Subclassifications Of Assets, Liabilities And Equities [Abstract]
| Concept | As at 2024-12-31 | As at 2023-12-31 | As at 2022-12-31 | 
|---|---|---|---|
| Subclassifications of assets, liabilities and equities [abstract] | |||
| Property, plant and equipment [abstract] | |||
| Property, plant and equipment | 
                                                146,000,000
                                                
                                                    
                                                        SEK
                                                    
                                                
                                             | 
                                                148,000,000
                                                
                                                    
                                                        SEK
                                                    
                                                
                                             | — | 
| Intangible assets and goodwill [abstract] | |||
| Intangible assets other than goodwill [abstract] | |||
| Intangible assets other than goodwill | 
                                                87,000,000
                                                
                                                    
                                                        SEK
                                                    
                                                
                                             | 
                                                63,000,000
                                                
                                                    
                                                        SEK
                                                    
                                                
                                             | — | 
| Goodwill | 
                                                22,000,000
                                                
                                                    
                                                        SEK
                                                    
                                                
                                             | 
                                                22,000,000
                                                
                                                    
                                                        SEK
                                                    
                                                
                                             | — | 
| Trade and other non-current receivables [abstract] | |||
| Other non-current receivables | 
                                                5,000,000
                                                
                                                    
                                                        SEK
                                                    
                                                
                                             | 
                                                4,000,000
                                                
                                                    
                                                        SEK
                                                    
                                                
                                             | — | 
| Miscellaneous non-current assets [abstract] | |||
| Non-current derivative financial assets | 
                                                0
                                                
                                                    
                                                        SEK
                                                    
                                                
                                             | 
                                                10,000,000
                                                
                                                    
                                                        SEK
                                                    
                                                
                                             | — | 
| Trade and other current receivables [abstract] | |||
| Current prepayments and current accrued income other than current contract assets [abstract] | |||
| Current prepayments [abstract] | |||
| Current prepaid expenses | 
                                                33,000,000
                                                
                                                    
                                                        SEK
                                                    
                                                
                                             | 
                                                32,000,000
                                                
                                                    
                                                        SEK
                                                    
                                                
                                             | — | 
| Current prepayments and current accrued income including current contract assets [abstract] | |||
| Trade and other receivables [abstract] | |||
| Trade receivables | 
                                                227,000,000
                                                
                                                    
                                                        SEK
                                                    
                                                
                                             | 
                                                193,000,000
                                                
                                                    
                                                        SEK
                                                    
                                                
                                             | — | 
| Other receivables | 
                                                20,000,000
                                                
                                                    
                                                        SEK
                                                    
                                                
                                             | 
                                                27,000,000
                                                
                                                    
                                                        SEK
                                                    
                                                
                                             | — | 
| Classes of current inventories [abstract] | |||
| Current inventories | 
                                                339,000,000
                                                
                                                    
                                                        SEK
                                                    
                                                
                                             | 
                                                302,000,000
                                                
                                                    
                                                        SEK
                                                    
                                                
                                             | — | 
| Classes of current inventories, alternative [abstract] | |||
| Cash and cash equivalents [abstract] | |||
| Cash and cash equivalents | 
                                                132,000,000
                                                
                                                    
                                                        SEK
                                                    
                                                
                                             | 
                                                101,000,000
                                                
                                                    
                                                        SEK
                                                    
                                                
                                             | 
                                                30,000,000
                                                
                                                    
                                                        SEK
                                                    
                                                
                                             | 
| Classes of other provisions [abstract] | |||
| Warranty provision [abstract] | |||
| Non-current warranty provision | 
                                                7,000,000
                                                
                                                    
                                                        SEK
                                                    
                                                
                                             | 
                                                10,000,000
                                                
                                                    
                                                        SEK
                                                    
                                                
                                             | — | 
| Current warranty provision | 
                                                24,000,000
                                                
                                                    
                                                        SEK
                                                    
                                                
                                             | 
                                                22,000,000
                                                
                                                    
                                                        SEK
                                                    
                                                
                                             | — | 
| Borrowings [abstract] | |||
| Non-current portion of non-current borrowings | 
                                                0
                                                
                                                    
                                                        SEK
                                                    
                                                
                                             | 
                                                0
                                                
                                                    
                                                        SEK
                                                    
                                                
                                             | — | 
| Current borrowings and current portion of non-current borrowings [abstract] | |||
| Current portion of non-current borrowings | 
                                                33,000,000
                                                
                                                    
                                                        SEK
                                                    
                                                
                                             | 
                                                41,000,000
                                                
                                                    
                                                        SEK
                                                    
                                                
                                             | — | 
| Non-current portion of non-current borrowings, by type [abstract] | |||
| Trade and other current payables [abstract] | |||
| Current accruals and current deferred income including current contract liabilities [abstract] | |||
| Current accruals and current deferred income including current contract liabilities | 
                                                74,000,000
                                                
                                                    
                                                        SEK
                                                    
                                                
                                             | 
                                                50,000,000
                                                
                                                    
                                                        SEK
                                                    
                                                
                                             | — | 
| Trade and other current payables | 
                                                83,000,000
                                                
                                                    
                                                        SEK
                                                    
                                                
                                             | 
                                                82,000,000
                                                
                                                    
                                                        SEK
                                                    
                                                
                                             | — | 
| Miscellaneous current liabilities [abstract] | |||
| Other current liabilities | 
                                                37,000,000
                                                
                                                    
                                                        SEK
                                                    
                                                
                                             | 
                                                34,000,000
                                                
                                                    
                                                        SEK
                                                    
                                                
                                             | — | 
| Miscellaneous liabilities [abstract] | |||
| Derivative financial liabilities | 
                                                0
                                                
                                                    
                                                        SEK
                                                    
                                                
                                             | 
                                                0
                                                
                                                    
                                                        SEK
                                                    
                                                
                                             | — | 
| Issued capital [abstract] | |||
| Issued capital | 
                                                21,000,000
                                                
                                                    
                                                        SEK
                                                    
                                                
                                             | 
                                                21,000,000
                                                
                                                    
                                                        SEK
                                                    
                                                
                                             | — | 
| Retained earnings [abstract] | |||
| Retained earnings | 
                                                643,000,000
                                                
                                                    
                                                        SEK
                                                    
                                                
                                             | 
                                                571,000,000
                                                
                                                    
                                                        SEK
                                                    
                                                
                                             | — | 
| Accumulated other comprehensive income [abstract] | |||
| Reserve of exchange differences on translation | 
                                                23,000,000
                                                
                                                    
                                                        SEK
                                                    
                                                
                                             | 
                                                14,000,000
                                                
                                                    
                                                        SEK
                                                    
                                                
                                             | — | 
| Miscellaneous equity [abstract] | |||
| Additional paid-in capital | 
                                                6,000,000
                                                
                                                    
                                                        SEK
                                                    
                                                
                                             | 
                                                6,000,000
                                                
                                                    
                                                        SEK
                                                    
                                                
                                             | — | 
| Net assets (liabilities) [abstract] | |||
| Assets | 
                                                1 112
                                                
                                                    
                                                        SEK
                                                    
                                                
                                             | 
                                                1 012
                                                
                                                    
                                                        SEK
                                                    
                                                
                                             | — | 
| Liabilities | 
                                                380,000,000
                                                
                                                    
                                                        SEK
                                                    
                                                
                                             | 
                                                369,000,000
                                                
                                                    
                                                        SEK
                                                    
                                                
                                             | — | 
| Net current assets (liabilities) [abstract] | |||
| Current assets | 
                                                765,000,000
                                                
                                                    
                                                        SEK
                                                    
                                                
                                             | 
                                                667,000,000
                                                
                                                    
                                                        SEK
                                                    
                                                
                                             | — | 
| Current liabilities | 
                                                283,000,000
                                                
                                                    
                                                        SEK
                                                    
                                                
                                             | 
                                                261,000,000
                                                
                                                    
                                                        SEK
                                                    
                                                
                                             | — | 
| Assets less current liabilities [abstract] |