Employees
| Concept | As at 2024-12-31 | As at 2024-12-31 | As at 2024-12-31 | As at 2024-12-31 | As at 2024-12-31 | As at 2024-12-31 | As at 2024-12-31 | As at 2023-12-31 | As at 2023-12-31 | As at 2022-12-31 | As at 2022-12-31 | As at 2021-12-31 | As at 2021-12-31 | As at 2020-12-31 | As at 2020-12-31 | 
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Employees | |||||||||||||||
| Information about reporting company | |||||||||||||||
| Information about employees of reporting company | |||||||||||||||
| Number of employees | 
                                                3,705
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                368
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                12
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                368
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                10,410
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                10,030
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                3,337
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                10,395
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                3,672
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                10,574
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                3,674
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                3,694
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                10,324
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                11,258
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                3,725
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
| Average number of temporary employees | 
                                                486
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                69
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                32
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                69
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                842
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                741
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                417
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                872
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                506
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                1,170
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                525
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                513
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                1,200
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                1,168
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                550
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
| Average age (Years) | 
                                                40.6
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 
| Average length of service (Years) | 
                                                15.1
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 
| Average annual salary | 
                                                6,605,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | — |