Subclassifications Of Assets, Liabilities And Equities [Abstract]
| Concept | 
                                    
                                        As at 2021-12-31  | 
                            
                                
                                    
                                        As at 2020-12-31  | 
                            
                                
                                    
                                        As at 2019-12-31  | 
                            
                        
|---|---|---|---|
| Subclassifications of assets, liabilities and equities [abstract] | |||
| Property, plant and equipment [abstract] | |||
| Property, plant and equipment | 
                                        
                                             
                                                51,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    
                                        
                                             
                                                56,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    — | 
| Intangible assets and goodwill [abstract] | |||
| Intangible assets other than goodwill [abstract] | |||
| Intangible assets other than goodwill | — | 
                                        
                                             
                                                0
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    — | 
| Trade and other current receivables [abstract] | |||
| Current trade receivables | 
                                        
                                             
                                                0
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    
                                        
                                             
                                                0
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    — | 
| Other current receivables | 
                                        
                                             
                                                94,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    
                                        
                                             
                                                80,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    — | 
| Categories of non-current financial assets [abstract] | |||
| Non-current financial assets | 
                                        
                                             
                                                0
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    
                                        
                                             
                                                1,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    — | 
| Classes of current inventories [abstract] | |||
| Current merchandise | 
                                        
                                             
                                                0
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    
                                        
                                             
                                                496,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    — | 
| Cash and cash equivalents [abstract] | |||
| Cash and cash equivalents | 
                                        
                                             
                                                115,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    
                                        
                                             
                                                12,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    
                                        
                                             
                                                171,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             
                                        
                                     | 
                                
                            
| Borrowings [abstract] | |||
| Current borrowings and current portion of non-current borrowings [abstract] | |||
| Current borrowings and current portion of non-current borrowings | 
                                        
                                             
                                                0
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    
                                        
                                             
                                                0
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    — | 
| Current borrowings and current portion of non-current borrowings, by type [abstract] | |||
| Trade and other current payables [abstract] | |||
| Current trade payables | 
                                        
                                             
                                                225,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    
                                        
                                             
                                                257,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    — | 
| Categories of non-current financial liabilities [abstract] | |||
| Non-current financial liabilities | 
                                        
                                             
                                                27 262
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    
                                        
                                             
                                                26 809
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    — | 
| Miscellaneous current liabilities [abstract] | |||
| Other current liabilities | 
                                        
                                             
                                                3 105
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    
                                        
                                             
                                                2 955
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    — | 
| Issued capital [abstract] | |||
| Issued capital | 
                                        
                                             
                                                1 865
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    
                                        
                                             
                                                1 865
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    — | 
| Retained earnings [abstract] | |||
| Retained earnings, profit (loss) for reporting period | 
                                        
                                             
                                                523,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    
                                        
                                             
                                                463,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    — | 
| Retained earnings, excluding profit (loss) for reporting period | 
                                        
                                             
                                                32 338
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    
                                        
                                             
                                                31 876
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    — | 
| Net assets (liabilities) [abstract] | |||
| Assets | 
                                        
                                             
                                                260,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    
                                        
                                             
                                                645,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    — | 
| Net current assets (liabilities) [abstract] | |||
| Current assets | 
                                        
                                             
                                                209,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    
                                        
                                             
                                                588,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    — | 
| Current liabilities | 
                                        
                                             
                                                3 330
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    
                                        
                                             
                                                3 220
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    — | 
| Assets less current liabilities [abstract] |