Related Party Transactions - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019
Related Party Transaction [Line Items]
Gains and losses related to certain WisdomTree ETFs	$ (290)	$ 353
WisdomTree ETF [Member]
Related Party Transaction [Line Items]
Securities owned, at fair value	$ 19,636		$ 16,886

Amount of realized and unrealized gain (loss) on investment.

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