v3.25.4
Employee benefit obligations - Schedule of Sensitivity Analysis for Actuarial Assumptions (Details) - CHF (SFr)
SFr in Millions
Dec. 31, 2025
Dec. 31, 2024
Discount rate    
Disclosure of sensitivity analysis for actuarial assumptions [line items]    
Percentage of reasonably possible decrease in actuarial assumption 0.50%  
Percentage of reasonably possible increase in actuarial assumption 0.50%  
Increase (decrease) in defined benefit obligation due to reasonably possible decrease in actuarial assumption SFr 4.9 SFr 4.5
Increase (decrease) in defined benefit obligation due to reasonably possible increase in actuarial assumption SFr (4.2) (3.8)
Expected rate of salary increase    
Disclosure of sensitivity analysis for actuarial assumptions [line items]    
Percentage of reasonably possible decrease in actuarial assumption 0.50%  
Percentage of reasonably possible increase in actuarial assumption 0.50%  
Increase (decrease) in defined benefit obligation due to reasonably possible decrease in actuarial assumption SFr (1.4) (1.2)
Increase (decrease) in defined benefit obligation due to reasonably possible increase in actuarial assumption SFr 1.0 0.9
Life expectancy    
Disclosure of sensitivity analysis for actuarial assumptions [line items]    
Period of reasonably possible decrease in actuarial assumption 1 year  
Period of reasonably possible increase in actuarial assumption 1 year  
Increase (decrease) in defined benefit obligation due to reasonably possible decrease in actuarial assumption SFr (0.3) (0.5)
Increase (decrease) in defined benefit obligation due to reasonably possible increase in actuarial assumption SFr 0.4 SFr 0.5