v3.25.2
Credit risk - Macroeconomic variables (specific bases and 5-year averages) (Details)
Jun. 30, 2025
Dec. 31, 2024
Upside 2    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Scenario probability weighting 15.50% 17.40%
Upside 2 | GDP | Specific bases | UK    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Scenario probability weighting 14.50% 15.00%
Upside 2 | GDP | Specific bases | US    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Scenario probability weighting 14.80% 14.90%
Upside 2 | GDP | 5-year averages | UK    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Scenario probability weighting 2.60% 2.60%
Upside 2 | GDP | 5-year averages | US    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Scenario probability weighting 2.80% 2.90%
Upside 2 | Unemployment | Specific bases | UK    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Scenario probability weighting 3.70% 3.40%
Upside 2 | Unemployment | Specific bases | US    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Scenario probability weighting 3.90% 3.50%
Upside 2 | Unemployment | 5-year averages | UK    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Scenario probability weighting 3.90% 3.70%
Upside 2 | Unemployment | 5-year averages | US    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Scenario probability weighting 3.90% 3.70%
Upside 2 | HPI | Specific bases | UK    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Scenario probability weighting 35.80% 36.30%
Upside 2 | HPI | Specific bases | US    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Scenario probability weighting 27.10% 30.10%
Upside 2 | HPI | 5-year averages | UK    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Scenario probability weighting 6.30% 6.40%
Upside 2 | HPI | 5-year averages | US    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Scenario probability weighting 4.90% 5.40%
Upside 2 | Bank rate | Specific bases | UK    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Scenario probability weighting 2.50% 2.80%
Upside 2 | Bank rate | 5-year averages | UK    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Scenario probability weighting 3.00% 3.50%
Upside 2 | Federal funds rate | Specific bases | US    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Scenario probability weighting 2.80% 2.80%
Upside 2 | Federal funds rate | 5-year averages | US    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Scenario probability weighting 3.10% 3.60%
Upside 1    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Scenario probability weighting 26.40% 26.80%
Upside 1 | GDP | Specific bases | UK    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Scenario probability weighting 10.90% 11.60%
Upside 1 | GDP | Specific bases | US    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Scenario probability weighting 12.00% 12.80%
Upside 1 | GDP | 5-year averages | UK    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Scenario probability weighting 2.00% 2.00%
Upside 1 | GDP | 5-year averages | US    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Scenario probability weighting 2.30% 2.50%
Upside 1 | Unemployment | Specific bases | UK    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Scenario probability weighting 4.20% 3.90%
Upside 1 | Unemployment | Specific bases | US    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Scenario probability weighting 4.10% 3.80%
Upside 1 | Unemployment | 5-year averages | UK    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Scenario probability weighting 4.30% 4.00%
Upside 1 | Unemployment | 5-year averages | US    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Scenario probability weighting 4.20% 3.90%
Upside 1 | HPI | Specific bases | UK    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Scenario probability weighting 25.00% 25.90%
Upside 1 | HPI | Specific bases | US    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Scenario probability weighting 19.00% 24.40%
Upside 1 | HPI | 5-year averages | UK    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Scenario probability weighting 4.60% 4.70%
Upside 1 | HPI | 5-year averages | US    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Scenario probability weighting 3.50% 4.50%
Upside 1 | Bank rate | Specific bases | UK    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Scenario probability weighting 3.30% 3.30%
Upside 1 | Bank rate | 5-year averages | UK    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Scenario probability weighting 3.50% 3.90%
Upside 1 | Federal funds rate | Specific bases | US    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Scenario probability weighting 3.30% 3.30%
Upside 1 | Federal funds rate | 5-year averages | US    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Scenario probability weighting 3.60% 4.00%
Baseline    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Scenario probability weighting 34.40% 32.50%
Baseline | GDP | Specific bases | UK    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Scenario probability weighting 1.30% 1.40%
Baseline | GDP | Specific bases | US    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Scenario probability weighting 1.80% 2.20%
Baseline | GDP | 5-year averages | UK    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Scenario probability weighting 1.30% 1.40%
Baseline | GDP | 5-year averages | US    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Scenario probability weighting 1.80% 2.20%
Baseline | Unemployment | Specific bases | UK    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Scenario probability weighting 4.60% 4.40%
Baseline | Unemployment | Specific bases | US    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Scenario probability weighting 4.50% 4.20%
Baseline | Unemployment | 5-year averages | UK    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Scenario probability weighting 4.60% 4.40%
Baseline | Unemployment | 5-year averages | US    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Scenario probability weighting 4.50% 4.20%
Baseline | HPI | Specific bases | UK    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Scenario probability weighting 2.80% 3.00%
Baseline | HPI | Specific bases | US    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Scenario probability weighting 2.20% 3.50%
Baseline | HPI | 5-year averages | UK    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Scenario probability weighting 2.80% 3.00%
Baseline | HPI | 5-year averages | US    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Scenario probability weighting 2.20% 3.50%
Baseline | Bank rate | Specific bases | UK    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Scenario probability weighting 3.90% 4.20%
Baseline | Bank rate | 5-year averages | UK    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Scenario probability weighting 3.90% 4.20%
Baseline | Federal funds rate | Specific bases | US    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Scenario probability weighting 3.80% 4.20%
Baseline | Federal funds rate | 5-year averages | US    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Scenario probability weighting 3.80% 4.20%
Downside 1    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Scenario probability weighting 15.20% 14.70%
Downside 1 | GDP | Specific bases | UK    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Scenario probability weighting (1.30%) 0.20%
Downside 1 | GDP | Specific bases | US    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Scenario probability weighting (1.40%) 0.40%
Downside 1 | GDP | 5-year averages | UK    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Scenario probability weighting 0.90% 0.90%
Downside 1 | GDP | 5-year averages | US    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Scenario probability weighting 1.00% 1.70%
Downside 1 | Unemployment | Specific bases | UK    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Scenario probability weighting 6.50% 6.50%
Downside 1 | Unemployment | Specific bases | US    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Scenario probability weighting 6.50% 5.90%
Downside 1 | Unemployment | 5-year averages | UK    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Scenario probability weighting 5.40% 5.30%
Downside 1 | Unemployment | 5-year averages | US    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Scenario probability weighting 5.40% 5.00%
Downside 1 | HPI | Specific bases | UK    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Scenario probability weighting (13.20%) (11.30%)
Downside 1 | HPI | Specific bases | US    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Scenario probability weighting (2.20%) 1.10%
Downside 1 | HPI | 5-year averages | UK    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Scenario probability weighting 0.90% 0.80%
Downside 1 | HPI | 5-year averages | US    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Scenario probability weighting 1.90% 2.40%
Downside 1 | Bank rate | Specific bases | UK    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Scenario probability weighting 4.60% 5.30%
Downside 1 | Bank rate | 5-year averages | UK    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Scenario probability weighting 2.90% 3.30%
Downside 1 | Federal funds rate | Specific bases | US    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Scenario probability weighting 4.50% 5.30%
Downside 1 | Federal funds rate | 5-year averages | US    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Scenario probability weighting 3.30% 3.20%
Downside 2    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Scenario probability weighting 8.50% 8.60%
Downside 2 | GDP | Specific bases | UK    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Scenario probability weighting (4.00%) (2.90%)
Downside 2 | GDP | Specific bases | US    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Scenario probability weighting (5.30%) (2.10%)
Downside 2 | GDP | 5-year averages | UK    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Scenario probability weighting 0.50% 0.50%
Downside 2 | GDP | 5-year averages | US    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Scenario probability weighting 0.10% 1.20%
Downside 2 | Unemployment | Specific bases | UK    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Scenario probability weighting 8.40% 8.40%
Downside 2 | Unemployment | Specific bases | US    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Scenario probability weighting 8.40% 7.50%
Downside 2 | Unemployment | 5-year averages | UK    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Scenario probability weighting 6.20% 6.10%
Downside 2 | Unemployment | 5-year averages | US    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Scenario probability weighting 6.40% 5.80%
Downside 2 | HPI | Specific bases | UK    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Scenario probability weighting (28.10%) (26.80%)
Downside 2 | HPI | Specific bases | US    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Scenario probability weighting (8.40%) (4.00%)
Downside 2 | HPI | 5-year averages | UK    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Scenario probability weighting (1.10%) (1.60%)
Downside 2 | HPI | 5-year averages | US    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Scenario probability weighting 1.70% 1.20%
Downside 2 | Bank rate | Specific bases | UK    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Scenario probability weighting 4.60% 5.30%
Downside 2 | Bank rate | 5-year averages | UK    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Scenario probability weighting 1.60% 2.40%
Downside 2 | Federal funds rate | Specific bases | US    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Scenario probability weighting 4.50% 5.30%
Downside 2 | Federal funds rate | 5-year averages | US    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Scenario probability weighting 2.70% 2.10%