Statement Of Cash Flows [Abstract]
| Concept | 
                                    
                                        As at 2021-12-31  | 
                            
                                
                                    
                                        2021-01-01 to 2021-12-31  | 
                            
                                
                                    
                                        As at 2020-12-31  | 
                            
                                
                                    
                                        2020-01-01 to 2020-12-31  | 
                            
                        
|---|---|---|---|---|
| Statement of cash flows [abstract] | ||||
| Cash flows from (used in) operating activities [abstract] | ||||
| Profit (loss) | — | 
                                        
                                             
                                                4 133
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    — | 
                                        
                                             
                                                17 553
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             
                                        
                                     | 
                                
                            
| Income taxes paid (refund), classified as operating activities | — | 
                                        
                                             
                                                4 378
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    — | 
                                        
                                             
                                                699,000
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             
                                        
                                     | 
                                
                            
| Other inflows (outflows) of cash, classified as operating activities | — | 
                                        
                                             
                                                226,000
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    — | 
                                        
                                             
                                                71,000
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             
                                        
                                     | 
                                
                            
| Cash flows from (used in) operating activities | — | 
                                        
                                             
                                                19 598
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    — | 
                                        
                                             
                                                10 838
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             
                                        
                                     | 
                                
                            
| Cash flows from (used in) investing activities [abstract] | ||||
| Proceeds from sales of property, plant and equipment, classified as investing activities | — | 
                                        
                                             
                                                2 050
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    — | 
                                        
                                             
                                                6 462
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             
                                        
                                     | 
                                
                            
| Purchase of property, plant and equipment, classified as investing activities | — | 
                                        
                                             
                                                5 261
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    — | 
                                        
                                             
                                                12 027
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             
                                        
                                     | 
                                
                            
| Proceeds from sales of other long-term assets, classified as investing activities | — | 
                                        
                                             
                                                -
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    — | 
                                        
                                             
                                                2 138
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             
                                        
                                     | 
                                
                            
| Proceeds from government grants, classified as investing activities | — | 
                                        
                                             
                                                161,000
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    — | — | 
| Cash advances and loans made to other parties, classified as investing activities | — | 
                                        
                                             
                                                46,000
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    — | 
                                        
                                             
                                                4,000
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             
                                        
                                     | 
                                
                            
| Cash receipts from repayment of advances and loans made to other parties, classified as investing activities | — | 
                                        
                                             
                                                4,000
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    — | 
                                        
                                             
                                                436,000
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             
                                        
                                     | 
                                
                            
| Dividends received, classified as investing activities | — | 
                                        
                                             
                                                -
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    — | 
                                        
                                             
                                                11,000
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             
                                        
                                     | 
                                
                            
| Cash flows from (used in) investing activities | — | 
                                        
                                             
                                                3 092
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    — | 
                                        
                                             
                                                2 984
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             
                                        
                                     | 
                                
                            
| Cash flows from (used in) financing activities [abstract] | ||||
| Proceeds from issuing other equity instruments | — | 
                                        
                                             
                                                -
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    — | 
                                        
                                             
                                                1 018
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             
                                        
                                     | 
                                
                            
| Proceeds from borrowings, classified as financing activities | — | 
                                        
                                             
                                                51 449
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    — | 
                                        
                                             
                                                1 448
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             
                                        
                                     | 
                                
                            
| Repayments of borrowings, classified as financing activities | — | 
                                        
                                             
                                                60 397
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    — | 
                                        
                                             
                                                12 487
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             
                                        
                                     | 
                                
                            
| Payments of lease liabilities, classified as financing activities | — | 
                                        
                                             
                                                328,000
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    — | 
                                        
                                             
                                                583,000
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             
                                        
                                     | 
                                
                            
| Dividends paid, classified as financing activities | — | 
                                        
                                             
                                                10,000
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    — | 
                                        
                                             
                                                974,000
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             
                                        
                                     | 
                                
                            
| Interest paid, classified as financing activities | — | 
                                        
                                             
                                                2 242
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    — | 
                                        
                                             
                                                1 197
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             
                                        
                                     | 
                                
                            
| Cash flows from (used in) financing activities | — | 
                                        
                                             
                                                11 528
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    — | 
                                        
                                             
                                                12 775
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             
                                        
                                     | 
                                
                            
| Increase (decrease) in cash and cash equivalents before effect of exchange rate changes | — | 
                                        
                                             
                                                4 978
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    — | 
                                        
                                             
                                                4 921
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             
                                        
                                     | 
                                
                            
| Effect of exchange rate changes on cash and cash equivalents [abstract] | ||||
| Effect of exchange rate changes on cash and cash equivalents | — | 
                                        
                                             
                                                4,000
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    — | 
                                        
                                             
                                                2,000
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             
                                        
                                     | 
                                
                            
| Cash and cash equivalents | 
                                        
                                             
                                                11 794
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    — | 
                                        
                                             
                                                6 814
                                                
                                                    
                                                        BGN
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    — |