Accumulated Comprehensive Income (Schedule Of Accumulated Other Comprehensive Income (Loss), Net Of Tax) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013	Dec. 31, 2013
Accumulated other comprehensive income, Unrealized Holding Gains on Investments	$ 2,308		$ 2,308		$ 1,386
Accumulated Other Comprehensive Income	3,821		3,821		1,487
Other Comprehensive Income, Foreign Currency Transaction and Translation Gain (Loss) Arising During Period, Net of Tax			1,412
Other Comprehensive Income, Available-for-sale Securities Adjustment, before Reclassification Adjustments, Net of Tax			991
Other Comprehensive Income before Reclassification, Net of Tax			2,403
Other Comprehensive Income, Foreign Currency Transaction and Translation Reclassification Adjustment from AOCI, Realized upon Sale or Liquidation, Net of Tax			0
Other Comprehensive Income, Reclassification Adjustment from AOCI for Sale of Securities, Net of Tax	24	121	69	342
Other Comprehensive Income, Reclassification Adjustment, Net of Tax			69
Total comprehensive income, Foreign Currency Translation Adjustments	3,378	(1,800)	1,412	(7,107)
Total comprehensive income, Unrealized Holding Gains (Losses) on Investments			922
Total other comprehensive income (loss), net of tax	3,807	(3,282)	2,334	(8,689)
SEI Investments Company [Member]
Accumulated other comprehensive income, Foreign Currency Translation Adjustments	1,513		1,513		101
Accumulated other comprehensive income, Unrealized Holding Gains on Investments	2,308		2,308		1,386
Accumulated Other Comprehensive Income	$ 3,821		$ 3,821		$ 1,487