Investments - Summary of Other Equity Investments (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Schedule of Equity Method Investments [Line Items]
Equity Method Investment	$ 55,100	$ 57,275
ABS [Member]
Schedule of Equity Method Investments [Line Items]
Equity Method Investment	37,310	40,052
Atalanta Sosnoff [Member]
Schedule of Equity Method Investments [Line Items]
Equity Method Investment	12,268	12,300
Luminis [Member]
Schedule of Equity Method Investments [Line Items]
Equity Method Investment	$ 5,522	$ 4,923