Statement Of Cash Flows [Abstract]
| Concept | 2024-01-01 to 2024-12-31 | As at 2024-12-31 | 2023-01-01 to 2023-12-31 | As at 2023-12-31 | As at 2022-12-31 | 
|---|---|---|---|---|---|
| Statement of cash flows [abstract] | |||||
| Cash flows from (used in) operating activities [abstract] | |||||
| Interest paid, classified as operating activities | 
                                                30,000,000
                                                
                                                    
                                                        SEK
                                                    
                                                
                                             | — | 
                                                16,000,000
                                                
                                                    
                                                        SEK
                                                    
                                                
                                             | — | — | 
| Interest received, classified as operating activities | 
                                                18,000,000
                                                
                                                    
                                                        SEK
                                                    
                                                
                                             | — | 
                                                42,000,000
                                                
                                                    
                                                        SEK
                                                    
                                                
                                             | — | — | 
| Income taxes paid (refund), classified as operating activities | 
                                                72,000,000
                                                
                                                    
                                                        SEK
                                                    
                                                
                                             | — | 
                                                156,000,000
                                                
                                                    
                                                        SEK
                                                    
                                                
                                             | — | — | 
| Cash flows from (used in) operating activities | 
                                                239,000,000
                                                
                                                    
                                                        SEK
                                                    
                                                
                                             | — | 
                                                486,000,000
                                                
                                                    
                                                        SEK
                                                    
                                                
                                             | — | — | 
| Cash flows from (used in) investing activities [abstract] | |||||
| Purchase of property, plant and equipment, classified as investing activities | 
                                                19,000,000
                                                
                                                    
                                                        SEK
                                                    
                                                
                                             | — | 
                                                27,000,000
                                                
                                                    
                                                        SEK
                                                    
                                                
                                             | — | — | 
| Purchase of intangible assets, classified as investing activities | 
                                                25,000,000
                                                
                                                    
                                                        SEK
                                                    
                                                
                                             | — | 
                                                31,000,000
                                                
                                                    
                                                        SEK
                                                    
                                                
                                             | — | — | 
| Proceeds from sales of other long-term assets, classified as investing activities | 
                                                2,000,000
                                                
                                                    
                                                        SEK
                                                    
                                                
                                             | — | 
                                                -
                                                
                                                    
                                                        SEK
                                                    
                                                
                                             | — | — | 
| Purchase of other long-term assets, classified as investing activities | 
                                                2,000,000
                                                
                                                    
                                                        SEK
                                                    
                                                
                                             | — | 
                                                3,000,000
                                                
                                                    
                                                        SEK
                                                    
                                                
                                             | — | — | 
| Cash flows from (used in) investing activities | 
                                                44,000,000
                                                
                                                    
                                                        SEK
                                                    
                                                
                                             | — | 
                                                61,000,000
                                                
                                                    
                                                        SEK
                                                    
                                                
                                             | — | — | 
| Cash flows from (used in) financing activities [abstract] | |||||
| Proceeds from borrowings, classified as financing activities | 
                                                -
                                                
                                                    
                                                        SEK
                                                    
                                                
                                             | — | 
                                                136,000,000
                                                
                                                    
                                                        SEK
                                                    
                                                
                                             | — | — | 
| Repayments of borrowings, classified as financing activities | 
                                                27,000,000
                                                
                                                    
                                                        SEK
                                                    
                                                
                                             | — | 
                                                39,000,000
                                                
                                                    
                                                        SEK
                                                    
                                                
                                             | — | — | 
| Dividends paid, classified as financing activities | 
                                                149,000,000
                                                
                                                    
                                                        SEK
                                                    
                                                
                                             | — | 
                                                143,000,000
                                                
                                                    
                                                        SEK
                                                    
                                                
                                             | — | — | 
| Cash flows from (used in) financing activities | 
                                                176,000,000
                                                
                                                    
                                                        SEK
                                                    
                                                
                                             | — | 
                                                317,000,000
                                                
                                                    
                                                        SEK
                                                    
                                                
                                             | — | — | 
| Increase (decrease) in cash and cash equivalents before effect of exchange rate changes | 
                                                19,000,000
                                                
                                                    
                                                        SEK
                                                    
                                                
                                             | — | 
                                                108,000,000
                                                
                                                    
                                                        SEK
                                                    
                                                
                                             | — | — | 
| Effect of exchange rate changes on cash and cash equivalents [abstract] | |||||
| Effect of exchange rate changes on cash and cash equivalents | 
                                                12,000,000
                                                
                                                    
                                                        SEK
                                                    
                                                
                                             | — | 
                                                37,000,000
                                                
                                                    
                                                        SEK
                                                    
                                                
                                             | — | — | 
| Cash and cash equivalents | — | 
                                                132,000,000
                                                
                                                    
                                                        SEK
                                                    
                                                
                                             | — | 
                                                101,000,000
                                                
                                                    
                                                        SEK
                                                    
                                                
                                             | 
                                                30,000,000
                                                
                                                    
                                                        SEK
                                                    
                                                
                                             |