| 
       CHF millions  | 
    
       Note  | 
    
       30.06.2023  | 
    
       31.12.2022  | 
    
       30.06.2022  | 
  
| 
       ASSETS  | 
    
       
  | 
    
       
  | 
    
       
  | 
    
       
  | 
  
| 
       Short-term assets  | 
    
       
  | 
    
       
  | 
    
       
  | 
    
       
  | 
  
| 
       Liquid funds  | 
    
       
  | 
    
       83.4  | 
    
       180.3  | 
    
       229.3  | 
  
| 
       Marketable securities  | 
    
       
  | 
    
       –  | 
    
       –  | 
    
       –  | 
  
| 
       Accounts receivables  | 
    
       
  | 
    
       187.5  | 
    
       179.0  | 
    
       178.2  | 
  
| 
       Other short-term receivables  | 
    
       
  | 
    
       40.9  | 
    
       31.3  | 
    
       17.3  | 
  
| 
       Inventories  | 
    
       
  | 
    
       198.6  | 
    
       155.5  | 
    
       151.0  | 
  
| 
       Accruals  | 
    
       
  | 
    
       6.2  | 
    
       6.2  | 
    
       4.5  | 
  
| 
       Subtotal short-term assets  | 
    
       
  | 
    
       516.6  | 
    
       552.3  | 
    
       580.3  | 
  
| 
       Long-term assets  | 
    
       
  | 
    
       
  | 
    
       
  | 
    
       
  | 
  
| 
       Tangible assets  | 
    
       
  | 
    
       751.3  | 
    
       661.6  | 
    
       559.2  | 
  
| 
       Financial assets  | 
    
       
  | 
    
       18.6  | 
    
       17.3  | 
    
       17.6  | 
  
| 
       Intangible assets  | 
    
       
  | 
    
       3.2  | 
    
       3.3  | 
    
       3.9  | 
  
| 
       Subtotal long-term assets  | 
    
       
  | 
    
       773.1  | 
    
       682.2  | 
    
       580.7  | 
  
| 
       Total assets  | 
    
       
  | 
    
       1 289.7  | 
    
       1 234.5  | 
    
       1 161.0  | 
  
| 
       LIABILITIES  | 
    
       
  | 
    
       
  | 
    
       
  | 
    
       
  | 
  
| 
       Liabilities  | 
    
       
  | 
    
       
  | 
    
       
  | 
    
       
  | 
  
| 
       Short-term liabilities  | 
    
       
  | 
    
       
  | 
    
       
  | 
    
       
  | 
  
| 
       – Accounts payables  | 
    
       
  | 
    
       165.0  | 
    
       209.0  | 
    
       139.1  | 
  
| 
       – Short-term financial debts  | 
    
       
  | 
    
       56.1  | 
    
       10.2  | 
    
       11.9  | 
  
| 
       – Other short-term liabilities  | 
    
       
  | 
    
       30.8  | 
    
       25.9  | 
    
       30.1  | 
  
| 
       – Deferrals  | 
    
       
  | 
    
       53.1  | 
    
       31.8  | 
    
       43.6  | 
  
| 
       – Short-term provisions  | 
    
       
  | 
    
       9.5  | 
    
       6.7  | 
    
       6.7  | 
  
| 
       Subtotal short-term liabilities  | 
    
       
  | 
    
       314.5  | 
    
       283.6  | 
    
       231.4  | 
  
| 
       Long-term liabilities  | 
    
       
  | 
    
       
  | 
    
       
  | 
    
       
  | 
  
| 
       – Long-term financial debts  | 
    
       
  | 
    
       166.1  | 
    
       168.6  | 
    
       177.8  | 
  
| 
       – Other long-term liabilities  | 
    
       
  | 
    
       0.6  | 
    
       0.7  | 
    
       0.8  | 
  
| 
       – Long-term provisions  | 
    
       
  | 
    
       31.1  | 
    
       32.3  | 
    
       32.9  | 
  
| 
       Subtotal long-term liabilities  | 
    
       
  | 
    
       197.8  | 
    
       201.6  | 
    
       211.5  | 
  
| 
       Total liabilities  | 
    
       
  | 
    
       512.3  | 
    
       485.2  | 
    
       442.9  | 
  
| 
       Shareholders' equity  | 
    
       
  | 
    
       
  | 
    
       
  | 
    
       
  | 
  
| 
       Share capital  | 
    
       
  | 
    
       19.8  | 
    
       19.8  | 
    
       19.8  | 
  
| 
       Capital reserves  | 
    
       
  | 
    
       0.3  | 
    
       0.3  | 
    
       0.3  | 
  
| 
       Retained earnings  | 
    
       
  | 
    
       706.6  | 
    
       688.5  | 
    
       707.7  | 
  
| 
       Consolidated result  | 
    
       
  | 
    
       50.7  | 
    
       40.7  | 
    
       – 9.7  | 
  
| 
       Subtotal shareholders' equity  | 
    
       
  | 
    
       777.4  | 
    
       749.3  | 
    
       718.1  | 
  
| 
       Total liabilities  | 
    
       
  | 
    
       1 289.7  | 
    
       1 234.5  | 
    
       1 161.0  |