v3.26.1
Fair value of assets and liabilities - Valuation techniques and range of unobservable inputs (Details)
€ in Millions
 6 Months Ended 12 Months Ended
Jun. 30, 2026
EUR (€)
€ / shares
Jun. 30, 2025
Dec. 31, 2025
EUR (€)
€ / shares
Dec. 31, 2024
EUR (€)
Disclosure of significant unobservable inputs used in fair value measurement of assets [line items]        
Financial assets at fair value through profit or loss € 160,057   € 133,157  
Financial assets at fair value through other comprehensive income 63,043   56,662  
Financial liabilities at fair value through profit or loss 103,313   80,532  
Level 3        
Disclosure of significant unobservable inputs used in fair value measurement of assets [line items]        
Financial assets at fair value through profit or loss 10,503   11,435  
Financial assets at fair value through other comprehensive income 350   307  
Total financial assets 10,854   11,742 € 11,005
Financial liabilities at fair value through profit or loss 1,076   802  
Financial liabilities, at fair value 1,076   802 € 770
Level 3 | Debt securities        
Disclosure of significant unobservable inputs used in fair value measurement of assets [line items]        
Financial assets at fair value through profit or loss 1,883   1,934  
Financial liabilities at fair value through profit or loss 9   9  
Level 3 | Equity securities        
Disclosure of significant unobservable inputs used in fair value measurement of assets [line items]        
Financial assets at fair value through profit or loss 155   187  
Level 3 | Loans and advances        
Disclosure of significant unobservable inputs used in fair value measurement of assets [line items]        
Financial assets at fair value through profit or loss 1,312   1,978  
Financial liabilities at fair value through profit or loss 0   0  
Level 3 | (Reverse) repos        
Disclosure of significant unobservable inputs used in fair value measurement of assets [line items]        
Financial assets at fair value through profit or loss 6,460   6,563  
Level 3 | Structured notes        
Disclosure of significant unobservable inputs used in fair value measurement of assets [line items]        
Financial liabilities at fair value through profit or loss 209   15  
Level 3 | Derivatives at rates        
Disclosure of significant unobservable inputs used in fair value measurement of assets [line items]        
Financial assets at fair value through profit or loss 638   628  
Financial liabilities at fair value through profit or loss 628   670  
Level 3 | Derivatives at foreign exchange        
Disclosure of significant unobservable inputs used in fair value measurement of assets [line items]        
Financial assets at fair value through profit or loss 3   2  
Financial liabilities at fair value through profit or loss 7   4  
Level 3 | Derivative at credit        
Disclosure of significant unobservable inputs used in fair value measurement of assets [line items]        
Financial assets at fair value through profit or loss 37   134  
Financial liabilities at fair value through profit or loss 124   48  
Level 3 | Derivatives at equity        
Disclosure of significant unobservable inputs used in fair value measurement of assets [line items]        
Financial assets at fair value through profit or loss 13   7  
Financial liabilities at fair value through profit or loss 79   46  
Level 3 | Other derivatives        
Disclosure of significant unobservable inputs used in fair value measurement of assets [line items]        
Financial assets at fair value through profit or loss 3   2  
Financial liabilities at fair value through profit or loss 20   10  
Level 3 | Loan and advances at FVOCI        
Disclosure of significant unobservable inputs used in fair value measurement of assets [line items]        
Financial assets at fair value through other comprehensive income 25   0  
Level 3 | Equity at FVOCI        
Disclosure of significant unobservable inputs used in fair value measurement of assets [line items]        
Financial assets at fair value through other comprehensive income € 325   € 307  
Level 3 | Minimum | Price based | Price (price per share) | Other derivatives        
Disclosure of significant unobservable inputs used in fair value measurement of assets [line items]        
Significant unobservable inputs, price (in EUR per share) 70 66    
Level 3 | Minimum | Price based | Debt securities | Price (%)        
Disclosure of significant unobservable inputs used in fair value measurement of assets [line items]        
Significant unobservable inputs, percentage 0   0  
Level 3 | Minimum | Price based | Debt securities | Price (price per share)        
Disclosure of significant unobservable inputs used in fair value measurement of assets [line items]        
Significant unobservable inputs, price (in EUR per share) | € / shares 203   201  
Level 3 | Minimum | Price based | Equity securities | Price (price per share)        
Disclosure of significant unobservable inputs used in fair value measurement of assets [line items]        
Significant unobservable inputs, price (in EUR per share) | € / shares 0   0  
Level 3 | Minimum | Price based | Loans and advances | Price (%)        
Disclosure of significant unobservable inputs used in fair value measurement of assets [line items]        
Significant unobservable inputs, percentage 0   0  
Level 3 | Minimum | Price based | Structured notes | Price (%)        
Disclosure of significant unobservable inputs used in fair value measurement of assets [line items]        
Significant unobservable inputs, percentage 0.98   0.96  
Level 3 | Minimum | Price based | Derivative at credit | Price (%)        
Disclosure of significant unobservable inputs used in fair value measurement of assets [line items]        
Significant unobservable inputs, percentage 0   0  
Level 3 | Minimum | Price based | Loan and advances at FVOCI | Price (%)        
Disclosure of significant unobservable inputs used in fair value measurement of assets [line items]        
Significant unobservable inputs, percentage 0.91      
Level 3 | Minimum | Price based | Equity at FVOCI | Price (price per share)        
Disclosure of significant unobservable inputs used in fair value measurement of assets [line items]        
Significant unobservable inputs, price (in EUR per share) | € / shares 126   126  
Level 3 | Minimum | Present value techniques | Debt securities | Price (%)        
Disclosure of significant unobservable inputs used in fair value measurement of assets [line items]        
Significant unobservable inputs, percentage 0.90      
Level 3 | Minimum | Present value techniques | Loans and advances | Credit spread (bps)        
Disclosure of significant unobservable inputs used in fair value measurement of assets [line items]        
Significant unobservable inputs, percentage 0.0582   0.0120  
Level 3 | Minimum | Present value techniques | Loans and advances | Prepayment rate (%)        
Disclosure of significant unobservable inputs used in fair value measurement of assets [line items]        
Significant unobservable inputs, percentage 0.02   0.02  
Level 3 | Minimum | Present value techniques | Structured notes | Price (%)        
Disclosure of significant unobservable inputs used in fair value measurement of assets [line items]        
Significant unobservable inputs, percentage 0.99      
Level 3 | Minimum | Present value techniques | Derivatives at rates | Reset spread (%)        
Disclosure of significant unobservable inputs used in fair value measurement of assets [line items]        
Significant unobservable inputs, percentage     0.01  
Level 3 | Minimum | Present value techniques | Derivative at credit | Credit spread (bps)        
Disclosure of significant unobservable inputs used in fair value measurement of assets [line items]        
Significant unobservable inputs, percentage 0.0009   0.0010  
Level 3 | Minimum | Present value techniques | Equity at FVOCI | Credit spread (bps)        
Disclosure of significant unobservable inputs used in fair value measurement of assets [line items]        
Significant unobservable inputs, percentage 0.000541   0.000515  
Level 3 | Minimum | Present value techniques | Equity at FVOCI | Interest rate (%)        
Disclosure of significant unobservable inputs used in fair value measurement of assets [line items]        
Significant unobservable inputs, percentage 0.025   0.025  
Level 3 | Minimum | Present value techniques | Equity at FVOCI | Payout ratio (%)        
Disclosure of significant unobservable inputs used in fair value measurement of assets [line items]        
Significant unobservable inputs, percentage 0.70   0.70  
Level 3 | Minimum | Option pricing model | Structured notes | Equity volatility (%)        
Disclosure of significant unobservable inputs used in fair value measurement of assets [line items]        
Significant unobservable inputs, percentage 0.10   0.18  
Level 3 | Minimum | Option pricing model | Structured notes | Equity/Equity correlation        
Disclosure of significant unobservable inputs used in fair value measurement of assets [line items]        
Significant unobservable inputs, percentage 0.6   0.7  
Level 3 | Minimum | Option pricing model | Structured notes | Equity/FX correlation        
Disclosure of significant unobservable inputs used in fair value measurement of assets [line items]        
Significant unobservable inputs, percentage (0.6)   (0.6)  
Level 3 | Minimum | Option pricing model | Structured notes | Dividend yield (%)        
Disclosure of significant unobservable inputs used in fair value measurement of assets [line items]        
Significant unobservable inputs, percentage 0.005   0.004  
Level 3 | Minimum | Option pricing model | Derivatives at rates | Interest rate volatility (bps)        
Disclosure of significant unobservable inputs used in fair value measurement of assets [line items]        
Significant unobservable inputs, percentage 0.0055   0.0045  
Level 3 | Minimum | Option pricing model | Derivatives at foreign exchange | Implied volatility (%)        
Disclosure of significant unobservable inputs used in fair value measurement of assets [line items]        
Significant unobservable inputs, percentage 0.007   0.017  
Level 3 | Minimum | Option pricing model | Derivatives at equity | Equity volatility (%)        
Disclosure of significant unobservable inputs used in fair value measurement of assets [line items]        
Significant unobservable inputs, percentage 0.15   0.13  
Level 3 | Minimum | Option pricing model | Derivatives at equity | Equity/Equity correlation        
Disclosure of significant unobservable inputs used in fair value measurement of assets [line items]        
Significant unobservable inputs, percentage 0.0   0.0  
Level 3 | Minimum | Option pricing model | Derivatives at equity | Equity/FX correlation        
Disclosure of significant unobservable inputs used in fair value measurement of assets [line items]        
Significant unobservable inputs, percentage (0.7)   (0.7)  
Level 3 | Minimum | Option pricing model | Derivatives at equity | Dividend yield (%)        
Disclosure of significant unobservable inputs used in fair value measurement of assets [line items]        
Significant unobservable inputs, percentage 0   0  
Level 3 | Minimum | Option pricing model | Other derivatives | Commodity volatility (%)        
Disclosure of significant unobservable inputs used in fair value measurement of assets [line items]        
Significant unobservable inputs, percentage 0.16   0.20  
Level 3 | Minimum | Option pricing model | Other derivatives | Com/FX correlation        
Disclosure of significant unobservable inputs used in fair value measurement of assets [line items]        
Significant unobservable inputs, percentage     (0.25)  
Level 3 | Maximum | Price based | Price (price per share) | Other derivatives        
Disclosure of significant unobservable inputs used in fair value measurement of assets [line items]        
Significant unobservable inputs, price (in EUR per share) 70 66    
Level 3 | Maximum | Price based | Debt securities | Price (%)        
Disclosure of significant unobservable inputs used in fair value measurement of assets [line items]        
Significant unobservable inputs, percentage 1.01   1.03  
Level 3 | Maximum | Price based | Debt securities | Price (price per share)        
Disclosure of significant unobservable inputs used in fair value measurement of assets [line items]        
Significant unobservable inputs, price (in EUR per share) | € / shares 392   412  
Level 3 | Maximum | Price based | Equity securities | Price (price per share)        
Disclosure of significant unobservable inputs used in fair value measurement of assets [line items]        
Significant unobservable inputs, price (in EUR per share) | € / shares 2,587   5,475  
Level 3 | Maximum | Price based | Loans and advances | Price (%)        
Disclosure of significant unobservable inputs used in fair value measurement of assets [line items]        
Significant unobservable inputs, percentage 1.08   1.09  
Level 3 | Maximum | Price based | Structured notes | Price (%)        
Disclosure of significant unobservable inputs used in fair value measurement of assets [line items]        
Significant unobservable inputs, percentage 1.02   1.03  
Level 3 | Maximum | Price based | Derivative at credit | Price (%)        
Disclosure of significant unobservable inputs used in fair value measurement of assets [line items]        
Significant unobservable inputs, percentage 0.99   1  
Level 3 | Maximum | Price based | Loan and advances at FVOCI | Price (%)        
Disclosure of significant unobservable inputs used in fair value measurement of assets [line items]        
Significant unobservable inputs, percentage 0.95      
Level 3 | Maximum | Price based | Equity at FVOCI | Price (price per share)        
Disclosure of significant unobservable inputs used in fair value measurement of assets [line items]        
Significant unobservable inputs, price (in EUR per share) | € / shares 126   126  
Level 3 | Maximum | Present value techniques | Debt securities | Price (%)        
Disclosure of significant unobservable inputs used in fair value measurement of assets [line items]        
Significant unobservable inputs, percentage 1      
Level 3 | Maximum | Present value techniques | Loans and advances | Credit spread (bps)        
Disclosure of significant unobservable inputs used in fair value measurement of assets [line items]        
Significant unobservable inputs, percentage 0.0690   0.0709  
Level 3 | Maximum | Present value techniques | Loans and advances | Prepayment rate (%)        
Disclosure of significant unobservable inputs used in fair value measurement of assets [line items]        
Significant unobservable inputs, percentage 0.02   0.02  
Level 3 | Maximum | Present value techniques | Structured notes | Price (%)        
Disclosure of significant unobservable inputs used in fair value measurement of assets [line items]        
Significant unobservable inputs, percentage 1      
Level 3 | Maximum | Present value techniques | Derivatives at rates | Reset spread (%)        
Disclosure of significant unobservable inputs used in fair value measurement of assets [line items]        
Significant unobservable inputs, percentage     0.01  
Level 3 | Maximum | Present value techniques | Derivative at credit | Credit spread (bps)        
Disclosure of significant unobservable inputs used in fair value measurement of assets [line items]        
Significant unobservable inputs, percentage 0.0095   0.0088  
Level 3 | Maximum | Present value techniques | Equity at FVOCI | Credit spread (bps)        
Disclosure of significant unobservable inputs used in fair value measurement of assets [line items]        
Significant unobservable inputs, percentage 0.000541   0.000515  
Level 3 | Maximum | Present value techniques | Equity at FVOCI | Interest rate (%)        
Disclosure of significant unobservable inputs used in fair value measurement of assets [line items]        
Significant unobservable inputs, percentage 0.025   0.025  
Level 3 | Maximum | Present value techniques | Equity at FVOCI | Payout ratio (%)        
Disclosure of significant unobservable inputs used in fair value measurement of assets [line items]        
Significant unobservable inputs, percentage 0.90   0.90  
Level 3 | Maximum | Option pricing model | Structured notes | Equity volatility (%)        
Disclosure of significant unobservable inputs used in fair value measurement of assets [line items]        
Significant unobservable inputs, percentage 0.30   0.22  
Level 3 | Maximum | Option pricing model | Structured notes | Equity/Equity correlation        
Disclosure of significant unobservable inputs used in fair value measurement of assets [line items]        
Significant unobservable inputs, percentage 0.9   0.8  
Level 3 | Maximum | Option pricing model | Structured notes | Equity/FX correlation        
Disclosure of significant unobservable inputs used in fair value measurement of assets [line items]        
Significant unobservable inputs, percentage 0.2   0.2  
Level 3 | Maximum | Option pricing model | Structured notes | Dividend yield (%)        
Disclosure of significant unobservable inputs used in fair value measurement of assets [line items]        
Significant unobservable inputs, percentage 0.04   0.019  
Level 3 | Maximum | Option pricing model | Derivatives at rates | Interest rate volatility (bps)        
Disclosure of significant unobservable inputs used in fair value measurement of assets [line items]        
Significant unobservable inputs, percentage 0.0158   0.0091  
Level 3 | Maximum | Option pricing model | Derivatives at foreign exchange | Implied volatility (%)        
Disclosure of significant unobservable inputs used in fair value measurement of assets [line items]        
Significant unobservable inputs, percentage 0.37   0.42  
Level 3 | Maximum | Option pricing model | Derivatives at equity | Equity volatility (%)        
Disclosure of significant unobservable inputs used in fair value measurement of assets [line items]        
Significant unobservable inputs, percentage 1.27   0.75  
Level 3 | Maximum | Option pricing model | Derivatives at equity | Equity/Equity correlation        
Disclosure of significant unobservable inputs used in fair value measurement of assets [line items]        
Significant unobservable inputs, percentage 1.0   1.0  
Level 3 | Maximum | Option pricing model | Derivatives at equity | Equity/FX correlation        
Disclosure of significant unobservable inputs used in fair value measurement of assets [line items]        
Significant unobservable inputs, percentage 0.4   0.5  
Level 3 | Maximum | Option pricing model | Derivatives at equity | Dividend yield (%)        
Disclosure of significant unobservable inputs used in fair value measurement of assets [line items]        
Significant unobservable inputs, percentage 0.43   0.51  
Level 3 | Maximum | Option pricing model | Other derivatives | Commodity volatility (%)        
Disclosure of significant unobservable inputs used in fair value measurement of assets [line items]        
Significant unobservable inputs, percentage 0.84   0.76  
Level 3 | Maximum | Option pricing model | Other derivatives | Com/FX correlation        
Disclosure of significant unobservable inputs used in fair value measurement of assets [line items]        
Significant unobservable inputs, percentage     (0.25)