XML 60 R43.htm IDEA: XBRL DOCUMENT
v3.10.0.1

Summary of Significant Accounting Policies (Narrative) (Details) - USD ($) $ / shares in Units, shares in Thousands | 3 Months Ended | 12 Months Ended |  |
--- | --- | --- | --- | ---
Dec. 31, 2018 | Sep. 30, 2018 | Jun. 30, 2018 | Mar. 31, 2018 | Dec. 31, 2017 | Sep. 30, 2017 | Jun. 30, 2017 | Mar. 31, 2017 | Dec. 31, 2018 | Dec. 31, 2017 | Dec. 31, 2016 | Jan. 01, 2018 | Dec. 31, 2015
Summary of Significant Accounting Policies [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |
Expense related to soft dollar arrangement |  |  |  |  |  |  |  |  | $ 16,680,000 | $ 14,623,000 | $ 18,409,000 |  |
Cash and cash equivalents | $ 754,525,000 |  |  |  | $ 744,247,000 |  |  |  | 754,525,000 | 744,247,000 |  |  |
Restricted cash | 3,514,000 |  |  |  | 3,505,000 |  |  |  | 3,514,000 | 3,505,000 |  |  |
Impairment charges related to marketable securities |  |  |  |  |  |  |  |  | 0 | 0 | 0 |  |
Net book value of capitalized software | $ 309,500,000 |  |  |  | $ 310,405,000 |  |  |  | 309,500,000 | 310,405,000 |  |  |
Increase in net income from change in estimate |  |  |  |  |  |  |  |  | $ 505,868,000 | $ 404,389,000 | $ 333,817,000 |  |
Increase in diluted earnings per share from change in estimate | $ 0.73 | $ 0.80 | $ 0.75 | $ 0.86 | $ 0.75 | $ 0.63 | $ 0.57 | $ 0.55 | $ 3.14 | $ 2.49 | $ 2.03 |  |
Capitalized software development costs |  |  |  |  |  |  |  |  | $ 44,221,000 | $ 61,043,000 | $ 50,392,000 |  |
Impairment charges related to capitalized software development costs |  |  |  |  |  |  |  |  | 0 | 0 | $ 0 |  |
Goodwill and intangible assets impairment |  |  |  |  |  |  |  |  | $ 0 | $ 0 |  |  |
Anti-dilutive employee stock options |  |  |  |  |  |  |  |  | 6,224 | 5,196 | 10,632 |  |
Anti-dilutive employee stock options, average exercise price per share |  |  |  |  |  |  |  |  | $ 53.60 | $ 45.49 | $ 35.02 |  |
SEI Wealth Platform |  |  |  |  |  |  |  |  |  |  |  |  |
Summary of Significant Accounting Policies [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |
Net book value of capitalized software | $ 288,666,000 |  |  |  |  |  |  |  | $ 288,666,000 |  |  |  |
Capitalized software development costs in progress | 42,238,000 |  |  |  |  |  |  |  | 42,238,000 |  |  |  |
Capitalized software development costs |  |  |  |  |  |  |  |  | 43,376,000 | $ 51,353,000 | $ 39,785,000 |  |
Amortization expense related to the SEI Wealth Platform |  |  |  |  |  |  |  |  | 39,917,000 | 46,505,000 | 45,047,000 |  |
Application for the Investment Managers segment |  |  |  |  |  |  |  |  |  |  |  |  |
Summary of Significant Accounting Policies [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |
Net book value of capitalized software | 20,834,000 |  |  |  |  |  |  |  | 20,834,000 |  |  |  |
Capitalized software development costs |  |  |  |  |  |  |  |  | $ 845,000 | 9,690,000 | 10,607,000 |  |
Estimated useful life of the SEI Wealth Platform |  |  |  |  |  |  |  |  | 5 years |  |  |  |
Amortization expense related to the SEI Wealth Platform |  |  |  |  |  |  |  |  | $ 5,209,000 |  |  |  |
SEI Sponsored Open Ended Money Market Mutual Funds |  |  |  |  |  |  |  |  |  |  |  |  |
Summary of Significant Accounting Policies [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |
Cash and cash equivalents | 315,840,000 |  |  |  | $ 401,292,000 |  |  |  | 315,840,000 | 401,292,000 |  |  |
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 | $ 514,000 |  |  |  | 505,000 |  |  |  | $ 514,000 | 505,000 |  |  |
Minimum |  |  |  |  |  |  |  |  |  |  |  |  |
Summary of Significant Accounting Policies [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |
Contract acquisition costs, amortization period | 6 years |  |  |  |  |  |  |  | 6 years |  |  |  |
Maximum |  |  |  |  |  |  |  |  |  |  |  |  |
Summary of Significant Accounting Policies [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |
Ownership interest in unconsolidated affiliate | 50.00% |  |  |  |  |  |  |  | 50.00% |  |  |  |
Contract acquisition costs, amortization period | 15 years |  |  |  |  |  |  |  | 15 years |  |  |  |
Weighted Average | SEI Wealth Platform |  |  |  |  |  |  |  |  |  |  |  |  |
Summary of Significant Accounting Policies [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |
Estimated useful life of the SEI Wealth Platform |  |  |  |  |  |  |  |  | 8 years 6 months |  |  |  |
Building and Building Improvements | Minimum |  |  |  |  |  |  |  |  |  |  |  |  |
Summary of Significant Accounting Policies [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |
Estimated useful life of property and equipment |  |  |  |  |  |  |  |  | 25 years |  |  |  |
Building and Building Improvements | Maximum |  |  |  |  |  |  |  |  |  |  |  |  |
Summary of Significant Accounting Policies [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |
Estimated useful life of property and equipment |  |  |  |  |  |  |  |  | 39 years |  |  |  |
Computer Equipment | Minimum |  |  |  |  |  |  |  |  |  |  |  |  |
Summary of Significant Accounting Policies [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |
Estimated useful life of property and equipment |  |  |  |  |  |  |  |  | 3 years |  |  |  |
Computer Equipment | Maximum |  |  |  |  |  |  |  |  |  |  |  |  |
Summary of Significant Accounting Policies [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |
Estimated useful life of property and equipment |  |  |  |  |  |  |  |  | 5 years |  |  |  |
Furniture and fixtures | Minimum |  |  |  |  |  |  |  |  |  |  |  |  |
Summary of Significant Accounting Policies [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |
Estimated useful life of property and equipment |  |  |  |  |  |  |  |  | 3 years |  |  |  |
Furniture and fixtures | Maximum |  |  |  |  |  |  |  |  |  |  |  |  |
Summary of Significant Accounting Policies [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |
Estimated useful life of property and equipment |  |  |  |  |  |  |  |  | 5 years |  |  |  |
Equity Method Investee | Minimum |  |  |  |  |  |  |  |  |  |  |  |  |
Summary of Significant Accounting Policies [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |
Ownership interest in unconsolidated affiliate | 20.00% |  |  |  |  |  |  |  | 20.00% |  |  |  |
Equity Method Investee | Maximum |  |  |  |  |  |  |  |  |  |  |  |  |
Summary of Significant Accounting Policies [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |
Ownership interest in unconsolidated affiliate | 50.00% |  |  |  |  |  |  |  | 50.00% |  |  |  |
Remaining Useful Life of SEI Wealth Platform | SEI Wealth Platform |  |  |  |  |  |  |  |  |  |  |  |  |
Summary of Significant Accounting Policies [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |
Decrease in amortization expense from change in estimate |  |  |  |  |  |  |  |  |  | 4,347,000 |  |  |
Increase in net income from change in estimate |  |  |  |  |  |  |  |  |  | $ 3,156,000 |  |  |
Increase in diluted earnings per share from change in estimate |  |  |  |  |  |  |  |  |  | $ 0.02 |  |  |
Retained Earnings |  |  |  |  |  |  |  |  |  |  |  |  |
Summary of Significant Accounting Policies [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |
Increase in net income from change in estimate |  |  |  |  |  |  |  |  | $ 505,868,000 | $ 404,389,000 | 333,817,000 |  |
Accounting Standards Update 2014-09 | Retained Earnings |  |  |  |  |  |  |  |  |  |  |  |  |
Summary of Significant Accounting Policies [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |
Cumulative effect upon adoption of ASUs |  |  |  |  | $ 14,402,000 |  |  |  |  | 14,402,000 | 0 | $ 14,402,000 | $ 0
Cumulative effect adjustment, before tax |  |  |  |  |  |  |  |  |  |  |  | $ 18,641,000 |
SEI Sponsored Open Ended Money Market Mutual Funds |  |  |  |  |  |  |  |  |  |  |  |  |
Summary of Significant Accounting Policies [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |
Fees waived according to expense limitation agreements |  |  |  |  |  |  |  |  | $ 26,229,000 | $ 27,434,000 | $ 41,227,000 |  |

X
- Definition Capitalized software development costs in progress associated with future releases. + References No definition available. + Details
Name: | seic_CapitalizedSoftwareDevelopmentCostsInProgress
Namespace Prefix: | seic_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Cumulative Effect Of New Accounting Principle In Period Of Adoption, Before Tax + References No definition available. + Details
Name: | seic_CumulativeEffectOfNewAccountingPrincipleInPeriodOfAdoptionBeforeTax
Namespace Prefix: | seic_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Expense Related To Soft Dollar Arrangement + References No definition available. + Details
Name: | seic_ExpenseRelatedToSoftDollarArrangement
Namespace Prefix: | seic_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Summary of Significant Accounting Policies [Line Items] + References No definition available. + Details
Name: | seic_SummaryofSignificantAccountingPoliciesLineItems
Namespace Prefix: | seic_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Securities (including those issuable pursuant to contingent stock agreements) that could potentially dilute basic earnings per share (EPS) or earnings per unit (EPU) in the future that were not included in the computation of diluted EPS or EPU because to do so would increase EPS or EPU amounts or decrease loss per share or unit amounts for the period presented. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 260 -SubTopic 10 -Section 50 -Paragraph 1 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=6371337&loc=d3e3550-109257 + Details
Name: | us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount
Namespace Prefix: | us-gaap_
Data Type: | xbrli:sharesItemType
Balance Type: | na
Period Type: | duration

X
- Definition Securities (including those issuable pursuant to contingent stock agreements) that could potentially dilute basic net Income or Loss per outstanding limited partnership unit in the future and that were not included in the computation of diluted net income per limited partnership unit, because to do so would increase net income per unit amounts or decrease loss per unit amounts for the period presented. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 260 -SubTopic 10 -Section 50 -Paragraph 1 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=6371337&loc=d3e3550-109257 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 260 -SubTopic 10 -Section 45 -Paragraph 18 -URI http://asc.fasb.org/extlink&oid=109260490&loc=d3e1536-109256 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 260 -SubTopic 10 -Section 45 -Paragraph 17 -URI http://asc.fasb.org/extlink&oid=109260490&loc=d3e1533-109256 + Details
Name: | us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfNetIncomePerOutstandingUnitAmount
Namespace Prefix: | us-gaap_
Data Type: | num:perShareItemType
Balance Type: | na
Period Type: | duration

X
- Definition Additions made to capitalized computer software costs during the period. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 350 -SubTopic 30 -Section 50 -Paragraph 1 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=66006027&loc=d3e16265-109275 + Details
Name: | us-gaap_CapitalizedComputerSoftwareAdditions
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Amount of expense for amortization of capitalized computer software costs. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 985 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (b)(1) -URI http://asc.fasb.org/extlink&oid=6501960&loc=d3e128462-111756 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 985 -SubTopic 20 -Section 50 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=6501960&loc=d3e128487-111756 + Details
Name: | us-gaap_CapitalizedComputerSoftwareAmortization1
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Amount of impairment loss from capitalized computer software costs. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 985 -SubTopic 20 -Section 50 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=6501960&loc=d3e128487-111756 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 985 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (b)(2) -URI http://asc.fasb.org/extlink&oid=6501960&loc=d3e128462-111756 + Details
Name: | us-gaap_CapitalizedComputerSoftwareImpairments1
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition The carrying amount of capitalized computer software costs net of accumulated amortization as of the balance sheet date. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 985 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=6501960&loc=d3e128462-111756 + Details
Name: | us-gaap_CapitalizedComputerSoftwareNet
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amount of increase (decrease) in capitalized computer software costs. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 985 -SubTopic 20 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6501960&loc=d3e128462-111756 + Details
Name: | us-gaap_CapitalizedComputerSoftwarePeriodIncreaseDecrease
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | na
Period Type: | duration

X
- Definition Amortization period of cost capitalized in obtaining or fulfilling contract with customer, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 340 -SubTopic 40 -Section 50 -Paragraph 2 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=68051541&loc=SL49131251-203054 + Details
Name: | us-gaap_CapitalizedContractCostAmortizationPeriod
Namespace Prefix: | us-gaap_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | instant

X
- Definition Amount of currency on hand as well as demand deposits with banks or financial institutions. Includes other kinds of accounts that have the general characteristics of demand deposits. Also includes short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates. Excludes cash and cash equivalents within disposal group and discontinued operation. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 4 -URI http://asc.fasb.org/extlink&oid=109223946&loc=d3e3044-108585 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section 45 -Paragraph 1 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=82887183&loc=d3e6676-107765 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.1) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 + Details
Name: | us-gaap_CashAndCashEquivalentsAtCarryingValue
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amount after tax of increase (decrease) to equity or (increase) decrease to net assets, resulting from the cumulative effect adjustment of a new accounting principle applied in the period of adoption. + References No definition available. + Details
Name: | us-gaap_CumulativeEffectOfNewAccountingPrincipleInPeriodOfAdoption
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition The amount of net income (loss) for the period available to each share of common stock or common unit outstanding during the reporting period and to each share or unit that would have been outstanding assuming the issuance of common shares or units for all dilutive potential common shares or units outstanding during the reporting period. + References Reference 1: http://www.xbrl.org/2003/role/exampleRef -Publisher FASB -Name Accounting Standards Codification -Topic 260 -SubTopic 10 -Section 55 -Paragraph 52 -URI http://asc.fasb.org/extlink&oid=109256448&loc=d3e4984-109258 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 260 -SubTopic 10 -Section 45 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=109260490&loc=d3e1252-109256 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 260 -SubTopic 10 -Section 50 -Paragraph 1 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=6371337&loc=d3e3550-109257 Reference 4: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 220 -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-04(23)) -URI http://asc.fasb.org/extlink&oid=114873765&loc=SL114874048-224260 Reference 5: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 250 -SubTopic 10 -Section 50 -Paragraph 11 -URI http://asc.fasb.org/extlink&oid=109234566&loc=d3e22694-107794 Reference 6: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 260 -SubTopic 10 -Section 45 -Paragraph 7 -URI http://asc.fasb.org/extlink&oid=109260490&loc=d3e1337-109256 Reference 7: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 220 -SubTopic 10 -Section S99 -Paragraph 2 -Subparagraph (SX 210.5-03(21)) -URI http://asc.fasb.org/extlink&oid=115205541&loc=SL114868664-224227 Reference 8: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 260 -SubTopic 10 -Section 45 -Paragraph 60B -Subparagraph (d) -URI http://asc.fasb.org/extlink&oid=109260490&loc=SL5780133-109256 Reference 9: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 220 -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-04(19)) -URI http://asc.fasb.org/extlink&oid=114873790&loc=SL114874131-224263 + Details
Name: | us-gaap_EarningsPerShareDiluted
Namespace Prefix: | us-gaap_
Data Type: | num:perShareItemType
Balance Type: | na
Period Type: | duration

X
- Definition The percentage of ownership of common stock or equity participation in the investee accounted for under the equity method of accounting. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 323 -SubTopic 10 -Section 50 -Paragraph 3 -Subparagraph (a)(1) -URI http://asc.fasb.org/extlink&oid=114001798&loc=d3e33918-111571 + Details
Name: | us-gaap_EquityMethodInvestmentOwnershipPercentage
Namespace Prefix: | us-gaap_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant

X
- Definition Useful life of finite-lived intangible assets, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. + References No definition available. + Details
Name: | us-gaap_FiniteLivedIntangibleAssetUsefulLife
Namespace Prefix: | us-gaap_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

X
- Definition Total loss recognized during the period from the impairment of goodwill plus the loss recognized in the period resulting from the impairment of the carrying amount of intangible assets, other than goodwill. + References No definition available. + Details
Name: | us-gaap_GoodwillAndIntangibleAssetImpairment
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition The amount by which the fair value of an investment is less than the amortized cost basis or carrying amount of that investment at the balance sheet date and the decline in fair value is deemed to be other than temporary, before considering whether or not such amount is recognized in earnings or other comprehensive income. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 45 -Paragraph 8A -URI http://asc.fasb.org/extlink&oid=109979856&loc=SL6284422-111562 + Details
Name: | us-gaap_ImpairmentOfInvestments
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition The portion of profit or loss for the period, net of income taxes, which is attributable to the parent. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 220 -SubTopic 10 -Section 45 -Paragraph 1A -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=114867106&loc=SL7669619-108580 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 220 -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-04(22)) -URI http://asc.fasb.org/extlink&oid=114873765&loc=SL114874048-224260 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 220 -SubTopic 10 -Section 45 -Paragraph 1B -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=114867106&loc=SL7669625-108580 Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 220 -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-04(18)) -URI http://asc.fasb.org/extlink&oid=114873790&loc=SL114874131-224263 Reference 5: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 220 -SubTopic 10 -Section S99 -Paragraph 2 -Subparagraph (SX 210.5-03(20)) -URI http://asc.fasb.org/extlink&oid=115205541&loc=SL114868664-224227 Reference 6: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -URI http://asc.fasb.org/extlink&oid=109223946&loc=d3e3602-108585 Reference 7: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 260 -SubTopic 10 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6371337&loc=d3e3550-109257 + Details
Name: | us-gaap_NetIncomeLoss
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Amount of financial support provided to a nonconsolidated legal entity that is required to comply with or operate in accordance with requirements that are similar to those included in Rule 2a-7 of the Investment Company Act of 1940 for registered money market funds. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 946 -SubTopic 20 -Section 50 -Paragraph 15 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=66023616&loc=SL35737432-115832 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 810 -SubTopic 10 -Section 15 -Paragraph 12 -Subparagraph (f)(2) -URI http://asc.fasb.org/extlink&oid=66022390&loc=d3e923-111674 + Details
Name: | us-gaap_NonconsolidatedLegalEntityFinancialSupportAmount
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Useful life of long lived, physical assets used in the normal conduct of business and not intended for resale, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. Examples include, but not limited to, land, buildings, machinery and equipment, office equipment, furniture and fixtures, and computer equipment. + References No definition available. + Details
Name: | us-gaap_PropertyPlantAndEquipmentUsefulLife
Namespace Prefix: | us-gaap_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

X
- Definition Amount of cash and cash equivalents restricted as to withdrawal or usage, classified as current. Cash includes, but is not limited to, currency on hand, demand deposits with banks or financial institutions, and other accounts with general characteristics of demand deposits. Cash equivalents include, but are not limited to, short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section 45 -Paragraph 1 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=82887183&loc=d3e6676-107765 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 4 -URI http://asc.fasb.org/extlink&oid=109223946&loc=d3e3044-108585 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02(1)) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 50 -Paragraph 8 -URI http://asc.fasb.org/extlink&oid=98513485&loc=SL98516268-108586 + Details
Name: | us-gaap_RestrictedCashAndCashEquivalentsAtCarryingValue
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Details
Name: | us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis=seic_SeiWealthPlatformMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis=seic_PlatformfortheInvestmentManagerssegmentMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsAxis=seic_SeiSponsoredOpenEndedMoneyMarketMutualFundsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsAxis=seic_SeiInvestmentsEuropeLimitedMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsAxis=seic_SeiInvestmentsDistributionCoSidcoMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_RangeAxis=srt_MinimumMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_RangeAxis=srt_MaximumMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_RangeAxis=srt_WeightedAverageMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_PropertyPlantAndEquipmentByTypeAxis=us-gaap_BuildingAndBuildingImprovementsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_PropertyPlantAndEquipmentByTypeAxis=us-gaap_ComputerEquipmentMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_PropertyPlantAndEquipmentByTypeAxis=us-gaap_FurnitureAndFixturesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_ConsolidatedEntitiesAxis=us-gaap_EquityMethodInvesteeMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_ChangeInAccountingEstimateByTypeAxis=us-gaap_ServiceLifeMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_StatementEquityComponentsAxis=us-gaap_RetainedEarningsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_AdjustmentsForNewAccountingPronouncementsAxis=us-gaap_AccountingStandardsUpdate201409Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_RelatedPartyTransactionsByRelatedPartyAxis=seic_SeiSponsoredOpenEndedMoneyMarketMutualFundsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |