Fair Value Measurements for Operating Entities and Consolidated Funds Unobservable Input Roll Forward (Details) (USD $)	12 Months Ended
	Dec. 31, 2013		Dec. 31, 2012		Dec. 31, 2011
Operating Entities | Preferred Stock
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Transfers In	$ 0		$ 0
Transfers Out	(2,000,000)	[1]	0
Purchases/(covers)	0		2,000,000
(Sales)/short buys	0		0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Realized Gain (Loss) Included in Earnings	0		0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Unrealized Gain (Loss) Included in Earnings	(8,000)		82,000
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value	324,000		2,332,000		250,000
Operating Entities | Common Stock
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Transfers In	0		0
Transfers Out	0		0
Purchases/(covers)	4,000		1,789,000
(Sales)/short buys	(275,000)		(6,000)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Realized Gain (Loss) Included in Earnings	260,000		6,000
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Unrealized Gain (Loss) Included in Earnings	1,021,000		(59,000)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value	3,559,000		2,549,000		819,000
Operating Entities | Corporate Bonds
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Transfers In	0		0
Transfers Out	0		0
Purchases/(covers)	2,735,000		4,600,000
(Sales)/short buys	(3,346,000)		(3,050,000)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Realized Gain (Loss) Included in Earnings	(914,000)		0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Unrealized Gain (Loss) Included in Earnings	1,010,000		(1,035,000)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value	0		515,000		0
Operating Entities | Convertible Bonds
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Transfers In	0
Transfers Out	0
Purchases/(covers)	3,938,000
(Sales)/short buys	(1,988,000)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Realized Gain (Loss) Included in Earnings	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Unrealized Gain (Loss) Included in Earnings	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value	1,950,000		0
Operating Entities | Warrants and Rights
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Transfers In	291,000	[2]	0
Transfers Out	0		(89,000)	[3]
Purchases/(covers)	166,000		632,000
(Sales)/short buys	(110,000)		(212,000)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Realized Gain (Loss) Included in Earnings	(1,000)		56,000
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Unrealized Gain (Loss) Included in Earnings	3,746,000		(208,000)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value	5,805,000		1,713,000		1,534,000
Operating Entities | Warrants and Rights, sold not yet purchased
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Liability, Transfers out of Level 3	0		1,004,000	[4]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Purchases	0		(297,000)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Sales	0		977,000
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Realized Gain (Loss), Included in Earnings	(4,000)		(37,000)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Unrealized Gain (Loss) Included in Earnings	(1,000)		(364,000)
Fair Value, Measurement with Unobservable Inputs Reconciliations, Recurring Basis, Liability Value	0		3,000		0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Liability, Transfers Into Level 3	0		0
Operating Entities | Portfolio Funds, at fair value
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Transfers In	13,128,000	[5]	0
Transfers Out	0		0
Purchases/(covers)	16,932,000		10,116,000
(Sales)/short buys	(9,012,000)		(3,482,000)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Realized Gain (Loss) Included in Earnings	(366,000)		(41,000)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Unrealized Gain (Loss) Included in Earnings	5,297,000		2,158,000
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value	51,649,000		25,670,000		16,919,000
Operating Entities | Real Estate Investments, at fair value
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Transfers In	0		0
Transfers Out	0		0
Purchases/(covers)	0		153,000
(Sales)/short buys	(124,000)		(781,000)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Realized Gain (Loss) Included in Earnings	0		0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Unrealized Gain (Loss) Included in Earnings	348,000		139,000
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value	2,088,000		1,864,000		2,353,000
Operating Entities | Lehman claims, at fair value
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Transfers In	0		0
Transfers Out	0		0
Purchases/(covers)	0		0
(Sales)/short buys	(607,000)		(234,000)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Realized Gain (Loss) Included in Earnings	0		0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Unrealized Gain (Loss) Included in Earnings	279,000		387,000
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value	378,000		706,000		553,000
Consolidated Funds | Portfolio Funds, at fair value
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Transfers In	0		16,227,000	[6]
Transfers Out	0		(17,151,000)	[6]
Purchases/(covers)	0		434,000
(Sales)/short buys	(33,504,000)		(28,892,000)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Realized Gain (Loss) Included in Earnings	211,000		(3,823,000)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Unrealized Gain (Loss) Included in Earnings	6,047,000		2,723,000
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value	155,674,000		182,920,000		213,402,000
Consolidated Funds | Lehman claims, at fair value
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Transfers In	0		0
Transfers Out	0		0
Purchases/(covers)	0		0
(Sales)/short buys	(13,377,000)		(2,292,000)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Realized Gain (Loss) Included in Earnings	8,597,000		1,914,000
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Unrealized Gain (Loss) Included in Earnings	(4,502,000)		7,162,000
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value	4,842,000		14,124,000		7,340,000
Level 3 | Operating Entities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Investments at fair value, end of period	16,216,000
Contingent liability payable [Member] | Operating Entities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Liability, Transfers out of Level 3	0		0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Purchases	(779,000)		(64,000)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Sales	0		8,180,000
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Realized Gain (Loss), Included in Earnings	0		0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Unrealized Gain (Loss) Included in Earnings	400,000		0
Fair Value, Measurement with Unobservable Inputs Reconciliations, Recurring Basis, Liability Value			8,116,000		0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Liability, Transfers Into Level 3	$ 0		$ 0

[1] The company completed an initial public offering.

[2] The security was acquired through an acquisition (See Note 2).

[3] The security was listed on an exchange subsequent to a private funding.

[4] The security began trading on an exchange due to a business combination.

[5] The investment was transferred into level 3 due to Company’s commitment as part of its long term extension of its partnership with credit funds.

[6] Change in consolidated funds (from master-feeder to stand alone funds).