Investments - Summary of Investments (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Summary of Investment Holdings [Line Items]
Investments owned	$ 228,646	$ 253,375
Long-term incentive compensation obligations	61,500	60,100
Seed capital
Summary of Investment Holdings [Line Items]
Investments owned	299,300	310,300
Equity securities | Long-term incentive compensation-related
Summary of Investment Holdings [Line Items]
Investments owned	30,808	34,351
Equity securities | Seed capital
Summary of Investment Holdings [Line Items]
Investments owned	102,828	75,766
Equity securities | Other
Summary of Investment Holdings [Line Items]
Investments owned	8,415	55,439
Exchange-traded options
Summary of Investment Holdings [Line Items]
Investments owned	2,165	7,527
Investments in limited partnership hedge funds | Long-term incentive compensation-related
Summary of Investment Holdings [Line Items]
Investments owned	30,705	25,762
Investments in limited partnership hedge funds | Seed capital
Summary of Investment Holdings [Line Items]
Investments owned	20,100	16,646
Time deposits
Summary of Investment Holdings [Line Items]
Investments owned	18,120	18,602
Other
Summary of Investment Holdings [Line Items]
Investments owned	$ 15,505	$ 19,282