Salaries and Benefits Expense (Details 1) (USD $) In Millions	3 Months Ended	6 Months Ended
Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2011	Jun. 30, 2010
Cash Retention Awards
Cash retention awards made	$ 11	$ 16	$ 206	$ 185
Amortization of cash retention awards included in salaries and benefits	$ 44	$ 32	$ 88	$ 60

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wsh_AmortizationOfCashRetentionAwardsIncludedInSalariesAndBenefits

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wsh

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xbrli:monetaryItemType

Balance Type:

debit

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duration