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Credit risk - Schedule of Loans and Advances by Credit Grade (Details) - GBP (£)
£ in Millions
Dec. 31, 2025
Dec. 31, 2024
Dec. 31, 2023
Disclosure of credit risk exposure [line items]      
Total financial assets £ 907,307 £ 870,816  
Total loans and advances to customers      
Disclosure of credit risk exposure [line items]      
Total financial assets 481,463 459,857  
Total loans and advances to customers | Stage 1 and 2 | 12-month expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 429,456 404,624  
Total loans and advances to customers | Stage 1 and 2 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 41,602 43,605  
Total loans and advances to customers | Stage 3 £m | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 5,488 5,608  
Total loans and advances to customers | POCI £m | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 4,917 6,020  
Retail – UK mortgages      
Disclosure of credit risk exposure [line items]      
Total financial assets 323,087 312,280  
Retail – UK mortgages | Stage 1 and 2 | 12-month expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 284,256 269,707  
Retail – UK mortgages | Stage 1 and 2 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 30,207 32,722  
Retail – UK mortgages | Stage 3 £m | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 3,707 3,831  
Retail – UK mortgages | POCI £m | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 4,917 6,020  
Credit cards      
Disclosure of credit risk exposure [line items]      
Total financial assets 17,344 15,661  
Credit cards | Stage 1 and 2 | 12-month expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 15,113 13,385  
Credit cards | Stage 1 and 2 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 2,078 2,144  
Credit cards | Stage 3 £m | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 153 132  
Commercial Banking      
Disclosure of credit risk exposure [line items]      
Total financial assets 90,307 87,602  
Commercial Banking | Stage 1 and 2 | 12-month expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 83,847 81,272  
Commercial Banking | Stage 1 and 2 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 5,085 4,904  
Commercial Banking | Stage 3 £m | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 1,375 1,426  
Gross carrying amount | Total loans and advances to customers      
Disclosure of credit risk exposure [line items]      
Total financial assets 484,474 463,048 £ 453,462
Gross carrying amount | Total loans and advances to customers | Stage 1 and 2 | 12-month expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 430,193 405,360 385,294
Gross carrying amount | Total loans and advances to customers | Stage 1 and 2 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 42,679 44,765 53,167
Gross carrying amount | Total loans and advances to customers | Stage 3 £m | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 6,526 6,716 7,147
Gross carrying amount | Total loans and advances to customers | POCI £m | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 5,076 6,207 7,854
Gross carrying amount | Total Retail      
Disclosure of credit risk exposure [line items]      
Total financial assets 392,793 374,559  
Gross carrying amount | Total Retail | Stage 1 and 2 | 12-month expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 345,633 323,878  
Gross carrying amount | Total Retail | Stage 1 and 2 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 37,315 39,597  
Gross carrying amount | Total Retail | Stage 3 £m | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 4,769 4,877  
Gross carrying amount | Total Retail | POCI £m | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 5,076 6,207  
Gross carrying amount | Retail – UK mortgages      
Disclosure of credit risk exposure [line items]      
Total financial assets 323,813 313,128 307,320
Gross carrying amount | Retail – UK mortgages | RMS 1–3      
Disclosure of credit risk exposure [line items]      
Total financial assets 295,737 282,314  
Gross carrying amount | Retail – UK mortgages | RMS 4–6      
Disclosure of credit risk exposure [line items]      
Total financial assets 14,308 15,871  
Gross carrying amount | Retail – UK mortgages | RMS 7–9      
Disclosure of credit risk exposure [line items]      
Total financial assets 1,347 1,408  
Gross carrying amount | Retail – UK mortgages | RMS 10      
Disclosure of credit risk exposure [line items]      
Total financial assets 361 290  
Gross carrying amount | Retail – UK mortgages | RMS 11–13      
Disclosure of credit risk exposure [line items]      
Total financial assets 2,968 2,872  
Gross carrying amount | Retail – UK mortgages | RMS 14      
Disclosure of credit risk exposure [line items]      
Total financial assets 9,092 10,373  
Gross carrying amount | Retail – UK mortgages | Stage 1 and 2 | 12-month expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 284,307 269,760 256,596
Gross carrying amount | Retail – UK mortgages | Stage 1 and 2 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 30,414 32,995 38,533
Gross carrying amount | Retail – UK mortgages | Stage 1 and 2 | RMS 1–3 | 12-month expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 276,020 261,101  
Gross carrying amount | Retail – UK mortgages | Stage 1 and 2 | RMS 1–3 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 19,717 21,213  
Gross carrying amount | Retail – UK mortgages | Stage 1 and 2 | RMS 4–6 | 12-month expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 8,034 8,487  
Gross carrying amount | Retail – UK mortgages | Stage 1 and 2 | RMS 4–6 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 6,274 7,384  
Gross carrying amount | Retail – UK mortgages | Stage 1 and 2 | RMS 7–9 | 12-month expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 154 112  
Gross carrying amount | Retail – UK mortgages | Stage 1 and 2 | RMS 7–9 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 1,193 1,296  
Gross carrying amount | Retail – UK mortgages | Stage 1 and 2 | RMS 10 | 12-month expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 23 17  
Gross carrying amount | Retail – UK mortgages | Stage 1 and 2 | RMS 10 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 338 273  
Gross carrying amount | Retail – UK mortgages | Stage 1 and 2 | RMS 11–13 | 12-month expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 76 43  
Gross carrying amount | Retail – UK mortgages | Stage 1 and 2 | RMS 11–13 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 2,892 2,829  
Gross carrying amount | Retail – UK mortgages | Stage 1 and 2 | RMS 14 | 12-month expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 0 0  
Gross carrying amount | Retail – UK mortgages | Stage 1 and 2 | RMS 14 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 0 0  
Gross carrying amount | Retail – UK mortgages | Stage 3 £m | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 4,016 4,166 4,337
Gross carrying amount | Retail – UK mortgages | Stage 3 £m | RMS 1–3 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 0 0  
Gross carrying amount | Retail – UK mortgages | Stage 3 £m | RMS 4–6 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 0 0  
Gross carrying amount | Retail – UK mortgages | Stage 3 £m | RMS 7–9 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 0 0  
Gross carrying amount | Retail – UK mortgages | Stage 3 £m | RMS 10 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 0 0  
Gross carrying amount | Retail – UK mortgages | Stage 3 £m | RMS 11–13 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 0 0  
Gross carrying amount | Retail – UK mortgages | Stage 3 £m | RMS 14 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 4,016 4,166  
Gross carrying amount | Retail – UK mortgages | POCI £m | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 5,076 6,207 7,854
Gross carrying amount | Retail – UK mortgages | POCI £m | RMS 1–3 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 0 0  
Gross carrying amount | Retail – UK mortgages | POCI £m | RMS 4–6 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 0 0  
Gross carrying amount | Retail – UK mortgages | POCI £m | RMS 7–9 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 0 0  
Gross carrying amount | Retail – UK mortgages | POCI £m | RMS 10 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 0 0  
Gross carrying amount | Retail – UK mortgages | POCI £m | RMS 11–13 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 0 0  
Gross carrying amount | Retail – UK mortgages | POCI £m | RMS 14 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 5,076 6,207  
Gross carrying amount | Credit cards      
Disclosure of credit risk exposure [line items]      
Total financial assets 17,858 16,240 15,817
Gross carrying amount | Credit cards | RMS 1–3      
Disclosure of credit risk exposure [line items]      
Total financial assets 5,714 5,068  
Gross carrying amount | Credit cards | RMS 4–6      
Disclosure of credit risk exposure [line items]      
Total financial assets 9,329 8,360  
Gross carrying amount | Credit cards | RMS 7–9      
Disclosure of credit risk exposure [line items]      
Total financial assets 2,114 2,101  
Gross carrying amount | Credit cards | RMS 10      
Disclosure of credit risk exposure [line items]      
Total financial assets 148 152  
Gross carrying amount | Credit cards | RMS 11–13      
Disclosure of credit risk exposure [line items]      
Total financial assets 279 294  
Gross carrying amount | Credit cards | RMS 14      
Disclosure of credit risk exposure [line items]      
Total financial assets 274 265  
Gross carrying amount | Credit cards | Stage 1 and 2 | 12-month expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 15,258 13,534 12,625
Gross carrying amount | Credit cards | Stage 1 and 2 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 2,326 2,441 2,908
Gross carrying amount | Credit cards | Stage 1 and 2 | RMS 1–3 | 12-month expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 5,708 5,058  
Gross carrying amount | Credit cards | Stage 1 and 2 | RMS 1–3 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 6 10  
Gross carrying amount | Credit cards | Stage 1 and 2 | RMS 4–6 | 12-month expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 8,221 7,231  
Gross carrying amount | Credit cards | Stage 1 and 2 | RMS 4–6 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 1,108 1,129  
Gross carrying amount | Credit cards | Stage 1 and 2 | RMS 7–9 | 12-month expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 1,321 1,242  
Gross carrying amount | Credit cards | Stage 1 and 2 | RMS 7–9 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 793 859  
Gross carrying amount | Credit cards | Stage 1 and 2 | RMS 10 | 12-month expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 8 3  
Gross carrying amount | Credit cards | Stage 1 and 2 | RMS 10 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 140 149  
Gross carrying amount | Credit cards | Stage 1 and 2 | RMS 11–13 | 12-month expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 0 0  
Gross carrying amount | Credit cards | Stage 1 and 2 | RMS 11–13 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 279 294  
Gross carrying amount | Credit cards | Stage 1 and 2 | RMS 14 | 12-month expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 0 0  
Gross carrying amount | Credit cards | Stage 1 and 2 | RMS 14 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 0 0  
Gross carrying amount | Credit cards | Stage 3 £m | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 274 265 284
Gross carrying amount | Credit cards | Stage 3 £m | RMS 1–3 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 0 0  
Gross carrying amount | Credit cards | Stage 3 £m | RMS 4–6 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 0 0  
Gross carrying amount | Credit cards | Stage 3 £m | RMS 7–9 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 0 0  
Gross carrying amount | Credit cards | Stage 3 £m | RMS 10 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 0 0  
Gross carrying amount | Credit cards | Stage 3 £m | RMS 11–13 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 0 0  
Gross carrying amount | Credit cards | Stage 3 £m | RMS 14 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 274 265  
Gross carrying amount | Credit cards | POCI £m | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 0 0  
Gross carrying amount | Credit cards | POCI £m | RMS 1–3 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 0 0  
Gross carrying amount | Credit cards | POCI £m | RMS 4–6 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 0 0  
Gross carrying amount | Credit cards | POCI £m | RMS 7–9 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 0 0  
Gross carrying amount | Credit cards | POCI £m | RMS 10 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 0 0  
Gross carrying amount | Credit cards | POCI £m | RMS 11–13 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 0 0  
Gross carrying amount | Credit cards | POCI £m | RMS 14 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 0 0  
Gross carrying amount | Retail – UK unsecured loans and overdrafts      
Disclosure of credit risk exposure [line items]      
Total financial assets 12,191 10,736  
Gross carrying amount | Retail – UK unsecured loans and overdrafts | RMS 1–3      
Disclosure of credit risk exposure [line items]      
Total financial assets 1,378 1,209  
Gross carrying amount | Retail – UK unsecured loans and overdrafts | RMS 4–6      
Disclosure of credit risk exposure [line items]      
Total financial assets 8,754 7,504  
Gross carrying amount | Retail – UK unsecured loans and overdrafts | RMS 7–9      
Disclosure of credit risk exposure [line items]      
Total financial assets 1,386 1,354  
Gross carrying amount | Retail – UK unsecured loans and overdrafts | RMS 10      
Disclosure of credit risk exposure [line items]      
Total financial assets 136 142  
Gross carrying amount | Retail – UK unsecured loans and overdrafts | RMS 11–13      
Disclosure of credit risk exposure [line items]      
Total financial assets 344 352  
Gross carrying amount | Retail – UK unsecured loans and overdrafts | RMS 14      
Disclosure of credit risk exposure [line items]      
Total financial assets 193 175  
Gross carrying amount | Retail – UK unsecured loans and overdrafts | Stage 1 and 2 | 12-month expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 10,601 9,314  
Gross carrying amount | Retail – UK unsecured loans and overdrafts | Stage 1 and 2 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 1,397 1,247  
Gross carrying amount | Retail – UK unsecured loans and overdrafts | Stage 1 and 2 | RMS 1–3 | 12-month expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 1,376 1,207  
Gross carrying amount | Retail – UK unsecured loans and overdrafts | Stage 1 and 2 | RMS 1–3 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 2 2  
Gross carrying amount | Retail – UK unsecured loans and overdrafts | Stage 1 and 2 | RMS 4–6 | 12-month expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 8,130 7,020  
Gross carrying amount | Retail – UK unsecured loans and overdrafts | Stage 1 and 2 | RMS 4–6 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 624 484  
Gross carrying amount | Retail – UK unsecured loans and overdrafts | Stage 1 and 2 | RMS 7–9 | 12-month expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 1,062 1,047  
Gross carrying amount | Retail – UK unsecured loans and overdrafts | Stage 1 and 2 | RMS 7–9 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 324 307  
Gross carrying amount | Retail – UK unsecured loans and overdrafts | Stage 1 and 2 | RMS 10 | 12-month expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 26 31  
Gross carrying amount | Retail – UK unsecured loans and overdrafts | Stage 1 and 2 | RMS 10 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 110 111  
Gross carrying amount | Retail – UK unsecured loans and overdrafts | Stage 1 and 2 | RMS 11–13 | 12-month expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 7 9  
Gross carrying amount | Retail – UK unsecured loans and overdrafts | Stage 1 and 2 | RMS 11–13 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 337 343  
Gross carrying amount | Retail – UK unsecured loans and overdrafts | Stage 1 and 2 | RMS 14 | 12-month expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 0 0  
Gross carrying amount | Retail – UK unsecured loans and overdrafts | Stage 1 and 2 | RMS 14 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 0 0  
Gross carrying amount | Retail – UK unsecured loans and overdrafts | Stage 3 £m | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 193 175  
Gross carrying amount | Retail – UK unsecured loans and overdrafts | Stage 3 £m | RMS 1–3 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 0 0  
Gross carrying amount | Retail – UK unsecured loans and overdrafts | Stage 3 £m | RMS 4–6 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 0 0  
Gross carrying amount | Retail – UK unsecured loans and overdrafts | Stage 3 £m | RMS 7–9 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 0 0  
Gross carrying amount | Retail – UK unsecured loans and overdrafts | Stage 3 £m | RMS 10 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 0 0  
Gross carrying amount | Retail – UK unsecured loans and overdrafts | Stage 3 £m | RMS 11–13 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 0 0  
Gross carrying amount | Retail – UK unsecured loans and overdrafts | Stage 3 £m | RMS 14 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 193 175  
Gross carrying amount | Retail – UK unsecured loans and overdrafts | POCI £m | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 0 0  
Gross carrying amount | Retail – UK unsecured loans and overdrafts | POCI £m | RMS 1–3 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 0 0  
Gross carrying amount | Retail – UK unsecured loans and overdrafts | POCI £m | RMS 4–6 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 0 0  
Gross carrying amount | Retail – UK unsecured loans and overdrafts | POCI £m | RMS 7–9 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 0 0  
Gross carrying amount | Retail – UK unsecured loans and overdrafts | POCI £m | RMS 10 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 0 0  
Gross carrying amount | Retail – UK unsecured loans and overdrafts | POCI £m | RMS 11–13 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 0 0  
Gross carrying amount | Retail – UK unsecured loans and overdrafts | POCI £m | RMS 14 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 0 0  
Gross carrying amount | Retail – UK Motor Finance      
Disclosure of credit risk exposure [line items]      
Total financial assets 17,149 16,419  
Gross carrying amount | Retail – UK Motor Finance | RMS 1–3      
Disclosure of credit risk exposure [line items]      
Total financial assets 9,441 9,727  
Gross carrying amount | Retail – UK Motor Finance | RMS 4–6      
Disclosure of credit risk exposure [line items]      
Total financial assets 6,358 5,656  
Gross carrying amount | Retail – UK Motor Finance | RMS 7–9      
Disclosure of credit risk exposure [line items]      
Total financial assets 965 687  
Gross carrying amount | Retail – UK Motor Finance | RMS 10      
Disclosure of credit risk exposure [line items]      
Total financial assets 77 46  
Gross carrying amount | Retail – UK Motor Finance | RMS 11–13      
Disclosure of credit risk exposure [line items]      
Total financial assets 167 179  
Gross carrying amount | Retail – UK Motor Finance | RMS 14      
Disclosure of credit risk exposure [line items]      
Total financial assets 141 124  
Gross carrying amount | Retail – UK Motor Finance | Stage 1 and 2 | 12-month expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 14,222 13,897  
Gross carrying amount | Retail – UK Motor Finance | Stage 1 and 2 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 2,786 2,398  
Gross carrying amount | Retail – UK Motor Finance | Stage 1 and 2 | RMS 1–3 | 12-month expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 8,531 8,967  
Gross carrying amount | Retail – UK Motor Finance | Stage 1 and 2 | RMS 1–3 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 910 760  
Gross carrying amount | Retail – UK Motor Finance | Stage 1 and 2 | RMS 4–6 | 12-month expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 5,083 4,487  
Gross carrying amount | Retail – UK Motor Finance | Stage 1 and 2 | RMS 4–6 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 1,275 1,169  
Gross carrying amount | Retail – UK Motor Finance | Stage 1 and 2 | RMS 7–9 | 12-month expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 606 440  
Gross carrying amount | Retail – UK Motor Finance | Stage 1 and 2 | RMS 7–9 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 359 247  
Gross carrying amount | Retail – UK Motor Finance | Stage 1 and 2 | RMS 10 | 12-month expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 0 0  
Gross carrying amount | Retail – UK Motor Finance | Stage 1 and 2 | RMS 10 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 77 46  
Gross carrying amount | Retail – UK Motor Finance | Stage 1 and 2 | RMS 11–13 | 12-month expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 2 3  
Gross carrying amount | Retail – UK Motor Finance | Stage 1 and 2 | RMS 11–13 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 165 176  
Gross carrying amount | Retail – UK Motor Finance | Stage 1 and 2 | RMS 14 | 12-month expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 0 0  
Gross carrying amount | Retail – UK Motor Finance | Stage 1 and 2 | RMS 14 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 0 0  
Gross carrying amount | Retail – UK Motor Finance | Stage 3 £m | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 141 124  
Gross carrying amount | Retail – UK Motor Finance | Stage 3 £m | RMS 1–3 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 0 0  
Gross carrying amount | Retail – UK Motor Finance | Stage 3 £m | RMS 4–6 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 0 0  
Gross carrying amount | Retail – UK Motor Finance | Stage 3 £m | RMS 7–9 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 0 0  
Gross carrying amount | Retail – UK Motor Finance | Stage 3 £m | RMS 10 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 0 0  
Gross carrying amount | Retail – UK Motor Finance | Stage 3 £m | RMS 11–13 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 0 0  
Gross carrying amount | Retail – UK Motor Finance | Stage 3 £m | RMS 14 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 141 124  
Gross carrying amount | Retail – UK Motor Finance | POCI £m | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 0 0  
Gross carrying amount | Retail – UK Motor Finance | POCI £m | RMS 1–3 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 0 0  
Gross carrying amount | Retail – UK Motor Finance | POCI £m | RMS 4–6 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 0 0  
Gross carrying amount | Retail – UK Motor Finance | POCI £m | RMS 7–9 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 0 0  
Gross carrying amount | Retail – UK Motor Finance | POCI £m | RMS 10 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 0 0  
Gross carrying amount | Retail – UK Motor Finance | POCI £m | RMS 11–13 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 0 0  
Gross carrying amount | Retail – UK Motor Finance | POCI £m | RMS 14 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 0 0  
Gross carrying amount | Retail – other      
Disclosure of credit risk exposure [line items]      
Total financial assets 21,782 18,036  
Gross carrying amount | Retail – other | RMS 1–3      
Disclosure of credit risk exposure [line items]      
Total financial assets 18,557 15,401  
Gross carrying amount | Retail – other | RMS 4–6      
Disclosure of credit risk exposure [line items]      
Total financial assets 2,829 2,322  
Gross carrying amount | Retail – other | RMS 7–9      
Disclosure of credit risk exposure [line items]      
Total financial assets 161 150  
Gross carrying amount | Retail – other | RMS 10      
Disclosure of credit risk exposure [line items]      
Total financial assets 57 7  
Gross carrying amount | Retail – other | RMS 11–13      
Disclosure of credit risk exposure [line items]      
Total financial assets 33 9  
Gross carrying amount | Retail – other | RMS 14      
Disclosure of credit risk exposure [line items]      
Total financial assets 145 147  
Gross carrying amount | Retail – other | Stage 1 and 2 | 12-month expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 21,245 17,373  
Gross carrying amount | Retail – other | Stage 1 and 2 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 392 516  
Gross carrying amount | Retail – other | Stage 1 and 2 | RMS 1–3 | 12-month expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 18,554 15,163  
Gross carrying amount | Retail – other | Stage 1 and 2 | RMS 1–3 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 3 238  
Gross carrying amount | Retail – other | Stage 1 and 2 | RMS 4–6 | 12-month expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 2,616 2,132  
Gross carrying amount | Retail – other | Stage 1 and 2 | RMS 4–6 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 213 190  
Gross carrying amount | Retail – other | Stage 1 and 2 | RMS 7–9 | 12-month expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 75 78  
Gross carrying amount | Retail – other | Stage 1 and 2 | RMS 7–9 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 86 72  
Gross carrying amount | Retail – other | Stage 1 and 2 | RMS 10 | 12-month expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 0 0  
Gross carrying amount | Retail – other | Stage 1 and 2 | RMS 10 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 57 7  
Gross carrying amount | Retail – other | Stage 1 and 2 | RMS 11–13 | 12-month expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 0 0  
Gross carrying amount | Retail – other | Stage 1 and 2 | RMS 11–13 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 33 9  
Gross carrying amount | Retail – other | Stage 1 and 2 | RMS 14 | 12-month expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 0 0  
Gross carrying amount | Retail – other | Stage 1 and 2 | RMS 14 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 0 0  
Gross carrying amount | Retail – other | Stage 3 £m | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 145 147  
Gross carrying amount | Retail – other | Stage 3 £m | RMS 1–3 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 0 0  
Gross carrying amount | Retail – other | Stage 3 £m | RMS 4–6 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 0 0  
Gross carrying amount | Retail – other | Stage 3 £m | RMS 7–9 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 0 0  
Gross carrying amount | Retail – other | Stage 3 £m | RMS 10 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 0 0  
Gross carrying amount | Retail – other | Stage 3 £m | RMS 11–13 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 0 0  
Gross carrying amount | Retail – other | Stage 3 £m | RMS 14 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 145 147  
Gross carrying amount | Retail – other | POCI £m | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 0 0  
Gross carrying amount | Retail – other | POCI £m | RMS 1–3 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 0 0  
Gross carrying amount | Retail – other | POCI £m | RMS 4–6 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 0 0  
Gross carrying amount | Retail – other | POCI £m | RMS 7–9 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 0 0  
Gross carrying amount | Retail – other | POCI £m | RMS 10 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 0 0  
Gross carrying amount | Retail – other | POCI £m | RMS 11–13 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 0 0  
Gross carrying amount | Retail – other | POCI £m | RMS 14 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 0 0  
Gross carrying amount | Commercial Banking      
Disclosure of credit risk exposure [line items]      
Total financial assets 91,141 88,484 89,629
Gross carrying amount | Commercial Banking | CMS 1–5      
Disclosure of credit risk exposure [line items]      
Total financial assets 32,068 26,931  
Gross carrying amount | Commercial Banking | CMS 6–10      
Disclosure of credit risk exposure [line items]      
Total financial assets 17,958 17,182  
Gross carrying amount | Commercial Banking | CMS 11–14      
Disclosure of credit risk exposure [line items]      
Total financial assets 33,840 33,552  
Gross carrying amount | Commercial Banking | CMS 15–18      
Disclosure of credit risk exposure [line items]      
Total financial assets 4,810 8,255  
Gross carrying amount | Commercial Banking | CMS 19      
Disclosure of credit risk exposure [line items]      
Total financial assets 708 725  
Gross carrying amount | Commercial Banking | CMS 20–23      
Disclosure of credit risk exposure [line items]      
Total financial assets 1,757 1,839  
Gross carrying amount | Commercial Banking | Stage 1 and 2 | 12-month expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 84,020 81,477 79,574
Gross carrying amount | Commercial Banking | Stage 1 and 2 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 5,364 5,168 7,987
Gross carrying amount | Commercial Banking | Stage 1 and 2 | CMS 1–5 | 12-month expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 31,945 26,925  
Gross carrying amount | Commercial Banking | Stage 1 and 2 | CMS 1–5 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 123 6  
Gross carrying amount | Commercial Banking | Stage 1 and 2 | CMS 6–10 | 12-month expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 17,918 17,126  
Gross carrying amount | Commercial Banking | Stage 1 and 2 | CMS 6–10 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 40 56  
Gross carrying amount | Commercial Banking | Stage 1 and 2 | CMS 11–14 | 12-month expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 31,833 32,424  
Gross carrying amount | Commercial Banking | Stage 1 and 2 | CMS 11–14 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 2,007 1,128  
Gross carrying amount | Commercial Banking | Stage 1 and 2 | CMS 15–18 | 12-month expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 2,324 5,002  
Gross carrying amount | Commercial Banking | Stage 1 and 2 | CMS 15–18 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 2,486 3,253  
Gross carrying amount | Commercial Banking | Stage 1 and 2 | CMS 19 | 12-month expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 0 0  
Gross carrying amount | Commercial Banking | Stage 1 and 2 | CMS 19 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 708 725  
Gross carrying amount | Commercial Banking | Stage 1 and 2 | CMS 20–23 | 12-month expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 0 0  
Gross carrying amount | Commercial Banking | Stage 1 and 2 | CMS 20–23 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 0 0  
Gross carrying amount | Commercial Banking | Stage 3 £m | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 1,757 1,839 2,068
Gross carrying amount | Commercial Banking | Stage 3 £m | CMS 1–5 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 0 0  
Gross carrying amount | Commercial Banking | Stage 3 £m | CMS 6–10 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 0 0  
Gross carrying amount | Commercial Banking | Stage 3 £m | CMS 11–14 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 0 0  
Gross carrying amount | Commercial Banking | Stage 3 £m | CMS 15–18 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 0 0  
Gross carrying amount | Commercial Banking | Stage 3 £m | CMS 19 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 0 0  
Gross carrying amount | Commercial Banking | Stage 3 £m | CMS 20–23 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 1,757 1,839  
Gross carrying amount | Commercial Banking | POCI £m | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 0 0  
Gross carrying amount | Commercial Banking | POCI £m | CMS 1–5 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 0 0  
Gross carrying amount | Commercial Banking | POCI £m | CMS 6–10 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 0 0  
Gross carrying amount | Commercial Banking | POCI £m | CMS 11–14 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 0 0  
Gross carrying amount | Commercial Banking | POCI £m | CMS 15–18 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 0 0  
Gross carrying amount | Commercial Banking | POCI £m | CMS 19 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 0 0  
Gross carrying amount | Commercial Banking | POCI £m | CMS 20–23 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 0 0  
Gross carrying amount | Other      
Disclosure of credit risk exposure [line items]      
Total financial assets 540 5  
Gross carrying amount | Other | Stage 1 and 2 | 12-month expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 540 5  
Gross carrying amount | Other | Stage 1 and 2 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 0 0  
Gross carrying amount | Other | Stage 3 £m | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 0 0  
Gross carrying amount | Other | POCI £m | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 0 0  
Allowance for expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets (3,228) (3,481)  
Allowance for expected credit losses | Stage 1 and 2 | 12-month expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets (861) (889)  
Allowance for expected credit losses | Stage 1 and 2 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets (1,160) (1,286)  
Allowance for expected credit losses | Stage 3 £m | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets (1,048) (1,119)  
Allowance for expected credit losses | POCI £m | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets (159) (187)  
Allowance for expected credit losses | Total loans and advances to customers      
Disclosure of credit risk exposure [line items]      
Total financial assets (3,011) (3,191) (3,717)
Allowance for expected credit losses | Total loans and advances to customers | Stage 1 and 2 | 12-month expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets (737) (736) (900)
Allowance for expected credit losses | Total loans and advances to customers | Stage 1 and 2 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets (1,077) (1,160) (1,467)
Allowance for expected credit losses | Total loans and advances to customers | Stage 3 £m | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets (1,038) (1,108) (1,137)
Allowance for expected credit losses | Total loans and advances to customers | POCI £m | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets (159) (187) (213)
Allowance for expected credit losses | Total Retail      
Disclosure of credit risk exposure [line items]      
Total financial assets (2,177) (2,309)  
Allowance for expected credit losses | Total Retail | Stage 1 and 2 | 12-month expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets (564) (531)  
Allowance for expected credit losses | Total Retail | Stage 1 and 2 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets (798) (896)  
Allowance for expected credit losses | Total Retail | Stage 3 £m | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets (656) (695)  
Allowance for expected credit losses | Total Retail | POCI £m | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets (159) (187)  
Allowance for expected credit losses | Retail – UK mortgages      
Disclosure of credit risk exposure [line items]      
Total financial assets (726) (848) (1,105)
Allowance for expected credit losses | Retail – UK mortgages | RMS 1–3      
Disclosure of credit risk exposure [line items]      
Total financial assets (142) (189)  
Allowance for expected credit losses | Retail – UK mortgages | RMS 4–6      
Disclosure of credit risk exposure [line items]      
Total financial assets (40) (57)  
Allowance for expected credit losses | Retail – UK mortgages | RMS 7–9      
Disclosure of credit risk exposure [line items]      
Total financial assets (13) (15)  
Allowance for expected credit losses | Retail – UK mortgages | RMS 10      
Disclosure of credit risk exposure [line items]      
Total financial assets (5) (5)  
Allowance for expected credit losses | Retail – UK mortgages | RMS 11–13      
Disclosure of credit risk exposure [line items]      
Total financial assets (58) (60)  
Allowance for expected credit losses | Retail – UK mortgages | RMS 14      
Disclosure of credit risk exposure [line items]      
Total financial assets (468) (522)  
Allowance for expected credit losses | Retail – UK mortgages | Stage 1 and 2 | 12-month expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets (51) (53) (161)
Allowance for expected credit losses | Retail – UK mortgages | Stage 1 and 2 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets (207) (273) (374)
Allowance for expected credit losses | Retail – UK mortgages | Stage 1 and 2 | RMS 1–3 | 12-month expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets (43) (46)  
Allowance for expected credit losses | Retail – UK mortgages | Stage 1 and 2 | RMS 1–3 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets (99) (143)  
Allowance for expected credit losses | Retail – UK mortgages | Stage 1 and 2 | RMS 4–6 | 12-month expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets (6) (6)  
Allowance for expected credit losses | Retail – UK mortgages | Stage 1 and 2 | RMS 4–6 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets (34) (51)  
Allowance for expected credit losses | Retail – UK mortgages | Stage 1 and 2 | RMS 7–9 | 12-month expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets (1) 0  
Allowance for expected credit losses | Retail – UK mortgages | Stage 1 and 2 | RMS 7–9 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets (12) (15)  
Allowance for expected credit losses | Retail – UK mortgages | Stage 1 and 2 | RMS 10 | 12-month expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 0 0  
Allowance for expected credit losses | Retail – UK mortgages | Stage 1 and 2 | RMS 10 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets (5) (5)  
Allowance for expected credit losses | Retail – UK mortgages | Stage 1 and 2 | RMS 11–13 | 12-month expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets (1) (1)  
Allowance for expected credit losses | Retail – UK mortgages | Stage 1 and 2 | RMS 11–13 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets (57) (59)  
Allowance for expected credit losses | Retail – UK mortgages | Stage 1 and 2 | RMS 14 | 12-month expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 0 0  
Allowance for expected credit losses | Retail – UK mortgages | Stage 1 and 2 | RMS 14 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 0 0  
Allowance for expected credit losses | Retail – UK mortgages | Stage 3 £m | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets (309) (335) (357)
Allowance for expected credit losses | Retail – UK mortgages | Stage 3 £m | RMS 1–3 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 0 0  
Allowance for expected credit losses | Retail – UK mortgages | Stage 3 £m | RMS 4–6 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 0 0  
Allowance for expected credit losses | Retail – UK mortgages | Stage 3 £m | RMS 7–9 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 0 0  
Allowance for expected credit losses | Retail – UK mortgages | Stage 3 £m | RMS 10 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 0 0  
Allowance for expected credit losses | Retail – UK mortgages | Stage 3 £m | RMS 11–13 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 0 0  
Allowance for expected credit losses | Retail – UK mortgages | Stage 3 £m | RMS 14 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets (309) (335)  
Allowance for expected credit losses | Retail – UK mortgages | POCI £m | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets (159) (187) (213)
Allowance for expected credit losses | Retail – UK mortgages | POCI £m | RMS 1–3 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 0 0  
Allowance for expected credit losses | Retail – UK mortgages | POCI £m | RMS 4–6 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 0 0  
Allowance for expected credit losses | Retail – UK mortgages | POCI £m | RMS 7–9 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 0 0  
Allowance for expected credit losses | Retail – UK mortgages | POCI £m | RMS 10 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 0 0  
Allowance for expected credit losses | Retail – UK mortgages | POCI £m | RMS 11–13 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 0 0  
Allowance for expected credit losses | Retail – UK mortgages | POCI £m | RMS 14 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets (159) (187)  
Allowance for expected credit losses | Credit cards      
Disclosure of credit risk exposure [line items]      
Total financial assets (514) (579) (699)
Allowance for expected credit losses | Credit cards | RMS 1–3      
Disclosure of credit risk exposure [line items]      
Total financial assets (11) (12)  
Allowance for expected credit losses | Credit cards | RMS 4–6      
Disclosure of credit risk exposure [line items]      
Total financial assets (129) (139)  
Allowance for expected credit losses | Credit cards | RMS 7–9      
Disclosure of credit risk exposure [line items]      
Total financial assets (135) (158)  
Allowance for expected credit losses | Credit cards | RMS 10      
Disclosure of credit risk exposure [line items]      
Total financial assets (27) (31)  
Allowance for expected credit losses | Credit cards | RMS 11–13      
Disclosure of credit risk exposure [line items]      
Total financial assets (91) (106)  
Allowance for expected credit losses | Credit cards | RMS 14      
Disclosure of credit risk exposure [line items]      
Total financial assets (121) (133)  
Allowance for expected credit losses | Credit cards | Stage 1 and 2 | 12-month expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets (145) (149) (168)
Allowance for expected credit losses | Credit cards | Stage 1 and 2 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets (248) (297) (401)
Allowance for expected credit losses | Credit cards | Stage 1 and 2 | RMS 1–3 | 12-month expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets (11) (11)  
Allowance for expected credit losses | Credit cards | Stage 1 and 2 | RMS 1–3 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 0 (1)  
Allowance for expected credit losses | Credit cards | Stage 1 and 2 | RMS 4–6 | 12-month expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets (85) (87)  
Allowance for expected credit losses | Credit cards | Stage 1 and 2 | RMS 4–6 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets (44) (52)  
Allowance for expected credit losses | Credit cards | Stage 1 and 2 | RMS 7–9 | 12-month expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets (48) (51)  
Allowance for expected credit losses | Credit cards | Stage 1 and 2 | RMS 7–9 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets (87) (107)  
Allowance for expected credit losses | Credit cards | Stage 1 and 2 | RMS 10 | 12-month expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets (1) 0  
Allowance for expected credit losses | Credit cards | Stage 1 and 2 | RMS 10 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets (26) (31)  
Allowance for expected credit losses | Credit cards | Stage 1 and 2 | RMS 11–13 | 12-month expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 0 0  
Allowance for expected credit losses | Credit cards | Stage 1 and 2 | RMS 11–13 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets (91) (106)  
Allowance for expected credit losses | Credit cards | Stage 1 and 2 | RMS 14 | 12-month expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 0 0  
Allowance for expected credit losses | Credit cards | Stage 1 and 2 | RMS 14 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 0 0  
Allowance for expected credit losses | Credit cards | Stage 3 £m | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets (121) (133) (130)
Allowance for expected credit losses | Credit cards | Stage 3 £m | RMS 1–3 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 0 0  
Allowance for expected credit losses | Credit cards | Stage 3 £m | RMS 4–6 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 0 0  
Allowance for expected credit losses | Credit cards | Stage 3 £m | RMS 7–9 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 0 0  
Allowance for expected credit losses | Credit cards | Stage 3 £m | RMS 10 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 0 0  
Allowance for expected credit losses | Credit cards | Stage 3 £m | RMS 11–13 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 0 0  
Allowance for expected credit losses | Credit cards | Stage 3 £m | RMS 14 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets (121) (133)  
Allowance for expected credit losses | Credit cards | POCI £m | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 0 0  
Allowance for expected credit losses | Credit cards | POCI £m | RMS 1–3 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 0 0  
Allowance for expected credit losses | Credit cards | POCI £m | RMS 4–6 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 0 0  
Allowance for expected credit losses | Credit cards | POCI £m | RMS 7–9 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 0 0  
Allowance for expected credit losses | Credit cards | POCI £m | RMS 10 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 0 0  
Allowance for expected credit losses | Credit cards | POCI £m | RMS 11–13 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 0 0  
Allowance for expected credit losses | Credit cards | POCI £m | RMS 14 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 0 0  
Allowance for expected credit losses | Retail – UK unsecured loans and overdrafts      
Disclosure of credit risk exposure [line items]      
Total financial assets (447) (460)  
Allowance for expected credit losses | Retail – UK unsecured loans and overdrafts | RMS 1–3      
Disclosure of credit risk exposure [line items]      
Total financial assets (4) (3)  
Allowance for expected credit losses | Retail – UK unsecured loans and overdrafts | RMS 4–6      
Disclosure of credit risk exposure [line items]      
Total financial assets (140) (125)  
Allowance for expected credit losses | Retail – UK unsecured loans and overdrafts | RMS 7–9      
Disclosure of credit risk exposure [line items]      
Total financial assets (70) (76)  
Allowance for expected credit losses | Retail – UK unsecured loans and overdrafts | RMS 10      
Disclosure of credit risk exposure [line items]      
Total financial assets (21) (25)  
Allowance for expected credit losses | Retail – UK unsecured loans and overdrafts | RMS 11–13      
Disclosure of credit risk exposure [line items]      
Total financial assets (100) (113)  
Allowance for expected credit losses | Retail – UK unsecured loans and overdrafts | RMS 14      
Disclosure of credit risk exposure [line items]      
Total financial assets (112) (118)  
Allowance for expected credit losses | Retail – UK unsecured loans and overdrafts | Stage 1 and 2 | 12-month expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets (150) (145)  
Allowance for expected credit losses | Retail – UK unsecured loans and overdrafts | Stage 1 and 2 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets (185) (197)  
Allowance for expected credit losses | Retail – UK unsecured loans and overdrafts | Stage 1 and 2 | RMS 1–3 | 12-month expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets (4) (3)  
Allowance for expected credit losses | Retail – UK unsecured loans and overdrafts | Stage 1 and 2 | RMS 1–3 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 0 0  
Allowance for expected credit losses | Retail – UK unsecured loans and overdrafts | Stage 1 and 2 | RMS 4–6 | 12-month expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets (106) (98)  
Allowance for expected credit losses | Retail – UK unsecured loans and overdrafts | Stage 1 and 2 | RMS 4–6 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets (34) (27)  
Allowance for expected credit losses | Retail – UK unsecured loans and overdrafts | Stage 1 and 2 | RMS 7–9 | 12-month expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets (37) (40)  
Allowance for expected credit losses | Retail – UK unsecured loans and overdrafts | Stage 1 and 2 | RMS 7–9 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets (33) (36)  
Allowance for expected credit losses | Retail – UK unsecured loans and overdrafts | Stage 1 and 2 | RMS 10 | 12-month expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets (2) (3)  
Allowance for expected credit losses | Retail – UK unsecured loans and overdrafts | Stage 1 and 2 | RMS 10 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets (19) (22)  
Allowance for expected credit losses | Retail – UK unsecured loans and overdrafts | Stage 1 and 2 | RMS 11–13 | 12-month expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets (1) (1)  
Allowance for expected credit losses | Retail – UK unsecured loans and overdrafts | Stage 1 and 2 | RMS 11–13 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets (99) (112)  
Allowance for expected credit losses | Retail – UK unsecured loans and overdrafts | Stage 1 and 2 | RMS 14 | 12-month expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 0 0  
Allowance for expected credit losses | Retail – UK unsecured loans and overdrafts | Stage 1 and 2 | RMS 14 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 0 0  
Allowance for expected credit losses | Retail – UK unsecured loans and overdrafts | Stage 3 £m | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets (112) (118)  
Allowance for expected credit losses | Retail – UK unsecured loans and overdrafts | Stage 3 £m | RMS 1–3 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 0 0  
Allowance for expected credit losses | Retail – UK unsecured loans and overdrafts | Stage 3 £m | RMS 4–6 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 0 0  
Allowance for expected credit losses | Retail – UK unsecured loans and overdrafts | Stage 3 £m | RMS 7–9 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 0 0  
Allowance for expected credit losses | Retail – UK unsecured loans and overdrafts | Stage 3 £m | RMS 10 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 0 0  
Allowance for expected credit losses | Retail – UK unsecured loans and overdrafts | Stage 3 £m | RMS 11–13 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 0 0  
Allowance for expected credit losses | Retail – UK unsecured loans and overdrafts | Stage 3 £m | RMS 14 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets (112) (118)  
Allowance for expected credit losses | Retail – UK unsecured loans and overdrafts | POCI £m | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 0 0  
Allowance for expected credit losses | Retail – UK unsecured loans and overdrafts | POCI £m | RMS 1–3 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 0 0  
Allowance for expected credit losses | Retail – UK unsecured loans and overdrafts | POCI £m | RMS 4–6 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 0 0  
Allowance for expected credit losses | Retail – UK unsecured loans and overdrafts | POCI £m | RMS 7–9 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 0 0  
Allowance for expected credit losses | Retail – UK unsecured loans and overdrafts | POCI £m | RMS 10 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 0 0  
Allowance for expected credit losses | Retail – UK unsecured loans and overdrafts | POCI £m | RMS 11–13 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 0 0  
Allowance for expected credit losses | Retail – UK unsecured loans and overdrafts | POCI £m | RMS 14 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 0 0  
Allowance for expected credit losses | Retail – UK Motor Finance      
Disclosure of credit risk exposure [line items]      
Total financial assets (428) (356)  
Allowance for expected credit losses | Retail – UK Motor Finance | RMS 1–3      
Disclosure of credit risk exposure [line items]      
Total financial assets (157) (128)  
Allowance for expected credit losses | Retail – UK Motor Finance | RMS 4–6      
Disclosure of credit risk exposure [line items]      
Total financial assets (115) (95)  
Allowance for expected credit losses | Retail – UK Motor Finance | RMS 7–9      
Disclosure of credit risk exposure [line items]      
Total financial assets (28) (19)  
Allowance for expected credit losses | Retail – UK Motor Finance | RMS 10      
Disclosure of credit risk exposure [line items]      
Total financial assets (10) (6)  
Allowance for expected credit losses | Retail – UK Motor Finance | RMS 11–13      
Disclosure of credit risk exposure [line items]      
Total financial assets (39) (36)  
Allowance for expected credit losses | Retail – UK Motor Finance | RMS 14      
Disclosure of credit risk exposure [line items]      
Total financial assets (79) (72)  
Allowance for expected credit losses | Retail – UK Motor Finance | Stage 1 and 2 | 12-month expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets (201) (169)  
Allowance for expected credit losses | Retail – UK Motor Finance | Stage 1 and 2 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets (148) (115)  
Allowance for expected credit losses | Retail – UK Motor Finance | Stage 1 and 2 | RMS 1–3 | 12-month expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets (135) (112)  
Allowance for expected credit losses | Retail – UK Motor Finance | Stage 1 and 2 | RMS 1–3 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets (22) (16)  
Allowance for expected credit losses | Retail – UK Motor Finance | Stage 1 and 2 | RMS 4–6 | 12-month expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets (63) (55)  
Allowance for expected credit losses | Retail – UK Motor Finance | Stage 1 and 2 | RMS 4–6 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets (52) (40)  
Allowance for expected credit losses | Retail – UK Motor Finance | Stage 1 and 2 | RMS 7–9 | 12-month expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets (3) (2)  
Allowance for expected credit losses | Retail – UK Motor Finance | Stage 1 and 2 | RMS 7–9 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets (25) (17)  
Allowance for expected credit losses | Retail – UK Motor Finance | Stage 1 and 2 | RMS 10 | 12-month expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 0 0  
Allowance for expected credit losses | Retail – UK Motor Finance | Stage 1 and 2 | RMS 10 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets (10) (6)  
Allowance for expected credit losses | Retail – UK Motor Finance | Stage 1 and 2 | RMS 11–13 | 12-month expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 0 0  
Allowance for expected credit losses | Retail – UK Motor Finance | Stage 1 and 2 | RMS 11–13 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets (39) (36)  
Allowance for expected credit losses | Retail – UK Motor Finance | Stage 1 and 2 | RMS 14 | 12-month expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 0 0  
Allowance for expected credit losses | Retail – UK Motor Finance | Stage 1 and 2 | RMS 14 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 0 0  
Allowance for expected credit losses | Retail – UK Motor Finance | Stage 3 £m | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets (79) (72)  
Allowance for expected credit losses | Retail – UK Motor Finance | Stage 3 £m | RMS 1–3 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 0 0  
Allowance for expected credit losses | Retail – UK Motor Finance | Stage 3 £m | RMS 4–6 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 0 0  
Allowance for expected credit losses | Retail – UK Motor Finance | Stage 3 £m | RMS 7–9 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 0 0  
Allowance for expected credit losses | Retail – UK Motor Finance | Stage 3 £m | RMS 10 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 0 0  
Allowance for expected credit losses | Retail – UK Motor Finance | Stage 3 £m | RMS 11–13 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 0 0  
Allowance for expected credit losses | Retail – UK Motor Finance | Stage 3 £m | RMS 14 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets (79) (72)  
Allowance for expected credit losses | Retail – UK Motor Finance | POCI £m | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 0 0  
Allowance for expected credit losses | Retail – UK Motor Finance | POCI £m | RMS 1–3 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 0 0  
Allowance for expected credit losses | Retail – UK Motor Finance | POCI £m | RMS 4–6 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 0 0  
Allowance for expected credit losses | Retail – UK Motor Finance | POCI £m | RMS 7–9 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 0 0  
Allowance for expected credit losses | Retail – UK Motor Finance | POCI £m | RMS 10 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 0 0  
Allowance for expected credit losses | Retail – UK Motor Finance | POCI £m | RMS 11–13 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 0 0  
Allowance for expected credit losses | Retail – UK Motor Finance | POCI £m | RMS 14 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 0 0  
Allowance for expected credit losses | Retail – other      
Disclosure of credit risk exposure [line items]      
Total financial assets (62) (66)  
Allowance for expected credit losses | Retail – other | RMS 1–3      
Disclosure of credit risk exposure [line items]      
Total financial assets (7) (8)  
Allowance for expected credit losses | Retail – other | RMS 4–6      
Disclosure of credit risk exposure [line items]      
Total financial assets (17) (18)  
Allowance for expected credit losses | Retail – other | RMS 7–9      
Disclosure of credit risk exposure [line items]      
Total financial assets (1) (3)  
Allowance for expected credit losses | Retail – other | RMS 10      
Disclosure of credit risk exposure [line items]      
Total financial assets (1) 0  
Allowance for expected credit losses | Retail – other | RMS 11–13      
Disclosure of credit risk exposure [line items]      
Total financial assets (1) 0  
Allowance for expected credit losses | Retail – other | RMS 14      
Disclosure of credit risk exposure [line items]      
Total financial assets (35) (37)  
Allowance for expected credit losses | Retail – other | Stage 1 and 2 | 12-month expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets (17) (15)  
Allowance for expected credit losses | Retail – other | Stage 1 and 2 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets (10) (14)  
Allowance for expected credit losses | Retail – other | Stage 1 and 2 | RMS 1–3 | 12-month expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets (7) (4)  
Allowance for expected credit losses | Retail – other | Stage 1 and 2 | RMS 1–3 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 0 (4)  
Allowance for expected credit losses | Retail – other | Stage 1 and 2 | RMS 4–6 | 12-month expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets (10) (11)  
Allowance for expected credit losses | Retail – other | Stage 1 and 2 | RMS 4–6 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets (7) (7)  
Allowance for expected credit losses | Retail – other | Stage 1 and 2 | RMS 7–9 | 12-month expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 0 0  
Allowance for expected credit losses | Retail – other | Stage 1 and 2 | RMS 7–9 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets (1) (3)  
Allowance for expected credit losses | Retail – other | Stage 1 and 2 | RMS 10 | 12-month expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 0 0  
Allowance for expected credit losses | Retail – other | Stage 1 and 2 | RMS 10 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets (1) 0  
Allowance for expected credit losses | Retail – other | Stage 1 and 2 | RMS 11–13 | 12-month expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 0 0  
Allowance for expected credit losses | Retail – other | Stage 1 and 2 | RMS 11–13 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets (1) 0  
Allowance for expected credit losses | Retail – other | Stage 1 and 2 | RMS 14 | 12-month expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 0 0  
Allowance for expected credit losses | Retail – other | Stage 1 and 2 | RMS 14 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 0 0  
Allowance for expected credit losses | Retail – other | Stage 3 £m | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets (35) (37)  
Allowance for expected credit losses | Retail – other | Stage 3 £m | RMS 1–3 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 0 0  
Allowance for expected credit losses | Retail – other | Stage 3 £m | RMS 4–6 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 0 0  
Allowance for expected credit losses | Retail – other | Stage 3 £m | RMS 7–9 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 0 0  
Allowance for expected credit losses | Retail – other | Stage 3 £m | RMS 10 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 0 0  
Allowance for expected credit losses | Retail – other | Stage 3 £m | RMS 11–13 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 0 0  
Allowance for expected credit losses | Retail – other | Stage 3 £m | RMS 14 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets (35) (37)  
Allowance for expected credit losses | Retail – other | POCI £m | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 0 0  
Allowance for expected credit losses | Retail – other | POCI £m | RMS 1–3 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 0 0  
Allowance for expected credit losses | Retail – other | POCI £m | RMS 4–6 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 0 0  
Allowance for expected credit losses | Retail – other | POCI £m | RMS 7–9 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 0 0  
Allowance for expected credit losses | Retail – other | POCI £m | RMS 10 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 0 0  
Allowance for expected credit losses | Retail – other | POCI £m | RMS 11–13 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 0 0  
Allowance for expected credit losses | Retail – other | POCI £m | RMS 14 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 0 0  
Allowance for expected credit losses | Commercial Banking      
Disclosure of credit risk exposure [line items]      
Total financial assets (834) (882) (1,022)
Allowance for expected credit losses | Commercial Banking | CMS 1–5      
Disclosure of credit risk exposure [line items]      
Total financial assets (6) (3)  
Allowance for expected credit losses | Commercial Banking | CMS 6–10      
Disclosure of credit risk exposure [line items]      
Total financial assets (18) (13)  
Allowance for expected credit losses | Commercial Banking | CMS 11–14      
Disclosure of credit risk exposure [line items]      
Total financial assets (151) (143)  
Allowance for expected credit losses | Commercial Banking | CMS 15–18      
Disclosure of credit risk exposure [line items]      
Total financial assets (183) (233)  
Allowance for expected credit losses | Commercial Banking | CMS 19      
Disclosure of credit risk exposure [line items]      
Total financial assets (94) (77)  
Allowance for expected credit losses | Commercial Banking | CMS 20–23      
Disclosure of credit risk exposure [line items]      
Total financial assets (382) (413)  
Allowance for expected credit losses | Commercial Banking | Stage 1 and 2 | 12-month expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets (173) (205) (232)
Allowance for expected credit losses | Commercial Banking | Stage 1 and 2 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets (279) (264) (372)
Allowance for expected credit losses | Commercial Banking | Stage 1 and 2 | CMS 1–5 | 12-month expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets (6) (3)  
Allowance for expected credit losses | Commercial Banking | Stage 1 and 2 | CMS 1–5 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 0 0  
Allowance for expected credit losses | Commercial Banking | Stage 1 and 2 | CMS 6–10 | 12-month expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets (18) (13)  
Allowance for expected credit losses | Commercial Banking | Stage 1 and 2 | CMS 6–10 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 0 0  
Allowance for expected credit losses | Commercial Banking | Stage 1 and 2 | CMS 11–14 | 12-month expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets (110) (122)  
Allowance for expected credit losses | Commercial Banking | Stage 1 and 2 | CMS 11–14 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets (41) (21)  
Allowance for expected credit losses | Commercial Banking | Stage 1 and 2 | CMS 15–18 | 12-month expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets (39) (67)  
Allowance for expected credit losses | Commercial Banking | Stage 1 and 2 | CMS 15–18 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets (144) (166)  
Allowance for expected credit losses | Commercial Banking | Stage 1 and 2 | CMS 19 | 12-month expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 0 0  
Allowance for expected credit losses | Commercial Banking | Stage 1 and 2 | CMS 19 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets (94) (77)  
Allowance for expected credit losses | Commercial Banking | Stage 1 and 2 | CMS 20–23 | 12-month expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 0 0  
Allowance for expected credit losses | Commercial Banking | Stage 1 and 2 | CMS 20–23 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 0 0  
Allowance for expected credit losses | Commercial Banking | Stage 3 £m | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets (382) (413) £ (418)
Allowance for expected credit losses | Commercial Banking | Stage 3 £m | CMS 1–5 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 0 0  
Allowance for expected credit losses | Commercial Banking | Stage 3 £m | CMS 6–10 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 0 0  
Allowance for expected credit losses | Commercial Banking | Stage 3 £m | CMS 11–14 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 0 0  
Allowance for expected credit losses | Commercial Banking | Stage 3 £m | CMS 15–18 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 0 0  
Allowance for expected credit losses | Commercial Banking | Stage 3 £m | CMS 19 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 0 0  
Allowance for expected credit losses | Commercial Banking | Stage 3 £m | CMS 20–23 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets (382) (413)  
Allowance for expected credit losses | Commercial Banking | POCI £m | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 0 0  
Allowance for expected credit losses | Commercial Banking | POCI £m | CMS 1–5 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 0 0  
Allowance for expected credit losses | Commercial Banking | POCI £m | CMS 6–10 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 0 0  
Allowance for expected credit losses | Commercial Banking | POCI £m | CMS 11–14 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 0 0  
Allowance for expected credit losses | Commercial Banking | POCI £m | CMS 15–18 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 0 0  
Allowance for expected credit losses | Commercial Banking | POCI £m | CMS 19 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 0 0  
Allowance for expected credit losses | Commercial Banking | POCI £m | CMS 20–23 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 0 0  
Allowance for expected credit losses | Other      
Disclosure of credit risk exposure [line items]      
Total financial assets 0 0  
Allowance for expected credit losses | Other | Stage 1 and 2 | 12-month expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 0 0  
Allowance for expected credit losses | Other | Stage 1 and 2 | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 0 0  
Allowance for expected credit losses | Other | Stage 3 £m | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets 0 0  
Allowance for expected credit losses | Other | POCI £m | Lifetime expected credit losses      
Disclosure of credit risk exposure [line items]      
Total financial assets £ 0 £ 0