Investments - Investments in Variable Interest Entities (Parenthetical) (Detail) - USD ($)	Mar. 31, 2021	Dec. 31, 2020
Variable Interest Entity [Line Items]
Receivables from related parties	$ 6,919,000	$ 11,953,000
Maximum exposure to loss	4,500,000	4,800,000
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