Fair Value Measurements for Operating Entities and Consolidated Funds - Fair Value Inputs, Unobservable Inputs, Quantitative Information (Details) - USD ($) $ in Thousands		3 Months Ended
		Mar. 31, 2020		Mar. 31, 2019	Dec. 31, 2019	Dec. 31, 2018
Contingent liability payable
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Balance Liability Value		$ 28,658		$ 29,536	$ 30,896	$ 3,070
Options
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Balance Asset Value		332			336
Trade Claims
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Balance Asset Value		9,648		5,487	7,320	5,543
Warrants and Rights [Member]
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Balance Asset Value		598		454	594	1,666
Corporate Bonds
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Balance Asset Value		2,812		$ 261	2,421	$ 0
Balance Liability Value		800			1,000
Level 3
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Balance Asset Value		151,890			48,432
Balance Liability Value		$ 32,760			36,766
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					30,896
Level 3 | Contingent liability payable | Valuation Technique, Discounted Cash Flow
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Weighted average percent Fair Value technique		16.00%		15.00%
Level 3 | Contingent liability payable | Valuation Technique, Discounted Cash Flow | Minimum
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Fair value inputs		16.00%		15.00%
Level 3 | Contingent liability payable | Valuation Technique, Discounted Cash Flow | Maximum
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Fair value inputs		22.00%		22.00%
Level 3 | Contingent liability payable | Monte Carlo [Member]
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Fair value inputs		22.00%		17.00%
Weighted average percent Fair Value technique		22.00%		17.00%
Level 3 | Other Liabilities [Member] | Income Approach and Market Approach Valuation Techniques
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Balance Liability Value		$ 2,300	[1]		2,950
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					10,876
Level 3 | Common and Preferred Stock | Valuation Technique, Discounted Cash Flow
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Weighted average percent Fair Value technique				10.40%
Level 3 | Common and Preferred Stock | Valuation Technique, Discounted Cash Flow | Minimum
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Fair value inputs				8.00%
Level 3 | Common and Preferred Stock | Valuation Technique, Discounted Cash Flow | Maximum
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Fair value inputs				11.25%
Level 3 | Common and Preferred Stock | Valuation, Market Approach
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Weighted average percent Fair Value technique				675.00%
Level 3 | Common and Preferred Stock | Valuation, Market Approach | Minimum
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Fair value inputs				650.00%
Level 3 | Common and Preferred Stock | Valuation, Market Approach | Maximum
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Fair value inputs				700.00%
Level 3 | Options | Market Approach, Income Approach and Replacement Cost Valuation Techniques [Member]
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Balance Asset Value		$ 331			336
Level 3 | Options | Valuation Technique, Discounted Cash Flow
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Weighted average percent Fair Value technique		11.00%		10.50%
Level 3 | Options | Valuation Technique, Discounted Cash Flow | Minimum
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Fair value inputs		10.00%		9.75%
Level 3 | Options | Valuation Technique, Discounted Cash Flow | Maximum
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Fair value inputs		12.00%		11.25%
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		$ 3,747			24
Level 3 | Warrants and Rights [Member] | Market Approach, Income Approach and Replacement Cost Valuation Techniques [Member]
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Balance Asset Value					6,162
Level 3 | Warrants and Rights [Member] | Income Approach and Market Approach Valuation Techniques
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Balance Asset Value		$ 6,210
Level 3 | Warrants and Rights [Member] | Valuation Technique, Discounted Cash Flow
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Fair value inputs		6.60%
Weighted average percent Fair Value technique		6.60%		6.10%
Level 3 | Warrants and Rights [Member] | Valuation Technique, Discounted Cash Flow | Minimum
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Fair value inputs				6.00%
Level 3 | Warrants and Rights [Member] | Valuation Technique, Discounted Cash Flow | Maximum
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Fair value inputs				7.00%
Level 3 | Corporate Bonds | Income Approach and Market Approach Valuation Techniques
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Balance Asset Value		$ 311			311
Level 3 | Bonds | Valuation Technique, Discounted Cash Flow
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Fair value inputs		20.00%		20.00%
Weighted average percent Fair Value technique		20.00%		20.00%
Level 3 | Bonds | Probability of recovery valuation technique
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Weighted average percent Fair Value technique		2.25%		2.30%
Level 3 | Bonds | Probability of recovery valuation technique | Minimum
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Fair value inputs		1.00%		1.00%
Level 3 | Bonds | Probability of recovery valuation technique | Maximum
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Fair value inputs		3.00%		3.00%
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	[1]				30,723
Level 3 | Other Investments | Income Approach and Market Approach Valuation Techniques
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Balance Asset Value	[1]	$ 141,291
Level 3 | Options | Valuation, Market Approach
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Weighted average percent Fair Value technique		650.00%		675.00%
Level 3 | Options | Valuation, Market Approach | Minimum
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Fair value inputs		625.00%		650.00%
Level 3 | Options | Valuation, Market Approach | Maximum
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Fair value inputs		675.00%		700.00%
Fair Value, Measurements, Recurring | Level 3 | 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					$ 2,920
Discount rate | Level 3 | Trade Claims | Valuation Technique, Discounted Cash Flow
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Fair value inputs		20.00%		20.00%
Weighted average percent Fair Value technique		20.00%		20.00%
Volatility | Level 3 | Warrants and Rights [Member] | Market Approach Valuation Technique
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Fair value inputs		36.00%		30.00%
Weighted average percent Fair Value technique		36.00%		0.00%
Volatility | Level 3 | Option | Market Approach Valuation Technique
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Fair value inputs		35.00%
Weighted average percent Fair Value technique		35.00%		35.00%
Volatility | Level 3 | Option | Market Approach Valuation Technique | Minimum
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Fair value inputs				35.00%
Volatility | Level 3 | Option | Market Approach Valuation Technique | Maximum
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Fair value inputs				40.00%

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