Revenues (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Disaggregation of Revenue [Line Items]
Revenues	$ 197,874	$ 252,440
Total investment management fees
Disaggregation of Revenue [Line Items]
Revenues	164,478	206,817
Open-end funds
Disaggregation of Revenue [Line Items]
Revenues	71,266	97,377
Closed-end funds
Disaggregation of Revenue [Line Items]
Revenues	14,678	16,940
Retail separate accounts
Disaggregation of Revenue [Line Items]
Revenues	40,079	49,603
Institutional accounts
Disaggregation of Revenue [Line Items]
Revenues	$ 38,455	$ 42,897