Fair Value Measurements for Operating Entities and Consolidated Funds Unobservable Input Roll Forward (Details) - USD ($)		12 Months Ended
		Dec. 31, 2018		Dec. 31, 2017
Preferred Stock
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance Asset Value		$ 8,115,000		$ 15,811,000
Asset, Transfers In		0		0
Asset, Transfers Out		1,141,000		25,098,000	[1],[2]
Purchases/(covers)		1,415,000		25,785,000
(Sales)/short buys		(695,000)		(2,956,000)
Realized and unrealized gains (losses), asset		(2,526,000)		(5,427,000)
Change in Unrealized Gain (Loss), instruments still held, asset	[3]	860,000		486,000
Balance Asset Value		5,168,000		8,115,000
Common Stock
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance Asset Value		7,570,000		10,121,000
Asset, Transfers In		0		0
Asset, Transfers Out		569,000		0
Purchases/(covers)		3,324,000		2,670,000
(Sales)/short buys		(1,416,000)		(2,688,000)
Realized and unrealized gains (losses), asset		941,000		(2,533,000)
Change in Unrealized Gain (Loss), instruments still held, asset	[3]	1,797,000		(412,000)
Balance Asset Value		9,850,000		7,570,000
Convertible Bonds
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance Asset Value		282,000		250,000
Asset, Transfers In		0		0
Asset, Transfers Out		0		0
Purchases/(covers)		3,000,000		282,000
(Sales)/short buys		(307,000)		0
Realized and unrealized gains (losses), asset		25,000		(250,000)
Change in Unrealized Gain (Loss), instruments still held, asset	[3]	0		0
Balance Asset Value		3,000,000		282,000
Options
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance Asset Value		1,455,000		14,753,000
Asset, Transfers In		0		0
Asset, Transfers Out		0		0
Purchases/(covers)		0		0
(Sales)/short buys		(1,455,000)		0
Realized and unrealized gains (losses), asset		0		(13,298,000)
Change in Unrealized Gain (Loss), instruments still held, asset	[3]	0		(13,298,000)
Balance Asset Value		0		1,455,000
Warrants and Rights
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance Asset Value		2,517,000		3,719,000
Asset, Transfers In		0		2,173,000	[4],[5]
Asset, Transfers Out		0		0
Purchases/(covers)		0		0
(Sales)/short buys		(143,000)		(4,118,000)
Realized and unrealized gains (losses), asset		(708,000)		743,000
Change in Unrealized Gain (Loss), instruments still held, asset	[3]	(850,000)		510,000
Balance Asset Value		1,666,000		2,517,000
Trade Claims
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance Asset Value		5,950,000		562,000
Asset, Transfers In		0		0
Asset, Transfers Out		0		0
Purchases/(covers)		44,000		5,865,000
(Sales)/short buys		(536,000)		(611,000)
Realized and unrealized gains (losses), asset		85,000		134,000
Change in Unrealized Gain (Loss), instruments still held, asset	[3]	0		202,000
Balance Asset Value		5,543,000		5,950,000
Lehman claims, at fair value
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance Asset Value		301,000		265,000
Asset, Transfers In		0		0
Asset, Transfers Out		0		0
Purchases/(covers)		0		0
(Sales)/short buys		(234,000)		0
Realized and unrealized gains (losses), asset		(67,000)		36,000
Change in Unrealized Gain (Loss), instruments still held, asset	[3]	0		36,000
Balance Asset Value		0		301,000
Consolidated Funds | Preferred Stock
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance Asset Value		50,445,000		36,928,000
Asset, Transfers In		0		22,644,000	[1]
Asset, Transfers Out		38,552,000	[6]	13,668,000	[2]
Purchases/(covers)		3,066,000		8,437,000
(Sales)/short buys		0		(11,903,000)
Realized and unrealized gains (losses), asset		9,355,000		8,007,000
Change in Unrealized Gain (Loss), instruments still held, asset	[3]	9,355,000		3,896,000
Balance Asset Value		24,314,000		50,445,000
Consolidated Funds | Common Stock
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance Asset Value		50,000		295,000
Asset, Transfers In		0		0
Asset, Transfers Out		0		0
Purchases/(covers)		0		526,000
(Sales)/short buys		0		(848,000)
Realized and unrealized gains (losses), asset		44,000		77,000
Change in Unrealized Gain (Loss), instruments still held, asset	[3]	44,000		0
Balance Asset Value		94,000		50,000
Consolidated Funds | Warrants and Rights
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance Asset Value		3,568,000		3,000
Asset, Transfers In		0		0
Asset, Transfers Out		20,000	[6]	0
Purchases/(covers)		(1,340,000)		0
(Sales)/short buys		0		0
Realized and unrealized gains (losses), asset		3,071,000		3,565,000
Change in Unrealized Gain (Loss), instruments still held, asset	[3]	1,730,000		3,565,000
Balance Asset Value		5,279,000		3,568,000
Consolidated Funds | Loans
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance Asset Value		0		657,000
Asset, Transfers In				0
Asset, Transfers Out				0
Purchases/(covers)				202,000
(Sales)/short buys				(1,021,000)
Realized and unrealized gains (losses), asset				162,000
Change in Unrealized Gain (Loss), instruments still held, asset	[3]			0
Balance Asset Value				0
Options, liability
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance Liability Value		22,401,000		14,753,000
Liability, Transfers In		0		0
Liability, Transfers Out		(28,973,000)	[7]	0
Liability, Purchases		0		0
Liability, Sales		(259,000)		0
Realized and unrealized gains (losses), liability		8,927,000		7,648,000
Change in Unrealized Gain (Loss), instruments still held, liabilities	[3]	8,927,000		7,648,000
Balance Liability Value		2,096,000		22,401,000
Contingent liability payable
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance Liability Value		3,440,000		5,997,000
Liability, Transfers In		0		0
Liability, Transfers Out		0		0
Liability, Purchases		427,000		0
Liability, Sales		(797,000)		(392,000)
Realized and unrealized gains (losses), liability		0		(2,165,000)
Change in Unrealized Gain (Loss), instruments still held, liabilities	[3]	0		(2,165,000)
Balance Liability Value		$ 3,070,000		$ 3,440,000

[1] The Company transferred investments to a Consolidated Fund.

[2] The investments were converted to common stock.

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

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

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

[6] The Company deconsolidated an investment fund (See note 3)

[7] On June 26, 2018, the Company received shareholder approval which will allow the Company to settle its convertible note (see Note 23) 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 24)