Statement Of Financial Position [Abstract]
| Concept | As at 2024-12-31 | As at 2024-12-31 | As at 2024-12-31 | As at 2024-12-31 | As at 2024-12-31 | As at 2024-12-31 | As at 2024-12-31 | As at 2024-12-31 | As at 2024-12-31 | As at 2023-12-31 | As at 2023-12-31 | As at 2023-12-31 | As at 2023-12-31 | As at 2023-12-31 | As at 2023-12-31 | As at 2023-12-31 | As at 2023-12-31 | As at 2023-12-31 | As at 2022-12-31 | As at 2022-12-31 | As at 2022-12-31 | As at 2022-12-31 | As at 2022-12-31 | As at 2022-12-31 | As at 2022-12-31 | As at 2022-12-31 | As at 2022-12-31 | 
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Statement of financial position [abstract] | |||||||||||||||||||||||||||
| Assets [abstract] | |||||||||||||||||||||||||||
| Property, plant and equipment | — | — | — | — | — | — | — | — | 
                                                33,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
                                                90,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 
| Right-of-use assets | — | — | — | — | — | — | — | — | 
                                                19,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
                                                51,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 
| Goodwill | — | — | — | — | — | — | — | — | 
                                                465,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
                                                468,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 
| Intangible assets other than goodwill | — | — | — | — | — | — | — | — | 
                                                163,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
                                                133,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 
| Investments accounted for using equity method | — | — | — | — | — | — | — | — | 
                                                0
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
                                                2,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 
| Deferred tax assets | — | — | — | — | — | — | — | — | 
                                                11,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
                                                20,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 
| Cash and cash equivalents | — | — | — | — | — | — | — | — | 
                                                30,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
                                                133,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | 
                                                167,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | 
| Assets | — | — | — | — | — | — | — | — | 
                                                1 720
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
                                                1 665
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 
| Equity and liabilities [abstract] | |||||||||||||||||||||||||||
| Equity [abstract] | |||||||||||||||||||||||||||
| Issued capital | — | — | — | — | — | — | — | — | 
                                                5,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
                                                4,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 
| Equity attributable to owners of parent | — | — | — | — | — | — | — | — | 
                                                238,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
                                                6,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 
| Non-controlling interests | — | — | — | — | — | — | — | — | 
                                                0
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
                                                0
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 
| Equity | 
                                                500,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
                                                1 115
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
                                                246,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
                                                5,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
                                                -
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
                                                51,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
                                                238,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
                                                177,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
                                                238,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
                                                6,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
                                                500,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
                                                833,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
                                                167,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
                                                -
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
                                                231,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
                                                4,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
                                                63,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
                                                6,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
                                                320,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
                                                500,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
                                                173,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
                                                -
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
                                                232,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
                                                549,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
                                                4,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
                                                41,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
                                                320,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
| Liabilities [abstract] | |||||||||||||||||||||||||||
| Deferred tax liabilities | — | — | — | — | — | — | — | — | 
                                                13,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
                                                3,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 
| Liabilities included in disposal groups classified as held for sale | — | — | — | — | — | — | — | — | 
                                                184,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
                                                0
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 
| Liabilities | — | — | — | — | — | — | — | — | 
                                                1 958
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
                                                1 658
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 
| Equity and liabilities | — | — | — | — | — | — | — | — | 
                                                1 720
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
                                                1 665
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — |