v3.26.1
Note 27 - Contingencies, commitments and restrictions on the distribution of profits (Details Textual)
R$ / shares in Units, R$ in Millions, $ in Millions
12 Months Ended 36 Months Ended
Sep. 05, 2025
Jun. 06, 2025
Nov. 14, 2022
Oct. 09, 2018
USD ($)
Dec. 31, 2025
BRL (R$)
Dec. 31, 2024
USD ($)
May 06, 2026
shares
Dec. 31, 2025
USD ($)
May 06, 2025
shares
Apr. 30, 2024
shares
Jun. 24, 2022
USD ($)
Oct. 10, 2018
BRL (R$)
Oct. 10, 2018
USD ($)
Jan. 31, 2012
Subsidiaries
R$ / shares
shares
Disclosure of contingent liabilities [line items]                            
Cancellation Of Ordinary Shares | shares                 90,762,598 17,779,302        
Performance Guarantees Issued               $ 4,000.0            
First Share Buyback Program [Member] | First tranche [member]                            
Disclosure of contingent liabilities [line items]                            
Cancellation Of Ordinary Shares | shares                   17,779,302        
First And Second Share Buyback Program [Member]                            
Disclosure of contingent liabilities [line items]                            
Cancellation Of Ordinary Shares | shares             90,762,598              
Praxair S.A. [member]                            
Disclosure of contingent liabilities [line items]                            
Term of supply contract (Year)         14 years                  
Purchase commitments               24.8            
Vestas Group [member]                            
Disclosure of contingent liabilities [line items]                            
Purchase commitments               $ 23.2            
Techgen S.A. [member]                            
Disclosure of contingent liabilities [line items]                            
Proportion of power generation capacity         22.00%     22.00%            
Usiminas [member]                            
Disclosure of contingent liabilities [line items]                            
Purchase commitments               $ 24.4            
Usiminas [member] | Voestalpine Grobblech GmbH [member]                            
Disclosure of contingent liabilities [line items]                            
Purchase commitments               47.8            
Ternium S.A. [member] | Transportadora de Gas del Norte S.A. [member]                            
Disclosure of contingent liabilities [line items]                            
Term of supply contract (Year)         25 years                  
Argentina                            
Disclosure of contingent liabilities [line items]                            
Dumping rate imposed   6.76% 78.30%                      
Mexico                            
Disclosure of contingent liabilities [line items]                            
Dumping rate imposed 26.10%   44.93%                      
Luxembourg                            
Disclosure of contingent liabilities [line items]                            
Percent of minimum transfer of net profit to legal reserve         5.00%                  
Percent of maximum issued share capital until which transfer of net profit to legal reserve         10.00%                  
Confab [member] | Chubb [member]                            
Disclosure of contingent liabilities [line items]                            
Payments for settlement       $ 3.5                    
Confab [member] | Veracel Celulose S.A. [member]                            
Disclosure of contingent liabilities [line items]                            
Settlement, amount ordered to pay, insurance deductible                       R$ 121.0 $ 22.0  
Settlement, amount ordered to pay, damages                       R$ 103.8 $ 18.9  
Mechanical and other pipe [member]                            
Disclosure of contingent liabilities [line items]                            
Loss of revenue to US           $ 49.6                
Tax contingent liability [member] | Petroleo Brasileiro S.A. [member]                            
Disclosure of contingent liabilities [line items]                            
Estimated financial effect of contingent liabilities         R$ 201.7     36.7            
Contingent liability for disgorgement and prejudgment interest [member]                            
Disclosure of contingent liabilities [line items]                            
Settlement, amount ordered to pay                     $ 53.1      
Contingent liability for civil penalty [member]                            
Disclosure of contingent liabilities [line items]                            
Settlement, amount ordered to pay                     $ 25.0      
CONFAB INDUSTRIAL S.A. and Ternium Subsidiaries [member] | Companhia Siderúrgica Nacional [member]                            
Disclosure of contingent liabilities [line items]                            
Professional fees expense | R$         R$ 5.0                  
Tag-along tender offer to non-controlling interests, percentage                           80.00%
Tag-along tender offer to non-controlling interests (in BRL per share) | R$ / shares                           R$ 28.8
Tag-along tender offer to non-controlling interests, shares (in shares) | shares                           182,609,851
Ternium S.A. [member]                            
Disclosure of contingent liabilities [line items]                            
Number of subsidiaries | Subsidiaries                           3
IPSCO Tubulars, Inc. | Commitments and guarantees                            
Disclosure of contingent liabilities [line items]                            
Term of supply contract (Year)         6 years                  
Term of supply contract, available extension         12 months                  
TENARIS BAY CITY, INC. [member] | Nucor Steel Memphis Inc. [member]                            
Disclosure of contingent liabilities [line items]                            
Term of supply contract (Year)         1 year                  
JFE Steel Corporation [member]                            
Disclosure of contingent liabilities [line items]                            
Purchase commitments               18.9            
CONFAB INDUSTRIAL S.A. [member]                            
Disclosure of contingent liabilities [line items]                            
Estimated financial effect of contingent liabilities         R$ 632.5     $ 114.9            
CONFAB INDUSTRIAL S.A. [member] | Companhia Siderúrgica Nacional [member]                            
Disclosure of contingent liabilities [line items]                            
Tag-along tender offer to non-controlling interests, contingent liability                           17.90%