Note 8 - Fair Value Disclosures - Fair Value Measurements on a Recurring Basis (Details) - USD ($) $ in Thousands	Mar. 31, 2024		Dec. 31, 2023
Investments-trading	$ 165,903		$ 181,328
Total other investments, at fair value	59,533		72,217
Trading securities sold, not yet purchased	57,115		65,751
Other investments, sold not yet purchased	20,217		24,742
US Government Agencies Debt Securities [Member]
Trading securities sold, not yet purchased	114		0
Mortgage-Backed Security, Issued by US Government-Sponsored Enterprise [Member]
Trading securities sold, not yet purchased	1		0
US Treasury Securities [Member]
Trading securities sold, not yet purchased	33,481		34,284
Residential Mortgage [Member]
Total other investments, at fair value	131		132
Fair Value, Recurring [Member]
Investments-trading	165,903		181,328
Total other investments, at fair value	59,533		72,217
Trading securities sold, not yet purchased	57,115		65,751
Other investments, sold not yet purchased	20,217		24,742
Fair Value, Recurring [Member] | Residential Mortgage Loans [Member]
Investments-trading	1,554		3,113
Fair Value, Recurring [Member] | Residential Mortgage-Backed Securities [Member]
Investments-trading	8		9
Fair Value, Recurring [Member] | US Government Agencies Debt Securities [Member]
Investments-trading	8,615		6,567
Trading securities sold, not yet purchased	114		0
Fair Value, Recurring [Member] | Mortgage-Backed Security, Issued by US Government-Sponsored Enterprise [Member]
Investments-trading	86,264		88,000
Trading securities sold, not yet purchased	1		0
Fair Value, Recurring [Member] | US Treasury Securities [Member]
Investments-trading	1,270		1,012
Trading securities sold, not yet purchased	33,481		34,284
Fair Value, Recurring [Member] | Residential Mortgage [Member]
Total other investments, at fair value	131		132
Fair Value, Recurring [Member] | Total Investments not Measured at NAV [Member]
Total other investments, at fair value	51,060		64,327
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 1 [Member]
Investments-trading	429		1,651
Trading securities sold, not yet purchased	33,624		34,677
Other investments, sold not yet purchased	113		97
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Residential Mortgage Loans [Member]
Investments-trading	0		0
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Residential Mortgage-Backed Securities [Member]
Investments-trading	0		0
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | US Government Agencies Debt Securities [Member]
Investments-trading	0		0
Trading securities sold, not yet purchased	0		0
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Mortgage-Backed Security, Issued by US Government-Sponsored Enterprise [Member]
Investments-trading	0		0
Trading securities sold, not yet purchased	0		0
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | US Treasury Securities [Member]
Investments-trading	0		1,012
Trading securities sold, not yet purchased	33,481		34,284
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Residential Mortgage [Member]
Total other investments, at fair value	0		0
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Total Investments not Measured at NAV [Member]
Total other investments, at fair value	33,592		38,038
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member]
Investments-trading	165,474		179,677
Trading securities sold, not yet purchased	23,491		31,074
Other investments, sold not yet purchased	20,104		24,645
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Residential Mortgage Loans [Member]
Investments-trading	1,554		3,113
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Residential Mortgage-Backed Securities [Member]
Investments-trading	8		9
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | US Government Agencies Debt Securities [Member]
Investments-trading	8,615		6,567
Trading securities sold, not yet purchased	114		0
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Mortgage-Backed Security, Issued by US Government-Sponsored Enterprise [Member]
Investments-trading	86,264		88,000
Trading securities sold, not yet purchased	1		0
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | US Treasury Securities [Member]
Investments-trading	1,270		0
Trading securities sold, not yet purchased	0		0
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Residential Mortgage [Member]
Total other investments, at fair value	131		132
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Total Investments not Measured at NAV [Member]
Total other investments, at fair value	17,468		26,289
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 3 [Member]
Investments-trading	0		0
Trading securities sold, not yet purchased	0		0
Other investments, sold not yet purchased	0		0
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Residential Mortgage Loans [Member]
Investments-trading	0		0
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Residential Mortgage-Backed Securities [Member]
Investments-trading	0		0
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | US Government Agencies Debt Securities [Member]
Investments-trading	0		0
Trading securities sold, not yet purchased	0		0
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Mortgage-Backed Security, Issued by US Government-Sponsored Enterprise [Member]
Investments-trading	0		0
Trading securities sold, not yet purchased	0		0
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | US Treasury Securities [Member]
Investments-trading	0		0
Trading securities sold, not yet purchased	0		0
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Residential Mortgage [Member]
Total other investments, at fair value	0		0
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Total Investments not Measured at NAV [Member]
Total other investments, at fair value	0		0
Fair Value, Recurring [Member] | Fair Value Measured at Net Asset Value Per Share [Member]
Total other investments, at fair value	8,473	[1]	7,890	[2]
Corporate Bonds and Redeemable Preferred Stock [Member]
Investments-trading	44,611		53,657
Trading securities sold, not yet purchased	20,994		24,355
Corporate Bonds and Redeemable Preferred Stock [Member] | Fair Value, Recurring [Member]
Investments-trading	44,611		53,657
Total other investments, at fair value	522		506
Trading securities sold, not yet purchased	20,994		24,355
Corporate Bonds and Redeemable Preferred Stock [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 1 [Member]
Investments-trading	0		0
Total other investments, at fair value	0		0
Trading securities sold, not yet purchased	0		0
Corporate Bonds and Redeemable Preferred Stock [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member]
Investments-trading	44,611		53,657
Total other investments, at fair value	522		506
Trading securities sold, not yet purchased	20,994		24,355
Corporate Bonds and Redeemable Preferred Stock [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 3 [Member]
Investments-trading	0		0
Total other investments, at fair value	0		0
Trading securities sold, not yet purchased	0		0
Derivative [Member]
Investments-trading	2,768		7,470
Trading securities sold, not yet purchased	2,382		6,719
Derivative [Member] | Fair Value, Recurring [Member]
Investments-trading	2,768		7,470
Trading securities sold, not yet purchased	2,382		6,719
Derivative [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 1 [Member]
Investments-trading	0		0
Trading securities sold, not yet purchased	0		0
Derivative [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member]
Investments-trading	2,768		7,470
Trading securities sold, not yet purchased	2,382		6,719
Derivative [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 3 [Member]
Investments-trading	0		0
Trading securities sold, not yet purchased	0		0
Equity Securities [Member]
Investments-trading	644		928
Total other investments, at fair value	27,773		38,038
Trading securities sold, not yet purchased	143		393
Other investments, sold not yet purchased	3,371		97
Equity Securities [Member] | Fair Value, Recurring [Member]
Investments-trading	644		928
Total other investments, at fair value	27,773		38,038
Trading securities sold, not yet purchased	143		393
Other investments, sold not yet purchased	3,371		97
Equity Securities [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 1 [Member]
Investments-trading	429		639
Total other investments, at fair value	27,773		38,038
Trading securities sold, not yet purchased	143		393
Other investments, sold not yet purchased	113		97
Equity Securities [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member]
Investments-trading	215		289
Total other investments, at fair value	0		0
Trading securities sold, not yet purchased	0		0
Other investments, sold not yet purchased	3,258		0
Equity Securities [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 3 [Member]
Investments-trading	0		0
Total other investments, at fair value	0		0
Trading securities sold, not yet purchased	0		0
Other investments, sold not yet purchased	0		0
Municipal Bonds [Member]
Investments-trading	20,169		20,572
Municipal Bonds [Member] | Fair Value, Recurring [Member]
Investments-trading	20,169		20,572
Municipal Bonds [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 1 [Member]
Investments-trading	0		0
Municipal Bonds [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member]
Investments-trading	20,169		20,572
Municipal Bonds [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 3 [Member]
Investments-trading	0		0
Equity Derivatives [Member]
Total other investments, at fair value	956		1,447
Equity Derivatives [Member] | Fair Value, Recurring [Member]
Total other investments, at fair value	956		1,447
Equity Derivatives [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 1 [Member]
Total other investments, at fair value	0		0
Equity Derivatives [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member]
Total other investments, at fair value	956		1,447
Equity Derivatives [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 3 [Member]
Total other investments, at fair value	0		0
Restricted Equity Securities [Member] | Fair Value, Recurring [Member]
Total other investments, at fair value	7,743		2,054
Restricted Equity Securities [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 1 [Member]
Total other investments, at fair value	5,819		0
Restricted Equity Securities [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member]
Total other investments, at fair value	1,924		2,054
Restricted Equity Securities [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 3 [Member]
Total other investments, at fair value	0		0
Fair Value Receivables [Member]
Total other investments, at fair value	9,824		9,541
Fair Value Receivables [Member] | Fair Value, Recurring [Member]
Total other investments, at fair value	9,824		9,541
Fair Value Receivables [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 1 [Member]
Total other investments, at fair value	0		0
Fair Value Receivables [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member]
Total other investments, at fair value	9,824		9,541
Fair Value Receivables [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 3 [Member]
Total other investments, at fair value	0		0
Interest In SPVs [Member]
Total other investments, at fair value	4,111		12,609
Interest In SPVs [Member] | Fair Value, Recurring [Member]
Total other investments, at fair value	4,111		12,609
Interest In SPVs [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 1 [Member]
Total other investments, at fair value	0		0
Interest In SPVs [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member]
Total other investments, at fair value	4,111		12,609
Interest In SPVs [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 3 [Member]
Total other investments, at fair value	0		0
Share Forward Liabilities [Member]
Other investments, sold not yet purchased	16,846		24,645
Share Forward Liabilities [Member] | Fair Value, Recurring [Member]
Other investments, sold not yet purchased	16,846		24,645
Share Forward Liabilities [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 1 [Member]
Other investments, sold not yet purchased	0		0
Share Forward Liabilities [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member]
Other investments, sold not yet purchased	16,846		24,645
Share Forward Liabilities [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 3 [Member]
Other investments, sold not yet purchased	$ 0		$ 0

[1] As a practical expedient, the Company uses NAV (or its equivalent) to measure the fair value of its investments in the U.S. Insurance JV and the CREO JV. The U.S. Insurance JV invests in U.S. Dollar ("USD") denominated debt issued by small insurance and reinsurance companies. The CREO JV invests in primarily multi-family commercial real estate mortgage-backed loans. According to ASC 820, these investments are not categorized within the valuation hierarchy.

[2] As a practical expedient, the Company uses NAV (or its equivalent) to measure the fair value of its investments in the U.S. Insurance JV and the CREO JV. The U.S. Insurance JV invests in USD denominated debt issued by small insurance and reinsurance companies. The CREO JV invests in primarily multi-family commercial real estate mortgage-backed loans. According to ASC 820, these investments are not categorized within the valuation hierarchy.