Annual report pursuant to Section 13 and 15(d)

Business Summary And Significant Accounting Policies (Schedule Of Subsidiaries) (Details)

v2.4.0.6
Business Summary And Significant Accounting Policies (Schedule Of Subsidiaries) (Details)
12 Months Ended
Dec. 31, 2011
Northshore [Member]
 
Related Party Transaction [Line Items]  
Location Minnesota
Percent ownership interest 100.00%
Operation Iron Ore
United Taconite [Member]
 
Related Party Transaction [Line Items]  
Location Minnesota
Percent ownership interest 100.00%
Operation Iron Ore
Wabush [Member]
 
Related Party Transaction [Line Items]  
Location Labrador/ Quebec, Canada
Percent ownership interest 100.00%
Operation Iron Ore
Bloom Lake [Member]
 
Related Party Transaction [Line Items]  
Location Quebec, Canada
Percent ownership interest 75.00%
Operation Iron Ore
Tilden [Member]
 
Related Party Transaction [Line Items]  
Location Michigan
Percent ownership interest 85.00%
Operation Iron Ore
Empire [Member]
 
Related Party Transaction [Line Items]  
Location Michigan
Percent ownership interest 79.00%
Operation Iron Ore
Asia Pacific Iron Ore [Member]
 
Related Party Transaction [Line Items]  
Location Western Australia
Percent ownership interest 100.00%
Operation Iron Ore
Pinnacle [Member]
 
Related Party Transaction [Line Items]  
Location West Virginia
Percent ownership interest 100.00%
Operation Coal
Oak Grove [Member]
 
Related Party Transaction [Line Items]  
Location Alabama
Percent ownership interest 100.00%
Operation Coal
CLCC [Member]
 
Related Party Transaction [Line Items]  
Location West Virginia
Percent ownership interest 100.00%
Operation Coal
Freewest [Member]
 
Related Party Transaction [Line Items]  
Location Ontario, Canada
Percent ownership interest 100.00%
Operation Chromite
Spider [Member]
 
Related Party Transaction [Line Items]  
Location Ontario, Canada
Percent ownership interest 100.00%
Operation Chromite