v3.26.1
Other Assets and Receivable - Summary of information about right of use assets (Detail) - EUR (€)
€ in Millions
 12 Months Ended
Dec. 31, 2025
Dec. 31, 2024
Disclosure of quantitative information about right-of-use assets [line items]    
On January 1 € 162 € 150
Additions 19 34
Disposals (1) (5)
Modification of lease contracts 1 6
Depreciation through income statement (30) (30)
Net exchange differences (10) 7
Other (5)  
On December 31 137 162
Gross carrying amount [member]    
Disclosure of quantitative information about right-of-use assets [line items]    
On January 1 314  
On December 31 279 314
Accumulated depreciation and amortisation [member]    
Disclosure of quantitative information about right-of-use assets [line items]    
On January 1 (152)  
On December 31 (143) (152)
Real estate held for own use [member]    
Disclosure of quantitative information about right-of-use assets [line items]    
On January 1 154 138
Additions 15 31
Disposals (1) (5)
Modification of lease contracts 1 6
Depreciation through income statement (24) (22)
Net exchange differences (9) 6
Other (5)  
On December 31 131 154
Real estate held for own use [member] | Gross carrying amount [member]    
Disclosure of quantitative information about right-of-use assets [line items]    
On January 1 284  
On December 31 253 284
Real estate held for own use [member] | Accumulated depreciation and amortisation [member]    
Disclosure of quantitative information about right-of-use assets [line items]    
On January 1 (130)  
On December 31 (122) (130)
Equipment 1 [member]    
Disclosure of quantitative information about right-of-use assets [line items]    
On January 1 4 10
Additions 1  
Depreciation through income statement (4) (6)
On December 31 1 4
Equipment 1 [member] | Gross carrying amount [member]    
Disclosure of quantitative information about right-of-use assets [line items]    
On January 1 21  
On December 31 15 21
Equipment 1 [member] | Accumulated depreciation and amortisation [member]    
Disclosure of quantitative information about right-of-use assets [line items]    
On January 1 (16)  
On December 31 (14) (16)
Other Assets [Member]    
Disclosure of quantitative information about right-of-use assets [line items]    
On January 1 4 3
Additions 3 3
Depreciation through income statement (2) (2)
On December 31 5 4
Other Assets [Member] | Gross carrying amount [member]    
Disclosure of quantitative information about right-of-use assets [line items]    
On January 1 10  
On December 31 11 10
Other Assets [Member] | Accumulated depreciation and amortisation [member]    
Disclosure of quantitative information about right-of-use assets [line items]    
On January 1 (5)  
On December 31 € (7) € (5)