Annual report pursuant to Section 13 and 15(d)

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

v2.4.0.6
BASIS OF PRESENTATION AND SIGNIFICANT ACCOUNTING POLICIES (Schedule Of Subsidiaries) (Details)
12 Months Ended
Dec. 31, 2012
Northshore [Member]
 
Related Party Transaction [Line Items]  
Location Minnesota
Ownership Interest 100.00%
Operation Iron Ore
United Taconite [Member]
 
Related Party Transaction [Line Items]  
Location Minnesota
Ownership Interest 100.00%
Operation Iron Ore
Wabush [Member]
 
Related Party Transaction [Line Items]  
Location Newfoundland and Labrador/Quebec, Canada
Ownership Interest 100.00%
Operation Iron Ore
Bloom Lake [Member]
 
Related Party Transaction [Line Items]  
Location Quebec, Canada
Ownership Interest 75.00%
Operation Iron Ore
Tilden [Member]
 
Related Party Transaction [Line Items]  
Location Michigan
Ownership Interest 85.00%
Operation Iron Ore
Empire [Member]
 
Related Party Transaction [Line Items]  
Location Michigan
Ownership Interest 79.00%
Operation Iron Ore
Koolyanobbing [Member]
 
Related Party Transaction [Line Items]  
Location Western Australia
Ownership Interest 100.00%
Operation Iron Ore
Pinnacle [Member]
 
Related Party Transaction [Line Items]  
Location West Virginia
Ownership Interest 100.00%
Operation Coal
Oak Grove [Member]
 
Related Party Transaction [Line Items]  
Location Alabama
Ownership Interest 100.00%
Operation Coal
CLCC [Member]
 
Related Party Transaction [Line Items]  
Location West Virginia
Ownership Interest 100.00%
Operation Coal