SEI Investments (SEIC) 10-K 22 Feb 16 2015 FY Annual report Financial data

Document And Entity Information

Document And Entity Information - USD ($) $ in Billions	12 Months Ended
	Dec. 31, 2015	Jan. 29, 2016	Jun. 30, 2015
Document And Entity Information [Abstract]
Entity Registrant Name	SEI INVESTMENTS CO
Entity Central Index Key	350,894
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Document Type	10-K
Document Period End Date	Dec. 31, 2015
Document Fiscal Year Focus	2,015
Document Fiscal Period Focus	FY
Trading Symbol	SEIC
Amendment Flag	false
Entity Common Stock, Shares Outstanding		163,649,718
Entity Public Float			$ 6.4
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Current Assets:
Cash and cash equivalents	$ 679,661	$ 667,446
Restricted cash	5,500	5,801
Receivables from regulated investment companies	48,098	48,393
Receivables, net of allowance for doubtful accounts of $649 and $784	223,023	194,419
Securities owned	21,235	21,175
Other current assets	26,207	18,193
Total Current Assets	1,003,724	955,427
Property and Equipment, net of accumulated depreciation of $259,501 and $241,295	143,977	125,535
Capitalized Software, net of accumulated amortization of $259,358 and $218,514	290,522	309,040
Investments Available for Sale	81,294	77,609
Investments in Affiliated Funds, at fair value	4,039	4,523
Investment in Unconsolidated Affiliates	49,580	54,290
Other Assets, net	15,492	16,451
Total Assets	1,588,628	1,542,875
Current Liabilities:
Accounts payable	4,511	10,588
Accrued liabilities	217,587	207,429
Deferred revenue	2,385	1,749
Total Current Liabilities	224,483	219,766
Deferred Income Taxes	63,028	65,169
Other Long-term Liabilities	11,397	10,327
Total Liabilities	$ 298,908	$ 295,262
Commitments and Contingencies
SEI Investments shareholders' equity:
Series Preferred stock, $.05 par value, 50 shares authorized; no shares issued and outstanding	$ 0	$ 0
Common stock, $.01 par value, 750,000 shares authorized; 163,733 and 166,688 shares issued and outstanding	1,637	1,667
Capital in excess of par value	910,513	834,615
Retained earnings	402,860	420,226
Accumulated other comprehensive loss, net	(25,290)	(8,895)
Total Shareholders' Equity	1,289,720	1,247,613
Total Liabilities and Equity	$ 1,588,628	$ 1,542,875

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Current Assets:
Receivables, allowance for doubtful accounts	$ 649	$ 784
Property and Equipment, accumulated depreciation	259,501	241,295
Capitalized Software, accumulated amortization	$ 259,358	$ 218,514
Equity:
Series Preferred stock, par value	$ 0.05	$ 0.05
Series Preferred stock, shares authorized	50,000	50,000
Series Preferred stock, shares issued	0	0
Series Preferred stock, shares outstanding	0	0
Common stock, par value	$ 0.01	$ 0.01
Common stock, shares authorized	750,000,000	750,000,000
Common stock, shares issued	163,733,000	166,688,000
Common stock, shares outstanding	163,733,000	166,668,000

Consolidated Statements Of Oper

Consolidated Statements Of Operations - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Revenues:
Asset management, administration and distribution fees	$ 1,010,511	$ 948,932	$ 831,720
Information processing and software servicing fees	290,893	285,463	261,691
Transaction-based and trade execution fees	32,804	31,610	32,721
Total revenues	1,334,208	1,266,005	1,126,132
Expenses:
Subadvisory, distribution and other asset management costs	160,062	149,791	121,989
Software royalties and other information processing costs	31,497	33,522	31,255
Brokerage commissions	24,388	23,002	24,649
Compensation, benefits and other personnel	395,774	376,873	357,453
Stock-based compensation	17,312	13,463	37,865
Consulting, outsourcing and professional fees	146,436	136,818	131,399
Data processing and computer related	58,884	52,512	51,401
Facilities, supplies and other costs	74,968	66,113	64,613
Amortization	42,630	38,679	34,602
Depreciation	24,044	22,448	22,497
Total expenses	975,995	913,221	877,723
Income from operations	358,213	352,784	248,409
Net (loss) gain from investments	(456)	614	659
Interest and dividend income	3,358	3,354	3,248
Interest expense	(483)	(458)	(535)
Equity in earnings of unconsolidated affiliates	137,057	127,786	118,076
Gain on sale of subsidiary	2,791	5,582	22,112
Other income	0	0	43,429
Income before income taxes	500,480	489,662	435,398
Income taxes	168,825	170,949	146,924
Net income	331,655	318,713	288,474
Less: Net income attributable to the noncontrolling interest	0	0	(350)
Net income attributable to SEI Investments Company	$ 331,655	$ 318,713	$ 288,124
Basic earnings per common share	$ 2	$ 1.89	$ 1.68
Shares used to compute basic earnings per share	165,725	168,246	171,561
Diluted earnings per common share	$ 1.96	$ 1.85	$ 1.64
Shares used to compute diluted earnings per share	169,598	172,565	175,718
Dividends declared per common share	$ 0.50	$ 0.46	$ 0.42

Consolidated Statements Of Comp

Consolidated Statements Of Comprehensive Income - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Statement of Comprehensive Income [Abstract]
Net income	$ 331,655	$ 318,713	$ 288,474
Other comprehensive loss, net of tax:
Foreign currency translation adjustments	(14,900)	(10,189)	(3,760)
Unrealized holding (loss) gain on investments:
Unrealized holding (losses) gains during the period, net of income taxes of $822, $(592) and $(954)	(1,659)	441	(1,149)
Less: reclassification adjustment for losses (gains) realized in net income, net of income taxes of $(76), $319 and $170	164	(634)	(294)
Total other comprehensive loss, net of taxes	(16,395)	(10,382)	(5,203)
Comprehensive income	315,260	308,331	283,271
Less: Comprehensive loss attributable to noncontrolling interest	0	0	101
Comprehensive income attributable to SEI Investments	$ 315,260	$ 308,331	$ 283,372

Consolidated Statements Of Com6

Consolidated Statements Of Comprehensive Income (Parenthetical) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Statement of Comprehensive Income [Abstract]
Unrealized holding (losses) gains during the period, income taxes	$ 822	$ (592)	$ (954)
Reclassification adjustment for losses (gains) realized in net income, income taxes	$ (76)	$ 319	$ 170

Consolidated Statements Of Chan

Consolidated Statements Of Changes In Equity - USD ($) $ in Thousands	Total	Common Stock [Member]	Capital In Excess Of Par Value [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive (Loss) Income [Member]
Beginning balance at Dec. 31, 2012		$ 1,722	$ 624,305	$ 405,914	$ 6,239
Beginning 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	288,124			288,124
Dividends declared ($0.50, $0.46 and $0.42 per share)	(71,665)			(71,665)
Other comprehensive loss	(5,203)				(4,752)
Total Equity at Dec. 31, 2013	$ 1,156,002	$ 1,692	721,219	431,604	1,487
Ending balance, shares at Dec. 31, 2013		169,242,000
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	318,713			318,713
Dividends declared ($0.50, $0.46 and $0.42 per share)	(77,158)			(77,158)
Other comprehensive loss	(10,382)				(10,382)
Total Equity at Dec. 31, 2014	$ 1,247,613	$ 1,667	834,615	420,226	(8,895)
Ending balance, shares at Dec. 31, 2014	166,688,000	166,688,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Purchase and retirement of common stock		$ (60)	(22,984)	(266,543)
Purchase and retirement of common stock, shares		(5,951,000)
Issuance of common stock under the employee stock purchase plan		$ 1	2,798
Issuance of common stock under the employee stock purchase plan, shares		69,000
Issuance of common stock upon exercise of stock options		$ 29	62,716
Issuance of common stock upon exercise of stock options, shares	2,927,000	2,927,000
Stock-based compensation	$ (17,312)		17,312
Tax benefit on stock options exercised			16,056
Net income attributable to SEI Investments Company	331,655			331,655
Dividends declared ($0.50, $0.46 and $0.42 per share)	(82,478)			(82,478)
Other comprehensive loss	(16,395)				(16,395)
Total Equity at Dec. 31, 2015	$ 1,289,720	$ 1,637	$ 910,513	$ 402,860	$ (25,290)
Ending balance, shares at Dec. 31, 2015	163,733,000	163,733,000

Consolidated Statements Of Cha8

Consolidated Statements Of Changes In Equity (Parenthetical) - $ / shares	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Dividends declared per common share	$ 0.50	$ 0.46	$ 0.42
Retained Earnings [Member]
Dividends declared per common share	$ 0.50	$ 0.46	$ 0.42

Consolidated Statements Of Cash

Consolidated Statements Of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Cash flows from operating activities:
Net income	$ 331,655	$ 318,713	$ 288,474
Depreciation	24,044	22,448	22,497
Amortization	42,630	38,679	34,602
Equity in earnings of unconsolidated affiliates	(137,057)	(127,786)	(118,076)
Distributions received from unconsolidated affiliate	141,767	137,866	137,104
Stock-based compensation	17,312	13,463	37,865
Provision for losses on receivables	(135)	133	(154)
Deferred income tax expense	(1,394)	(3,330)	(22,825)
Gain from sale of SEI AK	(2,791)	(5,582)	(22,112)
Net realized loss (gain) from investments	456	(614)	(659)
Change in other long-term liabilities	1,070	1,720	1,575
Change in other assets	783	(5,886)	600
Write off of capitalized and purchased software	6,055	0	0
Other	(2,440)	(2,439)	(3,972)
Decrease (increase) in Restricted cash for broker-dealer operations	0	0	500
Decrease (increase) in Receivables from regulated investment companies	295	(9,029)	(8,280)
Decrease (increase) in Receivables	(28,469)	(7,888)	(17,513)
Decrease (increase) in Other current assets	(8,014)	(2,027)	1,971
(Decrease) increase in Accounts payable	(5,441)	(6,283)	5,000
(Decrease) increase in Accrued liabilities	10,498	12,873	15,102
(Decrease) increase in Deferred revenue	636	(228)	(475)
Total adjustments	59,805	56,090	62,750
Net cash provided by operating activities	391,460	374,803	351,224
Cash flows from investing activities:
Decrease (increase) in restricted cash	301	(301)	0
Additions to property and equipment	(44,465)	(28,469)	(16,351)
Additions to capitalized software	(29,416)	(34,877)	(39,500)
Purchases of marketable securities	(52,538)	(56,754)	(57,560)
Prepayments and maturities of marketable securities	38,551	38,973	40,257
Sales of marketable securities	7,761	24,461	7,317
Purchases of other investments	(1,000)	(2,000)	(2,604)
Sale of subsidiary, net of cash transferred	2,791	5,582	6,028
Net cash used in investing activities	(78,015)	(53,385)	(62,413)
Cash flows from financing activities:
Purchase and retirement of common stock	(291,374)	(275,788)	(206,577)
Proceeds from issuance of common stock	65,543	104,897	66,367
Tax benefit on stock options exercised	16,056	20,435	11,825
Payment of dividends	(80,030)	(74,294)	(34,400)
Net cash used in financing activities	(289,805)	(224,750)	(162,785)
Effect of exchange rate changes on cash and cash equivalents	(11,425)	(7,495)	0
Net increase in cash and cash equivalents	12,215	89,173	126,026
Cash and cash equivalents, beginning of year	667,446	578,273	452,247
Cash and cash equivalents, end of year	679,661	667,446	578,273
Interest paid	460	458	458
Income taxes paid	159,605	151,250	163,834
Non-cash financing activities
Dividends declared but not paid	$ 42,625	$ 40,178	$ 37,314

Summary of Significant Accounti

Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2015
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	Summary of Significant Accounting Policies Nature of Operations SEI Investments Company (the Company), a Pennsylvania corporation, provides investment processing, investment management, and investment operations solutions to financial institutions, financial advisors, institutional investors, investment managers and ultra-high-net-worth families in the United States, Canada, the United Kingdom, continental Europe and other various locations throughout the world. Investment processing solutions consist of application and business process outsourcing services, professional services and transaction-based services. Revenues from investment processing solutions are recognized in Information processing and software servicing fees on the accompanying Consolidated Statements of Operations, except for fees earned associated with trade execution services. Investment management programs consist of mutual funds, alternative investments and separate accounts. These include a series of money market, equity, fixed-income and alternative investment portfolios, primarily in the form of registered investment companies. The Company serves as the administrator and investment advisor for many of these products. Revenues from investment management programs are recognized in Asset management, administration and distribution fees on the accompanying Consolidated Statements of Operations. Investment operations solutions offer investment managers support for traditional investment products such as mutual funds, collective investment trusts, exchange-traded funds, and institutional and separate accounts, by providing outsourcing services including fund and investment accounting, administration, reconciliation, investor servicing and client reporting. These solutions also provide support to managers focused on alternative investments who manage hedge funds, funds of hedge funds, private equity funds and real estate funds, across registered, partnership and separate account structures domiciled in the United States and overseas. Revenues from investment operations solutions are recognized in Asset management, administration and distribution fees on the accompanying Consolidated Statements of Operations. Principles of Consolidation The Consolidated Financial Statements include the accounts of the Company and its wholly-owned subsidiaries and entities in which it holds a controlling financial interest. The Company determines whether it has a controlling financial interest either by its decision-making ability through voting interests or by the extent of the Company’s participation in the economic risks and rewards of the entity through variable interests. The Company’s principal subsidiaries are SEI Investments Distribution Co. (SIDCO), SEI Investments Management Corporation (SIMC), SEI Private Trust Company (SPTC), SEI Trust Company (STC), SEI Global Services, Inc. (SGSI) and SEI Investments (Europe) Limited (SIEL). All intercompany accounts and transactions have been eliminated. The Company accounts for investments in unconsolidated entities that are 20 percent to 50 percent owned or are 20 percent or less owned and have the ability to exercise significant influence over the operating and financial policies of the entity under the equity method of accounting. Under this method of accounting, the Company’s interest in the net assets of unconsolidated entities is reflected in Investment in unconsolidated affiliates on the accompanying Consolidated Balance Sheet and its interest in the earnings or losses of unconsolidated entities is reflected in Equity in earnings of unconsolidated affiliates on the accompanying Consolidated Statement of Operations. Variable Interest Entities The Company has involvement with various variable interest entities (VIE or VIEs). These VIEs consist of LSV Employee Group III, LLC (LSV Employee Group III) and investment products established for clients created in the form of various types of legal entity structures. According to the most recent accounting guidance issued by the Financial Accounting Standards Board (FASB), the determination of whether a company is required to consolidate an entity is based on, among other things, an entity’s purpose and design, a company’s ability to direct the activities of the entity that most significantly impact the entity’s economic performance, and whether a company is obligated to absorb losses or receive benefits that could be potentially significant to the entity. The guidance requires ongoing reassessments of whether an enterprise is the primary beneficiary of a VIE and requires disclosures about an enterprises involvement in VIEs. The FASB deferred the accounting guidance for certain types of investment entities. The deferral allows asset managers that have no obligation to fund potentially significant losses of an investment entity to continue to apply the previous guidance to investment entities that have attributes of entities defined in the “Investment Company Guide.” The deferral applies to many mutual funds, hedge funds, private equity funds, venture capital and certain other types of entities. Also, money market funds subject to rule 2a-7 of the Investment Company Act of 1940 qualify for deferral. However, the deferral does not apply to the new disclosure requirements. All of the Company’s investment products where the Company is the sponsor and/or investment manager that are VIEs qualify for the deferral; therefore, the Company will continue to apply the previous guidance for the consolidation of VIEs (See Note 3). On February 18, 2015, the FASB issued Accounting Standards Update No. 2015-02, Consolidation (Topic 810) - Amendments to the Consolidation Analysis (ASU 2015-02). The new guidance applies to entities in all industries and provides a new scope exception to registered money market funds and similar unregistered money market funds. It makes targeted amendments to the current consolidation guidance and ends the deferral granted to investment companies from applying the VIE guidance. ASU 2015-02 became effective for the Company during the first quarter 2016. The Company has completed its evaluation of ASU 2015-02 and has determined that the standard will not have any effect on its consolidated financial statements. Management’s Use of Estimates The preparation of financial statements in conformity with accounting principles generally accepted in the United States requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates. Revenue Recognition The Company’s principal sources of revenues are: (1) asset management, administration and distribution fees earned based upon a contractual percentage of net assets under management or administration; (2) information processing and software servicing fees that are either recurring and primarily earned based upon the number of trust accounts being serviced or non-recurring and based upon project-oriented contractual agreements related to client implementations; and (3) transaction-based fees for providing trade-execution services. The Company’s revenues are based on contractual arrangements. Revenues are recognized in the periods in which the related services are performed provided that persuasive evidence of an agreement exists, the fee is fixed or determinable, and collectibility is reasonably assured. Cash received by the Company in advance of the performance of services is deferred and recognized as revenue when earned. Reimbursements received for out-of-pocket expenses incurred are recorded as revenue. Certain portions of the Company’s revenues require management’s consideration of the nature of the client relationship in determining whether to recognize as revenue the gross amount billed or net amount retained after payments are made to suppliers for certain services related to the product or service offering. For the majority of our services, we are the primary obligor responsible for fulfilling the performance obligations of the contract. In addition, we retain full discretion in establishing the price charged to the customer, control the nature, type, characteristics or specifications of the performance obligations identified in the contract, and assume all credit risk associated with the client. Based on the foregoing, fees received from our clients for these services are recorded as gross revenues and vendor costs are recorded as gross expenses. However, we are also party to certain arrangements whereby we are not the primary obligor responsible for fulfilling the performance obligations of the contract. Fees received for those arrangements are reported net of costs associated with the provision of those services. Cash and Cash Equivalents The Company considers investment instruments purchased with an original maturity of three months or less to be cash equivalents. Cash and cash equivalents include $448,957 and $435,268 at December 31, 2015 and 2014 , respectively, primarily invested in SEI-sponsored open-ended money market mutual funds. The SEI-sponsored mutual funds are considered Level 1 assets. Restricted Cash Restricted cash includes $5,000 at December 31, 2015 and 2014 segregated for regulatory purposes related to trade-execution services conducted by SIEL. Restricted cash also includes $500 at December 31, 2015 and 2014 segregated in special reserve accounts for the benefit of SIDCO customers in accordance with certain rules established by the Securities and Exchange Commission for broker-dealers. Allowances for Doubtful Accounts The Company provides an allowance for doubtful accounts equal to the estimated uncollectible amounts. The Company’s estimate is based on historical collection experience and a review of the current status of trade accounts receivable. Concentration of Credit Risk Financial instruments which potentially expose the Company to concentrations of credit risk consist primarily of cash equivalents and trade receivables. Cash equivalents are principally invested in short-term money market funds or placed with major banks and high-credit qualified financial institutions. Cash deposits maintained with institutions are in excess of federally insured limits. Concentrations of credit risk with respect to our receivables are limited due to the large number of clients and their dispersion across geographic areas. No single group or customer represents greater than ten percent of total accounts receivable. Property and Equipment Property and Equipment are recorded at cost. Expenditures for major additions and improvements are capitalized and minor replacements, maintenance, and repairs are charged to expense as incurred. Construction in progress includes the cost of construction and other direct costs attributable to the construction. When property and equipment are retired or disposed of, the related cost and accumulated depreciation are removed from the accounts and any resulting gain or loss is included in the results of operations for the respective period. Depreciation is provided over the estimated useful lives using the straight line method for financial statement purposes. No provision for depreciation is made for construction in progress until such time as the relevant assets are completed and put into service. The Company uses other depreciation methods, generally accelerated, for tax purposes where appropriate. Buildings and building improvements are depreciated over 25 to 39 years . Equipment, purchased software and furniture and fixtures have useful lives ranging from 3 to 5 years . Amortization of leasehold improvements is computed using the straight line method over the shorter of the remaining lease term or the estimated useful lives of the improvements. Marketable Securities The classification of investments in marketable securities is determined at the time of purchase and reevaluated at each balance sheet date. Debt and equity securities classified as available-for-sale are reported at fair value as determined by the most recently traded price of each security at the balance sheet date. Unrealized gains and losses, net of income taxes, are reported as a separate component of comprehensive income. SIDCO, the Company’s broker-dealer subsidiary, reports changes in fair value of marketable securities through current period earnings due to specialized accounting practices related to investments by broker-dealers. The Company records its investments in funds sponsored by LSV on the accompanying Consolidated Balance Sheets at fair value. Unrealized gains and losses from the change in fair value of these securities are recognized in current period earnings. The specific identification method is used to compute the realized gains and losses on all of the Company’s marketable securities (See Note 6). The Company evaluates the realizable value of its marketable securities on a quarterly basis. In the event that the carrying value of an investment exceeds its fair value and the decline in value is determined to be other-than-temporary, an impairment charge is recorded and a new cost basis for the investment is established. Some of the factors considered in determining other-than-temporary impairment for equity securities include, but are not limited to, significant or prolonged declines in the fair value of the investments, the Company’s ability and intent to retain the investment for a period sufficient to allow the value to recover, and the financial condition of the investment. Some of the factors considered in determining other-than-temporary impairment for debt securities include, but are not limited to, the intent of management to sell the security, the likelihood that the Company will be required to sell the security before recovering its cost, and management’s expectation to recover the entire amortized cost basis of the security even if there is no intent to sell the security. Fair Value of Financial Instruments Fair value is defined as the exchange price that would be received for an asset or paid to transfer a liability (an exit price) in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants on the measurement date. The fair value hierarchy requires an entity to maximize the use of observable inputs and minimize the use of unobservable inputs when measuring fair value. The fair value hierarchy describes three levels of inputs that may be used by the Company to measure fair value: Level 1 – Quoted prices in active markets for identical assets or liabilities without adjustment. The Company’s Level 1 assets primarily include investments in mutual funds sponsored by SEI that are quoted daily. Level 2 – Observable inputs other than Level 1 prices, such as quoted prices for similar assets, quoted prices in markets that are not active, or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the assets or liabilities. Level 2 financial assets consist of Government National Mortgage Association (GNMA) mortgage-backed securities, Federal Home Loan Bank (FHLB) and other U.S. government agency short-term notes and investment grade commercial paper, and investment funds sponsored by LSV. The investments in GNMA mortgage-backed securities were purchased for the sole purpose of satisfying applicable regulatory requirements imposed on our wholly-owned limited purpose federal thrift subsidiary, SPTC. The investments in FHLB and other U.S. government agency short-term notes and investment grade commercial paper were purchased as part of a cash management program requiring only short term, top-tier investment grade government and corporate securities. The investment funds sponsored by LSV primarily invest in equity securities of non-U.S. developed nations which are traded in active markets. Level 3 – Unobservable inputs that are supported by little or no market activity and that are significant to the fair value of the assets or liabilities. Level 3 assets and liabilities include financial instruments whose value is determined using pricing models, or similar techniques, as well as instruments for which the determination of fair value requires significant judgment by management. The Company had no Level 3 financial assets at December 31, 2015 or 2014 . The fair value of an asset or liability may include inputs from more than one level in the fair value hierarchy. The lowest level of significant inputs used to value the asset or liability determines which level the asset or liability is classified in its entirety. Transfers between levels of the fair value hierarchy are reported at fair value as of the beginning of the period in which the transfers occur. See Note 5 for information on related disclosures regarding fair value measurements. Capitalized Software Costs incurred for the development of internal use software to be offered in a hosting arrangement is capitalized during the development stage of the software application. These costs include direct external and internal costs to design the software configuration and interfaces, coding, installation, and testing. Costs incurred during the preliminary and post-implementation stages of the software application are expensed as incurred. Costs associated with significant enhancements to a software application are capitalized while costs incurred to maintain existing software applications are expensed as incurred. The capitalization of software development costs requires considerable judgment by management with respect to certain external factors, including, but not limited to, technological and economic feasibility, and estimated economic life. Amortization of capitalized software development costs begins when the product is ready for its intended use. Capitalized software development costs are amortized on a product-by-product basis using the straight-line method over the estimated economic life of the product or enhancement. The Company capitalized $29,416 , $34,877 and $39,500 of software development costs during 2015 , 2014 and 2013 , respectively. The Company's capitalized software development costs primarily relate to the further development of the SEI Wealth Platform SM (the Platform). The Company capitalized $24,515 , $34,877 and $39,500 of software development costs for significant enhancements to the Platform during 2015 , 2014 and 2013 , respectively. Included in the amount for 2013 is a one-time contractual payment of $8,812 to exercise a conversion option in lieu of periodic fee payments pertaining to a software license for functionality utilized by the Platform. The remaining amount of the Company's software development costs capitalized during 2015 is related to a project within the Investment Managers segment. As of December 31, 2015 , the net book value of the Platform was $285,621 . The Platform has an estimated useful life of 15 years and a weighted average remaining life of 6.5 years . Amortization expense for the Platform was $42,401 , $38,357 and $34,045 in 2015 , 2014 and 2013 , respectively, and is included in Amortization expense on the accompanying Consolidated Statements of Operations. The Company evaluates the carrying value of capitalized software development costs when circumstances indicate the carrying value may not be recoverable. The review of capitalized software development costs for impairment requires significant assumptions about operating strategies, underlying technologies utilized, and external market factors. External market factors include, but are not limited to, expected levels of competition, barriers to entry by potential competitors, stability in the target market and governmental regulations. During 2015, the Company determined that specific functionality within the Platform is no longer in use and wrote off $5,533 of previously capitalized software development costs reported under the Private Banks and Investment Advisors business segments. The expense associated with the write off is included in Facilities, supplies and other costs on the accompanying Consolidated Statement of Operations. The Company did not recognize any impairment charges related to its capitalized software development costs in 2014 or 2013 . Income Taxes The Company applies the asset and liability approach to account for income taxes whereby deferred tax assets and liabilities are recognized for the future tax consequences attributable to differences between the financial statement carrying amounts of existing assets and liabilities and their respective tax bases. Deferred tax assets and liabilities are measured using enacted tax rates expected to apply to taxable income in the years in which those temporary differences are expected to be recovered or settled. The Company has adopted the amendments contained in Accounting Standards Update No. 2015-17, Balance Sheet Classification of Deferred Taxes (ASU 2015-17) for the fiscal year ended December 31, 2015. ASU 2015-17 requires entities with a classified balance sheet to present all deferred tax assets and liabilities as noncurrent. The Company has elected retrospective application of ASU 2015-17 for all periods presented. As a result of the retrospective application of ASU 2015-17, the Company reclassified $1,414 from Current liabilities to Long-term liabilities on the accompanying Consolidated Balance Sheet as of December 31, 2014. Foreign Currency Translation The assets and liabilities and results of operations of the Company’s foreign subsidiaries are measured using the foreign subsidiary’s local currency as the functional currency. Assets and liabilities have been translated into U.S. dollars using the rates of exchange at the balance sheet dates. The results of operations have been translated into U.S. dollars at average exchange rates prevailing during the period. The resulting translation gain and loss adjustments are recorded as a separate component of comprehensive income. Transaction gains and losses from exchange rate fluctuations are included in the results of operations in the periods in which they occur. There were no material gains or losses from exchange rate fluctuations in 2015 , 2014 or 2013 . Earnings Per Common Share Basic earnings per common share is computed by dividing net income attributable to SEI Investments common shareholders by the weighted average number of common shares outstanding during the period. Diluted earnings per common share is computed by dividing net income attributable to SEI Investments common shareholders by the combination of the weighted average number of common shares outstanding and the dilutive potential common shares, such as stock options, outstanding during the period. The calculations of basic and diluted earnings per share for 2015 , 2014 and 2013 are: For the Year Ended December 31, 2015 Net income attributable to SEI (Numerator) Shares (Denominator) Per-Share Amount Basic earnings per common share $ 331,655 165,725,000 $ 2.00 Dilutive effect of stock options — 3,873,000 Diluted earnings per common share $ 331,655 169,598,000 $ 1.96 For the Year Ended December 31, 2014 Net income attributable to SEI (Numerator) Shares (Denominator) Per-Share Amount Basic earnings per common share $ 318,713 168,246,000 $ 1.89 Dilutive effect of stock options — 4,319,000 Diluted earnings per common share $ 318,713 172,565,000 $ 1.85 For the Year Ended December 31, 2013 Net income attributable to SEI (Numerator) Shares (Denominator) Per-Share Amount Basic earnings per common share $ 288,124 171,561,000 $ 1.68 Dilutive effect of stock options — 4,157,000 Diluted earnings per common share $ 288,124 175,718,000 $ 1.64 Employee stock options to purchase approximately 10,730,000 , 10,166,000 and 7,736,000 shares of common stock, with an average exercise price per share of $33.99 , $30.00 and $30.54 , were outstanding during 2015 , 2014 and 2013 , respectively, but not included in the computation of diluted earnings per common share because either the performance conditions have not been satisfied or would have been satisfied if the reporting date was the end of the contingency period or the option’s exercise price was greater than the average market price of the Company’s common stock and the effect on diluted earnings per common share would have been anti-dilutive (See Note 8). Stock-Based Compensation Stock-based compensation cost is measured at the grant date based on the fair value of the award and is recognized as expense over the requisite service period, which is the vesting period. The Company uses historical data to estimate pre-vesting forfeitures and record stock-based compensation expense only for those awards that are expected to vest. The amount of stock-based compensation expense that is recognized in a given period is dependent upon management’s estimate of when the vesting targets are expected to be achieved. If this estimate proves to be inaccurate, the remaining amount of stock-based compensation expense could be accelerated, spread out over a longer period, or reversed (See Note 8). New Accounting Pronouncements On May 28, 2014, the FASB issued Accounting Standards Update No. 2014-09, Revenue from Contracts with Customers (ASU 2014-09), requiring an entity to recognize the amount of revenue to which it expects to be entitled for the transfer of promised goods or services to customers. ASU 2014-09 also requires additional disclosure about the nature, amount, timing and uncertainty of revenue and cash flows arising from customer contracts, including significant judgments and changes in judgments and assets recognized from costs incurred to obtain or fulfill a contract. The updated standard permits the use of either the retrospective or cumulative effect transition method. ASU 2014-09 currently becomes effective for the Company during the first quarter 2018. The Company is currently evaluating the transition method that will be elected and the effect that the updated standard will have on its consolidated financial statements and related disclosures. In April 2015, the FASB issued Accounting Standards Update No. 2015-05, Customer's Accounting for Fees Paid in a Cloud Computing Arrangement (ASU 2015-05), which provides explicit guidance to help companies evaluate the accounting for fees paid by a customer in a cloud computing arrangement. The new guidance clarifies that if a cloud computing arrangement includes a software license, the customer should account for the license consistent with its accounting for other software licenses. If the arrangement does not include a software license, the customer should account for the arrangement as a service contract. ASU 2015-05 became effective for the Company during the first quarter 2016. The Company is currently evaluating the guidance in ASU 2015-05 but does not believe it will have a material impact on its consolidated financial statements. In May 2015, the FASB issued new guidance that eliminates the current requirement to categorize within the fair value hierarchy investments with fair values measured at NAV using the practical expedient in Accounting Standards Codification 820, Fair Value Measurement (ASC 820). The new guidance will require entities to disclose the fair values of such investments as a reconciling item between the amounts reported on the balance sheets and the amounts reported in the fair value hierarchy table. Entities will be required to continue to disclose information describing the nature and risks of the investments measured using the NAV practical expedient. The new disclosures become effective for the Company during the first quarter 2016. Early adoption is permitted. The new guidance only impacts footnote disclosures and will have no impact on the Company's financial statements. In January 2016, the FASB issued Accounting Standards Update No. 2016-01, Recognition and Measurement of Financial Assets and Financial Liabilities (ASU 2016-01) that will significantly change the income statement impact of equity investments held by an entity, and the recognition of changes in fair value of financial liabilities when the fair value option is elected. ASU 2016-01 becomes effective for the Company during the first quarter 2018. The Company is currently evaluating the effect that the updated standard will have on its consolidated financial statements and related disclosures. Reclassifications Certain prior year amounts have been reclassified to conform to current year presentation.

Investment In Unconsolidated Af

Investment In Unconsolidated Affiliates	12 Months Ended
	Dec. 31, 2015
Equity Method Investments and Joint Ventures [Abstract]
Investment In Unconsolidated Affiliates	Investment in Unconsolidated Affiliates LSV Asset Management The Company has an investment in the general partnership LSV Asset Management (LSV), a registered investment advisor that provides investment advisory services primarily to institutions, including pension plans and investment companies. LSV is currently an investment sub-advisor for a limited number of SEI-sponsored mutual funds. As of December 31, 2015 , the Company's total partnership interest in LSV was approximately 39.2 percent . The Company accounts for its interest in LSV using the equity method because of its less than 50 percent ownership. The Company’s interest in the net assets of LSV is reflected in Investment in unconsolidated affiliates on the accompanying Consolidated Balance Sheets and its interest in the earnings of LSV is reflected in Equity in earnings of unconsolidated affiliates on the accompanying Consolidated Statements of Operations. At December 31, 2015 , the Company’s total investment in LSV was $49,580 . The Company’s proportionate share in the earnings of LSV was $138,407 , $140,211 and $118,983 in 2015 , 2014 and 2013 , respectively. The Company receives partnership distributions from LSV on a quarterly basis. The Company received partnership distribution payments from LSV of $141,767 , $137,866 and $137,104 in 2015 , 2014 and 2013 , respectively. The Company received an additional partnership distribution payment from LSV during 2013 due to a change in the payment schedule. These tables contain condensed financial information of LSV: Condensed Statement of Operations Year ended December 31, 2015 2014 2013 Revenues $ 427,653 $ 422,064 $ 354,094 Net income $ 352,845 $ 356,824 $ 302,316 Condensed Balance Sheets December 31, 2015 2014 Current assets $ 127,225 $ 133,657 Non-current assets 2,375 2,269 Total assets $ 129,600 $ 135,926 Current liabilities $ 40,876 $ 35,208 Partners’ capital 88,724 100,718 Total liabilities and partners’ capital $ 129,600 $ 135,926 Guaranty Agreement with LSV Employee Group III In October 2012, a group of existing employees of LSV formed a new limited liability company called LSV Employee Group III and agreed to purchase a portion of the partnership interest of existing LSV employees for $77,700 , of which $69,930 was financed through syndicated term loan facilities contained in a credit agreement with The PrivateBank and Trust Company. LSV Employee Group III owns the purchased partnership interest. The Company provided an unsecured guaranty for $45,000 of the obligations of LSV Employee Group III to the lenders through a guaranty agreement. In addition, LSV agreed to provide an unsecured guaranty for the remaining $24,930 of the obligations of LSV Employee Group III to the lenders through a separate guaranty agreement. In September 2014, LSV Employee Group III made the final principal payment related to the term loan guaranteed by LSV. With regard to the loan facility guaranteed by the Company, the lenders will have the right to seek payment from the Company in the event of a default by LSV Employee Group III. The loan facility has a five year term and will be repaid from the quarterly distributions of LSV. No principal payments were made by LSV Employee Group III on the loan facility guaranteed by the Company until the separate loan facility guaranteed by LSV was fully repaid. The Company’s direct interest in LSV was unchanged as a result of this transaction. The Company has determined that LSV Employee Group III is a VIE; however, the Company is not considered the primary beneficiary because it does not have the power to direct the activities that most significantly impact the economic performance of LSV Employee Group III either directly or through any financial responsibility from the guaranty. As of January 29, 2016 , the remaining unpaid principal balances of the term loan guaranteed by the Company was $21,468 . The Company, in its capacity as guarantor, currently has no obligation of payment relating to the term loan of LSV Employee Group III and, furthermore, fully expects that LSV Employee Group III will meet all of their future obligations regarding the term loan. Investment in Gao Fu Limited The Company had an investment in Gao Fu, a wealth services firm based in Shanghai, China. The Company accounted for its interest in Gao Fu using the equity method. The Company's interest in the losses of Gao Fu is reflected in Equity in earnings of unconsolidated affiliates on the accompanying Consolidated Statements of Operations. The Company's interest in the net assets of Gao Fu as of December 31, 2014 is reflected in Investment in unconsolidated affiliates on the accompanying Consolidated Balance Sheet. The Company's proportionate share in the losses of Gao Fu was $1,350 , $1,159 and $907 in 2015 , 2014 and 2013 , respectively. The Company's investment in Gao Fu resulted from a series of cash purchases of common stock between 2011 and 2013 which, in total, amounted to $13,000 . In June and December of 2014, the Company funded an aggregate of $3,000 of convertible loans to Gao Fu. The June 2014 convertible loan agreement contains specific revenue and net income targets for Gao Fu to achieve by December 31, 2014. In December 2014, the Company conducted a review of the financial statements of Gao Fu and determined that the achievement of such performance targets as stipulated in the June 2014 convertible loan agreement was unlikely. As a result, the Company wrote down its investment in Gao Fu to its net realizable value based on its ownership percentage of the remaining net assets of the firm and recognized an impairment charge of $11,266 during the three months ended December 31, 2014. The impairment charge is reflected in Equity in earnings of unconsolidated affiliates on the accompanying Consolidated Statements of Operations. During the three months ended June 30, 2015, the Company wrote off the remaining carrying value of its investment and currently has no remaining interest in Gao Fu.

Variable Interest Entities - In

Variable Interest Entities - Investment Products	12 Months Ended
	Dec. 31, 2015
Variable Interest Entities Disclosure [Abstract]
Variable Interest Entities - Investment Products	Variable Interest Entities – Investment Products The Company has created numerous investment products for its clients in various types of legal entity structures. The Company serves as the Manager, Administrator and Distributor for these investment products and may also serve as the Trustee for some of the investment products. Clients are the equity investors and participate in proportion to their ownership percentage in the net income or loss and net capital gains or losses of the products, and, on liquidation, will participate in proportion to their ownership percentage in the remaining net assets of the products after satisfaction of outstanding liabilities. An entity that lacks decision-making rights is a VIE. In some circumstances, the Manager or Trustee of the Company’s investment products controls the governing decisions about the investment activities with respect to the ongoing operations of the investment products without the equity investors possessing the right to remove the Manager or Trustee. Therefore, the equity investors, as a group, do not have the ability to make decisions that have an impact on the ongoing activities of such investment products. Consequently, some of the Company’s investment products have been determined to be VIEs at inception. The VIEs are marketed with investment objectives to generate positive returns; however, the nature of such investments exposes the investors to the risk that the value of the VIEs may increase or decrease. The purpose and design of the VIEs are to achieve the investment objective by implementing strategies which are designed to minimize potential losses; however, there is no assurance given that these strategies will be successful. The Company does not have a significant equity investment in any of the VIEs and does not have an obligation to enter into any guarantee agreements with the VIEs. The fees paid to the decision maker of a VIE are considered to be variable interests if the decision maker is not subject to substantive kick-out rights. The fees paid to the Company represent a variable interest when the decision maker is not subject to substantive kick-out rights. The Company is not the primary beneficiary of the VIEs because the expected fees and the expected return on any investment into the VIE by the Company relative to the expected returns of the VIE to the equity investor holders does not approach 50 percent of the expected losses or gains of the VIEs. Therefore, the Company is not required to consolidate any investment products that are VIEs into its financial statements. The Company’s variable interest in the VIEs, which consists of management fees and in some situations, seed capital, would not be considered a significant variable interest. The risks to the Company associated with its involvement with any of the investment products that are VIEs are limited to the cash flows received from the revenue generated for asset management, administration and distribution services and any equity investments in the VIEs. Both of these items are immaterial. The Company has no other financial obligation to the VIEs. Amounts relating to fees due from the VIEs included in Receivables and amounts relating to equity investments in the VIEs included in Investments Available for Sale on the Company’s Consolidated Balance Sheets are immaterial to the total current assets of the Company.

Composition of Certain Financia

Composition of Certain Financial Statement Captions	12 Months Ended
	Dec. 31, 2015
Items Included in Consolidated Statement of Financial Condition [Abstract]
Composition of Certain Financial Statement Captions	Composition of Certain Financial Statement Captions Receivables Receivables on the accompanying Consolidated Balance Sheets consist of: 2015 2014 Trade receivables $ 47,179 $ 48,394 Fees earned, not billed 154,919 139,038 Other receivables 21,574 7,771 223,672 195,203 Less: Allowance for doubtful accounts (649 ) (784 ) Receivables, net $ 223,023 $ 194,419 Fees earned, not billed represents receivables earned but unbilled and results from timing differences between services provided and contractual billing schedules. These billing schedules generally provide for fees to be billed on a quarterly basis. Property and Equipment Property and Equipment on the accompanying Consolidated Balance Sheets consists of: 2015 2014 Buildings $ 151,604 $ 149,890 Equipment 86,941 78,266 Land 10,003 9,997 Purchased software 122,433 104,964 Furniture and fixtures 16,143 16,944 Leasehold improvements 15,393 5,675 Construction in progress 961 1,094 403,478 366,830 Less: Accumulated depreciation (259,501 ) (241,295 ) Property and Equipment, net $ 143,977 $ 125,535 Depreciation expense related to property and equipment for 2015 , 2014 and 2013 was $24,044 , $22,448 and $22,497 , respectively. During 2015, the Company determined that certain purchased software related to the SEI Wealth Platform is no longer in use and wrote off $522 of the software classified as Purchased software reported under the Private Banks business segment. The expense associated with the write off of the software is included in Facilities, supplies and other costs on the accompanying Consolidated Statement of Operations. Other Assets Other assets consist of long-term prepaid expenses, deposits, other investments at cost and various other assets. Amortization expense for certain other assets for 2015 was $229 and for 2014 and 2013 was $227 . Accrued Liabilities Accrued Liabilities on the accompanying Consolidated Balance Sheets consist of: 2015 2014 Accrued employee compensation $ 74,687 $ 73,269 Accrued consulting, outsourcing and professional fees 21,575 18,915 Accrued sub-advisory, distribution and other asset management fees 32,674 31,913 Accrued dividend payable 42,625 40,178 Other accrued liabilities 46,026 43,154 Accrued liabilities $ 217,587 $ 207,429

Fair Value Measurements

Fair Value Measurements	12 Months Ended
	Dec. 31, 2015
Fair Value Disclosures [Abstract]
Fair Value Measurements	Fair Value Measurements The fair value of the Company’s financial assets and liabilities is determined in accordance with the fair value hierarchy. The fair value of the Company’s Level 1 financial assets consist mainly of investments in open-ended mutual funds that are quoted daily. The fair value of the Company’s Level 2 financial assets consist of GNMA mortgage-backed securities held by SPTC, FHLB and other U.S. government agency short-term notes and investment grade commercial paper held by SIDCO, and investment funds sponsored by LSV. The financial assets held by SIDCO were purchased as part of a cash management program requiring only short term, top-tier investment grade government and corporate securities. The financial assets held by SPTC are debt securities issued by GNMA and are backed by the full faith and credit of the U.S. government. These securities were purchased for the sole purpose of satisfying applicable regulatory requirements as a limited-purpose federal thrift subsidiary and have maturity dates which range from 2020 to 2041 . The valuation of the Company's Level 2 financial assets held by SIDCO and SPTC are based upon securities pricing policies and procedures utilized by third-party pricing vendors. As a practical expedient, the Company relies on the net asset values (NAVs) of the investment funds sponsored by LSV as the fair value. The NAVs of the funds are calculated by the funds' independent custodian and are derived from the fair values of the underlying investments as of the reporting date. The Company had no Level 3 financial assets or liabilities at December 31, 2015 or 2014 . Valuation of GNMA, Other U.S. Government Agency Securities and Investment Grade Commercial Paper All of the Company's investments in GNMA, FHLB and other U.S. government agency securities and investment grade commercial paper are held in accounts at well-established financial institutions. The Company's selection of a financial institution for the purpose of purchasing securities considered a number of various factors including, but not limited to, securities pricing policies and procedures utilized by that financial institution. Each financial institution utilizes the services of independent pricing vendors. These vendors utilize evaluated and industry accepted pricing models that vary by asset class and incorporate available trade, bid and other market information to determine the fair value of the securities. The market inputs, listed in approximate order of priority, include: benchmark yields, reported trade, broker/dealer quotes, issuer spreads, two-sided markets, benchmark securities, bids, offers and reference data. The Company evaluated the information regarding the pricing methodologies and processes utilized by the independent pricing vendors during the selection process of the financial institution. The Company analyzed this information for the purpose of classifying the securities into the appropriate level within the fair value hierarchy and to ensure that each pricing model for each asset class provided the fair value of those specific securities in accordance with generally accepted accounting principles. The Company continually monitors the price of each security for any unanticipated deviations from the previously quoted price or deviations from anticipated changes in a security's price based upon an assessment of market factors and other factors relative to a specific issue expected to affect a security's price. In the event of any unanticipated deviations in a security's price, additional analysis is conducted which may include the comparison of the security's price as determined by other independent pricing vendors. The Company's investments in GNMA, FHLB and other U.S. government agency securities and investment grade commercial paper have been recorded at the prices provided by the independent pricing vendor without adjustment. The fair value of certain financial assets and liabilities of the Company was determined using the following inputs: December 31, 2015 Fair Value Measurements at Reporting Date Using Total Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Assets Equity available-for-sale securities $ 10,657 $ 10,657 $ — Fixed-income available-for-sale securities 70,637 — 70,637 Fixed income securities owned 21,235 — 21,235 Investment funds sponsored by LSV 4,039 — 4,039 $ 106,568 $ 10,657 $ 95,911 December 31, 2014 Fair Value Measurements at Reporting Date Using Total Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Assets Equity available-for-sale securities $ 11,588 $ 11,588 $ — Fixed-income available-for-sale securities 66,021 — 66,021 Fixed income securities owned 21,175 — 21,175 Investment funds sponsored by LSV 4,523 — 4,523 $ 103,307 $ 11,588 $ 91,719

Marketable Securities

Marketable Securities	12 Months Ended
	Dec. 31, 2015
Marketable Securities [Abstract]
Marketable Securities	Marketable Securities Investments Available For Sale Investments available for sale classified as non-current assets consist of: At December 31, 2015 Cost Gross Unrealized Gains Gross Unrealized (Losses) Fair Value SEI-sponsored mutual funds $ 8,474 $ — $ (742 ) $ 7,732 Equities and other mutual funds 2,857 68 — 2,925 Debt securities 70,308 329 — 70,637 $ 81,639 $ 397 $ (742 ) $ 81,294 At December 31, 2014 Cost Gross Unrealized Gains Gross Unrealized (Losses) Fair Value SEI-sponsored mutual funds $ 8,685 $ 134 $ (95 ) $ 8,724 Equities and other mutual funds 2,695 169 — 2,864 Debt securities 64,333 1,688 — 66,021 $ 75,713 $ 1,991 $ (95 ) $ 77,609 Net unrealized holding losses at December 31, 2015 were $302 (net of income tax benefit of $43 ) and net unrealized holding gains as December 31, 2014 were $1,193 (net of income tax expense of $703 ). These net unrealized gains and losses are reported as a separate component of Accumulated other comprehensive loss on the accompanying Consolidated Balance Sheets. There were gross realized gains of $489 and gross realized losses of $729 from available-for-sale securities during 2015 . In 2014 , there were gross realized gains of $1,401 and gross realized losses of $448 from available-for-sale securities. There were gross realized gains of $1,236 and gross realized losses of $772 from available-for-sale securities during 2013 . Gains and losses from available-for-sale securities, including amounts reclassified from accumulated comprehensive income (loss), are reflected in Net (loss) gain from investments on the accompanying Consolidated Statements of Operations. Investments in Affiliated Funds The Company has an investment related to the startup of investment funds sponsored by LSV. The Company records this investment on the accompanying Consolidated Balance Sheets at fair value. Unrealized gains and losses from the change in fair value of these funds are recognized in Net (loss) gain from investments on the accompanying Consolidated Statements of Operations. The investment primarily consists of U.S. dollar denominated funds that invests in equity securities of Canadian, Australian and Japanese companies. The underlying securities held by the funds are translated into U.S. dollars within the funds. The funds had a fair value of $4,039 and $4,523 at December 31, 2015 and 2014 , respectively. The Company recognized losses of $389 and $326 and gains of $143 from the change in fair value of the funds during 2015 , 2014 and 2013 , respectively. Securities Owned The Company’s broker-dealer subsidiary, SIDCO, has investments in U.S. government agency and commercial paper securities with maturity dates less than one year. These investments are reflected as Securities owned on the accompanying Consolidated Balance Sheets. Due to specialized accounting practices applicable to investments by broker-dealers, the securities are reported at fair value and changes in fair value are recorded in current period earnings. The securities had a fair value of $21,235 and $21,175 at December 31, 2015 and 2014 , respectively. There were no material net gains or losses from the change in fair value of the securities during 2015 , 2014 and 2013 .

Line Of Credit

Line Of Credit	12 Months Ended
	Dec. 31, 2015
Line of Credit Facility [Abstract]
Line Of Credit	Line of Credit On February 2, 2012, the Company entered into a five -year $300,000 Credit Agreement (the Credit Facility) with Wells Fargo Bank, National Association, and a syndicate of other lenders. The Credit Facility is scheduled to expire in February 2017 , at which time any aggregate principal amount of loans outstanding becomes payable in full. Any borrowings made under the Credit Facility will accrue interest at 1.25 percent above the London Interbank Offer Rate (LIBOR). There is also a commitment fee equal to 0.15 percent per annum on the daily unused portion of the facility. The aggregate amount of the Credit Facility may be increased by an additional $100,000 under certain conditions set forth in the agreement. The Credit Facility contains covenants that restrict the ability of the Company to engage in mergers, consolidations, asset sales, investments, transactions with affiliates, or to incur liens, as defined in the agreement. In the event of a default under the Credit Facility, the Company would also be restricted from paying dividends on, or repurchasing, its common stock without the approval of the lenders. None of the covenants of the Credit Facility negatively affect the Company’s liquidity or capital resources. Both the interest rate and commitment fee prices may increase if the Company’s leverage ratio reaches certain levels. Upon the occurrence of certain financial or economic events, significant corporate events, or certain other events of default constituting an event of default under the Credit Facility, all loans outstanding may be declared immediately due and payable and all commitments under the Credit Facility may be terminated. The Company had no borrowings through the Credit Facility at December 31, 2015 or 2014 . The Company was in compliance with all covenants of the Credit Facility during 2015 . The Company incurred $483 during 2015 and $458 during 2014 and 2013 in commitment fees related to the Credit Facility which are reflected in Interest expense on the accompanying Consolidated Statements of Operations.

Shareholders' Equity

Shareholders' Equity	12 Months Ended
	Dec. 31, 2015
Stockholders' Equity Note [Abstract]
Shareholders' Equity	Shareholders’ Equity Stock-Based Compensation The Company's active equity compensation plan, the 2014 Omnibus Equity Compensation Plan (the 2014 Plan), is the successor plan to the 2007 Equity Compensation Plan (the 2007 Plan) which was merged with and into the 2014 Plan in May 2014. The 2014 Plan provides for the grant of stock options, stock units, stock awards, stock appreciation rights, dividend equivalents and other stock-based awards. Outstanding grants under the 2007 Plan will continue according to the terms in effect before the plan merger, but the outstanding shares will be issued or transferred under the 2014 Plan. Permitted grantees under the 2014 Plan include employees, non-employee directors and consultants who perform services for the Company. The plan is administered by the Compensation Committee of the Board of Directors of the Company. The Company has only non-qualified stock options outstanding under the 2014 Plan. All outstanding stock options have performance-based vesting provisions that tie the vesting of stock options to the Company’s financial performance. The Company’s stock options vest at a rate of 50 percent when a specified diluted earnings per share target is achieved, and the remaining 50 percent when a second, higher-specified diluted earnings per share target is achieved. Options do not vest due to the passage of time but solely as a result of achievement of the financial vesting targets. Earnings per share targets are calculated exclusive of stock-based compensation expense, net of tax. The diluted earnings per share targets are established at time of grant and are measured annually on December 31. The amount of stock-based compensation expense is based upon management’s estimate of when the earnings per share targets may be achieved. If management’s estimate of the attainment of the earnings per share targets proves to be inaccurate, the remaining amount of stock-based compensation expense could be accelerated, spread out over a longer period, or reversed. This may cause volatility in the recognition of stock-based compensation expense in future periods and could materially affect the Company’s net income and net income per share. The Company uses the Black-Scholes option pricing model to determine the fair value of stock options. The determination of the fair value of stock options on the date of grant using an option-pricing model is affected by the price of the Company’s common stock as well as other variables. These variables include expected stock price volatility over the term of the awards, actual and projected employee stock exercise behaviors, risk-free interest rate and expected dividends. The Company primarily uses historical data to estimate the variables used in the option-pricing model except expected volatility. The Company uses a combination of historical and implied volatility. The Company estimates forfeitures at the time of grant and may revise those estimates in subsequent periods if actual forfeitures differ from those estimates. The Company uses historical data to estimate pre-vesting forfeitures and record stock-based compensation expense only for those awards that are expected to vest. Stock-based compensation is amortized over the requisite service periods of the awards, which are generally the vesting periods. The weighted average fair value of the Company’s stock options granted during 2015 , 2014 and 2013 were $12.16 , $10.88 and $10.45 , respectively, using the following assumptions: 2015 2014 2013 Expected term (in years) 5.58 6.79 6.92 Expected volatility 23.86 % 26.98 % 31.46 % Expected dividend yield 1.00 % 1.15 % 1.21 % Risk-free interest rate 1.90 % 2.04 % 2.12 % The Company recognized stock-based compensation expense in its Consolidated Financial Statements in 2015 , 2014 and 2013 as follows: 2015 2014 2013 Stock-based compensation expense $ 17,312 $ 13,463 $ 37,865 Less: Deferred tax benefit (6,107 ) (4,704 ) (13,823 ) Stock-based compensation expense, net of tax $ 11,205 $ 8,759 $ 24,042 During 2015 and 2013, the Company revised its estimate of when some vesting targets were expected to be achieved. These changes in management’s estimates resulted in an increase of $1,360 and $19,637 in stock-based compensation expense in 2015 and 2013, respectively. As of December 31, 2015 , there was approximately $51,693 of unrecognized compensation cost, adjusted for estimated forfeitures, related to unvested employee stock options that the Company expects will vest and be expensed through 2020 with a weighted average period of 2.1 years . This table presents certain information relating to the Company’s stock option plans for 2015 , 2014 and 2013 : Number of Shares Weighted Avg. Price Balance as of December 31, 2012 25,610,000 $ 20.81 Granted 2,281,000 33.67 Exercised (3,733,000 ) 17.26 Expired or canceled (521,000 ) 22.25 Balance as of December 31, 2013 23,637,000 $ 22.58 Granted 2,293,000 40.05 Exercised (5,261,000 ) 19.52 Expired or canceled (208,000 ) 28.83 Balance as of December 31, 2014 20,461,000 $ 25.26 Granted 2,005,000 53.34 Exercised (2,927,000 ) 21.44 Expired or canceled (302,000 ) 28.97 Balance as of December 31, 2015 19,237,000 $ 28.71 Exercisable as of December 31, 2015 8,508,000 $ 22.04 Available for future grant as of December 31, 2015 26,890,000 As of December 31, 2014 and 2013 , there were 10,295,000 and 14,601,000 shares exercisable, respectively. The expiration dates for options outstanding at December 31, 2015 range from December 8, 2016 to December 8, 2025 with a weighted average remaining contractual life of 5.7 years . Upon exercise of stock options, the Company will issue new shares of its common shares. The Company does not hold any shares in treasury. The total intrinsic value of options exercised during 2015 and 2014 was $76,676 and $83,196 , respectively. The total options exercisable as of December 31, 2015 had an intrinsic value of $258,270 . The total options outstanding as of December 31, 2015 had an intrinsic value of $455,766 . The total intrinsic value for options outstanding and options exercisable is calculated as the difference between the market value of the Company’s common stock as of December 31, 2015 and the exercise price of the shares. The market value of the Company’s common stock as of December 31, 2015 was $52.40 as reported by the Nasdaq Stock Market, LLC. This table summarizes information relating to all options outstanding and exercisable at December 31, 2015 : Options Outstanding at December 31, 2015 Options Exercisable at December 31, 2015 Range of Exercise Prices (Per Share) Number of Shares Weighted Average Exercise Price (Per Share) Weighted Average Remaining Contractual Life (Years) Number of Shares Weighted Average Exercise Price (Per Share) Weighted Average Remaining Contractual Life (Years) $ 14.62 - 16.48 3,513,000 $ 15.23 4.58 2,396,000 $ 14.97 3.92 17.65 - 21.05 2,100,000 17.67 4.03 2,085,000 17.65 4.00 22.45 - 23.86 4,028,000 23.20 5.93 1,678,000 23.20 5.93 27.03 - 36.16 5,515,000 32.08 4.23 2,349,000 32.32 4.68 40.64 - 53.34 4,081,000 46.88 9.49 — — — 19,237,000 8,508,000 Employee Stock Purchase Plan The Company has an employee stock purchase plan that provides for offerings of common stock to eligible employees at a price equal to 85 percent of the fair market value of the stock at the end of the stock purchase period, as defined. The Company has reserved 15,600,000 shares for issuance under this plan. At December 31, 2015 , 11,801,000 cumulative shares have been issued. There were no material costs incurred by the Company related to the employee stock purchase plan in 2015 , 2014 and 2013 . Common Stock Buyback The Board of Directors, under multiple authorizations, has authorized the purchase of the Company’s common stock on the open market or through private transactions. As of December 31, 2015 , the Company had approximately $113,126 of authorization remaining for the purchase of common stock. The following table provides the total number of shares repurchased and the related total costs in 2015 , 2014 and 2013 : Year Total Number of Shares Repurchased Total Cost 2015 5,951,000 $ 289,587 2014 7,888,000 278,357 2013 6,789,000 209,942 The Company immediately retires its common stock when purchased. Upon retirement, the Company reduces Capital in excess of par value for the average capital per share outstanding and the remainder is charged against Retained earnings. If the Company reduces its Retained earnings to zero, any subsequent purchases of common stock will be charged entirely to Capital in excess of par value. Rights Agreement In December 2008, the Company’s Board of Directors declared a dividend distribution pursuant to a Rights Agreement (the Rights Agreement) which became effective on January 6, 2009. The purpose of the Rights Agreement is to deter coercive or unfair takeover tactics and to prevent a person or group (an Acquiring Person) from acquiring control of the Company without offering a fair price to all shareholders. Under the Rights Agreement, all common shareholders receive one Right for each common share outstanding. Each Right entitles the registered holder to purchase from the Company a unit consisting of one twenty-thousandths of a share of Series A Junior Participating Preferred Shares, $0.05 par value per share, or a combination of securities and assets of equivalent value, at a purchase price of $150.00 per unit, subject to adjustment. The Rights will become exercisable and trade separately from the common stock ten days days following a public announcement that an Acquiring Person has beneficial ownership of more than 20 percent of the outstanding common stock of the Company or the commencement of a tender or exchange offer that would result in an Acquiring Person owning 20 percent or more of the outstanding common stock of the Company. Upon exercise, holders, other than an Acquiring Person, will have the right to purchase the common stock of the Company equal to twice the value of the exercise price of the Rights. In lieu of requiring payment of the purchase price upon exercise of the Rights following certain events, the Company may permit the holders simply to surrender the Rights, in which event they will be entitled to receive common shares and other property, as the case may be, with a value of 50 percent of what could be purchased by payment of the full purchase price. The Rights, which do not have voting rights, will expire on January 6, 2019, and may be redeemed by the Company any time until ten days following the announcement of an Acquiring Person at a price of $0.01 per Right. Cash Dividends On May 27, 2015 , the Board of Directors declared a cash dividend of $0.24 per share on the Company’s common stock, which was paid on June 24, 2015 , to shareholders of record on June 16, 2015 . On December 8, 2015 , the Board of Directors declared a cash dividend of $0.26 per share on the Company’s common stock, which was paid on January 5, 2016 , to shareholders of record on December 21, 2015 . The cash dividends declared in 2015 , 2014 and 2013 were $82,478 , $77,158 and $71,665 , respectively. The Board of Directors has indicated its intention to declare future cash dividends on a semiannual basis.

Accumulated Other Comprehensive

Accumulated Other Comprehensive Income (Loss)	12 Months Ended
	Dec. 31, 2015
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]
Accumulated Other Comprehensive Income (Loss)	Accumulated Other Comprehensive Income (Loss) Other comprehensive income (loss) consists of net income and other gains and losses affecting shareholders’ equity that are excluded from net income. For the Company, other comprehensive income (loss) includes unrealized gains and losses on available for sale securities and foreign currency translation adjustments. The Company presents other comprehensive income (loss) in its Consolidated Statements of Comprehensive Income. Components of Accumulated other comprehensive income (loss), net of tax, attributable to SEI Investments shareholders consisted of: Foreign Currency Translation Adjustments Unrealized Holding Gains (Losses) on Investments Accumulated Other Comprehensive Income (Loss) Balance, January 1, 2013 $ 3,410 $ 2,829 $ 6,239 Other comprehensive loss before reclassifications (3,309 ) (1,149 ) (4,458 ) Amounts reclassified from accumulated other comprehensive income — (294 ) (294 ) Net current-period other comprehensive loss (3,309 ) (1,443 ) (4,752 ) Balance, December 31, 2013 $ 101 $ 1,386 $ 1,487 Other comprehensive loss before reclassifications (10,189 ) 441 (9,748 ) Amounts reclassified from accumulated other comprehensive income — (634 ) (634 ) Net current-period other comprehensive loss (10,189 ) (193 ) (10,382 ) Balance, December 31, 2014 $ (10,088 ) $ 1,193 $ (8,895 ) Other comprehensive loss before reclassifications (14,900 ) (1,659 ) (16,559 ) Amounts reclassified from accumulated other comprehensive loss — 164 164 Net current-period other comprehensive loss (14,900 ) (1,495 ) (16,395 ) Balance, December 31, 2015 $ (24,988 ) $ (302 ) $ (25,290 )

Employee Benefit Plan

Employee Benefit Plan	12 Months Ended
	Dec. 31, 2015
Compensation and Retirement Disclosure [Abstract]
Employee Benefit Plan	Employee Benefit Plan The Company has a tax-qualified defined contribution plan (the Plan). The Plan provides retirement benefits, including provisions for early retirement and disability benefits, as well as a tax-deferred savings feature. After satisfying certain requirements, participants are vested in employer contributions at the time the contributions are made. All Company contributions are discretionary and are made from available profits. The Company contributed $9,162 , $6,157 and $5,664 to the Plan in 2015 , 2014 and 2013 , respectively.

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2015
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Commitments and Contingencies The Company leases certain of its facilities, data processing equipment, and software under non-cancelable operating leases, some which contain escalation clauses for increased taxes and operating expenses. The Company has entered into maintenance agreements primarily for its data processing equipment. Rent expense was $25,074 , $23,011 and $21,519 in 2015 , 2014 and 2013 , respectively. The aggregate noncancellable minimum commitments at December 31, 2015 are: 2016 $ 4,397 2017 5,578 2018 8,436 2019 7,354 2020 and thereafter 37,414 $ 63,179 In the ordinary course of business, the Company from time to time enters into contracts containing indemnification obligations of the Company. These obligations may require the Company to make payments to another party upon the occurrence of certain events including the failure by the Company to meet its performance obligations under the contract. These contractual indemnification provisions are often standard contractual terms of the nature customarily found in the type of contracts entered into by the Company. In many cases, there are no stated or notional amounts included in the indemnification provisions. There are no amounts reflected on the Consolidated Balance Sheets as of December 31, 2015 and 2014 related to these indemnifications. In the normal course of business, the Company is party to various claims and legal proceedings. SEI has been named in six lawsuits filed in Louisiana. Five lawsuits were filed in the 19th Judicial District Court for the Parish of East Baton Rouge. One of the five actions purports to set forth claims on behalf of a class and also names SPTC as a defendant. Two of the other actions also name SPTC as a defendant. All five actions name various defendants in addition to SEI, and, in all five actions, the plaintiffs purport to bring a cause of action against SEI and/or SPTC under the Louisiana Securities Act. Two of the five actions include claims for violations of the Louisiana Racketeering Act and possibly conspiracy. In addition, another group of plaintiffs filed a lawsuit in the 23rd Judicial District Court for the Parish of Ascension against SEI and SPTC and other defendants, asserting claims of negligence, breach of contract, breach of fiduciary duty, violations of the uniform fiduciaries law, negligent misrepresentation, detrimental reliance, violations of the Louisiana Securities Act and Louisiana Racketeering Act, and conspiracy. The underlying allegations in all actions relate to the purported role of SPTC in providing back-office services to Stanford Trust Company. The petitions allege that SEI and SPTC aided and abetted or otherwise participated in the sale of “certificates of deposit” issued by Stanford International Bank. The case filed in Ascension Parish was removed to federal court and transferred by the Judicial Panel on Multidistrict Litigation to the United States District Court for the Northern District of Texas. The schedule for responding to that petition has not yet been established. The plaintiffs in two of the cases filed in East Baton Rouge have granted SEI and SPTC an indefinite extension to respond to the petitions. In a third East Baton Rouge action, brought as a class action, SEI and SPTC filed exceptions, which the Court granted in part, dismissing the claims under the Louisiana Unfair Trade Practices Act. Plaintiffs then filed a motion for class certification, and SEI and SPTC also filed a motion for summary judgment. The Court deferred the motion for summary judgment, stating that the motion would not be set for hearing until after the hearing on class certification. After the Court held a hearing on class certification, it certified a class composed of persons who purchased or renewed any Stanford International Bank certificates of deposit (SIB CDs) in Louisiana between January 1, 2007 and February 13, 2009 or any person for whom the Stanford Trust Company purchased SIB CDs in Louisiana between January 1, 2007 and February 13, 2009. SEI and SPTC filed motions for appeal from the class certification judgments. On February 1, 2013, plaintiffs filed a motion for Leave to File a First Amended and Restated Class Action Petition in which they asked the Court to allow them to amend the petition and add claims against certain of SEI's insurance carriers. On February 5, 2013, the Court granted two of the motions for appeal and the motion for leave to amend. On February 28, 2013, SEI responded to the First Amended and Restated Class Action Petition by seeking dismissal of the action. On March 11, 2013, the newly-added insurance carrier defendants removed the case to the Middle District of Louisiana. SEI notified the Judicial Panel on Multidistrict Litigation (MDL) of this case as a potential tag-along action. Plaintiffs filed a motion to remand the action to state court. On March 25, 2013, SEI filed a motion requesting that the federal court decline to adopt the state court's order regarding class certification, which the court dismissed without prejudice to renew upon a determination of the jurisdictional issue. On August 7, 2013, the MDL Panel transferred the matter against SEI to the Northern District of Texas. On October 1, 2014, SEI filed a renewed motion to dismiss in the Northern District of Texas, and on October 6, 2014, the District Court denied plaintiffs’ motion to remand. On June 17, 2015, the Court denied the motion to dismiss, and on June 24, 2015 set a briefing schedule for SEI and SPTC’s motion challenging the Louisiana court’s decision to certify a class, which motion was filed on July 15, 2015. SEI and SPTC filed their answer on July 1, 2015, and this case is now pending in the Northern District of Texas. On July 15, 2015, SEI and SPTC also filed motions seeking reconsideration of the District Court’s June 17 denial of the motion to dismiss or, in the alternative, seeking leave to pursue an interlocutory appeal of certain elements of the denial, as well as a motion seeking partial judgment on the pleadings pursuant to Federal Rule of Civil Procedure 12(c) with respect to claims brought under Section 712(D) of the Louisiana Securities Law. On September 22, 2015, the District Court granted SEI and SPTC’s motion for reconsideration of the June 17 denial of the motion to dismiss and dismissed plaintiffs’ claims under Section 714(A) of the Louisiana Securities Law, but declined to dismiss, or certify for interlocutory appeal, plaintiffs’ claims under Section 714(B) of the Louisiana Securities Law. On November 4, 2015, the District Court granted SEI and SPTC's motion to dismiss plaintiff's claims under Section 712(D) of the Louisiana Securities Law. Consequently, the only claims of plaintiffs still pending before the District Court are plaintiff's claims for secondary liability against SEI and SPTC under Section 714(B) of the Louisiana Securities Law. In the two other cases filed in East Baton Rouge, brought by the same counsel who filed the class action, virtually all of the litigation to date has involved motions practice and appellate litigation regarding the existence of federal subjection matter jurisdiction under the federal Securities Litigation Uniform Standards Act (SLUSA). After the matter was removed to the United States District Court for the Northern District of Texas, that court dismissed the action under SLUSA. The Court of Appeals for the Fifth Circuit reversed that order, and the Supreme Court of the United States affirmed the Court of Appeals judgment on February 26, 2014. The matter was remanded to state court and no material activity has taken place since that date. While the outcome of this litigation is uncertain given its early phase, SEI and SPTC believe that they have valid defenses to plaintiffs' claims and intend to defend the lawsuits vigorously. Because of the uncertainty of the make-up of the classes, the specific theories of liability that may survive a motion for summary judgment or other dispositive motion, the lack of discovery regarding damages, causation, mitigation and other aspects that may ultimately bear upon loss, the Company is not reasonably able to provide an estimate of loss, if any, with respect to the foregoing lawsuits. A lawsuit entitled Steven Curd and Rebel Curd v. SEI Investments Management Corporation was filed against SIMC in the United States District Court for the Eastern District of Pennsylvania on December 11, 2013. On August 28, 2014, the Court granted SIMC’s motion to dismiss the initial complaint in the lawsuit, but also granted plaintiffs leave to amend the complaint. On October 2, 2014, plaintiffs filed an amended complaint. In the amended complaint, SEI Investments Global Funds Services (SGFS) was added as a defendant. The plaintiffs bring the case as a shareholder derivative action against SIMC and SGFS on behalf of certain SEI funds. The claims are based on Section 36(b) of the Investment Company Act of 1940, as amended, which allows shareholders of a mutual fund to sue the investment adviser of the fund or its affiliates for an alleged breach of fiduciary duty with respect to compensation received by the adviser or its affiliates. The plaintiffs have brought the suit against SIMC and SGFS with respect to five specific SEI Funds: the High Yield Bond, Tax-Managed Large Cap, and Tax-Managed Small/Mid Cap Funds, each of which is a series of the SEI Institutional Managed Trust, the Intermediate Term Municipal Fund, which is a series of the SEI Tax Exempt Trust, and the International Equity Fund, which is a series of the SEI Institutional International Trust (the SEI Funds). The plaintiffs seek: (1) damages for the SEI Funds in the amount of the alleged “excessive” fees earned by SIMC and SGFS beginning from the one year period prior to the filing of the lawsuit, plus interest, costs, and fees; (2) orders declaring that SIMC and SGFS allegedly violated Section 36(b) and enjoining SIMC and SGFS from further alleged violations; and (3) rescission of SIMC’s and SGFS’s contracts with the funds, and restitution of all allegedly excessive fees paid beginning from the one year period prior to the filing of the lawsuit, plus interest, costs, and fees. On November 24, 2014, SIMC and SGFS filed a motion to dismiss the amended complaint. On July 13, 2015, the Court denied the motion to dismiss with respect to SIMC, and granted the motion to dismiss with respect to SGFS. On September 18, 2015, plaintiffs filed a second amended complaint reinstating SGFS as a defendant in the case. The parties are currently engaged in discovery, which is expected to be completed in the fall of 2017. While the outcome of this litigation is uncertain given its early phase, SIMC and SGFS believe that they have valid defenses to plaintiffs' claims and intend to defend the lawsuit vigorously, and SIMC and SGFS are not reasonably able to provide an estimate of the ultimate loss, if any, with respect to this lawsuit. On November 26, 2014, a Writ of Summons was issued to two of our subsidiaries, SEI Investments - Global Fund Services Limited (GFSL) and SEI Investments - Trustee & Custodial Services (Ireland) Limited (T&C), to appear before the Court of First Instance Antwerp, Belgium. The plaintiffs in this case allege that through their initial investments in collective investment funds domiciled in Netherlands and subsequent transfer of claim rights to a Belgium domiciled partnership, they are beneficial owners of a portfolio of life settlement policies (the Portfolio) which lapsed due to a failure to make premium payments. The plaintiffs seek to recover jointly and severally from nine defendants including GFSL and T&C, damages of approximately $84 million. GFSL and T&C’s involvement in the litigation appears to arise out of their historical provision of administration and custody services, respectively, to the Strategic Life Settlement Fund PLC, who, together with its managers, appear to be the principal defendants in this claim. On December 4, 2015, the Belgium Court dismissed plaintiff's claims for a lack of jurisdiction. On December 22, 2015, the plaintiffs appealed the dismissal. While the outcome of this action is uncertain given its early phase and the lack of specific theories of liability asserted against GFSL and T&C, each of GFSL and T&C believe that they have valid defenses to plaintiffs’ claims and intend to defend the lawsuit vigorously, and GFSL and T&C are not reasonably able to provide an estimate of the ultimate loss, if any, with respect to this lawsuit.

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes The federal and state and foreign income tax provision is summarized as follows: Year Ended December 31, 2015 2014 2013 Current Federal $ 159,774 $ 155,273 $ 153,856 State 7,756 8,744 11,542 Foreign 5,224 5,254 4,727 172,754 169,271 170,125 Deferred, including current deferred Federal (5,343 ) 1,667 (2,214 ) State 1,414 11 (16,264 ) Foreign — — (4,814 ) (3,929 ) 1,678 (23,292 ) Income taxes attributable to the noncontrolling interest — — 91 Total income taxes $ 168,825 $ 170,949 $ 146,924 Annual tax provisions include amounts considered sufficient to pay assessments that may result from examination of prior year tax returns; however, the amount ultimately paid upon resolution of issues raised may differ materially from the amount accrued. The examination and the resolution process may last longer than one year. The components of Income before income taxes are summarized as follows: Year Ended December 31, 2015 2014 2013 Domestic $ 472,384 $ 475,175 $ 427,915 Foreign 28,096 14,487 7,042 $ 500,480 $ 489,662 $ 434,957 The effective income tax rate differs from the federal income tax statutory rate due to the following: Year Ended December 31, 2015 2014 2013 Statutory rate 35.0 % 35.0 % 35.0 % State taxes, net of federal tax benefit 1.6 1.2 1.5 Foreign tax expense and tax rate differential (1.2 ) (0.7 ) 0.5 Research and development tax credit (0.6 ) (0.4 ) (0.8 ) Domestic Production Activities Deduction (0.6 ) (0.4 ) (0.5 ) PA Tax Law changes and change in valuation allowance on loss carryforwards — — (2.4 ) Net change in uncertain tax positions — 0.3 0.1 Settlement of state tax petition (0.8 ) — — Other, net 0.3 (0.1 ) 0.3 33.7 % 34.9 % 33.7 % The decrease in the Company's effective income tax rate in 2015 was primarily due to a one-time reduction resulting from a favorable settlement of a tax petition filed with the State of Pennsylvania relating to the apportionment methodology of net income for prior years. In 2014, the Company completed international tax planning which reduced the effective income tax rate for international operations. Additionally, there was an increase in the pre-tax income in certain foreign jurisdictions which were taxed at a lower rate or was offset by foreign tax credit. The impact on the Company's effective income tax rate from the net change in uncertain tax positions in 2014 relates to federal issues mainly associated with the compilation of foreign tax credits and state tax issues. For 2013 , the impact from the net change in uncertain tax positions relates to federal and state tax issues and foreign tax issues. Undistributed earnings of the Company’s foreign subsidiaries amounted to approximately $84,620 at December 31, 2015 . Those earnings are considered to be indefinitely reinvested and, accordingly, no U.S. federal and state income taxes have been provided thereon. Upon distribution of those earnings, in the form of dividends or otherwise, the Company would be subject to both U.S. income taxes, subject to an adjustment for foreign tax credits, and withholding taxes payable to the various foreign countries. Determination of the amount of unrecognized deferred U.S. income tax liability is not practicable because of the complexities associated with its hypothetical calculation, including the availability, or lack thereof, of foreign tax credits to reduce a portion of the U.S. liability. Deferred income taxes for 2015 , 2014 and 2013 reflect the impact of temporary differences between the amount of assets and liabilities for financial reporting purposes and such amounts as measured by tax laws and regulations. In 2013, the Company's deferred income tax net liability decreased significantly due to the following: (1) Pennsylvania Tax Law changes enacted on July 18, 2013 which became effective on January 1, 2014. These changes reduced the deferred tax liability which had accumulated during prior years. In accordance with the tax accounting rules, the effect of the law change is recorded in the year in which the law was signed. The primary change that affects the Company results from the reduction of net income apportioned to the State of Pennsylvania. The bill adopts “market-based” sourcing for apportionment. This method apportions sales to the state where the benefits are being derived by the customer. The method prior to 2014 apportions sales of services to the state where the cost was incurred to perform those services; (2) the Company's current payable decreased as a result of the sale of SEI AK. The net deferred income tax liability is comprised of: Year Ended December 31, 2015 2014 Deferred income taxes: Gross assets 70,106 69,287 Gross liabilities (118,586 ) (117,947 ) (48,480 ) (48,660 ) Valuation allowance (14,548 ) (16,509 ) Net deferred income tax liability $ (63,028 ) $ (65,169 ) The valuation allowances against deferred tax assets at December 31, 2015 and 2014 are related to state net operating losses from certain domestic subsidiaries. Certain state tax statutes significantly limit the utilization of net operating losses for domestic subsidiaries. Furthermore, these net operating losses cannot be used to offset the net income of other subsidiaries. In 2014, the valuation also includes valuation of foreign tax credit. The tax effect of significant temporary differences representing deferred tax liabilities is: Year Ended December 31, 2015 2014 Difference in financial reporting and income tax depreciation methods $ (2,695 ) $ (3,637 ) Reserves not currently deductible 245 209 Capitalized software currently deductible for tax purposes, net of amortization (111,174 ) (118,841 ) State deferred income taxes 1,444 (420 ) Revenue and expense recognized in different periods for financial reporting and income tax purposes 5,534 6,212 Unrealized holding loss (gain) on investments 772 (475 ) Stock-based compensation expense 34,739 38,989 State net operating loss carryforward 19,580 24,150 Valuation allowance on deferred tax assets (14,548 ) (16,509 ) Federal benefit of state tax deduction for uncertain tax positions 3,014 2,913 Foreign tax credit — 2,327 Foreign deferred 61 (87 ) Net deferred income tax liability $ (63,028 ) $ (65,169 ) The Company recognizes uncertain tax positions in accordance with the applicable accounting guidance and adjusts these liabilities when management’s judgment changes as a result of the evaluation of new information not previously available. Due to the complexity of some of these uncertainties, the ultimate resolution may result in a payment that is materially different from our current estimate of the tax liabilities. The Company’s total unrecognized tax benefit, not including interest and penalties, as of December 31, 2015 was $14,517 , of which $12,898 would affect the effective tax rate if the Company were to recognize the tax benefit. The gross amount of uncertain tax liability of $4,512 which is expected to be paid within one year is netted against the current payable account while the remaining amount of $11,397 is included in Other long-term liabilities on the accompanying Consolidated Balance Sheets. During the year ended December 31, 2015 , the Company recognized $1,752 of previously unrecognized tax benefits relating to the lapse of the statute of limitation. The Company files a consolidated federal income tax return and separate income tax returns with various states. Certain subsidiaries of the Company file tax returns in foreign jurisdictions. The Company is no longer subject to U.S. federal income tax examination for years before 2012 and is no longer subject to state, local or foreign income tax examinations by authorities for years before 2008. A reconciliation of the beginning and ending amount of unrecognized tax benefit is as follows: 2015 2014 2013 Balance as of January 1 $ 14,018 $ 12,028 $ 11,553 Tax positions related to current year: Gross additions 1,954 1,957 1,834 Gross reductions — — — 1,954 1,957 1,834 Tax positions related to prior years: Gross additions 297 1,369 3,435 Gross reductions — — — 297 1,369 3,435 Settlements — — (3,772 ) Lapses on statute of limitations (1,752 ) (1,336 ) (1,022 ) Balance as of December 31 $ 14,517 $ 14,018 $ 12,028 The above reconciliation of the gross unrecognized tax benefit will differ from the amount which would affect the effective tax rate because of the recognition of the federal and state tax benefits. The Company classifies all interest and penalties as income tax expense. The Company has recorded $1,391 , $1,066 and $754 in liabilities for tax related interest and penalties in 2015 , 2014 and 2013 , respectively. The Company estimates it will recognize $4,512 of unrecognized tax benefits within the next twelve months due to lapses on the statute of limitation. The Company includes its direct and indirect subsidiaries in its U.S. consolidated federal income tax return. The Company’s tax sharing allocation agreement provides that any subsidiary having taxable income will pay a tax liability equivalent to what that subsidiary would have paid if it filed a separate income tax return. If the separately calculated federal income tax provision for any subsidiary results in a tax loss, the current benefit resulting from such loss, to the extent utilizable on a separate return basis, is accrued and paid to that subsidiary.

Business Segment Information

Business Segment Information	12 Months Ended
	Dec. 31, 2015
Segment Reporting [Abstract]
Business Segment Information	Business Segment Information The Company’s reportable business segments are: Private Banks – provides investment processing and investment management programs to banks and trust institutions, independent wealth advisers and financial advisors worldwide; Investment Advisors – provides investment management programs to affluent investors through a network of independent registered investment advisors, financial planners and other investment professionals in the United States; Institutional Investors – provides investment management programs and administrative outsourcing solutions to retirement plan sponsors, hospitals and not-for-profit organizations worldwide; Investment Managers – provides investment operations outsourcing solutions to fund companies, banking institutions and both traditional and non-traditional investment managers worldwide; and Investments in New Businesses – focuses on providing investment management programs to ultra-high-net-worth families residing in the United States; developing internet-based investment services and advice solutions; entering new markets; and conducting other research and development activities. In 2015 , 2014 and 2013 , no single customer accounted for more than ten percent of revenues in any business segment. The following tables highlight certain financial information about each of the Company’s business segments for the years ended December 31, 2015 , 2014 and 2013 : Private Banks Investment Advisors Institutional Investors Investment Managers Investments In New Businesses Total For the Year Ended December 31, 2015 Revenues $ 456,516 $ 306,620 $ 297,568 $ 267,963 $ 5,541 $ 1,334,208 Expenses 410,975 171,968 145,851 172,094 20,656 921,544 Operating profit (loss) $ 45,541 $ 134,652 $ 151,717 $ 95,869 $ (15,115 ) $ 412,664 Gain on sale of subsidiary 2,791 — — — — 2,791 Total profit (loss) $ 48,332 $ 134,652 $ 151,717 $ 95,869 $ (15,115 ) $ 415,455 Private Banks Investment Advisors Institutional Investors Investment Managers Investments In New Businesses Total For the Year Ended December 31, 2014 Revenues $ 441,467 $ 283,811 $ 284,677 $ 251,310 $ 4,740 $ 1,266,005 Expenses 399,620 146,500 140,659 159,176 18,377 864,332 Operating profit (loss) $ 41,847 $ 137,311 $ 144,018 $ 92,134 $ (13,637 ) $ 401,673 Gain on sale of subsidiary 5,582 — — — — 5,582 Total profit (loss) $ 47,429 $ 137,311 $ 144,018 $ 92,134 $ (13,637 ) $ 407,255 Private Banks Investment Advisors Institutional Investors Investment Managers Investments In New Businesses Total For the Year Ended December 31, 2013 Revenues $ 397,138 $ 241,252 $ 257,658 $ 226,081 $ 4,003 $ 1,126,132 Expenses 392,399 133,962 133,218 148,977 15,723 824,279 Operating profit (loss) $ 4,739 $ 107,290 $ 124,440 $ 77,104 $ (11,720 ) $ 301,853 Gain on sale of subsidiary 22,112 — — — — 22,112 Total profit (loss) $ 26,851 $ 107,290 $ 124,440 $ 77,104 $ (11,720 ) $ 323,965 A reconciliation of the total reported for the business segments to income from operations in the Consolidated Statements of Operations for the years ended December 31, 2015 , 2014 and 2013 is as follows: Year Ended December 31, 2015 2014 2013 Total operating profit from segments above $ 412,664 $ 401,673 $ 301,853 Corporate overhead expenses (54,451 ) (48,889 ) (53,733 ) Noncontrolling interest reflected in segments — — 289 Income from operations $ 358,213 $ 352,784 $ 248,409 The following tables provide additional information for the years ended December 31, 2015 , 2014 and 2013 pertaining to our business segments: Capital Expenditures (1) Depreciation Year Ended December 31, 2015 2014 2013 2015 2014 2013 Private Banks $ 41,972 $ 30,883 $ 34,258 $ 12,348 $ 13,393 $ 15,506 Investment Advisors 13,206 13,783 12,611 3,410 2,507 2,091 Institutional Investors 5,301 4,575 2,712 1,200 1,041 893 Investment Managers 10,119 9,505 4,871 4,040 2,917 1,970 Investments in New Businesses 736 2,547 639 2,278 1,983 1,589 Total from business segments $ 71,334 $ 61,293 $ 55,091 $ 23,276 $ 21,841 $ 22,049 Corporate Overhead 2,547 2,053 760 768 607 448 $ 73,881 $ 63,346 $ 55,851 $ 24,044 $ 22,448 $ 22,497 (1) Capital expenditures include additions to property and equipment and capitalized software. Amortization Year Ended December 31, 2015 2014 2013 Private Banks $ 29,819 $ 24,993 $ 22,379 Investment Advisors 9,880 9,228 8,234 Institutional Investors 1,558 1,430 1,274 Investment Managers 1,029 954 851 Investments in New Businesses 116 1,846 1,636 Total from business segments $ 42,402 $ 38,451 $ 34,374 Corporate Overhead 228 228 228 $ 42,630 $ 38,679 $ 34,602 Total Assets 2015 2014 Private Banks $ 451,079 $ 417,890 Investment Advisors 138,459 134,371 Institutional Investors 105,443 118,397 Investment Managers 154,432 134,614 Investments in New Businesses 5,355 21,830 Total from business segments $ 854,768 $ 827,102 Corporate Overhead (2) 733,860 715,773 $ 1,588,628 $ 1,542,875 (2) Unallocated assets primarily consist of cash and cash equivalents, marketable securities, and certain other shared services assets. The following table presents revenues based on the location of the use of the products or services: For the Year Ended December 31, 2015 2014 2013 United States $ 1,123,165 $ 1,063,223 $ 962,266 International operations 211,043 202,782 163,866 $ 1,334,208 $ 1,266,005 $ 1,126,132 The following table presents assets based on their location: 2015 2014 United States $ 1,330,738 $ 1,315,036 International operations 257,890 227,839 $ 1,588,628 $ 1,542,875

Related Party Transactions

Related Party Transactions	12 Months Ended
	Dec. 31, 2015
Related Party Transactions [Abstract]
Related Party Transactions	Related Party Transactions The Company, either by itself or through its wholly-owned subsidiaries, serves as the sponsor, administrator, investment advisor, distributor and shareholder servicer for SEI-sponsored investment products. These investment products are offered to clients of the Company and its subsidiaries. Fees earned by the Company for the related services are recognized pursuant to the provisions of investment advisory, fund administration, distribution, and shareholder services agreements directly with the investment products. These fees totaled $426,301 , $411,206 and $470,813 in 2015 , 2014 and 2013 , respectively, and are reflected in Asset management, administration and distribution fees on the accompanying Consolidated Statements of Operations. The Company also serves as an introducing broker-dealer for securities transactions of SEI-sponsored investment products. The Company recognized $365 , $2,332 and $620 in commissions during 2015 , 2014 and 2013 , respectively. These fees are reflected in Transaction-based and trade execution fees on the accompanying Consolidated Statements of Operations. Receivables from regulated investment companies (RICs) on the accompanying Consolidated Balance Sheets primarily represent fees receivable for distribution, investment advisory, and administration services to various RICs sponsored by SEI.

Sale of SEI Asset Korea

Sale of SEI Asset Korea	12 Months Ended
	Dec. 31, 2015
Discontinued Operations and Disposal Groups [Abstract]
Sale of SEI Asset Korea	Sale of SEI Asset Korea On July 31, 2012, the Company, MetLife International Holdings, Inc. (MetLife) and International Finance Corporation (IFC) entered into a definitive agreement with Baring Asset Management Limited (Barings) to sell all ownership interest in SEI Asset Korea (SEI AK). SEI AK was located in South Korea and provided domestic equity and fixed income investment management services to financial institutions and pension funds. On March 28, 2013, all conditions subject to closing the transaction were satisfied and all ownership interests in SEI AK were transferred to Barings. The net working capital of SEI AK at closing in excess of required regulatory capital, and subject to certain other adjustments, was distributed to the Company, MetLife and IFC in accordance with the ownership interests. The Company recognized a pre-tax gain of $22,112 , or $0.08 diluted earnings per share, during 2013. Under the terms of the agreement, a portion of the purchase price was paid upon closing with up to an additional $11,220 payable to the Company as a contingent purchase price with respect to three one-year periods ending on December 31, 2013, 2014 and 2015 depending upon whether SEI AK achieves specified revenue measures during such periods. The Company recognized a pre-tax gain of $5,582 , or $0.02 diluted earnings per share, during 2014 and a pre-tax gain of $2,791 , or $0.01 diluted earnings per share, during 2015. The Company's gains from the sale of SEI AK are included in Gain on sale of subsidiary on the accompanying Consolidated Statement of Operations. The operating results of SEI AK were included in the Private Banks business segment. SEI AK revenues and net income included in the Company's Consolidated Statement of Operations were as follows: For the Period January 1, 2013 through March 28, 2013 Revenues $ 2,889 Net income $ 796 Less: Income attributable to the noncontrolling interests (350 ) Net income attributable to SEI AK $ 446

Settlement Agreement

Settlement Agreement	12 Months Ended
	Dec. 31, 2015
Litigation Settlement [Abstract]
Settlement Agreement	Settlement Agreement On April 24, 2013 , the Company entered into a Settlement Agreement with respect to litigation captioned Abu Dhabi Commercial Bank, et. al. v. Morgan Stanley & Co., Incorporated, et. al., brought by a group of plaintiffs, including the Company, related to the purchase of securities by the Company and others of Cheyne Finance LLC, a SIV security. In accordance with the Settlement Agreement, the Company received a cash settlement payment of $43,429 after fees and expenses during the three months ended June 30, 2013. The income related to the cash settlement payment is reflected in Other income on the accompanying Consolidated Statements of Operations.

Quarterly Financial Data

Quarterly Financial Data	12 Months Ended
	Dec. 31, 2015
Quarterly Financial Data [Abstract]
Quarterly Financial Data	Quarterly Financial Data (Unaudited) For the Three Months Ended 2015 March 31 June 30 September 30 December 31 Revenues $ 325,444 $ 337,745 $ 335,622 $ 335,397 Income before income taxes $ 131,000 $ 133,810 $ 120,588 $ 115,082 Net income attributable to SEI $ 84,611 $ 86,240 $ 79,425 $ 81,379 Basic earnings per share $ 0.51 $ 0.52 $ 0.48 $ 0.49 Diluted earnings per share $ 0.50 $ 0.51 $ 0.47 $ 0.48 Effective income tax rate 35.4 % 35.6 % 34.1 % 29.3 % Gain on sale of subsidiary (Note 15) $ 2,791 $ — $ — $ — Diluted earnings per share (1) $ 0.01 $ — $ — $ — (1) Attributable to gain on sale of subsidiary. For the Three Months Ended 2014 March 31 June 30 September 30 December 31 Revenues $ 302,386 $ 318,815 $ 322,047 $ 322,757 Income before income taxes $ 116,665 $ 128,854 $ 128,618 $ 115,525 Net income attributable to SEI $ 74,820 $ 82,813 $ 83,983 $ 77,097 Basic earnings per share $ 0.44 $ 0.49 $ 0.50 $ 0.46 Diluted earnings per share $ 0.43 $ 0.48 $ 0.49 $ 0.45 Effective income tax rate 35.9 % 35.7 % 34.7 % 33.3 % Gain on sale of subsidiary (Note 15) $ 5,582 $ — $ — $ — Diluted earnings per share (2) $ 0.02 $ — $ — $ — Loss from impairment charge (Note 2) $ — $ — $ — $ 11,266 Diluted earnings per share (3) $ — $ — $ — $ 0.06 (2) Attributable to gain on sale of subsidiary. (3) Attributable to loss from impairment charge related to investment in Gao Fu Limited.

Schedule II - Valuation And Qua

Schedule II - Valuation And Qualifying Accounts And Reserves	12 Months Ended
	Dec. 31, 2015
Valuation and Qualifying Accounts [Abstract]
Schedule II - Valuation and Qualifying Accounts and Reserves	Year Ended December 31, Additions Description Balance at Beginning of Year Charged to Costs and Expenses Charged to Other Accounts (Deductions) Balance at End of Year Allowance for doubtful accounts: 2015 $ 784 $ — $ — $ (135 ) $ 649 2014 651 133 — — 784 2013 805 — — (154 ) 651 Deferred income tax valuation allowance: 2015 $ 16,509 $ (1,142 ) $ (819 ) $ — $ 14,548 2014 14,738 — 1,771 — 16,509 2013 6,879 (485 ) 8,344 — 14,738

Summary of Significant Accoun28

Summary of Significant Accounting Policies (Policy)	12 Months Ended
	Dec. 31, 2015
Accounting Policies [Abstract]
Principles of Consolidation	Principles of Consolidation The Consolidated Financial Statements include the accounts of the Company and its wholly-owned subsidiaries and entities in which it holds a controlling financial interest. The Company determines whether it has a controlling financial interest either by its decision-making ability through voting interests or by the extent of the Company’s participation in the economic risks and rewards of the entity through variable interests. The Company’s principal subsidiaries are SEI Investments Distribution Co. (SIDCO), SEI Investments Management Corporation (SIMC), SEI Private Trust Company (SPTC), SEI Trust Company (STC), SEI Global Services, Inc. (SGSI) and SEI Investments (Europe) Limited (SIEL). All intercompany accounts and transactions have been eliminated. The Company accounts for investments in unconsolidated entities that are 20 percent to 50 percent owned or are 20 percent or less owned and have the ability to exercise significant influence over the operating and financial policies of the entity under the equity method of accounting. Under this method of accounting, the Company’s interest in the net assets of unconsolidated entities is reflected in Investment in unconsolidated affiliates on the accompanying Consolidated Balance Sheet and its interest in the earnings or losses of unconsolidated entities is reflected in Equity in earnings of unconsolidated affiliates on the accompanying Consolidated Statement of Operations.
Variable Interest Entities	Variable Interest Entities The Company has involvement with various variable interest entities (VIE or VIEs). These VIEs consist of LSV Employee Group III, LLC (LSV Employee Group III) and investment products established for clients created in the form of various types of legal entity structures. According to the most recent accounting guidance issued by the Financial Accounting Standards Board (FASB), the determination of whether a company is required to consolidate an entity is based on, among other things, an entity’s purpose and design, a company’s ability to direct the activities of the entity that most significantly impact the entity’s economic performance, and whether a company is obligated to absorb losses or receive benefits that could be potentially significant to the entity. The guidance requires ongoing reassessments of whether an enterprise is the primary beneficiary of a VIE and requires disclosures about an enterprises involvement in VIEs. The FASB deferred the accounting guidance for certain types of investment entities. The deferral allows asset managers that have no obligation to fund potentially significant losses of an investment entity to continue to apply the previous guidance to investment entities that have attributes of entities defined in the “Investment Company Guide.” The deferral applies to many mutual funds, hedge funds, private equity funds, venture capital and certain other types of entities. Also, money market funds subject to rule 2a-7 of the Investment Company Act of 1940 qualify for deferral. However, the deferral does not apply to the new disclosure requirements. All of the Company’s investment products where the Company is the sponsor and/or investment manager that are VIEs qualify for the deferral; therefore, the Company will continue to apply the previous guidance for the consolidation of VIEs (See Note 3). On February 18, 2015, the FASB issued Accounting Standards Update No. 2015-02, Consolidation (Topic 810) - Amendments to the Consolidation Analysis (ASU 2015-02). The new guidance applies to entities in all industries and provides a new scope exception to registered money market funds and similar unregistered money market funds. It makes targeted amendments to the current consolidation guidance and ends the deferral granted to investment companies from applying the VIE guidance. ASU 2015-02 became effective for the Company during the first quarter 2016. The Company has completed its evaluation of ASU 2015-02 and has determined that the standard will not have any effect on its consolidated financial statements.
Management's Use of Estimates	Management’s Use of Estimates The preparation of financial statements in conformity with accounting principles generally accepted in the United States requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates.
Revenue Recognition	Revenue Recognition The Company’s principal sources of revenues are: (1) asset management, administration and distribution fees earned based upon a contractual percentage of net assets under management or administration; (2) information processing and software servicing fees that are either recurring and primarily earned based upon the number of trust accounts being serviced or non-recurring and based upon project-oriented contractual agreements related to client implementations; and (3) transaction-based fees for providing trade-execution services. The Company’s revenues are based on contractual arrangements. Revenues are recognized in the periods in which the related services are performed provided that persuasive evidence of an agreement exists, the fee is fixed or determinable, and collectibility is reasonably assured. Cash received by the Company in advance of the performance of services is deferred and recognized as revenue when earned. Reimbursements received for out-of-pocket expenses incurred are recorded as revenue. Certain portions of the Company’s revenues require management’s consideration of the nature of the client relationship in determining whether to recognize as revenue the gross amount billed or net amount retained after payments are made to suppliers for certain services related to the product or service offering. For the majority of our services, we are the primary obligor responsible for fulfilling the performance obligations of the contract. In addition, we retain full discretion in establishing the price charged to the customer, control the nature, type, characteristics or specifications of the performance obligations identified in the contract, and assume all credit risk associated with the client. Based on the foregoing, fees received from our clients for these services are recorded as gross revenues and vendor costs are recorded as gross expenses. However, we are also party to certain arrangements whereby we are not the primary obligor responsible for fulfilling the performance obligations of the contract. Fees received for those arrangements are reported net of costs associated with the provision of those services.
Cash and Cash Equivalents	Cash and Cash Equivalents The Company considers investment instruments purchased with an original maturity of three months or less to be cash equivalents.
Allowance for Doubtful Accounts	Allowances for Doubtful Accounts The Company provides an allowance for doubtful accounts equal to the estimated uncollectible amounts. The Company’s estimate is based on historical collection experience and a review of the current status of trade accounts receivable.
Concentration of Credit Risk	Concentration of Credit Risk Financial instruments which potentially expose the Company to concentrations of credit risk consist primarily of cash equivalents and trade receivables. Cash equivalents are principally invested in short-term money market funds or placed with major banks and high-credit qualified financial institutions. Cash deposits maintained with institutions are in excess of federally insured limits. Concentrations of credit risk with respect to our receivables are limited due to the large number of clients and their dispersion across geographic areas. No single group or customer represents greater than ten percent of total accounts receivable.
Property and Equipment	Property and Equipment Property and Equipment are recorded at cost. Expenditures for major additions and improvements are capitalized and minor replacements, maintenance, and repairs are charged to expense as incurred. Construction in progress includes the cost of construction and other direct costs attributable to the construction. When property and equipment are retired or disposed of, the related cost and accumulated depreciation are removed from the accounts and any resulting gain or loss is included in the results of operations for the respective period. Depreciation is provided over the estimated useful lives using the straight line method for financial statement purposes. No provision for depreciation is made for construction in progress until such time as the relevant assets are completed and put into service. The Company uses other depreciation methods, generally accelerated, for tax purposes where appropriate. Buildings and building improvements are depreciated over 25 to 39 years . Equipment, purchased software and furniture and fixtures have useful lives ranging from 3 to 5 years . Amortization of leasehold improvements is computed using the straight line method over the shorter of the remaining lease term or the estimated useful lives of the improvements.
Marketable Securities	Marketable Securities The classification of investments in marketable securities is determined at the time of purchase and reevaluated at each balance sheet date. Debt and equity securities classified as available-for-sale are reported at fair value as determined by the most recently traded price of each security at the balance sheet date. Unrealized gains and losses, net of income taxes, are reported as a separate component of comprehensive income. SIDCO, the Company’s broker-dealer subsidiary, reports changes in fair value of marketable securities through current period earnings due to specialized accounting practices related to investments by broker-dealers. The Company records its investments in funds sponsored by LSV on the accompanying Consolidated Balance Sheets at fair value. Unrealized gains and losses from the change in fair value of these securities are recognized in current period earnings. The specific identification method is used to compute the realized gains and losses on all of the Company’s marketable securities (See Note 6). The Company evaluates the realizable value of its marketable securities on a quarterly basis. In the event that the carrying value of an investment exceeds its fair value and the decline in value is determined to be other-than-temporary, an impairment charge is recorded and a new cost basis for the investment is established. Some of the factors considered in determining other-than-temporary impairment for equity securities include, but are not limited to, significant or prolonged declines in the fair value of the investments, the Company’s ability and intent to retain the investment for a period sufficient to allow the value to recover, and the financial condition of the investment. Some of the factors considered in determining other-than-temporary impairment for debt securities include, but are not limited to, the intent of management to sell the security, the likelihood that the Company will be required to sell the security before recovering its cost, and management’s expectation to recover the entire amortized cost basis of the security even if there is no intent to sell the security.
Fair Value of Financial Instruments	Fair Value of Financial Instruments Fair value is defined as the exchange price that would be received for an asset or paid to transfer a liability (an exit price) in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants on the measurement date. The fair value hierarchy requires an entity to maximize the use of observable inputs and minimize the use of unobservable inputs when measuring fair value. The fair value hierarchy describes three levels of inputs that may be used by the Company to measure fair value: Level 1 – Quoted prices in active markets for identical assets or liabilities without adjustment. The Company’s Level 1 assets primarily include investments in mutual funds sponsored by SEI that are quoted daily. Level 2 – Observable inputs other than Level 1 prices, such as quoted prices for similar assets, quoted prices in markets that are not active, or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the assets or liabilities. Level 2 financial assets consist of Government National Mortgage Association (GNMA) mortgage-backed securities, Federal Home Loan Bank (FHLB) and other U.S. government agency short-term notes and investment grade commercial paper, and investment funds sponsored by LSV. The investments in GNMA mortgage-backed securities were purchased for the sole purpose of satisfying applicable regulatory requirements imposed on our wholly-owned limited purpose federal thrift subsidiary, SPTC. The investments in FHLB and other U.S. government agency short-term notes and investment grade commercial paper were purchased as part of a cash management program requiring only short term, top-tier investment grade government and corporate securities. The investment funds sponsored by LSV primarily invest in equity securities of non-U.S. developed nations which are traded in active markets. Level 3 – Unobservable inputs that are supported by little or no market activity and that are significant to the fair value of the assets or liabilities. Level 3 assets and liabilities include financial instruments whose value is determined using pricing models, or similar techniques, as well as instruments for which the determination of fair value requires significant judgment by management. The Company had no Level 3 financial assets at December 31, 2015 or 2014 . The fair value of an asset or liability may include inputs from more than one level in the fair value hierarchy. The lowest level of significant inputs used to value the asset or liability determines which level the asset or liability is classified in its entirety. Transfers between levels of the fair value hierarchy are reported at fair value as of the beginning of the period in which the transfers occur.
Capitalized Software	Capitalized Software Costs incurred for the development of internal use software to be offered in a hosting arrangement is capitalized during the development stage of the software application. These costs include direct external and internal costs to design the software configuration and interfaces, coding, installation, and testing. Costs incurred during the preliminary and post-implementation stages of the software application are expensed as incurred. Costs associated with significant enhancements to a software application are capitalized while costs incurred to maintain existing software applications are expensed as incurred. The capitalization of software development costs requires considerable judgment by management with respect to certain external factors, including, but not limited to, technological and economic feasibility, and estimated economic life. Amortization of capitalized software development costs begins when the product is ready for its intended use. Capitalized software development costs are amortized on a product-by-product basis using the straight-line method over the estimated economic life of the product or enhancement. The Company capitalized $29,416 , $34,877 and $39,500 of software development costs during 2015 , 2014 and 2013 , respectively. The Company's capitalized software development costs primarily relate to the further development of the SEI Wealth Platform SM (the Platform). The Company capitalized $24,515 , $34,877 and $39,500 of software development costs for significant enhancements to the Platform during 2015 , 2014 and 2013 , respectively. Included in the amount for 2013 is a one-time contractual payment of $8,812 to exercise a conversion option in lieu of periodic fee payments pertaining to a software license for functionality utilized by the Platform. The remaining amount of the Company's software development costs capitalized during 2015 is related to a project within the Investment Managers segment. As of December 31, 2015 , the net book value of the Platform was $285,621 . The Platform has an estimated useful life of 15 years and a weighted average remaining life of 6.5 years . Amortization expense for the Platform was $42,401 , $38,357 and $34,045 in 2015 , 2014 and 2013 , respectively, and is included in Amortization expense on the accompanying Consolidated Statements of Operations. The Company evaluates the carrying value of capitalized software development costs when circumstances indicate the carrying value may not be recoverable. The review of capitalized software development costs for impairment requires significant assumptions about operating strategies, underlying technologies utilized, and external market factors. External market factors include, but are not limited to, expected levels of competition, barriers to entry by potential competitors, stability in the target market and governmental regulations.
Income Taxes	Income Taxes The Company applies the asset and liability approach to account for income taxes whereby deferred tax assets and liabilities are recognized for the future tax consequences attributable to differences between the financial statement carrying amounts of existing assets and liabilities and their respective tax bases. Deferred tax assets and liabilities are measured using enacted tax rates expected to apply to taxable income in the years in which those temporary differences are expected to be recovered or settled. The Company has adopted the amendments contained in Accounting Standards Update No. 2015-17, Balance Sheet Classification of Deferred Taxes (ASU 2015-17) for the fiscal year ended December 31, 2015. ASU 2015-17 requires entities with a classified balance sheet to present all deferred tax assets and liabilities as noncurrent. The Company has elected retrospective application of ASU 2015-17 for all periods presented.
Foreign Currency Translation	Foreign Currency Translation The assets and liabilities and results of operations of the Company’s foreign subsidiaries are measured using the foreign subsidiary’s local currency as the functional currency. Assets and liabilities have been translated into U.S. dollars using the rates of exchange at the balance sheet dates. The results of operations have been translated into U.S. dollars at average exchange rates prevailing during the period. The resulting translation gain and loss adjustments are recorded as a separate component of comprehensive income. Transaction gains and losses from exchange rate fluctuations are included in the results of operations in the periods in which they occur.
Earnings Per Share	Earnings Per Common Share Basic earnings per common share is computed by dividing net income attributable to SEI Investments common shareholders by the weighted average number of common shares outstanding during the period. Diluted earnings per common share is computed by dividing net income attributable to SEI Investments common shareholders by the combination of the weighted average number of common shares outstanding and the dilutive potential common shares, such as stock options, outstanding during the period.
Stock-based Compensation	Stock-Based Compensation Stock-based compensation cost is measured at the grant date based on the fair value of the award and is recognized as expense over the requisite service period, which is the vesting period. The Company uses historical data to estimate pre-vesting forfeitures and record stock-based compensation expense only for those awards that are expected to vest. The amount of stock-based compensation expense that is recognized in a given period is dependent upon management’s estimate of when the vesting targets are expected to be achieved. If this estimate proves to be inaccurate, the remaining amount of stock-based compensation expense could be accelerated, spread out over a longer period, or reversed
New Accounting Pronouncements	New Accounting Pronouncements On May 28, 2014, the FASB issued Accounting Standards Update No. 2014-09, Revenue from Contracts with Customers (ASU 2014-09), requiring an entity to recognize the amount of revenue to which it expects to be entitled for the transfer of promised goods or services to customers. ASU 2014-09 also requires additional disclosure about the nature, amount, timing and uncertainty of revenue and cash flows arising from customer contracts, including significant judgments and changes in judgments and assets recognized from costs incurred to obtain or fulfill a contract. The updated standard permits the use of either the retrospective or cumulative effect transition method. ASU 2014-09 currently becomes effective for the Company during the first quarter 2018. The Company is currently evaluating the transition method that will be elected and the effect that the updated standard will have on its consolidated financial statements and related disclosures. In April 2015, the FASB issued Accounting Standards Update No. 2015-05, Customer's Accounting for Fees Paid in a Cloud Computing Arrangement (ASU 2015-05), which provides explicit guidance to help companies evaluate the accounting for fees paid by a customer in a cloud computing arrangement. The new guidance clarifies that if a cloud computing arrangement includes a software license, the customer should account for the license consistent with its accounting for other software licenses. If the arrangement does not include a software license, the customer should account for the arrangement as a service contract. ASU 2015-05 became effective for the Company during the first quarter 2016. The Company is currently evaluating the guidance in ASU 2015-05 but does not believe it will have a material impact on its consolidated financial statements. In May 2015, the FASB issued new guidance that eliminates the current requirement to categorize within the fair value hierarchy investments with fair values measured at NAV using the practical expedient in Accounting Standards Codification 820, Fair Value Measurement (ASC 820). The new guidance will require entities to disclose the fair values of such investments as a reconciling item between the amounts reported on the balance sheets and the amounts reported in the fair value hierarchy table. Entities will be required to continue to disclose information describing the nature and risks of the investments measured using the NAV practical expedient. The new disclosures become effective for the Company during the first quarter 2016. Early adoption is permitted. The new guidance only impacts footnote disclosures and will have no impact on the Company's financial statements. In January 2016, the FASB issued Accounting Standards Update No. 2016-01, Recognition and Measurement of Financial Assets and Financial Liabilities (ASU 2016-01) that will significantly change the income statement impact of equity investments held by an entity, and the recognition of changes in fair value of financial liabilities when the fair value option is elected. ASU 2016-01 becomes effective for the Company during the first quarter 2018. The Company is currently evaluating the effect that the updated standard will have on its consolidated financial statements and related disclosures.
Reclassifications	Reclassifications Certain prior year amounts have been reclassified to conform to current year presentation.
Investments in Equity Method Investments	The Company accounted for its interest in Gao Fu using the equity method. The Company's interest in the losses of Gao Fu is reflected in Equity in earnings of unconsolidated affiliates on the accompanying Consolidated Statements of Operations. The Company's interest in the net assets of Gao Fu as of December 31, 2014 is reflected in Investment in unconsolidated affiliates on the accompanying Consolidated Balance Sheet. The Company accounts for its interest in LSV using the equity method because of its less than 50 percent ownership. The Company’s interest in the net assets of LSV is reflected in Investment in unconsolidated affiliates on the accompanying Consolidated Balance Sheets and its interest in the earnings of LSV is reflected in Equity in earnings of unconsolidated affiliates on the accompanying Consolidated Statements of Operations.
Investments in Affiliated Funds	As a practical expedient, the Company relies on the net asset values (NAVs) of the investment funds sponsored by LSV as the fair value. The NAVs of the funds are calculated by the funds' independent custodian and are derived from the fair values of the underlying investments as of the reporting date.
Securities Owned	The Company’s broker-dealer subsidiary, SIDCO, has investments in U.S. government agency and commercial paper securities with maturity dates less than one year. These investments are reflected as Securities owned on the accompanying Consolidated Balance Sheets. Due to specialized accounting practices applicable to investments by broker-dealers, the securities are reported at fair value and changes in fair value are recorded in current period earnings.
Unremitted Earnings in Foreign Investment	Those earnings are considered to be indefinitely reinvested and, accordingly, no U.S. federal and state income taxes have been provided thereon. Upon distribution of those earnings, in the form of dividends or otherwise, the Company would be subject to both U.S. income taxes, subject to an adjustment for foreign tax credits, and withholding taxes payable to the various foreign countries. Determination of the amount of unrecognized deferred U.S. income tax liability is not practicable because of the complexities associated with its hypothetical calculation, including the availability, or lack thereof, of foreign tax credits to reduce a portion of the U.S. liability.
Uncertain Tax Positions	The Company recognizes uncertain tax positions in accordance with the applicable accounting guidance and adjusts these liabilities when management’s judgment changes as a result of the evaluation of new information not previously available. Due to the complexity of some of these uncertainties, the ultimate resolution may result in a payment that is materially different from our current estimate of the tax liabilities.

Summary of Significant Accoun29

Summary of Significant Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2015
Accounting Policies [Abstract]
Calculation Of Basic And Diluted Earnings Per Share	The calculations of basic and diluted earnings per share for 2015 , 2014 and 2013 are: For the Year Ended December 31, 2015 Net income attributable to SEI (Numerator) Shares (Denominator) Per-Share Amount Basic earnings per common share $ 331,655 165,725,000 $ 2.00 Dilutive effect of stock options — 3,873,000 Diluted earnings per common share $ 331,655 169,598,000 $ 1.96 For the Year Ended December 31, 2014 Net income attributable to SEI (Numerator) Shares (Denominator) Per-Share Amount Basic earnings per common share $ 318,713 168,246,000 $ 1.89 Dilutive effect of stock options — 4,319,000 Diluted earnings per common share $ 318,713 172,565,000 $ 1.85 For the Year Ended December 31, 2013 Net income attributable to SEI (Numerator) Shares (Denominator) Per-Share Amount Basic earnings per common share $ 288,124 171,561,000 $ 1.68 Dilutive effect of stock options — 4,157,000 Diluted earnings per common share $ 288,124 175,718,000 $ 1.64

Investment In Unconsolidated 30

Investment In Unconsolidated Affiliates (Tables)	12 Months Ended
	Dec. 31, 2015
Equity Method Investments and Joint Ventures [Abstract]
Equity Method Investments	These tables contain condensed financial information of LSV: Condensed Statement of Operations Year ended December 31, 2015 2014 2013 Revenues $ 427,653 $ 422,064 $ 354,094 Net income $ 352,845 $ 356,824 $ 302,316 Condensed Balance Sheets December 31, 2015 2014 Current assets $ 127,225 $ 133,657 Non-current assets 2,375 2,269 Total assets $ 129,600 $ 135,926 Current liabilities $ 40,876 $ 35,208 Partners’ capital 88,724 100,718 Total liabilities and partners’ capital $ 129,600 $ 135,926

Composition of Certain Financ31

Composition of Certain Financial Statement Captions (Tables)	12 Months Ended
	Dec. 31, 2015
Items Included in Consolidated Statement of Financial Condition [Abstract]
Receivables	Receivables on the accompanying Consolidated Balance Sheets consist of: 2015 2014 Trade receivables $ 47,179 $ 48,394 Fees earned, not billed 154,919 139,038 Other receivables 21,574 7,771 223,672 195,203 Less: Allowance for doubtful accounts (649 ) (784 ) Receivables, net $ 223,023 $ 194,419
Property And Equipment	Property and Equipment on the accompanying Consolidated Balance Sheets consists of: 2015 2014 Buildings $ 151,604 $ 149,890 Equipment 86,941 78,266 Land 10,003 9,997 Purchased software 122,433 104,964 Furniture and fixtures 16,143 16,944 Leasehold improvements 15,393 5,675 Construction in progress 961 1,094 403,478 366,830 Less: Accumulated depreciation (259,501 ) (241,295 ) Property and Equipment, net $ 143,977 $ 125,535
Accrued Liabilities	Accrued Liabilities on the accompanying Consolidated Balance Sheets consist of: 2015 2014 Accrued employee compensation $ 74,687 $ 73,269 Accrued consulting, outsourcing and professional fees 21,575 18,915 Accrued sub-advisory, distribution and other asset management fees 32,674 31,913 Accrued dividend payable 42,625 40,178 Other accrued liabilities 46,026 43,154 Accrued liabilities $ 217,587 $ 207,429

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	12 Months Ended
	Dec. 31, 2015
Fair Value Disclosures [Abstract]
Fair Value Of Certain Financial Assets And Liabilities	The fair value of certain financial assets and liabilities of the Company was determined using the following inputs: December 31, 2015 Fair Value Measurements at Reporting Date Using Total Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Assets Equity available-for-sale securities $ 10,657 $ 10,657 $ — Fixed-income available-for-sale securities 70,637 — 70,637 Fixed income securities owned 21,235 — 21,235 Investment funds sponsored by LSV 4,039 — 4,039 $ 106,568 $ 10,657 $ 95,911 December 31, 2014 Fair Value Measurements at Reporting Date Using Total Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Assets Equity available-for-sale securities $ 11,588 $ 11,588 $ — Fixed-income available-for-sale securities 66,021 — 66,021 Fixed income securities owned 21,175 — 21,175 Investment funds sponsored by LSV 4,523 — 4,523 $ 103,307 $ 11,588 $ 91,719

Marketable Securities (Tables)

Marketable Securities (Tables)	12 Months Ended
	Dec. 31, 2015
Marketable Securities [Abstract]
Investments Available For Sale	Investments available for sale classified as non-current assets consist of: At December 31, 2015 Cost Gross Unrealized Gains Gross Unrealized (Losses) Fair Value SEI-sponsored mutual funds $ 8,474 $ — $ (742 ) $ 7,732 Equities and other mutual funds 2,857 68 — 2,925 Debt securities 70,308 329 — 70,637 $ 81,639 $ 397 $ (742 ) $ 81,294 At December 31, 2014 Cost Gross Unrealized Gains Gross Unrealized (Losses) Fair Value SEI-sponsored mutual funds $ 8,685 $ 134 $ (95 ) $ 8,724 Equities and other mutual funds 2,695 169 — 2,864 Debt securities 64,333 1,688 — 66,021 $ 75,713 $ 1,991 $ (95 ) $ 77,609

Shareholders' Equity (Tables)

Shareholders' Equity (Tables)	12 Months Ended
	Dec. 31, 2015
Stockholders' Equity Note [Abstract]
Assumptions Used In The Weighted Average Fair Value Of The Stock Options Granted	The weighted average fair value of the Company’s stock options granted during 2015 , 2014 and 2013 were $12.16 , $10.88 and $10.45 , respectively, using the following assumptions: 2015 2014 2013 Expected term (in years) 5.58 6.79 6.92 Expected volatility 23.86 % 26.98 % 31.46 % Expected dividend yield 1.00 % 1.15 % 1.21 % Risk-free interest rate 1.90 % 2.04 % 2.12 %
Stock-based Compensation Expense	The Company recognized stock-based compensation expense in its Consolidated Financial Statements in 2015 , 2014 and 2013 as follows: 2015 2014 2013 Stock-based compensation expense $ 17,312 $ 13,463 $ 37,865 Less: Deferred tax benefit (6,107 ) (4,704 ) (13,823 ) Stock-based compensation expense, net of tax $ 11,205 $ 8,759 $ 24,042
Stock Option Plans	This table presents certain information relating to the Company’s stock option plans for 2015 , 2014 and 2013 : Number of Shares Weighted Avg. Price Balance as of December 31, 2012 25,610,000 $ 20.81 Granted 2,281,000 33.67 Exercised (3,733,000 ) 17.26 Expired or canceled (521,000 ) 22.25 Balance as of December 31, 2013 23,637,000 $ 22.58 Granted 2,293,000 40.05 Exercised (5,261,000 ) 19.52 Expired or canceled (208,000 ) 28.83 Balance as of December 31, 2014 20,461,000 $ 25.26 Granted 2,005,000 53.34 Exercised (2,927,000 ) 21.44 Expired or canceled (302,000 ) 28.97 Balance as of December 31, 2015 19,237,000 $ 28.71 Exercisable as of December 31, 2015 8,508,000 $ 22.04 Available for future grant as of December 31, 2015 26,890,000
Stock Options Outstanding And Exercisable	This table summarizes information relating to all options outstanding and exercisable at December 31, 2015 : Options Outstanding at December 31, 2015 Options Exercisable at December 31, 2015 Range of Exercise Prices (Per Share) Number of Shares Weighted Average Exercise Price (Per Share) Weighted Average Remaining Contractual Life (Years) Number of Shares Weighted Average Exercise Price (Per Share) Weighted Average Remaining Contractual Life (Years) $ 14.62 - 16.48 3,513,000 $ 15.23 4.58 2,396,000 $ 14.97 3.92 17.65 - 21.05 2,100,000 17.67 4.03 2,085,000 17.65 4.00 22.45 - 23.86 4,028,000 23.20 5.93 1,678,000 23.20 5.93 27.03 - 36.16 5,515,000 32.08 4.23 2,349,000 32.32 4.68 40.64 - 53.34 4,081,000 46.88 9.49 — — — 19,237,000 8,508,000
Common Stock Buyback	The following table provides the total number of shares repurchased and the related total costs in 2015 , 2014 and 2013 : Year Total Number of Shares Repurchased Total Cost 2015 5,951,000 $ 289,587 2014 7,888,000 278,357 2013 6,789,000 209,942

Accumulated Other Comprehensi35

Accumulated Other Comprehensive Income (Loss), Net of Tax (Tables)	12 Months Ended
	Dec. 31, 2015
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]
Schedule Of Accumulated Other Comprehensive Income (Loss), Net Of Tax	Components of Accumulated other comprehensive income (loss), net of tax, attributable to SEI Investments shareholders consisted of: Foreign Currency Translation Adjustments Unrealized Holding Gains (Losses) on Investments Accumulated Other Comprehensive Income (Loss) Balance, January 1, 2013 $ 3,410 $ 2,829 $ 6,239 Other comprehensive loss before reclassifications (3,309 ) (1,149 ) (4,458 ) Amounts reclassified from accumulated other comprehensive income — (294 ) (294 ) Net current-period other comprehensive loss (3,309 ) (1,443 ) (4,752 ) Balance, December 31, 2013 $ 101 $ 1,386 $ 1,487 Other comprehensive loss before reclassifications (10,189 ) 441 (9,748 ) Amounts reclassified from accumulated other comprehensive income — (634 ) (634 ) Net current-period other comprehensive loss (10,189 ) (193 ) (10,382 ) Balance, December 31, 2014 $ (10,088 ) $ 1,193 $ (8,895 ) Other comprehensive loss before reclassifications (14,900 ) (1,659 ) (16,559 ) Amounts reclassified from accumulated other comprehensive loss — 164 164 Net current-period other comprehensive loss (14,900 ) (1,495 ) (16,395 ) Balance, December 31, 2015 $ (24,988 ) $ (302 ) $ (25,290 )

Commitments and Contingencies (

Commitments and Contingencies (Tables)	12 Months Ended
	Dec. 31, 2015
Commitments and Contingencies Disclosure [Abstract]
Schedule Of Noncancellable Minimum Commitments	The aggregate noncancellable minimum commitments at December 31, 2015 are: 2016 $ 4,397 2017 5,578 2018 8,436 2019 7,354 2020 and thereafter 37,414 $ 63,179

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Schedule of Federal and State and Foreign Income Tax Provision	The federal and state and foreign income tax provision is summarized as follows: Year Ended December 31, 2015 2014 2013 Current Federal $ 159,774 $ 155,273 $ 153,856 State 7,756 8,744 11,542 Foreign 5,224 5,254 4,727 172,754 169,271 170,125 Deferred, including current deferred Federal (5,343 ) 1,667 (2,214 ) State 1,414 11 (16,264 ) Foreign — — (4,814 ) (3,929 ) 1,678 (23,292 ) Income taxes attributable to the noncontrolling interest — — 91 Total income taxes $ 168,825 $ 170,949 $ 146,924
Components of Net Income Before Income Taxes	The components of Income before income taxes are summarized as follows: Year Ended December 31, 2015 2014 2013 Domestic $ 472,384 $ 475,175 $ 427,915 Foreign 28,096 14,487 7,042 $ 500,480 $ 489,662 $ 434,957
Effective Income Tax Rate Reconciliation At Federal Statutory Income Tax Rate	The effective income tax rate differs from the federal income tax statutory rate due to the following: Year Ended December 31, 2015 2014 2013 Statutory rate 35.0 % 35.0 % 35.0 % State taxes, net of federal tax benefit 1.6 1.2 1.5 Foreign tax expense and tax rate differential (1.2 ) (0.7 ) 0.5 Research and development tax credit (0.6 ) (0.4 ) (0.8 ) Domestic Production Activities Deduction (0.6 ) (0.4 ) (0.5 ) PA Tax Law changes and change in valuation allowance on loss carryforwards — — (2.4 ) Net change in uncertain tax positions — 0.3 0.1 Settlement of state tax petition (0.8 ) — — Other, net 0.3 (0.1 ) 0.3 33.7 % 34.9 % 33.7 %
Schedule of Deferred Tax Assets and Liabilities	The net deferred income tax liability is comprised of: Year Ended December 31, 2015 2014 Deferred income taxes: Gross assets 70,106 69,287 Gross liabilities (118,586 ) (117,947 ) (48,480 ) (48,660 ) Valuation allowance (14,548 ) (16,509 ) Net deferred income tax liability $ (63,028 ) $ (65,169 )
Schedule of Temporary Differences Representing Net Deferred Tax Assets or Liabilities	The tax effect of significant temporary differences representing deferred tax liabilities is: Year Ended December 31, 2015 2014 Difference in financial reporting and income tax depreciation methods $ (2,695 ) $ (3,637 ) Reserves not currently deductible 245 209 Capitalized software currently deductible for tax purposes, net of amortization (111,174 ) (118,841 ) State deferred income taxes 1,444 (420 ) Revenue and expense recognized in different periods for financial reporting and income tax purposes 5,534 6,212 Unrealized holding loss (gain) on investments 772 (475 ) Stock-based compensation expense 34,739 38,989 State net operating loss carryforward 19,580 24,150 Valuation allowance on deferred tax assets (14,548 ) (16,509 ) Federal benefit of state tax deduction for uncertain tax positions 3,014 2,913 Foreign tax credit — 2,327 Foreign deferred 61 (87 ) Net deferred income tax liability $ (63,028 ) $ (65,169 )
Schedule of Unrecognized Tax Benefits Roll Forward	A reconciliation of the beginning and ending amount of unrecognized tax benefit is as follows: 2015 2014 2013 Balance as of January 1 $ 14,018 $ 12,028 $ 11,553 Tax positions related to current year: Gross additions 1,954 1,957 1,834 Gross reductions — — — 1,954 1,957 1,834 Tax positions related to prior years: Gross additions 297 1,369 3,435 Gross reductions — — — 297 1,369 3,435 Settlements — — (3,772 ) Lapses on statute of limitations (1,752 ) (1,336 ) (1,022 ) Balance as of December 31 $ 14,517 $ 14,018 $ 12,028

Business Segment Information (T

Business Segment Information (Tables)	12 Months Ended
	Dec. 31, 2015
Segment Reporting [Abstract]
Financial Information About Business Segments	The following tables highlight certain financial information about each of the Company’s business segments for the years ended December 31, 2015 , 2014 and 2013 : Private Banks Investment Advisors Institutional Investors Investment Managers Investments In New Businesses Total For the Year Ended December 31, 2015 Revenues $ 456,516 $ 306,620 $ 297,568 $ 267,963 $ 5,541 $ 1,334,208 Expenses 410,975 171,968 145,851 172,094 20,656 921,544 Operating profit (loss) $ 45,541 $ 134,652 $ 151,717 $ 95,869 $ (15,115 ) $ 412,664 Gain on sale of subsidiary 2,791 — — — — 2,791 Total profit (loss) $ 48,332 $ 134,652 $ 151,717 $ 95,869 $ (15,115 ) $ 415,455 Private Banks Investment Advisors Institutional Investors Investment Managers Investments In New Businesses Total For the Year Ended December 31, 2014 Revenues $ 441,467 $ 283,811 $ 284,677 $ 251,310 $ 4,740 $ 1,266,005 Expenses 399,620 146,500 140,659 159,176 18,377 864,332 Operating profit (loss) $ 41,847 $ 137,311 $ 144,018 $ 92,134 $ (13,637 ) $ 401,673 Gain on sale of subsidiary 5,582 — — — — 5,582 Total profit (loss) $ 47,429 $ 137,311 $ 144,018 $ 92,134 $ (13,637 ) $ 407,255 Private Banks Investment Advisors Institutional Investors Investment Managers Investments In New Businesses Total For the Year Ended December 31, 2013 Revenues $ 397,138 $ 241,252 $ 257,658 $ 226,081 $ 4,003 $ 1,126,132 Expenses 392,399 133,962 133,218 148,977 15,723 824,279 Operating profit (loss) $ 4,739 $ 107,290 $ 124,440 $ 77,104 $ (11,720 ) $ 301,853 Gain on sale of subsidiary 22,112 — — — — 22,112 Total profit (loss) $ 26,851 $ 107,290 $ 124,440 $ 77,104 $ (11,720 ) $ 323,965
Reconciliation Of Total Operating Profit Reported For Business Segments To Income From Operations In Consolidated Statements Of Operations	A reconciliation of the total reported for the business segments to income from operations in the Consolidated Statements of Operations for the years ended December 31, 2015 , 2014 and 2013 is as follows: Year Ended December 31, 2015 2014 2013 Total operating profit from segments above $ 412,664 $ 401,673 $ 301,853 Corporate overhead expenses (54,451 ) (48,889 ) (53,733 ) Noncontrolling interest reflected in segments — — 289 Income from operations $ 358,213 $ 352,784 $ 248,409
Additional Information Pertaining To Business Segments	The following tables provide additional information for the years ended December 31, 2015 , 2014 and 2013 pertaining to our business segments: Capital Expenditures (1) Depreciation Year Ended December 31, 2015 2014 2013 2015 2014 2013 Private Banks $ 41,972 $ 30,883 $ 34,258 $ 12,348 $ 13,393 $ 15,506 Investment Advisors 13,206 13,783 12,611 3,410 2,507 2,091 Institutional Investors 5,301 4,575 2,712 1,200 1,041 893 Investment Managers 10,119 9,505 4,871 4,040 2,917 1,970 Investments in New Businesses 736 2,547 639 2,278 1,983 1,589 Total from business segments $ 71,334 $ 61,293 $ 55,091 $ 23,276 $ 21,841 $ 22,049 Corporate Overhead 2,547 2,053 760 768 607 448 $ 73,881 $ 63,346 $ 55,851 $ 24,044 $ 22,448 $ 22,497 (1) Capital expenditures include additions to property and equipment and capitalized software. Amortization Year Ended December 31, 2015 2014 2013 Private Banks $ 29,819 $ 24,993 $ 22,379 Investment Advisors 9,880 9,228 8,234 Institutional Investors 1,558 1,430 1,274 Investment Managers 1,029 954 851 Investments in New Businesses 116 1,846 1,636 Total from business segments $ 42,402 $ 38,451 $ 34,374 Corporate Overhead 228 228 228 $ 42,630 $ 38,679 $ 34,602 Total Assets 2015 2014 Private Banks $ 451,079 $ 417,890 Investment Advisors 138,459 134,371 Institutional Investors 105,443 118,397 Investment Managers 154,432 134,614 Investments in New Businesses 5,355 21,830 Total from business segments $ 854,768 $ 827,102 Corporate Overhead (2) 733,860 715,773 $ 1,588,628 $ 1,542,875 (2) Unallocated assets primarily consist of cash and cash equivalents, marketable securities, and certain other shared services assets.
Revenues And Assets Based On Location	The following table presents revenues based on the location of the use of the products or services: For the Year Ended December 31, 2015 2014 2013 United States $ 1,123,165 $ 1,063,223 $ 962,266 International operations 211,043 202,782 163,866 $ 1,334,208 $ 1,266,005 $ 1,126,132 The following table presents assets based on their location: 2015 2014 United States $ 1,330,738 $ 1,315,036 International operations 257,890 227,839 $ 1,588,628 $ 1,542,875

Sale of SEI Asset Korea (Tables

Sale of SEI Asset Korea (Tables)	12 Months Ended
	Dec. 31, 2015
Discontinued Operations and Disposal Groups [Abstract]
Schedule of Revenues and Net Income of Sold Segment	SEI AK revenues and net income included in the Company's Consolidated Statement of Operations were as follows: For the Period January 1, 2013 through March 28, 2013 Revenues $ 2,889 Net income $ 796 Less: Income attributable to the noncontrolling interests (350 ) Net income attributable to SEI AK $ 446

Quarterly Financial Data (Table

Quarterly Financial Data (Tables)	12 Months Ended
	Dec. 31, 2015
Quarterly Financial Data [Abstract]
Quarterly Financial Data	Quarterly Financial Data (Unaudited) For the Three Months Ended 2015 March 31 June 30 September 30 December 31 Revenues $ 325,444 $ 337,745 $ 335,622 $ 335,397 Income before income taxes $ 131,000 $ 133,810 $ 120,588 $ 115,082 Net income attributable to SEI $ 84,611 $ 86,240 $ 79,425 $ 81,379 Basic earnings per share $ 0.51 $ 0.52 $ 0.48 $ 0.49 Diluted earnings per share $ 0.50 $ 0.51 $ 0.47 $ 0.48 Effective income tax rate 35.4 % 35.6 % 34.1 % 29.3 % Gain on sale of subsidiary (Note 15) $ 2,791 $ — $ — $ — Diluted earnings per share (1) $ 0.01 $ — $ — $ — (1) Attributable to gain on sale of subsidiary. For the Three Months Ended 2014 March 31 June 30 September 30 December 31 Revenues $ 302,386 $ 318,815 $ 322,047 $ 322,757 Income before income taxes $ 116,665 $ 128,854 $ 128,618 $ 115,525 Net income attributable to SEI $ 74,820 $ 82,813 $ 83,983 $ 77,097 Basic earnings per share $ 0.44 $ 0.49 $ 0.50 $ 0.46 Diluted earnings per share $ 0.43 $ 0.48 $ 0.49 $ 0.45 Effective income tax rate 35.9 % 35.7 % 34.7 % 33.3 % Gain on sale of subsidiary (Note 15) $ 5,582 $ — $ — $ — Diluted earnings per share (2) $ 0.02 $ — $ — $ — Loss from impairment charge (Note 2) $ — $ — $ — $ 11,266 Diluted earnings per share (3) $ — $ — $ — $ 0.06

Summary of Significant Accoun41

Summary of Significant Accounting Policies (Narrative) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Summary of Significant Accounting Policies [Line Items]
Cash and cash equivalents	$ 679,661	$ 679,661	$ 667,446	$ 578,273	$ 452,247
Restricted cash	5,500	5,500	5,801
Capitalized software development costs		29,416	34,877	$ 39,500
Net book value of the SEI Wealth Platform	290,522	$ 290,522	309,040
Prior period reclassification adjustment			$ 1,414
Anti-dilutive employee stock options		10,730	10,166	7,736
Anti-dilutive employee stock options, average exercise price per share		$ 33.99	$ 30	$ 30.54
SEI Wealth Platform [Member]
Summary of Significant Accounting Policies [Line Items]
Capitalized software development costs		$ 24,515	$ 34,877	$ 39,500
Conversion option payment included in software development costs				8,812
Net book value of the SEI Wealth Platform	$ 285,621	285,621
Estimated useful life of the SEI Wealth Platform	15 years
Amortization expense related to the SEI Wealth Platform		$ 42,401	38,357	$ 34,045
Income statement classification for capitalized software write off related to the SEI Wealth Platform		Facilities, supplies and other costs
Sei Sponsored Open Ended Money Market Mutual Funds [Member]
Summary of Significant Accounting Policies [Line Items]
Cash and cash equivalents	$ 448,957	$ 448,957	435,268
Sei Investments Europe Limited [Member]
Summary of Significant Accounting Policies [Line Items]
Restricted cash	5,000	5,000	5,000
Sei Investments Distribution Co Sidco [Member]
Summary of Significant Accounting Policies [Line Items]
Restricted cash	$ 500	$ 500	$ 500
Maximum [Member]
Summary of Significant Accounting Policies [Line Items]
Equity method investment, ownership percentage	50.00%	50.00%
Weighted Average [Member] | SEI Wealth Platform [Member]
Summary of Significant Accounting Policies [Line Items]
Estimated useful life of the SEI Wealth Platform	6 years 6 months
Building and Building Improvements [Member] | Minimum [Member]
Summary of Significant Accounting Policies [Line Items]
Estimated useful life of property and equipment		25 years
Building and Building Improvements [Member] | Maximum [Member]
Summary of Significant Accounting Policies [Line Items]
Estimated useful life of property and equipment		39 years
Computer Equipment [Member] | Minimum [Member]
Summary of Significant Accounting Policies [Line Items]
Estimated useful life of property and equipment		3 years
Computer Equipment [Member] | Maximum [Member]
Summary of Significant Accounting Policies [Line Items]
Estimated useful life of property and equipment		5 years
Furniture and Fixtures [Member] | Minimum [Member]
Summary of Significant Accounting Policies [Line Items]
Estimated useful life of property and equipment		3 years
Furniture and Fixtures [Member] | Maximum [Member]
Summary of Significant Accounting Policies [Line Items]
Estimated useful life of property and equipment		5 years
Equity Method Investee [Member] | Minimum [Member]
Summary of Significant Accounting Policies [Line Items]
Equity method investment, ownership percentage	20.00%	20.00%
Equity Method Investee [Member] | Maximum [Member]
Summary of Significant Accounting Policies [Line Items]
Equity method investment, ownership percentage	50.00%	50.00%
Capitalized software [Member] | SEI Wealth Platform [Member]
Summary of Significant Accounting Policies [Line Items]
Loss on write off of capitalized software related to the SEI Wealth Platform		$ 5,533
Private Banks [Member] | SEI Wealth Platform [Member]
Summary of Significant Accounting Policies [Line Items]
Segment classification for capitalized software write off related to the SEI Wealth Platform		Private Banks
Investment Advisors [Member] | SEI Wealth Platform [Member]
Summary of Significant Accounting Policies [Line Items]
Segment classification for capitalized software write off related to the SEI Wealth Platform		Investment Advisors

Summary of Significant Accoun42

Summary of Significant Accounting Policies (Calculation Of Basic And Diluted Earnings Per Share) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Earnings Per Share [Abstract]
Basic earnings per common share, Net income attributable to SEI (Numerator)	$ 81,379	$ 79,425	$ 86,240	$ 84,611	$ 77,097	$ 83,983	$ 82,813	$ 74,820	$ 331,655	$ 318,713	$ 288,124
Shares used to compute basic earnings per share									165,725	168,246	171,561
Basic earnings per common share	$ 0.49	$ 0.48	$ 0.52	$ 0.51	$ 0.46	$ 0.50	$ 0.49	$ 0.44	$ 2	$ 1.89	$ 1.68
Dilutive effect of stock options, Net income attributable to SEI (Numerator)									$ 0	$ 0	$ 0
Dilutive effect of stock options, shares									3,873	4,319	4,157
Diluted earnings per common share, Net income attributable to SEI (Numerator)									$ 331,655	$ 318,713	$ 288,124
Shares used to compute diluted earnings per share									169,598	172,565	175,718
Diluted earnings per common share	$ 0.48	$ 0.47	$ 0.51	$ 0.50	$ 0.45	$ 0.49	$ 0.48	$ 0.43	$ 1.96	$ 1.85	$ 1.64

Investment In Unconsolidated 43

Investment In Unconsolidated Affiliates (Narrative) (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended			36 Months Ended
	Dec. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2013	Jan. 29, 2016	Oct. 31, 2012
Investments in and Advances to Affiliates [Line Items]
Company's share in the earnings (losses) of equity method investee		$ 137,057	$ 127,786	$ 118,076
Distributions received from unconsolidated affiliate		141,767	137,866	137,104
Payments for ownership interest in Gao Fu		$ 1,000	2,000	2,604
LSV Employee Group III [Member]
Investments in and Advances to Affiliates [Line Items]
Purchase price of partnership interest							$ 77,700
Loans payable							69,930
Financial Guarantee [Member] | LSV Employee Group III [Member]
Investments in and Advances to Affiliates [Line Items]
Guarantor obligations, maximum exposure							45,000
Guarantor obligations, term		5 years
Financial Guarantee [Member] | LSV Employee Group III [Member] | Subsequent Event [Member]
Investments in and Advances to Affiliates [Line Items]
Guarantor obligations, maximum exposure						$ 21,468
Guarantor obligations, current carrying value						$ 0
Financial Guarantee [Member] | LSV Asset Management [Member]
Investments in and Advances to Affiliates [Line Items]
Guarantor obligations, maximum exposure							$ 24,930
LSV Asset Management [Member]
Investments in and Advances to Affiliates [Line Items]
Equity method investment, ownership percentage		39.20%
Total investment in equity method investee		$ 49,580
Company's share in the earnings (losses) of equity method investee		138,407	140,211	118,983
Distributions received from unconsolidated affiliate		141,767	137,866	137,104
Gao Fu [Member]
Investments in and Advances to Affiliates [Line Items]
Company's share in the earnings (losses) of equity method investee		$ (1,350)	(1,159)	$ (907)
Payments for ownership interest in Gao Fu			$ 3,000		$ 13,000
Loss from impairment charge	$ 11,266
Maximum [Member]
Investments in and Advances to Affiliates [Line Items]
Equity method investment, ownership percentage		50.00%

Investment In Unconsolidated 44

Investment In Unconsolidated Affiliates (Condensed Statements of Operations of LSV) (Details) - LSV Asset Management [Member] - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Schedule of Equity Method Investments [Line Items]
Revenues	$ 427,653	$ 422,064	$ 354,094
Net Income	$ 352,845	$ 356,824	$ 302,316

Investment In Unconsolidated 45

Investment In Unconsolidated Affiliates (Condensed Balance Sheets of LSV) (Details) - LSV Asset Management [Member] - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Schedule of Equity Method Investments [Line Items]
Current assets	$ 127,225	$ 133,657
Non-current assets	2,375	2,269
Total assets	129,600	135,926
Current liabilities	40,876	35,208
Partners' capital	88,724	100,718
Total liabilities and partners' capital	$ 129,600	$ 135,926

Variable Interest Entities - 46

Variable Interest Entities - Investment Products (Details)	12 Months Ended
	Dec. 31, 2015
Variable Interest Entities Disclosure [Abstract]
Percentage not approached by expected return on any VIE investment	50.00%

Composition of Certain Financ47

Composition of Certain Financial Statement Captions (Receivables) (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Items Included in Consolidated Statement of Financial Condition [Abstract]
Trade receivables	$ 47,179	$ 48,394
Fees earned, not billed	154,919	139,038
Other receivables	21,574	7,771
Gross receivables	223,672	195,203
Less: Allowance for doubtful accounts	(649)	(784)
Receivables, net	$ 223,023	$ 194,419

Composition of Certain Financ48

Composition of Certain Financial Statement Captions (Property And Equipment) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Property, Plant and Equipment [Line Items]
Property and Equipment, gross	$ 403,478	$ 366,830
Less: Accumulated depreciation	(259,501)	(241,295)
Property and Equipment, net	143,977	125,535
Depreciation expense	24,044	22,448	$ 22,497
Loss on write off of purchased software related to the SEI Wealth Platform	(6,055)	0	$ 0
Buildings [Member]
Property, Plant and Equipment [Line Items]
Property and Equipment, gross	151,604	149,890
Equipment [Member]
Property, Plant and Equipment [Line Items]
Property and Equipment, gross	86,941	78,266
Land [Member]
Property, Plant and Equipment [Line Items]
Property and Equipment, gross	10,003	9,997
Purchased software [Member]
Property, Plant and Equipment [Line Items]
Property and Equipment, gross	122,433	104,964
Furniture and fixtures [Member]
Property, Plant and Equipment [Line Items]
Property and Equipment, gross	16,143	16,944
Leasehold improvements [Member]
Property, Plant and Equipment [Line Items]
Property and Equipment, gross	15,393	5,675
Construction in progress [Member]
Property, Plant and Equipment [Line Items]
Property and Equipment, gross	$ 961	$ 1,094
SEI Wealth Platform [Member]
Property, Plant and Equipment [Line Items]
Income statement classification for purchased software write off related to the SEI Wealth Platform	Facilities, supplies and other costs
SEI Wealth Platform [Member] | Property, Plant and Equipment [Member]
Property, Plant and Equipment [Line Items]
Loss on write off of purchased software related to the SEI Wealth Platform	$ 522
Private Banks [Member] | SEI Wealth Platform [Member]
Property, Plant and Equipment [Line Items]
Segment classification for purchased software write off related to the SEI Wealth Platform	Private Banks

Composition of Certain Financ49

Composition of Certain Financial Statement Captions (Other Assets) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Other Assets [Abstract]
Amortization expense for certain other assets	$ 229	$ 227	$ 227

Composition of Certain Financ50

Composition of Certain Financial Statement Captions (Accrued Liabilities) (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Items Included in Consolidated Statement of Financial Condition [Abstract]
Accrued employee compensation	$ 74,687	$ 73,269
Accrued consulting, outsourcing and professional fees	21,575	18,915
Accrued sub-advisory, distribution and other asset management fees	32,674	31,913
Accrued dividend payable	42,625	40,178
Other accrued liabilities	46,026	43,154
Total accrued liabilities	$ 217,587	$ 207,429

Fair Value Measurements (Fair V

Fair Value Measurements (Fair Value Of Certain Financial Assets And Liabilities) (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity available-for-sale securities	$ 10,657	$ 11,588
Fixed income available-for-sale securities	70,637	66,021
Fixed income securities owned	21,235	21,175
Investment funds sponsored by LSV	4,039	4,523
Assets, fair value	106,568	103,307
Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity available-for-sale securities	10,657	11,588
Fixed income available-for-sale securities	0	0
Fixed income securities owned	0	0
Investment funds sponsored by LSV	0	0
Assets, fair value	10,657	11,588
Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity available-for-sale securities	0	0
Fixed income available-for-sale securities	70,637	66,021
Fixed income securities owned	21,235	21,175
Investment funds sponsored by LSV	4,039	4,523
Assets, fair value	$ 95,911	$ 91,719

Marketable Securities (Narrativ

Marketable Securities (Narrative) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Schedule of Investments [Line Items]
Net unrealized holding gains (losses)	$ (302)	$ 1,193
Unrealized holding gains (losses) during the period, income tax expense (benefit)	(43)	703
Available-for-sale securities, gross realized gains	489	1,401	$ 1,236
Available-for-sale securities, gross realized losses	729	448	772
Investment funds sponsored by LSV	4,039	4,523
Securities owned	21,235	21,175
Investment funds sponsored by LSV [Member]
Schedule of Investments [Line Items]
Investment funds sponsored by LSV	4,039	4,523
Change in fair value of investment funds sponsored by LSV	$ (389)	$ (326)	$ 143

Marketable Securities (Investme

Marketable Securities (Investments Available For Sale) (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Schedule of Available-for-sale Securities [Line Items]
Investment Available for Sale, Cost Amount	$ 81,639	$ 75,713
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	397	1,991
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	(742)	(95)
Available-for-sale Securities	81,294	77,609
SEI-sponsored mutual funds [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment Available for Sale, Cost Amount	8,474	8,685
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	0	134
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	(742)	(95)
Available-for-sale Securities	7,732	8,724
Equities and other mutual funds [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment Available for Sale, Cost Amount	2,857	2,695
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	68	169
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	0	0
Available-for-sale Securities	2,925	2,864
Debt securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment Available for Sale, Cost Amount	70,308	64,333
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	329	1,688
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	0	0
Available-for-sale Securities	$ 70,637	$ 66,021

Line Of Credit (Details)

Line Of Credit (Details) - Line of Credit [Member] - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Line of Credit Facility [Line Items]
Debt Instrument, Term	5 years
Credit facility	$ 300,000
Credit facility, expiration date	Feb. 2, 2017
Credit facility, commitment fee per annum on daily unused portion, percent	0.15%
Aggregate amount that may increase under credit facility	$ 100,000
Credit Facility, commitment fees	$ 483	$ 458	$ 458
London Interbank Offered Rate (LIBOR) [Member]
Line of Credit Facility [Line Items]
Credit facility interest accrued, percentage above LIBOR	1.25%

Shareholders' Equity (Narrative

Shareholders' Equity (Narrative) (Details) $ / shares in Units, $ in Thousands	Jan. 05, 2016$ / shares	Dec. 08, 2015$ / shares	Jun. 24, 2015$ / shares	May. 27, 2015$ / shares	Dec. 31, 2015USD ($)right / shares$ / right$ / sharesshares	Dec. 31, 2014USD ($)$ / sharesshares	Dec. 31, 2013USD ($)$ / sharesshares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted average fair value of stock options granted | $ / shares					$ 12.16	$ 10.88	$ 10.45
Change in management estimate of stock-based compensation expense amortization | $					$ 1,360		$ 19,637
Unrecognized compensation cost | $					$ 51,693
Weighted average period for recognition of unrecognized compensation cost					2 years 1 month 21 days
Total options that were exercisable | shares					8,508,000	10,295,000	14,601,000
Options outstanding weighted average remaining contractual life, years					5 years 8 months 27 days
Total intrinsic value of options exercised | $					$ 76,676	$ 83,196
Aggregate intrinsic value of options exercisable | $					258,270
Total intrinsic value of options outstanding | $					$ 455,766
Share price of SEI common stock | $ / shares					$ 52.40
Rights received by common shareholder for each common share outstanding, rights | right / shares					1
Series A Junior Participating Preferred stock, par value | $ / shares					$ 0.05	$ 0.05
Securities and assets of equivalent value, purchase price, per unit | $ / shares					$ 150
Number of days, rights become exercisable following public announcement					10 days
Acquiring Person, beneficial ownership of the outstanding common stock, minimum percentage					20.00%
Common shares received by holders upon surrender of rights, percentage					50.00%
Rights non-voting, redeemable days					10 days
Right redeemable price, per right | $ / right					0.01
Dividends declared per common share | $ / shares		$ 0.26		$ 0.24	$ 0.50	$ 0.46	$ 0.42
Dividends paid per common share | $ / shares			$ 0.24
Dividends declared | $					$ 82,478	$ 77,158	$ 71,665
Subsequent Event [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Dividends paid per common share | $ / shares	$ 0.26
Common Stock Buyback [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Remaining stock repurchase authorization amount | $					$ 113,126
Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expiration date for options outstanding					Dec. 8, 2016
Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expiration date for options outstanding					Dec. 8, 2025
2014 Equity Compensation Plan [Member] | Tranche One [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting rate					50.00%
2014 Equity Compensation Plan [Member] | Tranche Two [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting rate					50.00%
Employee Stock Purchase Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Employee stock purchase plan, employee eligible percentage on offerings of common stock					85.00%
Shares reserved under the plan | shares					15,600,000
Issuance of common stock under the employee stock purchase plan, shares | shares					11,801,000

Shareholders' Equity (Assumptio

Shareholders' Equity (Assumptions Used In The Weighted Average Fair Value Of Stock Options Granted) (Details)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions and Methodology [Abstract]
Expected term	5 years 6 months 29 days	6 years 9 months 15 days	6 years 11 months 1 day
Expected volatility	23.86%	26.98%	31.46%
Expected dividend yield	1.00%	1.15%	1.21%
Risk-free interest rate	1.90%	2.04%	2.12%

Shareholders' Equity (Stock-Bas

Shareholders' Equity (Stock-Based Compensation Expense) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Stockholders' Equity Note [Abstract]
Stock-based compensation expense	$ 17,312	$ 13,463	$ 37,865
Less: Deferred tax benefit	(6,107)	(4,704)	(13,823)
Stock-based compensation expense, net of tax	$ 11,205	$ 8,759	$ 24,042

Shareholders' Equity (Stock Opt

Shareholders' Equity (Stock Option Plans) (Details) - $ / shares shares in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Balance	20,461	23,637	25,610
Balance, weighted avg. price	$ 25.26	$ 22.58	$ 20.81
Granted	2,005	2,293	2,281
Granted, weighted avg. price	$ 53.34	$ 40.05	$ 33.67
Exercised	(2,927)	(5,261)	(3,733)
Exercised, weighted avg. price	$ 21.44	$ 19.52	$ 17.26
Expired or canceled	(302)	(208)	(521)
Expired or canceled, weighted avg. price	$ 28.97	$ 28.83	$ 22.25
Balance	19,237	20,461	23,637
Balance, weighted avg. price	$ 28.71	$ 25.26	$ 22.58
Total options that were exercisable	8,508	10,295	14,601
Exercisable shares, weighted avg. price	$ 22.04
Available for future grant as of December 31, 2015	26,890

Shareholders' Equity (Stock O59

Shareholders' Equity (Stock Options Outstanding And Exercisable) (Details) - $ / shares shares in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Number of Shares	19,237	20,461	23,637	25,610
Weighted Average Exercise Price (Per Share)	$ 28.71	$ 25.26	$ 22.58	$ 20.81
Weighted Average Remaining Contractual Life (Years)	5 years 8 months 27 days
Number of Shares	8,508	10,295	14,601
Weighted Average Exercise Price (Per Share)	$ 22.04
Exercise Price $14.62-16.48 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Lower range	14.62
Upper range	$ 16.48
Number of Shares	3,513
Weighted Average Exercise Price (Per Share)	$ 15.23
Weighted Average Remaining Contractual Life (Years)	4 years 6 months 29 days
Number of Shares	2,396
Weighted Average Exercise Price (Per Share)	$ 14.97
Weighted Average Remaining Contractual Life (Years)	3 years 11 months 1 day
Exercise Price $17.65-21.05 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Lower range	$ 17.65
Upper range	$ 21.05
Number of Shares	2,100
Weighted Average Exercise Price (Per Share)	$ 17.67
Weighted Average Remaining Contractual Life (Years)	4 years 11 days
Number of Shares	2,085
Weighted Average Exercise Price (Per Share)	$ 17.65
Weighted Average Remaining Contractual Life (Years)	4 years
Exercise Price $22.45-23.86 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Lower range	$ 22.45
Upper range	$ 23.86
Number of Shares	4,028
Weighted Average Exercise Price (Per Share)	$ 23.20
Weighted Average Remaining Contractual Life (Years)	5 years 11 months 5 days
Number of Shares	1,678
Weighted Average Exercise Price (Per Share)	$ 23.20
Weighted Average Remaining Contractual Life (Years)	5 years 11 months 5 days
Exercise Price $27.03-36.16 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Lower range	$ 27.03
Upper range	$ 36.16
Number of Shares	5,515
Weighted Average Exercise Price (Per Share)	$ 32.08
Weighted Average Remaining Contractual Life (Years)	4 years 2 months 23 days
Number of Shares	2,349
Weighted Average Exercise Price (Per Share)	$ 32.32
Weighted Average Remaining Contractual Life (Years)	4 years 8 months 5 days
Exercise Price $40.64-53.34 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Lower range	$ 40.64
Upper range	$ 53.34
Number of Shares	4,081
Weighted Average Exercise Price (Per Share)	$ 46.88
Weighted Average Remaining Contractual Life (Years)	9 years 5 months 27 days
Number of Shares	0
Weighted Average Exercise Price (Per Share)	$ 0

Shareholders' Equity (Common St

Shareholders' Equity (Common Stock Buyback) (Details) - Common Stock Buyback [Member] - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Equity, Class of Treasury Stock [Line Items]
Stock Repurchased and Retired During Period, Shares	5,951	7,888	6,789
Stock Repurchased During Period, Value	$ 289,587	$ 278,357	$ 209,942

Accumulated Other Comprehensi61

Accumulated Other Comprehensive Income (Loss), Net of Tax (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance	$ (8,895)	$ 1,487	$ 6,239
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax [Abstract]
Other comprehensive income (loss) before reclassifications	(16,559)	(9,748)	(4,458)
Amounts reclassified from accumulated other comprehensive income	164	(634)	(294)
Total other comprehensive (loss) gain, net of taxes	(16,395)	(10,382)	(4,752)
Ending Balance	(25,290)	(8,895)	1,487
Accumulated Translation Adjustment [Member]
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance	(10,088)	101	3,410
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax [Abstract]
Other comprehensive income (loss) before reclassifications	(14,900)	(10,189)	(3,309)
Amounts reclassified from accumulated other comprehensive income	0	0	0
Total other comprehensive (loss) gain, net of taxes	(14,900)	(10,189)	(3,309)
Ending Balance	(24,988)	(10,088)	101
Accumulated Net Unrealized Investment Gain (Loss) [Member]
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance	1,193	1,386	2,829
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax [Abstract]
Other comprehensive income (loss) before reclassifications	(1,659)	441	(1,149)
Amounts reclassified from accumulated other comprehensive income	164	(634)	(294)
Total other comprehensive (loss) gain, net of taxes	(1,495)	(193)	(1,443)
Ending Balance	$ (302)	$ 1,193	$ 1,386

Employee Benefit Plan (Details)

Employee Benefit Plan (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Compensation and Retirement Disclosure [Abstract]
Defined contribution plan, cost recognized	$ 9,162	$ 6,157	$ 5,664

Commitments and Contingencies63

Commitments and Contingencies (Narrative) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Commitments and Contingencies Disclosure [Abstract]
Rent Expense	$ 25,074	$ 23,011	$ 21,519

Commitments and Contingencies64

Commitments and Contingencies (Schedule Of Noncancellable Minimum Commitments) (Details) $ in Thousands	Dec. 31, 2015USD ($)
Commitments and Contingencies Disclosure [Abstract]
2,016	$ 4,397
2,017	5,578
2,018	8,436
2,019	7,354
2020 and thereafter	37,414
Operating leases, future minimum payments due	$ 63,179

Income Taxes (Schedule Of Feder

Income Taxes (Schedule Of Federal And State And Foreign Income Tax Provision) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Income Tax Expense (Benefit), Continuing Operations [Abstract]
Federal, current	$ 159,774	$ 155,273	$ 153,856
State, current	7,756	8,744	11,542
Foreign, current	5,224	5,254	4,727
Current federal, state and foreign income tax	172,754	169,271	170,125
Federal, deferred	(5,343)	1,667	(2,214)
State, deferred	1,414	11	(16,264)
Foreign, deferred	0	0	(4,814)
Deferred income tax expense (benefit)	(3,929)	1,678	(23,292)
Income taxes attributable to the Noncontrolling interest	0	0	91
Total income taxes	$ 168,825	$ 170,949	$ 146,924

Income Taxes (Components Of Net

Income Taxes (Components Of Net Income Before Income Taxes) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Income Tax Disclosure [Abstract]
Domestic	$ 472,384	$ 475,175	$ 427,915
Foreign	28,096	14,487	7,042
Income Loss From Continuing Operations Before Income Taxes And Minority Interest	$ 500,480	$ 489,662	$ 434,957

Income Taxes (Effective Income

Income Taxes (Effective Income Tax Rate Reconciliation At Federal Statutory Income Tax Rate) (Details)	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Effective Income Tax Rate Reconciliation, Percent [Abstract]
Statutory rate									35.00%	35.00%	35.00%
State taxes, net of federal tax benefit									1.60%	1.20%	1.50%
Foreign tax expense and tax rate differential									(1.20%)	(0.70%)	0.50%
Research and development tax credit									(0.60%)	(0.40%)	(0.80%)
Domestic Production Activities Deduction									(0.60%)	(0.40%)	(0.50%)
PA Tax Law changes and change in valuation allowance on loss carryforwards									0.00%	0.00%	(2.40%)
Net change in uncertain tax positions									0.00%	0.30%	0.10%
Settlement of state tax petition									(0.80%)	0.00%	0.00%
Other, net									0.30%	(0.10%)	0.30%
Effective tax rates	29.30%	34.10%	35.60%	35.40%	33.30%	34.70%	35.70%	35.90%	33.70%	34.90%	33.70%

Income Taxes (Narrative) (Detai

Income Taxes (Narrative) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Significant Change in Unrecognized Tax Benefits is Reasonably Possible [Line Items]
Undistributed earnings of foreign subsidiaries	$ 84,620
Unrecognized tax benefit, excluding interest and penalties	14,517	$ 14,018	$ 12,028	$ 11,553
Unrecognized tax benefits that would affect effective tax rate	12,898
Amount included in Other long-term liabilities	11,397	10,327
Amount of previously unrecognized tax benefits recognized	1,752
Tax related interest and penalties	1,391	$ 1,066	$ 754
Current liabilities [Member]
Significant Change in Unrecognized Tax Benefits is Reasonably Possible [Line Items]
Amount netted against current payable account	4,512
Other long-term liabilities [Member]
Significant Change in Unrecognized Tax Benefits is Reasonably Possible [Line Items]
Amount included in Other long-term liabilities	11,397
Settlement and Lapse of Statute [Member]
Significant Change in Unrecognized Tax Benefits is Reasonably Possible [Line Items]
Unrecognized tax benefits within the next 12 months	$ 4,512

Income Taxes (Schedule Of Defer

Income Taxes (Schedule Of Deferred Tax Assets and Liabilities) (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Deferred Tax Liabilities, Net, Classification [Abstract]
Gross assets	$ 70,106	$ 69,287
Gross liabilities	(118,586)	(117,947)
Net deferred income tax assets and liabilities	(48,480)	(48,660)
Valuation allowance	(14,548)	(16,509)
Net deferred income tax liability	$ (63,028)	$ (65,169)

Income Taxes (Tax Effect Of Sig

Income Taxes (Tax Effect Of Significant Temporary Differences Representing Deferred Tax Liabilities) (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Deferred Tax Liabilities, Net [Abstract]
Difference in financial reporting and income tax depreciation methods	$ (2,695)	$ (3,637)
Reserves not currently deductible	245	209
Capitalized software currently deductible for tax purposes, net of amortization	(111,174)	(118,841)
State deferred income tax asset	1,444	0
State deferred income tax liability	0	(420)
Revenue and expense recognized in different periods for financial reporting and income tax purpose	5,534	6,212
Unrealized holding loss on investments	772	0
Unrealized holding gain on investments	0	(475)
Stock-based compensation expense	(34,739)	(38,989)
State net operating loss carryforward	19,580	24,150
Valuation allowance on deferred tax assets	(14,548)	(16,509)
Federal benefit of state tax deduction for uncertain tax positions	3,014	2,913
Foreign tax credit	0	2,327
Foreign deferred tax assets	61	0
Foreign deferred including taxes on cumulative undistributed earnings of SEI AK	0	(87)
Net deferred income tax liability	$ (63,028)	$ (65,169)

Income Taxes (Unrecognized Tax

Income Taxes (Unrecognized Tax Benefit) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Income Tax Disclosure [Abstract]
Unrecognized tax benefits, Beginning Balance	$ 14,018	$ 12,028	$ 11,553
Gross additions, current year	(1,954)	(1,957)	(1,834)
Gross reductions, current year	0	0	0
Tax positions related to current year	1,954	1,957	1,834
Gross additions, prior year	(297)	(1,369)	(3,435)
Gross reductions, prior year	0	0	0
Tax positions related to prior years tax positions	297	1,369	3,435
Settlements	0	0	(3,772)
Lapses on statute of limitations	(1,752)	(1,336)	(1,022)
Unrecognized tax benefits, Ending Balance	$ 14,517	$ 14,018	$ 12,028

Business Segment Information (S

Business Segment Information (Schedule Of Financial Information About Business Segments) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Segment Reporting Information [Line Items]
Revenues	$ 335,397	$ 335,622	$ 337,745	$ 325,444	$ 322,757	$ 322,047	$ 318,815	$ 302,386	$ 1,334,208	$ 1,266,005	$ 1,126,132
Expenses									921,544	864,332	824,279
Operating profit (loss)									412,664	401,673	301,853
Gain on sale of subsidiary									2,791	5,582	22,112
Total Profit (Loss)									415,455	407,255	323,965
Private Banks [Member]
Segment Reporting Information [Line Items]
Revenues									456,516	441,467	397,138
Expenses									410,975	399,620	392,399
Operating profit (loss)									45,541	41,847	4,739
Gain on sale of subsidiary									2,791	5,582	22,112
Total Profit (Loss)									48,332	47,429	26,851
Investment Advisors [Member]
Segment Reporting Information [Line Items]
Revenues									306,620	283,811	241,252
Expenses									171,968	146,500	133,962
Operating profit (loss)									134,652	137,311	107,290
Gain on sale of subsidiary									0	0	0
Total Profit (Loss)									134,652	137,311	107,290
Institutional Investors [Member]
Segment Reporting Information [Line Items]
Revenues									297,568	284,677	257,658
Expenses									145,851	140,659	133,218
Operating profit (loss)									151,717	144,018	124,440
Gain on sale of subsidiary									0	0	0
Total Profit (Loss)									151,717	144,018	124,440
Investment Managers [Member]
Segment Reporting Information [Line Items]
Revenues									267,963	251,310	226,081
Expenses									172,094	159,176	148,977
Operating profit (loss)									95,869	92,134	77,104
Gain on sale of subsidiary									0	0	0
Total Profit (Loss)									95,869	92,134	77,104
Investments In New Businesses [Member]
Segment Reporting Information [Line Items]
Revenues									5,541	4,740	4,003
Expenses									20,656	18,377	15,723
Operating profit (loss)									(15,115)	(13,637)	(11,720)
Gain on sale of subsidiary									0	0	0
Total Profit (Loss)									$ (15,115)	$ (13,637)	$ (11,720)

Business Segment Information (R

Business Segment Information (Reconciliation Of Total Operating Profit Reported For Business Segments To Income From Operations In Consolidated Statements Of Operations) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Segment Reporting Information [Line Items]
Total operating profit from segments above	$ 412,664	$ 401,673	$ 301,853
Noncontrolling interest reflected in segments	0	0	350
Income from operations	358,213	352,784	248,409
Operating Segments [Member]
Segment Reporting Information [Line Items]
Total operating profit from segments above	412,664	401,673	301,853
Corporate, Non-Segment [Member]
Segment Reporting Information [Line Items]
Corporate overhead expenses	(54,451)	(48,889)	(53,733)
Segment Reconciling Items [Member]
Segment Reporting Information [Line Items]
Noncontrolling interest reflected in segments	$ 0	$ 0	$ 289

Business Segment Information 74

Business Segment Information (Schedule Of Additional Information Pertaining To Business Segments) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Segment Reporting Information [Line Items]
Capital Expenditures	$ 73,881	$ 63,346	$ 55,851
Depreciation	24,044	22,448	22,497
Amortization	42,630	38,679	34,602
Assets	1,588,628	1,542,875
Private Banks [Member]
Segment Reporting Information [Line Items]
Capital Expenditures	41,972	30,883	34,258
Depreciation	12,348	13,393	15,506
Amortization	29,819	24,993	22,379
Assets	451,079	417,890
Investment Advisors [Member]
Segment Reporting Information [Line Items]
Capital Expenditures	13,206	13,783	12,611
Depreciation	3,410	2,507	2,091
Amortization	9,880	9,228	8,234
Assets	138,459	134,371
Institutional Investors [Member]
Segment Reporting Information [Line Items]
Capital Expenditures	5,301	4,575	2,712
Depreciation	1,200	1,041	893
Amortization	1,558	1,430	1,274
Assets	105,443	118,397
Investment Managers [Member]
Segment Reporting Information [Line Items]
Capital Expenditures	10,119	9,505	4,871
Depreciation	4,040	2,917	1,970
Amortization	1,029	954	851
Assets	154,432	134,614
Investments In New Businesses [Member]
Segment Reporting Information [Line Items]
Capital Expenditures	736	2,547	639
Depreciation	2,278	1,983	1,589
Amortization	116	1,846	1,636
Assets	5,355	21,830
Total From Business Segments [Member]
Segment Reporting Information [Line Items]
Capital Expenditures	71,334	61,293	55,091
Depreciation	23,276	21,841	22,049
Amortization	42,402	38,451	34,374
Assets	854,768	827,102
Corporate, Non-Segment [Member]
Segment Reporting Information [Line Items]
Capital Expenditures	2,547	2,053	760
Depreciation	768	607	448
Amortization	228	228	$ 228
Assets	$ 733,860	$ 715,773

Business Segment Information 75

Business Segment Information (Schedule of Revenues And Assets Based On Location) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Revenues	$ 335,397	$ 335,622	$ 337,745	$ 325,444	$ 322,757	$ 322,047	$ 318,815	$ 302,386	$ 1,334,208	$ 1,266,005	$ 1,126,132
Assets	1,588,628				1,542,875				1,588,628	1,542,875
United States [Member]
Revenues									1,123,165	1,063,223	962,266
Assets	1,330,738				1,315,036				1,330,738	1,315,036
International Operations [Member]
Revenues									211,043	202,782	$ 163,866
Assets	$ 257,890				$ 227,839				$ 257,890	$ 227,839

Related Party Transactions (Det

Related Party Transactions (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Asset management, administration and distribution fees [Member]
Related Party Transaction [Line Items]
Revenue from related parties	$ 426,301	$ 411,206	$ 470,813
Transaction-based and trade execution fees [Member]
Related Party Transaction [Line Items]
Revenue from related parties	$ 365	$ 2,332	$ 620

Sale of SEI Asset Korea (Detail

Sale of SEI Asset Korea (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 28, 2013	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Gain on sale of subsidiary		$ 2,791	$ 5,582	$ 22,112
Gain on sale of subsidiary, diluted earnings per share impact, net		$ 0.01	$ 0.02	$ 0.08
SEI Asset Korea Co., Ltd. [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Contingent purchase price from sale of SEI AK	$ 11,220
Revenues and Net Income Included on Company's Consolidated Statement of Operations
Revenues	2,889
Net income	796
Less: Income attributable to the noncontrolling interests	(350)
Net income attributable to SEI AK	$ 446

Settlement Agreement (Details)

Settlement Agreement (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2013USD ($)
Positive Outcome of Litigation [Member] | Other Income [Member]
Gain Contingencies [Line Items]
Cash settlement payment	$ 43,429

Quarterly Financial Data (Detai

Quarterly Financial Data (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Revenues	$ 335,397	$ 335,622	$ 337,745	$ 325,444	$ 322,757	$ 322,047	$ 318,815	$ 302,386	$ 1,334,208	$ 1,266,005	$ 1,126,132
Income before income taxes	115,082	120,588	133,810	131,000	115,525	128,618	128,854	116,665	500,480	489,662	435,398
Net income attributable to SEI Investments Company	$ 81,379	$ 79,425	$ 86,240	$ 84,611	$ 77,097	$ 83,983	$ 82,813	$ 74,820	$ 331,655	$ 318,713	$ 288,124
Basic earnings per common share	$ 0.49	$ 0.48	$ 0.52	$ 0.51	$ 0.46	$ 0.50	$ 0.49	$ 0.44	$ 2	$ 1.89	$ 1.68
Diluted earnings per common share	$ 0.48	$ 0.47	$ 0.51	$ 0.50	$ 0.45	$ 0.49	$ 0.48	$ 0.43	$ 1.96	$ 1.85	$ 1.64
Effective income tax rate	29.30%	34.10%	35.60%	35.40%	33.30%	34.70%	35.70%	35.90%	33.70%	34.90%	33.70%
Gain on sale of subsidiary									$ 2,791	$ 5,582	$ 22,112
Income (Loss) from extraordinary items, net of tax, per diluted share									$ 0.01	$ 0.02	$ 0.08
Gain on sale of subsidiary [Member]
Gain on sale of subsidiary	$ 0	$ 0	$ 0	$ 2,791	$ 0	$ 0	$ 0	$ 5,582
Income (Loss) from extraordinary items, net of tax, per diluted share	$ 0	$ 0	$ 0	$ 0.01	$ 0	$ 0	$ 0	$ 0.02
Equity in earnings of unconsolidated affiliates [Member]
Loss from impairment charge					$ 11,266	$ 0	$ 0	$ 0
Income (Loss) from extraordinary items, net of tax, per diluted share					$ 0.06	$ 0	$ 0	$ 0

Schedule II - Valuation And Q80

Schedule II - Valuation And Qualifying Accounts And Reserves (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Allowance For Doubtful Accounts [Member]
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Year	$ 784	$ 651	$ 805
Additions, Charged to Costs and Expenses	0	133	0
Additions, Charged to Other Accounts	0	0	0
(Deductions)	(135)	0	(154)
Balance at End of Year	649	784	651
Deferred Income Tax Valuation Allowance [Member]
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Year	16,509	14,738	6,879
Additions, Charged to Costs and Expenses	(1,142)	0	(485)
Additions, Charged to Other Accounts	(819)	1,771	8,344
(Deductions)	0	0	0
Balance at End of Year	$ 14,548	$ 16,509	$ 14,738