Fair Value Measurements for Operating Entities and Consolidated Funds Unobservable Input Roll Forward (Details) - USD ($)		3 Months Ended			9 Months Ended
		Sep. 30, 2018		Sep. 30, 2017	Sep. 30, 2018		Sep. 30, 2017
Preferred Stock
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance Asset Value		$ 7,422,000		$ 18,576,000	$ 8,115,000		$ 15,811,000
Asset, Transfers In		0		0	0		0
Asset, Transfers Out		1,141,000	[1]	0	1,141,000		3,472,000	[1]
Purchases/(covers)		0		0	1,415,000		9,000,000
(Sales)/short buys		0		0	(695,000)		(31,000)
Realized and unrealized gains (losses), asset		(1,123,000)		(587,000)	(2,536,000)		(3,319,000)
Change in Unrealized Gain (Loss), instruments still held, asset	[2]	(1,124,000)		(587,000)	(2,301,000)		(1,006,000)
Balance Asset Value		5,158,000		17,989,000	5,158,000		17,989,000
Common Stock
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance Asset Value		5,848,000		10,588,000	7,570,000		10,121,000
Asset, Transfers In		0		0	0		0
Asset, Transfers Out		0		0	0		0
Purchases/(covers)		0		3,151,000	531,000		3,182,000
(Sales)/short buys		0		(1,946,000)	(1,333,000)		(2,121,000)
Realized and unrealized gains (losses), asset		(174,000)		297,000	(1,094,000)		908,000
Change in Unrealized Gain (Loss), instruments still held, asset	[2]	(174,000)		297,000	(1,128,000)		908,000
Balance Asset Value		5,674,000		12,090,000	5,674,000		12,090,000
Convertible Bonds
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance Asset Value				282,000	282,000		250,000
Asset, Transfers In				0	0		0
Asset, Transfers Out				0	0		0
Purchases/(covers)				250,000	0		282,000
(Sales)/short buys				0	(307,000)		0
Realized and unrealized gains (losses), asset				(250,000)	25,000		(250,000)
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				9,860,000	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				499,000	0		(4,394,000)
Change in Unrealized Gain (Loss), instruments still held, asset	[2]			499,000	0		(4,394,000)
Balance Asset Value		0		10,359,000	0		10,359,000
Warrants and Rights
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance Asset Value		1,544,000		3,409,000	2,517,000		3,719,000
Asset, Transfers In		0		0	0		3,192,000	[3],[4]
Asset, Transfers Out		0	[1]	0	0		0
Purchases/(covers)		0		0	0		0
(Sales)/short buys		0		0	(143,000)		(4,367,000)
Realized and unrealized gains (losses), asset		38,000		(1,013,000)	(792,000)		(148,000)
Change in Unrealized Gain (Loss), instruments still held, asset	[2]	38,000		187,000	(933,000)		510,000
Balance Asset Value		1,582,000		2,396,000	1,582,000		2,396,000
Trade Claims
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance Asset Value		5,699,000		4,648,000	5,950,000		562,000
Asset, Transfers In		0		0	0		0
Asset, Transfers Out		0		0	0		0
Purchases/(covers)		44,000		1,925,000	44,000		5,865,000
(Sales)/short buys		0		(630,000)	(334,000)		(700,000)
Realized and unrealized gains (losses), asset		3,000		3,000	86,000		219,000
Change in Unrealized Gain (Loss), instruments still held, asset	[2]	3,000		3,000	23,000		198,000
Balance Asset Value		5,746,000		5,946,000	5,746,000		5,946,000
Lehman claims, at fair value
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance Asset Value		295,000		309,000	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		(234,000)		0	(234,000)		0
Realized and unrealized gains (losses), asset		(61,000)		10,000	(67,000)		54,000
Change in Unrealized Gain (Loss), instruments still held, asset	[2]	0		10,000	0		54,000
Balance Asset Value		0		319,000	0		319,000
Consolidated Funds | Preferred Stock
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance Asset Value		24,314,000		18,224,000	50,445,000		36,928,000
Asset, Transfers In		0		0	0		0
Asset, Transfers Out		0		0	38,552,000	[5]	13,668,000	[1]
Purchases/(covers)		0		467,000	3,066,000		467,000
(Sales)/short buys		0		0	0		(11,853,000)
Realized and unrealized gains (losses), asset		0		252,000	9,355,000		7,069,000
Change in Unrealized Gain (Loss), instruments still held, asset	[2]	0		252,000	9,355,000		2,958,000
Balance Asset Value		24,314,000		18,943,000	24,314,000		18,943,000
Consolidated Funds | Common Stock
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance Asset Value		94,000		848,000	50,000		295,000
Asset, Transfers In		0		0	0		0
Asset, Transfers Out		0		0	0		0
Purchases/(covers)		0		0	0		476,000
(Sales)/short buys		0		848,000	0		(848,000)
Realized and unrealized gains (losses), asset		0		0	44,000		77,000
Change in Unrealized Gain (Loss), instruments still held, asset	[2]	0		0	44,000		0
Balance Asset Value		94,000		0	94,000		0
Consolidated Funds | Warrants and Rights
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance Asset Value		4,738,000		3,369,000	3,568,000		3,000
Asset, Transfers In		0		0	0		0
Asset, Transfers Out		0		0	20,000	[5]	0
Purchases/(covers)		0		0	(1,340,000)		0
(Sales)/short buys		0		0	0		0
Realized and unrealized gains (losses), asset		110,000		9,000	2,640,000		3,375,000
Change in Unrealized Gain (Loss), instruments still held, asset	[2]	110,000		9,000	1,300,000		3,375,000
Balance Asset Value		4,848,000		3,378,000	4,848,000		3,378,000
Consolidated Funds | Loans
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance Asset Value				202,000			657,000
Asset, Transfers In				0			0
Asset, Transfers Out				0			0
Purchases/(covers)				0			202,000
(Sales)/short buys				200,000			(1,021,000)
Realized and unrealized gains (losses), asset				(2,000)			162,000
Change in Unrealized Gain (Loss), instruments still held, asset	[2]			0			0
Balance Asset Value				0			0
Options, liability
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance Liability Value		301,000		9,860,000	22,401,000		14,753,000
Liability, Transfers In		0		0	0		0
Liability, Transfers Out		0		0	(28,973,000)	[6]	0
Liability, Purchases		0		0	0		0
Liability, Sales		0		0	(259,000)		0
Realized and unrealized gains (losses), liability		2,246,000		499,000	9,378,000		(4,394,000)
Change in Unrealized Gain (Loss), instruments still held, liabilities	[2]	2,246,000		499,000	9,378,000		(4,394,000)
Balance Liability Value		2,547,000		10,359,000	2,547,000		10,359,000
Contingent liability payable
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance Liability Value		2,870,000		5,174,000	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		(227,000)		(125,000)	(797,000)		(392,000)
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		$ 2,643,000		$ 5,049,000	$ 2,643,000		$ 5,049,000

[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)