Subclassifications Of Assets, Liabilities And Equities [Abstract]
| Concept | 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 | 
                                                -
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
                                                5 320
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
| Intangible assets and goodwill [abstract] | ||
| Intangible assets other than goodwill [abstract] | ||
| Intangible assets other than goodwill | 
                                                -
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
                                                2 065
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
| Goodwill | 
                                                -
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
                                                7 867
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
| Investment property [abstract] | ||
| Investment property | 
                                                -
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
                                                562,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
| Investments accounted for using equity method [abstract] | ||
| Investments accounted for using equity method | 
                                                -
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
                                                376,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
| Miscellaneous non-current assets [abstract] | ||
| Other non-current assets | 
                                                -
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
                                                1 319
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
| Trade and other current receivables [abstract] | ||
| Current trade receivables | 
                                                2,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
                                                855,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
| Classes of current inventories [abstract] | ||
| Current inventories | 
                                                4,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
                                                3 645
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
| Classes of current inventories, alternative [abstract] | ||
| Cash and cash equivalents [abstract] | ||
| Cash and cash equivalents | 
                                                31,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
                                                2 560
                                                
                                                    
                                                        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 | 
                                                18 459
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
                                                110,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
| Miscellaneous current assets [abstract] | ||
| Other current assets | 
                                                4,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
                                                1 598
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
| Classes of other provisions [abstract] | ||
| Other provisions [abstract] | ||
| Other non-current provisions | 
                                                -
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
                                                516,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
| Other current provisions | 
                                                25,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
                                                229,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
| Trade and other current payables [abstract] | ||
| Current trade payables | 
                                                8,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
                                                6 531
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
| Miscellaneous non-current liabilities [abstract] | ||
| Other non-current liabilities | 
                                                -
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
                                                421,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
| Miscellaneous current liabilities [abstract] | ||
| Other current liabilities | 
                                                117,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
                                                3 074
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
| Issued capital [abstract] | ||
| Issued capital | 
                                                149,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
                                                149,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
| Net assets (liabilities) [abstract] | ||
| Assets | 
                                                18 500
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
                                                32 427
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
| Net current assets (liabilities) [abstract] | ||
| Current assets | 
                                                18 500
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
                                                8 942
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
| Current liabilities | 
                                                23 864
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
                                                12 708
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
| Assets less current liabilities [abstract] |