Statement Of Changes In Equity [Abstract]
| Concept | 2024-01-01 to 2024-12-31 | 2024-01-01 to 2024-12-31 | As at 2024-12-31 | As at 2024-12-31 | 2024-01-01 to 2024-12-31 | As at 2024-12-31 | As at 2024-12-31 | 2024-01-01 to 2024-12-31 | 2024-01-01 to 2024-12-31 | As at 2024-12-31 | 2024-01-01 to 2024-12-31 | As at 2024-12-31 | As at 2023-12-31 | 2023-01-01 to 2023-12-31 | 2023-01-01 to 2023-12-31 | As at 2023-12-31 | As at 2023-12-31 | 2023-01-01 to 2023-12-31 | 2023-01-01 to 2023-12-31 | 2023-01-01 to 2023-12-31 | As at 2023-12-31 | 2023-01-01 to 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 | 
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Statement of changes in equity [abstract] | ||||||||||||||||||||||||||||||
| Statement of changes in equity [line items] | ||||||||||||||||||||||||||||||
| Equity | — | — | 
                                                2,745,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
                                                2,198,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | — | 
                                                396,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
                                                53,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | — | — | 
                                                5,307,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | — | 
                                                85,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
                                                115,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | — | — | 
                                                4,989,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
                                                2,498,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | — | — | — | 
                                                2,198,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | — | 
                                                11,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
                                                396,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
                                                3,711,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
                                                95,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
                                                2,198,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
                                                1,232,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
                                                396,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
                                                20,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
| Changes in equity [abstract] | ||||||||||||||||||||||||||||||
| Comprehensive income [abstract] | ||||||||||||||||||||||||||||||
| Profit (loss) | 
                                                –
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
                                                –
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | — | — | 
                                                –
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | — | — | 
                                                264,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
                                                264,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | — | 
                                                –
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | — | — | 
                                                1,270,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
                                                –
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | — | — | 
                                                1,270,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
                                                –
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
                                                –
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | — | 
                                                –
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | 
| Other comprehensive income | 
                                                –
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
                                                –
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | — | — | 
                                                42,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | — | — | 
                                                –
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
                                                72,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | — | 
                                                30,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | — | — | 
                                                8,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
                                                20,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | — | — | 
                                                –
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
                                                –
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
                                                28,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | — | 
                                                –
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | 
| Comprehensive income | 
                                                –
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
                                                –
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | — | — | 
                                                42,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | — | — | 
                                                264,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
                                                336,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | — | 
                                                30,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | — | — | 
                                                1,278,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
                                                20,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | — | — | 
                                                1,267,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
                                                –
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
                                                31,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | — | 
                                                –
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | 
| Dividends recognised as distributions to owners | 
                                                –
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
                                                –
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | — | — | 
                                                –
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | — | — | 
                                                16,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
                                                16,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | — | 
                                                –
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | — | — | 
                                                –
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
                                                –
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | — | — | 
                                                –
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
                                                –
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
                                                –
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | — | 
                                                –
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | 
| Increase (decrease) through other changes, equity | — | — | — | — | — | — | — | — | — | — | — | — | — | 
                                                –
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
                                                –
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | — | — | 
                                                3,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
                                                –
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
                                                3,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | — | 
                                                –
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | — | — | — | — | — | — | — | — |