Annual report pursuant to Section 13 and 15(d)

DISCONTINUED OPERATIONS SCHEDULE OF DISPOSAL GROUPS (Details)

v2.4.1.9
DISCONTINUED OPERATIONS SCHEDULE OF DISPOSAL GROUPS (Details) (USD $)
In Millions, unless otherwise specified
3 Months Ended 12 Months Ended
Dec. 31, 2014
Sep. 30, 2014
Dec. 31, 2013
Sep. 30, 2013
Jun. 30, 2013
Mar. 31, 2013
Dec. 31, 2014
Dec. 31, 2013
Dec. 31, 2012
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]                  
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Extraordinary Items, Noncontrolling Interest             $ (9,603.7)us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments $ 489.3us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments $ (501.8)us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments
INCOME and GAIN ON SALE FROM DISCONTINUED OPERATIONS, net of tax 0us-gaap_IncomeLossFromDiscontinuedOperationsNetOfTax 0us-gaap_IncomeLossFromDiscontinuedOperationsNetOfTax 0us-gaap_IncomeLossFromDiscontinuedOperationsNetOfTax 2.0us-gaap_IncomeLossFromDiscontinuedOperationsNetOfTax 0us-gaap_IncomeLossFromDiscontinuedOperationsNetOfTax 0us-gaap_IncomeLossFromDiscontinuedOperationsNetOfTax 0us-gaap_IncomeLossFromDiscontinuedOperationsNetOfTax 2.0us-gaap_IncomeLossFromDiscontinuedOperationsNetOfTax 35.9us-gaap_IncomeLossFromDiscontinuedOperationsNetOfTax
Sonoma [Member]                  
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]                  
Disposal Group, Including Discontinued Operation, Revenue             0us-gaap_DisposalGroupIncludingDiscontinuedOperationRevenue
/ us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis
= clf_SonomaMember
0us-gaap_DisposalGroupIncludingDiscontinuedOperationRevenue
/ us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis
= clf_SonomaMember
151.6us-gaap_DisposalGroupIncludingDiscontinuedOperationRevenue
/ us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis
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INCOME and GAIN ON SALE FROM DISCONTINUED OPERATIONS, net of tax 0us-gaap_IncomeLossFromDiscontinuedOperationsNetOfTax
/ us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis
= clf_SonomaMember
          0us-gaap_IncomeLossFromDiscontinuedOperationsNetOfTax
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= clf_SonomaMember
2.0us-gaap_IncomeLossFromDiscontinuedOperationsNetOfTax
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= clf_SonomaMember
35.9us-gaap_IncomeLossFromDiscontinuedOperationsNetOfTax
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= clf_SonomaMember
Income (Loss) From Discontinued Operations [Member] | Sonoma [Member]                  
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]                  
Discontinued Operation, Gain (Loss) on Disposal of Discontinued Operation, Net of Tax             0us-gaap_DiscontinuedOperationGainLossOnDisposalOfDiscontinuedOperationNetOfTax
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= clf_SonomaMember
/ us-gaap_IncomeStatementLocationAxis
= clf_IncomeLossFromDiscontinuedOperationsMember
0us-gaap_DiscontinuedOperationGainLossOnDisposalOfDiscontinuedOperationNetOfTax
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= clf_SonomaMember
/ us-gaap_IncomeStatementLocationAxis
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38.0us-gaap_DiscontinuedOperationGainLossOnDisposalOfDiscontinuedOperationNetOfTax
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= clf_SonomaMember
/ us-gaap_IncomeStatementLocationAxis
= clf_IncomeLossFromDiscontinuedOperationsMember
INCOME and GAIN ON SALE FROM DISCONTINUED OPERATIONS, net of tax                 (2.1)us-gaap_IncomeLossFromDiscontinuedOperationsNetOfTax
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= clf_SonomaMember
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= clf_IncomeLossFromDiscontinuedOperationsMember
Wabush [Member]                  
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]                  
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Extraordinary Items, Noncontrolling Interest             (345.6)us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments
/ clf_ReportingUnitAxis
= clf_WabushMember
(258.6)us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments
/ clf_ReportingUnitAxis
= clf_WabushMember
(131.8)us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments
/ clf_ReportingUnitAxis
= clf_WabushMember
CLCC [Member]                  
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]                  
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Extraordinary Items, Noncontrolling Interest             $ (669.9)us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments
/ clf_ReportingUnitAxis
= clf_ClccMember
$ (55.0)us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments
/ clf_ReportingUnitAxis
= clf_ClccMember
$ (41.8)us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments
/ clf_ReportingUnitAxis
= clf_ClccMember