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Note 8 - Investments, Including Investments Accounted for Using the Equity Method (Details Textual) - USD ($) |  |  | 1 Months Ended | 3 Months Ended | 9 Months Ended |
--- | --- | --- | --- | --- | --- | ---
May 31, 2018 | Dec. 31, 2017 | May 31, 2019 | Jan. 31, 2018 | Sep. 30, 2020 | Sep. 30, 2019 | Sep. 30, 2020 | Sep. 30, 2019 | Sep. 25, 2020
Gain (Loss) on Sale of Investments, Total |  |  |  |  | $ 2,026,193 | $ 7,565 | $ 5,696,068 | $ 432,409 |
Proceeds from Redemption of Preferred Units |  |  |  |  |  |  | 12,000,000 | 0 |
Payments to Acquire Equity Method Investments |  |  |  |  |  |  | 3,175,000 | $ 225,978 |
Unconsolidated Affiliates [Member] | Board of Directors [Member] |  |  |  |  |  |  |  |  |
Equity Method Investments |  |  |  |  | $ 753,904 |  | $ 753,904 |  |
Unconsolidated Affiliates [Member] | Minimum [Member] |  |  |  |  |  |  |  |  |
Equity Method Investment, Ownership Percentage |  |  |  |  | 5.60% |  | 5.60% |  |
Unconsolidated Affiliates [Member] | Maximum [Member] |  |  |  |  |  |  |  |  |
Equity Method Investment, Ownership Percentage |  |  |  |  | 30.00% |  | 30.00% |  |
The 24th Street Fund I, LLC [Member] |  |  |  |  |  |  |  |  |
Payments to Acquire Equity Method Investments |  |  |  |  |  |  | $ 3,000,000 |  |
Yellowstone [Member] |  |  |  |  |  |  |  |  |
Equity Method Investment, Ownership Percentage |  |  |  |  |  |  |  |  | 20.00%
Breezeway Homes Inc. [Member] |  |  |  |  |  |  |  |  |
Preferred Stock, Dividend Rate, Per-Dollar-Amount (in dollars per share) |  |  |  | $ 2,665 |  |  |  |  |
Preferred Stock [Member] | Breezeway Homes Inc. [Member] |  |  |  |  |  |  |  |  |
Debt Conversion, Converted Instrument, Shares Issued (in shares) |  |  |  | 31,227 |  |  |  |  |
US Treasury Notes Securities [Member] |  |  |  |  |  |  |  |  |
Gain (Loss) on Sale of Investments, Total |  |  |  |  |  |  | 7,318 |  |
Proceeds from Sale and Maturity of Debt Securities, Available-for-sale, Total |  |  |  |  |  |  | 333,109,337 |  |
Corporate Bond Securities [Member] |  |  |  |  |  |  |  |  |
Debt Securities, Unrealized Gain (Loss), Total |  |  |  |  |  |  | (161,068) |  |
Voting Common Stock of Privately Held Company CB&T Holding Corporation [Member] |  |  |  |  |  |  |  |  |
Payments to Acquire Long-term Investments | $ 19,058,485 |  |  |  |  |  |  |  |
Cost Method Investment, Ownership Percentage | 14.99% |  |  |  |  |  |  |  |
Non-voting Common Units of LLC [Member] |  |  |  |  |  |  |  |  |
Payments to Acquire Long-term Investments |  | $ 10,000,000 |  |  |  |  |  |  |
Cost Method Investment, Ownership Percentage |  | 5.60% |  |  |  |  |  |  |
Non-voting Preferred Units of DFH LLC [Member] |  |  |  |  |  |  |  |  |
Payments to Acquire Long-term Investments |  |  | $ 12,000,000 |  |  |  |  |  |
Mandatory Preferred Return, Percent |  |  | 14.00% |  |  |  |  |  |
Percent of Preferred Units Convertible to Non-voting Common Units |  |  | 25.00% |  |  |  |  |  |
Proceeds from Redemption of Preferred Units |  |  |  |  |  |  | 12,000,000 |  |
Voting Convertible Preferred Stock of Breezeway Homes, Inc. [Member] |  |  |  |  |  |  |  |  |
Cost-method Investments, Other than Temporary Impairment |  |  |  |  |  |  | $ 0 |  |

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