Fair Value Measurements for Operating Entities and Consolidated Funds Fair Value Inputs, Unobservable Inputs, Quantitative Information (Details) $ in Thousands		12 Months Ended
		Dec. 31, 2017 USD ($)		Dec. 31, 2016 USD ($)		Dec. 31, 2015 USD ($)
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Financial Liabilities Fair Value Disclosure		$ 395,847		$ 294,304
Contingent liability payable
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Financial Liabilities Fair Value Disclosure		3,440	[1]	5,997
Balance Liability Value				5,997		$ 6,158
Trade Claims
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Balance Asset Value		5,950		562		0
Warrants and Rights
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Balance Asset Value		2,517		3,719		2,572
Options
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Balance Asset Value		1,455		14,753		$ 18,194
Put Option | Options
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Financial Liabilities Fair Value Disclosure		41,563		19,939
Level 3
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Balance Asset Value		80,253		83,364
Financial Liabilities Fair Value Disclosure		25,841		20,750
Balance Liability Value		$ 25,841		$ 20,750
Level 3 | Options | Market Approach Valuation Technique
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Volatility		28.00%		40.00%
Level 3 | Options | Market Approach Valuation Technique | Minimum
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Volatility
Level 3 | Contingent liability payable
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Financial Liabilities Fair Value Disclosure		$ 3,440	[1]	$ 5,997	[2]
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		8.00%		8.00%
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		23.00%		25.00%
Level 3 | Contingent liability payable | Market Approach Valuation Technique
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Fair Value Assumptions, Weighted Average Volatility Rate		22.00%		23.00%
Level 3 | Contingent liability payable | Market Approach, Income Approach and Replacement Cost Valuation Techniques [Member]
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Balance Liability Value		$ 3,440		$ 5,997
Level 3 | Common and Preferred Stock | Market Approach Valuation Technique
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Volatility				37.00%
Level 3 | Common and Preferred Stock | Market Approach Valuation Technique | Minimum
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Fair Value Assumptions, Projected cash flow				9.50%
Level 3 | Common and Preferred Stock | Market Approach Valuation Technique | Maximum
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Fair Value Assumptions, Projected cash flow				10.00%
Level 3 | Common and Preferred Stock | Market Approach, Income Approach and Replacement Cost Valuation Techniques [Member]
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Balance Asset Value		$ 5,642		$ 10,917
Level 3 | Common and Preferred Stock | Market Approach, Income Approach and Replacement Cost Valuation Techniques [Member] | Minimum
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Market multiple		4.8		0.8
Level 3 | Common and Preferred Stock | Market Approach, Income Approach and Replacement Cost Valuation Techniques [Member] | Maximum
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Market multiple		8.5		9.3
Level 3 | Trade Claims | Market Approach Valuation Technique
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
DCF discount rate		20.00%		20.00%
Market multiple				6
Level 3 | Trade Claims | Market Approach, Income Approach and Replacement Cost Valuation Techniques [Member]
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Balance Asset Value		$ 70		$ 520
Level 3 | Warrants and Rights | Income Approach and Market Approach Valuation Techniques
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Balance Asset Value		$ 2,516
Level 3 | Warrants and Rights | Market Approach Valuation Technique
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
DCF discount rate		22.00%
Volatility		61.00%
Fair Value Assumptions, Weighted Average Volatility Rate				73.00%
Level 3 | Warrants and Rights | Market Approach Valuation Technique | Minimum
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Volatility				30.00%
Level 3 | Warrants and Rights | Market Approach Valuation Technique | Maximum
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Volatility				85.00%
Level 3 | Warrants and Rights | Market Approach, Income Approach and Replacement Cost Valuation Techniques [Member]
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Balance Asset Value				$ 3,719
Level 3 | Other Investments | Income Approach and Market Approach Valuation Techniques
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Balance Asset Value	[3]	$ 70,570
Level 3 | Other Investments | Market Approach, Income Approach and Replacement Cost Valuation Techniques [Member]
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Balance Asset Value	[3]			$ 53,455
Level 3 | Options | Market Approach Valuation Technique
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Volatility		28.00%		40.00%
Level 3 | Options | Market Approach Valuation Technique | Minimum
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Volatility
Level 3 | Options | Derivative Assets | Income Approach and Market Approach Valuation Techniques
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Balance Asset Value		$ 1,455
Level 3 | Options | Derivative Assets | Market Approach, Income Approach and Replacement Cost Valuation Techniques [Member]
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Balance Asset Value				$ 14,753
Level 3 | Put Option | Options
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Financial Liabilities Fair Value Disclosure		$ 22,401		14,753
Level 3 | Put Option | Options | Market Approach, Income Approach and Replacement Cost Valuation Techniques [Member]
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Financial Liabilities Fair Value Disclosure				$ 14,753

[1] In accordance with the terms of the purchase agreements for acquisitions that closed during the third and fourth quarter of 2015 and 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 businesses, if certain targets are achieved through the periods ended December 2018, December 2020, and June 2018, respectively. 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, 2017 can range from $0.1 million to $15.0 million.

[2] In accordance with the terms of the purchase agreements for acquisitions that closed during 2012 and the third and fourth quarter of 2015, 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 2018, and December 2020, respectively. 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, 2016 can range from $0.1 million to $15.1 million.

[3] The quantitative disclosures exclude financial instruments for which the determination of fair value is based on prices from recent transactions.