Investments of Operating Entities and Consolidated Funds - Operating Entities - Equity Method Investment - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2020
Schedule of Equity Method Investments [Line Items]
Net gains (losses) on other investments	$ 12,645	$ (62)
Equity Method Investment, Other than Temporary Impairment	0	0
Equity method investments	$ 34,498		$ 38,681
Surf House Ocean Views Holdings, LLC
Schedule of Equity Method Investments [Line Items]
Equity Method Investment, Ownership Percentage	40.00%
Other than Temporary Impairment Losses, Investments		$ 7,300
Minimum
Schedule of Equity Method Investments [Line Items]
Equity Method Investment, Ownership Percentage	15.00%
Maximum
Schedule of Equity Method Investments [Line Items]
Equity Method Investment, Ownership Percentage	55.00%
Starboard Value LP
Schedule of Equity Method Investments [Line Items]
Equity method investments	$ 27,769		31,528
Healthcare Royalty GP III, LLC
Schedule of Equity Method Investments [Line Items]
Equity method investments	2,221		2,213
RCG Longview Management, LLC
Schedule of Equity Method Investments [Line Items]
Equity method investments	268		268
Healthcare Royalty GP, LLC
Schedule of Equity Method Investments [Line Items]
Equity method investments	442		920
Healthcare Royalty GP II, LLC
Schedule of Equity Method Investments [Line Items]
Equity method investments	272		269
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	1,159		1,025
Liberty Harbor North
Schedule of Equity Method Investments [Line Items]
Equity method investments	222		222
Equity Method Investee, Other
Schedule of Equity Method Investments [Line Items]
Equity method investments	$ 1,709		$ 1,800