v3.26.1
Credit risk - Narrative (Details)
£ in Millions
 6 Months Ended
Jun. 30, 2026
GBP (£)
economic_scenario
Mar. 31, 2026
GBP (£)
Dec. 31, 2025
GBP (£)
Credit risk      
Disclosure of financial assets [line items]      
Number of economic scenarios | economic_scenario 5    
Stress horizon period 5 years    
Impairment allowance | Post-model adjustment      
Disclosure of financial assets [line items]      
Increase (decrease) in financial assets £ 81    
Financial assets 66    
Impairment allowance | Post-model adjustment | Barclays US Consumer Bank & Investment Bank      
Disclosure of financial assets [line items]      
Financial assets   £ 81  
Impairment allowance | Post-model adjustment | Barclays Investment Bank      
Disclosure of financial assets [line items]      
Financial assets 66    
Impairment allowance | Other adjustments      
Disclosure of financial assets [line items]      
Financial assets 70   £ 118
Impairment allowance | ECL from other financial assets subject to impairment, adjustment | Barclays US Consumer Bank & Investment Bank      
Disclosure of financial assets [line items]      
Financial assets (2)    
Impairment allowance | ECL from assets classified as held for sale, adjustment | Barclays US Consumer Bank & Investment Bank      
Disclosure of financial assets [line items]      
Financial assets (5)    
Impairment allowance | Retail mortgages      
Disclosure of financial assets [line items]      
Increase (decrease) in financial assets (4)    
Financial assets 37   33
Impairment allowance | Retail mortgages | Other adjustments      
Disclosure of financial assets [line items]      
Financial assets 0   8
Impairment allowance | Retail credit cards      
Disclosure of financial assets [line items]      
Increase (decrease) in financial assets (673)    
Financial assets 2,647   2,586
Impairment allowance | Retail credit cards | Other adjustments      
Disclosure of financial assets [line items]      
Financial assets 55   87
Impairment allowance | Corporate loans      
Disclosure of financial assets [line items]      
Increase (decrease) in financial assets (432)    
Financial assets 1,088   966
Impairment allowance | Corporate loans | Other adjustments      
Disclosure of financial assets [line items]      
Financial assets £ 14   £ 24