v3.26.1
(Re)Insurance contracts and investment contracts with discretionary participation features - Additional Information (Detail) - EUR (€)
€ in Millions
 12 Months Ended
Dec. 31, 2025
Dec. 31, 2024
Disclosure of Insurance Contracts Reinsurance Contracts held and Investment Contracts with Discretionary Participating Features [Line Items]    
Amount of financial economic assumption on favorable impact € 269  
Percentage of adjustment for default risk premium 30.00%  
Unrealized gains loss through equity € 1,159 € 1,073
Net gains and losses transferred from other comprehensive income to the income statement due to rebalancing of asset portfolios € 174 € 56
Discount rates converge linearly 10 years  
Ultimate forward rate 3.40% 3.40%
Percentage of illiquidity factor assigned to cash flows are not dependent on the underlying assets 100.00%  
Percentage of illiquidity factor assigned to cash flows are dependent on the underlying assets 0.00%  
Risk mitigation adjustment to contractual service margin € 836 € 2,020
EUR [member]    
Disclosure of Insurance Contracts Reinsurance Contracts held and Investment Contracts with Discretionary Participating Features [Line Items]    
Uniform last liquid point for all Aegon's major currencies (EUR, USD and GBP) 30  
GBP [member]    
Disclosure of Insurance Contracts Reinsurance Contracts held and Investment Contracts with Discretionary Participating Features [Line Items]    
Uniform last liquid point for all Aegon's major currencies (EUR, USD and GBP) 50  
US variable annuity products [member]    
Disclosure of Insurance Contracts Reinsurance Contracts held and Investment Contracts with Discretionary Participating Features [Line Items]    
Percentage of illiquidity factor assigned to cash flows are dependent on the underlying assets 100.00%  
Percentage of illiquidity premium 0.00%