Revenues - Disaggregation of Revenue (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Disaggregation of Revenue [Line Items]
Revenues	$ 886,379	$ 979,234	$ 603,896
Investment management fees
Disaggregation of Revenue [Line Items]
Revenues	728,339	781,585	505,338
Open-end funds
Disaggregation of Revenue [Line Items]
Revenues	335,585	395,152	250,030
Closed-end funds
Disaggregation of Revenue [Line Items]
Revenues	63,841	63,301	36,833
Retail separate accounts
Disaggregation of Revenue [Line Items]
Revenues	171,509	174,919	104,932
Institutional accounts
Disaggregation of Revenue [Line Items]
Revenues	$ 157,404	$ 148,213	$ 113,543