Note 24 - Consolidating Financial Statements - Condensed Consolidating Balance Sheet (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Mar. 19, 2019	Dec. 31, 2018	Mar. 31, 2018	Dec. 31, 2017
Asset
Cash and cash equivalents	$ 41,909		$ 70,927
Restricted cash	1,221		61,881
Investment banking fees receivable, net of allowance for doubtful accounts	5,608		6,647
Marketable securities owned	92,190		18,874
Other investments	23,447		16,124
Loans held for investment, net of allowance for loan losses	4,962		29,608
Interest receivable	311		3,004
Fixed assets, net	2,575		2,351
Operating Lease, Right-of-Use Asset	22,104
Other assets	27,438		20,363
Investment in subsidiaries
Total assets	221,765		1,391,242	$ 1,101,818
Loans collateralizing asset-backed securities issued, net of allowance for loan losses			1,161,463
Liabilities and Equity
Marketable securities sold, but not yet purchased, at fair value	2,696		4,626
Accrued compensation	5,647		41,609
Interest payable	1,035		11,210
Note payable	829		829
Bond payable, net of debt issuance costs	83,600		83,497
Operating Lease, Liability, Total	27,470
Other liabilities	14,041		17,423
Total liabilities	135,318		1,294,036
Total shareholders' equity	86,633		83,707
Non-controlling interest, at carrying value	(186)	$ 12,842	13,499
Total equity	86,447		97,206	$ 106,136	$ 110,179
Total liabilities and equity	221,765		1,391,242
Asset-backed securities issued, net of debt issuance costs			1,112,342
CLO warehouse credit facilities			22,500
Reportable Legal Entities [Member] | Parent Company [Member]
Asset
Cash and cash equivalents	2,963		4,863
Restricted cash
Investment banking fees receivable, net of allowance for doubtful accounts
Marketable securities owned	48,088		10,027
Other investments	4,391		10,922
Loans held for investment, net of allowance for loan losses	1,648		1,139
Interest receivable	27		137
Fixed assets, net
Operating Lease, Right-of-Use Asset
Other assets	(13,531)		(18,812)
Investment in subsidiaries	288,388		317,113
Total assets	331,974		325,389
Loans collateralizing asset-backed securities issued, net of allowance for loan losses
Liabilities and Equity
Marketable securities sold, but not yet purchased, at fair value
Accrued compensation	407
Interest payable
Note payable	127,603		127,603
Bond payable, net of debt issuance costs
Operating Lease, Liability, Total
Other liabilities	3,348		2,700
Total liabilities	131,358		130,303
Total shareholders' equity	200,616		181,497
Non-controlling interest, at carrying value			13,589
Total equity	200,616		195,086
Total liabilities and equity	331,974		325,389
Asset-backed securities issued, net of debt issuance costs
CLO warehouse credit facilities
Reportable Legal Entities [Member] | Subsidiary Issuer [Member]
Asset
Cash and cash equivalents	6,103		8,755
Restricted cash	1,221		1,221
Investment banking fees receivable, net of allowance for doubtful accounts
Marketable securities owned	666
Other investments	1,497		1,785
Loans held for investment, net of allowance for loan losses	885
Interest receivable	7		1
Fixed assets, net
Operating Lease, Right-of-Use Asset	22,104
Other assets	143,239		121,932
Investment in subsidiaries	76,688		77,427
Total assets	252,410		211,121
Loans collateralizing asset-backed securities issued, net of allowance for loan losses
Liabilities and Equity
Marketable securities sold, but not yet purchased, at fair value
Accrued compensation	575		150
Interest payable	1,071		1,071
Note payable
Bond payable, net of debt issuance costs	83,675		83,572
Operating Lease, Liability, Total	27,470
Other liabilities	2,233		7,603
Total liabilities	115,024		92,396
Total shareholders' equity	137,386		118,725
Non-controlling interest, at carrying value
Total equity	137,386		118,725
Total liabilities and equity	252,410		211,121
Asset-backed securities issued, net of debt issuance costs
CLO warehouse credit facilities
Reportable Legal Entities [Member] | Non-Guarantor Subsidiaries [Member]
Asset
Cash and cash equivalents	32,843		57,309
Restricted cash			60,660
Investment banking fees receivable, net of allowance for doubtful accounts	5,608		6,647
Marketable securities owned	43,510		8,921
Other investments	17,559		13,262
Loans held for investment, net of allowance for loan losses	2,429		28,469
Interest receivable	636		3,345
Fixed assets, net	2,575		2,351
Operating Lease, Right-of-Use Asset
Other assets	42,306		63,386
Investment in subsidiaries
Total assets	147,466		1,405,813
Loans collateralizing asset-backed securities issued, net of allowance for loan losses			1,161,463
Liabilities and Equity
Marketable securities sold, but not yet purchased, at fair value	2,696		4,626
Accrued compensation	4,665		41,459
Interest payable	323		10,614
Note payable	17,763		17,763
Bond payable, net of debt issuance costs
Operating Lease, Liability, Total
Other liabilities	8,393		8,620
Total liabilities	33,840		1,227,769
Total shareholders' equity	114,024		178,346
Non-controlling interest, at carrying value	(398)		(302)
Total equity	113,626		178,044
Total liabilities and equity	147,466		1,405,813
Asset-backed securities issued, net of debt issuance costs			1,122,187
CLO warehouse credit facilities			22,500
Consolidation, Eliminations [Member]
Asset
Cash and cash equivalents
Restricted cash
Investment banking fees receivable, net of allowance for doubtful accounts
Marketable securities owned	(74)		(74)
Other investments			(9,845)
Loans held for investment, net of allowance for loan losses
Interest receivable	(359)		(479)
Fixed assets, net
Operating Lease, Right-of-Use Asset
Other assets	(144,576)		(146,143)
Investment in subsidiaries	(365,076)		(394,540)
Total assets	(510,085)		(551,081)
Loans collateralizing asset-backed securities issued, net of allowance for loan losses
Liabilities and Equity
Marketable securities sold, but not yet purchased, at fair value
Accrued compensation
Interest payable	(359)		(475)
Note payable	(144,537)		(144,537)
Bond payable, net of debt issuance costs	(75)		(75)
Operating Lease, Liability, Total
Other liabilities	67		(1,500)
Total liabilities	(144,904)		(156,432)
Total shareholders' equity	(365,393)		(394,861)
Non-controlling interest, at carrying value	212		212
Total equity	(365,181)		(394,649)
Total liabilities and equity	$ (510,085)		(551,081)
Asset-backed securities issued, net of debt issuance costs			(9,845)
CLO warehouse credit facilities