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FAIR VALUE OF FINANCIAL INSTRUMENTS (Schedule Of Quantitative Inputs And Assumptions For Level 3 Assets And Liabilities) (Details) (USD $)
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3 Months Ended |
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Mar. 31, 2015
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Dec. 31, 2014
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| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
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| Derivative asset, fair value |
$ 34,500,000us-gaap_DerivativeFairValueOfDerivativeAsset
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$ 63,200,000us-gaap_DerivativeFairValueOfDerivativeAsset
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| Derivative liability, fair value |
26,500,000us-gaap_DerivativeFairValueOfDerivativeLiability
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41,000,000us-gaap_DerivativeFairValueOfDerivativeLiability
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| Management Estimate of 62% Fe |
62.00%clf_ManagementEstimateOf62Fe
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| Not Designated as Hedging Instrument [Member] |
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| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
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| Derivative asset, fair value |
34,500,000us-gaap_DerivativeFairValueOfDerivativeAsset
/ us-gaap_HedgingDesignationAxis
= us-gaap_NondesignatedMember
|
63,200,000us-gaap_DerivativeFairValueOfDerivativeAsset
/ us-gaap_HedgingDesignationAxis
= us-gaap_NondesignatedMember
|
| Derivative liability, fair value |
26,500,000us-gaap_DerivativeFairValueOfDerivativeLiability
/ us-gaap_HedgingDesignationAxis
= us-gaap_NondesignatedMember
|
19,400,000us-gaap_DerivativeFairValueOfDerivativeLiability
/ us-gaap_HedgingDesignationAxis
= us-gaap_NondesignatedMember
|
| Fair Value, Inputs, Level 3 [Member] | Not Designated as Hedging Instrument [Member] | Managements Estimate Of 62% Fee [Member] |
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| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
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|
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|
| Management Estimate of 62% Fe |
62.00%clf_ManagementEstimateOf62Fe
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ clf_FairValueOfAssetsAndLiabilitiesMeasureOnUnobservableInputAxis
= clf_ManagementsEstimateOfSixtyTwoPercentMember
/ us-gaap_HedgingDesignationAxis
= us-gaap_NondesignatedMember
|
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| Fair Value, Inputs, Level 3 [Member] | Not Designated as Hedging Instrument [Member] | Market Approach Valuation Technique [Member] | Provisional Pricing Arrangements [Member] | Managements Estimate Of 62% Fee [Member] |
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| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
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| Fair value measurement with unobservable inputs derivative asset range |
51clf_FairValueMeasurementWithUnobservableInputsDerivativeAssetRange
/ us-gaap_DerivativeInstrumentRiskAxis
= clf_ProvisionalPricingArrangementsMember
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ clf_FairValueOfAssetsAndLiabilitiesMeasureOnUnobservableInputAxis
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/ us-gaap_HedgingDesignationAxis
= us-gaap_NondesignatedMember
/ us-gaap_ValuationTechniqueAxis
= us-gaap_MarketApproachValuationTechniqueMember
|
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| Fair Value, Inputs, Level 3 [Member] | Not Designated as Hedging Instrument [Member] | Market Approach Valuation Technique [Member] | Customer Supply Agreement [Member] | Hot-Rolled Steel Estimate [Member] |
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| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
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| Fair value measurement with unobservable inputs derivative asset range |
563clf_FairValueMeasurementWithUnobservableInputsDerivativeAssetRange
/ us-gaap_DerivativeInstrumentRiskAxis
= clf_CustomerSupplyAgreementMember
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ clf_FairValueOfAssetsAndLiabilitiesMeasureOnUnobservableInputAxis
= clf_HotRolledSteelEstimateMember
/ us-gaap_HedgingDesignationAxis
= us-gaap_NondesignatedMember
/ us-gaap_ValuationTechniqueAxis
= us-gaap_MarketApproachValuationTechniqueMember
|
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| Fair Value, Inputs, Level 3 [Member] | Not Designated as Hedging Instrument [Member] | Market Approach Valuation Technique [Member] | Customer Supply Agreement [Member] | Hot-Rolled Steel Estimate [Member] | Minimum [Member] |
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| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
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|
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| Fair value measurement with unobservable inputs derivative asset range |
540clf_FairValueMeasurementWithUnobservableInputsDerivativeAssetRange
/ us-gaap_DerivativeInstrumentRiskAxis
= clf_CustomerSupplyAgreementMember
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ clf_FairValueOfAssetsAndLiabilitiesMeasureOnUnobservableInputAxis
= clf_HotRolledSteelEstimateMember
/ us-gaap_HedgingDesignationAxis
= us-gaap_NondesignatedMember
/ us-gaap_RangeAxis
= us-gaap_MinimumMember
/ us-gaap_ValuationTechniqueAxis
= us-gaap_MarketApproachValuationTechniqueMember
|
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| Fair Value, Inputs, Level 3 [Member] | Not Designated as Hedging Instrument [Member] | Market Approach Valuation Technique [Member] | Customer Supply Agreement [Member] | Hot-Rolled Steel Estimate [Member] | Maximum [Member] |
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| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
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|
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|
| Fair value measurement with unobservable inputs derivative asset range |
575clf_FairValueMeasurementWithUnobservableInputsDerivativeAssetRange
/ us-gaap_DerivativeInstrumentRiskAxis
= clf_CustomerSupplyAgreementMember
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
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/ clf_FairValueOfAssetsAndLiabilitiesMeasureOnUnobservableInputAxis
= clf_HotRolledSteelEstimateMember
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= us-gaap_NondesignatedMember
/ us-gaap_RangeAxis
= us-gaap_MaximumMember
/ us-gaap_ValuationTechniqueAxis
= us-gaap_MarketApproachValuationTechniqueMember
|
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|
| Derivative Financial Instruments, Assets [Member] | Fair Value, Inputs, Level 3 [Member] | Not Designated as Hedging Instrument [Member] | Market Approach Valuation Technique [Member] | Provisional Pricing Arrangements [Member] |
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| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
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|
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| Derivative asset, fair value |
0us-gaap_DerivativeFairValueOfDerivativeAsset
/ us-gaap_BalanceSheetLocationAxis
= us-gaap_DerivativeFinancialInstrumentsAssetsMember
/ us-gaap_DerivativeInstrumentRiskAxis
= clf_ProvisionalPricingArrangementsMember
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_HedgingDesignationAxis
= us-gaap_NondesignatedMember
/ us-gaap_ValuationTechniqueAxis
= us-gaap_MarketApproachValuationTechniqueMember
|
0us-gaap_DerivativeFairValueOfDerivativeAsset
/ us-gaap_BalanceSheetLocationAxis
= us-gaap_DerivativeFinancialInstrumentsAssetsMember
/ us-gaap_DerivativeInstrumentRiskAxis
= clf_ProvisionalPricingArrangementsMember
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_HedgingDesignationAxis
= us-gaap_NondesignatedMember
/ us-gaap_ValuationTechniqueAxis
= us-gaap_MarketApproachValuationTechniqueMember
|
| Derivative Financial Instruments, Assets [Member] | Fair Value, Inputs, Level 3 [Member] | Not Designated as Hedging Instrument [Member] | Market Approach Valuation Technique [Member] | Customer Supply Agreement [Member] |
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|
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|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
Ìý
|
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|
| Derivative asset, fair value |
34,500,000us-gaap_DerivativeFairValueOfDerivativeAsset
/ us-gaap_BalanceSheetLocationAxis
= us-gaap_DerivativeFinancialInstrumentsAssetsMember
/ us-gaap_DerivativeInstrumentRiskAxis
= clf_CustomerSupplyAgreementMember
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_HedgingDesignationAxis
= us-gaap_NondesignatedMember
/ us-gaap_ValuationTechniqueAxis
= us-gaap_MarketApproachValuationTechniqueMember
|
63,200,000us-gaap_DerivativeFairValueOfDerivativeAsset
/ us-gaap_BalanceSheetLocationAxis
= us-gaap_DerivativeFinancialInstrumentsAssetsMember
/ us-gaap_DerivativeInstrumentRiskAxis
= clf_CustomerSupplyAgreementMember
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_HedgingDesignationAxis
= us-gaap_NondesignatedMember
/ us-gaap_ValuationTechniqueAxis
= us-gaap_MarketApproachValuationTechniqueMember
|
| Derivative Financial Instruments, Liabilities [Member] | Fair Value, Inputs, Level 3 [Member] | Not Designated as Hedging Instrument [Member] | Market Approach Valuation Technique [Member] | Provisional Pricing Arrangements [Member] |
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|
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|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
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|
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|
| Derivative liability, fair value |
16,200,000us-gaap_DerivativeFairValueOfDerivativeLiability
/ us-gaap_BalanceSheetLocationAxis
= us-gaap_DerivativeFinancialInstrumentsLiabilitiesMember
/ us-gaap_DerivativeInstrumentRiskAxis
= clf_ProvisionalPricingArrangementsMember
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_HedgingDesignationAxis
= us-gaap_NondesignatedMember
/ us-gaap_ValuationTechniqueAxis
= us-gaap_MarketApproachValuationTechniqueMember
|
9,500,000us-gaap_DerivativeFairValueOfDerivativeLiability
/ us-gaap_BalanceSheetLocationAxis
= us-gaap_DerivativeFinancialInstrumentsLiabilitiesMember
/ us-gaap_DerivativeInstrumentRiskAxis
= clf_ProvisionalPricingArrangementsMember
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_HedgingDesignationAxis
= us-gaap_NondesignatedMember
/ us-gaap_ValuationTechniqueAxis
= us-gaap_MarketApproachValuationTechniqueMember
|
| Derivative Financial Instruments, Liabilities [Member] | Fair Value, Inputs, Level 3 [Member] | Not Designated as Hedging Instrument [Member] | Market Approach Valuation Technique [Member] | Customer Supply Agreement [Member] |
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| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
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|
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|
| Derivative liability, fair value |
$ 0us-gaap_DerivativeFairValueOfDerivativeLiability
/ us-gaap_BalanceSheetLocationAxis
= us-gaap_DerivativeFinancialInstrumentsLiabilitiesMember
/ us-gaap_DerivativeInstrumentRiskAxis
= clf_CustomerSupplyAgreementMember
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
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/ us-gaap_HedgingDesignationAxis
= us-gaap_NondesignatedMember
/ us-gaap_ValuationTechniqueAxis
= us-gaap_MarketApproachValuationTechniqueMember
|
$ 0us-gaap_DerivativeFairValueOfDerivativeLiability
/ us-gaap_BalanceSheetLocationAxis
= us-gaap_DerivativeFinancialInstrumentsLiabilitiesMember
/ us-gaap_DerivativeInstrumentRiskAxis
= clf_CustomerSupplyAgreementMember
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_HedgingDesignationAxis
= us-gaap_NondesignatedMember
/ us-gaap_ValuationTechniqueAxis
= us-gaap_MarketApproachValuationTechniqueMember
|