Related Party Transactions - Summary of Key Management Personnel Compensation (Detail) - GBP (£) £ in Millions	12 Months Ended
Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Disclosure of transactions between related parties [abstract]
Short-term employee benefits	£ 9	£ 7	£ 6
Retirement benefits	1	1	1
Share-based payment costs	11	9	8
Total	£ 21	£ 17	£ 15

No definition available.

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- Definition

The amount of compensation to key management personnel. [Refer: Key management personnel of entity or parent [member]]

+ References

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- Definition

The amount of compensation to key management personnel in the form of post-employment benefits. [Refer: Key management personnel of entity or parent [member]]

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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- Definition

The amount of compensation to key management personnel in the form of share-based payments. [Refer: Key management personnel of entity or parent [member]]

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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- Definition

The amount of compensation to key management personnel in the form of short-term employee benefits. [Refer: Key management personnel of entity or parent [member]]

+ References

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