Employee benefit obligations - Net Employee Benefit Obligation (Details) - CHF (SFr) SFr in Millions |
Dec. 31, 2023 |
Dec. 31, 2022 |
Dec. 31, 2021 |
|---|---|---|---|
| Disclosure of defined benefit plans [abstract] | |||
| Present value of defined benefit obligation | SFr (35.3) | SFr (23.7) | |
| Fair value of plan assets | 33.1 | 17.4 | |
| Employee benefit obligations | SFr (2.2) | SFr (6.3) | SFr (5.9) |