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Fair Value Measurements (Details) - USD ($) $ in Thousands | Mar. 31, 2019 | Dec. 31, 2018 | Apr. 02, 2018
--- | --- | --- | ---
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |  |
Equity securities, FV-NI | $ 5,339 | $ 4,887 |
Fixed-income securities owned | 33,433 | 30,892 |
Assets, fair value | 148,596 | 147,680 |
Quoted Prices in Active Markets for Identical Assets (Level 1) |  |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |  |
Fixed-income securities owned | 0 | 0 |
Assets, fair value | 11,111 | 10,218 |
Significant Other Observable Inputs (Level 2) |  |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |  |
Fixed-income securities owned | 33,433 | 30,892 |
Assets, fair value | 132,146 | 132,575 |
Huntington Steele, LLC |  |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |  |
Contingent purchase price |  |  | $ 12,120
Huntington Steele, LLC | Level 3 |  |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |  |
Contingent purchase price | 12,120 | 12,120 |
SEI Sponsored Mutual Funds, Equities and Other Mutual Funds |  |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |  |
Equity securities, FV-NI | 11,111 | 10,218 |
SEI Sponsored Mutual Funds, Equities and Other Mutual Funds | Quoted Prices in Active Markets for Identical Assets (Level 1) |  |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |  |
Equity securities, FV-NI | 11,111 | 10,218 |
SEI Sponsored Mutual Funds, Equities and Other Mutual Funds | Significant Other Observable Inputs (Level 2) |  |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |  |
Equity securities, FV-NI | 0 | 0 |
Fixed income securities |  |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |  |
Available-for-sale securities | 98,713 | 101,683 |
Fixed income securities | Quoted Prices in Active Markets for Identical Assets (Level 1) |  |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |  |
Available-for-sale securities | 0 | 0 |
Fixed income securities | Significant Other Observable Inputs (Level 2) |  |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |  |
Available-for-sale securities | 98,713 | 101,683 |
Investment funds sponsored by LSV |  |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |  |
Equity securities, FV-NI | $ 5,339 | $ 4,887 |

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- Definition Fair value portion of probable future economic benefits obtained or controlled by an entity as a result of past transactions or events. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=99377789&loc=d3e19207-110258 + Details
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- Definition Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale). + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 45 -Paragraph 1 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=109979856&loc=d3e26610-111562 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (aa) -URI http://asc.fasb.org/extlink&oid=82897076&loc=d3e27161-111563 + Details
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- Definition The amount of liability arising from an inherited contingency (as defined) which has been recognized as of the acquisition date. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 805 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=84161108&loc=d3e4845-128472 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 805 -SubTopic 10 -Section 55 -Paragraph 37 -URI http://asc.fasb.org/extlink&oid=108330185&loc=d3e2207-128464 + Details
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- Definition Amount of investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI). + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 825 -SubTopic 10 -Section 45 -Paragraph 1A -URI http://asc.fasb.org/extlink&oid=99377092&loc=SL75136599-209740 + Details
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- Definition The fair value as of the balance sheet date of firm holdings in debt obligations issued by the US government including short-term Treasury bills, medium-term Treasury notes, and long-term Treasury bonds, as well as debt issued by agencies. Includes both pledged (to counterparties as collateral for financing transactions) and unpledged holdings. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 940 -SubTopic 320 -Section 45 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=35711157&loc=d3e42546-110969 + Details
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