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Data Type:	xbrli:monetaryItemType
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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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Data Type:	xbrli:monetaryItemType
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Earnout receivable in cash not recognized as an asset on balance sheet.

No definition available.

Name:	wtw_EarnoutReceivableInCash
Namespace Prefix:	wtw_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

Fees earned under service agreement.

No definition available.

Name:	wtw_FeesEarnedUnderServiceAgreement
Namespace Prefix:	wtw_
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Fiduciary liabilities excluded from held for sale.

No definition available.

Name:	wtw_FiduciaryLiabilitiesExcludedFromHeldForSale
Namespace Prefix:	wtw_
Data Type:	xbrli:monetaryItemType
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Maximum expected service period.

No definition available.

Name:	wtw_MaximumExpectedServicePeriod
Namespace Prefix:	wtw_
Data Type:	xbrli:durationItemType
Balance Type:	na
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Other current liabilities excluded from held for sale.

No definition available.

Name:	wtw_OtherCurrentLiabilitiesExcludedFromHeldForSale
Namespace Prefix:	wtw_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
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Name:	us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis=wtw_GallagherMember
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Data Type:	na
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Name:	us-gaap_DeferredRevenueArrangementTypeAxis=wtw_TransitionServicesAgreementMember
Namespace Prefix:
Data Type:	na
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Name:	us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis=wtw_WillisReMember
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