Statement Of Cash Flows [Abstract]
| Concept | 
                                    
                                        2024-01-01 to 2024-12-31  | 
                            
                                
                                    
                                        2023-01-01 to 2023-12-31  | 
                            
                        
|---|---|---|
| Statement of cash flows [abstract] | ||
| Cash flows from (used in) operating activities [abstract] | ||
| Profit (loss) | 
                                        
                                             
                                                2,403,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    
                                        
                                             
                                                2,697,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             
                                        
                                     | 
                                
                            
| Adjustments to reconcile profit (loss) [abstract] | ||
| Adjustments for income tax expense | 
                                        
                                             
                                                1,013,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    
                                        
                                             
                                                847,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             
                                        
                                     | 
                                
                            
| Adjustments for fair value losses (gains) | 
                                        
                                             
                                                1,946,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    
                                        
                                             
                                                463,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             
                                        
                                     | 
                                
                            
| Other adjustments for non-cash items | 
                                        
                                             
                                                750,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    
                                        
                                             
                                                676,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             
                                        
                                     | 
                                
                            
| Interest paid, classified as operating activities | 
                                        
                                             
                                                10,419,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    
                                        
                                             
                                                9,812,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             
                                        
                                     | 
                                
                            
| Interest received, classified as operating activities | 
                                        
                                             
                                                17,016,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    
                                        
                                             
                                                16,183,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             
                                        
                                     | 
                                
                            
| Cash flows from (used in) operating activities | 
                                        
                                             
                                                10,795,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    
                                        
                                             
                                                9,028,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             
                                        
                                     | 
                                
                            
| Cash flows from (used in) investing activities [abstract] | ||
| Proceeds from sales of property, plant and equipment, classified as investing activities | 
                                        
                                             
                                                48,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    
                                        
                                             
                                                111,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             
                                        
                                     | 
                                
                            
| Purchase of property, plant and equipment, classified as investing activities | 
                                        
                                             
                                                312,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    
                                        
                                             
                                                209,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             
                                        
                                     | 
                                
                            
| Purchase of intangible assets, classified as investing activities | 
                                        
                                             
                                                140,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    
                                        
                                             
                                                81,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             
                                        
                                     | 
                                
                            
| Other inflows (outflows) of cash, classified as investing activities | 
                                        
                                             
                                                0
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    
                                        
                                             
                                                28,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             
                                        
                                     | 
                                
                            
| Cash flows from (used in) investing activities | 
                                        
                                             
                                                4,811,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    
                                        
                                             
                                                1,722,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             
                                        
                                     | 
                                
                            
| Cash flows from (used in) financing activities [abstract] | ||
| Payments to acquire or redeem entity's shares | 
                                        
                                             
                                                500,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    
                                        
                                             
                                                500,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             
                                        
                                     | 
                                
                            
| Proceeds from borrowings, classified as financing activities | 
                                        
                                             
                                                42,885,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    
                                        
                                             
                                                49,985,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             
                                        
                                     | 
                                
                            
| Repayments of borrowings, classified as financing activities | 
                                        
                                             
                                                36,980,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    
                                        
                                             
                                                43,196,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             
                                        
                                     | 
                                
                            
| Payments of lease liabilities, classified as financing activities | 
                                        
                                             
                                                112,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    
                                        
                                             
                                                138,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             
                                        
                                     | 
                                
                            
| Other inflows (outflows) of cash, classified as financing activities | 
                                        
                                             
                                                1,488,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    
                                        
                                             
                                                2,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             
                                        
                                     | 
                                
                            
| Cash flows from (used in) financing activities | 
                                        
                                             
                                                6,162,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    
                                        
                                             
                                                3,218,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             
                                        
                                     | 
                                
                            
| Increase (decrease) in cash and cash equivalents before effect of exchange rate changes | 
                                        
                                             
                                                9,444,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    
                                        
                                             
                                                7,533,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             
                                        
                                     | 
                                
                            
| Effect of exchange rate changes on cash and cash equivalents [abstract] | ||
| Effect of exchange rate changes on cash and cash equivalents | 
                                        
                                             
                                                19,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    
                                        
                                             
                                                22,000,000
                                                
                                                    
                                                        EUR
                                                    
                                                
                                             
                                        
                                     |