SEI Investments (SEIC) 10-K 22 Feb 21 2020 FY Annual report Financial data

Cover

Cover - USD ($) $ in Billions	12 Months Ended
	Dec. 31, 2020	Jan. 29, 2021	Jun. 30, 2020
Cover [Abstract]
Document Type	10-K
Document Annual Report	true
Document Period End Date	Dec. 31, 2020
Current Fiscal Year End Date	--12-31
Document Transition Report	false
Entity File Number	0-10200
Entity Registrant Name	SEI INVESTMENTS COMPANY
Entity Incorporation, State or Country Code	PA
Entity Tax Identification Number	23-1707341
Entity Address, Address Line One	1 Freedom Valley Drive
Entity Address, City or Town	Oaks
Entity Address, State or Province	PA
Entity Address, Postal Zip Code	19456
City Area Code	610
Local Phone Number	676-1000
Title of 12(b) Security	Common Stock, par value $.01 per share
Trading Symbol	SEIC
Security Exchange Name	NASDAQ
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
ICFR Auditor Attestation Flag	true
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Public Float			$ 6.3
Entity Common Stock, Shares Outstanding		143,516,670
Documents Incorporated by Reference	Portions of the following documents are incorporated by reference herein: 1. The definitive proxy statement relating to the registrant’s 2021 Annual Meeting of Shareholders, to be filed within 120 days after the end of the fiscal year covered by this annual report, is incorporated by reference in Part III hereof.
Entity Central Index Key	0000350894
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	FY
Amendment Flag	false

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Current Assets:
Cash and cash equivalents	$ 784,626	$ 841,446
Restricted cash	3,101	3,101
Receivables from investment products	55,271	54,165
Receivables, net of allowance for doubtful accounts of $1,100 and $1,201	385,219	340,358
Securities owned	34,064	33,486
Other current assets	38,696	32,289
Total Current Assets	1,300,977	1,304,845
Property and Equipment, net of accumulated depreciation of $378,639 and $353,453	189,052	160,859
Operating Lease Right-of-Use Assets	38,397	42,789
Capitalized Software, net of accumulated amortization of $491,739 and $442,677	270,977	296,068
Available For Sale and Equity Securities	105,419	116,917
Investments in Affiliated Funds, at fair value	6,166	5,988
Investment in Unconsolidated Affiliate	98,433	67,413
Goodwill	64,489	64,489
Intangible Assets, net of accumulated amortization of $12,456 and $8,773	24,304	27,987
Deferred Contract Costs	33,781	30,991
Deferred Income Taxes	2,972	2,822
Other Assets, net	32,289	30,202
Total Assets	2,167,256	2,151,370
Current Liabilities:
Accounts payable	7,766	4,423
Accrued liabilities	299,845	272,801
Current portion of long-term operating lease liabilities	8,579	9,156
Deferred revenue	1,085	7,185
Total Current Liabilities	317,275	293,565
Long-term Income Taxes Payable	803	803
Deferred Income Taxes	55,159	55,722
Long-term Operating Lease Liabilities	34,058	38,450
Other Long-term Liabilities	20,054	24,052
Total Liabilities	427,349	412,592
Commitments and Contingencies
Shareholders' Equity:
Common stock, $.01 par value, 750,000 shares authorized; 143,396 and 149,745 shares issued and outstanding	1,434	1,497
Capital in excess of par value	1,190,001	1,158,900
Retained earnings	565,270	601,885
Accumulated other comprehensive loss, net	(16,798)	(23,504)
Total Shareholders' Equity	1,739,907	1,738,778
Total Liabilities and Equity	$ 2,167,256	$ 2,151,370
Common stock, par value (in USD per share)	$ 0.01	$ 0.01
Common stock, shares authorized	750,000,000	750,000,000

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Statement of Financial Position [Abstract]
Receivables, allowance for doubtful accounts	$ 1,100	$ 1,201
Property and Equipment, accumulated depreciation	378,639	353,453
Capitalized software, accumulated amortization	491,739	442,677
Intangible assets, accumulated amortization	$ 12,456	$ 8,773
Common stock, par value (in USD per share)	$ 0.01	$ 0.01
Common stock, shares authorized	750,000,000	750,000,000
Common stock, shares issued	143,396,000	149,745,000

Consolidated Statements of Oper

Consolidated Statements of Operations - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Revenues:
Revenues	$ 1,684,058	$ 1,649,885	$ 1,624,167
Expenses:
Subadvisory, distribution and other asset management costs	181,618	181,418	180,488
Software royalties and other information processing costs	28,937	29,993	32,449
Compensation, benefits and other personnel	527,509	517,917	511,258
Stock-based compensation	27,014	24,582	23,805
Consulting, outsourcing and professional fees	227,916	194,560	200,862
Data processing and computer related	96,328	88,058	84,790
Facilities, supplies and other costs	64,915	72,078	70,840
Amortization	52,975	51,419	48,895
Depreciation	30,959	29,436	28,792
Total expenses	1,238,171	1,189,461	1,182,179
Income from operations	445,887	460,424	441,988
Net (loss) gain from investments	(286)	3,174	(325)
Interest and dividend income	6,568	16,582	13,397
Interest expense	(609)	(630)	(645)
Equity in earnings of unconsolidated affiliates	117,134	151,891	159,791
Income before income taxes	568,694	631,441	614,206
Income taxes	121,408	130,015	108,338
Net income	$ 447,286	$ 501,426	$ 505,868
Basic earnings per common share (in USD per share)	$ 3.05	$ 3.31	$ 3.23
Shares used to compute basic earnings per share	146,709	151,540	156,579
Diluted earnings per common share (in USD per share)	$ 3	$ 3.24	$ 3.14
Shares used to compute diluted earnings per share	149,003	154,901	161,232
Dividends declared per common share (in USD per share)	$ 0.72	$ 0.68	$ 0.63
Asset management, administration and distribution fees
Revenues:
Revenues	$ 1,345,649	$ 1,307,044	$ 1,270,180
Information processing and software servicing fees
Revenues:
Revenues	$ 338,409	$ 342,841	$ 353,987

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Statement of Comprehensive Income [Abstract]
Net income	$ 447,286	$ 501,426	$ 505,868
Other comprehensive income (loss), net of tax:
Foreign currency translation adjustments	5,620	7,618	(12,065)
Unrealized holding gain (loss) on investments:
Unrealized holding gains (losses) during the period, net of income taxes of $(134), $(461) and $285	374	1,486	(1,088)
Less: reclassification adjustment for losses realized in net income, net of income taxes of $(190), $(101) and $(96)	712	392	61
Total other comprehensive income (loss), net of taxes	6,706	9,496	(13,092)
Comprehensive income	$ 453,992	$ 510,922	$ 492,776

Consolidated Statements of Co_2

Consolidated Statements of Comprehensive Income (Parenthetical) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Statement of Comprehensive Income [Abstract]
Unrealized holding gains (losses) during the period, income taxes	$ (134)	$ (461)	$ 285
Reclassification adjustment for losses realized in net income, income taxes	$ (190)	$ (101)	$ (96)

Consolidated Statements of Chan

Consolidated Statements of Changes in Equity - USD ($) shares in Thousands, $ in Thousands	Total	Common Stock	Capital In Excess of Par Value	Retained Earnings	Retained EarningsCumulative Effect, Period of Adoption, Adjustment	Accumulated Other Comprehensive Loss
Beginning balance at Dec. 31, 2017		$ 1,571	$ 1,027,709	$ 467,467	$ 14,402	$ (19,908)
Beginning balance, shares at Dec. 31, 2017		157,069
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Purchase and retirement of common stock		$ (67)	(32,823)	(371,867)
Purchase and retirement of common stock, shares		(6,744)
Issuance of common stock under the employee stock purchase plan			4,170
Issuance of common stock under the employee stock purchase plan, shares		77
Issuance of common stock upon exercise of stock options		$ 32	83,780
Issuance of common stock upon exercise of stock options, shares	3,232	3,232
Stock-based compensation			23,805
Net income	$ 505,868			505,868
Dividends declared ($0.72, $0.68 and $0.63 per share)	(97,900)			(97,900)
Other comprehensive income (loss)	(13,092)					(13,092)
Ending balance at Dec. 31, 2018	$ 1,593,147	$ 1,536	1,106,641	517,970		(33,000)
Ending balance, shares at Dec. 31, 2018		153,634
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Purchase and retirement of common stock		$ (62)	(33,210)	(315,076)
Purchase and retirement of common stock, shares		(6,225)
Issuance of common stock under the employee stock purchase plan		$ 1	4,224
Issuance of common stock under the employee stock purchase plan, shares		93
Issuance of common stock upon exercise of stock options		$ 22	56,663
Issuance of common stock upon exercise of stock options, shares	2,243	2,243
Stock-based compensation			24,582
Net income	$ 501,426			501,426
Dividends declared ($0.72, $0.68 and $0.63 per share)	(102,435)			(102,435)
Other comprehensive income (loss)	9,496					9,496
Ending balance at Dec. 31, 2019	$ 1,738,778	$ 1,497	1,158,900	601,885		(23,504)
Ending balance, shares at Dec. 31, 2019	149,745	149,745
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Purchase and retirement of common stock		$ (80)	(45,309)	(379,313)
Purchase and retirement of common stock, shares		(8,007)
Issuance of common stock under the employee stock purchase plan		$ 1	4,346
Issuance of common stock under the employee stock purchase plan, shares		95
Issuance of common stock upon exercise of stock options		$ 16	45,050
Issuance of common stock upon exercise of stock options, shares	1,563	1,563
Stock-based compensation			27,014
Net income	$ 447,286			447,286
Dividends declared ($0.72, $0.68 and $0.63 per share)	(104,588)			(104,588)
Other comprehensive income (loss)	6,706					6,706
Ending balance at Dec. 31, 2020	$ 1,739,907	$ 1,434	$ 1,190,001	$ 565,270		$ (16,798)
Ending balance, shares at Dec. 31, 2020	143,396	143,396

Consolidated Statements of Ch_2

Consolidated Statements of Changes in Equity (Parenthetical) - $ / shares	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Dividends declared per common share (in USD per share)	$ 0.72	$ 0.68	$ 0.63
Retained Earnings
Dividends declared per common share (in USD per share)	$ 0.72	$ 0.68	$ 0.63

Consolidated Statements of Cash

Consolidated Statements of Cash Flows $ in Thousands	12 Months Ended
	Dec. 31, 2020USD ($)	Dec. 31, 2019USD ($)	Dec. 31, 2018USD ($)
Cash flows from operating activities:
Net income	$ 447,286	$ 501,426	$ 505,868
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation	30,959	29,436	28,792
Amortization	52,975	51,419	48,895
Equity in earnings of unconsolidated affiliates	(117,134)	(151,891)	(159,791)
Partner distributions received from unconsolidated affiliate	125,534	148,936	166,698
Stock-based compensation	27,014	24,582	23,805
Provision for losses on receivables	(101)	483	23
Deferred income tax (benefit) expense	(1,036)	(3,414)	5,998
Net loss (gain) from investments	286	(3,174)	325
Change in long-term taxes payable	0	0	(9,826)
Change in other long-term liabilities	(420)	(163)	145
Change in other assets	(1,449)	1,791	(4,785)
Contract costs capitalized, net	(2,790)	(6,984)	(5,366)
Other	912	620	(294)
Decrease (increase) in:
Receivables from investment products	(1,106)	(4,296)	6,797
Receivables	(44,761)	(25,505)	(32,652)
Other current assets	(6,407)	3,334	(5,518)
Advances due from unconsolidated affiliate	(39,420)	(12,116)	243
Increase (decrease) in:
Accounts payable	3,343	(6,497)	5,652
Accrued liabilities	21,097	(4,896)	13,079
Deferred revenue	(6,100)	2,031	313
Total adjustments	41,396	43,696	82,533
Net cash provided by operating activities	488,682	545,122	588,401
Cash flows from investing activities:
Additions to property and equipment	(54,448)	(43,097)	(29,095)
Additions to capitalized software	(24,119)	(34,074)	(44,221)
Purchases of marketable securities	(143,493)	(174,997)	(203,460)
Prepayments and maturities of marketable securities	155,110	171,399	167,876
Sales of marketable securities	842	51	0
Cash paid for acquisition, net of cash acquired	0	0	(5,794)
Other investing activities	(1,388)	2,538	(8,676)
Net cash used in investing activities	(67,496)	(78,180)	(123,370)
Cash flows from financing activities:
Payment of contingent consideration	(633)	(433)	0
Repayments under revolving credit facility	0	0	(30,000)
Purchase and retirement of common stock	(427,001)	(346,352)	(407,384)
Proceeds from issuance of common stock	49,413	60,910	87,982
Payment of dividends	(103,914)	(100,745)	(94,318)
Net cash used in financing activities	(482,135)	(386,620)	(443,720)
Effect of exchange rate changes on cash, cash equivalents and restricted cash	4,129	6,186	(11,024)
Net (decrease) increase in cash, cash equivalents and restricted cash	(56,820)	86,508	10,287
Cash, cash equivalents and restricted cash, beginning of year	844,547	758,039	747,752
Cash, cash equivalents and restricted cash, end of year	787,727	844,547	758,039
Interest paid	612	493	806
Income taxes paid	121,987	139,326	110,203
Non-cash operating activities
Operating lease right-of-use assets and net lease liabilities recorded upon adoption of ASC 842	0	44,169
Non-cash financing activities
Dividends declared but not paid	$ 53,127	$ 52,452	$ 50,761

Summary of Significant Accounti

Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2020
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 comprehensive platforms for investment processing, investment operations and investment management to wealth managers, financial institutions, financial advisors, investment managers, institutional investors and ultra-high-net-worth families in the United States, Canada, the United Kingdom, continental Europe and various other locations throughout the world. Investment processing platforms consist of application and business process outsourcing services, professional services and transaction-based services. Revenues from investment processing platforms are recognized in Information processing and software servicing fees on the accompanying Consolidated Statements of Operations. Investment operations platforms consist of outsourcing services including fund and investment accounting, administration, reconciliation, investor servicing and client reporting. Revenues from investment operations platforms are recognized in Asset management, administration and distribution fees on the accompanying Consolidated Statements of Operations. Investment management platforms consists of investment products including mutual funds, collective investment products, alternative investment portfolios and separately managed accounts. The Company serves as the administrator and investment advisor for many of these products. Revenues from investment management platforms 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% to 50% owned or are 20% 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. Any investments in entities not consolidated or accounted for under the equity method are accounted for under the cost method of accounting. Variable Interest Entities The Company or its affiliates have 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. The Company receives asset management, distribution, administration and custodial fees for these services. 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. The Company has concluded that it is not the primary beneficiary of the entities and, therefore, is not required to consolidate any of the pooled investment vehicles for which it receives asset management, distribution, administration and custodial fees under the VIE model. The entities either do not meet the definition of a VIE or the Company does not hold a variable interest in the entities. The entities either qualify for the money market scope exception, or are entities in which the Company’s asset management, distribution, administration and custodial fees are commensurate with the services provided and include fair terms and conditions, or are entities that are limited partnerships which have substantive kick-out rights. The Company acts as a fiduciary and does not hold any other interests other than insignificant seed money investments in the pooled investment vehicles. For this reason, the Company also concluded that it is not required to consolidate the pooled investment vehicles under the voting interest entity model. The Company is a party to expense limitation agreements with certain SEI-sponsored money market funds subject to Rule 2a-7 of the Investment Company Act of 1940 which establish a maximum level of ordinary operating expenses incurred by the fund in any fiscal year including, but not limited to, fees of the administrator or its affiliates. Under the terms of these agreements, the Company waived $33,408, $27,544 and $26,229 in fees during 2020, 2019 and 2018, respectively. Management’s Use of Estimates The preparation of financial statements in conformity with accounting principles generally accepted in the United States (U.S. GAAP) 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 is recognized when the transfer of control of promised goods or services under the terms of a contract with customers are satisfied in an amount that reflects the consideration to which the Company expects to be entitled in exchange for those promised goods or services. Certain portions of the Company’s revenues involve a third party in providing goods or services to its customers. In such circumstances, the Company must determine whether the nature of its promise to the customer is to provide the underlying goods or services (the Company is the principal in the transaction and reports the transaction gross) or to arrange for a third party to provide the underlying goods or services (the entity is the agent in the transaction and reports the transaction net). The Company does not disclose the value of unsatisfied performance obligations as the majority of its contracts relate to: 1) contracts with an original term of one year or less; 2) contracts for which the Company recognizes revenue at the amount to which it has the right to invoice for services performed; and 3) contracts that are based on the value of assets under management or administration. See Note 15 for related disclosures regarding revenue recognition. 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 $347,082 and $414,581 at December 31, 2020 and 2019, 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 $3,000 at December 31, 2020 and 2019 segregated for regulatory purposes related to trade-execution services conducted by SIEL. Restricted cash also includes $101 at December 31, 2020 and 2019 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 the Company's receivables are limited due to the large number of clients and their dispersion across geographic areas. No single group or customer represents greater than 10% 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 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 associated with the Company's available for sale debt securities, net of income taxes, are reported as a separate component of comprehensive income. SIDCO, the Company’s broker-dealer subsidiary, reports changes in fair value of marketable securities through current period earnings due to specialized accounting practices related to investments by broker-dealers. The Company records its investments in money market funds and commercial paper classified as cash equivalents, funds sponsored by LSV and equity securities not accounted for under the equity method 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 5). The Company evaluates the realizable value of its available for sale debt securities on a quarterly basis. In the event that an other-than-temporary decline in fair value has occurred, the amount of the decline related to a credit loss is reported through current period earnings. Some of the factors considered in determining other-than-temporary impairment 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. The Company did not recognize any impairment charges related to its available for sale debt securities in 2020, 2019 or 2018. Fair Value of Financial Instruments Fair value is defined as the exchange price that would be received for an asset or paid to transfer a liability (an exit price) in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants on the measurement date. The fair value hierarchy requires an entity to maximize the use of observable inputs and minimize the use of unobservable inputs when measuring fair value. The fair value hierarchy describes three levels of inputs that may be used by the Company to measure fair value: Level 1 – Quoted prices in active markets for identical assets or liabilities without adjustment. The Company’s Level 1 assets primarily include investments in mutual funds sponsored by SEI that are quoted daily. Level 2 – Observable inputs other than Level 1 prices, such as quoted prices for similar assets, quoted prices in markets that are not active, or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the assets or liabilities. Level 2 financial assets consist of GNMA mortgage-backed securities, Federal Home Loan Bank (FHLB) and other U.S. government agency short-term notes. The investments in GNMA mortgage-backed securities were purchased for the sole purpose of satisfying applicable regulatory requirements imposed on our wholly-owned limited purpose federal thrift subsidiary, SPTC. The investments in FHLB and other U.S. government agency short-term notes were purchased as part of a cash management program requiring only short term, top-tier investment grade government and corporate 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 had no Level 3 financial assets at December 31, 2020 or 2019 that were required to be measured at fair value on a recurring basis. The Company's Level 3 financial liabilities at December 31, 2020 and 2019 consist entirely of an estimated contingent consideration resulting from the Company's acquisition of Huntington Steele, LLC (See Note 14). The fair value of an asset or liability may include inputs from more than one level in the fair value hierarchy. The lowest level of significant inputs used to value the asset or liability determines which level the asset or liability is classified in its entirety. Transfers between levels of the fair value hierarchy are reported at fair value as of the beginning of the period in which the transfers occur. See Note 4 for 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 to ensure the costs incurred will result in additional functionality of the software. Amortization of capitalized software development costs begins when the product is ready for its intended use. Capitalized software development costs are amortized on a product-by-product basis using the straight-line method over the estimated economic life of the product or enhancement. The Company capitalized $24,119, $34,074 and $44,221 of software development costs during 2020, 2019 and 2018, respectively. The Company's capitalized software development costs primarily relate to the further development of the SEI Wealth Platform SM (SWP). The Company capitalized $22,257, $33,084 and $43,376 of software development costs for significant enhancements to SWP during 2020, 2019 and 2018, respectively. As of December 31, 2020, the net book value of SWP was $257,709. The net book value includes $13,409 of capitalized software development costs in-progress associated with future releases. Management continually reassesses the estimated useful life of SWP and any change in management’s estimate could result in the remaining amortization expense to be accelerated or spread out over a longer period. As of December 31, 2020, SWP has a weighted average remaining life of 9.9 years. Amortization expense for SWP was $43,853, $42,297 and $39,917 in 2020, 2019 and 2018, respectively, and is included in Amortization expense on the accompanying Consolidated Statements of Operations. The Company also capitalized $845 of software development costs during 2018 related to an application for the Investment Managers segment. The application was placed into service during 2018 and has a net book value of $10,416 with an estimated remaining useful life of 2.0 years as of December 31, 2020. Amortization expense for the application was $5,209 during 2020 and 2019 and is included in Amortization expense on the accompanying Consolidated Statements of Operations. The Company currently expects to recognize amortization expense related to all capitalized software development costs placed into service as of December 31, 2020 each year from 2021 through 2025 as follows: Year Expected Amortization Expense Related to Capitalized Software 2021 $ 52,466 2022 37,621 2023 18,838 2024 18,838 2025 18,838 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. The Company did not recognize any impairment charges related to its capitalized software development costs in 2020, 2019 or 2018. Goodwill and Other Intangible Assets The Company adopted the requirements of ASU 2017-04, Simplifying the Test for Goodwill Impairment (ASU 2017-04) on January 1, 2020. The adoption of ASU 2017-04 did not have a material impact on the Company's consolidated financial statements and related disclosures. The Company reviews long-lived assets and identifiable definite-lived intangible assets for impairment at least annually or whenever events or changes in circumstances indicate that the carrying amount of these assets may not be recoverable. For purposes of recognizing and measuring an impairment loss, a long-lived asset is grouped with other assets and liabilities at the lowest level for which identifiable cash flows are largely independent. Identifiable definite-lived intangible assets on the Company’s Consolidated Balance Sheet are amortized on a straight-line basis according to their estimated useful lives. Goodwill is not amortized but is reviewed for impairment annually or more frequently if an event occurs or circumstances change that would more likely than not reduce the fair value of a reporting unit below its carrying amount. Current guidance requires that a qualitative assessment be performed to assess goodwill for impairment. The fair value of each reporting unit is compared with its carrying value, including goodwill. If the fair value exceeds the carrying value, goodwill is not impaired and no further testing is performed. If the qualitative assessment indicates the carrying value exceeds the fair value, a quantitative impairment test is then utilized to identify potential goodwill impairment and measure the amount of a goodwill impairment loss to be recognized. The Company did not recognize any impairment charges related to its goodwill or other intangible assets in 2020, 2019 or 2018. See Note 14 for related disclosures regarding goodwill and intangible assets. Contingent Consideration Liabilities The Company may be required to pay additional future consideration in connection with business acquisitions based on the attainment of specified financial measures. The Company estimates the fair value of these potential future obligations at the time a business combination is consummated and records a contingent consideration liability on the Consolidated Balance Sheets. If the expected payment amounts subsequently change, the contingent consideration liabilities are adjusted through current period earnings and included in Facilities, supplies and other costs on the accompanying Consolidated Statement of Operations. See Note 14 for related disclosures regarding contingent consideration liabilities. 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. See Note 11 for related disclosures regarding income taxes. 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 2020, 2019 or 2018. 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 2020, 2019 and 2018 are: 2020 2019 2018 Net income $ 447,286 $ 501,426 $ 505,868 Shares used to compute basic earnings per common share 146,709,000 151,540,000 156,579,000 Dilutive effect of stock options 2,294,000 3,361,000 4,653,000 Shares used to compute diluted earnings per common share 149,003,000 154,901,000 161,232,000 Basic earnings per common share $ 3.05 $ 3.31 $ 3.23 Diluted earnings per common share $ 3.00 $ 3.24 $ 3.14 Employee stock options to purchase approximately 9,220,000, 6,574,000 and 6,224,000 shares of common stock, with an average exercise price per share of $58.12, $55.95 and $53.60, were outstanding during 2020, 2019 and 2018, respectively, but not included in the computation of diluted earnings per common share because either the performance conditions have not been satisfied or the option’s exercise price was greater than the average market price of the Company’s common stock and the effect on diluted earnings per common share would have been anti-dilutive (See Note 7). 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 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 7). Leases The Company adopted the requirements of the ASU 2016-02 Leases (Topic 842) (ASC 842) using the modified retrospective method on January 1, 2019. As a result of the adoption of ASC 842, the Company recorded additional lease assets and net lease liabilities of $44,169 as of January 1, 2019. Upon implementation, the Company elected the package of practical expedients permitted under the transition guidance within the new standard which allowed the Company to carryforward the historical lease identification, classification and initial direct cost. ASC 842 did not materially impact the Company’s consolidated net income or consolidated cash flows. The Company determines if an arrangement is a lease at the inception of the contract. The Company's operating leases are included in Operating lease right-of-use (ROU) assets, Current portion of long-term operating lease liabilities, and Long-term operating lease liabilities on the accompanying Consolidated Balance Sheets. The operating lease ROU assets and operating lease liabilities are recognized based on the present value of future minimum lease payments over the lease term at commencement date. As most of the Company’s leases do not provide an implicit interest rate, the Company utilizes an estimated incremental borrowing rate based on the information available at commencement date in determining the present value of future payments. In determining the discount rate used in the present value calculation, the Company has elected to apply the portfolio approach for leases of equipment provided the leases commenced at or around the same time. This election allows the Company to account for leases at a portfolio level provided that the resulting accounting at this level would not differ materially from the accounting at the individual lease level. Lease expense for minimum lease payments is recognized on a straight-line basis over the lease term. The Company has elected to account for lease and non-lease components separately. Operating lease ROU assets include all contractual lease payments and initial direct costs incurred, less any lease incentives. Facility leases generally only contain lease expense and non-component items such as taxes and pass through charges. Only the lease components are included in the ROU assets and lease liabilities. Additionally, the Company has elected not to apply the recognition requirements of ASC 842 to leases which have a lease term of less than one year at the commencement date. The majority of the Company's leases for corporate facilities and equipment contain terms for renewal and extension of the lease agreement. The exercise of lease renewal options is generally at the Company’s sole discretion. The Company includes the lease extensions when it is reasonably certain the Company will exercise the extension. The Company’s lease agreements do not contain any material variable lease payments, material residual value guarantees or any material restrictive covenants. The Company does not currently have any finance leases. See Note 16 for related disclosures regarding leases. Reclassifications Certain prior year amounts have been reclassified to conform to current year presentation. Other Recently Adopted Accounting Pronouncements The Company adopted the requirements of Accounting Standards Update (ASU) 2016-13, Financial Instruments-Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments (Accounting Standards Codification (ASC) 326)) (ASU 2016-13) and subsequent amendments ASU 2019-04, Codification Improvements to Topic 326, Financial Instruments-Credit Losses, Topic 815, Derivatives and Hedging, and Topic 825, Financial Instruments (ASU 2019-04) and ASU 2019-11, Codification Improvements to Topic 326, Financial Instruments-Credit Losses (ASU 2019-11) on January 1, 2020. ASU 2016-13 and the related amendments are hereafter referred to as ASC 326. ASC 326 requires that expected credit losses relating to financial assets measured on an amortized cost basis and available-for-sale debt securities be recorded through an allowance for credit losses. The Company owns mortgage-backed securities issued by the Government National Mortgage Association (GNMA), a federal agency of the U.S. government classified as Available-for-sale debt securities which qualify for the zero credit risk allowance. The Company's U.S. Treasury and other U.S. government agency securities classified as Securities owned are outside the scope of ASC 326. There was no impact to the Company's disclosures related to its marketable securities from the implementation of ASC 326. In accordance with ASC 326, the Company evaluated its receivable balances for credit risk based upon the source of revenue, its ability to collect fees directly from investment products or directly from assets in the client's account, a review of actual historical credit losses, and the potential for expected credit loss from its current client base. The Company has no meaningful historical credit loss data and a very limited amount of losses pertaining directly to a client's inability to satisfy its receivable balance even during periods of economic distress. The credit loss reserve recognized by the Company through the implementation of ASC 326 during 2020 was immaterial. New Accounting Pronouncements In December 2019, the Financial Accounting Standards Board (FASB) issued ASU 2019-12, Income Taxes (Topic 740): Simplifying the Accounting for Income Taxes (ASU 2019-12). The standard removes certain exceptions to the general principles in Topic 740 and also clarifies and amends existing guidance to improve consistent application. ASU 2019-12 is

Investment in Unconsolidated Af

Investment in Unconsolidated Affiliates	12 Months Ended
	Dec. 31, 2020
Equity Method Investments and Joint Ventures [Abstract]
Investment in Unconsolidated Affiliates	Investment in Unconsolidated Affiliates LSV Asset Management The Company has an investment in the general partnership LSV Asset Management (LSV), a registered investment advisor that provides investment advisory services primarily to institutions, including pension plans and investment companies. LSV is currently an investment sub-advisor for a limited number of SEI-sponsored mutual funds. As of December 31, 2020, the Company's total partnership interest in LSV was approximately 38.8%. The Company accounts for its interest in LSV using the equity method because of its less than 50% ownership. The Company’s interest in the net assets of LSV is reflected in Investment in unconsolidated affiliates on the accompanying Consolidated Balance Sheets and its interest in the earnings of LSV is reflected in Equity in earnings of unconsolidated affiliates on the accompanying Consolidated Statements of Operations. At December 31, 2020, the Company’s total investment in LSV was $98,433. The Company’s proportionate share in the earnings of LSV was $117,134, $151,891 and $159,791 in 2020, 2019 and 2018, respectively. The Company receives partnership distributions related to the earnings of LSV on a quarterly basis. As such, the Company considers these distribution payments as returns on investment rather than returns of the Company's original investment in LSV and has therefore classified the associated cash inflows as an operating activity on the Consolidated Statements of Cash Flows. The Company received partnership distribution payments from LSV of $125,534, $148,936 and $166,698 in 2020, 2019 and 2018, respectively. These tables contain condensed financial information of LSV: Condensed Statement of Operations Year ended December 31, 2020 2019 2018 Revenues $ 391,648 $ 491,700 $ 517,203 Net income $ 301,620 $ 390,533 $ 410,846 Condensed Balance Sheets December 31, 2020 2019 Current assets $ 151,515 $ 144,547 Non-current assets 4,296 5,048 Total assets $ 155,811 $ 149,595 Current liabilities $ 77,077 $ 46,828 Non-current liabilities 4,620 5,326 Partners’ capital 74,114 97,441 Total liabilities and partners’ capital $ 155,811 $ 149,595

Composition of Certain Financia

Composition of Certain Financial Statement Captions	12 Months Ended
	Dec. 31, 2020
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Composition of Certain Financial Statement Captions	Composition of Certain Financial Statement Captions Receivables Receivables on the accompanying Consolidated Balance Sheets consist of: 2020 2019 Trade receivables $ 99,106 $ 86,043 Fees earned, not billed 262,167 240,239 Other receivables 25,046 15,277 386,319 341,559 Less: Allowance for doubtful accounts (1,100) (1,201) Receivables, net $ 385,219 $ 340,358 Fees earned, not billed represents receivables from contracts from customers 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 calculated based on assets under administration that have an extended valuation process. Billings to these clients occur once the asset valuation processes are completed. Property and Equipment Property and Equipment on the accompanying Consolidated Balance Sheets consists of: 2020 2019 Buildings $ 206,151 $ 162,882 Equipment 141,820 123,945 Land 24,179 10,830 Purchased software 147,838 143,705 Furniture and fixtures 21,439 18,835 Leasehold improvements 21,604 20,700 Construction in progress 4,660 33,415 567,691 514,312 Less: Accumulated depreciation (378,639) (353,453) Property and Equipment, net $ 189,052 $ 160,859 Depreciation expense related to property and equipment for 2020, 2019 and 2018 was $30,959, $29,436 and $28,792, respectively. Deferred Contract Costs The Company's incremental contract acquisition costs are related to information processing contracts in the Private Banks segment and investment operations contracts in the Investment Managers segment. These deferred costs primarily consist of sales compensation payments to the Company's sales personnel. The Company defers and amortizes incremental contract acquisition costs using the straight-line method over the expected client life, which ranges from 6 to 15 years. Deferred contract costs were $33,781 and $30,991 as of December 31, 2020 and 2019, respectively. The Company deferred expenses related to contract costs of $10,284, $11,495 and $8,122 during 2020, 2019 and 2018, respectively. Amortization expense related to deferred contract costs were $7,494, $4,511 and $2,756 during 2020, 2019 and 2018, respectively, and is included in Compensation, benefits and other personnel on the accompanying Consolidated Statements of Operations. There were no material impairment losses in relation to deferred contract costs during 2020, 2019 or 2018. 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 2020, 2019 and 2018 was $230, $230 and $231, respectively. Accrued Liabilities Accrued Liabilities on the accompanying Consolidated Balance Sheets consist of: 2020 2019 Accrued employee compensation $ 95,656 $ 96,991 Accrued employee benefits and other personnel 18,770 9,222 Accrued consulting, outsourcing and professional fees 31,907 28,610 Accrued sub-advisory, distribution and other asset management fees 49,924 46,245 Accrued dividend payable 53,127 52,452 Other accrued liabilities 50,461 39,281 Accrued liabilities $ 299,845 $ 272,801

Fair Value Measurements

Fair Value Measurements	12 Months Ended
	Dec. 31, 2020
Fair Value Disclosures [Abstract]
Fair Value Measurements	Fair Value MeasurementsThe fair value of the Company’s financial assets and liabilities, except for the Company's investment funds sponsored by LSV, is determined in accordance with the fair value hierarchy. The fair value of the Company’s Level 1 financial assets consists mainly of investments in open-ended mutual funds that are quoted daily. Level 2 financial assets consist of Government National Mortgage Association (GNMA) mortgage-backed securities held by the Company's wholly-owned limited purpose federal thrift subsidiary, SEI Private Trust Company (SPTC), Federal Home Loan Bank (FHLB) and other U.S. government agency short-term notes held by SIDCO. The financial assets held by SIDCO were purchased as part of a cash management program requiring only short term, top-tier investment grade government and corporate securities. The financial assets held by SPTC are debt securities issued by GNMA and are backed by the full faith and credit of the U.S. government. These securities were purchased for the sole purpose of satisfying applicable regulatory requirements and have maturity dates which range from 2023 to 2041. The fair value of the Company's investment funds sponsored by LSV is measured using the net asset value per share (NAV) as a practical expedient. The NAVs of the funds are calculated by the funds' independent custodian and are derived from the fair values of the underlying investments as of the reporting date. The funds allow for investor redemptions at the end of each calendar month. This investment has not been classified in the fair value hierarchy but is presented in the tables below to permit reconciliation to the amounts presented on the accompanying Consolidated Balance Sheets. The valuation of the Company's Level 2 financial assets held by SIDCO and SPTC are based upon securities pricing policies and procedures utilized by third-party pricing vendors. The Company had no Level 3 financial assets at December 31, 2020 or 2019 that were required to be measured at fair value on a recurring basis. The Company's Level 3 financial liabilities at December 31, 2020 and 2019 consist entirely of the estimated fair value of the contingent consideration resulting from an acquisition (See Note 14). The fair value of the contingent consideration was determined using a Monte-Carlo simulation model. Key assumptions for the Monte-Carlo simulation model include expected revenues, expected volatility, risk-free rate and other factors. There were no transfers of financial assets between levels within the fair value hierarchy during 2020. Valuation of GNMA and Other U.S. Government Agency Securities All of the Company's investments in GNMA, FHLB and other U.S. government agency securities 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. In the event of any significant unanticipated deviations in a security's price, additional analysis is conducted. The Company's investments in GNMA, FHLB and other U.S. government agency securities 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: Fair Value Measurements at Reporting Date Using December 31, 2020 Quoted Prices in Significant Assets Equity securities $ 12,142 $ 12,142 $ — Available-for-sale debt securities 93,277 — 93,277 Fixed-income securities owned 34,064 — 34,064 Investment funds sponsored by LSV (1) 6,166 $ 145,649 $ 12,142 $ 127,341 Fair Value Measurements at Reporting Date Using December 31, 2019 Quoted Prices in Significant Assets Equity securities $ 12,119 $ 12,119 $ — Available-for-sale debt securities 104,798 — 104,798 Fixed-income securities owned 33,486 — 33,486 Investment funds sponsored by LSV (1) 5,988 $ 156,391 $ 12,119 $ 138,284 (1) The fair value amounts presented in the tables above are intended to permit reconciliation of the fair value hierarchy to the amounts presented on the accompanying Consolidated Balance Sheets (See Note 5).

Marketable Securities

Marketable Securities	12 Months Ended
	Dec. 31, 2020
Marketable Securities [Abstract]
Marketable Securities	Marketable Securities The Company's marketable securities include investments in money market funds and commercial paper classified as cash equivalents, available-for-sale debt securities, investments in SEI-sponsored and non-SEI-sponsored mutual funds, equities, investments in funds sponsored by LSV and securities owned by SIDCO. Cash Equivalents The Company's investments in money market funds and commercial paper classified as cash equivalents had a fair value of $462,624 and $543,765 at December 31, 2020 and 2019, respectively. There were no material unrealized or realized gains or losses from these investments during 2020 and 2019. Available For Sale and Equity Securities Available For Sale and Equity Securities on the accompanying Consolidated Balance Sheets consist of: At December 31, 2020 Cost Gross Gross Fair Available for sale debt securities $ 91,262 $ 2,015 $ — $ 93,277 SEI-sponsored mutual funds 6,866 382 — 7,248 Equities and other mutual funds 4,421 473 — 4,894 $ 102,549 $ 2,870 $ — $ 105,419 At December 31, 2019 Cost Gross Gross Fair Available for sale debt securities $ 104,193 $ 605 $ — $ 104,798 SEI-sponsored mutual funds 7,564 125 (39) 7,650 Equities and other mutual funds 3,637 832 — 4,469 $ 115,394 $ 1,562 $ (39) $ 116,917 Net unrealized holding gains at December 31, 2020 of the Company's available-for-sale debt securities were $1,551 (net of income tax expense of $464). Net unrealized losses at December 31, 2019 of the Company's available-for-sale debt securities were $465 (net of income tax benefit of $140). These net unrealized gains and losses are reported as a separate component of Accumulated other comprehensive loss on the accompanying Consolidated Balance Sheets. There were gross realized losses of $902 and $493 from available-for-sale debt securities during 2020 and 2019, respectively. There were no gross realized gains from available-for-sale debt securities during 2020 and 2019. Realized losses from available-for-sale debt securities, including amounts reclassified from accumulated comprehensive loss, are reflected in Net (loss) gain from investments on the accompanying Consolidated Statements of Operations. There were gross realized gains of $1,100 and gross realized losses of $250 from mutual funds and equities during 2020. In 2019, there were gross realized gains of $297 and gross realized losses of $48 from mutual funds and equities. Gains and losses from mutual funds and equities are reflected in Net (loss) gain from investments on the accompanying Consolidated Statements of Operations. Investments in Affiliated Funds The Company has an investment in funds sponsored by LSV. The Company records this investment on the accompanying Consolidated Balance Sheets at fair value. Unrealized gains and losses from the change in fair value of these funds are recognized in Net (loss) gain from investments on the accompanying Consolidated Statements of Operations. The funds had a fair value of $6,166 and $5,988 at December 31, 2020 and 2019, respectively. The Company recognized gains of $178 and $1,101 from the change in fair value of the funds during 2020 and 2019, respectively. The Company recognized losses of $1,147 from the change in fair value of the funds during 2018. Securities Owned The Company’s broker-dealer subsidiary, SIDCO, has investments in U.S. government agency 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 $34,064 and $33,486 at December 31, 2020 and 2019, respectively. There were no material net gains or losses from the change in fair value of the securities during 2020, 2019 and 2018.

Line of Credit

Line of Credit	12 Months Ended
	Dec. 31, 2020
Line of Credit Facility [Abstract]
Lines of Credit	Line of Credit The Company has a five-year $300,000 Credit Agreement (the Credit Facility) with Wells Fargo Bank, National Association (Wells Fargo) and a syndicate of other lenders. The Credit Facility is scheduled to expire in June 2021, 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 rates that, at the Company's option, are based on a base rate (the Base Rate) plus a premium that can range from 0.25 percent to 1.00 percent or the London InterBank Offered Rate (LIBOR) plus a premium that can range from 1.25 percent to 2.00 percent depending on the Company’s Leverage Ratio (a ratio of consolidated indebtedness to consolidated EBITDA for the four preceding fiscal quarters, all as defined in the related agreement). The Base Rate is defined as the highest of a) the Federal Funds Rate, as published by the Federal Reserve Bank of New York, plus 0.50 percent, b) the prime commercial lending rate of Wells Fargo, c) the applicable LIBOR plus 1.00 percent, or d) 0 percent. The Company also pays quarterly commitment fees based on the unused portion of the Credit Facility. The quarterly fees for the Credit Facility can range from 0.15 percent of the amount of the unused portion to 0.30 percent, depending on the Company’s Leverage Ratio. Certain wholly-owned subsidiaries of the Company have guaranteed the obligations of the Company under the agreement. The aggregate amount of the Credit Facility may be increased by an additional $100,000 under certain conditions set forth in the agreement. The Company may issue up to $15,000 in letters of credit under the terms of the Credit Facility. The Company pays a periodic commission fee of 1.250 percent plus a fronting fee of 0.175 percent of the aggregate face amount of the outstanding letters of credit issued under the Credit Facility. 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. 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 agreement may be terminated. As of December 31, 2020, the Company had outstanding letters of credit of $4,630 under the Credit Facility. These letters of credit were issued primarily for the expansion of the Company's headquarters and are scheduled to expire during 2021. The amount of the Credit Facility that is available for general corporate purposes as of December 31, 2020 was $295,370. The Company was in compliance with all covenants of the Credit Facility during 2020.

Shareholders' Equity

Shareholders' Equity	12 Months Ended
	Dec. 31, 2020
Equity [Abstract]
Shareholders' Equity	Shareholders’ Equity Stock-Based Compensation The Company's active equity compensation plan, the 2014 Omnibus Equity Compensation Plan (the 2014 Plan), is the successor plan to the 2007 Equity Compensation Plan (the 2007 Plan) which was merged with and into the 2014 Plan in May 2014. Outstanding grants under the 2007 Plan will continue according to the terms in effect before the plan merger, but the outstanding shares will be issued or transferred under the 2014 Plan. The 2014 Plan provides for the grant of stock options, stock units, stock awards, stock appreciation rights, dividend equivalents and other stock-based awards. Permitted grantees under the 2014 Plan include employees, non-employee directors and consultants who perform services for the Company. The plan is administered by the Compensation Committee of the Board of Directors of the Company. The Company has only non-qualified stock options outstanding under the 2014 Plan. All outstanding stock options have performance-based vesting provisions that tie the vesting of stock options to the Company’s financial performance which are established at the time of grant. The Company’s stock options vest at a rate of 50 percent when a specified financial vesting target is achieved, and the remaining 50 percent when a second, higher-specified financial vesting target is achieved. Options do not vest due to the passage of time but as a result of achievement of the financial vesting targets. Options granted in December 2017 and thereafter include a service condition which requires a minimum two 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 accounts for forfeitures as they occur. The weighted average fair value of the Company’s stock options granted during 2020, 2019 and 2018 were $13.53, $13.94 and $13.04, respectively, using the following assumptions: 2020 2019 2018 Expected term (in years) 5.79 5.53 6.34 Expected volatility 29.02 % 23.36 % 25.27 % Expected dividend yield 1.29 % 1.10 % 1.35 % Risk-free interest rate 0.62 % 1.80 % 2.75 % The Company recognized stock-based compensation expense in its Consolidated Financial Statements in 2020, 2019 and 2018 as follows: 2020 2019 2018 Stock-based compensation expense $ 27,014 $ 24,582 $ 23,805 Less: Deferred tax benefit (5,182) (4,814) (5,078) Stock-based compensation expense, net of tax $ 21,832 $ 19,768 $ 18,727 The Company revised its estimates of when some vesting targets are expected to be achieved. The change in management's estimate during 2020 resulted in a decrease of $2,659 in stock-based compensation. The changes in management’s estimates during 2019 and 2018 resulted in an increase of $2,903 and $1,909, respectively, in stock-based compensation expense. As of December 31, 2020, there was approximately 11,854,000 unvested employee stock options with an unrecognized compensation cost of $112,593 that the Company expects will vest and be expensed through 2024 with a weighted average period of 1.7 years. This table presents certain information relating to the Company’s stock option plans for 2020, 2019 and 2018: Number of Weighted Balance as of December 31, 2017 16,712,000 $ 37.63 Granted 2,468,000 49.94 Exercised (3,232,000) 25.93 Expired or canceled (135,000) 49.58 Balance as of December 31, 2018 15,813,000 $ 41.84 Granted 2,480,000 64.04 Exercised (2,243,000) 25.27 Expired or canceled (344,000) 55.07 Balance as of December 31, 2019 15,706,000 $ 47.43 Granted 4,529,000 56.54 Exercised (1,563,000) 28.83 Expired or canceled (177,000) 55.76 Balance as of December 31, 2020 18,495,000 $ 51.15 Exercisable as of December 31, 2020 6,641,000 $ 39.35 Available for future grant as of December 31, 2020 15,287,000 As of December 31, 2020 and 2019, there were 6,641,000 and 8,214,000 shares exercisable, respectively. The expiration dates for options outstanding at December 31, 2020 range from December 13, 2021 to December 8, 2030 with a weighted average remaining contractual life of 6.9 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 2020 and 2019 was $46,426 and $74,163, respectively. The total options exercisable as of December 31, 2020 had an intrinsic value of $120,357. The total options outstanding as of December 31, 2020 had an intrinsic value of $158,204. 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, 2020 and the exercise price of the shares. The market value of the Company’s common stock as of December 31, 2020 was $57.47 as reported by the Nasdaq Stock Market, LLC. This table summarizes information relating to all options outstanding and exercisable at December 31, 2020: Options Outstanding at December 31, 2020 Options Exercisable at December 31, 2020 Range of Exercise Prices (Per Share) Number of Shares Weighted Average Weighted Average Number of Shares Weighted Average Weighted Average $ 15.77 - $ 21.05 665,000 $ 15.79 0.95 665,000 $ 15.79 0.95 22.45 - 23.86 944,000 22.45 1.95 944,000 22.45 1.95 27.03 - 40.64 2,699,000 37.35 3.49 1,857,000 35.85 3.29 45.99 - 56.60 8,398,000 62.57 8.09 3,170,000 51.34 5.53 57.48 - 71.12 5,789,000 49.76 8.08 5,000 63.50 6.82 18,495,000 6,641,000 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 15,652,000 shares for issuance under this plan. At December 31, 2020, 12,225,000 cumulative shares have been issued. There were no material costs incurred by the Company related to the employee stock purchase plan in 2020, 2019 and 2018. 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, 2020, the Company had approximately $192,827 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 2020, 2019 and 2018: Year Total Number of Total Cost 2020 8,008,000 $ 424,702 2019 6,225,000 348,348 2018 6,744,000 404,759 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. Cash Dividends On June 3, 2020, the Board of Directors declared a cash dividend of $0.35 per share on the Company’s common stock, which was paid on June 23, 2020, to shareholders of record on June 15, 2020. On December 8, 2020, the Board of Directors declared a cash dividend of $0.37 per share on the Company’s common stock, which was paid on January 7, 2021, to shareholders of record on December 21, 2020. The cash dividends declared in 2020, 2019 and 2018 were $104,588, $102,435 and $97,900, respectively. The Board of Directors has indicated its intention to declare future cash dividends on a semiannual basis.

Accumulated Other Comprehensive

Accumulated Other Comprehensive Income (Loss)	12 Months Ended
	Dec. 31, 2020
Equity [Abstract]
Accumulated Other Comprehensive Income (Loss)	Accumulated Other Comprehensive Income (Loss) Other comprehensive income (loss) consists of net income and other gains and losses affecting shareholders’ equity that are excluded from net income. Other comprehensive income (loss) includes unrealized gains and losses on available for sale debt securities and foreign currency translation adjustments. The Company presents other comprehensive income (loss) in its Consolidated Statements of Comprehensive Income. Components of Accumulated other comprehensive income (loss), net of tax, consisted of: Foreign Currency Translation Adjustments Unrealized Accumulated Balance, January 1, 2018 $ (19,522) $ (386) $ (19,908) Other comprehensive loss before reclassifications (12,065) (1,088) (13,153) Amounts reclassified from accumulated other comprehensive loss — 61 61 Net current-period other comprehensive loss (12,065) (1,027) (13,092) Balance, December 31, 2018 $ (31,587) $ (1,413) $ (33,000) Other comprehensive income before reclassifications 7,618 1,486 9,104 Amounts reclassified from accumulated other comprehensive loss — 392 392 Net current-period other comprehensive income 7,618 1,878 9,496 Balance, December 31, 2019 $ (23,969) $ 465 $ (23,504) Other comprehensive income before reclassifications 5,620 374 5,994 Amounts reclassified from accumulated other comprehensive loss — 712 712 Net current-period other comprehensive income 5,620 1,086 6,706 Balance, December 31, 2020 $ (18,349) $ 1,551 $ (16,798)

Employee Benefit Plan

Employee Benefit Plan	12 Months Ended
	Dec. 31, 2020
Retirement Benefits [Abstract]
Employee Benefit Plan	Employee Benefit PlanThe 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 $14,087, $12,923 and $12,362 to the Plan in 2020, 2019 and 2018, respectively.

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2020
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Commitments and Contingencies The Company leases software, facilities, and equipment 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 equipment. Rent expense, primarily related to user licenses for software, was $41,091, $33,600 and $34,679 in 2020, 2019 and 2018, respectively. The aggregate noncancellable minimum commitments at December 31, 2020 are: Year Aggregate Noncancellable Minimum Commitments 2021 $ 9,183 2022 8,917 2023 8,922 2024 7,252 2025 and thereafter 11,172 $ 45,446 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, 2020 and 2019 related to these indemnifications. Stanford Trust Company Litigation SEI has been named in seven lawsuits filed in Louisiana courts; four of the cases also name SPTC as a defendant. The underlying allegations in all actions relate to the purported role of SPTC in providing back-office services to Stanford Trust Company. The complaints allege that SEI and SPTC participated in some manner in the sale of “certificates of deposit” issued by Stanford International Bank so as to be a “seller” of the certificates of deposit for purposes of primary liability under the Louisiana Securities Law or so as to be secondarily liable under that statute for sales of certificates of deposit made by Stanford Trust Company. Two of the actions also include claims for violations of the Louisiana Racketeering Act and possibly conspiracy, and a third also asserts claims of negligence, breach of contract, breach of fiduciary duty, violations of the uniform fiduciaries law, negligent misrepresentation, detrimental reliance, violations of the Louisiana Racketeering Act, and conspiracy. The procedural status of the seven cases varies. The Lillie case, filed originally in the 19th Judicial District Court for the Parish of East Baton Rouge, was brought as a class action and is procedurally the most advanced of the cases. SEI and SPTC filed exceptions, which the Court granted in part, dismissing claims under the Louisiana Unfair Trade Practices Act and permitting the claims under the Louisiana Securities Law to go forward. On March 11, 2013, newly-added insurance carrier defendants removed the case to the United States District Court for the Middle District of Louisiana. On August 7, 2013, the Judicial Panel on Multidistrict Litigation transferred the matter to the Northern District of Texas where MDL 2099, In re: Stanford Entities Securities Litigation (“the Stanford MDL”), is pending. On September 22, 2015, the District Court on the motion of SEI and SPTC dismissed plaintiffs’ claims for primary liability under Section 714(A) of the Louisiana Securities Law, but declined to dismiss plaintiffs’ claims for secondary liability under Section 714(B) of the Louisiana Securities Law based on the allegations pled by plaintiffs. On November 4, 2015, the District Court granted SEI and SPTC's motion to dismiss plaintiffs' claims under Section 712(D) of the Louisiana Securities Law. Consequently, the only claims of plaintiffs remaining in Lillie are plaintiffs' claims for secondary liability against SEI and SPTC under Section 714(B) of the Louisiana Securities Law. On May 2, 2016, the District Court certified the class as being "all persons for whom Stanford Trust Company purchased or renewed Stanford Investment Bank Limited certificates of deposit in Louisiana between January 1, 2007 and February 13, 2009". Notice of the pendency of the class action was mailed to potential class members on October 4, 2016. On December 1, 2016, a group of plaintiffs who opted out of the Lillie class filed a complaint against SEI and SPTC in the United States District Court in the Middle District of Louisiana (“Ahders Complaint”), alleging claims essentially the same as those in Lillie. In January 2017, the Judicial Panel on Multidistrict Litigation transferred the Ahders proceeding to the Northern District of Texas and the Stanford MDL. During February 2017, SEI and SPTC filed their response to the Ahders Complaint, and in March 2017 the District Court for the Northern District of Texas approved the stipulated dismissal of all claims in this Complaint predicated on Section 712(D) or Section 714(A) of the Louisiana Securities Law. In both cases, as a result of the proceedings in the Northern District of Texas, only the plaintiffs’ secondary liability claims under Section 714(B) of the Louisiana Securities Law remain. Limited discovery and motions practice have occurred, including SEI and SPTC’s filing of a dispositive summary judgment motion in the Lillie proceeding. On January 31, 2019, the Judicial Panel on Multidistrict Litigation remanded the Lillie and Ahders proceedings to the Middle District of Louisiana. With respect to the Lillie proceeding, on July 9, 2019, the District Court issued an order granting SEI’s Summary Judgment Motion to dismiss the remaining Section 714(B) claim and denying Plaintiffs’ Motion for Continuance of SEI and SPTC’s Motion for Summary Judgment pursuant to Rule 56(d). On July 17, 2019, Plaintiffs filed a Motion for Reconsideration and/or New Trial. The Court denied Plaintiffs’ Motion for Reconsideration and/or New Trial and entered a Final Judgment in favor of SEI and SPTC on August 15, 2019. On August 27, 2019, Plaintiffs-Appellants filed a Notice of Appeal to the United States Court of Appeals for the Fifth Circuit of the District Court's dismissal of the Lillie matter. On November 20, 2019, Plaintiffs-Appellants filed a Motion in Support of the Notice of Appeal. On January 17, 2020, SEI and SPTC timely filed their brief in opposition to the Plaintiffs-Appellants' motion for appeal. On February 7, 2020, Plaintiffs- Appellants filed their reply brief. The parties are currently waiting for oral argument to be scheduled. With respect to the Ahders proceeding, on July 16, 2019, SEI and SPTC filed a Motion for Summary Judgment pursuant to Rule 56(d) to have the remaining Section 714(B) claim dismissed. On January 24, 2020, the District Court issued an order granting SEI’s Summary Judgment Motion to dismiss the remaining Section 714(B) claim. On March 17, 2020, Plaintiffs-Appellants filed a Notice of Appeal to the United States Court of Appeals for the Fifth Circuit of the District Court's dismissal of the Ahders matter. On December 3, 2020, the United States Court of Appeals for the Fifth Circuit unanimously affirmed the District Court’s order granting summary judgment in favor SEI and the Insurer Defendants in the Adhers matter. Another case, filed in the 23rd Judicial District Court for the Parish of Ascension, also was removed to federal court and transferred by the Judicial Panel on Multidistrict Litigation to the Northern District of Texas and the Stanford MDL. The schedule for responding to that Complaint has not yet been established. Two additional cases remain in the Parish of East Baton Rouge. Plaintiffs filed petitions in 2010 and have granted SEI and SPTC indefinite extensions to respond. No material activity has taken place since. In two additional cases, filed in East Baton Rouge and brought by the same counsel who filed the Lillie action, virtually all of the litigation to date has involved motions practice and appellate litigation regarding the existence of federal subject matter jurisdiction under the federal Securities Litigation Uniform Standards Act (SLUSA). The matters were removed to the United States District Court for the Northern District of Texas and consolidated. The court then dismissed the action under SLUSA. The Court of Appeals for the Fifth Circuit reversed that order, and the Supreme Court of the United States affirmed the Court of Appeals judgment on February 26, 2014. The matters were remanded to state court and no material activity has taken place since that date. While the outcome of this litigation remains uncertain, SEI and SPTC believe that they have valid defenses to plaintiffs' claims and intend to defend the lawsuits vigorously. Because of uncertainty in the make-up of the Lillie class, the specific theories of liability that may survive a motion for summary judgment or other dispositive motion, the relative 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. SS&C Advent Litigation On February 28, 2020, SEI Global Services, Inc. ("SGSI"), a wholly-owned subsidiary of the Company, filed a complaint under seal in the United States District Court for the Eastern District of Pennsylvania against SS&C Advent ("Advent") and SS&C Technologies Holdings, Inc. ("SS&C") alleging that SS&C and Advent breached the terms of the contract between the parties (the “SLSA”) and asking the Court to hold SS&C and Advent to their bargained-for obligations (the "Advent Matter"). In addition to Breach of Contract, the complaint also includes counts for Declaratory Judgment, Tortious Interference with Existing and Prospective Contractual Relations, Violation of the New York General Business Law Section 349, Violations of Section 2 of the Sherman Antitrust Act, Promissory Estoppel and Breach of the Covenant of Good Faith and Fair Dealing. SGSI seeks various forms of relief, including declaratory judgment, specific performance under the SLSA, and monetary damages, including treble damages and attorney’s fees. Following various procedural actions, including an amendment of SGSI’s complaint to include additional breach of contract claims, Advent filed a motion to dismiss SGSI’s compliant. On October 23, 2020, the United States District Court for the Eastern District of Pennsylvania dismissed SEI’s federal anti-trust claim and declined to rule on the state law breach of contract or tortious on the basis that in the absence of the anti-trust claim, the court had no jurisdiction over the state law claims. SGSI has appealed the dismissal of the federal anti-trust claims to the Third Circuit Court of Appeals, which is currently pending. Upon the dismissal of the federal anti-trust claim, on October 23, 2020, each of Advent and SGSI filed competing lawsuits in New York and Pennsylvania, respectively, to litigate the remaining breach contract and tortious interference of contract claims. Additionally, SGSI made a motion for injunctive relief to ensure that Advent provided SGSI with access to the Geneva, Moxy and APX software modules as SGSI believes is required pursuant to the terms of a valid contract. Although SGSI had the right to litigate the matter in the Pennsylvania Commonwealth courts and had moved to dismiss Advent’s New York action so that the dispute could proceed in SGSI’s designated forum, critical timing imperatives related to access to the relevant software led SGSI to consent to the jurisdiction of the New York court and litigate the matter in that forum. SEI filed counterclaims in New York against Advent and SS&C that are materially the same as its affirmative claims pled in Pennsylvania. There is effectively no material difference in the claims, defenses, or burdens of proof for either of Advent, as the plaintiff, or SGSI, as defendant, in New York courts, or in Pennsylvania with the roles of plaintiff and defendant reversed. On January 13, 2021, Judge Borrok of the Supreme Court of the State of New York, New York, granted SGSI’s motion for injunctive relief and issued an Order in which he characterized the basis for Advent’s claim for breach of contract as appearing to be “pre-textual” and found that SGSI’s claims for breach of contract would likely succeed on the merits. Judge Borrok granted SGSI’s motion for injunctive relief, precluding Advent from: Dishonoring their contractual obligations and commitments under the SLSA, including, denying licenses, rights, and privileges under the SLSA; Failing to provide new license keys for the license keys due to Geneva, Moxy, and APX, and other software products licensed pursuant to the SLSA (such new license keys to be provided no later than January 15, 2021 at 10 A.M.); Denying to SEI any and all access to the Geneva, Moxy, and APX software and related modules as are reasonably necessary to provide access to such software to SGSI’s clients; and Denying to SGSI any and all support, maintenance and technical support services for Geneva, Moxy, and APX. Advent provided SEI with the necessary access to the Geneva, Moxy and APX software modules on January 14, 2021. These have been tested, verified and are now running in the SEI production environment. On January 15, 2021, Advent appealed Judge Borrok’s order granting SGSI’s motion for preliminary injunctive relief to the Appellate Division of the Supreme Court of the State of New York, First Department. SEI does not believe that it will have to change providers under the current terms of the SLSA and that the process of litigating its rights under this contract may be a multi-year process. Consequently, SEI does not believe that the Advent Matter will create any consequence to the services SGSI provides to SEI’s clients in the near term. SEI believes that it has alternatives available to it that will enable it to continue to provide currently provided services to its clients in all material respects in the unlikely event that there ultimately is a negative outcome in the Advent Matter. SEI believes SGSI has a strong basis for proving the actions it alleges in the Advent Matter and defeating Advent’s defenses thereto, and looks forward to the opportunity to continue to assert its rights under contract and pursue relief for what SEI believes may be business tort violations. SEI expects the financial impact of litigating the Advent Matter to be immaterial. Other Matters The Company is also a party to various other actions and claims arising in the normal course of business that the Company does not believe are material. The Company believes that the ultimate resolution of these matters will not have a material adverse effect on the Company's financial position or the manner in which the Company conducts its business. Currently, the Company does not believe the amount of losses associated with these matters can be estimated. While the Company does not believe that the amount of such losses will, when liquidated or estimable, be material to its financial position, the assumptions may be incorrect and any such loss could have a material adverse effect on the Company's

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2020
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, 2020 2019 2018 Current Federal $ 92,649 $ 100,986 $ 82,493 State 21,479 19,902 13,709 Foreign 8,256 11,722 8,405 122,384 132,610 104,607 Deferred Federal (701) (1,635) 2,550 State (275) (960) 1,166 Foreign — — 15 (976) (2,595) 3,731 Total income taxes $ 121,408 $ 130,015 $ 108,338 Annual tax provisions include amounts considered sufficient to pay assessments that may result from examination of prior year tax returns; however, the amount ultimately paid upon resolution of issues raised may differ materially from the amount accrued. The examination and the resolution process may last longer than one year. The components of Income before income taxes are summarized as follows: Year Ended December 31, 2020 2019 2018 Domestic $ 517,451 $ 565,842 $ 579,622 Foreign 51,243 65,599 34,584 $ 568,694 $ 631,441 $ 614,206 The Company's foreign income is primarily earned in Canada, the Republic of Ireland and the United Kingdom. The increase in the Company's foreign income during 2019 is primarily due to the increase of income from certain foreign subsidiaries subject to tax in non-U.S. jurisdictions. The effective income tax rate differs from the federal income tax statutory rate due to the following: Year Ended December 31, 2020 2019 2018 Statutory rate 21.0 % 21.0 % 21.0 % State taxes, net of federal tax benefit 3.0 2.4 1.9 Foreign tax expense and tax rate differential (0.4) — (0.1) Tax benefit from stock option exercises (1.1) (1.9) (3.8) Research and development tax credit (1.0) (1.1) (0.8) Foreign-Derived Intangible Income Deduction (FDII) (0.3) (0.2) (0.2) Other, net 0.1 0.4 (0.4) 21.3 % 20.6 % 17.6 % The increases in the Company's effective tax rates in 2020 and 2019 were primarily due to reduced tax benefits related to the lower volume of stock option exercises as compared to the prior year and an increase in the Company's state effective tax rate partially offset by a decrease in foreign tax expense mainly related to a one time change in method for the Global Intangible Low Taxed Income (GILTI). Deferred income taxes for 2020 and 2019 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. Significant components of deferred tax assets and liabilities at December 31, 2020 and 2019 are as follows: 2020 2019 Deferred Tax Assets: Stock-based compensation expense $ 26,893 $ 24,686 State net operating loss carryforward 65,114 67,472 Foreign net operating loss carryforward and other 6,634 6,081 Basis differences in investments 3,965 4,436 Federal benefit of state tax deduction for uncertain tax positions 2,255 2,124 Revenue and expense recognized in different periods for financial reporting and income tax purposes 3,025 1,960 Other assets 1,584 1,271 Total deferred income tax assets 109,470 108,030 Less: State net operating loss valuation allowance (62,229) (64,737) Less: Foreign net operating loss valuation allowance (6,547) (5,994) Net deferred income tax assets $ 40,694 $ 37,299 Deferred Tax Liabilities: Capitalized software currently deductible for tax purposes, net of amortization $ (63,588) $ (68,265) Difference in financial reporting and income tax depreciation methods (11,422) (6,032) Difference between book and tax basis of other assets (5,747) (4,593) Goodwill and other intangibles (2,462) (2,170) Foreign dividend withholding tax — (312) Capitalized contract costs (7,762) (7,072) Other liabilities (1,900) (1,755) Total deferred income tax liabilities $ (92,881) $ (90,199) Net deferred income tax liabilities $ (52,187) $ (52,900) The valuation allowances against deferred tax assets at December 31, 2020 and 2019 are related to state net operating losses from certain domestic subsidiaries, foreign net operating losses from certain foreign subsidiaries and the restriction of the use of the foreign tax credits. Certain state and foreign tax statutes significantly limit the utilization of net operating losses for domestic and foreign subsidiaries. Furthermore, these net operating losses cannot be used to offset the net income of other subsidiaries. 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 the Company's current estimate of the tax liabilities. The Company’s total unrecognized tax benefit, including interest and penalties, as of December 31, 2020 was $18,016, of which $15,761 would affect the effective tax rate if the Company were to recognize the tax benefit. The gross amount of uncertain tax liability of $6,546 is expected to be paid within one year is netted against the current payable account while the remaining amount of $11,470 is included in Other long-term liabilities on the accompanying Consolidated Balance Sheet. During the year ended December 31, 2020, the Company recognized $3,033 of previously unrecognized tax benefits relating to the lapse of the statute of limitation. The Company files a consolidated federal income tax return and separate income tax returns with various states. Certain subsidiaries of the Company file tax returns in foreign jurisdictions. The Company is no longer subject to U.S. federal income tax examination for years before 2017 and is no longer subject to state, local or foreign income tax examinations by authorities for years before 2015. A reconciliation of the beginning and ending amount of unrecognized tax benefit is as follows: 2020 2019 2018 Balance as of January 1 $ 15,356 $ 14,367 $ 14,480 Tax positions related to current year: Gross additions 3,352 3,054 2,446 Tax positions related to prior years: Gross additions 236 1,465 340 Settlements — (145) (278) Lapses on statute of limitations (3,033) (3,385) (2,621) Balance as of December 31 $ 15,911 $ 15,356 $ 14,367 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 and interest and penalties. The Company classifies all interest and penalties as income tax expense. The Company has recorded $2,105, $1,962 and $1,289 in liabilities for tax-related interest and penalties in 2020, 2019 and 2018, respectively. The Company estimates it will recognize $6,546 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, 2020
Segment Reporting [Abstract]
Business Segment Information	Business Segment Information The Company’s reportable business segments are: Private Banks – Provides outsourced investment processing and investment management platforms to banks and trust institutions, independent wealth advisers and financial advisors worldwide; Investment Advisors – Provides investment management and investment processing platforms to affluent investors through a network of independent registered investment advisors, financial planners and other investment professionals in the United States; Institutional Investors – Provides OCIO solutions, including investment management and administrative outsourcing platforms to retirement plan sponsors, healthcare systems, higher education and other not-for-profit organizations worldwide; Investment Managers – Provides investment operations outsourcing platforms to fund companies, banking institutions, traditional and non-traditional investment managers worldwide and family offices in the United States; and Investments in New Businesses – Focuses on providing investment management solutions to ultra-high-net-worth families residing in the United States; developing network and data protection services; modularizing larger technology platforms into stand-alone components; entering new markets; and conducting other research and development activities. In 2020, 2019 and 2018, no single customer accounted for more than 10% 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, 2020, 2019 and 2018: Private Banks Investment Institutional Investment Investments Total For the Year Ended December 31, 2020 Revenues $ 455,393 $ 407,564 $ 317,627 $ 489,462 $ 14,012 $ 1,684,058 Expenses 446,481 205,913 149,909 308,999 52,871 1,164,173 Operating profit (loss) $ 8,912 $ 201,651 $ 167,718 $ 180,463 $ (38,859) $ 519,885 Private Investment Institutional Investment Investments Total For the Year Ended December 31, 2019 Revenues $ 470,276 $ 403,778 $ 322,062 $ 440,796 $ 12,973 $ 1,649,885 Expenses 443,136 208,508 153,937 282,024 29,660 1,117,265 Operating profit (loss) $ 27,140 $ 195,270 $ 168,125 $ 158,772 $ (16,687) $ 532,620 Private Investment Institutional Investment Investments Total For the Year Ended December 31, 2018 Revenues $ 483,097 $ 399,089 $ 333,299 $ 398,076 $ 10,606 $ 1,624,167 Expenses 457,894 212,439 163,536 259,693 22,971 1,116,533 Operating profit (loss) $ 25,203 $ 186,650 $ 169,763 $ 138,383 $ (12,365) $ 507,634 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, 2020, 2019 and 2018 is as follows: Year Ended December 31, 2020 2019 2018 Total operating profit from segments above $ 519,885 $ 532,620 $ 507,634 Corporate overhead expenses (73,998) (72,196) (65,646) Income from operations $ 445,887 $ 460,424 $ 441,988 The following tables provide additional information for the years ended December 31, 2020, 2019 and 2018 pertaining to our business segments: Capital Expenditures (1) Depreciation Year Ended December 31, 2020 2019 2018 2020 2019 2018 Private Banks $ 29,061 $ 33,068 $ 36,763 $ 16,206 $ 14,349 $ 13,773 Investment Advisors 15,588 17,413 16,572 4,821 4,653 4,607 Institutional Investors 3,958 4,057 3,863 1,214 1,600 1,672 Investment Managers 25,909 18,970 13,639 7,336 7,145 6,988 Investments in New Businesses 1,211 1,349 972 341 383 547 Total from business segments $ 75,727 $ 74,857 $ 71,809 $ 29,918 $ 28,130 $ 27,587 Corporate Overhead 2,840 2,314 1,507 1,041 1,306 1,205 $ 78,567 $ 77,171 $ 73,316 $ 30,959 $ 29,436 $ 28,792 (1) Capital expenditures include additions to property and equipment and capitalized software. Amortization Year Ended December 31, 2020 2019 2018 Private Banks $ 30,240 $ 29,054 $ 27,312 Investment Advisors 10,694 10,311 9,668 Institutional Investors 1,707 1,726 1,707 Investment Managers 9,365 9,358 9,382 Investments in New Businesses 739 740 595 Total from business segments $ 52,745 $ 51,189 $ 48,664 Corporate Overhead 230 230 231 $ 52,975 $ 51,419 $ 48,895 Total Assets 2020 2019 Private Banks $ 557,953 $ 567,796 Investment Advisors 169,197 165,556 Institutional Investors 119,784 115,012 Investment Managers 421,093 373,986 Investments in New Businesses 22,014 19,735 Total from business segments $ 1,290,041 $ 1,242,085 Corporate Overhead (2) 877,215 909,285 $ 2,167,256 $ 2,151,370 (2) Unallocated assets primarily consist of cash and cash equivalents, marketable securities, and certain other shared services assets. The following table presents revenues based on the location of the use of the products or services: For the Year Ended December 31, 2020 2019 2018 United States $ 1,427,152 $ 1,385,744 $ 1,348,130 International operations 256,906 264,141 276,037 $ 1,684,058 $ 1,649,885 $ 1,624,167 The following table presents assets based on their location: 2020 2019 United States $ 1,772,179 $ 1,732,427 International operations 395,077 418,943 $ 2,167,256 $ 2,151,370

Related Party Transactions

Related Party Transactions	12 Months Ended
	Dec. 31, 2020
Related Party Transactions [Abstract]
Related Party Transactions	Related Party Transactions The Company, either by itself or through its wholly-owned subsidiaries, serves as the sponsor, administrator, investment advisor, distributor and shareholder servicer for SEI-sponsored investment products. These investment products are offered to clients of the Company and its subsidiaries. Fees earned by the Company for the related services are recognized pursuant to the provisions of investment advisory, fund administration, distribution, and shareholder services agreements directly with the investment products. These fees totaled $432,806, $449,725 and $462,101 in 2020, 2019 and 2018, respectively. The Company also serves as an introducing broker-dealer for securities transactions of SEI-sponsored investment products. The Company recognized $2,159, $632 and $2,001 in commissions during 2020, 2019 and 2018, respectively. Both of these fees are reflected in Asset management, administration and distribution fees on the accompanying Consolidated Statements of Operations. Receivables from investment products on the accompanying Consolidated Balance Sheets primarily represent fees receivable for distribution, investment advisory, and administration services to various investment products sponsored by SEI.

Goodwill and Intangible Assets

Goodwill and Intangible Assets	12 Months Ended
	Dec. 31, 2020
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill and Intangible Assets	Goodwill and Intangible Assets In April 2018, the Company acquired all ownership interests of Huntington Steele, LLC (Huntington Steele). The excess purchase price over the estimated value of the net tangible and identifiable intangible assets was allocated to goodwill. The total amount of goodwill from this transaction of $11,499 was allocated to the Investments in New Businesses segment and is included on the accompanying Consolidated Balance Sheets. The total purchase price for Huntington Steele included a contingent purchase price payable to the sellers upon the attainment of specified financial measures determined at various intervals occurring between 2019 and 2023. The Company made payments of $633 and $433 during 2020 and 2019, respectively, to the sellers and recorded fair value adjustments of $893 and $568 during 2020 and 2019, respectively, to increase the fair value of the remaining contingent consideration. As of December 31, 2020, the current portion of the contingent consideration of $3,931 is included in Accrued liabilities on the accompanying Balance Sheet. The long-term portion of the contingent consideration of $8,584 is included in Other long-term liabilities on the accompanying Balance Sheet. In July 2017, the Company acquired all ownership interests of Archway Technology Partners, LLC, Archway Finance & Operations, Inc. and Keystone Capital Holdings, LLC (collectively, Archway), a provider of operating technologies and services to the family office industry. The total purchase price was allocated to Archway’s net tangible and intangible assets based upon their estimated fair values at the date of purchase. The excess purchase price over the value of the net tangible and identifiable intangible assets was recorded as goodwill. The total amount of goodwill from this transaction of $52,990 was allocated to the Investment Managers segment and is included on the accompanying Consolidated Balance Sheets. There was no change in the carrying amount of the Company's goodwill during 2020 or 2019. The Company's intangible assets consist of: 2020 Weighted Average Estimated Useful Life 2019 Weighted Average Estimated Useful Life Acquired technology $ 13,510 10.0 years $ 13,510 10.0 years Client relationships 16,940 13.9 years 16,940 13.9 years Non-competition agreements 3,470 5.0 years 3,470 5.0 years Trade name 2,840 7.0 years 2,840 7.0 years 36,760 36,760 Less: Accumulated amortization (12,456) (8,773) Intangible assets, net $ 24,304 $ 27,987 The Company recognized $3,683 of amortization expense related to intangible assets during 2020 and 2019. The Company currently expects to recognize amortization expense related to intangible assets as of December 31, 2020 each year from 2021 through 2025 as follows: Year Expected Amortization Expense Related to Intangible Assets 2021 $ 3,683 2022 3,336 2023 2,989 2024 2,818 2025 2,599

Revenues from Contracts with Cu

Revenues from Contracts with Customers	12 Months Ended
	Dec. 31, 2020
Revenue from Contract with Customer [Abstract]
Revenues from Contracts with Customers	Revenues from Contracts with CustomersThe Company’s principal sources of revenues are: (1) asset management, administration and distribution fees primarily earned based upon a contractual percentage of net assets under management or administration; and (2) information processing and software servicing fees that are either recurring and primarily earned based upon the number of trust accounts being serviced or a percentage of the market value of the clients' assets processed on the Company's platforms, or non-recurring and based upon project-oriented contractual agreements related to client implementations. Disaggregation of Revenue The following tables provide additional information pertaining to our revenues disaggregated by major product line and primary geographic market based on the location of the use of the products or services for each of the Company’s business segments for 2020, 2019 and 2018: Private Banks Investment Institutional Investment Investments Total Major Product Lines: For the Year Ended December 31, 2020 Investment management fees from pooled investment products $ 127,883 $ 271,627 $ 53,283 $ 637 $ 1,411 $ 454,841 Investment management fees from investment management agreements 1,470 115,887 262,709 — 12,105 392,171 Investment operations fees 1,804 — — 447,517 — 449,321 Investment processing fees - PaaS 184,711 — — — — 184,711 Investment processing fees - SaaS 113,012 — — 13,739 — 126,751 Professional services fees 21,594 — — 5,753 — 27,347 Account fees and other 4,919 20,050 1,635 21,816 496 48,916 Total revenues $ 455,393 $ 407,564 $ 317,627 $ 489,462 $ 14,012 $ 1,684,058 Primary Geographic Markets: United States $ 298,708 $ 407,564 $ 250,321 $ 456,547 $ 14,012 $ 1,427,152 United Kingdom 97,896 — 51,292 — — 149,188 Canada 41,762 — 5,610 — — 47,372 Ireland 17,027 — 9,850 32,915 — 59,792 Other — — 554 — — 554 Total revenues $ 455,393 $ 407,564 $ 317,627 $ 489,462 $ 14,012 $ 1,684,058 Private Investment Institutional Investment Investments Total Major Product Lines: For the Year Ended December 31, 2019 Investment management fees from pooled investment products $ 135,503 $ 282,253 $ 54,726 $ 766 $ 1,293 $ 474,541 Investment management fees from investment management agreements 1,616 103,428 266,323 — 11,571 382,938 Investment operations fees 1,634 — — 403,208 — 404,842 Investment processing fees - PaaS 177,046 — — — — 177,046 Investment processing fees - SaaS 132,661 — — 11,036 — 143,697 Professional services fees 15,687 — — 5,209 — 20,896 Account fees and other 6,129 18,097 1,013 20,577 109 45,925 Total revenues $ 470,276 $ 403,778 $ 322,062 $ 440,796 $ 12,973 $ 1,649,885 Primary Geographic Markets: United States $ 304,860 $ 403,778 $ 252,149 $ 411,984 $ 12,973 $ 1,385,744 United Kingdom 102,518 — 52,584 — — 155,102 Canada 43,661 — 6,889 — — 50,550 Ireland 19,237 — 9,588 28,812 — 57,637 Other — — 852 — — 852 Total revenues $ 470,276 $ 403,778 $ 322,062 $ 440,796 $ 12,973 $ 1,649,885 Private Investment Institutional Investment Investments Total Major Product Lines: For the Year Ended December 31, 2018 Investment management fees from pooled investment products $ 138,616 $ 288,030 $ 59,739 $ 928 $ 1,017 $ 488,330 Investment management fees from investment management agreements 793 94,526 271,600 331 9,457 376,707 Investment operations fees 1,517 — — 360,382 — 361,899 Investment processing fees - PaaS 182,068 — — 2,519 — 184,587 Investment processing fees - SaaS 136,222 — — 9,598 — 145,820 Professional services fees 16,643 — — 7,280 — 23,923 Account fees and other 7,238 16,533 1,960 17,038 132 42,901 Total revenues $ 483,097 $ 399,089 $ 333,299 $ 398,076 $ 10,606 $ 1,624,167 Primary Geographic Markets: United States $ 304,762 $ 399,089 $ 257,080 $ 376,593 $ 10,606 $ 1,348,130 United Kingdom 112,980 — 55,471 — — 168,451 Canada 45,941 — 8,526 — — 54,467 Ireland 19,414 — 10,419 21,483 — 51,316 Other — — 1,803 — — 1,803 Total revenues $ 483,097 $ 399,089 $ 333,299 $ 398,076 $ 10,606 $ 1,624,167 Investment management fees from pooled investment products - Revenues associated with clients' assets invested in Company-sponsored pooled investment products. Contractual fees are stated as a percentage of the market value of assets under management and collected on a monthly basis. Revenues are recognized in Asset management, administration and distribution fees on the accompanying Consolidated Statements of Operations. Investment management fees from investment management agreements - Revenues based on assets of clients of the Institutional Investors segment primarily invested in Company-sponsored products. Each client is charged an investment management fee that is stated as a percentage of the market value of all assets under management. The client is billed directly on a quarterly basis. Revenues are recognized in Asset management, administration and distribution fees on the accompanying Consolidated Statements of Operations. Revenues associated with the separately managed account program offered through registered investment advisors located throughout the United States. The contractual fee is stated as a percentage of the market value of all assets invested in the separately managed account and collected on a quarterly basis. Revenues are recognized in Asset management, administration and distribution fees on the accompanying Consolidated Statements of Operations. Investment operations fees - Revenues earned from accounting and administrative services, distribution support services and regulatory and compliance services to investment management firms and family offices. The Company contracts directly with the investment management firm or family office. The contractual fees are stated as a percentage of net assets under administration and billed when asset valuations are finalized. Revenues are recognized in Asset management, administration and distribution fees on the accompanying Consolidated Statements of Operations. Investment processing fees - Platform as a Service - Revenues associated with clients that outsource their entire investment operation and back-office processing functions. Through the use of the Company's proprietary platforms, the Company assumes all back-office investment processing services including investment processing, custody and safekeeping of assets, income collections, securities settlement and other related trust activities. The contractual fee is based on a monthly fee plus additional fees determined on a per-account or per-transaction basis. Contractual fees can also be stated as a percentage of the value of assets processed on the Company's platforms each month as long as the fee is in excess of a monthly contractual minimum. The client is billed directly on a monthly basis. Revenues are recognized in Information processing and software servicing fees on the accompanying Consolidated Statements of Operations. Investment processing fees - Software as a Service - Revenues associated with clients that outsource investment processing technology software and computer processing by accessing our proprietary software and data center remotely but retain responsibility for all investment operations, client administration and other back-office trust operations. The contractual fee is based on a monthly fee plus additional fees determined on a per-account or per-transaction basis. The client is billed directly on a monthly basis. Revenues are recognized in Information processing and software servicing fees on the accompanying Consolidated Statements of Operations. Professional services fees - Revenues associated with the business services migration for investment processing clients of the Private Banks segment and investment operations clients of the Investment Managers segment. In addition, Professional services include other services such as business transformation consulting. Typically, fees are stated as a contractual fixed fee. The client is billed directly and fees are collected according to the terms of the agreement. Account fees and other - Revenues associated with custody account servicing, account terminations, reimbursements received for out-of-pocket expenses, and other fees for the provision of ancillary services.

Leases

Leases	12 Months Ended
	Dec. 31, 2020
Leases [Abstract]
Leases	Leases The Company has operating leases for corporate facilities and equipment. The Company's expense related to leases during 2020 and 2019 was $9,711 and $10,159, respectively, and is included in Facilities, supplies and other costs on the accompanying Consolidated Statements of Operations. The Company's future minimum lease payments under non-cancelable leases as of December 31, 2020 are as follows: Year Future Minimum Lease Payment 2021 $ 9,183 2022 8,917 2023 8,922 2024 7,252 2025 5,184 Thereafter 5,988 Total future minimum lease payments 45,446 Less: Imputed interest (2,809) Total $ 42,637 The following table provides supplemental Consolidated Balance Sheet information related to the Company's leases: 2020 2019 Current portion of long-term operating lease liabilities $ 8,579 $ 9,156 Long-term operating lease liabilities 34,058 38,450 Total operating lease liabilities $ 42,637 $ 47,606 Weighted average remaining lease term 5.5 years 6.3 years Weighted average discount rate 2.43 % 2.61 % The following table provides supplemental cash flow information related to the Company's leases: Year Ended December 31, 2020 2019 Cash paid for amounts included in the measurement of lease liabilities $ 10,361 $ 10,932 Right-of-use assets obtained in exchange for lease obligations $ 3,272 $ 6,372

Quarterly Financial Data (Unaud

Quarterly Financial Data (Unaudited)	12 Months Ended
	Dec. 31, 2020
Quarterly Financial Data [Abstract]
Quarterly Financial Data (Unaudited)	Quarterly Financial Data (Unaudited) For the Three Months Ended 2020 March 31 June 30 September 30 December 31 Revenues $ 414,762 $ 400,646 $ 424,927 $ 443,723 Income before income taxes $ 139,197 $ 131,710 $ 141,274 $ 156,513 Net income $ 109,242 $ 101,066 $ 111,096 $ 125,882 Basic earnings per share $ 0.73 $ 0.69 $ 0.76 $ 0.87 Diluted earnings per share (1) $ 0.72 $ 0.68 $ 0.75 $ 0.86 Effective income tax rate 21.5 % 23.3 % 21.4 % 19.6 % For the Three Months Ended 2019 March 31 June 30 September 30 December 31 Revenues $ 400,820 $ 409,586 $ 416,254 $ 423,225 Income before income taxes $ 146,257 $ 162,346 $ 162,870 $ 159,968 Net income $ 113,981 $ 126,540 $ 132,168 $ 128,737 Basic earnings per share $ 0.74 $ 0.83 $ 0.88 $ 0.86 Diluted earnings per share (1) $ 0.73 $ 0.82 $ 0.86 $ 0.84 Effective income tax rate 22.1 % 22.1 % 18.9 % 19.5 %

Schedule II - Valuation And Qua

Schedule II - Valuation And Qualifying Accounts And Reserves	12 Months Ended
	Dec. 31, 2020
SEC Schedule, 12-09, Valuation and Qualifying Accounts [Abstract]
Schedule II - Valuation and Qualifying Accounts and Reserves	Schedule II - Valuation and Qualifying Accounts and Reserves SEI Investments Company (In thousands) and Subsidiaries Year Ended December 31, Additions Description Balance at Charged to Charged (Deductions) Balance Allowance for doubtful accounts: 2020 $ 1,201 $ — $ — $ (101) $ 1,100 2019 718 483 — — 1,201 2018 695 23 — — 718 Deferred income tax valuation allowance: 2020 $ 70,731 $ — $ — $ (1,955) $ 68,776 2019 72,316 — — (1,585) 70,731 2018 68,469 — 3,847 — 72,316

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2020
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.
Variable Interest Entities	Variable Interest Entities The Company or its affiliates have 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. The Company receives asset management, distribution, administration and custodial fees for these services. 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. The Company has concluded that it is not the primary beneficiary of the entities and, therefore, is not required to consolidate any of the pooled investment vehicles for which it receives asset management, distribution, administration and custodial fees under the VIE model. The entities either do not meet the definition of a VIE or the Company does not hold a variable interest in the entities. The entities either qualify for the money market scope exception, or are entities in which the Company’s asset management, distribution, administration and custodial fees are commensurate with the services provided and include fair terms and conditions, or are entities that are limited partnerships which have substantive kick-out rights. The Company acts as a fiduciary and does not hold any other interests other than insignificant seed money investments in the pooled investment vehicles. For this reason, the Company also concluded that it is not required to consolidate the pooled investment vehicles under the voting interest entity model. The Company is a party to expense limitation agreements with certain SEI-sponsored money market funds subject to Rule 2a-7 of the Investment Company Act of 1940 which establish a maximum level of ordinary operating expenses incurred by
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 (U.S. GAAP) 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 and Deferred Contract Costs	Revenue Recognition Revenue is recognized when the transfer of control of promised goods or services under the terms of a contract with customers are satisfied in an amount that reflects the consideration to which the Company expects to be entitled in exchange for those promised goods or services. Certain portions of the Company’s revenues involve a third party in providing goods or services to its customers. In such circumstances, the Company must determine whether the nature of its promise to the customer is to provide the underlying goods or services (the Company is the principal in the transaction and reports the transaction gross) or to arrange for a third party to provide the underlying goods or services (the entity is the agent in the transaction and reports the transaction net). The Company does not disclose the value of unsatisfied performance obligations as the majority of its contracts relate to: 1) contracts with an original term of one year or less; 2) contracts for which the Company recognizes revenue at the amount to which it has the right to invoice for services performed; and 3) contracts that are based on the value of assets under management or administration. See Note 15 for related disclosures regarding revenue recognition.
Cash and Cash Equivalents	Cash and Cash EquivalentsThe Company considers investment instruments purchased with an original maturity of three months or less to be cash equivalents.
Restricted Cash	Restricted Cash Restricted cash includes $3,000 at December 31, 2020 and 2019 segregated for regulatory purposes related to trade-execution services conducted by SIEL. Restricted cash also includes $101 at December 31, 2020 and 2019 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	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 the Company's receivables are limited due to the large number of clients and their dispersion across geographic areas. No single group or customer represents greater than 10% 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 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 associated with the Company's available for sale debt securities, net of income taxes, are reported as a separate component of comprehensive income. SIDCO, the Company’s broker-dealer subsidiary, reports changes in fair value of marketable securities through current period earnings due to specialized accounting practices related to investments by broker-dealers. The Company records its investments in money market funds and commercial paper classified as cash equivalents, funds sponsored by LSV and equity securities not accounted for under the equity method 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 5).
Fair Value of Financial Instruments	Fair Value of Financial Instruments Fair value is defined as the exchange price that would be received for an asset or paid to transfer a liability (an exit price) in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants on the measurement date. The fair value hierarchy requires an entity to maximize the use of observable inputs and minimize the use of unobservable inputs when measuring fair value. The fair value hierarchy describes three levels of inputs that may be used by the Company to measure fair value: Level 1 – Quoted prices in active markets for identical assets or liabilities without adjustment. The Company’s Level 1 assets primarily include investments in mutual funds sponsored by SEI that are quoted daily. Level 2 – Observable inputs other than Level 1 prices, such as quoted prices for similar assets, quoted prices in markets that are not active, or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the assets or liabilities. Level 2 financial assets consist of GNMA mortgage-backed securities, Federal Home Loan Bank (FHLB) and other U.S. government agency short-term notes. The investments in GNMA mortgage-backed securities were purchased for the sole purpose of satisfying applicable regulatory requirements imposed on our wholly-owned limited purpose federal thrift subsidiary, SPTC. The investments in FHLB and other U.S. government agency short-term notes were purchased as part of a cash management program requiring only short term, top-tier investment grade government and corporate 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 had no Level 3 financial assets at December 31, 2020 or 2019 that were required to be measured at fair value on a recurring basis. The Company's Level 3 financial liabilities at December 31, 2020 and 2019 consist entirely of an estimated contingent consideration resulting from the Company's acquisition of Huntington Steele, LLC (See Note 14).
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 to ensure the costs incurred will result in additional functionality of the software. Amortization of capitalized software development costs begins when the product is ready for its intended use. Capitalized software development costs are amortized on a product-by-product basis using the straight-line method over the estimated economic life of the product or enhancement. The Company capitalized $24,119, $34,074 and $44,221 of software development costs during 2020, 2019 and 2018, respectively. The Company's capitalized software development costs primarily relate to the further development of the SEI Wealth Platform SM (SWP). The Company capitalized $22,257, $33,084 and $43,376 of software development costs for significant enhancements to SWP during 2020, 2019 and 2018, respectively. As of December 31, 2020, the net book value of SWP was $257,709. The net book value includes $13,409 of capitalized software development costs in-progress associated with future releases. Management continually reassesses the estimated useful life of SWP and any change in management’s estimate could result in the remaining amortization expense to be accelerated or spread out over a longer period. As of December 31, 2020, SWP has a weighted average remaining life of 9.9 years. Amortization expense for SWP was $43,853, $42,297 and $39,917 in 2020, 2019 and 2018, respectively, and is included in Amortization expense on the accompanying Consolidated Statements of Operations. The Company also capitalized $845 of software development costs during 2018 related to an application for the Investment Managers segment. The application was placed into service during 2018 and has a net book value of $10,416 with an estimated remaining useful life of 2.0 years as of December 31, 2020. Amortization expense for the application was $5,209 during 2020 and 2019 and is included in Amortization expense on the accompanying Consolidated Statements of Operations. The Company currently expects to recognize amortization expense related to all capitalized software development costs placed into service as of December 31, 2020 each year from 2021 through 2025 as follows: Year Expected Amortization Expense Related to Capitalized Software 2021 $ 52,466 2022 37,621 2023 18,838 2024 18,838 2025 18,838
Goodwill and Other Intangible Assets	Goodwill and Other Intangible Assets The Company adopted the requirements of ASU 2017-04, Simplifying the Test for Goodwill Impairment (ASU 2017-04) on January 1, 2020. The adoption of ASU 2017-04 did not have a material impact on the Company's consolidated financial statements and related disclosures. The Company reviews long-lived assets and identifiable definite-lived intangible assets for impairment at least annually or whenever events or changes in circumstances indicate that the carrying amount of these assets may not be recoverable. For purposes of recognizing and measuring an impairment loss, a long-lived asset is grouped with other assets and liabilities at the lowest level for which identifiable cash flows are largely independent.
Contingent Consideration Liabilities	Contingent Consideration LiabilitiesThe Company may be required to pay additional future consideration in connection with business acquisitions based on the attainment of specified financial measures. The Company estimates the fair value of these potential future obligations at the time a business combination is consummated and records a contingent consideration liability on the Consolidated Balance Sheets. If the expected payment amounts subsequently change, the contingent consideration liabilities are adjusted through current period earnings and included in Facilities, supplies and other costs on the accompanying Consolidated Statement of Operations.
Income Taxes	Income TaxesThe 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.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.
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.
Earnings Per Common 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 CompensationStock-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 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
Leases	Leases The Company adopted the requirements of the ASU 2016-02 Leases (Topic 842) (ASC 842) using the modified retrospective method on January 1, 2019. As a result of the adoption of ASC 842, the Company recorded additional lease assets and net lease liabilities of $44,169 as of January 1, 2019. Upon implementation, the Company elected the package of practical expedients permitted under the transition guidance within the new standard which allowed the Company to carryforward the historical lease identification, classification and initial direct cost. ASC 842 did not materially impact the Company’s consolidated net income or consolidated cash flows. The Company determines if an arrangement is a lease at the inception of the contract. The Company's operating leases are included in Operating lease right-of-use (ROU) assets, Current portion of long-term operating lease liabilities, and Long-term operating lease liabilities on the accompanying Consolidated Balance Sheets. The operating lease ROU assets and operating lease liabilities are recognized based on the present value of future minimum lease payments over the lease term at commencement date. As most of the Company’s leases do not provide an implicit interest rate, the Company utilizes an estimated incremental borrowing rate based on the information available at commencement date in determining the present value of future payments. In determining the discount rate used in the present value calculation, the Company has elected to apply the portfolio approach for leases of equipment provided the leases commenced at or around the same time. This election allows the Company to account for leases at a portfolio level provided that the resulting accounting at this level would not differ materially from the accounting at the individual lease level. Lease expense for minimum lease payments is recognized on a straight-line basis over the lease term. The Company has elected to account for lease and non-lease components separately. Operating lease ROU assets include all contractual lease payments and initial direct costs incurred, less any lease incentives. Facility leases generally only contain lease expense and non-component items such as taxes and pass through charges. Only the lease components are included in the ROU assets and lease liabilities. Additionally, the Company has elected not to apply the recognition requirements of ASC 842 to leases which have a lease term of less than one year at the commencement date.
Reclassifications	Reclassifications Certain prior year amounts have been reclassified to conform to current year presentation.
Other Recently Adopted and New Accounting Pronouncements and New Accounting Pronouncements	Other Recently Adopted Accounting Pronouncements The Company adopted the requirements of Accounting Standards Update (ASU) 2016-13, Financial Instruments-Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments (Accounting Standards Codification (ASC) 326)) (ASU 2016-13) and subsequent amendments ASU 2019-04, Codification Improvements to Topic 326, Financial Instruments-Credit Losses, Topic 815, Derivatives and Hedging, and Topic 825, Financial Instruments (ASU 2019-04) and ASU 2019-11, Codification Improvements to Topic 326, Financial Instruments-Credit Losses (ASU 2019-11) on January 1, 2020. ASU 2016-13 and the related amendments are hereafter referred to as ASC 326. ASC 326 requires that expected credit losses relating to financial assets measured on an amortized cost basis and available-for-sale debt securities be recorded through an allowance for credit losses. The Company owns mortgage-backed securities issued by the Government National Mortgage Association (GNMA), a federal agency of the U.S. government classified as Available-for-sale debt securities which qualify for the zero credit risk allowance. The Company's U.S. Treasury and other U.S. government agency securities classified as Securities owned are outside the scope of ASC 326. There was no impact to the Company's disclosures related to its marketable securities from the implementation of ASC 326. In accordance with ASC 326, the Company evaluated its receivable balances for credit risk based upon the source of revenue, its ability to collect fees directly from investment products or directly from assets in the client's account, a review of actual historical credit losses, and the potential for expected credit loss from its current client base. The Company has no meaningful historical credit loss data and a very limited amount of losses pertaining directly to a client's inability to satisfy its receivable balance even during periods of economic distress. The credit loss reserve recognized by the Company through the implementation of ASC 326 during 2020 was immaterial. New Accounting Pronouncements In December 2019, the Financial Accounting Standards Board (FASB) issued ASU 2019-12, Income Taxes (Topic 740): Simplifying the Accounting for Income Taxes (ASU 2019-12). The standard removes certain exceptions to the general principles in Topic 740 and also clarifies and amends existing guidance to improve consistent application. ASU 2019-12 is
Investments in Unconsolidated Affiliates	The Company accounts for its interest in LSV using the equity method because of its less than 50% ownership. The Company’s interest in the net assets of LSV is reflected in Investment in unconsolidated affiliates on the accompanying Consolidated Balance Sheets and its interest in the earnings of LSV is reflected in Equity in earnings of unconsolidated affiliates on the accompanying Consolidated Statements of Operations.
Investments in Affiliated Funds	The fair value of the Company's investment funds sponsored by LSV is measured using the net asset value per share (NAV) as a practical expedient. The NAVs of the funds are calculated by the funds' independent custodian and are derived from the fair values of the underlying investments as of the reporting date. The funds allow for investor redemptions at the end of each calendar month.
Securities Owned	The Company’s broker-dealer subsidiary, SIDCO, has investments in U.S. government agency 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.
Accumulated Other Comprehensive Income (Loss)	Other comprehensive income (loss) consists of net income and other gains and losses affecting shareholders’ equity that are excluded from net income. Other comprehensive income (loss) includes unrealized gains and losses on available for sale debt securities and foreign currency translation adjustments. The Company presents other comprehensive income (loss) in its Consolidated Statements of Comprehensive Income.
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 the Company's current estimate of the tax liabilities.

Summary of Significant Accoun_3

Summary of Significant Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2020
Accounting Policies [Abstract]
Schedule of Amortization Expense Related to the SEI Wealth Platform	The Company currently expects to recognize amortization expense related to all capitalized software development costs placed into service as of December 31, 2020 each year from 2021 through 2025 as follows: Year Expected Amortization Expense Related to Capitalized Software 2021 $ 52,466 2022 37,621 2023 18,838 2024 18,838 2025 18,838
Schedule of Calculation of Basic and Diluted Earnings Per Share	The calculations of basic and diluted earnings per share for 2020, 2019 and 2018 are: 2020 2019 2018 Net income $ 447,286 $ 501,426 $ 505,868 Shares used to compute basic earnings per common share 146,709,000 151,540,000 156,579,000 Dilutive effect of stock options 2,294,000 3,361,000 4,653,000 Shares used to compute diluted earnings per common share 149,003,000 154,901,000 161,232,000 Basic earnings per common share $ 3.05 $ 3.31 $ 3.23 Diluted earnings per common share $ 3.00 $ 3.24 $ 3.14

Investment in Unconsolidated _2

Investment in Unconsolidated Affiliates (Tables)	12 Months Ended
	Dec. 31, 2020
Equity Method Investments and Joint Ventures [Abstract]
Schedule of Equity Method Investments	These tables contain condensed financial information of LSV: Condensed Statement of Operations Year ended December 31, 2020 2019 2018 Revenues $ 391,648 $ 491,700 $ 517,203 Net income $ 301,620 $ 390,533 $ 410,846 Condensed Balance Sheets December 31, 2020 2019 Current assets $ 151,515 $ 144,547 Non-current assets 4,296 5,048 Total assets $ 155,811 $ 149,595 Current liabilities $ 77,077 $ 46,828 Non-current liabilities 4,620 5,326 Partners’ capital 74,114 97,441 Total liabilities and partners’ capital $ 155,811 $ 149,595

Composition of Certain Financ_2

Composition of Certain Financial Statement Captions (Tables)	12 Months Ended
	Dec. 31, 2020
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Schedule of Receivables	Receivables on the accompanying Consolidated Balance Sheets consist of: 2020 2019 Trade receivables $ 99,106 $ 86,043 Fees earned, not billed 262,167 240,239 Other receivables 25,046 15,277 386,319 341,559 Less: Allowance for doubtful accounts (1,100) (1,201) Receivables, net $ 385,219 $ 340,358
Schedule of Property and Equipment	Property and Equipment on the accompanying Consolidated Balance Sheets consists of: 2020 2019 Buildings $ 206,151 $ 162,882 Equipment 141,820 123,945 Land 24,179 10,830 Purchased software 147,838 143,705 Furniture and fixtures 21,439 18,835 Leasehold improvements 21,604 20,700 Construction in progress 4,660 33,415 567,691 514,312 Less: Accumulated depreciation (378,639) (353,453) Property and Equipment, net $ 189,052 $ 160,859
Schedule of Accrued Liabilities	Accrued Liabilities on the accompanying Consolidated Balance Sheets consist of: 2020 2019 Accrued employee compensation $ 95,656 $ 96,991 Accrued employee benefits and other personnel 18,770 9,222 Accrued consulting, outsourcing and professional fees 31,907 28,610 Accrued sub-advisory, distribution and other asset management fees 49,924 46,245 Accrued dividend payable 53,127 52,452 Other accrued liabilities 50,461 39,281 Accrued liabilities $ 299,845 $ 272,801

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	12 Months Ended
	Dec. 31, 2020
Fair Value Disclosures [Abstract]
Schedule of 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: Fair Value Measurements at Reporting Date Using December 31, 2020 Quoted Prices in Significant Assets Equity securities $ 12,142 $ 12,142 $ — Available-for-sale debt securities 93,277 — 93,277 Fixed-income securities owned 34,064 — 34,064 Investment funds sponsored by LSV (1) 6,166 $ 145,649 $ 12,142 $ 127,341 Fair Value Measurements at Reporting Date Using December 31, 2019 Quoted Prices in Significant Assets Equity securities $ 12,119 $ 12,119 $ — Available-for-sale debt securities 104,798 — 104,798 Fixed-income securities owned 33,486 — 33,486 Investment funds sponsored by LSV (1) 5,988 $ 156,391 $ 12,119 $ 138,284 (1) The fair value amounts presented in the tables above are intended to permit reconciliation of the fair value hierarchy to the amounts presented on the accompanying Consolidated Balance Sheets (See Note 5).

Marketable Securities (Tables)

Marketable Securities (Tables)	12 Months Ended
	Dec. 31, 2020
Marketable Securities [Abstract]
Schedule of Available For Sale and Equity Securities	Available For Sale and Equity Securities on the accompanying Consolidated Balance Sheets consist of: At December 31, 2020 Cost Gross Gross Fair Available for sale debt securities $ 91,262 $ 2,015 $ — $ 93,277 SEI-sponsored mutual funds 6,866 382 — 7,248 Equities and other mutual funds 4,421 473 — 4,894 $ 102,549 $ 2,870 $ — $ 105,419 At December 31, 2019 Cost Gross Gross Fair Available for sale debt securities $ 104,193 $ 605 $ — $ 104,798 SEI-sponsored mutual funds 7,564 125 (39) 7,650 Equities and other mutual funds 3,637 832 — 4,469 $ 115,394 $ 1,562 $ (39) $ 116,917

Shareholders' Equity (Tables)

Shareholders' Equity (Tables)	12 Months Ended
	Dec. 31, 2020
Equity [Abstract]
Schedule of 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 2020, 2019 and 2018 were $13.53, $13.94 and $13.04, respectively, using the following assumptions: 2020 2019 2018 Expected term (in years) 5.79 5.53 6.34 Expected volatility 29.02 % 23.36 % 25.27 % Expected dividend yield 1.29 % 1.10 % 1.35 % Risk-free interest rate 0.62 % 1.80 % 2.75 %
Schedule of Stock-based Compensation Expense	The Company recognized stock-based compensation expense in its Consolidated Financial Statements in 2020, 2019 and 2018 as follows: 2020 2019 2018 Stock-based compensation expense $ 27,014 $ 24,582 $ 23,805 Less: Deferred tax benefit (5,182) (4,814) (5,078) Stock-based compensation expense, net of tax $ 21,832 $ 19,768 $ 18,727
Schedule of Stock Option Plans	This table presents certain information relating to the Company’s stock option plans for 2020, 2019 and 2018: Number of Weighted Balance as of December 31, 2017 16,712,000 $ 37.63 Granted 2,468,000 49.94 Exercised (3,232,000) 25.93 Expired or canceled (135,000) 49.58 Balance as of December 31, 2018 15,813,000 $ 41.84 Granted 2,480,000 64.04 Exercised (2,243,000) 25.27 Expired or canceled (344,000) 55.07 Balance as of December 31, 2019 15,706,000 $ 47.43 Granted 4,529,000 56.54 Exercised (1,563,000) 28.83 Expired or canceled (177,000) 55.76 Balance as of December 31, 2020 18,495,000 $ 51.15 Exercisable as of December 31, 2020 6,641,000 $ 39.35 Available for future grant as of December 31, 2020 15,287,000
Schedule of Stock Options Outstanding and Exercisable	This table summarizes information relating to all options outstanding and exercisable at December 31, 2020: Options Outstanding at December 31, 2020 Options Exercisable at December 31, 2020 Range of Exercise Prices (Per Share) Number of Shares Weighted Average Weighted Average Number of Shares Weighted Average Weighted Average $ 15.77 - $ 21.05 665,000 $ 15.79 0.95 665,000 $ 15.79 0.95 22.45 - 23.86 944,000 22.45 1.95 944,000 22.45 1.95 27.03 - 40.64 2,699,000 37.35 3.49 1,857,000 35.85 3.29 45.99 - 56.60 8,398,000 62.57 8.09 3,170,000 51.34 5.53 57.48 - 71.12 5,789,000 49.76 8.08 5,000 63.50 6.82 18,495,000 6,641,000
Schedule of Common Stock Buyback	The following table provides the total number of shares repurchased and the related total costs in 2020, 2019 and 2018: Year Total Number of Total Cost 2020 8,008,000 $ 424,702 2019 6,225,000 348,348 2018 6,744,000 404,759

Accumulated Other Comprehensi_2

Accumulated Other Comprehensive Income (Loss) (Tables)	12 Months Ended
	Dec. 31, 2020
Equity [Abstract]
Schedule of Accumulated Other Comprehensive Income (Loss), Net of Tax	Components of Accumulated other comprehensive income (loss), net of tax, consisted of: Foreign Currency Translation Adjustments Unrealized Accumulated Balance, January 1, 2018 $ (19,522) $ (386) $ (19,908) Other comprehensive loss before reclassifications (12,065) (1,088) (13,153) Amounts reclassified from accumulated other comprehensive loss — 61 61 Net current-period other comprehensive loss (12,065) (1,027) (13,092) Balance, December 31, 2018 $ (31,587) $ (1,413) $ (33,000) Other comprehensive income before reclassifications 7,618 1,486 9,104 Amounts reclassified from accumulated other comprehensive loss — 392 392 Net current-period other comprehensive income 7,618 1,878 9,496 Balance, December 31, 2019 $ (23,969) $ 465 $ (23,504) Other comprehensive income before reclassifications 5,620 374 5,994 Amounts reclassified from accumulated other comprehensive loss — 712 712 Net current-period other comprehensive income 5,620 1,086 6,706 Balance, December 31, 2020 $ (18,349) $ 1,551 $ (16,798)

Commitments and Contingencies (

Commitments and Contingencies (Tables)	12 Months Ended
	Dec. 31, 2020
Commitments and Contingencies Disclosure [Abstract]
Schedule of Aggregate Noncancelable Minimum Commitments	The aggregate noncancellable minimum commitments at December 31, 2020 are: Year Aggregate Noncancellable Minimum Commitments 2021 $ 9,183 2022 8,917 2023 8,922 2024 7,252 2025 and thereafter 11,172 $ 45,446 The Company's future minimum lease payments under non-cancelable leases as of December 31, 2020 are as follows: Year Future Minimum Lease Payment 2021 $ 9,183 2022 8,917 2023 8,922 2024 7,252 2025 5,184 Thereafter 5,988 Total future minimum lease payments 45,446 Less: Imputed interest (2,809) Total $ 42,637

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2020
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, 2020 2019 2018 Current Federal $ 92,649 $ 100,986 $ 82,493 State 21,479 19,902 13,709 Foreign 8,256 11,722 8,405 122,384 132,610 104,607 Deferred Federal (701) (1,635) 2,550 State (275) (960) 1,166 Foreign — — 15 (976) (2,595) 3,731 Total income taxes $ 121,408 $ 130,015 $ 108,338
Schedule of Components of Net Income Before Income Taxes	The components of Income before income taxes are summarized as follows: Year Ended December 31, 2020 2019 2018 Domestic $ 517,451 $ 565,842 $ 579,622 Foreign 51,243 65,599 34,584 $ 568,694 $ 631,441 $ 614,206
Schedule of 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, 2020 2019 2018 Statutory rate 21.0 % 21.0 % 21.0 % State taxes, net of federal tax benefit 3.0 2.4 1.9 Foreign tax expense and tax rate differential (0.4) — (0.1) Tax benefit from stock option exercises (1.1) (1.9) (3.8) Research and development tax credit (1.0) (1.1) (0.8) Foreign-Derived Intangible Income Deduction (FDII) (0.3) (0.2) (0.2) Other, net 0.1 0.4 (0.4) 21.3 % 20.6 % 17.6 %
Schedule of Deferred Tax Assets and Liabilities	Significant components of deferred tax assets and liabilities at December 31, 2020 and 2019 are as follows: 2020 2019 Deferred Tax Assets: Stock-based compensation expense $ 26,893 $ 24,686 State net operating loss carryforward 65,114 67,472 Foreign net operating loss carryforward and other 6,634 6,081 Basis differences in investments 3,965 4,436 Federal benefit of state tax deduction for uncertain tax positions 2,255 2,124 Revenue and expense recognized in different periods for financial reporting and income tax purposes 3,025 1,960 Other assets 1,584 1,271 Total deferred income tax assets 109,470 108,030 Less: State net operating loss valuation allowance (62,229) (64,737) Less: Foreign net operating loss valuation allowance (6,547) (5,994) Net deferred income tax assets $ 40,694 $ 37,299 Deferred Tax Liabilities: Capitalized software currently deductible for tax purposes, net of amortization $ (63,588) $ (68,265) Difference in financial reporting and income tax depreciation methods (11,422) (6,032) Difference between book and tax basis of other assets (5,747) (4,593) Goodwill and other intangibles (2,462) (2,170) Foreign dividend withholding tax — (312) Capitalized contract costs (7,762) (7,072) Other liabilities (1,900) (1,755) Total deferred income tax liabilities $ (92,881) $ (90,199) Net deferred income tax liabilities $ (52,187) $ (52,900)
Schedule of Unrecognized Tax Benefits Roll Forward	A reconciliation of the beginning and ending amount of unrecognized tax benefit is as follows: 2020 2019 2018 Balance as of January 1 $ 15,356 $ 14,367 $ 14,480 Tax positions related to current year: Gross additions 3,352 3,054 2,446 Tax positions related to prior years: Gross additions 236 1,465 340 Settlements — (145) (278) Lapses on statute of limitations (3,033) (3,385) (2,621) Balance as of December 31 $ 15,911 $ 15,356 $ 14,367

Business Segment Information (T

Business Segment Information (Tables)	12 Months Ended
	Dec. 31, 2020
Segment Reporting [Abstract]
Schedule of 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, 2020, 2019 and 2018: Private Banks Investment Institutional Investment Investments Total For the Year Ended December 31, 2020 Revenues $ 455,393 $ 407,564 $ 317,627 $ 489,462 $ 14,012 $ 1,684,058 Expenses 446,481 205,913 149,909 308,999 52,871 1,164,173 Operating profit (loss) $ 8,912 $ 201,651 $ 167,718 $ 180,463 $ (38,859) $ 519,885 Private Investment Institutional Investment Investments Total For the Year Ended December 31, 2019 Revenues $ 470,276 $ 403,778 $ 322,062 $ 440,796 $ 12,973 $ 1,649,885 Expenses 443,136 208,508 153,937 282,024 29,660 1,117,265 Operating profit (loss) $ 27,140 $ 195,270 $ 168,125 $ 158,772 $ (16,687) $ 532,620 Private Investment Institutional Investment Investments Total For the Year Ended December 31, 2018 Revenues $ 483,097 $ 399,089 $ 333,299 $ 398,076 $ 10,606 $ 1,624,167 Expenses 457,894 212,439 163,536 259,693 22,971 1,116,533 Operating profit (loss) $ 25,203 $ 186,650 $ 169,763 $ 138,383 $ (12,365) $ 507,634
Schedule of 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, 2020, 2019 and 2018 is as follows: Year Ended December 31, 2020 2019 2018 Total operating profit from segments above $ 519,885 $ 532,620 $ 507,634 Corporate overhead expenses (73,998) (72,196) (65,646) Income from operations $ 445,887 $ 460,424 $ 441,988
Schedule of Additional Information Pertaining to Business Segments	The following tables provide additional information for the years ended December 31, 2020, 2019 and 2018 pertaining to our business segments: Capital Expenditures (1) Depreciation Year Ended December 31, 2020 2019 2018 2020 2019 2018 Private Banks $ 29,061 $ 33,068 $ 36,763 $ 16,206 $ 14,349 $ 13,773 Investment Advisors 15,588 17,413 16,572 4,821 4,653 4,607 Institutional Investors 3,958 4,057 3,863 1,214 1,600 1,672 Investment Managers 25,909 18,970 13,639 7,336 7,145 6,988 Investments in New Businesses 1,211 1,349 972 341 383 547 Total from business segments $ 75,727 $ 74,857 $ 71,809 $ 29,918 $ 28,130 $ 27,587 Corporate Overhead 2,840 2,314 1,507 1,041 1,306 1,205 $ 78,567 $ 77,171 $ 73,316 $ 30,959 $ 29,436 $ 28,792 (1) Capital expenditures include additions to property and equipment and capitalized software. Amortization Year Ended December 31, 2020 2019 2018 Private Banks $ 30,240 $ 29,054 $ 27,312 Investment Advisors 10,694 10,311 9,668 Institutional Investors 1,707 1,726 1,707 Investment Managers 9,365 9,358 9,382 Investments in New Businesses 739 740 595 Total from business segments $ 52,745 $ 51,189 $ 48,664 Corporate Overhead 230 230 231 $ 52,975 $ 51,419 $ 48,895 Total Assets 2020 2019 Private Banks $ 557,953 $ 567,796 Investment Advisors 169,197 165,556 Institutional Investors 119,784 115,012 Investment Managers 421,093 373,986 Investments in New Businesses 22,014 19,735 Total from business segments $ 1,290,041 $ 1,242,085 Corporate Overhead (2) 877,215 909,285 $ 2,167,256 $ 2,151,370 (2) Unallocated assets primarily consist of cash and cash equivalents, marketable securities, and certain other shared services assets.
Schedule of 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, 2020 2019 2018 United States $ 1,427,152 $ 1,385,744 $ 1,348,130 International operations 256,906 264,141 276,037 $ 1,684,058 $ 1,649,885 $ 1,624,167 The following table presents assets based on their location: 2020 2019 United States $ 1,772,179 $ 1,732,427 International operations 395,077 418,943 $ 2,167,256 $ 2,151,370

Goodwill and Intangible Assets

Goodwill and Intangible Assets (Tables)	12 Months Ended
	Dec. 31, 2020
Goodwill and Intangible Assets Disclosure [Abstract]
Schedule of Intangible Assets	The Company's intangible assets consist of: 2020 Weighted Average Estimated Useful Life 2019 Weighted Average Estimated Useful Life Acquired technology $ 13,510 10.0 years $ 13,510 10.0 years Client relationships 16,940 13.9 years 16,940 13.9 years Non-competition agreements 3,470 5.0 years 3,470 5.0 years Trade name 2,840 7.0 years 2,840 7.0 years 36,760 36,760 Less: Accumulated amortization (12,456) (8,773) Intangible assets, net $ 24,304 $ 27,987
Schedule of Finite-Lived Intangible Assets, Future Amortization Expense	The Company currently expects to recognize amortization expense related to intangible assets as of December 31, 2020 each year from 2021 through 2025 as follows: Year Expected Amortization Expense Related to Intangible Assets 2021 $ 3,683 2022 3,336 2023 2,989 2024 2,818 2025 2,599

Revenues from Contracts with _2

Revenues from Contracts with Customers (Tables)	12 Months Ended
	Dec. 31, 2020
Revenue from Contract with Customer [Abstract]
Schedule of Disaggregation of Revenue	The following tables provide additional information pertaining to our revenues disaggregated by major product line and primary geographic market based on the location of the use of the products or services for each of the Company’s business segments for 2020, 2019 and 2018: Private Banks Investment Institutional Investment Investments Total Major Product Lines: For the Year Ended December 31, 2020 Investment management fees from pooled investment products $ 127,883 $ 271,627 $ 53,283 $ 637 $ 1,411 $ 454,841 Investment management fees from investment management agreements 1,470 115,887 262,709 — 12,105 392,171 Investment operations fees 1,804 — — 447,517 — 449,321 Investment processing fees - PaaS 184,711 — — — — 184,711 Investment processing fees - SaaS 113,012 — — 13,739 — 126,751 Professional services fees 21,594 — — 5,753 — 27,347 Account fees and other 4,919 20,050 1,635 21,816 496 48,916 Total revenues $ 455,393 $ 407,564 $ 317,627 $ 489,462 $ 14,012 $ 1,684,058 Primary Geographic Markets: United States $ 298,708 $ 407,564 $ 250,321 $ 456,547 $ 14,012 $ 1,427,152 United Kingdom 97,896 — 51,292 — — 149,188 Canada 41,762 — 5,610 — — 47,372 Ireland 17,027 — 9,850 32,915 — 59,792 Other — — 554 — — 554 Total revenues $ 455,393 $ 407,564 $ 317,627 $ 489,462 $ 14,012 $ 1,684,058 Private Investment Institutional Investment Investments Total Major Product Lines: For the Year Ended December 31, 2019 Investment management fees from pooled investment products $ 135,503 $ 282,253 $ 54,726 $ 766 $ 1,293 $ 474,541 Investment management fees from investment management agreements 1,616 103,428 266,323 — 11,571 382,938 Investment operations fees 1,634 — — 403,208 — 404,842 Investment processing fees - PaaS 177,046 — — — — 177,046 Investment processing fees - SaaS 132,661 — — 11,036 — 143,697 Professional services fees 15,687 — — 5,209 — 20,896 Account fees and other 6,129 18,097 1,013 20,577 109 45,925 Total revenues $ 470,276 $ 403,778 $ 322,062 $ 440,796 $ 12,973 $ 1,649,885 Primary Geographic Markets: United States $ 304,860 $ 403,778 $ 252,149 $ 411,984 $ 12,973 $ 1,385,744 United Kingdom 102,518 — 52,584 — — 155,102 Canada 43,661 — 6,889 — — 50,550 Ireland 19,237 — 9,588 28,812 — 57,637 Other — — 852 — — 852 Total revenues $ 470,276 $ 403,778 $ 322,062 $ 440,796 $ 12,973 $ 1,649,885 Private Investment Institutional Investment Investments Total Major Product Lines: For the Year Ended December 31, 2018 Investment management fees from pooled investment products $ 138,616 $ 288,030 $ 59,739 $ 928 $ 1,017 $ 488,330 Investment management fees from investment management agreements 793 94,526 271,600 331 9,457 376,707 Investment operations fees 1,517 — — 360,382 — 361,899 Investment processing fees - PaaS 182,068 — — 2,519 — 184,587 Investment processing fees - SaaS 136,222 — — 9,598 — 145,820 Professional services fees 16,643 — — 7,280 — 23,923 Account fees and other 7,238 16,533 1,960 17,038 132 42,901 Total revenues $ 483,097 $ 399,089 $ 333,299 $ 398,076 $ 10,606 $ 1,624,167 Primary Geographic Markets: United States $ 304,762 $ 399,089 $ 257,080 $ 376,593 $ 10,606 $ 1,348,130 United Kingdom 112,980 — 55,471 — — 168,451 Canada 45,941 — 8,526 — — 54,467 Ireland 19,414 — 10,419 21,483 — 51,316 Other — — 1,803 — — 1,803 Total revenues $ 483,097 $ 399,089 $ 333,299 $ 398,076 $ 10,606 $ 1,624,167

Leases (Tables)

Leases (Tables)	12 Months Ended
	Dec. 31, 2020
Leases [Abstract]
Schedule of Aggregate Noncancelable Minimum Commitments	The aggregate noncancellable minimum commitments at December 31, 2020 are: Year Aggregate Noncancellable Minimum Commitments 2021 $ 9,183 2022 8,917 2023 8,922 2024 7,252 2025 and thereafter 11,172 $ 45,446 The Company's future minimum lease payments under non-cancelable leases as of December 31, 2020 are as follows: Year Future Minimum Lease Payment 2021 $ 9,183 2022 8,917 2023 8,922 2024 7,252 2025 5,184 Thereafter 5,988 Total future minimum lease payments 45,446 Less: Imputed interest (2,809) Total $ 42,637
Schedule of Supplemental Consolidated Balance Sheet Information Related to Operating Leases	The following table provides supplemental Consolidated Balance Sheet information related to the Company's leases: 2020 2019 Current portion of long-term operating lease liabilities $ 8,579 $ 9,156 Long-term operating lease liabilities 34,058 38,450 Total operating lease liabilities $ 42,637 $ 47,606 Weighted average remaining lease term 5.5 years 6.3 years Weighted average discount rate 2.43 % 2.61 %
Schedule of Supplemental Cash Flow Information Related to Operating Leases	The following table provides supplemental cash flow information related to the Company's leases: Year Ended December 31, 2020 2019 Cash paid for amounts included in the measurement of lease liabilities $ 10,361 $ 10,932 Right-of-use assets obtained in exchange for lease obligations $ 3,272 $ 6,372

Quarterly Financial Data (Una_2

Quarterly Financial Data (Unaudited) (Tables)	12 Months Ended
	Dec. 31, 2020
Quarterly Financial Data [Abstract]
Schedule of Quarterly Financial Data	For the Three Months Ended 2020 March 31 June 30 September 30 December 31 Revenues $ 414,762 $ 400,646 $ 424,927 $ 443,723 Income before income taxes $ 139,197 $ 131,710 $ 141,274 $ 156,513 Net income $ 109,242 $ 101,066 $ 111,096 $ 125,882 Basic earnings per share $ 0.73 $ 0.69 $ 0.76 $ 0.87 Diluted earnings per share (1) $ 0.72 $ 0.68 $ 0.75 $ 0.86 Effective income tax rate 21.5 % 23.3 % 21.4 % 19.6 % For the Three Months Ended 2019 March 31 June 30 September 30 December 31 Revenues $ 400,820 $ 409,586 $ 416,254 $ 423,225 Income before income taxes $ 146,257 $ 162,346 $ 162,870 $ 159,968 Net income $ 113,981 $ 126,540 $ 132,168 $ 128,737 Basic earnings per share $ 0.74 $ 0.83 $ 0.88 $ 0.86 Diluted earnings per share (1) $ 0.73 $ 0.82 $ 0.86 $ 0.84 Effective income tax rate 22.1 % 22.1 % 18.9 % 19.5 %

Summary of Significant Accoun_4

Summary of Significant Accounting Policies (Narrative) (Details) - USD ($) $ / shares in Units, shares in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Jan. 01, 2019
Summary of Significant Accounting Policies [Line Items]
Cash and cash equivalents	$ 784,626,000				$ 841,446,000				$ 784,626,000	$ 841,446,000
Restricted cash	3,101,000				3,101,000				3,101,000	3,101,000
Impairment charges related to marketable securities									0	0	$ 0
Capitalized software development costs									24,119,000	34,074,000	44,221,000
Net book value of capitalized software	270,977,000				296,068,000				270,977,000	296,068,000
Increase in net income from change in estimate	$ 125,882,000	$ 111,096,000	$ 101,066,000	$ 109,242,000	$ 128,737,000	$ 132,168,000	$ 126,540,000	$ 113,981,000	$ 447,286,000	$ 501,426,000	$ 505,868,000
Increase in diluted earnings per share from change in estimate	$ 0.86	$ 0.75	$ 0.68	$ 0.72	$ 0.84	$ 0.86	$ 0.82	$ 0.73	$ 3	$ 3.24	$ 3.14
Impairment charges related to capitalized software development costs									$ 0
Goodwill and intangible assets impairment									$ 0
Anti-dilutive employee stock options (in shares)									9,220	6,574	6,224
Anti-dilutive employee stock options, average exercise price per share									$ 58.12	$ 55.95	$ 53.60
Operating lease, right-of-use asset	$ 38,397,000				$ 42,789,000				$ 38,397,000	$ 42,789,000
SEI Wealth Platform
Summary of Significant Accounting Policies [Line Items]
Capitalized software development costs									22,257,000	33,084,000	$ 43,376,000
Net book value of capitalized software	257,709,000								257,709,000
Capitalized software development costs in progress	13,409,000								13,409,000
Amortization expense related to the SEI Wealth Platform									43,853,000	42,297,000	39,917,000
Application for the Investment Managers segment
Summary of Significant Accounting Policies [Line Items]
Capitalized software development costs											845,000
Net book value of capitalized software	10,416,000								$ 10,416,000
Estimated useful life of the SEI Wealth Platform									2 years
Amortization expense related to the SEI Wealth Platform									$ 5,209,000	5,209,000
Accounting Standards Update 2016-02
Summary of Significant Accounting Policies [Line Items]
Operating lease, right-of-use asset												$ 44,169,000
Minimum | Building and Building Improvements
Summary of Significant Accounting Policies [Line Items]
Estimated useful life of property and equipment									25 years
Minimum | Computer Equipment
Summary of Significant Accounting Policies [Line Items]
Estimated useful life of property and equipment									3 years
Maximum | Building and Building Improvements
Summary of Significant Accounting Policies [Line Items]
Estimated useful life of property and equipment									39 years
Maximum | Computer Equipment
Summary of Significant Accounting Policies [Line Items]
Estimated useful life of property and equipment									5 years
Weighted Average | SEI Wealth Platform
Summary of Significant Accounting Policies [Line Items]
Estimated useful life of the SEI Wealth Platform									9 years 10 months 24 days
SEI Sponsored Open Ended Money Market Mutual Funds
Summary of Significant Accounting Policies [Line Items]
Cash and cash equivalents	347,082,000				414,581,000				$ 347,082,000	414,581,000
SEI Investments Europe Limited
Summary of Significant Accounting Policies [Line Items]
Restricted cash	3,000,000				3,000,000				3,000,000	3,000,000
SEI Investments Distribution Co
Summary of Significant Accounting Policies [Line Items]
Restricted cash	$ 101,000				$ 101,000				101,000	101,000
SEI Sponsored Open Ended Money Market Mutual Funds
Summary of Significant Accounting Policies [Line Items]
Fees waived according to expense limitation agreements									$ 33,408,000	$ 27,544,000	$ 26,229,000

Summary of Significant Accoun_5

Summary of Significant Accounting Policies (Expected Amortization Expenses) (Details) $ in Thousands	Dec. 31, 2020USD ($)
Expected Amortization Expense Related to Capitalized Software
2021	$ 3,683
2022	3,336
2023	2,989
2024	2,818
2025	2,599
Software development
Expected Amortization Expense Related to Capitalized Software
2021	52,466
2022	37,621
2023	18,838
2024	18,838
2025	$ 18,838

Summary of Significant Accoun_6

Summary of Significant Accounting Policies (Calculation Of Basic And Diluted Earnings Per Share) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Earnings Per Share [Abstract]
Net income	$ 125,882	$ 111,096	$ 101,066	$ 109,242	$ 128,737	$ 132,168	$ 126,540	$ 113,981	$ 447,286	$ 501,426	$ 505,868
Shares used to compute basic earnings per common share (in shares)									146,709	151,540	156,579
Dilutive effect of stock options (in shares)									2,294	3,361	4,653
Shares used to compute diluted earnings per common share (in shares)									149,003	154,901	161,232
Basic earnings per common share (in USD per share)	$ 0.87	$ 0.76	$ 0.69	$ 0.73	$ 0.86	$ 0.88	$ 0.83	$ 0.74	$ 3.05	$ 3.31	$ 3.23
Diluted earnings per common share (in USD per share)	$ 0.86	$ 0.75	$ 0.68	$ 0.72	$ 0.84	$ 0.86	$ 0.82	$ 0.73	$ 3	$ 3.24	$ 3.14

Investment in Unconsolidated _3

Investment in Unconsolidated Affiliates (Narrative) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Investments in and Advances to Affiliates [Line Items]
Company's share in the earnings of LSV	$ 117,134	$ 151,891	$ 159,791
Distributions received from LSV	$ 125,534	148,936	166,698
LSV Asset Management
Investments in and Advances to Affiliates [Line Items]
Ownership interest in LSV	38.80%
Total investment in LSV	$ 98,433
Company's share in the earnings of LSV	117,134	151,891	159,791
Distributions received from LSV	$ 125,534	$ 148,936	$ 166,698

Investment in Unconsolidated _4

Investment in Unconsolidated Affiliates (Condensed Statements of Operations of LSV) (Details) - LSV Asset Management - Equity Method Investment, Nonconsolidated Investee - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Schedule of Equity Method Investments [Line Items]
Revenues	$ 391,648	$ 491,700	$ 517,203
Net income	$ 301,620	$ 390,533	$ 410,846

Investment in Unconsolidated _5

Investment in Unconsolidated Affiliates (Condensed Balance Sheets of LSV) (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Schedule of Equity Method Investments [Line Items]
Current assets	$ 1,300,977	$ 1,304,845
Total Assets	2,167,256	2,151,370
Current liabilities	317,275	293,565
Total Liabilities and Equity	2,167,256	2,151,370
LSV Asset Management | Equity Method Investment, Nonconsolidated Investee
Schedule of Equity Method Investments [Line Items]
Current assets	151,515	144,547
Non-current assets	4,296	5,048
Total Assets	155,811	149,595
Current liabilities	77,077	46,828
Non-current liabilities	4,620	5,326
Partners’ capital	74,114	97,441
Total Liabilities and Equity	$ 155,811	$ 149,595

Composition of Certain Financ_3

Composition of Certain Financial Statement Captions (Receivables) (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Trade receivables	$ 99,106	$ 86,043
Fees earned, not billed	262,167	240,239
Other receivables	25,046	15,277
Gross receivables	386,319	341,559
Less: Allowance for doubtful accounts	(1,100)	(1,201)
Receivables, net	$ 385,219	$ 340,358

Composition of Certain Financ_4

Composition of Certain Financial Statement Captions (Property And Equipment) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Property, Plant and Equipment [Line Items]
Property and Equipment, gross	$ 567,691	$ 514,312
Less: Accumulated depreciation	(378,639)	(353,453)
Property and Equipment, net	189,052	160,859
Depreciation expense	30,959	29,436	$ 28,792
Buildings
Property, Plant and Equipment [Line Items]
Property and Equipment, gross	206,151	162,882
Equipment
Property, Plant and Equipment [Line Items]
Property and Equipment, gross	141,820	123,945
Land
Property, Plant and Equipment [Line Items]
Property and Equipment, gross	24,179	10,830
Purchased software
Property, Plant and Equipment [Line Items]
Property and Equipment, gross	147,838	143,705
Furniture and fixtures
Property, Plant and Equipment [Line Items]
Property and Equipment, gross	21,439	18,835
Leasehold improvements
Property, Plant and Equipment [Line Items]
Property and Equipment, gross	21,604	20,700
Construction in progress
Property, Plant and Equipment [Line Items]
Property and Equipment, gross	$ 4,660	$ 33,415

Composition of Certain Financ_5

Composition of Certain Financial Statement Captions Composition of Certain Financial Statement Captions (Deferred Contract Costs) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Capitalized Contract Cost [Line Items]
Deferred contract costs	$ 33,781	$ 30,991
Capitalized contract cost, amount capitalized during period	10,284	11,495	$ 8,122
Amortization of deferred contract costs	7,494	4,511	2,756
Capitalized contract cost impairment	$ 0	$ 0	$ 0
Minimum
Capitalized Contract Cost [Line Items]
Deferred contract acquisition costs, amortization period	6 years
Maximum
Capitalized Contract Cost [Line Items]
Deferred contract acquisition costs, amortization period	15 years

Composition of Certain Financ_6

Composition of Certain Financial Statement Captions (Other Assets) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Amortization expense for certain other assets	$ 230	$ 230	$ 231

Composition of Certain Financ_7

Composition of Certain Financial Statement Captions (Accrued Liabilities) (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Accrued employee compensation	$ 95,656	$ 96,991
Accrued employee benefits and other personnel	18,770	9,222
Accrued consulting, outsourcing and professional fees	31,907	28,610
Accrued sub-advisory, distribution and other asset management fees	49,924	46,245
Accrued dividend payable	53,127	52,452
Other accrued liabilities	50,461	39,281
Accrued liabilities	$ 299,845	$ 272,801

Fair Value Measurements (Detail

Fair Value Measurements (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed-income securities owned	$ 34,064	$ 33,486
Assets, fair value	145,649	156,391
Quoted Prices in Active  Markets for Identical Assets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed-income securities owned	0	0
Assets, fair value	12,142	12,119
Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed-income securities owned	34,064	33,486
Assets, fair value	127,341	138,284
Equity securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale debt securities	12,142	12,119
Equity securities | Quoted Prices in Active  Markets for Identical Assets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale debt securities	12,142	12,119
Equity securities | Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale debt securities	0	0
Available-for-sale debt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale debt securities	93,277	104,798
Available-for-sale debt securities | Quoted Prices in Active  Markets for Identical Assets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale debt securities	0	0
Available-for-sale debt securities | Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale debt securities	93,277	104,798
Investment Funds Sponsored by LSV
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment funds sponsored by LSV	$ 6,166	$ 5,988

Marketable Securities (Investme

Marketable Securities (Investments Available For Sale) (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Debt Securities, Available-for-sale [Line Items]
Available For Sale and Equity Securities, Cost	$ 102,549	$ 115,394
Available For Sale and Equity Securities, Gross Unrealized Gains	2,870	1,562
Available For Sale and Equity Securities, Gross Unrealized (Losses)	0	(39)
Available For Sale and Equity Securities, Fair Value	105,419	116,917
Available for sale debt securities
Debt Securities, Available-for-sale [Line Items]
Available for sale debt securities, Cost	91,262	104,193
Available for sale debt securities, Gross Unrealized Gains	2,015	605
Available for sale debt securities, Gross Unrealized (Losses)	0	0
Available for sale debt securities, Fair Value	93,277	104,798
SEI-sponsored mutual funds
Debt Securities, Available-for-sale [Line Items]
Equity securities, FV-NI, Cost	6,866	7,564
Equity securities, FV-NI, Gross Unrealized Gains	382	125
Equity securities, FV-NI, Gross Unrealized (Losses)	0	(39)
Equity securities, FV-NI, Fair Value	7,248	7,650
Equities and other mutual funds
Debt Securities, Available-for-sale [Line Items]
Equity securities, FV-NI, Cost	4,421	3,637
Equity securities, FV-NI, Gross Unrealized Gains	473	832
Equity securities, FV-NI, Gross Unrealized (Losses)	0	0
Equity securities, FV-NI, Fair Value	$ 4,894	$ 4,469

Marketable Securities (Narrativ

Marketable Securities (Narrative) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Schedule of Investments [Line Items]
Cash equivalents fair value	$ 462,624	$ 543,765
Net unrealized holding gain (loss)	1,551	(465)
Net unrealized holding gains (losses), income tax expense (benefit)	464	(140)
Equity securities, gross realized gains	1,100	297
Equity securities, gross realized losses	250	48
Investment funds sponsored by LSV	98,433	67,413
Securities owned	34,064	33,486
Available for sale debt securities
Schedule of Investments [Line Items]
Available-for-sale securities, gross realized losses	902	493
Available-for-sale securities, gross realized gains	0	0
Investment funds sponsored by LSV
Schedule of Investments [Line Items]
Investment funds sponsored by LSV	6,166	5,988
Gains (losses) from the change in fair value of the funds	$ 178	$ 1,101	$ (1,147)

Line of Credit (Details)

Line of Credit (Details) - USD ($)	Jun. 13, 2016	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Line of Credit Facility [Line Items]
Letters of credit outstanding amount		$ 4,630,000
Revolving Credit Facility
Line of Credit Facility [Line Items]
Debt instrument, term	5 years
Credit facility maximum borrowing capacity		$ 300,000,000
Credit facility stated percentage		0.00%
Credit facility accordion feature, increase limit		$ 100,000,000
Credit facility remaining borrowing capacity		295,370,000
Credit facility commitment fees		$ 609,000	$ 630,000	$ 645,000
Revolving Credit Facility | London Interbank Offered Rate (LIBOR)
Line of Credit Facility [Line Items]
Credit facility variable interest rate basis spread (as a percent)		1.00%
Revolving Credit Facility | Federal Funds Rate
Line of Credit Facility [Line Items]
Credit facility variable interest rate basis spread (as a percent)		0.50%
Letter of Credit
Line of Credit Facility [Line Items]
Credit facility maximum borrowing capacity		$ 15,000,000
Credit facility, commitment fee percentage		1.25%
Credit facility, fronting fee percentage		0.175%
Minimum | Revolving Credit Facility
Line of Credit Facility [Line Items]
Credit facility commitment fee per annum on daily unused portion (as a percent)		0.15%
Minimum | Revolving Credit Facility | Base Rate
Line of Credit Facility [Line Items]
Credit facility variable interest rate basis spread (as a percent)		0.25%
Minimum | Revolving Credit Facility | London Interbank Offered Rate (LIBOR)
Line of Credit Facility [Line Items]
Credit facility variable interest rate basis spread (as a percent)		1.25%
Maximum | Revolving Credit Facility
Line of Credit Facility [Line Items]
Credit facility commitment fee per annum on daily unused portion (as a percent)		0.30%
Maximum | Revolving Credit Facility | Base Rate
Line of Credit Facility [Line Items]
Credit facility variable interest rate basis spread (as a percent)		1.00%
Maximum | Revolving Credit Facility | London Interbank Offered Rate (LIBOR)
Line of Credit Facility [Line Items]
Credit facility variable interest rate basis spread (as a percent)		2.00%

Shareholders' Equity (Narrative

Shareholders' Equity (Narrative) (Details) $ / shares in Units, $ in Thousands	Dec. 08, 2020$ / shares	Jun. 03, 2020$ / shares	Dec. 31, 2020USD ($)$ / sharesshares	Dec. 31, 2019USD ($)$ / sharesshares	Dec. 31, 2018USD ($)$ / shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted average fair value of stock options granted (in USD per share) | $ / shares			$ 13.53	$ 13.94	$ 13.04
Increase (decrease) in stock-based compensation from change in management's estimate			$ (2,659)	$ 2,903	$ 1,909
Unvested employee stock options outstanding (in shares) | shares			11,854,000
Unrecognized compensation cost from employee stock options			$ 112,593
Weighted average period for recognition of unrecognized compensation cost			1 year 8 months 12 days
Total options that were exercisable (in shares) | shares			6,641,000	8,214,000
Options outstanding weighted average remaining contractual life, years			6 years 10 months 24 days
Total intrinsic value of options exercised			$ 46,426	$ 74,163
Aggregate intrinsic value of options exercisable			120,357
Total intrinsic value of options outstanding			$ 158,204
Share price of SEI common stock (in USD per share) | $ / shares			$ 57.47
Percentage of one share for each unit purchased in Rights Agreement			0.020
Dividends declared per common share (in USD per share) | $ / shares	$ 0.37	$ 0.35	$ 0.72	$ 0.68	$ 0.63
Dividends declared			$ 104,588	$ 102,435	$ 97,900
Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award waiting period			2 years
Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award waiting period			4 years
Common Stock Buyback
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Remaining stock repurchase authorization amount			$ 192,827
2014 Equity Compensation Plan | Tranche One
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting rate			50.00%
2014 Equity Compensation Plan | Tranche Two
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting rate			50.00%
Employee Stock Purchase Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Employee stock purchase plan, employee eligible percentage on offerings of common stock			85.00%
Shares reserved under the plan | shares			15,652,000
Issuance of common stock under the employee stock purchase plan, shares | shares			12,225,000
Employee stock purchase plan			$ 0	$ 0	$ 0

Shareholders' Equity (Assumptio

Shareholders' Equity (Assumptions Used In The Weighted Average Fair Value Of Stock Options Granted) (Details)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Equity [Abstract]
Expected term (in years)	5 years 9 months 14 days	5 years 6 months 10 days	6 years 4 months 2 days
Expected volatility	29.02%	23.36%	25.27%
Expected dividend yield	1.29%	1.10%	1.35%
Risk-free interest rate	0.62%	1.80%	2.75%

Shareholders' Equity (Stock-Bas

Shareholders' Equity (Stock-Based Compensation Expense) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Equity [Abstract]
Stock-based compensation expense	$ 27,014	$ 24,582	$ 23,805
Less: Deferred tax benefit	(5,182)	(4,814)	(5,078)
Stock-based compensation expense, net of tax	$ 21,832	$ 19,768	$ 18,727

Shareholders' Equity (Stock Opt

Shareholders' Equity (Stock Option Plans) (Details) - $ / shares shares in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Number of Shares
Beginning balance (in shares)	15,706	15,813	16,712
Granted (in shares)	4,529	2,480	2,468
Exercised (in shares)	(1,563)	(2,243)	(3,232)
Expired or canceled (in shares)	(177)	(344)	(135)
Ending balance (in shares)	18,495	15,706	15,813
Weighted Average Price
Beginning balance (in USD per share)	$ 47.43	$ 41.84	$ 37.63
Granted (in USD per share)	56.54	64.04	49.94
Exercised (in USD per share)	28.83	25.27	25.93
Expired or canceled (in USD per share)	55.76	55.07	49.58
Ending balance (in USD per share)	$ 51.15	$ 47.43	$ 41.84
Total options that were exercisable (in shares)	6,641	8,214
Exercisable shares, weighted avg. price (in USD per share)	$ 39.35
Available for future grant as of December 31, 2018 (in shares)	15,287

Shareholders' Equity (Stock O_2

Shareholders' Equity (Stock Options Outstanding and Exercisable) (Details) - $ / shares shares in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Share-based Payment Arrangement, Option, Exercise Price Range [Line Items]
Number of options outstanding (in shares)	18,495	15,706	15,813	16,712
Options outstanding, weighted average exercise price (in USD per share)	$ 51.15	$ 47.43	$ 41.84	$ 37.63
Options outstanding weighted average remaining contractual life, years	6 years 10 months 24 days
Number of options exercisable (in shares)	6,641	8,214
Exercisable shares, weighted avg. price (in USD per share)	$ 39.35
Exercise Price $14.62-21.05
Share-based Payment Arrangement, Option, Exercise Price Range [Line Items]
Lower range (in USD per share)	15.77
Upper range (in USD per share)	$ 21.05
Number of options outstanding (in shares)	665
Options outstanding, weighted average exercise price (in USD per share)	$ 15.79
Options outstanding weighted average remaining contractual life, years	11 months 12 days
Number of options exercisable (in shares)	665
Exercisable shares, weighted avg. price (in USD per share)	$ 15.79
Options exercisable, weighted average remaining contractual life, years	11 months 12 days
Exercise Price $22.45-23.86
Share-based Payment Arrangement, Option, Exercise Price Range [Line Items]
Lower range (in USD per share)	$ 22.45
Upper range (in USD per share)	$ 23.86
Number of options outstanding (in shares)	944
Options outstanding, weighted average exercise price (in USD per share)	$ 22.45
Options outstanding weighted average remaining contractual life, years	1 year 11 months 12 days
Number of options exercisable (in shares)	944
Exercisable shares, weighted avg. price (in USD per share)	$ 22.45
Options exercisable, weighted average remaining contractual life, years	1 year 11 months 12 days
Exercise Price $27.03-40.64
Share-based Payment Arrangement, Option, Exercise Price Range [Line Items]
Lower range (in USD per share)	$ 27.03
Upper range (in USD per share)	$ 40.64
Number of options outstanding (in shares)	2,699
Options outstanding, weighted average exercise price (in USD per share)	$ 37.35
Options outstanding weighted average remaining contractual life, years	3 years 5 months 26 days
Number of options exercisable (in shares)	1,857
Exercisable shares, weighted avg. price (in USD per share)	$ 35.85
Options exercisable, weighted average remaining contractual life, years	3 years 3 months 14 days
Exercise Price $45.99-53.16
Share-based Payment Arrangement, Option, Exercise Price Range [Line Items]
Lower range (in USD per share)	$ 45.99
Upper range (in USD per share)	$ 56.60
Number of options outstanding (in shares)	8,398
Options outstanding, weighted average exercise price (in USD per share)	$ 62.57
Options outstanding weighted average remaining contractual life, years	8 years 1 month 2 days
Number of options exercisable (in shares)	3,170
Exercisable shares, weighted avg. price (in USD per share)	$ 51.34
Options exercisable, weighted average remaining contractual life, years	5 years 6 months 10 days
Exercise Price $53.34-71.12
Share-based Payment Arrangement, Option, Exercise Price Range [Line Items]
Lower range (in USD per share)	$ 57.48
Upper range (in USD per share)	$ 71.12
Number of options outstanding (in shares)	5,789
Options outstanding, weighted average exercise price (in USD per share)	$ 49.76
Options outstanding weighted average remaining contractual life, years	8 years 29 days
Number of options exercisable (in shares)	5
Exercisable shares, weighted avg. price (in USD per share)	$ 63.50
Options exercisable, weighted average remaining contractual life, years	6 years 9 months 25 days

Shareholders' Equity (Common St

Shareholders' Equity (Common Stock Buyback) (Details) - Common Stock Buyback - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Equity, Class of Treasury Stock [Line Items]
Shares repurchased and retired during period	8,008	6,225	6,744
Value of shares repurchased during period	$ 424,702	$ 348,348	$ 404,759

Accumulated Other Comprehensi_3

Accumulated Other Comprehensive Income (Loss), Net of Tax (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance	$ 1,738,778	$ 1,593,147
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax [Abstract]
Other comprehensive income (loss) before reclassifications	5,994	9,104	$ (13,153)
Amounts reclassified from accumulated other comprehensive loss	712	392	61
Total other comprehensive income (loss), net of taxes	6,706	9,496	(13,092)
Ending balance	1,739,907	1,738,778	1,593,147
Foreign Currency Translation Adjustments
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance	(23,969)	(31,587)	(19,522)
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax [Abstract]
Other comprehensive income (loss) before reclassifications	5,620	7,618	(12,065)
Amounts reclassified from accumulated other comprehensive loss	0	0	0
Total other comprehensive income (loss), net of taxes	5,620	7,618	(12,065)
Ending balance	(18,349)	(23,969)	(31,587)
Unrealized Holding Gains (Losses) on Investments
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance	465	(1,413)	(386)
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax [Abstract]
Other comprehensive income (loss) before reclassifications	374	1,486	(1,088)
Amounts reclassified from accumulated other comprehensive loss	712	392	61
Total other comprehensive income (loss), net of taxes	1,086	1,878	(1,027)
Ending balance	1,551	465	(1,413)
AOCI Attributable to Parent
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance	(23,504)	(33,000)	(19,908)
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax [Abstract]
Total other comprehensive income (loss), net of taxes	6,706	9,496	(13,092)
Ending balance	$ (16,798)	$ (23,504)	$ (33,000)

Employee Benefit Plan (Details)

Employee Benefit Plan (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Retirement Benefits [Abstract]
Defined contribution plan, cost recognized	$ 14,087	$ 12,923	$ 12,362

Commitments and Contingencies_2

Commitments and Contingencies (Narrative) (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2020USD ($)lawsuit	Dec. 31, 2019USD ($)	Dec. 31, 2018USD ($)
Loss Contingencies [Line Items]
Rent expense | $	$ 9,711	$ 10,159
Number of lawsuits filed	7
Cases with SPTC as Defendant
Loss Contingencies [Line Items]
Number of lawsuits filed	4
Claims for Violations of Louisiana Racketeering Act
Loss Contingencies [Line Items]
Number of lawsuits filed	2
Cases Remaining in Parish of East Baton Rouge Granted Indefinite Extensions to Respond
Loss Contingencies [Line Items]
Number of lawsuits filed	2
Cases Filed in East Baton Rouge
Loss Contingencies [Line Items]
Number of lawsuits filed	2
User licenses for software
Loss Contingencies [Line Items]
Rent expense | $	$ 41,091	$ 33,600
Rent expense | $			$ 34,679

Commitments and Contingencies_3

Commitments and Contingencies (Schedule Of Noncancellable Minimum Commitments) (Details) $ in Thousands	Dec. 31, 2020USD ($)
Aggregate Noncancellable Minimum Commitments
2021	$ 9,183
2022	8,917
2023	8,922
2024	7,252
2025 and thereafter	11,172
Total future minimum lease payments	$ 45,446

Income Taxes (Schedule of Feder

Income Taxes (Schedule of Federal and State and Foreign Income Tax Provision) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Current
Federal	$ 92,649	$ 100,986	$ 82,493
State	21,479	19,902	13,709
Foreign	8,256	11,722	8,405
Current federal, state and foreign income tax	122,384	132,610	104,607
Deferred
Federal	(701)	(1,635)	2,550
State	(275)	(960)	1,166
Foreign	0	0	15
Deferred income tax expense (benefit)	(976)	(2,595)	3,731
Total income taxes	$ 121,408	$ 130,015	$ 108,338

Income Taxes (Components of Net

Income Taxes (Components of Net Income Before Income Taxes) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Income Tax Disclosure [Abstract]
Domestic									$ 517,451	$ 565,842	$ 579,622
Foreign									51,243	65,599	34,584
Income before income taxes	$ 156,513	$ 141,274	$ 131,710	$ 139,197	$ 159,968	$ 162,870	$ 162,346	$ 146,257	$ 568,694	$ 631,441	$ 614,206

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, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Income Tax Disclosure [Abstract]
Statutory rate									21.00%	21.00%	21.00%
State taxes, net of federal tax benefit									3.00%	2.40%	1.90%
Foreign tax expense and tax rate differential									(0.40%)	0.00%	(0.10%)
Tax benefit from stock option exercises									(1.10%)	(1.90%)	(3.80%)
Research and development tax credit									(1.00%)	(1.10%)	(0.80%)
Foreign-Derived Intangible Income Deduction (FDII)									(0.30%)	(0.20%)	(0.20%)
Other, net									0.10%	0.40%	(0.40%)
Effective income tax rate	19.60%	21.40%	23.30%	21.50%	19.50%	18.90%	22.10%	22.10%	21.30%	20.60%	17.60%

Income Taxes (Narrative) (Detai

Income Taxes (Narrative) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Significant Change in Unrecognized Tax Benefits is Reasonably Possible [Line Items]
Unrecognized tax benefit, including interest and penalties	$ 18,016
Unrecognized tax benefits that would affect effective tax rate	15,761
Amount of uncertain tax liability expected to be paid within one year	6,546
Amount of uncertain tax liability included in Other long-term liabilities	11,470
Unrecognized tax benefits related to lapse of statute of limitations, previously unrecognized	3,033
Liabilities for tax-related interest and penalties	2,105	$ 1,962	$ 1,289
Settlement and Lapse of Statute
Significant Change in Unrecognized Tax Benefits is Reasonably Possible [Line Items]
Unrecognized tax benefits expected to be recognized within the next 12 months	$ 6,546

Income Taxes Income Taxes (Sche

Income Taxes Income Taxes (Schedule of Deferred Tax Assets and Liabilities) (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Deferred Tax Assets:
Stock-based compensation expense	$ 26,893	$ 24,686
State net operating loss carryforward	65,114	67,472
Foreign net operating loss carryforward and other	6,634	6,081
Basis differences in investments	3,965	4,436
Federal benefit of state tax deduction for uncertain tax positions	2,255	2,124
Revenue and expense recognized in different periods for financial reporting and income tax purposes	3,025	1,960
Other assets	1,584	1,271
Total deferred income tax assets	109,470	108,030
Operating Loss Carryforwards [Line Items]
Net deferred income tax assets	40,694	37,299
Deferred Tax Liabilities:
Capitalized software currently deductible for tax purposes, net of amortization	(63,588)	(68,265)
Difference in financial reporting and income tax depreciation methods	(11,422)	(6,032)
Difference between book and tax basis of other assets	(5,747)	(4,593)
Goodwill and other intangibles	(2,462)	(2,170)
Foreign dividend withholding tax	0	(312)
Capitalized contract costs	(7,762)	(7,072)
Other liabilities	(1,900)	(1,755)
Total deferred income tax liabilities	(92,881)	(90,199)
Net deferred income tax liabilities	(52,187)	(52,900)
State
Operating Loss Carryforwards [Line Items]
Less: Net operating loss valuation allowance	(62,229)	(64,737)
Foreign
Operating Loss Carryforwards [Line Items]
Less: Net operating loss valuation allowance	$ (6,547)	$ (5,994)

Income Taxes (Unrecognized Tax

Income Taxes (Unrecognized Tax Benefit) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Beginning balance	$ 15,356	$ 14,367	$ 14,480
Tax positions related to current year:
Gross additions	3,352	3,054	2,446
Tax positions related to prior years:
Gross additions	236	1,465	340
Settlements	0	(145)	(278)
Lapses on statute of limitations	(3,033)	(3,385)	(2,621)
Ending balance	$ 15,911	$ 15,356	$ 14,367

Business Segment Information (S

Business Segment Information (Schedule of Financial Information about Business Segments) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Segment Reporting Information [Line Items]
Revenues	$ 443,723	$ 424,927	$ 400,646	$ 414,762	$ 423,225	$ 416,254	$ 409,586	$ 400,820	$ 1,684,058	$ 1,649,885	$ 1,624,167
Expenses									1,164,173	1,117,265	1,116,533
Operating profit (loss)									519,885	532,620	507,634
Private Banks
Segment Reporting Information [Line Items]
Revenues									455,393	470,276	483,097
Expenses									446,481	443,136	457,894
Operating profit (loss)									8,912	27,140	25,203
Investment Advisors
Segment Reporting Information [Line Items]
Revenues									407,564	403,778	399,089
Expenses									205,913	208,508	212,439
Operating profit (loss)									201,651	195,270	186,650
Institutional Investors
Segment Reporting Information [Line Items]
Revenues									317,627	322,062	333,299
Expenses									149,909	153,937	163,536
Operating profit (loss)									167,718	168,125	169,763
Investment Managers
Segment Reporting Information [Line Items]
Revenues									489,462	440,796	398,076
Expenses									308,999	282,024	259,693
Operating profit (loss)									180,463	158,772	138,383
Investments In New Businesses
Segment Reporting Information [Line Items]
Revenues									14,012	12,973	10,606
Expenses									52,871	29,660	22,971
Operating profit (loss)									$ (38,859)	$ (16,687)	$ (12,365)

Business Segment Information (R

Business Segment Information (Reconciliation of Total Operating Profit Reported for Business Segments to Income from Operations in Consolidated Statements of Operations) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Segment Reporting [Abstract]
Total operating profit from segments above	$ 519,885	$ 532,620	$ 507,634
Corporate overhead expenses	(73,998)	(72,196)	(65,646)
Income from operations	$ 445,887	$ 460,424	$ 441,988

Business Segment Information _2

Business Segment Information (Schedule Of Additional Information Pertaining To Business Segments) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Segment Reporting Information [Line Items]
Capital Expenditures	$ 78,567	$ 77,171	$ 73,316
Depreciation	30,959	29,436	28,792
Amortization	52,975	51,419	48,895
Assets	2,167,256	2,151,370
Operating Segments
Segment Reporting Information [Line Items]
Capital Expenditures	75,727	74,857	71,809
Depreciation	29,918	28,130	27,587
Amortization	52,745	51,189	48,664
Assets	1,290,041	1,242,085
Operating Segments | Private Banks
Segment Reporting Information [Line Items]
Capital Expenditures	29,061	33,068	36,763
Depreciation	16,206	14,349	13,773
Amortization	30,240	29,054	27,312
Assets	557,953	567,796
Operating Segments | Investment Advisors
Segment Reporting Information [Line Items]
Capital Expenditures	15,588	17,413	16,572
Depreciation	4,821	4,653	4,607
Amortization	10,694	10,311	9,668
Assets	169,197	165,556
Operating Segments | Institutional Investors
Segment Reporting Information [Line Items]
Capital Expenditures	3,958	4,057	3,863
Depreciation	1,214	1,600	1,672
Amortization	1,707	1,726	1,707
Assets	119,784	115,012
Operating Segments | Investment Managers
Segment Reporting Information [Line Items]
Capital Expenditures	25,909	18,970	13,639
Depreciation	7,336	7,145	6,988
Amortization	9,365	9,358	9,382
Assets	421,093	373,986
Operating Segments | Investments In New Businesses
Segment Reporting Information [Line Items]
Capital Expenditures	1,211	1,349	972
Depreciation	341	383	547
Amortization	739	740	595
Assets	22,014	19,735
Corporate Overhead
Segment Reporting Information [Line Items]
Capital Expenditures	2,840	2,314	1,507
Depreciation	1,041	1,306	1,205
Amortization	230	230	$ 231
Assets	$ 877,215	$ 909,285

Business Segment Information _3

Business Segment Information (Schedule of Revenues And Assets Based On Location) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues	$ 443,723	$ 424,927	$ 400,646	$ 414,762	$ 423,225	$ 416,254	$ 409,586	$ 400,820	$ 1,684,058	$ 1,649,885	$ 1,624,167
Assets	2,167,256				2,151,370				2,167,256	2,151,370
United States
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues									1,427,152	1,385,744	1,348,130
Assets	1,772,179				1,732,427				1,772,179	1,732,427
International operations
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues									256,906	264,141	$ 276,037
Assets	$ 395,077				$ 418,943				$ 395,077	$ 418,943

Related Party Transactions (Det

Related Party Transactions (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Asset management, administration and distribution fees
Related Party Transaction [Line Items]
Revenue from related parties	$ 432,806	$ 449,725	$ 462,101
Transaction-based and trade execution fees
Related Party Transaction [Line Items]
Revenue from related parties	$ 2,159	$ 632	$ 2,001

Goodwill and Intangible Asset_2

Goodwill and Intangible Assets (Narrative) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Apr. 30, 2018	Jul. 31, 2017
Goodwill [Line Items]
Goodwill	$ 64,489	$ 64,489
Payment for contingent consideration liability	633	433	$ 0
Remaining contingent consideration resulting in loss	893	568
Amortization of intangible assets	3,683	3,683
Huntington Steele, LLC
Goodwill [Line Items]
Goodwill				$ 11,499
Payment for contingent consideration liability	633	$ 433
Contingent purchase price, current	3,931
Contingent purchase price, noncurrent	$ 8,584
Archway
Goodwill [Line Items]
Goodwill					$ 52,990

Goodwill and Intangible Asset_3

Goodwill and Intangible Assets (Schedule of Intangible Assets) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Finite-Lived Intangible Assets [Line Items]
Intangible assets, gross	$ 36,760	$ 36,760
Less: Accumulated amortization	(12,456)	(8,773)
Intangible assets, net	24,304	27,987
Acquired technology
Finite-Lived Intangible Assets [Line Items]
Intangible assets, gross	$ 13,510	$ 13,510
Weighted Average Estimated Useful Life	10 years	10 years
Client relationships
Finite-Lived Intangible Assets [Line Items]
Intangible assets, gross	$ 16,940	$ 16,940
Weighted Average Estimated Useful Life	13 years 10 months 24 days	13 years 10 months 24 days
Non-competition agreements
Finite-Lived Intangible Assets [Line Items]
Intangible assets, gross	$ 3,470	$ 3,470
Weighted Average Estimated Useful Life	5 years	5 years
Trade names
Finite-Lived Intangible Assets [Line Items]
Intangible assets, gross	$ 2,840	$ 2,840
Weighted Average Estimated Useful Life	7 years	7 years

Goodwill and Intangible Asset_4

Goodwill and Intangible Assets (Future Amortization Expenses) (Details) $ in Thousands	Dec. 31, 2020USD ($)
Expected Amortization Expense Related to Intangible Assets
2021	$ 3,683
2022	3,336
2023	2,989
2024	2,818
2025	$ 2,599

Revenues from Contracts with _3

Revenues from Contracts with Customers (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Disaggregation of Revenue [Line Items]
Revenues	$ 443,723	$ 424,927	$ 400,646	$ 414,762	$ 423,225	$ 416,254	$ 409,586	$ 400,820	$ 1,684,058	$ 1,649,885	$ 1,624,167
United States
Disaggregation of Revenue [Line Items]
Revenues									1,427,152	1,385,744	1,348,130
United Kingdom
Disaggregation of Revenue [Line Items]
Revenues									149,188	155,102	168,451
Canada
Disaggregation of Revenue [Line Items]
Revenues									47,372	50,550	54,467
Ireland
Disaggregation of Revenue [Line Items]
Revenues									59,792	57,637	51,316
Other
Disaggregation of Revenue [Line Items]
Revenues									554	852	1,803
Investment management fees from pooled investment products
Disaggregation of Revenue [Line Items]
Revenues									454,841	474,541	488,330
Investment management fees from investment management agreements
Disaggregation of Revenue [Line Items]
Revenues									392,171	382,938	376,707
Investment operations fees
Disaggregation of Revenue [Line Items]
Revenues									449,321	404,842	361,899
Investment processing fees - PaaS
Disaggregation of Revenue [Line Items]
Revenues									184,711	177,046	184,587
Investment processing fees - SaaS
Disaggregation of Revenue [Line Items]
Revenues									126,751	143,697	145,820
Professional services fees
Disaggregation of Revenue [Line Items]
Revenues									27,347	20,896	23,923
Account fees and other
Disaggregation of Revenue [Line Items]
Revenues									48,916	45,925	42,901
Private Banks
Disaggregation of Revenue [Line Items]
Revenues									455,393	470,276	483,097
Private Banks | United States
Disaggregation of Revenue [Line Items]
Revenues									298,708	304,860	304,762
Private Banks | United Kingdom
Disaggregation of Revenue [Line Items]
Revenues									97,896	102,518	112,980
Private Banks | Canada
Disaggregation of Revenue [Line Items]
Revenues									41,762	43,661	45,941
Private Banks | Ireland
Disaggregation of Revenue [Line Items]
Revenues									17,027	19,237	19,414
Private Banks | Other
Disaggregation of Revenue [Line Items]
Revenues									0	0	0
Private Banks | Investment management fees from pooled investment products
Disaggregation of Revenue [Line Items]
Revenues									127,883	135,503	138,616
Private Banks | Investment management fees from investment management agreements
Disaggregation of Revenue [Line Items]
Revenues									1,470	1,616	793
Private Banks | Investment operations fees
Disaggregation of Revenue [Line Items]
Revenues									1,804	1,634	1,517
Private Banks | Investment processing fees - PaaS
Disaggregation of Revenue [Line Items]
Revenues									184,711	177,046	182,068
Private Banks | Investment processing fees - SaaS
Disaggregation of Revenue [Line Items]
Revenues									113,012	132,661	136,222
Private Banks | Professional services fees
Disaggregation of Revenue [Line Items]
Revenues									21,594	15,687	16,643
Private Banks | Account fees and other
Disaggregation of Revenue [Line Items]
Revenues									4,919	6,129	7,238
Investment Advisors
Disaggregation of Revenue [Line Items]
Revenues									407,564	403,778	399,089
Investment Advisors | United States
Disaggregation of Revenue [Line Items]
Revenues									407,564	403,778	399,089
Investment Advisors | United Kingdom
Disaggregation of Revenue [Line Items]
Revenues									0	0	0
Investment Advisors | Canada
Disaggregation of Revenue [Line Items]
Revenues									0	0	0
Investment Advisors | Ireland
Disaggregation of Revenue [Line Items]
Revenues									0	0	0
Investment Advisors | Other
Disaggregation of Revenue [Line Items]
Revenues									0	0	0
Investment Advisors | Investment management fees from pooled investment products
Disaggregation of Revenue [Line Items]
Revenues									271,627	282,253	288,030
Investment Advisors | Investment management fees from investment management agreements
Disaggregation of Revenue [Line Items]
Revenues									115,887	103,428	94,526
Investment Advisors | Investment operations fees
Disaggregation of Revenue [Line Items]
Revenues									0	0	0
Investment Advisors | Investment processing fees - PaaS
Disaggregation of Revenue [Line Items]
Revenues									0	0	0
Investment Advisors | Investment processing fees - SaaS
Disaggregation of Revenue [Line Items]
Revenues									0	0	0
Investment Advisors | Professional services fees
Disaggregation of Revenue [Line Items]
Revenues									0	0	0
Investment Advisors | Account fees and other
Disaggregation of Revenue [Line Items]
Revenues									20,050	18,097	16,533
Institutional Investors
Disaggregation of Revenue [Line Items]
Revenues									317,627	322,062	333,299
Institutional Investors | United States
Disaggregation of Revenue [Line Items]
Revenues									250,321	252,149	257,080
Institutional Investors | United Kingdom
Disaggregation of Revenue [Line Items]
Revenues									51,292	52,584	55,471
Institutional Investors | Canada
Disaggregation of Revenue [Line Items]
Revenues									5,610	6,889	8,526
Institutional Investors | Ireland
Disaggregation of Revenue [Line Items]
Revenues									9,850	9,588	10,419
Institutional Investors | Other
Disaggregation of Revenue [Line Items]
Revenues									554	852	1,803
Institutional Investors | Investment management fees from pooled investment products
Disaggregation of Revenue [Line Items]
Revenues									53,283	54,726	59,739
Institutional Investors | Investment management fees from investment management agreements
Disaggregation of Revenue [Line Items]
Revenues									262,709	266,323	271,600
Institutional Investors | Investment operations fees
Disaggregation of Revenue [Line Items]
Revenues									0	0	0
Institutional Investors | Investment processing fees - PaaS
Disaggregation of Revenue [Line Items]
Revenues									0	0	0
Institutional Investors | Investment processing fees - SaaS
Disaggregation of Revenue [Line Items]
Revenues									0	0	0
Institutional Investors | Professional services fees
Disaggregation of Revenue [Line Items]
Revenues									0	0	0
Institutional Investors | Account fees and other
Disaggregation of Revenue [Line Items]
Revenues									1,635	1,013	1,960
Investment Managers
Disaggregation of Revenue [Line Items]
Revenues									489,462	440,796	398,076
Investment Managers | United States
Disaggregation of Revenue [Line Items]
Revenues									456,547	411,984	376,593
Investment Managers | United Kingdom
Disaggregation of Revenue [Line Items]
Revenues									0	0	0
Investment Managers | Canada
Disaggregation of Revenue [Line Items]
Revenues									0	0	0
Investment Managers | Ireland
Disaggregation of Revenue [Line Items]
Revenues									32,915	28,812	21,483
Investment Managers | Other
Disaggregation of Revenue [Line Items]
Revenues									0	0	0
Investment Managers | Investment management fees from pooled investment products
Disaggregation of Revenue [Line Items]
Revenues									637	766	928
Investment Managers | Investment management fees from investment management agreements
Disaggregation of Revenue [Line Items]
Revenues									0	0	331
Investment Managers | Investment operations fees
Disaggregation of Revenue [Line Items]
Revenues									447,517	403,208	360,382
Investment Managers | Investment processing fees - PaaS
Disaggregation of Revenue [Line Items]
Revenues									0	0	2,519
Investment Managers | Investment processing fees - SaaS
Disaggregation of Revenue [Line Items]
Revenues									13,739	11,036	9,598
Investment Managers | Professional services fees
Disaggregation of Revenue [Line Items]
Revenues									5,753	5,209	7,280
Investment Managers | Account fees and other
Disaggregation of Revenue [Line Items]
Revenues									21,816	20,577	17,038
Investments In New Businesses
Disaggregation of Revenue [Line Items]
Revenues									14,012	12,973	10,606
Investments In New Businesses | United States
Disaggregation of Revenue [Line Items]
Revenues									14,012	12,973	10,606
Investments In New Businesses | United Kingdom
Disaggregation of Revenue [Line Items]
Revenues									0	0	0
Investments In New Businesses | Canada
Disaggregation of Revenue [Line Items]
Revenues									0	0	0
Investments In New Businesses | Ireland
Disaggregation of Revenue [Line Items]
Revenues									0	0	0
Investments In New Businesses | Other
Disaggregation of Revenue [Line Items]
Revenues									0	0	0
Investments In New Businesses | Investment management fees from pooled investment products
Disaggregation of Revenue [Line Items]
Revenues									1,411	1,293	1,017
Investments In New Businesses | Investment management fees from investment management agreements
Disaggregation of Revenue [Line Items]
Revenues									12,105	11,571	9,457
Investments In New Businesses | Investment operations fees
Disaggregation of Revenue [Line Items]
Revenues									0	0	0
Investments In New Businesses | Investment processing fees - PaaS
Disaggregation of Revenue [Line Items]
Revenues									0	0	0
Investments In New Businesses | Investment processing fees - SaaS
Disaggregation of Revenue [Line Items]
Revenues									0	0	0
Investments In New Businesses | Professional services fees
Disaggregation of Revenue [Line Items]
Revenues									0	0	0
Investments In New Businesses | Account fees and other
Disaggregation of Revenue [Line Items]
Revenues									$ 496	$ 109	$ 132

Leases (Narrative) (Details)

Leases (Narrative) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Leases [Abstract]
Operating leases expense	$ 9,711	$ 10,159

Leases (Schedule of Future Mini

Leases (Schedule of Future Minimum Lease Payments) (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Leases [Abstract]
2021	$ 9,183
2022	8,917
2023	8,922
2024	7,252
2025	5,184
Thereafter	5,988
Total future minimum lease payments	45,446
Less: Imputed interest	(2,809)
Total	$ 42,637	$ 47,606

Leases (Supplemental Consolidat

Leases (Supplemental Consolidated Balance Sheet Information Related to Operating Leases) (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Leases [Abstract]
Current portion of long-term operating lease liabilities	$ 8,579	$ 9,156
Long-term operating lease liabilities	34,058	38,450
Total operating lease liabilities	$ 42,637	$ 47,606
Weighted average remaining lease term	5 years 6 months	6 years 3 months 18 days
Weighted average discount rate	2.43%	2.61%

Leases (Supplemental Cash Flow

Leases (Supplemental Cash Flow Information Related to Operating Leases) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Leases [Abstract]
Cash paid for amounts included in the measurement of lease liabilities	$ 10,361	$ 10,932
Right-of-use assets obtained in exchange for lease obligations	$ 3,272	$ 6,372

Quarterly Financial Data (Una_3

Quarterly Financial Data (Unaudited) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Quarterly Financial Data [Abstract]
Revenues	$ 443,723	$ 424,927	$ 400,646	$ 414,762	$ 423,225	$ 416,254	$ 409,586	$ 400,820	$ 1,684,058	$ 1,649,885	$ 1,624,167
Income before income taxes	156,513	141,274	131,710	139,197	159,968	162,870	162,346	146,257	568,694	631,441	614,206
Net income	$ 125,882	$ 111,096	$ 101,066	$ 109,242	$ 128,737	$ 132,168	$ 126,540	$ 113,981	$ 447,286	$ 501,426	$ 505,868
Basic earnings per common share (in USD per share)	$ 0.87	$ 0.76	$ 0.69	$ 0.73	$ 0.86	$ 0.88	$ 0.83	$ 0.74	$ 3.05	$ 3.31	$ 3.23
Diluted earnings per common share (in USD per share)	$ 0.86	$ 0.75	$ 0.68	$ 0.72	$ 0.84	$ 0.86	$ 0.82	$ 0.73	$ 3	$ 3.24	$ 3.14
Effective income tax rate	19.60%	21.40%	23.30%	21.50%	19.50%	18.90%	22.10%	22.10%	21.30%	20.60%	17.60%

Schedule II - Valuation and Q_2

Schedule II - Valuation and Qualifying Accounts and Reserves (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Allowance for doubtful accounts
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Year	$ 1,201	$ 718	$ 695
Additions, Charged to Costs and Expenses	0	483	23
Additions, Charged to Other Accounts	0	0	0
(Deductions)	(101)	0	0
Balance at End of Year	1,100	1,201	718
Deferred income tax valuation allowance
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Year	70,731	72,316	68,469
Additions, Charged to Costs and Expenses	0	0	0
Additions, Charged to Other Accounts	0	0	3,847
(Deductions)	(1,955)	(1,585)	0
Balance at End of Year	$ 68,776	$ 70,731	$ 72,316

Uncategorized Items - seic-2020

Label	Element	Value
Accounting Standards Update [Extensible List]	us-gaap_AccountingStandardsUpdateExtensibleList	us-gaap:AccountingStandardsUpdate201409Member