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Amount of gain (loss) from sale and disposal of integrated set of activities and assets capable of being conducted and managed for purpose of providing return in form of dividend, lower cost, or other economic benefit to investor, owner, member and participant.

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-Subparagraph (b)
-URI https://asc.fasb.org/extlink&oid=126954810&loc=d3e3602-108585

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 810
-SubTopic 10
-Section 50
-Paragraph 1B
-Subparagraph (a)
-URI https://asc.fasb.org/extlink&oid=109239629&loc=SL4582445-111684

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

No definition available.

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Accounts receivable, net balances excluded from held-for-sale.

No definition available.

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Earnout receivable in cash not recognized as an asset on balance sheet.

No definition available.

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Fees earned under service agreement.

No definition available.

Name:	wtw_FeesEarnedUnderServiceAgreement
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Fiduciary assets excluded from held-for-sale.

No definition available.

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Maximum expected service period.

No definition available.

Name:	wtw_MaximumExpectedServicePeriod
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Other current liabilities excluded from held for sale.

No definition available.

Name:	wtw_OtherCurrentLiabilitiesExcludedFromHeldForSale
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Data Type:	xbrli:monetaryItemType
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Namespace Prefix:
Data Type:	na
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Name:	us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis=wtw_WillisReMember
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