Investments of Operating Entities and Consolidated Funds - Equity Method Investments - (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015	Dec. 31, 2015
Schedule of Equity Method Investments [Line Items]
Other investments	$ 158,978		$ 158,978		$ 140,647
Net Gains (Losses) on Securities, Derivatives and Other Investments
Schedule of Equity Method Investments [Line Items]
Income (Loss) from Equity Method Investments	200	$ (5,000)	4,900	$ 9,200
Equity Method Investments
Schedule of Equity Method Investments [Line Items]
Other investments	42,629		42,629		27,067
RCG Longview Debt Fund IV Management, LLC | Equity Method Investments
Schedule of Equity Method Investments [Line Items]
Other investments	331		331		331
RCG Longview Debt Fund V Partners, LLC | Equity Method Investments
Schedule of Equity Method Investments [Line Items]
Other investments	5,942		5,942		4,655
Healthcare Royalty GP, LLC | Equity Method Investments
Schedule of Equity Method Investments [Line Items]
Other investments	827		827		989
Healthcare Royalty GP II, LLC | Equity Method Investments
Schedule of Equity Method Investments [Line Items]
Other investments	1,022		1,022		1,017
Healthcare Royalty GP III, LLC | Equity Method Investments
Schedule of Equity Method Investments [Line Items]
Other investments	78		78		88
Healthcare Overflow Fund GP, LLC [Member] | Equity Method Investments
Schedule of Equity Method Investments [Line Items]
Other investments	85		85		0
Surf House Ocean Views Holdings, LLC | Equity Method Investments
Schedule of Equity Method Investments [Line Items]
Other investments	13,254		13,254		0
Starboard Value LP | Equity Method Investments
Schedule of Equity Method Investments [Line Items]
Other investments	16,844		16,844		15,769
RCG Longview Management, LLC | Equity Method Investments
Schedule of Equity Method Investments [Line Items]
Other investments	695		695		656
RCG Urban American, LLC | Equity Method Investments
Schedule of Equity Method Investments [Line Items]
Other investments	107		107		120
RCG Urban American Management, LLC | Equity Method Investments
Schedule of Equity Method Investments [Line Items]
Other investments	379		379		379
RCG Longview Equity Management, LLC | Equity Method Investments
Schedule of Equity Method Investments [Line Items]
Other investments	114		114		114
Urban American Real Estate Fund II, LLC | Equity Method Investments
Schedule of Equity Method Investments [Line Items]
Other investments	1,312		1,312		1,211
RCG Kennedy House, LLC | Equity Method Investments
Schedule of Equity Method Investments [Line Items]
Other investments	212		212		304
Equity Method Investee, Other | Equity Method Investments
Schedule of Equity Method Investments [Line Items]
Other investments	$ 1,427		$ 1,427		1,434
Minimum
Schedule of Equity Method Investments [Line Items]
Equity Method Investment, Ownership Percentage	20.00%		20.00%
Maximum
Schedule of Equity Method Investments [Line Items]
Equity Method Investment, Ownership Percentage	55.00%		55.00%
Clawback Obligation [Member]
Schedule of Equity Method Investments [Line Items]
Other Commitment	$ 6,200		$ 6,200		6,200
Clawback Obligation [Member] | RCG Longview Partners II, LLC
Schedule of Equity Method Investments [Line Items]
Other Commitment	$ 6,200		$ 6,200		$ 6,200