Revenues (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Disaggregation of Revenue [Line Items]
Revenues	$ 225,307	$ 244,011	$ 477,747	$ 460,908
Investment management fees
Disaggregation of Revenue [Line Items]
Revenues	185,024	193,510	391,841	366,779
Open-end funds
Disaggregation of Revenue [Line Items]
Revenues	84,875	97,273	182,252	186,393
Closed-end funds
Disaggregation of Revenue [Line Items]
Revenues	16,174	16,395	33,114	29,335
Retail separate accounts
Disaggregation of Revenue [Line Items]
Revenues	45,312	42,475	94,915	79,987
Institutional accounts
Disaggregation of Revenue [Line Items]
Revenues	$ 38,663	$ 37,367	$ 81,560	$ 71,064