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Quarterly report pursuant to Section 13 or 15(d)

FAIR VALUE OF FINANCIAL INSTRUMENTS (Schedule Of Quantitative Inputs And Assumptions For Level 3 Assets And Liabilities) (Details)

v2.4.1.9
FAIR VALUE OF FINANCIAL INSTRUMENTS (Schedule Of Quantitative Inputs And Assumptions For Level 3 Assets And Liabilities) (Details) (USD $)
3 Months Ended
Mar. 31, 2015
Dec. 31, 2014
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] Ìý Ìý
Derivative asset, fair value $ 34,500,000us-gaap_DerivativeFairValueOfDerivativeAsset $ 63,200,000us-gaap_DerivativeFairValueOfDerivativeAsset
Derivative liability, fair value 26,500,000us-gaap_DerivativeFairValueOfDerivativeLiability 41,000,000us-gaap_DerivativeFairValueOfDerivativeLiability
Management Estimate of 62% Fe 62.00%clf_ManagementEstimateOf62Fe Ìý
Not Designated as Hedging Instrument [Member] Ìý Ìý
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] Ìý Ìý
Derivative asset, fair value 34,500,000us-gaap_DerivativeFairValueOfDerivativeAsset
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63,200,000us-gaap_DerivativeFairValueOfDerivativeAsset
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Derivative liability, fair value 26,500,000us-gaap_DerivativeFairValueOfDerivativeLiability
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19,400,000us-gaap_DerivativeFairValueOfDerivativeLiability
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Fair Value, Inputs, Level 3 [Member] | Not Designated as Hedging Instrument [Member] | Managements Estimate Of 62% Fee [Member] Ìý Ìý
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] Ìý Ìý
Management Estimate of 62% Fe 62.00%clf_ManagementEstimateOf62Fe
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Ìý
Fair Value, Inputs, Level 3 [Member] | Not Designated as Hedging Instrument [Member] | Market Approach Valuation Technique [Member] | Provisional Pricing Arrangements [Member] | Managements Estimate Of 62% Fee [Member] Ìý Ìý
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] Ìý Ìý
Fair value measurement with unobservable inputs derivative asset range 51clf_FairValueMeasurementWithUnobservableInputsDerivativeAssetRange
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Ìý
Fair Value, Inputs, Level 3 [Member] | Not Designated as Hedging Instrument [Member] | Market Approach Valuation Technique [Member] | Customer Supply Agreement [Member] | Hot-Rolled Steel Estimate [Member] Ìý Ìý
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] Ìý Ìý
Fair value measurement with unobservable inputs derivative asset range 563clf_FairValueMeasurementWithUnobservableInputsDerivativeAssetRange
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Ìý
Fair Value, Inputs, Level 3 [Member] | Not Designated as Hedging Instrument [Member] | Market Approach Valuation Technique [Member] | Customer Supply Agreement [Member] | Hot-Rolled Steel Estimate [Member] | Minimum [Member] Ìý Ìý
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] Ìý Ìý
Fair value measurement with unobservable inputs derivative asset range 540clf_FairValueMeasurementWithUnobservableInputsDerivativeAssetRange
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Ìý
Fair Value, Inputs, Level 3 [Member] | Not Designated as Hedging Instrument [Member] | Market Approach Valuation Technique [Member] | Customer Supply Agreement [Member] | Hot-Rolled Steel Estimate [Member] | Maximum [Member] Ìý Ìý
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] Ìý Ìý
Fair value measurement with unobservable inputs derivative asset range 575clf_FairValueMeasurementWithUnobservableInputsDerivativeAssetRange
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Ìý
Derivative Financial Instruments, Assets [Member] | Fair Value, Inputs, Level 3 [Member] | Not Designated as Hedging Instrument [Member] | Market Approach Valuation Technique [Member] | Provisional Pricing Arrangements [Member] Ìý Ìý
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] Ìý Ìý
Derivative asset, fair value 0us-gaap_DerivativeFairValueOfDerivativeAsset
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0us-gaap_DerivativeFairValueOfDerivativeAsset
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Derivative Financial Instruments, Assets [Member] | Fair Value, Inputs, Level 3 [Member] | Not Designated as Hedging Instrument [Member] | Market Approach Valuation Technique [Member] | Customer Supply Agreement [Member] Ìý Ìý
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] Ìý Ìý
Derivative asset, fair value 34,500,000us-gaap_DerivativeFairValueOfDerivativeAsset
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63,200,000us-gaap_DerivativeFairValueOfDerivativeAsset
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Derivative Financial Instruments, Liabilities [Member] | Fair Value, Inputs, Level 3 [Member] | Not Designated as Hedging Instrument [Member] | Market Approach Valuation Technique [Member] | Provisional Pricing Arrangements [Member] Ìý Ìý
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] Ìý Ìý
Derivative liability, fair value 16,200,000us-gaap_DerivativeFairValueOfDerivativeLiability
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9,500,000us-gaap_DerivativeFairValueOfDerivativeLiability
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Derivative Financial Instruments, Liabilities [Member] | Fair Value, Inputs, Level 3 [Member] | Not Designated as Hedging Instrument [Member] | Market Approach Valuation Technique [Member] | Customer Supply Agreement [Member] Ìý Ìý
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] Ìý Ìý
Derivative liability, fair value $ 0us-gaap_DerivativeFairValueOfDerivativeLiability
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$ 0us-gaap_DerivativeFairValueOfDerivativeLiability
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