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] | |||||
| Income taxes paid (refund), classified as operating activities | 
                                                3 039
                                                
                                                    
                                                        SEK
                                                    
                                                
                                             | — | 
                                                3 531
                                                
                                                    
                                                        SEK
                                                    
                                                
                                             | — | — | 
| Cash flows from (used in) operating activities | 
                                                10 460
                                                
                                                    
                                                        SEK
                                                    
                                                
                                             | — | 
                                                7 143
                                                
                                                    
                                                        SEK
                                                    
                                                
                                             | — | — | 
| Cash flows from (used in) investing activities [abstract] | |||||
| Cash flows used in obtaining control of subsidiaries or other businesses, classified as investing activities | 
                                                9 658
                                                
                                                    
                                                        SEK
                                                    
                                                
                                             | — | 
                                                3 666
                                                
                                                    
                                                        SEK
                                                    
                                                
                                             | — | — | 
| Proceeds from sales of intangible assets, classified as investing activities | 
                                                -
                                                
                                                    
                                                        SEK
                                                    
                                                
                                             | — | 
                                                3,000,000
                                                
                                                    
                                                        SEK
                                                    
                                                
                                             | — | — | 
| Purchase of intangible assets, classified as investing activities | 
                                                966,000,000
                                                
                                                    
                                                        SEK
                                                    
                                                
                                             | — | 
                                                643,000,000
                                                
                                                    
                                                        SEK
                                                    
                                                
                                             | — | — | 
| Other inflows (outflows) of cash, classified as investing activities | 
                                                192,000,000
                                                
                                                    
                                                        SEK
                                                    
                                                
                                             | — | 
                                                467,000,000
                                                
                                                    
                                                        SEK
                                                    
                                                
                                             | — | — | 
| Cash flows from (used in) investing activities | 
                                                11 690
                                                
                                                    
                                                        SEK
                                                    
                                                
                                             | — | 
                                                5 237
                                                
                                                    
                                                        SEK
                                                    
                                                
                                             | — | — | 
| Cash flows from (used in) financing activities [abstract] | |||||
| Proceeds from borrowings, classified as financing activities | 
                                                12 164
                                                
                                                    
                                                        SEK
                                                    
                                                
                                             | — | 
                                                7 786
                                                
                                                    
                                                        SEK
                                                    
                                                
                                             | — | — | 
| Repayments of borrowings, classified as financing activities | 
                                                5 295
                                                
                                                    
                                                        SEK
                                                    
                                                
                                             | — | 
                                                5 922
                                                
                                                    
                                                        SEK
                                                    
                                                
                                             | — | — | 
| Payments of lease liabilities, classified as financing activities | 
                                                667,000,000
                                                
                                                    
                                                        SEK
                                                    
                                                
                                             | — | 
                                                573,000,000
                                                
                                                    
                                                        SEK
                                                    
                                                
                                             | — | — | 
| Cash flows from (used in) financing activities | 
                                                1 899
                                                
                                                    
                                                        SEK
                                                    
                                                
                                             | — | 
                                                2 641
                                                
                                                    
                                                        SEK
                                                    
                                                
                                             | — | — | 
| Increase (decrease) in cash and cash equivalents before effect of exchange rate changes | 
                                                669,000,000
                                                
                                                    
                                                        SEK
                                                    
                                                
                                             | — | 
                                                735,000,000
                                                
                                                    
                                                        SEK
                                                    
                                                
                                             | — | — | 
| Effect of exchange rate changes on cash and cash equivalents [abstract] | |||||
| Effect of exchange rate changes on cash and cash equivalents | 
                                                109,000,000
                                                
                                                    
                                                        SEK
                                                    
                                                
                                             | — | 
                                                190,000,000
                                                
                                                    
                                                        SEK
                                                    
                                                
                                             | — | — | 
| Cash and cash equivalents | — | 
                                                7 179
                                                
                                                    
                                                        SEK
                                                    
                                                
                                             | — | 
                                                6 401
                                                
                                                    
                                                        SEK
                                                    
                                                
                                             | 
                                                7 326
                                                
                                                    
                                                        SEK
                                                    
                                                
                                             |