Consolidated Balance Sheets (USD $) In Thousands, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Current Assets:
Cash and cash equivalents	$ 527,214	$ 452,247
Restricted cash	5,500	6,000
Receivables from regulated investment companies	39,579	31,084
Receivables, net of allowance for doubtful accounts of $625 and $805 (Note 4)	186,382	171,734
Deferred income taxes	1,284	2,012
Securities owned (Note 6)	20,728	20,088
Other current assets	19,345	18,239
Total Current Assets	800,032	701,404
Property and Equipment, net of accumulated depreciation of $214,653 and $201,418 (Note 4)	118,494	127,581
Capitalized Software, net of accumulated amortization of $171,015 and $149,747	313,206	307,490
Investments Available for Sale (Note 6)	86,186	75,869
Trading Securities (Note 6)	4,841	5,909
Investment in Unconsolidated Affiliates (Note 2)	57,429	77,398
Other Assets, net	11,511	14,173
Total Assets	1,391,699	1,309,824
Current Liabilities:
Accounts payable	7,275	11,248
Accrued liabilities (Note 4)	136,639	138,305
Deferred revenue	1,364	2,452
Total Current Liabilities	145,278	152,005
Deferred Income Taxes	71,151	93,458
Other Long-term Liabilities (Note 11)	8,703	7,032
Total Liabilities	225,132	252,495
Commitments and Contingencies (Note 12)
SEI Investments shareholders' equity:
Common stock, $.01 par value, 750,000 shares authorized;170,500 and 172,220 shares issued and outstanding	1,705	1,722
Capital in excess of par value	700,673	624,305
Retained earnings	462,633	405,914
Accumulated other comprehensive income, net	1,556	6,239
Total SEI Investments shareholders' equity	1,166,567	1,038,180
Noncontrolling interest	0	19,149
Total Equity	1,166,567	1,057,329
Total Liabilities and Equity	$ 1,391,699	$ 1,309,824