3.26.1 html 397 353 1 false 92 0 false 9 false false R1.htm 0000001 - Document - Cover page Sheet http://www.seic.com/role/Coverpage Cover page Cover 1 false false R2.htm 9952151 - Statement - Consolidated Balance Sheets (unaudited) Sheet http://www.seic.com/role/ConsolidatedBalanceSheetsunaudited Consolidated Balance Sheets (unaudited) Statements 2 false false R3.htm 9952152 - Statement - Consolidated Balance Sheets (unaudited) (Parenthetical) Sheet http://www.seic.com/role/ConsolidatedBalanceSheetsunauditedParenthetical Consolidated Balance Sheets (unaudited) (Parenthetical) Statements 3 false false R4.htm 9952153 - Statement - Consolidated Statements of Operations (unaudited) Sheet http://www.seic.com/role/ConsolidatedStatementsofOperationsunaudited Consolidated Statements of Operations (unaudited) Statements 4 false false R5.htm 9952154 - Statement - Consolidated Statements of Comprehensive Income (unaudited) Sheet http://www.seic.com/role/ConsolidatedStatementsofComprehensiveIncomeunaudited Consolidated Statements of Comprehensive Income (unaudited) Statements 5 false false R6.htm 9952155 - Statement - Consolidated Statements of Comprehensive Income (unaudited) (Parenthetical) Sheet http://www.seic.com/role/ConsolidatedStatementsofComprehensiveIncomeunauditedParenthetical Consolidated Statements of Comprehensive Income (unaudited) (Parenthetical) Statements 6 false false R7.htm 9952156 - Statement - Consolidated Statements of Changes in Equity (unaudited) Sheet http://www.seic.com/role/ConsolidatedStatementsofChangesinEquityunaudited Consolidated Statements of Changes in Equity (unaudited) Statements 7 false false R8.htm 9952157 - Statement - Consolidated Statements of Cash Flows (unaudited) Sheet http://www.seic.com/role/ConsolidatedStatementsofCashFlowsunaudited Consolidated Statements of Cash Flows (unaudited) Statements 8 false false R9.htm 9952158 - Statement - Consolidated Statements of Cash Flows (unaudited) - Consolidated Variable Interest Entities Sheet http://www.seic.com/role/ConsolidatedStatementsofCashFlowsunauditedConsolidatedVariableInterestEntities Consolidated Statements of Cash Flows (unaudited) - Consolidated Variable Interest Entities Statements 9 false false R10.htm 9952159 - Disclosure - Summary of Significant Accounting Policies Sheet http://www.seic.com/role/SummaryofSignificantAccountingPolicies Summary of Significant Accounting Policies Notes 10 false false R11.htm 9952160 - Disclosure - Equity Method Investments Sheet http://www.seic.com/role/EquityMethodInvestments Equity Method Investments Notes 11 false false R12.htm 9952161 - Disclosure - Composition of Certain Financial Statement Captions Sheet http://www.seic.com/role/CompositionofCertainFinancialStatementCaptions Composition of Certain Financial Statement Captions Notes 12 false false R13.htm 9952162 - Disclosure - Fair Value Measurements Sheet http://www.seic.com/role/FairValueMeasurements Fair Value Measurements Notes 13 false false R14.htm 9952163 - Disclosure - Investments and Other Marketable Securities Sheet http://www.seic.com/role/InvestmentsandOtherMarketableSecurities Investments and Other Marketable Securities Notes 14 false false R15.htm 9952164 - Disclosure - Line of Credit Sheet http://www.seic.com/role/LineofCredit Line of Credit Notes 15 false false R16.htm 9952165 - Disclosure - Shareholders' Equity Sheet http://www.seic.com/role/ShareholdersEquity Shareholders' Equity Notes 16 false false R17.htm 9952166 - Disclosure - Accumulated Other Comprehensive Loss Sheet http://www.seic.com/role/AccumulatedOtherComprehensiveLoss Accumulated Other Comprehensive Loss Notes 17 false false R18.htm 9952167 - Disclosure - Business Segment Information Sheet http://www.seic.com/role/BusinessSegmentInformation Business Segment Information Notes 18 false false R19.htm 9952168 - Disclosure - Income Taxes Sheet http://www.seic.com/role/IncomeTaxes Income Taxes Notes 19 false false R20.htm 9952169 - Disclosure - Commitments and Contingencies Sheet http://www.seic.com/role/CommitmentsandContingencies Commitments and Contingencies Notes 20 false false R21.htm 9952170 - Disclosure - Business Acquisitions and Divestitures Sheet http://www.seic.com/role/BusinessAcquisitionsandDivestitures Business Acquisitions and Divestitures Notes 21 false false R22.htm 9952171 - Disclosure - Goodwill and Intangible Assets Sheet http://www.seic.com/role/GoodwillandIntangibleAssets Goodwill and Intangible Assets Notes 22 false false R23.htm 9952172 - Disclosure - Revenues from Contracts with Customers Sheet http://www.seic.com/role/RevenuesfromContractswithCustomers Revenues from Contracts with Customers Notes 23 false false R24.htm 9952173 - Disclosure - Consolidated Variable Interest Entities Sheet http://www.seic.com/role/ConsolidatedVariableInterestEntities Consolidated Variable Interest Entities Notes 24 false false R25.htm 995445 - Disclosure - Insider Trading Arrangements Sheet http://xbrl.sec.gov/ecd/role/InsiderTradingArrangements Insider Trading Arrangements Notes 25 false false R26.htm 9955511 - Disclosure - Summary of Significant Accounting Policies (Policies) Sheet http://www.seic.com/role/SummaryofSignificantAccountingPoliciesPolicies Summary of Significant Accounting Policies (Policies) Policies http://www.seic.com/role/SummaryofSignificantAccountingPolicies 26 false false R27.htm 9955512 - Disclosure - Summary of Significant Accounting Policies (Tables) Sheet http://www.seic.com/role/SummaryofSignificantAccountingPoliciesTables Summary of Significant Accounting Policies (Tables) Tables http://www.seic.com/role/SummaryofSignificantAccountingPolicies 27 false false R28.htm 9955513 - Disclosure - Equity Method Investments (Tables) Sheet http://www.seic.com/role/EquityMethodInvestmentsTables Equity Method Investments (Tables) Tables http://www.seic.com/role/EquityMethodInvestments 28 false false R29.htm 9955514 - Disclosure - Composition of Certain Financial Statement Captions (Tables) Sheet http://www.seic.com/role/CompositionofCertainFinancialStatementCaptionsTables Composition of Certain Financial Statement Captions (Tables) Tables http://www.seic.com/role/CompositionofCertainFinancialStatementCaptions 29 false false R30.htm 9955515 - Disclosure - Fair Value Measurements (Tables) Sheet http://www.seic.com/role/FairValueMeasurementsTables Fair Value Measurements (Tables) Tables http://www.seic.com/role/FairValueMeasurements 30 false false R31.htm 9955516 - Disclosure - Investments and Other Marketable Securities (Tables) Sheet http://www.seic.com/role/InvestmentsandOtherMarketableSecuritiesTables Investments and Other Marketable Securities (Tables) Tables http://www.seic.com/role/InvestmentsandOtherMarketableSecurities 31 false false R32.htm 9955517 - Disclosure - Shareholders' Equity (Tables) Sheet http://www.seic.com/role/ShareholdersEquityTables Shareholders' Equity (Tables) Tables http://www.seic.com/role/ShareholdersEquity 32 false false R33.htm 9955518 - Disclosure - Accumulated Other Comprehensive Loss (Tables) Sheet http://www.seic.com/role/AccumulatedOtherComprehensiveLossTables Accumulated Other Comprehensive Loss (Tables) Tables http://www.seic.com/role/AccumulatedOtherComprehensiveLoss 33 false false R34.htm 9955519 - Disclosure - Business Segment Information (Tables) Sheet http://www.seic.com/role/BusinessSegmentInformationTables Business Segment Information (Tables) Tables http://www.seic.com/role/BusinessSegmentInformation 34 false false R35.htm 9955520 - Disclosure - Income Taxes (Tables) Sheet http://www.seic.com/role/IncomeTaxesTables Income Taxes (Tables) Tables http://www.seic.com/role/IncomeTaxes 35 false false R36.htm 9955521 - Disclosure - Business Acquisitions and Divestitures (Tables) Sheet http://www.seic.com/role/BusinessAcquisitionsandDivestituresTables Business Acquisitions and Divestitures (Tables) Tables http://www.seic.com/role/BusinessAcquisitionsandDivestitures 36 false false R37.htm 9955522 - Disclosure - Goodwill and Intangible Assets (Tables) Sheet http://www.seic.com/role/GoodwillandIntangibleAssetsTables Goodwill and Intangible Assets (Tables) Tables http://www.seic.com/role/GoodwillandIntangibleAssets 37 false false R38.htm 9955523 - Disclosure - Revenues from Contracts with Customers (Tables) Sheet http://www.seic.com/role/RevenuesfromContractswithCustomersTables Revenues from Contracts with Customers (Tables) Tables http://www.seic.com/role/RevenuesfromContractswithCustomers 38 false false R39.htm 9955524 - Disclosure - Consolidated Variable Interest Entities (Tables) Sheet http://www.seic.com/role/ConsolidatedVariableInterestEntitiesTables Consolidated Variable Interest Entities (Tables) Tables http://www.seic.com/role/ConsolidatedVariableInterestEntities 39 false false R40.htm 9955525 - Disclosure - Summary of Significant Accounting Policies - Narrative (Details) Sheet http://www.seic.com/role/SummaryofSignificantAccountingPoliciesNarrativeDetails Summary of Significant Accounting Policies - Narrative (Details) Details 40 false false R41.htm 9955526 - Disclosure - Summary of Significant Accounting Policies - Schedule of Noncontrolling Interests (Details) Sheet http://www.seic.com/role/SummaryofSignificantAccountingPoliciesScheduleofNoncontrollingInterestsDetails Summary of Significant Accounting Policies - Schedule of Noncontrolling Interests (Details) Details 41 false false R42.htm 9955527 - Disclosure - Summary of Significant Accounting Policies - Earnings Per Share (Details) Sheet http://www.seic.com/role/SummaryofSignificantAccountingPoliciesEarningsPerShareDetails Summary of Significant Accounting Policies - Earnings Per Share (Details) Details 42 false false R43.htm 9955528 - Disclosure - Equity Method Investments - Schedule of Equity Method Investments (Details) Sheet http://www.seic.com/role/EquityMethodInvestmentsScheduleofEquityMethodInvestmentsDetails Equity Method Investments - Schedule of Equity Method Investments (Details) Details 43 false false R44.htm 9955529 - Disclosure - Equity Method Investments - Narrative (Details) Sheet http://www.seic.com/role/EquityMethodInvestmentsNarrativeDetails Equity Method Investments - Narrative (Details) Details 44 false false R45.htm 9955530 - Disclosure - Equity Method Investments - Condensed Statements of Operations of LSV (Details) Sheet http://www.seic.com/role/EquityMethodInvestmentsCondensedStatementsofOperationsofLSVDetails Equity Method Investments - Condensed Statements of Operations of LSV (Details) Details 45 false false R46.htm 9955531 - Disclosure - Composition of Certain Financial Statement Captions - Receivables (Details) Sheet http://www.seic.com/role/CompositionofCertainFinancialStatementCaptionsReceivablesDetails Composition of Certain Financial Statement Captions - Receivables (Details) Details 46 false false R47.htm 9955532 - Disclosure - Composition of Certain Financial Statement Captions - Property and Equipment (Details) Sheet http://www.seic.com/role/CompositionofCertainFinancialStatementCaptionsPropertyandEquipmentDetails Composition of Certain Financial Statement Captions - Property and Equipment (Details) Details 47 false false R48.htm 9955533 - Disclosure - Composition of Certain Financial Statement Captions - Narrative (Details) Sheet http://www.seic.com/role/CompositionofCertainFinancialStatementCaptionsNarrativeDetails Composition of Certain Financial Statement Captions - Narrative (Details) Details http://www.seic.com/role/CompositionofCertainFinancialStatementCaptionsTables 48 false false R49.htm 9955534 - Disclosure - Composition of Certain Financial Statement Captions - Accrued Liabilities (Details) Sheet http://www.seic.com/role/CompositionofCertainFinancialStatementCaptionsAccruedLiabilitiesDetails Composition of Certain Financial Statement Captions - Accrued Liabilities (Details) Details 49 false false R50.htm 9955535 - Disclosure - Fair Value Measurements (Details) Sheet http://www.seic.com/role/FairValueMeasurementsDetails Fair Value Measurements (Details) Details http://www.seic.com/role/FairValueMeasurementsTables 50 false false R51.htm 9955536 - Disclosure - Investments and Other Marketable Securities - Schedule of Equity Method Investments (Details) Sheet http://www.seic.com/role/InvestmentsandOtherMarketableSecuritiesScheduleofEquityMethodInvestmentsDetails Investments and Other Marketable Securities - Schedule of Equity Method Investments (Details) Details 51 false false R52.htm 9955537 - Disclosure - Investments and Other Marketable Securities - Available-for-Sale and Equity Securities (Details) Sheet http://www.seic.com/role/InvestmentsandOtherMarketableSecuritiesAvailableforSaleandEquitySecuritiesDetails Investments and Other Marketable Securities - Available-for-Sale and Equity Securities (Details) Details 52 false false R53.htm 9955538 - Disclosure - Investments and Other Marketable Securities - Schedule of Unrealized Holding Losses (Details) Sheet http://www.seic.com/role/InvestmentsandOtherMarketableSecuritiesScheduleofUnrealizedHoldingLossesDetails Investments and Other Marketable Securities - Schedule of Unrealized Holding Losses (Details) Details 53 false false R54.htm 9955539 - Disclosure - Investments and Other Marketable Securities - Schedule of Available-for-Sale Debt Securities by Maturity (Details) Sheet http://www.seic.com/role/InvestmentsandOtherMarketableSecuritiesScheduleofAvailableforSaleDebtSecuritiesbyMaturityDetails Investments and Other Marketable Securities - Schedule of Available-for-Sale Debt Securities by Maturity (Details) Details 54 false false R55.htm 9955540 - Disclosure - Investments and Other Marketable Securities - Narrative (Details) Sheet http://www.seic.com/role/InvestmentsandOtherMarketableSecuritiesNarrativeDetails Investments and Other Marketable Securities - Narrative (Details) Details 55 false false R56.htm 9955541 - Disclosure - Line of Credit (Details) Sheet http://www.seic.com/role/LineofCreditDetails Line of Credit (Details) Details http://www.seic.com/role/LineofCredit 56 false false R57.htm 9955542 - Disclosure - Shareholders' Equity - Stock-Based Compensation Expense (Details) Sheet http://www.seic.com/role/ShareholdersEquityStockBasedCompensationExpenseDetails Shareholders' Equity - Stock-Based Compensation Expense (Details) Details 57 false false R58.htm 9955543 - Disclosure - Shareholders' Equity - Narrative (Details) Sheet http://www.seic.com/role/ShareholdersEquityNarrativeDetails Shareholders' Equity - Narrative (Details) Details 58 false false R59.htm 9955544 - Disclosure - Accumulated Other Comprehensive Loss (Details) Sheet http://www.seic.com/role/AccumulatedOtherComprehensiveLossDetails Accumulated Other Comprehensive Loss (Details) Details http://www.seic.com/role/AccumulatedOtherComprehensiveLossTables 59 false false R60.htm 9955545 - Disclosure - Business Segment Information - Narrative (Details) Sheet http://www.seic.com/role/BusinessSegmentInformationNarrativeDetails Business Segment Information - Narrative (Details) Details 60 false false R61.htm 9955546 - Disclosure - Business Segment Information - Schedule of Financial Information About Business Segments (Details) Sheet http://www.seic.com/role/BusinessSegmentInformationScheduleofFinancialInformationAboutBusinessSegmentsDetails Business Segment Information - Schedule of Financial Information About Business Segments (Details) Details 61 false false R62.htm 9955547 - Disclosure - Business Segment Information - Reconciliation of Total Operating Profit (Details) Sheet http://www.seic.com/role/BusinessSegmentInformationReconciliationofTotalOperatingProfitDetails Business Segment Information - Reconciliation of Total Operating Profit (Details) Details 62 false false R63.htm 9955548 - Disclosure - Business Segment Information - Schedule Of Additional Information Pertaining To Business Segments (Details) Sheet http://www.seic.com/role/BusinessSegmentInformationScheduleOfAdditionalInformationPertainingToBusinessSegmentsDetails Business Segment Information - Schedule Of Additional Information Pertaining To Business Segments (Details) Details 63 false false R64.htm 9955549 - Disclosure - Income Taxes - Narrative (Details) Sheet http://www.seic.com/role/IncomeTaxesNarrativeDetails Income Taxes - Narrative (Details) Details 64 false false R65.htm 9955550 - Disclosure - Income Taxes - Interest and Penalties (Details) Sheet http://www.seic.com/role/IncomeTaxesInterestandPenaltiesDetails Income Taxes - Interest and Penalties (Details) Details 65 false false R66.htm 9955551 - Disclosure - Income Taxes - Effective Income Tax Rate Reconciliation (Details) Sheet http://www.seic.com/role/IncomeTaxesEffectiveIncomeTaxRateReconciliationDetails Income Taxes - Effective Income Tax Rate Reconciliation (Details) Details 66 false false R67.htm 9955552 - Disclosure - Commitments and Contingencies (Details) Sheet http://www.seic.com/role/CommitmentsandContingenciesDetails Commitments and Contingencies (Details) Details http://www.seic.com/role/CommitmentsandContingencies 67 false false R68.htm 9955553 - Disclosure - Business Acquisitions and Divestitures - Narrative (Details) Sheet http://www.seic.com/role/BusinessAcquisitionsandDivestituresNarrativeDetails Business Acquisitions and Divestitures - Narrative (Details) Details 68 false false R69.htm 9955554 - Disclosure - Business Acquisitions and Divestitures - Pro Forma Revenue and Net Income (Details) Sheet http://www.seic.com/role/BusinessAcquisitionsandDivestituresProFormaRevenueandNetIncomeDetails Business Acquisitions and Divestitures - Pro Forma Revenue and Net Income (Details) Details 69 false false R70.htm 9955555 - Disclosure - Business Acquisitions and Divestitures - Purchase Price Allocation (Details) Sheet http://www.seic.com/role/BusinessAcquisitionsandDivestituresPurchasePriceAllocationDetails Business Acquisitions and Divestitures - Purchase Price Allocation (Details) Details 70 false false R71.htm 9955556 - Disclosure - Business Acquisitions and Divestitures - Purchase Consideration (Details) Sheet http://www.seic.com/role/BusinessAcquisitionsandDivestituresPurchaseConsiderationDetails Business Acquisitions and Divestitures - Purchase Consideration (Details) Details 71 false false R72.htm 9955557 - Disclosure - Business Acquisitions and Divestitures - Fair Value of Intangible Assets (Details) Sheet http://www.seic.com/role/BusinessAcquisitionsandDivestituresFairValueofIntangibleAssetsDetails Business Acquisitions and Divestitures - Fair Value of Intangible Assets (Details) Details 72 false false R73.htm 9955558 - Disclosure - Goodwill and Intangible Assets - Schedule of Goodwill (Details) Sheet http://www.seic.com/role/GoodwillandIntangibleAssetsScheduleofGoodwillDetails Goodwill and Intangible Assets - Schedule of Goodwill (Details) Details 73 false false R74.htm 9955559 - Disclosure - Goodwill and Intangible Assets - Narrative (Details) Sheet http://www.seic.com/role/GoodwillandIntangibleAssetsNarrativeDetails Goodwill and Intangible Assets - Narrative (Details) Details 74 false false R75.htm 9955560 - Disclosure - Revenues from Contracts with Customers (Details) Sheet http://www.seic.com/role/RevenuesfromContractswithCustomersDetails Revenues from Contracts with Customers (Details) Details http://www.seic.com/role/RevenuesfromContractswithCustomersTables 75 false false R76.htm 9955561 - Disclosure - Consolidated Variable Interest Entities - Narrative (Details) Sheet http://www.seic.com/role/ConsolidatedVariableInterestEntitiesNarrativeDetails Consolidated Variable Interest Entities - Narrative (Details) Details 76 false false R77.htm 9955562 - Disclosure - Consolidated Variable Interest Entities - Schedule of Variable Interest Entities (Details) Sheet http://www.seic.com/role/ConsolidatedVariableInterestEntitiesScheduleofVariableInterestEntitiesDetails Consolidated Variable Interest Entities - Schedule of Variable Interest Entities (Details) Details 77 false false All Reports Book All Reports seic-20260331.htm seic-20260331.xsd seic-20260331_cal.xml seic-20260331_def.xml seic-20260331_lab.xml seic-20260331_pre.xml seic-20260331_g1.gif http://fasb.org/us-gaap/2025 http://xbrl.sec.gov/dei/2025 http://xbrl.sec.gov/ecd/2025 true true