Statement Of Financial Position [Abstract]
| Concept | As at 2024-12-31 | As at 2024-12-31 | As at 2024-12-31 | As at 2024-12-31 | As at 2024-12-31 | As at 2024-12-31 | As at 2024-12-31 | As at 2023-12-31 | As at 2023-12-31 | As at 2023-12-31 | 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 2022-12-31 | As at 2022-12-31 | As at 2022-12-31 | 
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Statement of financial position [abstract] | |||||||||||||||||||||
| Assets [abstract] | |||||||||||||||||||||
| Property, plant and equipment | — | — | — | — | — | — | 
                                                146,000,000
                                                
                                                    
                                                        SEK
                                                    
                                                
                                             | 
                                                148,000,000
                                                
                                                    
                                                        SEK
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | 
| Right-of-use assets | — | — | — | — | — | — | 
                                                79,000,000
                                                
                                                    
                                                        SEK
                                                    
                                                
                                             | 
                                                93,000,000
                                                
                                                    
                                                        SEK
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | 
| Goodwill | — | — | — | — | — | — | 
                                                22,000,000
                                                
                                                    
                                                        SEK
                                                    
                                                
                                             | 
                                                22,000,000
                                                
                                                    
                                                        SEK
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | 
| Intangible assets other than goodwill | — | — | — | — | — | — | 
                                                87,000,000
                                                
                                                    
                                                        SEK
                                                    
                                                
                                             | 
                                                63,000,000
                                                
                                                    
                                                        SEK
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | 
| Deferred tax assets | — | — | — | — | — | — | 
                                                8,000,000
                                                
                                                    
                                                        SEK
                                                    
                                                
                                             | 
                                                4,000,000
                                                
                                                    
                                                        SEK
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | 
| Cash and cash equivalents | — | — | — | — | — | — | 
                                                132,000,000
                                                
                                                    
                                                        SEK
                                                    
                                                
                                             | 
                                                101,000,000
                                                
                                                    
                                                        SEK
                                                    
                                                
                                             | — | — | — | — | — | — | 
                                                30,000,000
                                                
                                                    
                                                        SEK
                                                    
                                                
                                             | — | — | — | — | — | — | 
| Assets | — | — | — | — | — | — | 
                                                1 112
                                                
                                                    
                                                        SEK
                                                    
                                                
                                             | 
                                                1 012
                                                
                                                    
                                                        SEK
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | 
| Equity and liabilities [abstract] | |||||||||||||||||||||
| Equity [abstract] | |||||||||||||||||||||
| Issued capital | — | — | — | — | — | — | 
                                                21,000,000
                                                
                                                    
                                                        SEK
                                                    
                                                
                                             | 
                                                21,000,000
                                                
                                                    
                                                        SEK
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | 
| Retained earnings | — | — | — | — | — | — | 
                                                643,000,000
                                                
                                                    
                                                        SEK
                                                    
                                                
                                             | 
                                                571,000,000
                                                
                                                    
                                                        SEK
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | 
| Equity attributable to owners of parent | — | — | — | — | — | — | 
                                                693,000,000
                                                
                                                    
                                                        SEK
                                                    
                                                
                                             | 
                                                612,000,000
                                                
                                                    
                                                        SEK
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | 
| Non-controlling interests | — | — | — | — | — | — | 
                                                39,000,000
                                                
                                                    
                                                        SEK
                                                    
                                                
                                             | 
                                                32,000,000
                                                
                                                    
                                                        SEK
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | 
| Equity | 
                                                643,000,000
                                                
                                                    
                                                        SEK
                                                    
                                                
                                             | 
                                                21,000,000
                                                
                                                    
                                                        SEK
                                                    
                                                
                                             | 
                                                39,000,000
                                                
                                                    
                                                        SEK
                                                    
                                                
                                             | 
                                                693,000,000
                                                
                                                    
                                                        SEK
                                                    
                                                
                                             | 
                                                23,000,000
                                                
                                                    
                                                        SEK
                                                    
                                                
                                             | 
                                                6,000,000
                                                
                                                    
                                                        SEK
                                                    
                                                
                                             | 
                                                732,000,000
                                                
                                                    
                                                        SEK
                                                    
                                                
                                             | 
                                                643,000,000
                                                
                                                    
                                                        SEK
                                                    
                                                
                                             | 
                                                571,000,000
                                                
                                                    
                                                        SEK
                                                    
                                                
                                             | 
                                                14,000,000
                                                
                                                    
                                                        SEK
                                                    
                                                
                                             | 
                                                32,000,000
                                                
                                                    
                                                        SEK
                                                    
                                                
                                             | 
                                                21,000,000
                                                
                                                    
                                                        SEK
                                                    
                                                
                                             | 
                                                612,000,000
                                                
                                                    
                                                        SEK
                                                    
                                                
                                             | 
                                                6,000,000
                                                
                                                    
                                                        SEK
                                                    
                                                
                                             | 
                                                501,000,000
                                                
                                                    
                                                        SEK
                                                    
                                                
                                             | 
                                                14,000,000
                                                
                                                    
                                                        SEK
                                                    
                                                
                                             | 
                                                35,000,000
                                                
                                                    
                                                        SEK
                                                    
                                                
                                             | 
                                                425,000,000
                                                
                                                    
                                                        SEK
                                                    
                                                
                                             | 
                                                21,000,000
                                                
                                                    
                                                        SEK
                                                    
                                                
                                             | 
                                                466,000,000
                                                
                                                    
                                                        SEK
                                                    
                                                
                                             | 
                                                6,000,000
                                                
                                                    
                                                        SEK
                                                    
                                                
                                             | 
| Liabilities [abstract] | |||||||||||||||||||||
| Deferred tax liabilities | — | — | — | — | — | — | 
                                                25,000,000
                                                
                                                    
                                                        SEK
                                                    
                                                
                                             | 
                                                23,000,000
                                                
                                                    
                                                        SEK
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | 
| Liabilities | — | — | — | — | — | — | 
                                                380,000,000
                                                
                                                    
                                                        SEK
                                                    
                                                
                                             | 
                                                369,000,000
                                                
                                                    
                                                        SEK
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | 
| Equity and liabilities | — | — | — | — | — | — | 
                                                1 112
                                                
                                                    
                                                        SEK
                                                    
                                                
                                             | 
                                                1 012
                                                
                                                    
                                                        SEK
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — |