Variable Interest Entities - Investment Products (Details)	12 Months Ended
Dec. 31, 2014
Variable Interest Entities Disclosure [Abstract]
Percentage not approached by expected return on any VIE investment	50.00%

Variable Interest Entities, Investment Objective Threshold Percentage

No definition available.

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