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 |
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 |
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) | — | — | — | — | — | — | — |
995,000,000
GBP
|
— | — | — |
838,000,000
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 | — | — | — | — | — | — | — |
117,000,000
GBP
|
— | — | — |
280,000,000
GBP
|
— | — | — | — | — | — |
| Share of other comprehensive income of associates and joint ventures accounted for using equity method that will not be reclassified to profit or loss, before tax | — | — | — | — | — | — | — |
12,000,000
GBP
|
— | — | — |
13,000,000
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 | — | — | — | — | — | — | — |
2,000,000
GBP
|
— | — | — |
8,000,000
GBP
|
— | — | — | — | — | — |
| Reclassification adjustments on exchange differences on translation of foreign operations, before tax | — | — | — | — | — | — | — |
18,000,000
GBP
|
— | — | — |
6,000,000
GBP
|
— | — | — | — | — | — |
| Cash flow hedges [abstract] | ||||||||||||||||||
| Gains (losses) on cash flow hedges, before tax | — | — | — | — | — | — | — |
19,000,000
GBP
|
— | — | — |
3,000,000
GBP
|
— | — | — | — | — | — |
| Reclassification adjustments on cash flow hedges, before tax | — | — | — | — | — | — | — |
10,000,000
GBP
|
— | — | — |
13,000,000
GBP
|
— | — | — | — | — | — |
| Share of other comprehensive income of associates and joint ventures accounted for using equity method that will be reclassified to profit or loss, before tax | — | — | — | — | — | — | — |
4,000,000
GBP
|
— | — | — |
13,000,000
GBP
|
— | — | — | — | — | — |
| Income tax relating to components of other comprehensive income that will not be reclassified to profit or loss [abstract] | ||||||||||||||||||
| Income tax relating to components of other comprehensive income that will not be reclassified to profit or loss | — | — | — | — | — | — | — |
3,000,000
GBP
|
— | — | — |
2,000,000
GBP
|
— | — | — | — | — | — |
| Income tax relating to components of other comprehensive income that will be reclassified to profit or loss [abstract] | ||||||||||||||||||
| Income tax relating to components of other comprehensive income that will be reclassified to profit or loss | — | — | — | — | — | — | — |
3,000,000
GBP
|
— | — | — |
2,000,000
GBP
|
— | — | — | — | — | — |
| Other comprehensive income | — | — | — | — | — | — | — |
141,000,000
GBP
|
— | — | — |
288,000,000
GBP
|
— | — | — | — | — | — |
| Comprehensive income |
–
GBP
|
1,000,000
GBP
|
–
GBP
|
–
GBP
|
22,000,000
GBP
|
–
GBP
|
1,135,000,000
GBP
|
1,136,000,000
GBP
|
1,113,000,000
GBP
|
1,115,000,000
GBP
|
–
GBP
|
1,126,000,000
GBP
|
5,000,000
GBP
|
–
GBP
|
–
GBP
|
–
GBP
|
1,121,000,000
GBP
|
6,000,000
GBP
|