Revenues (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Disaggregation of Revenue [Line Items]
Revenues	$ 210,261	$ 252,064	$ 688,008	$ 712,972
Total investment management fees
Disaggregation of Revenue [Line Items]
Revenues	172,850	201,133	564,691	567,912
Open-end funds
Disaggregation of Revenue [Line Items]
Revenues	80,234	99,711	262,486	286,104
Closed-end funds
Disaggregation of Revenue [Line Items]
Revenues	15,773	17,116	48,887	46,451
Retail separate accounts
Disaggregation of Revenue [Line Items]
Revenues	39,154	46,625	134,069	126,612
Institutional accounts
Disaggregation of Revenue [Line Items]
Revenues	$ 37,689	$ 37,681	$ 119,249	$ 108,745