ÐÇ¿Õ´«Ã½

Quarterly report pursuant to Section 13 or 15(d)

BASIS OF PRESENTATION AND SIGNIFICANT ACCOUNTING POLICIES (Schedule Of Subsidiaries) (Details)

v2.4.1.9
BASIS OF PRESENTATION AND SIGNIFICANT ACCOUNTING POLICIES (Schedule Of Subsidiaries) (Details)
3 Months Ended
Mar. 31, 2015
Northshore [Member] Ìý
Related Party Transaction [Line Items] Ìý
Entity Address, State or Province Minnesota
Noncontrolling Interest, Ownership Percentage by Parent 100.00%us-gaap_MinorityInterestOwnershipPercentageByParent
/ clf_NameofOperationAxis
= clf_NorthshoreMember
Segment Reporting Information, Description of Products and Services Iron Ore
United Taconite [Member] Ìý
Related Party Transaction [Line Items] Ìý
Entity Address, State or Province Minnesota
Noncontrolling Interest, Ownership Percentage by Parent 100.00%us-gaap_MinorityInterestOwnershipPercentageByParent
/ clf_NameofOperationAxis
= clf_UnitedTaconiteMember
Segment Reporting Information, Description of Products and Services Iron Ore
Wabush [Member] Ìý
Related Party Transaction [Line Items] Ìý
Entity Address, State or Province Newfoundland and Labrador/ Quebec, Canada
Noncontrolling Interest, Ownership Percentage by Parent 100.00%us-gaap_MinorityInterestOwnershipPercentageByParent
/ clf_NameofOperationAxis
= clf_WabushMember
Segment Reporting Information, Description of Products and Services Iron Ore
Bloom Lake [Member] Ìý
Related Party Transaction [Line Items] Ìý
Entity Address, State or Province Quebec, Canada
Noncontrolling Interest, Ownership Percentage by Parent 82.80%us-gaap_MinorityInterestOwnershipPercentageByParent
/ clf_NameofOperationAxis
= clf_BloomLakeMember
Segment Reporting Information, Description of Products and Services Iron Ore
Tilden [Member] Ìý
Related Party Transaction [Line Items] Ìý
Entity Address, State or Province Michigan
Noncontrolling Interest, Ownership Percentage by Parent 85.00%us-gaap_MinorityInterestOwnershipPercentageByParent
/ clf_NameofOperationAxis
= clf_TildenMember
Segment Reporting Information, Description of Products and Services Iron Ore
Empire [Member] Ìý
Related Party Transaction [Line Items] Ìý
Entity Address, State or Province Michigan
Noncontrolling Interest, Ownership Percentage by Parent 79.00%us-gaap_MinorityInterestOwnershipPercentageByParent
/ clf_NameofOperationAxis
= clf_EmpireMember
Segment Reporting Information, Description of Products and Services Iron Ore
Koolyanobbing [Member] Ìý
Related Party Transaction [Line Items] Ìý
Entity Address, State or Province Western Australia
Noncontrolling Interest, Ownership Percentage by Parent 100.00%us-gaap_MinorityInterestOwnershipPercentageByParent
/ clf_NameofOperationAxis
= clf_KoolyanobbingMember
Segment Reporting Information, Description of Products and Services Iron Ore
Pinnacle [Member] Ìý
Related Party Transaction [Line Items] Ìý
Entity Address, State or Province West Virginia
Noncontrolling Interest, Ownership Percentage by Parent 100.00%us-gaap_MinorityInterestOwnershipPercentageByParent
/ clf_NameofOperationAxis
= clf_PinnacleMember
Segment Reporting Information, Description of Products and Services Coal
Oak Grove [Member] Ìý
Related Party Transaction [Line Items] Ìý
Entity Address, State or Province Alabama
Noncontrolling Interest, Ownership Percentage by Parent 100.00%us-gaap_MinorityInterestOwnershipPercentageByParent
/ clf_NameofOperationAxis
= clf_OakGroveMember
Segment Reporting Information, Description of Products and Services Coal
Black Label Deposit [Member] Ìý
Related Party Transaction [Line Items] Ìý
Entity Address, State or Province Ontario, Canada
Noncontrolling Interest, Ownership Percentage by Parent 100.00%us-gaap_MinorityInterestOwnershipPercentageByParent
/ clf_NameofOperationAxis
= clf_BlackLabelDepositMember
Segment Reporting Information, Description of Products and Services Chromite
Black Thor Deposit [Member] Ìý
Related Party Transaction [Line Items] Ìý
Entity Address, State or Province Ontario, Canada
Noncontrolling Interest, Ownership Percentage by Parent 100.00%us-gaap_MinorityInterestOwnershipPercentageByParent
/ clf_NameofOperationAxis
= clf_BlackThorDepositMember
Segment Reporting Information, Description of Products and Services Chromite
Big Daddy Chromite Deposit [Member] Ìý
Related Party Transaction [Line Items] Ìý
Entity Address, State or Province Ontario, Canada
Noncontrolling Interest, Ownership Percentage by Parent 70.00%us-gaap_MinorityInterestOwnershipPercentageByParent
/ clf_NameofOperationAxis
= clf_BigDaddyChromiteDepositMember
Segment Reporting Information, Description of Products and Services Chromite