Investments of Operating Entities and Consolidated Funds - Operating Entities - Equity Method Investment (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Schedule of Equity Method Investments [Line Items]
Equity method investments	$ 28,918	$ 40,858
Surf House Ocean Views Holdings, LLC
Schedule of Equity Method Investments [Line Items]
Equity method investments	4,000	7,804
Starboard Value LP
Schedule of Equity Method Investments [Line Items]
Equity method investments	18,527	24,292
RCG Longview Debt Fund V Partners, LLC
Schedule of Equity Method Investments [Line Items]
Equity method investments	1,737	2,889
RCG Longview Management, LLC
Schedule of Equity Method Investments [Line Items]
Equity method investments	105	583
Healthcare Royalty GP, LLC
Schedule of Equity Method Investments [Line Items]
Equity method investments	143	108
Healthcare Royalty GP II, LLC
Schedule of Equity Method Investments [Line Items]
Equity method investments	304	302
RCG Longview Debt Fund IV Management, LLC
Schedule of Equity Method Investments [Line Items]
Equity method investments	330	331
Healthcare Royalty GP III, LLC
Schedule of Equity Method Investments [Line Items]
Equity method investments	2,237	2,230
RCG Longview Equity Management, LLC
Schedule of Equity Method Investments [Line Items]
Equity method investments	250	105
HCR Stafford Fund GP, LLC [Member]
Schedule of Equity Method Investments [Line Items]
Equity method investments	125	880
Liberty Harbor North
Schedule of Equity Method Investments [Line Items]
Equity method investments	292	292
Equity Method Investee, Other
Schedule of Equity Method Investments [Line Items]
Equity method investments	$ 868	$ 1,042