Statement Of Cash Flows [Abstract]
| Concept | 2023-01-01 to 2023-12-31 | As at 2023-12-31 | 2023-01-01 to 2023-12-31 | 2023-01-01 to 2023-12-31 | 2023-01-01 to 2023-12-31 | As at 2022-12-31 | 2022-01-01 to 2022-12-31 | 2022-01-01 to 2022-12-31 | 2022-01-01 to 2022-12-31 | 2022-01-01 to 2022-12-31 | 
|---|---|---|---|---|---|---|---|---|---|---|
| Statement of cash flows [abstract] | ||||||||||
| Cash flows from (used in) operating activities [abstract] | ||||||||||
| Profit (loss) | 
                                                8 564
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | — | 
                                                6 621
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
                                                1 943
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
                                                1 943
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | — | 
                                                141,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
                                                413,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
                                                141,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
                                                272,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
| Adjustments to reconcile profit (loss) [abstract] | ||||||||||
| Adjustments for depreciation and amortisation expense | 
                                                6,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | — | — | — | — | — | — | 
                                                6,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | — | — | 
| Adjustments for share-based payments | 
                                                -
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | — | — | — | — | — | — | 
                                                1,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | — | — | 
| Adjustments for losses (gains) on disposal of non-current assets | 
                                                1,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | — | — | — | — | — | — | 
                                                -
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | — | — | 
| Other adjustments for which cash effects are investing or financing cash flow | 
                                                -
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | — | — | — | — | — | — | 
                                                139,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | — | — | 
| Cash flows from (used in) operating activities | 
                                                660,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | — | — | — | — | — | — | 
                                                1 166
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | — | — | 
| Cash flows from (used in) investing activities [abstract] | ||||||||||
| Cash flows from (used in) investing activities | 
                                                144,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | — | — | — | — | — | — | 
                                                111,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | — | — | 
| Cash flows from (used in) financing activities [abstract] | ||||||||||
| Proceeds from borrowings, classified as financing activities | 
                                                1,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | — | — | — | — | — | — | 
                                                54,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | — | — | 
| Repayments of borrowings, classified as financing activities | 
                                                47,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | — | — | — | — | — | — | 
                                                48,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | — | — | 
| Cash flows from (used in) financing activities | 
                                                165,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | — | — | — | — | — | — | 
                                                1 315
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | — | — | 
| Increase (decrease) in cash and cash equivalents after effect of exchange rate changes | 
                                                534,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | — | — | — | — | — | — | 
                                                59,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | — | — | 
| Cash and cash equivalents | — | 
                                                31,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | — | — | — | 
                                                2 560
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | — | — | — | — |