Amount of increase in additional paid in capital (APIC) resulting from a tax benefit associated with share-based compensation plan other than an employee stock ownership plan (ESOP). Includes, but is not limited to, excess tax benefit.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 505

-SubTopic 10

-Section 50

-Paragraph 2

-URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21463-112644

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 505

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.3-04)

-URI http://asc.fasb.org/extlink&oid=27012166&loc=d3e187085-122770

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 740

-Section 45

-Paragraph 2

-URI http://asc.fasb.org/extlink&oid=6419406&loc=d3e23524-113945

Consolidated Statements Of Changes In Equity (USD $) In Thousands, except Share data, unless otherwise specified	Total	Common Stock [Member]	Capital In Excess Of Par Value [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Income [Member]	SEI Investments [Member]	Noncontrolling Interest [Member]
Beginning balance at Dec. 31, 2011		$ 1,765	$ 577,949	$ 443,702	$ 1,900
Beginning balance, shares at Dec. 31, 2011		176,506,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Purchase and retirement of common stock		(75)	(19,370)	(135,819)
Purchase and retirement of common stock, shares		(7,528,000)
Issuance of common stock under the employee stock purchase plan		1	1,794
Issuance of common stock under the employee stock purchase plan, shares		105,000
Issuance of common stock upon exercise of stock options		31	47,613
Issuance of common stock upon exercise of stock options, shares	3,136,000	3,137,000
Stock-based compensation	(15,736)		15,736
Tax benefit on stock options exercised			583
Net income attributable to SEI Investments Company	206,848us-gaap_NetIncomeLoss			206,848
Dividends declared ($0.46, $0.42 and $0.63 per share)	(108,817)us-gaap_DividendsCommonStock			(108,817)
Other comprehensive (loss) income	6,159				4,339
Total SEI Investments Shareholders' Equity						1,038,180
Noncontrolling Interest							19,149
Total Equity at Dec. 31, 2012	1,057,329	1,722	624,305	405,914	6,239
Ending balance, shares at Dec. 31, 2012		172,220,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Purchase and retirement of common stock		(68)	(19,105)	(190,769)
Purchase and retirement of common stock, shares		(6,789,000)
Issuance of common stock under the employee stock purchase plan		1	1,950
Issuance of common stock under the employee stock purchase plan, shares		78,000
Issuance of common stock upon exercise of stock options		37	64,379
Issuance of common stock upon exercise of stock options, shares	3,733,000	3,733,000
Stock-based compensation	(37,865)		37,865
Tax benefit on stock options exercised			11,825
Net income attributable to SEI Investments Company	288,124us-gaap_NetIncomeLoss			288,124
Dividends declared ($0.46, $0.42 and $0.63 per share)	(71,665)us-gaap_DividendsCommonStock			(71,665)
Other comprehensive (loss) income	(5,203)				(4,752)
Total SEI Investments Shareholders' Equity						1,156,002
Noncontrolling Interest							0
Total Equity at Dec. 31, 2013	1,156,002	1,692	721,219	431,604	1,487
Ending balance, shares at Dec. 31, 2013	169,242,000us-gaap_CommonStockSharesIssued	169,242,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Purchase and retirement of common stock		(79)	(25,345)	(252,933)
Purchase and retirement of common stock, shares		(7,888,000)
Issuance of common stock under the employee stock purchase plan		1	2,197
Issuance of common stock under the employee stock purchase plan, shares		73,000
Issuance of common stock upon exercise of stock options		53	102,646
Issuance of common stock upon exercise of stock options, shares	5,261,000	5,261,000
Stock-based compensation	(13,463)		13,463
Tax benefit on stock options exercised			20,435
Net income attributable to SEI Investments Company	318,713us-gaap_NetIncomeLoss			318,713
Dividends declared ($0.46, $0.42 and $0.63 per share)	(77,158)us-gaap_DividendsCommonStock			(77,158)
Other comprehensive (loss) income	(10,382)				(10,382)
Total SEI Investments Shareholders' Equity						1,247,613
Noncontrolling Interest							0
Total Equity at Dec. 31, 2014	$ 1,247,613	$ 1,667	$ 834,615	$ 420,226	$ (8,895)
Ending balance, shares at Dec. 31, 2014	166,688,000us-gaap_CommonStockSharesIssued	166,688,000