Subclassifications Of Assets, Liabilities And Equities [Abstract]
| Concept | As at 2024-12-31 | As at 2023-12-31 | As at 2022-12-31 | 
|---|---|---|---|
| Subclassifications of assets, liabilities and equities [abstract] | |||
| Property, plant and equipment [abstract] | |||
| Property, plant and equipment | 
                                                33,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
                                                90,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | — | 
| Intangible assets and goodwill [abstract] | |||
| Intangible assets other than goodwill [abstract] | |||
| Intangible assets other than goodwill | 
                                                163,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
                                                133,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | — | 
| Goodwill | 
                                                465,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
                                                468,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | — | 
| Investments accounted for using equity method [abstract] | |||
| Investments accounted for using equity method | 
                                                0
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
                                                2,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | — | 
| Miscellaneous non-current assets [abstract] | |||
| Non-current investments other than investments accounted for using equity method | 
                                                15,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
                                                19,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | — | 
| Trade and other current receivables [abstract] | |||
| Trade and other current receivables | 
                                                401,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
                                                274,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | — | 
| Current prepayments and current accrued income including current contract assets [abstract] | |||
| Current accrued income including current contract assets [abstract] | |||
| Current contract assets | 
                                                15,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
                                                20,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | — | 
| Categories of non-current financial assets [abstract] | |||
| Non-current financial assets | 
                                                45,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
                                                35,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | — | 
| Classes of current inventories [abstract] | |||
| Current inventories | 
                                                182,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
                                                204,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | — | 
| Classes of current inventories, alternative [abstract] | |||
| Cash and cash equivalents [abstract] | |||
| Cash and cash equivalents | 
                                                30,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
                                                133,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
                                                167,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
| Non-current assets or disposal groups classified as held for sale or as held for distribution to owners [abstract] | |||
| Non-current assets or disposal groups classified as held for sale | 
                                                160,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
                                                1,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | — | 
| Classes of other provisions [abstract] | |||
| Other provisions [abstract] | |||
| Other non-current provisions | 
                                                32,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
                                                27,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | — | 
| Other current provisions | 
                                                65,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
                                                32,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | — | 
| Borrowings [abstract] | |||
| Non-current portion of non-current borrowings | 
                                                477,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
                                                391,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | — | 
| Current borrowings and current portion of non-current borrowings [abstract] | |||
| Current borrowings | 
                                                2,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
                                                92,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | — | 
| Non-current portion of non-current borrowings, by type [abstract] | |||
| Trade and other non-current payables [abstract] | |||
| Non-current accruals and non-current deferred income including non-current contract liabilities [abstract] | |||
| Non-current deferred income including non-current contract liabilities [abstract] | |||
| Non-current contract liabilities [abstract] | |||
| Non-current contract liabilities | 
                                                1,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
                                                0
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | — | 
| Trade and other current payables [abstract] | |||
| Current accruals and current deferred income including current contract liabilities [abstract] | |||
| Current deferred income including current contract liabilities [abstract] | |||
| Current contract liabilities [abstract] | |||
| Current contract liabilities | 
                                                13,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
                                                10,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | — | 
| Accruals classified as current | — | — | — | 
| Short-term employee benefits accruals | 
                                                64,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
                                                67,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | — | 
| Trade and other current payables | 
                                                610,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
                                                540,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | — | 
| Issued capital [abstract] | |||
| Issued capital | 
                                                5,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
                                                4,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | — | 
| Accumulated other comprehensive income [abstract] | |||
| Reserve of exchange differences on translation | 
                                                51,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
                                                63,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | — | 
| Net assets (liabilities) [abstract] | |||
| Assets | 
                                                1 720
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
                                                1 665
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | — | 
| Liabilities | 
                                                1 958
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
                                                1 658
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | — | 
| Net current assets (liabilities) [abstract] | |||
| Current assets | 
                                                974,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
                                                859,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | — | 
| Current liabilities | 
                                                1 255
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
                                                1 017
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | — | 
| Assets less current liabilities [abstract] |