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Related Party Transactions - Additional Information (Detail) - USD ($) $ in Thousands | 3 Months Ended | 9 Months Ended |
--- | --- | --- | ---
Sep. 30, 2020 | Sep. 30, 2019 | Sep. 30, 2020 | Sep. 30, 2019 | Dec. 31, 2019
Related Party Transaction [Line Items] |  |  |  |  |
Securities owned, at fair value | $ 32,574 |  | $ 32,574 |  | $ 17,319
Gains and losses related to certain WisdomTree ETFs | 86 | $ 64 | 94 | $ 212 |
WisdomTree ETF [Member] |  |  |  |  |
Related Party Transaction [Line Items] |  |  |  |  |
Securities owned, at fair value | $ 23,906 |  | $ 23,906 |  | $ 16,886

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- Definition Fair value of financial instruments held by a broker-dealer for their own account (proprietary securities) for trading or investment purposes determined by management based upon quoted prices of a financial instrument with similar characteristics or on a valuation technique or model. + 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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