Trade and Other Payables Amounts Falling Due After More than One Year - Summary of Contingent Consideration (Detail) - GBP (£) £ in Millions	6 Months Ended	12 Months Ended
Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017
Disclosure Of Fair Value Of Contingent Consideration [Abstract]
At the beginning of the period	£ 630.7	£ 976.5	£ 976.5
Earnouts paid	(38.0)	(61.7)	(199.1)
New acquisitions	11.9	71.4	163.7
Revision of estimates taken to goodwill	(26.3)	(23.2)	(60.7)
Revaluation of payments due to vendors (note 7)	(29.7)	(69.4)	(208.6)
Exchange adjustments	(5.7)	(22.9)	(41.1)
At the end of the period	£ 542.9	£ 870.7	£ 630.7

Contingent consideration current and non-current payable to vendors (earnout agreements).

No definition available.

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Disclosure Of Fair Value Of Contingent Consideration [Abstract].

No definition available.

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Earnouts paid.

No definition available.

Increase (decrease) through business combinations, contingent consideration.

No definition available.

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Increase (decrease) through net exchange differences, contingent consideration.

No definition available.

Name:	wpp_IncreaseDecreaseThroughNetExchangeDifferencesContingentConsideration
Namespace Prefix:	wpp_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
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Revaluation of payments due to vendors, Increase decrease in payables

No definition available.

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Namespace Prefix:	wpp_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
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Revision of estimates taken to goodwill.

No definition available.

Name:	wpp_RevisionOfEstimatesTakenToGoodwill
Namespace Prefix:	wpp_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration