Statement Of Changes In Equity [Abstract]
| Concept |
As at 2021-12-31 |
As at 2021-12-31 |
2021-01-01 to 2021-12-31 |
As at 2021-12-31 |
2021-01-01 to 2021-12-31 |
As at 2021-12-31 |
As at 2021-12-31 |
2021-01-01 to 2021-12-31 |
As at 2021-12-31 |
As at 2021-12-31 |
2021-01-01 to 2021-12-31 |
As at 2021-12-31 |
As at 2021-12-31 |
2021-01-01 to 2021-12-31 |
2021-01-01 to 2021-12-31 |
As at 2020-12-31 |
2020-01-01 to 2020-12-31 |
As at 2020-12-31 |
As at 2020-12-31 |
2020-01-01 to 2020-12-31 |
As at 2020-12-31 |
2020-01-01 to 2020-12-31 |
As at 2020-12-31 |
As at 2020-12-31 |
As at 2020-12-31 |
As at 2020-12-31 |
2020-01-01 to 2020-12-31 |
2020-01-01 to 2020-12-31 |
2020-01-01 to 2020-12-31 |
As at 2020-12-31 |
As at 2019-12-31 |
As at 2019-12-31 |
As at 2019-12-31 |
As at 2019-12-31 |
As at 2019-12-31 |
As at 2019-12-31 |
As at 2019-12-31 |
As at 2019-12-31 |
As at 2019-12-31 |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Statement of changes in equity [abstract] | |||||||||||||||||||||||||||||||||||||||
| Statement of changes in equity [line items] | |||||||||||||||||||||||||||||||||||||||
| Equity |
2,204,400,000
GBP
|
16,100,000
GBP
|
— |
2,203,900,000
GBP
|
— |
400,000
GBP
|
52,900,000
GBP
|
— |
2,500,000
GBP
|
194,200,000
GBP
|
— |
269,200,000
GBP
|
108,400,000
GBP
|
— | — |
1,873,100,000
GBP
|
— |
4,300,000
GBP
|
108,300,000
GBP
|
— |
2,500,000
GBP
|
— |
190,900,000
GBP
|
73,400,000
GBP
|
187,700,000
GBP
|
1,919,100,000
GBP
|
— | — | — |
16,100,000
GBP
|
111,800,000
GBP
|
69,900,000
GBP
|
184,000,000
GBP
|
1,744,300,000
GBP
|
2,500,000
GBP
|
1,617,500,000
GBP
|
16,100,000
GBP
|
2,400,000
GBP
|
108,300,000
GBP
|
| Changes in equity [abstract] | |||||||||||||||||||||||||||||||||||||||
| Comprehensive income [abstract] | |||||||||||||||||||||||||||||||||||||||
| Profit (loss) | — | — | — | — | — | — | — | — | — | — | — | — | — |
442,800,000
GBP
|
442,800,000
GBP
|
— |
430,000,000
GBP
|
— | — |
430,000,000
GBP
|
— | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — |
| Other comprehensive income | — | — | — | — | — | — | — | — | — | — | — | — | — |
19,100,000
GBP
|
— | — |
99,200,000
GBP
|
— | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — |
| Comprehensive income | — | — |
3,600,000
GBP
|
— | — | — | — |
78,300,000
GBP
|
— | — | — | — | — |
423,700,000
GBP
|
498,400,000
GBP
|
— |
330,800,000
GBP
|
— | — |
416,800,000
GBP
|
— |
6,900,000
GBP
|
— | — | — | — | — |
79,100,000
GBP
|
— | — | — | — | — | — | — | — | — | — | — |
| Issue of equity | — | — | — | — |
6,500,000
GBP
|
— | — | — | — | — |
100,000
GBP
|
— | — |
6,600,000
GBP
|
— | — |
3,700,000
GBP
|
— | — | — | — | — | — | — | — | — |
–
GBP
|
— |
3,700,000
GBP
|
— | — | — | — | — | — | — | — | — | — |
| Increase (decrease) through share-based payment transactions, equity | — | — | — | — | — | — | — | — | — | — | — | — | — |
18,300,000
GBP
|
18,300,000
GBP
|
— |
16,200,000
GBP
|
— | — |
16,200,000
GBP
|
— | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — |
| Amount removed from reserve of cash flow hedges and included in initial cost or other carrying amount of non-financial asset (liability) or firm commitment for which fair value hedge accounting is applied | — | — |
1,100,000
GBP
|
— | — | — | — | — | — | — | — | — | — |
1,100,000
GBP
|
— | — |
5,000,000
GBP
|
— | — | — | — |
5,000,000
GBP
|
— | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — |