Related Party Transactions - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
Mar. 31, 2021	Dec. 31, 2020
Related Party Transaction [Line Items]
Losses related to certain WisdomTree ETFs	$ 384	$ 290
WisdomTree ETF [Member]
Related Party Transaction [Line Items]
Investment	$ 23,626	$ 23,932

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

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