Subclassifications Of Assets, Liabilities And Equities [Abstract]
| Concept | As at 2024-12-31 | As at 2023-12-31 | As at 2022-12-31 | 
|---|---|---|---|
| Subclassifications of assets, liabilities and equities [abstract] | |||
| Investment property [abstract] | |||
| Investment property | 
                                                91,100,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
                                                91,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | — | 
| Trade and other non-current receivables [abstract] | |||
| Other non-current receivables | 
                                                1,264,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
                                                1,307,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | — | 
| Trade and other current receivables [abstract] | |||
| Current trade receivables | 
                                                257,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
                                                164,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | — | 
| Other current receivables | 
                                                1,364,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
                                                1,289,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | — | 
| Cash and cash equivalents [abstract] | |||
| Cash and cash equivalents | 
                                                3,590,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
                                                2,648,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
                                                7,787,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
| Non-current assets or disposal groups classified as held for sale or as held for distribution to owners [abstract] | |||
| Non-current assets or disposal groups classified as held for sale | 
                                                0
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
                                                5,374,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | — | 
| Borrowings [abstract] | |||
| Non-current portion of non-current borrowings | 
                                                27,269,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
                                                33,237,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | — | 
| Current borrowings and current portion of non-current borrowings [abstract] | |||
| Current borrowings | 
                                                646,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
                                                4,420,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | — | 
| Non-current portion of non-current borrowings, by type [abstract] | |||
| Trade and other non-current payables [abstract] | |||
| Other non-current payables | 
                                                0
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
                                                0
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | — | 
| Trade and other current payables [abstract] | |||
| Current trade payables | 
                                                251,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
                                                432,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | — | 
| Other current payables | 
                                                926,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
                                                645,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | — | 
| Issued capital [abstract] | |||
| Issued capital | 
                                                4,900,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
                                                4,082,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | — | 
| Retained earnings [abstract] | |||
| Retained earnings | 
                                                10,696,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
                                                11,193,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | — | 
| Accumulated other comprehensive income [abstract] | |||
| Reserve of exchange differences on translation | 
                                                13,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
                                                13,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | — | 
| Net assets (liabilities) [abstract] | |||
| Assets | 
                                                97,718,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
                                                102,121,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | — | 
| Net current assets (liabilities) [abstract] | |||
| Current assets | 
                                                5,354,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
                                                9,591,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | — | 
| Current liabilities | 
                                                1,823,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
                                                5,497,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | — | 
| Assets less current liabilities [abstract] |