Employee benefit obligations - Reconciliation of Employee Benefit Obligation (Details) - CHF (SFr) SFr in Millions |
12 Months Ended | |
|---|---|---|
Dec. 31, 2023 |
Dec. 31, 2022 |
|
| Disclosure of defined benefit plans [abstract] | ||
| Employee benefit obligations at January 1 | SFr (6.3) | SFr (5.9) |
| Amounts recognized in income statement | (3.8) | (3.1) |
| Amounts recognized in other comprehensive income | (3.4) | 4.4 |
| Contributions by the employer | 11.3 | (1.8) |
| Employee benefit obligations at December 31 | SFr (2.2) | SFr (6.3) |