v3.26.1
Financial Risks - Summary of Changes in the Gross Carrying Amount / Market Value of the Financial Assets - Private Loans (Detail) - EUR (€)
€ in Millions
 12 Months Ended
Dec. 31, 2025
Dec. 31, 2024
Disclosure of reconciliation of changes in loss allowance and explanation of changes in gross carrying amount for financial instruments [line items]    
Beginning balance € 76,020  
Ending balance 69,293 € 76,020
Debt securities [member] | Gross carrying amount [member]    
Disclosure of reconciliation of changes in loss allowance and explanation of changes in gross carrying amount for financial instruments [line items]    
Beginning balance 52,247 47,242
Financial assets derecognized during the period other than write-offs (8,963) (5,394)
New financial assets originated or purchased 8,663 8,434
Unrealized gains/losses through equity 1,488 (1,329)
Amortizations through income statement 162 138
Changes in interest accrual   (2)
Net exchange differences (6,120) 3,201
Other movements (2) (2)
Transfer to/from other headings (28) (43)
Ending balance 47,446 52,247
Debt securities [member] | Gross carrying amount [member] | Lifetime ECL not credit impaired [member]    
Disclosure of reconciliation of changes in loss allowance and explanation of changes in gross carrying amount for financial instruments [line items]    
Beginning balance 335 357
Financial assets derecognized during the period other than write-offs (146) (69)
New financial assets originated or purchased 4 21
Unrealized gains/losses through equity 18 (7)
Amortizations through income statement 1 1
Net exchange differences (42) 22
Other movements (23) 0
Transfer to/from other headings 0 2
Ending balance 358 335
Debt securities [member] | Gross carrying amount [member] | Purchased credit impaired [member]    
Disclosure of reconciliation of changes in loss allowance and explanation of changes in gross carrying amount for financial instruments [line items]    
Beginning balance 92 100
Financial assets derecognized during the period other than write-offs (13) (21)
Unrealized gains/losses through equity (12) (10)
Amortizations through income statement 19 17
Net exchange differences (11) 6
Other movements 0 0
Ending balance 75 92
Debt securities [member] | Gross carrying amount [member] | 12-month ECL [member]    
Disclosure of reconciliation of changes in loss allowance and explanation of changes in gross carrying amount for financial instruments [line items]    
Beginning balance 51,529 46,461
Financial assets derecognized during the period other than write-offs (8,729) (5,201)
New financial assets originated or purchased 8,632 8,421
Unrealized gains/losses through equity 1,528 (1,294)
Amortizations through income statement 115 94
Changes in interest accrual   (2)
Net exchange differences (6,035) 3,154
Other movements 7 (1)
Transfer to/from other headings (21) (45)
Ending balance 46,782 51,529
Debt securities [member] | Gross carrying amount [member] | Lifetime ECL credit impaired [member]    
Disclosure of reconciliation of changes in loss allowance and explanation of changes in gross carrying amount for financial instruments [line items]    
Beginning balance 291 325
Financial assets derecognized during the period other than write-offs (75) (102)
New financial assets originated or purchased 27 (9)
Unrealized gains/losses through equity (46) (17)
Amortizations through income statement 27 27
Net exchange differences (33) 19
Other movements 14 (1)
Transfer to/from other headings (7)  
Ending balance 232 291
Debt securities [member] | Gross carrying amount [member] | Transfer from Stage 1 to Stage 2 [member] | Lifetime ECL not credit impaired [member]    
Disclosure of reconciliation of changes in loss allowance and explanation of changes in gross carrying amount for financial instruments [line items]    
Transfers 269 200
Debt securities [member] | Gross carrying amount [member] | Transfer from Stage 1 to Stage 2 [member] | 12-month ECL [member]    
Disclosure of reconciliation of changes in loss allowance and explanation of changes in gross carrying amount for financial instruments [line items]    
Transfers (269) (200)
Debt securities [member] | Gross carrying amount [member] | Transfer from Stage 1 to Stage 3 [member] | 12-month ECL [member]    
Disclosure of reconciliation of changes in loss allowance and explanation of changes in gross carrying amount for financial instruments [line items]    
Transfers (12) (10)
Debt securities [member] | Gross carrying amount [member] | Transfer from Stage 1 to Stage 3 [member] | Lifetime ECL credit impaired [member]    
Disclosure of reconciliation of changes in loss allowance and explanation of changes in gross carrying amount for financial instruments [line items]    
Transfers 12 10
Debt securities [member] | Gross carrying amount [member] | Transfer from Stage 2 to Stage 3 [member] | Lifetime ECL not credit impaired [member]    
Disclosure of reconciliation of changes in loss allowance and explanation of changes in gross carrying amount for financial instruments [line items]    
Transfers (36) (48)
Debt securities [member] | Gross carrying amount [member] | Transfer from Stage 2 to Stage 3 [member] | Lifetime ECL credit impaired [member]    
Disclosure of reconciliation of changes in loss allowance and explanation of changes in gross carrying amount for financial instruments [line items]    
Transfers 36 48
Debt securities [member] | Gross carrying amount [member] | Transfer from Stage 3 to Stage 2 [member] | Lifetime ECL not credit impaired [member]    
Disclosure of reconciliation of changes in loss allowance and explanation of changes in gross carrying amount for financial instruments [line items]    
Transfers 1 7
Debt securities [member] | Gross carrying amount [member] | Transfer from Stage 3 to Stage 2 [member] | Lifetime ECL credit impaired [member]    
Disclosure of reconciliation of changes in loss allowance and explanation of changes in gross carrying amount for financial instruments [line items]    
Transfers (1) (7)
Debt securities [member] | Gross carrying amount [member] | Transfer from Stage 2 to Stage 1 [member] | Lifetime ECL not credit impaired [member]    
Disclosure of reconciliation of changes in loss allowance and explanation of changes in gross carrying amount for financial instruments [line items]    
Transfers (24) (150)
Debt securities [member] | Gross carrying amount [member] | Transfer from Stage 2 to Stage 1 [member] | 12-month ECL [member]    
Disclosure of reconciliation of changes in loss allowance and explanation of changes in gross carrying amount for financial instruments [line items]    
Transfers 24 150
Debt securities [member] | Gross carrying amount [member] | Transfer from Stage 3 to Stage 1 [member] | 12-month ECL [member]    
Disclosure of reconciliation of changes in loss allowance and explanation of changes in gross carrying amount for financial instruments [line items]    
Transfers 12 2
Debt securities [member] | Gross carrying amount [member] | Transfer from Stage 3 to Stage 1 [member] | Lifetime ECL credit impaired [member]    
Disclosure of reconciliation of changes in loss allowance and explanation of changes in gross carrying amount for financial instruments [line items]    
Transfers (12) (2)
Debt securities [member] | Expected credit loss [member]    
Disclosure of reconciliation of changes in loss allowance and explanation of changes in gross carrying amount for financial instruments [line items]    
Beginning balance (341)  
Ending balance (347) (341)
Debt securities [member] | Expected credit loss [member] | Lifetime ECL not credit impaired [member]    
Disclosure of reconciliation of changes in loss allowance and explanation of changes in gross carrying amount for financial instruments [line items]    
Beginning balance (41)  
Ending balance (27) (41)
Debt securities [member] | Expected credit loss [member] | Purchased credit impaired [member]    
Disclosure of reconciliation of changes in loss allowance and explanation of changes in gross carrying amount for financial instruments [line items]    
Beginning balance (4)  
Ending balance (1) (4)
Debt securities [member] | Expected credit loss [member] | 12-month ECL [member]    
Disclosure of reconciliation of changes in loss allowance and explanation of changes in gross carrying amount for financial instruments [line items]    
Beginning balance (187)  
Ending balance (188) (187)
Debt securities [member] | Expected credit loss [member] | Lifetime ECL credit impaired [member]    
Disclosure of reconciliation of changes in loss allowance and explanation of changes in gross carrying amount for financial instruments [line items]    
Beginning balance (108)  
Ending balance € (130) € (108)