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Variable Interest Entities - Investment Products (Details)	9 Months Ended
	Sep. 30, 2015
Variable Interest Entities - Investment Products [Abstract]
Percentage not approached by expected return on any VIE investment	50.00%

X

- Definition

Variable Interest Entities, Investment Objective Threshold Percentage

+ References

No definition available.

+ Details

Name:	seic_VariableInterestEntitiesInvestmentObjectiveThresholdPercentage
Namespace Prefix:	seic_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

X

- Definition

Variable interest entities investment products.

+ References

No definition available.

+ Details

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