Statement Of Changes In Equity [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 |
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 changes in equity [abstract] | ||||||||||||||||
| Statement of changes in equity [line items] | ||||||||||||||||
| Increase (decrease) through appropriation of retained earnings, equity |
–
GBP
|
–
GBP
|
–
GBP
|
1,000,000
GBP
|
–
GBP
|
–
GBP
|
–
GBP
|
1,000,000
GBP
|
— | — | — | — | — | — | — | — |
| Increase (decrease) through transactions with owners, equity |
12 4
GBP
|
–
GBP
|
–
GBP
|
–
GBP
|
9,000,000
GBP
|
9,000,000
GBP
|
292,000,000
GBP
|
16 8
GBP
|
2 78
GBP
|
8,000,000
GBP
|
281,000,000
GBP
|
–
GBP
|
8,000,000
GBP
|
–
GBP
|
3,000,000
GBP
|
–
GBP
|