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Quarterly report pursuant to Section 13 or 15(d)

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

v3.7.0.1
RELATED PARTIES (Summary Of Other Ownership Interests) (Details)
Jun. 30, 2017
Dec. 31, 2016
Hibbing [Member] | Arcelor Mittal [Member] Ìý Ìý
Related Party Transaction [Line Items] Ìý Ìý
Ownership interest, equity method investment 62.30% Ìý
Hibbing [Member] | U. S. Steel Canada [Member] Ìý Ìý
Related Party Transaction [Line Items] Ìý Ìý
Ownership interest, equity method investment 14.70% Ìý
Empire [Member] Ìý Ìý
Related Party Transaction [Line Items] Ìý Ìý
Noncontrolling Interest, Ownership Percentage by Parent 79.00% Ìý
Empire [Member] | Arcelor Mittal [Member] Ìý Ìý
Related Party Transaction [Line Items] Ìý Ìý
Noncontrolling Interest, Ownership Percentage by Noncontrolling Owners 21.00% Ìý
Empire [Member] | U. S. Steel Canada [Member] Ìý Ìý
Related Party Transaction [Line Items] Ìý Ìý
Noncontrolling Interest, Ownership Percentage by Noncontrolling Owners 0.00% Ìý
Tilden [Member] Ìý Ìý
Related Party Transaction [Line Items] Ìý Ìý
Noncontrolling Interest, Ownership Percentage by Parent 85.00% Ìý
Tilden [Member] | Arcelor Mittal [Member] Ìý Ìý
Related Party Transaction [Line Items] Ìý Ìý
Noncontrolling Interest, Ownership Percentage by Noncontrolling Owners 0.00% Ìý
Tilden [Member] | U. S. Steel Canada [Member] Ìý Ìý
Related Party Transaction [Line Items] Ìý Ìý
Noncontrolling Interest, Ownership Percentage by Noncontrolling Owners 15.00% Ìý
Other Noncurrent Assets [Member] | Hibbing [Member] Ìý Ìý
Related Party Transaction [Line Items] Ìý Ìý
Ownership interest, equity method investment 23.00% 23.00%