Statement Of Cash Flows [Abstract]
| Concept | 2024-01-01 to 2024-12-31 | As at 2024-12-31 | 2023-01-01 to 2023-12-31 | As at 2023-12-31 | As at 2022-12-31 | 
|---|---|---|---|---|---|
| Statement of cash flows [abstract] | |||||
| Cash flows from (used in) operating activities [abstract] | |||||
| Interest paid, classified as operating activities | 
                                                203,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | — | 
                                                242,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | — | — | 
| Cash flows from (used in) operating activities | 
                                                609,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | — | 
                                                27,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | — | — | 
| Cash flows from (used in) investing activities [abstract] | |||||
| Cash flows from losing control of subsidiaries or other businesses, classified as investing activities | 
                                                –
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | — | 
                                                350,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | — | — | 
| Proceeds from sales of property, plant and equipment, classified as investing activities | 
                                                2,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | — | 
                                                10,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | — | — | 
| Interest received, classified as investing activities | 
                                                11,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | — | 
                                                11,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | — | — | 
| Cash flows from (used in) investing activities | 
                                                257,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | — | 
                                                13,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | — | — | 
| Cash flows from (used in) financing activities [abstract] | |||||
| Proceeds from borrowings, classified as financing activities | 
                                                1,974,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | — | 
                                                101,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | — | — | 
| Repayments of borrowings, classified as financing activities | 
                                                2,251,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | — | 
                                                120,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | — | — | 
| Payments of lease liabilities, classified as financing activities | 
                                                51,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | — | 
                                                70,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | — | — | 
| Dividends paid, classified as financing activities | 
                                                16,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | — | 
                                                –
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | — | — | 
| Other inflows (outflows) of cash, classified as financing activities | 
                                                10,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | — | 
                                                21,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | — | — | 
| Cash flows from (used in) financing activities | 
                                                354,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | — | 
                                                68,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | — | — | 
| Increase (decrease) in cash and cash equivalents before effect of exchange rate changes | 
                                                2,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | — | 
                                                82,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | — | — | 
| Effect of exchange rate changes on cash and cash equivalents [abstract] | |||||
| Effect of exchange rate changes on cash and cash equivalents | 
                                                1,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | — | 
                                                1,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | — | — | 
| Cash and cash equivalents | — | 
                                                1,078,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | — | 
                                                1,081,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
                                                1,166,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             |