Fair Value Measurements for Operating Entities and Consolidated Funds Unobservable Input Roll Forward (Details) - USD ($)		3 Months Ended				6 Months Ended
		Jun. 30, 2018		Jun. 30, 2017		Jun. 30, 2018		Jun. 30, 2017
Preferred Stock
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance Asset Value		$ 8,817,000		$ 16,516,000		$ 8,115,000		$ 15,811,000
Asset, Transfers In		0		0		0		0
Asset, Transfers Out		0		4,204,000		0		4,204,000	[1]
Purchases/(covers)		0		7,999,000		1,415,000		9,731,000
(Sales)/short buys		(217,000)		0		(695,000)		(31,000)
Realized and unrealized gains (losses), asset		(1,178,000)		(1,735,000)		(1,413,000)		(2,731,000)
Change in Unrealized Gain (Loss), instruments still held, asset	[2]	(1,817,000)		(1,735,000)		(1,331,000)		(2,731,000)
Balance Asset Value		7,422,000		18,576,000		7,422,000		18,576,000
Common Stock
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance Asset Value		7,400,000		10,504,000		7,570,000		10,121,000
Asset, Transfers In		0		0		0		0
Asset, Transfers Out		0		0		0		0
Purchases/(covers)		221,000		3,087,000		531,000		3,118,000
(Sales)/short buys		(1,200,000)		(123,000)		(1,333,000)		(175,000)
Realized and unrealized gains (losses), asset		(572,000)		207,000		(919,000)		611,000
Change in Unrealized Gain (Loss), instruments still held, asset	[2]	(547,000)		205,000		(959,000)		611,000
Balance Asset Value		5,849,000		13,675,000		5,849,000		13,675,000
Convertible Bonds
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance Asset Value				250,000		282,000		250,000
Asset, Transfers In				0		0		0
Asset, Transfers Out				0		0		0
Purchases/(covers)				32,000		0		32,000
(Sales)/short buys				0		(307,000)		0
Realized and unrealized gains (losses), asset				0		25,000		0
Change in Unrealized Gain (Loss), instruments still held, asset	[2]			0		0		0
Balance Asset Value		0		282,000		0		282,000
Options
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance Asset Value				6,971,000		1,455,000		14,753,000
Asset, Transfers In				0		0		0
Asset, Transfers Out				0		0		0
Purchases/(covers)				0		0		0
(Sales)/short buys				0		(1,455,000)		0
Realized and unrealized gains (losses), asset				2,889,000		0		(4,893,000)
Change in Unrealized Gain (Loss), instruments still held, asset	[2]			2,889,000		0		(4,893,000)
Balance Asset Value		0		9,860,000		0		9,860,000
Warrants and Rights
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance Asset Value		1,702,000		4,139,000		2,517,000		3,719,000
Asset, Transfers In		0		2,741,000		0		3,192,000	[3],[4]
Asset, Transfers Out		374,000	[1]	0		374,000	[1]	0
Purchases/(covers)		0		0		0		0
(Sales)/short buys		(143,000)		(4,118,000)		(143,000)		(4,118,000)
Realized and unrealized gains (losses), asset		71,000		647,000		(744,000)		616,000
Change in Unrealized Gain (Loss), instruments still held, asset	[2]	(1,176,000)		72,000		(666,000)		42,000
Balance Asset Value		1,256,000		3,409,000		1,256,000		3,409,000
Trade Claims
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance Asset Value		5,955,000		703,000		5,950,000		562,000
Asset, Transfers In		0		0		0		0
Asset, Transfers Out		0		0		0		0
Purchases/(covers)		0		3,940,000		0		3,940,000
(Sales)/short buys		(334,000)		0		(334,000)		(70,000)
Realized and unrealized gains (losses), asset		78,000		5,000		83,000		216,000
Change in Unrealized Gain (Loss), instruments still held, asset	[2]	14,000		5,000		20,000		195,000
Balance Asset Value		5,699,000		4,648,000		5,699,000		4,648,000
Lehman claims, at fair value
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance Asset Value		312,000		297,000		301,000		265,000
Asset, Transfers In		0		0		0		0
Asset, Transfers Out		0		0		0		0
Purchases/(covers)		0		0		0		0
(Sales)/short buys		0		0		0		0
Realized and unrealized gains (losses), asset		(17,000)		12,000		(6,000)		44,000
Change in Unrealized Gain (Loss), instruments still held, asset	[2]	(18,000)		12,000		(6,000)		44,000
Balance Asset Value		295,000		309,000		295,000		309,000
Consolidated Funds | Preferred Stock
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance Asset Value		11,893,000		40,315,000		50,445,000		36,928,000
Asset, Transfers In		0		0		0		0
Asset, Transfers Out		0		(13,668,000)	[5]	38,552,000	[5]	13,668,000	[1]
Purchases/(covers)		3,066,000		0		3,066,000		0
(Sales)/short buys		0		11,853,000		0		(11,853,000)
Realized and unrealized gains (losses), asset		9,355,000		3,430,000		9,355,000		6,817,000
Change in Unrealized Gain (Loss), instruments still held, asset	[2]	9,356,000		(2,423,000)		9,356,000		964,000
Balance Asset Value		24,314,000		18,224,000		24,314,000		18,224,000
Consolidated Funds | Common Stock
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance Asset Value		50,000		296,000		50,000		295,000
Asset, Transfers In		0		0		0		0
Asset, Transfers Out		0		0	[5]	0		0
Purchases/(covers)		0		476,000		0		476,000
(Sales)/short buys		0		0		0		0
Realized and unrealized gains (losses), asset		44,000		76,000		44,000		77,000
Change in Unrealized Gain (Loss), instruments still held, asset	[2]	43,000		76,000		43,000		77,000
Balance Asset Value		94,000		848,000		94,000		848,000
Consolidated Funds | Warrants and Rights
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance Asset Value		5,254,000		2,000		3,568,000		3,000
Asset, Transfers In		0		0		0		0
Asset, Transfers Out		0		0	[5]	20,000	[5]	0
Purchases/(covers)		(1,340,000)		0		(1,340,000)		0
(Sales)/short buys		0		0		0		0
Realized and unrealized gains (losses), asset		824,000		3,367,000		2,530,000		3,366,000
Change in Unrealized Gain (Loss), instruments still held, asset	[2]	(516,000)		3,367,000		1,190,000		3,366,000
Balance Asset Value		4,738,000		3,369,000		4,738,000		3,369,000
Consolidated Funds | Loans
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance Asset Value				711,000				657,000
Asset, Transfers In				0				0
Asset, Transfers Out				0	[5]			0
Purchases/(covers)				202,000				202,000
(Sales)/short buys				821,000				(821,000)
Realized and unrealized gains (losses), asset				110,000				164,000
Change in Unrealized Gain (Loss), instruments still held, asset	[2]			0				0
Balance Asset Value				202,000				202,000
Options, liability
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance Liability Value		21,395,000		6,971,000		22,401,000		14,753,000
Liability, Transfers In		0		0		0		0
Liability, Transfers Out		(28,973,000)	[6]	0		(28,973,000)	[6]	0
Liability, Purchases		0		0		0		0
Liability, Sales		(259,000)		0		(259,000)		0
Realized and unrealized gains (losses), liability		8,138,000		2,889,000		7,132,000		(4,893,000)
Change in Unrealized Gain (Loss), instruments still held, liabilities	[2]	8,138,000		2,889,000		7,132,000		(4,893,000)
Balance Liability Value		301,000		9,860,000		301,000		9,860,000
Contingent liability payable
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance Liability Value		3,440,000		5,274,000		3,440,000		5,997,000
Liability, Transfers In		0		0		0		0
Liability, Transfers Out		0		0		0		0
Liability, Purchases		0		0		0		0
Liability, Sales		(570,000)		(100,000)		(570,000)		(267,000)
Realized and unrealized gains (losses), liability		0		0		0		(556,000)
Change in Unrealized Gain (Loss), instruments still held, liabilities	[2]	0		0		0		(556,000)
Balance Liability Value		$ 2,870,000		$ 5,174,000		$ 2,870,000		$ 5,174,000

[1] The investments were converted to common stock.

[2] Unrealized gains/losses are reported in other income (loss) in the accompanying condensed consolidated statements of operations.

[3] As part of the preferred stock sale, the sellers received contingent value rights to be paid in the event certain milestones are reached.

[4] The Company received warrants as consideration as part of an investment banking transaction.

[5] The Company deconsolidated a fund (See note 3)

[6] On June 26, 2018, the Company received shareholder approval which will allow the Company to settle its convertible note (see Note 17) entirely in class A common shares. Upon receiving shareholder approval, the Company reclassified the embedded conversion option, associated with the convertible debt, to equity. (See Note 18)