Fair Value Measurements for Operating Entities and Consolidated Funds Assets and Liabilities at Fair Value on a Recurring Basis (Details) - USD ($) $ in Thousands		Dec. 31, 2019		Dec. 31, 2018		Dec. 31, 2017
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities sold, not yet purchased, at fair value		$ 451,836		$ 195,307
Securities sold, not yet purchased, at fair value		451,836		195,307
Derivative Liability		60,761		16,082
Derivative Asset		62,977		25,125
Business Combination, Contingent Consideration, Liability		30,896		3,070
Business Combination, Contingent Consideration Arrangements, Range of Outcomes, Value, Low		1,300		2,800
Business Combination, Contingent Consideration Arrangements, Range of Outcomes, Value, High		40,000		3,400
Other investments		185,722		181,407
Other Investments, Consolidated Funds		175,769		186,395
Investments		$ 2,439,131		$ 1,105,864
Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Percentage of Total Assets at Fair Value		95.90%		86.60%
Percentage of Total Liabilities at Fair Value		87.30%		95.60%
Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Percentage of Total Assets at Fair Value		1.70%		6.00%
Percentage of Total Liabilities at Fair Value		6.00%		2.00%
Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Balance Liability Value		$ 36,766		$ 5,166
Percentage of Total Assets at Fair Value		2.30%		7.40%
Percentage of Total Liabilities at Fair Value		6.70%		2.40%
Contingent liability payable
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Balance Liability Value		$ 30,896		$ 3,070		$ 3,440
Futures
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Liability		217		0
Derivative Asset		0		334
Swaps
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Liability		23,169		2,162
Derivative Asset		2,911		917
Options
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Asset	[1]	60,066		23,130
Pay to hold
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Asset		0		743
Corporate Bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Balance Liability Value		1,000		0
Portfolio Funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other investments		114,504	[2]	124,741	[3]
Other Investments, Consolidated Funds		175,769	[2]	186,395	[3]
Carried interest [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other investments		30,360	[2]	17,995	[3]
Equity Method Investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other investments		40,858		38,671
Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment Sold, Not yet Purchased and Derivative Liability, at Fair Value		548,262		216,122
Assets, Fair Value Disclosure, Recurring (Deprecated 2018-01-31)		2,077,640		738,062
Fair Value, Measurements, Recurring | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment Sold, Not yet Purchased and Derivative Liability, at Fair Value		478,524		206,526
Assets, Fair Value Disclosure, Recurring (Deprecated 2018-01-31)		1,993,268		638,837
Fair Value, Measurements, Recurring | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment Sold, Not yet Purchased and Derivative Liability, at Fair Value		32,972		4,430
Assets, Fair Value Disclosure, Recurring (Deprecated 2018-01-31)		35,940		44,311
Fair Value, Measurements, Recurring | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment Sold, Not yet Purchased and Derivative Liability, at Fair Value		36,766		5,166
Assets, Fair Value Disclosure, Recurring (Deprecated 2018-01-31)		48,432		54,914
Fair Value, Measurements, Recurring | Preferred Stock
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities sold, not yet purchased, at fair value		3,686		199
Fair Value, Measurements, Recurring | Preferred Stock | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities sold, not yet purchased, at fair value		3,686		199
Fair Value, Measurements, Recurring | Preferred Stock | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities sold, not yet purchased, at fair value		0		0
Fair Value, Measurements, Recurring | Preferred Stock | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities sold, not yet purchased, at fair value		0		0
Fair Value, Measurements, Recurring | Common Stock
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities sold, not yet purchased, at fair value		425,448		194,305
Fair Value, Measurements, Recurring | Common Stock | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities sold, not yet purchased, at fair value		425,448		194,305
Fair Value, Measurements, Recurring | Common Stock | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities sold, not yet purchased, at fair value		0		0
Fair Value, Measurements, Recurring | Common Stock | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities sold, not yet purchased, at fair value		0		0
Fair Value, Measurements, Recurring | Corporate Bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities sold, not yet purchased, at fair value		5,933		750
Fair Value, Measurements, Recurring | Corporate Bonds | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities sold, not yet purchased, at fair value		0		0
Fair Value, Measurements, Recurring | Corporate Bonds | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities sold, not yet purchased, at fair value		4,933		750
Fair Value, Measurements, Recurring | Corporate Bonds | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities sold, not yet purchased, at fair value		1,000		0
Fair Value, Measurements, Recurring | Warrants and Rights
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities sold, not yet purchased, at fair value		14,819		53
Fair Value, Measurements, Recurring | Warrants and Rights | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities sold, not yet purchased, at fair value		14,819		53
Fair Value, Measurements, Recurring | Warrants and Rights | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities sold, not yet purchased, at fair value		0		0
Fair Value, Measurements, Recurring | Warrants and Rights | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities sold, not yet purchased, at fair value		0		0
Fair Value, Measurements, Recurring | Contingent liability payable
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Business Combination, Contingent Consideration, Liability		30,896	[4]	3,070
Fair Value, Measurements, Recurring | Contingent liability payable | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Business Combination, Contingent Consideration, Liability		0	[4]	0	[5]
Fair Value, Measurements, Recurring | Contingent liability payable | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Business Combination, Contingent Consideration, Liability		0	[4]	0	[5]
Fair Value, Measurements, Recurring | Contingent liability payable | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Business Combination, Contingent Consideration, Liability		30,896	[4]	3,070	[5]
Fair Value, Measurements, Recurring | Futures | Options
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Liability		217
Fair Value, Measurements, Recurring | Futures | Options | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Liability		217
Fair Value, Measurements, Recurring | Futures | Options | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Liability		0
Fair Value, Measurements, Recurring | Futures | Options | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Liability		0
Fair Value, Measurements, Recurring | Currency forward
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Asset				1
Fair Value, Measurements, Recurring | Currency forward | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Asset				0
Fair Value, Measurements, Recurring | Currency forward | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Asset				1
Fair Value, Measurements, Recurring | Currency forward | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Asset				0
Fair Value, Measurements, Recurring | Currency forward | Options
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Liability		851		709
Fair Value, Measurements, Recurring | Currency forward | Options | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Liability		0		0
Fair Value, Measurements, Recurring | Currency forward | Options | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Liability		851		709
Fair Value, Measurements, Recurring | Currency forward | Options | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Liability		0		0
Fair Value, Measurements, Recurring | Swaps
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Asset		2,911
Fair Value, Measurements, Recurring | Swaps | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Asset		0
Fair Value, Measurements, Recurring | Swaps | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Asset		2,911
Fair Value, Measurements, Recurring | Swaps | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Asset		0
Fair Value, Measurements, Recurring | Swaps | Options
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Liability		23,169		2,162
Fair Value, Measurements, Recurring | Swaps | Options | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Liability		0		0
Fair Value, Measurements, Recurring | Swaps | Options | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Liability		23,169		2,162
Fair Value, Measurements, Recurring | Swaps | Options | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Liability		0		0
Fair Value, Measurements, Recurring | Options
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Asset		60,066
Fair Value, Measurements, Recurring | Options | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Asset		59,730
Fair Value, Measurements, Recurring | Options | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Asset		0
Fair Value, Measurements, Recurring | Options | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Asset		336
Fair Value, Measurements, Recurring | Options | Options
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Liability		36,524		13,211
Fair Value, Measurements, Recurring | Options | Options | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Liability		33,604		11,115
Fair Value, Measurements, Recurring | Options | Options | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Liability		0		0
Fair Value, Measurements, Recurring | Options | Options | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Liability				2,096
Fair Value, Measurements, Recurring | Pay to hold
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Asset				743
Fair Value, Measurements, Recurring | Pay to hold | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Asset				0
Fair Value, Measurements, Recurring | Pay to hold | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Asset				743
Fair Value, Measurements, Recurring | Pay to hold | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Asset				0
Fair Value, Measurements, Recurring | Government Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Securities, Trading		15,916		13,398
Fair Value, Measurements, Recurring | Government Securities | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Securities, Trading		15,916		13,398
Fair Value, Measurements, Recurring | Government Securities | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Securities, Trading		0		0
Fair Value, Measurements, Recurring | Government Securities | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Securities, Trading		0		0
Fair Value, Measurements, Recurring | Preferred Stock
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading Securities, Equity		12,656		5,617
Fair Value, Measurements, Recurring | Preferred Stock | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading Securities, Equity		4,821		449
Fair Value, Measurements, Recurring | Preferred Stock | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading Securities, Equity		0		0
Fair Value, Measurements, Recurring | Preferred Stock | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading Securities, Equity		7,835		5,168
Fair Value, Measurements, Recurring | Common Stock
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading Securities, Equity		1,546,484		472,299
Fair Value, Measurements, Recurring | Common Stock | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading Securities, Equity		1,527,769		459,601
Fair Value, Measurements, Recurring | Common Stock | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading Securities, Equity		1,249		2,848
Fair Value, Measurements, Recurring | Common Stock | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading Securities, Equity		17,466		9,850
Fair Value, Measurements, Recurring | Corporate Bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Securities, Trading		25,500		13,041
Fair Value, Measurements, Recurring | Corporate Bonds | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Securities, Trading		0		0
Fair Value, Measurements, Recurring | Corporate Bonds | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Securities, Trading		23,079		13,041
Fair Value, Measurements, Recurring | Corporate Bonds | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Securities, Trading		2,421		0
Fair Value, Measurements, Recurring | Convertible Bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Securities, Trading		2,500		3,000
Fair Value, Measurements, Recurring | Convertible Bonds | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Securities, Trading		0		0
Fair Value, Measurements, Recurring | Convertible Bonds | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Securities, Trading		0		0
Fair Value, Measurements, Recurring | Convertible Bonds | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Securities, Trading		2,500		3,000
Fair Value, Measurements, Recurring | Trade Claims
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Securities, Trading		7,320		5,543
Fair Value, Measurements, Recurring | Trade Claims | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Securities, Trading		0		0
Fair Value, Measurements, Recurring | Trade Claims | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Securities, Trading		0		0
Fair Value, Measurements, Recurring | Trade Claims | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Securities, Trading		7,320		5,543
Fair Value, Measurements, Recurring | Warrants and Rights
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading Securities, Equity		22,109		7,990
Fair Value, Measurements, Recurring | Warrants and Rights | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading Securities, Equity		21,515		6,324
Fair Value, Measurements, Recurring | Warrants and Rights | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading Securities, Equity		0		0
Fair Value, Measurements, Recurring | Warrants and Rights | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading Securities, Equity		594		1,666
Fair Value, Measurements, Recurring | Derivative Assets | Futures
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Asset				334
Fair Value, Measurements, Recurring | Derivative Assets | Futures | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Asset				334
Fair Value, Measurements, Recurring | Derivative Assets | Futures | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Asset				0
Fair Value, Measurements, Recurring | Derivative Assets | Futures | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Asset				0
Fair Value, Measurements, Recurring | Derivative Assets | Swaps
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Asset				917
Fair Value, Measurements, Recurring | Derivative Assets | Swaps | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Asset				0
Fair Value, Measurements, Recurring | Derivative Assets | Swaps | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Asset				917
Fair Value, Measurements, Recurring | Derivative Assets | Swaps | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Asset				0
Fair Value, Measurements, Recurring | Derivative Assets | Options
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Asset				23,130
Fair Value, Measurements, Recurring | Derivative Assets | Options | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Asset				23,130
Fair Value, Measurements, Recurring | Derivative Assets | Options | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Asset				0
Fair Value, Measurements, Recurring | Derivative Assets | Options | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Asset				0
Fair Value, Measurements, Recurring | Term loan
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Securities, Trading		1,067
Fair Value, Measurements, Recurring | Term loan | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Securities, Trading		0
Fair Value, Measurements, Recurring | Term loan | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Securities, Trading		1,067
Fair Value, Measurements, Recurring | Term loan | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Securities, Trading		0
Fair Value, Measurements, Recurring | Operating Companies [Member] | US Government Debt Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities sold, not yet purchased, at fair value		1,950
Fair Value, Measurements, Recurring | Operating Companies [Member] | US Government Debt Securities | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities sold, not yet purchased, at fair value		0
Fair Value, Measurements, Recurring | Operating Companies [Member] | US Government Debt Securities | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities sold, not yet purchased, at fair value		0
Fair Value, Measurements, Recurring | Operating Companies [Member] | US Government Debt Securities | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities sold, not yet purchased, at fair value		1,950
Fair Value, Measurements, Recurring | Consolidated Funds | Currency forward | Options
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Liability		88		96
Fair Value, Measurements, Recurring | Consolidated Funds | Currency forward | Options | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Liability		0		0
Fair Value, Measurements, Recurring | Consolidated Funds | Currency forward | Options | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Liability		88		96
Fair Value, Measurements, Recurring | Consolidated Funds | Currency forward | Options | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Liability		0		0
Fair Value, Measurements, Recurring | Consolidated Funds | Equity Swap | Options
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Liability		3,931		713
Fair Value, Measurements, Recurring | Consolidated Funds | Equity Swap | Options | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Liability		0		0
Fair Value, Measurements, Recurring | Consolidated Funds | Equity Swap | Options | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Liability		3,931		713
Fair Value, Measurements, Recurring | Consolidated Funds | Equity Swap | Options | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Liability		0		0
Fair Value, Measurements, Recurring | Consolidated Funds | Options | Options
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Liability		750		854
Fair Value, Measurements, Recurring | Consolidated Funds | Options | Options | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Liability		750		854
Fair Value, Measurements, Recurring | Consolidated Funds | Options | Options | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Liability		0		0
Fair Value, Measurements, Recurring | Consolidated Funds | Options | Options | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Liability		0		0
Fair Value, Measurements, Recurring | Consolidated Funds | Government Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Securities, Trading		161,607		38,377
Fair Value, Measurements, Recurring | Consolidated Funds | Government Securities | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Securities, Trading		161,607		38,377
Fair Value, Measurements, Recurring | Consolidated Funds | Government Securities | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Securities, Trading		0		0
Fair Value, Measurements, Recurring | Consolidated Funds | Government Securities | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Securities, Trading		0		0
Fair Value, Measurements, Recurring | Consolidated Funds | Preferred Stock
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading Securities, Equity		4,393		24,314
Fair Value, Measurements, Recurring | Consolidated Funds | Preferred Stock | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading Securities, Equity		0		0
Fair Value, Measurements, Recurring | Consolidated Funds | Preferred Stock | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading Securities, Equity		0		0
Fair Value, Measurements, Recurring | Consolidated Funds | Preferred Stock | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading Securities, Equity		4,393		24,314
Fair Value, Measurements, Recurring | Consolidated Funds | Common Stock
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading Securities, Equity		200,306		95,565
Fair Value, Measurements, Recurring | Consolidated Funds | Common Stock | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading Securities, Equity		200,306		95,471
Fair Value, Measurements, Recurring | Consolidated Funds | Common Stock | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading Securities, Equity		0		0
Fair Value, Measurements, Recurring | Consolidated Funds | Common Stock | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading Securities, Equity		0		94
Fair Value, Measurements, Recurring | Consolidated Funds | Corporate Bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Securities, Trading		3,405		24,098
Fair Value, Measurements, Recurring | Consolidated Funds | Corporate Bonds | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Securities, Trading		0		0
Fair Value, Measurements, Recurring | Consolidated Funds | Corporate Bonds | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Securities, Trading		3,405		24,098
Fair Value, Measurements, Recurring | Consolidated Funds | Corporate Bonds | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Securities, Trading		0		0
Fair Value, Measurements, Recurring | Consolidated Funds | Warrants and Rights
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading Securities, Equity		5,567		5,279
Fair Value, Measurements, Recurring | Consolidated Funds | Warrants and Rights | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading Securities, Equity		0		0
Fair Value, Measurements, Recurring | Consolidated Funds | Warrants and Rights | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading Securities, Equity		0		0
Fair Value, Measurements, Recurring | Consolidated Funds | Warrants and Rights | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading Securities, Equity		5,567		5,279
Fair Value, Measurements, Recurring | Consolidated Funds | Derivative Assets | Currency forward
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Asset		3,302		186
Fair Value, Measurements, Recurring | Consolidated Funds | Derivative Assets | Currency forward | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Asset		0		0
Fair Value, Measurements, Recurring | Consolidated Funds | Derivative Assets | Currency forward | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Asset		3,302		186
Fair Value, Measurements, Recurring | Consolidated Funds | Derivative Assets | Currency forward | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Asset		0		0
Fair Value, Measurements, Recurring | Consolidated Funds | Derivative Assets | Equity Swap
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Asset		927		2,477
Fair Value, Measurements, Recurring | Consolidated Funds | Derivative Assets | Equity Swap | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Asset		0		0
Fair Value, Measurements, Recurring | Consolidated Funds | Derivative Assets | Equity Swap | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Asset		927		2,477
Fair Value, Measurements, Recurring | Consolidated Funds | Derivative Assets | Equity Swap | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Asset		0		0
Fair Value, Measurements, Recurring | Consolidated Funds | Derivative Assets | Options
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Asset		1,604		1,753
Fair Value, Measurements, Recurring | Consolidated Funds | Derivative Assets | Options | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Asset		1,604		1,753
Fair Value, Measurements, Recurring | Consolidated Funds | Derivative Assets | Options | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Asset		0		0
Fair Value, Measurements, Recurring | Consolidated Funds | Derivative Assets | Options | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Asset		$ 0		$ 0

[1] Includes the volume of contracts for index, equity, commodity future and cash conversion options.

[2] In accordance with US GAAP, certain investments are measured at fair value using the net asset value per share (or its equivalent) as a practical expedient. Carried interest in portfolio funds have not been classified in the fair value hierarchy. The fair value amounts presented in this table are intended to permit reconciliation of the fair value hierarchy to the amounts presented in the consolidated statement of financial condition.

[3] In accordance with US GAAP, certain investments are measured at fair value using the net asset value per share (or its equivalent) as a practical expedient. Carried interest in portfolio funds have not been classified in the fair value hierarchy. The fair value amounts presented in this table are intended to permit reconciliation of the fair value hierarchy to the amounts presented in the consolidated statement of financial condition.

[4] In accordance with the terms of the purchase agreements for acquisitions that closed during the second quarter of 2016 and the first quarter of 2019, the Company is required to pay to the sellers a portion of future net income and/or revenues of the acquired businesses, if certain targets are achieved through the periods ended December 31, 2019 and December 31, 2023, respectively. For the acquisition that closed during 2016, the Company estimated the contingent consideration liability using the income approach (discounted cash flow method) which requires the Company to make estimates and assumptions regarding the future cash flows and profits. For the acquisition that closed during 2019, the Company estimated the contingent consideration liability using the present value of the Monte Carlo simulated revenue. Changes in these estimates and assumptions could have a significant impact on the amounts recognized. The undiscounted amounts as of December 31, 2019 can range from $1.3 million to $40.0 million.

[5] In accordance with the terms of the purchase agreements for the acquisition that closed during the second quarter of 2016, the Company is required to pay to the sellers a portion of future net income and/or revenues of the acquired business, if certain targets are achieved through the periods ended December 31, 2020. The Company estimated the contingent consideration liability using the income approach (discounted cash flow method) which requires the Company to make estimates and assumptions regarding the future cash flows and profits. Changes in these estimates and assumptions could have a significant impact on the amounts recognized. The undiscounted amounts as of December 31, 2018 can range from $2.8 million to $3.4 million.