Consolidated Statements Of Operations (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Revenues:
Asset management, administration and distribution fees	$ 208,780	$ 183,083	$ 611,135	$ 532,650
Information processing and software servicing fees	64,606	60,901	191,606	174,355
Transaction-based and trade execution fees	7,269	7,768	24,367	23,882
Total revenues	280,655	251,752	827,108	730,887
Expenses:
Subadvisory, distribution and other asset management costs	31,209	26,022	88,795	79,442
Software royalties and other information processing costs	7,541	6,701	22,912	19,337
Brokerage commissions	5,519	5,542	18,291	17,483
Compensation, benefits and other personnel	89,311	85,781	264,636	244,855
Stock-based compensation	11,097	3,879	26,997	11,777
Consulting, outsourcing and professional fees	33,367	27,314	98,667	80,598
Data processing and computer related	12,654	11,749	37,028	34,873
Facilities, supplies and other costs	13,573	15,129	47,280	44,909
Amortization	8,829	10,384	25,498	25,413
Depreciation	5,616	5,761	17,050	16,823
Total expenses	218,716	198,262	647,154	575,510
Income from operations	61,939	53,490	179,954	155,377
Net gain from investments	535	3,708	638	7,577
Interest and dividend income	679	1,490	2,420	4,417
Interest expense	(195)	(115)	(422)	(389)
Equity in earnings of unconsolidated affiliates	31,028	24,928	86,204	74,970
Gain on sale of subsidiary (Note 13)	0	0	22,112	0
Other income (Note 14)	0	0	43,429	0
Net income before income taxes	93,986	83,501	334,335	241,952
Income taxes	26,791	32,415	111,376	90,892
Net income	67,195	51,086	222,959	151,060
Less: Net income attributable to the noncontrolling interest	0	(343)	(350)	(797)
Net income attributable to SEI Investments Company	$ 67,195	$ 50,743	$ 222,609	$ 150,263
Basic earnings per common share	$ 0.39	$ 0.29	$ 1.29	$ 0.86
Shares used to compute basic earnings per share	171,308	173,429	172,043	174,869
Diluted earnings per common share	$ 0.38	$ 0.29	$ 1.26	$ 0.85
Shares used to compute diluted earnings per share	176,043	175,369	176,036	176,317
Dividends declared per common share	$ 0.00	$ 0.00	$ 0.20	$ 0.15