v3.26.1
Tangible assets - Disclosure of detailed information about property, plant and equipment (Details) - EUR (€)
€ in Millions
Dec. 31, 2025
Dec. 31, 2024
Dec. 31, 2023
Property, plant and equipment for own use      
Carrying amount € 26,416 € 31,212 € 32,926
For own use | Property, plant and equipment      
Property, plant and equipment for own use      
Carrying amount 11,663 12,636 13,408
For own use | Cost | Property, plant and equipment      
Property, plant and equipment for own use      
Carrying amount 24,141 25,656 26,243
For own use | Cost | Right-of-use for operating lease      
Property, plant and equipment for own use      
Carrying amount 1,556 1,918 2,183
For own use | Accumulated depreciation | Property, plant and equipment      
Property, plant and equipment for own use      
Carrying amount (12,129) (12,619) (12,637)
For own use | Impairment losses | Property, plant and equipment      
Property, plant and equipment for own use      
Carrying amount (349) (401) (198)
Land and buildings | Property, plant and equipment      
Property, plant and equipment for own use      
Carrying amount 8,404 9,244 9,809
Land and buildings | Cost | Property, plant and equipment      
Property, plant and equipment for own use      
Carrying amount 14,067 15,113 14,973
Land and buildings | Cost | Right-of-use for operating lease      
Property, plant and equipment for own use      
Carrying amount 1,536 1,882 2,104
Land and buildings | Accumulated depreciation | Property, plant and equipment      
Property, plant and equipment for own use      
Carrying amount (5,359) (5,516) (5,010)
Land and buildings | Impairment losses | Property, plant and equipment      
Property, plant and equipment for own use      
Carrying amount (304) (353) (154)
IT equipment and fixtures | Property, plant and equipment      
Property, plant and equipment for own use      
Carrying amount 1,191 1,357 1,460
IT equipment and fixtures | Cost | Property, plant and equipment      
Property, plant and equipment for own use      
Carrying amount 4,204 5,283 5,614
IT equipment and fixtures | Cost | Right-of-use for operating lease      
Property, plant and equipment for own use      
Carrying amount 13 23 60
IT equipment and fixtures | Accumulated depreciation | Property, plant and equipment      
Property, plant and equipment for own use      
Carrying amount (3,003) (3,926) (4,154)
IT equipment and fixtures | Impairment losses | Property, plant and equipment      
Property, plant and equipment for own use      
Carrying amount (10) 0 0
Furniture and vehicles | Property, plant and equipment      
Property, plant and equipment for own use      
Carrying amount 1,801 1,833 1,988
Furniture and vehicles | Cost | Property, plant and equipment      
Property, plant and equipment for own use      
Carrying amount 5,548 4,963 5,412
Furniture and vehicles | Cost | Right-of-use for operating lease      
Property, plant and equipment for own use      
Carrying amount 7 13 19
Furniture and vehicles | Accumulated depreciation | Property, plant and equipment      
Property, plant and equipment for own use      
Carrying amount (3,746) (3,130) (3,424)
Furniture and vehicles | Impairment losses | Property, plant and equipment      
Property, plant and equipment for own use      
Carrying amount (1) 0 0
Construction in progress and other items | Property, plant and equipment      
Property, plant and equipment for own use      
Carrying amount 267 202 151
Construction in progress and other items | Cost | Property, plant and equipment      
Property, plant and equipment for own use      
Carrying amount 322 297 244
Construction in progress and other items | Cost | Right-of-use for operating lease      
Property, plant and equipment for own use      
Carrying amount 0 0 0
Construction in progress and other items | Accumulated depreciation | Property, plant and equipment      
Property, plant and equipment for own use      
Carrying amount (21) (47) (49)
Construction in progress and other items | Impairment losses | Property, plant and equipment      
Property, plant and equipment for own use      
Carrying amount € (34) € (48) € (44)