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 | 
                                                13,643
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                13,643
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                4,105
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                4,105
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                4,806
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                14,754
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                14,484
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                4,867
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                3,943
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                14,522
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                15,455
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                4,647
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
| Average age (Years) | — | — | 
                                                42.3
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | 
| Average length of service (Years) | — | — | 
                                                15.7
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | 
| Average annual salary | — | — | 
                                                10,462,753
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — |