Subclassifications Of Assets, Liabilities And Equities [Abstract]
| Concept | 
                                    
                                        As at 2021-12-31  | 
                            
                                
                                    
                                        As at 2020-12-31  | 
                            
                        
|---|---|---|
| Subclassifications of assets, liabilities and equities [abstract] | ||
| Property, plant and equipment [abstract] | ||
| Property, plant and equipment | 
                                        
                                             
                                                554 508
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    
                                        
                                             
                                                573 542
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             
                                        
                                     | 
                                
                            
| Intangible assets and goodwill [abstract] | ||
| Intangible assets other than goodwill [abstract] | ||
| Intangible assets other than goodwill | 
                                        
                                             
                                                14 476
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    
                                        
                                             
                                                14 663
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             
                                        
                                     | 
                                
                            
| Investment property [abstract] | ||
| Investment property | 
                                        
                                             
                                                13 352
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    
                                        
                                             
                                                13 656
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             
                                        
                                     | 
                                
                            
| Investments accounted for using equity method [abstract] | ||
| Investments accounted for using equity method | 
                                        
                                             
                                                906,000
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    
                                        
                                             
                                                947,000
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             
                                        
                                     | 
                                
                            
| Trade and other non-current receivables [abstract] | ||
| Non-current receivables due from related parties | 
                                        
                                             
                                                29,000
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    
                                        
                                             
                                                34,000
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             
                                        
                                     | 
                                
                            
| Other non-current receivables | 
                                        
                                             
                                                28,000
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    
                                        
                                             
                                                28,000
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             
                                        
                                     | 
                                
                            
| Trade and other current receivables [abstract] | ||
| Trade and other current receivables | 
                                        
                                             
                                                3 405
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    
                                        
                                             
                                                880,000
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             
                                        
                                     | 
                                
                            
| Trade and other receivables [abstract] | ||
| Receivables due from related parties | 
                                        
                                             
                                                5,000
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    
                                        
                                             
                                                8,000
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             
                                        
                                     | 
                                
                            
| Other receivables | 
                                        
                                             
                                                1 904
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    
                                        
                                             
                                                1 371
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             
                                        
                                     | 
                                
                            
| Categories of non-current financial assets [abstract] | ||
| Non-current financial assets at fair value through other comprehensive income [abstract] | ||
| Non-current financial assets measured at fair value through other comprehensive income | 
                                        
                                             
                                                22,000
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    
                                        
                                             
                                                22,000
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             
                                        
                                     | 
                                
                            
| Classes of current inventories [abstract] | ||
| Current inventories | 
                                        
                                             
                                                10 400
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    
                                        
                                             
                                                11 480
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             
                                        
                                     | 
                                
                            
| Classes of current inventories, alternative [abstract] | ||
| Cash and cash equivalents [abstract] | ||
| Cash and cash equivalents | 
                                        
                                             
                                                11 794
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    
                                        
                                             
                                                6 814
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             
                                        
                                     | 
                                
                            
| Trade and other non-current payables [abstract] | ||
| Non-current trade payables | 
                                        
                                             
                                                3 950
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    
                                        
                                             
                                                4 734
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             
                                        
                                     | 
                                
                            
| Non-current payables to related parties | 
                                        
                                             
                                                -
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    
                                        
                                             
                                                130,000
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             
                                        
                                     | 
                                
                            
| Non-current accruals and non-current deferred income including non-current contract liabilities [abstract] | ||
| Non-current deferred income including non-current contract liabilities [abstract] | ||
| Non-current deferred income other than non-current contract liabilities | — | — | 
| Non-current government grants | 
                                        
                                             
                                                790,000
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    
                                        
                                             
                                                812,000
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             
                                        
                                     | 
                                
                            
| Trade and other current payables [abstract] | ||
| Current accruals and current deferred income including current contract liabilities [abstract] | ||
| Current deferred income including current contract liabilities [abstract] | ||
| Current deferred income other than current contract liabilities | — | — | 
| Current government grants | 
                                        
                                             
                                                22,000
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    
                                        
                                             
                                                22,000
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             
                                        
                                     | 
                                
                            
| Trade and other payables [abstract] | ||
| Payables to related parties | 
                                        
                                             
                                                152,000
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    
                                        
                                             
                                                208,000
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             
                                        
                                     | 
                                
                            
| Issued capital [abstract] | ||
| Issued capital | 
                                        
                                             
                                                4 273
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    
                                        
                                             
                                                4 273
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             
                                        
                                     | 
                                
                            
| Retained earnings [abstract] | ||
| Retained earnings | 
                                        
                                             
                                                162 260
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    
                                        
                                             
                                                147 830
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             
                                        
                                     | 
                                
                            
| Net assets (liabilities) [abstract] | ||
| Assets | 
                                        
                                             
                                                615 565
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    
                                        
                                             
                                                627 803
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             
                                        
                                     | 
                                
                            
| Liabilities | 
                                        
                                             
                                                130 350
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    
                                        
                                             
                                                146 782
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             
                                        
                                     | 
                                
                            
| Net current assets (liabilities) [abstract] | ||
| Current assets | 
                                        
                                             
                                                29 456
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    
                                        
                                             
                                                21 719
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             
                                        
                                     | 
                                
                            
| Current liabilities | 
                                        
                                             
                                                27 843
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    
                                        
                                             
                                                37 311
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             
                                        
                                     | 
                                
                            
| Assets less current liabilities [abstract] |