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 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 | 
                                                2,037
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                2,546
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                286
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                2,161
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                631
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                594
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                1,556
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                11,512
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                324
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                2,794
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                105
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                3,391
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                1,869
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                11,544
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                3,390
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                3,447
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                11,545
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                11,335
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                3,472
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                11,272
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                3,551
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
| Average number of temporary employees | 
                                                340
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                616
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                72
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                199
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                62
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                39
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                250
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                1,824
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                43
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                351
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                59
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                466
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                259
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                1,793
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                453
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                415
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                1,739
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                1,717
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                386
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                1,730
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                372
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
| Average age (Years) | — | — | — | — | — | — | — | — | — | — | — | — | 
                                                41
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | 
| Average age (Months) | — | — | — | — | — | — | — | — | — | — | — | — | 
                                                6
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | 
| Average length of service (Years) | — | — | — | — | — | — | — | — | — | — | — | — | 
                                                17
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | 
| Average length of service (Months) | — | — | — | — | — | — | — | — | — | — | — | — | 
                                                3
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | 
| Average annual salary | — | — | — | — | — | — | — | — | — | — | — | — | 
                                                8,125,682
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — |