Subclassifications Of Assets, Liabilities And Equities [Abstract]
| Concept |
As at 2023-12-31 |
As at 2022-12-31 |
As at 2021-12-31 |
As at 2020-12-31 |
|---|---|---|---|---|
| Subclassifications of assets, liabilities and equities [abstract] | ||||
| Property, plant and equipment [abstract] | ||||
| Property, plant and equipment |
1,494,000,000
GBP
|
1,513,000,000
GBP
|
— | — |
| Intangible assets and goodwill [abstract] | ||||
| Intangible assets and goodwill |
1,548,000,000
GBP
|
1,550,000,000
GBP
|
— | — |
| Investments accounted for using equity method [abstract] | ||||
| Investments in joint ventures accounted for using equity method |
245,000,000
GBP
|
252,000,000
GBP
|
— | — |
| Categories of financial assets [abstract] | ||||
| Financial assets at fair value through other comprehensive income [abstract] | ||||
| Financial assets at fair value through other comprehensive income |
8,481,000,000
GBP
|
6,024,000,000
GBP
|
— | — |
| Cash and cash equivalents [abstract] | ||||
| Cash and cash equivalents |
42,502,000,000
GBP
|
46,484,000,000
GBP
|
49,254,000,000
GBP
|
46,697,000,000
GBP
|
| Non-current assets or disposal groups classified as held for sale or as held for distribution to owners [abstract] | ||||
| Non-current assets or disposal groups classified as held for sale |
13,000,000
GBP
|
49,000,000
GBP
|
— | — |
| Miscellaneous assets [abstract] | ||||
| Net defined benefit asset |
723,000,000
GBP
|
1,050,000,000
GBP
|
— | — |
| Derivative financial assets |
1,432,000,000
GBP
|
2,407,000,000
GBP
|
— | — |
| Loans and advances | — | — | — | — |
| Loans and advances to banks |
1,080,000,000
GBP
|
992,000,000
GBP
|
— | — |
| Loans and advances to customers |
207,435,000,000
GBP
|
219,716,000,000
GBP
|
— | — |
| Cash and bank balances at central banks |
38,214,000,000
GBP
|
44,190,000,000
GBP
|
48,139,000,000
GBP
|
— |
| Mandatory reserve deposits at central banks |
2,311,000,000
GBP
|
2,223,000,000
GBP
|
2,498,000,000
GBP
|
— |
| Bank balances at central banks other than mandatory reserve deposits |
35,903,000,000
GBP
|
41,967,000,000
GBP
|
45,641,000,000
GBP
|
— |
| Reverse repurchase agreements and cash collateral on securities borrowed |
12,468,000,000
GBP
|
7,348,000,000
GBP
|
— | — |
| Other assets |
2,043,000,000
GBP
|
2,016,000,000
GBP
|
— | — |
| Miscellaneous liabilities [abstract] | ||||
| Net defined benefit liability |
66,000,000
GBP
|
25,000,000
GBP
|
— | — |
| Derivative financial liabilities |
818,000,000
GBP
|
951,000,000
GBP
|
— | — |
| Deposit liabilities | — | — | — | — |
| Deposits from banks |
20,332,000,000
GBP
|
28,525,000,000
GBP
|
— | — |
| Deposits from customers [abstract] | ||||
| Deposits from customers |
190,850,000,000
GBP
|
195,568,000,000
GBP
|
— | — |
| Subordinated liabilities [abstract] | ||||
| Subordinated liabilities |
2,386,000,000
GBP
|
2,332,000,000
GBP
|
— | — |
| Debt instruments issued |
33,910,000,000
GBP
|
31,531,000,000
GBP
|
— | — |
| Repurchase agreements and cash collateral on securities lent |
8,411,000,000
GBP
|
7,982,000,000
GBP
|
— | — |
| Other liabilities |
2,479,000,000
GBP
|
2,581,000,000
GBP
|
— | — |
| Issued capital [abstract] | ||||
| Issued capital |
3,105,000,000
GBP
|
3,105,000,000
GBP
|
— | — |
| Retained earnings [abstract] | ||||
| Retained earnings |
4,295,000,000
GBP
|
4,848,000,000
GBP
|
— | — |
| Net assets (liabilities) [abstract] | ||||
| Assets |
275,448,000,000
GBP
|
285,213,000,000
GBP
|
— | — |
| Liabilities |
260,825,000,000
GBP
|
270,806,000,000
GBP
|
— | — |
| Assets less current liabilities [abstract] |