Annual report pursuant to Section 13 and 15(d)

ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS) Details of Accumulated Other Comprehensive Income (Loss) Components (Details)

Betfred-casino review_1 -Subparagraph (j) -URI v2.4.1.9
Betfred
 12 Months Ended
Dec. 31, 2014
Dec. 31, 2013
Dec. 31, 2012
Details of Accumulated Other Comprehensive Income (Loss) Components [Line Items]      
Derivative Instruments, (Gain) Loss Reclassified from Accumulated OCI into betfred gamesIncome, Effective Portion, Net $ (31.0)us-gaap_DerivativeInstrumentsGainLossReclassifiedFromAccumulatedOCIIntoIncomeEffectivePortionNet $ (22.1)us-gaap_DerivativeInstrumentsGainLossReclassifiedFromAccumulatedOCIIntoIncomeEffectivePortionNet $ 18.1us-gaap_DerivativeInstrumentsGainLossReclassifiedFromAccumulatedOCIIntoIncomeEffectivePortionNet
Total Amount Reclassified from Accumulated Other Comprehensive Income (Loss) During the Period 33.3clf_TotalAmountReclassifiedFromAccumulatedOtherComprehensiveIncomeLossDuringPeriod 53.6clf_TotalAmountReclassifiedFromAccumulatedOtherComprehensiveIncomeLossDuringPeriod  
Accumulated Defined Benefit Plans Adjustment [Member]      
Details of Accumulated Other Comprehensive Income (Loss) Components [Line Items]      
Amortization of prior service (cost) credit 0.9us-gaap_DefinedBenefitPlanAmortizationOfPriorServiceCostCredit
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= us-gaap_AccumulatedDefinedBenefitPlansAdjustmentMember 		[1]  
Defined Benefit Plan, Amortization of Gains (Losses) 19.1us-gaap_DefinedBenefitPlanAmortizationOfGainsLosses
/ us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeAxis
= us-gaap_AccumulatedDefinedBenefitPlansAdjustmentMember 		[1] 41.4us-gaap_DefinedBenefitPlanAmortizationOfGainsLosses
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= us-gaap_AccumulatedDefinedBenefitPlansAdjustmentMember 		[1]  
Defined Benefit Plan, Curtailments (5.0)us-gaap_DefinedBenefitPlanCurtailments
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= us-gaap_AccumulatedDefinedBenefitPlansAdjustmentMember 		 
Defined Benefit Plan, Special Termination Benefits 3.4us-gaap_DefinedBenefitPlanSpecialTerminationBenefits
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= us-gaap_AccumulatedDefinedBenefitPlansAdjustmentMember 		 
Other Comprehensive Income (Loss), Reclassification, Pension and Other Postretirement Benefit Plans, Net Gain (Loss) Recognized in Net Periodic Benefit Cost, before Tax 16.6us-gaap_OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetGainLossBeforeTax
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= us-gaap_AccumulatedDefinedBenefitPlansAdjustmentMember 		40.8us-gaap_OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetGainLossBeforeTax
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= us-gaap_AccumulatedDefinedBenefitPlansAdjustmentMember 		 
Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Net Unamortized Gain (Loss) Arising During Period, Tax (5.8)us-gaap_OtherComprehensiveIncomeDefinedBenefitPlansNetUnamortizedGainLossArisingDuringPeriodTax
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= us-gaap_AccumulatedDefinedBenefitPlansAdjustmentMember 		(14.3)us-gaap_OtherComprehensiveIncomeDefinedBenefitPlansNetUnamortizedGainLossArisingDuringPeriodTax
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= us-gaap_AccumulatedDefinedBenefitPlansAdjustmentMember 		 
Amounts Reclassified from Accumulated Other Comprehensive Income (Loss) 10.8us-gaap_OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetGainLossNetOfTax
/ us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeAxis
= us-gaap_AccumulatedDefinedBenefitPlansAdjustmentMember 		26.5us-gaap_OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetGainLossNetOfTax
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= us-gaap_AccumulatedDefinedBenefitPlansAdjustmentMember 		 
Unrealized Gain (Loss) on Marketable Securities [Member] [Member]      
Details of Accumulated Other Comprehensive Income (Loss) Components [Line Items]      
Marketable Securities, Unrealized Gain (Loss) (11.4)us-gaap_MarketableSecuritiesUnrealizedGainLoss
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= clf_UnrealizedGainLossonMarketableSecuritiesMemberMember 		(0.2)us-gaap_MarketableSecuritiesUnrealizedGainLoss
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= clf_UnrealizedGainLossonMarketableSecuritiesMemberMember 		 
Accumulated Other-than-Temporary Impairment [Member]      
Details of Accumulated Other Comprehensive Income (Loss) Components [Line Items]      
Other than Temporary Impairment Losses, Investments, Portion in Other Comprehensive Loss, before Tax, Including Portion Attributable to Noncontrolling Interest, Available-for-sale Securities (0.5)us-gaap_OtherThanTemporaryImpairmentLossesInvestmentsPortionInOtherComprehensiveIncomeLossBeforeTaxIncludingPortionAttributableToNoncontrollingInterestAvailableforsaleSecurities
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= us-gaap_AccumulatedOtherThanTemporaryImpairmentMember 		 
Unrealized Gain (Loss) on Marketable Securities and Other than Temporary Impairment [Member] [Member]      
Details of Accumulated Other Comprehensive Income (Loss) Components [Line Items]      
Other Comprehensive Income (Loss), Unrealized Holding Gain (Loss) on Securities Arising During Period, before Tax (11.9)us-gaap_OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodBeforeTax
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Other Comprehensive Income (Loss), Unrealized Holding Gain (Loss) on Securities Arising During Period, Tax 3.4us-gaap_OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodTax
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Other Comprehensive Income (Loss), Unrealized Holding Gain (Loss) on Securities Arising During Period, Net of Tax (8.5)us-gaap_OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodNetOfTax
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Unrealized Gain Loss On Derivatives [Member]      
Details of Accumulated Other Comprehensive Income (Loss) Components [Line Items]      
Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, before Tax 45.6us-gaap_OtherComprehensiveIncomeUnrealizedGainLossOnDerivativesArisingDuringPeriodBeforeTax
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= clf_UnrealizedGainLossOnDerivativesMember 		32.3us-gaap_OtherComprehensiveIncomeUnrealizedGainLossOnDerivativesArisingDuringPeriodBeforeTax
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= clf_UnrealizedGainLossOnDerivativesMember 		 
Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, Tax (14.6)us-gaap_OtherComprehensiveIncomeUnrealizedGainLossOnDerivativesArisingDuringPeriodTax
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= clf_UnrealizedGainLossOnDerivativesMember 		(10.2)us-gaap_OtherComprehensiveIncomeUnrealizedGainLossOnDerivativesArisingDuringPeriodTax
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= clf_UnrealizedGainLossOnDerivativesMember 		 
Unrealized net gain (loss) on derivative financial instruments, net of tax 31.0us-gaap_OtherComprehensiveIncomeUnrealizedGainLossOnDerivativesArisingDuringPeriodNetOfTax
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= clf_UnrealizedGainLossOnDerivativesMember 		22.1us-gaap_OtherComprehensiveIncomeUnrealizedGainLossOnDerivativesArisingDuringPeriodNetOfTax
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= clf_UnrealizedGainLossOnDerivativesMember 		 
Unrealized Gain Loss On Derivatives [Member] | Australian Hedge Contracts [Member]      
Details of Accumulated Other Comprehensive Income (Loss) Components [Line Items]      
Derivative Instruments, (Gain) Loss Reclassified from Accumulated OCI into betfred gamesIncome, Effective Portion, Net 18.9us-gaap_DerivativeInstrumentsGainLossReclassifiedFromAccumulatedOCIIntoIncomeEffectivePortionNet
/ us-gaap_DerivativeInstrumentRiskAxis
= clf_AustralianHedgeContractsMember
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= clf_UnrealizedGainLossOnDerivativesMember 		17.0us-gaap_DerivativeInstrumentsGainLossReclassifiedFromAccumulatedOCIIntoIncomeEffectivePortionNet
/ us-gaap_DerivativeInstrumentRiskAxis
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= clf_UnrealizedGainLossOnDerivativesMember 		 
Unrealized Gain Loss On Derivatives [Member] | Canadian Hedge Contracts [Member]      
Details of Accumulated Other Comprehensive Income (Loss) Components [Line Items]      
Derivative Instruments, (Gain) Loss Reclassified from Accumulated OCI into betfred gamesIncome, Effective Portion, Net $ 26.7us-gaap_DerivativeInstrumentsGainLossReclassifiedFromAccumulatedOCIIntoIncomeEffectivePortionNet
/ us-gaap_DerivativeInstrumentRiskAxis
= clf_CanadianHedgeContractsMember
/ us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeAxis
= clf_UnrealizedGainLossOnDerivativesMember 		$ 15.3us-gaap_DerivativeInstrumentsGainLossReclassifiedFromAccumulatedOCIIntoIncomeEffectivePortionNet
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= clf_UnrealizedGainLossOnDerivativesMember 		 
[1] hese accumulated other comprehensive income components are included in the net periodic benefit cost recognized for the year ended December 31, 2014 and 2013. See NOTE 7 - PENSIONS AND OTHER POSTRETIREMENT BENEFITS for further information.