Investments - Company's Investments and Securities Sold, Not Yet Purchased (Detail) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Schedule of Investments [Line Items]
Total investments	$ 1,007,339	$ 658,532
Equity method	16,250
Investments, at fair value	991,089	658,532
Securities sold, not yet purchased, at fair value (included in "other liabilities")	6,828	1,176
Debt [Member]
Schedule of Investments [Line Items]
Total investments	299,990	99,987
Investments, at fair value	299,990	99,987
Equities [Member]
Schedule of Investments [Line Items]
Total investments	54,040	37,365
Investments, at fair value	54,040	37,365
Alternative Investment Funds [Member]
Schedule of Investments [Line Items]
Total investments	49,757	34,264
Investments, at fair value	49,757	34,264
Debt Funds [Member]
Schedule of Investments [Line Items]
Total investments	164,952	123,554
Investments, at fair value	164,952	123,554
Equity Funds [Member]
Schedule of Investments [Line Items]
Total investments	375,761	325,795
Investments, at fair value	375,761	325,795
Private Equity Funds [Member]
Schedule of Investments [Line Items]
Total investments	46,589	37,567
Investments, at fair value	46,589	37,567
Funds Total [Member]
Schedule of Investments [Line Items]
Total investments	637,059	$ 521,180
Equity Method [Member]
Schedule of Investments [Line Items]
Total investments	$ 16,250