| Concept | 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 | 
                                                2,210
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                1,465
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                1,446
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                2,154
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                2,130
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                1,433
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                1,440
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                2,116
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                2,029
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                1,376
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
| Average number of temporary employees | 
                                                1,008
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                826
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                811
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                977
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                991
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                826
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                863
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                1,016
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                1,066
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                812
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
| Average age (Years) | — | 
                                                40.3
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | 
| Average length of service (Years) | — | 
                                                14.6
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | 
| Average annual salary | — | 
                                                6,589,298
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — |