Statement Of Comprehensive Income [Abstract]
| Concept | 2024-01-01 to 2024-12-31 | 2024-01-01 to 2024-12-31 | 2024-01-01 to 2024-12-31 | 2024-01-01 to 2024-12-31 | 2024-01-01 to 2024-12-31 | 2024-01-01 to 2024-12-31 | 2023-01-01 to 2023-12-31 | 2023-01-01 to 2023-12-31 | 2023-01-01 to 2023-12-31 | 2023-01-01 to 2023-12-31 | 2023-01-01 to 2023-12-31 | 2023-01-01 to 2023-12-31 | 
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Statement of comprehensive income [abstract] | ||||||||||||
| Profit (loss) | 
                                                –
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
                                                264,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
                                                –
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
                                                –
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
                                                –
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
                                                264,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
                                                –
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
                                                1,270,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
                                                –
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
                                                1,270,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
                                                –
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
                                                –
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
| Other comprehensive income [abstract] | ||||||||||||
| Components of other comprehensive income that will not be reclassified to profit or loss, before tax [abstract] | ||||||||||||
| Other comprehensive income, before tax, gains (losses) on remeasurements of defined benefit plans | — | 
                                                32,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | — | — | — | — | — | 
                                                28,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | — | — | — | — | 
| Income tax relating to components of other comprehensive income that will not be reclassified to profit or loss [abstract] | ||||||||||||
| Income tax relating to remeasurements of defined benefit plans included in other comprehensive income | — | 
                                                2,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | — | — | — | — | — | 
                                                8,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | — | — | — | — | 
| Other comprehensive income | 
                                                –
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
                                                72,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
                                                –
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
                                                42,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
                                                30,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
                                                –
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
                                                –
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
                                                8,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
                                                20,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
                                                –
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
                                                –
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
                                                28,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
| Comprehensive income | 
                                                –
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
                                                336,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
                                                –
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
                                                42,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
                                                30,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
                                                264,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
                                                –
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
                                                1,278,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
                                                20,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
                                                1,267,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
                                                –
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
                                                31,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
| Comprehensive income attributable to [abstract] | ||||||||||||
| Comprehensive income, attributable to owners of parent | — | 
                                                336,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | — | — | — | — | — | 
                                                1,278,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | — | — | — | — |