Employees
| Concept | 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 | 
                                                807
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                517
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                807
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                517
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                484
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                761
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                727
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                469
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                455
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                707
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                709
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                461
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
| Average number of temporary employees | 
                                                123
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                80
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                123
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                80
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                81
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                128
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                122
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                76
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                79
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                124
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                122
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                71
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
| Average age (Years) | — | — | — | 
                                                37.10
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | 
| Average length of service (Years) | — | — | — | 
                                                13.10
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | 
| Average annual salary | — | — | — | 
                                                6,815,834
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — |