Note 1 - Organization and Description of Business (Details Textual) - USD ($) $ in Thousands			3 Months Ended
	Mar. 19, 2019		Mar. 31, 2019	Mar. 18, 2019	Jan. 17, 2019	Dec. 31, 2018
Deconsolidation, Gain (Loss), Amount	$ 3,192
Proceeds from Divestiture of Interest in Consolidated Subsidiaries	7,942
Investments, Fair Value Disclosure, Total	74,989	[1]	$ 13,530			$ 9,913
CLO III [Member]
Net Assets, Ending Balance	24,500
CLO IV [Member]
Net Assets, Ending Balance	30,200
CLO V [Member]
Net Assets, Ending Balance	25,800
CLO VI [Member]
Net Assets, Ending Balance	11,600
JMPCA [Member]
Net Assets, Ending Balance	500
CLO III [Member]
Investments, Fair Value Disclosure, Total	13,300
CLO IV [Member]
Investments, Fair Value Disclosure, Total	27,800
CLO V [Member]
Investments, Fair Value Disclosure, Total	26,500
CLO VI [Member]
Investments, Fair Value Disclosure, Total	3,800
JMPCA [Member]
Investments, Fair Value Disclosure, Total	$ 3,600
Medalist Partners LP [Member]
Percentage of Outstanding Preference Shares Sold	66.00%
Proceeds from Sale of Preference shares	$ 7,600
Gain (Loss) on Sale of Preference Shares	0
CLO III [Member]
Ownership Percentage of Junior Subordinated Notes					47.00%
Deconsolidation, Gain (Loss), Amount			1,600
JMPCA [Member]
Deconsolidation, Gain (Loss), Amount	$ 3,400
Ownership Percentage	45.00%
Proceeds from Divestiture of Interest in Consolidated Subsidiaries	$ 300
JMPCA [Member] | Medalist Partners LP [Member]
Ownership Interest, Sold	50.10%
JMPCA [Member] | Management Employees of JMPCA [Member]
Ownership Interest, Sold	4.90%
CLO's [Member]
Ownership Percentage				100.00%
CLO IV [Member]
Ownership Percentage of Junior Subordinated Notes	100.00%
Ownership Percentage of Senior Subordinated Notes	100.00%
CLO V [Member]
Ownership Percentage of Junior Subordinated Notes	100.00%
Ownership Percentage of Senior Subordinated Notes	25.00%
CLO VI [Member]
Ownership Percentage of Outstanding Preference Shares	33.00%
CLO IV, CLO V, and CLO VI [Member]
Deconsolidation, Gain (Loss), Amount			$ (1,900)

[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