Disclosure Of Income Tax [Text Block]
| Concept | As at 2024-12-31 | 2024-01-01 to 2024-12-31 | As at 2023-12-31 | 2023-01-01 to 2023-12-31 | 
|---|---|---|---|---|
| Disclosure of income tax [text block] | — | — | — | — | 
| Major components of tax expense (income) [abstract] | ||||
| Tax expense (income) | — | 
                                                2 683
                                                
                                                    
                                                        SEK
                                                    
                                                
                                             | — | 
                                                2 777
                                                
                                                    
                                                        SEK
                                                    
                                                
                                             | 
| Income tax relating to components of other comprehensive income [abstract] | ||||
| Income tax relating to remeasurements of defined benefit plans included in other comprehensive income | — | 
                                                45,000,000
                                                
                                                    
                                                        SEK
                                                    
                                                
                                             | — | 
                                                81,000,000
                                                
                                                    
                                                        SEK
                                                    
                                                
                                             | 
| Disclosure of temporary difference, unused tax losses and unused tax credits [text block] | — | — | — | — | 
| Disclosure of temporary difference, unused tax losses and unused tax credits [abstract] | ||||
| Disclosure of temporary difference, unused tax losses and unused tax credits [line items] | ||||
| Deferred tax assets and liabilities [abstract] | ||||
| Deferred tax assets | 
                                                1 576
                                                
                                                    
                                                        SEK
                                                    
                                                
                                             | — | 
                                                1 509
                                                
                                                    
                                                        SEK
                                                    
                                                
                                             | — | 
| Deferred tax liabilities | 
                                                1 737
                                                
                                                    
                                                        SEK
                                                    
                                                
                                             | — | 
                                                922,000,000
                                                
                                                    
                                                        SEK
                                                    
                                                
                                             | — | 
| Reconciliation of accounting profit multiplied by applicable tax rates [abstract] |