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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
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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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