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Annual report pursuant to Section 13 and 15(d)

ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS) Accumulated Other Comprehensive Income (Loss) and Related Tax Effects (Details)

v2.4.1.9
ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS) Accumulated Other Comprehensive Income (Loss) and Related Tax Effects (Details) (USD $)
In Millions, unless otherwise specified
Dec. 31, 2014
Sep. 30, 2014
Jun. 30, 2014
Mar. 31, 2014
Dec. 31, 2013
Sep. 30, 2013
Jun. 30, 2013
Mar. 31, 2013
Dec. 31, 2012
Dec. 31, 2011
Accumulated Other Comprehensive Income (Loss), Before Taxes $ (388.1)clf_AccumulatedOtherComprehensiveIncomeLossBeforeTaxes Ìý Ìý Ìý $ (213.3)clf_AccumulatedOtherComprehensiveIncomeLossBeforeTaxes Ìý Ìý Ìý $ (244.7)clf_AccumulatedOtherComprehensiveIncomeLossBeforeTaxes Ìý
Accumulated Other Comprehensive Income (Loss), Tax 142.3clf_AccumulatedOtherComprehensiveIncomeLossTax Ìý Ìý Ìý 100.4clf_AccumulatedOtherComprehensiveIncomeLossTax Ìý Ìý Ìý 189.1clf_AccumulatedOtherComprehensiveIncomeLossTax Ìý
Accumulated other comprehensive loss (245.8)us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax (101.4)us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax (20.2)us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax (55.1)us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax (112.9)us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax (178.4)us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax (239.6)us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax (51.4)us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax (55.6)us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax (92.6)us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax
Postretirement Benefit Liability [Member] Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý
Accumulated Other Comprehensive Income (Loss), Before Taxes (425.3)clf_AccumulatedOtherComprehensiveIncomeLossBeforeTaxes
/ clf_AccumulatedOtherComprehensiveIncomeComponentsAxis
= clf_PostretirementBenefitLiabilityMember
Ìý Ìý Ìý (299.3)clf_AccumulatedOtherComprehensiveIncomeLossBeforeTaxes
/ clf_AccumulatedOtherComprehensiveIncomeComponentsAxis
= clf_PostretirementBenefitLiabilityMember
Ìý Ìý Ìý (576.7)clf_AccumulatedOtherComprehensiveIncomeLossBeforeTaxes
/ clf_AccumulatedOtherComprehensiveIncomeComponentsAxis
= clf_PostretirementBenefitLiabilityMember
Ìý
Accumulated Other Comprehensive Income (Loss), Tax 134.2clf_AccumulatedOtherComprehensiveIncomeLossTax
/ clf_AccumulatedOtherComprehensiveIncomeComponentsAxis
= clf_PostretirementBenefitLiabilityMember
Ìý Ìý Ìý 94.4clf_AccumulatedOtherComprehensiveIncomeLossTax
/ clf_AccumulatedOtherComprehensiveIncomeComponentsAxis
= clf_PostretirementBenefitLiabilityMember
Ìý Ìý Ìý 194.0clf_AccumulatedOtherComprehensiveIncomeLossTax
/ clf_AccumulatedOtherComprehensiveIncomeComponentsAxis
= clf_PostretirementBenefitLiabilityMember
Ìý
Accumulated other comprehensive loss (291.1)us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax
/ clf_AccumulatedOtherComprehensiveIncomeComponentsAxis
= clf_PostretirementBenefitLiabilityMember
Ìý Ìý Ìý (204.9)us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax
/ clf_AccumulatedOtherComprehensiveIncomeComponentsAxis
= clf_PostretirementBenefitLiabilityMember
Ìý Ìý Ìý (382.7)us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax
/ clf_AccumulatedOtherComprehensiveIncomeComponentsAxis
= clf_PostretirementBenefitLiabilityMember
Ìý
Foreign Currency Translation Adjustment [Member] Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý
Accumulated Other Comprehensive Income (Loss), Before Taxes 64.4clf_AccumulatedOtherComprehensiveIncomeLossBeforeTaxes
/ clf_AccumulatedOtherComprehensiveIncomeComponentsAxis
= clf_ForeignCurrencyTranslationAdjustmentMember
Ìý Ìý Ìý 106.7clf_AccumulatedOtherComprehensiveIncomeLossBeforeTaxes
/ clf_AccumulatedOtherComprehensiveIncomeComponentsAxis
= clf_ForeignCurrencyTranslationAdjustmentMember
Ìý Ìý Ìý 316.3clf_AccumulatedOtherComprehensiveIncomeLossBeforeTaxes
/ clf_AccumulatedOtherComprehensiveIncomeComponentsAxis
= clf_ForeignCurrencyTranslationAdjustmentMember
Ìý
Accumulated Other Comprehensive Income (Loss), Tax 0clf_AccumulatedOtherComprehensiveIncomeLossTax
/ clf_AccumulatedOtherComprehensiveIncomeComponentsAxis
= clf_ForeignCurrencyTranslationAdjustmentMember
Ìý Ìý Ìý 0clf_AccumulatedOtherComprehensiveIncomeLossTax
/ clf_AccumulatedOtherComprehensiveIncomeComponentsAxis
= clf_ForeignCurrencyTranslationAdjustmentMember
Ìý Ìý Ìý 0clf_AccumulatedOtherComprehensiveIncomeLossTax
/ clf_AccumulatedOtherComprehensiveIncomeComponentsAxis
= clf_ForeignCurrencyTranslationAdjustmentMember
Ìý
Accumulated other comprehensive loss 64.4us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax
/ clf_AccumulatedOtherComprehensiveIncomeComponentsAxis
= clf_ForeignCurrencyTranslationAdjustmentMember
Ìý Ìý Ìý 106.7us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax
/ clf_AccumulatedOtherComprehensiveIncomeComponentsAxis
= clf_ForeignCurrencyTranslationAdjustmentMember
Ìý Ìý Ìý 316.3us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax
/ clf_AccumulatedOtherComprehensiveIncomeComponentsAxis
= clf_ForeignCurrencyTranslationAdjustmentMember
Ìý
Unrealized Gain Loss On Derivatives [Member] Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý
Accumulated Other Comprehensive Income (Loss), Before Taxes (25.9)clf_AccumulatedOtherComprehensiveIncomeLossBeforeTaxes
/ clf_AccumulatedOtherComprehensiveIncomeComponentsAxis
= clf_UnrealizedGainLossOnDerivativesMember
Ìý Ìý Ìý (30.0)clf_AccumulatedOtherComprehensiveIncomeLossBeforeTaxes
/ clf_AccumulatedOtherComprehensiveIncomeComponentsAxis
= clf_UnrealizedGainLossOnDerivativesMember
Ìý Ìý Ìý 12.4clf_AccumulatedOtherComprehensiveIncomeLossBeforeTaxes
/ clf_AccumulatedOtherComprehensiveIncomeComponentsAxis
= clf_UnrealizedGainLossOnDerivativesMember
Ìý
Accumulated Other Comprehensive Income (Loss), Tax 7.8clf_AccumulatedOtherComprehensiveIncomeLossTax
/ clf_AccumulatedOtherComprehensiveIncomeComponentsAxis
= clf_UnrealizedGainLossOnDerivativesMember
Ìý Ìý Ìý 9.1clf_AccumulatedOtherComprehensiveIncomeLossTax
/ clf_AccumulatedOtherComprehensiveIncomeComponentsAxis
= clf_UnrealizedGainLossOnDerivativesMember
Ìý Ìý Ìý (3.7)clf_AccumulatedOtherComprehensiveIncomeLossTax
/ clf_AccumulatedOtherComprehensiveIncomeComponentsAxis
= clf_UnrealizedGainLossOnDerivativesMember
Ìý
Accumulated other comprehensive loss (18.1)us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax
/ clf_AccumulatedOtherComprehensiveIncomeComponentsAxis
= clf_UnrealizedGainLossOnDerivativesMember
Ìý Ìý Ìý (20.9)us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax
/ clf_AccumulatedOtherComprehensiveIncomeComponentsAxis
= clf_UnrealizedGainLossOnDerivativesMember
Ìý Ìý Ìý 8.7us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax
/ clf_AccumulatedOtherComprehensiveIncomeComponentsAxis
= clf_UnrealizedGainLossOnDerivativesMember
Ìý
Accumulated Net Unrealized Investment Gain (Loss) [Member] Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý
Accumulated Other Comprehensive Income (Loss), Before Taxes (1.3)clf_AccumulatedOtherComprehensiveIncomeLossBeforeTaxes
/ clf_AccumulatedOtherComprehensiveIncomeComponentsAxis
= us-gaap_AccumulatedNetUnrealizedInvestmentGainLossMember
Ìý Ìý Ìý 9.3clf_AccumulatedOtherComprehensiveIncomeLossBeforeTaxes
/ clf_AccumulatedOtherComprehensiveIncomeComponentsAxis
= us-gaap_AccumulatedNetUnrealizedInvestmentGainLossMember
Ìý Ìý Ìý 3.3clf_AccumulatedOtherComprehensiveIncomeLossBeforeTaxes
/ clf_AccumulatedOtherComprehensiveIncomeComponentsAxis
= us-gaap_AccumulatedNetUnrealizedInvestmentGainLossMember
Ìý
Accumulated Other Comprehensive Income (Loss), Tax 0.3clf_AccumulatedOtherComprehensiveIncomeLossTax
/ clf_AccumulatedOtherComprehensiveIncomeComponentsAxis
= us-gaap_AccumulatedNetUnrealizedInvestmentGainLossMember
Ìý Ìý Ìý (3.1)clf_AccumulatedOtherComprehensiveIncomeLossTax
/ clf_AccumulatedOtherComprehensiveIncomeComponentsAxis
= us-gaap_AccumulatedNetUnrealizedInvestmentGainLossMember
Ìý Ìý Ìý (1.2)clf_AccumulatedOtherComprehensiveIncomeLossTax
/ clf_AccumulatedOtherComprehensiveIncomeComponentsAxis
= us-gaap_AccumulatedNetUnrealizedInvestmentGainLossMember
Ìý
Accumulated other comprehensive loss $ (1.0)us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax
/ clf_AccumulatedOtherComprehensiveIncomeComponentsAxis
= us-gaap_AccumulatedNetUnrealizedInvestmentGainLossMember
Ìý Ìý Ìý $ 6.2us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax
/ clf_AccumulatedOtherComprehensiveIncomeComponentsAxis
= us-gaap_AccumulatedNetUnrealizedInvestmentGainLossMember
Ìý Ìý Ìý $ 2.1us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax
/ clf_AccumulatedOtherComprehensiveIncomeComponentsAxis
= us-gaap_AccumulatedNetUnrealizedInvestmentGainLossMember
Ìý