.23.44.74.84.44.2
Percentage of DefinedBenefitPlanServiceCost116.7107.7148.9385.7378.61060.01100.0920.01050.01025.0783.3783.3920.0940.0840.01133.3940.0960.01100.01050.0

us-gaap:Depreciation

us-gaap:Depreciation


Depreciation
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-31
Value20821511571753514222019
Percentage of Depreciation100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:DerivativeInstrumentsGainLossReclassificationFromAccumulatedOCIToIncomeEstimatedNetAmountToBeTransferred us-gaap:DerivativeInstrumentRisk, us-gaap:HedgingDesignation

us-gaap:DerivativeInstrumentsGainLossReclassificationFromAccumulatedOCIToIncomeEstimatedNetAmountToBeTransferred

clf:Zinc, us-gaap:DesignatedAsHedgingInstrument


Derivative
Period End2020-09-30
Value1.7
Percentage of DerivativeInstrumentsGainLossReclassificationFromAccumulatedOCIToIncomeEstimatedNetAmountToBeTransferred100.0

srt:NaturalGasReserves, us-gaap:DesignatedAsHedgingInstrument


Derivative
Period End2020-09-302020-06-302020-03-31
Value152.4-7.0
Percentage of DerivativeInstrumentsGainLossReclassificationFromAccumulatedOCIToIncomeEstimatedNetAmountToBeTransferred905.90.00.0

us-gaap:Electricity, us-gaap:DesignatedAsHedgingInstrument


Derivative
Period End2020-09-302020-06-302020-03-31
Value2.10.5-1.5
Percentage of DerivativeInstrumentsGainLossReclassificationFromAccumulatedOCIToIncomeEstimatedNetAmountToBeTransferred123.50.00.0

us-gaap:DerivativeInstrumentsNotDesignatedAsHedgingInstrumentsGainLossNet

us-gaap:DerivativeInstrumentsNotDesignatedAsHedgingInstrumentsGainLossNet


Derivative
Period End2020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-31
Value3341-32.8-35.9-40.97415411632421121-1.62.416-4.1-15.66159172037757.22140401404224024038710044290429110
Percentage of DerivativeInstrumentsNotDesignatedAsHedgingInstrumentsGainLossNet100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:DerivativeInstrumentsNotDesignatedAsHedgingInstrumentsGainLossNet us-gaap:DerivativeInstrumentRisk, us-gaap:IncomeStatementLocation

clf:CustomerSupplyAgreement, us-gaap:Sales


Derivative
Period End2020-12-312020-09-302020-06-302020-03-312019-12-312019-09-30
Value1078.83126-4.17.6
Percentage of DerivativeInstrumentsNotDesignatedAsHedgingInstrumentsGainLossNet0.026.675.1-79.311.4-18.6

clf:ProvisionalPricingArrangements, us-gaap:Sales


Derivative
Period End2020-09-302019-12-312019-09-30
Value20-31.8-48.5
Percentage of DerivativeInstrumentsNotDesignatedAsHedgingInstrumentsGainLossNet61.688.6118.6

us-gaap:CommodityContract, us-gaap:CostOfSales


Derivative
Period End2020-09-302020-06-302020-03-312019-06-302019-03-312015-09-302015-06-302015-03-312014-09-302014-06-302014-03-31
Value3.91.2-5.90.00.00.00.2-3.60.00.00.0
Percentage of DerivativeInstrumentsNotDesignatedAsHedgingInstrumentsGainLossNet11.82.918.00.00.00.0-4.923.10.00.00.0

us-gaap:DerivativeNonmonetaryNotionalAmountEnergyMeasure us-gaap:DerivativeInstrumentRisk, us-gaap:HedgingDesignation

us-gaap:DerivativeNonmonetaryNotionalAmountEnergyMeasure

us-gaap:Electricity, us-gaap:DesignatedAsHedgingInstrument


Derivative
Period End2020-09-30
Value-0.7
Percentage of DerivativeNonmonetaryNotionalAmountEnergyMeasure100.0

us-gaap:EffectiveIncomeTaxRateReconciliationAtFederalStatutoryIncomeTaxRate

us-gaap:EffectiveIncomeTaxRateReconciliationAtFederalStatutoryIncomeTaxRate


Effective
Period End2021-06-302021-03-312020-12-31
Value021.00
Percentage of EffectiveIncomeTaxRateReconciliationAtFederalStatutoryIncomeTaxRate0.0100.00.0

us-gaap:ExtinguishmentOfDebtAmount

us-gaap:ExtinguishmentOfDebtAmount


Extinguishment
Period End2021-06-302021-03-312020-12-312020-09-302020-04-242020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302017-12-312017-09-302017-06-302017-03-31
Value421857250.07367477390.00.071410.02101.0150.0504351070
Percentage of ExtinguishmentOfDebtAmount100.0100.0100.00.0100.0100.0100.00.00.0100.0100.0100.0100.0100.00.0100.0100.0100.0

us-gaap:ExtinguishmentOfDebtAmount dei:LegalEntity, us-gaap:DebtInstrument, us-gaap:SubsequentEventType

clf:AKSteel, clf:A63752025AKSeniorNotes, us-gaap:SubsequentEvent


Extinguishment
Period End2021-03-12
Value29
Percentage of ExtinguishmentOfDebtAmount0.0

clf:AKSteel, clf:A7.502023AKSeniorNotes, us-gaap:SubsequentEvent


Extinguishment
Period End2021-03-12
Value13
Percentage of ExtinguishmentOfDebtAmount0.0

clf:AKSteel, clf:A76252021AKSeniorNotes, us-gaap:SubsequentEvent


Extinguishment
Period End2021-03-12
Value34
Percentage of ExtinguishmentOfDebtAmount0.0

clf:ClevelandCliffsInc., clf:A48752024SeniorSecuredNotes, us-gaap:SubsequentEvent


Extinguishment
Period End2021-03-12
Value395
Percentage of ExtinguishmentOfDebtAmount0.0

clf:ClevelandCliffsInc., clf:A6.3752025SeniorNotes, us-gaap:SubsequentEvent


Extinguishment
Period End2021-03-12
Value64
Percentage of ExtinguishmentOfDebtAmount0.0

clf:ClevelandCliffsInc., clf:A98752025SeniorSecuredNotes, us-gaap:SubsequentEvent


Extinguishment
Period End2021-03-11
Value322
Percentage of ExtinguishmentOfDebtAmount0.0

us-gaap:ExtinguishmentOfDebtAmount us-gaap:DebtInstrument

clf:A1.502025ConvertibleSeniorNotes


Extinguishment
Period End2020-12-312020-09-302020-06-30
Value0.00.020
Percentage of ExtinguishmentOfDebtAmount0.00.02.7

clf:A4.8752024SeniorSecuredNotes


Extinguishment
Period End2021-06-302021-03-312020-09-302020-06-30
Value0.03950.05.5
Percentage of ExtinguishmentOfDebtAmount0.046.10.00.7

clf:A5.752025SeniorNotes


Extinguishment
Period End2021-06-302020-12-312020-09-302020-06-302019-12-312019-09-302019-06-30
Value396-0.10.0770.00.0600
Percentage of ExtinguishmentOfDebtAmount94.1-0.40.010.30.00.084.0

clf:A5.8752027SeniorNotes


Extinguishment
Period End2020-12-312020-09-302020-06-30
Value0.50.0194
Percentage of ExtinguishmentOfDebtAmount2.00.026.0

clf:A6.252040SeniorNotes


Extinguishment
Period End2020-12-312020-09-302020-06-30
Value0.30.035
Percentage of ExtinguishmentOfDebtAmount1.20.04.8

clf:A6.3752025SeniorNotes


Extinguishment
Period End2021-06-302021-03-312020-12-312020-09-302020-06-30
Value0.0640.50.0167
Percentage of ExtinguishmentOfDebtAmount0.07.52.00.022.4

clf:A63752025AKSeniorNotes


Extinguishment
Period End2021-06-302021-03-31
Value0.029
Percentage of ExtinguishmentOfDebtAmount0.03.4

clf:A7.002027SeniorNotes


Extinguishment
Period End2020-12-312020-09-302020-06-30
Value140.0247
Percentage of ExtinguishmentOfDebtAmount57.60.033.1

clf:A7.502023AKSeniorNotes


Extinguishment
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-272020-03-132020-03-31
Value0.013-0.20.00.056310367
Percentage of ExtinguishmentOfDebtAmount0.01.5-0.80.00.049.60.00.0

clf:A7.6252021AKSeniorNotes


Extinguishment
Period End2021-06-302021-03-312020-09-302020-06-302020-03-272020-03-132020-03-31
Value0.0340.00.08.5364372
Percentage of ExtinguishmentOfDebtAmount0.04.00.00.050.40.00.0

clf:A98752025SeniorSecuredNotes


Extinguishment
Period End2021-06-302021-03-112021-03-31
Value25322322
Percentage of ExtinguishmentOfDebtAmount5.937.60.0

us-gaap:SeniorNotes


Extinguishment
Period End2021-03-122020-06-30
Value53511
Percentage of ExtinguishmentOfDebtAmount0.01.5

us-gaap:FairValueAssetsMeasuredOnRecurringBasisChangeInUnrealizedGainLoss

us-gaap:FairValueAssetsMeasuredOnRecurringBasisChangeInUnrealizedGainLoss


Fair
Period End2020-09-302020-06-302020-03-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-30
Value2733-25.3-6.57315-49.6158044-14.00.12033-1.08.2213.66.4120.61063623329345732284524
Percentage of FairValueAssetsMeasuredOnRecurringBasisChangeInUnrealizedGainLoss100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:FairValueLiabilitiesMeasuredOnRecurringBasisChangeInUnrealizedGainLoss

us-gaap:FairValueLiabilitiesMeasuredOnRecurringBasisChangeInUnrealizedGainLoss


Fair
Period End2020-09-302020-03-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-30
Value-0.30.0-30.20.0-9.85.7-2.7-3.0-4.2126.0-11.7-9.12.2-2.7-0.7-4.4-2.6-0.5-5.8-16.211-3.1-12.8-7.41.120-25.2-6.80.44.1
Percentage of FairValueLiabilitiesMeasuredOnRecurringBasisChangeInUnrealizedGainLoss100.00.0100.00.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInEarnings1

us-gaap:FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInEarnings1


Fair
Period End2020-09-302020-06-302020-03-312019-09-302019-06-302019-03-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-30
Value-29.5-40.0266.5-74.3-15.3-139.0-158.6-49.1-39.8-60.6-53.3-42.5-41.2-14.6-34.5-11.2-7.0-15.0-0.6-10.1-63.2-62.6-33.0-29.0-34.3-57.6-32.4-28.0-45.3-24.9-61.4-43.3-258.1-53.8-46.5
Percentage of FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInEarnings1100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetSettlements

us-gaap:FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetSettlements


Fair
Period End2020-09-302020-06-302019-09-302019-06-302019-03-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-31
Value3.42438620.0123776.58943401438121710.09.61227385441434442364037385246-132.02175030-22.1
Percentage of FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetSettlements100.0100.0100.0100.00.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityGainLossIncludedInEarnings

us-gaap:FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityGainLossIncludedInEarnings


Fair
Period End2020-09-302020-06-302020-03-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-30
Value-0.30.0-0.6-34.44.5-9.81.3-3.1-3.7-4.0-26.2-19.3-36.8-8.9-1.3-2.9-2.8-5.6-15.6-13.71.1-16.211-3.1-12.8-7.41.120-25.2-6.8-23.0-4.1-1.47e-05-1.1-19.50.0
Percentage of FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityGainLossIncludedInEarnings100.00.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.00.0

us-gaap:FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilitySettlements

us-gaap:FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilitySettlements


Fair
Period End2020-09-302020-06-302020-03-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-30
Value0.00.01.74.25.30.04.40.40.72.23330250.03.52.86.42.813207.19.50.00.00.0100.00.00.0110.00.00.0190.00.0
Percentage of FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilitySettlements0.00.0100.0100.0100.00.0100.0100.0100.0100.0100.0100.0100.00.0100.0100.0100.0100.0100.0100.0100.0100.00.00.00.0100.00.00.00.0100.00.00.00.0100.00.00.0

us-gaap:FinitelivedIntangibleAssetsAcquired1 us-gaap:BusinessAcquisition

us-gaap:FinitelivedIntangibleAssetsAcquired1

clf:AKSteel


Finitelived
Period End2021-06-302021-03-31
Value0.0148
Percentage of FinitelivedIntangibleAssetsAcquired10.0100.0

clf:AKSteelHoldingCorporation


Finitelived
Period End2020-09-302020-06-302020-03-31
Value0.0-15.0163
Percentage of FinitelivedIntangibleAssetsAcquired10.00.00.0

us-gaap:FinitelivedIntangibleAssetsAcquired1 us-gaap:BusinessAcquisition, us-gaap:FiniteLivedIntangibleAssetsByMajorClass

clf:AKSteel, us-gaap:CustomerRelationships


Finitelived
Period End2021-06-302021-03-31
Value0.077
Percentage of FinitelivedIntangibleAssetsAcquired10.052.0

clf:AKSteel, us-gaap:TechnologyBasedIntangibleAssets


Finitelived
Period End2021-06-302021-03-31
Value0.060
Percentage of FinitelivedIntangibleAssetsAcquired10.040.5

clf:AKSteel, us-gaap:TrademarksAndTradeNames


Finitelived
Period End2021-06-302021-03-31
Value0.011
Percentage of FinitelivedIntangibleAssetsAcquired10.07.4

clf:AKSteelHoldingCorporation, us-gaap:CustomerRelationships


Finitelived
Period End2020-09-302020-06-302020-03-31
Value0.0-14.091
Percentage of FinitelivedIntangibleAssetsAcquired10.00.00.0

clf:AKSteelHoldingCorporation, us-gaap:TechnologyBasedIntangibleAssets


Finitelived
Period End2020-09-302020-06-302020-03-31
Value0.0-1.061
Percentage of FinitelivedIntangibleAssetsAcquired10.00.00.0

clf:AKSteelHoldingCorporation, us-gaap:TrademarksAndTradeNames


Finitelived
Period End2020-09-302020-06-302020-03-31
Value0.00.011
Percentage of FinitelivedIntangibleAssetsAcquired10.00.00.0

us-gaap:GoodwillPeriodIncreaseDecrease us-gaap:StatementBusinessSegments

us-gaap:GoodwillPeriodIncreaseDecrease

clf:Steelmaking


Goodwill
Period End2021-06-302021-03-31
Value76-412.0
Percentage of GoodwillPeriodIncreaseDecrease100.0100.0

us-gaap:GoodwillPurchaseAccountingAdjustments us-gaap:BusinessAcquisition

us-gaap:GoodwillPurchaseAccountingAdjustments

clf:AKSteel


Goodwill
Period End2021-03-31
Value0.0
Percentage of GoodwillPurchaseAccountingAdjustments0.0

clf:ArcelorMittalUSA


Goodwill
Period End2021-06-302021-03-31
Value76-412.0
Percentage of GoodwillPurchaseAccountingAdjustments0.00.0

us-gaap:IncomeLossFromDiscontinuedOperationsNetOfTaxAttributableToReportingEntity

us-gaap:IncomeLossFromDiscontinuedOperationsNetOfTaxAttributableToReportingEntity


Income
Period End2021-06-302020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-31
Value1.0-0.3-0.30.6-0.2-0.9-0.60.0-14.6238-64.3-70.9-5.132-46.40.5-19.3-2.7-0.42.5-23.1-43.9103-928.5-1451.8-5602.9-76.4-140.4
Percentage of IncomeLossFromDiscontinuedOperationsNetOfTaxAttributableToReportingEntity100.0100.0100.0100.0100.0100.0100.00.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:IncomeLossFromDiscontinuedOperationsNetOfTaxAttributableToReportingEntity clf:EBITDACalculation

clf:AdjustedEBITDACalculation


Income
Period End2021-06-302020-09-302020-06-302020-03-312019-09-302019-06-302019-03-312018-09-302018-06-302018-03-31
Value1.0-0.3-0.40.7-0.8-0.40.0238-54.7-63.1
Percentage of IncomeLossFromDiscontinuedOperationsNetOfTaxAttributableToReportingEntity100.0100.0133.3116.788.966.70.0100.185.189.0

us-gaap:IncomeTaxReconciliationOtherReconcilingItems

us-gaap:IncomeTaxReconciliationOtherReconcilingItems


Income
Period End2020-09-302020-06-302020-03-312019-09-302019-06-302019-03-312018-09-302018-06-302018-03-312017-09-302017-06-302016-09-30
Value-5.00.3-4.0-0.5-0.4-0.4-0.2-2.0155.9-0.32.9
Percentage of IncomeTaxReconciliationOtherReconcilingItems100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:IncreaseDecreaseInAccountsPayableAndAccruedLiabilities

us-gaap:IncreaseDecreaseInAccountsPayableAndAccruedLiabilities


Increase
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-31
Value6122160170-218.7-109.2-10.4-7.625-88.216-74.066-70.939-52.733-90.062-38.3-11.0-86.88.5-80.6-2.9-152.7-15.85144-117.78.0-47.568-139.2-113.836-185.0-103.9184166-64.43883-45.071-19.8
Percentage of IncreaseDecreaseInAccountsPayableAndAccruedLiabilities100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:IncreaseDecreaseInAccountsReceivableAndOtherOperatingAssets

us-gaap:IncreaseDecreaseInAccountsReceivableAndOtherOperatingAssets


Increase
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-31
Value423480301105-111.6-254.1-98.0-28.772-199.943-34.4134-196.3317-0.618-86.594-33.9-65.1-38.5-76.0-156.5-64.9-71.7181-13.476-161.5-102.65115-102.7-43.8
Percentage of IncreaseDecreaseInAccountsReceivableAndOtherOperatingAssets100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:IncreaseDecreaseInDeferredRevenue

us-gaap:IncreaseDecreaseInDeferredRevenue


Increase
Period End2021-03-312020-03-31
Value-3000000.0-48000000.0
Percentage of IncreaseDecreaseInDeferredRevenue100.0100.0

us-gaap:IncrementalCommonSharesAttributableToConversionOfDebtSecurities

us-gaap:IncrementalCommonSharesAttributableToConversionOfDebtSecurities


Incremental
Period End2021-06-302021-03-312020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-30
Value22190.00.0-1.43.76.70.01.58.00.0
Percentage of IncrementalCommonSharesAttributableToConversionOfDebtSecurities100.0100.00.00.0100.0100.0100.00.0100.0100.00.0

us-gaap:IncrementalCommonSharesAttributableToShareBasedPaymentArrangements

us-gaap:IncrementalCommonSharesAttributableToShareBasedPaymentArrangements


Incremental
Period End2021-06-302021-03-312020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-31
Value5000000.04000000.000-300000.02900000.03000000.00-500000.04300000.03700000.00-100000.05000000.04600000.00386000.002300000.0285000.0375000.000296000.00000236000.0214000.0200000.0254000.0-448000.0499000.0400000.0500000.00800000.0800000.0700000.037000.0900000.0800000.0800000.0
Percentage of IncrementalCommonSharesAttributableToShareBasedPaymentArrangements100.0100.00.00.0100.0100.0100.00.0100.0100.0100.00.0100.0100.0100.00.0100.00.0100.0100.0100.00.00.0100.00.00.00.00.0100.0100.0100.0100.0100.0100.0100.0100.00.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:InterestCostsCapitalized

us-gaap:InterestCostsCapitalized


Interest
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-31
Value2.01.01514139.77.97.05.94.02.61.81.11.0
Percentage of InterestCostsCapitalized100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:NetCashProvidedByUsedInContinuingOperations

us-gaap:NetCashProvidedByUsedInContinuingOperations


Net
Period End2020-12-312020-09-302019-12-312019-09-30
Value55600000.0-17700000.0-46100000.022100000.0
Percentage of NetCashProvidedByUsedInContinuingOperations100.0100.0100.0100.0

us-gaap:NetCashProvidedByUsedInDiscontinuedOperations

us-gaap:NetCashProvidedByUsedInDiscontinuedOperations


Net
Period End2020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-30
Value-0.4-1.0-4.42.81.01.24.8-1.63.213
Percentage of NetCashProvidedByUsedInDiscontinuedOperations100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:NetPeriodicDefinedBenefitsExpenseReversalOfExpenseExcludingServiceCostComponent

us-gaap:NetPeriodicDefinedBenefitsExpenseReversalOfExpenseExcludingServiceCostComponent


Net
Period End2021-06-302021-03-312020-06-302020-03-31
Value-46000000.0-47000000.0-15000000.0-6000000.0
Percentage of NetPeriodicDefinedBenefitsExpenseReversalOfExpenseExcludingServiceCostComponent100.0100.0100.0100.0

us-gaap:OtherComprehensiveIncomeLossAmortizationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetPriorServiceCostCreditBeforeTax us-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncome

us-gaap:OtherComprehensiveIncomeLossAmortizationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetPriorServiceCostCreditBeforeTax

us-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncome


Other
Period End2020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-31
Value-0.2-0.3-0.2-0.3-0.4-0.2-0.2-0.2
Percentage of OtherComprehensiveIncomeLossAmortizationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetPriorServiceCostCreditBeforeTax100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:OtherComprehensiveIncomeLossBeforeReclassificationsNetOfTax

us-gaap:OtherComprehensiveIncomeLossBeforeReclassificationsNetOfTax


Other
Period End2021-06-302021-03-312020-06-302020-03-31
Value517.02.0-6.0
Percentage of OtherComprehensiveIncomeLossBeforeReclassificationsNetOfTax100.0100.0100.0100.0

us-gaap:OtherComprehensiveIncomeLossBeforeReclassificationsNetOfTax us-gaap:StatementEquityComponents

us-gaap:AccumulatedDefinedBenefitPlansAdjustment


Other
Period End2020-09-302020-06-302020-03-312019-09-302019-06-302019-03-312018-09-302018-06-302018-03-312017-09-302017-06-302017-03-312016-09-302016-06-302016-03-312015-09-302015-06-302015-03-31
Value0.40.40.00.30.30.20.30.20.5-18.7-0.13.3-0.5-0.4-1.5-0.71.39.3
Percentage of OtherComprehensiveIncomeLossBeforeReclassificationsNetOfTax0.020.0-0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:AccumulatedForeignCurrencyAdjustmentIncludingPortionAttributableToNoncontrollingInterest


Other
Period End2021-03-312020-06-302020-03-31
Value-1.01.0-1.0
Percentage of OtherComprehensiveIncomeLossBeforeReclassificationsNetOfTax-14.350.016.7

us-gaap:AccumulatedGainLossCashFlowHedgeIncludingNoncontrollingInterest


Other
Period End2021-06-302021-03-312020-06-302020-03-31
Value518.01.0-5.0
Percentage of OtherComprehensiveIncomeLossBeforeReclassificationsNetOfTax100.0114.350.083.3

us-gaap:AccumulatedNetGainLossFromDesignatedOrQualifyingCashFlowHedges


Other
Period End2020-09-302020-06-302020-03-312019-09-302019-06-302019-03-312018-09-302018-06-302018-03-312016-09-302016-06-302016-03-312015-09-302015-06-302015-03-31
Value121.4-5.2-0.5-2.32.50.20.20.40.00.1-3.44.80.5-7.1
Percentage of OtherComprehensiveIncomeLossBeforeReclassificationsNetOfTax0.070.086.70.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:AccumulatedOtherComprehensiveIncome


Other
Period End2020-09-302020-06-302020-03-312019-09-302019-06-302019-03-312018-09-302018-06-302018-03-312017-09-302017-06-302017-03-312016-09-302016-06-302016-03-312015-09-302015-06-302015-03-31
Value142.5-6.1-0.2-2.02.70.32.61.6-18.2-1.6-9.40.4-3.0-0.6-7.24.0-9.7
Percentage of OtherComprehensiveIncomeLossBeforeReclassificationsNetOfTax0.0125.0101.70.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:AccumulatedTranslationAdjustment


Other
Period End2020-09-302020-06-302020-03-312018-09-302018-06-302018-03-312017-09-302017-06-302017-03-312016-09-302016-06-302016-03-312015-09-302015-06-302015-03-31
Value1.60.7-0.9-0.22.20.70.5-1.5-12.70.9-2.74.4-11.41.2-14.7
Percentage of OtherComprehensiveIncomeLossBeforeReclassificationsNetOfTax0.035.015.00.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:OtherComprehensiveIncomeLossCashFlowHedgeGainLossReclassificationAfterTax

us-gaap:OtherComprehensiveIncomeLossCashFlowHedgeGainLossReclassificationAfterTax


Other
Period End2021-06-302021-03-312020-06-302020-03-31
Value-47000000.0-7000000.0-4000000.03000000.0
Percentage of OtherComprehensiveIncomeLossCashFlowHedgeGainLossReclassificationAfterTax100.0100.0100.0100.0

us-gaap:OtherComprehensiveIncomeLossCashFlowHedgeGainLossReclassificationAfterTax us-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncome

us-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncome


Other
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-31
Value4000000.01000000.0800000.0-3500000.0-3100000.0-2200000.03300000.0-900000.0-200000.0-200000.0
Percentage of OtherComprehensiveIncomeLossCashFlowHedgeGainLossReclassificationAfterTax-8.5-14.30.00.077.5-73.30.00.00.00.0

us-gaap:OtherComprehensiveIncomeLossCashFlowHedgeGainLossReclassificationBeforeTax us-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncome

us-gaap:OtherComprehensiveIncomeLossCashFlowHedgeGainLossReclassificationBeforeTax

us-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncome


Other
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-31
Value5000000.01000000.01200000.0-4500000.0-3900000.0-2800000.04200000.0-1200000.0-200000.0-300000.0
Percentage of OtherComprehensiveIncomeLossCashFlowHedgeGainLossReclassificationBeforeTax100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:OtherComprehensiveIncomeLossCashFlowHedgeGainLossReclassificationTax us-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncome

us-gaap:OtherComprehensiveIncomeLossCashFlowHedgeGainLossReclassificationTax

us-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncome


Other
Period End2021-06-302020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-31
Value1000000.0400000.0-1000000.0-800000.0-600000.0900000.0-300000.00-100000.0
Percentage of OtherComprehensiveIncomeLossCashFlowHedgeGainLossReclassificationTax100.0100.0100.0100.0100.0100.0100.00.0100.0

us-gaap:OtherComprehensiveIncomeLossDerivativesQualifyingAsHedgesNetOfTax

us-gaap:OtherComprehensiveIncomeLossDerivativesQualifyingAsHedgesNetOfTax


Other
Period End2020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-30
Value-15.2154.5-3.0-1.30.4-2.12.7-3.10.3-0.20.3-44.4-7.0-6.114-4.43.812-16.71.7
Percentage of OtherComprehensiveIncomeLossDerivativesQualifyingAsHedgesNetOfTax100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax

us-gaap:OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax


Other
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-30
Value-7.0-7.0-162.8-6.6-6.0-5.651-5.8-5.8-5.737-6.8-6.7-6.77.4-7.5-6.7-4.738-7.1-6.5-5.4-9.2-6.6-0.6-28.8109-11.6-3.2-3.4-187.5-6.6-7.7-6.5-12.9-7.6-7.1-6.2135-4.9-0.8
Percentage of OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansBeforeTax us-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncome

us-gaap:OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansBeforeTax

us-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncome


Other
Period End2021-06-302020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-31
Value9.01.07.87.17.17.17.06.97.0
Percentage of OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansBeforeTax100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetGainLossBeforeTax us-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncome

us-gaap:OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetGainLossBeforeTax

us-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncome


Other
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-31
Value-9.0-9.0-7.2-8.1-7.3-7.449-7.2-7.1-7.2
Percentage of OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetGainLossBeforeTax100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansNetOfTax us-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncome

us-gaap:OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansNetOfTax

us-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncome


Other
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-31
Value7.07.00.66.25.65.65.55.55.55.5
Percentage of OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansNetOfTax100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansTax us-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncome

us-gaap:OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansTax

us-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncome


Other
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-31
Value2000000.02000000.0400000.01600000.01500000.01500000.01600000.01500000.01400000.01500000.0
Percentage of OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansTax100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:OtherNoncashIncomeExpense

us-gaap:OtherNoncashIncomeExpense


Other
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-30
Value-26.02.0-24.0-15.0-3.631-16.0-2.8-36.8-9.8-15.06.913-25.9-2.2-27.3-8.616-23.6-3.813-18.5-60.41.6-22.7-31.61547-21.6-3.2-11.4-11.334-5.227-30.4355.73.8-13.9-12.42222-43.8
Percentage of OtherNoncashIncomeExpense100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:OtherOperatingIncomeExpenseNet

us-gaap:OtherOperatingIncomeExpenseNet


Other
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-30
Value-25.0-3.0-19.5-15.5-13.1-13.3-8.0-7.8-5.6-3.6-3.4-6.0-4.1-8.724-5.9-3.011-13.8-19.65.7-3.09.0-3.5-0.820-70.2-53.7-47.8-58.649-43.5551.5-31.2-12.5289.48.564-8.23.8-12.0-19.21.3
Percentage of OtherOperatingIncomeExpenseNet100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:OtherPostretirementBenefitsPayments

us-gaap:OtherPostretirementBenefitsPayments


Other
Period End2021-06-30
Value5000000.0
Percentage of OtherPostretirementBenefitsPayments100.0

us-gaap:OtherSignificantNoncashTransactionValueOfConsiderationGiven1 us-gaap:AwardType

us-gaap:OtherSignificantNoncashTransactionValueOfConsiderationGiven1

us-gaap:StockCompensationPlan


Other
Period End2020-09-30
Value0.0
Percentage of OtherSignificantNoncashTransactionValueOfConsiderationGiven10.0

us-gaap:OtherSignificantNoncashTransactionValueOfConsiderationGiven1 us-gaap:StatementEquityComponents

us-gaap:CommonStock


Other
Period End2020-09-30
Value0.0
Percentage of OtherSignificantNoncashTransactionValueOfConsiderationGiven10.0

us-gaap:PaymentsForProceedsFromOtherInvestingActivities

us-gaap:PaymentsForProceedsFromOtherInvestingActivities


Payments
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302010-12-312010-09-30
Value-1.0-1.0-2.0-8.20.10.1-0.4-2.70.0-8.5-20.512-14.60.0-1.26.6-0.6-0.55.5-0.4-0.4-5.5-6.1-0.3-0.2-0.2-0.2-9.3-3.4-12.6-42.5-6.91.1-2.0-4.2-12.84.2-0.3-17.6-16.7-73.8-16.8
Percentage of PaymentsForProceedsFromOtherInvestingActivities100.0100.0100.0100.0100.0100.0100.0100.00.0100.0100.0100.0100.00.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:PaymentsOfDebtIssuanceCosts

us-gaap:PaymentsOfDebtIssuanceCosts


Payments
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312012-12-312011-12-31
Value1.01618-0.413440.00.06.80.00.00.00.01.5163.50.08.50.00.00.05.20.00.00.5336.92.10.00.04.30.0
Percentage of PaymentsOfDebtIssuanceCosts100.0100.0100.0100.0100.0100.00.00.0100.00.00.00.00.0100.0100.0100.00.0100.00.00.00.0100.00.00.0100.0100.0100.0100.00.00.0100.00.0

us-gaap:PaymentsToAcquireBusinessesGross

us-gaap:PaymentsToAcquireBusinessesGross


Payments
Period End2020-12-09
Value631
Percentage of PaymentsToAcquireBusinessesGross100.0

us-gaap:PaymentsToAcquireBusinessesGross us-gaap:BusinessAcquisition

clf:ArcelorMittalUSA


Payments
Period End2020-12-09
Value631
Percentage of PaymentsToAcquireBusinessesGross100.0

us-gaap:PaymentsToAcquireBusinessesGross us-gaap:StatementScenario, us-gaap:BusinessAcquisition

srt:ScenarioForecast, clf:ArcelorMittalUSA


Payments
Period End2020-12-31
Value505
Percentage of PaymentsToAcquireBusinessesGross0.0

us-gaap:PaymentsToAcquireBusinessesNetOfCashAcquired

us-gaap:PaymentsToAcquireBusinessesNetOfCashAcquired


Payments
Period End2020-09-302020-06-302020-03-312019-06-302019-03-312012-12-312011-12-312010-12-312010-09-30
Value0.00.08690.00.00.0-4423.523864
Percentage of PaymentsToAcquireBusinessesNetOfCashAcquired0.00.0100.00.00.00.0100.0100.0100.0

us-gaap:PensionAndOtherPostretirementBenefitContributions

us-gaap:PensionAndOtherPostretirementBenefitContributions


Pension
Period End2021-06-302021-03-312020-06-302020-03-31
Value481754.013
Percentage of PensionAndOtherPostretirementBenefitContributions100.0100.0100.0100.0

us-gaap:PensionContributions us-gaap:RetirementPlanType

us-gaap:PensionContributions

us-gaap:PensionPlansDefinedBenefit


Pension
Period End2021-06-302021-01-042021-03-312020-09-302020-06-302020-03-312019-09-302019-06-302019-03-312018-09-302018-06-302018-03-312017-09-302017-06-302017-03-312016-09-30
Value7.01181460.90.23.85.63.53.2183.32.3192.30.00.5
Percentage of PensionContributions100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.00.0100.0

us-gaap:ProceedsFromIncomeTaxRefunds

us-gaap:ProceedsFromIncomeTaxRefunds


Proceeds
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-31
Value1.0140.7580.0600.00.01170.0
Percentage of ProceedsFromIncomeTaxRefunds100.0100.0100.0100.00.0100.00.00.0100.00.0

us-gaap:ProceedsFromIssuanceOfCommonStock

us-gaap:ProceedsFromIssuanceOfCommonStock


Proceeds
Period End2021-06-302021-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312013-02-212012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-132011-06-30
Value0.03220.00.00.00.00.00.00.0661-0.22870.00.00.00.00.00.00.00.00.0-0.32852850.00.00.00.00.0853854853
Percentage of ProceedsFromIssuanceOfCommonStock0.0100.00.00.00.00.00.00.00.0100.0100.0100.00.00.00.00.00.00.00.00.00.0100.0100.0100.00.00.00.00.00.0100.0100.0100.0

us-gaap:ProceedsFromIssuanceOfSeniorLongTermDebt

us-gaap:ProceedsFromIssuanceOfSeniorLongTermDebt


Proceeds
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312012-12-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-31
Value0.010000.10.010467160.00.07200.00.00.00.00.07135570.05000.00.00.00.00.00.00.05030.00.00.00.04970.00.02986990.19920.0395
Percentage of ProceedsFromIssuanceOfSeniorLongTermDebt0.0100.0100.00.0100.0100.00.00.0100.00.00.00.00.00.0100.0100.00.0100.00.00.00.00.00.00.00.0100.00.00.00.00.0100.00.00.0100.0100.0100.0100.00.0100.0

us-gaap:ProceedsFromLinesOfCredit

us-gaap:ProceedsFromLinesOfCredit


Proceeds
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-06-302019-03-312012-12-312011-12-31
Value1522115812600.00.08000.00.00.00.0
Percentage of ProceedsFromLinesOfCredit100.0100.0100.00.00.0100.00.00.00.00.0

us-gaap:ProceedsFromPaymentsForOtherFinancingActivities

us-gaap:ProceedsFromPaymentsForOtherFinancingActivities


Proceeds
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-31
Value1.0-40.01020-23.7-19.9-0.21.4-2.5-8.4-1.8-36.8-3.4-5.5-9.7-3.1-8.3-5.6-5.2-5.7-9.4-4.2-7.13.8-28.3-14.318-35.6-61.28.7-26.4-2.3-10.9-15.4-12.6-12.8-12.11.0-19.9-7.6-20.71.212-8.9-7.5-9.1
Percentage of ProceedsFromPaymentsForOtherFinancingActivities100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:PropertyPlantAndEquipmentAdditions

us-gaap:PropertyPlantAndEquipmentAdditions


Property
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-31
Value16716215010273157184184191129152927078762725272426116.8251715134954527912721121819536135426635340725520691121834623
Percentage of PropertyPlantAndEquipmentAdditions100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:PropertyPlantAndEquipmentAdditions us-gaap:ConsolidatedEntities

us-gaap:CorporateNonSegment


Property
Period End2021-06-302021-03-312020-06-302020-03-31
Value0.0180.01.0
Percentage of PropertyPlantAndEquipmentAdditions0.011.10.00.6

us-gaap:PropertyPlantAndEquipmentAdditions us-gaap:StatementBusinessSegments

clf:CorporateandOtherSegments


Property
Period End2020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-31
Value0.71.00.00.60.22.10.90.1
Percentage of PropertyPlantAndEquipmentAdditions0.51.00.00.40.11.10.50.1

clf:MiningandPelletizing


Property
Period End2020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-31
Value1317342322354647512618
Percentage of PropertyPlantAndEquipmentAdditions13.023.821.712.812.018.636.231.355.937.923.7

clf:OtherBusinesses


Property
Period End2021-06-302021-03-312020-06-302020-03-31
Value21117.03.0
Percentage of PropertyPlantAndEquipmentAdditions12.66.89.61.9

clf:SteelandManufacturing


Property
Period End2020-09-302020-06-302020-03-312019-09-302019-06-302019-03-31
Value885512216015582
Percentage of PropertyPlantAndEquipmentAdditions86.076.277.986.980.963.7

clf:Steelmaking


Property
Period End2021-06-302021-03-312020-06-302020-03-31
Value14613366154
Percentage of PropertyPlantAndEquipmentAdditions87.482.190.497.7

us-gaap:ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTax us-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncome

us-gaap:ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTax

us-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncome


Reclassification
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-30
Value-3.0-6.00.2-9.7-8.7-7.86.36.45.75.74.8-221.56.56.16.86.86.56.46.67.46.36.34.2115.3
Percentage of ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTax100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTax us-gaap:StatementEquityComponents

us-gaap:AccumulatedDefinedBenefitPlansAdjustment


Reclassification
Period End2020-09-302020-06-302020-03-312019-09-302019-06-302019-03-312018-09-302018-06-302018-03-312017-09-302017-06-302017-03-312016-09-302016-06-302016-03-312015-09-302015-06-302015-03-31
Value-6.2-5.6-5.65.55.55.56.56.56.26.86.56.46.76.36.36.6-1.630
Percentage of ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTax63.964.471.885.996.596.5-2.9100.0101.6100.0100.0100.090.5100.0100.060.0-30.20.0

us-gaap:AccumulatedNetGainLossFromDesignatedOrQualifyingCashFlowHedges


Reclassification
Period End2020-09-302020-06-302020-03-312019-09-302019-06-302019-03-312018-09-302018-06-302018-03-312016-09-302016-06-302016-03-312015-09-302015-06-302015-03-31
Value-3.5-3.1-2.20.90.20.20.10.0-0.10.70.00.04.47.86.3
Percentage of ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTax36.135.628.214.13.53.5-0.00.0-1.69.50.00.040.0147.20.0

us-gaap:AccumulatedOtherComprehensiveIncome


Reclassification
Period End2020-09-302020-06-302020-03-312019-09-302019-06-302019-03-312018-09-302018-06-302018-03-312017-09-302017-06-302017-03-312016-09-302016-06-302016-03-312015-09-302015-06-302015-03-31
Value-9.7-8.7-7.86.45.75.7-221.56.56.16.86.56.47.46.36.3115.3217
Percentage of ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTax100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.00.0

us-gaap:ReclassificationFromAociCurrentPeriodNetOfTaxAttributableToParent

us-gaap:ReclassificationFromAociCurrentPeriodNetOfTaxAttributableToParent


Reclassification
Period End2021-06-302021-03-312020-06-302020-03-31
Value3.06.09.08.0
Percentage of ReclassificationFromAociCurrentPeriodNetOfTaxAttributableToParent100.0100.0100.0100.0

us-gaap:ReclassificationFromAociCurrentPeriodNetOfTaxAttributableToParent us-gaap:StatementEquityComponents

us-gaap:AccumulatedDefinedBenefitPlansAdjustmentIncludingPortionAttributableToNoncontrollingInterest


Reclassification
Period End2021-06-302021-03-312020-06-302020-03-31
Value7.07.06.06.0
Percentage of ReclassificationFromAociCurrentPeriodNetOfTaxAttributableToParent233.3116.766.775.0

us-gaap:AccumulatedGainLossCashFlowHedgeIncludingNoncontrollingInterest


Reclassification
Period End2021-06-302021-03-312020-06-302020-03-31
Value-4.0-1.03.02.0
Percentage of ReclassificationFromAociCurrentPeriodNetOfTaxAttributableToParent-133.3-16.733.325.0

us-gaap:RelatedPartyTransactionPurchasesFromRelatedParty

us-gaap:RelatedPartyTransactionPurchasesFromRelatedParty


Related
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-06-302019-03-31
Value1527-4.48.29.72.50.00.0
Percentage of RelatedPartyTransactionPurchasesFromRelatedParty100.0100.0100.0100.0100.0100.00.00.0

us-gaap:RepaymentsOfLinesOfCredit

us-gaap:RepaymentsOfLinesOfCredit


Repayments
Period End2021-06-302021-03-312020-12-312020-09-302012-12-312011-12-31
Value148010101501500.00.0
Percentage of RepaymentsOfLinesOfCredit100.0100.0100.0100.00.00.0

us-gaap:RevenueFromRelatedParties

us-gaap:RevenueFromRelatedParties


Revenue
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-31
Value3577305294281102222934154137039240962204265227118261223241103203208149110449390322216453455455288381476465331187822488313
Percentage of RevenueFromRelatedParties100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:RightOfUseAssetObtainedInExchangeForFinanceLeaseLiability

us-gaap:RightOfUseAssetObtainedInExchangeForFinanceLeaseLiability


Right
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-31
Value123.01.53.19.5290.04.59.7150.0
Percentage of RightOfUseAssetObtainedInExchangeForFinanceLeaseLiability100.0100.0100.0100.0100.0100.00.0100.0100.0100.00.0

us-gaap:SeveranceCosts1 clf:EBITDACalculation

us-gaap:SeveranceCosts1

clf:AdjustedEBITDACalculation


Severance
Period End2021-06-302021-03-312020-09-302020-06-302020-03-312019-09-302019-06-302019-03-312018-09-30
Value1.0112.416190.00.01.70.0
Percentage of SeveranceCosts1100.0100.0100.0100.0100.00.00.0100.00.0

us-gaap:SeveranceCosts1 us-gaap:BusinessAcquisition

clf:AKSteelHoldingCorporation


Severance
Period End2020-09-302020-06-302020-03-31
Value2.41517
Percentage of SeveranceCosts1100.091.091.2

us-gaap:StockIssuedDuringPeriodSharesAcquisitions us-gaap:BusinessAcquisition, us-gaap:StatementClassOfStock

us-gaap:StockIssuedDuringPeriodSharesAcquisitions

clf:ArcelorMittalUSA, us-gaap:CommonStock


Stock
Period End2020-12-09
Value78
Percentage of StockIssuedDuringPeriodSharesAcquisitions100.0

us-gaap:StockIssuedDuringPeriodSharesNewIssues us-gaap:StatementEquityComponents

us-gaap:StockIssuedDuringPeriodSharesNewIssues

us-gaap:CommonStock


Stock
Period End2021-03-31
Value20
Percentage of StockIssuedDuringPeriodSharesNewIssues100.0

us-gaap:StockIssuedDuringPeriodSharesShareBasedCompensation us-gaap:StatementEquityComponents

us-gaap:StockIssuedDuringPeriodSharesShareBasedCompensation

us-gaap:CommonStock


Stock
Period End2021-06-302021-03-312020-06-302020-03-312019-09-302019-06-302019-03-312018-09-302018-06-302018-03-31
Value1000000.01000000.0600000.01700000.0100000.0100000.01700000.0200000.0100000.0300000.0
Percentage of StockIssuedDuringPeriodSharesShareBasedCompensation100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:StockIssuedDuringPeriodValueShareBasedCompensation

us-gaap:StockIssuedDuringPeriodValueShareBasedCompensation


Stock
Period End2021-06-302021-03-312020-09-302020-06-302020-03-312019-09-302019-06-302019-03-312018-09-302018-06-302018-03-31
Value10.0-5.03.82.52.14.54.6-10.03.54.51.9
Percentage of StockIssuedDuringPeriodValueShareBasedCompensation100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:StockIssuedDuringPeriodValueShareBasedCompensation us-gaap:StatementEquityComponents

us-gaap:AdditionalPaidInCapital


Stock
Period End2020-09-302020-06-302020-03-312019-09-302019-06-302019-03-312018-09-302018-06-302018-03-31
Value2.7-6.6-23.64.13.4-56.5-5.00.2-15.8
Percentage of StockIssuedDuringPeriodValueShareBasedCompensation71.1-264.0-1123.891.173.9565.0-142.94.4-831.6

us-gaap:TreasuryStock


Stock
Period End2021-06-302021-03-312020-09-302020-06-302020-03-312019-09-302019-06-302019-03-312018-09-302018-06-302018-03-31
Value6.0171.19.1250.41.2468.54.317
Percentage of StockIssuedDuringPeriodValueShareBasedCompensation60.0-340.028.9364.01223.88.926.1-465.0242.995.6931.6

us-gaap:StockRedeemedOrCalledDuringPeriodValue us-gaap:StatementClassOfStock, us-gaap:SubsequentEventType

us-gaap:StockRedeemedOrCalledDuringPeriodValue

us-gaap:SeriesBPreferredStock, us-gaap:SubsequentEvent


Stock
Period End2021-07-27
Value1200
Percentage of StockRedeemedOrCalledDuringPeriodValue100.0

us-gaap:UndistributedEarningsLossAllocatedToParticipatingSecuritiesBasic

us-gaap:UndistributedEarningsLossAllocatedToParticipatingSecuritiesBasic


Undistributed
Period End2021-06-302021-03-31
Value824.0
Percentage of UndistributedEarningsLossAllocatedToParticipatingSecuritiesBasic100.0100.0

us-gaap:UnrealizedGainLossOnDerivativesAndCommodityContracts

us-gaap:UnrealizedGainLossOnDerivativesAndCommodityContracts


Unrealized
Period End2020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-31
Value842724-32.01.6-75.6215.7-26.2128240-43.4281.4177.5
Percentage of UnrealizedGainLossOnDerivativesAndCommodityContracts100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

clf:BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentAssetsIncomeTaxReceivable

clf:BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentAssetsIncomeTaxReceivable


Business
Period End2020-12-312020-03-13
Value123.0
Percentage of BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentAssetsIncomeTaxReceivable100.0100.0

clf:BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentAssetsIncomeTaxReceivable us-gaap:BusinessAcquisition

clf:AKSteel


Business
Period End2020-12-31
Value3.0
Percentage of BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentAssetsIncomeTaxReceivable25.0

clf:BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentLiabilitiesAccruedEmploymentCosts us-gaap:BusinessAcquisition

clf:BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentLiabilitiesAccruedEmploymentCosts

clf:AKSteel


Business
Period End2021-03-312020-12-312020-03-13
Value939394
Percentage of BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentLiabilitiesAccruedEmploymentCosts100.0100.0100.0

clf:ArcelorMittalUSA


Business
Period End2021-06-302021-03-312020-12-312020-12-09
Value272274271271
Percentage of BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentLiabilitiesAccruedEmploymentCosts0.0294.6291.40.0

clf:BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentLiabilitiesPensionAndOPEBLiabilities us-gaap:BusinessAcquisition

clf:BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentLiabilitiesPensionAndOPEBLiabilities

clf:AKSteel


Business
Period End2021-03-312020-12-312020-03-13
Value787875
Percentage of BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentLiabilitiesPensionAndOPEBLiabilities100.0100.0100.0

clf:BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentLiabilitiesStateAndLocalTaxes us-gaap:BusinessAcquisition

clf:BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentLiabilitiesStateAndLocalTaxes

clf:AKSteel


Business
Period End2020-12-312020-03-13
Value3135
Percentage of BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentLiabilitiesStateAndLocalTaxes100.0100.0

clf:ArcelorMittalUSA


Business
Period End2020-12-31
Value76
Percentage of BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentLiabilitiesStateAndLocalTaxes245.2

clf:BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNonCurrentLiabilitiesPensionAndOPEBLiabilities us-gaap:BusinessAcquisition

clf:BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNonCurrentLiabilitiesPensionAndOPEBLiabilities

clf:AKSteel


Business
Period End2021-03-312020-12-312020-03-13
Value871871873
Percentage of BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNonCurrentLiabilitiesPensionAndOPEBLiabilities100.0100.0100.0

clf:BusinessCombinationRecognizedIdentifiableAssetsAcquiredandLiabilitiesAssumedAssetRetirementObligations us-gaap:BusinessAcquisition

clf:BusinessCombinationRecognizedIdentifiableAssetsAcquiredandLiabilitiesAssumedAssetRetirementObligations

clf:AKSteelHoldingCorporation


Business
Period End2020-09-302020-06-302020-03-31
Value151313
Percentage of BusinessCombinationRecognizedIdentifiableAssetsAcquiredandLiabilitiesAssumedAssetRetirementObligations100.0100.0100.0

clf:BusinessCombinationRecognizedIdentifiableAssetsAcquiredandLiabilitiesAssumedCurrentLiabilitiesAcruedLiabilities us-gaap:BusinessAcquisition

clf:BusinessCombinationRecognizedIdentifiableAssetsAcquiredandLiabilitiesAssumedCurrentLiabilitiesAcruedLiabilities

clf:AKSteelHoldingCorporation


Business
Period End2020-09-302020-06-302020-03-31
Value222224222
Percentage of BusinessCombinationRecognizedIdentifiableAssetsAcquiredandLiabilitiesAssumedCurrentLiabilitiesAcruedLiabilities100.0100.0100.0

clf:BusinessCombinationRecognizedIdentifiableAssetsAcquiredandLiabilitiesAssumedDeferredIncomeTaxes us-gaap:BusinessAcquisition

clf:BusinessCombinationRecognizedIdentifiableAssetsAcquiredandLiabilitiesAssumedDeferredIncomeTaxes

clf:AKSteel


Business
Period End2021-03-312020-12-31
Value-69.030
Percentage of BusinessCombinationRecognizedIdentifiableAssetsAcquiredandLiabilitiesAssumedDeferredIncomeTaxes100.0100.0

clf:AKSteelHoldingCorporation


Business
Period End2020-09-302020-06-302020-03-31
Value192119
Percentage of BusinessCombinationRecognizedIdentifiableAssetsAcquiredandLiabilitiesAssumedDeferredIncomeTaxes0.00.00.0

clf:BusinessCombinationRecognizedIdentifiableAssetsAcquiredandLiabilitiesAssumedIntangibleLiability us-gaap:BusinessAcquisition

clf:BusinessCombinationRecognizedIdentifiableAssetsAcquiredandLiabilitiesAssumedIntangibleLiability

clf:AKSteelHoldingCorporation


Business
Period End2020-09-302020-06-302020-03-31
Value7075140
Percentage of BusinessCombinationRecognizedIdentifiableAssetsAcquiredandLiabilitiesAssumedIntangibleLiability100.0100.0100.0

clf:BusinessCombinationRecognizedIdentifiableAssetsAcquiredandLiabilitiesAssumedOperatingLeaseLiabilityNoncurrent us-gaap:BusinessAcquisition

clf:BusinessCombinationRecognizedIdentifiableAssetsAcquiredandLiabilitiesAssumedOperatingLeaseLiabilityNoncurrent

clf:AKSteelHoldingCorporation


Business
Period End2020-09-302020-06-302020-03-31
Value175188188
Percentage of BusinessCombinationRecognizedIdentifiableAssetsAcquiredandLiabilitiesAssumedOperatingLeaseLiabilityNoncurrent100.0100.0100.0

clf:BusinessCombinationRecognizedIdentifiableAssetsAcquiredandLiabilitiesAssumedPensionandOPEBLiabilities us-gaap:BusinessAcquisition

clf:BusinessCombinationRecognizedIdentifiableAssetsAcquiredandLiabilitiesAssumedPensionandOPEBLiabilities

clf:AKSteelHoldingCorporation


Business
Period End2020-09-302020-06-302020-03-31
Value870873873
Percentage of BusinessCombinationRecognizedIdentifiableAssetsAcquiredandLiabilitiesAssumedPensionandOPEBLiabilities100.0100.0100.0

clf:BusinessCombinationRecognizedIdentifiableAssetsAcquiredandLiabilitiesAssumedRightofuseAssetOperatingLease us-gaap:BusinessAcquisition

clf:BusinessCombinationRecognizedIdentifiableAssetsAcquiredandLiabilitiesAssumedRightofuseAssetOperatingLease

clf:AKSteelHoldingCorporation


Business
Period End2020-09-302020-06-302020-03-31
Value209209225
Percentage of BusinessCombinationRecognizedIdentifiableAssetsAcquiredandLiabilitiesAssumedRightofuseAssetOperatingLease100.0100.0100.0

clf:BusinessCombinationSeparatelyRecognizedTransactionsAccountsReceivable us-gaap:BusinessAcquisition

clf:BusinessCombinationSeparatelyRecognizedTransactionsAccountsReceivable

clf:ArcelorMittalUSA


Business
Period End2020-12-09
Value97
Percentage of BusinessCombinationSeparatelyRecognizedTransactionsAccountsReceivable100.0

clf:CommonStockSharesOptionToPurchaseAdditionalShares us-gaap:SubsequentEventType

clf:CommonStockSharesOptionToPurchaseAdditionalShares

us-gaap:SubsequentEvent


Common
Period End2021-02-11
Value9000000.0
Percentage of CommonStockSharesOptionToPurchaseAdditionalShares100.0

clf:CommonStockSharesSold dei:LegalEntity

clf:CommonStockSharesSold

clf:ArcelorMittal


Common
Period End2021-02-11
Value40
Percentage of CommonStockSharesSold100.0

clf:CommonStockSharesSold dei:LegalEntity, us-gaap:SubsequentEventType

clf:ArcelorMittal, us-gaap:SubsequentEvent


Common
Period End2021-02-11
Value40
Percentage of CommonStockSharesSold100.0

clf:Costsynergies us-gaap:StatementScenario, us-gaap:BusinessAcquisition

clf:Costsynergies

srt:ScenarioForecast, clf:AKSteelHoldingCorporation


Costsynergiesus-gaap:
Period End2020-10-01
Value150
Percentage of Costsynergies100.0

clf:EstimatedProjectCapitalExpenditures

clf:EstimatedProjectCapitalExpenditures


Estimated
Period End2020-09-30
Value1000
Percentage of EstimatedProjectCapitalExpenditures100.0

clf:FairValueMeasurementWithUnobservableInputsRange us-gaap:Range, us-gaap:BalanceSheetLocation, us-gaap:DerivativeInstrumentRisk, us-gaap:FairValueByFairValueHierarchyLevel, us-gaap:HedgingDesignation, us-gaap:MeasurementInputType, us-gaap:ValuationTechnique

clf:FairValueMeasurementWithUnobservableInputsRange

srt:Maximum, us-gaap:OtherCurrentAssets, clf:CustomerSupplyAgreement, us-gaap:FairValueInputsLevel3, us-gaap:Nondesignated, clf:CustomersHotRolledSteelEstimate, us-gaap:MarketApproachValuationTechnique


Fair
Period End2020-09-30
Value634.0
Percentage of FairValueMeasurementWithUnobservableInputsRange100.0

srt:Maximum, us-gaap:OtherCurrentAssets, clf:ProvisionalPricingArrangements, us-gaap:FairValueInputsLevel3, us-gaap:Nondesignated, clf:Platts62Price, us-gaap:MarketApproachValuationTechnique


Fair
Period End2020-09-30
Value123.0
Percentage of FairValueMeasurementWithUnobservableInputsRange19.4

srt:Minimum, us-gaap:OtherCurrentAssets, clf:CustomerSupplyAgreement, us-gaap:FairValueInputsLevel3, us-gaap:Nondesignated, clf:CustomersHotRolledSteelEstimate, us-gaap:MarketApproachValuationTechnique


Fair
Period End2020-09-30
Value542.0
Percentage of FairValueMeasurementWithUnobservableInputsRange85.5

srt:Minimum, us-gaap:OtherCurrentAssets, clf:ProvisionalPricingArrangements, us-gaap:FairValueInputsLevel3, us-gaap:Nondesignated, clf:Platts62Price, us-gaap:MarketApproachValuationTechnique


Fair
Period End2020-09-30
Value104.0
Percentage of FairValueMeasurementWithUnobservableInputsRange16.4

srt:WeightedAverage, us-gaap:OtherCurrentAssets, clf:CustomerSupplyAgreement, us-gaap:FairValueInputsLevel3, us-gaap:Nondesignated, clf:CustomersHotRolledSteelEstimate, us-gaap:MarketApproachValuationTechnique


Fair
Period End2020-09-30
Value548.0
Percentage of FairValueMeasurementWithUnobservableInputsRange86.4

srt:WeightedAverage, us-gaap:OtherCurrentAssets, clf:ProvisionalPricingArrangements, us-gaap:FairValueInputsLevel3, us-gaap:Nondesignated, clf:AtlanticBasinPelletPremium, us-gaap:MarketApproachValuationTechnique


Fair
Period End2020-09-30
Value30.0
Percentage of FairValueMeasurementWithUnobservableInputsRange4.7

srt:WeightedAverage, us-gaap:OtherCurrentAssets, clf:ProvisionalPricingArrangements, us-gaap:FairValueInputsLevel3, us-gaap:Nondesignated, clf:Platts62Price, us-gaap:MarketApproachValuationTechnique


Fair
Period End2020-09-30
Value105.0
Percentage of FairValueMeasurementWithUnobservableInputsRange16.6

srt:WeightedAverage, us-gaap:OtherCurrentLiabilities, clf:ProvisionalPricingArrangements, us-gaap:FairValueInputsLevel3, us-gaap:Nondesignated, clf:Platts62Price, us-gaap:MarketApproachValuationTechnique


Fair
Period End2020-09-30
Value104.0
Percentage of FairValueMeasurementWithUnobservableInputsRange16.4

srt:WeightedAverage, us-gaap:OtherCurrentLiabilities, clf:ProvisionalPricingArrangements, us-gaap:FairValueInputsLevel3, us-gaap:Nondesignated, clf:ProducerPriceIndices, us-gaap:MarketApproachValuationTechnique


Fair
Period End2020-09-30
Value110.0
Percentage of FairValueMeasurementWithUnobservableInputsRange17.4

clf:FiniteLivedIntangibleLiabilitiesAmortizationCreditNextTwelveMonths

clf:FiniteLivedIntangibleLiabilitiesAmortizationCreditNextTwelveMonths


Finite
Period End2021-06-302021-03-312020-12-312020-09-30
Value5000000.05000000.08000000.07800000.0
Percentage of FiniteLivedIntangibleLiabilitiesAmortizationCreditNextTwelveMonths100.0100.0100.0100.0

clf:FiniteLivedIntangibleLiabilitiesAmortizationCreditRemainderofFiscalYear

clf:FiniteLivedIntangibleLiabilitiesAmortizationCreditRemainderofFiscalYear


Finite
Period End2021-06-302021-03-312020-09-30
Value4000000.06000000.02000000.0
Percentage of FiniteLivedIntangibleLiabilitiesAmortizationCreditRemainderofFiscalYear100.0100.0100.0

clf:FiniteLivedIntangibleLiabilitiesAmortizationCreditYearFive

clf:FiniteLivedIntangibleLiabilitiesAmortizationCreditYearFive


Finite
Period End2021-06-302021-03-312020-12-312020-09-30
Value5000000.05000000.08000000.07800000.0
Percentage of FiniteLivedIntangibleLiabilitiesAmortizationCreditYearFive100.0100.0100.0100.0

clf:FiniteLivedIntangibleLiabilitiesAmortizationCreditYearFour

clf:FiniteLivedIntangibleLiabilitiesAmortizationCreditYearFour


Finite
Period End2021-06-302021-03-312020-12-312020-09-30
Value5000000.05000000.08000000.07800000.0
Percentage of FiniteLivedIntangibleLiabilitiesAmortizationCreditYearFour100.0100.0100.0100.0

clf:FiniteLivedIntangibleLiabilitiesAmortizationCreditYearThree

clf:FiniteLivedIntangibleLiabilitiesAmortizationCreditYearThree


Finite
Period End2021-06-302021-03-312020-12-312020-09-30
Value5000000.05000000.08000000.07800000.0
Percentage of FiniteLivedIntangibleLiabilitiesAmortizationCreditYearThree100.0100.0100.0100.0

clf:FiniteLivedIntangibleLiabilitiesAmortizationCreditYearTwo

clf:FiniteLivedIntangibleLiabilitiesAmortizationCreditYearTwo


Finite
Period End2021-06-302021-03-312020-12-312020-09-30
Value5000000.05000000.08000000.07800000.0
Percentage of FiniteLivedIntangibleLiabilitiesAmortizationCreditYearTwo100.0100.0100.0100.0

clf:FiniteLivedIntangibleLiabilityAccumulatedAmortization

clf:FiniteLivedIntangibleLiabilityAccumulatedAmortization


Finite
Period End2021-06-302021-03-312020-12-312020-09-30
Value10000000.08000000.07000000.04600000.0
Percentage of FiniteLivedIntangibleLiabilityAccumulatedAmortization100.0100.0100.0100.0

clf:FiniteLivedIntangibleLiabilityGross

clf:FiniteLivedIntangibleLiabilityGross


Finite
Period End2021-06-302021-03-312020-12-312020-09-30
Value71717170
Percentage of FiniteLivedIntangibleLiabilityGross100.0100.0100.0100.0

clf:FiniteLivedIntangibleLiabilityNet

clf:FiniteLivedIntangibleLiabilityNet


Finite
Period End2021-06-302021-03-312020-12-312020-09-30
Value61636465
Percentage of FiniteLivedIntangibleLiabilityNet100.0100.0100.0100.0

clf:FinitelivedIntangibleLiabilityAssumed us-gaap:BusinessAcquisition

clf:FinitelivedIntangibleLiabilityAssumed

clf:AKSteelHoldingCorporation


Finitelived
Period End2020-09-30
Value70
Percentage of FinitelivedIntangibleLiabilityAssumed100.0

clf:IntangibleLiabilityNet

clf:IntangibleLiabilityNet


Intangible
Period End2020-09-302020-06-302020-03-312019-12-31
Value65721370.0
Percentage of IntangibleLiabilityNet100.0100.0100.00.0

clf:LineOfCreditFacilityMaximumBorrowingCapacityTrancheA us-gaap:CreditFacility, us-gaap:LongtermDebtType

clf:LineOfCreditFacilityMaximumBorrowingCapacityTrancheA

us-gaap:RevolvingCreditFacility, us-gaap:LineOfCredit


Line
Period End2020-12-09
Value1500
Percentage of LineOfCreditFacilityMaximumBorrowingCapacityTrancheA100.0

clf:OtherAssetsLiabilitiesNet dei:LegalEntity, us-gaap:ConsolidatedEntities

clf:OtherAssetsLiabilitiesNet

clf:SunCokeMiddletown, us-gaap:VariableInterestEntityPrimaryBeneficiary


Other
Period End2021-06-302021-03-312020-12-312020-09-30
Value-6000000.01000000.0-10000000.0-5600000.0
Percentage of OtherAssetsLiabilitiesNet100.0100.0100.0100.0

clf:ReserveForInvestmentCommitments us-gaap:DefinedBenefitPlanByPlanAssetCategories, us-gaap:RetirementPlanType

clf:ReserveForInvestmentCommitments

us-gaap:PrivateEquityFunds, us-gaap:PensionPlansDefinedBenefit


Reserve
Period End2020-12-31
Value86
Percentage of ReserveForInvestmentCommitments100.0

us-gaap:AccountsPayableRelatedPartiesCurrent

us-gaap:AccountsPayableRelatedPartiesCurrent


Accounts
Period End2020-12-31
Value6000000.0
Percentage of AccountsPayableRelatedPartiesCurrent100.0

us-gaap:AccountsReceivableRelatedPartiesCurrent

us-gaap:AccountsReceivableRelatedPartiesCurrent


Accounts
Period End2020-12-312019-12-312011-09-302011-06-302010-12-31
Value2.03169706.8
Percentage of AccountsReceivableRelatedPartiesCurrent100.0100.0100.0100.0100.0

us-gaap:AccrualForEnvironmentalLossContingencies

us-gaap:AccrualForEnvironmentalLossContingencies


Accrual
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312009-12-31
Value1591341354041402.02.12.42.42.52.73.23.12.92.92.82.82.83.03.53.53.64.34.23.75.55.611118.48.49.11515161415151513131314
Percentage of AccrualForEnvironmentalLossContingencies100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:AccruedEnvironmentalLossContingenciesCurrent

us-gaap:AccruedEnvironmentalLossContingenciesCurrent


Accrued
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-31
Value1520186.46.56.40.3
Percentage of AccruedEnvironmentalLossContingenciesCurrent100.0100.0100.0100.0100.0100.0100.0

us-gaap:AccruedEnvironmentalLossContingenciesNoncurrent

us-gaap:AccruedEnvironmentalLossContingenciesNoncurrent


Accrued
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-31
Value1441141173434331.7
Percentage of AccruedEnvironmentalLossContingenciesNoncurrent100.0100.0100.0100.0100.0100.0100.0

us-gaap:AccumulatedOtherComprehensiveIncomeLossBeforeTax1

us-gaap:AccumulatedOtherComprehensiveIncomeLossBeforeTax1