v3.25.4
Retirement benefit plan - Actuarial Assumptions and Sensitivity Analysis (Details) - CHF (SFr)
SFr in Thousands
Dec. 31, 2025
Dec. 31, 2024
Dec. 31, 2023
Actuarial assumptions [Abstract]      
Discount rate 1.30% 1.00% 1.50%
Rate of future increase in compensations 2.00% 2.00% 1.75%
Rate of future increase in current pensions 0.00% 0.00% 0.00%
Interest rate on retirement savings capital 3.25% 1.25% 1.50%
Sensitivity analysis [Abstract]      
Potential defined benefit obligation SFr 48,261 SFr 52,455 SFr 41,060
+0.5% Increase      
Sensitivity analysis [Abstract]      
Percentage increase in actuarial assumption 0.50% 0.50%  
-0.5% Decrease      
Sensitivity analysis [Abstract]      
Percentage decrease in actuarial assumption 0.50% 0.50%  
Discount rate | +0.5% Increase      
Sensitivity analysis [Abstract]      
Percentage increase in actuarial assumption 0.50% 0.50%  
Potential defined benefit obligation SFr 44,698 SFr 48,532  
Decrease/(increase) from actual defined benefit obligation SFr 3,563 SFr 3,923  
Discount rate | -0.5% Decrease      
Sensitivity analysis [Abstract]      
Percentage decrease in actuarial assumption 0.50% 0.50%  
Potential defined benefit obligation SFr 52,332 SFr 56,936  
Decrease/(increase) from actual defined benefit obligation SFr (4,071) SFr (4,481)  
Future salary increase | +0.5% Increase      
Sensitivity analysis [Abstract]      
Percentage increase in actuarial assumption 0.50% 0.50%  
Potential defined benefit obligation SFr 49,343 SFr 53,728  
Decrease/(increase) from actual defined benefit obligation SFr (1,082) SFr (1,273)  
Future salary increase | -0.5% Decrease      
Sensitivity analysis [Abstract]      
Percentage decrease in actuarial assumption 0.50% 0.50%  
Potential defined benefit obligation SFr 47,256 SFr 51,262  
Decrease/(increase) from actual defined benefit obligation SFr 1,005 SFr 1,193  
Future pension cost | +0.5% Increase      
Sensitivity analysis [Abstract]      
Percentage increase in actuarial assumption 0.50% 0.50%  
Potential defined benefit obligation SFr 50,262 SFr 54,683  
Decrease/(increase) from actual defined benefit obligation SFr (2,001) SFr (2,228)  
Future pension cost | -0.5% Decrease      
Sensitivity analysis [Abstract]      
Percentage decrease in actuarial assumption 0.50% 0.50%  
Potential defined benefit obligation SFr 46,435 SFr 50,423  
Decrease/(increase) from actual defined benefit obligation SFr 1,826 SFr 2,032  
Interest rate on savings capital | +0.5% Increase      
Sensitivity analysis [Abstract]      
Percentage increase in actuarial assumption 0.50% 0.50%  
Potential defined benefit obligation SFr 49,613 SFr 53,865  
Decrease/(increase) from actual defined benefit obligation SFr (1,352) SFr (1,410)  
Interest rate on savings capital | -0.5% Decrease      
Sensitivity analysis [Abstract]      
Percentage decrease in actuarial assumption 0.50% 0.50%  
Potential defined benefit obligation SFr 46,984 SFr 51,118  
Decrease/(increase) from actual defined benefit obligation SFr 1,277 SFr 1,337