Fair Value Measurements for Operating Entities and Consolidated Funds Unobservable Input Roll Forward (Details) - USD ($)		3 Months Ended
		Mar. 31, 2016	Mar. 31, 2015
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance Asset Value		$ 70,034,000
Balance Liability Value		24,352,000
Balance Asset Value		71,851,000
Balance Liability Value		29,185,000
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		12,872,000	$ 12,517,000
Asset, Transfers In		0	0
Asset, Transfers Out		0	0
Purchases/(covers)		0	7,375,000
(Sales)/short buys		(218,000)	0
Realized and unrealized gains (losses), asset		992,000	(412,000)
Change in Unrealized Gain (Loss), instruments still held, asset	[1]	566,000	(412,000)
Balance Asset Value		13,646,000	19,480,000
Common Stock
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance Asset Value		3,278,000	412,000
Asset, Transfers In		0	0
Asset, Transfers Out		0	0
Purchases/(covers)		1,069,000	0
(Sales)/short buys		0	(3,000)
Realized and unrealized gains (losses), asset		1,918,000	2,000
Change in Unrealized Gain (Loss), instruments still held, asset	[1]	2,054,000	5,000
Balance Asset Value		6,265,000	411,000
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	0
(Sales)/short buys		(569,000)	0
Realized and unrealized gains (losses), asset		0	(21,000)
Change in Unrealized Gain (Loss), instruments still held, asset	[1]	0	(21,000)
Balance Asset Value		250,000	879,000
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		2,698,000	4,835,000
Change in Unrealized Gain (Loss), instruments still held, asset	[1]	2,698,000	4,835,000
Balance Asset Value		20,892,000	41,642,000
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	(14,000)	[2]
Purchases/(covers)		0	26,000
(Sales)/short buys		0	0
Realized and unrealized gains (losses), asset		(67,000)	1,225,000
Change in Unrealized Gain (Loss), instruments still held, asset	[1]	150,000	1,224,000
Balance Asset Value		2,505,000	2,559,000
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		(6,000)	(19,000)
Change in Unrealized Gain (Loss), instruments still held, asset	[1]	(6,000)	(19,000)
Balance Asset Value		293,000	361,000
Consolidated Funds | Preferred Stock
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance Asset Value		$ 32,000,000
Asset, Transfers In
Asset, Transfers Out	[2]	$ (4,000,000)
Purchases/(covers)		0
(Sales)/short buys		0
Realized and unrealized gains (losses), asset		0
Change in Unrealized Gain (Loss), instruments still held, asset	[1]	0
Balance Asset Value		28,000,000
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
Asset, Transfers In			0
Asset, Transfers Out			0
Purchases/(covers)			0
(Sales)/short buys			0
Realized and unrealized gains (losses), asset			1,000
Change in Unrealized Gain (Loss), instruments still held, asset	[1]		1,000
Balance Asset Value			494,000
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		2,698,000	4,835,000
Change in Unrealized Gain (Loss), instruments still held, liabilities	[1]	2,698,000	4,835,000
Balance Liability Value		20,892,000	41,642,000
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			0
Liability, Sales			(109,000)
Realized and unrealized gains (losses), liability		$ 2,135,000	0
Change in Unrealized Gain (Loss), instruments still held, liabilities	[1]	2,135,000	0
Balance Liability Value		$ 8,293,000	$ 3,974,000

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

[2] The investment was converted to equity.