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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 - Canadian Entities (Details)

v2.4.1.9
DISCONTINUED OPERATIONS Schedule of Disposal Groups, including Discontinued Operations, Assets and Liabilities - Canadian Entities (Details) (Canadian Entities [Member], USD $)
In Millions, unless otherwise specified
Mar. 31, 2015
Dec. 31, 2014
Canadian Entities [Member]
Ìý Ìý
Schedule of Disposal Groups, Including Discontinued Operations, Assets and Liabilities [Line Items] Ìý Ìý
Disposal Group, Including Discontinued Operation, Cash and Cash Equivalents Ìý $ 19.7us-gaap_DisposalGroupIncludingDiscontinuedOperationCashAndCashEquivalents
/ us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis
= clf_CanadianEntitiesMember
Disposal Group, Including Discontinued Operation, Accounts, Notes and Loans Receivable, Net 3.0us-gaap_DisposalGroupIncludingDiscontinuedOperationAccountsNotesAndLoansReceivableNet
/ us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis
= clf_CanadianEntitiesMember
37.9us-gaap_DisposalGroupIncludingDiscontinuedOperationAccountsNotesAndLoansReceivableNet
/ us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis
= clf_CanadianEntitiesMember
Disposal Group, Including Discontinued Operation, Inventory Ìý 16.3us-gaap_DisposalGroupIncludingDiscontinuedOperationInventory1
/ us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis
= clf_CanadianEntitiesMember
Disposal group, including Discontinued Operations, Prepaid Supplies Ìý 48.5clf_DisposalgroupincludingDiscontinuedOperationsPrepaidSupplies
/ us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis
= clf_CanadianEntitiesMember
Disposal group, including Discontinued Operations, Income taxes receivable 1.8clf_DisposalgroupincludingDiscontinuedOperationsIncometaxesreceivable
/ us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis
= clf_CanadianEntitiesMember
20.1clf_DisposalgroupincludingDiscontinuedOperationsIncometaxesreceivable
/ us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis
= clf_CanadianEntitiesMember
Disposal Group, Including Discontinued Operation, Other Assets, Current Ìý 44.3us-gaap_DisposalGroupIncludingDiscontinuedOperationOtherCurrentAssets
/ us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis
= clf_CanadianEntitiesMember
Disposal Group, Including Discontinued Operation, Property, Plant and Equipment Ìý 249.8us-gaap_DisposalGroupIncludingDiscontinuedOperationPropertyPlantAndEquipment
/ us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis
= clf_CanadianEntitiesMember
Disposal Group, Including Discontinued Operation, Other Assets, Noncurrent 3.8us-gaap_DisposalGroupIncludingDiscontinuedOperationOtherNoncurrentAssets
/ us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis
= clf_CanadianEntitiesMember
19.9us-gaap_DisposalGroupIncludingDiscontinuedOperationOtherNoncurrentAssets
/ us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis
= clf_CanadianEntitiesMember
Disposal Group, Including Discontinued Operation, Assets 8.6us-gaap_AssetsOfDisposalGroupIncludingDiscontinuedOperation
/ us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis
= clf_CanadianEntitiesMember
456.5us-gaap_AssetsOfDisposalGroupIncludingDiscontinuedOperation
/ us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis
= clf_CanadianEntitiesMember
Disposal Group, Including Discontinued Operation, Accounts Payable 0.5us-gaap_DisposalGroupIncludingDiscontinuedOperationAccountsPayable
/ us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis
= clf_CanadianEntitiesMember
83.6us-gaap_DisposalGroupIncludingDiscontinuedOperationAccountsPayable
/ us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis
= clf_CanadianEntitiesMember
Disposal Group, Including Discontinued Operation, Accrued Liabilities 51.1us-gaap_DisposalGroupIncludingDiscontinuedOperationAccruedLiabilities
/ us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis
= clf_CanadianEntitiesMember
200.0us-gaap_DisposalGroupIncludingDiscontinuedOperationAccruedLiabilities
/ us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis
= clf_CanadianEntitiesMember
Disposal Group, Including Discontinued Operation, Other Liabilities, Current Ìý 35.7us-gaap_DisposalGroupIncludingDiscontinuedOperationOtherCurrentLiabilities
/ us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis
= clf_CanadianEntitiesMember
Disposal group, Including Discontinued Operation, Pension and Other Postretirement Obligations Ìý 79.8clf_DisposalgroupIncludingDiscontinuedOperationPensionandOtherPostretirementObligations
/ us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis
= clf_CanadianEntitiesMember
Disposal Group Including Discontinued Operations Environmental Loss Contingency And Mine Reclamation And Closing Liability CurrentAnd Noncurrent Ìý 56.5clf_DisposalGroupIncludingDiscontinuedOperationsEnvironmentalLossContingencyAndMineReclamationAndClosingLiabilityCurrentAndNoncurrent
/ us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis
= clf_CanadianEntitiesMember
Disposal Group, Including Discontinued Operation, Other Liabilities, Noncurrent 140.9us-gaap_DisposalGroupIncludingDiscontinuedOperationOtherNoncurrentLiabilities
/ us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis
= clf_CanadianEntitiesMember
173.9us-gaap_DisposalGroupIncludingDiscontinuedOperationOtherNoncurrentLiabilities
/ us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis
= clf_CanadianEntitiesMember
Disposal Group, Including Discontinued Operation, Liabilities $ 192.5us-gaap_LiabilitiesOfDisposalGroupIncludingDiscontinuedOperation
/ us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis
= clf_CanadianEntitiesMember
$ 629.5us-gaap_LiabilitiesOfDisposalGroupIncludingDiscontinuedOperation
/ us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis
= clf_CanadianEntitiesMember