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Significant Accounting Policies (Tables) | 3 Months Ended
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Mar. 31, 2019
Accounting Policies [Abstract] |
Amortized Cost Basis, Aggregate Fair Value, Unrealized (Gains)/Losses and Net Carrying Value of Investments in Held-to-maturity Securities | The following table provides the amortized cost basis, aggregate fair value, unrealized gains/losses, and the net carrying value of investments in held-to-maturity securities as of March 31, 2019:
| March 31, 2019 |
| Amortized |  |  | Aggregate |  |  | Unrealized |  |  | Unrealized |  |  | Net Carrying |
| Cost |  |  | Fair Value |  |  | Gains |  |  | Losses |  |  | Value |
Marketable securities: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Corporate bonds/notes | $ | 10,823,308 |  |  | $ | 10,832,228 |  |  | $ | — |  |  | $ | (8,920 | ) |  | $ | 10,823,308 |
Commercial paper |  | 25,819,617 |  |  |  | 25,819,617 |  |  |  | — |  |  |  | — |  |  |  | 25,819,617 |
U.S. government agency securities |  | 11,913,633 |  |  |  | 11,916,320 |  |  |  | — |  |  |  | (2,687 | ) |  |  | 11,913,633 |
Marketable securities current total | $ | 48,556,558 |  |  | $ | 48,568,165 |  |  | $ | — |  |  | $ | (11,607 | ) |  | $ | 48,556,558 |
| December 31, 2018 |
| Amortized |  |  | Aggregate |  |  | Unrealized |  |  | Unrealized |  |  | Net Carrying |
| Cost |  |  | Fair Value |  |  | Gains |  |  | Losses |  |  | Value |
Marketable securities: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Corporate bonds/notes | $ | 16,054,071 |  |  | $ | 16,050,462 |  |  | $ | 3,609 |  |  | $ | — |  |  | $ | 16,054,071 |
Commercial paper |  | 17,756,394 |  |  |  | 17,756,394 |  |  |  | — |  |  |  | — |  |  |  | 17,756,394 |
U.S. government agency securities |  | 3,951,974 |  |  |  | 3,951,040 |  |  |  | 934 |  |  |  | — |  |  |  | 3,951,974 |
Marketable securities current total | $ | 37,762,439 |  |  | $ | 37,757,896 |  |  | $ | 4,543 |  |  | $ | — |  |  | $ | 37,762,439 |

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- Definition Tabular disclosure of information about investment in debt security measured at amortized cost (held-to-maturity). + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 5 -URI http://asc.fasb.org/extlink&oid=82897076&loc=d3e27232-111563 + Details
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