Statement Of Financial Position [Abstract]
| Concept | 
                                    
                                        As at 2023-12-31  | 
                            
                                
                                    
                                        As at 2023-12-31  | 
                            
                                
                                    
                                        As at 2023-12-31  | 
                            
                                
                                    
                                        As at 2023-12-31  | 
                            
                                
                                    
                                        As at 2022-12-31  | 
                            
                                
                                    
                                        As at 2022-12-31  | 
                            
                                
                                    
                                        As at 2022-12-31  | 
                            
                                
                                    
                                        As at 2022-12-31  | 
                            
                                
                                    
                                        As at 2021-12-31  | 
                            
                                
                                    
                                        As at 2021-12-31  | 
                            
                                
                                    
                                        As at 2021-12-31  | 
                            
                                
                                    
                                        As at 2021-12-31  | 
                            
                        
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Statement of financial position [abstract] | ||||||||||||
| Assets [abstract] | ||||||||||||
| Property, plant and equipment | — | — | — | 
                                        
                                             
                                                4  718
                                                
                                                    
                                                        SEK
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    
                                        
                                             
                                                5 350
                                                
                                                    
                                                        SEK
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    — | — | — | — | — | — | — | 
| Right-of-use assets | — | — | — | 
                                        
                                             
                                                35  672
                                                
                                                    
                                                        SEK
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    
                                        
                                             
                                                45  924
                                                
                                                    
                                                        SEK
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    — | — | — | — | — | — | — | 
| Cash and cash equivalents | — | — | — | 
                                        
                                             
                                                107  898
                                                
                                                    
                                                        SEK
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    
                                        
                                             
                                                117  0 0 2
                                                
                                                    
                                                        SEK
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    — | — | — | 
                                        
                                             
                                                130    611
                                                
                                                    
                                                        SEK
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    — | — | — | 
| Assets | — | — | — | 
                                        
                                             
                                                459   413
                                                
                                                    
                                                        SEK
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    
                                        
                                             
                                                433  849
                                                
                                                    
                                                        SEK
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    — | — | — | — | — | — | — | 
| Equity and liabilities [abstract] | ||||||||||||
| Equity [abstract] | ||||||||||||
| Issued capital | — | — | — | 
                                        
                                             
                                                21 053
                                                
                                                    
                                                        SEK
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    
                                        
                                             
                                                21 053
                                                
                                                    
                                                        SEK
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    — | — | — | — | — | — | — | 
| Retained earnings | — | — | — | 
                                        
                                             
                                                219   922
                                                
                                                    
                                                        SEK
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    
                                        
                                             
                                                188  514
                                                
                                                    
                                                        SEK
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    — | — | — | — | — | — | — | 
| Equity attributable to owners of parent | — | — | — | 
                                        
                                             
                                                284  979
                                                
                                                    
                                                        SEK
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    
                                        
                                             
                                                253  571
                                                
                                                    
                                                        SEK
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    — | — | — | — | — | — | — | 
| Equity | 
                                        
                                             
                                                21 053
                                                
                                                    
                                                        SEK
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    
                                        
                                             
                                                219   922
                                                
                                                    
                                                        SEK
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    
                                        
                                             
                                                44  004
                                                
                                                    
                                                        SEK
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    
                                        
                                             
                                                284  979
                                                
                                                    
                                                        SEK
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    
                                        
                                             
                                                253  571
                                                
                                                    
                                                        SEK
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    
                                        
                                             
                                                188  514
                                                
                                                    
                                                        SEK
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    
                                        
                                             
                                                21 053
                                                
                                                    
                                                        SEK
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    
                                        
                                             
                                                44  004
                                                
                                                    
                                                        SEK
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    
                                        
                                             
                                                2 5 6  4 01
                                                
                                                    
                                                        SEK
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    
                                        
                                             
                                                191  3 44
                                                
                                                    
                                                        SEK
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    
                                        
                                             
                                                44  004
                                                
                                                    
                                                        SEK
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    
                                        
                                             
                                                21 053
                                                
                                                    
                                                        SEK
                                                    
                                                
                                             
                                        
                                     | 
                                
                            
| Liabilities [abstract] | ||||||||||||
| Deferred tax liabilities | — | — | — | 
                                        
                                             
                                                1  724
                                                
                                                    
                                                        SEK
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    
                                        
                                             
                                                1 933
                                                
                                                    
                                                        SEK
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    — | — | — | — | — | — | — | 
| Equity and liabilities | — | — | — | 
                                        
                                             
                                                459   413
                                                
                                                    
                                                        SEK
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    
                                        
                                             
                                                433  849
                                                
                                                    
                                                        SEK
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    — | — | — | — | — | — | — |