Investments - Summary of Other Equity Investments (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Schedule of Equity Method Investments [Line Items]
Equity Method Investment	$ 59,508	$ 57,275
ABS [Member]
Schedule of Equity Method Investments [Line Items]
Equity Method Investment	41,439	40,052
Atalanta Sosnoff [Member]
Schedule of Equity Method Investments [Line Items]
Equity Method Investment	11,950	12,300
Luminis [Member]
Schedule of Equity Method Investments [Line Items]
Equity Method Investment	$ 6,119	$ 4,923