v3.26.1
(Re)Insurance contracts and investment contracts with discretionary participation features - Summary of Investments and Other Assets Allocated to Contracts that were not Transitioned Fully Retrospectively (Detail) - EUR (€)
€ in Millions
 12 Months Ended
Dec. 31, 2025
Dec. 31, 2024
Disclosure of Detailed Information About Investments and Other Assets Allocated to Contracts that were not Transitioned Fully Retrospectively [Line Items]    
Beginning balance € 327,390  
Ending balance 317,233 € 327,390
Investments and other assets allocated to insurance contracts [member] | Fair value through other comprehensive income [member] | Insurance contracts [member]    
Disclosure of Detailed Information About Investments and Other Assets Allocated to Contracts that were not Transitioned Fully Retrospectively [Line Items]    
Beginning balance (2,131) (1,147)
Gross revaluation 1,090 (1,125)
Net gains/losses transferred to income statement 53 (62)
Foreign currency translation differences 216 (115)
Tax effect (271) 233
Other 46 86
Ending balance € (997) € (2,131)