XML 72 R96.htm IDEA: XBRL DOCUMENT
v2.4.1.9

SHAREHOLDERS' EQUITY Details of Accumulated Other Comprehensive Income (Loss) Components (Details) (USD $) In Millions, unless otherwise specified | 3 Months Ended
--- | ---
Mar. 31, 2015 | Mar. 31, 2014
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items] |  |  |  |
Derivative Instruments, (Gain) Loss Reclassified from Accumulated OCI into Income, Effective Portion, Net | $ (6.3)us-gaap_DerivativeInstrumentsGainLossReclassifiedFromAccumulatedOCIIntoIncomeEffectivePortionNet |  | $ (12.8)us-gaap_DerivativeInstrumentsGainLossReclassifiedFromAccumulatedOCIIntoIncomeEffectivePortionNet |
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax | 195.5 us-gaap_ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTax |  | 16.1 us-gaap_ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTax |
Accumulated Defined Benefit Plans Adjustment [Member] |  |  |  |
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items] |  |  |  |
Defined Benefit Plan, Amortization of Prior Service Cost (Credit) | (0.3)us-gaap_DefinedBenefitPlanAmortizationOfPriorServiceCostCredit / us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeAxis = us-gaap_AccumulatedDefinedBenefitPlansAdjustmentMember | [1] | (0.3)us-gaap_DefinedBenefitPlanAmortizationOfPriorServiceCostCredit / us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeAxis = us-gaap_AccumulatedDefinedBenefitPlansAdjustmentMember | [1]
Defined Benefit Plan, Amortization of Gains (Losses) | 8.5 us-gaap_DefinedBenefitPlanAmortizationOfGainsLosses / us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeAxis = us-gaap_AccumulatedDefinedBenefitPlansAdjustmentMember | [1] | 4.8 us-gaap_DefinedBenefitPlanAmortizationOfGainsLosses / us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeAxis = us-gaap_AccumulatedDefinedBenefitPlansAdjustmentMember | [1]
Defined Benefit Plan, Curtailments | 0.3 us-gaap_DefinedBenefitPlanCurtailments / us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeAxis = us-gaap_AccumulatedDefinedBenefitPlansAdjustmentMember | [1] | 0.3 us-gaap_DefinedBenefitPlanCurtailments / us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeAxis = us-gaap_AccumulatedDefinedBenefitPlansAdjustmentMember | [1]
Other Comprehensive Income (Loss), Reclassification, Pension and Other Postretirement Benefit Plans, Net Gain (Loss) Recognized in Net Periodic Benefit Cost, before Tax | 8.5 us-gaap_OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetGainLossBeforeTax / us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeAxis = us-gaap_AccumulatedDefinedBenefitPlansAdjustmentMember |  | 4.8 us-gaap_OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetGainLossBeforeTax / us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeAxis = us-gaap_AccumulatedDefinedBenefitPlansAdjustmentMember |
Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Net Unamortized Gain (Loss) Arising During Period, Tax | 0 us-gaap_OtherComprehensiveIncomeDefinedBenefitPlansNetUnamortizedGainLossArisingDuringPeriodTax / us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeAxis = us-gaap_AccumulatedDefinedBenefitPlansAdjustmentMember |  | (1.6)us-gaap_OtherComprehensiveIncomeDefinedBenefitPlansNetUnamortizedGainLossArisingDuringPeriodTax / us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeAxis = us-gaap_AccumulatedDefinedBenefitPlansAdjustmentMember |
Amounts Reclassified from Accumulated Other Comprehensive Income (Loss) | 8.5 us-gaap_OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetGainLossNetOfTax / us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeAxis = us-gaap_AccumulatedDefinedBenefitPlansAdjustmentMember |  | 3.2 us-gaap_OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetGainLossNetOfTax / us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeAxis = us-gaap_AccumulatedDefinedBenefitPlansAdjustmentMember |
Realized Gain (Loss) on Marketable Securities [Member] |  |  |  |
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items] |  |  |  |
Marketable Securities, Realized Gain (Loss) | 0 us-gaap_MarketableSecuritiesRealizedGainLoss / us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeAxis = clf_RealizedGainLossonMarketableSecuritiesMember |  | 0.1 us-gaap_MarketableSecuritiesRealizedGainLoss / us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeAxis = clf_RealizedGainLossonMarketableSecuritiesMember |
Accumulated Other-than-Temporary Impairment [Member] |  |  |  |
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [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 | (2.0)us-gaap_OtherThanTemporaryImpairmentLossesInvestmentsPortionInOtherComprehensiveIncomeLossBeforeTaxIncludingPortionAttributableToNoncontrollingInterestAvailableforsaleSecurities / us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeAxis = us-gaap_AccumulatedOtherThanTemporaryImpairmentMember |  | 0 us-gaap_OtherThanTemporaryImpairmentLossesInvestmentsPortionInOtherComprehensiveIncomeLossBeforeTaxIncludingPortionAttributableToNoncontrollingInterestAvailableforsaleSecurities / us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeAxis = us-gaap_AccumulatedOtherThanTemporaryImpairmentMember |
Realized Gain (Loss) on Marketable Securities and Other than Temporary Impairment [Member] |  |  |  |
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items] |  |  |  |
Other Comprehensive Income (Loss), Unrealized Holding Gain (Loss) on Securities and Impairment on Securities Arising During Period, before tax | (2.0)clf_OtherComprehensiveIncomeLossRealizedHoldingGainLossonSecuritiesandImpairmentonSecuritiesArisingDuringPeriodbeforetax / us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeAxis = clf_RealizedGainLossonMarketableSecuritiesandOtherthanTemporaryImpairmentMember |  | 0.1 clf_OtherComprehensiveIncomeLossRealizedHoldingGainLossonSecuritiesandImpairmentonSecuritiesArisingDuringPeriodbeforetax / us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeAxis = clf_RealizedGainLossonMarketableSecuritiesandOtherthanTemporaryImpairmentMember |
Other Comprehensive Income (Loss), Realized Holding Gain (Loss) on Securities and Impairment on Securities Arising During Period, Tax | 0 clf_OtherComprehensiveIncomeLossRealizedHoldingGainLossonSecuritiesandImpairmentonSecuritiesArisingDuringPeriodTax / us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeAxis = clf_RealizedGainLossonMarketableSecuritiesandOtherthanTemporaryImpairmentMember |  | 0 clf_OtherComprehensiveIncomeLossRealizedHoldingGainLossonSecuritiesandImpairmentonSecuritiesArisingDuringPeriodTax / us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeAxis = clf_RealizedGainLossonMarketableSecuritiesandOtherthanTemporaryImpairmentMember |
Other Comprehensive Income (Loss), Realized Holding Gain (Loss) on Securities and Impairment on Securities Arising During Period, net of tax | (2.0)clf_OtherComprehensiveIncomeLossRealizedHoldingGainLossonSecuritiesandImpairmentonSecuritiesArisingDuringPeriodnetoftax / us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeAxis = clf_RealizedGainLossonMarketableSecuritiesandOtherthanTemporaryImpairmentMember |  | 0.1 clf_OtherComprehensiveIncomeLossRealizedHoldingGainLossonSecuritiesandImpairmentonSecuritiesArisingDuringPeriodnetoftax / us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeAxis = clf_RealizedGainLossonMarketableSecuritiesandOtherthanTemporaryImpairmentMember |
Foreign Currency Translation Adjustment [Member] |  |  |  |
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items] |  |  |  |
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Adjustment, before Tax | 182.7 us-gaap_OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationAdjustmentBeforeTax / us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeAxis = clf_ForeignCurrencyTranslationAdjustmentMember | [2] | 0 us-gaap_OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationAdjustmentBeforeTax / us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeAxis = clf_ForeignCurrencyTranslationAdjustmentMember | [2]
Other Comprehensive Income (Loss), Foreign Currency Translation Adjustment, Tax | 0 us-gaap_OtherComprehensiveIncomeLossForeignCurrencyTranslationAdjustmentTax / us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeAxis = clf_ForeignCurrencyTranslationAdjustmentMember |  | 0 us-gaap_OtherComprehensiveIncomeLossForeignCurrencyTranslationAdjustmentTax / us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeAxis = clf_ForeignCurrencyTranslationAdjustmentMember |
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Gain (Loss) Arising During Period, Net of Tax | 182.7 us-gaap_OtherComprehensiveIncomeForeignCurrencyTransactionAndTranslationGainLossArisingDuringPeriodNetOfTax / us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeAxis = clf_ForeignCurrencyTranslationAdjustmentMember |  | 0 us-gaap_OtherComprehensiveIncomeForeignCurrencyTransactionAndTranslationGainLossArisingDuringPeriodNetOfTax / us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeAxis = clf_ForeignCurrencyTranslationAdjustmentMember |
Realized Gain Loss On Derivatives [Member] |  |  |  |
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items] |  |  |  |
(Gain) Loss on Derivative Instruments, Net, Pretax | 9.0 us-gaap_GainLossOnDerivativeInstrumentsNetPretax / us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeAxis = clf_RealizedGainLossOnDerivativesMember |  | 18.5 us-gaap_GainLossOnDerivativeInstrumentsNetPretax / us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeAxis = clf_RealizedGainLossOnDerivativesMember |
Tax on Derivative Instruments Gain/Loss Reclassified from Accumulated OCI in to Earnings | (2.7)clf_Taxonderivativeinstrumentsgainlossreclassifiedfromaccumulatedociintoearnings / us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeAxis = clf_RealizedGainLossOnDerivativesMember |  | (5.7)clf_Taxonderivativeinstrumentsgainlossreclassifiedfromaccumulatedociintoearnings / us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeAxis = clf_RealizedGainLossOnDerivativesMember |
Amount of (gain)/loss recognized in income on derivative | 6.3 us-gaap_DerivativeGainLossOnDerivativeNet / us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeAxis = clf_RealizedGainLossOnDerivativesMember |  | 12.8 us-gaap_DerivativeGainLossOnDerivativeNet / us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeAxis = clf_RealizedGainLossOnDerivativesMember |
Australian Hedge Contracts [Member] | Realized Gain Loss On Derivatives [Member] |  |  |  |
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items] |  |  |  |
Derivative Instruments, (Gain) Loss Reclassified from Accumulated OCI into Income, Effective Portion, Net | 9.0 us-gaap_DerivativeInstrumentsGainLossReclassifiedFromAccumulatedOCIIntoIncomeEffectivePortionNet / us-gaap_DerivativeInstrumentRiskAxis = clf_AustralianHedgeContractsMember / us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeAxis = clf_RealizedGainLossOnDerivativesMember |  | 13.0 us-gaap_DerivativeInstrumentsGainLossReclassifiedFromAccumulatedOCIIntoIncomeEffectivePortionNet / us-gaap_DerivativeInstrumentRiskAxis = clf_AustralianHedgeContractsMember / us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeAxis = clf_RealizedGainLossOnDerivativesMember |
Canadian Hedge Contracts [Member] | Realized Gain Loss On Derivatives [Member] |  |  |  |
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items] |  |  |  |
Derivative Instruments, (Gain) Loss Reclassified from Accumulated OCI into Income, Effective Portion, Net | $ 0 us-gaap_DerivativeInstrumentsGainLossReclassifiedFromAccumulatedOCIIntoIncomeEffectivePortionNet / us-gaap_DerivativeInstrumentRiskAxis = clf_CanadianHedgeContractsMember / us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeAxis = clf_RealizedGainLossOnDerivativesMember |  | $ 5.5 us-gaap_DerivativeInstrumentsGainLossReclassifiedFromAccumulatedOCIIntoIncomeEffectivePortionNet / us-gaap_DerivativeInstrumentRiskAxis = clf_CanadianHedgeContractsMember / us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeAxis = clf_RealizedGainLossOnDerivativesMember |
[1] | These accumulated other comprehensive income components are included in the computation of net periodic benefit cost. See NOTE 7 - PENSIONS AND OTHER POSTRETIREMENT BENEFITS for further information.
[2] | Represents Canadian accumulated currency translation adjustments deconsolidated on January 27, 2015.

X
- Definition Other Comprehensive Income (Loss), Realized Holding Gain (Loss) on Securities and Impairment on Securities Arising During Period, before tax + References No definition available. + Details
Name: | clf_OtherComprehensiveIncomeLossRealizedHoldingGainLossonSecuritiesandImpairmentonSecuritiesArisingDuringPeriodbeforetax
Namespace Prefix: | clf_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Other Comprehensive Income (Loss), Realized Holding Gain (Loss) on Securities and Impairment on Securities Arising During Period, net of tax + References No definition available. + Details
Name: | clf_OtherComprehensiveIncomeLossRealizedHoldingGainLossonSecuritiesandImpairmentonSecuritiesArisingDuringPeriodnetoftax
Namespace Prefix: | clf_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Other Comprehensive Income (Loss), Realized Holding Gain (Loss) on Securities and Impairment on Securities Arising During Period, Tax + References No definition available. + Details
Name: | clf_OtherComprehensiveIncomeLossRealizedHoldingGainLossonSecuritiesandImpairmentonSecuritiesArisingDuringPeriodTax
Namespace Prefix: | clf_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Tax On Derivative Instruments Gain Loss Reclassified From Accumulated OCI Into Earnings + References No definition available. + Details
Name: | clf_Taxonderivativeinstrumentsgainlossreclassifiedfromaccumulatedociintoearnings
Namespace Prefix: | clf_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition The amount of gains or losses recognized in net periodic benefit cost. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (h)(4) -URI http://asc.fasb.org/extlink&oid=35743120&loc=d3e1928-114920 + Details
Name: | us-gaap_DefinedBenefitPlanAmortizationOfGainsLosses
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition The amount of the prior service cost or credit recognized in net periodic benefit cost relating to benefit changes attributable to plan participants' prior service pursuant to a plan amendment or a plan initiation. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (h)(1) -URI http://asc.fasb.org/extlink&oid=35743120&loc=d3e1928-114920 + Details
Name: | us-gaap_DefinedBenefitPlanAmortizationOfPriorServiceCostCredit
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition The amount of decrease that is related to an event that significantly reduces the expected years of future service of present employees or eliminates for a significant number of employees the accrual of defined benefits for some or all of their future services. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (a)(10) -URI http://asc.fasb.org/extlink&oid=35743120&loc=d3e1928-114920 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Plan Curtailment -URI http://asc.fasb.org/extlink&oid=6520938 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 30 -Section 15 -Paragraph 6 -Subparagraph (a)(2) -URI http://asc.fasb.org/extlink&oid=7577095&loc=d3e8001-114927 + Details
Name: | us-gaap_DefinedBenefitPlanCurtailments
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Amount of increase (decrease) in the fair value of derivatives recognized in the income statement. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 4A -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=35706170&loc=SL5618551-113959 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 4C -Subparagraph (a),(c),(d),(e) -URI http://asc.fasb.org/extlink&oid=35706170&loc=SL5624171-113959 + Details
Name: | us-gaap_DerivativeGainLossOnDerivativeNet
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition The effective portion of net gain (loss) reclassified from accumulated other comprehensive income into income on derivative instruments designated and qualifying as hedging instruments. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 4C -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=35706170&loc=SL5624171-113959 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 4D -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=35706170&loc=SL5624177-113959 + Details
Name: | us-gaap_DerivativeInstrumentsGainLossReclassifiedFromAccumulatedOCIIntoIncomeEffectivePortionNet
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Aggregate net gain (loss) on all derivative instruments recognized in earnings during the period, before tax effects. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 4A -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=35706170&loc=SL5618551-113959 + Details
Name: | us-gaap_GainLossOnDerivativeInstrumentsNetPretax
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition This item represents the total realized gain (loss) included in earnings for the period as a result of selling marketable securities categorized as trading, available-for-sale, or held-to-maturity. Additionally, this item would include any losses recognized for other than temporary impairments (OTTI) of the subject investments in debt and equity securities. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 9 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=27724398&loc=d3e27357-111563 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 225 -SubTopic 10 -Section S99 -Paragraph 2 -Subparagraph (SX 210.5-03.7(c)) -URI http://asc.fasb.org/extlink&oid=26872669&loc=d3e20235-122688 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 10 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=27724398&loc=d3e27405-111563 + Details
Name: | us-gaap_MarketableSecuritiesRealizedGainLoss
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Amount of tax expense (benefit) related to (increase) decrease in the value of the projected benefit obligation related to a change in an actuarial assumption and increase (decrease) in the value of the plan assets resulting from experience different from that assumed, that has not been recognized in net periodic benefit (cost) credit. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 220 -SubTopic 10 -Section 45 -Paragraph 12 -URI http://asc.fasb.org/extlink&oid=36458714&loc=d3e640-108580 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 220 -SubTopic 10 -Section 45 -Paragraph 10A -Subparagraph (i-k) -URI http://asc.fasb.org/extlink&oid=36458714&loc=SL7669646-108580 + Details
Name: | us-gaap_OtherComprehensiveIncomeDefinedBenefitPlansNetUnamortizedGainLossArisingDuringPeriodTax
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Amount after tax, before reclassification adjustments of gain (loss) on foreign currency translation adjustments, foreign currency transactions designated and effective as economic hedges of a net investment in a foreign entity and intra-entity foreign currency transactions that are of a long-term-investment nature. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 220 -SubTopic 10 -Section 45 -Paragraph 11 -URI http://asc.fasb.org/extlink&oid=36458714&loc=d3e637-108580 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 830 -SubTopic 30 -Section 45 -Paragraph 12 -URI http://asc.fasb.org/extlink&oid=6915805&loc=d3e32022-110900 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 830 -SubTopic 30 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6450520&loc=d3e32583-110901 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 830 -SubTopic 30 -Section 45 -Paragraph 18 -URI http://asc.fasb.org/extlink&oid=6915805&loc=d3e32157-110900 Reference 5: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 830 -SubTopic 30 -Section 45 -Paragraph 20 -URI http://asc.fasb.org/extlink&oid=6915805&loc=d3e32211-110900 Reference 6: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 220 -SubTopic 10 -Section 45 -Paragraph 10A -Subparagraph (a-c) -URI http://asc.fasb.org/extlink&oid=36458714&loc=SL7669646-108580 + Details
Name: | us-gaap_OtherComprehensiveIncomeForeignCurrencyTransactionAndTranslationGainLossArisingDuringPeriodNetOfTax
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Amount before tax, after reclassification adjustments of gain (loss) on foreign currency translation adjustments, foreign currency transactions designated and effective as economic hedges of a net investment in a foreign entity and intra-entity foreign currency transactions that are of a long-term-investment nature. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 220 -SubTopic 10 -Section 45 -Paragraph 11 -URI http://asc.fasb.org/extlink&oid=36458714&loc=d3e637-108580 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 220 -SubTopic 10 -Section 45 -Paragraph 10A -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=36458714&loc=SL7669646-108580 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 830 -SubTopic 20 -Section 35 -Paragraph 3 -URI http://asc.fasb.org/extlink&oid=6939497&loc=d3e30304-110892 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 830 -SubTopic 30 -Section 45 -Paragraph 20 -Subparagraph (b,d) -URI http://asc.fasb.org/extlink&oid=6915805&loc=d3e32211-110900 + Details
Name: | us-gaap_OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationAdjustmentBeforeTax
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Amount of tax expense (benefit), after reclassification adjustments of gain (loss) on foreign currency translation adjustments, foreign currency transactions designated and effective as economic hedges of a net investment in a foreign entity and intra-entity foreign currency transactions that are of a long-term-investment nature. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 220 -SubTopic 10 -Section 45 -Paragraph 10A -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=36458714&loc=SL7669646-108580 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 220 -SubTopic 10 -Section 45 -Paragraph 12 -URI http://asc.fasb.org/extlink&oid=36458714&loc=d3e640-108580 + Details
Name: | us-gaap_OtherComprehensiveIncomeLossForeignCurrencyTranslationAdjustmentTax
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Amount before tax of reclassification adjustment from accumulated other comprehensive income (loss) for actuarial gain (loss) related to pension and other postretirement benefit plans. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 220 -SubTopic 10 -Section 45 -Paragraph 11 -URI http://asc.fasb.org/extlink&oid=36458714&loc=d3e637-108580 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (i) -URI http://asc.fasb.org/extlink&oid=35743120&loc=d3e1928-114920 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 220 -SubTopic 10 -Section 45 -Paragraph 15 -URI http://asc.fasb.org/extlink&oid=36458714&loc=d3e689-108580 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (j) -URI http://asc.fasb.org/extlink&oid=35743120&loc=d3e1928-114920 + Details
Name: | us-gaap_OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetGainLossBeforeTax
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Amount after tax of reclassification adjustment from accumulated other comprehensive income (loss) for actuarial gain (loss) related to pension and other postretirement benefit plans. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 220 -SubTopic 10 -Section 45 -Paragraph 11 -URI http://asc.fasb.org/extlink&oid=36458714&loc=d3e637-108580 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (i) -URI http://asc.fasb.org/extlink&oid=35743120&loc=d3e1928-114920 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 220 -SubTopic 10 -Section 45 -Paragraph 15 -URI http://asc.fasb.org/extlink&oid=36458714&loc=d3e689-108580 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (j) -URI http://asc.fasb.org/extlink&oid=35743120&loc=d3e1928-114920 + Details
Name: | us-gaap_OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetGainLossNetOfTax
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Amount before tax of other than temporary impairment (OTTI) on investment in available-for-sale debt security, recognized in other comprehensive loss. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 220 -SubTopic 10 -Section 45 -Paragraph 10A -Subparagraph (g) -URI http://asc.fasb.org/extlink&oid=36458714&loc=SL7669646-108580 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 35 -Paragraph 35 -URI http://asc.fasb.org/extlink&oid=27723805&loc=d3e25362-111560 + Details
Name: | us-gaap_OtherThanTemporaryImpairmentLossesInvestmentsPortionInOtherComprehensiveIncomeLossBeforeTaxIncludingPortionAttributableToNoncontrollingInterestAvailableforsaleSecurities
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Details
Name: | us-gaap_ReclassificationAdjustmentOutOfAccumulatedOtherComprehensiveIncomeOnDerivativesLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Amount after tax of reclassification adjustments of other comprehensive income (loss). + References No definition available. + Details
Name: | us-gaap_ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTax
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Details
Name: | us-gaap_DerivativeInstrumentRiskAxis=clf_AustralianHedgeContractsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DerivativeInstrumentRiskAxis=clf_CanadianHedgeContractsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeAxis=clf_ForeignCurrencyTranslationAdjustmentMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeAxis=clf_RealizedGainLossOnDerivativesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeAxis=clf_RealizedGainLossonMarketableSecuritiesandOtherthanTemporaryImpairmentMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeAxis=clf_RealizedGainLossonMarketableSecuritiesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeAxis=us-gaap_AccumulatedDefinedBenefitPlansAdjustmentMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeAxis=us-gaap_AccumulatedOtherThanTemporaryImpairmentMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |