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Summary of Significant Unobservable Inputs Used in Fair Value Measurements Categorized Within Level 3 of Fair Value Hierarchy (Parenthetical) (Detail) - Level 3 - Option Pricing Method - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Debt Investments | Discount for Lack of Marketability (“DLOM”)
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Sensitivity analysis of fair value, 1% change in DLOM resulting in variation in fair value amount	$ 93	$ 120
Debt Investments | Volatility
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Sensitivity analysis of fair value, 1% change in volatility resulting in variation in fair value amount	9	$ 30
Equity Investments | Discount for Lack of Marketability (“DLOM”)
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Sensitivity analysis of fair value, 1% change in DLOM resulting in variation in fair value amount	26
Equity Investments | Volatility
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Sensitivity analysis of fair value, 1% change in volatility resulting in variation in fair value amount	$ 13

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