根据第13和15(d)条提交的年度报告

累计其他综合收益（亏损）累计其他综合收益（亏损）（详情）

v2.4.1.9
累计其他综合收益（损失）累计其他综合收益（损失）（详情）（美元）
除非另有说明，单位为百万
12个月结束 3个月结束
2014年12月31日
2013年12月31日
2012年12月31日
2014年12月31日
2014年9月30日
2014.6.30
2014年3月31日
2013年12月31日
2013年9月30日
2013年6月30日
2013年3月31日
2011年12月31日
累计其他综合收益（损失），养老金和其他退休后福利计划，税后 (291.1美元)us-gaap_AccumulatedOtherComprehensiveIncomeLossDefinedBenefitPensionAndOtherPostretirementPlansNetOfTax (204.9美元)us-gaap_AccumulatedOtherComprehensiveIncomeLossDefinedBenefitPensionAndOtherPostretirementPlansNetOfTax (382.7美元)us-gaap_AccumulatedOtherComprehensiveIncomeLossDefinedBenefitPensionAndOtherPostretirementPlansNetOfTax (291.1美元)us-gaap_AccumulatedOtherComprehensiveIncomeLossDefinedBenefitPensionAndOtherPostretirementPlansNetOfTax (188.3美元)us-gaap_AccumulatedOtherComprehensiveIncomeLossDefinedBenefitPensionAndOtherPostretirementPlansNetOfTax (199.4美元)us-gaap_AccumulatedOtherComprehensiveIncomeLossDefinedBenefitPensionAndOtherPostretirementPlansNetOfTax (202.0美元)us-gaap_AccumulatedOtherComprehensiveIncomeLossDefinedBenefitPensionAndOtherPostretirementPlansNetOfTax (204.9美元)us-gaap_AccumulatedOtherComprehensiveIncomeLossDefinedBenefitPensionAndOtherPostretirementPlansNetOfTax (365.1美元)us-gaap_AccumulatedOtherComprehensiveIncomeLossDefinedBenefitPensionAndOtherPostretirementPlansNetOfTax (370.8美元)us-gaap_AccumulatedOtherComprehensiveIncomeLossDefinedBenefitPensionAndOtherPostretirementPlansNetOfTax (377.4美元)us-gaap_AccumulatedOtherComprehensiveIncomeLossDefinedBenefitPensionAndOtherPostretirementPlansNetOfTax (408.9美元)us-gaap_AccumulatedOtherComprehensiveIncomeLossDefinedBenefitPensionAndOtherPostretirementPlansNetOfTax
累计其他综合损失 (245.8)us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax (112.9)us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax (55.6)us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax (245.8)us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax (101.4)us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax (20.2)us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax (55.1)us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax (112.9)us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax (178.4)us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax (239.6)us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax (51.4)us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax (92.6)us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax
累计其他综合收益（损失），可供出售证券调整，税后 (1.0)us-gaap_AccumulatedOtherComprehensiveIncomeLossAvailableForSaleSecuritiesAdjustmentNetOfTax 6.2us-gaap_AccumulatedOtherComprehensiveIncomeLossAvailableForSaleSecuritiesAdjustmentNetOfTax 2.1us-gaap_AccumulatedOtherComprehensiveIncomeLossAvailableForSaleSecuritiesAdjustmentNetOfTax (1.0)us-gaap_AccumulatedOtherComprehensiveIncomeLossAvailableForSaleSecuritiesAdjustmentNetOfTax 0.6us-gaap_AccumulatedOtherComprehensiveIncomeLossAvailableForSaleSecuritiesAdjustmentNetOfTax 6.4us-gaap_AccumulatedOtherComprehensiveIncomeLossAvailableForSaleSecuritiesAdjustmentNetOfTax 10.1us-gaap_AccumulatedOtherComprehensiveIncomeLossAvailableForSaleSecuritiesAdjustmentNetOfTax 6.2us-gaap_AccumulatedOtherComprehensiveIncomeLossAvailableForSaleSecuritiesAdjustmentNetOfTax 10.7us-gaap_AccumulatedOtherComprehensiveIncomeLossAvailableForSaleSecuritiesAdjustmentNetOfTax 6.3us-gaap_AccumulatedOtherComprehensiveIncomeLossAvailableForSaleSecuritiesAdjustmentNetOfTax 4.7us-gaap_AccumulatedOtherComprehensiveIncomeLossAvailableForSaleSecuritiesAdjustmentNetOfTax 2.6us-gaap_AccumulatedOtherComprehensiveIncomeLossAvailableForSaleSecuritiesAdjustmentNetOfTax
累计其他综合收益（损失），外币折算调整，税后净额 64.4us-gaap_AccumulatedOtherComprehensiveIncomeLossForeignCurrencyTranslationAdjustmentNetOfTax 106.7us-gaap_AccumulatedOtherComprehensiveIncomeLossForeignCurrencyTranslationAdjustmentNetOfTax 316.3us-gaap_AccumulatedOtherComprehensiveIncomeLossForeignCurrencyTranslationAdjustmentNetOfTax 64.4us-gaap_AccumulatedOtherComprehensiveIncomeLossForeignCurrencyTranslationAdjustmentNetOfTax 101.0us-gaap_AccumulatedOtherComprehensiveIncomeLossForeignCurrencyTranslationAdjustmentNetOfTax 166.9us-gaap_AccumulatedOtherComprehensiveIncomeLossForeignCurrencyTranslationAdjustmentNetOfTax 147.2us-gaap_AccumulatedOtherComprehensiveIncomeLossForeignCurrencyTranslationAdjustmentNetOfTax 106.7us-gaap_AccumulatedOtherComprehensiveIncomeLossForeignCurrencyTranslationAdjustmentNetOfTax 190.4us-gaap_AccumulatedOtherComprehensiveIncomeLossForeignCurrencyTranslationAdjustmentNetOfTax 167.6us-gaap_AccumulatedOtherComprehensiveIncomeLossForeignCurrencyTranslationAdjustmentNetOfTax 319.6us-gaap_AccumulatedOtherComprehensiveIncomeLossForeignCurrencyTranslationAdjustmentNetOfTax 312.5us-gaap_AccumulatedOtherComprehensiveIncomeLossForeignCurrencyTranslationAdjustmentNetOfTax
累计其他综合收益（损失），现金流套期保值产生的净收益（损失）累计变化，税后影响 (18.1)us-gaap_AccumulatedOtherComprehensiveIncomeLossCumulativeChangesInNetGainLossFromCashFlowHedgesEffectNetOfTax (20.9)us-gaap_AccumulatedOtherComprehensiveIncomeLossCumulativeChangesInNetGainLossFromCashFlowHedgesEffectNetOfTax 8.7us-gaap_AccumulatedOtherComprehensiveIncomeLossCumulativeChangesInNetGainLossFromCashFlowHedgesEffectNetOfTax (18.1)us-gaap_AccumulatedOtherComprehensiveIncomeLossCumulativeChangesInNetGainLossFromCashFlowHedgesEffectNetOfTax (14.7)us-gaap_AccumulatedOtherComprehensiveIncomeLossCumulativeChangesInNetGainLossFromCashFlowHedgesEffectNetOfTax 5.9us-gaap_AccumulatedOtherComprehensiveIncomeLossCumulativeChangesInNetGainLossFromCashFlowHedgesEffectNetOfTax (10.4)us-gaap_AccumulatedOtherComprehensiveIncomeLossCumulativeChangesInNetGainLossFromCashFlowHedgesEffectNetOfTax (20.9)us-gaap_AccumulatedOtherComprehensiveIncomeLossCumulativeChangesInNetGainLossFromCashFlowHedgesEffectNetOfTax (14.4)us-gaap_AccumulatedOtherComprehensiveIncomeLossCumulativeChangesInNetGainLossFromCashFlowHedgesEffectNetOfTax (42.7)us-gaap_AccumulatedOtherComprehensiveIncomeLossCumulativeChangesInNetGainLossFromCashFlowHedgesEffectNetOfTax 1.7us-gaap_AccumulatedOtherComprehensiveIncomeLossCumulativeChangesInNetGainLossFromCashFlowHedgesEffectNetOfTax 1.2us-gaap_AccumulatedOtherComprehensiveIncomeLossCumulativeChangesInNetGainLossFromCashFlowHedgesEffectNetOfTax
其他综合（收入）损失，养老金和其他退休后福利计划，调整，税后 91.0us-gaap_OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax (208.3)us-gaap_OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax (33.8)us-gaap_OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax                  
有价证券未实现净利得（亏损），税后净额 (7.2)us-gaap_OtherComprehensiveIncomeLossAvailableForSaleSecuritiesAdjustmentNetOfTax 3.1us-gaap_OtherComprehensiveIncomeLossAvailableForSaleSecuritiesAdjustmentNetOfTax (0.5)us-gaap_OtherComprehensiveIncomeLossAvailableForSaleSecuritiesAdjustmentNetOfTax                  
外币折算未实现净利得（亏损） (42.3)us-gaap_OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationAdjustmentNetOfTax (208.6)us-gaap_OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationAdjustmentNetOfTax 3.8us-gaap_OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationAdjustmentNetOfTax                  
其他综合损益，税后净额 (137.7)us-gaap_OtherComprehensiveIncomeLossNetOfTax (26.8)us-gaap_OtherComprehensiveIncomeLossNetOfTax 44.6us-gaap_OtherComprehensiveIncomeLossNetOfTax                  
累计其他综合收益（损失）[成员]                        
其他综合收益（亏损），未重新分类，税前       (152.3)us-gaap_OtherComprehensiveIncomeLossBeforeReclassificationsBeforeTax
/ us-gaap_OtherComprehensiveIncomeLocationAxis
= us-gaap_AccumulatedOtherComprehensiveIncomeMember 		(81.1)us-gaap_OtherComprehensiveIncomeLossBeforeReclassificationsBeforeTax
/ us-gaap_OtherComprehensiveIncomeLocationAxis
= us-gaap_AccumulatedOtherComprehensiveIncomeMember 		25.6us-gaap_OtherComprehensiveIncomeLossBeforeReclassificationsBeforeTax
/ us-gaap_OtherComprehensiveIncomeLocationAxis
= us-gaap_AccumulatedOtherComprehensiveIncomeMember 		41.6us-gaap_OtherComprehensiveIncomeLossBeforeReclassificationsBeforeTax
/ us-gaap_OtherComprehensiveIncomeLocationAxis
= us-gaap_AccumulatedOtherComprehensiveIncomeMember 		49.3us-gaap_OtherComprehensiveIncomeLossBeforeReclassificationsBeforeTax
/ us-gaap_OtherComprehensiveIncomeLocationAxis
= us-gaap_AccumulatedOtherComprehensiveIncomeMember 		37.8us-gaap_OtherComprehensiveIncomeLossBeforeReclassificationsBeforeTax
/ us-gaap_OtherComprehensiveIncomeLocationAxis
= us-gaap_AccumulatedOtherComprehensiveIncomeMember 		(197.7)us-gaap_OtherComprehensiveIncomeLossBeforeReclassificationsBeforeTax
/ us-gaap_OtherComprehensiveIncomeLocationAxis
= us-gaap_AccumulatedOtherComprehensiveIncomeMember 		(0.3)us-gaap_OtherComprehensiveIncomeLossBeforeReclassificationsBeforeTax
/ us-gaap_OtherComprehensiveIncomeLocationAxis
= us-gaap_AccumulatedOtherComprehensiveIncomeMember 		 
从累计其他综合收益（损失）中重新分类的金额       7.9clf_AmountsReclassifiedFromAccumulatedOtherComprehensiveIncomeLoss
/ us-gaap_OtherComprehensiveIncomeLocationAxis
= us-gaap_AccumulatedOtherComprehensiveIncomeMember 		(0.1)clf_AmountsReclassifiedFromAccumulatedOtherComprehensiveIncomeLoss
/ us-gaap_OtherComprehensiveIncomeLocationAxis
= us-gaap_AccumulatedOtherComprehensiveIncomeMember 		9.3clf_AmountsReclassifiedFromAccumulatedOtherComprehensiveIncomeLoss
/ us-gaap_OtherComprehensiveIncomeLocationAxis
= us-gaap_AccumulatedOtherComprehensiveIncomeMember 		16.2clf_AmountsReclassifiedFromAccumulatedOtherComprehensiveIncomeLoss
/ us-gaap_OtherComprehensiveIncomeLocationAxis
= us-gaap_AccumulatedOtherComprehensiveIncomeMember 		16.2clf_AmountsReclassifiedFromAccumulatedOtherComprehensiveIncomeLoss
/ us-gaap_OtherComprehensiveIncomeLocationAxis
= us-gaap_AccumulatedOtherComprehensiveIncomeMember 		23.4clf_AmountsReclassifiedFromAccumulatedOtherComprehensiveIncomeLoss
/ us-gaap_OtherComprehensiveIncomeLocationAxis
= us-gaap_AccumulatedOtherComprehensiveIncomeMember 		9.5clf_AmountsReclassifiedFromAccumulatedOtherComprehensiveIncomeLoss
/ us-gaap_OtherComprehensiveIncomeLocationAxis
= us-gaap_AccumulatedOtherComprehensiveIncomeMember 		4.5clf_AmountsReclassifiedFromAccumulatedOtherComprehensiveIncomeLoss
/ us-gaap_OtherComprehensiveIncomeLocationAxis
= us-gaap_AccumulatedOtherComprehensiveIncomeMember 		 
累积设定受益计划调整〔成员〕                        
其他综合收益（亏损），未重新分类，税前       (98.7)us-gaap_OtherComprehensiveIncomeLossBeforeReclassificationsBeforeTax
/ us-gaap_OtherComprehensiveIncomeLocationAxis
= us-gaap_AccumulatedDefinedBenefitPlansAdjustmentMember 		3.5us-gaap_OtherComprehensiveIncomeLossBeforeReclassificationsBeforeTax
/ us-gaap_OtherComprehensiveIncomeLocationAxis
= us-gaap_AccumulatedDefinedBenefitPlansAdjustmentMember 		(1.4)us-gaap_OtherComprehensiveIncomeLossBeforeReclassificationsBeforeTax
/ us-gaap_OtherComprehensiveIncomeLocationAxis
= us-gaap_AccumulatedDefinedBenefitPlansAdjustmentMember 		(0.4)us-gaap_OtherComprehensiveIncomeLossBeforeReclassificationsBeforeTax
/ us-gaap_OtherComprehensiveIncomeLocationAxis
= us-gaap_AccumulatedDefinedBenefitPlansAdjustmentMember 		154.5us-gaap_OtherComprehensiveIncomeLossBeforeReclassificationsBeforeTax
/ us-gaap_OtherComprehensiveIncomeLocationAxis
= us-gaap_AccumulatedDefinedBenefitPlansAdjustmentMember 		(0.6)us-gaap_OtherComprehensiveIncomeLossBeforeReclassificationsBeforeTax
/ us-gaap_OtherComprehensiveIncomeLocationAxis
= us-gaap_AccumulatedDefinedBenefitPlansAdjustmentMember 		(1.5)us-gaap_OtherComprehensiveIncomeLossBeforeReclassificationsBeforeTax
/ us-gaap_OtherComprehensiveIncomeLocationAxis
= us-gaap_AccumulatedDefinedBenefitPlansAdjustmentMember 		(1.1)us-gaap_OtherComprehensiveIncomeLossBeforeReclassificationsBeforeTax
/ us-gaap_OtherComprehensiveIncomeLocationAxis
= us-gaap_AccumulatedDefinedBenefitPlansAdjustmentMember 		 
累计未实现投资净收益（亏损）[成员]                        
其他综合收益（亏损），未重新分类，税前       (1.4)us-gaap_OtherComprehensiveIncomeLossBeforeReclassificationsBeforeTax
/ us-gaap_OtherComprehensiveIncomeLocationAxis
= us-gaap_AccumulatedNetUnrealizedInvestmentGainLossMember 		1.3us-gaap_OtherComprehensiveIncomeLossBeforeReclassificationsBeforeTax
/ us-gaap_OtherComprehensiveIncomeLocationAxis
= us-gaap_AccumulatedNetUnrealizedInvestmentGainLossMember 		(2.4)us-gaap_OtherComprehensiveIncomeLossBeforeReclassificationsBeforeTax
/ us-gaap_OtherComprehensiveIncomeLocationAxis
= us-gaap_AccumulatedNetUnrealizedInvestmentGainLossMember 		3.8us-gaap_OtherComprehensiveIncomeLossBeforeReclassificationsBeforeTax
/ us-gaap_OtherComprehensiveIncomeLocationAxis
= us-gaap_AccumulatedNetUnrealizedInvestmentGainLossMember 		(4.9)us-gaap_OtherComprehensiveIncomeLossBeforeReclassificationsBeforeTax
/ us-gaap_OtherComprehensiveIncomeLocationAxis
= us-gaap_AccumulatedNetUnrealizedInvestmentGainLossMember 		3.5us-gaap_OtherComprehensiveIncomeLossBeforeReclassificationsBeforeTax
/ us-gaap_OtherComprehensiveIncomeLocationAxis
= us-gaap_AccumulatedNetUnrealizedInvestmentGainLossMember 		(2.0)us-gaap_OtherComprehensiveIncomeLossBeforeReclassificationsBeforeTax
/ us-gaap_OtherComprehensiveIncomeLocationAxis
= us-gaap_AccumulatedNetUnrealizedInvestmentGainLossMember 		2.5us-gaap_OtherComprehensiveIncomeLossBeforeReclassificationsBeforeTax
/ us-gaap_OtherComprehensiveIncomeLocationAxis
= us-gaap_AccumulatedNetUnrealizedInvestmentGainLossMember 		 
累计翻译调整数[成员]                        
其他综合收益（亏损），未重新分类，税前       (36.6)us-gaap_OtherComprehensiveIncomeLossBeforeReclassificationsBeforeTax
/ us-gaap_OtherComprehensiveIncomeLocationAxis
= us-gaap_AccumulatedTranslationAdjustmentMember 		(65.9)us-gaap_OtherComprehensiveIncomeLossBeforeReclassificationsBeforeTax
/ us-gaap_OtherComprehensiveIncomeLocationAxis
= us-gaap_AccumulatedTranslationAdjustmentMember 		19.7us-gaap_OtherComprehensiveIncomeLossBeforeReclassificationsBeforeTax
/ us-gaap_OtherComprehensiveIncomeLocationAxis
= us-gaap_AccumulatedTranslationAdjustmentMember 		40.5us-gaap_OtherComprehensiveIncomeLossBeforeReclassificationsBeforeTax
/ us-gaap_OtherComprehensiveIncomeLocationAxis
= us-gaap_AccumulatedTranslationAdjustmentMember 		(83.7)us-gaap_OtherComprehensiveIncomeLossBeforeReclassificationsBeforeTax
/ us-gaap_OtherComprehensiveIncomeLocationAxis
= us-gaap_AccumulatedTranslationAdjustmentMember 		22.8us-gaap_OtherComprehensiveIncomeLossBeforeReclassificationsBeforeTax
/ us-gaap_OtherComprehensiveIncomeLocationAxis
= us-gaap_AccumulatedTranslationAdjustmentMember 		(152.0)us-gaap_OtherComprehensiveIncomeLossBeforeReclassificationsBeforeTax
/ us-gaap_OtherComprehensiveIncomeLocationAxis
= us-gaap_AccumulatedTranslationAdjustmentMember 		3.3us-gaap_OtherComprehensiveIncomeLossBeforeReclassificationsBeforeTax
/ us-gaap_OtherComprehensiveIncomeLocationAxis
= us-gaap_AccumulatedTranslationAdjustmentMember 		 
指定或合资格现金流量套期累积净收益（亏损）[成员]                        
其他综合收益（亏损），未重新分类，税前       (15.6)us-gaap_OtherComprehensiveIncomeLossBeforeReclassificationsBeforeTax
/ us-gaap_OtherComprehensiveIncomeLocationAxis
= us-gaap_AccumulatedNetGainLossFromDesignatedOrQualifyingCashFlowHedgesMember 		(20.0)us-gaap_OtherComprehensiveIncomeLossBeforeReclassificationsBeforeTax
/ us-gaap_OtherComprehensiveIncomeLocationAxis
= us-gaap_AccumulatedNetGainLossFromDesignatedOrQualifyingCashFlowHedgesMember 		9.7us-gaap_OtherComprehensiveIncomeLossBeforeReclassificationsBeforeTax
/ us-gaap_OtherComprehensiveIncomeLocationAxis
= us-gaap_AccumulatedNetGainLossFromDesignatedOrQualifyingCashFlowHedgesMember 		(2.3)us-gaap_OtherComprehensiveIncomeLossBeforeReclassificationsBeforeTax
/ us-gaap_OtherComprehensiveIncomeLocationAxis
= us-gaap_AccumulatedNetGainLossFromDesignatedOrQualifyingCashFlowHedgesMember 		(16.6)us-gaap_OtherComprehensiveIncomeLossBeforeReclassificationsBeforeTax
/ us-gaap_OtherComprehensiveIncomeLocationAxis
= us-gaap_AccumulatedNetGainLossFromDesignatedOrQualifyingCashFlowHedgesMember 		12.1us-gaap_OtherComprehensiveIncomeLossBeforeReclassificationsBeforeTax
/ us-gaap_OtherComprehensiveIncomeLocationAxis
= us-gaap_AccumulatedNetGainLossFromDesignatedOrQualifyingCashFlowHedgesMember 		(42.2)us-gaap_OtherComprehensiveIncomeLossBeforeReclassificationsBeforeTax
/ us-gaap_OtherComprehensiveIncomeLocationAxis
= us-gaap_AccumulatedNetGainLossFromDesignatedOrQualifyingCashFlowHedgesMember 		(5.0)us-gaap_OtherComprehensiveIncomeLossBeforeReclassificationsBeforeTax
/ us-gaap_OtherComprehensiveIncomeLocationAxis
= us-gaap_AccumulatedNetGainLossFromDesignatedOrQualifyingCashFlowHedgesMember 		 
累积设定受益计划调整〔成员〕                        
从累计其他综合收益（损失）中重新分类的金额       (4.1)clf_AmountsReclassifiedFromAccumulatedOtherComprehensiveIncomeLoss
/ us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeAxis
= us-gaap_AccumulatedDefinedBenefitPlansAdjustmentMember 		7.6clf_AmountsReclassifiedFromAccumulatedOtherComprehensiveIncomeLoss
/ us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeAxis
= us-gaap_AccumulatedDefinedBenefitPlansAdjustmentMember 		4.0clf_AmountsReclassifiedFromAccumulatedOtherComprehensiveIncomeLoss
/ us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeAxis
= us-gaap_AccumulatedDefinedBenefitPlansAdjustmentMember 		3.3clf_AmountsReclassifiedFromAccumulatedOtherComprehensiveIncomeLoss
/ us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeAxis
= us-gaap_AccumulatedDefinedBenefitPlansAdjustmentMember 		5.7clf_AmountsReclassifiedFromAccumulatedOtherComprehensiveIncomeLoss
/ us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeAxis
= us-gaap_AccumulatedDefinedBenefitPlansAdjustmentMember 		6.3clf_AmountsReclassifiedFromAccumulatedOtherComprehensiveIncomeLoss
/ us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeAxis
= us-gaap_AccumulatedDefinedBenefitPlansAdjustmentMember 		8.1clf_AmountsReclassifiedFromAccumulatedOtherComprehensiveIncomeLoss
/ us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeAxis
= us-gaap_AccumulatedDefinedBenefitPlansAdjustmentMember 		6.4clf_AmountsReclassifiedFromAccumulatedOtherComprehensiveIncomeLoss
/ us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeAxis
= us-gaap_AccumulatedDefinedBenefitPlansAdjustmentMember 		 
累计未实现投资净收益（亏损）[成员]                        
从累计其他综合收益（损失）中重新分类的金额       (0.2)clf_AmountsReclassifiedFromAccumulatedOtherComprehensiveIncomeLoss
/ us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeAxis
= us-gaap_AccumulatedNetUnrealizedInvestmentGainLossMember 		(7.1)clf_AmountsReclassifiedFromAccumulatedOtherComprehensiveIncomeLoss
/ us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeAxis
= us-gaap_AccumulatedNetUnrealizedInvestmentGainLossMember 		(1.3)clf_AmountsReclassifiedFromAccumulatedOtherComprehensiveIncomeLoss
/ us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeAxis
= us-gaap_AccumulatedNetUnrealizedInvestmentGainLossMember 		0.1clf_AmountsReclassifiedFromAccumulatedOtherComprehensiveIncomeLoss
/ us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeAxis
= us-gaap_AccumulatedNetUnrealizedInvestmentGainLossMember 		0.4clf_AmountsReclassifiedFromAccumulatedOtherComprehensiveIncomeLoss
/ us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeAxis
= us-gaap_AccumulatedNetUnrealizedInvestmentGainLossMember 		0.9clf_AmountsReclassifiedFromAccumulatedOtherComprehensiveIncomeLoss
/ us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeAxis
= us-gaap_AccumulatedNetUnrealizedInvestmentGainLossMember 		3.6clf_AmountsReclassifiedFromAccumulatedOtherComprehensiveIncomeLoss
/ us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeAxis
= us-gaap_AccumulatedNetUnrealizedInvestmentGainLossMember 		0.1clf_AmountsReclassifiedFromAccumulatedOtherComprehensiveIncomeLoss
/ us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeAxis
= us-gaap_AccumulatedNetUnrealizedInvestmentGainLossMember 		 
累计翻译调整数[成员]                        
从累计其他综合收益（损失）中重新分类的金额       0clf_AmountsReclassifiedFromAccumulatedOtherComprehensiveIncomeLoss
/ us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeAxis
= us-gaap_AccumulatedTranslationAdjustmentMember 		0clf_AmountsReclassifiedFromAccumulatedOtherComprehensiveIncomeLoss
/ us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeAxis
= us-gaap_AccumulatedTranslationAdjustmentMember 		0clf_AmountsReclassifiedFromAccumulatedOtherComprehensiveIncomeLoss
/ us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeAxis
= us-gaap_AccumulatedTranslationAdjustmentMember 		0clf_AmountsReclassifiedFromAccumulatedOtherComprehensiveIncomeLoss
/ us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeAxis
= us-gaap_AccumulatedTranslationAdjustmentMember 		0clf_AmountsReclassifiedFromAccumulatedOtherComprehensiveIncomeLoss
/ us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeAxis
= us-gaap_AccumulatedTranslationAdjustmentMember 		0clf_AmountsReclassifiedFromAccumulatedOtherComprehensiveIncomeLoss
/ us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeAxis
= us-gaap_AccumulatedTranslationAdjustmentMember 		0clf_AmountsReclassifiedFromAccumulatedOtherComprehensiveIncomeLoss
/ us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeAxis
= us-gaap_AccumulatedTranslationAdjustmentMember 		0clf_AmountsReclassifiedFromAccumulatedOtherComprehensiveIncomeLoss
/ us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeAxis
= us-gaap_AccumulatedTranslationAdjustmentMember 		 
指定或合资格现金流量套期累积净收益（亏损）[成员]                        
从累计其他综合收益（损失）中重新分类的金额       12.2clf_AmountsReclassifiedFromAccumulatedOtherComprehensiveIncomeLoss
/ us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeAxis
= us-gaap_AccumulatedNetGainLossFromDesignatedOrQualifyingCashFlowHedgesMember 		(0.6)clf_AmountsReclassifiedFromAccumulatedOtherComprehensiveIncomeLoss
/ us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeAxis
= us-gaap_AccumulatedNetGainLossFromDesignatedOrQualifyingCashFlowHedgesMember 		6.6clf_AmountsReclassifiedFromAccumulatedOtherComprehensiveIncomeLoss
/ us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeAxis
= us-gaap_AccumulatedNetGainLossFromDesignatedOrQualifyingCashFlowHedgesMember 		12.8clf_AmountsReclassifiedFromAccumulatedOtherComprehensiveIncomeLoss
/ us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeAxis
= us-gaap_AccumulatedNetGainLossFromDesignatedOrQualifyingCashFlowHedgesMember 		10.1clf_AmountsReclassifiedFromAccumulatedOtherComprehensiveIncomeLoss
/ us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeAxis
= us-gaap_AccumulatedNetGainLossFromDesignatedOrQualifyingCashFlowHedgesMember 		16.2clf_AmountsReclassifiedFromAccumulatedOtherComprehensiveIncomeLoss
/ us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeAxis
= us-gaap_AccumulatedNetGainLossFromDesignatedOrQualifyingCashFlowHedgesMember 		(2.2)clf_AmountsReclassifiedFromAccumulatedOtherComprehensiveIncomeLoss
/ us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeAxis
= us-gaap_AccumulatedNetGainLossFromDesignatedOrQualifyingCashFlowHedgesMember 		(2.0)clf_AmountsReclassifiedFromAccumulatedOtherComprehensiveIncomeLoss
/ us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeAxis
= us-gaap_AccumulatedNetGainLossFromDesignatedOrQualifyingCashFlowHedgesMember 		 
Cliffs股东权益[成员]                        
其他综合（收入）损失，养老金和其他退休后福利计划，调整，税后     26.2us-gaap_OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax
/ us-gaap_StatementEquityComponentsAxis
= us-gaap_ParentMember 		                 
有价证券未实现净利得（亏损），税后净额     (0.5)us-gaap_OtherComprehensiveIncomeLossAvailableForSaleSecuritiesAdjustmentNetOfTax
/ us-gaap_StatementEquityComponentsAxis
= us-gaap_ParentMember 		                 
其他综合收益（损失）、外币折算调整、税收     3.8us-gaap_OtherComprehensiveIncomeLossForeignCurrencyTranslationAdjustmentTax
/ us-gaap_StatementEquityComponentsAxis
= us-gaap_ParentMember 		                 
其他综合收益（损失），期间衍生品未实现收益（损失），税后净额     7.5us-gaap_OtherComprehensiveIncomeUnrealizedGainLossOnDerivativesArisingDuringPeriodNetOfTax
/ us-gaap_StatementEquityComponentsAxis
= us-gaap_ParentMember 		                 
其他综合损益，税后净额     37.0美元us-gaap_OtherComprehensiveIncomeLossNetOfTax
/ us-gaap_StatementEquityComponentsAxis
= us-gaap_ParentMember