Statement Of Changes In Net Assets Available For Benefits [Abstract]
| Concept | 2024-01-01 to 2024-12-31 | 2023-01-01 to 2023-12-31 | 
|---|---|---|
| Statement of changes in net assets available for benefits [abstract] | ||
| Reconciliation of changes in net assets available for benefits [abstract] | ||
| Changes in net assets available for benefits [abstract] | ||
| Other income | 
                                                84,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
                                                269,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
| Administrative expenses | 
                                                384,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
                                                306,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
| Other expense, by function | 
                                                5,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
                                                160,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
| Tax expense (income) | 
                                                202,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
                                                207,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             |