Marketable Securities - Additional Information (Detail) |
9 Months Ended | 12 Months Ended |
|---|---|---|
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Sep. 30, 2018
USD ($)
Security
|
Dec. 31, 2017
USD ($)
Security
|
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| Marketable Securities [Abstract] | ||
| Maturity period classified current investments | Less than one year | Less than one year |
| Number of securities in unrealized loss position for less than one year | Security | 26 | 32 |
| Aggregate fair value of debt securities | $ | $ 24,066,817 | $ 39,858,864 |
| X | ||||||||||
- Definition Maturity period for marketable securities investments classification as current investments. No definition available.
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| X | ||||||||||
- Definition Number of investment positions in available-for-sale investments in a continuous unrealized loss position for less than one year or normal operating cycle, if longer, for which an other-than-temporary impairment (OTTI) has not been recognized in the income statement. No definition available.
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| X | ||||||||||
- Definition Fair value of investment in debt security measured at amortized cost (held-to-maturity), in continuous unrealized loss position for less than 12 months. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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| X | ||||||||||
- References No definition available.
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