Employees
| Concept | As at 2024-03-31 | As at 2024-03-31 | As at 2024-03-31 | As at 2024-03-31 | As at 2023-03-31 | As at 2023-03-31 | As at 2022-03-31 | As at 2022-03-31 | As at 2021-03-31 | As at 2021-03-31 | As at 2020-03-31 | As at 2020-03-31 | 
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Employees | ||||||||||||
| Information about group | ||||||||||||
| Number of employees of group | ||||||||||||
| Number of employees | 
                                                900
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                900
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                934
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                934
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                879
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                854
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                797
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                816
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                732
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                719
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                654
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                667
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             |