Employees
| Concept | As at 2025-03-31 | As at 2025-03-31 | As at 2025-03-31 | As at 2025-03-31 | As at 2025-03-31 | As at 2025-03-31 | As at 2025-03-31 | 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 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 | 
                                                1,208
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                715
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                123
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                64
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                74
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                2,061
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                1,987
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                316
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                390
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                74
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                193
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                2,123
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                389
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                385
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                2,151
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                1,920
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                372
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                1,814
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                363
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
| Average number of temporary employees | 
                                                1,019
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                246
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                5
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                2
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                3
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                1,270
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                1,267
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                47
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                50
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                3
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                42
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                1,286
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                39
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                47
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                823
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                1,264
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                32
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                911
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                25
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
| Average age (Years) | — | — | — | — | — | — | — | — | 
                                                43.5
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | 
| Average length of service (Years) | — | — | — | — | — | — | — | — | 
                                                17.1
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | 
| Average annual salary | — | — | — | — | — | — | — | — | 
                                                6,948,444
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — |