v3.26.1
Segment Information - Summary of Detailed Information About Insurance, Reinsurance and Investment Contracts (Detail) - EUR (€)
€ in Millions
Jun. 30, 2026
Dec. 31, 2025
Disclosure Of Detailed Information About Insurance Reinsurance And Investment Contracts Assets and Liabilities Per Segment [Line Items]    
Insurance contracts € 137,391 € 176,049
Investment contracts with DPF 41,839 97,814
Insurance contracts and investment contracts with discretionary participation features 137,410 197,331
Reinsurance contracts held 17,173 16,958
Eliminations [member]    
Disclosure Of Detailed Information About Insurance Reinsurance And Investment Contracts Assets and Liabilities Per Segment [Line Items]    
Insurance contracts and investment contracts with discretionary participation features (4,218) (4,292)
Reinsurance contracts held (4,091) (4,106)
International [member]    
Disclosure Of Detailed Information About Insurance Reinsurance And Investment Contracts Assets and Liabilities Per Segment [Line Items]    
Insurance contracts and investment contracts with discretionary participation features 5,250 5,220
Reinsurance contracts held 3,967 3,981
Americas [member]    
Disclosure Of Detailed Information About Insurance Reinsurance And Investment Contracts Assets and Liabilities Per Segment [Line Items]    
Insurance contracts and investment contracts with discretionary participation features 136,378 130,429
Reinsurance contracts held 17,298 17,086
United Kingdom [member]    
Disclosure Of Detailed Information About Insurance Reinsurance And Investment Contracts Assets and Liabilities Per Segment [Line Items]    
Insurance contracts and investment contracts with discretionary participation features   65,974
Reinsurance contracts held   (3)
Direct Participating Contracts [member]    
Disclosure Of Detailed Information About Insurance Reinsurance And Investment Contracts Assets and Liabilities Per Segment [Line Items]    
Insurance contracts 70,419 111,508
Direct Participating Contracts [member] | International [member]    
Disclosure Of Detailed Information About Insurance Reinsurance And Investment Contracts Assets and Liabilities Per Segment [Line Items]    
Insurance contracts 274 246
Direct Participating Contracts [member] | Americas [member]    
Disclosure Of Detailed Information About Insurance Reinsurance And Investment Contracts Assets and Liabilities Per Segment [Line Items]    
Insurance contracts 70,145 67,074
Direct Participating Contracts [member] | United Kingdom [member]    
Disclosure Of Detailed Information About Insurance Reinsurance And Investment Contracts Assets and Liabilities Per Segment [Line Items]    
Insurance contracts   44,188
Without Direct Participating Contracts [member]    
Disclosure Of Detailed Information About Insurance Reinsurance And Investment Contracts Assets and Liabilities Per Segment [Line Items]    
Insurance contracts 66,922 64,497
Investment contracts with DPF 20 12
Without Direct Participating Contracts [member] | Eliminations [member]    
Disclosure Of Detailed Information About Insurance Reinsurance And Investment Contracts Assets and Liabilities Per Segment [Line Items]    
Insurance contracts (4,218) (4,292)
Without Direct Participating Contracts [member] | International [member]    
Disclosure Of Detailed Information About Insurance Reinsurance And Investment Contracts Assets and Liabilities Per Segment [Line Items]    
Insurance contracts 4,907 4,918
Investment contracts with DPF 20 12
Without Direct Participating Contracts [member] | Americas [member]    
Disclosure Of Detailed Information About Insurance Reinsurance And Investment Contracts Assets and Liabilities Per Segment [Line Items]    
Insurance contracts 66,233 63,355
Without Direct Participating Contracts [member] | United Kingdom [member]    
Disclosure Of Detailed Information About Insurance Reinsurance And Investment Contracts Assets and Liabilities Per Segment [Line Items]    
Insurance contracts   517
Contracts measured under the PAA [member]    
Disclosure Of Detailed Information About Insurance Reinsurance And Investment Contracts Assets and Liabilities Per Segment [Line Items]    
Insurance contracts 50 44
Contracts measured under the PAA [member] | International [member]    
Disclosure Of Detailed Information About Insurance Reinsurance And Investment Contracts Assets and Liabilities Per Segment [Line Items]    
Insurance contracts € 50 44
Direct Participation Contracts [Member]    
Disclosure Of Detailed Information About Insurance Reinsurance And Investment Contracts Assets and Liabilities Per Segment [Line Items]    
Investment contracts with DPF   21,269
Direct Participation Contracts [Member] | United Kingdom [member]    
Disclosure Of Detailed Information About Insurance Reinsurance And Investment Contracts Assets and Liabilities Per Segment [Line Items]    
Investment contracts with DPF   € 21,269