XML 110 R63.htm IDEA: XBRL DOCUMENT
v2.4.1.9

FAIR VALUE OF FINANCIAL INSTRUMENTS FAIR VALUE OF FINANCIAL INSTRUMENTS (Fair Value Measurements, Nonrecurring) (Details) (USD $) In Millions, unless otherwise specified | 3 Months Ended | 12 Months Ended
--- | --- | ---
Mar. 31, 2015 | Dec. 31, 2014
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Goodwill, Impairment Loss | $ 0 us-gaap_GoodwillImpairmentLoss | $ 73.5 us-gaap_GoodwillImpairmentLoss
Assets, Fair Value Disclosure, Nonrecurring | 397.2 us-gaap_AssetsFairValueDisclosureNonrecurring | 79.4 us-gaap_AssetsFairValueDisclosureNonrecurring
Impairment of goodwill and other long-lived assets | 269.5 clf_ImpairmentCharges | 644.7 clf_ImpairmentCharges
Fair Value, Inputs, Level 1 [Member] |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Assets, Fair Value Disclosure, Nonrecurring | 0 us-gaap_AssetsFairValueDisclosureNonrecurring / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel1Member | 0 us-gaap_AssetsFairValueDisclosureNonrecurring / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel1Member
Fair Value, Inputs, Level 2 [Member] |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Assets, Fair Value Disclosure, Nonrecurring | 397.2 us-gaap_AssetsFairValueDisclosureNonrecurring / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel2Member | 0 us-gaap_AssetsFairValueDisclosureNonrecurring / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel2Member
Fair Value, Inputs, Level 3 [Member] |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Assets, Fair Value Disclosure, Nonrecurring | 0 us-gaap_AssetsFairValueDisclosureNonrecurring / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member | 79.4 us-gaap_AssetsFairValueDisclosureNonrecurring / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member
Global Exploration Investment in Venture [Member] |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Equity Method Investments, Fair Value Disclosure |  | 0 us-gaap_EquityMethodInvestmentsFairValueDisclosure / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = clf_GlobalExplorationInvestmentinVentureMember
Equity Method Investment, Other than Temporary Impairment |  | 9.2 us-gaap_EquityMethodInvestmentOtherThanTemporaryImpairment / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = clf_GlobalExplorationInvestmentinVentureMember
Global Exploration Investment in Venture [Member] | Fair Value, Inputs, Level 1 [Member] |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Equity Method Investments, Fair Value Disclosure |  | 0 us-gaap_EquityMethodInvestmentsFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel1Member / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = clf_GlobalExplorationInvestmentinVentureMember
Global Exploration Investment in Venture [Member] | Fair Value, Inputs, Level 2 [Member] |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Equity Method Investments, Fair Value Disclosure |  | 0 us-gaap_EquityMethodInvestmentsFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel2Member / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = clf_GlobalExplorationInvestmentinVentureMember
Global Exploration Investment in Venture [Member] | Fair Value, Inputs, Level 3 [Member] |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Equity Method Investments, Fair Value Disclosure |  | 0 us-gaap_EquityMethodInvestmentsFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = clf_GlobalExplorationInvestmentinVentureMember
Asia Pacific Iron Ore [Member] |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Goodwill, Fair Value Disclosure |  | 0 us-gaap_GoodwillFairValueDisclosure / clf_ReportingUnitAxis = clf_AsiaPacificIronOreMember
Goodwill, Impairment Loss |  | 73.5 us-gaap_GoodwillImpairmentLoss / clf_ReportingUnitAxis = clf_AsiaPacificIronOreMember
Asia Pacific Iron Ore [Member] | Fair Value, Inputs, Level 1 [Member] |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Goodwill, Fair Value Disclosure |  | 0 us-gaap_GoodwillFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel1Member / clf_ReportingUnitAxis = clf_AsiaPacificIronOreMember
Asia Pacific Iron Ore [Member] | Fair Value, Inputs, Level 2 [Member] |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Goodwill, Fair Value Disclosure |  | 0 us-gaap_GoodwillFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel2Member / clf_ReportingUnitAxis = clf_AsiaPacificIronOreMember
Asia Pacific Iron Ore [Member] | Fair Value, Inputs, Level 3 [Member] |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Goodwill, Fair Value Disclosure |  | 0 us-gaap_GoodwillFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member / clf_ReportingUnitAxis = clf_AsiaPacificIronOreMember
Other Reporting Units [Member] |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Property, Plant, and Equipment, Fair Value Disclosure |  | 0 us-gaap_PropertyPlantAndEquipmentFairValueDisclosure / clf_ReportingUnitAxis = clf_OtherReportingUnitsMember
Tangible Asset Impairment Charges |  | 11.3 us-gaap_TangibleAssetImpairmentCharges / clf_ReportingUnitAxis = clf_OtherReportingUnitsMember
Other Reporting Units [Member] | Fair Value, Inputs, Level 1 [Member] |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Property, Plant, and Equipment, Fair Value Disclosure |  | 0 us-gaap_PropertyPlantAndEquipmentFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel1Member / clf_ReportingUnitAxis = clf_OtherReportingUnitsMember
Other Reporting Units [Member] | Fair Value, Inputs, Level 2 [Member] |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Property, Plant, and Equipment, Fair Value Disclosure |  | 0 us-gaap_PropertyPlantAndEquipmentFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel2Member / clf_ReportingUnitAxis = clf_OtherReportingUnitsMember
Other Reporting Units [Member] | Fair Value, Inputs, Level 3 [Member] |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Property, Plant, and Equipment, Fair Value Disclosure |  | 0 us-gaap_PropertyPlantAndEquipmentFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member / clf_ReportingUnitAxis = clf_OtherReportingUnitsMember
Asia Pacific [Member] | Asia Pacific Iron Ore [Member] | Fair Value, Inputs, Level 2 [Member] |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Property, Plant, and Equipment, Fair Value Disclosure |  | 0 us-gaap_PropertyPlantAndEquipmentFairValueDisclosure / clf_AssetgroupAxis = us-gaap_AsiaPacificMember / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel2Member / clf_ReportingUnitAxis = clf_AsiaPacificIronOreMember
Finite-lived Intangible Assets, Fair Value Disclosure |  | 0 us-gaap_FiniteLivedIntangibleAssetsFairValueDisclosure / clf_AssetgroupAxis = us-gaap_AsiaPacificMember / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel2Member / clf_ReportingUnitAxis = clf_AsiaPacificIronOreMember
Asia Pacific Iron Ore [Member] | Asia Pacific Iron Ore [Member] |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Property, Plant, and Equipment, Fair Value Disclosure |  | 72.4 us-gaap_PropertyPlantAndEquipmentFairValueDisclosure / clf_AssetgroupAxis = clf_AsiaPacificIronOreMember / clf_ReportingUnitAxis = clf_AsiaPacificIronOreMember
Tangible Asset Impairment Charges |  | 526.5 us-gaap_TangibleAssetImpairmentCharges / clf_AssetgroupAxis = clf_AsiaPacificIronOreMember / clf_ReportingUnitAxis = clf_AsiaPacificIronOreMember
Other Asset Impairment Charges |  | 24.2 us-gaap_ImpairmentOfIntangibleAssetsExcludingGoodwill / clf_AssetgroupAxis = clf_AsiaPacificIronOreMember / clf_ReportingUnitAxis = clf_AsiaPacificIronOreMember
Finite-lived Intangible Assets, Fair Value Disclosure |  | 7.0 us-gaap_FiniteLivedIntangibleAssetsFairValueDisclosure / clf_AssetgroupAxis = clf_AsiaPacificIronOreMember / clf_ReportingUnitAxis = clf_AsiaPacificIronOreMember
Asia Pacific Iron Ore [Member] | Asia Pacific Iron Ore [Member] | Fair Value, Inputs, Level 1 [Member] |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Property, Plant, and Equipment, Fair Value Disclosure |  | 0 us-gaap_PropertyPlantAndEquipmentFairValueDisclosure / clf_AssetgroupAxis = clf_AsiaPacificIronOreMember / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel1Member / clf_ReportingUnitAxis = clf_AsiaPacificIronOreMember
Finite-lived Intangible Assets, Fair Value Disclosure |  | 0 us-gaap_FiniteLivedIntangibleAssetsFairValueDisclosure / clf_AssetgroupAxis = clf_AsiaPacificIronOreMember / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel1Member / clf_ReportingUnitAxis = clf_AsiaPacificIronOreMember
Asia Pacific Iron Ore [Member] | Asia Pacific Iron Ore [Member] | Fair Value, Inputs, Level 3 [Member] |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Property, Plant, and Equipment, Fair Value Disclosure |  | 72.4 us-gaap_PropertyPlantAndEquipmentFairValueDisclosure / clf_AssetgroupAxis = clf_AsiaPacificIronOreMember / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member / clf_ReportingUnitAxis = clf_AsiaPacificIronOreMember
Finite-lived Intangible Assets, Fair Value Disclosure |  | 7.0 us-gaap_FiniteLivedIntangibleAssetsFairValueDisclosure / clf_AssetgroupAxis = clf_AsiaPacificIronOreMember / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member / clf_ReportingUnitAxis = clf_AsiaPacificIronOreMember
Five hundred Forty-four Million Seven Point Seven Five Twenty Twenty Second Lien Notes [Member] |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Debt Instrument, Fair Value Disclosure | 397.2 us-gaap_DebtInstrumentFairValue / us-gaap_DebtInstrumentAxis = clf_FivehundredFortyfourMillionSevenPointSevenFiveTwentyTwentySecondLienNotesMember |
Gain on new debt issued | 269.5 clf_Gainonnewdebtissued / us-gaap_DebtInstrumentAxis = clf_FivehundredFortyfourMillionSevenPointSevenFiveTwentyTwentySecondLienNotesMember |
Five hundred Forty-four Million Seven Point Seven Five Twenty Twenty Second Lien Notes [Member] | Fair Value, Inputs, Level 1 [Member] |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Debt Instrument, Fair Value Disclosure | 0 us-gaap_DebtInstrumentFairValue / us-gaap_DebtInstrumentAxis = clf_FivehundredFortyfourMillionSevenPointSevenFiveTwentyTwentySecondLienNotesMember / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel1Member |
Five hundred Forty-four Million Seven Point Seven Five Twenty Twenty Second Lien Notes [Member] | Fair Value, Inputs, Level 2 [Member] |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Debt Instrument, Fair Value Disclosure | 397.2 us-gaap_DebtInstrumentFairValue / us-gaap_DebtInstrumentAxis = clf_FivehundredFortyfourMillionSevenPointSevenFiveTwentyTwentySecondLienNotesMember / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel2Member | 0 us-gaap_DebtInstrumentFairValue / us-gaap_DebtInstrumentAxis = clf_FivehundredFortyfourMillionSevenPointSevenFiveTwentyTwentySecondLienNotesMember / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel2Member
Five hundred Forty-four Million Seven Point Seven Five Twenty Twenty Second Lien Notes [Member] | Fair Value, Inputs, Level 3 [Member] |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Debt Instrument, Fair Value Disclosure | $ 0 us-gaap_DebtInstrumentFairValue / us-gaap_DebtInstrumentAxis = clf_FivehundredFortyfourMillionSevenPointSevenFiveTwentyTwentySecondLienNotesMember / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member |

X
- Definition Gain on new debt issued + References No definition available. + Details
Name: | clf_Gainonnewdebtissued
Namespace Prefix: | clf_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Impairment charges including, but not limited to, impairment charges related to intangible and tangible assets, investment, and goodwill. + References No definition available. + Details
Name: | clf_ImpairmentCharges
Namespace Prefix: | clf_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition This element represents the aggregate of the assets reported on the balance sheet at period end measured at fair value on a nonrecurring basis by the entity. This element is intended to be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. + References No definition available. + Details
Name: | us-gaap_AssetsFairValueDisclosureNonrecurring
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Fair value portion of debt instrument payable, including, but not limited to, notes payable and loans payable. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 825 -SubTopic 10 -Section 50 -Paragraph 10 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=35750535&loc=d3e13433-108611 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 825 -SubTopic 10 -Section 50 -Paragraph 12 -URI http://asc.fasb.org/extlink&oid=35750535&loc=d3e13476-108611 + Details
Name: | us-gaap_DebtInstrumentFairValue
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition This item represents an other than temporary decline in value that has been recognized against an investment accounted for under the equity method of accounting. The excess of the carrying amount over the fair value of the investment represents the amount of the write down which is or was reflected in earnings. The written down value is a new cost basis with the adjusted value of the investment becoming its new carrying value subject to the equity accounting method. Evidence of a loss in value might include, but would not necessarily be limited to, absence of an ability to recover the carrying amount of the investment or inability of the investee to sustain an earnings capacity which would justify the carrying amount of the investment. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 323 -SubTopic 10 -Section 35 -Paragraph 32 -URI http://asc.fasb.org/extlink&oid=35687916&loc=d3e32787-111569 + Details
Name: | us-gaap_EquityMethodInvestmentOtherThanTemporaryImpairment
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Fair value portion of investments accounted under the equity method. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 323 -SubTopic 10 -Section 25 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=35740979&loc=d3e32014-111567 + Details
Name: | us-gaap_EquityMethodInvestmentsFairValueDisclosure
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Details
Name: | us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Fair value portion of assets, excluding financial assets, that lack physical substance, having a limited useful life. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 1 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=36462937&loc=d3e19190-110258 + Details
Name: | us-gaap_FiniteLivedIntangibleAssetsFairValueDisclosure
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Fair value portion of asset representing the future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 1 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=36462937&loc=d3e19190-110258 + Details
Name: | us-gaap_GoodwillFairValueDisclosure
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amount of loss from the write-down of an asset representing the future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3602-108585 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 350 -SubTopic 20 -Section 50 -Paragraph 2 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=35741047&loc=d3e13854-109267 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 350 -SubTopic 20 -Section 45 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=6388280&loc=d3e13777-109266 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 350 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (e) -URI http://asc.fasb.org/extlink&oid=35741047&loc=d3e13816-109267 + Details
Name: | us-gaap_GoodwillImpairmentLoss
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition The amount of impairment loss recognized in the period resulting from the write-down of the carrying amount of an intangible asset (excluding goodwill) to fair value. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3602-108585 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 350 -SubTopic 30 -Section 50 -Paragraph 3 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=26713463&loc=d3e16373-109275 + Details
Name: | us-gaap_ImpairmentOfIntangibleAssetsExcludingGoodwill
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Fair value portion of physical assets used in the normal conduct of business to produce goods and services and not intended for resale. Examples include, but are not limited to, land, buildings, machinery and equipment, office equipment, and furniture and fixtures. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 1 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=36462937&loc=d3e19190-110258 + Details
Name: | us-gaap_PropertyPlantAndEquipmentFairValueDisclosure
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition The charge against earnings resulting from the aggregate write down of tangible assets from their carrying value to their fair value. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 205 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=6360339&loc=d3e1361-107760 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 360 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=6391110&loc=d3e2921-110230 + Details
Name: | us-gaap_TangibleAssetImpairmentCharges
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Details
Name: | clf_AssetgroupAxis=clf_AsiaPacificIronOreMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | clf_AssetgroupAxis=us-gaap_AsiaPacificMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | clf_ReportingUnitAxis=clf_AsiaPacificIronOreMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | clf_ReportingUnitAxis=clf_OtherReportingUnitsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DebtInstrumentAxis=clf_FivehundredFortyfourMillionSevenPointSevenFiveTwentyTwentySecondLienNotesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FairValueByFairValueHierarchyLevelAxis=us-gaap_FairValueInputsLevel1Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FairValueByFairValueHierarchyLevelAxis=us-gaap_FairValueInputsLevel2Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FairValueByFairValueHierarchyLevelAxis=us-gaap_FairValueInputsLevel3Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis=clf_GlobalExplorationInvestmentinVentureMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |