Fair Value Measurements for Operating Entities and Consolidated Funds - Unobservable Input Roll Forward (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2021		Dec. 31, 2020		Dec. 31, 2019
Preferred Stock
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance Asset Value		$ 122,631		$ 59,967		$ 7,835
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3		0		45,530	[1]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers out of Level 3		1,531	[2]	1,653	[3]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases		75,562		5,891
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Sales		9,828		4,993
Realized and unrealized gains (losses), asset		(1,539)		7,357
Change in Unrealized Gain (Loss), instruments still held, asset	[4]	(2,570)		10,846
Common Stock
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance Asset Value		32,658		23,786		17,466
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3		3,409	[5]	102	[6]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers out of Level 3		7,357	[2],[7]	29	[8],[9]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases		19,072		7,138
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Sales		13,582		3,818
Realized and unrealized gains (losses), asset		7,330		2,927
Change in Unrealized Gain (Loss), instruments still held, asset	[4]	5,517		1,990
Convertible Bonds
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance Asset Value		5,250		6,040		2,500
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3		0		0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers out of Level 3		4,031	[7]	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases		11,802		3,787
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Sales		11,159		1,050
Realized and unrealized gains (losses), asset		2,598		803
Change in Unrealized Gain (Loss), instruments still held, asset	[4]	(975)		803
Corporate Bonds
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance Asset Value		2,419		135		2,421
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3		0		0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers out of Level 3		0		312	[3]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases		2,414		666
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Sales		103		2,432
Realized and unrealized gains (losses), asset		(27)		(208)
Change in Unrealized Gain (Loss), instruments still held, asset	[4]	6		(180)
Options (held long)
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance Asset Value		234		251		336
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3		0		0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers out of Level 3		0		(102)	[6]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases		0		0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Sales		0		0
Realized and unrealized gains (losses), asset		(17)		17
Change in Unrealized Gain (Loss), instruments still held, asset	[4]	(17)		(1)
Warrants and Rights
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance Asset Value		15,403		6,547		594
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3		3,806	[5],[9]	4,528	[1],[8]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers out of Level 3		0		0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases		10,706		0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Sales		1,610		0
Realized and unrealized gains (losses), asset		(4,046)		1,425
Change in Unrealized Gain (Loss), instruments still held, asset	[4]	(2,812)		1,425
Trade Claims
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance Asset Value		3,496		8,713		7,083
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3		0		1,044	[8],[9]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers out of Level 3		1,389	[9]	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases		3,056		4,283
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Sales		5,254		2,944
Realized and unrealized gains (losses), asset		(1,630)		(753)
Change in Unrealized Gain (Loss), instruments still held, asset	[4]	(2,698)		(777)
Term Loans
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance Asset Value		0		12,623		0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3		0		11,149	[1]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers out of Level 3		0		0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases		638		245
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Sales		12,162		0
Realized and unrealized gains (losses), asset		(1,099)		1,229
Change in Unrealized Gain (Loss), instruments still held, asset		0	[4]	1,229
Private Investments
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance Asset Value		410		642		237
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3		0		0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers out of Level 3		0		0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases		707		641
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Sales		1,153		0
Realized and unrealized gains (losses), asset		214		(236)
Change in Unrealized Gain (Loss), instruments still held, asset		0		(236)
Consolidated Funds | Preferred Stock
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance Asset Value				0		4,393
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3				0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers out of Level 3	[10]			4,000
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases				0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Sales				0
Realized and unrealized gains (losses), asset				(393)
Change in Unrealized Gain (Loss), instruments still held, asset	[4]			0
Consolidated Funds | Common Stock
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance Asset Value		0		2,951		0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3		(4,000)	[5]	4,000	[10]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers out of Level 3		0		100,000	[7]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases		0		100,000
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Sales		0		0
Realized and unrealized gains (losses), asset		1,049		(1,049)
Change in Unrealized Gain (Loss), instruments still held, asset	[4]	0		(1,049)
Consolidated Funds | Convertible Bonds
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance Asset Value				0		0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3				0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers out of Level 3	[7]			76,114
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases				75,000
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Sales				0
Realized and unrealized gains (losses), asset				1,114
Change in Unrealized Gain (Loss), instruments still held, asset	[4]			0
Consolidated Funds | Warrants and Rights
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance Asset Value		0		5,806		5,567
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3		0		0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers out of Level 3		0		0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases		0		0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Sales		4,447		0
Realized and unrealized gains (losses), asset		(1,359)		239
Change in Unrealized Gain (Loss), instruments still held, asset	[4]	0		239
Options (held short)
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance Liability Value		3,419		3,915		2,920
Liability, Transfers In		0		0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Liability, Transfers out of Level 3		0		0
Liability, Purchases		0		0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Sales		0		0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Gain (Loss) Included in Earnings		496		(995)
Fair Value, Liability, Recurring Basis, Still Held, Unrealized Gain (Loss)	[4]	(496)		995
Contingent liability payable
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance Liability Value		62,223		36,718		30,896
Liability, Transfers In		0		0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Liability, Transfers out of Level 3		0		1,235	[11]
Liability, Purchases		20,729		4,218
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Sales		10,077		5,653
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Gain (Loss) Included in Earnings		(14,853)		(8,492)
Fair Value, Liability, Recurring Basis, Still Held, Unrealized Gain (Loss)	[4]	14,853		8,492
Corporate Bonds
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance Asset Value				704
Balance Liability Value		0		704		1,000
Liability, Transfers In		0		0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Liability, Transfers out of Level 3		0		0
Liability, Purchases		0		0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Sales		(399)		0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Gain (Loss) Included in Earnings		(305)		(296)
Fair Value, Liability, Recurring Basis, Still Held, Unrealized Gain (Loss)	[4]	0		(248)
Government Debt Securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance Asset Value				1,500
Balance Liability Value		0		1,500		$ 1,950
Liability, Transfers In		0		0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Liability, Transfers out of Level 3		0		0
Liability, Purchases		0		0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Sales		(1,569)		0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Gain (Loss) Included in Earnings		69		(450)
Fair Value, Liability, Recurring Basis, Still Held, Unrealized Gain (Loss)	[4]	$ 0		$ (450)

[1] The company consolidated an operating entity which holds preferred stock, loans and warrants.

[2] The entity in which the Company is invested completed an initial public offering

[3] The investments were converted to common stock.

[4] Unrealized gains/losses are reported in Investment income - Securities principal transactions, net in the accompanying consolidated statements of operations

[5] Fair market value derived using models and private transaction levels.

[6] The options expired and converted into common stock.

[7] The Company deconsolidated an investment fund.    

[8] The security stopped trading on an open market.

[9] The transfers between level 1, level 2 and level 3 are due to the change in the availability of observable inputs.

[10] The investment was involved in a reverse merger and preferred stock was converted to common shares.

[11] The contingent liability reached the end of its earnout period and is now valued based on actual cash payout.