Annual report pursuant to Section 13 and 15(d)

RELATED PARTIES - Narrative (Details)

v3.22.0.1
RELATED PARTIES - Narrative (Details) - Hibbing
Dec. 31, 2021
Dec. 31, 2020
Dec. 09, 2020
Dec. 31, 2019
Related Party Transaction [Line Items]        
Ownership interest, equity method investment 85.30% 85.30% 62.30% 23.00%
ArcelorMittal USA        
Related Party Transaction [Line Items]        
Ownership interest, equity method investment     62.30%  
U. S. Steel Canada [Member]        
Related Party Transaction [Line Items]        
Ownership interest, equity method investment 14.70%