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Quarterly report pursuant to Section 13 or 15(d)

DISCONTINUED OPERATIONS Schedule of Disposal Groups, including Discontinued Operations, Assets and Liabilities - North American Coal (Details)

v2.4.1.9
DISCONTINUED OPERATIONS Schedule of Disposal Groups, including Discontinued Operations, Assets and Liabilities - North American Coal (Details) (North American Coal [Member], USD $)
In Millions, unless otherwise specified
Mar. 31, 2015
Dec. 31, 2014
North American Coal [Member]
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Schedule of Disposal Groups, Including Discontinued Operations, Assets and Liabilities [Line Items] Ìý Ìý
Disposal Group, Including Discontinued Operation, Accounts, Notes and Loans Receivable, Net $ 42.7us-gaap_DisposalGroupIncludingDiscontinuedOperationAccountsNotesAndLoansReceivableNet
/ us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis
= clf_NorthAmericanCoalMember
$ 44.8us-gaap_DisposalGroupIncludingDiscontinuedOperationAccountsNotesAndLoansReceivableNet
/ us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis
= clf_NorthAmericanCoalMember
Disposal Group, Including Discontinued Operation, Inventory 59.7us-gaap_DisposalGroupIncludingDiscontinuedOperationInventory1
/ us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis
= clf_NorthAmericanCoalMember
50.3us-gaap_DisposalGroupIncludingDiscontinuedOperationInventory1
/ us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis
= clf_NorthAmericanCoalMember
Disposal group, including Discontinued Operations, Prepaid Supplies 28.4clf_DisposalgroupincludingDiscontinuedOperationsPrepaidSupplies
/ us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis
= clf_NorthAmericanCoalMember
28.2clf_DisposalgroupincludingDiscontinuedOperationsPrepaidSupplies
/ us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis
= clf_NorthAmericanCoalMember
Disposal Group, Including Discontinued Operation, Other Assets, Current 29.4us-gaap_DisposalGroupIncludingDiscontinuedOperationOtherCurrentAssets
/ us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis
= clf_NorthAmericanCoalMember
20.5us-gaap_DisposalGroupIncludingDiscontinuedOperationOtherCurrentAssets
/ us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis
= clf_NorthAmericanCoalMember
Disposal Group, Including Discontinued Operation, Property, Plant and Equipment 20.4us-gaap_DisposalGroupIncludingDiscontinuedOperationPropertyPlantAndEquipment
/ us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis
= clf_NorthAmericanCoalMember
94.7us-gaap_DisposalGroupIncludingDiscontinuedOperationPropertyPlantAndEquipment
/ us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis
= clf_NorthAmericanCoalMember
Disposal Group, Including Discontinued Operation, Other Assets, Noncurrent 8.0us-gaap_DisposalGroupIncludingDiscontinuedOperationOtherNoncurrentAssets
/ us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis
= clf_NorthAmericanCoalMember
35.7us-gaap_DisposalGroupIncludingDiscontinuedOperationOtherNoncurrentAssets
/ us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis
= clf_NorthAmericanCoalMember
Disposal Group, Including Discontinued Operation, Assets 188.6us-gaap_AssetsOfDisposalGroupIncludingDiscontinuedOperation
/ us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis
= clf_NorthAmericanCoalMember
274.2us-gaap_AssetsOfDisposalGroupIncludingDiscontinuedOperation
/ us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis
= clf_NorthAmericanCoalMember
Disposal Group, Including Discontinued Operation, Accounts Payable 23.3us-gaap_DisposalGroupIncludingDiscontinuedOperationAccountsPayable
/ us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis
= clf_NorthAmericanCoalMember
22.4us-gaap_DisposalGroupIncludingDiscontinuedOperationAccountsPayable
/ us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis
= clf_NorthAmericanCoalMember
Disposal Group, Including Discontinued Operation, Accrued Liabilities 16.7us-gaap_DisposalGroupIncludingDiscontinuedOperationAccruedLiabilities
/ us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis
= clf_NorthAmericanCoalMember
27.9us-gaap_DisposalGroupIncludingDiscontinuedOperationAccruedLiabilities
/ us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis
= clf_NorthAmericanCoalMember
Disposal Group, Including Discontinued Operation, Other Liabilities, Current 34.7us-gaap_DisposalGroupIncludingDiscontinuedOperationOtherCurrentLiabilities
/ us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis
= clf_NorthAmericanCoalMember
31.0us-gaap_DisposalGroupIncludingDiscontinuedOperationOtherCurrentLiabilities
/ us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis
= clf_NorthAmericanCoalMember
Disposal group, Including Discontinued Operation, Pension and Other Postretirement Obligations 56.7clf_DisposalgroupIncludingDiscontinuedOperationPensionandOtherPostretirementObligations
/ us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis
= clf_NorthAmericanCoalMember
55.8clf_DisposalgroupIncludingDiscontinuedOperationPensionandOtherPostretirementObligations
/ us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis
= clf_NorthAmericanCoalMember
Disposal Group Including Discontinued Operations Environmental Loss Contingency And Mine Reclamation And Closing Liability CurrentAnd Noncurrent 34.4clf_DisposalGroupIncludingDiscontinuedOperationsEnvironmentalLossContingencyAndMineReclamationAndClosingLiabilityCurrentAndNoncurrent
/ us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis
= clf_NorthAmericanCoalMember
33.9clf_DisposalGroupIncludingDiscontinuedOperationsEnvironmentalLossContingencyAndMineReclamationAndClosingLiabilityCurrentAndNoncurrent
/ us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis
= clf_NorthAmericanCoalMember
Disposal Group, Including Discontinued Operation, Other Liabilities, Noncurrent 31.9us-gaap_DisposalGroupIncludingDiscontinuedOperationOtherNoncurrentLiabilities
/ us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis
= clf_NorthAmericanCoalMember
36.2us-gaap_DisposalGroupIncludingDiscontinuedOperationOtherNoncurrentLiabilities
/ us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis
= clf_NorthAmericanCoalMember
Disposal Group, Including Discontinued Operation, Liabilities $ 197.7us-gaap_LiabilitiesOfDisposalGroupIncludingDiscontinuedOperation
/ us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis
= clf_NorthAmericanCoalMember
$ 207.2us-gaap_LiabilitiesOfDisposalGroupIncludingDiscontinuedOperation
/ us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis
= clf_NorthAmericanCoalMember