v3.25.1
Investments - Investments in Associates and Joint Ventures (Details)
R$ in Thousands
 3 Months Ended 12 Months Ended
Mar. 31, 2025
BRL (R$)
Mar. 31, 2025
BRL (R$)
€ / shares
Mar. 31, 2024
BRL (R$)
Mar. 31, 2024
BRL (R$)
€ / shares
Dec. 31, 2024
BRL (R$)
Dec. 31, 2023
BRL (R$)
Disclosure of joint ventures [line items]            
Equity R$ 38,535,646 R$ 38,535,646 R$ 44,724,599 R$ 44,724,599 R$ 32,415,575 R$ 44,810,300
Income (expenses) of the period R$ 6,348,178   220,032      
% 100.00%       100.00%  
In the income (expenses) for the period R$ (17,077)   (9,907)      
Non-current financial assets at fair value through other comprehensive income 1,427,438 1,427,438     R$ 1,591,437  
Associate | Foreign            
Disclosure of joint ventures [line items]            
Carrying amount 111,247 111,247     125,316  
In the income (expenses) for the period R$ (12,252)   (10,473)      
Ensyn Corporation | Foreign            
Disclosure of joint ventures [line items]            
Participation equity (%) 24.80%          
Carrying amount R$ (232) (232)     2  
In the income (expenses) for the period R$ (3,091)   (1,408)      
Spinnova Plc | Foreign            
Disclosure of joint ventures [line items]            
Participation equity (%) 18.76%          
Carrying amount R$ 82,768 82,768     95,254  
In the income (expenses) for the period (9,161)   (9,065)      
Joint ventures            
Disclosure of joint ventures [line items]            
Carrying amount 309,371 309,371     328,055  
In the income (expenses) for the period R$ (4,825)   566      
Biomas | Domestic (Brazil)            
Disclosure of joint ventures [line items]            
Participation equity (%) 16.66%          
Carrying amount R$ 1,473 1,473     2,923  
In the income (expenses) for the period R$ (1,449)   (1,142)      
Ibema Companhia Brasileira de Papel | Domestic (Brazil)            
Disclosure of joint ventures [line items]            
Participation equity (%) 49.90%          
Carrying amount R$ 188,618 188,618     193,901  
In the income (expenses) for the period R$ 3,551   7,461      
F&E Technologies LLC | Foreign            
Disclosure of joint ventures [line items]            
Participation equity (%) 50.00%          
Carrying amount R$ 5,914 5,914     6,378  
In the income (expenses) for the period        
Woodspin Oy | Foreign            
Disclosure of joint ventures [line items]            
Participation equity (%) 50.00%          
Carrying amount R$ 113,366 113,366     124,853  
In the income (expenses) for the period (6,927)   (5,753)      
Total other investments evaluated at fair value            
Disclosure of joint ventures [line items]            
In the income (expenses) for the period        
Non-current financial assets at fair value through other comprehensive income R$ 1,006,820 1,006,820     1,138,066  
Bem Agro Integração e Desenvolvimento S.A. (Indirect)            
Disclosure of joint ventures [line items]            
% 5.82%          
Bem Agro Integração e Desenvolvimento S.A. (Indirect) | Domestic (Brazil)            
Disclosure of joint ventures [line items]            
Non-current financial assets at fair value through other comprehensive income R$ 3,737 3,737     4,026  
Celluforce Inc. (Direct)            
Disclosure of joint ventures [line items]            
% 8.28%          
Celluforce Inc. (Direct) | Foreign            
Disclosure of joint ventures [line items]            
Non-current financial assets at fair value through other comprehensive income R$ 25,813 25,813     27,823  
Nfinite Nanotechnology Inc. (Indirect)            
Disclosure of joint ventures [line items]            
% 5.00%          
Nfinite Nanotechnology Inc. (Indirect) | Foreign            
Disclosure of joint ventures [line items]            
Non-current financial assets at fair value through other comprehensive income R$ 5,886 5,886     6,347  
Lenzing Aktiengesellschaft (Indirect)            
Disclosure of joint ventures [line items]            
% 15.00%          
Lenzing Aktiengesellschaft (Indirect) | Foreign            
Disclosure of joint ventures [line items]            
Non-current financial assets at fair value through other comprehensive income R$ 971,384 971,384     1,099,870  
Simplifyber, Inc (Indirect) | Foreign            
Disclosure of joint ventures [line items]            
Participation equity (%) 14.20%          
Carrying amount R$ 28,711 28,711     R$ 30,060  
In the income (expenses) for the period        
Ensyn Corporation            
Disclosure of joint ventures [line items]            
Equity (936) (936)        
Income (expenses) of the period (7,046)          
Spinnova Plc            
Disclosure of joint ventures [line items]            
Equity 441,192 R$ 441,192        
Income (expenses) of the period (49,051)          
NASDAQ, Nordic Growth Market, Average Share Price | € / shares   R$ 0.52   R$ 0.95    
Biomas | Domestic (Brazil)            
Disclosure of joint ventures [line items]            
Equity 8,839 R$ 8,839        
Income (expenses) of the period (8,697)          
Ibema Companhia Brasileira de Papel | Domestic (Brazil)            
Disclosure of joint ventures [line items]            
Equity 377,992 377,992        
Income (expenses) of the period 7,117          
F&E Technologies LLC | Foreign            
Disclosure of joint ventures [line items]            
Equity 11,829 11,829        
Income (expenses) of the period          
Woodspin Oy | Foreign            
Disclosure of joint ventures [line items]            
Equity 226,731 226,731        
Income (expenses) of the period (13,855)          
Simplifyber, Inc (Indirect)            
Disclosure of joint ventures [line items]            
Equity        
Income (expenses) of the period