Employees
| Concept | As at 2024-05-15 | As at 2023-05-15 | As at 2022-05-15 | As at 2021-05-15 | As at 2020-05-15 | 
|---|---|---|---|---|---|
| Employees | |||||
| Information about group | |||||
| Number of employees of group | |||||
| Number of employees | 
                                                491
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                468
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                465
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                482
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                511
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
| Average number of temporary employees | 
                                                996
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                962
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                922
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                951
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                977
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             |