Goodwill and Other Intangible Assets - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Goodwill And Intangible Assets [Line Items]
Goodwill	$ 383,861	$ 371,773	$ 371,561	$ 385,292
Goodwill impairment loss	0	0	0
Amortization of intangible assets	1,795	2,240	$ 3,035
Financial Advisory Segment [Member]
Goodwill And Intangible Assets [Line Items]
Goodwill	319,320	307,232
Asset Management Segment [Member]
Goodwill And Intangible Assets [Line Items]
Goodwill	$ 64,541	$ 64,541