Note 4 - Fair Value Measurements - Fair Value of Financial Instruments (Details) - USD ($) $ in Thousands		Dec. 31, 2019	Dec. 31, 2018
Marketable securities owned		$ 73,101	$ 18,874
Marketable securities sold, but not yet purchased		3,855	4,626
Reported Value Measurement [Member]
Cash and cash equivalents		49,630	70,927
Restricted cash and deposits		1,287	61,881
Marketable securities owned		73,101	18,874
Other investments		3,956	490
Other investments measured at net asset value (1)	[1]	10,250	9,423
Loans held for sale		2,412
Loans held for investment, net of allowance for loan losses		1,210	29,608
Total assets:		141,846	1,352,666
Marketable securities sold, but not yet purchased		3,855	4,626
Notes payable		6,812	829
Bond payable		82,584	83,497
Total liabilities:		93,251	1,223,794
Loans collateralizing asset-backed securities issued, net of allowance for loan losses			1,161,463
Asset-backed securities issued, net of debt issuance costs			1,112,342
CLO VI warehouse credit facility			22,500
Estimate of Fair Value Measurement [Member]
Cash and cash equivalents		49,630	70,927
Restricted cash and deposits		1,287	61,881
Marketable securities owned		73,101	18,874
Other investments		3,956	490
Other investments measured at net asset value (1)	[1]
Loans held for sale		2,476
Loans held for investment, net of allowance for loan losses		1,087	28,764
Total assets:		131,537	1,307,419
Marketable securities sold, but not yet purchased		3,855	4,626
Notes payable		6,812	829
Bond payable		84,821	78,642
Total liabilities:		95,488	1,198,274
Loans collateralizing asset-backed securities issued, net of allowance for loan losses			1,126,483
Asset-backed securities issued, net of debt issuance costs			1,091,677
CLO VI warehouse credit facility			22,500
Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 1 [Member]
Cash and cash equivalents		49,630	70,927
Restricted cash and deposits		1,287	61,881
Marketable securities owned		15,245	18,874
Other investments
Other investments measured at net asset value (1)	[1]
Loans held for sale
Loans held for investment, net of allowance for loan losses
Total assets:		66,162	151,682
Marketable securities sold, but not yet purchased		3,855	4,626
Notes payable
Bond payable
Total liabilities:		3,855	4,626
Loans collateralizing asset-backed securities issued, net of allowance for loan losses
Asset-backed securities issued, net of debt issuance costs
CLO VI warehouse credit facility
Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 2 [Member]
Cash and cash equivalents
Restricted cash and deposits
Marketable securities owned
Other investments			490
Other investments measured at net asset value (1)	[1]
Loans held for sale
Loans held for investment, net of allowance for loan losses			26,188
Total assets:			1,151,988
Marketable securities sold, but not yet purchased
Notes payable		5,983
Bond payable		84,821	78,642
Total liabilities:		90,804	1,192,819
Loans collateralizing asset-backed securities issued, net of allowance for loan losses			1,125,310
Asset-backed securities issued, net of debt issuance costs			1,091,677
CLO VI warehouse credit facility			22,500
Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 3 [Member]
Cash and cash equivalents
Restricted cash and deposits
Marketable securities owned		57,856
Other investments		3,956
Other investments measured at net asset value (1)	[1]
Loans held for sale		2,476
Loans held for investment, net of allowance for loan losses		1,087	2,576
Total assets:		65,375	3,749
Marketable securities sold, but not yet purchased
Notes payable		829	829
Bond payable
Total liabilities:		$ 829	829
Loans collateralizing asset-backed securities issued, net of allowance for loan losses			1,173
Asset-backed securities issued, net of debt issuance costs
CLO VI warehouse credit facility

[1] In accordance with ASC 820-10, certain investments that are measured at fair value using the net asset value per share (or its equivalent) have not been classified in the fair value hierarchy. The fair value amounts presented in this table are intended to permit reconciliation of the fair value hierarchy to the amounts presented in the statement of financial position. The carrying values of these lines reconciles to the parenthetical disclosure of other investments on the Consolidated Statements of Financial Condition.