|
BASIS OF PRESENTATION AND SIGNIFICANT ACCOUNTING POLICIES (Schedule Of Subsidiaries) (Details)
|
12 Months Ended |
|
|
Dec. 31, 2014
|
Dec. 31, 2012
|
| Northshore [Member] |
听
|
听
|
| Related Party Transaction [Line Items] |
听
|
听
|
| Entity Address, State or Province |
Minnesota
|
听
|
| Noncontrolling Interest, Ownership Percentage by Parent |
100.00%us-gaap_MinorityInterestOwnershipPercentageByParent
/ clf_NameofOperationAxis
= clf_NorthshoreMember
|
听
|
| Segment Reporting Information, Description of Products and Services |
Iron Ore
|
听
|
| United Taconite [Member] |
听
|
听
|
| Related Party Transaction [Line Items] |
听
|
听
|
| Entity Address, State or Province |
Minnesota
|
听
|
| Noncontrolling Interest, Ownership Percentage by Parent |
100.00%us-gaap_MinorityInterestOwnershipPercentageByParent
/ clf_NameofOperationAxis
= clf_UnitedTaconiteMember
|
听
|
| Segment Reporting Information, Description of Products and Services |
Iron Ore
|
听
|
| Wabush [Member] |
听
|
听
|
| Related Party Transaction [Line Items] |
听
|
听
|
| Entity Address, State or Province |
Newfoundland and Labrador/ Qu茅bec, Canada
|
听
|
| Noncontrolling Interest, Ownership Percentage by Parent |
100.00%us-gaap_MinorityInterestOwnershipPercentageByParent
/ clf_NameofOperationAxis
= clf_WabushMember
|
听
|
| Segment Reporting Information, Description of Products and Services |
Iron Ore
|
听
|
| Bloom Lake [Member] |
听
|
听
|
| Related Party Transaction [Line Items] |
听
|
听
|
| Entity Address, State or Province |
Qu茅bec, Canada
|
听
|
| Noncontrolling Interest, Ownership Percentage by Parent |
82.80%us-gaap_MinorityInterestOwnershipPercentageByParent
/ clf_NameofOperationAxis
= clf_BloomLakeMember
|
75.00%us-gaap_MinorityInterestOwnershipPercentageByParent
/ clf_NameofOperationAxis
= clf_BloomLakeMember
|
| Segment Reporting Information, Description of Products and Services |
Iron Ore
|
听
|
| Tilden [Member] |
听
|
听
|
| Related Party Transaction [Line Items] |
听
|
听
|
| Entity Address, State or Province |
Michigan
|
听
|
| Noncontrolling Interest, Ownership Percentage by Parent |
85.00%us-gaap_MinorityInterestOwnershipPercentageByParent
/ clf_NameofOperationAxis
= clf_TildenMember
|
听
|
| Segment Reporting Information, Description of Products and Services |
Iron Ore
|
听
|
| Empire [Member] |
听
|
听
|
| Related Party Transaction [Line Items] |
听
|
听
|
| Entity Address, State or Province |
Michigan
|
听
|
| Noncontrolling Interest, Ownership Percentage by Parent |
79.00%us-gaap_MinorityInterestOwnershipPercentageByParent
/ clf_NameofOperationAxis
= clf_EmpireMember
|
听
|
| Segment Reporting Information, Description of Products and Services |
Iron Ore
|
听
|
| Koolyanobbing [Member] |
听
|
听
|
| Related Party Transaction [Line Items] |
听
|
听
|
| Entity Address, State or Province |
Western Australia
|
听
|
| Noncontrolling Interest, Ownership Percentage by Parent |
100.00%us-gaap_MinorityInterestOwnershipPercentageByParent
/ clf_NameofOperationAxis
= clf_KoolyanobbingMember
|
听
|
| Segment Reporting Information, Description of Products and Services |
Iron Ore
|
听
|
| Pinnacle [Member] |
听
|
听
|
| Related Party Transaction [Line Items] |
听
|
听
|
| Entity Address, State or Province |
West Virginia
|
听
|
| Noncontrolling Interest, Ownership Percentage by Parent |
100.00%us-gaap_MinorityInterestOwnershipPercentageByParent
/ clf_NameofOperationAxis
= clf_PinnacleMember
|
听
|
| Segment Reporting Information, Description of Products and Services |
Coal
|
听
|
| Oak Grove [Member] |
听
|
听
|
| Related Party Transaction [Line Items] |
听
|
听
|
| Entity Address, State or Province |
Alabama
|
听
|
| Noncontrolling Interest, Ownership Percentage by Parent |
100.00%us-gaap_MinorityInterestOwnershipPercentageByParent
/ clf_NameofOperationAxis
= clf_OakGroveMember
|
听
|
| Segment Reporting Information, Description of Products and Services |
Coal
|
听
|
| CLCC [Member] |
听
|
听
|
| Related Party Transaction [Line Items] |
听
|
听
|
| Entity Address, State or Province |
West Virginia
|
听
|
| Noncontrolling Interest, Ownership Percentage by Parent |
100.00%us-gaap_MinorityInterestOwnershipPercentageByParent
/ clf_NameofOperationAxis
= clf_ClccMember
|
听
|
| Segment Reporting Information, Description of Products and Services |
Coal
|
听
|
| Black Label Deposit [Member] |
听
|
听
|
| Related Party Transaction [Line Items] |
听
|
听
|
| Entity Address, State or Province |
Ontario, Canada
|
听
|
| Noncontrolling Interest, Ownership Percentage by Parent |
100.00%us-gaap_MinorityInterestOwnershipPercentageByParent
/ clf_NameofOperationAxis
= clf_BlackLabelDepositMember
|
听
|
| Segment Reporting Information, Description of Products and Services |
Chromite
|
听
|
| Black Thor Deposit [Member] |
听
|
听
|
| Related Party Transaction [Line Items] |
听
|
听
|
| Entity Address, State or Province |
Ontario, Canada
|
听
|
| Noncontrolling Interest, Ownership Percentage by Parent |
100.00%us-gaap_MinorityInterestOwnershipPercentageByParent
/ clf_NameofOperationAxis
= clf_BlackThorDepositMember
|
听
|
| Segment Reporting Information, Description of Products and Services |
Chromite
|
听
|
| Big Daddy Chromite Deposit [Member] |
听
|
听
|
| Related Party Transaction [Line Items] |
听
|
听
|
| Entity Address, State or Province |
Ontario, Canada
|
听
|
| Noncontrolling Interest, Ownership Percentage by Parent |
70.00%us-gaap_MinorityInterestOwnershipPercentageByParent
/ clf_NameofOperationAxis
= clf_BigDaddyChromiteDepositMember
|
听
|
| Segment Reporting Information, Description of Products and Services |
Chromite
|
听
|