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已终止业务已终止业务，非经常性公允价值计量项目-北美煤炭（详细信息）（美元）
除非另有说明，单位为百万
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3个月结束 |
12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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| 停止经营，非经常基础上以公允价值计量的项目[单行项目] |
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| 资产，公允价值披露，非经常性 |
397.2美元us-gaap_AssetsFairValueDisclosureNonrecurring |
79.4美元us-gaap_AssetsFairValueDisclosureNonrecurring |
| 减损支出 |
269.5clf_ImpairmentCharges |
644.7clf_ImpairmentCharges |
| 北美煤炭〔成员〕 |
|
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| 停止经营，非经常基础上以公允价值计量的项目[单行项目] |
|
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| 财产、厂房和设备，公允价值披露 |
20.4us-gaap_PropertyPlantAndEquipmentFairValueDisclosure
/ us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis
= clf_NorthAmericanCoalMember |
|
| 有形资产减值费用 |
(73.4)us-gaap_TangibleAssetImpairmentCharges
/ us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis
= clf_NorthAmericanCoalMember |
|
| 资产，公允价值披露，非经常性 |
20.4us-gaap_AssetsFairValueDisclosureNonrecurring
/ us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis
= clf_NorthAmericanCoalMember |
|
| 减损支出 |
(73.4)clf_ImpairmentCharges
/ us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis
= clf_NorthAmericanCoalMember |
|
| 公允价值，输入值，第1级[成员] |
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| 停止经营，非经常基础上以公允价值计量的项目[单行项目] |
|
|
| 资产，公允价值披露，非经常性 |
0us-gaap_AssetsFairValueDisclosureNonrecurring
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member |
0us-gaap_AssetsFairValueDisclosureNonrecurring
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member |
| 公允价值，投入，第1级[成员]|北美煤炭[成员] |
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| 停止经营，非经常基础上以公允价值计量的项目[单行项目] |
|
|
| 财产、厂房和设备，公允价值披露 |
0us-gaap_PropertyPlantAndEquipmentFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member
/ us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis
= clf_NorthAmericanCoalMember |
|
| 资产，公允价值披露，非经常性 |
0us-gaap_AssetsFairValueDisclosureNonrecurring
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member
/ us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis
= clf_NorthAmericanCoalMember |
|
| 公允价值，输入值，第2级[成员] |
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| 停止经营，非经常基础上以公允价值计量的项目[单行项目] |
|
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| 资产，公允价值披露，非经常性 |
397.2us-gaap_AssetsFairValueDisclosureNonrecurring
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member |
0us-gaap_AssetsFairValueDisclosureNonrecurring
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member |
| 公允价值，输入，第2级[成员]|北美煤炭[成员] |
|
|
| 停止经营，非经常基础上以公允价值计量的项目[单行项目] |
|
|
| 财产、厂房和设备，公允价值披露 |
0us-gaap_PropertyPlantAndEquipmentFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
/ us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis
= clf_NorthAmericanCoalMember |
|
| 资产，公允价值披露，非经常性 |
0us-gaap_AssetsFairValueDisclosureNonrecurring
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
/ us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis
= clf_NorthAmericanCoalMember |
|
| 公允价值，输入值，第3级[成员] |
|
|
| 停止经营，非经常基础上以公允价值计量的项目[单行项目] |
|
|
| 资产，公允价值披露，非经常性 |
0us-gaap_AssetsFairValueDisclosureNonrecurring
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member |
79.4us-gaap_AssetsFairValueDisclosureNonrecurring
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member |
| 公允价值，输入，第3级[成员]|北美煤炭[成员] |
|
|
| 停止经营，非经常基础上以公允价值计量的项目[单行项目] |
|
|
| 财产、厂房和设备，公允价值披露 |
20.4us-gaap_PropertyPlantAndEquipmentFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis
= clf_NorthAmericanCoalMember |
|
| 资产，公允价值披露，非经常性 |
20.4美元us-gaap_AssetsFairValueDisclosureNonrecurring
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis
= clf_NorthAmericanCoalMember |
|