Employees
| Concept | As at 2024-03-31 | As at 2024-03-31 | As at 2024-03-31 | As at 2024-03-31 | 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 reporting company | ||||||||||||||||
| Information about employees of reporting company | ||||||||||||||||
| Number of employees | 
                                                324
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                22
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                22
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                453
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                416
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                545
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                70
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                70
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                585
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                427
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                477
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                640
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                632
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                483
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                417
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                442
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
| Average number of temporary employees | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                42
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                42
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                42
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                42
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                43
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                71
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                115
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
| Average age (Years) | — | — | — | — | 
                                                49.1
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | 
| Average length of service (Years) | — | — | — | — | 
                                                18.4
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | 
| Average annual salary | — | — | — | — | 
                                                6,048,670
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — |