Investments - Investments in Variable Interest Entities Table Footnote (Detail) - USD ($)	Jun. 30, 2021	Dec. 31, 2020
Variable Interest Entity [Line Items]
Receivables from related parties	$ 7,890,000	$ 11,953,000
Maximum exposure to loss	4,800,000	$ 4,800,000
Aqua
Variable Interest Entity [Line Items]
Receivables from related parties	980,000.0
Subordinated Loan | Aqua
Variable Interest Entity [Line Items]
Receivables from related parties	980,000
Maximum exposure to loss	$ 980,000