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Related Party Transactions - Additional Information (Detail) - USD ($)
$ in Thousands
3 Months Ended 6 Months Ended 12 Months Ended
Jun. 30, 2021
Jun. 30, 2020
Jun. 30, 2021
Dec. 31, 2020
Related Party Transaction [Line Items]        
Gains and losses related to certain WisdomTree ETFs $ 167 $ 298 $ (217) $ 8
WisdomTree ETF [Member]        
Related Party Transaction [Line Items]        
Investment $ 21,330   $ 21,330 $ 23,932