| **Concentration of Risks and Uncertainties** | 6 Months Ended                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                             |
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| **Risks and Uncertainties [Abstract]**       |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                       |
| Concentration of Risks and Uncertainties     | Concentration of Risks and UncertaintiesThe Company’s real estate investments are concentrated in Northwest Florida in a number of specific development projects.  Uncertain economic conditions could have an adverse impact on the Company’s real estate values and could cause the Company to sell assets at depressed values in order to pay ongoing expenses.  Financial instruments that potentially subject the Company to a concentration of credit risk consist of cash, cash equivalents, investments, notes receivable, other receivables, investments held by special purpose entities and investments in retained interests.  The Company deposits and invests cash with a major financial institution in the United States, which balances exceed the amount of F.D.I.C. insurance provided on such deposits.  In addition, as of June 30, 2016, the Company had $174.6 million invested in U.S. Treasury securities, $19.0 million invested in five issuers of corporate debt securities that are non-investment grade, $18.9 million invested in two issuers of preferred stock that are non-investment grade and $3.8 million invested in one issuer of preferred stock that is investment grade.  In addition, as of June 30, 2016, the Company had investments in short term commercial paper from six issuers of $139.1 million. |

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| - Definition
The entire disclosure for any concentrations existing at the date of the financial statements that make an entity vulnerable to a reasonably possible, near-term, severe impact. This disclosure informs financial statement users about the general nature of the risk associated with the concentration, and may indicate the percentage of concentration risk as of the balance sheet date.
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