Revenues (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Disaggregation of Revenue [Line Items]
Revenues	$ 219,271	$ 210,261	$ 630,681	$ 688,008
Total investment management fees
Disaggregation of Revenue [Line Items]
Revenues	184,869	172,850	529,326	564,691
Open-end funds
Disaggregation of Revenue [Line Items]
Revenues	80,294	80,234	229,721	262,486
Closed-end funds
Disaggregation of Revenue [Line Items]
Revenues	14,673	15,773	44,025	48,887
Retail separate accounts
Disaggregation of Revenue [Line Items]
Revenues	44,441	39,154	127,323	134,069
Institutional accounts
Disaggregation of Revenue [Line Items]
Revenues	$ 45,461	$ 37,689	$ 128,257	$ 119,249