Revenue From Contracts With Customers - Additional Information (Detail) £ in Millions	12 Months Ended
Dec. 31, 2019 GBP (£)
Statement [line items]
Liability for sales return	£ 122
Sales Return [Member]
Statement [line items]
Percentage of entities sales	3.00%

The percentage of the entity's revenue. [Refer: Revenue]

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Name IFRS
-Number 8
-IssueDate 2019-01-01
-Paragraph 34
-URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IFRS&num=8&code=ifrs-tx-2019-en-r&anchor=para_34&doctype=Standard
-URIDate 2019-03-27

Name:	ifrs-full_PercentageOfEntitysRevenue
Namespace Prefix:	ifrs-full_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration