Employees
| Concept | As at 2023-12-31 | As at 2023-12-31 | 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 | As at 2019-12-31 | As at 2019-12-31 | 
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Employees | ||||||||||||
| Information about reporting company | ||||||||||||
| Information about employees of reporting company | ||||||||||||
| Number of employees | 
                                                1,353
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                3,830
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                2,477
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                2,023
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                3,716
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                1,912
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                1,815
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                3,359
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                3,088
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                1,729
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                1,633
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                3,012
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
| Average number of temporary employees | 
                                                471
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                1,109
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                638
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                564
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                1,094
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                531
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                520
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                1,078
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                936
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                507
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                491
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                919
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
| Average age (Years) | — | — | — | 
                                                42.51
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | 
| Average length of service (Years) | — | — | — | 
                                                12.51
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | 
| Average annual salary | — | — | — | 
                                                9,583,020
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — |