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金融工具公允价值（第三级资产和负债的量化投入和假设表）（详细信息）（美元）
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3个月结束 |
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2015年3月31日
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2014年12月31日
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| 公允价值、经常性和非经常性计量资产和负债[细目] |
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| 衍生资产，公允价值 |
34500000美元us-gaap_DerivativeFairValueOfDerivativeAsset |
63200000美元us-gaap_DerivativeFairValueOfDerivativeAsset |
| 衍生负债，公允价值 |
26500000年us-gaap_DerivativeFairValueOfDerivativeLiability |
41000000年us-gaap_DerivativeFairValueOfDerivativeLiability |
| 管理层估计62%的铁 |
62.00%clf_ManagementEstimateOf62Fe |
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| 非指定为套期工具〔成员〕 |
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| 公允价值、经常性和非经常性计量资产和负债[细目] |
|
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| 衍生资产，公允价值 |
34500000年us-gaap_DerivativeFairValueOfDerivativeAsset
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63200000年us-gaap_DerivativeFairValueOfDerivativeAsset
/ us-gaap_HedgingDesignationAxis
= us-gaap_NondesignatedMember |
| 衍生负债，公允价值 |
26500000年us-gaap_DerivativeFairValueOfDerivativeLiability
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19400000年us-gaap_DerivativeFairValueOfDerivativeLiability
/ us-gaap_HedgingDesignationAxis
= us-gaap_NondesignatedMember |
| 公允价值，投入，第3级[成员]|未被指定为套期工具[成员]|管理层估计62%费用[成员] |
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| 公允价值、经常性和非经常性计量资产和负债[细目] |
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| 管理层估计62%的铁 |
62.00%clf_ManagementEstimateOf62Fe
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
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= us-gaap_NondesignatedMember |
|
| 公允价值，投入，第3级[成员]|未被指定为套期保值工具[成员]|市场方法估值技术[成员]|临时定价安排[成员]|管理层估计62%费用[成员] |
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| 公允价值、经常性和非经常性计量资产和负债[细目] |
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| 公允价值计量包含不可观察输入的衍生资产范围 |
51clf_FairValueMeasurementWithUnobservableInputsDerivativeAssetRange
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/ clf_FairValueOfAssetsAndLiabilitiesMeasureOnUnobservableInputAxis
= clf_ManagementsEstimateOfSixtyTwoPercentMember
/ us-gaap_HedgingDesignationAxis
= us-gaap_NondesignatedMember
/ us-gaap_ValuationTechniqueAxis
= us-gaap_MarketApproachValuationTechniqueMember |
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| 公允价值，投入，第3级[成员]|未指定为套期保值工具[成员]|市场方法评估技术[成员]|客户供应协议[成员]|热轧钢估计[成员] |
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| 公允价值、经常性和非经常性计量资产和负债[细目] |
|
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| 公允价值计量包含不可观察输入的衍生资产范围 |
563clf_FairValueMeasurementWithUnobservableInputsDerivativeAssetRange
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/ clf_FairValueOfAssetsAndLiabilitiesMeasureOnUnobservableInputAxis
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/ us-gaap_HedgingDesignationAxis
= us-gaap_NondesignatedMember
/ us-gaap_ValuationTechniqueAxis
= us-gaap_MarketApproachValuationTechniqueMember |
|
| 公允价值，投入，第3级[成员]|未指定为套期保值工具[成员]|市场方法评估技术[成员]|客户供应协议[成员]|热轧钢估计[成员]|最低[成员] |
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| 公允价值、经常性和非经常性计量资产和负债[细目] |
|
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| 公允价值计量包含不可观察输入的衍生资产范围 |
540clf_FairValueMeasurementWithUnobservableInputsDerivativeAssetRange
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/ us-gaap_FairValueByFairValueHierarchyLevelAxis
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/ clf_FairValueOfAssetsAndLiabilitiesMeasureOnUnobservableInputAxis
= clf_HotRolledSteelEstimateMember
/ us-gaap_HedgingDesignationAxis
= us-gaap_NondesignatedMember
/ us-gaap_RangeAxis
= us-gaap_MinimumMember
/ us-gaap_ValuationTechniqueAxis
= us-gaap_MarketApproachValuationTechniqueMember |
|
| 公允价值，投入，第3级[成员]|未指定为套期保值工具[成员]|市场方法评估技术[成员]|客户供应协议[成员]|热轧钢估计[成员]|最大值[成员] |
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| 公允价值、经常性和非经常性计量资产和负债[细目] |
|
|
| 公允价值计量包含不可观察输入的衍生资产范围 |
575clf_FairValueMeasurementWithUnobservableInputsDerivativeAssetRange
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= clf_CustomerSupplyAgreementMember
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
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/ clf_FairValueOfAssetsAndLiabilitiesMeasureOnUnobservableInputAxis
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/ us-gaap_RangeAxis
= us-gaap_MaximumMember
/ us-gaap_ValuationTechniqueAxis
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|
| 衍生金融工具，资产[成员]|公允价值，投入，第3级[成员]|非指定对冲工具[成员]|市场方法估值技术[成员]|临时定价安排[成员] |
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| 公允价值、经常性和非经常性计量资产和负债[细目] |
|
|
| 衍生资产，公允价值 |
0us-gaap_DerivativeFairValueOfDerivativeAsset
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/ us-gaap_HedgingDesignationAxis
= us-gaap_NondesignatedMember
/ us-gaap_ValuationTechniqueAxis
= us-gaap_MarketApproachValuationTechniqueMember |
0us-gaap_DerivativeFairValueOfDerivativeAsset
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= 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 |
| 衍生金融工具，资产[成员]|公允价值，投入，第3级[成员]|非指定对冲工具[成员]|市场方法估值技术[成员]|客户供应协议[成员] |
|
|
| 公允价值、经常性和非经常性计量资产和负债[细目] |
|
|
| 衍生资产，公允价值 |
34500000年us-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 |
63200000年us-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 |
| 衍生金融工具，负债[成员]|公允价值，投入，第3级[成员]|非指定对冲工具[成员]|市场方法估值技术[成员]|临时定价安排[成员] |
|
|
| 公允价值、经常性和非经常性计量资产和负债[细目] |
|
|
| 衍生负债，公允价值 |
16200000年us-gaap_DerivativeFairValueOfDerivativeLiability
/ us-gaap_BalanceSheetLocationAxis
= us-gaap_DerivativeFinancialInstrumentsLiabilitiesMember
/ us-gaap_DerivativeInstrumentRiskAxis
= clf_ProvisionalPricingArrangementsMember
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
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/ us-gaap_HedgingDesignationAxis
= us-gaap_NondesignatedMember
/ us-gaap_ValuationTechniqueAxis
= us-gaap_MarketApproachValuationTechniqueMember |
9500000年us-gaap_DerivativeFairValueOfDerivativeLiability
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= us-gaap_DerivativeFinancialInstrumentsLiabilitiesMember
/ us-gaap_DerivativeInstrumentRiskAxis
= clf_ProvisionalPricingArrangementsMember
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= us-gaap_FairValueInputsLevel3Member
/ us-gaap_HedgingDesignationAxis
= us-gaap_NondesignatedMember
/ us-gaap_ValuationTechniqueAxis
= us-gaap_MarketApproachValuationTechniqueMember |
| 衍生金融工具，负债[成员]|公允价值，投入，第3级[成员]|非指定对冲工具[成员]|市场方法估值技术[成员]|客户供应协议[成员] |
|
|
| 公允价值、经常性和非经常性计量资产和负债[细目] |
|
|
| 衍生负债，公允价值 |
0美元us-gaap_DerivativeFairValueOfDerivativeLiability
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0美元us-gaap_DerivativeFairValueOfDerivativeLiability
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