Investments of Operating Entities and Consolidated Funds - Merger Master Derivatives (Details) - USD ($) $ in Thousands		Dec. 31, 2019	Dec. 31, 2018
Derivative [Line Items]
Derivative Asset		$ 62,977	$ 25,125
Derivative Liability		60,761	16,082
Merger Master
Derivative [Line Items]
Derivative Asset		2,453	8,770
Derivative Liability		1,426	1,728
Option
Derivative [Line Items]
Derivative Liability	[1]	36,524	13,211
Option | Merger Master
Derivative [Line Items]
Derivative Liability		1,158	1,430
Options
Derivative [Line Items]
Derivative Asset	[2]	60,066	23,130
Options | Merger Master
Derivative [Line Items]
Derivative Asset		2,047	3,450
Swaps
Derivative [Line Items]
Derivative Asset		2,911	917
Derivative Liability		23,169	2,162
Swaps | Merger Master
Derivative [Line Items]
Derivative Asset		406	5,320
Derivative Liability		268	28
Currency Forwards
Derivative [Line Items]
Derivative Asset		0	1
Derivative Liability		851	709
Currency Forwards | Merger Master
Derivative [Line Items]
Derivative Liability		$ 0	$ 270

[1] Includes the volume of contracts for index, equity, commodity future and cash conversion options.

[2] Includes the volume of contracts for index, equity, commodity future and cash conversion options.