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Investments - Summary of Short-term and Long-term Investments (Detail) - USD ($) | Mar. 31, 2019 | Sep. 30, 2018
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Schedule Of Held To Maturity Securities [Line Items] |  |
Amortized Cost | $ 124,096,728 | $ 46,400,176
Gross Unrealized Gains | 755,661 |
Gross Unrealized Losses | (162,798) | (429,050)
Fair Value | 124,689,591 | 45,971,126
Commercial Notes Due Within One Year |  |
Schedule Of Held To Maturity Securities [Line Items] |  |
Amortized Cost | 56,560,674 | 46,400,176
Gross Unrealized Gains | 52,189 |
Gross Unrealized Losses | (162,798) | (429,050)
Fair Value | 56,450,065 | $ 45,971,126
Commercial Notes Due Within Three Years |  |
Schedule Of Held To Maturity Securities [Line Items] |  |
Amortized Cost | 67,536,054 |
Gross Unrealized Gains | 703,472 |
Fair Value | $ 68,239,526 |

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