Employees
| Concept | As at 2024-09-30 | As at 2024-09-30 | As at 2024-09-30 | As at 2024-09-30 | As at 2024-09-30 | As at 2024-09-30 | As at 2024-09-30 | As at 2024-09-30 | As at 2023-09-30 | As at 2023-09-30 | As at 2022-09-30 | As at 2022-09-30 | As at 2021-09-30 | As at 2021-09-30 | As at 2020-09-30 | As at 2020-09-30 | 
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Employees | ||||||||||||||||
| Information about reporting company | ||||||||||||||||
| Information about employees of reporting company | ||||||||||||||||
| Number of employees | 
                                                808
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                847
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                669
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                1,758
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                649
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                103
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                20
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                1,504
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                664
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                1,291
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                743
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                1,300
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                742
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                709
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                1,268
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
| Average number of temporary employees | 
                                                112
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                100
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                130
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                92
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                18
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                8
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                186
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                107
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                177
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                118
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                198
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                121
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                121
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                205
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
| Average age (Years) | — | — | 
                                                37.1
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | 
| Average length of service (Years) | — | — | 
                                                8.0
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | 
| Average annual salary | — | — | 
                                                669,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — |