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Data Type:	xbrli:monetaryItemType
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Term of lessee's operating lease, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days.

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 842
-SubTopic 20
-Section 50
-Paragraph 3
-Subparagraph (a)(3)
-URI http://asc.fasb.org/extlink&oid=77888426&loc=SL77918673-209980

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The number of countries in which the entity operates as of balance sheet date.

No definition available.

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Data Type:	xbrli:integerItemType
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Percentage of lease denominated in major currencies such as U.S. dollars, Pounds Sterling or Euros.

No definition available.

Name:	wltw_PercentageOfLeaseDenominatedInMajorCurrencies
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Data Type:	num:percentItemType
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Period Type:	instant

Significant accounting policies and recent accounting pronouncements.

No definition available.