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Note 9 - Fair Value Disclosures - Fair Value Measurements on a Recurring Basis (Details) - USD ($) | Dec. 31, 2020 | Dec. 31, 2019
--- | --- | ---
Investments-trading |  | $ 242,961,000 | $ 307,852,000 |
Total other investments, at fair value |  | 58,540,000 | 14,864,000 |
Investment securities sold, not yet purchased |  | 44,439,000 | 77,947,000 |
Other investments sold, not yet purchased |  | 7,415,000 |  |
Corporate Bonds and Redeemable Preferred Stock [Member] |  |  |  |
Investments-trading |  | 36,388,000 | 38,503,000 |
Investment securities sold, not yet purchased |  | 29,206,000 | 58,083,000 |
Foreign Government Bonds [Member] |  |  |  |
Investments-trading |  | 659,000 | 844,000 |
Municipal Bonds [Member] |  |  |  |
Investments-trading |  | 19,400,000 | 13,737,000 |
Investment securities sold, not yet purchased |  | 20,000 | 20,000 |
Certificates of Deposit [Member] |  |  |  |
Investments-trading |  | 70,000 | 841,000 |
Derivative [Member] |  |  |  |
Investments-trading |  | 13,717,000 | 3,686,000 |
Investment securities sold, not yet purchased |  | 11,822,000 | 3,017,000 |
Other investments sold, not yet purchased |  | 233,000 |  |
Equity Securities [Member] |  |  |  |
Investments-trading |  | 428,000 | 561,000 |
Total other investments, at fair value |  | 51,593,000 | 8,875,000 |
Investment securities sold, not yet purchased |  | 43,000 |  |
Other investments sold, not yet purchased |  | 7,182,000 |  |
Residential Transition Loans [Member] |  |  |  |
Total other investments, at fair value |  | 2,300,000 |  |
Fair Value, Recurring [Member] |  |  |  |
Investments-trading |  | 242,961,000 | 307,852,000 |
Total other investments, at fair value |  | 58,540,000 | 14,864,000 |
Investment securities sold, not yet purchased |  | 44,439,000 | 77,947,000 |
Other investments sold, not yet purchased |  | 7,415,000 |  |
Fair Value, Recurring [Member] | Corporate Bonds and Redeemable Preferred Stock [Member] |  |  |  |
Investments-trading |  | 36,388,000 | 38,503,000 |
Total other investments, at fair value |  | 476,000 | 477,000 |
Fair Value, Recurring [Member] | Foreign Government Bonds [Member] |  |  |  |
Investments-trading |  | 659,000 | 844,000 |
Fair Value, Recurring [Member] | Municipal Bonds [Member] |  |  |  |
Investments-trading |  | 19,400,000 | 13,737,000 |
Investment securities sold, not yet purchased |  | 20,000 | 20,000 |
Fair Value, Recurring [Member] | Certificates of Deposit [Member] |  |  |  |
Investments-trading |  | 70,000 | 841,000 |
Fair Value, Recurring [Member] | Derivative [Member] |  |  |  |
Investments-trading |  | 13,717,000 | 3,686,000 |
Investment securities sold, not yet purchased |  | 11,822,000 | 3,017,000 |
Other investments sold, not yet purchased |  | 233,000 |  |
Fair Value, Recurring [Member] | Equity Securities [Member] |  |  |  |
Investments-trading |  | 428,000 | 561,000 |
Total other investments, at fair value |  | 51,593,000 | 8,875,000 |
Investment securities sold, not yet purchased |  | 43,000 |  |
Other investments sold, not yet purchased |  | 7,182,000 |  |
Fair Value, Recurring [Member] | Subordinated Debt [Member] |  |  |  |
Total other investments, at fair value |  | 1,519,000 |  |
Fair Value, Recurring [Member] | Residential Transition Loans [Member] |  |  |  |
Total other investments, at fair value |  | 2,300,000 |  |
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] |  |  |  |
Investments-trading |  | 607,000 | 11,105,000 |
Investment securities sold, not yet purchased |  | 3,391,000 | 16,827,000 |
Other investments sold, not yet purchased |  | 7,415,000 |  |
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Corporate Bonds and Redeemable Preferred Stock [Member] |  |  |  |
Investments-trading |  |  |  |
Total other investments, at fair value |  |  |  |
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Foreign Government Bonds [Member] |  |  |  |
Investments-trading |  |  |  |
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Municipal Bonds [Member] |  |  |  |
Investments-trading |  |  |  |
Investment securities sold, not yet purchased |  |  |  |
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Certificates of Deposit [Member] |  |  |  |
Investments-trading |  |  |  |
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Derivative [Member] |  |  |  |
Investments-trading |  |  |  |
Investment securities sold, not yet purchased |  |  |  |
Other investments sold, not yet purchased |  | 233,000 |  |
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Equity Securities [Member] |  |  |  |
Investments-trading |  |  |  |
Total other investments, at fair value |  | 17,422,000 | 2,009,000 |
Investment securities sold, not yet purchased |  | 43,000 |  |
Other investments sold, not yet purchased |  | 7,182,000 |  |
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Subordinated Debt [Member] |  |  |  |
Total other investments, at fair value |  |  |  |
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Residential Transition Loans [Member] |  |  |  |
Total other investments, at fair value |  |  |  |
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] |  |  |  |
Investments-trading |  | 242,354,000 | 296,747,000 |
Investment securities sold, not yet purchased |  | 41,048,000 | 61,120,000 |
Other investments sold, not yet purchased |  |  |  |
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Corporate Bonds and Redeemable Preferred Stock [Member] |  |  |  |
Investments-trading |  | 36,388,000 | 38,503,000 |
Total other investments, at fair value |  | 476,000 | 477,000 |
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Foreign Government Bonds [Member] |  |  |  |
Investments-trading |  | 659,000 | 844,000 |
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Municipal Bonds [Member] |  |  |  |
Investments-trading |  | 19,400,000 | 13,737,000 |
Investment securities sold, not yet purchased |  | 20,000 | 20,000 |
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Certificates of Deposit [Member] |  |  |  |
Investments-trading |  | 70,000 | 841,000 |
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Derivative [Member] |  |  |  |
Investments-trading |  | 13,717,000 | 3,686,000 |
Investment securities sold, not yet purchased |  | 11,822,000 | 3,017,000 |
Other investments sold, not yet purchased |  |  |  |
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Equity Securities [Member] |  |  |  |
Investments-trading |  | 428,000 | 561,000 |
Total other investments, at fair value |  | 34,171,000 | 6,866,000 |
Investment securities sold, not yet purchased |  |  |  |
Other investments sold, not yet purchased |  |  |  |
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Subordinated Debt [Member] |  |  |  |
Total other investments, at fair value |  | 1,519,000 |  |
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Residential Transition Loans [Member] |  |  |  |
Total other investments, at fair value |  | 2,300,000 |  |
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] |  |  |  |
Investments-trading |  |  |  |
Investment securities sold, not yet purchased |  |  |  |
Other investments sold, not yet purchased |  |  |  |
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Corporate Bonds and Redeemable Preferred Stock [Member] |  |  |  |
Investments-trading |  |  |  |
Total other investments, at fair value |  |  |  |
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Foreign Government Bonds [Member] |  |  |  |
Investments-trading |  |  |  |
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Municipal Bonds [Member] |  |  |  |
Investments-trading |  |  |  |
Investment securities sold, not yet purchased |  |  |  |
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Certificates of Deposit [Member] |  |  |  |
Investments-trading |  |  |  |
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Derivative [Member] |  |  |  |
Investments-trading |  |  |  |
Investment securities sold, not yet purchased |  |  |  |
Other investments sold, not yet purchased |  |  |  |
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Equity Securities [Member] |  |  |  |
Investments-trading |  |  |  |
Total other investments, at fair value |  |  |  |
Investment securities sold, not yet purchased |  |  |  |
Other investments sold, not yet purchased |  |  |  |
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Subordinated Debt [Member] |  |  |  |
Total other investments, at fair value |  |  |  |
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Residential Transition Loans [Member] |  |  |  |
Total other investments, at fair value |  |  |  |
Fair Value, Recurring [Member] | Fair Value Measured at Net Asset Value Per Share [Member] |  |  |  |
Total other investments, at fair value | [1] | 2,548,000 | 2,891,000 |
Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member] | Fair Value, Recurring [Member] |  |  |  |
Investments-trading |  | 162,031,000 | 196,146,000 |
Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] |  |  |  |
Investments-trading |  |  |  |
Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] |  |  |  |
Investments-trading |  | 162,031,000 | 196,146,000 |
Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] |  |  |  |
Investments-trading |  |  |  |
US Government Agencies Debt Securities [Member] | Fair Value, Recurring [Member] |  |  |  |
Investments-trading |  | 6,904,000 | 14,680,000 |
US Government Agencies Debt Securities [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] |  |  |  |
Investments-trading |  |  |  |
US Government Agencies Debt Securities [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] |  |  |  |
Investments-trading |  | 6,904,000 | 14,680,000 |
US Government Agencies Debt Securities [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] |  |  |  |
Investments-trading |  |  |  |
Residential Mortgage Backed Securities [Member] | Fair Value, Recurring [Member] |  |  |  |
Investments-trading |  | 14,000 | 15,000 |
Residential Mortgage Backed Securities [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] |  |  |  |
Investments-trading |  |  |  |
Residential Mortgage Backed Securities [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] |  |  |  |
Investments-trading |  | 14,000 | 15,000 |
Residential Mortgage Backed Securities [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] |  |  |  |
Investments-trading |  |  |  |
US Treasury Securities [Member] |  |  |  |
Investment securities sold, not yet purchased |  | 3,348,000 | 16,827,000 |
US Treasury Securities [Member] | Fair Value, Recurring [Member] |  |  |  |
Investments-trading |  | 607,000 | 11,105,000 |
Investment securities sold, not yet purchased |  | 3,348,000 | 16,827,000 |
US Treasury Securities [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] |  |  |  |
Investments-trading |  | 607,000 | 11,105,000 |
Investment securities sold, not yet purchased |  | 3,348,000 | 16,827,000 |
US Treasury Securities [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] |  |  |  |
Investments-trading |  |  |  |
Investment securities sold, not yet purchased |  |  |  |
US Treasury Securities [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] |  |  |  |
Investments-trading |  |  |  |
Investment securities sold, not yet purchased |  |  |  |
Asset-backed Securities [Member] | Fair Value, Recurring [Member] |  |  |  |
Investments-trading |  | 1,000 | 100,000 |
Asset-backed Securities [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] |  |  |  |
Investments-trading |  |  |  |
Asset-backed Securities [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] |  |  |  |
Investments-trading |  | 1,000 | 100,000 |
Asset-backed Securities [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] |  |  |  |
Investments-trading |  |  |  |
Small Business Administration Loans [Member] | Fair Value, Recurring [Member] |  |  |  |
Investments-trading |  | 2,742,000 | 27,634,000 |
Small Business Administration Loans [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] |  |  |  |
Investments-trading |  |  |  |
Small Business Administration Loans [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] |  |  |  |
Investments-trading |  | 2,742,000 | 27,634,000 |
Small Business Administration Loans [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] |  |  |  |
Investments-trading |  |  |  |
Collateralized Loan Obligations [Member] |  |  |  |
Total other investments, at fair value |  |  | 2,522,000 |
Collateralized Loan Obligations [Member] | Fair Value, Recurring [Member] |  |  |  |
Total other investments, at fair value |  |  | 2,522,000 |
Collateralized Loan Obligations [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] |  |  |  |
Total other investments, at fair value |  |  |  |
Collateralized Loan Obligations [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] |  |  |  |
Total other investments, at fair value |  |  |  |
Collateralized Loan Obligations [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] |  |  |  |
Total other investments, at fair value |  |  | 2,522,000 |
Residential Mortgage [Member] |  |  |  |
Total other investments, at fair value |  | 104,000 | 99,000 |
Residential Mortgage [Member] | Fair Value, Recurring [Member] |  |  |  |
Total other investments, at fair value |  | 104,000 | 99,000 | [1]
Residential Mortgage [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] |  |  |  |
Total other investments, at fair value |  |  |  | [1]
Residential Mortgage [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] |  |  |  |
Total other investments, at fair value |  | 104,000 | 99,000 | [1]
Residential Mortgage [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] |  |  |  |
Total other investments, at fair value |  |  |  | [1]
Total Investments not Measured at NAV [Member] | Fair Value, Recurring [Member] |  |  |  |
Total other investments, at fair value |  | 55,992,000 | 11,973 |
Total Investments not Measured at NAV [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] |  |  |  |
Total other investments, at fair value |  | 17,422,000 | 2,009 |
Total Investments not Measured at NAV [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] |  |  |  |
Total other investments, at fair value |  | 38,570,000 | 7,442 |
Total Investments not Measured at NAV [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] |  |  |  |
Total other investments, at fair value |  |  | 2,522 |
Corporate Bonds and Redeemable Preferred Stock [Member] |  |  |  |
Total other investments, at fair value |  | 476,000 | 477,000 |
Corporate Bonds and Redeemable Preferred Stock [Member] | Fair Value, Recurring [Member] |  |  |  |
Investment securities sold, not yet purchased |  | 29,206,000 | 58,083,000 |
Corporate Bonds and Redeemable Preferred Stock [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] |  |  |  |
Investment securities sold, not yet purchased |  |  |  |
Corporate Bonds and Redeemable Preferred Stock [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] |  |  |  |
Investment securities sold, not yet purchased |  | 29,206,000 | 58,083,000 |
Corporate Bonds and Redeemable Preferred Stock [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] |  |  |  |
Investment securities sold, not yet purchased |  |  |  |
[1] | As a practical expedient, the Company uses NAV per share (or its equivalent) to measure the fair value of its investments in the U.S. Insurance JV and the SPAC Fund. The U.S. Insurance JV invests in USD denominated debt issued by small insurance and reinsurance companies. The SPAC Fund invests in equity securities of SPACs. According to FASB ASC 820, these investments are not categorized within the valuation hierarchy.

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