Unrealized gains (losses) on investments Unrealized Gain (Loss) on Investments Summary of Significant Accounting Policies Significant Accounting Policies [Text Block] Intangible Assets, accumulated amortization Finite-Lived Intangible Assets, Accumulated Amortization Statistical Measurement [Domain] Statistical Measurement [Domain] Property and equipment, net Business Combination, Recognized Asset Acquired, Property, Plant, and Equipment Schedule of Available-for-Sale and Equity Securities Debt Securities, Available-for-Sale [Table Text Block] Award Timing Predetermined Award Timing Predetermined [Flag] Entity File Number Entity File Number Capital In Excess of Par Value Additional Paid-in Capital [Member] Number of majority interest businesses acquired Business Combination, Number of Majority Interest Businesses Acquired Business Combination, Number of Majority Interest Businesses Acquired Equity in earnings of unconsolidated affiliates Equity in earnings of unconsolidated affiliates Income (Loss) from Equity Method Investments Reclassification adjustment for gains realized in net income, net of income taxes of $147 and $9 Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI for Sale of Securities, Net of Tax Tabular List, Table Tabular List [Table Text Block] Fees earned, not billed Unbilled Contracts Receivable New Accounting Pronouncements New Accounting Pronouncements, Policy [Policy Text Block] Fair Value Measurements Fair Value Measurement and Measurement Inputs, Recurring and Nonrecurring [Text Block] Accounts payable Increase (Decrease) in Accounts Payable Pledged Status [Axis] Pledged Status [Axis] Secured Overnight Financing Rate (SOFR) Secured Overnight Financing Rate (SOFR) [Member] 2025 Credit Facility 2025 Credit Facility [Member] 2025 Credit Facility Promissory notes to sellers Business Combination, Consideration Transferred, Liabilities Incurred Goodwill [Line Items] Goodwill [Line Items] Available-for-sale debt securities, Gross Unrealized (Losses) Debt Securities, Available-for-Sale, Accumulated Gross Unrealized Loss, before Tax Trading Arrangements, by Individual Trading Arrangements, by Individual [Table] Federal Funds Rate Fed Funds Effective Rate Overnight Index Swap Rate [Member] Basic earnings per common share (in USD per share) Basic earnings per common share (in USD per share) Earnings Per Share, Basic Adjustment to Compensation: Adjustment to Compensation [Axis] Named Executive Officers, Footnote Named Executive Officers, Footnote [Text Block] Revenues from Contracts with Customers Revenue from Contract with Customer [Text Block] Net gain from consolidated variable interest entities Unrealized Gain (Loss) on Variable Interest Entity Investment Unrealized Gain (Loss) on Variable Interest Entity Investment Total other comprehensive (loss) income, net of tax Other comprehensive income (loss) Other Comprehensive Income (Loss), Net of Tax Schedule of Financial Information About Business Segments Schedule of Segment Reporting Information, by Segment [Table Text Block] Issuance of common stock under employee stock purchase plan (in shares) Stock Issued During Period, Shares, Employee Stock Purchase Plans Institutional Investors Institutional Investors [Member] Institutional Investors [Member] Asset management, administration and distribution fees Asset Management, Administration And Distribution Fees [Member] Asset Management, Administration And Distribution Fees [Member] Limited Partnership Funds Limited Partnership Funds [Member] Limited Partnership Funds Adjustment to Compensation, Amount Adjustment to Compensation Amount Significant Change in Unrecognized Tax Benefits is Reasonably Possible, Nature of Uncertainty [Domain] Significant Change in Unrecognized Tax Benefits is Reasonably Possible, Nature of Uncertainty [Domain] Employee Stock Option Share-Based Payment Arrangement, Option [Member] Corporate and government agency debt securities US Government Corporations and Agencies Securities [Member] Award Timing MNPI Disclosure Award Timing MNPI Disclosure [Text Block] Property and Equipment [Table] Property, Plant and Equipment [Table] Proceeds from fixed asset dispositions Proceeds from Sale of Productive Assets Cash and Cash Equivalents Cash and Cash Equivalents, Policy [Policy Text Block] Consolidated VIEs Variable Interest Entity, Primary Beneficiary [Member] Total SEI Shareholders' Equity Beginning balance Ending balance Equity, Attributable to Parent Other comprehensive loss before reclassifications OCI, before Reclassifications, Net of Tax, Attributable to Parent Other comprehensive (loss) income, net of tax: Other Comprehensive Income (Loss), Net of Tax [Abstract] Insider Trading Policies and Procedures [Line Items] Stock-based compensation Stock-based compensation expense Share-Based Payment Arrangement, Expense Schedule of Property and Equipment Property, Plant and Equipment [Table Text Block] Common stock, shares authorized (in shares) Common Stock, Shares Authorized Settlement and Lapse of Statute Settlement and Lapse of Statute [Member] Settlement and Lapse of Statute [Member] Goodwill and Intangible Assets Disclosure [Abstract] Goodwill and Intangible Assets Disclosure [Abstract] Current Assets: Assets, Current [Abstract] Total Liabilities, Redeemable Non-controlling Interests and Equity Liabilities and Equity Less: Net income attributable to non-controlling interests Temporary Equity, Net Income Securities sold short Security Sold Short, Fair Value Liabilities, Redeemable Non-controlling Interests and Equity Liabilities and Equity [Abstract] Call Option One Put Or Call Option One [Member] Put Or Call Option One Cover [Abstract] Cover [Abstract] Amounts reclassified from accumulated other comprehensive loss Reclassification from AOCI, Current Period, Net of Tax, Attributable to Parent Cash equivalents at fair value Cash and Cash Equivalents, Fair Value Disclosure Receivables Increase (Decrease) in Finance Receivables Business Acquisitions and Divestitures Disposal Groups, Including Discontinued Operations, Disclosure [Text Block] Maximum Maximum [Member] Weighted average exercise price per share (in USD per share) Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Exercisable, Weighted Average Exercise Price Stock-based compensation expense, net of tax Share-Based Payment Arrangement, Expense, after Tax Estimated useful life of the SEI Wealth Platform Finite-Lived Intangible Asset, Useful Life Equity Method Investment [Table] Equity Method Investment [Table] Less: Net income attributable to non-controlling interests Net Income (Loss) Attributable to Noncontrolling Interest Accounting Policies [Abstract] Accounting Policies [Abstract] Call option, term (in months) Option Contracts, Term Option Contracts, Term After 10 years Debt Securities, Available-for-Sale, Amortized Cost, Maturity, Allocated and Single Maturity Date, after Year 10 Income Tax Contingency [Line Items] Income Tax Contingency [Line Items] L S V Asset Management LSV Asset Management [Member] LSV Asset Management [Member] Non-PEO NEO Average Total Compensation Amount Non-PEO NEO Average Total Compensation Amount Schedule of Share-based Compensation Arrangements by Share-based Payment Award [Table] Schedule of Share-Based Compensation Arrangements by Share-Based Payment Award [Table] Adjustment to Non-PEO NEO Compensation Footnote Adjustment to Non-PEO NEO Compensation Footnote [Text Block] Pay vs Performance Disclosure [Line Items] Forgone Recovery due to Disqualification of Tax Benefits, Amount Forgone Recovery due to Disqualification of Tax Benefits, Amount Accrued sub-advisory, distribution and other asset management fees Accrued Sub-Advisory, Distribution And Other Asset Management Fees, Current Accrued Sub-Advisory, Distribution And Other Asset Management Fees, Current Liabilities of Consolidated Variable Interest Entities Liabilities [Abstract] Accrued employee compensation Accrued Salaries, Current Non-Rule 10b5-1 Arrangement Terminated Non-Rule 10b5-1 Arrangement Terminated [Flag] Income before income taxes Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest Entity Shell Company Entity Shell Company 2021 Credit Facility 2021 Credit Facility [Member] 2021 Credit Facility Acquired non-controlling interest Noncontrolling Interest, Increase from Business Combination Other Long-term Liabilities Other Liabilities, Noncurrent Recourse Status [Domain] Recourse Status [Domain] Schedule of Investments Investment [Table Text Block] Statement of Stockholders' Equity [Abstract] Statement of Stockholders' Equity [Abstract] Operating Segments Operating Segments [Member] Summary of Significant Accounting Policies [Table] Variable Interest Entity [Table] Statement of Cash Flows [Abstract] Statement of Cash Flows [Abstract] Company Selected Measure Amount Company Selected Measure Amount Less: Comprehensive income attributable to the non-controlling interests Comprehensive Income (Loss), Net of Tax, Attributable to Noncontrolling Interest Award Timing MNPI Considered Award Timing MNPI Considered [Flag] Line of Credit Facility [Table] Line of Credit Facility [Table] Net income Net Income (Loss), Including Portion Attributable to Noncontrolling Interest, Excluding Capital Distributions to Redeemable Noncontrolling Interest Net Income (Loss), Including Portion Attributable to Noncontrolling Interest, Excluding Capital Distributions to Redeemable Noncontrolling Interest Comprehensive income attributable to SEI Investments Company Comprehensive Income (Loss), Net of Tax, Attributable to Parent Option Indexed to Issuer's Equity, Type [Domain] Option Indexed to Issuer's Equity, Type [Domain] Name Measure Name Letter of Credit Letter of Credit [Member] Within one year Debt Securities, Available-for-Sale, Fair Value, Maturity, Allocated and Single Maturity Date, Year One Tax benefit from stock option exercises Effective Income Tax Rate Reconciliation, Tax Benefit From Stock Option Exercises, Percent Effective Income Tax Rate Reconciliation, Tax Benefit From Stock Option Exercises, Percent Line of Credit Facility [Abstract] Line of Credit Facility [Abstract] Current portion of long-term operating lease liabilities Operating Lease, Liability, Current Equity, Attributable to Noncontrolling Interest [Roll Forward] Equity, Attributable to Noncontrolling Interest [Roll Forward] Prepayments and maturities of marketable securities Proceeds from Maturities, Prepayments and Calls of Debt Securities, Available-for-Sale Deferred Income Taxes Deferred Income Tax Liabilities, Net Document Fiscal Period Focus Document Fiscal Period Focus Award Timing Method Award Timing Method [Text Block] Litigation Case [Domain] Litigation Case [Domain] Furniture and fixtures Furniture and Fixtures [Member] Award Type Award Type [Axis] Stratos Wealth Holdings Stratos Wealth Holdings [Member] Stratos Wealth Holdings Foreign Currency Translation Adjustments Accumulated Foreign Currency Adjustment Attributable to Parent [Member] Income Tax Contingency [Table] Income Tax Contingency [Table] SEI Investments Company Parent Company [Member] Long-term Debt Long-Term Debt Legal Entity [Axis] Legal Entity [Axis] Investment operations fees Investment Operations Fees [Member] Investment Operations Fees [Member] Business Combination, Pro Forma Information Business Combination, Pro Forma Information [Table Text Block] Assets of Consolidated Variable Interest Entities Total Assets Assets Equity Method Investee, Name [Domain] Investment, Name [Domain] Trading Symbol Trading Symbol Geographical [Domain] Geographical [Domain] Amount included in Current liabilities Liability for Uncertainty in Income Taxes, Current Issuance of common stock under share-based award plans (in shares) Shares Issued, Shares, Share-Based Payment Arrangement, after Forfeiture Entity Address, City or Town Entity Address, City or Town Target gross revenue percentage Business Combination, Revenue Clawback, Target Gross Revenue Percentage Business Combination, Revenue Clawback, Target Gross Revenue Percentage Cash flows from operating activities: Cash Provided by (Used in) Operating Activity, Including Discontinued Operation [Abstract] Other segment expenses Segment Reporting, Other Segment Item, Amount Investment Managers Investment Managers [Member] Investment Managers [Member] Estimated Useful Life (in years) Acquired Finite-Lived Intangible Assets, Weighted Average Useful Life Investment management fees from pooled investment products Investment Management Fees From Investment Products [Member] Investment Management Fees From Investment Products [Member] Effect of exchange rate changes on cash and cash equivalents Effect of Exchange Rate on Cash, Cash Equivalent, Restricted Cash, and Restricted Cash Equivalent, Continuing Operation Non-PEO NEO Average Compensation Actually Paid Amount Non-PEO NEO Average Compensation Actually Paid Amount Percentage ownership Subsidiary or Equity Method Investee, Cumulative Percentage Ownership after All Transactions Compensation Actually Paid vs. Other Measure Compensation Actually Paid vs. Other Measure [Text Block] Total purchase consideration Business Combination, Consideration Transferred Summary of Significant Accounting Policies [Line Items] Variable Interest Entity [Line Items] Entity Emerging Growth Company Entity Emerging Growth Company Variable Interest Entities Consolidation, Variable Interest Entity, Policy [Policy Text Block] Entity Common Stock, Shares Outstanding Entity Common Stock, Shares Outstanding Deferred Contract Costs Deferred contract costs Capitalized Contract Cost, Net Debt Securities, Available-for-sale [Line Items] Debt Securities, Available-for-Sale [Line Items] Total options outstanding (in shares) Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Outstanding, Number Trade receivables Billed Contracts Receivable Change in Fair Value as of Vesting Date of Prior Year Equity Awards Vested in Covered Year Change in Fair Value as of Vesting Date of Prior Year Equity Awards Vested in Covered Year [Member] Level 2 Fair Value, Inputs, Level 2 [Member] Equity method investments (See Note 2) Equity method investments Equity Method Investments Insider Trading Policies and Procedures Not Adopted Insider Trading Policies and Procedures Not Adopted [Text Block] Business Combination [Domain] Business Combination [Domain] SEI-Sponsored Open-Ended Money Market Mutual Funds Sei Sponsored Open Ended Money Market Mutual Funds [Member] SEI-Sponsored Open-Ended Money Market Mutual Funds [Member] Common stock, shares outstanding (in shares) Common Stock, Shares, Outstanding Asset Pledged as Collateral Asset Pledged as Collateral [Member] Provision for losses on receivables Accounts Receivable, Credit Loss Expense (Reversal) Net unrealized holding gains (losses), income tax (benefit) expense Accumulated Other Comprehensive Income (Loss), Debt Securities, Available For Sale Securities, Adjustment, Tax Accumulated Other Comprehensive Income (Loss), Debt Securities, Available For Sale Securities, Adjustment, Tax PEO PEO [Member] Purchased software Purchased Software [Member] Purchased Software [Member] Schedule of Disaggregation of Revenue Disaggregation of Revenue [Table Text Block] Schedule of Available-for-Sale Debt Securities by Maturity Investments Classified by Contractual Maturity Date [Table Text Block] Internal Revenue Service (IRS) Internal Revenue Service (IRS) [Member] Accrued income taxes Accrued Income Taxes, Current United States UNITED STATES Change in current assets and liabilities: Adjustment to Reconcile Net Income to Cash Provided by (Used in) Operating Activity, Increase (Decrease) in Operating Capital [Abstract] Dividends or Other Earnings Paid on Equity Awards not Otherwise Reflected in Total Compensation for Covered Year Dividends or Other Earnings Paid on Equity Awards not Otherwise Reflected in Total Compensation for Covered Year [Member] Retained Earnings Retained Earnings [Member] Pledged Status [Domain] Pledged Status [Domain] Summary of Significant Accounting Policies [Table] Summary of Significant Accounting Policies [Table] Summary of Significant Accounting Policies [Table] Schedule of Accrued Liabilities Schedule of Accrued Liabilities [Table Text Block] Entity Address, Postal Zip Code Entity Address, Postal Zip Code Restatement Determination Date Restatement Determination Date Income Statement [Abstract] Income Statement [Abstract] Cash and cash equivalents Cash, cash equivalents and cash and cash equivalents held at consolidated variable interest entities, beginning of period Cash, cash equivalents and cash and cash equivalents held at consolidated variable interest entities, end of period Cash, Cash Equivalent, Restricted Cash, and Restricted Cash Equivalent, Continuing Operation Income taxes Income Tax Expense (Benefit) Credit facility variable interest rate basis spread Debt Instrument, Basis Spread on Variable Rate Purchases of marketable securities Payments to Acquire Marketable Securities Other assets Other Assets Investment processing fees - PaaS Investment Processing Fees, PaaS [Member] Investment Processing Fees, PaaS [Member] Intangible Assets, net of accumulated amortization of $58,480 and $49,534 Intangible Assets, Net (Excluding Goodwill) Pension Adjustments Service Cost Pension Adjustments Service Cost [Member] Software royalties and other information processing costs Software Royalties And Other Information Processing Costs Costs for royalty fees paid to pricing vendors and software providers for systems used in the company's operations. These costs are either based upon the types of securities in client accounts or based upon other contractual terms for usage of the software. Product and Service [Domain] Product and Service [Domain] Fair Value Hierarchy and NAV [Axis] Fair Value Hierarchy and NAV [Axis] Property and equipment, gross Property, Plant and Equipment, Gross Gross receivables Receivables, Gross, Current Receivables, Gross, Current Net income Net income Net Income (Loss), Including Portion Attributable to Noncontrolling Interest Net unrealized holding gain (loss) AOCI, Debt Securities, Available-for-Sale, Adjustment, after Tax Restatement does not require Recovery Restatement Does Not Require Recovery [Text Block] Business Combination [Table] Business Combination [Table] Total financial liabilities measured at fair value Liabilities, Fair Value Disclosure Organization, Consolidation and Presentation of Financial Statements [Abstract] Due from broker for securities sold Due from Correspondent Brokers Other current assets Increase (Decrease) in Other Current Assets Notes Payable, Other Payables Notes Payable, Other Payables [Member] Schedule of Purchase Price Allocation Business Combination, Recognized Asset Acquired and Liability Assumed [Table Text Block] Compensation Actually Paid vs. Company Selected Measure Compensation Actually Paid vs. Company Selected Measure [Text Block] Acquisition of Stratos EMIs (See Note 12) Goodwill, Acquired During Period City Area Code City Area Code Award Timing, How MNPI Considered Award Timing, How MNPI Considered [Text Block] Other income Other Nonoperating Income All Trading Arrangements All Trading Arrangements [Member] Equity Awards Adjustments, Footnote Equity Awards Adjustments, Footnote [Text Block] Total Shareholder Return Vs Peer Group Total Shareholder Return Vs Peer Group [Text Block] Accrued liabilities Total accrued liabilities Accrued Liabilities, Current Commitments and Contingencies Disclosure [Abstract] Commitments and Contingencies Disclosure [Abstract] Corporate overhead expenses General and Administrative Expense Cash flows from investing activities: Cash Provided by (Used in) Investing Activity, Including Discontinued Operation [Abstract] Pay vs Performance Disclosure Pay vs Performance Disclosure [Table] Net cash provided by operating activities Cash Provided by (Used in) Operating Activity, Including Discontinued Operation Credit facility term of agreement Debt Instrument, Term Equity Method Investments and Joint Ventures [Abstract] Equity Method Investments and Joint Ventures [Abstract] Account fees and other Account Fees And Other [Member] Account Fees And Other [Member] Subsequent Event Subsequent Event [Member] Other current assets Business Combination, Recognized Asset Acquired, Other Asset, Current Equity Method Investment, Nonconsolidated Investee Equity Method Investment, Nonconsolidated Investee or Group of Investees [Member] Equity securities Equity Securities, FV-NI Schedule of Equity Method Investments [Line Items] Schedule of Equity Method Investments [Line Items] Goodwill Goodwill, beginning balance Goodwill, ending balance Goodwill Equity Valuation Assumption Difference, Footnote Equity Valuation Assumption Difference, Footnote [Text Block] Loss contingency, estimate of possible loss Loss Contingency, Estimate of Possible Loss PEO Total Compensation Amount PEO Total Compensation Amount Long-Term Debt, Type [Axis] Long-Term Debt, Type [Axis] Net (loss) gain from investments Net loss (gain) from investments Gain (Loss) on Investments Deposits Related to Acquisitions Deposits on Future Acquisitions Deposits on Future Acquisitions Taxes receivable Income Taxes Receivable Equity Components [Axis] Equity Components [Axis] Common Stock Buyback Common Stock Buyback [Member] Common Stock Buyback [Member] Property and Equipment [Line Items] Property, Plant and Equipment [Line Items] Redemption value remeasurement Redemption value remeasurement Noncontrolling Interest, Change in Redemption Value Non-Rule 10b5-1 Arrangement Adopted Non-Rule 10b5-1 Arrangement Adopted [Flag] Reclassification adjustment for (gains) losses realized in net income, tax expense (benefit) Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI for Sale of Securities, Tax Equipment Equipment [Member] Available-for-sale debt securities, Cost Amount Debt Securities, Available-for-Sale, Amortized Cost Capitalized software development costs Capitalized Computer Software, Additions Consolidated Variable Interest Entities Variable Interest Entity Disclosure [Text Block] Other Performance Measure, Amount Other Performance Measure, Amount Entity Address, State or Province Entity Address, State or Province Available-for-sale Securities Marketable Securities, Policy [Policy Text Block] Additional liability to be paid to taxing authority Income Tax Examination, Liability (Refund) Adjustment from Settlement with Taxing Authority Related Party [Domain] Related and Nonrelated Parties [Domain] Total Current Liabilities Liabilities, Current Individual: Individual [Axis] Fair Value of Financial Instruments Fair Value of Financial Instruments, Policy [Policy Text Block] Receivables from investment products Increase (Decrease) in Other Receivables Advance payment for acquisition Other Payments to Acquire Businesses Other current assets Other Assets, Current Capital in excess of par value Additional Paid in Capital, Common Stock EMI Entities EMI Entities [Member] EMI Entities Entity [Domain] Entity [Domain] Investments in affiliated funds Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures Net cash provided by (used in) investing activities Cash Provided by (Used in) Investing Activity, Including Discontinued Operation Amortization Amortization Aggregate Change in Present Value of Accumulated Benefit for All Pension Plans Reported in Summary Compensation Table Aggregate Change in Present Value of Accumulated Benefit for All Pension Plans Reported in Summary Compensation Table [Member] Non-controlling interest capital raised, net Proceeds from Noncontrolling Interests Document Fiscal Year Focus Document Fiscal Year Focus Basis of Presentation Basis of Accounting, Policy [Policy Text Block] Operating Lease Right-of-Use Assets Operating Lease, Right-of-Use Asset Forgone Recovery, Explanation of Impracticability Forgone Recovery, Explanation of Impracticability [Text Block] Effective income tax rate Effective Income Tax Rate Reconciliation, Percent Entity Interactive Data Current Entity Interactive Data Current Additions to capitalized software Payments for Software Equity Method Investment, Nonconsolidated Investee [Axis] Equity Method Investment, Nonconsolidated Investee [Axis] Rubicon Wealth Management Rubicon Wealth Management [Member] Rubicon Wealth Management Revenue Recognition Revenue from Contract with Customer [Policy Text Block] Aggregate intrinsic value of options exercisable Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Exercisable, Intrinsic Value Buildings Building [Member] Fees waived Nonconsolidated Legal Entity, Financial Support Amount Information processing and software servicing fees Information Processing And Software Servicing Fees [Member] Information Processing And Software Servicing Fees [Member] Business Segment Information Segment Reporting Disclosure [Text Block] Goodwill [Table] Goodwill [Table] Disaggregation of Revenue [Table] Disaggregation of Revenue [Table] Long-Lived Tangible Asset [Axis] Long-Lived Tangible Asset [Axis] Increase (Decrease) in Stockholders' Equity [Roll Forward] Increase (Decrease) in Stockholders' Equity [Roll Forward] Data processing and computer related Information Technology and Data Processing Ownership [Domain] Ownership [Domain] Accrued liabilities Business Combination, Recognized Liability Assumed, Other Liability, Noncurrent Compensation Actually Paid vs. Total Shareholder Return Compensation Actually Paid vs. Total Shareholder Return [Text Block] Contingent considerations Contingent considerations Business Combination, Contingent Consideration, Liability Accumulated Other Comprehensive Loss Comprehensive Income (Loss) Note [Text Block] Weighted Average Weighted Average [Member] Amortization expense Amortization of Intangible Assets Deferred Income Taxes Deferred Income Tax Assets, Net Company purchased, cost Stock Repurchased During Period, Value Schedule Of Accumulated Other Comprehensive Income (Loss), Net Of Tax Schedule of Accumulated Other Comprehensive Income (Loss) [Table Text Block] Stratos Mexico Stratos Mexico [Member] Stratos Mexico Other Assets, net Other Assets, Noncurrent Entity Central Index Key Entity Central Index Key PEO Name PEO Name Total revenue Revenues Prior Year End Fair Value of Equity Awards Granted in Any Prior Year that Fail to Meet Applicable Vesting Conditions During Covered Year Prior Year End Fair Value of Equity Awards Granted in Any Prior Year that Fail to Meet Applicable Vesting Conditions During Covered Year [Member] Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] Outstanding Aggregate Erroneous Compensation Amount Outstanding Aggregate Erroneous Compensation Amount Advances due from unconsolidated affiliate Increase (Decrease) Due from Affiliates Unrecognized tax benefits within the next twelve months Significant Change in Unrecognized Tax Benefits is Reasonably Possible, Amount of Unrecorded Benefit Arrangement Duration Trading Arrangement Duration Schedule of Segment Reporting Information, by Segment [Table] Schedule of Segment Reporting Information, by Segment [Table] Deferred revenue Contract with Customer, Liability, Current Scott Mason Scott Mason [Member] Scott Mason Segments [Axis] Segments [Axis] Investment processing fees - SaaS Investment Processing Fees, SaaS [Member] Investment Processing Fees, SaaS [Member] Total net assets acquired Business Combination, Recognized Asset Acquired to Liability Assumed, Excluding Noncontrolling Interest Business Combination, Recognized Asset Acquired to Liability Assumed, Excluding Noncontrolling Interest Exercise Price Award Exercise Price Entity Filer Category Entity Filer Category Limited Partner Limited Partner [Member] Local Phone Number Local Phone Number Additional 402(v) Disclosure Additional 402(v) Disclosure [Text Block] Capitalized contract cost, amount capitalized during period Capitalized Contract Cost, Amount Capitalized During Period Capitalized Contract Cost, Amount Capitalized During Period Increase from acquisition Temporary Equity, Increase from Business Acquisition Temporary Equity, Increase from Business Acquisition Statutory rate Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent Market value of Company's common stock (in USD per share) Share Price Other investing activities Payment for (Proceeds from) Other Investing Activity Subsequent Event Type [Axis] Subsequent Event Type [Axis] Purchase and retirement of common stock (in shares) Shares purchased and retired (in shares) Stock Repurchased and Retired During Period, Shares Cash and cash equivalents Business Combination, Recognized Asset Acquired, Cash and Cash Equivalent Summary of Significant Accounting Policies [Line Items] Summary of Significant Accounting Policies [Line Items] Summary of Significant Accounting Policies [Line Items] Assets Assets of Consolidated Variable Interest Entities Assets [Abstract] Credit Facility [Axis] Credit Facility [Axis] Underlying Security Market Price Change Underlying Security Market Price Change, Percent Debt Instrument [Axis] Debt Instrument [Axis] Business Combination [Line Items] Business Combination [Line Items] Credit Facility [Domain] Credit Facility [Domain] Shareholders' Equity: Equity, Attributable to Parent [Abstract] Vesting Date Fair Value of Equity Awards Granted and Vested in Covered Year Vesting Date Fair Value of Equity Awards Granted and Vested in Covered Year [Member] Entity Address, Address Line One Entity Address, Address Line One Accumulated Other Comprehensive Loss AOCI Attributable to Parent [Member] Debt interest rate Debt Instrument, Interest Rate, Stated Percentage Equity Method Investee, Name [Axis] Investment, Name [Axis] Receivables, allowance for doubtful accounts Less: Allowance for doubtful accounts Accounts Receivable, Allowance for Credit Loss, Current Long-term Operating Lease Liabilities Operating Lease, Liability, Noncurrent Operations & services Financial Operations And Services Financial Operations And Services Redeemable Non-controlling Interests Beginning balance Ending balance Redeemable Noncontrolling Interest, Equity, Carrying Amount Business Combination, Asset Acquisition, Transaction between Entities under Common Control, and Joint Venture Formation [Abstract] Ownership [Axis] Ownership [Axis] Investments in limited partnership funds Other Long-Term Investments Certain Legacy Stratos Equity Holders Certain Legacy Stratos Equity Holders [Member] Certain Legacy Stratos Equity Holders Fair Value as of Grant Date Award Grant Date Fair Value Entity Registrant Name Entity Registrant Name Change in other assets Increase (Decrease) in Other Noncurrent Assets Stock Price or TSR Estimation Method Stock Price or TSR Estimation Method [Text Block] Amortization expense related to the SEI Wealth Platform Capitalized Computer Software, Amortization Total adjustments Adjustment to Reconcile Net Income to Cash Provided by (Used in) Operating Activity Depreciation Depreciation, Nonproduction Application of previously funded acquisition deposits toward purchase consideration Application of Previously Funded Acquisition Deposits Toward Purchase Consideration Application of Previously Funded Acquisition Deposits Toward Purchase Consideration Gross liability for unrecognized tax benefits, exclusive of interest and penalties Gross Liability For Unrecognized Tax Benefits Exclusive Of Interest And Penalties Gross Liability For Unrecognized Tax Benefits Exclusive Of Interest And Penalties Number of quarterly installments Number Of Quarterly Installments Number Of Quarterly Installments Total expenses Costs and Expenses Compensation, benefits and other personnel Compensation, Benefits And Other Personnel The aggregate amount of expenditures for salaries, wages, incentive compensation, and other employee benefits such as postretirement benefit expense. Excludes stock-based compensation expense. Unrecognized compensation cost Share-Based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Amount Net gain from consolidated variable interest entities Net gain from investments Gain (Loss) on Variable Interest Entity Investment Gain (Loss) on Variable Interest Entity Investment Document Quarterly Report Document Quarterly Report Total financial assets measured at fair value Assets, Fair Value Disclosure Schedule of Additional Information Pertaining to Business Segments Segment, Reconciliation of Other Items from Segments to Consolidated [Table Text Block] Changed Peer Group, Footnote Changed Peer Group, Footnote [Text Block] Adjustment To PEO Compensation, Footnote Adjustment To PEO Compensation, Footnote [Text Block] Related Party [Axis] Related and Nonrelated Parties [Axis] Investments Investments Investments Title Trading Arrangement, Individual Title Peer Group Total Shareholder Return Amount Peer Group Total Shareholder Return Amount Restatement Determination Date: Restatement Determination Date [Axis] Cash in deposit account Payments to Acquire Businesses, Gross Number of call options Number Of Option Contracts Number Of Option Contracts Non-PEO NEO Non-PEO NEO [Member] Letters of credit outstanding amount Letters of Credit Outstanding, Amount Accumulated Other Comprehensive Income (Loss) [Table] Accumulated Other Comprehensive Income (Loss) [Table] Capital contributions from non-controlling interests, net Noncontrolling Interest, Increase from Subsidiary Equity Issuance Issuance of common stock under employee stock purchase plan Stock Issued During Period, Value, Employee Stock Purchase Plan Accumulated Other Comprehensive Income (Loss) [Line Items] Accumulated Other Comprehensive Income (Loss) [Line Items] Available-for-sale debt securities, Gross Unrealized Gains Debt Securities, Available-for-Sale, Accumulated Gross Unrealized Gain, before Tax Land Land [Member] Name Trading Arrangement, Individual Name All Award Types Award Type [Domain] Non-controlling interests Equity, Attributable to Noncontrolling Interest Equity Awards Adjustments Equity Awards Adjustments [Member] Leasehold improvements Leasehold Improvements [Member] Other Other Noncash Income (Expense) Pension Benefits Adjustments, Footnote Pension Benefits Adjustments, Footnote [Text Block] Lease liabilities Business Combination, Recognized Liability Assumed, Lease Obligation Disaggregation of Revenue [Line Items] Disaggregation of Revenue [Line Items] Investments In New Businesses Investments In New Businesses [Member] Investments In New Businesses [Member] Canada CANADA Compensation Amount Outstanding Recovery Compensation Amount Strategic initiatives & new business development Business Development Debt Instrument, Name [Domain] Debt Instrument, Name [Domain] Statement of Comprehensive Income [Abstract] Statement of Comprehensive Income [Abstract] Investment Managers Platform Investment Managers Platform [Member] Investment Managers Platform Recovery of Erroneously Awarded Compensation Disclosure [Line Items] Fair value of previously held equity method investments Business Combination, Consideration Transferred, Equity Interest Share Repurchase Program [Axis] Share Repurchase Program [Axis] Schedule of Investments [Line Items] Schedule of Investments [Line Items] MNPI Disclosure Timed for Compensation Value MNPI Disclosure Timed for Compensation Value [Flag] After one year through five years Debt Securities, Available-for-Sale, Amortized Cost, Maturity, Allocated and Single Maturity Date, after Year One Through Five Name Awards Close in Time to MNPI Disclosures, Individual Name Foreign tax expense and tax rate differential Effective Income Tax Rate Reconciliation, Foreign Income Tax Rate Differential, Percent Change from investment security transactions Increase (Decrease) From Investment Security Transactions, Net Increase (Decrease) From Investment Security Transactions, Net Contingent consideration fair value adjustments Business Combination, Contingent Consideration, Change in Contingent Consideration, Liability, Increase (Decrease) Aggregate Erroneous Compensation Not Yet Determined Aggregate Erroneous Compensation Not Yet Determined [Text Block] Revenues: Revenues [Abstract] Investments measured at NAV Alternative Investment After 5 years through 10 years Debt Securities, Available-for-Sale, Amortized Cost, Maturity, Allocated and Single Maturity Date, after Year 5 Through 10 Stock-based compensation APIC, Share-Based Payment Arrangement, Increase for Cost Recognition Unrealized (losses) gains during period, tax benefit (expense) OCI, Debt Securities, Available-for-Sale, Unrealized Holding Gain (Loss), before Adjustment, Tax Accumulated other comprehensive loss, net Accumulated Other Comprehensive Income (Loss), Net of Tax Sales, marketing & client service Selling and Marketing Expense Financial Instruments [Domain] Financial Instruments [Domain] Litigation Case [Axis] Litigation Case [Axis] Non-controlling interest & other, net Noncontrolling Interest And Other, Net Noncontrolling Interest And Other, Net Segments [Domain] Segments [Domain] Credit facility remaining borrowing capacity Line of Credit Facility, Remaining Borrowing Capacity Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract] Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract] Investments and Other Marketable Securities Investments in Debt and Marketable Equity Securities (and Certain Trading Assets) Disclosure [Text Block] Aggregate Pension Adjustments Service Cost Aggregate Pension Adjustments Service Cost [Member] Fair Value Hierarchy and NAV [Domain] Fair Value Hierarchy and NAV [Domain] Consolidated Entity, Excluding Consolidated VIE Consolidated Entity, Excluding Consolidated VIE [Member] Finite-Lived Intangible Assets by Major Class [Axis] Finite-Lived Intangible Assets by Major Class [Axis] Minimum Minimum [Member] Equilus Capital Equilus Capital [Member] Equilus Capital Income Tax 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Awarded Compensation Recovery [Table] Receivables, net of allowance for doubtful accounts of $1,759 and $1,916 Receivables, net Accounts Receivable, after Allowance for Credit Loss, Current Title of 12(b) Security Title of 12(b) Security Due to broker for securities purchased Due to Correspondent Brokers Non-cash investing activities: Cash Flow, Noncash Investing and Financing Activities Disclosure [Abstract] After 5 years through 10 years Debt Securities, Available-for-Sale, Fair Value, Maturity, Allocated and Single Maturity Date, after Year 5 Through 10 Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward] AOCI Attributable to Parent, Net of Tax [Roll Forward] Investments in limited partnership funds Investments In Limited Partnership Funds [Member] Investments In Limited Partnership Funds Amortization of deferred contract costs Capitalized Contract Cost, Amortization Debt interest rate accrual term, number of preceding fiscal quarters Debt Instrument, Interest 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Management Costs Sub-advisory fees for mutual funds. Sub-advisory fees that the fund's adviser pays for out of the management fee, which it receives from the fund. Also includes distribution fees paid to brokers and other related investment management costs associated with the company's other types of investment products. Accrued dividend payable Dividends Payable, Current Payment of dividends Payments of Dividends Facilities, supplies and other costs Occupancy, Net Amount awarded to other party Litigation Settlement, Amount Awarded to Other Party Schedule of Goodwill Schedule of Goodwill [Table Text Block] Interest expense Interest Expense, Nonoperating Trading Arrangement: Trading Arrangement [Axis] Call Option Three Put Or Call Option Three [Member] Put Or Call Option Three Total Shareholder Return Amount Total Shareholder Return Amount Loss Contingencies [Line Items] Loss Contingencies [Line Items] Foreign currency translation adjustments Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Adjustment, Net of Tax Insider Trading Arrangements [Line Items] Corporate overhead Segment Reporting, Reconciling Item, Corporate Nonsegment [Member] Security Exchange Name Security Exchange Name Equity securities Equity Securities [Member] Interest and dividend income Investment Income, Interest and Dividend Liabilities of Consolidated Variable Interest Entities Total Liabilities Liabilities Capitalized Software, net of accumulated amortization of $678,968 and $669,896 Net book value of capitalized software Capitalized Computer Software, Net Credit facility maximum borrowing capacity Line of Credit Facility, Maximum Borrowing Capacity Business Combination, Recognized Asset Acquired to Liability Assumed, Excess (Less), and Goodwill [Abstract] Business Combination, Recognized Asset Acquired to Liability Assumed, Excess (Less), and Goodwill [Abstract] Pension Adjustments Prior Service Cost Pension Adjustments Prior Service Cost [Member] Material Terms of Trading Arrangement Material Terms of Trading Arrangement [Text Block] Non-controlling interest Non-controlling interest Business Combination, Recognized Liability Assumed, Contingent Liability Issuance of common stock under share-based award plans Shares Granted, Value, Share-Based Payment Arrangement, after Forfeiture Statement [Line Items] Statement [Line Items] Operating lease right-of-use asset Business Combination, Recognized Asset Acquired, Operating Lease Right-of-use Asset Business Combination, Recognized Asset Acquired, Operating Lease Right-of-use Asset Consolidation Items [Axis] Consolidation Items [Axis] Variable Rate [Axis] Variable Rate [Axis] Rule 10b5-1 Arrangement Adopted Rule 10b5-1 Arrangement Adopted [Flag] Cash and cash equivalents Cash and cash equivalents invested in SEI-sponsored money market funds Cash and Cash Equivalent Deferred income tax benefit Increase (Decrease) in Deferred Income Taxes Common Stock Common Stock [Member] Available-for-sale securities Available for sale debt securities Available for sale debt securities, Fair Value Available for sale debt securities, Fair Value Debt Securities, Available-for-Sale Entity Incorporation, State or Country Code Entity Incorporation, State or Country Code Non-NEOs Non-NEOs [Member] Net change in cash and cash equivalents and cash and cash equivalents held at consolidated variable interest entities Cash, Cash Equivalent, Restricted Cash, and Restricted Cash Equivalent, Period Increase (Decrease), Including Exchange Rate Effect and Discontinued Operation Accrued consulting, outsourcing and professional fees Accrued Professional Fees, Current Dilutive effect of stock awards (in shares) Weighted Average Number of Shares Outstanding, Diluted, Adjustment Schedule of Interest and Penalties Summary of Income Tax Contingencies [Table Text Block] Items Included in Consolidated Statement of Financial Condition [Abstract] Items Included in Consolidated Statement of Financial Condition [Abstract]