The minimum amount the entity agreed to spend under the long-term purchase commitment.

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Namespace Prefix:	us-gaap
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

The cash outflow associated with other investments held by the entity for investment purposes not otherwise defined in the taxonomy.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 95
-Paragraph 15

+ Details

Name:	us-gaap_PaymentsToAcquireOtherInvestments
Namespace Prefix:	us-gaap
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Additional Commitments and Contingencies Textuals.

+ Details

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Namespace Prefix:	wsh
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount Of National Fund For Distribution To Certain Clients Relating to the Assurance of Discontinuance.

+ Details

Name:	wsh_AmountOfNationalFundForDistributionToCertainClientsRelatingToAssuranceOfDiscontinuance
Namespace Prefix:	wsh
Data Type:	xbrli:monetaryItemType
Balance Type:	na
Period Type:	duration

- Definition

Commitments and Contingencies.

+ Details

Name:	wsh_CommitmentsAndContingenciesTextualsAbstract
Namespace Prefix:	wsh
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

A settlement agreement with the FSA arising from lapses in the implementation and documentation of controls to counter the risks of improper payments being made to non-FSA authorized overseas third parties engaged to help win business, particularly in high risk jurisdictions.

+ Details

Name:	wsh_FsaRegulatorySettlement
Namespace Prefix:	wsh
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Legal Settlements Paid.

+ Details

Name:	wsh_LegalSettlementsPaid
Namespace Prefix:	wsh
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Minimum Damage Sought for Stanford related litigation.

+ Details

Name:	wsh_MinimumDamageSoughtForStanfordRelatedLitigation
Namespace Prefix:	wsh
Data Type:	xbrli:monetaryItemType
Balance Type:	na
Period Type:	instant

- Definition

Payments Made To Eligible Clients Under Assurance Of Discontinuance.

+ Details

Name:	wsh_PaymentsMadeToEligibleClientsUnderAssuranceOfDiscontinuance
Namespace Prefix:	wsh
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
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Commitments and Contingencies (Details) In Millions	6 Months Ended							1 Months Ended	6 Months Ended	1 Months Ended	6 Months Ended
Commitments and Contingencies (Details) In Millions	Jun. 30, 2011 USD ($)	Jul. 21, 2011 USD ($)	Jul. 21, 2011 GBP (£)	Jun. 09, 2009 ARIC [Member] USD ($)	Sep. 11, 2009 CNA [Member] USD ($)	Jul. 02, 2009 Troice [Member] USD ($)	Aug. 06, 2009 Canabal [Member] USD ($)	Jul. 31, 2010 Trident V Parallel Fund [Member] USD ($)	Jun. 30, 2011 Trident V Parallel Fund [Member] USD ($)	May 31, 2011 Dowling Capital Partners I [Member] USD ($)	Jun. 30, 2011 Dowling Capital Partners I [Member] USD ($)	Jun. 30, 2011 Casanova [Member] USD ($)	Mar. 11, 2011 Rishmague [Member] USD ($)	Jun. 30, 2011 Rupert [Member] USD ($)
Additional Commitments and Contingencies (Textuals) [Abstract]
Legal settlements paid				$ 139	$ 130
Minimum damage sought						1,000	1,000					5	37	300
Capital commitments								25		10
Capital contributions	4								5		0
Commitments and Contingencies (Textuals) [Abstract]
Payments made to eligible clients under Assurance of Discontinuance	50
Amount of national fund for distribution to certain clients	30
Amount of settlement of fine regarding investigation		$ 11	£ 7