v3.26.1
Derivatives - Summary of Detailed Information about Hedging Instruments (Detail)
€ in Millions
12 Months Ended
Dec. 31, 2025
EUR (€)
Dec. 31, 2024
EUR (€)
Interest rate contracts [member] | Fair value hedges [member]    
Disclosure of detailed information about hedging instruments [line items]    
Notional 28 32
Assets € 0 € 0
Liabilities 3 3
Changes in fair value used for calculating hedge ineffectiveness [1] € 0 € 2
Interest rate contracts [member] | Cash flow hedges [member]    
Disclosure of detailed information about hedging instruments [line items]    
Notional 3,770 5,352
Assets € 9 € 12
Liabilities 833 1,092
Changes in fair value used for calculating hedge ineffectiveness [1] € 134 € (106)
Foreign exchange contracts [member] | Fair value hedges [member]    
Disclosure of detailed information about hedging instruments [line items]    
Notional 8 9
Assets € 4 € 3
Liabilities 0 0
Changes in fair value used for calculating hedge ineffectiveness [1] € 1 € (1)
Foreign exchange contracts [member] | Cash flow hedges [member]    
Disclosure of detailed information about hedging instruments [line items]    
Notional 1,456 1,202
Assets € 81 € 124
Liabilities 36 8
Changes in fair value used for calculating hedge ineffectiveness [1] € (59) € 15
Foreign exchange - FX forward [member] | Net investment hedges [member]    
Disclosure of detailed information about hedging instruments [line items]    
Notional 760 27
Assets € 2 € 26
Liabilities 0 2
Changes in fair value used for calculating hedge ineffectiveness [1] € 0 € 0
[1] Changes in fair value used for calculating hedge ineffectiveness.