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 2024-03-31 | As at 2023-03-31 | As at 2022-03-31 | As at 2021-03-31 | 
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Employees | ||||||||||||||||
| Information about reporting company | ||||||||||||||||
| Information about employees of reporting company | ||||||||||||||||
| Number of employees | 
                                                2,312
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                455
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                427
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                555
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                398
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                1,132
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                55
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                7,981
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                1,659
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                251
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                4,055
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                1,633
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                1,594
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                1,538
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                1,612
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
| Average number of temporary employees | 
                                                166
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                39
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                9
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                139
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                9
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                129
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                4
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                845
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                205
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                18
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                537
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                207
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                264
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                275
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                226
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
| Average age (Years) | — | — | — | — | — | — | — | — | — | 
                                                45.9
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | — | — | — | 
| Average length of service (Years) | — | — | — | — | — | — | — | — | — | 
                                                21.9
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | — | — | — | 
| Average annual salary | — | — | — | — | — | — | — | — | — | 
                                                7,940,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — |