Revenues (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Disaggregation of Revenue [Line Items]
Revenues	$ 845,268	$ 886,379	$ 979,234
Investment management fees
Disaggregation of Revenue [Line Items]
Revenues	711,475	728,339	781,585
Open-end funds
Disaggregation of Revenue [Line Items]
Revenues	305,238	335,585	395,152
Closed-end funds
Disaggregation of Revenue [Line Items]
Revenues	58,136	63,841	63,301
Retail separate accounts
Disaggregation of Revenue [Line Items]
Revenues	171,357	171,509	174,919
Institutional accounts
Disaggregation of Revenue [Line Items]
Revenues	$ 176,744	$ 157,404	$ 148,213