Key Financial Data Of Reporting Company
| Concept | 
                                    
                                        2023-03-21 to 2023-12-20  | 
                            
                                
                                    
                                        2023-09-21 to 2023-12-20  | 
                            
                                
                                    
                                        As at 2023-12-20  | 
                            
                                
                                    
                                        As at 2023-03-20  | 
                            
                                
                                    
                                        2022-03-21 to 2023-03-20  | 
                            
                                
                                    
                                        2022-03-21 to 2022-12-20  | 
                            
                                
                                    
                                        2022-09-21 to 2022-12-20  | 
                            
                                
                                    
                                        As at 2022-12-20  | 
                            
                        
|---|---|---|---|---|---|---|---|---|
| Key financial data of reporting company | ||||||||
| Business results of reporting company | ||||||||
| Net sales | 
                                        
                                             
                                                44,914,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    — | — | — | 
                                        
                                             
                                                56,749,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    
                                        
                                             
                                                43,860,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    — | — | 
| Ordinary profit (loss) | 
                                        
                                             
                                                5,011,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    — | — | — | 
                                        
                                             
                                                2,317,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    
                                        
                                             
                                                2,347,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    — | — | 
| Net assets | — | — | 
                                        
                                             
                                                33,512,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    
                                        
                                             
                                                28,749,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    — | — | — | 
                                        
                                             
                                                28,685,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             
                                        
                                     | 
                                
                            
| Total assets | — | — | 
                                        
                                             
                                                93,476,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    
                                        
                                             
                                                86,536,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    — | — | — | 
                                        
                                             
                                                85,016,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             
                                        
                                     | 
                                
                            
| Basic earnings (loss) per share | 
                                        
                                             
                                                965.75
                                                
                                             
                                        
                                     | 
                                
                                    
                                        
                                             
                                                376.14
                                                
                                             
                                        
                                     | 
                                
                                    — | — | 
                                        
                                             
                                                60.26
                                                
                                             
                                        
                                     | 
                                
                                    
                                        
                                             
                                                47.16
                                                
                                             
                                        
                                     | 
                                
                                    
                                        
                                             
                                                16.86
                                                
                                             
                                        
                                     | 
                                
                                    — | 
| Diluted earnings per share | 
                                        
                                             | 
                                
                                    — | — | — | 
                                        
                                             | 
                                
                                    
                                        
                                             | 
                                
                                    — | — | 
| Equity-to-asset ratio | — | — | 
                                        
                                             
                                                0.317
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    
                                        
                                             
                                                0.290
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    — | — | — | 
                                        
                                             
                                                0.295
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             
                                        
                                     |