Fair Value Measurements for Operating Entities and Consolidated Funds Unobservable Input Roll Forward (Details) - USD ($)		12 Months Ended
		Dec. 31, 2016		Dec. 31, 2015
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value, Between Level 1 and 2 transfers, amount		$ 0
Preferred Stock
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance Asset Value		12,872,000		$ 12,517,000
Asset, Transfers In		0		0
Asset, Transfers Out	[1]	(1,000,000)		(11,322,000)	[2]
Purchases/(covers)		3,717,000		14,850,000
(Sales)/short buys		(218,000)		(6,665,000)
Realized and unrealized gains (losses), asset		440,000		3,492,000
Change in Unrealized Gain (Loss), instruments still held, asset	[3]	34,000		217,000
Balance Asset Value		15,811,000		12,872,000
Common Stock
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance Asset Value		2,278,000		412,000
Asset, Transfers In		0		0
Asset, Transfers Out		0		0
Purchases/(covers)		7,099,000		2,398,000
(Sales)/short buys		(3,222,000)		(441,000)
Realized and unrealized gains (losses), asset		3,966,000		(91,000)
Change in Unrealized Gain (Loss), instruments still held, asset	[3]	3,972,000		90,000
Balance Asset Value		10,121,000		2,278,000
Convertible Bonds
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance Asset Value		819,000		900,000
Asset, Transfers In		0		0
Asset, Transfers Out		0		0
Purchases/(covers)		0		250,000
(Sales)/short buys		(569,000)		0
Realized and unrealized gains (losses), asset		0		(331,000)
Change in Unrealized Gain (Loss), instruments still held, asset	[3]	0		(331,000)
Balance Asset Value		250,000		819,000
Corporate Bonds
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance Asset Value		0
Asset, Transfers In	[4]	675,000
Asset, Transfers Out		0
Purchases/(covers)		279,000
(Sales)/short buys		(325,000)
Realized and unrealized gains (losses), asset		(77,000)
Change in Unrealized Gain (Loss), instruments still held, asset	[3]	(111,000)
Balance Asset Value		552,000		0
Options
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance Asset Value		18,194,000		36,807,000
Asset, Transfers In		0		0
Asset, Transfers Out		0		0
Purchases/(covers)		0		0
(Sales)/short buys		0		0
Realized and unrealized gains (losses), asset		(3,441,000)		(18,613,000)
Change in Unrealized Gain (Loss), instruments still held, asset	[3]	(3,441,000)		(18,613,000)
Balance Asset Value		14,753,000		18,194,000
Warrants and Rights
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance Asset Value		2,572,000		1,322,000
Asset, Transfers In		0		0
Asset, Transfers Out		0		0
Purchases/(covers)		1,914,000		824,000
(Sales)/short buys		(817,000)		(71,000)
Realized and unrealized gains (losses), asset		50,000		497,000
Change in Unrealized Gain (Loss), instruments still held, asset	[3]	79,000		715,000
Balance Asset Value		3,719,000		2,572,000
Trade Claims
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance Asset Value		0
Asset, Transfers In		0
Asset, Transfers Out		0
Purchases/(covers)		10,000
(Sales)/short buys		0
Realized and unrealized gains (losses), asset		0
Change in Unrealized Gain (Loss), instruments still held, asset	[3]	0
Balance Asset Value		10,000		0
Lehman claims, at fair value
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance Asset Value		299,000		380,000
Asset, Transfers In		0		0
Asset, Transfers Out		0		0
Purchases/(covers)		0		0
(Sales)/short buys		0		0
Realized and unrealized gains (losses), asset		(34,000)		(81,000)
Change in Unrealized Gain (Loss), instruments still held, asset	[3]	(35,000)		(81,000)
Balance Asset Value		265,000		299,000
Consolidated Funds | Preferred Stock
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance Asset Value		32,000,000		0
Asset, Transfers In		0		7,000,000	[2]
Asset, Transfers Out		(11,000,000)	[1]	0
Purchases/(covers)		13,483,000		25,000,000
(Sales)/short buys		0		0
Realized and unrealized gains (losses), asset		2,445,000		0
Change in Unrealized Gain (Loss), instruments still held, asset	[3]	2,445,000		0
Balance Asset Value		36,928,000		32,000,000
Consolidated Funds | Common Stock
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance Asset Value		0
Asset, Transfers In		0
Asset, Transfers Out	[1]	0
Purchases/(covers)		314,000
(Sales)/short buys		0
Realized and unrealized gains (losses), asset		(19,000)
Change in Unrealized Gain (Loss), instruments still held, asset	[3]	(19,000)
Balance Asset Value		295,000		0
Consolidated Funds | Warrants and Rights
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance Asset Value		0
Asset, Transfers In		0
Asset, Transfers Out		0
Purchases/(covers)		0
(Sales)/short buys		0
Realized and unrealized gains (losses), asset		3,000
Change in Unrealized Gain (Loss), instruments still held, asset	[3]	3,000
Balance Asset Value		3,000		0
Consolidated Funds | Lehman claims, at fair value
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance Asset Value		0		493,000
Asset, Transfers In				0
Asset, Transfers Out				0
Purchases/(covers)				0
(Sales)/short buys				(739,000)
Realized and unrealized gains (losses), asset				246,000
Change in Unrealized Gain (Loss), instruments still held, asset	[3]			0
Balance Asset Value				0
Consolidated Funds | Loans
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance Asset Value		0
Asset, Transfers In		0
Asset, Transfers Out		0
Purchases/(covers)		590,000
(Sales)/short buys		0
Realized and unrealized gains (losses), asset		67,000
Change in Unrealized Gain (Loss), instruments still held, asset		67,000
Balance Asset Value		657,000		0
Options, liability
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance Liability Value		18,194,000		36,807,000
Liability, Transfers In		0		0
Liability, Transfers Out		0		0
Liability, Purchases		0		0
Liability, Sales		0		0
Realized and unrealized gains (losses), liability		(3,441,000)		(18,613,000)
Change in Unrealized Gain (Loss), instruments still held, liabilities	[3]	(3,441,000)		(18,613,000)
Balance Liability Value		14,753,000		18,194,000
Contingent liability payable
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance Liability Value		6,158,000		4,083,000
Liability, Transfers In		0		0
Liability, Transfers Out		0		0
Liability, Purchases		2,397,000		3,600,000
Liability, Sales		(4,697,000)		(1,725,000)
Realized and unrealized gains (losses), liability		2,139,000		200,000
Change in Unrealized Gain (Loss), instruments still held, liabilities	[3]	$ 0		200,000
Balance Liability Value				$ 6,158,000

[1] The investments were converted to common stock.

[2] The Company transferred investments to a consolidated fund.

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

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