v3.26.1
INVESTMENTS IN NON-CONSOLIDATED COMPANIES (Narrative) (Details)
$ in Thousands, T in Millions
 12 Months Ended
Dec. 31, 2025
USD ($)
T
km
MW
Dec. 31, 2024
USD ($)
Dec. 31, 2023
USD ($)
Dec. 31, 2022
USD ($)
Aug. 05, 2021
USD ($)
Feb. 28, 2019
Disclosure of unconsolidated structured entities [line items]            
Net sales $ 15,609,094 $ 17,649,060 $ 17,610,092      
Non-current assets 13,818,723 12,050,457        
Current assets 9,796,368 11,078,090        
Non-current liabilities 3,533,136 3,157,819        
Current liabilities 3,934,209 3,839,159        
Equity 16,147,746 16,131,569 $ 16,811,859 $ 13,768,393    
Borrowings 2,418,987 2,230,119        
Unigal Usiminas Ltda.            
Disclosure of unconsolidated structured entities [line items]            
Net sales 67,000 68,000        
Profit (loss) from continuing operations 27,000 28,000        
Non-current assets 140,000 126,000        
Current assets 37,000 35,000        
Non-current liabilities 43,000 38,000        
Current liabilities 10,000 9,000        
Equity $ 125,000 114,000        
Number of tons | T 1,030          
Usiminas | MRS Logística S.A.            
Disclosure of unconsolidated structured entities [line items]            
Proportion of ownership interest in associate (percent) 11.48%          
Net sales $ 1,357,000 1,304,000        
Profit (loss) from continuing operations 279,000 263,000        
Non-current assets 3,516,000 2,461,000        
Current assets 1,008,000 868,000        
Non-current liabilities 2,297,000 1,576,000        
Current liabilities 588,000 547,000        
Equity $ 1,639,000 1,206,000        
Usiminas | Unigal Usiminas Ltda.            
Disclosure of unconsolidated structured entities [line items]            
Proportion of ownership interest in associate (percent) 70.00%          
Nippon Steel Corporation | Unigal Usiminas Ltda.            
Disclosure of unconsolidated structured entities [line items]            
Proportion of ownership interest in associate (percent) 30.00%          
CSN | MRS Logística S.A.            
Disclosure of unconsolidated structured entities [line items]            
Proportion of ownership interest in associate (percent) 18.60%          
Congonhas Minérios | MRS Logística S.A.            
Disclosure of unconsolidated structured entities [line items]            
Proportion of ownership interest in associate (percent) 18.60%          
Vale S.A. | MRS Logística S.A.            
Disclosure of unconsolidated structured entities [line items]            
Proportion of ownership interest in associate (percent) 10.90%          
Gerdau            
Disclosure of unconsolidated structured entities [line items]            
Proportion of ownership interest in associate (percent) 1.30%          
Wide Group of Small Investors | MRS Logística S.A.            
Disclosure of unconsolidated structured entities [line items]            
Proportion of ownership interest in associate (percent) 6.50%          
MRS Logística S.A.            
Disclosure of unconsolidated structured entities [line items]            
Number of networks managed | km 1,634          
Techgen S.A. de C.V. Syndicated Loan Due February 2026 | Ternium Investments            
Disclosure of unconsolidated structured entities [line items]            
Payment for purchase of participation in borrowing arrangement         $ 68,000  
Techgen S.A. de C.V.            
Disclosure of unconsolidated structured entities [line items]            
Number of megawatts (per year) | MW 900          
Net sales $ 423,000 253,000        
Profit (loss) from continuing operations 64,000 27,000        
Non-current assets 676,000 692,000        
Current assets 92,000 104,000        
Non-current liabilities 1,000 415,000        
Current liabilities 431,000 109,000        
Equity 336,000 $ 272,000        
Subordinated liabilities $ 151,300          
Techgen S.A. de C.V. | Ternium S.A.            
Disclosure of unconsolidated structured entities [line items]            
Proportion of ownership interest in associate (percent) 48.00%          
Proportion of ownership interest in associate's power supply (percent) 78.00%          
Techgen S.A. de C.V. | Tecpetrol International S.A.            
Disclosure of unconsolidated structured entities [line items]            
Proportion of ownership interest in associate (percent) 30.00%          
Techgen S.A. de C.V. | HSBC Mexico, Natixis, Credit Agricole, BNP, Santander, Intesa SP and Norinchukin | Techgen S.A. de C.V. Syndicated Loan Due February 2026            
Disclosure of unconsolidated structured entities [line items]            
Debt instrument, average life           4 years 3 months 18 days
Debt instrument, percentage of debt service reserve account           10.00%
Borrowings $ 82,000          
Techgen S.A. de C.V. | HSBC Mexico, Natixis, Credit Agricole, BNP, Santander, Intesa SP and Norinchukin | Techgen S.A. de C.V. Syndicated Loan Due February 2026 | Ternium Investments            
Disclosure of unconsolidated structured entities [line items]            
Payment for purchase of participation in borrowing arrangement $ 17,000          
Techgen S.A. de C.V. | HSBC Mexico, Natixis, Credit Agricole, BNP, Santander, Intesa SP and Norinchukin | London Interbank Offered Rate (LIBOR) | Techgen S.A. de C.V. Syndicated Loan Due February 2026            
Disclosure of unconsolidated structured entities [line items]            
Borrowings, adjustment to interest rate basis           1.70%
Techgen S.A. de C.V. | Tenaris Investments            
Disclosure of unconsolidated structured entities [line items]            
Proportion of ownership interest in associate (percent) 22.00%          
Proportion of ownership interest in associate's power supply (percent) 22.00%