v3.26.1
Fair value - Disclosures of Changes in Level 3 Assets (Detail) - Level III [member] - Recurring fair value measurement [member] - EUR (€)
€ in Millions
 6 Months Ended 12 Months Ended
Jun. 30, 2026
Dec. 31, 2025
Changes in fair value measurement assets and liabilities [Line Items]    
Beginning balance € 5,163 € 5,856
Disposal of a business   (14)
Total gains /losses in income statement (147) (28)
Total gains /losses in OCI 5 5
Purchases 257 940
Sales (229) (573)
Settlements (53) (90)
Net exchange difference 136 (670)
Transfers from levels I and II 188 93
Transfers to levels I and II (3) (355)
Transfers to disposal groups (316)  
Ending balance 5,000 5,163
Total unrealized gains and (losses) for the period recorded in the P&L for instruments held (94) 26
Fair value through other comprehensive income [member]    
Changes in fair value measurement assets and liabilities [Line Items]    
Beginning balance 533 803
Total gains /losses in income statement 4 7
Total gains /losses in OCI 5 5
Purchases 79 125
Sales (46) (83)
Settlements (51) (86)
Net exchange difference 17 (84)
Transfers from levels I and II 162 71
Transfers to levels I and II (3) (226)
Ending balance 701 533
Fair value through other comprehensive income [member] | Shares [member]    
Changes in fair value measurement assets and liabilities [Line Items]    
Beginning balance 5 4
Ending balance 5 5
Fair value through other comprehensive income [member] | Debt securities [member]    
Changes in fair value measurement assets and liabilities [Line Items]    
Beginning balance 528 799
Total gains /losses in income statement 4 7
Total gains /losses in OCI 5 5
Purchases 78 124
Sales (46) (82)
Settlements (51) (86)
Net exchange difference 17 (84)
Transfers from levels I and II 162 71
Transfers to levels I and II (3) (226)
Ending balance 695 528
Fair value through other comprehensive income [member] | Money markets and other short-term investments [Member]    
Changes in fair value measurement assets and liabilities [Line Items]    
Purchases 1  
Ending balance 1  
Fair value through other comprehensive income [member] | Other investments [member]    
Changes in fair value measurement assets and liabilities [Line Items]    
Beginning balance 1  
Total gains /losses in OCI   (1)
Purchases   1
Ending balance   1
Financial assets at fair value through profit or loss, mandatorily measured at fair value, category [member]    
Changes in fair value measurement assets and liabilities [Line Items]    
Beginning balance 4,630 5,053
Disposal of a business   (14)
Total gains /losses in income statement (151) (35)
Purchases 178 815
Sales (183) (491)
Settlements (3) (5)
Net exchange difference 118 (585)
Transfers from levels I and II 25 23
Transfers to levels I and II   (129)
Transfers to disposal groups (316)  
Ending balance 4,299 4,630
Total unrealized gains and (losses) for the period recorded in the P&L for instruments held (94) 26
Financial assets at fair value through profit or loss, mandatorily measured at fair value, category [member] | Shares [member]    
Changes in fair value measurement assets and liabilities [Line Items]    
Beginning balance 54 86
Total gains /losses in income statement (2) 7
Purchases 4 17
Sales (10) (46)
Net exchange difference 1 (9)
Transfers from levels I and II 1  
Ending balance 49 54
Total unrealized gains and (losses) for the period recorded in the P&L for instruments held (2) 7
Financial assets at fair value through profit or loss, mandatorily measured at fair value, category [member] | Debt securities [member]    
Changes in fair value measurement assets and liabilities [Line Items]    
Beginning balance 110 107
Total gains /losses in income statement 1  
Purchases 13 2
Sales (22) (1)
Settlements (3) (5)
Net exchange difference 3 (13)
Transfers from levels I and II 24 23
Transfers to levels I and II   (2)
Ending balance 127 110
Total unrealized gains and (losses) for the period recorded in the P&L for instruments held (1)  
Financial assets at fair value through profit or loss, mandatorily measured at fair value, category [member] | Other investments [member]    
Changes in fair value measurement assets and liabilities [Line Items]    
Beginning balance 3,987 4,457
Total gains /losses in income statement (156) (9)
Purchases 147 463
Sales (141) (400)
Net exchange difference 107 (525)
Ending balance 3,944 3,987
Total unrealized gains and (losses) for the period recorded in the P&L for instruments held (90) 16
Financial assets at fair value through profit or loss, mandatorily measured at fair value, category [member] | Loans [member]    
Changes in fair value measurement assets and liabilities [Line Items]    
Beginning balance 82 82
Total gains /losses in income statement (1) 4
Purchases 1 12
Sales   (5)
Net exchange difference 2 (10)
Ending balance 84 82
Total unrealized gains and (losses) for the period recorded in the P&L for instruments held (1) 3
Financial assets at fair value through profit or loss, mandatorily measured at fair value, category [member] | Derivative [member]    
Changes in fair value measurement assets and liabilities [Line Items]    
Beginning balance 8 9
Total gains /losses in income statement 2  
Sales   (1)
Transfers to disposal groups (10)  
Ending balance   8
Total unrealized gains and (losses) for the period recorded in the P&L for instruments held   (1)
Financial assets at fair value through profit or loss, mandatorily measured at fair value, category [member] | Investments - Policyholder risk [member]    
Changes in fair value measurement assets and liabilities [Line Items]    
Beginning balance 389 312
Disposal of a business   (14)
Total gains /losses in income statement 4 (36)
Purchases 14 320
Sales (10) (38)
Net exchange difference 4 (28)
Transfers to levels I and II   (127)
Transfers to disposal groups (307)  
Ending balance € 96 389
Total unrealized gains and (losses) for the period recorded in the P&L for instruments held   € 1