v3.26.1
Financial assets and liabilities at fair value - Assets and liabilities Sensitivity analysis - level 3 (Details)
kr in Millions
 6 Months Ended 12 Months Ended
Jun. 30, 2026
SEK (kr)
Dec. 31, 2025
SEK (kr)
Dec. 31, 2024
SEK (kr)
Disclosure of significant unobservable inputs used in fair value measurement of assets      
Financial liabilities at fair value kr (322,449) kr (314,304)  
Level 3      
Disclosure of significant unobservable inputs used in fair value measurement of assets      
Net assets (liabilities) (1,614) (3,661) kr (4,903)
Level 3 | Top of range      
Disclosure of significant unobservable inputs used in fair value measurement of assets      
Sensitivity impact on total comprehensive income 7 10  
Level 3 | Bottom of range      
Disclosure of significant unobservable inputs used in fair value measurement of assets      
Sensitivity impact on total comprehensive income (7) (10)  
Level 3 | Derivatives      
Disclosure of significant unobservable inputs used in fair value measurement of assets      
Net assets (liabilities) (577) (1,063) (1,451)
Level 3 | Derivatives | Top of range      
Disclosure of significant unobservable inputs used in fair value measurement of assets      
Sensitivity impact on total comprehensive income (13) (17)  
Level 3 | Derivatives | Bottom of range      
Disclosure of significant unobservable inputs used in fair value measurement of assets      
Sensitivity impact on total comprehensive income 13 17  
Level 3 | Derivatives | Equity      
Disclosure of significant unobservable inputs used in fair value measurement of assets      
Net assets (liabilities) kr 0    
Level 3 | Derivatives | Equity | Option Model | Top of range      
Disclosure of significant unobservable inputs used in fair value measurement of assets      
Correlation 0.12    
Sensitivity impact on total comprehensive income kr 0    
Level 3 | Derivatives | Equity | Option Model | Bottom of range      
Disclosure of significant unobservable inputs used in fair value measurement of assets      
Correlation 0.12    
Sensitivity impact on total comprehensive income kr 0    
Level 3 | Derivatives | Interest rate      
Disclosure of significant unobservable inputs used in fair value measurement of assets      
Net assets (liabilities) kr 0    
Level 3 | Derivatives | Interest rate | Option Model | Top of range      
Disclosure of significant unobservable inputs used in fair value measurement of assets      
Correlation 0.12    
Sensitivity impact on total comprehensive income kr 0    
Level 3 | Derivatives | Interest rate | Option Model | Bottom of range      
Disclosure of significant unobservable inputs used in fair value measurement of assets      
Correlation 0.12    
Sensitivity impact on total comprehensive income kr 0    
Level 3 | Derivatives | FX      
Disclosure of significant unobservable inputs used in fair value measurement of assets      
Net assets (liabilities) kr (463)    
Level 3 | Derivatives | FX | Option Model | Top of range      
Disclosure of significant unobservable inputs used in fair value measurement of assets      
Correlation 0.12    
Sensitivity impact on total comprehensive income kr (13)    
Level 3 | Derivatives | FX | Option Model | Bottom of range      
Disclosure of significant unobservable inputs used in fair value measurement of assets      
Correlation 0.12    
Sensitivity impact on total comprehensive income kr 13    
Level 3 | Derivatives | Other      
Disclosure of significant unobservable inputs used in fair value measurement of assets      
Net assets (liabilities) kr (114)    
Level 3 | Derivatives | Other | Option Model | Top of range      
Disclosure of significant unobservable inputs used in fair value measurement of assets      
Correlation 0.12    
Sensitivity impact on total comprehensive income kr 0    
Level 3 | Derivatives | Other | Option Model | Bottom of range      
Disclosure of significant unobservable inputs used in fair value measurement of assets      
Correlation 0.12    
Sensitivity impact on total comprehensive income kr 0    
Level 3 | Debt securities issued      
Disclosure of significant unobservable inputs used in fair value measurement of assets      
Financial liabilities at fair value (1,037) (2,598) kr (3,452)
Level 3 | Debt securities issued | Top of range      
Disclosure of significant unobservable inputs used in fair value measurement of assets      
Sensitivity impact on total comprehensive income 20 27  
Level 3 | Debt securities issued | Bottom of range      
Disclosure of significant unobservable inputs used in fair value measurement of assets      
Sensitivity impact on total comprehensive income (20) kr (27)  
Level 3 | Debt securities issued | Equity      
Disclosure of significant unobservable inputs used in fair value measurement of assets      
Financial liabilities at fair value kr 0    
Level 3 | Debt securities issued | Equity | Option Model | Top of range      
Disclosure of significant unobservable inputs used in fair value measurement of assets      
Correlation 0.12    
Sensitivity impact on total comprehensive income kr 0    
Level 3 | Debt securities issued | Equity | Option Model | Bottom of range      
Disclosure of significant unobservable inputs used in fair value measurement of assets      
Correlation 0.12    
Sensitivity impact on total comprehensive income kr 0    
Level 3 | Debt securities issued | Equity | Discounted cash flow | Top of range      
Disclosure of significant unobservable inputs used in fair value measurement of assets      
Credit spreads (in basis points) 0.0010    
Sensitivity impact on total comprehensive income kr 0    
Level 3 | Debt securities issued | Equity | Discounted cash flow | Bottom of range      
Disclosure of significant unobservable inputs used in fair value measurement of assets      
Credit spreads (in basis points) 0.0010    
Sensitivity impact on total comprehensive income kr 0    
Level 3 | Debt securities issued | Interest rate      
Disclosure of significant unobservable inputs used in fair value measurement of assets      
Financial liabilities at fair value kr 0    
Level 3 | Debt securities issued | Interest rate | Option Model | Top of range      
Disclosure of significant unobservable inputs used in fair value measurement of assets      
Correlation 0.12    
Sensitivity impact on total comprehensive income kr 0    
Level 3 | Debt securities issued | Interest rate | Option Model | Bottom of range      
Disclosure of significant unobservable inputs used in fair value measurement of assets      
Correlation 0.12    
Sensitivity impact on total comprehensive income kr 0    
Level 3 | Debt securities issued | Interest rate | Discounted cash flow | Top of range      
Disclosure of significant unobservable inputs used in fair value measurement of assets      
Credit spreads (in basis points) 0.0010    
Sensitivity impact on total comprehensive income kr 0    
Level 3 | Debt securities issued | Interest rate | Discounted cash flow | Bottom of range      
Disclosure of significant unobservable inputs used in fair value measurement of assets      
Credit spreads (in basis points) 0.0010    
Sensitivity impact on total comprehensive income kr 0    
Level 3 | Debt securities issued | FX      
Disclosure of significant unobservable inputs used in fair value measurement of assets      
Financial liabilities at fair value kr (938)    
Level 3 | Debt securities issued | FX | Option Model | Top of range      
Disclosure of significant unobservable inputs used in fair value measurement of assets      
Correlation 0.12    
Sensitivity impact on total comprehensive income kr 13    
Level 3 | Debt securities issued | FX | Option Model | Bottom of range      
Disclosure of significant unobservable inputs used in fair value measurement of assets      
Correlation 0.12    
Sensitivity impact on total comprehensive income kr (13)    
Level 3 | Debt securities issued | FX | Discounted cash flow | Top of range      
Disclosure of significant unobservable inputs used in fair value measurement of assets      
Credit spreads (in basis points) 0.0010    
Sensitivity impact on total comprehensive income kr 7    
Level 3 | Debt securities issued | FX | Discounted cash flow | Bottom of range      
Disclosure of significant unobservable inputs used in fair value measurement of assets      
Credit spreads (in basis points) 0.0010    
Sensitivity impact on total comprehensive income kr (7)    
Level 3 | Debt securities issued | Other      
Disclosure of significant unobservable inputs used in fair value measurement of assets      
Financial liabilities at fair value kr (99)    
Level 3 | Debt securities issued | Other | Option Model | Top of range      
Disclosure of significant unobservable inputs used in fair value measurement of assets      
Correlation 0.12    
Sensitivity impact on total comprehensive income kr 0    
Level 3 | Debt securities issued | Other | Option Model | Bottom of range      
Disclosure of significant unobservable inputs used in fair value measurement of assets      
Correlation 0.12    
Sensitivity impact on total comprehensive income kr 0    
Level 3 | Debt securities issued | Other | Discounted cash flow | Top of range      
Disclosure of significant unobservable inputs used in fair value measurement of assets      
Credit spreads (in basis points) 0.0010    
Sensitivity impact on total comprehensive income kr 0    
Level 3 | Debt securities issued | Other | Discounted cash flow | Bottom of range      
Disclosure of significant unobservable inputs used in fair value measurement of assets      
Credit spreads (in basis points) 0.0010    
Sensitivity impact on total comprehensive income kr 0