v3.26.1
Credit risk - Macroeconomic variables (specific bases and 5-year averages) (Details)
Jun. 30, 2026
Dec. 31, 2025
Upside 2    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Scenario weighting 13.70% 14.40%
Upside 2 | GDP | Specific bases | UK    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Scenario weighting 14.40% 14.50%
Upside 2 | GDP | Specific bases | US    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Scenario weighting 14.50% 14.60%
Upside 2 | GDP | 5-year averages | UK    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Scenario weighting 2.60% 2.70%
Upside 2 | GDP | 5-year averages | US    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Scenario weighting 2.70% 2.70%
Upside 2 | Unemployment | Specific bases | UK    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Scenario weighting 4.00% 3.80%
Upside 2 | Unemployment | Specific bases | US    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Scenario weighting 3.60% 3.70%
Upside 2 | Unemployment | 5-year averages | UK    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Scenario weighting 4.30% 4.10%
Upside 2 | Unemployment | 5-year averages | US    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Scenario weighting 3.70% 3.90%
Upside 2 | HPI | Specific bases | UK    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Scenario weighting 35.40% 34.60%
Upside 2 | HPI | Specific bases | US    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Scenario weighting 26.70% 26.20%
Upside 2 | HPI | 5-year averages | UK    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Scenario weighting 6.30% 6.10%
Upside 2 | HPI | 5-year averages | US    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Scenario weighting 4.90% 4.80%
Upside 2 | Bank rate | Specific bases | UK    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Scenario weighting 3.00% 2.30%
Upside 2 | Bank rate | 5-year averages | UK    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Scenario weighting 3.40% 2.90%
Upside 2 | Federal funds rate | Specific bases | US    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Scenario weighting 2.80% 2.50%
Upside 2 | Federal funds rate | 5-year averages | US    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Scenario weighting 3.00% 2.90%
Upside 1    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Scenario weighting 27.30% 27.40%
Upside 1 | GDP | Specific bases | UK    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Scenario weighting 10.20% 10.80%
Upside 1 | GDP | Specific bases | US    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Scenario weighting 12.50% 12.40%
Upside 1 | GDP | 5-year averages | UK    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Scenario weighting 1.80% 2.00%
Upside 1 | GDP | 5-year averages | US    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Scenario weighting 2.40% 2.40%
Upside 1 | Unemployment | Specific bases | UK    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Scenario weighting 4.50% 4.30%
Upside 1 | Unemployment | Specific bases | US    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Scenario weighting 4.00% 4.10%
Upside 1 | Unemployment | 5-year averages | UK    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Scenario weighting 4.70% 4.50%
Upside 1 | Unemployment | 5-year averages | US    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Scenario weighting 4.00% 4.10%
Upside 1 | HPI | Specific bases | UK    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Scenario weighting 24.60% 24.90%
Upside 1 | HPI | Specific bases | US    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Scenario weighting 19.10% 19.30%
Upside 1 | HPI | 5-year averages | UK    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Scenario weighting 4.50% 4.50%
Upside 1 | HPI | 5-year averages | US    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Scenario weighting 3.60% 3.60%
Upside 1 | Bank rate | Specific bases | UK    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Scenario weighting 3.50% 2.80%
Upside 1 | Bank rate | 5-year averages | UK    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Scenario weighting 3.80% 3.20%
Upside 1 | Federal funds rate | Specific bases | US    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Scenario weighting 3.30% 2.80%
Upside 1 | Federal funds rate | 5-year averages | US    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Scenario weighting 3.30% 3.20%
Baseline    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Scenario weighting 39.50% 38.50%
Baseline | GDP | Specific bases | UK    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Scenario weighting 1.10% 1.40%
Baseline | GDP | Specific bases | US    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Scenario weighting 2.00% 2.00%
Baseline | GDP | 5-year averages | UK    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Scenario weighting 1.10% 1.40%
Baseline | GDP | 5-year averages | US    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Scenario weighting 2.00% 2.00%
Baseline | Unemployment | Specific bases | UK    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Scenario weighting 5.10% 4.80%
Baseline | Unemployment | Specific bases | US    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Scenario weighting 4.30% 4.40%
Baseline | Unemployment | 5-year averages | UK    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Scenario weighting 5.10% 4.80%
Baseline | Unemployment | 5-year averages | US    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Scenario weighting 4.30% 4.40%
Baseline | HPI | Specific bases | UK    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Scenario weighting 2.80% 3.00%
Baseline | HPI | Specific bases | US    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Scenario weighting 2.30% 2.40%
Baseline | HPI | 5-year averages | UK    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Scenario 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 weighting 2.30% 2.40%
Baseline | Bank rate | Specific bases | UK    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Scenario weighting 4.30% 3.60%
Baseline | Bank rate | 5-year averages | UK    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Scenario weighting 4.30% 3.60%
Baseline | Federal funds rate | Specific bases | US    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Scenario weighting 3.70% 3.50%
Baseline | Federal funds rate | 5-year averages | US    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Scenario weighting 3.70% 3.50%
Downside 1    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Scenario weighting 12.50% 12.70%
Downside 1 | GDP | Specific bases | UK    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Scenario weighting (1.90%) (0.30%)
Downside 1 | GDP | Specific bases | US    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Scenario weighting (1.10%) (0.20%)
Downside 1 | GDP | 5-year averages | UK    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Scenario weighting 0.50% 0.90%
Downside 1 | GDP | 5-year averages | US    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Scenario weighting 1.00% 1.10%
Downside 1 | Unemployment | Specific bases | UK    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Scenario weighting 6.70% 6.50%
Downside 1 | Unemployment | Specific bases | US    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Scenario weighting 6.60% 6.60%
Downside 1 | Unemployment | 5-year averages | UK    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Scenario weighting 6.00% 5.50%
Downside 1 | Unemployment | 5-year averages | US    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Scenario weighting 5.70% 5.40%
Downside 1 | HPI | Specific bases | UK    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Scenario weighting (14.10%) (12.60%)
Downside 1 | HPI | Specific bases | US    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Scenario weighting (3.00%) (1.50%)
Downside 1 | HPI | 5-year averages | UK    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Scenario weighting 0.00% 0.60%
Downside 1 | HPI | 5-year averages | US    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Scenario weighting 1.50% 1.90%
Downside 1 | Bank rate | Specific bases | UK    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Scenario weighting 4.80% 4.60%
Downside 1 | Bank rate | 5-year averages | UK    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Scenario weighting 4.50% 2.70%
Downside 1 | Federal funds rate | Specific bases | US    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Scenario weighting 4.30% 4.30%
Downside 1 | Federal funds rate | 5-year averages | US    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Scenario weighting 4.00% 3.10%
Downside 2    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Scenario weighting 7.00% 7.00%
Downside 2 | GDP | Specific bases | UK    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Scenario weighting (5.10%) (3.50%)
Downside 2 | GDP | Specific bases | US    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Scenario weighting (5.20%) (4.60%)
Downside 2 | GDP | 5-year averages | UK    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Scenario weighting 0.00% 0.30%
Downside 2 | GDP | 5-year averages | US    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Scenario weighting 0.00% 0.10%
Downside 2 | Unemployment | Specific bases | UK    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Scenario weighting 8.10% 8.10%
Downside 2 | Unemployment | Specific bases | US    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Scenario weighting 8.80% 8.80%
Downside 2 | Unemployment | 5-year averages | UK    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Scenario weighting 6.90% 6.20%
Downside 2 | Unemployment | 5-year averages | US    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Scenario weighting 7.10% 6.30%
Downside 2 | HPI | Specific bases | UK    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Scenario weighting (29.30%) (28.00%)
Downside 2 | HPI | Specific bases | US    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Scenario weighting (9.20%) (8.10%)
Downside 2 | HPI | 5-year averages | UK    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Scenario weighting (2.80%) (2.00%)
Downside 2 | HPI | 5-year averages | US    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Scenario weighting 0.70% 1.50%
Downside 2 | Bank rate | Specific bases | UK    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Scenario weighting 5.30% 4.60%
Downside 2 | Bank rate | 5-year averages | UK    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Scenario weighting 4.60% 1.70%
Downside 2 | Federal funds rate | Specific bases | US    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Scenario weighting 5.30% 4.30%
Downside 2 | Federal funds rate | 5-year averages | US    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Scenario weighting 4.30% 2.50%