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Quarterly report pursuant to Section 13 or 15(d)

DISCONTINUED OPERATIONS DISCONTINUED OPERATIONS (Narrative) (Details)

v2.4.1.9
DISCONTINUED OPERATIONS DISCONTINUED OPERATIONS (Narrative) (Details) (USD $)
3 Months Ended 12 Months Ended
Mar. 31, 2015
Mar. 31, 2014
Dec. 31, 2014
Canadian Entities [Member] Ìý Ìý Ìý
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items] Ìý Ìý Ìý
Discontinued Operation, Tax Effect of Discontinued Operation $ 0us-gaap_DiscontinuedOperationTaxEffectOfDiscontinuedOperation
/ us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis
= clf_CanadianEntitiesMember
$ 44,300,000us-gaap_DiscontinuedOperationTaxEffectOfDiscontinuedOperation
/ us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis
= clf_CanadianEntitiesMember
Ìý
Business Exit Costs (818,700,000)us-gaap_BusinessExitCosts1
/ us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis
= clf_CanadianEntitiesMember
0us-gaap_BusinessExitCosts1
/ us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis
= clf_CanadianEntitiesMember
Ìý
Cost Method Investments 0us-gaap_CostMethodInvestments
/ us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis
= clf_CanadianEntitiesMember
Ìý Ìý
North American Coal [Member] Ìý Ìý Ìý
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items] Ìý Ìý Ìý
Pension and Other Postretirement Defined Benefit Plans, Liabilities 330,000,000us-gaap_PensionAndOtherPostretirementDefinedBenefitPlansLiabilitiesCurrentAndNoncurrent
/ us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis
= clf_NorthAmericanCoalMember
Ìý Ìý
Discontinued Operation, Tax Effect of Discontinued Operation 100,000us-gaap_DiscontinuedOperationTaxEffectOfDiscontinuedOperation
/ us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis
= clf_NorthAmericanCoalMember
7,200,000us-gaap_DiscontinuedOperationTaxEffectOfDiscontinuedOperation
/ us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis
= clf_NorthAmericanCoalMember
Ìý
Tangible Asset Impairment Charges (73,400,000)us-gaap_TangibleAssetImpairmentCharges
/ us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis
= clf_NorthAmericanCoalMember
Ìý Ìý
Asia Pacific Iron Ore [Member] | Asia Pacific Iron Ore [Member] Ìý Ìý Ìý
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items] Ìý Ìý Ìý
Tangible Asset Impairment Charges Ìý Ìý 526,500,000us-gaap_TangibleAssetImpairmentCharges
/ clf_AssetgroupAxis
= clf_AsiaPacificIronOreMember
/ clf_ReportingUnitAxis
= clf_AsiaPacificIronOreMember
Other Current Assets [Member] | Canadian Entities [Member] Ìý Ìý Ìý
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items] Ìý Ìý Ìý
Loans, Associated Interest and Accounts Receivable recognized in Consolidated Financials at Fair Value 112,100,000clf_LoansAssociatedInterestandAccountsReceivablerecognizedinConsolidatedFinancialsatFairValue
/ us-gaap_BalanceSheetLocationAxis
= us-gaap_OtherCurrentAssetsMember
/ us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis
= clf_CanadianEntitiesMember
Ìý Ìý
Other Current Liabilities [Member] | Bloom Lake Group [Member] Ìý Ìý Ìý
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items] Ìý Ìý Ìý
Contingent Liabilities recognized in Consolidated Financials 166,100,000clf_ContingentLiabilitiesrecognizedinConsolidatedFinancials
/ us-gaap_BalanceSheetLocationAxis
= us-gaap_OtherCurrentLiabilitiesMember
/ us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis
= clf_BloomLakeGroupMember
Ìý Ìý
Short-term Liabilities of Discontinued Operations [Member] | Canadian Entities [Member] Ìý Ìý Ìý
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items] Ìý Ìý Ìý
Liabilities Recorded for Wholly-owned Subsidiaries of Bloom Lake Group that did not file CCAA 51,400,000clf_LiabilitiesRecordedforWhollyownedSubsidiariesofBloomLakeGroupthatdidnotfileCCAA
/ us-gaap_BalanceSheetLocationAxis
= clf_ShorttermLiabilitiesofDiscontinuedOperationsMember
/ us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis
= clf_CanadianEntitiesMember
Ìý Ìý
Long-term Liabilities of Discontinued Operations [Member] | Canadian Entities [Member] Ìý Ìý Ìý
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items] Ìý Ìý Ìý
Liabilities Recorded for Wholly-owned Subsidiaries of Bloom Lake Group that did not file CCAA $ 125,200,000clf_LiabilitiesRecordedforWhollyownedSubsidiariesofBloomLakeGroupthatdidnotfileCCAA
/ us-gaap_BalanceSheetLocationAxis
= clf_LongtermLiabilitiesofDiscontinuedOperationsMember
/ us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis
= clf_CanadianEntitiesMember
Ìý Ìý