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Annual report pursuant to Section 13 and 15(d)

PENSIONS AND OTHER POSTRETIREMENT BENEFITS (Narrative) (Details)

v2.4.1.9
PENSIONS AND OTHER POSTRETIREMENT BENEFITS (Narrative) (Details) (USD $)
12 Months Ended
Dec. 31, 2014
Dec. 31, 2013
Dec. 31, 2012
Sep. 30, 2014
Defined Benefit Plan Disclosure [Line Items] Ìý Ìý Ìý Ìý
Current Fiscal Year End Date --12-31 Ìý Ìý Ìý
Minimum participants percentage 15.00%clf_MinimumParticipantsCostPercentageToAverageCoverageCost Ìý Ìý Ìý
Accumulated benefit obligation for defined benefit pension plans $ 1,204,400,000us-gaap_DefinedBenefitPlanAccumulatedBenefitObligation $ 1,091,400,000us-gaap_DefinedBenefitPlanAccumulatedBenefitObligation Ìý Ìý
Maturity period of security 10 years Ìý Ìý Ìý
Reserve for investment commitments 55,500,000clf_ReserveForInvestmentCommitments Ìý Ìý 45,000,000clf_ReserveForInvestmentCommitments
Sei Special Situations Fund [Member] Ìý Ìý Ìý Ìý
Defined Benefit Plan Disclosure [Line Items] Ìý Ìý Ìý Ìý
Redemption request notice period, days 95 days Ìý Ìý Ìý
Structured Finance [Member] Ìý Ìý Ìý Ìý
Defined Benefit Plan Disclosure [Line Items] Ìý Ìý Ìý Ìý
Redemption request notice period, days 90 days Ìý Ìý Ìý
Real Estate [Member] Ìý Ìý Ìý Ìý
Defined Benefit Plan Disclosure [Line Items] Ìý Ìý Ìý Ìý
Redemption request notice period, days 45 days Ìý Ìý Ìý
Withdrawal request notice period, days 65 days Ìý Ìý Ìý
Pension Benefits [Member] Ìý Ìý Ìý Ìý
Defined Benefit Plan Disclosure [Line Items] Ìý Ìý Ìý Ìý
Increase in Projected Benefit Obligation due to new mortality tables 30,000,000clf_IncreaseinProjectedBenefitObligationduetonewmortalitytables
/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis
= us-gaap_PensionPlansDefinedBenefitMember
Ìý Ìý Ìý
Percentage Increase in Projected Benefit Obligation due to new mortality tables 4.00%clf_PercentageIncreaseinProjectedBenefitObligationduetonewmortalitytables
/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis
= us-gaap_PensionPlansDefinedBenefitMember
Ìý Ìý Ìý
Defined Benefit Plan, Net Periodic Benefit Cost 31,300,000us-gaap_DefinedBenefitPlanNetPeriodicBenefitCost
/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis
= us-gaap_PensionPlansDefinedBenefitMember
52,100,000us-gaap_DefinedBenefitPlanNetPeriodicBenefitCost
/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis
= us-gaap_PensionPlansDefinedBenefitMember
55,200,000us-gaap_DefinedBenefitPlanNetPeriodicBenefitCost
/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis
= us-gaap_PensionPlansDefinedBenefitMember
Ìý
Annual costs for defined contribution plan 6,300,000us-gaap_DefinedContributionPlanCostRecognized
/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis
= us-gaap_PensionPlansDefinedBenefitMember
6,800,000us-gaap_DefinedContributionPlanCostRecognized
/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis
= us-gaap_PensionPlansDefinedBenefitMember
6,700,000us-gaap_DefinedContributionPlanCostRecognized
/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis
= us-gaap_PensionPlansDefinedBenefitMember
Ìý
Participant contributions 0us-gaap_DefinedBenefitPlanContributionsByPlanParticipants
/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis
= us-gaap_PensionPlansDefinedBenefitMember
0us-gaap_DefinedBenefitPlanContributionsByPlanParticipants
/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis
= us-gaap_PensionPlansDefinedBenefitMember
Ìý Ìý
Other Postretirement Benefit Expense (700,000)us-gaap_OtherPostretirementBenefitExpense
/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis
= us-gaap_PensionPlansDefinedBenefitMember
17,400,000us-gaap_OtherPostretirementBenefitExpense
/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis
= us-gaap_PensionPlansDefinedBenefitMember
28,100,000us-gaap_OtherPostretirementBenefitExpense
/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis
= us-gaap_PensionPlansDefinedBenefitMember
Ìý
Pension and Other Postretirement Benefit Expense 36,900,000us-gaap_PensionAndOtherPostretirementBenefitExpense
/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis
= us-gaap_PensionPlansDefinedBenefitMember
76,300,000us-gaap_PensionAndOtherPostretirementBenefitExpense
/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis
= us-gaap_PensionPlansDefinedBenefitMember
90,000,000us-gaap_PensionAndOtherPostretirementBenefitExpense
/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis
= us-gaap_PensionPlansDefinedBenefitMember
Ìý
Defined Benefit Plan, Recognized Net Gain (Loss) Due to Curtailments (10,900,000)us-gaap_DefinedBenefitPlanRecognizedNetGainLossDueToCurtailments
/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis
= us-gaap_PensionPlansDefinedBenefitMember
0us-gaap_DefinedBenefitPlanRecognizedNetGainLossDueToCurtailments
/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis
= us-gaap_PensionPlansDefinedBenefitMember
Ìý Ìý
Increase in Canadian Plan Projected Benefit Obligation due to new mortality tables 12,000,000clf_IncreaseinCanadianPlanProjectedBenefitObligationduetonewmortalitytables
/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis
= us-gaap_PensionPlansDefinedBenefitMember
Ìý Ìý Ìý
Percentage Increase in Canadian Plan Projected Benefit Obligation due to new mortality tables 5.00%clf_PercentageIncreaseinCanadianPlanProjectedBenefitObligationduetonewmortalitytables
/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis
= us-gaap_PensionPlansDefinedBenefitMember
Ìý Ìý Ìý
Defined Benefit Plan, Recognized Net Gain (Loss) Due to Settlements and Curtailments (2,900,000)us-gaap_DefinedBenefitPlanRecognizedNetGainLossDueToSettlementsAndCurtailments1
/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis
= us-gaap_PensionPlansDefinedBenefitMember
0us-gaap_DefinedBenefitPlanRecognizedNetGainLossDueToSettlementsAndCurtailments1
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= us-gaap_PensionPlansDefinedBenefitMember
0us-gaap_DefinedBenefitPlanRecognizedNetGainLossDueToSettlementsAndCurtailments1
/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis
= us-gaap_PensionPlansDefinedBenefitMember
Ìý
Other Benefits [Member] Ìý Ìý Ìý Ìý
Defined Benefit Plan Disclosure [Line Items] Ìý Ìý Ìý Ìý
Increase in Projected Benefit Obligation due to new mortality tables 20,000,000clf_IncreaseinProjectedBenefitObligationduetonewmortalitytables
/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis
= us-gaap_OtherPostretirementBenefitPlansDefinedBenefitMember
Ìý Ìý Ìý
Percentage Increase in Projected Benefit Obligation due to new mortality tables 7.00%clf_PercentageIncreaseinProjectedBenefitObligationduetonewmortalitytables
/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis
= us-gaap_OtherPostretirementBenefitPlansDefinedBenefitMember
Ìý Ìý Ìý
Defined Benefit Plan, Net Periodic Benefit Cost (700,000)us-gaap_DefinedBenefitPlanNetPeriodicBenefitCost
/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis
= us-gaap_OtherPostretirementBenefitPlansDefinedBenefitMember
17,400,000us-gaap_DefinedBenefitPlanNetPeriodicBenefitCost
/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis
= us-gaap_OtherPostretirementBenefitPlansDefinedBenefitMember
28,100,000us-gaap_DefinedBenefitPlanNetPeriodicBenefitCost
/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis
= us-gaap_OtherPostretirementBenefitPlansDefinedBenefitMember
Ìý
Participant contributions 4,800,000us-gaap_DefinedBenefitPlanContributionsByPlanParticipants
/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis
= us-gaap_OtherPostretirementBenefitPlansDefinedBenefitMember
5,600,000us-gaap_DefinedBenefitPlanContributionsByPlanParticipants
/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis
= us-gaap_OtherPostretirementBenefitPlansDefinedBenefitMember
Ìý Ìý
Defined Benefit Plan, Recognized Net Gain (Loss) Due to Curtailments (8,800,000)us-gaap_DefinedBenefitPlanRecognizedNetGainLossDueToCurtailments
/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis
= us-gaap_OtherPostretirementBenefitPlansDefinedBenefitMember
0us-gaap_DefinedBenefitPlanRecognizedNetGainLossDueToCurtailments
/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis
= us-gaap_OtherPostretirementBenefitPlansDefinedBenefitMember
Ìý Ìý
Increase in Canadian Plan Projected Benefit Obligation due to new mortality tables 3,000,000clf_IncreaseinCanadianPlanProjectedBenefitObligationduetonewmortalitytables
/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis
= us-gaap_OtherPostretirementBenefitPlansDefinedBenefitMember
Ìý Ìý Ìý
Percentage Increase in Canadian Plan Projected Benefit Obligation due to new mortality tables 5.00%clf_PercentageIncreaseinCanadianPlanProjectedBenefitObligationduetonewmortalitytables
/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis
= us-gaap_OtherPostretirementBenefitPlansDefinedBenefitMember
Ìý Ìý Ìý
Defined Benefit Plan, Recognized Net Gain (Loss) Due to Settlements and Curtailments 7,900,000us-gaap_DefinedBenefitPlanRecognizedNetGainLossDueToSettlementsAndCurtailments1
/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis
= us-gaap_OtherPostretirementBenefitPlansDefinedBenefitMember
0us-gaap_DefinedBenefitPlanRecognizedNetGainLossDueToSettlementsAndCurtailments1
/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis
= us-gaap_OtherPostretirementBenefitPlansDefinedBenefitMember
0us-gaap_DefinedBenefitPlanRecognizedNetGainLossDueToSettlementsAndCurtailments1
/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis
= us-gaap_OtherPostretirementBenefitPlansDefinedBenefitMember
Ìý
Minimum [Member] Ìý Ìý Ìý Ìý
Defined Benefit Plan Disclosure [Line Items] Ìý Ìý Ìý Ìý
Discount rate 3.72%us-gaap_DefinedBenefitPlanAssumptionsUsedCalculatingBenefitObligationDiscountRate
/ us-gaap_RangeAxis
= us-gaap_MinimumMember
Ìý Ìý Ìý
Expected period of long-term return on assets 3 years Ìý Ìý Ìý
Maximum [Member] Ìý Ìý Ìý Ìý
Defined Benefit Plan Disclosure [Line Items] Ìý Ìý Ìý Ìý
Discount rate 3.92%us-gaap_DefinedBenefitPlanAssumptionsUsedCalculatingBenefitObligationDiscountRate
/ us-gaap_RangeAxis
= us-gaap_MaximumMember
Ìý Ìý Ìý
Expected period of long-term return on assets 5 years Ìý Ìý Ìý
United States [Member] | Pension Benefits [Member] Ìý Ìý Ìý Ìý
Defined Benefit Plan Disclosure [Line Items] Ìý Ìý Ìý Ìý
Discount rate 3.83%us-gaap_DefinedBenefitPlanAssumptionsUsedCalculatingBenefitObligationDiscountRate
/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis
= us-gaap_PensionPlansDefinedBenefitMember
/ clf_RegionReportingInformationByRegionAxis
= clf_UnitedStatesMember
4.57%us-gaap_DefinedBenefitPlanAssumptionsUsedCalculatingBenefitObligationDiscountRate
/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis
= us-gaap_PensionPlansDefinedBenefitMember
/ clf_RegionReportingInformationByRegionAxis
= clf_UnitedStatesMember
Ìý Ìý
Projected yield, number of bonds used 715clf_DefinedBenefitPlanAssumptionsUsedCalculatingBenefitObligationDiscountRateNumberOfBondsUsedForProjectedYieldCurve
/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis
= us-gaap_PensionPlansDefinedBenefitMember
/ clf_RegionReportingInformationByRegionAxis
= clf_UnitedStatesMember
Ìý Ìý Ìý
United States [Member] | Other Benefits [Member] Ìý Ìý Ìý Ìý
Defined Benefit Plan Disclosure [Line Items] Ìý Ìý Ìý Ìý
Discount rate 3.83%us-gaap_DefinedBenefitPlanAssumptionsUsedCalculatingBenefitObligationDiscountRate
/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis
= us-gaap_OtherPostretirementBenefitPlansDefinedBenefitMember
/ clf_RegionReportingInformationByRegionAxis
= clf_UnitedStatesMember
4.57%us-gaap_DefinedBenefitPlanAssumptionsUsedCalculatingBenefitObligationDiscountRate
/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis
= us-gaap_OtherPostretirementBenefitPlansDefinedBenefitMember
/ clf_RegionReportingInformationByRegionAxis
= clf_UnitedStatesMember
Ìý Ìý
Canada [Member] | Pension Benefits [Member] Ìý Ìý Ìý Ìý
Defined Benefit Plan Disclosure [Line Items] Ìý Ìý Ìý Ìý
Discount rate 3.75%us-gaap_DefinedBenefitPlanAssumptionsUsedCalculatingBenefitObligationDiscountRate
/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis
= us-gaap_PensionPlansDefinedBenefitMember
/ clf_RegionReportingInformationByRegionAxis
= clf_CanadaMember
4.50%us-gaap_DefinedBenefitPlanAssumptionsUsedCalculatingBenefitObligationDiscountRate
/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis
= us-gaap_PensionPlansDefinedBenefitMember
/ clf_RegionReportingInformationByRegionAxis
= clf_CanadaMember
Ìý Ìý
Projected yield, number of bonds used 285clf_DefinedBenefitPlanAssumptionsUsedCalculatingBenefitObligationDiscountRateNumberOfBondsUsedForProjectedYieldCurve
/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis
= us-gaap_PensionPlansDefinedBenefitMember
/ clf_RegionReportingInformationByRegionAxis
= clf_CanadaMember
Ìý Ìý Ìý
Canada [Member] | Other Benefits [Member] Ìý Ìý Ìý Ìý
Defined Benefit Plan Disclosure [Line Items] Ìý Ìý Ìý Ìý
Discount rate 3.75%us-gaap_DefinedBenefitPlanAssumptionsUsedCalculatingBenefitObligationDiscountRate
/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis
= us-gaap_OtherPostretirementBenefitPlansDefinedBenefitMember
/ clf_RegionReportingInformationByRegionAxis
= clf_CanadaMember
4.75%us-gaap_DefinedBenefitPlanAssumptionsUsedCalculatingBenefitObligationDiscountRate
/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis
= us-gaap_OtherPostretirementBenefitPlansDefinedBenefitMember
/ clf_RegionReportingInformationByRegionAxis
= clf_CanadaMember
Ìý Ìý
Tilden, Empire, Hibbing and United Taconite [Member] Ìý Ìý Ìý Ìý
Defined Benefit Plan Disclosure [Line Items] Ìý Ìý Ìý Ìý
Number of USW employees covered by labor contracts 2,200clf_NumberOfEmployeesInUnionCoveredByAnyUnionAgreement
/ clf_MineLocationAxis
= clf_TildenEmpireHibbingandUnitedTaconiteMember
Ìý Ìý Ìý
Percentage of total workforce covered by labor contract 40.90%clf_PercentageOfTotalWorkforceUnderLaborContract
/ clf_MineLocationAxis
= clf_TildenEmpireHibbingandUnitedTaconiteMember
Ìý Ìý Ìý
Pinnacle Complex and Oak Grove [Member] Ìý Ìý Ìý Ìý
Defined Benefit Plan Disclosure [Line Items] Ìý Ìý Ìý Ìý
Number of USW employees covered by labor contracts 800clf_NumberOfEmployeesInUnionCoveredByAnyUnionAgreement
/ clf_MineLocationAxis
= clf_PinnacleComplexandOakGroveMember
Ìý Ìý Ìý
Percentage of total workforce covered by labor contract 15.20%clf_PercentageOfTotalWorkforceUnderLaborContract
/ clf_MineLocationAxis
= clf_PinnacleComplexandOakGroveMember
Ìý Ìý Ìý
Contribution rate per hour worked 8.16clf_DefinedContributionPlanRates
/ clf_MineLocationAxis
= clf_PinnacleComplexandOakGroveMember
8.10clf_DefinedContributionPlanRates
/ clf_MineLocationAxis
= clf_PinnacleComplexandOakGroveMember
8.10clf_DefinedContributionPlanRates
/ clf_MineLocationAxis
= clf_PinnacleComplexandOakGroveMember
Ìý
Annual costs for defined contribution plan 14,900,000us-gaap_DefinedContributionPlanCostRecognized
/ clf_MineLocationAxis
= clf_PinnacleComplexandOakGroveMember
13,800,000us-gaap_DefinedContributionPlanCostRecognized
/ clf_MineLocationAxis
= clf_PinnacleComplexandOakGroveMember
Ìý Ìý
Underfunded Liability Estimate 330,000,000clf_UnderfundedLiabilityEstimate
/ clf_MineLocationAxis
= clf_PinnacleComplexandOakGroveMember
Ìý Ìý Ìý
Prior To Age65 [Member] | Defined Benefit Postretirement Health Coverage [Member] | United States [Member] Ìý Ìý Ìý Ìý
Defined Benefit Plan Disclosure [Line Items] Ìý Ìý Ìý Ìý
Annual limit on medical coverage for each participant 7,000clf_PostretirementBenefitsMedicalCoverageAnnualLimit
/ clf_CoverageAgeAxis
= clf_PriorToAge65Member
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/ us-gaap_RelatedPartyTransactionsByRelatedPartyAxis
= country_US
Ìý Ìý Ìý
Prior To Age65 [Member] | Minimum [Member] | Defined Benefit Postretirement Health Coverage [Member] | Northshore [Member] Ìý Ìý Ìý Ìý
Defined Benefit Plan Disclosure [Line Items] Ìý Ìý Ìý Ìý
Annual limit on medical coverage for each participant 4,020clf_PostretirementBenefitsMedicalCoverageAnnualLimit
/ clf_CoverageAgeAxis
= clf_PriorToAge65Member
/ us-gaap_DeferredCompensationArrangementWithIndividualPostretirementBenefitsByTypeOfDeferredCompensationAxis
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/ us-gaap_RangeAxis
= us-gaap_MinimumMember
/ us-gaap_RelatedPartyTransactionsByRelatedPartyAxis
= clf_NorthshoreMember
Ìý Ìý Ìý
Prior To Age65 [Member] | Maximum [Member] | Defined Benefit Postretirement Health Coverage [Member] | Northshore [Member] Ìý Ìý Ìý Ìý
Defined Benefit Plan Disclosure [Line Items] Ìý Ìý Ìý Ìý
Annual limit on medical coverage for each participant 4,500clf_PostretirementBenefitsMedicalCoverageAnnualLimit
/ clf_CoverageAgeAxis
= clf_PriorToAge65Member
/ us-gaap_DeferredCompensationArrangementWithIndividualPostretirementBenefitsByTypeOfDeferredCompensationAxis
= us-gaap_DefinedBenefitPostretirementHealthCoverageMember
/ us-gaap_RangeAxis
= us-gaap_MaximumMember
/ us-gaap_RelatedPartyTransactionsByRelatedPartyAxis
= clf_NorthshoreMember
Ìý Ìý Ìý
After Age65 [Member] | Defined Benefit Postretirement Health Coverage [Member] | United States [Member] Ìý Ìý Ìý Ìý
Defined Benefit Plan Disclosure [Line Items] Ìý Ìý Ìý Ìý
Annual limit on medical coverage for each participant 3,000clf_PostretirementBenefitsMedicalCoverageAnnualLimit
/ clf_CoverageAgeAxis
= clf_AfterAge65Member
/ us-gaap_DeferredCompensationArrangementWithIndividualPostretirementBenefitsByTypeOfDeferredCompensationAxis
= us-gaap_DefinedBenefitPostretirementHealthCoverageMember
/ us-gaap_RelatedPartyTransactionsByRelatedPartyAxis
= country_US
Ìý Ìý Ìý
After Age65 [Member] | Defined Benefit Postretirement Health Coverage [Member] | Northshore [Member] Ìý Ìý Ìý Ìý
Defined Benefit Plan Disclosure [Line Items] Ìý Ìý Ìý Ìý
Annual limit on medical coverage for each participant $ 2,000clf_PostretirementBenefitsMedicalCoverageAnnualLimit
/ clf_CoverageAgeAxis
= clf_AfterAge65Member
/ us-gaap_DeferredCompensationArrangementWithIndividualPostretirementBenefitsByTypeOfDeferredCompensationAxis
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/ us-gaap_RelatedPartyTransactionsByRelatedPartyAxis
= clf_NorthshoreMember
Ìý Ìý Ìý