Revenues (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Disaggregation of Revenue [Line Items]
Revenues	$ 252,440	$ 216,897
Investment management fees
Disaggregation of Revenue [Line Items]
Revenues	206,817	173,269
Open-end funds
Disaggregation of Revenue [Line Items]
Revenues	97,377	89,120
Closed-end funds
Disaggregation of Revenue [Line Items]
Revenues	16,940	12,940
Retail separate accounts
Disaggregation of Revenue [Line Items]
Revenues	49,603	37,512
Institutional accounts
Disaggregation of Revenue [Line Items]
Revenues	41,991	32,438
Structured products
Disaggregation of Revenue [Line Items]
Revenues	$ 906	$ 1,259