Employees
| Concept | 
                                    
                                        As at 2025-04-30  | 
                            
                                
                                    
                                        As at 2025-04-30  | 
                            
                                
                                    
                                        As at 2025-04-30  | 
                            
                                
                                    
                                        As at 2025-04-30  | 
                            
                                
                                    
                                        As at 2024-04-30  | 
                            
                                
                                    
                                        As at 2023-04-30  | 
                            
                                
                                    
                                        As at 2022-04-30  | 
                            
                                
                                    
                                        As at 2021-04-30  | 
                            
                        
|---|---|---|---|---|---|---|---|---|
| Employees | ||||||||
| Information about reporting company | ||||||||
| Information about employees of reporting company | ||||||||
| Number of employees | 
                                        
                                             
                                                672
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    
                                        
                                             
                                                173
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    
                                        
                                             
                                                167
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    
                                        
                                             
                                                332
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    
                                        
                                             
                                                657
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    
                                        
                                             
                                                629
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    
                                        
                                             
                                                620
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    
                                        
                                             
                                                606
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             
                                        
                                     | 
                                
                            
| Average age (Years) | 
                                        
                                             
                                                40.9
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    — | — | — | — | — | — | — | 
| Average length of service (Years) | 
                                        
                                             
                                                14.3
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    — | — | — | — | — | — | — | 
| Average annual salary | 
                                        
                                             
                                                5,725,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    — | — | — | — | — | — | — |