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 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 | 
                                                1,526
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                1,100
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                135
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                1,545
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                4,480
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                135
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                174
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                4,290
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                139
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                152
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                4,052
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                4,132
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                165
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                164
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                4,165
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
| Average number of temporary employees | 
                                                2,207
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                1,095
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                23
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                333
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                3,729
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                23
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                71
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                3,739
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                25
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                27
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                3,857
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                4,103
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                30
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                29
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                4,383
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
| Average age (Years) | — | — | 
                                                45.2
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | 
| Average length of service (Years) | — | — | 
                                                11.6
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | 
| Average annual salary | — | — | 
                                                5,892,412
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — |