v3.25.4
Post-employment benefit plans - Significant Assumptions (Details) - year
 12 Months Ended
Dec. 31, 2025
Dec. 31, 2024
Post-employment benefit obligations    
Discount rate 4.90% 4.70%
Rate of compensation increase 2.25% 2.25%
Cost of living indexation rate 1.60% 1.60%
Life expectancy at age 65 (years) 23.2 23.4
Net post-employment benefit plans cost    
Discount rate 4.80% 4.70%
Rate of compensation increase 2.25% 2.25%
Cost of living indexation rate 1.60% 1.60%
Life expectancy at age 65 (years) 23.4 23.4
Weighted average duration of defined benefit obligation 10 years  
Cost of medication    
Net post-employment benefit plans cost    
Actuarial assumption of medical cost trend rates 6.50%  
Ultimate actuarial assumption of medical cost trend rates 4.00%  
Term to reach ultimate actuarial assumption of medical cost trend rate 20 years  
Cost of covered dental benefits    
Net post-employment benefit plans cost    
Actuarial assumption of medical cost trend rates 4.50%  
Cost of covered hospital benefits    
Net post-employment benefit plans cost    
Actuarial assumption of medical cost trend rates 3.80%  
Cost of other covered healthcare benefits    
Net post-employment benefit plans cost    
Actuarial assumption of medical cost trend rates 4.50%