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Variable Interest Entities - Investment Products (Details) | 12 Months Ended
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Dec. 31, 2012
Variable Interest Entities - Investment Products [Abstract] |
Percentage not approached by expected return on any VIE investment | 50.00%

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- Definition Percentage not approached by expected return on any VIE investment + References No definition available. + Details
Name: | seic_PercentageNotApproachedByExpectedReturnOnAnyVieInvestment
Namespace Prefix: | seic_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

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- Details
Name: | seic_VariableInterestEntitiesInvestmentProductsAbstract
Namespace Prefix: | seic_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration