Statement Of Comprehensive Income [Abstract]
| Concept |
2021-01-01 to 2021-12-31 |
2021-01-01 to 2021-12-31 |
2021-01-01 to 2021-12-31 |
2021-01-01 to 2021-12-31 |
2021-01-01 to 2021-12-31 |
2020-01-01 to 2020-12-31 |
2020-01-01 to 2020-12-31 |
2020-01-01 to 2020-12-31 |
2020-01-01 to 2020-12-31 |
2020-01-01 to 2020-12-31 |
|---|---|---|---|---|---|---|---|---|---|---|
| Statement of comprehensive income [abstract] | ||||||||||
| Profit (loss) | — | — | — |
2,907,000,000
GBP
|
— | — |
536,000,000
GBP
|
— | — | — |
| Other comprehensive income [abstract] | ||||||||||
| Components of other comprehensive income that will not be reclassified to profit or loss, before tax [abstract] | ||||||||||
| Other comprehensive income, before tax, gains (losses) on remeasurements of defined benefit plans | — | — | — |
531,000,000
GBP
|
531,000,000
GBP
|
76,000,000
GBP
|
76,000,000
GBP
|
— | — | — |
| Components of other comprehensive income that will be reclassified to profit or loss, before tax [abstract] | ||||||||||
| Exchange differences on translation [abstract] | ||||||||||
| Gains (losses) on exchange differences on translation of foreign operations, before tax |
22,000,000
GBP
|
— | — | — | — | — | — |
5,000,000
GBP
|
— | — |
| Reclassification adjustments on exchange differences on translation of foreign operations, before tax |
—
GBP
|
— | — | — | — | — | — |
1,000,000
GBP
|
— | — |
| Other comprehensive income, before tax, exchange differences on translation of foreign operations | — | — | — |
22,000,000
GBP
|
— | — |
7,000,000
GBP
|
— | — | — |
| Cash flow hedges [abstract] | ||||||||||
| Gains (losses) on cash flow hedges, before tax | — |
102,000,000
GBP
|
— | — | — | — | — | — |
275,000,000
GBP
|
— |
| Reclassification adjustments on cash flow hedges, before tax | — |
78,000,000
GBP
|
— | — | — | — | — | — |
57,000,000
GBP
|
— |
| Other comprehensive income, before tax, cash flow hedges | — | — | — |
180,000,000
GBP
|
— | — |
218,000,000
GBP
|
— | — | — |
| Financial assets measured at fair value through other comprehensive income [abstract] | ||||||||||
| Gains (losses) on financial assets measured at fair value through other comprehensive income, before tax | — | — |
26,000,000
GBP
|
— | — | — | — | — | — |
157,000,000
GBP
|
| Other comprehensive income, before tax, financial assets measured at fair value through other comprehensive income | — | — |
122,000,000
GBP
|
— | — | — | — | — | — |
110,000,000
GBP
|
| Income tax relating to components of other comprehensive income that will not be reclassified to profit or loss [abstract] | ||||||||||
| Income tax relating to remeasurements of defined benefit plans included in other comprehensive income | — | — | — | — |
158,000,000
GBP
|
35,000,000
GBP
|
— | — | — | — |
| Income tax relating to components of other comprehensive income that will not be reclassified to profit or loss | — | — | — |
158,000,000
GBP
|
— | — |
35,000,000
GBP
|
— | — | — |
| Income tax relating to components of other comprehensive income that will be reclassified to profit or loss [abstract] | ||||||||||
| Income tax relating to cash flow hedges included in other comprehensive income | — |
48,000,000
GBP
|
— | — | — | — | — | — |
58,000,000
GBP
|
— |
| Income tax relating to financial assets measured at fair value through other comprehensive income included in other comprehensive income | — | — |
8,000,000
GBP
|
— | — | — | — | — | — |
17,000,000
GBP
|
| Income tax relating to components of other comprehensive income that will be reclassified to profit or loss | — | — | — |
40,000,000
GBP
|
— | — |
41,000,000
GBP
|
— | — | — |
| Other comprehensive income | — | — | — |
351,000,000
GBP
|
— | — |
164,000,000
GBP
|
— | — | — |
| Comprehensive income | — | — | — |
2,556,000,000
GBP
|
— | — |
372,000,000
GBP
|
— | — | — |
| Comprehensive income attributable to [abstract] | ||||||||||
| Comprehensive income, attributable to non-controlling interests | — | — | — |
5,000,000
GBP
|
— | — |
4,000,000
GBP
|
— | — | — |