Quarterly report pursuant to Section 13 or 15(d)

DISCONTINUED OPERATIONS Schedule of Disposal Groups, including Discontinued Operations, Income Statement - North American Coal (Details)

v2.4.1.9
DISCONTINUED OPERATIONS Schedule of Disposal Groups, including Discontinued Operations, Income Statement - North American Coal (Details) (USD $)
In Millions, unless otherwise specified
3 Months Ended
Mar. 31, 2015
Mar. 31, 2014
Schedule of Disposal Groups, Including Discontinued Operations, Assets and Liabilities [Line Items]    
LOSS FROM DISCONTINUED OPERATIONS, net of tax $ (928.5)us-gaap_IncomeLossFromDiscontinuedOperationsNetOfTax $ (140.4)us-gaap_IncomeLossFromDiscontinuedOperationsNetOfTax
North American Coal [Member]    
Schedule of Disposal Groups, Including Discontinued Operations, Assets and Liabilities [Line Items]    
Disposal Group, Including Discontinued Operation, Revenue 116.6us-gaap_DisposalGroupIncludingDiscontinuedOperationRevenue
/ us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis
= clf_NorthAmericanCoalMember
166.2us-gaap_DisposalGroupIncludingDiscontinuedOperationRevenue
/ us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis
= clf_NorthAmericanCoalMember
Disposal Group, Including Discontinued Operation, Costs of Goods Sold (107.3)us-gaap_DisposalGroupIncludingDiscontinuedOperationCostsOfGoodsSold
/ us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis
= clf_NorthAmericanCoalMember
(214.6)us-gaap_DisposalGroupIncludingDiscontinuedOperationCostsOfGoodsSold
/ us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis
= clf_NorthAmericanCoalMember
Disposal Group, Including Discontinued Operation, Gross Profit (Loss) 9.3us-gaap_DisposalGroupIncludingDiscontinuedOperationGrossProfitLoss
/ us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis
= clf_NorthAmericanCoalMember
(48.4)us-gaap_DisposalGroupIncludingDiscontinuedOperationGrossProfitLoss
/ us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis
= clf_NorthAmericanCoalMember
Disposal Group, Including Discontinued Operation, Operating Expense (11.3)us-gaap_DisposalGroupIncludingDiscontinuedOperationOperatingExpense
/ us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis
= clf_NorthAmericanCoalMember
(4.5)us-gaap_DisposalGroupIncludingDiscontinuedOperationOperatingExpense
/ us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis
= clf_NorthAmericanCoalMember
Disposal Group, Including Discontinued Operation, Other Expense (0.4)us-gaap_DisposalGroupIncludingDiscontinuedOperationOtherExpense
/ us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis
= clf_NorthAmericanCoalMember
(0.6)us-gaap_DisposalGroupIncludingDiscontinuedOperationOtherExpense
/ us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis
= clf_NorthAmericanCoalMember
Discontinued Operation, Income (Loss) from Discontinued Operation, before Income Tax (2.4)us-gaap_DiscontinuedOperationIncomeLossFromDiscontinuedOperationBeforeIncomeTax
/ us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis
= clf_NorthAmericanCoalMember
(53.5)us-gaap_DiscontinuedOperationIncomeLossFromDiscontinuedOperationBeforeIncomeTax
/ us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis
= clf_NorthAmericanCoalMember
Impairment of Long-Lived Assets to be Disposed of (73.4)us-gaap_ImpairmentOfLongLivedAssetsToBeDisposedOf
/ us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis
= clf_NorthAmericanCoalMember
0us-gaap_ImpairmentOfLongLivedAssetsToBeDisposedOf
/ us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis
= clf_NorthAmericanCoalMember
Discontinued Operation, Tax Effect of Discontinued Operation 0.1us-gaap_DiscontinuedOperationTaxEffectOfDiscontinuedOperation
/ us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis
= clf_NorthAmericanCoalMember
7.2us-gaap_DiscontinuedOperationTaxEffectOfDiscontinuedOperation
/ us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis
= clf_NorthAmericanCoalMember
LOSS FROM DISCONTINUED OPERATIONS, net of tax $ (75.7)us-gaap_IncomeLossFromDiscontinuedOperationsNetOfTax
/ us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis
= clf_NorthAmericanCoalMember
$ (46.3)us-gaap_IncomeLossFromDiscontinuedOperationsNetOfTax
/ us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis
= clf_NorthAmericanCoalMember