Subclassifications Of Assets, Liabilities And Equities [Abstract]
| Concept | 
                                    
                                        As at 2024-12-31  | 
                            
                                
                                    
                                        As at 2023-12-31  | 
                            
                        
|---|---|---|
| Subclassifications of assets, liabilities and equities [abstract] | ||
| Property, plant and equipment [abstract] | ||
| Land and buildings [abstract] | ||
| Land | 
                                        
                                             
                                                1 908
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    
                                        
                                             
                                                1 836
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             
                                        
                                     | 
                                
                            
| Buildings | 
                                        
                                             
                                                14 488
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    
                                        
                                             
                                                15 964
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             
                                        
                                     | 
                                
                            
| Vehicles [abstract] | ||
| Ships | 
                                        
                                             
                                                92 013
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    
                                        
                                             
                                                94 291
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             
                                        
                                     | 
                                
                            
| Intangible assets and goodwill [abstract] | ||
| Intangible assets other than goodwill [abstract] | ||
| Computer software | 
                                        
                                             
                                                1 624
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    
                                        
                                             
                                                1 367
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             
                                        
                                     | 
                                
                            
| Other intangible assets | 
                                        
                                             
                                                2 942
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    
                                        
                                             
                                                8,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             
                                        
                                     | 
                                
                            
| Trade and other current receivables [abstract] | ||
| Trade and other current receivables | 
                                        
                                             
                                                10 290
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    
                                        
                                             
                                                13 909
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             
                                        
                                     | 
                                
                            
| Classes of current inventories [abstract] | ||
| Current inventories | 
                                        
                                             
                                                3 573
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    
                                        
                                             
                                                4 114
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             
                                        
                                     | 
                                
                            
| Classes of current inventories, alternative [abstract] | ||
| Cash and cash equivalents [abstract] | ||
| Cash and cash equivalents | 
                                        
                                             
                                                38 251
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    
                                        
                                             
                                                28 301
                                                
                                                    
                                                        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 or as held for distribution to owners | 
                                        
                                             
                                                0
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    
                                        
                                             
                                                1 049
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             
                                        
                                     | 
                                
                            
| Borrowings [abstract] | ||
| Non-current portion of non-current borrowings | 
                                        
                                             
                                                28 845
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    
                                        
                                             
                                                31 562
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             
                                        
                                     | 
                                
                            
| Current borrowings and current portion of non-current borrowings [abstract] | ||
| Current borrowings | 
                                        
                                             
                                                2 640
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    
                                        
                                             
                                                3 920
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             
                                        
                                     | 
                                
                            
| Non-current portion of non-current borrowings, by type [abstract] | ||
| Trade and other current payables [abstract] | ||
| Trade and other current payables | 
                                        
                                             
                                                24 356
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    
                                        
                                             
                                                24 682
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             
                                        
                                     | 
                                
                            
| Issued capital [abstract] | ||
| Issued capital | 
                                        
                                             
                                                2 409
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    
                                        
                                             
                                                2 409
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             
                                        
                                     | 
                                
                            
| Retained earnings [abstract] | ||
| Retained earnings, profit (loss) for reporting period | 
                                        
                                             
                                                15 570
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    
                                        
                                             
                                                11 487
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             
                                        
                                     | 
                                
                            
| Retained earnings, excluding profit (loss) for reporting period | 
                                        
                                             
                                                60 222
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    
                                        
                                             
                                                53 749
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             
                                        
                                     | 
                                
                            
| Miscellaneous equity [abstract] | ||
| Additional paid-in capital | 
                                        
                                             
                                                1 270
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    
                                        
                                             
                                                1 270
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             
                                        
                                     | 
                                
                            
| Net assets (liabilities) [abstract] | ||
| Assets | 
                                        
                                             
                                                168 131
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    
                                        
                                             
                                                163 030
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             
                                        
                                     | 
                                
                            
| Net current assets (liabilities) [abstract] | ||
| Current assets | 
                                        
                                             
                                                52 113
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    
                                        
                                             
                                                46 333
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             
                                        
                                     | 
                                
                            
| Current liabilities | 
                                        
                                             
                                                29 401
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    
                                        
                                             
                                                31 248
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             
                                        
                                     | 
                                
                            
| Assets less current liabilities [abstract] |