Employees
| Concept | As at 2025-03-31 | As at 2025-03-31 | 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 | 
|---|---|---|---|---|---|---|---|---|---|---|
| Employees | ||||||||||
| Information about reporting company | ||||||||||
| Information about employees of reporting company | ||||||||||
| Number of employees | 
                                                2,445
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                2,070
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                2,007
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                2,221
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                2,143
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                1,958
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                1,906
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                2,055
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                1,981
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                1,867
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
| Average age (Years) | — | 
                                                42.0
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | 
| Average length of service (Years) | — | 
                                                16.6
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | 
| Average annual salary | — | 
                                                10,664,362
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — |