Employees
| Concept | As at 2025-03-31 | As at 2025-03-31 | As at 2025-03-31 | As at 2025-03-31 | As at 2025-03-31 | As at 2025-03-31 | 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 | 
                                                266
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                1,468
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                1,282
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                189
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                5,267
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                3,533
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                1,727
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                256
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                1,654
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                5,031
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                4,890
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                1,611
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                1,555
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                5,079
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                5,042
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                1,544
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
| Average age (Years) | — | — | — | — | — | — | 
                                                42.3
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | 
| Average length of service (Years) | — | — | — | — | — | — | 
                                                15.7
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | 
| Average annual salary | — | — | — | — | — | — | 
                                                11,811,745
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — |