Fair Value Measurements for Operating Entities and Consolidated Funds Unobservable Input Roll Forward (Details) - USD ($)		12 Months Ended
		Dec. 31, 2015		Dec. 31, 2014
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance Asset Value		$ 55,006,000
Balance Liability Value		40,890,000
Balance Asset Value		71,955,000		$ 55,006,000
Balance Liability Value		24,352,000		40,890,000
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		12,517,000		324,000
Asset, Transfers In		0		0
Asset, Transfers Out	[1]	(11,322,000)	[2]	(2,000,000)
Purchases/(covers)		14,850,000		14,396,000
(Sales)/short buys		(6,665,000)		0
Realized and unrealized gains (losses), asset		3,492,000		(203,000)
Change in Unrealized Gain (Loss), instruments still held, asset	[3]	217,000		(203,000)
Balance Asset Value		12,872,000		12,517,000
Common Stock
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance Asset Value		412,000		3,559,000
Asset, Transfers In		0		0
Asset, Transfers Out		0		(3,150,000)	[1]
Purchases/(covers)		3,398,000		12,000
(Sales)/short buys		(441,000)		(1,000)
Realized and unrealized gains (losses), asset		(91,000)		(8,000)
Change in Unrealized Gain (Loss), instruments still held, asset	[3]	90,000		(135,000)
Balance Asset Value		3,278,000		412,000
Convertible Bonds
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance Asset Value		900,000		1,950,000
Asset, Transfers In		0		0
Asset, Transfers Out		0		0
Purchases/(covers)		250,000		0
(Sales)/short buys		0		(200,000)
Realized and unrealized gains (losses), asset		(331,000)		(850,000)
Change in Unrealized Gain (Loss), instruments still held, asset	[3]	(331,000)		(850,000)
Balance Asset Value		819,000		900,000
Options
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance Asset Value		36,807,000		0
Asset, Transfers In		0		0
Asset, Transfers Out		0		0
Purchases/(covers)		0		35,710,000
(Sales)/short buys		0		0
Realized and unrealized gains (losses), asset		(18,613,000)		1,097,000
Change in Unrealized Gain (Loss), instruments still held, asset	[3]	(18,613,000)		1,097,000
Balance Asset Value		18,194,000		36,807,000
Warrants and Rights
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance Asset Value		1,322,000		5,805,000
Asset, Transfers In		0		0
Asset, Transfers Out		0		(1,288,000)	[4]
Purchases/(covers)		824,000		57,000
(Sales)/short buys		(71,000)		(97,000)
Realized and unrealized gains (losses), asset		497,000		(3,155,000)
Change in Unrealized Gain (Loss), instruments still held, asset	[3]	715,000		(1,415,000)
Balance Asset Value		2,572,000		1,322,000
Real Estate Investments, at fair value
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance Asset Value		2,175,000		2,088,000
Asset, Transfers In		0		0
Asset, Transfers Out		0		0
Purchases/(covers)		0		50,000,000
(Sales)/short buys		(390,000)		(50,168,000)
Realized and unrealized gains (losses), asset		136,000		255,000
Change in Unrealized Gain (Loss), instruments still held, asset	[3]	137,000		255,000
Balance Asset Value		1,921,000		2,175,000
Lehman claims, at fair value
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance Asset Value		380,000		378,000
Asset, Transfers In		0		0
Asset, Transfers Out		0		0
Purchases/(covers)		0		0
(Sales)/short buys		0		(76,000)
Realized and unrealized gains (losses), asset		(81,000)		78,000
Change in Unrealized Gain (Loss), instruments still held, asset	[3]	(81,000)		79,000
Balance Asset Value		299,000		380,000
Consolidated Funds | Preferred Stock
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance Asset Value		0
Asset, Transfers In	[2]	7,000,000
Asset, Transfers Out		0
Purchases/(covers)		25,000,000
(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		32,000,000		0
Consolidated Funds | Lehman claims, at fair value
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance Asset Value		493,000		4,842,000
Asset, Transfers In		0		0
Asset, Transfers Out		0		0
Purchases/(covers)		0		0
(Sales)/short buys		(739,000)		(4,711,000)
Realized and unrealized gains (losses), asset		246,000		362,000
Change in Unrealized Gain (Loss), instruments still held, asset	[3]	0		(3,897,000)
Balance Asset Value		0		493,000
Options, liability
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance Liability Value		36,807,000		0
Liability, Transfers In		0		0
Liability, Transfers Out		0		0
Liability, Purchases		0		35,710,000
Liability, Sales		0		0
Realized and unrealized gains (losses), liability		(18,613,000)		1,097,000
Change in Unrealized Gain (Loss), instruments still held, liabilities	[3]	(18,613,000)		1,097,000
Balance Liability Value		18,194,000		36,807,000
Contingent liability payable
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance Liability Value		4,083,000		6,937,000
Liability, Transfers In		0		0
Liability, Transfers Out		0		0
Liability, Purchases		3,600,000		21,000
Liability, Sales		(1,725,000)		(820,000)
Realized and unrealized gains (losses), liability		200,000		(2,055,000)
Change in Unrealized Gain (Loss), instruments still held, liabilities	[3]	200,000		0
Balance Liability Value		$ 6,158,000		$ 4,083,000

[1] The company completed an initial public offering.

[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.

[4] The investment was converted to equity.