v3.26.1
Share-based compensation - Restricted share awards (Details)
 6 Months Ended
Jun. 30, 2026
CHF (SFr)
EquityInstruments
Jun. 30, 2025
CHF (SFr)
Weighted Average grant date fair value [Abstract]    
Expense from share-based payment transactions with employees | SFr SFr 2,600,000 SFr 2,700,000
Restricted share awards, non-vested    
Share-based payment arrangement [Abstract]    
Number of non-vested share awards granted (in shares) | EquityInstruments 1,243,267  
Number of non-vested shares [Abstract]    
Non-vested at beginning of period | EquityInstruments 763,816  
Forfeited during the period | EquityInstruments (53,409)  
Exercised during the period | EquityInstruments (164,902)  
Granted during the period | EquityInstruments 1,243,267  
Vested during the period | EquityInstruments (483,081)  
Non-vested at end of period | EquityInstruments 1,473,029  
Weighted Average grant date fair value [Abstract]    
Weighted average grant date fair value, non-vested at beginning of period | SFr SFr 2.62  
Weighted average grant date fair value, forfeited during the period | SFr 2.63  
Weighted average grant date fair value, exercised during the period | SFr 2.57  
Weighted average grant date fair value, granted during the period | SFr 2.42  
Weighted average grant date fair value, vested during the period | SFr 2.33  
Weighted average grant date fair value, non-vested at end of period | SFr SFr 2.55  
Restricted share awards, vested    
Number of non-vested shares [Abstract]    
Vested and exercisable | EquityInstruments 2,891,435  
Weighted Average grant date fair value [Abstract]    
Weighted average grant date fair value, vested and exercisable | SFr SFr 2.83