Fair Value Measurements for Operating Entities and Consolidated Funds - Assets and Liabilities at Fair Value on a Recurring Basis (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2012	Jun. 30, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Dec. 31, 2010
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities sold, not yet purchased, at fair value	$ 210,705		$ 334,251
Operating Companies [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments at fair value	8,058
Operating Companies [Member] | Fair Value, Measurements, Recurring [Member] | Total Estimated Fair Value [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets at fair value	699,993		788,977
Liabilities at fair value	210,827		335,008
Operating Companies [Member] | Fair Value, Measurements, Recurring [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets at fair value	420,240		491,607
Liabilities at fair value	210,745		333,337
Operating Companies [Member] | Fair Value, Measurements, Recurring [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets at fair value	249,375		274,942
Liabilities at fair value	82		1,671
Operating Companies [Member] | Fair Value, Measurements, Recurring [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets at fair value	30,378		22,428
Liabilities at fair value	0		0
Operating Companies [Member] | Fair Value, Measurements, Recurring [Member] | US Government Securities [Member] | Total Estimated Fair Value [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities sold, not yet purchased, at fair value	8		165,197
Operating Companies [Member] | Fair Value, Measurements, Recurring [Member] | US Government Securities [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities sold, not yet purchased, at fair value	8		165,197
Operating Companies [Member] | Fair Value, Measurements, Recurring [Member] | US Government Securities [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities sold, not yet purchased, at fair value	0		0
Operating Companies [Member] | Fair Value, Measurements, Recurring [Member] | US Government Securities [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities sold, not yet purchased, at fair value	0		0
Operating Companies [Member] | Fair Value, Measurements, Recurring [Member] | Corporate Bonds [Member] | Total Estimated Fair Value [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities sold, not yet purchased, at fair value	61		1,529
Operating Companies [Member] | Fair Value, Measurements, Recurring [Member] | Corporate Bonds [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities sold, not yet purchased, at fair value	0		0
Operating Companies [Member] | Fair Value, Measurements, Recurring [Member] | Corporate Bonds [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities sold, not yet purchased, at fair value	61		1,529
Operating Companies [Member] | Fair Value, Measurements, Recurring [Member] | Corporate Bonds [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities sold, not yet purchased, at fair value	0		0
Operating Companies [Member] | Fair Value, Measurements, Recurring [Member] | Common Stocks [Member] | Total Estimated Fair Value [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities sold, not yet purchased, at fair value	195,911		123,877
Operating Companies [Member] | Fair Value, Measurements, Recurring [Member] | Common Stocks [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities sold, not yet purchased, at fair value	195,911		123,875
Operating Companies [Member] | Fair Value, Measurements, Recurring [Member] | Common Stocks [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities sold, not yet purchased, at fair value	0		2
Operating Companies [Member] | Fair Value, Measurements, Recurring [Member] | Common Stocks [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities sold, not yet purchased, at fair value	0	0	0	0	0	0
Operating Companies [Member] | Fair Value, Measurements, Recurring [Member] | Warrants and Rights [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities sold, not yet purchased, at fair value	0	3	0	0	0	0
Operating Companies [Member] | Fair Value, Measurements, Recurring [Member] | Futures [Member] | Derivative Liabilities [Member] | Total Estimated Fair Value [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liabilities	101		617
Operating Companies [Member] | Fair Value, Measurements, Recurring [Member] | Futures [Member] | Derivative Liabilities [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liabilities	101		617
Operating Companies [Member] | Fair Value, Measurements, Recurring [Member] | Futures [Member] | Derivative Liabilities [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liabilities	0		0
Operating Companies [Member] | Fair Value, Measurements, Recurring [Member] | Futures [Member] | Derivative Liabilities [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liabilities	0		0
Operating Companies [Member] | Fair Value, Measurements, Recurring [Member] | Equity Swap [Member] | Derivative Liabilities [Member] | Total Estimated Fair Value [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liabilities			140
Operating Companies [Member] | Fair Value, Measurements, Recurring [Member] | Equity Swap [Member] | Derivative Liabilities [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liabilities			0
Operating Companies [Member] | Fair Value, Measurements, Recurring [Member] | Equity Swap [Member] | Derivative Liabilities [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liabilities			140
Operating Companies [Member] | Fair Value, Measurements, Recurring [Member] | Equity Swap [Member] | Derivative Liabilities [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liabilities			0
Operating Companies [Member] | Fair Value, Measurements, Recurring [Member] | Forward Contracts [Member] | Derivative Liabilities [Member] | Total Estimated Fair Value [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liabilities	21
Operating Companies [Member] | Fair Value, Measurements, Recurring [Member] | Forward Contracts [Member] | Derivative Liabilities [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liabilities	0
Operating Companies [Member] | Fair Value, Measurements, Recurring [Member] | Forward Contracts [Member] | Derivative Liabilities [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liabilities	21
Operating Companies [Member] | Fair Value, Measurements, Recurring [Member] | Forward Contracts [Member] | Derivative Liabilities [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liabilities	0
Operating Companies [Member] | Fair Value, Measurements, Recurring [Member] | Options [Member] | Derivative Liabilities [Member] | Total Estimated Fair Value [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liabilities	14,725		43,648
Operating Companies [Member] | Fair Value, Measurements, Recurring [Member] | Options [Member] | Derivative Liabilities [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liabilities	14,725		43,648
Operating Companies [Member] | Fair Value, Measurements, Recurring [Member] | Options [Member] | Derivative Liabilities [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liabilities	0		0
Operating Companies [Member] | Fair Value, Measurements, Recurring [Member] | Options [Member] | Derivative Liabilities [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liabilities	0		0
Operating Companies [Member] | Fair Value, Measurements, Recurring [Member] | US Government Securities [Member] | Total Estimated Fair Value [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments at fair value	95,038		182,868
Operating Companies [Member] | Fair Value, Measurements, Recurring [Member] | US Government Securities [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments at fair value	95,038		182,868
Operating Companies [Member] | Fair Value, Measurements, Recurring [Member] | US Government Securities [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments at fair value	0		0
Operating Companies [Member] | Fair Value, Measurements, Recurring [Member] | US Government Securities [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments at fair value	0		0
Operating Companies [Member] | Fair Value, Measurements, Recurring [Member] | Convertible Bonds [Member] | Total Estimated Fair Value [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments at fair value	50,854		18,130
Operating Companies [Member] | Fair Value, Measurements, Recurring [Member] | Convertible Bonds [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments at fair value	0		0
Operating Companies [Member] | Fair Value, Measurements, Recurring [Member] | Convertible Bonds [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments at fair value	50,854		18,130
Operating Companies [Member] | Fair Value, Measurements, Recurring [Member] | Convertible Bonds [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments at fair value	0		0
Operating Companies [Member] | Fair Value, Measurements, Recurring [Member] | Corporate Bonds [Member] | Total Estimated Fair Value [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments at fair value	168,021		231,864
Operating Companies [Member] | Fair Value, Measurements, Recurring [Member] | Corporate Bonds [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments at fair value	0		0
Operating Companies [Member] | Fair Value, Measurements, Recurring [Member] | Corporate Bonds [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments at fair value	168,021		231,864
Operating Companies [Member] | Fair Value, Measurements, Recurring [Member] | Corporate Bonds [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments at fair value	0		0
Operating Companies [Member] | Fair Value, Measurements, Recurring [Member] | Common Stocks [Member] | Total Estimated Fair Value [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments at fair value	300,990		250,380
Operating Companies [Member] | Fair Value, Measurements, Recurring [Member] | Common Stocks [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments at fair value	297,987		248,598
Operating Companies [Member] | Fair Value, Measurements, Recurring [Member] | Common Stocks [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments at fair value	43		713
Operating Companies [Member] | Fair Value, Measurements, Recurring [Member] | Common Stocks [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments at fair value	2,960	959	1,069	812	953	334
Operating Companies [Member] | Fair Value, Measurements, Recurring [Member] | Warrants and Rights [Member] | Total Estimated Fair Value [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments at fair value	4,436		2,759
Operating Companies [Member] | Fair Value, Measurements, Recurring [Member] | Warrants and Rights [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments at fair value	374		1,225
Operating Companies [Member] | Fair Value, Measurements, Recurring [Member] | Warrants and Rights [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments at fair value	0		0
Operating Companies [Member] | Fair Value, Measurements, Recurring [Member] | Warrants and Rights [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments at fair value	4,062	2,844	1,534	1,354	3,534	1,977
Operating Companies [Member] | Fair Value, Measurements, Recurring [Member] | Mutual Funds [Member] | Total Estimated Fair Value [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments at fair value	2,890		3,214
Operating Companies [Member] | Fair Value, Measurements, Recurring [Member] | Mutual Funds [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments at fair value	2,890		3,214
Operating Companies [Member] | Fair Value, Measurements, Recurring [Member] | Mutual Funds [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments at fair value	0		0
Operating Companies [Member] | Fair Value, Measurements, Recurring [Member] | Mutual Funds [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments at fair value	0		0
Operating Companies [Member] | Fair Value, Measurements, Recurring [Member] | Derivative Assets [Member] | Futures [Member] | Total Estimated Fair Value [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	653		172
Operating Companies [Member] | Fair Value, Measurements, Recurring [Member] | Derivative Assets [Member] | Futures [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	653		172
Operating Companies [Member] | Fair Value, Measurements, Recurring [Member] | Derivative Assets [Member] | Futures [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	0		0
Operating Companies [Member] | Fair Value, Measurements, Recurring [Member] | Derivative Assets [Member] | Futures [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	0		0
Operating Companies [Member] | Fair Value, Measurements, Recurring [Member] | Derivative Assets [Member] | Equity Swap [Member] | Total Estimated Fair Value [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets			635
Operating Companies [Member] | Fair Value, Measurements, Recurring [Member] | Derivative Assets [Member] | Equity Swap [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets			0
Operating Companies [Member] | Fair Value, Measurements, Recurring [Member] | Derivative Assets [Member] | Equity Swap [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets			635
Operating Companies [Member] | Fair Value, Measurements, Recurring [Member] | Derivative Assets [Member] | Equity Swap [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets			0
Operating Companies [Member] | Fair Value, Measurements, Recurring [Member] | Derivative Assets [Member] | Forward Contracts [Member] | Total Estimated Fair Value [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	418
Operating Companies [Member] | Fair Value, Measurements, Recurring [Member] | Derivative Assets [Member] | Forward Contracts [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	0
Operating Companies [Member] | Fair Value, Measurements, Recurring [Member] | Derivative Assets [Member] | Forward Contracts [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	418
Operating Companies [Member] | Fair Value, Measurements, Recurring [Member] | Derivative Assets [Member] | Forward Contracts [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	0
Operating Companies [Member] | Fair Value, Measurements, Recurring [Member] | Derivative Assets [Member] | Options [Member] | Total Estimated Fair Value [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	26,543		55,699
Operating Companies [Member] | Fair Value, Measurements, Recurring [Member] | Derivative Assets [Member] | Options [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	23,298		55,530
Operating Companies [Member] | Fair Value, Measurements, Recurring [Member] | Derivative Assets [Member] | Options [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	3,245		169
Operating Companies [Member] | Fair Value, Measurements, Recurring [Member] | Derivative Assets [Member] | Options [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	0		0
Operating Companies [Member] | Fair Value, Measurements, Recurring [Member] | Portfolio Funds [Member] | Total Estimated Fair Value [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments at fair value	47,287		40,350
Operating Companies [Member] | Fair Value, Measurements, Recurring [Member] | Portfolio Funds [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments at fair value	0		0
Operating Companies [Member] | Fair Value, Measurements, Recurring [Member] | Portfolio Funds [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments at fair value	26,794		23,431
Operating Companies [Member] | Fair Value, Measurements, Recurring [Member] | Portfolio Funds [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments at fair value	20,493	19,876	16,919	13,909	17,744	17,081
Operating Companies [Member] | Fair Value, Measurements, Recurring [Member] | Real Estate Investments [Member] | Total Estimated Fair Value [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments at fair value	2,102		2,353
Operating Companies [Member] | Fair Value, Measurements, Recurring [Member] | Real Estate Investments [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments at fair value	0		0
Operating Companies [Member] | Fair Value, Measurements, Recurring [Member] | Real Estate Investments [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments at fair value	0		0
Operating Companies [Member] | Fair Value, Measurements, Recurring [Member] | Real Estate Investments [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments at fair value	2,102	2,079	2,353	2,307	2,289	1,882
Operating Companies [Member] | Fair Value, Measurements, Recurring [Member] | Lehman Claim [Member] | Total Estimated Fair Value [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments at fair value	761		553
Operating Companies [Member] | Fair Value, Measurements, Recurring [Member] | Lehman Claim [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments at fair value	0		0
Operating Companies [Member] | Fair Value, Measurements, Recurring [Member] | Lehman Claim [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments at fair value	0		0
Operating Companies [Member] | Fair Value, Measurements, Recurring [Member] | Lehman Claim [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments at fair value	761	731	553	501	501	313
Consolidated Funds [Member] | Fair Value, Measurements, Recurring [Member] | Total Estimated Fair Value [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets at fair value	208,190		235,154
Consolidated Funds [Member] | Fair Value, Measurements, Recurring [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets at fair value	1,501		2,006
Consolidated Funds [Member] | Fair Value, Measurements, Recurring [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets at fair value	12,032		12,406
Consolidated Funds [Member] | Fair Value, Measurements, Recurring [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets at fair value	194,657		220,742
Consolidated Funds [Member] | Fair Value, Measurements, Recurring [Member] | US Government Securities [Member] | Total Estimated Fair Value [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments at fair value	1,501		2,006
Consolidated Funds [Member] | Fair Value, Measurements, Recurring [Member] | US Government Securities [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments at fair value	1,501		2,006
Consolidated Funds [Member] | Fair Value, Measurements, Recurring [Member] | US Government Securities [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments at fair value	0		0
Consolidated Funds [Member] | Fair Value, Measurements, Recurring [Member] | US Government Securities [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments at fair value	0		0
Consolidated Funds [Member] | Fair Value, Measurements, Recurring [Member] | Corporate Bonds [Member] | Total Estimated Fair Value [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments at fair value			401
Consolidated Funds [Member] | Fair Value, Measurements, Recurring [Member] | Corporate Bonds [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments at fair value			0
Consolidated Funds [Member] | Fair Value, Measurements, Recurring [Member] | Corporate Bonds [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments at fair value			401
Consolidated Funds [Member] | Fair Value, Measurements, Recurring [Member] | Corporate Bonds [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments at fair value			0
Consolidated Funds [Member] | Fair Value, Measurements, Recurring [Member] | Commercial Paper [Member] | Total Estimated Fair Value [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments at fair value	1,594		3,927
Consolidated Funds [Member] | Fair Value, Measurements, Recurring [Member] | Commercial Paper [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments at fair value	0		0
Consolidated Funds [Member] | Fair Value, Measurements, Recurring [Member] | Commercial Paper [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments at fair value	1,594		3,927
Consolidated Funds [Member] | Fair Value, Measurements, Recurring [Member] | Commercial Paper [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments at fair value	0		0
Consolidated Funds [Member] | Fair Value, Measurements, Recurring [Member] | Portfolio Funds [Member] | Total Estimated Fair Value [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments at fair value	198,235		221,480
Consolidated Funds [Member] | Fair Value, Measurements, Recurring [Member] | Portfolio Funds [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments at fair value	0		0
Consolidated Funds [Member] | Fair Value, Measurements, Recurring [Member] | Portfolio Funds [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments at fair value	10,438		8,078
Consolidated Funds [Member] | Fair Value, Measurements, Recurring [Member] | Portfolio Funds [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments at fair value	187,797	209,507	213,402	219,156	239,588	311,242
Consolidated Funds [Member] | Fair Value, Measurements, Recurring [Member] | Lehman Claim [Member] | Total Estimated Fair Value [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments at fair value	6,860		7,340
Consolidated Funds [Member] | Fair Value, Measurements, Recurring [Member] | Lehman Claim [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments at fair value	0		0
Consolidated Funds [Member] | Fair Value, Measurements, Recurring [Member] | Lehman Claim [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments at fair value	0		0
Consolidated Funds [Member] | Fair Value, Measurements, Recurring [Member] | Lehman Claim [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments at fair value	$ 6,860	$ 6,538	$ 7,340	$ 7,195	$ 7,320	$ 6,243