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] | ||
| Investment income | 
                                                6,351,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
                                                4,137,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
| Other income | 
                                                107,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
                                                372,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
| Other expense, by function | 
                                                821,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
                                                927,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
| Tax expense (income) | 
                                                383,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
                                                275,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
| Profit (loss) on disposal of investments and changes in value of investments | 
                                                4,459,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             | 
                                                4,747,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             |