Quarterly report pursuant to Section 13 or 15(d)

RELATED PARTIES (Summary Of Other Ownership Interests) (Details)

v3.4.0.3
RELATED PARTIES (Summary Of Other Ownership Interests) (Details)
Mar. 31, 2016
Hibbing [Member] | Arcelor Mittal [Member]  
Related Party Transaction [Line Items]  
Ownership interest, equity method investment 62.30%
Hibbing [Member] | U. S. Steel Canada [Member]  
Related Party Transaction [Line Items]  
Ownership interest, equity method investment 14.70%
Empire [Member]  
Related Party Transaction [Line Items]  
Noncontrolling Interest, Ownership Percentage by Parent 79.00%
Empire [Member] | Arcelor Mittal [Member]  
Related Party Transaction [Line Items]  
Noncontrolling Interest, Ownership Percentage by Noncontrolling Owners 21.00%
Empire [Member] | U. S. Steel Canada [Member]  
Related Party Transaction [Line Items]  
Noncontrolling Interest, Ownership Percentage by Noncontrolling Owners 0.00%
Tilden [Member]  
Related Party Transaction [Line Items]  
Noncontrolling Interest, Ownership Percentage by Parent 85.00%
Tilden [Member] | Arcelor Mittal [Member]  
Related Party Transaction [Line Items]  
Noncontrolling Interest, Ownership Percentage by Noncontrolling Owners 0.00%
Tilden [Member] | U. S. Steel Canada [Member]  
Related Party Transaction [Line Items]  
Noncontrolling Interest, Ownership Percentage by Noncontrolling Owners 15.00%
Other Noncurrent Assets [Member] | Hibbing [Member]  
Related Party Transaction [Line Items]  
Ownership interest, equity method investment 23.00%