Share capital - Narrative (Details) - CHF (SFr) SFr / shares in Units, SFr in Millions |
12 Months Ended | ||
|---|---|---|---|
Dec. 31, 2025 |
Dec. 31, 2024 |
Dec. 31, 2023 |
|
| Disclosure of classes of share capital [line items] | |||
| Share capital | SFr 34.1 | SFr 33.7 | |
| Share capital, paid-in percentage | 100.00% | ||
| Proceeds on sale of treasury shares related to share-based compensation | SFr 8.6 | SFr 10.9 | SFr 10.1 |
| Class A | |||
| Disclosure of classes of share capital [line items] | |||
| Number of shares registered (in shares) | 306,847,124 | 302,455,664 | 299,998,125 |
| Par value per share (in CHF per share) | SFr 0.10 | ||
| Class A | Treasury shares | |||
| Disclosure of classes of share capital [line items] | |||
| Sale of shares held by On in treasury (in shares) | 3,189,789 | 2,633,847 | |
| Class B | |||
| Disclosure of classes of share capital [line items] | |||
| Number of shares registered (in shares) | 341,241,680 | 345,437,500 | 345,437,500 |
| Par value per share (in CHF per share) | SFr 0.01 | ||