SEI Investments (SEIC) 10-K 27 Feb 14 2013 FY Annual report Financial data

Document_And_Entity_Informatio

Document And Entity Information (USD $)	12 Months Ended
In Billions, except Share data, unless otherwise specified	Dec. 31, 2013	Jan. 31, 2014	Jun. 28, 2013
Document And Entity Information [Abstract]	'	'	'
Entity Registrant Name	'SEI INVESTMENTS CO	'	'
Entity Central Index Key	'0000350894	'	'
Current Fiscal Year End Date	'--12-31	'	'
Entity Filer Category	'Large Accelerated Filer	'	'
Document Type	'10-K	'	'
Document Period End Date	31-Dec-13	'	'
Document Fiscal Year Focus	'2013	'	'
Document Fiscal Period Focus	'FY	'	'
Trading Symbol	'SEIC	'	'
Amendment Flag	'false	'	'
Entity Common Stock, Shares Outstanding	'	169,489,439	'
Entity Public Float	'	'	$3.80
Entity Well-known Seasoned Issuer	'Yes	'	'
Entity Voluntary Filers	'No	'	'
Entity Current Reporting Status	'Yes	'	'

Consolidated_Balance_Sheets

Consolidated Balance Sheets (USD $)	Dec. 31, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified
Current Assets:	'	'
Cash and cash equivalents	$578,273	$452,247
Restricted cash	5,500	6,000
Receivables from regulated investment companies (Note 14)	39,364	31,084
Receivables, net of allowance for doubtful accounts of $651 and $805 (Note 4)	186,664	171,734
Deferred income taxes, net	0	2,012
Securities owned (Note 6)	21,133	20,088
Other current assets	16,166	18,239
Total Current Assets	847,100	701,404
Property and Equipment, net of accumulated depreciation of $220,064 and $201,418 (Note 4)	118,995	127,581
Capitalized Software, net of accumulated amortization of $180,062 and $149,747 (Note 1)	312,615	307,490
Investments Available for Sale (Note 6)	83,323	75,869
Trading Securities (Note 6)	4,849	5,909
Investment in Unconsolidated Affiliates (Note 2)	61,370	77,398
Other Assets, net (Note 4)	10,917	14,173
Total Assets	1,439,169	1,309,824
Current Liabilities:	'	'
Accounts payable	16,235	11,248
Accrued liabilities (Note 4)	188,123	138,305
Deferred income taxes, net	1,653	0
Deferred revenue	1,977	2,452
Total Current Liabilities	207,988	152,005
Deferred Income Taxes (Note 12)	66,572	93,458
Other Long-term Liabilities (Note 12)	8,607	7,032
Total Liabilities	283,167	252,495
Commitments and Contingencies (Note 11)	'	'
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; 169,242 and 172,220 shares issued and outstanding	1,692	1,722
Capital in excess of par value	721,219	624,305
Retained earnings	431,604	405,914
Accumulated other comprehensive income, net	1,487	6,239
Total SEI Investments Shareholders’ Equity	1,156,002	1,038,180
Noncontrolling Interest	0	19,149
Total Equity	1,156,002	1,057,329
Total Liabilities and Equity	$1,439,169	$1,309,824

Consolidated_Balance_Sheets_Pa

Consolidated Balance Sheets (Parenthetical) (USD $)	Dec. 31, 2013	Dec. 31, 2012
In Thousands, except Share data, unless otherwise specified
Current Assets:	'	'
Receivables, allowance for doubtful accounts	$651	$805
Property and Equipment, accumulated depreciation	220,064	201,418
Capitalized Software, accumulated amortization	$180,062	$149,747
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	169,242,000	172,220,000
Common stock, shares outstanding	169,242,000	172,220,000

Consolidated_Statements_Of_Ope

Consolidated Statements Of Operations (USD $)	12 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Revenues:	'	'	'
Asset management, administration and distribution fees	$831,720	$723,630	$669,788
Information processing and software servicing fees	261,691	236,190	222,417
Transaction-based and trade execution fees	32,721	32,702	37,522
Total revenues	1,126,132	992,522	929,727
Expenses:	'	'	'
Subadvisory, distribution and other asset management costs	121,989	106,048	103,134
Software royalties and other information processing costs	31,255	26,722	27,437
Brokerage commissions	24,649	23,889	27,022
Compensation, benefits and other personnel	357,453	335,296	289,445
Stock-based compensation	37,865	15,736	14,112
Consulting, outsourcing and professional fees	131,399	109,828	113,171
Data processing and computer related	51,401	46,617	47,003
Facilities, supplies and other costs	64,613	60,976	55,579
Amortization	34,602	33,258	27,288
Depreciation	22,497	22,586	21,471
Total expenses	877,723	780,956	725,662
Income from operations	248,409	211,566	204,065
Net gain from investments	659	14,067	3,360
Interest and dividend income	3,248	5,696	5,829
Interest expense	-535	-504	-585
Equity in earnings of unconsolidated affiliates	118,076	98,671	105,818
Gain on sale of subsidiary (Note 15)	22,112	0	0
Other income (Note 16)	43,429	0	0
Net income before income taxes	435,398	329,496	318,487
Income taxes	146,924	121,462	111,837
Net income	288,474	208,034	206,650
Less: Net income attributable to the noncontrolling interest	-350	-1,186	-1,691
Net income attributable to SEI Investments Company	$288,124	$206,848	$204,959
Basic earnings per common share	$1.68	$1.19	$1.12
Shares used to compute basic earnings per share	171,561	174,295	182,547
Diluted earnings per common share	$1.64	$1.18	$1.11
Shares used to compute diluted earnings per share	175,718	175,872	184,127
Dividends declared per common share	$0.42	$0.63	$0.27

Consolidated_Statements_Of_Com

Consolidated Statements Of Comprehensive Income (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Statement of Comprehensive Income [Abstract]	'	'	'
Net income	$288,474	$208,034	$206,650
Other comprehensive (loss) gain, net of tax:	'	'	'
Foreign currency translation adjustments	-3,760	5,904	-3,195
Unrealized holding (loss) gain on investments:	'	'	'
Unrealized holding (losses) gains during the period, net of income taxes of $(954), $86 and $811	-1,149	341	1,369
Less: reclassification adjustment for gains realized in net income, net of income taxes of $170, $50 and $77	-294	-86	-134
Total other comprehensive (loss) gain, net of taxes	-5,203	6,159	-1,960
Comprehensive income	283,271	214,193	204,690
Less: Comprehensive loss (income) attributable to noncontrolling interest	101	-3,006	-988
Comprehensive income attributable to SEI Investments	$283,372	$211,187	$203,702

Consolidated_Statements_Of_Com1

Consolidated Statements Of Comprehensive Income (Parenthetical) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Statement of Comprehensive Income [Abstract]	'	'	'
Unrealized holding (losses) gains during the period, income tax (benefit) expense	($954)	$86	$811
Reclassification adjustment for gains realized in net income, income tax expense	$170	$50	$77

Consolidated_Statements_Of_Cha

Consolidated Statements Of Changes In Equity (USD $)	Total	Common Stock [Member]	Capital In Excess Of Par Value [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Income [Member]	SEI Investments [Member]	Noncontrolling Interest [Member]
In Thousands, except Share data, unless otherwise specified
Beginning balance at Dec. 31, 2010	'	$1,861	$565,393	$471,159	$3,157	'	'
Beginning balance, shares at Dec. 31, 2010	'	186,141,000	'	'	'	'	'
Increase (Decrease) in Stockholders' Equity [Roll Forward]	'	'	'	'	'	'	'
Purchase and retirement of common stock	'	-111	-27,196	-183,858	'	'	'
Purchase and retirement of common stock, shares	'	-11,109,000	'	'	'	'	'
Issuance of common stock under the employee stock purchase plan	'	1	1,892	'	'	'	'
Issuance of common stock under the employee stock purchase plan, shares	'	110,000	'	'	'	'	'
Issuance of common stock upon exercise of stock options	'	14	22,314	'	'	'	'
Issuance of common stock upon exercise of stock options, shares	1,364,000	1,364,000	'	'	'	'	'
Stock-based compensation	-14,112	'	14,112	'	'	'	'
Tax benefit on stock options exercised	'	'	1,434	'	'	'	'
Net income attributable to SEI Investments Company	204,959	'	'	204,959	'	'	'
Dividends declared ($0.42, $0.63 and $0.27 per share)	-48,558	'	'	-48,558	'	'	'
Other comprehensive (loss) income	-1,960	'	'	'	-1,257	'	'
Total SEI Investments Shareholders' Equity	'	'	'	'	'	1,025,316	'
Noncontrolling Interest	16,143	'	'	'	'	'	16,143
Total Equity at Dec. 31, 2011	1,041,459	1,765	577,949	443,702	1,900	'	'
Ending balance, shares at Dec. 31, 2011	'	176,506,000	'	'	'	'	'
Increase (Decrease) in Stockholders' Equity [Roll Forward]	'	'	'	'	'	'	'
Purchase and retirement of common stock	'	-75	-19,370	-135,819	'	'	'
Purchase and retirement of common stock, shares	'	-7,528,000	'	'	'	'	'
Issuance of common stock under the employee stock purchase plan	'	1	1,794	'	'	'	'
Issuance of common stock under the employee stock purchase plan, shares	'	105,000	'	'	'	'	'
Issuance of common stock upon exercise of stock options	'	31	47,613	'	'	'	'
Issuance of common stock upon exercise of stock options, shares	3,136,000	3,137,000	'	'	'	'	'
Stock-based compensation	-15,736	'	15,736	'	'	'	'
Tax benefit on stock options exercised	'	'	583	'	'	'	'
Net income attributable to SEI Investments Company	206,848	'	'	206,848	'	'	'
Dividends declared ($0.42, $0.63 and $0.27 per share)	-108,817	'	'	-108,817	'	'	'
Other comprehensive (loss) income	6,159	'	'	'	4,339	'	'
Total SEI Investments Shareholders' Equity	1,038,180	'	'	'	'	1,038,180	'
Noncontrolling Interest	19,149	'	'	'	'	'	19,149
Total Equity at Dec. 31, 2012	1,057,329	1,722	624,305	405,914	6,239	'	'
Ending balance, shares at Dec. 31, 2012	172,220,000	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 ($0.42, $0.63 and $0.27 per share)	-71,665	'	'	-71,665	'	'	'
Other comprehensive (loss) income	-5,203	'	'	'	-4,752	'	'
Total SEI Investments Shareholders' Equity	1,156,002	'	'	'	'	1,156,002	'
Noncontrolling Interest	0	'	'	'	'	'	0
Total Equity at Dec. 31, 2013	$1,156,002	$1,692	$721,219	$431,604	$1,487	'	'
Ending balance, shares at Dec. 31, 2013	169,242,000	169,242,000	'	'	'	'	'

Consolidated_Statements_Of_Cha1

Consolidated Statements Of Changes In Equity (Parenthetical) (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Dividends declared per common share	$0.42	$0.63	$0.27
Retained Earnings [Member]	'	'	'
Dividends declared per common share	$0.42	$0.63	$0.27

Consolidated_Statements_Of_Cas

Consolidated Statements Of Cash Flows (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Cash flows from operating activities:	'	'	'
Net income	$288,474	$208,034	$206,650
Depreciation	22,497	22,586	21,471
Amortization	34,602	33,258	27,288
Equity in earnings of unconsolidated affiliates	-118,076	-98,671	-105,818
Distributions received from unconsolidated affiliate	137,104	92,227	109,273
Stock-based compensation	37,865	15,736	14,112
Provision for losses on receivables	-154	-119	-271
Deferred income tax expense	-22,825	-1,191	1,001
Gain from sale of SEI AK (See Note 15)	-22,112	0	0
Net realized gains from investments	-659	-14,067	-3,360
Change in other long-term liabilities	1,575	-1,244	2,631
Change in other assets	600	-619	315
Other	-3,972	6,680	-3,148
Decrease (increase) in Restricted cash for broker-dealer operations	500	0	0
Decrease (increase) in Receivables from regulated investment companies	-8,280	-5,284	3,482
Decrease (increase) in Receivables	-17,513	-30,852	-11,474
Decrease (increase) in Other current assets	1,971	-282	-1,689
Increase (decrease) in Accounts payable	5,000	9,249	-2,583
Increase (decrease) in Accrued liabilities	15,102	21,627	-1,340
Increase (decrease) in Deferred revenue	-475	422	422
Total adjustments	62,750	49,456	50,312
Net cash provided by operating activities	351,224	257,490	256,962
Cash flows from investing activities:	'	'	'
Additions to restricted cash	0	0	-2,000
Additions to property and equipment	-16,351	-23,070	-12,271
Additions to capitalized software	-39,500	-31,004	-40,954
Purchases of marketable securities	-57,560	-33,662	-73,960
Prepayments and maturities of marketable securities	40,257	53,352	61,582
Sales of marketable securities	7,317	54,830	38,247
Purchases of other investments	-2,604	-3,819	-7,500
Sales of other investments	0	0	4,906
Sale of subsidiary, net of cash transferred (See Note 15)	6,028	0	0
Net cash (used in) provided by investing activities	-62,413	16,627	-31,950
Cash flows from financing activities:	'	'	'
Payments on long-term debt	0	0	-95,000
Purchase and retirement of common stock	-206,577	-157,543	-208,932
Proceeds from issuance of common stock	66,367	49,439	24,221
Tax benefit on stock options exercised	11,825	583	1,434
Payment of dividends	-34,400	-135,335	-22,041
Net cash used in financing activities	-162,785	-242,856	-300,318
Net increase (decrease) in cash and cash equivalents	126,026	31,261	-75,306
Cash and cash equivalents, beginning of year	452,247	420,986	496,292
Cash and cash equivalents, end of year	578,273	452,247	420,986
Interest paid	458	367	559
Income taxes paid	163,834	113,160	116,483
Non-cash financing activities	'	'	'
Dividends declared but not paid	$37,314	$0	$26,518

Summary_of_Significant_Account

Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2013
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.
	On July 31, 2012, the Company entered into a definitive agreement to sell all ownership interest in the asset management firm SEI Asset Korea (SEI AK), a joint venture located in South Korea. The Company's ownership interest in SEI AK was 56.1 percent. On March 28, 2013, all conditions subject to closing the transaction were satisfied and all ownership interests in SEI AK were transferred to the buyer (See Note 15).
	Variable Interest Entities
	The Company has involvement with various variable interest entities (VIE or VIEs). These VIEs consist of LSV Employee Group II, LLC (LSV Employee Group II), 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).
	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.
	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 $387,201 and $247,314 at December 31, 2013 and 2012, 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, 2013 and 2012 segregated for regulatory purposes related to trade-execution services conducted by SIEL. Restricted cash also includes $500 and $1,000 at December 31, 2013 and 2012, respectively, 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 all of its trading securities 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 and LSV 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 pass-through certificates, Federal Home Loan Bank (FHLB) and other U.S. government agency short-term notes and investment grade commercial paper. The Company's Level 2 financial assets, with the exception of the GNMA securities, were purchased as part of a cash management program requiring only short term, top-tier investment grade government and corporate securities. The GNMA mortgage-backed pass-through certificates were purchased for the sole purpose of satisfying specific regulatory requirements imposed on our wholly-owned limited purpose federal thrift subsidiary, SPTC. As a result, the Company's Level 2 financial assets are limited to only these types of fixed income securities.
	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’s Level 3 financial assets at December 31, 2012 consisted of an investment product that was in the process of liquidation and was closed to new investors. The Company had no Level 3 financial assets at December 31, 2013.
	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.
	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. The Company's capitalized software development costs primarily relate to the further development of the SEI Wealth PlatformSM (the Platform). The initial version of the Platform was placed into service in July 2007. Further enhancements and upgrades will continue to occur through a series of releases. As of December 31, 2013, the net book value of the Platform was $309,725, net of accumulated amortization of $149,924. Capitalized software development costs in-progress at December 31, 2013 associated with future releases to the Platform were $2,796. The Company capitalized $39,500, $31,004 and $40,954 of software development costs during 2013, 2012 and 2011, 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 the Platform.
	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, which is primarily 3 to 15 years, with a weighted average remaining life of approximately 8.5 years. Amortization expense was $34,375, $32,647 and $26,153 in 2013, 2012 and 2011, respectively, and is included in Amortization expense on the accompanying Consolidated Statements of Operations. The Platform has an estimated useful life of 15 years and a weighted average remaining life of 8.5 years. Amortization expense for the Platform was $34,045, $32,177 and $25,610 in 2013, 2012 and 2011, respectively. During 2012, the Company decided to discontinue the use of specific functionality within the Platform and expensed the remaining net book value of $2,661 related to previously capitalized software development costs of the component. This cost is included in total amortization expense on the accompanying Consolidated Statements of Operations during 2012.
	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. In 2013 and 2012, the Company determined that no events or change in circumstances had occurred that would indicate that capitalized software development costs were impaired. Therefore, no impairment charges were recognized by the Company for any of its capitalized software development costs in 2013 or 2012.
	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 components of the deferred tax assets and liabilities are individually classified as current and non-current based on their characteristics.
	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 2013, 2012 or 2011.
	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 2013, 2012 and 2011 are:
		For the Year Ended December 31, 2013
		Net income		Shares	Per-Share
		attributable		(Denominator)	Amount
		to SEI
		(Numerator)
	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
		For the Year Ended December 31, 2012
		Net income		Shares	Per-Share
		attributable		(Denominator)	Amount
		to SEI
		(Numerator)
	Basic earnings per common share	$	206,848	174,295,000	$	1.19
	Dilutive effect of stock options	—		1,577,000
Diluted earnings per common share	$	206,848	175,872,000	$	1.18
	For the Year Ended December 31, 2011
	Net income		Shares	Per-Share
	attributable		(Denominator)	Amount
	to SEI
	(Numerator)
Basic earnings per common share	$	204,959	182,547,000	$	1.12
Dilutive effect of stock options	—		1,580,000
Diluted earnings per common share	$	204,959	184,127,000	$	1.11
Employee stock options to purchase approximately 7,736,000, 13,202,000 and 15,914,000 shares of common stock, with an average exercise price per share of $30.54, $24.76 and $23.07, were outstanding during 2013, 2012 and 2011, respectively, but not included in the computation of diluted earnings per common share because 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).

Investment_In_Unconsolidated_A

Investment In Unconsolidated Affiliates	12 Months Ended
	Dec. 31, 2013
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). LSV is 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. 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.
	In March 2009, certain partners (the Contributing partners) of LSV, including the Company, designated a portion of their partnership interest for the purpose of providing an interest in the partnership to a select group of key employees. Until such time an interest in the partnership is issued to a key employee, all profits, losses, distributions and other rights and obligations relating to such unissued interests remains with the Contributing partners. Each issuance must be authorized by unanimous vote of all Contributing partners. In April 2012 and April 2013, the Contributing partners agreed to provide certain key employees an interest in LSV, thereby reducing the Company’s interest in LSV from approximately 41.2 percent to approximately 39.3 percent. The issuance in April 2013 reflected the remaining amount of the designated partnership interest of the Contributing partners.
	At December 31, 2013, the Company’s total investment in LSV was $50,595. The investment in LSV exceeded the underlying equity in the net assets of LSV by $3,062 which is considered goodwill embedded in the investment. The Company’s proportionate share in the earnings of LSV was $118,983, $99,989 and $105,818 in 2013, 2012 and 2011, respectively. The Company receives partnership distributions from LSV on a quarterly basis. The Company received partnership distribution payments from LSV of $137,104, $92,227 and $109,273 in 2013, 2012 and 2011, respectively. The Company received an additional partnership distribution payment from LSV during 2013 due to a change in the timing of the payments.
	These tables contain condensed financial information of LSV:
	Condensed Statement of Operations	2013		2012		2011
	Year ended December 31,
	Revenues	$	354,094	$	296,261	$	296,361
	Net income	$	302,316	$	250,165	$	257,519
	Condensed Balance Sheets	2013		2012
	December 31,
	Current assets	$	118,630	$	145,367
	Non-current assets	2,588		3,120
	Total assets	$	121,218	$	148,487
	Current liabilities	$	26,103	$	17,869
	Partners’ capital	95,115		130,618
	Total liabilities and partners’ capital	$	121,218	$	148,487
	Guaranty Agreement with LSV Employee Group II
	In April 2011, a group of existing employees of LSV formed a new limited liability company, LSV Employee Group II, and agreed to purchase a partnership interest of an existing LSV employee for $4,300 of which $3,655 was financed through a new term loan with Bank of America. The Company provided an unsecured guaranty to the lenders of all the obligations of LSV Employee Group II. The lenders will have the right to seek payment from the Company in the event of a default by LSV Employee Group II. The term loan has a four year term and will be repaid from the quarterly distributions of LSV.
	The Company’s direct interest in LSV was unchanged as a result of this transaction. The Company has determined that LSV Employee Group II 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 II either directly or through any financial responsibility from the guaranty.
	As of January 31, 2014, the remaining unpaid principal balance of the term loan was $716. The Company, in its capacity as guarantor, currently has no obligation of payment relating to the term loan of LSV Employee Group II and, furthermore, fully expects that LSV Employee Group II will meet all of their future obligations regarding the term loan.
	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. The loan facility guaranteed by LSV has a three year term and will be repaid from the quarterly distributions of 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 will be made by LSV Employee Group III on the loan facility guaranteed by the Company until the separate loan facility guaranteed by LSV is 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 31, 2014, the remaining unpaid principal balances of the term loans guaranteed by LSV and the Company were $10,108 and $45,000, respectively. 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 has an investment in Gao Fu Limited (Gao Fu), a wealth services firm based in Shanghai in the Republic of China. The Company accounts for its interest in Gao Fu using the equity method because of its less than 50 percent ownership. The Company’s interest in the net assets of Gao Fu is reflected in Investment in unconsolidated affiliates on the accompanying Consolidated Balance Sheets and its interest in the earnings or losses of Gao Fu is reflected in Equity in earnings of unconsolidated affiliates on the accompanying Consolidated Statements of Operations.
	At December 31, 2013, the Company's total investment in Gao Fu was $10,775. The majority of the Company's investment exceeded the underlying equity in the net assets of Gao Fu and is considered goodwill embedded in the investment. The Company's proportionate share in the losses of Gao Fu was $907 and $1,318 in 2013 and 2012, respectively.

Variable_Interest_Entities_Inv

Variable Interest Entities - Investment Products	12 Months Ended
	Dec. 31, 2013
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 received 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_Financi

Composition of Certain Financial Statement Captions	12 Months Ended
	Dec. 31, 2013
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:
		2013			2012
	Trade receivables	$	44,502		$	46,650
	Fees earned, not billed	128,248			116,019
	Other receivables	14,565			9,870
		187,315			172,539
	Less: Allowance for doubtful accounts	(651		)	(805		)
	Receivables, net	$	186,664		$	171,734
	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. In addition, certain fees earned from investment operations services are determined from security valuations which delay billings to clients.
	Property and Equipment
	Property and Equipment on the accompanying Consolidated Balance Sheets consists of:
		2013			2012
	Buildings	$	138,426		$	137,751
	Equipment	70,117			66,167
	Land	9,929			9,929
	Purchased software	96,268			91,468
	Furniture and fixtures	17,060			18,535
	Leasehold improvements	4,670			5,037
	Construction in progress	2,589			112
		339,059			328,999
	Less: Accumulated depreciation	(220,064		)	(201,418		)
	Property and Equipment, net	$	118,995		$	127,581
	Depreciation expense related to property and equipment for 2013, 2012 and 2011 was $22,497, $22,586 and $21,471, respectively.
	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 2013, 2012 and 2011 was $227, $611 and $1,135, respectively.
	Accrued Liabilities
	Accrued Liabilities on the accompanying Consolidated Balance Sheets consist of:
		2013			2012
	Accrued employee compensation	$	69,256		$	63,996
	Accrued employee benefits and other personnel	9,647			7,299
	Accrued consulting, outsourcing and professional fees	19,311			16,676
	Accrued brokerage fees	5,251			5,733
	Accrued sub-advisory, distribution and other asset management fees	25,018			17,548
	Accrued dividend payable	37,314			—
	Other accrued liabilities	22,326			27,053
	Accrued liabilities	$	188,123		$	138,305

Fair_Value_Measurements

Fair Value Measurements	12 Months Ended
	Dec. 31, 2013
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 equity and fixed-income mutual funds that are quoted daily. Level 2 financial assets consist of GNMA mortgage-backed pass-through certificates, FHLB and other U.S. government agency short-term notes and investment grade commercial paper. The Company's Level 2 financial assets, with the exception of the GNMA securities, were purchased as part of a cash management program requiring only short term, top-tier investment grade government and corporate securities. The GNMA mortgage-backed pass-through certificates were purchased for the sole purpose of satisfying specific regulatory requirements imposed on our wholly-owned limited purpose federal thrift subsidiary, SPTC. As a result, the Company's Level 2 financial assets are limited to only these types of fixed income securities. The valuation of the Company's Level 2 financial assets are based upon securities pricing policies and procedures utilized by third-party pricing vendors. The Company's Level 3 financial assets at December 31, 2012 consisted of an investment product that was in the process of liquidation and was closed to new investors. The Company had no financial assets at December 31, 2013 and had no Level 3 financial liabilities at December 31, 2013 or 2012. There were no transfers of financial assets between levels within the fair value hierarchy during 2013 or 2012.
	Valuation of GNMA, Other U.S. Government Agency Securities and Investment Grade Commercial Paper
	All of the Company's investments in GNMA, 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 a security price changed in excess of management's pre-established tolerance levels, 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, 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, 2013
					Fair Value Measurements at Reporting Date Using
			Total		Quoted Prices in		Significant		Significant
					Active  Markets		Other		Unobservable
					for Identical		Observable		Inputs
					Assets		Inputs		(Level 3)
					(Level 1)		(Level 2)
	Assets
	Equity available-for-sale securities		$	11,633	$	11,633	$	—	$	—
	Fixed-income available-for-sale securities		71,690		—		71,690		—
	Fixed income securities owned		21,133		—		21,133		—
	Trading securities		4,849		4,849		—		—
			$	109,305	$	16,482	$	92,823	$	—
					December 31, 2012
					Fair Value Measurements at Reporting Date Using
			Total		Quoted Prices in		Significant		Significant
					Active Markets		Other		Unobservable
					for Identical		Observable		Inputs
					Assets		Inputs		(Level 3)
					(Level 1)		(Level 2)
	Assets
	Equity available-for-sale securities		$	15,926	$	15,926	$	—	$	—
	Fixed-income available-for-sale securities		59,943		—		59,943		—
	Fixed income securities owned		20,088		—		20,088		—
	Trading securities		5,909		4,706		—		1,203
			$	101,866	$	20,632	$	80,031	$	1,203
	The table below presents a reconciliation for all assets and liabilities of the Company measured at fair value on a recurring basis using significant unobservable inputs (Level 3) for the period from January 1, 2012 to December 31, 2013:
		Trading Securities
	Balance, January 1, 2012	$	52,623
	Purchases	13
	Issuances	—
	Principal prepayments and settlements	(10,728		)
	Sales	(53,920		)
	Total gains or (losses) (realized/unrealized):
	Included in earnings	13,215
	Included in other comprehensive income	—
	Transfers in and out of Level 3	—
	Balance, December 31, 2012	$	1,203
	Purchases	—
	Issuances	—
	Principal prepayments and settlements	(1,167		)
	Sales	—
	Total gains or (losses) (realized/unrealized):
	Included in earnings	(36		)
	Included in other comprehensive income	—
	Transfers in and out of Level 3	—
	Balance, December 31, 2013	$	—

Marketable_Securities

Marketable Securities	12 Months Ended
	Dec. 31, 2013
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, 2013
		Cost		Gross		Gross			Fair
				Unrealized		Unrealized			Value
				Gains		(Losses)
	SEI-sponsored mutual funds	$	7,612	$	1,242	$	—		$	8,854
	Equities and other mutual funds	2,615		164		—			2,779
	Debt securities	71,280		410		—			71,690
		$	81,507	$	1,816	$	—		$	83,323
		At December 31, 2012
		Cost		Gross		Gross			Fair
				Unrealized		Unrealized			Value
				Gains		(Losses)
	SEI-sponsored mutual funds	$	12,953	$	376	$	(13	)	$	13,316
	Equities and other mutual funds	2,610		—		—			2,610
	Debt securities	55,923		4,020		—			59,943
		$	71,486	$	4,396	$	(13	)	$	75,869
	Net unrealized holding gains at December 31, 2013 and 2012 were $1,386 (net of income tax expense of $430) and $2,829 (net of income tax expense of $1,554), respectively. These net unrealized gains are reported as a separate component of Accumulated other comprehensive income on the accompanying Consolidated Balance Sheets.
	There were gross realized gains of $1,236 and gross realized losses of $772 from available-for-sale securities during 2013. There were no material gross realized gains or losses from available-for-sale securities during 2012 and 2011. Gains and losses from available-for-sale securities, including amounts reclassified from accumulated comprehensive income, are reflected in Net gain from investments on the accompanying Consolidated Statements of Operations.
	The Company’s debt securities are issued by the Government National Mortgage Association and are backed by the full faith and credit of the U.S. government. These securities were purchased to satisfy applicable regulatory requirements of SPTC and have maturity dates which range from 2020 to 2043.
	Trading Securities
	The Company records all of its trading securities 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 Net gain from investments on the accompanying Consolidated Statements of Operations.
	Trading securities of the Company primarily consist of an investment related to the startup of mutual funds sponsored by LSV. These mutual funds are U.S. dollar denominated funds that invests primarily in securities of Canadian, Australian and Japanese companies as well as various other global securities. The underlying securities held by the funds are translated into U.S. dollars within the funds. The funds had a fair value of $4,849 and $4,706 at December 31, 2013 and 2012, respectively. The Company recognized gains of $143 and $1,004 from the change in fair value of the funds during 2013 and 2012, respectively. There were no material gains or losses from the change in fair value of the funds during 2011.
	During 2012 and 2011, the Company recognized gains from structured investment vehicle (SIV) securities of $13,240 and $3,390, respectively. Of the net gains recognized during 2012, gains of $6,776 resulted from cash payments received from the SIV securities and $1,142 was from a net increase in fair value at December 31, 2012. Of the net gains recognized during 2011, $10,614 resulted from cash payments received from the SIV securities offset by losses of $7,224 which resulted from a decrease in fair value at December 31, 2011. In November 2012, the Company sold its remaining SIV securities, the senior notes issued by Gryphon and recognized a gain of $5,322 from the sale. The Company no longer owns any SIV securities.
	The net gains from the SIV securities are reflected in Net gain from investments on the accompanying Consolidated Statements of Operations.
	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 $21,133 and $20,088 at December 31, 2013 and 2012, respectively. There were no material net gains or losses from the change in fair value of the securities during 2013, 2012 and 2011.

Lines_Of_Credit

Lines Of Credit	12 Months Ended
	Dec. 31, 2013
Line of Credit Facility [Abstract]	'
Lines Of Credit	'
	Lines 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, 2013 or 2012. The Company was in compliance with all covenants of the Credit Facility during 2013.
	The Company incurred $458, $585 and $1,478 in interest charges and commitment fees relating to the current and since expired lines of credit during 2013, 2012 and 2011, respectively, which are reflected in Interest expense on the accompanying Consolidated Statements of Operations.
	The Company’s Canadian subsidiary has a credit facility agreement (the Canadian Credit Facility) for the purpose of facilitating the settlement of mutual fund transactions. The Canadian Credit Facility has no stated expiration date. The amount of the facility is generally limited to $2,000 Canadian dollars or the equivalent amount in U.S. dollars. The Canadian Credit Facility does not contain any covenants which restrict the liquidity or capital resources of the Company. The Company had no borrowings under the Canadian Credit Facility and was in compliance with all covenants during 2013.

Shareholders_Equity

Shareholders' Equity	12 Months Ended
	Dec. 31, 2013
Stockholders' Equity Note [Abstract]	'
Shareholders' Equity	'
	Shareholders’ Equity
	Stock-Based Compensation
	The Company currently has one active equity compensation plan, the 2007 Equity Compensation Plan (the 2007 Plan), which provides for the grant of incentive stock options, non-qualified stock options and stock appreciation rights with respect to up to 20 million shares of common stock of the Company, subject to adjustment for stock splits, reclassifications, mergers and other events. Permitted grantees under the 2007 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 granted non-qualified stock options under the plan.
	The Company discontinued any further grants under the Company’s 1998 Equity Compensation Plan (the 1998 Plan) as a result of the approval of the 2007 Plan. There are no options available for grant from this plan. Grants made from the 1998 Plan continue in effect under the terms of the grant.
	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. Stock options granted prior to 2006 fully vest after seven years from the date of grant. Beginning in 2006, the seven year vesting trigger was eliminated and, as a result, 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 2013, 2012 and 2011 were $10.45, $6.73 and $5.70, respectively, using the following assumptions:
			2013			2012			2011
	Expected term (in years)		6.92			6.75			7.65
	Expected volatility		31.46	%		34.9	%		40.43	%
	Expected dividend yield		1.21	%		1.46	%		1.9	%
	Risk-free interest rate		2.12	%		1.03	%		1.66	%
	The Company recognized stock-based compensation expense in its Consolidated Financial Statements in 2013, 2012 and 2011 as follows:
			2013				2012				2011
	Stock-based compensation expense		$	37,865			$	15,736			$	14,112
	Less: Deferred tax benefit		(13,823		)		(5,650		)		(5,332		)
	Stock-based compensation expense, net of tax		$	24,042			$	10,086			$	8,780
	During 2013, the Company revised its estimates of when some vesting targets are expected to be achieved. These changes in management’s estimates resulted in an increase of $19,637 in stock-based compensation expense in 2013.
	As of December 31, 2013, there was approximately $37,266 of unrecognized compensation cost, adjusted for estimated forfeitures, related to unvested employee stock options that the Company expects will vest and is being amortized. As of December 31, 2013, these costs are expected to be recognized over a weighted average period of 2.6 years.
	This table presents certain information relating to the Company’s stock option plans for 2013, 2012 and 2011:
			Number of			Weighted
			Shares			Avg. Price
	Balance as of December 31, 2010		27,881,000			$	20.42
	Granted		2,534,000			15.77
	Exercised		(1,364,000	)		16.37
	Expired or canceled		(2,008,000	)		22.07
	Balance as of December 31, 2011		27,043,000			$	20.06
	Granted		2,470,000			22.4
	Exercised		(3,136,000	)		15.19
	Expired or canceled		(767,000	)		22.61
	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
	Exercisable as of December 31, 2013		14,601,000			$	19.45
	Available for future grant as of December 31, 2013		744,000
	As of December 31, 2012 and 2011, there were 9,760,000 and 11,680,000 shares exercisable, respectively. The expiration dates for options outstanding at December 31, 2013 range from December 14, 2014 to December 10, 2023 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 2013 and 2012 was $47,392 and $19,565, respectively. The total options exercisable as of December 31, 2013 had an intrinsic value of $223,061. The total options outstanding as of December 31, 2013 had an intrinsic value of $287,237. 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, 2013 and the exercise price of the shares. The market value of the Company’s common stock as of December 31, 2013 was $34.73 as reported by the Nasdaq Stock Market, LLC.
	This table summarizes information relating to all options outstanding and exercisable at December 31, 2013:
						Options Outstanding at December 31, 2013								Options Exercisable at December 31, 2013
	Range of Exercise Prices (Per Share)					Number of Shares			Weighted Average				Weighted Average	Number of Shares	Weighted Average		Weighted Average
									Exercise Price				Remaining		Exercise Price		Remaining
									(Per Share)				Contractual		(Per Share)		Contractual
													Life (Years)				Life (Years)
	$	14.62		-	15.77	5,498,000			$	15.13			6.19	4,304,000	$	14.95	5.69
	17.65			-	19.28	4,921,000			18.27				4.5	4,912,000	18.27		4.49
	20.54			-	23.77	4,051,000			22.08				5.7	2,858,000	21.92		4.35
	23.86			-	29.61	4,979,000			26.57				5.13	2,492,000	26.57		5.09
	31.17			-	33.76	4,188,000			33.15				7.22	35,000	31.17		4
						23,637,000								14,601,000
	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, 2013, 11,658,000 cumulative shares have been issued. There were no material costs incurred by the Company related to the employee stock purchase plan in 2013, 2012 and 2011.
	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, 2013, the Company had approximately $81,070 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 2013, 2012 and 2011:
	Year		Total Number of			Total Cost
			Shares Repurchased
	2013		6,789,000			$	209,942
	2012		7,528,000			155,264
	2011		11,109,000			211,165
	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 22, 2013, the Board of Directors declared a cash dividend of $0.20 per share on the Company’s common stock, which was paid on June 25, 2013, to shareholders of record on June 17, 2013. On December 10, 2013, the Board of Directors declared a cash dividend of $0.22 per share on the Company’s common stock, which was paid on January 10, 2014, to shareholders of record on December 23, 2013.
The cash dividends declared in 2013, 2012 and 2011 were $71,665, $108,817 and $48,558 respectively. The Board of Directors has indicated its intention to declare future cash dividends on a semiannual basis.
Noncontrolling Interest
The following table provides a reconciliation of Noncontrolling interest on the Consolidated Statements of Changes in Equity:
Year Ended December 31,		2013				2012				2011
Noncontrolling interest
Beginning balance		$	19,149			$	16,143			$	15,155
Net income attributable to noncontrolling interest		350				1,186				1,691
Foreign currency translation adjustments		(451		)		1,820				(703		)
Sale of subsidiary (See Note 15)		(19,048		)		—				—
Ending balance		$	—			$	19,149			$	16,143

Accumulated_Other_Comprehensiv

Accumulated Other Comprehensive Income	12 Months Ended
	Dec. 31, 2013
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]	'
Accumulated Other Comprehensive Income (Loss)	'
	Accumulated Other Comprehensive Income
	Other comprehensive income consists of net income and other gains and losses affecting shareholders’ equity that are excluded from net income. For the Company, other comprehensive income includes unrealized gains and losses on available for sale securities and foreign currency translation adjustments. The Company presents other comprehensive income in its Consolidated Statements of Comprehensive Income. Components of Accumulated other comprehensive income consisted of:
		Foreign			Unrealized			Accumulated
		Currency			Holding			Other
		Translation			Gains (Losses)			Comprehensive
		Adjustments			on Investments			Income
	Total accumulated other comprehensive income at January 1, 2011	$	1,152		$	1,339		$	2,491
	Less: Total accumulated other comprehensive loss attributable to noncontrolling interest at January 1, 2011	666			—			666
	Total accumulated other comprehensive income attributable to SEI Investments Company at January 1, 2011	$	1,818		$	1,339		$	3,157
	Other comprehensive loss before reclassifications	(3,195		)	1,369			(1,826		)
	Amounts reclassified from accumulated other comprehensive income	—			(134		)	(134		)
	Total other comprehensive loss	(3,195		)	1,235			(1,960		)
	Less: Total other comprehensive loss attributable to noncontrolling interest	703			—			703
	Total other comprehensive loss attributable to SEI Investments Company	$	(2,492	)	$	1,235		$	(1,257	)
	Total accumulated other comprehensive income at December 31, 2011	(2,043		)	2,574			531
	Less: Total accumulated other comprehensive loss attributable to noncontrolling interest at December 31, 2011	1,369			—			1,369
	Total accumulated other comprehensive income attributable to SEI Investments Company at December 31, 2011	$	(674	)	$	2,574		$	1,900
	Other comprehensive income before reclassifications	5,904			341			6,245
	Amounts reclassified from accumulated other comprehensive income	—			(86		)	(86		)
	Total other comprehensive income	5,904			255			6,159
	Less: Total other comprehensive income attributable to noncontrolling interest	(1,820		)	—			(1,820		)
	Total other comprehensive income attributable to SEI Investments Company	$	4,084		$	255		$	4,339
	Total accumulated other comprehensive income at December 31, 2012	3,861			2,829			6,690
	Less: Total accumulated other comprehensive income attributable to noncontrolling interest at December 31, 2012	(451		)	—			(451		)
	Total accumulated other comprehensive income attributable to SEI Investments Company at December 31, 2012	$	3,410		$	2,829		$	6,239
	Other comprehensive loss before reclassifications	(3,760		)	(1,149		)	(4,909		)
	Amounts reclassified from accumulated other comprehensive income	—			(294		)	(294		)
	Total other comprehensive loss	(3,760		)	(1,443		)	(5,203		)
	Less: Total other comprehensive loss attributable to noncontrolling interest	451			—			451
	Total other comprehensive loss attributable to SEI Investments Company	$	(3,309	)	$	(1,443	)	$	(4,752	)
	Total accumulated other comprehensive income at December 31, 2013	101			1,386			1,487
	Less: Total accumulated other comprehensive income attributable to noncontrolling interest at December 31, 2013	—			—			—
	Total accumulated other comprehensive income attributable to SEI Investments Company at December 31, 2013	$	101		$	1,386		$	1,487

Employee_Benefit_Plan

Employee Benefit Plan	12 Months Ended
	Dec. 31, 2013
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 $5,664, $5,168 and $4,783 to the Plan in 2013, 2012 and 2011, respectively.

Commitments_and_Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2013
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 $21,519, $21,614 and $19,760 in 2013, 2012 and 2011, respectively.
	The aggregate noncancellable minimum commitments at December 31, 2013 are:
	2014	$	7,625
	2015	3,918
	2016	3,160
	2017	2,739
	2018 and thereafter	7,697
		$	25,139
	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, 2013 and 2012 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, State of Louisiana. One of the five actions purports to set forth claims on behalf of a class and also names SPTC as a defendant and, as described below, was certified as a class in December 2012. 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 SPTC under the Louisiana Securities Act. The class action originally included a claim against SEI and SPTC for an alleged violation of the Louisiana Unfair Trade Practices Act. Two of the other 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, State of Louisiana, 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 the actions are purportedly related to the 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.
	Two of the five actions filed in East Baton Rouge were removed to federal court and transferred by the Judicial Panel on Multidistrict Litigation to United States District Court for the Northern District of Texas. On August 31, 2011, the United States District Court for the Northern District of Texas issued an order and judgment that the causes of action alleged against SEI in the two removed actions were preempted by federal law and the court dismissed these cases with prejudice. Plaintiffs appealed this ruling, and on March 19, 2012, a panel of the Court of Appeals for the Fifth Circuit reversed the decision of the United States District Court and remanded the actions for further proceedings. On July 18, 2012, SEI filed a petition for a writ of certiorari in the United States Supreme Court, seeking review of the decision by the United States Court of Appeals in the Fifth Circuit to permit the claims against SEI to proceed. SEI believes that the trial court correctly concluded that the claims against SEI were barred by the federal Securities Litigation Uniform Standards Act and is requesting that the Supreme Court reinstate that dismissal. On January 18, 2013, the Supreme Court granted the petition for a writ of certiorari. On October 7, 2013, the Supreme Court heard oral argument on the appeal and on February 26, 2014 the Supreme Court affirmed the judgment of the Court of Appeals.
	The case filed in Ascension was also removed to federal court and transferred by the Judicial Panel on Multidistrict Litigation to the Northern District of Texas. The schedule for responding to that complaint has not yet been established. The plaintiffs in the remaining two cases in East Baton Rouge have granted SEI and SPTC an extension to respond to the filings. SEI and SPTC filed exceptions in the class action pending in East Baton Rouge, which the Court granted in part and dismissed the claims under the Louisiana Unfair Trade Practices Act and denied in part as to the other exceptions.
	SEI and SPTC filed an answer to the East Baton Rouge class action, plaintiffs filed a motion for class certification; and SEI and SPTC also filed a motion for summary judgment against certain named plaintiffs which the Court stated will not be set for hearing until after the hearing on the class certification motion. The Court in the East Baton Rouge action held a hearing on class certification on September 20, 2012. By oral decision on December 5, 2012 and later entered in a judgment signed on December 17, 2012 that was subsequently amended, the Court in East Baton Rouge certified a class to be composed of persons who purchased any Stanford International Bank certificates of deposit (SIB CDs) in Louisiana between January 1, 2007 and February 13, 2009; persons who renewed any SIB CD 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. On January 30, 2013, SEI and SPTC filed motions for appeal from the judgments that stated SEI's and SPTC's intention to move to stay the litigation. On February 1, 2013, plaintiffs filed a motion for Leave to File First Amended and Restated Class Action Petition in which they ask the Court to allow them to amend the petition in this case to add additional facts that were developed during discovery and adding 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 15, 2013, SEI filed a motion for new trial, or, in the alternative, for reconsideration of the Court's order allowing amendment. On February 22, 2013, SEI filed a motion to stay proceedings in view of the pending Supreme Court case. On February 28, 2013, SEI responded to the First Amended and Restated Class Action Petition by filing an exception. On March 11, 2013, the insurance carrier defendants filed a notice of removal removing the case to the Middle District of Louisiana and on March 18, 2013, the insurance carrier defendants filed answers. On March 13, 2013, SEI notified the Judicial Panel on Multidistrict Litigation (MDL) of this case as a potential tag-along action. On March 19, 2013, plaintiffs filed a motion to remand, a motion for expedited briefing schedule, expedited status conference and expedited consideration of their motion to remand, a motion for leave to file under seal and a motion for order pursuant to 28 U.S.C. 1447(b) requiring removing defendants to supplement federal court record with certified copy of state court record. These motions are now fully briefed. On March 25, 2013, SEI filed a motion that the court decline to adopt the state court's order regarding class certification, which the court dismissed without prejudice to renew upon a determination of removal jurisdiction in an April 12, 2013 order that also dismissed without prejudice a motion to dismiss for lack of jurisdiction and improper venue filed on April 9, 2013 by one of the insurers. On April 1, 2013, the Louisiana Office of Financial Institutions (OFI) filed a motion to remand and sever claims, and a response to that motion by the insurers and opposition to that motion by the plaintiffs were filed on April 22, 2013. Along with the briefing in the Middle District of Louisiana, on March 13, 2013, SEI notified the MDL of this case as a potential tag-along action. On March 19, 2013, plaintiffs notified the MDL that they had filed a motion to remand and asked the panel to decline to issue a conditional transfer order. On March 29, 2013, the MDL issued a conditional transfer order (CTO). On April 18, 2013, OFI filed a motion to vacate the CTO or, in the alternative, stay any ruling to transfer the matter until after the Middle District of Louisiana ruled on OFI's motion to remand and sever. Plaintiffs filed a motion to vacate the CTO on April 19, 2013. SEI's responses to those motions were filed on May 9, 2013. On June 12, 2013, the MDL Panel issued an order notifying the parties that on July 25, 2013, it would consider, without oral argument, Plaintiffs' and OFI's motions to vacate the CTO. On August 7, 2013, the MDL Panel affirmed the CTO and transferred the matter against SEI to the United States District Court for the Northern District of Texas; the MDL Panel also severed the claims against OFI and remanded those claims to the Middle District of Louisiana. On September 11, 2013, defendants filed a motion requesting a status conference with the Court to address the status of all pending motions. On October 4, 2013, Plaintiffs filed a petition for a writ of mandamus asking the United States Court of Appeals for the Fifth Circuit to review the MDL Panel’s transfer Order and on February 14, 2014, the Court denied the petition.
	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 outcome of the proceeding in the United States Supreme Court, 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. The plaintiffs bring the case as a shareholder derivative action against SIMC 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 for an alleged breach of fiduciary duty with respect to compensation received by the adviser. The plaintiffs have brought the suit against SIMC 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 plaintiffs seek: (1) damages for the funds in the amount of the alleged “excessive” fees earned by SIMC beginning from the one year period prior to the filing of the lawsuit, plus interest, costs, and fees; (2) orders declaring that SIMC allegedly violated Section 36(b) and enjoining SIMC from further alleged violations; and (3) rescission of the advisory contracts between SIMC and 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 February 24, 2014, SIMC filed a motion to dismiss the complaint in this lawsuit. While the outcome of this litigation is uncertain given its early phase, SIMC believes that it has valid defenses to plaintiffs' claims and intends to defend the lawsuit vigorously and SIMC is 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, 2013
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,		2013				2012			2011
	Current
	Federal		$	153,856			$	112,247		$	99,448
	State		11,542				5,284			7,067
	Foreign		4,727				4,511			4,603
			170,125				122,042			111,118
	Deferred, including current deferred
	Federal		(2,214		)		(2,708		)	(2,317		)
	State		(16,264		)		(2,199		)	2,477
	Foreign		(4,814		)		3,970			6
			(23,292		)		(937		)	166
	Income taxes attributable to the noncontrolling interest		91				357			553
	Total income taxes		$	146,924			$	121,462		$	111,837
	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 Net income before income taxes are summarized as follows:
	Year Ended December 31,		2013				2012			2011
	Domestic		$	427,915			$	319,907		$	309,391
	Foreign		7,042				8,046			6,852
			$	434,957			$	327,953		$	316,243
	The effective income tax rate differs from the federal income tax statutory rate due to the following:
	Year Ended December 31,	2013			2012			2011
	Statutory rate	35	%		35	%		35	%
	State taxes, net of Federal tax benefit	1.5			1			2
	Foreign tax expense and tax rate differential	0.5			1.6			0.6
	Research and development tax credit	(0.8	)		—			(0.7	)
	Domestic Production Activities Deduction	(0.5	)		(0.6	)		(0.7	)
	PA Tax Law changes and change in valuation allowance on loss carryforwards	(2.4	)		(0.3	)		—
	Domestic Production Activities Deduction, prior years, net	—			—			(1.5	)
	Net change in uncertain tax positions (1)	0.1			0.5			0.4
	Other, net	0.3			(0.3	)		0.1
		33.7	%		36.9	%		35.2	%
	(1) For 2013, (0.23) percent relates to federal issues mainly associated with compilation of foreign tax credits, 0.32 percent relates to state tax issues and the remaining 0.01 percent relates to foreign tax issues. For 2012, 0.15 percent relates to federal issues, 0.33 percent relates to state tax issues and the remaining 0.02 percent relates to foreign tax issues. For 2011, 0.25 percent relates to federal issues and the remaining 0.14 percent relates to state tax issues.
	Undistributed earnings of the Company’s foreign subsidiaries amounted to approximately $52,546 at December 31, 2013. 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 2013, 2012 and 2011 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. 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 current method apportions sales of services to the state where the cost was incurred to perform those services; (2) the Company's current payable was increased by unfavorable temporary differences such as stock option compensation which is not currently deductible but will reverse in the future; thus reducing the Company's deferred tax liability; (3) the Company's current payable decreased as a result of the sale of SEI AK. The deferred taxes accrued in 2012 relating to the cumulative undistributed earnings were included in 2013 tax provision.
	The net deferred income tax liability is comprised of:
	Year Ended December 31,		2013				2012
	Current deferred income taxes:
	Gross assets		$	2,458			$	2,012
	Gross liabilities		(4,111		)		—
			(1,653		)		2,012
	Valuation allowance		—				—
			(1,653		)		2,012
	Long-term deferred income taxes:
	Gross assets		69,483				63,129
	Gross liabilities		(121,317		)		(149,708		)
			(51,834		)		(86,579		)
	Valuation allowance		(14,738		)		(6,879		)
			(66,572		)		(93,458		)
	Net deferred income tax liability		$	(68,225	)		$	(91,446	)
	The valuation allowances against deferred tax assets at December 31, 2013 and 2012 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.
	The tax effect of significant temporary differences representing deferred tax liabilities is:
	Year Ended December 31,		2013				2012
	Difference in financial reporting and income tax depreciation methods		$	(7,043	)		$	(10,104	)
	Reserves not currently deductible		235				325
	Capitalized software currently deductible for tax purposes, net of amortization		(119,800		)		(137,467		)
	State deferred income taxes		251				5,943
	Revenue and expense recognized in different periods for financial reporting and income tax purposes		3,856				4,397
	Unrealized holding gain on investments		(308		)		(1,428		)
	Stock-based compensation expense		45,555				42,133
	State net operating loss carryforward		21,215				13,883
	Valuation allowance on deferred tax assets		(14,738		)		(6,879		)
Federal benefit of state tax deduction for uncertain tax positions		2,643				2,359
Foreign currency exchange		—				(39		)
Foreign deferred including taxes on cumulative undistributed earnings of SEI AK		(91		)		(4,569		)
Net deferred income tax liability		$	(68,225	)		$	(91,446	)
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, 2013 was $12,028, of which $10,139 would affect the effective tax rate if the Company were to recognize the tax benefit. The gross amount of uncertain tax liability of $4,175 which is expected to be paid within one year is netted against the current payable account while the remaining amount of $8,607 is included in Other long-term liabilities on the accompanying Consolidated Balance Sheets. During the year ended December 31, 2013, the Company recognized $1,022 of previously unrecognized tax benefits relating to the lapse of the statute of limitation for certain state filings.
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 2010 and is no longer subject to state, local or foreign income tax examinations by authorities for years before 2007.
A reconciliation of the beginning and ending amount of unrecognized tax benefit is as follows:
		2013				2012			2011
Balance as of January 1		$	11,553			$	9,410		$	5,723
Tax positions related to current year:
Gross additions		1,834				2,196			2,392
Gross reductions		—				—			—
		1,834				2,196			2,392
Tax positions related to prior years:
Gross additions		3,435				1,990			1,992
Gross reductions		—				—			—
		3,435				1,990			1,992
Settlements		(3,772		)		(99		)	—
Lapses on statute of limitations		(1,022		)		(1,944		)	(697		)
Balance as of December 31		$	12,028			$	11,553		$	9,410
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 $754, $770 and $634 in liabilities for tax related interest and penalties in 2013, 2012 and 2011, respectively.
The Company estimates it will recognize $1,067 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, 2013
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 2013, 2012 and 2011, 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, 2013, 2012 and 2011:
		Private			Investment			Institutional			Investment		Investments			Total
		Banks			Advisors			Investors			Managers		In New
													Businesses
		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
		Private			Investment			Institutional			Investment		Investments			Total
		Banks			Advisors			Investors			Managers		In New
													Businesses
		For the Year Ended December 31, 2012
	Revenues	$	364,788		$	202,703		$	227,889		$	193,484	$	3,658		$	992,522
	Expenses	357,001			120,146			116,546			127,525		14,954			736,172
	Operating profit (loss)	$	7,787		$	82,557		$	111,343		$	65,959	$	(11,296	)	$	256,350
		Private			Investment			Institutional			Investment		Investments			Total
		Banks			Advisors			Investors			Managers		In New
													Businesses
		For the Year Ended December 31, 2011
	Revenues	$	348,122		$	189,780		$	210,027		$	177,975	$	3,823		$	929,727
	Expenses	339,339			110,438			106,585			115,963		11,559			683,884
	Operating profit (loss)	$	8,783		$	79,342		$	103,442		$	62,012	$	(7,736	)	$	245,843
	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, 2013, 2012 and 2011 is as follows:
	Year Ended December 31,	2013			2012			2011
	Total operating profit from segments above	$	301,853		$	256,350		$	245,843
	Corporate overhead expenses	(53,733		)	(45,759		)	(43,398		)
	Noncontrolling interest reflected in segments	289			975			1,620
	Income from operations	$	248,409		$	211,566		$	204,065
	The following tables provide additional information for the years ended December 31, 2013, 2012 and 2011 pertaining to our business segments:
		Capital Expenditures									Depreciation
	Year Ended December 31,	2013			2012			2011			2013		2012			2011
	Private Banks	$	34,258		$	32,509		$	35,045		$	15,506	$	15,226		$	15,648
	Investment Advisors	12,611			11,193			11,933			2,091		1,981			2,251
	Institutional Investors	2,712			2,781			2,059			893		1,012			1,079
	Investment Managers	4,871			5,494			3,081			1,970		1,914			1,809
	Investments in New Businesses	639			632			577			1,589		1,716			114
	Total from business segments	$	55,091		$	52,609		$	52,695		$	22,049	$	21,849		$	20,901
	Corporate Overhead	760			1,465			530			448		737			570
		$	55,851		$	54,074		$	53,225		$	22,497	$	22,586		$	21,471
		Amortization
	Year Ended December 31,	2013			2012			2011
	Private Banks	$	22,379		$	22,218		$	18,081
	Investment Advisors	8,234			7,167			6,201
	Institutional Investors	1,274			1,208			864
	Investment Managers	851			804			580
	Investments in New Businesses	1,636			1,249			433
	Total from business segments	$	34,374		$	32,646		$	26,159
	Corporate Overhead	228			612			1,129
		$	34,602		$	33,258		$	27,288
		Total Assets
		2013			2012
	Private Banks	$	430,613		$	481,602
	Investment Advisors	124,028			120,255
Institutional Investors	97,816			99,461
Investment Managers	122,969			118,221
Investments in New Businesses	6,064			5,846
Total from business segments	$	781,490		$	825,385
Corporate Overhead (1)	657,679			484,439
	$	1,439,169		$	1,309,824
(1) 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,	2013			2012			2011
United States	$	962,266		$	843,407		$	785,506
International operations	163,866			149,115			144,221
	$	1,126,132		$	992,522		$	929,727
The following table presents assets based on their location:
	2013			2012
United States	$	1,231,565		$	1,066,451
International operations	207,604			243,373
	$	1,439,169		$	1,309,824

Related_Party_Transactions

Related Party Transactions	12 Months Ended
	Dec. 31, 2013
Related Party Transactions [Abstract]	'
Related Party Transactions	'
	Related Party Transactions
	The Company, either by itself or through its wholly-owned subsidiaries, is a party to Investment Advisory and Administration Agreements with regulated investment companies (RICs) and other investment products which are administered by the Company. These investment products are offered to clients of the Company and its subsidiaries. Under the Investment Advisory and Administration Agreements, the Company receives a fee for providing investment advisory, administrative, and accounting services. The investment advisory and administration fee is a fixed percentage, referred to as basis points, of the average daily net assets, subject to certain limitations. Investment advisory and administration fees received by the Company totaled $422,825, $380,645 and $364,602 in 2013, 2012 and 2011, respectively. The Company is also a party to various agreements with several RICs which are advised and/or administered by the Company. The Company receives a fee for providing shareholder, administrative and distribution services pursuant to the provisions of various shareholder service, administrative service, and distribution plans adopted by the RICs. These fees totaled $47,988, $37,827 and $39,017 in 2013, 2012 and 2011, respectively. A portion of the transaction costs incurred by the RICs for securities transactions are directed to the Company’s broker-dealer subsidiary in its capacity as an introducing broker-dealer. The Company recognized $620, $1,213 and $2,772 in commissions during 2013, 2012 and 2011, respectively.
	Receivables from regulated investment companies 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, 2013
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 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 Asset Management Limited. 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 expects to receive the full amount of the portion of the contingent purchase price related to the one-year period ended December 31, 2013 during the three months ended March 31, 2014. Also, 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. Without regard to the contingent purchase price, the Company recognized a gain of $22,112, or $0.08 diluted and basic earnings per share, during 2013 as a result of the sale. The Company's gain from the sale of SEI AK is included in Gain on sale of subsidiary on the accompanying Consolidated Statement of Operations.
	Excluding the contingent purchase price, the Company received gross proceeds of $56,879 from the sale. The Company incurred $2,545 in transaction costs during 2013 for net proceeds of $54,334 resulting from the sale. The net effect of the cash received from the sale and the transfer of cash balances to the owners is reflected in Sale of subsidiary, net of cash transferred in the investing section of the Consolidated Statement of Cash flows.
	The Company's ownership interest in SEI AK was 56.1 percent. The Company consolidated the assets, liabilities and operations of SEI AK in its Consolidated Financial Statements. As of December 31, 2012, SEI AK had total corporate assets of $54,783, of which $48,306 was included in Cash and cash equivalents on the Consolidated Balance Sheet. All other accounts of SEI AK were not material to any financial statement line item in the Consolidated Financial Statements. The ownership interests in SEI AK of MetLife and IFC were reflected in Noncontrolling interest in the Consolidated Financial Statements.
	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
					2012			2011
	Revenues	$	2,889		$	11,514		$	11,932
	Net income	$	796		$	2,703		$	3,851
	Less: Income attributable to the noncontrolling interests	(350		)	(1,186		)	(1,691		)
	Net income attributable to SEI AK	$	446		$	1,517		$	2,160

Settlement_Agreement

Settlement Agreement	12 Months Ended
	Dec. 31, 2013
Litigation Settlement [Abstract]	'
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, 2013
Quarterly Financial Data [Abstract]	'
Quarterly Financial Data	'
	Quarterly Financial Data (Unaudited)
		For the Three Months Ended
	2013	March 31			June 30			30-Sep			31-Dec
	Revenues	$	271,879		$	274,574		$	280,655		$	299,024
	Income before income taxes	$	110,962		$	129,387		$	93,986		$	101,063
	Net income attributable to SEI	$	71,920		$	83,494		$	67,195		$	65,515
	Basic earnings per share	$	0.42		$	0.48		$	0.39		$	0.39
	Diluted earnings per share	$	0.41		$	0.47		$	0.38		$	0.37
	Effective income tax rate	34.9		%	35.5		%	28.5		%	35.2		%
	Gain on sale of subsidiary (Note 15)	$	22,112		$	—		$	—		$	—
	Diluted earnings per share (1)	$	0.08		$	—		$	—		$	—
	Settlement agreement (Note 16)	$	—		$	43,429		$	—		$	—
	Diluted earnings per share (2)	$	—		$	0.16		$	—		$	—
	(1) Attributable to gain on sale of subsidiary.
	(2) Attributable to settlement agreement.
		For the Three Months Ended
	2012	March 31			June 30			30-Sep			31-Dec
	Revenues	$	237,898		$	241,237		$	251,752		$	261,635
	Income before income taxes	$	79,950		$	78,501		$	83,501		$	87,544
	Net income attributable to SEI	$	49,965		$	49,555		$	50,743		$	56,585
	Basic earnings per share	$	0.28		$	0.28		$	0.29		$	0.33
	Diluted earnings per share	$	0.28		$	0.28		$	0.29		$	0.32
	Effective income tax rate	37.2		%	36.6		%	39		%	35		%
	Total SIV-related gains	$	2,882		$	1,072		$	3,389		$	5,897
	Diluted earnings per share (3)	$	0.01		$	—		$	0.01		$	0.02
	(3) Attributable to SIV-related gains.

Schedule_II_Valuation_And_Qual

Schedule II - Valuation And Qualifying Accounts And Reserves	12 Months Ended
	Dec. 31, 2013
Valuation and Qualifying Accounts [Abstract]	'
Schedule II - Valuation and Qualifying Accounts and Reserves	'
	Year Ended December 31,			Additions
	Description	Balance at		Charged to			Charged		(Deductions)			Balance
		Beginning		Costs and			to Other					at End
		of Year		Expenses			Accounts					of Year
	Allowance for doubtful accounts:
	2013	$	805	$	—		$	—	$	(154	)	$	651
	2012	924		—			—		(119		)	805
	2011	1,195		—			—		(271		)	924
	Deferred income tax valuation allowance:
	2013	$	6,879	$	(485	)	$	8,344	$	—		$	14,738
	2012	8,585		(1,706		)	—		—			6,879
	2011	9,008		(423		)	—		—			8,585

Summary_of_Significant_Account1

Summary of Significant Accounting Policies (Policy)	12 Months Ended
	Dec. 31, 2013
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 II, LLC (LSV Employee Group II), 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).
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.
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 all of its trading securities 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 and LSV 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 pass-through certificates, Federal Home Loan Bank (FHLB) and other U.S. government agency short-term notes and investment grade commercial paper. The Company's Level 2 financial assets, with the exception of the GNMA securities, were purchased as part of a cash management program requiring only short term, top-tier investment grade government and corporate securities. The GNMA mortgage-backed pass-through certificates were purchased for the sole purpose of satisfying specific regulatory requirements imposed on our wholly-owned limited purpose federal thrift subsidiary, SPTC. As a result, the Company's Level 2 financial assets are limited to only these types of fixed income securities.
	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’s Level 3 financial assets at December 31, 2012 consisted of an investment product that was in the process of liquidation and was closed to new investors. The Company had no Level 3 financial assets at December 31, 2013.
	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.
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. The Company's capitalized software development costs primarily relate to the further development of the SEI Wealth PlatformSM (the Platform). The initial version of the Platform was placed into service in July 2007. Further enhancements and upgrades will continue to occur through a series of releases. As of December 31, 2013, the net book value of the Platform was $309,725, net of accumulated amortization of $149,924. Capitalized software development costs in-progress at December 31, 2013 associated with future releases to the Platform were $2,796. The Company capitalized $39,500, $31,004 and $40,954 of software development costs during 2013, 2012 and 2011, 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 the Platform.
	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, which is primarily 3 to 15 years, with a weighted average remaining life of approximately 8.5 years. Amortization expense was $34,375, $32,647 and $26,153 in 2013, 2012 and 2011, respectively, and is included in Amortization expense on the accompanying Consolidated Statements of Operations. The Platform has an estimated useful life of 15 years and a weighted average remaining life of 8.5 years. Amortization expense for the Platform was $34,045, $32,177 and $25,610 in 2013, 2012 and 2011, respectively. During 2012, the Company decided to discontinue the use of specific functionality within the Platform and expensed the remaining net book value of $2,661 related to previously capitalized software development costs of the component. This cost is included in total amortization expense on the accompanying Consolidated Statements of Operations during 2012.
	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 components of the deferred tax assets and liabilities are individually classified as current and non-current based on their characteristics.
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
Investments in Equity Method Investments	'
	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.
Trading Securities	'
	The Company records all of its trading securities 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 Net gain from investments on the accompanying Consolidated Statements of Operations.
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_Account2

Summary of Significant Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2013
Accounting Policies [Abstract]	'
Calculation Of Basic And Diluted Earnings Per Share	'
	The calculations of basic and diluted earnings per share for 2013, 2012 and 2011 are:
		For the Year Ended December 31, 2013
		Net income		Shares	Per-Share
		attributable		(Denominator)	Amount
		to SEI
		(Numerator)
	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
		For the Year Ended December 31, 2012
		Net income		Shares	Per-Share
		attributable		(Denominator)	Amount
		to SEI
		(Numerator)
	Basic earnings per common share	$	206,848	174,295,000	$	1.19
	Dilutive effect of stock options	—		1,577,000
	Diluted earnings per common share	$	206,848	175,872,000	$	1.18
		For the Year Ended December 31, 2011
		Net income		Shares	Per-Share
		attributable		(Denominator)	Amount
		to SEI
		(Numerator)
	Basic earnings per common share	$	204,959	182,547,000	$	1.12
	Dilutive effect of stock options	—		1,580,000
	Diluted earnings per common share	$	204,959	184,127,000	$	1.11

Investment_In_Unconsolidated_A1

Investment In Unconsolidated Affiliates (Tables)	12 Months Ended
	Dec. 31, 2013
Equity Method Investments and Joint Ventures [Abstract]	'
Equity Method Investments	'
	These tables contain condensed financial information of LSV:
	Condensed Statement of Operations	2013		2012		2011
	Year ended December 31,
	Revenues	$	354,094	$	296,261	$	296,361
	Net income	$	302,316	$	250,165	$	257,519
	Condensed Balance Sheets	2013		2012
	December 31,
	Current assets	$	118,630	$	145,367
	Non-current assets	2,588		3,120
	Total assets	$	121,218	$	148,487
	Current liabilities	$	26,103	$	17,869
	Partners’ capital	95,115		130,618
	Total liabilities and partners’ capital	$	121,218	$	148,487

Composition_of_Certain_Financi1

Composition of Certain Financial Statement Captions (Tables)	12 Months Ended
	Dec. 31, 2013
Items Included in Consolidated Statement of Financial Condition [Abstract]	'
Receivables	'
	Receivables on the accompanying Consolidated Balance Sheets consist of:
		2013			2012
	Trade receivables	$	44,502		$	46,650
	Fees earned, not billed	128,248			116,019
	Other receivables	14,565			9,870
		187,315			172,539
	Less: Allowance for doubtful accounts	(651		)	(805		)
	Receivables, net	$	186,664		$	171,734
Property And Equipment	'
	Property and Equipment on the accompanying Consolidated Balance Sheets consists of:
		2013			2012
	Buildings	$	138,426		$	137,751
	Equipment	70,117			66,167
	Land	9,929			9,929
	Purchased software	96,268			91,468
	Furniture and fixtures	17,060			18,535
	Leasehold improvements	4,670			5,037
	Construction in progress	2,589			112
		339,059			328,999
	Less: Accumulated depreciation	(220,064		)	(201,418		)
	Property and Equipment, net	$	118,995		$	127,581
Accrued Liabilities	'
	Accrued Liabilities on the accompanying Consolidated Balance Sheets consist of:
		2013			2012
	Accrued employee compensation	$	69,256		$	63,996
	Accrued employee benefits and other personnel	9,647			7,299
	Accrued consulting, outsourcing and professional fees	19,311			16,676
	Accrued brokerage fees	5,251			5,733
	Accrued sub-advisory, distribution and other asset management fees	25,018			17,548
	Accrued dividend payable	37,314			—
	Other accrued liabilities	22,326			27,053
	Accrued liabilities	$	188,123		$	138,305

Fair_Value_Measurements_Tables

Fair Value Measurements (Tables)	12 Months Ended
	Dec. 31, 2013
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, 2013
					Fair Value Measurements at Reporting Date Using
			Total		Quoted Prices in		Significant		Significant
					Active  Markets		Other		Unobservable
					for Identical		Observable		Inputs
					Assets		Inputs		(Level 3)
					(Level 1)		(Level 2)
	Assets
	Equity available-for-sale securities		$	11,633	$	11,633	$	—	$	—
	Fixed-income available-for-sale securities		71,690		—		71,690		—
	Fixed income securities owned		21,133		—		21,133		—
	Trading securities		4,849		4,849		—		—
			$	109,305	$	16,482	$	92,823	$	—
					December 31, 2012
					Fair Value Measurements at Reporting Date Using
			Total		Quoted Prices in		Significant		Significant
					Active Markets		Other		Unobservable
					for Identical		Observable		Inputs
					Assets		Inputs		(Level 3)
					(Level 1)		(Level 2)
	Assets
	Equity available-for-sale securities		$	15,926	$	15,926	$	—	$	—
	Fixed-income available-for-sale securities		59,943		—		59,943		—
	Fixed income securities owned		20,088		—		20,088		—
	Trading securities		5,909		4,706		—		1,203
			$	101,866	$	20,632	$	80,031	$	1,203
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation	'
	The table below presents a reconciliation for all assets and liabilities of the Company measured at fair value on a recurring basis using significant unobservable inputs (Level 3) for the period from January 1, 2012 to December 31, 2013:
		Trading Securities
	Balance, January 1, 2012	$	52,623
	Purchases	13
	Issuances	—
	Principal prepayments and settlements	(10,728		)
	Sales	(53,920		)
	Total gains or (losses) (realized/unrealized):
	Included in earnings	13,215
	Included in other comprehensive income	—
	Transfers in and out of Level 3	—
	Balance, December 31, 2012	$	1,203
	Purchases	—
	Issuances	—
	Principal prepayments and settlements	(1,167		)
	Sales	—
	Total gains or (losses) (realized/unrealized):
	Included in earnings	(36		)
	Included in other comprehensive income	—
	Transfers in and out of Level 3	—
	Balance, December 31, 2013	$	—

Marketable_Securities_Tables

Marketable Securities (Tables)	12 Months Ended
	Dec. 31, 2013
Marketable Securities [Abstract]	'
Investments Available For Sale	'
	Investments available for sale classified as non-current assets consist of:
		At December 31, 2013
		Cost		Gross		Gross			Fair
				Unrealized		Unrealized			Value
				Gains		(Losses)
	SEI-sponsored mutual funds	$	7,612	$	1,242	$	—		$	8,854
	Equities and other mutual funds	2,615		164		—			2,779
	Debt securities	71,280		410		—			71,690
		$	81,507	$	1,816	$	—		$	83,323
		At December 31, 2012
		Cost		Gross		Gross			Fair
				Unrealized		Unrealized			Value
				Gains		(Losses)
	SEI-sponsored mutual funds	$	12,953	$	376	$	(13	)	$	13,316
	Equities and other mutual funds	2,610		—		—			2,610
	Debt securities	55,923		4,020		—			59,943
		$	71,486	$	4,396	$	(13	)	$	75,869

Shareholders_Equity_Tables

Shareholders' Equity (Tables)	12 Months Ended
	Dec. 31, 2013
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 2013, 2012 and 2011 were $10.45, $6.73 and $5.70, respectively, using the following assumptions:
			2013			2012			2011
	Expected term (in years)		6.92			6.75			7.65
	Expected volatility		31.46	%		34.9	%		40.43	%
	Expected dividend yield		1.21	%		1.46	%		1.9	%
	Risk-free interest rate		2.12	%		1.03	%		1.66	%
Stock-based Compensation Expense	'
	The Company recognized stock-based compensation expense in its Consolidated Financial Statements in 2013, 2012 and 2011 as follows:
			2013				2012				2011
	Stock-based compensation expense		$	37,865			$	15,736			$	14,112
	Less: Deferred tax benefit		(13,823		)		(5,650		)		(5,332		)
	Stock-based compensation expense, net of tax		$	24,042			$	10,086			$	8,780
Stock Option Plans	'
	This table presents certain information relating to the Company’s stock option plans for 2013, 2012 and 2011:
			Number of			Weighted
			Shares			Avg. Price
	Balance as of December 31, 2010		27,881,000			$	20.42
	Granted		2,534,000			15.77
	Exercised		(1,364,000	)		16.37
	Expired or canceled		(2,008,000	)		22.07
	Balance as of December 31, 2011		27,043,000			$	20.06
	Granted		2,470,000			22.4
	Exercised		(3,136,000	)		15.19
	Expired or canceled		(767,000	)		22.61
	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
	Exercisable as of December 31, 2013		14,601,000			$	19.45
	Available for future grant as of December 31, 2013		744,000
Stock Options Outstanding And Exercisable	'
	This table summarizes information relating to all options outstanding and exercisable at December 31, 2013:
						Options Outstanding at December 31, 2013								Options Exercisable at December 31, 2013
	Range of Exercise Prices (Per Share)					Number of Shares			Weighted Average				Weighted Average	Number of Shares	Weighted Average		Weighted Average
									Exercise Price				Remaining		Exercise Price		Remaining
									(Per Share)				Contractual		(Per Share)		Contractual
													Life (Years)				Life (Years)
	$	14.62		-	15.77	5,498,000			$	15.13			6.19	4,304,000	$	14.95	5.69
	17.65			-	19.28	4,921,000			18.27				4.5	4,912,000	18.27		4.49
	20.54			-	23.77	4,051,000			22.08				5.7	2,858,000	21.92		4.35
	23.86			-	29.61	4,979,000			26.57				5.13	2,492,000	26.57		5.09
	31.17			-	33.76	4,188,000			33.15				7.22	35,000	31.17		4
						23,637,000								14,601,000
Common Stock Buyback	'
	The following table provides the total number of shares repurchased and the related total costs in 2013, 2012 and 2011:
	Year		Total Number of			Total Cost
			Shares Repurchased
	2013		6,789,000			$	209,942
	2012		7,528,000			155,264
	2011		11,109,000			211,165
Reconciliation Of Noncontrolling Interest On The Consolidated Statements Of Changes In Equity	'
	The following table provides a reconciliation of Noncontrolling interest on the Consolidated Statements of Changes in Equity:
	Year Ended December 31,		2013				2012				2011
	Noncontrolling interest
	Beginning balance		$	19,149			$	16,143			$	15,155
	Net income attributable to noncontrolling interest		350				1,186				1,691
	Foreign currency translation adjustments		(451		)		1,820				(703		)
	Sale of subsidiary (See Note 15)		(19,048		)		—				—
	Ending balance		$	—			$	19,149			$	16,143

Accumulated_Other_Comprehensiv1

Accumulated Other Comprehensive Income (Tables)	12 Months Ended
	Dec. 31, 2013
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 consisted of:
		Foreign			Unrealized			Accumulated
		Currency			Holding			Other
		Translation			Gains (Losses)			Comprehensive
		Adjustments			on Investments			Income
	Total accumulated other comprehensive income at January 1, 2011	$	1,152		$	1,339		$	2,491
	Less: Total accumulated other comprehensive loss attributable to noncontrolling interest at January 1, 2011	666			—			666
	Total accumulated other comprehensive income attributable to SEI Investments Company at January 1, 2011	$	1,818		$	1,339		$	3,157
	Other comprehensive loss before reclassifications	(3,195		)	1,369			(1,826		)
	Amounts reclassified from accumulated other comprehensive income	—			(134		)	(134		)
	Total other comprehensive loss	(3,195		)	1,235			(1,960		)
	Less: Total other comprehensive loss attributable to noncontrolling interest	703			—			703
	Total other comprehensive loss attributable to SEI Investments Company	$	(2,492	)	$	1,235		$	(1,257	)
	Total accumulated other comprehensive income at December 31, 2011	(2,043		)	2,574			531
	Less: Total accumulated other comprehensive loss attributable to noncontrolling interest at December 31, 2011	1,369			—			1,369
	Total accumulated other comprehensive income attributable to SEI Investments Company at December 31, 2011	$	(674	)	$	2,574		$	1,900
	Other comprehensive income before reclassifications	5,904			341			6,245
	Amounts reclassified from accumulated other comprehensive income	—			(86		)	(86		)
	Total other comprehensive income	5,904			255			6,159
	Less: Total other comprehensive income attributable to noncontrolling interest	(1,820		)	—			(1,820		)
	Total other comprehensive income attributable to SEI Investments Company	$	4,084		$	255		$	4,339
	Total accumulated other comprehensive income at December 31, 2012	3,861			2,829			6,690
	Less: Total accumulated other comprehensive income attributable to noncontrolling interest at December 31, 2012	(451		)	—			(451		)
	Total accumulated other comprehensive income attributable to SEI Investments Company at December 31, 2012	$	3,410		$	2,829		$	6,239
	Other comprehensive loss before reclassifications	(3,760		)	(1,149		)	(4,909		)
	Amounts reclassified from accumulated other comprehensive income	—			(294		)	(294		)
	Total other comprehensive loss	(3,760		)	(1,443		)	(5,203		)
	Less: Total other comprehensive loss attributable to noncontrolling interest	451			—			451
	Total other comprehensive loss attributable to SEI Investments Company	$	(3,309	)	$	(1,443	)	$	(4,752	)
	Total accumulated other comprehensive income at December 31, 2013	101			1,386			1,487
	Less: Total accumulated other comprehensive income attributable to noncontrolling interest at December 31, 2013	—			—			—
	Total accumulated other comprehensive income attributable to SEI Investments Company at December 31, 2013	$	101		$	1,386		$	1,487

Commitments_and_Contingencies_

Commitments and Contingencies (Tables)	12 Months Ended
	Dec. 31, 2013
Commitments and Contingencies Disclosure [Abstract]	'
Schedule Of Noncancellable Minimum Commitments	'
	The aggregate noncancellable minimum commitments at December 31, 2013 are:
	2014	$	7,625
	2015	3,918
	2016	3,160
	2017	2,739
	2018 and thereafter	7,697
		$	25,139

Income_Taxes_Tables

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2013
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,		2013				2012			2011
	Current
	Federal		$	153,856			$	112,247		$	99,448
	State		11,542				5,284			7,067
	Foreign		4,727				4,511			4,603
			170,125				122,042			111,118
	Deferred, including current deferred
	Federal		(2,214		)		(2,708		)	(2,317		)
	State		(16,264		)		(2,199		)	2,477
	Foreign		(4,814		)		3,970			6
			(23,292		)		(937		)	166
	Income taxes attributable to the noncontrolling interest		91				357			553
	Total income taxes		$	146,924			$	121,462		$	111,837
Components of Net Income Before Income Taxes	'
	The components of Net income before income taxes are summarized as follows:
	Year Ended December 31,		2013				2012			2011
	Domestic		$	427,915			$	319,907		$	309,391
	Foreign		7,042				8,046			6,852
			$	434,957			$	327,953		$	316,243
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,	2013			2012			2011
	Statutory rate	35	%		35	%		35	%
	State taxes, net of Federal tax benefit	1.5			1			2
	Foreign tax expense and tax rate differential	0.5			1.6			0.6
	Research and development tax credit	(0.8	)		—			(0.7	)
	Domestic Production Activities Deduction	(0.5	)		(0.6	)		(0.7	)
	PA Tax Law changes and change in valuation allowance on loss carryforwards	(2.4	)		(0.3	)		—
	Domestic Production Activities Deduction, prior years, net	—			—			(1.5	)
	Net change in uncertain tax positions (1)	0.1			0.5			0.4
	Other, net	0.3			(0.3	)		0.1
		33.7	%		36.9	%		35.2	%
	(1) For 2013, (0.23) percent relates to federal issues mainly associated with compilation of foreign tax credits, 0.32 percent relates to state tax issues and the remaining 0.01 percent relates to foreign tax issues. For 2012, 0.15 percent relates to federal issues, 0.33 percent relates to state tax issues and the remaining 0.02 percent relates to foreign tax issues. For 2011, 0.25 percent relates to federal issues and the remaining 0.14 percent relates to state tax issues.
Schedule of Deferred Tax Assets and Liabilities	'
	The net deferred income tax liability is comprised of:
	Year Ended December 31,		2013				2012
	Current deferred income taxes:
	Gross assets		$	2,458			$	2,012
	Gross liabilities		(4,111		)		—
			(1,653		)		2,012
	Valuation allowance		—				—
			(1,653		)		2,012
	Long-term deferred income taxes:
	Gross assets		69,483				63,129
	Gross liabilities		(121,317		)		(149,708		)
			(51,834		)		(86,579		)
	Valuation allowance		(14,738		)		(6,879		)
			(66,572		)		(93,458		)
	Net deferred income tax liability		$	(68,225	)		$	(91,446	)
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,		2013				2012
	Difference in financial reporting and income tax depreciation methods		$	(7,043	)		$	(10,104	)
	Reserves not currently deductible		235				325
	Capitalized software currently deductible for tax purposes, net of amortization		(119,800		)		(137,467		)
	State deferred income taxes		251				5,943
	Revenue and expense recognized in different periods for financial reporting and income tax purposes		3,856				4,397
	Unrealized holding gain on investments		(308		)		(1,428		)
	Stock-based compensation expense		45,555				42,133
	State net operating loss carryforward		21,215				13,883
	Valuation allowance on deferred tax assets		(14,738		)		(6,879		)
	Federal benefit of state tax deduction for uncertain tax positions		2,643				2,359
	Foreign currency exchange		—				(39		)
	Foreign deferred including taxes on cumulative undistributed earnings of SEI AK		(91		)		(4,569		)
	Net deferred income tax liability		$	(68,225	)		$	(91,446	)
Schedule of Unrecognized Tax Benefits Roll Forward	'
	A reconciliation of the beginning and ending amount of unrecognized tax benefit is as follows:
			2013				2012			2011
	Balance as of January 1		$	11,553			$	9,410		$	5,723
	Tax positions related to current year:
	Gross additions		1,834				2,196			2,392
	Gross reductions		—				—			—
			1,834				2,196			2,392
	Tax positions related to prior years:
	Gross additions		3,435				1,990			1,992
	Gross reductions		—				—			—
			3,435				1,990			1,992
	Settlements		(3,772		)		(99		)	—
	Lapses on statute of limitations		(1,022		)		(1,944		)	(697		)
	Balance as of December 31		$	12,028			$	11,553		$	9,410

Business_Segment_Information_T

Business Segment Information (Tables)	12 Months Ended
	Dec. 31, 2013
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, 2013, 2012 and 2011:
		Private			Investment			Institutional			Investment		Investments			Total
		Banks			Advisors			Investors			Managers		In New
													Businesses
		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
		Private			Investment			Institutional			Investment		Investments			Total
		Banks			Advisors			Investors			Managers		In New
													Businesses
		For the Year Ended December 31, 2012
	Revenues	$	364,788		$	202,703		$	227,889		$	193,484	$	3,658		$	992,522
	Expenses	357,001			120,146			116,546			127,525		14,954			736,172
	Operating profit (loss)	$	7,787		$	82,557		$	111,343		$	65,959	$	(11,296	)	$	256,350
		Private			Investment			Institutional			Investment		Investments			Total
		Banks			Advisors			Investors			Managers		In New
													Businesses
		For the Year Ended December 31, 2011
	Revenues	$	348,122		$	189,780		$	210,027		$	177,975	$	3,823		$	929,727
	Expenses	339,339			110,438			106,585			115,963		11,559			683,884
	Operating profit (loss)	$	8,783		$	79,342		$	103,442		$	62,012	$	(7,736	)	$	245,843
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, 2013, 2012 and 2011 is as follows:
	Year Ended December 31,	2013			2012			2011
	Total operating profit from segments above	$	301,853		$	256,350		$	245,843
	Corporate overhead expenses	(53,733		)	(45,759		)	(43,398		)
	Noncontrolling interest reflected in segments	289			975			1,620
	Income from operations	$	248,409		$	211,566		$	204,065
Additional Information Pertaining To Business Segments	'
	The following tables provide additional information for the years ended December 31, 2013, 2012 and 2011 pertaining to our business segments:
		Capital Expenditures									Depreciation
	Year Ended December 31,	2013			2012			2011			2013		2012			2011
	Private Banks	$	34,258		$	32,509		$	35,045		$	15,506	$	15,226		$	15,648
	Investment Advisors	12,611			11,193			11,933			2,091		1,981			2,251
	Institutional Investors	2,712			2,781			2,059			893		1,012			1,079
	Investment Managers	4,871			5,494			3,081			1,970		1,914			1,809
	Investments in New Businesses	639			632			577			1,589		1,716			114
	Total from business segments	$	55,091		$	52,609		$	52,695		$	22,049	$	21,849		$	20,901
	Corporate Overhead	760			1,465			530			448		737			570
		$	55,851		$	54,074		$	53,225		$	22,497	$	22,586		$	21,471
		Amortization
	Year Ended December 31,	2013			2012			2011
	Private Banks	$	22,379		$	22,218		$	18,081
	Investment Advisors	8,234			7,167			6,201
	Institutional Investors	1,274			1,208			864
	Investment Managers	851			804			580
	Investments in New Businesses	1,636			1,249			433
	Total from business segments	$	34,374		$	32,646		$	26,159
	Corporate Overhead	228			612			1,129
		$	34,602		$	33,258		$	27,288
		Total Assets
		2013			2012
	Private Banks	$	430,613		$	481,602
	Investment Advisors	124,028			120,255
	Institutional Investors	97,816			99,461
	Investment Managers	122,969			118,221
	Investments in New Businesses	6,064			5,846
	Total from business segments	$	781,490		$	825,385
	Corporate Overhead (1)	657,679			484,439
		$	1,439,169		$	1,309,824
	(1) 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,	2013			2012			2011
	United States	$	962,266		$	843,407		$	785,506
	International operations	163,866			149,115			144,221
		$	1,126,132		$	992,522		$	929,727
	The following table presents assets based on their location:
		2013			2012
	United States	$	1,231,565		$	1,066,451
	International operations	207,604			243,373
		$	1,439,169		$	1,309,824

Sale_of_SEI_Asset_Korea_Tables

Sale of SEI Asset Korea (Tables)	12 Months Ended
	Dec. 31, 2013
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
					2012			2011
	Revenues	$	2,889		$	11,514		$	11,932
	Net income	$	796		$	2,703		$	3,851
	Less: Income attributable to the noncontrolling interests	(350		)	(1,186		)	(1,691		)
	Net income attributable to SEI AK	$	446		$	1,517		$	2,160

Quarterly_Financial_Data_Table

Quarterly Financial Data (Tables)	12 Months Ended
	Dec. 31, 2013
Quarterly Financial Data [Abstract]	'
Quarterly Financial Data	'
	Quarterly Financial Data (Unaudited)
		For the Three Months Ended
	2013	March 31			June 30			30-Sep			31-Dec
	Revenues	$	271,879		$	274,574		$	280,655		$	299,024
	Income before income taxes	$	110,962		$	129,387		$	93,986		$	101,063
	Net income attributable to SEI	$	71,920		$	83,494		$	67,195		$	65,515
	Basic earnings per share	$	0.42		$	0.48		$	0.39		$	0.39
	Diluted earnings per share	$	0.41		$	0.47		$	0.38		$	0.37
	Effective income tax rate	34.9		%	35.5		%	28.5		%	35.2		%
	Gain on sale of subsidiary (Note 15)	$	22,112		$	—		$	—		$	—
	Diluted earnings per share (1)	$	0.08		$	—		$	—		$	—
	Settlement agreement (Note 16)	$	—		$	43,429		$	—		$	—
	Diluted earnings per share (2)	$	—		$	0.16		$	—		$	—
	(1) Attributable to gain on sale of subsidiary.
	(2) Attributable to settlement agreement.
		For the Three Months Ended
	2012	March 31			June 30			30-Sep			31-Dec
	Revenues	$	237,898		$	241,237		$	251,752		$	261,635
	Income before income taxes	$	79,950		$	78,501		$	83,501		$	87,544
	Net income attributable to SEI	$	49,965		$	49,555		$	50,743		$	56,585
	Basic earnings per share	$	0.28		$	0.28		$	0.29		$	0.33
	Diluted earnings per share	$	0.28		$	0.28		$	0.29		$	0.32
	Effective income tax rate	37.2		%	36.6		%	39		%	35		%
	Total SIV-related gains	$	2,882		$	1,072		$	3,389		$	5,897
	Diluted earnings per share (3)	$	0.01		$	—		$	0.01		$	0.02
	(3) Attributable to SIV-related gains.

Summary_of_Significant_Account3

Summary of Significant Accounting Policies (Narrative) (Details) (USD $)

12 Months Ended

12 Months Ended

12 Months Ended

12 Months Ended

3 Months Ended

12 Months Ended

In Thousands, except Per Share data, unless otherwise specified

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2011

Dec. 31, 2010

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2011

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2011

Dec. 31, 2012

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Mar. 28, 2013

Dec. 31, 2013

Apr. 30, 2013

Dec. 31, 2011

Dec. 31, 2013

Dec. 31, 2013

Software Development [Member]

Software Development [Member]

Software Development [Member]

SEI Wealth Platform [Member]

SEI Wealth Platform [Member]

SEI Wealth Platform [Member]

SEI Wealth Platform [Member]

Sei Investments Europe Limited [Member]

Sei Investments Europe Limited [Member]

Sei Investments Distribution Co Sidco [Member]

Sei Investments Distribution Co Sidco [Member]

Minimum [Member]

Maximum [Member]

Maximum [Member]

Weighted Average [Member]

Weighted Average [Member]

Building and Building Improvements [Member]

Building and Building Improvements [Member]

Computer Equipment [Member]

Computer Equipment [Member]

Furniture and Fixtures [Member]

Furniture and Fixtures [Member]

SEI Asset Korea Co., Ltd. [Member]

SEI Asset Korea Co., Ltd. [Member]

LSV Asset Management [Member]

LSV Asset Management [Member]

Equity Method Investee [Member]

Equity Method Investee [Member]

Amortization [Member]

Software Development [Member]

Software Development [Member]

Software Development [Member]

SEI Wealth Platform [Member]

Minimum [Member]

Maximum [Member]

Minimum [Member]

Maximum [Member]

Minimum [Member]

Maximum [Member]

Minimum [Member]

Maximum [Member]

Summary of Significant Accounting Policies [Line Items]

'

'

'

'

'

'

'

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'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Percentage of ownership before sale of subsidiary

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

56.10%

'

'

'

'

'

Closing date, sale of subsidiary

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

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'

'

'

28-Mar-13

'

'

'

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Equity Method Investment, Ownership Percentage

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

50.00%

'

'

'

'

'

'

'

'

'

'

'

39.30%

41.20%

20.00%

50.00%

Cash and cash equivalents

$578,273

$452,247

$420,986

$496,292

'

'

'

'

'

'

'

$387,201

$247,314

'

'

'

'

'

'

'

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'

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'

'

'

'

'

'

Restricted cash

'

'

'

'

'

'

'

'

'

'

'

'

'

5,000

5,000

500

1,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Property, Plant and Equipment, Useful Life

'

'

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'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'25 years

'39 years

'3 years

'5 years

'3 years

'5 years

'

'

'

'

'

'

Net book value of the Platform

312,615

307,490

'

'

'

'

'

309,725

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Capitalized software, accumulated amortization

180,062

149,747

'

'

'

'

'

149,924

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Capitalized software development costs in-progress associated with future releases

'

'

'

'

'

'

'

2,796

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Additions to capitalized software

-39,500

-31,004

-40,954

'

'

'

'

-8,812

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Finite-Lived Intangible Asset, Useful Life

'

'

'

'

'

'

'

'15 years

'

'

'

'

'

'

'

'

'

'3 years

'

'15 years

'8 years 6 months

'8 years 6 months

'

'

'

'

'

'

'

'

'

'

'

'

Amortization expense related to capitalized software

'

'

'

'

34,375

32,647

26,153

34,045

32,177

25,610

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Capitalized computer software impairments

'

'

'

'

'

'

'

'

'

'

$2,661

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Anti-dilutive employee stock options

7,736

13,202

15,914

'

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'

'

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'

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'

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'

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Antidilutive Securities Excluded from Computation of Net Income, Per Outstanding Unit, Amount

$30.54

$24.76

$23.07

'

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'

Summary_of_Significant_Account4

Summary of Significant Accounting Policies (Calculation Of Basic And Diluted Earnings Per Share) (Details) (USD $)	3 Months Ended								12 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Earnings Per Share [Abstract]	'	'	'	'	'	'	'	'	'	'	'
Basic earnings per common share, Net income attributable to SEI (Numerator)	$65,515	$67,195	$83,494	$71,920	$56,585	$50,743	$49,555	$49,965	$288,124	$206,848	$204,959
Shares used to compute basic earnings per share	'	'	'	'	'	'	'	'	171,561	174,295	182,547
Basic earnings per common share	$0.39	$0.39	$0.48	$0.42	$0.33	$0.29	$0.28	$0.28	$1.68	$1.19	$1.12
Dilutive effect of stock options, Net income attributable to SEI (Numerator)	'	'	'	'	'	'	'	'	0	0	0
Dilutive effect of stock options, shares	'	'	'	'	'	'	'	'	4,157	1,577	1,580
Diluted earnings per common share, Net income attributable to SEI (Numerator)	'	'	'	'	'	'	'	'	$288,124	$206,848	$204,959
Shares used to compute diluted earnings per share	'	'	'	'	'	'	'	'	175,718	175,872	184,127
Diluted earnings per common share	$0.37	$0.38	$0.47	$0.41	$0.32	$0.29	$0.28	$0.28	$1.64	$1.18	$1.11

Investment_In_Unconsolidated_A2

Investment In Unconsolidated Affiliates (Narrative) (Details) (USD $)

12 Months Ended

12 Months Ended

12 Months Ended

12 Months Ended

12 Months Ended

12 Months Ended

In Thousands, unless otherwise specified

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2011

Jan. 31, 2014

Apr. 30, 2011

Oct. 31, 2012

Dec. 31, 2013

Jan. 31, 2014

Apr. 30, 2011

Dec. 31, 2013

Jan. 31, 2014

Oct. 31, 2012

Dec. 31, 2013

Oct. 31, 2012

Jan. 31, 2014

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2011

Apr. 30, 2013

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2013

LSV Employee Group II [Member]

LSV Employee Group II [Member]

LSV Employee Group III [Member]

Financial Guarantee [Member]

Financial Guarantee [Member]

Financial Guarantee [Member]

Financial Guarantee [Member]

Financial Guarantee [Member]

Financial Guarantee [Member]

Financial Guarantee [Member]

Financial Guarantee [Member]

Financial Guarantee [Member]

LSV Asset Management [Member]

LSV Asset Management [Member]

LSV Asset Management [Member]

LSV Asset Management [Member]

Gao Fu [Member]

Gao Fu [Member]

Maximum [Member]

LSV Employee Group II [Member]

LSV Employee Group II [Member]

LSV Employee Group II [Member]

LSV Employee Group III [Member]

LSV Employee Group III [Member]

LSV Employee Group III [Member]

LSV Asset Management [Member]

LSV Asset Management [Member]

LSV Asset Management [Member]

Subsequent Event [Member]

Investments in and Advances to Affiliates [Line Items]

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Equity Method Investment, Ownership Percentage

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

41.20%

39.30%

'

'

50.00%

Total investment in equity method investee

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

$50,595

'

'

'

$10,775

'

'

Investment in equity method investee in excess of the underlying equity in net assets

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

3,062

'

'

'

'

'

'

Company's share in the earnings of equity method investee

118,076

98,671

105,818

'

'

'

'

'

'

'

'

'

'

'

'

118,983

99,989

105,818

'

-907

-1,318

'

Distributions received from unconsolidated affiliate

137,104

92,227

109,273

'

'

'

'

'

'

'

'

'

'

'

'

137,104

92,227

109,273

'

'

'

'

Guarantor Obligations, Maximum Exposure, Undiscounted

'

'

'

'

'

'

'

'

3,655

'

45,000

45,000

'

24,930

10,108

'

'

'

'

'

'

'

Guarantor Obligations, Current Carrying Value

'

'

'

'

'

'

'

0

'

'

0

'

'

'

'

'

'

'

'

'

'

'

Purchase Of Partnership Interest Value

'

'

'

'

'

77,700

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Business Acquisition, Equity Interest Issued or Issuable, Value Assigned

'

'

'

'

4,300

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Guarantor Obligations, Term

'

'

'

'

'

'

'4 years

'

'

'5 years

'

'

'3 years

'

'

'

'

'

'

'

'

'

Unpaid Principal Balance

'

'

'

716

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Loans Payable

'

'

'

'

'

$69,930

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Investment_In_Unconsolidated_A3

Investment In Unconsolidated Affiliates (Condensed Statements of Operations of LSV) (Details) (LSV Asset Management [Member], USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
LSV Asset Management [Member]	'	'	'
Schedule of Equity Method Investments [Line Items]	'	'	'
Equity Method Investment, Summarized Financial Information, Revenue	$354,094	$296,261	$296,361
Equity Method Investment, Summarized Financial Information, Net Income (Loss)	$302,316	$250,165	$257,519

Investment_In_Unconsolidated_A4

Investment In Unconsolidated Affiliates (Condensed Balance Sheets of LSV) (Details) (LSV Asset Management [Member], USD $)	Dec. 31, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified
LSV Asset Management [Member]	'	'
Schedule of Equity Method Investments [Line Items]	'	'
Equity Method Investment, Summarized Financial Information, Current Assets	$118,630	$145,367
Equity Method Investment, Summarized Financial Information, Noncurrent Assets	2,588	3,120
Equity Method Investment, Summarized Financial Information, Assets	121,218	148,487
Equity Method Investment, Summarized Financial Information, Current Liabilities	26,103	17,869
Equity Method Investment Summarized Financial Information, Equity	95,115	130,618
Equity Method Investment, Summarized Financial Information, Liabilities and Equity	$121,218	$148,487

Variable_Interest_Entities_Inv1

Variable Interest Entities - Investment Products (Details)	12 Months Ended
	Dec. 31, 2013
Variable Interest Entities Disclosure [Abstract]	'
Percentage not approached by expected return on any VIE investment	50.00%

Composition_of_Certain_Financi2

Composition of Certain Financial Statement Captions (Receivables) (Details) (USD $)	Dec. 31, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified
Items Included in Consolidated Statement of Financial Condition [Abstract]	'	'
Trade receivables	$44,502	$46,650
Fees earned, not billed	128,248	116,019
Other receivables	14,565	9,870
Gross receivables	187,315	172,539
Less: Allowance for doubtful accounts	-651	-805
Receivables, net	$186,664	$171,734

Composition_of_Certain_Financi3

Composition of Certain Financial Statement Captions (Property And Equipment) (Details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Property, Plant and Equipment [Line Items]	'	'	'
Property and Equipment, gross	$339,059	$328,999	'
Less: Accumulated depreciation	-220,064	-201,418	'
Property and Equipment, net	118,995	127,581	'
Depreciation expense	22,497	22,586	21,471
Buildings [Member]	'	'	'
Property, Plant and Equipment [Line Items]	'	'	'
Property and Equipment, gross	138,426	137,751	'
Equipment [Member]	'	'	'
Property, Plant and Equipment [Line Items]	'	'	'
Property and Equipment, gross	70,117	66,167	'
Land [Member]	'	'	'
Property, Plant and Equipment [Line Items]	'	'	'
Property and Equipment, gross	9,929	9,929	'
Purchased software [Member]	'	'	'
Property, Plant and Equipment [Line Items]	'	'	'
Property and Equipment, gross	96,268	91,468	'
Furniture and fixtures [Member]	'	'	'
Property, Plant and Equipment [Line Items]	'	'	'
Property and Equipment, gross	17,060	18,535	'
Leasehold improvements [Member]	'	'	'
Property, Plant and Equipment [Line Items]	'	'	'
Property and Equipment, gross	4,670	5,037	'
Construction in progress [Member]	'	'	'
Property, Plant and Equipment [Line Items]	'	'	'
Property and Equipment, gross	$2,589	$112	'

Composition_of_Certain_Financi4

Composition of Certain Financial Statement Captions (Other Assets) (Details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Other Assets [Abstract]	'	'	'
Other Deferred Cost, Amortization Expense	$227	$611	$1,135

Composition_of_Certain_Financi5

Composition of Certain Financial Statement Captions (Accrued Liabilities) (Details) (USD $)	Dec. 31, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified
Items Included in Consolidated Statement of Financial Condition [Abstract]	'	'
Accrued employee compensation	$69,256	$63,996
Accrued employee benefits and other personnel	9,647	7,299
Accrued consulting, outsourcing and professional fees	19,311	16,676
Accrued brokerage fees	5,251	5,733
Accrued sub-advisory, distribution and other asset management fees	25,018	17,548
Accrued dividend payable	37,314	0
Other accrued liabilities	22,326	27,053
Total accrued liabilities	$188,123	$138,305

Fair_Value_Measurements_Fair_V

Fair Value Measurements (Fair Value Of Certain Financial Assets And Liabilities) (Details) (USD $)	Dec. 31, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Fixed income securities owned	$21,133	$20,088
Trading Securities	4,849	5,909
Fair Value, Inputs, Level 1 [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Equity available-for-sale securities	11,633	15,926
Fixed income available-for-sale securities	0	0
Fixed income securities owned	0	0
Trading Securities	4,849	4,706
Assets, fair value	16,482	20,632
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	71,690	59,943
Fixed income securities owned	21,133	20,088
Trading Securities	0	0
Assets, fair value	92,823	80,031
Fair Value, Inputs, Level 3 [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	0	0
Fixed income securities owned	0	0
Trading Securities	0	1,203
Assets, fair value	0	1,203
Estimate of Fair Value Measurement [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Equity available-for-sale securities	11,633	15,926
Fixed income available-for-sale securities	71,690	59,943
Fixed income securities owned	21,133	20,088
Trading Securities	4,849	5,909
Assets, fair value	$109,305	$101,866

Fair_Value_Measurements_Reconc

Fair Value Measurements (Reconciliation For All Assets And Liabilities Of The Company Measured At Fair Value On A Recurring Basis Using Significant Unobservable Inputs (Level 3)) (Details) (Trading Securities [Member], USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Trading Securities [Member]	'	'
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]	'	'
Beginning balance	$1,203	$52,623
Purchases	0	13
Issuances	0	0
Principal prepayments and settlements	1,167	10,728
Sales	0	53,920
Total gains or (losses) (realized/unrealized), Included in earnings	36	-13,215
Total gains or (losses) (realized/unrealized), Included in other comprehensive income	0	0
Transfers in and out of Level 3	0	0
Ending balance	$0	$1,203

Marketable_Securities_Narrativ

Marketable Securities (Narrative) (Details) (USD $)

12 Months Ended

12 Months Ended

1 Months Ended

3 Months Ended

12 Months Ended

In Thousands, unless otherwise specified

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2011

Dec. 31, 2010

Dec. 31, 2013

Dec. 31, 2012

Nov. 30, 2012

Dec. 31, 2012

Sep. 30, 2012

Jun. 30, 2012

Mar. 31, 2012

Dec. 31, 2012

Dec. 31, 2011

Dec. 31, 2013

Dec. 31, 2012

Trading Securities [Member]

Trading Securities [Member]

SIV Securities [Member]

SIV Securities [Member]

SIV Securities [Member]

SIV Securities [Member]

SIV Securities [Member]

SIV Securities [Member]

SIV Securities [Member]

U.S. Government Agency And Commercial Paper Securities [Member]

U.S. Government Agency And Commercial Paper Securities [Member]

Schedule of Investments [Line Items]

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Net unrealized holding gains

$1,386

$2,829

$2,574

$1,339

'

'

'

'

'

'

'

'

'

'

'

Unrealized holding gains during the period, income tax expense

430

1,554

'

'

'

'

'

'

'

'

'

'

'

'

'

Available-for-sale securities, gross realized gains

1,236

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Available-for-sale securities, gross realized losses

772

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Trading Securities

4,849

5,909

'

'

4,849

4,706

'

'

'

'

'

'

'

'

'

Trading Securities, Realized Gain

'

'

'

'

143

1,004

'

'

'

'

'

13,240

3,390

'

'

Gains From Cash Payments Received From SIV Securities

'

'

'

'

'

'

'

'

'

'

'

6,776

10,614

'

'

Unrealized Gain (Loss) on Securities

'

'

'

'

'

'

'

'

'

'

'

1,142

-7,224

'

'

Trading Securities, Realized Loss

'

'

'

'

'

'

5,322

5,897

3,389

1,072

2,882

'

'

'

'

Securities owned

$21,133

$20,088

'

'

'

'

'

'

'

'

'

'

'

$21,133

$20,088

Marketable_Securities_Investme

Marketable Securities (Investments Available For Sale) (Details) (USD $)	Dec. 31, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified
Schedule of Available-for-sale Securities [Line Items]	'	'
Investment Available for Sale, Cost Amount	$81,507	$71,486
Investment Available for Sale, Gross Unrealized Gains	1,816	4,396
Investment Available for Sale, Gross Unrealized (Losses)	0	-13
Investment Available for Sale, Fair Value	83,323	75,869
Equity Funds [Member]	'	'
Schedule of Available-for-sale Securities [Line Items]	'	'
Investment Available for Sale, Cost Amount	7,612	12,953
Investment Available for Sale, Gross Unrealized Gains	1,242	376
Investment Available for Sale, Gross Unrealized (Losses)	0	-13
Investment Available for Sale, Fair Value	8,854	13,316
Equity Securities [Member]	'	'
Schedule of Available-for-sale Securities [Line Items]	'	'
Investment Available for Sale, Cost Amount	2,615	2,610
Investment Available for Sale, Gross Unrealized Gains	164	0
Investment Available for Sale, Gross Unrealized (Losses)	0	0
Investment Available for Sale, Fair Value	2,779	2,610
Debt Securities [Member]	'	'
Schedule of Available-for-sale Securities [Line Items]	'	'
Investment Available for Sale, Cost Amount	71,280	55,923
Investment Available for Sale, Gross Unrealized Gains	410	4,020
Investment Available for Sale, Gross Unrealized (Losses)	0	0
Investment Available for Sale, Fair Value	$71,690	$59,943

Lines_Of_Credit_Details

Lines Of Credit (Details) (Line of Credit [Member])	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2013	Dec. 31, 2013	Dec. 31, 2013
	USD ($)	USD ($)	USD ($)	2012 Credit Facility [Member]	2012 Credit Facility [Member]	Canadian Subsidiary Credit Facility [Member]
				USD ($)	London Interbank Offered Rate (LIBOR) [Member]	CAD
Line of Credit Facility [Line Items]	'	'	'	'	'	'
Debt Instrument, Term	'	'	'	'5 years	'	'
Credit facility	'	'	'	$300,000	'	2,000
Credit facility, expiration date	'	'	'	2-Feb-17	'	'
Credit facility interest accrued, percentage above LIBOR	'	'	'	'	1.25%	'
Credit facility, commitment fee per annum on daily unused portion, percent	'	'	'	0.15%	'	'
Aggregate amount that may increase under credit facility	'	'	'	100,000	'	'
Interest Expense and Commitment Fees	$458	$585	$1,478	'	'	'

Shareholders_Equity_Narrative_

Shareholders' Equity (Narrative) (Details) (USD $)

0 Months Ended

12 Months Ended

0 Months Ended

12 Months Ended

In Thousands, except Share data, unless otherwise specified

Dec. 10, 2013

Jun. 25, 2013

23-May-13

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2011

Jan. 10, 2014

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Subsequent Event [Member]

Common Stock Buyback [Member]

Minimum [Member]

Maximum [Member]

Time-based [Member]

2007 Equity Compensation Plan [Member]

2007 Equity Compensation Plan [Member]

2007 Equity Compensation Plan [Member]

Employee Stock Purchase Plan [Member]

plans

Tranche One [Member]

Tranche Two [Member]

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Number of active equity compensation plans

'

'

'

'

'

'

'

'

'

'

'

1

'

'

'

Number of shares available for grant

'

'

'

744,000

'

'

'

'

'

'

'

20,000,000

'

'

'

Vesting rate

'

'

'

'

'

'

'

'

'

'

'

'

50.00%

50.00%

'

Stock options vesting period, years

'

'

'

'

'

'

'

'

'

'

'7 years

'

'

'

'

Weighted average fair value of stock options granted

'

'

'

$10.45

$6.73

$5.70

'

'

'

'

'

'

'

'

'

Change in management estimate of stock-based compensation expense amortization

'

'

'

$19,637

'

'

'

'

'

'

'

'

'

'

'

Unrecognized compensation cost

'

'

'

37,266

'

'

'

'

'

'

'

'

'

'

'

Weighted average period for recognition of unrecognized compensation cost

'

'

'

'2 years 6 months 22 days

'

'

'

'

'

'

'

'

'

'

'

Total options that were exercisable

'

'

'

14,601,000

9,760,000

11,680,000

'

'

'

'

'

'

'

'

'

Expiration date for options outstanding

'

'

'

'

'

'

'

'

14-Dec-14

10-Dec-23

'

'

'

'

'

Options outstanding weighted average remaining contractual life, years

'

'

'

'5 years 8 months 16 days

'

'

'

'

'

'

'

'

'

'

'

Total intrinsic value of options exercised

'

'

'

47,392

19,565

'

'

'

'

'

'

'

'

'

'

Aggregate intrinsic value of options exercisable

'

'

'

223,061

'

'

'

'

'

'

'

'

'

'

'

Total intrinsic value of options outstanding

'

'

'

287,237

'

'

'

'

'

'

'

'

'

'

'

Share price

'

'

'

$34.73

'

'

'

'

'

'

'

'

'

'

'

Employee stock purchase plan, employee eligible percentage on offerings of common stock

'

'

'

'

'

'

'

'

'

'

'

'

'

'

85.00%

Shares reserved under the plan

'

'

'

'

'

'

'

'

'

'

'

'

'

'

15,600,000

Issuance of common stock under the employee stock purchase plan, shares

'

'

'

'

'

'

'

'

'

'

'

'

'

'

11,658,000

Remaining stock repurchase authorization amount

'

'

'

'

'

'

'

81,070

'

'

'

'

'

'

'

Rights received by common shareholder for each common share outstanding, rights

'

'

'

1

'

'

'

'

'

'

'

'

'

'

'

Series A Junior Participating Preferred stock, par value

'

'

'

$0.05

$0.05

'

'

'

'

'

'

'

'

'

'

Securities and assets of equivalent value, purchase price, per unit

'

'

'

$150

'

'

'

'

'

'

'

'

'

'

'

Number of days, rights become exercisable following public announcement

'

'

'

'0 years 0 months 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

'

'

'

'0 years 0 months 10 days

'

'

'

'

'

'

'

'

'

'

'

Right redeemable price, per right

'

'

'

0.01

'

'

'

'

'

'

'

'

'

'

'

Dividends declared per common share

$0.22

'

$0.20

$0.42

$0.63

$0.27

'

'

'

'

'

'

'

'

'

Dividends paid per common share

'

$0.20

'

'

'

'

$0.22

'

'

'

'

'

'

'

'

Dividends declared

'

'

'

$71,665

$108,817

$48,558

'

'

'

'

'

'

'

'

'

Shareholders_Equity_Assumption

Shareholders' Equity (Assumptions Used In The Weighted Average Fair Value Of Stock Options Granted) (Details)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions and Methodology [Abstract]	'	'	'
Expected Term	'6 years 11 months 1 day	'6 years 9 months	'7 years 7 months 24 days
Expected Volatility Rate	31.46%	34.90%	40.43%
Expected Dividend Rate	1.21%	1.46%	1.90%
Risk Free Interest Rate	2.12%	1.03%	1.66%

Shareholders_Equity_StockBased

Shareholders' Equity (Stock-Based Compensation Expense) (Details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Stockholders' Equity Note [Abstract]	'	'	'
Stock-based compensation expense	$37,865	$15,736	$14,112
Less: Deferred tax benefit	-13,823	-5,650	-5,332
Stock-based compensation expense, net of tax	$24,042	$10,086	$8,780

Shareholders_Equity_Stock_Opti

Shareholders' Equity (Stock Option Plans) (Details) (USD $)	12 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]	'	'	'
Balance	25,610	27,043	27,881
Balance, weighted avg. price	$20.81	$20.06	$20.42
Granted	2,281	2,470	2,534
Granted, weighted avg. price	$33.67	$22.40	$15.77
Exercised	-3,733	-3,136	-1,364
Exercised, weighted avg. price	$17.26	$15.19	$16.37
Expired or canceled	-521	-767	-2,008
Expired or canceled, weighted avg. price	$22.25	$22.61	$22.07
Balance	23,637	25,610	27,043
Balance, weighted avg. price	$22.58	$20.81	$20.06
Total options that were exercisable	14,601	9,760	11,680
Exercisable shares, weighted avg. price	$19.45	'	'
Available for future grant as of December 31, 2013	744	'	'

Shareholders_Equity_Stock_Opti1

Shareholders' Equity (Stock Options Outstanding And Exercisable) (Details) (USD $)	12 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]	'	'	'	'
Number of Shares	23,637	25,610	27,043	27,881
Weighted Average Exercise Price (Per Share)	$22.58	$20.81	$20.06	$20.42
Weighted Average Remaining Contractual Life (Years)	'5 years 8 months 16 days	'	'	'
Number of Shares	14,601	9,760	11,680	'
Weighted Average Exercise Price (Per Share)	$19.45	'	'	'
Exercise Price $14.62-15.77 [Member]	'	'	'	'
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]	'	'	'	'
Lower range	$14.62	'	'	'
Upper range	$15.77	'	'	'
Number of Shares	5,498	'	'	'
Weighted Average Exercise Price (Per Share)	$15.13	'	'	'
Weighted Average Remaining Contractual Life (Years)	'6 years 2 months 9 days	'	'	'
Number of Shares	4,304	'	'	'
Weighted Average Exercise Price (Per Share)	$14.95	'	'	'
Weighted Average Remaining Contractual Life (Years)	'5 years 8 months 9 days	'	'	'
Exercise Price $17.65-19.28 [Member]	'	'	'	'
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]	'	'	'	'
Lower range	$17.65	'	'	'
Upper range	$19.28	'	'	'
Number of Shares	4,921	'	'	'
Weighted Average Exercise Price (Per Share)	$18.27	'	'	'
Weighted Average Remaining Contractual Life (Years)	'4 years 6 months	'	'	'
Number of Shares	4,912	'	'	'
Weighted Average Exercise Price (Per Share)	$18.27	'	'	'
Weighted Average Remaining Contractual Life (Years)	'4 years 5 months 27 days	'	'	'
Exercise Price $20.54-23.77 [Member]	'	'	'	'
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]	'	'	'	'
Lower range	$20.54	'	'	'
Upper range	$23.77	'	'	'
Number of Shares	4,051	'	'	'
Weighted Average Exercise Price (Per Share)	$22.08	'	'	'
Weighted Average Remaining Contractual Life (Years)	'5 years 8 months 12 days	'	'	'
Number of Shares	2,858	'	'	'
Weighted Average Exercise Price (Per Share)	$21.92	'	'	'
Weighted Average Remaining Contractual Life (Years)	'4 years 4 months 6 days	'	'	'
Exercise Price $23.86-29.61 [Member]	'	'	'	'
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]	'	'	'	'
Lower range	$23.86	'	'	'
Upper range	$29.61	'	'	'
Number of Shares	4,979	'	'	'
Weighted Average Exercise Price (Per Share)	$26.57	'	'	'
Weighted Average Remaining Contractual Life (Years)	'5 years 1 month 17 days	'	'	'
Number of Shares	2,492	'	'	'
Weighted Average Exercise Price (Per Share)	$26.57	'	'	'
Weighted Average Remaining Contractual Life (Years)	'5 years 1 month 2 days	'	'	'
Exercise Price $31.17-33.76 [Member]	'	'	'	'
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]	'	'	'	'
Lower range	$31.17	'	'	'
Upper range	$33.76	'	'	'
Number of Shares	4,188	'	'	'
Weighted Average Exercise Price (Per Share)	$33.15	'	'	'
Weighted Average Remaining Contractual Life (Years)	'7 years 2 months 19 days	'	'	'
Number of Shares	35	'	'	'
Weighted Average Exercise Price (Per Share)	$31.17	'	'	'
Weighted Average Remaining Contractual Life (Years)	'4 years	'	'	'

Shareholders_Equity_Common_Sto

Shareholders' Equity (Common Stock Buyback) (Details) (Common Stock Buyback [Member], USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Common Stock Buyback [Member]	'	'	'
Equity, Class of Treasury Stock [Line Items]	'	'	'
Stock Repurchased and Retired During Period, Shares	6,789	7,528	11,109
Stock Repurchased During Period, Value	$209,942	$155,264	$211,165

Shareholders_Equity_Schedule_O

Shareholders' Equity (Schedule Of Reconciliation Of Noncontrolling Interest On The Consolidated Balance Sheet) (Details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Stockholders' Equity Attributable to Noncontrolling Interest [Roll Forward]	'	'	'
Beginning balance	$19,149	$16,143	$15,155
Net income attributable to noncontrolling interest	350	1,186	1,691
Foreign currency translation adjustments	-451	1,820	-703
Sale of subsidiary (See Note 15)	-19,048	0	0
Ending balance	$0	$19,149	$16,143

Accumulated_Other_Comprehensiv2

Accumulated Other Comprehensive Income (Schedule Of Accumulated Other Comprehensive Income (Loss), Net Of Tax) (Details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Accumulated other comprehensive income (loss), Foreign Currency Translation Adjustments	$101	$3,410	($674)	$1,818
Accumulated other comprehensive income (loss), Unrealized Holding Gains (Losses) on Investments	1,386	2,829	2,574	1,339
Accumulated Other Comprehensive Income (Loss)	1,487	6,239	1,900	3,157
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Gain (Loss) Arising During Period, Net of Tax	-3,760	5,904	-3,195	'
Other Comprehensive Income (Loss), Available-for-sale Securities Adjustment, before Reclassification Adjustments, Net of Tax	-1,149	341	1,369	'
Other Comprehensive Income (Loss) before Reclassification, Net of Tax	-4,909	6,245	-1,826	'
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Reclassification Adjustment from AOCI, Realized upon Sale or Liquidation, Net of Tax	0	0	0	'
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI for Sale of Securities, Net of Tax	-294	-86	-134	'
Other Comprehensive Income (Loss) Reclassification Adjustment, Net of Tax	-294	-86	-134	'
Total comprehensive income (loss), Foreign Currency Translation Adjustments	-3,760	5,904	-3,195	'
Total comprehensive income (loss), Unrealized Holding Gains (Losses) on Investments	-1,443	255	1,235	'
Total other comprehensive (loss) gain, net of taxes	-5,203	6,159	-1,960	'
Total comprehensive loss (income) attributable to noncontrolling interest, Foreign Currency Translation Adjustments	451	-1,820	703	'
Total comprehensive income attributable to noncontrolling interest, Unrealized Holding Gains (Losses) on Investments	0	0	0	'
Total comprehensive loss (income) attributable to noncontrolling interest	451	-1,820	703	'
Total comprehensive (loss) income attributable to SEI Investments Company, Foreign Currency Translation Adjustments	-3,309	4,084	-2,492	'
Total comprehensive (loss) attributable to SEI Investments Company, Unrealized Holding Gains (Losses) on Investments	-1,443	255	1,235	'
Total comprehensive (loss) income attributable to SEI Investments Company	-4,752	4,339	-1,257	'
SEI Investments [Member]	'	'	'	'
Accumulated other comprehensive income (loss), Foreign Currency Translation Adjustments	101	3,861	-2,043	1,152
Accumulated other comprehensive income (loss), Unrealized Holding Gains (Losses) on Investments	1,386	2,829	2,574	1,339
Accumulated Other Comprehensive Income (Loss)	1,487	6,690	531	2,491
Noncontrolling Interest [Member]	'	'	'	'
Accumulated other comprehensive income (loss), Foreign Currency Translation Adjustments	0	-451	1,369	666
Accumulated other comprehensive income (loss), Unrealized Holding Gains (Losses) on Investments	0	0	0	0
Accumulated Other Comprehensive Income (Loss)	$0	($451)	$1,369	$666

Employee_Benefit_Plan_Details

Employee Benefit Plan (Details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Compensation and Retirement Disclosure [Abstract]	'	'	'
Defined contribution plan, cost recognized	$5,664	$5,168	$4,783

Commitments_and_Contingencies_1

Commitments and Contingencies (Narrative) (Details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Commitments and Contingencies Disclosure [Abstract]	'	'	'
Rent Expense	$21,519	$21,614	$19,760

Commitments_and_Contingencies_2

Commitments and Contingencies (Schedule Of Noncancellable Minimum Commitments) (Details) (USD $)	Dec. 31, 2013
In Thousands, unless otherwise specified
Commitments and Contingencies Disclosure [Abstract]	'
2014	$7,625
2015	3,918
2016	3,160
2017	2,739
2018 and thereafter	7,697
Operating leases, future minimum payments due	$25,139

Income_Taxes_Schedule_Of_Feder

Income Taxes (Schedule Of Federal And State And Foreign Income Tax Provision) (Details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Income Tax Expense (Benefit), Continuing Operations [Abstract]	'	'	'
Federal, current	$153,856	$112,247	$99,448
State, current	11,542	5,284	7,067
Foreign, current	4,727	4,511	4,603
Current federal, state and foreign income tax	170,125	122,042	111,118
Federal, deferred	-2,214	-2,708	-2,317
State, deferred	-16,264	-2,199	2,477
Foreign, deferred	-4,814	3,970	6
Deferred income tax expense (benefit)	-23,292	-937	166
Income taxes attributable to the Noncontrolling interest	91	357	553
Total income taxes	$146,924	$121,462	$111,837

Income_Taxes_Components_Of_Net

Income Taxes (Components Of Net Income Before Income Taxes) (Details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Income Tax Disclosure [Abstract]	'	'	'
Domestic	$427,915	$319,907	$309,391
Foreign	7,042	8,046	6,852
Income Loss From Continuing Operations Before Income Taxes And Minority Interest	$434,957	$327,953	$316,243

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, 2013

Sep. 30, 2013

Jun. 30, 2013

Mar. 31, 2013

Dec. 31, 2012

Sep. 30, 2012

Jun. 30, 2012

Mar. 31, 2012

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2011

Effective Income Tax Rate Reconciliation, Percent [Abstract]

'

'

'

'

'

'

'

'

'

'

'

Statutory rate

'

'

'

'

'

'

'

'

35.00%

35.00%

35.00%

State taxes, net of Federal tax benefit

'

'

'

'

'

'

'

'

1.50%

1.00%

2.00%

Foreign tax expense and tax rate differential

'

'

'

'

'

'

'

'

0.50%

1.60%

0.60%

Research and development tax credit

'

'

'

'

'

'

'

'

-0.80%

0.00%

-0.70%

Domestic Production Activities Deduction

'

'

'

'

'

'

'

'

-0.50%

-0.60%

-0.70%

Valuation allowance on capital losses and PA loss carryforwards

'

'

'

'

'

'

'

'

-2.40%

-0.30%

0.00%

Domestic Production Activities Deduction, prior years, net

'

'

'

'

'

'

'

'

0.00%

0.00%

-1.50%

Net change in uncertain tax positions

'

'

'

'

'

'

'

'

0.10%

[1]

0.50%

[1]

0.40%

[1]

Other, net

'

'

'

'

'

'

'

'

0.30%

-0.30%

0.10%

Effective tax rates

35.20%

28.50%

35.50%

34.90%

35.00%

39.00%

36.60%

37.20%

33.70%

36.90%

35.20%

Effective Income Tax Rate Reconciliation, Tax Contingencies, Domestic

'

'

'

'

'

'

'

'

-0.23%

0.15%

0.25%

Effective Income Tax Rate Reconciliation, Tax Contingencies, State and Local

'

'

'

'

'

'

'

'

0.32%

0.33%

0.14%

Effective Income Tax Rate Reconciliation, Tax Contingencies, Foreign

'

'

'

'

'

'

'

'

0.01%

0.02%

'

[1]

For 2013, (0.23) percent relates to federal issues mainly associated with compilation of foreign tax credits, 0.32 percent relates to state tax issues and the remaining 0.01 percent relates to foreign tax issues. For 2012, 0.15 percent relates to federal issues, 0.33 percent relates to state tax issues and the remaining 0.02 percent relates to foreign tax issues. For 2011, 0.25 percent relates to federal issues and the remaining 0.14 percent relates to state tax issues.

Income_Taxes_Narrative_Details

Income Taxes (Narrative) (Details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Significant Change in Unrecognized Tax Benefits is Reasonably Possible [Line Items]	'	'	'	'
Undistributed earnings of foreign subsidiaries	$52,546	'	'	'
Unrecognized tax benefit, excluding interest and penalties	12,028	11,553	9,410	5,723
Unrecognized tax benefits that would affect effective tax rate	10,139	'	'	'
Amount included in Other long-term liabilities	8,607	7,032	'	'
Amount of previously unrecognized tax benefits recognized	1,022	'	'	'
Tax related interest and penalties	754	770	634	'
Current liabilities [Member]	'	'	'	'
Significant Change in Unrecognized Tax Benefits is Reasonably Possible [Line Items]	'	'	'	'
Amount netted against current payable account	4,175	'	'	'
Other long-term liabilities [Member]	'	'	'	'
Significant Change in Unrecognized Tax Benefits is Reasonably Possible [Line Items]	'	'	'	'
Amount included in Other long-term liabilities	8,607	'	'	'
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	$1,067	'	'	'

Income_Taxes_Schedule_Of_Defer

Income Taxes (Schedule Of Deferred Tax Assets and Liabilities) (Details) (USD $)	Dec. 31, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified
Deferred Tax Liabilities, Net, Classification [Abstract]	'	'
Gross assets	$2,458	$2,012
Gross liabilities	-4,111	0
Current deferred income tax assets and liabilities	-1,653	2,012
Valuation allowance	0	0
Current deferred income taxes	-1,653	2,012
Gross assets	69,483	63,129
Gross liabilities	-121,317	-149,708
Long term deferred income tax assets and liabilities	-51,834	-86,579
Valuation allowance	-14,738	-6,879
Long term deferred income taxes	-66,572	-93,458
Net deferred income tax liability	($68,225)	($91,446)

Income_Taxes_Tax_Effect_Of_Sig

Income Taxes (Tax Effect Of Significant Temporary Differences Representing Deferred Tax Liabilities) (Details) (USD $)	Dec. 31, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified
Deferred Tax Liabilities, Net [Abstract]	'	'
Difference in financial reporting and income tax depreciation methods	($7,043)	($10,104)
Reserves not currently deductible	235	325
Capitalized software currently deductible for tax purposes, net of amortization	-119,800	-137,467
State deferred income taxes	251	5,943
Revenue and expense recognized in different periods for financial reporting and income tax purpose	3,856	4,397
Unrealized holding loss (gain) on investments	-308	-1,428
Stock-based compensation expense	-45,555	-42,133
State net operating loss carryforward	21,215	13,883
Valuation allowance on deferred tax assets	-14,738	-6,879
Federal benefit of state tax deduction for uncertain tax positions	2,643	2,359
Foreign currency exchange	0	-39
Foreign deferred including taxes on cumulative undistributed earnings of SEI AK	-91	-4,569
Net deferred income tax liability	($68,225)	($91,446)

Income_Taxes_Unrecognized_Tax_

Income Taxes (Unrecognized Tax Benefit) (Details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Income Tax Disclosure [Abstract]	'	'	'
Unrecognized tax benefits, Beginning Balance	$11,553	$9,410	$5,723
Gross additions, current year	1,834	2,196	2,392
Gross reductions, current year	0	0	0
Tax positions related to current year	1,834	2,196	2,392
Gross additions, prior year	3,435	1,990	1,992
Gross reductions, prior year	0	0	0
Tax positions related to prior years tax positions	3,435	1,990	1,992
Settlements	-3,772	-99	0
Lapses on statute of limitations	-1,022	-1,944	-697
Unrecognized tax benefits, Ending Balance	$12,028	$11,553	$9,410

Business_Segment_Information_S

Business Segment Information (Schedule Of Financial Information About Business Segments) (Details) (USD $)	3 Months Ended								12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Segment Reporting Information [Line Items]	'	'	'	'	'	'	'	'	'	'	'
Revenues	$299,024	$280,655	$274,574	$271,879	$261,635	$251,752	$241,237	$237,898	$1,126,132	$992,522	$929,727
Expenses	'	'	'	'	'	'	'	'	824,279	736,172	683,884
Operating profit (loss)	'	'	'	'	'	'	'	'	301,853	256,350	245,843
Disposal Group, Not Discontinued Operation, Gain (Loss) on Disposal	'	'	'	'	'	'	'	'	22,112	'	'
Total Profit (Loss)	'	'	'	'	'	'	'	'	323,965	'	'
Private Banks [Member]	'	'	'	'	'	'	'	'	'	'	'
Segment Reporting Information [Line Items]	'	'	'	'	'	'	'	'	'	'	'
Revenues	'	'	'	'	'	'	'	'	397,138	364,788	348,122
Expenses	'	'	'	'	'	'	'	'	392,399	357,001	339,339
Operating profit (loss)	'	'	'	'	'	'	'	'	4,739	7,787	8,783
Disposal Group, Not Discontinued Operation, Gain (Loss) on Disposal	'	'	'	'	'	'	'	'	22,112	'	'
Total Profit (Loss)	'	'	'	'	'	'	'	'	26,851	'	'
Investment Advisors [Member]	'	'	'	'	'	'	'	'	'	'	'
Segment Reporting Information [Line Items]	'	'	'	'	'	'	'	'	'	'	'
Revenues	'	'	'	'	'	'	'	'	241,252	202,703	189,780
Expenses	'	'	'	'	'	'	'	'	133,962	120,146	110,438
Operating profit (loss)	'	'	'	'	'	'	'	'	107,290	82,557	79,342
Disposal Group, Not Discontinued Operation, Gain (Loss) on Disposal	'	'	'	'	'	'	'	'	0	'	'
Total Profit (Loss)	'	'	'	'	'	'	'	'	107,290	'	'
Institutional Investors [Member]	'	'	'	'	'	'	'	'	'	'	'
Segment Reporting Information [Line Items]	'	'	'	'	'	'	'	'	'	'	'
Revenues	'	'	'	'	'	'	'	'	257,658	227,889	210,027
Expenses	'	'	'	'	'	'	'	'	133,218	116,546	106,585
Operating profit (loss)	'	'	'	'	'	'	'	'	124,440	111,343	103,442
Disposal Group, Not Discontinued Operation, Gain (Loss) on Disposal	'	'	'	'	'	'	'	'	0	'	'
Total Profit (Loss)	'	'	'	'	'	'	'	'	124,440	'	'
Investment Managers [Member]	'	'	'	'	'	'	'	'	'	'	'
Segment Reporting Information [Line Items]	'	'	'	'	'	'	'	'	'	'	'
Revenues	'	'	'	'	'	'	'	'	226,081	193,484	177,975
Expenses	'	'	'	'	'	'	'	'	148,977	127,525	115,963
Operating profit (loss)	'	'	'	'	'	'	'	'	77,104	65,959	62,012
Disposal Group, Not Discontinued Operation, Gain (Loss) on Disposal	'	'	'	'	'	'	'	'	0	'	'
Total Profit (Loss)	'	'	'	'	'	'	'	'	77,104	'	'
Investments In New Businesses [Member]	'	'	'	'	'	'	'	'	'	'	'
Segment Reporting Information [Line Items]	'	'	'	'	'	'	'	'	'	'	'
Revenues	'	'	'	'	'	'	'	'	4,003	3,658	3,823
Expenses	'	'	'	'	'	'	'	'	15,723	14,954	11,559
Operating profit (loss)	'	'	'	'	'	'	'	'	-11,720	-11,296	-7,736
Disposal Group, Not Discontinued Operation, Gain (Loss) on Disposal	'	'	'	'	'	'	'	'	0	'	'
Total Profit (Loss)	'	'	'	'	'	'	'	'	($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 $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Segment Reporting Information [Line Items]	'	'	'
Total operating profit from segments above	$301,853	$256,350	$245,843
Noncontrolling interest reflected in segments	350	1,186	1,691
Income from operations	248,409	211,566	204,065
Operating Segments [Member]	'	'	'
Segment Reporting Information [Line Items]	'	'	'
Total operating profit from segments above	301,853	256,350	245,843
Corporate, Non-Segment [Member]	'	'	'
Segment Reporting Information [Line Items]	'	'	'
Corporate overhead expenses	-53,733	-45,759	-43,398
Segment Reconciling Items [Member]	'	'	'
Segment Reporting Information [Line Items]	'	'	'
Noncontrolling interest reflected in segments	$289	$975	$1,620

Business_Segment_Information_S1

Business Segment Information (Schedule Of Additional Information Pertaining To Business Segments) (Details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Segment Reporting Information [Line Items]	'	'	'
Capital Expenditures	$55,851	$54,074	$53,225
Depreciation	22,497	22,586	21,471
Amortization	34,602	33,258	27,288
Assets	1,439,169	1,309,824	'
Corporate, Non-Segment [Member]	'	'	'
Segment Reporting Information [Line Items]	'	'	'
Capital Expenditures	760	1,465	530
Depreciation	448	737	570
Amortization	228	612	1,129
Assets	657,679	484,439	'
Private Banks [Member]	'	'	'
Segment Reporting Information [Line Items]	'	'	'
Capital Expenditures	34,258	32,509	35,045
Depreciation	15,506	15,226	15,648
Amortization	22,379	22,218	18,081
Assets	430,613	481,602	'
Investment Advisors [Member]	'	'	'
Segment Reporting Information [Line Items]	'	'	'
Capital Expenditures	12,611	11,193	11,933
Depreciation	2,091	1,981	2,251
Amortization	8,234	7,167	6,201
Assets	124,028	120,255	'
Institutional Investors [Member]	'	'	'
Segment Reporting Information [Line Items]	'	'	'
Capital Expenditures	2,712	2,781	2,059
Depreciation	893	1,012	1,079
Amortization	1,274	1,208	864
Assets	97,816	99,461	'
Investment Managers [Member]	'	'	'
Segment Reporting Information [Line Items]	'	'	'
Capital Expenditures	4,871	5,494	3,081
Depreciation	1,970	1,914	1,809
Amortization	851	804	580
Assets	122,969	118,221	'
Investments In New Businesses [Member]	'	'	'
Segment Reporting Information [Line Items]	'	'	'
Capital Expenditures	639	632	577
Depreciation	1,589	1,716	114
Amortization	1,636	1,249	433
Assets	6,064	5,846	'
Total From Business Segments [Member]	'	'	'
Segment Reporting Information [Line Items]	'	'	'
Capital Expenditures	55,091	52,609	52,695
Depreciation	22,049	21,849	20,901
Amortization	34,374	32,646	26,159
Assets	$781,490	$825,385	'

Business_Segment_Information_S2

Business Segment Information (Schedule of Revenues And Assets Based On Location) (Details) (USD $)	3 Months Ended								12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Revenues	$299,024	$280,655	$274,574	$271,879	$261,635	$251,752	$241,237	$237,898	$1,126,132	$992,522	$929,727
Assets	1,439,169	'	'	'	1,309,824	'	'	'	1,439,169	1,309,824	'
United States [Member]	'	'	'	'	'	'	'	'	'	'	'
Revenues	'	'	'	'	'	'	'	'	962,266	843,407	785,506
Assets	1,231,565	'	'	'	1,066,451	'	'	'	1,231,565	1,066,451	'
International Operations [Member]	'	'	'	'	'	'	'	'	'	'	'
Revenues	'	'	'	'	'	'	'	'	163,866	149,115	144,221
Assets	$207,604	'	'	'	$243,373	'	'	'	$207,604	$243,373	'

Related_Party_Transactions_Det

Related Party Transactions (Details) (RICs [Member], USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
RICs [Member]	'	'	'
Related Party Transaction [Line Items]	'	'	'
Investment Advisory and Administration Fees	$422,825	$380,645	$364,602
Distribution and Servicing Fees	47,988	37,827	39,017
Brokerage commissions revenue	$620	$1,213	$2,772

Sale_of_SEI_Asset_Korea_Detail

Sale of SEI Asset Korea (Details) (USD $)	3 Months Ended	12 Months Ended			3 Months Ended	12 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Mar. 28, 2013	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
					SEI Asset Korea Co., Ltd. [Member]	SEI Asset Korea Co., Ltd. [Member]	SEI Asset Korea Co., Ltd. [Member]	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	'	'
Gain on sale of subsidiary	'	22,112	0	0	'	'	'	'
Gain on sale of subsidiary, diluted earnings per share impact, net	$0.08	'	'	'	'	'	'	'
Gain on sale of subsidiary, basic earnings per share impact, net	$0.08	'	'	'	'	'	'	'
Expected proceeds by Company from purchase price from sale of SEI AK	'	'	'	'	'	56,879	'	'
Sale of subsidiary transaction costs	'	'	'	'	'	2,545	'	'
Proceeds received at closing, net of transaction costs	'	'	'	'	'	54,334	'	'
Percentage of ownership before sale of subsidiary	'	'	'	'	56.10%	'	'	'
Assets	'	'	'	'	'	'	54,783	'
Cash and cash equivalents	'	'	'	'	'	'	48,306	'
Revenues and Net Income Included on Company's Consolidated Statement of Operations	'	'	'	'	'	'	'	'
Revenues	'	'	'	'	2,889	'	11,514	11,932
Net income	'	'	'	'	796	'	2,703	3,851
Less: Income attributable to the noncontrolling interests	'	'	'	'	-350	'	-1,186	-1,691
Net income attributable to SEI AK	'	'	'	'	$446	'	$1,517	$2,160

Settlement_Agreement_Details

Settlement Agreement (Details) (Other Income [Member], USD $)	3 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013
Gain Contingencies [Line Items]	'	'	'	'
Cash settlement payment	$0	$0	$43,429	$0
Positive Outcome of Litigation [Member]	'	'	'	'
Gain Contingencies [Line Items]	'	'	'	'
Cash settlement payment	'	'	$43,429	'

Quarterly_Financial_Data_Detai

Quarterly Financial Data (Details) (USD $)

3 Months Ended

12 Months Ended

3 Months Ended

1 Months Ended

3 Months Ended

In Thousands, except Per Share data, unless otherwise specified

Dec. 31, 2013

Sep. 30, 2013

Jun. 30, 2013

Mar. 31, 2013

Dec. 31, 2012

Sep. 30, 2012

Jun. 30, 2012

Mar. 31, 2012

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2011

Dec. 31, 2013

Sep. 30, 2013

Jun. 30, 2013

Mar. 31, 2013

Dec. 31, 2013

Sep. 30, 2013

Jun. 30, 2013

Mar. 31, 2013

Nov. 30, 2012

Dec. 31, 2012

Sep. 30, 2012

Jun. 30, 2012

Mar. 31, 2012

Gain on sale of subsidiary [Member]

Gain on sale of subsidiary [Member]

Gain on sale of subsidiary [Member]

Gain on sale of subsidiary [Member]

Settlement agreement [Member]

Settlement agreement [Member]

Settlement agreement [Member]

Settlement agreement [Member]

SIV Securities [Member]

SIV Securities [Member]

SIV Securities [Member]

SIV Securities [Member]

SIV Securities [Member]

Revenues

$299,024

$280,655

$274,574

$271,879

$261,635

$251,752

$241,237

$237,898

$1,126,132

$992,522

$929,727

'

'

'

'

'

'

'

'

'

'

'

'

'

Income before income taxes

101,063

93,986

129,387

110,962

87,544

83,501

78,501

79,950

435,398

329,496

318,487

'

'

'

'

'

'

'

'

'

'

'

'

'

Net income attributable to SEI Investments Company

65,515

67,195

83,494

71,920

56,585

50,743

49,555

49,965

288,124

206,848

204,959

'

'

'

'

'

'

'

'

'

'

'

'

'

Basic earnings per common share

$0.39

$0.39

$0.48

$0.42

$0.33

$0.29

$0.28

$0.28

$1.68

$1.19

$1.12

'

'

'

'

'

'

'

'

'

'

'

'

'

Diluted earnings per common share

$0.37

$0.38

$0.47

$0.41

$0.32

$0.29

$0.28

$0.28

$1.64

$1.18

$1.11

'

'

'

'

'

'

'

'

'

$0.02

$0.01

$0

$0.01

Effective income tax rate

35.20%

28.50%

35.50%

34.90%

35.00%

39.00%

36.60%

37.20%

33.70%

36.90%

35.20%

'

'

'

'

'

'

'

'

'

'

'

'

'

Gain on sale of subsidiary (Note 15)

'

'

'

'

'

'

'

'

22,112

0

0

0

0

0

22,112

'

'

'

'

'

'

'

'

'

Settlement agreement (Note 16)

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

0

0

43,429

0

'

'

'

'

'

Total SIV-related gains

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

$5,322

$5,897

$3,389

$1,072

$2,882

Income (Loss) from Extraordinary Items, Net of Tax, Per Diluted Share

'

'

'

$0.08

'

'

'

'

'

'

'

$0

$0

$0

$0.08

$0

$0

$0.16

$0

'

'

'

'

'

Schedule_II_Valuation_And_Qual1

Schedule II - Valuation And Qualifying Accounts And Reserves (Details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Allowance For Doubtful Accounts [Member]	'	'	'
Movement in Valuation Allowances and Reserves [Roll Forward]	'	'	'
Balance at Beginning of Year	$805	$924	$1,195
Additions, Charged to Costs and Expenses	0	0	0
Additions, Charged to Other Accounts	0	0	0
(Deductions)	-154	-119	-271
Balance at End of Year	651	805	924
Deferred Income Tax Valuation Allowance [Member]	'	'	'
Movement in Valuation Allowances and Reserves [Roll Forward]	'	'	'
Balance at Beginning of Year	6,879	8,585	9,008
Additions, Charged to Costs and Expenses	-485	-1,706	-423
Additions, Charged to Other Accounts	8,344	0	0
(Deductions)	0	0	0
Balance at End of Year	$14,738	$6,879	$8,585