Revenues from Contracts with Customers - Summary of Revenues from Contracts with Customers (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Revenues Categorized as Revenues from Contracts with Customers and Other Sources of Revenues [Line Items]
Total operating revenues	$ 72,414	$ 78,112	$ 228,035	$ 225,143
Advisory Fees [Member]
Revenues Categorized as Revenues from Contracts with Customers and Other Sources of Revenues [Line Items]
Total operating revenues	70,616	76,400	222,719	220,611
Other Income [Member]
Revenues Categorized as Revenues from Contracts with Customers and Other Sources of Revenues [Line Items]
Total operating revenues	$ 1,798	$ 1,712	$ 5,316	$ 4,532