v3.26.1
Investments - Summary of Financial Assets, Excluding Derivatives, by Measurement Category (Detail) - Financial Assets Excluding Derivatives Measurement Category [Member] - EUR (€)
€ in Millions
Jun. 30, 2026
Dec. 31, 2025
Investments where Aegon bears the risk [member]    
Disclosure of financial assets [line items]    
FVOCI (With recycling) € 52,531 € 49,747
FVOCI (no recycling) 10 10
Amortized cost 9,522 9,719
Financial assets measured at FVPL – designated 659 2,066
Financial assets measured at FVPL – mandatory 6,884 7,306
Total 69,606 68,848
Fair value 68,742 68,078
Investments where policyholders bears the risk [member]    
Disclosure of financial assets [line items]    
Total 97,527 215,814
Shares [member] | Investments where Aegon bears the risk [member]    
Disclosure of financial assets [line items]    
FVOCI (no recycling) 10 10
Financial assets measured at FVPL – mandatory 247 263
Total 257 273
Fair value 257 273
Shares [member] | Investments where policyholders bears the risk [member]    
Disclosure of financial assets [line items]    
Total 25 15,321
Debt securities [member] | Investments where Aegon bears the risk [member]    
Disclosure of financial assets [line items]    
FVOCI (With recycling) 50,293 47,411
Amortized cost 36 36
Financial assets measured at FVPL – designated 554 1,123
Financial assets measured at FVPL – mandatory 1,604 1,315
Total 52,486 49,884
Fair value 52,486 49,884
Debt securities [member] | Investments where policyholders bears the risk [member]    
Disclosure of financial assets [line items]    
Total 6 6,318
Money market and other short-term investments [member] | Investments where Aegon bears the risk [member]    
Disclosure of financial assets [line items]    
FVOCI (With recycling) 2,209 2,308
Financial assets measured at FVPL – designated 21 146
Financial assets measured at FVPL – mandatory 1,068 1,722
Total 3,299 4,176
Fair value 3,299 4,176
Money market and other short-term investments [member] | Investments where policyholders bears the risk [member]    
Disclosure of financial assets [line items]    
Total   1,788
Deposits with financial institutions [member] | Investments where Aegon bears the risk [member]    
Disclosure of financial assets [line items]    
Amortized cost 11 11
Total 11 11
Fair value 11 11
Deposits with financial institutions [member] | Investments where policyholders bears the risk [member]    
Disclosure of financial assets [line items]    
Total 2 1,716
Unconsolidated Investment Funds [member] | Investments where policyholders bears the risk [member]    
Disclosure of financial assets [line items]    
Total 97,495 190,671
Loans [member] | Investments where Aegon bears the risk [member]    
Disclosure of financial assets [line items]    
Amortized cost 9,475 9,672
Financial assets measured at FVPL – designated 84 82
Total 9,558 9,754
Fair value 8,694 8,985
Other [member] | Investments where Aegon bears the risk [member]    
Disclosure of financial assets [line items]    
FVOCI (With recycling) 29 28
Financial assets measured at FVPL – designated 1 716
Financial assets measured at FVPL – mandatory 3,966 4,005
Total 3,996 4,749
Fair value € 3,996 € 4,749