根据第13和15(d)条提交的年度报告

金融工具的公允价值金融工具的公允价值（金融和非金融资产的减值费用）（详情）

v2.4.1.9
金融工具公允价值（金融和非金融资产减值支出）（详细信息）（美元）
除非另有说明，单位为百万
12个月结束
2014年12月31日
2013年12月31日
2012年12月31日
公允价值、经常性和非经常性计量资产和负债[细目]      
商誉、减值损失 73.5美元us-gaap_GoodwillImpairmentLoss 80.9美元us-gaap_GoodwillImpairmentLoss  
有形资产减值费用 8,839.0us-gaap_TangibleAssetImpairmentCharges    
有限寿命无形资产，公允价值披露   1.6us-gaap_FiniteLivedIntangibleAssetsFairValueDisclosure  
无形资产减值（不含商誉） 15.5us-gaap_ImpairmentOfIntangibleAssetsExcludingGoodwill 14.5us-gaap_ImpairmentOfIntangibleAssetsExcludingGoodwill  
其他资产减值费用 8,956.4us-gaap_OtherAssetImpairmentCharges    
权益法投资，临时减值除外 0us-gaap_EquityMethodInvestmentOtherThanTemporaryImpairment 0us-gaap_EquityMethodInvestmentOtherThanTemporaryImpairment (365.4)us-gaap_EquityMethodInvestmentOtherThanTemporaryImpairment
资产，公允价值披露，非经常性 438.9us-gaap_AssetsFairValueDisclosureNonrecurring 47.9us-gaap_AssetsFairValueDisclosureNonrecurring  
减损支出 9039年1。clf_ImpairmentCharges 318.4clf_ImpairmentCharges  
公允价值，输入值，第1级[成员]      
公允价值、经常性和非经常性计量资产和负债[细目]      
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，输入值，第2级[成员]      
公允价值、经常性和非经常性计量资产和负债[细目]      
资产，公允价值披露，非经常性 0us-gaap_AssetsFairValueDisclosureNonrecurring
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member 		0us-gaap_AssetsFairValueDisclosureNonrecurring
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member 		 
公允价值，输入值，第3级[成员]      
公允价值、经常性和非经常性计量资产和负债[细目]      
有限寿命无形资产，公允价值披露   1.6us-gaap_FiniteLivedIntangibleAssetsFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member 		 
资产，公允价值披露，非经常性 438.9us-gaap_AssetsFairValueDisclosureNonrecurring
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member 		47.9us-gaap_AssetsFairValueDisclosureNonrecurring
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member 		 
全球勘探投资风险[成员]      
公允价值、经常性和非经常性计量资产和负债[细目]      
权益法投资，公允价值披露 0us-gaap_EquityMethodInvestmentsFairValueDisclosure
/ us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis
= clf_GlobalExplorationInvestmentinVentureMember 		   
权益法投资，临时减值除外 9.2us-gaap_EquityMethodInvestmentOtherThanTemporaryImpairment
/ us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis
= clf_GlobalExplorationInvestmentinVentureMember 		   
全球勘探风险投资[成员]|公允价值、投入、一级[成员]      
公允价值、经常性和非经常性计量资产和负债[细目]      
权益法投资，公允价值披露 0us-gaap_EquityMethodInvestmentsFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member
/ us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis
= clf_GlobalExplorationInvestmentinVentureMember 		   
全球勘探风险投资[成员]|公允价值、投入、第2级[成员]      
公允价值、经常性和非经常性计量资产和负债[细目]      
权益法投资，公允价值披露 0us-gaap_EquityMethodInvestmentsFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
/ us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis
= clf_GlobalExplorationInvestmentinVentureMember 		   
全球勘探风险投资[成员]|公允价值，投入，第3级[成员]      
公允价值、经常性和非经常性计量资产和负债[细目]      
权益法投资，公允价值披露 0us-gaap_EquityMethodInvestmentsFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis
= clf_GlobalExplorationInvestmentinVentureMember 		   
阿马帕(成员)      
公允价值、经常性和非经常性计量资产和负债[细目]      
权益法投资，公允价值披露   0us-gaap_EquityMethodInvestmentsFairValueDisclosure
/ us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis
= clf_AmapaMember 		 
权益法投资，临时减值除外   67.6us-gaap_EquityMethodInvestmentOtherThanTemporaryImpairment
/ us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis
= clf_AmapaMember 		(365.4)us-gaap_EquityMethodInvestmentOtherThanTemporaryImpairment
/ us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis
= clf_AmapaMember
Amapa[成员]|公允价值，输入，第1级[成员]      
公允价值、经常性和非经常性计量资产和负债[细目]      
权益法投资，公允价值披露   0us-gaap_EquityMethodInvestmentsFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member
/ us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis
= clf_AmapaMember 		 
Amapa[成员]|公允价值，输入，第2级[成员]      
公允价值、经常性和非经常性计量资产和负债[细目]      
权益法投资，公允价值披露   0us-gaap_EquityMethodInvestmentsFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
/ us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis
= clf_AmapaMember 		 
Amapa[成员]|公允价值，输入，第3级[成员]      
公允价值、经常性和非经常性计量资产和负债[细目]      
权益法投资，公允价值披露   0us-gaap_EquityMethodInvestmentsFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis
= clf_AmapaMember 		 
亚太铁矿石〔成员〕      
公允价值、经常性和非经常性计量资产和负债[细目]      
商誉，公允价值披露 0us-gaap_GoodwillFairValueDisclosure
/ clf_ReportingUnitAxis
= clf_AsiaPacificIronOreMember 		   
商誉、减值损失 73.5us-gaap_GoodwillImpairmentLoss
/ clf_ReportingUnitAxis
= clf_AsiaPacificIronOreMember 		   
亚太地区铁矿石[成员]|公允价值，投入，第一级[成员]      
公允价值、经常性和非经常性计量资产和负债[细目]      
商誉，公允价值披露 0us-gaap_GoodwillFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member
/ clf_ReportingUnitAxis
= clf_AsiaPacificIronOreMember 		   
亚太地区铁矿石[成员]|公允价值，投入，第2级[成员]      
公允价值、经常性和非经常性计量资产和负债[细目]      
商誉，公允价值披露 0us-gaap_GoodwillFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
/ clf_ReportingUnitAxis
= clf_AsiaPacificIronOreMember 		   
亚太地区铁矿石[成员]|公允价值，投入，第3级[成员]      
公允价值、经常性和非经常性计量资产和负债[细目]      
商誉，公允价值披露 0us-gaap_GoodwillFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ clf_ReportingUnitAxis
= clf_AsiaPacificIronOreMember 		   
Cliffs铬铁矿安大略和Cliffs铬铁矿远北[成员]      
公允价值、经常性和非经常性计量资产和负债[细目]      
商誉，公允价值披露   0us-gaap_GoodwillFairValueDisclosure
/ clf_ReportingUnitAxis
= clf_CliffsChromiteOntarioandCliffsChromiteFarNorthMember 		 
商誉、减值损失   80.9us-gaap_GoodwillImpairmentLoss
/ clf_ReportingUnitAxis
= clf_CliffsChromiteOntarioandCliffsChromiteFarNorthMember 		 
Cliffs铬铁矿安大略和Cliffs铬铁矿远北[成员]|公允价值，输入，第1级[成员]      
公允价值、经常性和非经常性计量资产和负债[细目]      
商誉，公允价值披露   0us-gaap_GoodwillFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member
/ clf_ReportingUnitAxis
= clf_CliffsChromiteOntarioandCliffsChromiteFarNorthMember 		 
Cliffs铬铁矿安大略和Cliffs铬铁矿远北[成员]|公允价值，输入，第2级[成员]      
公允价值、经常性和非经常性计量资产和负债[细目]      
商誉，公允价值披露   0us-gaap_GoodwillFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
/ clf_ReportingUnitAxis
= clf_CliffsChromiteOntarioandCliffsChromiteFarNorthMember 		 
Cliffs铬铁矿安大略和Cliffs铬铁矿远北[成员]|公允价值，输入，第3级[成员]      
公允价值、经常性和非经常性计量资产和负债[细目]      
商誉，公允价值披露   0us-gaap_GoodwillFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ clf_ReportingUnitAxis
= clf_CliffsChromiteOntarioandCliffsChromiteFarNorthMember 		 
Wabush(成员)      
公允价值、经常性和非经常性计量资产和负债[细目]      
有形资产减值费用   145.1us-gaap_TangibleAssetImpairmentCharges
/ clf_ReportingUnitAxis
= clf_WabushMember 		 
持有使用的长期资产减值 140.1us-gaap_ImpairmentOfLongLivedAssetsHeldForUse
/ clf_ReportingUnitAxis
= clf_WabushMember 		49.9us-gaap_ImpairmentOfLongLivedAssetsHeldForUse
/ clf_ReportingUnitAxis
= clf_WabushMember 		 
无形资产减值（不含商誉）   9.5us-gaap_ImpairmentOfIntangibleAssetsExcludingGoodwill
/ clf_ReportingUnitAxis
= clf_WabushMember 		 
Wabush[成员]|公允价值，输入，第1层[成员]      
公允价值、经常性和非经常性计量资产和负债[细目]      
有限寿命无形资产，公允价值披露   0us-gaap_FiniteLivedIntangibleAssetsFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member
/ clf_ReportingUnitAxis
= clf_WabushMember 		 
Wabush[成员]|公允价值，输入，第2级[成员]      
公允价值、经常性和非经常性计量资产和负债[细目]      
有限寿命无形资产，公允价值披露   0us-gaap_FiniteLivedIntangibleAssetsFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
/ clf_ReportingUnitAxis
= clf_WabushMember 		 
沃布什和悬崖铬铁矿安大略和悬崖铬铁矿远北[成员]      
公允价值、经常性和非经常性计量资产和负债[细目]      
财产、厂房和设备，公允价值披露   46.3us-gaap_PropertyPlantAndEquipmentFairValueDisclosure
/ clf_ReportingUnitAxis
= clf_WabushandCliffsChromiteOntarioandCliffsChromiteFarNorthMember 		 
有形资产减值费用   155.4us-gaap_TangibleAssetImpairmentCharges
/ clf_ReportingUnitAxis
= clf_WabushandCliffsChromiteOntarioandCliffsChromiteFarNorthMember 		 
Wabush and Cliffs铬铁矿安大略和Cliffs铬铁矿远北[成员]|公允价值，输入，第1级[成员]      
公允价值、经常性和非经常性计量资产和负债[细目]      
财产、厂房和设备，公允价值披露   0us-gaap_PropertyPlantAndEquipmentFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member
/ clf_ReportingUnitAxis
= clf_WabushandCliffsChromiteOntarioandCliffsChromiteFarNorthMember 		 
Wabush and Cliffs铬铁矿安大略和Cliffs铬铁矿远北[成员]|公允价值，输入，第2级[成员]      
公允价值、经常性和非经常性计量资产和负债[细目]      
财产、厂房和设备，公允价值披露   0us-gaap_PropertyPlantAndEquipmentFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
/ clf_ReportingUnitAxis
= clf_WabushandCliffsChromiteOntarioandCliffsChromiteFarNorthMember 		 
Wabush and Cliffs铬铁矿安大略和Cliffs铬铁矿远北[成员]|公允价值，输入，第3级[成员]      
公允价值、经常性和非经常性计量资产和负债[细目]      
财产、厂房和设备，公允价值披露   46.3us-gaap_PropertyPlantAndEquipmentFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ clf_ReportingUnitAxis
= clf_WabushandCliffsChromiteOntarioandCliffsChromiteFarNorthMember 		 
CQIM报告小组〔成员〕      
公允价值、经常性和非经常性计量资产和负债[细目]      
商誉、减值损失   997.3us-gaap_GoodwillImpairmentLoss
/ clf_ReportingUnitAxis
= clf_CqimReportingUnitMember 		 
其他报告单位[成员]|其他报告单位[成员]      
公允价值、经常性和非经常性计量资产和负债[细目]      
财产、厂房和设备，公允价值披露 0us-gaap_PropertyPlantAndEquipmentFairValueDisclosure
/ clf_AssetgroupAxis
= clf_OtherReportingUnitsMember
/ clf_ReportingUnitAxis
= clf_OtherReportingUnitsMember 		   
有形资产减值费用 19.2us-gaap_TangibleAssetImpairmentCharges
/ clf_AssetgroupAxis
= clf_OtherReportingUnitsMember
/ clf_ReportingUnitAxis
= clf_OtherReportingUnitsMember 		   
其他报告单位[成员]|其他报告单位[成员]|公允价值，输入值，第一级[成员]      
公允价值、经常性和非经常性计量资产和负债[细目]      
财产、厂房和设备，公允价值披露 0us-gaap_PropertyPlantAndEquipmentFairValueDisclosure
/ clf_AssetgroupAxis
= clf_OtherReportingUnitsMember
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member
/ clf_ReportingUnitAxis
= clf_OtherReportingUnitsMember 		   
其他报告单位[成员]|其他报告单位[成员]|公允价值，输入值，第二层[成员]      
公允价值、经常性和非经常性计量资产和负债[细目]      
财产、厂房和设备，公允价值披露 0us-gaap_PropertyPlantAndEquipmentFairValueDisclosure
/ clf_AssetgroupAxis
= clf_OtherReportingUnitsMember
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
/ clf_ReportingUnitAxis
= clf_OtherReportingUnitsMember 		   
其他报告单位[成员]|其他报告单位[成员]|公允价值，输入值，第3级[成员]      
公允价值、经常性和非经常性计量资产和负债[细目]      
财产、厂房和设备，公允价值披露 0us-gaap_PropertyPlantAndEquipmentFairValueDisclosure
/ clf_AssetgroupAxis
= clf_OtherReportingUnitsMember
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ clf_ReportingUnitAxis
= clf_OtherReportingUnitsMember 		   
Bloom Lake[成员]|加拿大东部铁矿石[成员]      
公允价值、经常性和非经常性计量资产和负债[细目]      
财产、厂房和设备，公允价值披露 187.9us-gaap_PropertyPlantAndEquipmentFairValueDisclosure
/ clf_AssetgroupAxis
= clf_BloomLakeMember
/ clf_ReportingUnitAxis
= clf_EasternCanadianIronOreMember 		   
有形资产减值费用 达到7043us-gaap_TangibleAssetImpairmentCharges
/ clf_AssetgroupAxis
= clf_BloomLakeMember
/ clf_ReportingUnitAxis
= clf_EasternCanadianIronOreMember 		   
有限寿命无形资产，公允价值披露 0us-gaap_FiniteLivedIntangibleAssetsFairValueDisclosure
/ clf_AssetgroupAxis
= clf_BloomLakeMember
/ clf_ReportingUnitAxis
= clf_EasternCanadianIronOreMember 		   
无形资产减值（不含商誉） 56.2us-gaap_ImpairmentOfIntangibleAssetsExcludingGoodwill
/ clf_AssetgroupAxis
= clf_BloomLakeMember
/ clf_ReportingUnitAxis
= clf_EasternCanadianIronOreMember 		   
布卢姆湖[成员]|加拿大东部铁矿石[成员]|公允价值，输入，第一级[成员]      
公允价值、经常性和非经常性计量资产和负债[细目]      
财产、厂房和设备，公允价值披露 0us-gaap_PropertyPlantAndEquipmentFairValueDisclosure
/ clf_AssetgroupAxis
= clf_BloomLakeMember
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member
/ clf_ReportingUnitAxis
= clf_EasternCanadianIronOreMember 		   
有限寿命无形资产，公允价值披露 0us-gaap_FiniteLivedIntangibleAssetsFairValueDisclosure
/ clf_AssetgroupAxis
= clf_BloomLakeMember
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member
/ clf_ReportingUnitAxis
= clf_EasternCanadianIronOreMember 		   
布卢姆湖[成员]|加拿大东部铁矿石[成员]|公允价值，投入，第2级[成员]      
公允价值、经常性和非经常性计量资产和负债[细目]      
财产、厂房和设备，公允价值披露 0us-gaap_PropertyPlantAndEquipmentFairValueDisclosure
/ clf_AssetgroupAxis
= clf_BloomLakeMember
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
/ clf_ReportingUnitAxis
= clf_EasternCanadianIronOreMember 		   
有限寿命无形资产，公允价值披露 0us-gaap_FiniteLivedIntangibleAssetsFairValueDisclosure
/ clf_AssetgroupAxis
= clf_BloomLakeMember
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
/ clf_ReportingUnitAxis
= clf_EasternCanadianIronOreMember 		   
布卢姆湖[成员]|加拿大东部铁矿石[成员]|公允价值，输入，第3级[成员]      
公允价值、经常性和非经常性计量资产和负债[细目]      
财产、厂房和设备，公允价值披露 187.9us-gaap_PropertyPlantAndEquipmentFairValueDisclosure
/ clf_AssetgroupAxis
= clf_BloomLakeMember
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ clf_ReportingUnitAxis
= clf_EasternCanadianIronOreMember 		   
有限寿命无形资产，公允价值披露 0us-gaap_FiniteLivedIntangibleAssetsFairValueDisclosure
/ clf_AssetgroupAxis
= clf_BloomLakeMember
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ clf_ReportingUnitAxis
= clf_EasternCanadianIronOreMember 		   
CLCC[会员]|北美煤炭[会员]      
公允价值、经常性和非经常性计量资产和负债[细目]      
财产、厂房和设备，公允价值披露 62.6us-gaap_PropertyPlantAndEquipmentFairValueDisclosure
/ clf_AssetgroupAxis
= clf_ClccMember
/ clf_ReportingUnitAxis
= clf_NorthAmericanCoalMember 		   
有形资产减值费用 195.5us-gaap_TangibleAssetImpairmentCharges
/ clf_AssetgroupAxis
= clf_ClccMember
/ clf_ReportingUnitAxis
= clf_NorthAmericanCoalMember 		   
CLCC[成员]|北美煤炭[成员]|公允价值，投入，第一级[成员]      
公允价值、经常性和非经常性计量资产和负债[细目]      
财产、厂房和设备，公允价值披露 0us-gaap_PropertyPlantAndEquipmentFairValueDisclosure
/ clf_AssetgroupAxis
= clf_ClccMember
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member
/ clf_ReportingUnitAxis
= clf_NorthAmericanCoalMember 		   
CLCC[成员]|北美煤炭[成员]|公允价值，投入，第2级[成员]      
公允价值、经常性和非经常性计量资产和负债[细目]      
财产、厂房和设备，公允价值披露 0us-gaap_PropertyPlantAndEquipmentFairValueDisclosure
/ clf_AssetgroupAxis
= clf_ClccMember
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
/ clf_ReportingUnitAxis
= clf_NorthAmericanCoalMember 		   
CLCC[成员]|北美煤炭[成员]|公允价值，投入，第3级[成员]      
公允价值、经常性和非经常性计量资产和负债[细目]      
财产、厂房和设备，公允价值披露 62.6us-gaap_PropertyPlantAndEquipmentFairValueDisclosure
/ clf_AssetgroupAxis
= clf_ClccMember
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ clf_ReportingUnitAxis
= clf_NorthAmericanCoalMember 		   
亚太地区[会员]|亚太铁矿石[会员]|公允价值、投入、第2级[会员]      
公允价值、经常性和非经常性计量资产和负债[细目]      
财产、厂房和设备，公允价值披露 0us-gaap_PropertyPlantAndEquipmentFairValueDisclosure
/ clf_AssetgroupAxis
= us-gaap_AsiaPacificMember
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
/ clf_ReportingUnitAxis
= clf_AsiaPacificIronOreMember 		   
有限寿命无形资产，公允价值披露 0us-gaap_FiniteLivedIntangibleAssetsFairValueDisclosure
/ clf_AssetgroupAxis
= us-gaap_AsiaPacificMember
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
/ clf_ReportingUnitAxis
= clf_AsiaPacificIronOreMember 		   
亚太铁矿石[成员]|亚太铁矿石[成员]      
公允价值、经常性和非经常性计量资产和负债[细目]      
财产、厂房和设备，公允价值披露 72.4us-gaap_PropertyPlantAndEquipmentFairValueDisclosure
/ clf_AssetgroupAxis
= clf_AsiaPacificIronOreMember
/ clf_ReportingUnitAxis
= clf_AsiaPacificIronOreMember 		   
有形资产减值费用 526.5us-gaap_TangibleAssetImpairmentCharges
/ clf_AssetgroupAxis
= clf_AsiaPacificIronOreMember
/ clf_ReportingUnitAxis
= clf_AsiaPacificIronOreMember 		   
有限寿命无形资产，公允价值披露 7.0us-gaap_FiniteLivedIntangibleAssetsFairValueDisclosure
/ clf_AssetgroupAxis
= clf_AsiaPacificIronOreMember
/ clf_ReportingUnitAxis
= clf_AsiaPacificIronOreMember 		   
无形资产减值（不含商誉） 24.2us-gaap_ImpairmentOfIntangibleAssetsExcludingGoodwill
/ clf_AssetgroupAxis
= clf_AsiaPacificIronOreMember
/ clf_ReportingUnitAxis
= clf_AsiaPacificIronOreMember 		   
亚太地区铁矿石[成员]|00亚太地区铁矿石[成员]|公允价值，投入，第一级[成员]      
公允价值、经常性和非经常性计量资产和负债[细目]      
财产、厂房和设备，公允价值披露 0us-gaap_PropertyPlantAndEquipmentFairValueDisclosure
/ clf_AssetgroupAxis
= clf_AsiaPacificIronOreMember
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member
/ clf_ReportingUnitAxis
= clf_AsiaPacificIronOreMember 		   
有限寿命无形资产，公允价值披露 0us-gaap_FiniteLivedIntangibleAssetsFairValueDisclosure
/ clf_AssetgroupAxis
= clf_AsiaPacificIronOreMember
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member
/ clf_ReportingUnitAxis
= clf_AsiaPacificIronOreMember 		   
亚太地区铁矿石[会员]|亚太地区铁矿石[会员]|公允价值、投入、三级[会员]      
公允价值、经常性和非经常性计量资产和负债[细目]      
财产、厂房和设备，公允价值披露 72.4us-gaap_PropertyPlantAndEquipmentFairValueDisclosure
/ clf_AssetgroupAxis
= clf_AsiaPacificIronOreMember
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ clf_ReportingUnitAxis
= clf_AsiaPacificIronOreMember 		   
有限寿命无形资产，公允价值披露 7.0us-gaap_FiniteLivedIntangibleAssetsFairValueDisclosure
/ clf_AssetgroupAxis
= clf_AsiaPacificIronOreMember
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ clf_ReportingUnitAxis
= clf_AsiaPacificIronOreMember 		   
铁合金[成员]|铁合金[成员]      
公允价值、经常性和非经常性计量资产和负债[细目]      
财产、厂房和设备，公允价值披露 12.2us-gaap_PropertyPlantAndEquipmentFairValueDisclosure
/ clf_AssetgroupAxis
= clf_FerroalloysMember
/ clf_ReportingUnitAxis
= clf_FerroalloysMember 		   
有形资产减值费用 259.5us-gaap_TangibleAssetImpairmentCharges
/ clf_AssetgroupAxis
= clf_FerroalloysMember
/ clf_ReportingUnitAxis
= clf_FerroalloysMember 		   
有限寿命无形资产，公允价值披露 0us-gaap_FiniteLivedIntangibleAssetsFairValueDisclosure
/ clf_AssetgroupAxis
= clf_FerroalloysMember
/ clf_ReportingUnitAxis
= clf_FerroalloysMember 		   
无形资产减值（不含商誉） 0.3us-gaap_ImpairmentOfIntangibleAssetsExcludingGoodwill
/ clf_AssetgroupAxis
= clf_FerroalloysMember
/ clf_ReportingUnitAxis
= clf_FerroalloysMember 		   
铁合金[成员]|铁合金[成员]|公允价值，输入，第一级[成员]      
公允价值、经常性和非经常性计量资产和负债[细目]      
财产、厂房和设备，公允价值披露 0us-gaap_PropertyPlantAndEquipmentFairValueDisclosure
/ clf_AssetgroupAxis
= clf_FerroalloysMember
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member
/ clf_ReportingUnitAxis
= clf_FerroalloysMember 		   
有限寿命无形资产，公允价值披露 0us-gaap_FiniteLivedIntangibleAssetsFairValueDisclosure
/ clf_AssetgroupAxis
= clf_FerroalloysMember
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member
/ clf_ReportingUnitAxis
= clf_FerroalloysMember 		   
铁合金[成员]|铁合金[成员]|公允价值，输入，第2级[成员]      
公允价值、经常性和非经常性计量资产和负债[细目]      
财产、厂房和设备，公允价值披露 0us-gaap_PropertyPlantAndEquipmentFairValueDisclosure
/ clf_AssetgroupAxis
= clf_FerroalloysMember
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
/ clf_ReportingUnitAxis
= clf_FerroalloysMember 		   
有限寿命无形资产，公允价值披露 0us-gaap_FiniteLivedIntangibleAssetsFairValueDisclosure
/ clf_AssetgroupAxis
= clf_FerroalloysMember
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
/ clf_ReportingUnitAxis
= clf_FerroalloysMember 		   
铁合金[成员]|铁合金[成员]|公允价值，输入，第3级[成员]      
公允价值、经常性和非经常性计量资产和负债[细目]      
财产、厂房和设备，公允价值披露 12.2us-gaap_PropertyPlantAndEquipmentFairValueDisclosure
/ clf_AssetgroupAxis
= clf_FerroalloysMember
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ clf_ReportingUnitAxis
= clf_FerroalloysMember 		   
有限寿命无形资产，公允价值披露 0us-gaap_FiniteLivedIntangibleAssetsFairValueDisclosure
/ clf_AssetgroupAxis
= clf_FerroalloysMember
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ clf_ReportingUnitAxis
= clf_FerroalloysMember 		   
Wabush[成员]|加拿大东部铁矿石[成员]      
公允价值、经常性和非经常性计量资产和负债[细目]      
财产、厂房和设备，公允价值披露 42.7us-gaap_PropertyPlantAndEquipmentFairValueDisclosure
/ clf_AssetgroupAxis
= clf_WabushMember
/ clf_ReportingUnitAxis
= clf_EasternCanadianIronOreMember 		   
有形资产减值费用 132.6us-gaap_TangibleAssetImpairmentCharges
/ clf_AssetgroupAxis
= clf_WabushMember
/ clf_ReportingUnitAxis
= clf_EasternCanadianIronOreMember 		   
有限寿命无形资产，公允价值披露 0us-gaap_FiniteLivedIntangibleAssetsFairValueDisclosure
/ clf_AssetgroupAxis
= clf_WabushMember
/ clf_ReportingUnitAxis
= clf_EasternCanadianIronOreMember 		   
无形资产减值（不含商誉） 36.7us-gaap_ImpairmentOfIntangibleAssetsExcludingGoodwill
/ clf_AssetgroupAxis
= clf_WabushMember
/ clf_ReportingUnitAxis
= clf_EasternCanadianIronOreMember 		   
Wabush[成员]|加拿大东部铁矿石[成员]|公允价值，投入，第一级[成员]      
公允价值、经常性和非经常性计量资产和负债[细目]      
财产、厂房和设备，公允价值披露 0us-gaap_PropertyPlantAndEquipmentFairValueDisclosure
/ clf_AssetgroupAxis
= clf_WabushMember
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member
/ clf_ReportingUnitAxis
= clf_EasternCanadianIronOreMember 		   
有限寿命无形资产，公允价值披露 0us-gaap_FiniteLivedIntangibleAssetsFairValueDisclosure
/ clf_AssetgroupAxis
= clf_WabushMember
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member
/ clf_ReportingUnitAxis
= clf_EasternCanadianIronOreMember 		   
Wabush[成员]|加拿大东部铁矿石[成员]|公允价值，投入，第2级[成员]      
公允价值、经常性和非经常性计量资产和负债[细目]      
财产、厂房和设备，公允价值披露 0us-gaap_PropertyPlantAndEquipmentFairValueDisclosure
/ clf_AssetgroupAxis
= clf_WabushMember
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
/ clf_ReportingUnitAxis
= clf_EasternCanadianIronOreMember 		   
有限寿命无形资产，公允价值披露 0us-gaap_FiniteLivedIntangibleAssetsFairValueDisclosure
/ clf_AssetgroupAxis
= clf_WabushMember
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
/ clf_ReportingUnitAxis
= clf_EasternCanadianIronOreMember 		   
Wabush[成员]|加拿大东部铁矿石[成员]|公允价值，投入，第3级[成员]      
公允价值、经常性和非经常性计量资产和负债[细目]      
财产、厂房和设备，公允价值披露 42.7us-gaap_PropertyPlantAndEquipmentFairValueDisclosure
/ clf_AssetgroupAxis
= clf_WabushMember
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ clf_ReportingUnitAxis
= clf_EasternCanadianIronOreMember 		   
有限寿命无形资产，公允价值披露 0us-gaap_FiniteLivedIntangibleAssetsFairValueDisclosure
/ clf_AssetgroupAxis
= clf_WabushMember
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ clf_ReportingUnitAxis
= clf_EasternCanadianIronOreMember 		   
Oak Grove[成员]| North American Coal[成员]      
公允价值、经常性和非经常性计量资产和负债[细目]      
财产、厂房和设备，公允价值披露 23.4us-gaap_PropertyPlantAndEquipmentFairValueDisclosure
/ clf_AssetgroupAxis
= clf_OakGroveMember
/ clf_ReportingUnitAxis
= clf_NorthAmericanCoalMember 		   
有形资产减值费用 267.5us-gaap_TangibleAssetImpairmentCharges
/ clf_AssetgroupAxis
= clf_OakGroveMember
/ clf_ReportingUnitAxis
= clf_NorthAmericanCoalMember 		   
橡树林[成员]|北美煤炭[成员]|公允价值，输入，一级[成员]      
公允价值、经常性和非经常性计量资产和负债[细目]      
财产、厂房和设备，公允价值披露 0us-gaap_PropertyPlantAndEquipmentFairValueDisclosure
/ clf_AssetgroupAxis
= clf_OakGroveMember
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member
/ clf_ReportingUnitAxis
= clf_NorthAmericanCoalMember 		   
橡树林[成员]|北美煤炭[成员]|公允价值，输入，第2级[成员]      
公允价值、经常性和非经常性计量资产和负债[细目]      
财产、厂房和设备，公允价值披露 0us-gaap_PropertyPlantAndEquipmentFairValueDisclosure
/ clf_AssetgroupAxis
= clf_OakGroveMember
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
/ clf_ReportingUnitAxis
= clf_NorthAmericanCoalMember 		   
橡树林[成员]|北美煤炭[成员]|公允价值，输入，第3级[成员]      
公允价值、经常性和非经常性计量资产和负债[细目]      
财产、厂房和设备，公允价值披露 23.4us-gaap_PropertyPlantAndEquipmentFairValueDisclosure
/ clf_AssetgroupAxis
= clf_OakGroveMember
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ clf_ReportingUnitAxis
= clf_NorthAmericanCoalMember 		   
Pinnacle【会员】|北美煤炭【会员】      
公允价值、经常性和非经常性计量资产和负债[细目]      
财产、厂房和设备，公允价值披露 30.7us-gaap_PropertyPlantAndEquipmentFairValueDisclosure
/ clf_AssetgroupAxis
= clf_PinnacleMember
/ clf_ReportingUnitAxis
= clf_NorthAmericanCoalMember 		   
有形资产减值费用 394.5us-gaap_TangibleAssetImpairmentCharges
/ clf_AssetgroupAxis
= clf_PinnacleMember
/ clf_ReportingUnitAxis
= clf_NorthAmericanCoalMember 		   
Pinnacle[成员]|北美煤炭[成员]|公允价值，输入，一级[成员]      
公允价值、经常性和非经常性计量资产和负债[细目]      
财产、厂房和设备，公允价值披露 0us-gaap_PropertyPlantAndEquipmentFairValueDisclosure
/ clf_AssetgroupAxis
= clf_PinnacleMember
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member
/ clf_ReportingUnitAxis
= clf_NorthAmericanCoalMember 		   
Pinnacle[成员]|北美煤炭[成员]|公允价值，输入，第2级[成员]      
公允价值、经常性和非经常性计量资产和负债[细目]      
财产、厂房和设备，公允价值披露 0us-gaap_PropertyPlantAndEquipmentFairValueDisclosure
/ clf_AssetgroupAxis
= clf_PinnacleMember
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
/ clf_ReportingUnitAxis
= clf_NorthAmericanCoalMember 		   
Pinnacle[成员]|北美煤炭[成员]|公允价值，输入，第3级[成员]      
公允价值、经常性和非经常性计量资产和负债[细目]      
财产、厂房和设备，公允价值披露 30.7美元us-gaap_PropertyPlantAndEquipmentFairValueDisclosure
/ clf_AssetgroupAxis
= clf_PinnacleMember
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ clf_ReportingUnitAxis
= clf_NorthAmericanCoalMember