Investments of Operating Entities and Consolidated Funds - Operating Entities - Equity Method Investment (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Schedule of Equity Method Investments [Line Items]
Equity method investments	$ 38,681	$ 40,858
Starboard Value LP
Schedule of Equity Method Investments [Line Items]
Equity method investments	31,528	24,292
Surf House Ocean Views Holdings, LLC
Schedule of Equity Method Investments [Line Items]
Equity method investments	0	7,804
Healthcare Royalty GP III, LLC
Schedule of Equity Method Investments [Line Items]
Equity method investments	2,213	2,230
RCG Longview Debt Fund V Partners, LLC
Schedule of Equity Method Investments [Line Items]
Equity method investments	0	2,889
RCG Longview Management, LLC
Schedule of Equity Method Investments [Line Items]
Equity method investments	268	583
Healthcare Royalty GP, LLC
Schedule of Equity Method Investments [Line Items]
Equity method investments	920	108
Healthcare Royalty GP II, LLC
Schedule of Equity Method Investments [Line Items]
Equity method investments	269	302
RCG Longview Debt Fund IV Management, LLC
Schedule of Equity Method Investments [Line Items]
Equity method investments	331	331
RCG Longview Equity Management, LLC
Schedule of Equity Method Investments [Line Items]
Equity method investments	105	105
HCR Stafford Fund GP, LLC [Member]
Schedule of Equity Method Investments [Line Items]
Equity method investments	1,025	880
Liberty Harbor North
Schedule of Equity Method Investments [Line Items]
Equity method investments	222	292
Equity Method Investee, Other
Schedule of Equity Method Investments [Line Items]
Equity method investments	$ 1,800	$ 1,042