Note 4 - Fair Value Measurements - Significant Unobservable Inputs Used in Fair Value Measurements (Details) $ in Thousands	Mar. 31, 2019 USD ($)	Mar. 19, 2019 USD ($)	[1]	Dec. 31, 2018 USD ($)
Investments fair value	$ 13,530	$ 74,989		$ 9,913
Fair Value, Recurring [Member]
Equity investment	3,568
Investments fair value				490
Fair Value, Inputs, Level 3 [Member] | Fair Value, Recurring [Member]
Equity investment	3,568
Investments fair value
Collateralized Loan Obligations [Member] | Valuation, Income Approach [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Recurring [Member]
CLO debt security	$ 66,640
Collateralized Loan Obligations [Member] | Valuation, Income Approach [Member] | Measurement Input, Risk Free Interest Rate [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Recurring [Member] | Minimum [Member]
CLO debt security, measurement input	0.1
Collateralized Loan Obligations [Member] | Valuation, Income Approach [Member] | Measurement Input, Risk Free Interest Rate [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Recurring [Member] | Maximum [Member]
CLO debt security, measurement input	0.15
Collateralized Loan Obligations [Member] | Valuation, Income Approach [Member] | Measurement Input, Risk Free Interest Rate [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Recurring [Member] | Weighted Average [Member]
CLO debt security, measurement input	0.115
Collateralized Loan Obligations [Member] | Valuation, Income Approach [Member] | Measurement Input, Default Rate [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Recurring [Member] | Minimum [Member]
CLO debt security, measurement input	0
Collateralized Loan Obligations [Member] | Valuation, Income Approach [Member] | Measurement Input, Default Rate [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Recurring [Member] | Maximum [Member]
CLO debt security, measurement input	0.02
Collateralized Loan Obligations [Member] | Valuation, Income Approach [Member] | Measurement Input, Default Rate [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Recurring [Member] | Weighted Average [Member]
CLO debt security, measurement input	0.013
Collateralized Loan Obligations [Member] | Valuation, Income Approach [Member] | Measurement Input, Loss Severity [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Recurring [Member]
CLO debt security, measurement input	0.25
Limited Partner Investment in Private Equity Fund [Member] | Nonredeemable Funds [Member]
Investments fair value	$ 4,718			3,920
Unfunded Commitments	68			68
Investments in Private Equity Funds Managed by HCS [Member] | Nonredeemable Funds [Member]
Investments fair value	5,045			5,503
Unfunded Commitments	$ 1,945			$ 1,945
Equity Securities [Member] | Valuation, Income Approach [Member] | Measurement Input, Credit Factor [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Recurring [Member]
Equity investment, measurement input	0.2
Equity Securities [Member] | Valuation, Income Approach [Member] | Measurement Input, Discount Rate [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Recurring [Member]
Equity investment, measurement input	0.18

[1] The fair value of the Company's retained interest in CLO III, CLO IV, CLO V, CLO VI, and JMPCA as of the deconsolidation date was $13.3 million, $27.8 million, $26.5 million, $3.8 million, and $3.6 million, respectively