Employees
| Concept | As at 2024-03-31 | As at 2023-03-31 | As at 2022-03-31 | As at 2021-03-31 | As at 2020-03-31 | 
|---|---|---|---|---|---|
| Employees | |||||
| Information about group | |||||
| Number of employees of group | |||||
| Number of employees | 
                                                407
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                413
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                427
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                407
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                378
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
| Average number of temporary employees | 
                                                38
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                40
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                44
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                47
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                52
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             |