Fair Value Measurements for Operating Entities and Consolidated Funds Fair Value Inputs, Unobservable Inputs, Quantitative Information (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014		Dec. 31, 2013		Dec. 31, 2012
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Balance Asset Value	259,530		226,269
Balance Liability Value	40,890		6,937
Options
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Balance Liability Value	36,807
Contingent liability payable
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Balance Liability Value	4,083		6,937		8,116
Common and Preferred Stock
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Balance Asset Value	12,269		3,474
Warrants and Rights
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Balance Asset Value	1,322		5,805		1,713
Options
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Balance Asset Value	36,807
Other Investments
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Balance Asset Value	209,132	[1]	216,990	[1]
Level 3 | Options | Market Approach Valuation Technique | Minimum
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Volatility	30.00%
Fair Value Assumptions, Credit Spread	5.00%
Level 3 | Options | Market Approach Valuation Technique | Maximum
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Volatility	40.00%
Fair Value Assumptions, Credit Spread	7.50%
Level 3 | Contingent liability payable | Income Approach and Market Approach Valuation Techniques
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
DCF discount rate	9.00%
Level 3 | Contingent liability payable | Income Approach and Market Approach Valuation Techniques | Minimum
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
DCF discount rate			0.00%
Level 3 | Contingent liability payable | Income Approach and Market Approach Valuation Techniques | Maximum
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
DCF discount rate			15.00%
Level 3 | Common and Preferred Stock | Income Approach and Market Approach Valuation Techniques | Minimum
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Market multiple	1		2
Level 3 | Common and Preferred Stock | Income Approach and Market Approach Valuation Techniques | Maximum
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Market multiple	6		3
Level 3 | Common and Preferred Stock | Market Approach Valuation Technique
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Volatility	40.00%
Level 3 | Warrants and Rights | Market Approach Valuation Technique
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Fair Value Assumptions, Weighted Average Volatility Rate	34.00%		37.00%
Level 3 | Warrants and Rights | Market Approach Valuation Technique | Minimum
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Volatility	20.00%		20.00%
Level 3 | Warrants and Rights | Market Approach Valuation Technique | Maximum
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Volatility	60.00%		100.00%
Level 3 | Options | Market Approach Valuation Technique | Minimum
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Volatility	30.00%
Fair Value Assumptions, Credit Spread	5.00%
Level 3 | Options | Market Approach Valuation Technique | Maximum
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Volatility	40.00%
Fair Value Assumptions, Credit Spread	7.50%

[1] Quantitative disclosures of unobservable inputs and assumptions are not required for investments for which NAV per share is used as a practical expedient to determine fair value, as their redemption features rather than observability of inputs cause them to be classified as a level 3 type asset within the fair value hierarchy. In addition, the fair value of the Consolidated Funds' investments are determined based on net asset value and therefore quantitative disclosures are not included in the table above. The quantitative disclosures also exclude financial instruments for which the determination of fair value is based on prices from prior transactions.