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Investments - Investments in Variable Interest Entities (Parenthetical) (Detail) - USD ($) | Dec. 31, 2020 | Dec. 31, 2019
--- | --- | ---
Variable Interest Entity [Line Items] |  |
Receivables from related parties | $ 11,953,000 | $ 14,273,000
Maximum exposure to loss | 4,800,000 | 2,800,000
Aqua [Member] |  |
Variable Interest Entity [Line Items] |  |
Receivables from related parties | 980,000.0 |
Subordinated Loan [Member] | Aqua [Member] |  |
Variable Interest Entity [Line Items] |  |
Receivables from related parties | 980,000 | 980,000
Maximum exposure to loss | $ 980,000 | $ 980,000

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