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Financial Instruments Owned, at Fair Value - Narrative (Detail) - USD ($)
3 Months Ended 6 Months Ended
Jun. 30, 2023
Jun. 30, 2022
Jun. 30, 2023
Jun. 30, 2022
Dec. 31, 2022
Investments, Debt and Equity Securities [Abstract]          
Aggregate securities owned $ 40,519,000   $ 40,519,000   $ 39,319,000
Unrealized gains (losses) $ 0 $ (100,000) $ 0 $ (100,000)