v3.26.1
CONTINGENCIES, COMMITMENTS AND RESTRICTIONS ON THE DISTRIBUTION OF PROFITS (Tax assessment relating to the use of certain ICMS tax credits, BPEM arbitration, PIS and COFINS credits defense action) (Details)
R$ in Millions, $ in Millions
 1 Months Ended
Dec. 31, 2025
USD ($)
Dec. 31, 2025
BRL (R$)
Aug. 31, 2024
USD ($)
claim
Aug. 31, 2024
BRL (R$)
claim
Dec. 31, 2024
USD ($)
Sep. 30, 2024
USD ($)
Jun. 09, 2024
USD ($)
Feb. 28, 2022
USD ($)
Sep. 07, 2017
USD ($)
Federal Government | Usiminas                  
Disclosure of contingent liabilities [line items]                  
Number of tax claims filed | claim     2 2          
Tax contingent liability $ 102.0 R$ 562 $ 92.0 R$ 503          
Legal proceedings contingent liability | BP Energia Mexico (BPEM)                  
Disclosure of contingent liabilities [line items]                  
Other provisions           $ 34.2      
Contingent liability, legal proceedings, additional expenses and costs             $ 2.4    
Legal proceedings contingent liability | BP Energia Mexico (BPEM) | Gas Industrial de Monterrey, S.A. de C.V.                  
Disclosure of contingent liabilities [line items]                  
Contingent liability, legal proceedings, original claim               $ 27.6  
Contingent liability, legal proceedings, arbitration reward             22.0    
Legal proceedings contingent liability | BP Energia Mexico (BPEM) | Ternium Mexico                  
Disclosure of contingent liabilities [line items]                  
Contingent liability, legal proceedings, original claim               12.4  
Contingent liability, legal proceedings, arbitration reward             9.9    
Legal proceedings contingent liability | BP Energia Mexico (BPEM) | Ternium Gas Mexico                  
Disclosure of contingent liabilities [line items]                  
Contingent liability, legal proceedings, original claim               $ 2.4  
Contingent liability, legal proceedings, arbitration reward             $ 2.1    
Thyssenkrupp Slab International B.V. & CSA Siderúrgica do Atlântico Ltda. | Legal proceedings contingent liability | Rio de Janeiro State Treasury Office | Ternium Brasil Ltda.                  
Disclosure of contingent liabilities [line items]                  
Other provisions $ 33.0       $ 29.3       $ 57.7