Employees
| Concept | 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 2023-03-31 | As at 2022-03-31 | As at 2021-03-31 | 
|---|---|---|---|---|---|---|---|---|
| Employees | ||||||||
| Information about reporting company | ||||||||
| Information about employees of reporting company | ||||||||
| Number of employees | 
                                                1,279
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                1
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                60
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                1,340
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                1,307
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                1,314
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                1,344
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                1,356
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
| Average age (Years) | — | — | — | 
                                                41.9
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | — | 
| Average length of service (Years) | — | — | — | 
                                                19.4
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | — | 
| Average annual salary | — | — | — | 
                                                5,850,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — |