v3.26.1
Risk management - Disclosure of concentrations by risk factor, structural risk (Details) - EUR (€)
€ in Millions
 12 Months Ended
Dec. 31, 2025
Dec. 31, 2024
Dec. 31, 2023
Structural VaR      
Disclosure of nature and extent of risks arising from financial instruments [line items]      
VaR percentage 99.00%    
Time horizon 1 day    
Diversification effect      
Disclosure of nature and extent of risks arising from financial instruments [line items]      
VaR € (17.7) € (27.3) € (17.1)
Diversification effect | Min      
Disclosure of nature and extent of risks arising from financial instruments [line items]      
VaR (10.7)    
Diversification effect | Average      
Disclosure of nature and extent of risks arising from financial instruments [line items]      
VaR (21.0) (19.8) (14.9)
Diversification effect | Max      
Disclosure of nature and extent of risks arising from financial instruments [line items]      
VaR (59.3)    
Exchange rate      
Disclosure of nature and extent of risks arising from financial instruments [line items]      
VaR 6.3 5.9 4.8
Exchange rate | Min      
Disclosure of nature and extent of risks arising from financial instruments [line items]      
VaR 3.3    
Exchange rate | Average      
Disclosure of nature and extent of risks arising from financial instruments [line items]      
VaR 7.4 5.8 5.3
Exchange rate | Max      
Disclosure of nature and extent of risks arising from financial instruments [line items]      
VaR 37.5    
VaR Equities      
Disclosure of nature and extent of risks arising from financial instruments [line items]      
VaR 8.1 9.5 6.0
VaR Equities | Min      
Disclosure of nature and extent of risks arising from financial instruments [line items]      
VaR 2.4    
VaR Equities | Average      
Disclosure of nature and extent of risks arising from financial instruments [line items]      
VaR 6.5 6.0 3.2
VaR Equities | Max      
Disclosure of nature and extent of risks arising from financial instruments [line items]      
VaR 10.8    
Banking book | Structural VaR      
Disclosure of nature and extent of risks arising from financial instruments [line items]      
VaR 690.1 687.5 749.5
Banking book | Structural VaR | Min      
Disclosure of nature and extent of risks arising from financial instruments [line items]      
VaR 598.5    
Banking book | Structural VaR | Average      
Disclosure of nature and extent of risks arising from financial instruments [line items]      
VaR 662.9 747.7 705.0
Banking book | Structural VaR | Max      
Disclosure of nature and extent of risks arising from financial instruments [line items]      
VaR 751.9    
Banking book | Diversification effect      
Disclosure of nature and extent of risks arising from financial instruments [line items]      
VaR (206.6) (268.6) (444.7)
Banking book | Diversification effect | Min      
Disclosure of nature and extent of risks arising from financial instruments [line items]      
VaR (155.9)    
Banking book | Diversification effect | Average      
Disclosure of nature and extent of risks arising from financial instruments [line items]      
VaR (258.4) (386.4) (416.6)
Banking book | Diversification effect | Max      
Disclosure of nature and extent of risks arising from financial instruments [line items]      
VaR (265.6)    
Banking book | VaR Interest Rate      
Disclosure of nature and extent of risks arising from financial instruments [line items]      
VaR 177.6 235.2 380.2
Banking book | VaR Interest Rate | Min      
Disclosure of nature and extent of risks arising from financial instruments [line items]      
VaR 158.3    
Banking book | VaR Interest Rate | Average      
Disclosure of nature and extent of risks arising from financial instruments [line items]      
VaR 177.3 412.0 348.4
Banking book | VaR Interest Rate | Max      
Disclosure of nature and extent of risks arising from financial instruments [line items]      
VaR 205.8    
Banking book | Exchange rate      
Disclosure of nature and extent of risks arising from financial instruments [line items]      
VaR 572.4 594.4 642.9
Banking book | Exchange rate | Min      
Disclosure of nature and extent of risks arising from financial instruments [line items]      
VaR 486.0    
Banking book | Exchange rate | Average      
Disclosure of nature and extent of risks arising from financial instruments [line items]      
VaR 597.7 571.7 580.4
Banking book | Exchange rate | Max      
Disclosure of nature and extent of risks arising from financial instruments [line items]      
VaR 648.7    
Banking book | VaR Equities      
Disclosure of nature and extent of risks arising from financial instruments [line items]      
VaR 146.7 126.5 171.1
Banking book | VaR Equities | Min      
Disclosure of nature and extent of risks arising from financial instruments [line items]      
VaR 110.1    
Banking book | VaR Equities | Average      
Disclosure of nature and extent of risks arising from financial instruments [line items]      
VaR 146.3 € 150.4 € 192.8
Banking book | VaR Equities | Max      
Disclosure of nature and extent of risks arising from financial instruments [line items]      
VaR € 163.0